JP6182061B2 - Secondary battery - Google Patents

Description

  The present invention relates to a secondary battery in which a flat wound electrode group is accommodated in a rectangular battery can.

  A lithium ion secondary battery is widely known as a vehicle driving battery. As a structure of the lithium ion secondary battery, for example, a structure described in Patent Document 1 is known. In the structure described in Patent Document 1, a wound electrode group obtained by winding a positive electrode plate and a negative electrode plate through a separator and an electrolytic solution are accommodated in a flat container, and each of the positive electrode plate and the negative electrode plate is accommodated. External terminals are joined. The current collector foil corresponding to the uncoated part where the active material mixture is not coated is exposed at each end of the positive electrode plate and the negative electrode plate, and the current collector foil is connected to the current collector connector by ultrasonic bonding or resistance welding. Are joined and welded. The current collector connection body is connected to an external terminal attached to the battery lid.

JP 2012-178235 A

  However, the lithium ion secondary battery has a problem that the wound electrode group is deformed depending on the state of charge / discharge of the secondary battery, and the battery performance is not sufficiently exhibited.

  By the way, immediately after the battery is assembled, the gap between the wound electrode group and the battery can inside the battery is uniform, but at the time of charging, lithium ions are released from the positive electrode active material, and the negative electrode active material is charged with lithium. When ions are inserted, the particle size of the negative electrode active material increases, and the thickness of the negative electrode active material mixture portion of the negative electrode increases. Therefore, the sum of the thickness of the positive electrode and the thickness of the negative electrode in the charged state is the same as that of the positive electrode in the discharged state (that is, a state in which lithium ions are released from the negative electrode active material and lithium ions are inserted into the positive electrode active material). It becomes larger than the sum of the thickness and the thickness of the negative electrode.

As described above, the exposed portions of the metal foil at the ends of the wound positive electrode and negative electrode in the winding axis direction are connected to and constrained by the positive electrode current collector plate and the negative electrode current collector plate, respectively. for that reason,
When the wound electrode group expands and deforms in the thickness direction in the charged state, the wound electrode group becomes the thickest at the center in the width direction and deforms into a shape that contacts the inner wall of the battery can. At this time, in the battery can, the gap generated between the inner wall of the battery can and the wound electrode group in the charged state is not uniform, and the pressure received by the flat part of the wound electrode group from the battery can is the central part of the wound electrode group Only the portion that is in contact with the battery can, and the battery performance is not sufficiently exhibited.

A secondary battery according to the present invention includes a positive electrode having a positive electrode mixture layer formed on a positive foil, a separator, and a flat wound electrode group obtained by winding a negative electrode having a negative electrode mixture layer formed on a negative electrode foil. the a that electrostatic Ikekan be wound accommodating the electrode assembly, a pair of first plate-shaped member and a pair of second plate members respectively disposed between the battery can and the flat wound electrode group The wound electrode group is formed at one end in the winding axis direction, and the positive electrode current collector plate connecting portion to which the bundled positive electrode foil exposed portions are connected to each other to connect the positive electrode current collector plate; A negative electrode current collector plate connection part formed on the other end in the winding axis direction, the bundled negative electrode foil exposed parts being connected to each other and connected to the negative electrode current collector plate, and a pair horizontally parallel to the winding axis direction flat surface of the said pair of pair of wound curved portions formed at both ends of a direction perpendicular to the winding axis direction of the flat surface It has, at the time of charge, in contact with the inner surface of the central region of the pair of flat surfaces of the flat wound electrode group said battery can, and the pair of flat surfaces of the outside than the central region be one gap is formed between the battery can in the peripheral region of the pair of first plate-shaped member, said central region of the peripheral region excluding the central region of the pair of flat surfaces wherein said peripheral area between the positive electrode current collector plate connecting portion, and the battery can, the gap between the so that filling each are arranged to face the pair of flat surfaces, the pair the second plate-like member, and the peripheral area between the negative electrode current collector plate connecting portion and the central region of the peripheral region excluding the central region of the pair of flat surfaces, and the battery can, the gap between the to fill each said one Are arranged each flat surface of the facing, characterized in that is.

