JP2015011895A - Square secondary battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a square secondary battery of which the dimension in a thickness direction is reduced.SOLUTION: A square secondary battery C1 comprises an insulation protective film 2 interposed between a battery can 1 and a wound electrode body 3. The wound electrode body 3 is disposed while separating a pair of curved surfaces into a cover side and a can bottom side and a winding end terminal portion 33a of a separator 33 wound around an outermost circumference is disposed in a direction from the side of a cover 6 to the side of a can bottom 22 on one flat surface 3a of the wound electrode body 3. The insulation protective film 2 includes: a first flat surface opposing part 51a which opposes the other flat surface of the wound electrode body 3; a curved surface opposing part 52a which opposes the can bottom side curved surface of the wound electrode body 3; and a folded-back piece part 52b which opposes one flat surface 3a of the wound electrode body 3. A distal end portion 52d of the folded-back piece part 52b is disposed at a position separated closer to the side of the can bottom 22 than the winding end terminal portion 33a of the separator 33.

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, the positive electrode current collector laminated portion, the negative electrode current collector laminated portion of the wound electrode body located inside the battery, and the positive electrode connecting terminal and the negative electrode connecting terminal connected to these are the inner wall of the battery container. In order to prevent a short circuit through the wound electrode body and to prevent the wound electrode body from being scratched when inserted into the battery container, the wound electrode body and the inner wall of the battery container Various materials have been proposed which are protected by interposing an insulating protective sheet or film between them.

  For example, the battery case is a portion in which the insulating material sheet exists between a pair of wide surface forming portions that form a pair of wide surfaces facing the flat surface of the wound electrode body and the pair of wide surface forming portions. A bottom surface forming portion that forms a bottom surface that faces the bottom surface of the battery, and two pairs of narrow side surface forming portions that are respectively present on both sides of the pair of wide surface forming portions and form a narrow side surface between the wide surfaces of the battery case And the narrow side surface forming portion disposed on the inner side folded into a bag shape is formed smaller than the narrow side surface forming portion disposed on the outer side, and can be easily inserted into the battery outer can. Such a device is known (for example, see Patent Document 1).

JP 2010-287456 A

In order to mount a plurality of prismatic secondary batteries for in-vehicle use, it is desirable that each prismatic secondary battery be miniaturized as much as possible.
An object of the present invention is to provide a prismatic secondary battery that can reduce the dimension in the thickness direction by paying attention to the thickness of the prismatic secondary battery.

  The prismatic secondary battery of the present invention that solves the above problems includes a flat wound electrode body in which a positive electrode body and a negative electrode body are wound with a separator interposed therebetween, and a bottomed body that houses the wound electrode body A rectangular secondary battery having a battery can, a lid that seals an opening that opens to the bottom of the battery can, and an insulating protective film interposed between the battery can and the wound electrode body In the battery, the wound electrode body includes a pair of curved surfaces of the wound electrode body that are separately arranged on a lid side and a can bottom side, and is wound around an outermost end of the separator. Is accommodated in the battery can in a posture arranged in a direction from the lid side toward the bottom of the can on one flat surface of the wound electrode body, and the insulating protective film is formed of the wound electrode body. A first flat surface facing portion facing the other flat surface, and the wound electrode continuous to the first flat surface facing portion A curved surface facing portion that faces the curved surface on the bottom side of the can, and a folded piece portion that continues to the curved surface facing portion and faces one flat surface of the wound electrode body. The tip of the one part is disposed at a position separated from the end of the separator by a predetermined distance toward the bottom of the can.

  According to the present invention, it is possible to flatten the flat surface of the wound electrode body by reducing the number of places where the thickness in the battery thickness direction is locally increased due to the overlap between the wound electrode body and the insulating protective film. . Therefore, it is possible to provide a prismatic secondary battery having a small dimension in the thickness direction. Problems, configurations, and effects other than those described above will be clarified by the following description of the embodiments.

