JP2018107054A - Square secondary battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a secondary battery arranged so that an electrolyte solution forced out by a charging action can be led into a wound electrode body rapidly.SOLUTION: A square secondary battery according to the present invention comprises: a flattened wound body (3) winding a positive electrode body (31) and a negative electrode body (32) with a separator (33) arranged therebetween and having an open face in a winding axis direction; a battery container (1) containing the flattened wound body (3) and having a side face part opposed to the open face and a bottom face part connecting to the side face part; and an insulative protection film (2) covering the flattened wound body (3) and disposed between the flattened wound body (3) and the battery container (1). The insulative protection film (2) is in the state of being opened on the side of the bottom face part, and has a protrusion part protruding by a given length on the bottom face side.SELECTED DRAWING: Figure 7

Description

  The present invention relates to a prismatic secondary battery used for in-vehicle applications, for example.

  In recent years, prismatic lithium ion secondary batteries with high energy density have been developed as power sources for electric vehicles and the like. Since a secondary battery for in-vehicle use requires a larger capacity than that for a mobile phone or the like, a plurality of secondary batteries may be mounted. In the rectangular battery, a flat wound electrode body as a power generation element is accommodated in a rectangular battery container. The wound electrode body is configured by winding a positive electrode plate and a negative electrode plate in a state of being insulated with a separator interposed therebetween. A positive electrode current collector laminated portion in which positive electrode uncoated portions are bundled is provided on one side in the winding axis direction of the wound electrode body, and a negative electrode uncoated portion is bundled on the other side in the winding axis direction. In addition, a negative electrode current collector laminate is provided, and a positive electrode connection terminal is joined to the positive electrode current collector laminate, and a negative electrode connection terminal is joined to the negative electrode current collector laminate. The positive electrode connection terminal and the negative electrode connection terminal are electrically connected to, for example, the positive electrode external terminal and the negative electrode external terminal arranged on the same surface of the battery container such as a battery lid on the outside of the battery container. The structure is neutral, that is, the battery container is insulated from the wound electrode body.

  In this type of prismatic battery, when charged, the electrolyte taken in the wound electrode body is pushed out due to the expansion of the electrode. If the wound electrode body is in contact with the bottom wall portion of the battery can, the liquid is absorbed by contraction of the electrode due to discharge. However, if the wound electrode body is so close that it comes into contact with the bottom wall portion of the battery can, electrical insulation becomes difficult.

  In order to return such an extruded electrolyte to the wound electrode body, Patent Document 1 discloses an apparatus having an electrolyte absorbing member that guides the electrolyte to the separator in the wound electrode body.

JP2012-109102A

  The electrolyte solution absorbing member described in Patent Document 1 guides the electrolyte solution to the outermost separator of the wound electrode body, and requires a sufficient time to guide the electrolyte solution to the periphery of the wound electrode body. .

  The present invention has been made in view of the above points, and an object of the present invention is to provide a secondary battery that quickly guides the extruded electrolyte into the wound electrode body.

  In order to solve the above-described problem, the present application relates to a flat wound body in which a positive electrode body and a negative electrode body are wound through a separator and has an open surface in the winding axis direction, and the flat wound body is accommodated in an open surface. An insulating protective film comprising: a battery container having a side surface portion facing the surface portion and a bottom surface portion connected to the side surface portion; and an insulating protective film covering the flat wound body and disposed between the flat wound body and the battery container. Further, it has a protruding portion that protrudes a predetermined length on the bottom surface side in a state where the bottom surface portion side is opened.

  In the present invention by the above means, in the present invention, the electrolytic solution pushed out by charging is guided to the wound electrode body by the insulating protective film released toward the bottom of the can, and the electrolytic solution is not only from the outside of the wound electrode body but also from the side surface. It is possible to provide a prismatic secondary battery that is guided to the wound electrode body.