  According to the present invention, the wound electrode group can be appropriately pressed, and the battery performance can be improved.

FIG. 1 is an external perspective view showing an embodiment of a secondary battery according to the present invention. FIG. 2 is an exploded perspective view of the flat wound secondary battery 100. FIG. 3 is a diagram showing the wound electrode group 3. FIG. 4 is a diagram showing the arrangement of the pressing members 200a and 200b. FIG. 5 is a diagram illustrating the shapes of the pressing members 200a and 200b. FIG. 6 is a cross-sectional view showing the wound electrode group 3 and the pressing members 200a and 200b housed in the battery can 1, and shows a case where the wound electrode group 3 is cut along the winding axis direction. FIG. 7 is a cross-sectional view showing the wound electrode group 3 and the pressing members 200a and 200b housed in the battery can 1, and shows a case where the wound electrode group 3 is cut along a direction perpendicular to the winding axis. FIG. 8 is a diagram showing the arrangement of the pressing members 200a and 200b during charging. FIG. 9 is a diagram showing the shape of the wound electrode group 3 before and after charging.

  Hereinafter, embodiments for carrying out the present invention will be described with reference to the drawings. In the present embodiment, a prismatic lithium ion secondary battery embodying the present invention will be described as an example. First, an overall configuration of the flat wound secondary battery 100 will be described with reference to FIGS. FIG. 1 is an external perspective view of a flat wound secondary battery 100. FIG. 2 is an exploded perspective view of the flat wound secondary battery 100. FIG. 3 is a view showing the wound electrode group 3 and shows a part of the wound electrode group 3 developed.

  The flat wound secondary battery 100 includes a battery can 1 and a battery lid 6 as battery containers. As shown in FIG. 2, the battery can 1 has a pair of opposed wide side surfaces 1b having a relatively large area and a pair of opposed narrow side surfaces 1c having a relatively small area. These side surfaces 1b and 1c are formed so as to rise from the bottom surface 1d, and constitute a rectangular tube-shaped side surface. A portion facing the bottom surface 1d is an opening 1a. A wound electrode group 3 shown in FIG. 3 is accommodated in the battery can 1, and the opening 1 a of the battery can 1 is sealed by a battery lid 6. By welding the substantially rectangular flat battery cover 6 to the substantially rectangular opening 1a, the opening 1a is closed and the battery can 1 is sealed.

  As shown in FIG. 1, the battery lid 6 is provided with a positive external terminal 14 and a negative external terminal 12. The wound electrode group 3 is charged via the positive external terminal 14 and the negative external terminal 12, and power is supplied to the external load. The battery cover 6 is integrally provided with a gas discharge valve 10. When the pressure in the battery container rises, the gas discharge valve 10 opens to discharge gas from the inside, and the pressure in the battery container is reduced. Thereby, the safety of the flat wound secondary battery 100 is ensured.

  As shown in FIG. 2, a wound electrode group 3 is accommodated in a rectangular tube-shaped battery can 1 via an insulating sheet 2. The flat wound electrode group 3 is wound in a flat shape with the left-right direction in FIG. 2 (the direction from one side surface 1c toward the other side surface 1c) as an axis (hereinafter referred to as a wound shaft). A pair of curved portions 30a and 30b are formed above and below the wound electrode group 3. As shown in FIG. 2, the wound electrode group 3 is inserted into the battery can 1 such that one curved portion 30b is disposed on the bottom surface 1d side and the other curved portion 30a is disposed on the opening portion 1a side.

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

  The structure from the positive external terminal 14 to the positive current collector 44 and the structure from the negative external terminal 12 to the negative current collector 24 will be described. The positive external terminal 14 and the negative external terminal 12 have a weld joint that is welded to a bus bar or the like. Each welded joint has a rectangular parallelepiped block shape protruding upward from the battery lid 6, 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. It has a configuration.