The external appearance perspective view of a square secondary battery. The disassembled perspective view of a square secondary battery. The exploded perspective view of a wound electrode body. The perspective view of an electric power generation element assembly. The development view of an insulating protective film. The perspective view which shows the positional relationship of an insulating protective film and a winding electrode body. The perspective view which shows the state which wound the side cover part of the insulation protective film around the winding electrode body. The perspective view which shows the state which wound the bottom face cover part of the insulation protective film around the winding electrode body. FIG. 9 is a cross-sectional view taken along line AA in FIG. 8. The perspective view which shows the state which fixed the insulation protective film with the adhesive tape. The perspective view which shows the other Example of the sticking position of an adhesive tape. The perspective view which shows the other Example of an insulation protective film. The perspective view which shows the other Example of an insulation protective film.

  Next, embodiments of the present invention 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, and FIG. 2 is an exploded perspective view of the 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 is accommodated in the battery can 1, and an 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 square secondary battery C1 is charged to the wound electrode body 3 via the positive external terminal 8A and the negative external terminal 8B, and supplies power to the external load. The lid 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. The safety of the prismatic secondary battery C1 is ensured.

  The battery can 1 of the square secondary battery C1 has a so-called square shape, a rectangular can bottom 22, a square tubular side wall 21 rising from the four sides of the can bottom 22 in the cell height direction (+ Y direction), and a side wall. And an opening 1a opened toward the cell height direction at the upper end of 21. The side wall 21 of the battery can 1 includes a pair of wide surface portions that are separated from each other in the cell thickness direction (+ Z direction) and a pair of narrow surface portions that are separated from each other in the cell width direction (+ X direction) and are opposed to each other. have.

  The wound electrode body 3 is accommodated in the battery can 1 in a state of being wrapped in an insulating protective film 2. The wound electrode body 3 has a flat shape, and has a pair of flat surfaces and a pair of curved surfaces having a cross-sectional arc shape facing each other with the pair of flat surfaces interposed therebetween. The wound electrode body 3 is inserted into the battery can 1 from one curved surface side, and is accommodated in the battery can 1 with the wound axis direction being in a lateral orientation along the cell width direction (+ X direction).

  The positive electrode foil connection portion 31d and the negative electrode foil connection portion 32d, which are electrode foil exposed portions of the wound electrode body 3, are at least partially bundled in a flat thickness direction to form a flat plate. The current collector terminal) 4A is joined to the positive electrode side connection end portion 42A and the negative electrode current collector plate (current collection terminal) 4B to the negative electrode side connection end portion 42B by ultrasonic welding. The base ends of the positive current collector 4A and the negative current collector 4B are connected to the positive external terminal 8A and the negative external terminal 8B, respectively. The lid 6 is provided with a gasket 5 and an insulating plate 7 to electrically insulate the positive electrode current collector plate 4A and the negative electrode current collector plate 4B, and the positive electrode external terminal 8A and the negative electrode external terminal 8B from the lid 6, respectively. ing.

  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 is arranged so that 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. It is bent at the side end of the negative electrode current collector plate base 41B and extends to the can bottom 22 side along the wide side surface of the battery can 1 to form the positive electrode foil connection part 31d and the negative electrode foil connection part 32d 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 each other. 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.

  The positive electrode external terminal 8A and the positive electrode current collector plate 4A constitute a positive electrode side terminal component, and the negative electrode external terminal 8B and the negative electrode current collector plate 4B constitute a negative electrode side terminal component. The positive electrode side terminal component and the negative electrode side terminal component are integrally assembled to the lid 6 via the gasket 5 and the insulating plate 7 to constitute a lid assembly. Then, the power generation element assembly (see FIG. 4) is configured by assembling the wound electrode body 3 to the lid assembly.

  The wound electrode body 3 is supported between the positive electrode current collector plate 4A and the negative electrode current collector plate 4B of the lid assembly, the winding axis direction extends parallel to the lid 6, and the flat surface is the lid 6 A pair of curved surfaces of the wound electrode body 3 are arranged separately on the lid 6 side and the can bottom 22 side of the battery can 1.

  The insulating protective film 2 covers the wound electrode body 3 assembled to the lid assembly from the outside together with the positive electrode current collector plate 4A and the negative electrode current collector plate 4B, and between the side wall 21 in the battery can 1 and the can Each is interposed between the bottom 22. The insulating protective film 2 is made of an insulating synthetic resin material, and insulates the battery can 1 from the wound electrode body 3, the positive current collector plate 4A, and the negative current collector plate 4B. The wound electrode body 3, so that the wound electrode body 3, the positive current collector plate 4A, and the negative current collector plate 4B are not in direct contact with the battery can 1 when an impact or vibration is applied to the battery C1 from the outside. The positive electrode current collector plate 4A and the negative electrode current collector plate 4B are protected. The configuration and operational effects of the insulating protective film 2 will be described later in detail.