External perspective view of prismatic secondary battery Exploded perspective view of prismatic secondary battery Exploded perspective view of wound electrode body Perspective view after welding wound electrode body and positive and negative current collector plates The perspective view which shows the positional relationship of an insulating protective film and a wound electrode body Perspective view after winding the side cover Perspective view after sticking adhesive tape Perspective view after winding the side cover part with overlap Perspective view after winding the adhesive tape part avoiding side cover part

  Hereinafter, examples will be described with reference to the drawings.

  In the following embodiments, a case of a lithium ion secondary battery used in a hybrid vehicle or an electric vehicle will be described as an example of a square secondary battery.

<First embodiment>
FIG. 1 is an external perspective view of a prismatic secondary battery according to the present embodiment.
The square secondary battery C <b> 1 includes a battery can 1 and a lid (battery lid) 6. A wound electrode body 3 (see FIG. 2) is accommodated in the battery can 1, and the opening 1 a of the battery can 1 is sealed with a lid 6. The lid 6 is joined to the battery can 1 by laser welding to constitute a battery container sealed by the battery can 1 and the lid 6. The lid 6 is provided with a positive external terminal 8A and a negative external terminal 8B. The wound electrode body 3 (see FIG. 2) is charged via the positive external terminal 8A and the negative external terminal 8B, and power is supplied to the external load. The lid 6 is integrally provided with a gas discharge valve 10, and 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 square secondary battery C1 is ensured.
Next, with reference to FIG. 2, the structure in the battery can 1 of the square secondary battery C1 will be described.

FIG. 2 is an exploded perspective view of the prismatic secondary battery according to the present embodiment.
The battery can 1 of the prismatic secondary battery C1 has a so-called square shape, and is open upward at the rectangular bottom wall portion 22, the rectangular tubular side wall portion 21 rising from the bottom wall portion 22, and the upper end of the side wall portion 21. Opening 1a. A wound electrode body 3 is accommodated in the battery can 1 via an insulating protective film 2. The wound electrode body 3 is an electrode body obtained by winding a positive electrode body 31 and a negative electrode body 32 in a flat shape with a separator 33 interposed therebetween, and a positive electrode mixture 31b and a negative electrode mixture are provided on both end surfaces in the winding axis direction. A positive electrode foil exposed portion 31c and a negative electrode foil exposed portion 32c that are not coated with 32b are provided.

  Since the wound electrode body 3 is wound in a flat shape, the wound electrode body 3 has a pair of opposed curved portions having a semicircular cross section and a plane portion formed continuously between the pair of curved portions. doing. The wound electrode body 3 is inserted into the battery can 1 from one curved portion side so that the winding axis direction is along the lateral width direction of the battery can 1, and the other curved portion side is disposed on the upper opening side.

  At least a part of the positive electrode foil connection part 31d and the negative electrode foil connection part 32d, which are the flat part of the wound electrode body 3 and the electrode foil exposed part, are bundled into a flat plate shape. (Electrical terminal) 4A and one end of the negative electrode current collector plate (current collecting terminal) 4B are overlapped and connected.

  The other end of the positive electrode current collector plate 4A and the other end of the negative electrode current collector plate 4B are connected to the positive electrode external terminal 8A and the negative electrode external terminal 8B, respectively.

  In order to electrically insulate the positive electrode collector plate 4A and the negative electrode collector plate 4B, and the positive electrode external terminal 8A and the negative electrode external terminal 8B from the lid 6, a gasket 5 and an insulating plate 7 are provided on the lid 6, respectively. Yes. Moreover, after pouring electrolyte solution into the battery can 1 from the liquid injection port 9, the liquid injection stopper 11 is joined to the cover 6 by laser welding, the liquid injection port 9 is sealed, and the square secondary battery C1 is sealed. .

  As the material for the battery can 1 and the lid 6, aluminum or aluminum alloy, which is a metal material, is used. Aluminum or an aluminum alloy is used as a material for the positive electrode current collector plate 4A and the positive electrode external terminal 8A. Copper or copper alloy is used as a material for the negative electrode current collector plate 4B and the negative electrode external terminal 8B.