  The positive electrode connection portion 14 a protrudes from the lower surface of the positive electrode external terminal 14 and has a cylindrical shape whose tip can be inserted into the positive electrode side through hole 46 of the battery lid 6. The positive electrode connection portion 14 a penetrates through the battery lid 6, penetrates through a through hole 43 provided in the positive electrode current collector plate base 41 of the positive electrode current collector plate 44, and protrudes toward the inside of the battery can 1. The tip of the positive electrode connection portion 14 a is caulked, and the positive electrode external terminal 14 and the positive electrode current collector plate 44 are integrally fixed to the battery lid 6. A gasket 5 is interposed between the positive electrode external terminal 14 and the battery cover 6, and an insulating plate 7 is interposed between the positive electrode current collector plate 44 and the battery cover 6.

  Similarly, the negative electrode connection portion 12 a protrudes from the lower surface of the negative electrode external terminal 12 and has a cylindrical shape whose tip can be inserted into the negative electrode side through hole 26 of the battery lid 6. The negative electrode connection portion 12 a penetrates the battery lid 6, penetrates the through hole 23 provided in the negative electrode current collector plate base 21 of the negative electrode current collector plate 24, and protrudes to the inside of the battery can 1. The tip of the negative electrode connection portion 12 a is caulked, and the negative electrode external terminal 12 and the negative electrode current collector plate 24 are integrally fixed to the battery lid 6.

  Note that a gasket 5 is interposed between the negative electrode external terminal 12 and the battery cover 6, and an insulating plate 7 is interposed between the negative electrode current collector plate 24 and the battery cover 6. The gasket 5 and the insulating plate 7 are provided to electrically insulate the positive electrode current collecting plate 44 and the negative electrode current collecting plate 24, and the positive electrode external terminal 14 and the negative electrode external terminal 12 from the battery lid 6, respectively.

  A rectangular plate-shaped positive current collector plate base 41 provided on the positive current collector plate 44 is disposed to face the lower surface of the battery lid 6. The positive electrode current collector plate base 41 is formed with a positive electrode side connection end 42 extending toward the bottom surface along the wide surface of the battery can 1. The positive electrode side connection end portion 42 is connected in a state where the positive electrode side connection end portion 42 is overlapped with the positive electrode foil exposed portion 34 c of the wound electrode group 3. Similarly, a rectangular plate-shaped negative electrode current collector plate base 21 provided on the negative electrode current collector plate 24 is disposed so as to face the lower surface of the battery lid 6, and toward the bottom surface side along the wide surface of the battery can 1. An extended negative electrode side connection end 22 is formed. The negative electrode side connection end portion 22 is connected in a state of being overlapped with the negative electrode foil exposed portion 32 c of the wound electrode group 3.

  A plurality of plate-like pressing members 200 a and 200 b are arranged on the flat surface of the wound electrode group 3, that is, the surface facing the side surfaces 1 b and 1 c of the battery can 1. Then, the insulating sheet 2 is wound around the wound electrode group 3 from above the pressing members 200a and 200b, that is, on the surface facing the side surfaces 1b and 1c and the bottom surface 1d of the battery can 1. The insulating sheet 2 is made of a single sheet made of synthetic resin such as PP (polypropylene) or a plurality of film members. Details of the pressing members 200a and 200b will be described later.

  The battery cover 6 to which the wound electrode group 3 is fixed is attached to the opening 1a so that the wound electrode group 3 is disposed in the battery can 1, and the periphery of the battery cover 6 is opened by laser welding or the like. To be joined. And after inject | pouring electrolyte solution into the battery can 1 from the injection hole 9 of the battery cover 6, the injection stopper 11 is joined to the battery cover 6 by laser welding, the injection hole 9 is sealed, and flat winding is carried out. The 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 cited. On the other hand, examples of a material for forming the negative electrode external terminal 12 and the negative electrode current collector plate 24 include a copper alloy. Examples of the material for forming the insulating plate 7 and the gasket 5 include resin materials having insulating properties such as polybutylene terephthalate, polyphenylene sulfide, and perfluoroalkoxy fluororesin. Moreover, as an electrolyte solution injected into the battery can 1, for example, a non-aqueous electrolyte 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 applied.