  When the wound electrode body 3 is inserted into the battery can 1 from the opening 1a with the periphery of the wound electrode body 3 covered with the insulating protective film 2, the battery can 1 is paired with the pair of wound electrode bodies 3. The flat surface and the wide side surface of the side wall portion 21 of the battery can 1 are in contact with the insulating protective film 2 sandwiched therebetween, and have a size and shape that can be inserted by pressing with a slight pressing force. A slight gap is formed between the end surfaces on both sides in the winding axis direction of the wound electrode body 3 and the narrow side surface of the side wall portion 21 of the battery can 1.

  The opening 1 a of the battery can 1 is closed by the lid 6 and sealed by laser welding the lid 6 to the battery can 1. Thereafter, the battery can 1 is filled with an electrolytic solution. The electrolytic solution is injected into the battery can 1 from the injection port 9 of the lid 6. The injection port 9 is closed by an injection plug 11 after the injection of the electrolytic solution, and sealed by laser welding the injection plug 11 to the battery lid 6.

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 in which the positive electrode body 31 and the negative electrode body 32 are overlapped and wound in a flat shape with the separator 33 interposed therebetween, and the positive electrode mixture is formed on both end faces in the winding axis direction. A positive electrode foil exposed portion 31c and a negative electrode foil exposed portion 32c to which the layer 31b and the negative electrode mixture layer 32b are not applied are respectively disposed. 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 separator 33 has a winding end portion 33a (see FIG. 4) arranged on one flat surface of the wound electrode body 3, and is rolled up by an adhesive tape 20a (see FIG. 4) as a separator fixing tape. By fixing the portion 33a, the wound state is maintained. In the wound electrode body 3, two separators 33 are used, and the respective winding end ends 33a are arranged so as to overlap at the same position (see an enlarged view of the B part in FIG. 9).

  The winding end end portion 33 a of the separator 33 extends from one curved surface side to the other curved surface side on one flat surface of the wound electrode body 3, and the other end of the wound electrode body 3 from the center position. It is arranged at a position biased to the curved surface side.

  The separator 33 has a role of insulating between the positive electrode body 31 and the negative electrode body 32. The negative electrode mixture layer 32 b of the negative electrode body 32 is formed larger in the width direction than the positive electrode mixture layer 31 b of the positive electrode body 31. The positive electrode body 31 and the negative electrode body 32 have both ends of the positive electrode mixture layer 31b inside the both ends of the negative electrode mixture layer 32b so that the entire surface of the positive electrode mixture layer 31b is always opposed to the negative electrode mixture 31b. The parts are overlaid so that the parts are arranged. The separator 33 is a porous polyethylene resin having a thickness of 20 to 30 μm. The thickness of the separator 33 is preferably 0.01 mm to 0.50 mm, and more preferably 0.03 mm to 0.20 mm.

  The positive electrode body 31 is obtained by applying a positive electrode mixture layer 31b on both surfaces of a positive electrode foil 31a, and has an uncoated positive electrode foil exposed portion 31c 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 layer 32b to 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 part 31c and the negative electrode foil exposed part 32c are arranged on opposite sides in the winding axis direction, respectively.

  The positive electrode foil 31a is an aluminum alloy foil having a thickness of about 20 to 30 μm, and the negative electrode foil 32a is a copper alloy foil having a thickness of about 15 to 20 μm. 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 of the power generation element assembly.
The wound electrode body 3 includes a positive electrode foil connection portion 31d and a negative electrode foil connection portion 32d formed by previously crushing the positive electrode foil exposure portion 31c and the negative electrode foil exposure portion 32c in the thickness direction. The power generation element assembly is assembled by joining the current collector plate 4A and the negative electrode current collector plate 4B by ultrasonic welding.

  In the power generating element assembly, the wound electrode body 3 is arranged on one flat surface, that is, on the flat surface 3a on the front side shown in the + Z direction in the figure, and the winding end portion 33a of the separator 33 is on the lid 6 side. The battery can 1 is attached so as to be accommodated in the posture state in which the battery can 1 is disposed in a direction toward the can bottom 22 side.