  The positive external terminal 8A and the negative external terminal 8B have weld joints that are welded to a bus bar or the like (not shown). The welded joint has a rectangular parallelepiped block shape protruding upward from the lid 6, and has a configuration in which the lower surface faces the surface of the lid 6 and the upper surface is parallel to the lid 6 at a predetermined height position. Yes.

  The positive electrode connecting portion 12A and the negative electrode connecting portion 12B have cylindrical shapes that protrude from the lower surfaces of the positive electrode external terminal 8A and the negative electrode external terminal 8B, respectively, and can be inserted into the positive electrode side through hole 6A and the negative electrode side through hole 6B. doing. 12 A of positive electrode connection parts and the negative electrode connection part 12B penetrate the cover 6, and are inside the battery can 1 rather than the positive electrode current collecting plate base 41A of the positive electrode current collecting plate 4A and the negative electrode current collecting plate 4B, and the negative electrode current collecting plate base 41B. The positive electrode external terminal 8A, the negative electrode external terminal 8B, the positive electrode current collector plate 4A, and the negative electrode current collector plate 4B are integrally fixed to the lid 6. A gasket 5 is interposed between the positive electrode external terminal 8A and the negative electrode external terminal 8B and the lid 6, and an insulating plate 7 is interposed between the positive electrode current collector plate 4A, the negative electrode current collector plate 4B and the lid 6. Intervened.

  The positive electrode current collector plate 4A and the negative electrode current collector plate 4B are a rectangular plate-shaped positive electrode current collector plate base portion 41A, a negative electrode current collector plate base portion 41B, a positive electrode current collector plate base portion 41A, which are disposed to face the lower surface of the lid 6. Bent at the side end of the negative electrode current collector base 41B and extends toward the bottom wall along the wide surface of the battery can 1, and the positive foil connecting part 31d and the negative foil connecting part of the wound electrode body 3 It has a positive electrode side connection end portion 42A and a negative electrode side connection end portion 42B which are connected in a state of being overlapped facing 32d. The positive electrode collector plate base 41A and the negative electrode collector plate base 41B are respectively formed with a positive electrode side opening hole 43A and a negative electrode side opening hole 43B through which the positive electrode connecting part 12A and the negative electrode connecting part 12B are inserted.

  Next, the configuration of the insulating protective film 2 will be described in detail. As shown in FIG. 2, for example, the insulating protective film 2 is made of a transparent member, but is not limited to being transparent, and may be opaque.

  The insulating protective film 2 is wound around the wound electrode body 3 with the direction along the flat surface of the wound electrode body 3 and the direction perpendicular to the wound axis direction of the wound electrode body 3 as the central axis direction. A side cover portion A2c and a side cover portion B2d that cover the side surface of the wound electrode body 3 are provided.

  The insulating protective film 2 is made of a single sheet or film member made of a synthetic resin such as PP (polypropylene), for example, and has a direction parallel to the flat surface of the wound electrode body 3 and perpendicular to the winding axis direction. It has a length that can be wound as a winding center.

  The thickness of the insulating protective film 2 is preferably 0.01 mm to 0.50 mm, and more preferably 0.03 mm to 0.20 mm. However, when the space volume inside the battery is large, the present invention is not limited to this. For example, the thickness of the insulating protective film 2 can be interposed between the wound electrode body 3 and the battery container, and the insulation can be maintained. The thickness is not limited to this as long as the thickness can be protected.

  In this embodiment, the case where PP is used as the material of the insulating protective film 2 is shown as an example. However, the present invention is not limited to this. For example, PFA (polytetrafluoroethylene), PPS (polyphenylene sulfide) is used. ), PET (polyethylene terephthalate), or a synthetic resin made of a material that does not react or denature due to the electrolytic solution. Moreover, the length of the insulating protective film 2 is not limited to the above-described example.