  FIG. 3 is a view showing the wound electrode group 3. The wound electrode group 3 is configured by winding the negative electrode 32 and the positive electrode 34 stacked via separators 33 and 35 in a flat shape. The separators 33 and 35 have a role of insulating between the positive electrode 34 and the negative electrode 32. In the wound electrode group 3, the outermost electrode is the negative electrode 32, and the separator 35 is wound further outside. The width dimension of the portion of the negative electrode 32 where the negative electrode mixture layer 32b is applied (that is, the axial dimension of the wound electrode group 3) is greater than the width dimension of the portion of the positive electrode 34 where the positive electrode mixture layer 34b is applied. Is also set larger. By setting in this way, the portion where the positive electrode mixture layer 34b is applied is surely sandwiched between the portions where the negative electrode mixture layer 32b is applied.

  The positive electrode 34 has a positive electrode active material mixture on both surfaces of a positive electrode foil that is a positive electrode current collector, and the positive electrode active material mixture is not applied to an end portion on one side in the width direction of the positive electrode foil. A positive foil exposed portion 34c is provided. The negative electrode 32 has a negative electrode active material mixture on both surfaces of a negative electrode foil that is a negative electrode current collector, and the negative electrode active material mixture is not applied to the other end in the width direction of the negative electrode foil. A negative foil exposed portion 32c is provided. The positive foil exposed portion 34c and the negative foil exposed portion 32c are regions where the metal surface of the electrode foil is exposed. The positive electrode 34 and the negative electrode 32 are wound so that the positive foil exposed portion 34c and the negative foil exposed portion 32c are arranged separately at positions on one side and the other side in the winding axis direction.

  As shown in FIG. 2, the positive electrode foil exposed portions 34c are bundled at a plane portion between the curved portions 30a and 30b and connected to each other by welding or the like. Similarly to the positive foil exposed portion 34c, the negative foil exposed portion 32c is also bundled at a plane portion between the curved portions 30a and 30b and connected to each other by welding or the like. In addition, although the width direction dimension of the separators 33 and 35 is set larger than the width direction dimension of the part to which the negative electrode mixture layer 32b was applied, the separators 33 and 35 have the positive electrode foil exposed part 34c and the negative electrode foil exposed part. Since it winds so that the metal foil surface of the both ends of 32c may be exposed, it does not become a hindrance at the time of bundling and welding.

  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 on both sides of a copper foil (negative electrode foil) having a thickness of 10 μm leaving a welded portion (negative electrode uncoated portion). 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 this 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, and natural graphite capable of inserting and removing lithium ions and various artificial graphite materials , Carbonaceous materials such as coke, compounds such as Si and Sn (for example, SiO, TiSi ₂ etc.), or composite materials thereof may be used. It is not limited.

On the other hand, with respect to 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 with respect 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 thereto. This positive electrode mixture was applied to both surfaces of an aluminum foil (positive electrode foil) having a thickness of 20 μm leaving a welded portion (positive electrode uncoated portion). 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 or layered 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 a part thereof is substituted or doped with a metal element may be used.

  Furthermore, in this embodiment, the case where PVDF is used as the binder of the coating portion in the positive electrode and the negative electrode is exemplified, but polytetrafluoroethylene (PTFE), polyethylene, polystyrene, polybutadiene, butyl rubber, nitrile rubber, Use polymers such as styrene butadiene rubber, polysulfide rubber, nitrocellulose, cyanoethyl cellulose, various latexes, acrylonitrile, vinyl fluoride, vinylidene fluoride, propylene fluoride, chloroprene fluoride, acrylic resins, and mixtures thereof. be able to. Moreover, as a shaft core, what was comprised by winding the resin sheet whose bending rigidity is higher than any of positive electrode foil, negative electrode foil, and a separator can be used, for example.

(Description of pressing members 200a and 200b)
Next, the pressing members 200a and 200b will be described. FIG. 4 is a diagram showing the arrangement of the pressing members 200a and 200b, and shows the wound electrode group 3 provided with the pressing members 200a and 200b. In FIG. 4, four pressing members 200 a and 200 b provided on one surface of the flat wound electrode group 3 (one side surface 1 b of the battery can 1) are illustrated, but the other of the wound electrode group 3 is illustrated. The pressing members 200a and 200b are similarly provided on the surface.