  The winding end end portion 33 a of the separator 33 is disposed at a position that is biased toward the bottom of the can from the center position of the wound electrode body 3. The adhesive tape 20a is stuck on the flat surface 3a on the front side of the wound electrode body 3 so as to extend from the lid side to the can bottom side of the winding end end portion 33a of the separator 33. For example, when the battery can 1 of the square secondary battery C1 constituting the assembled battery expands, the center position of the wide side surface of the side wall portion 21 that is the most expanded portion in the battery can 1 is pressed by lashing as much as possible. It is preferably flat without unevenness. Therefore, by arranging the winding end end portion 33a of the separator 33 at a position deviated from the center position of the wound electrode body 3 to the other curved surface side, the unevenness due to the step of the winding end end portion 33a is formed on the side wall portion 21. It is possible to prevent formation at the center position of the wide side surface.

Next, the configuration of the insulating protective film will be described in detail.
FIG. 5 is a development view of the insulating protective film. In the following, the insulating protective film is shown as being made of an opaque member, but is not limited to being opaque and may be transparent.

  The insulating protective film 2 has a side cover portion 51 that covers the side surface of the wound electrode body 3 and a bottom surface cover portion 52 that covers the curved surface of the wound electrode body 3 on the can bottom side. The side cover 51 is wound around the wound electrode body 3 with the direction orthogonal to the winding axis direction of the wound electrode body 3 as the central axis direction, and the side surface of the wound electrode body 3 is disposed on the positive electrode current collector plate 4A. The bottom face cover portion 52 has a configuration in which the negative electrode current collector plate 4B is covered from the outside, and the bottom cover portion 52 is a wound electrode with the direction along the winding axis direction of the wound electrode body 3 being continuous with the side surface cover portion 51 It has a structure that is wound around the body 3 and covers the curved surface on the bottom side of the can. In the insulating protective film 2, as shown in FIG. 5, the upper horizontally long rectangular portion forms the side surface cover portion 51, and the lower portion continuously protruding from the side surface cover portion 51 forms the bottom surface cover portion 52.

  The side cover portion 51 has a band shape extending with a constant width, and a back surface facing portion 51a (first surface) facing the entire flat surface (the other flat surface) on the back surface side of the wound electrode body 3. 1 flat surface facing portion) and the flat surface 3a (one flat surface) on the front side of the wound electrode body 3 by projecting continuously from the back surface facing portion 51a in a direction away from each other along the long side direction. And a pair of front facing portions 51b and 51c (a pair of second flat surface facing portions). A pair of end surface facing portions 51d and 51e facing the end surfaces on both sides of the wound electrode body 3 are provided between the back facing portion 51a and the front facing portions 51b and 51c.

  The pair of front facing portions 51 b and 51 c are divided into one side and the other side in the long side direction of the side cover portion 51, and the front surface of the wound electrode body 3 when the side cover portion 51 is wound around the wound electrode body 3. The side end portion 51g on one side in the long side direction and the side end portion 51f on the other side in the long side direction are mutually overlapped with the flat surface 3a on the side. A gap is formed between the side end 51g and the side end 51f, which is disposed at a position separated by a predetermined distance d1 (see FIG. 7) in the winding axis direction.

  The pair of front facing portions 51b and 51c are fixed to each other by an adhesive tape 20b (second insulating protective film fixing tape). The adhesive tape 20b is stuck from one side end 51g to the other side end 51f.

  The front facing portions 51b and 51c of the side cover portion 51 have different lengths in the long side direction. In the present embodiment, the front facing portion 51c is longer than the 51b, and the side end portions 51f and 51g are It is arranged on the flat surface 3a of the wound electrode body 3 and at a position deviated to one side in the winding axis direction from the center position of the flat surface 3a.

  By arranging the side end portions 51f and 51g of the front facing portions 51b and 51c at a position biased to one side in the winding axis direction from the center position of the wound electrode body 3, the side ends when the rectangular secondary battery C1 is expanded. It is possible to prevent the unevenness due to the steps of the portions 51f and 51g from being formed at the center position of the wide side surface of the side wall portion 21, and to make the wide side surface of the side wall portion 21 as flat as possible.