  The insulating protective film 2 is wound so that an end portion on one side in the width direction of the insulating protective film 2 is disposed at a position close to the side of the lid 6 so as not to overlap.

FIG. 3 is an exploded perspective view showing a state in which a part of the wound electrode body is developed.
The wound electrode body 3 is an electrode body obtained by winding a positive electrode body 31 and a negative electrode body 32 in a flat shape with a separator 33 interposed therebetween. As shown in FIG. 3, in the wound electrode body 3, the outermost electrode body is a negative electrode body 32, and a separator 33 is wound outside thereof. The end of the separator 33 is fixed to the outermost peripheral surface of the separator 33 with an adhesive tape (not shown), and the wound state is maintained. The winding end of the separator 33 is disposed at a substantially central position on one flat surface of the wound electrode body 3, and the central portion in the winding axis direction is fixed by an adhesive tape (not shown). The separator 33 has a role of insulating the positive electrode body 31 and the negative electrode body 32. The negative electrode mixture 32b of the negative electrode body 32 is larger in the width direction than the positive electrode mixture 31b of the positive electrode body 31, and thus, the positive electrode mixture 31b is configured to be sandwiched between the negative electrode mixture 31b without fail. The positive electrode body 31 is obtained by applying a positive electrode mixture 31b on both surfaces of a positive electrode foil 31a, and has an uncoated positive electrode foil exposed portion 31c31c on one side in the width direction of the positive electrode foil 31a. The negative electrode body 32 is obtained by applying a negative electrode mixture 32b on both surfaces of a negative electrode foil 32a, and has an uncoated negative electrode foil exposed portion 32c on the other side in the width direction of the negative electrode foil 32a. The positive electrode foil exposed portion 31c and the negative electrode foil exposed portion 32c are wound so as to be positioned on opposite sides in the winding axis direction.

  The positive electrode foil 31a is an aluminum alloy foil having a thickness of about 10 to 30 μm, and the negative electrode foil 32a is a copper alloy foil having a thickness of about 6 to 20 μm. The material of the separator 33 is a porous polyethylene resin. The positive electrode active material is a lithium-containing transition metal double oxide such as lithium manganate, and the negative electrode active material is a carbon material such as graphite capable of reversibly occluding and releasing lithium ions.

FIG. 4 is a perspective view after welding the wound electrode body and the positive and negative current collector plates.
As shown in FIG. 4, the positive electrode foil exposed portion 31c and the negative electrode foil exposed portion 32c are respectively crushed in advance, and the positive electrode current collector plate 4A and the negative electrode current collector plate 4B are welded by ultrasonic welding.

  The winding end of the separator 33 is disposed at a substantially central position on one flat surface of the wound electrode body 3, and the central portion in the winding axis direction is fixed by the adhesive tape 20a.

  5 and 6 are perspective views showing the positional relationship between the insulating protective film 2 and the wound electrode body according to the present invention. First, it arrange | positions so that the upper end which is an edge part of the width direction one side (+ Y direction side of FIG. 5) of the insulating protective film 2 may fit in the back surface of the lid | cover 6. FIG. Next, both ends of the upper rectangular portion of the insulating protective film 2 are wound so as to cover the entire wound electrode body 3 from the outside as indicated by arrows (1) and (2) in FIG.

  FIG. 6 shows a perspective view after winding the side cover portion. As shown in FIG. 6, after the one side cover portion A2c and the other side cover portion B2d are wound, the insulating protective film 2 is disposed so as to protrude downward from the wound electrode body 3 (C in FIG. 6). -Below part C). The protrusion width is about 1 mm to 10 mm, and 3 mm to 5 mm is desirable in terms of ensuring the insulation between the wound electrode body and the battery container. By disposing the protruding portion on the bottom wall portion 22 of the battery can 1, the electrolyte pushed out by charging is guided to the wound electrode body by the insulating protective film 2 released toward the bottom of the can, and the wound The electrolyte solution is guided to the wound electrode body not only from the outside of the electrode body but also from the side surface, and performance degradation due to insufficient electrolyte solution can be suppressed.