  FIG. 5 is a diagram illustrating the shape of the pressing member 200a. The pressing member 200b has the same shape as that of the pressing member 200a, and both of the pressing members 200a and 200b are formed of a plate-like member having a trapezoidal shape. In the present embodiment, the pressing members 200a and 200b are formed of a synthetic resin that is not affected by an electrolytic solution such as PP (polypropylene). As shown in FIG. 5, the trapezoidal pressing member 200a increases in thickness from the upper base 201 side to the lower base 202 side. The shape of the pressing member 200a viewed from the side is a wedge shape, and the shape viewed from the lower bottom 202 side is a rectangle. In the example shown in FIG. 5, the side shape is a right triangle.

  FIG. 6 is a cross-sectional view showing the wound electrode group 3 and the pressing members 200a and 200b housed in the battery can 1, and shows a case where the wound electrode group 3 is cut along the winding axis direction. On the other hand, FIG. 7 is a cross-sectional view taken along the direction orthogonal to the winding axis, that is, the direction from the opening 1a of the battery can 1 toward the bottom surface 1d. 6 and 7, the illustration of the insulating sheet 2 is omitted. The shape of the wound electrode group 3 in FIGS. 6 and 7 indicates a state before being charged and expanded and deformed.

  As described above, the wound electrode group 3 is wound in a flat shape, and as shown in FIG. 7, the bending portion 30 a is disposed on the battery lid 6 side, and the bending portion 30 b is on the bottom surface 1 d side of the battery can 1. It is accommodated in the battery can 1 so that it may be arrange | positioned. For this reason, the surface of the flat portion (referred to herein as the flat portion 30 e) between the curved portion 30 a and the curved portion 30 b faces the wide side surface 1 b of the battery can 1.

  As shown in FIG. 6, the negative electrode foil exposed portion 32 c is bundled and connected to each other at one end in the winding axis direction of the wound electrode group 3, and the negative electrode side connection end portion 22 of the negative electrode current collector plate 24 is connected to each other. It is connected. On the other hand, at the other end, the positive foil exposed portions 34c are bundled and connected to each other, and the positive electrode side connection end portion 42 of the positive electrode current collector plate 44 is connected. The wound electrode group 3 before being charged and deformed has a thickness in a region between the curved portion 30a and the curved portion 30b and a region between the negative foil exposed portion 32c and the positive foil exposed portion 34c, that is, flatness. The portion 30e has a substantially flat plate thickness.

  However, as described above, when lithium ions are released from the positive electrode active material and lithium ions are inserted into the negative electrode active material during charging, the particle size of the negative electrode active material increases, and the negative electrode active material composition of the negative electrode is increased. The thickness of the material part is increased. As a result, as shown in FIG. 9B, the shape of the wound electrode group 3 changes so that the thickness of the flat portion 30e increases. FIG. 9 is a view showing the shape of the wound electrode group 3 before and after charging, and shows the case where the pressing members 200a and 200b are not arranged.

  FIG. 9 is a cross-sectional view of the battery can 1 in the winding axis direction. FIG. 9A shows a state before charging, and FIG. 9B shows a case where the battery can 1 is most deformed by charging. The flat portion 30e of the wound electrode group 3 before charging has a flat plate shape with substantially the same thickness. However, when charging is performed, the flat portion 30e is deformed as shown in FIG. In the wound electrode group 3, since the negative electrode foil exposed portion 32c and the positive electrode foil exposed portion 34c are connected by welding or the like at both ends, the increase in the thickness dimension is greatest at the center portion of the flat portion 30e, and the negative electrode foil exposed The closer to the portion 32c and the positive foil exposed portion 34c, the smaller. Therefore, a gap having a wedge-shaped cross section is formed between the wound electrode group 3 and the battery can 1. Further, also in the cross section in the direction orthogonal to the winding axis shown in FIG. 7, the increase in the thickness dimension is the largest in the central portion of the flat portion 30 e, as in the cross section in the winding axis direction shown in FIG. The closer to the curved portions 30a and 30b, the smaller.