  Further, by arranging the side end portions 51f and 51g at the biased position, the adhesive tape 20b for fixing the side end portions 51f and 51g can also be arranged at the biased position, and the winding axis of the wound electrode body 3 can be arranged. It is possible to prevent the winding electrode body 3 from becoming thick due to the adhesive tape 20b being overlapped and disposed at the position of the adhesive tape 20a that fixes the winding end portion 33a of the separator 33 at the center in the direction.

  The bottom cover part 52 is provided so as to protrude in a direction orthogonal to the long side direction of the side cover part 51 continuously to the lower end of the back facing part 51 a of the side cover part 51. The bottom cover portion 52 includes a curved surface facing portion 52a that faces the curved surface on the can bottom side of the wound electrode body 3, and a curved surface facing portion that is wound around the curved surface on the can bottom side of the wound electrode body 3. A folded piece portion 52b that faces the flat surface 3a on the front side of the wound electrode body 3 continuously to 52a and a pair of flap portions that face the end surface of the wound electrode body 3 continuously to the curved surface facing portion 52a. 52c.

  The curved surface facing portion 52a has a length substantially equal to the length of the wound electrode body 3 in the winding axis direction and a width that curves along the curved surface of the wound electrode body 3 and covers the entire curved surface. ing. The folded piece 52b is formed so as to protrude continuously from the curved surface facing portion 52a. The pair of flap portions 52c continuously protrude from both side ends of the bottom surface cover portion 52 in directions away from each other, bent by insertion into the battery can 1, and the winding axis direction of the wound electrode body 3 They are respectively interposed between the end surfaces on both sides and the narrow surface portion of the side wall portion 21 of the battery can 1.

  The folded piece portion 52b is overlapped with the front facing portions 51b and 51c when the bottom cover portion 52 is rubbed against the curved surface on the can bottom side of the wound electrode body 3, and the folded piece portion 52b is placed on the front side of the wound electrode body 3. The flat surface 3a is partially covered. And when inserted in the battery can 1, it is interposed between the flat surface 3a on the front side of the wound electrode body 3 and the wide surface portion of the side wall portion 21 of the battery can 1, and is folded back on the flat surface 3a. The front end 52d of the piece 52b is disposed at a position spaced apart from the end portion 33a of the separator 33 by a predetermined distance d2 (see FIG. 9) on the can bottom side.

  The insulating protective film 2 is made of a single sheet or film member made of a synthetic resin such as PP (polypropylene). The thickness of the insulating protective film 2 is set to be thicker than the thickness of one separator 33 and thinner than three, and in this embodiment, the separator 33 is equivalent to one. The thickness of the insulating protective film 2 is set to 50 μm, which is about twice that thickness.

  In addition, although the case where PP was used as an example of the material of the insulation protective film 2 was shown, it is not limited to this. For example, PFA (polytetrafluoroethylene), PPS (polyphenylene sulfide), PET (polyethylene terephthalate) ) Or a synthetic resin of a material that does not react or change in quality due to the electrolytic solution.

Next, the attachment method of an insulation protective film is demonstrated using FIGS.
6 is a perspective view showing a positional relationship between the insulating protective film and the wound electrode body, FIG. 7 is a perspective view showing a state in which the side cover portion of the insulating protective film is wound around the wound electrode body, and FIG. It is a perspective view which shows the state which wound the bottom face cover part of the insulation protective film around the rotating electrode body.

  First, as shown in FIG. 6, the insulating protective film 2 is disposed on the power generation element assembly with the upper end portion of the insulating protective film 2 along the lower surface of the lid 6. And the back facing part 51a of the side cover part 51 of the insulating protective film 2 is arranged to face the flat surface on the back side of the wound electrode body 3, and the boundary part between the side cover part 51 and the bottom cover part 52 is Positioning is performed so as to be arranged at the lower end portion of the flat surface on the back side of the wound electrode body 3.

  Next, both ends of the side cover 51 of the insulating protective film 2 are covered together with the positive current collector 4A and the negative current collector 4B from the outside of the wound electrode body 3, as indicated by arrows I and II in FIG. Wrap like so. As shown in FIG. 7, when the side cover 51 is wound around the side surface of the wound electrode body 3, the insulating protective film 2 has a side end 51 f of the front facing portion 51 b and a side end of the other front facing portion 51 c. 51g is arranged at a position spaced apart from each other by a predetermined distance d1 in the winding axis direction of the wound electrode body 3, and a gap is formed between the side end 51g and the side end 51f.