  Moreover, it is set as the state covered with the insulating protective film 2 except the clearance gap d1 provided between the edge part of the winding electrode body 3, side cover part A2c, and the edge part of said other side surface cover part B2d. The presence of the gap d1 also guides the electrolyte to the wound electrode body 3 due to surface tension. After winding the insulating protective film 2, a part of the end of the one side cover A2c and the other side cover B2d and a part of the end of the bottom wall cover 2b are adhesive tape (not shown). Fixed. As a fixing method, in addition to the method of fastening with an adhesive tape, it may be fastened with an adhesive. In addition, for example, a seal-like pressure-sensitive adhesive film in which a pressure-sensitive adhesive that does not react or change with an electrolyte solution is applied to one film surface may be used, and can be fixed more easily than when a pressure-sensitive adhesive tape or adhesive is used. it can.

  FIG. 7 shows a perspective view after sticking the adhesive tape. As shown in FIG. 7, after winding the insulating protective film 2, the end portions of the one side cover portion A2c and the other side cover portion B2d are fixed with an adhesive tape 20b. As a fixing method, in addition to the method of fastening with the adhesive tape 20b, it may be fastened with an adhesive. In addition, for example, a seal-like pressure-sensitive adhesive film in which a pressure-sensitive adhesive that does not react or change with an electrolyte solution is applied to one film surface may be used, and can be fixed more easily than when a pressure-sensitive adhesive tape or adhesive is used. it can. In this embodiment, the adhesive tape 20b is used for fixing. However, the present invention is not limited to this, and it is sufficient that the winding of the insulating protective film 2 can be maintained.

  The present invention will be briefly described above.

  The prismatic secondary battery according to the present invention is a flat wound body (3) in which a positive electrode body (31) and a negative electrode body (32) are wound through a separator (33) and have an open surface in the winding axis direction. ), A flat wound body (3), a battery container (1) having a side part facing the open surface and a bottom part connected to the side part, and covering the flat wound body (3), An insulating protective film (2) disposed between the rotating body (3) and the battery case (1), and the insulating protective film (2) is predetermined on the bottom surface side with the bottom surface side opened. It has a protruding portion that protrudes in length. With such a configuration, it is possible to guide the electrolytic solution pushed out by charging to the wound electrode body by the insulating protective film released toward the bottom of the can without using a special member. Moreover, since it protrudes 3-5 mm, the insulation distance of the winding electrode body 3 and the battery container 1 can also be ensured enough.

  Moreover, the square secondary battery described in the present invention is sowed that the insulating protective film (2) covers the two open surfaces and the two flat surfaces of the flat wound body. With this configuration, the electrolytic solution can be guided to the wound electrode body not only from the wide surface side of the wound electrode body 3 but also from the side surface, and the electrolyte solution is more reliably guided to the wound electrode body. be able to.

  In the prismatic secondary battery according to the present invention, a gap (d1) is provided between one end portion of the insulating protective film (2) in the winding direction and the other end portion in the winding direction. With such a configuration, the electrolytic solution is guided to the wound electrode body 3 by the surface tension, so that the electrolytic solution can be more reliably guided to the wound electrode body 3.

  The insulating protective film 2 wound around the wound electrode body 3 may be flat, but the surface may be processed, and the processing is more preferably slit processing. By processing the surface of the insulating protective film 2, the electrolytic solution pushed out by charging can be more quickly guided into the wound electrode body 3 by utilizing the surface tension of the liquid.

<Second Embodiment>
Next, a second embodiment will be described. The difference from the first embodiment is that there is no gap d1 and the insulating protective films 2 are in close contact with each other. The embodiment of the second embodiment will be described below.