  As shown in FIG. 9B, when only the central portion of the wound electrode group 3 is in contact with the battery can 1, the pressure received from the battery can 1 is only the central portion in contact with the battery can 1. Battery performance is not fully demonstrated.

  Therefore, in the present embodiment, by arranging the pressing members 200a and 200b as shown in FIGS. 2, 6 and 7, when the wound electrode group 3 is deformed by charging, the entire surface of the flat portion 30e is almost uniform. It was set as the structure pressed by. 6 and 7, the pressing members 200 a and 200 b are attached to the flat portion 30 e of the wound electrode group 3. As described above, in the substantially rectangular flat portion 30e, an increase in thickness is suppressed at the negative electrode foil exposed portion 32c and the positive electrode foil exposed portion 34c and the curved portions 30a and 30b. Therefore, when the wound electrode group 3 is deformed by charging, the surface shape of the flat portion 30e becomes a shape like a truncated pyramid.

  Therefore, as shown in FIG. 5, the lower bottom 202 side of the trapezoidal pressing members 200a, 200b is thickened, and as shown in FIG. 4, the upper bottom 201 of the pressing members 200a, 200b is on the center side of the flat portion 30e. The lower bottom 202 is arranged so as to be on the curved portions 30a, 30b side, the negative foil exposed portion 32c, and the positive foil exposed portion 34c side. Note that the pressing members 200a and 200b are not disposed in the central region 30c that contacts the side surface 1b of the battery can 1 when the wound electrode group 3 is expanded and deformed by charging.

  8A shows the shape of the wound electrode group 3 in the middle of charging. FIG. 8B shows the shape of the wound electrode group 3 most deformed, and the central portion of the flat portion 30e is the battery can 1. The case where it is contact | abutting to the side surface 1b is shown. In the state shown in FIG. 8A, the thickness of the central portion of the flat portion 30e is increased, but there is a gap between the pressing member 200a and the central region 30c of the flat portion 30e and the side surface 1b of the battery can 1. Is made. Furthermore, when the wound electrode group 3 is deformed by charging and the central region 30c of the flat portion 30e comes into contact with the side surface 1b, the pressing members 200a and 200b also come into contact with the side surface 1b.

  As a result, the pressing force from the battery can 1 is applied almost uniformly to the entire area of the flat portion 30e, and the battery performance can be improved compared to the case of FIG. 9 in which the pressing members 200a and 200b are not used. it can. In addition, by adjusting the thickness of the pressing members 200a and 200b, it is possible to adjust the pressing force in the charged state where the deformation amount of the wound electrode group 3 is the largest.

  6 to 9, the insulating sheet 2 is omitted. However, in the state of FIGS. 6 and 7, the insulating sheet 2 is wrapped so as to wrap the wound electrode group 3 provided with the pressing members 200 a and 200 b. It arrange | positions between the rotation electrode group 3 and the battery can 1, and in the state of FIG.8 (b), it will be pinched | interposed between pressing member 200a, 200b and the center area | region 30c, and the side surface 1b.

  In the above-described example, the pressing members 200a and 200b are attached to the flat portion 30e of the wound electrode group 3, but the pressing members 200a and 200b are simply disposed so as to face the flat portion 30e, and the insulating sheet 2 You can also wrap them up. Further, the pressing members 200a and 200b may be attached to the insulating sheet 2 side. As described above, since the surface of the flat part 30e is deformed by charging, there is a possibility that the affixing state of the pressing members 200a and 200b may be changed by the deformation of the wound electrode group 3, but it is affixed to the insulating sheet 2 side. In some cases, such problems can be avoided. Furthermore, instead of providing the insulating sheet 2, an insulating coat may be applied to the inner peripheral surface of the battery can 1.