  The gap d1 is about 1 mm to 10 mm, and preferably 3 mm to 5 mm. Thus, by providing the gap d1 and preventing the side end portion 51f of the one front facing portion 51b and the side end portion 51g of the other front facing portion 51c from overlapping, the dimension in the battery thickness direction is reduced. It is possible to prevent the insulation protective film 2 from becoming larger by the overlapping amount.

  Then, after winding the side cover 51, the bottom cover 52 is wound along the curved surface on the can bottom side of the wound electrode body 3 as indicated by an arrow III in FIG. 7. The curved surface facing portion 52 a of the bottom surface cover portion 52 has a curved shape along the curved portion on the can bottom side of the wound electrode body 3. The folded piece portion 52b is disposed so as to overlap the outside of the one front facing portion 51b and the other front facing portion 51c.

  As shown in FIG. 8, the wound electrode body 3 is provided between the end surface portion of the curved portion on the can bottom side, the side end portion 51f of the front facing portion 51b, and the side end portion 51g of the front facing portion 51c. Except for the gap d <b> 1, the insulating protective film 2 covers the state.

9 is a cross-sectional view taken along line AA in FIG.
The wound electrode body 3 is disposed on the flat surface 3a on the front side in such a direction that the winding end portion 33a of the separator 33 faces the can bottom 22 of the battery can 1 from the lid 6 side. The insulating protective film 2 has a flat surface on the front side so that the tip 52d of the folded piece 52b of the bottom cover 52 is directed from the curved surface on the can bottom side of the wound electrode body 3 toward the curved surface on the lid 6 side. It is arranged on 3a. As shown in the enlarged view of part B in FIG. 9, the tip 52d of the folded piece 52b is disposed at a position spaced apart by a predetermined distance d2 toward the bottom of the can with respect to the end end 33a of the separator 33. The leading end 52d of the piece 52b and the winding end 33a of the separator 33 are opposed to each other through the gap d2, and are arranged so as not to overlap each other.

  Thus, the dimension in the battery thickness direction of the insulating protective film 2 is such that the end end portion 33a of the separator 33 and the tip end portion 52d of the folded piece portion 52b of the insulating protective film 2 do not overlap each other. It is possible to prevent the size of the secondary battery C1 from being increased, and to reduce the size of the rectangular secondary battery C1 in the thickness direction.

  In the present embodiment, the insulating protective film 2 having the folded piece portion 52b has a thickness of about 50 μm, and the separator 33 has a thickness of about 20 to 30 μm. And as shown to the B section enlarged view of FIG. 9, since the separator 33 is piled up two sheets, the thickness becomes 40-60 micrometers in total and becomes the same thickness as the insulation protective film 2. FIG.

  Therefore, the surface of the folded piece portion 52b and the surfaces of the front facing portions 51b and 51c can be made to be a smooth surface with substantially the same height, and the formation of a step can be prevented. Therefore, it is possible to prevent the step from being caught when inserted into the battery can 1 and to facilitate the assembling work of the rectangular secondary battery C1.

FIG. 10 is a perspective view showing a state in which the insulating protective film is fixed with an adhesive tape.
As shown in FIG. 10, the insulating protective film 2 is fixed with the adhesive tape 20 b and the adhesive tape 20 c after being wound around the wound electrode body 3. The adhesive tape 20b (second insulating protective film fixing tape) is adhered from one side end 51f of the front facing portion 51b to the other side end 51g of the front facing portion 51c. The adhesive tape 20c (first insulating protective film fixing tape) is stuck from the folded piece portion 52b of the bottom cover portion 52 to the front facing portion 51c.

  The adhesive tapes 20a, 20b, and 20c are disposed at positions separated from each other in the direction along the flat surface 3a of the wound electrode body 3. The position where the adhesive tapes 20b and 20c are arranged is preferably a position deviated in the cell height direction or the cell width direction from the center position of the flat surface 3a. In the present embodiment, the adhesive tape 20b is attached to a position that is biased to the lower side in the cell height direction of the wound electrode body 3 than the center position of the flat surface 3a, and the adhesive tape 20c is a wound electrode. The body 3 is attached at a position biased toward the positive electrode side with respect to the center position in the cell width direction.