  FIG. 8 is a diagram for explaining the second embodiment. As shown in FIG. 8, both end portions of the insulating protective film 2 surrounding the side surface of the wound electrode body 3 overlap each other to form an overlapping portion 30. Thus, if the protrusion part (part below CC part) of the insulation protective film 2 is formed under the winding electrode body 3, side cover part A2c and side cover part B2d will be without gap. You can overlap. In the gap between the overlapping portions, the liquid is guided by the surface tension, and the electrolytic solution pushed out by charging can be quickly guided into the wound electrode body 3.

<Third Embodiment>
Next, a third embodiment will be described. The difference from the first embodiment is that a gap d2 for avoiding the adhesive tape portion is provided.

FIG. 9 is a diagram for explaining the third embodiment. In this embodiment, it has the gap | interval part d2 which avoids the adhesive tape 20a. Thus, if the protruding part of the insulating protective film 2 is formed below the wound electrode body 3, the side cover part A2c and the side cover part B2d are attached to the adhesive tape 20a that prevents the wound electrode body 3 from being wound. It may be arranged avoiding. By doing so, the thickness direction dimension can be reduced by the thickness of the adhesive tape 20a, and the material cost of the insulating protective film 2 can be reduced.
The present embodiment is summarized as above. In the prismatic secondary battery described in this embodiment, the separator (33) is fixed using the adhesive tape (20a) at the outermost periphery of the wound group (3), and the gap (d2) is the adhesive tape (20a). It is provided to be exposed. By adopting such a configuration, in addition to the effects of the first embodiment, the thickness of the adhesive tape 20a can be reduced in the thickness direction, and the material cost of the insulating protective film 2 can be reduced. Can do.

  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.

C1 Square secondary battery 1 Battery can 1a Opening part 2 Insulating protective film 2a Flat surface facing part 2c Side cover part A
2d Side cover part B
3 Winding electrode body 4A Positive electrode current collector plate 4B Negative electrode current collector plate 5 Gasket 6 Lid 6A Positive electrode side through hole 6B Negative electrode side through hole 7 Insulating plate
8A Positive electrode external terminal 8B Negative electrode external terminal 9 Injection port 10 Gas discharge valve 11 Injection plug 12A Positive electrode connection part 12B Negative electrode connection part 20a Adhesive tape 20b Adhesive tape 21 Side wall part 22 Bottom wall part 31 Positive electrode body 31a Positive electrode foil 31b Positive electrode combination Agent 31c Positive electrode foil exposed portion 32 Negative electrode body 32a Negative electrode foil 32b Negative electrode mixture 32c Negative electrode foil exposed portion 31d Positive electrode foil connecting portion 32d Negative electrode foil connecting portion 33 Separator

Claims (5)

A flat wound body having a positive electrode body and a negative electrode body wound through a separator and having an open surface in the winding axis direction;
A battery container that houses the flat wound body and has a side surface portion that faces the open surface and a bottom surface portion that is connected to the side surface portion;
In the rectangular secondary battery that covers the flat wound body and includes an insulating protective film disposed between the flat wound body and the battery container,
The prismatic secondary battery according to claim 1, wherein the insulating protective film has a protruding portion that protrudes to the bottom surface side by a predetermined length in a state where the bottom surface portion side is opened. The prismatic secondary battery according to claim 1,
The prismatic secondary battery according to claim 1, wherein the insulating protective film is wound so as to cover two open surfaces and two flat surfaces of the flat wound body. The prismatic secondary battery according to claim 2,
A prismatic secondary battery, wherein a gap portion is provided between one end portion of the insulating protective film in the soaking direction and the other end portion in the soaking direction. The prismatic secondary battery according to claim 3,
The separator is fixed using an adhesive tape at the outermost periphery of the wound group,
The prismatic secondary battery, wherein the gap is provided to expose the adhesive tape. The prismatic secondary battery according to any one of claims 1 to 4,
A prismatic secondary battery, wherein the insulating protective film is slit.

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