  As described above, the secondary battery of this embodiment includes the positive electrode 34 in which the positive electrode mixture layer 34b is formed on the positive foil, the separators 33 and 35, and the negative electrode in which the negative electrode mixture layer 32b is formed on the negative electrode foil. A flat wound electrode group 3 in which the electrode 32 is wound, a substantially rectangular parallelepiped battery can 1 that accommodates the wound electrode group 3, and a front surface and a back surface of the wound electrode group 3 and the battery can 1 are disposed respectively. And a pressing member 200a which is a first plate-like member and a second plate-like member. The wound electrode group 3 is formed at one end in the winding axis direction, and the positive electrode current collector plate connection portion (the positive electrode current collector plate 44 is connected to the bundled positive electrode foil exposed portions 34c connected to each other). 34c), a negative electrode current collector plate connection part (32c) formed on the other end in the winding axis direction and bundled with the bundled negative electrode foil exposed parts 32c and connected to the negative electrode current collector plate 24; A pair of curved portions 30a and 30b formed at both ends in a direction orthogonal to the rotational axis direction, and the central regions 30c on both the front and back surfaces of the wound electrode group 3 are in contact with the inner surface of the battery can during charging. In addition, in the peripheral region outside the central region 30c (the region excluding the central region 30c of the flat portion 30e), a gap is formed between the battery can 1 and the pressing member 200a includes the wound electrode group 3 The center region 30c and the positive current collector connecting portion on both front and back surfaces Fills a gap in the peripheral region between 34c), it fills the gap in the peripheral region between the central region 30c and the anode current collector plate connecting portion and (32c).

  Since the wound electrode group 3 has the positive electrode foil exposed portion 34c and the negative electrode foil exposed portion 32c in the winding axis direction, when the wound electrode group 3 is expanded and deformed by charging, a flat portion is formed as shown in FIG. The central region 30c of 30e (see FIG. 8A) contacts the side surface 1b of the battery can 1, and a gap S having a wedge-shaped cross section is formed around the central region 30c. In the present embodiment, by arranging the pressing member 200a so as to fill the gap S, the pressing force in the central region 30c and the pressing force in the peripheral region in the winding axis direction of the central region 30c can be made substantially uniform. it can.

  Furthermore, on both front and back surfaces of the wound electrode group 3, the pressing member 200b is further provided to fill the gaps in the peripheral region between the central region 30c and the pair of curved portions 30a and 30b, thereby reducing the pressing force to the flat portion 30e. Can be made substantially uniform over the entire front and back surfaces.

  It is preferable that the pressing members 200a and 200b have a shape that increases in thickness from the central region 30c to the positive foil exposed portion 34c, the negative foil exposed portion 32c, and the curved portions 30a and 30b. By setting it as such a shape, the clearance gap produced between the winding electrode group 3 and the side surface 1b of the battery can 1 at the time of charge deformation can be filled up appropriately.

  The shape of the pressing members 200a and 200b is preferably a trapezoid as shown in FIG. 5 so that the thickness increases from the upper base 201 to the lower base 202 of the trapezoid. With such a shape, as shown in FIG. 4, the pressing members 200 a and 200 b can be arranged so as to cover the region excluding the central region 30 c of the flat portion 30 e. As a result, when the wound electrode group 3 is deformed by charging as shown in FIG. 8B, the entire surface of the flat portion 30e is pressed almost uniformly by the pressing members 200a and 200b and the side surface 1b of the battery can 1. Can do.

  Moreover, the insulating sheet 2 arrange | positioned between the winding electrode group 3 and the battery can 1 is provided, and each of 1st, 2nd, 3rd and 4th press member 200a, 200b is wound electrode group 3 And the insulating sheet 2 may be arranged. Furthermore, by attaching the first, second, third and fourth pressing members 200a, 200b to the insulating sheet 2, misalignment of the pressing members 200a, 200b can be prevented, and the battery assembly workability can be improved. be able to.

  Each of the embodiments described above may be used alone or in combination. This is because the effects of the respective embodiments can be achieved independently or synergistically. In addition, the present invention is not limited to the above embodiment as long as the characteristics of the present invention are not impaired.

1, battery can, 1b, 1c: side surface, 1d: bottom surface, 2: insulating sheet, 3: wound electrode group, 6: battery lid, 24: negative electrode current collector plate, 30a, 30b: curved portion, 30c: central region 30e: flat portion, 32: negative electrode, 32c: negative foil exposed portion, 32b: negative electrode composite layer, 33, 35: separator, 34: positive electrode, 34c: positive foil exposed portion, 34b: positive electrode composite layer, 44: positive current collector plate, 100: flat wound secondary battery, 200a, 200b: pressing member

Claims (7)

A flat wound electrode group obtained by winding a positive electrode having a positive electrode mixture layer formed on the positive electrode foil, a separator, and a negative electrode having a negative electrode mixture layer formed on the negative electrode foil;
A conductive Ikekan you accommodating an electrode group wound above,
A pair of first plate-like members and a pair of second plate-like members respectively disposed between the flat wound electrode group and the battery can,
The wound electrode group includes:
A positive electrode current collector plate connection part formed at one end in the winding axis direction and connected to the positive electrode foil exposed parts bundled together and connected to the positive electrode current collector plate;
A negative electrode current collector plate connection part formed on the other end in the winding axis direction, the bundled negative electrode foil exposed parts being connected to each other and connected to the negative electrode current collector plate;
A pair of flat surfaces horizontal in the winding axis direction;
A pair of wound curved portions formed at both ends of the pair of flat planes in a direction orthogonal to the winding axis direction;
Wherein at the time of charge, in contact with the inner surface of the central region the battery can of the pair of flat surfaces of the flat wound electrode group, and, in the peripheral region of the pair of flat surfaces of the outside than the central region There is a gap between the battery can and
The pair of first plate-shaped members includes the peripheral region between the central region and the positive current collector connecting portion of the peripheral region excluding the central region of the pair of flat surfaces, and the battery can When, the clearance so that filling each between, are arranged to face the pair of flat surfaces,
The pair of second plate-shaped members include the peripheral region between the central region and the negative electrode current collector connecting portion of the peripheral region excluding the central region of the pair of flat surfaces, and the battery can And the pair of flat surfaces so as to respectively fill the gaps between them. The secondary battery according to claim 1,
The gap between the peripheral region between the central region and one of the pair of wound curved portions among the peripheral regions excluding the central region of the pair of flat surfaces, and the battery can. A pair of third plate-like members respectively disposed to face the pair of flat surfaces so as to be buried,
The gap between the battery can and the peripheral region between the central region and the other of the pair of wound curved portions among the peripheral regions excluding the central region of the pair of flat surfaces. A secondary battery, further comprising: a pair of fourth plate-like members respectively disposed to face the pair of flat surfaces so as to be buried. The secondary battery according to claim 2,
The first plate-like member is disposed opposite to the peripheral region between the positive current collector connection portion and the central region, and the thickness increases from the central region to the positive current collector connection portion side,
The second plate-like member is disposed opposite to the peripheral region between the negative electrode current collector plate connection portion and the central region, and the thickness increases from the central region to the negative electrode current collector plate connection portion side,
The third plate-like member is disposed to face the peripheral region between the one wound curved portion and the central region, and the thickness increases from the central region to the one wound curved portion side,
The fourth plate-like member is disposed opposite to the peripheral region between the other wound curved portion and the central region, and the thickness increases from the central region to the other wound curved portion side. Each of the secondary batteries is configured as follows. The secondary battery according to claim 3,
An outer shape of the first, second , third, and fourth plate-like members is trapezoidal, and the thickness increases from the trapezoid upper bottom side to the trapezoid lower bottom side. The secondary battery according to claim 4,
The secondary battery according to claim 1, wherein a side shape of the first, second, third and fourth plate-like members is a triangle. The secondary battery according to claim 4 or 5 ,
An insulating sheet disposed between the wound electrode group and the battery can so as to surround the wound electrode group;
Each of the first, second , third and fourth plate-like members is disposed between the wound electrode group and the insulating sheet. The secondary battery according to claim 6 ,
Each of said 1st, 2nd , 3rd and 4th plate-shaped member is affixed on the said insulating sheet, The secondary battery characterized by the above-mentioned.

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