  And the adhesive tape 20b is affixed on the position which covers the winding end part 33a of the separator 33 exposed from the clearance gap d1. Therefore, it is possible to protect the firing end portion 33 a and prevent the firing end portion 33 a from being caught by the opening 1 a of the battery can 1 when inserted into the battery can 1.

FIG. 11 is a perspective view showing another embodiment of the adhesive tape application position.
The adhering tape 20d is 1 at a position where the side end 51f of the front facing portion 51b and the side end 51g of the front facing portion 51b approach each other and the tip 52d of the folded piece 52b of the bottom cover portion 52 approaches. Only the portions are pasted, and the insulating protective film 2 is fixed to the wound electrode body 3. That is, the adhesive tape 20d is stuck across both the pair of front facing portions 51b and 51c from the folded piece portion 52. The adhesive tapes 20a and 20d are provided at positions separated from each other in the direction along the flat surface 3a of the wound electrode body 3. According to this embodiment, the dimension in the thickness direction can be reduced similarly to the configuration of FIG. 10, and the number of the adhesive tapes 20 can be reduced as compared with the configuration of FIG.

  As a fixing method, in addition to the method of fastening with adhesive tapes 20b, 20c, 20d, etc., 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 the embodiment shown in FIG. 10, the adhesive tapes 20 b and 20 c are fixed at two locations. However, the embodiment is not limited to this, and may be one location as long as the winding of the insulating protective film 2 can be maintained.

  According to the prismatic secondary battery C1 according to the present embodiment, the front end 52d of the folded piece 52b is spaced apart by a predetermined distance d2 on the bottom side of the separation end 33a of the separator 33 on the flat surface 3a. Are arranged so that they do not overlap each other. Then, the side end 51f of the front facing part 51b of the side cover 51 and the side end 51g of the other front facing part 51c are mutually separated by a predetermined distance d1 in the winding axis direction of the wound electrode body 3 (see FIG. 7). ) Are separated from each other, and are arranged so as not to overlap each other.

  Therefore, it is possible to prevent the dimension in the battery thickness direction from increasing by the overlapping amount of the insulating protective film 2. That is, the flat surface 3a of the wound electrode body 3 can be flattened by reducing the number of places where the thickness in the battery thickness direction is locally thickened by the overlap of the wound electrode body 3 and the insulating protective film 2. The battery can be downsized or the capacity can be increased.

  In addition, the arrangement position of the front end portion 52d of the folded piece portion 52b and the separation end portion 33a of the separator 33, the side end portion 51f of the front facing portion 51b of the side cover portion 51, and the side end portion 51g of the other front facing portion 51c. The arrangement position and the arrangement position of the adhesive tapes 20a to 20c are limited to the position shown in the above-described embodiment, that is, the position displaced in the winding axis direction or the cell height direction from the center position of the flat surface 3a. However, it is more preferable to arrange at such a position, and it does not exclude the arrangement at the center position in the winding axis direction.

12 and 13 are diagrams showing another embodiment of the insulating protective film.
12 and 13 are perspective views showing a state in which the side cover portion of the insulating protective film is wound around the wound electrode body, and corresponds to FIG.

  In the insulating protective film 2 shown in FIG. 12, the lengths of the front facing portions 51b and 51c of the side cover portion 51 are equal. For example, as described above, if only one of the front facing portions 51b and 51c is extremely long, when it is wound around the wound electrode body 3, the side end portions 51g and 51f in the cell height direction There is a possibility that the amount of misalignment will be large, so care must be taken in the work of scraping. On the other hand, if the lengths in the winding axis direction are substantially equal, it is possible to prevent the amount of deviation in either cell height direction from increasing, and the side cover portion 51 is accurately placed at the normal position. can do.

  In the example shown in FIG. 12, the adhesive tape 20a is disposed in the gap d1 between the side end portion 51f of the front facing portion 51b and the side end portion 51g of the front facing portion 51c. Therefore, it is possible to prevent the adhesive tape 20a and the front facing portion 51b or 51c from overlapping each other and to increase the size in the battery thickness direction, and to reduce the size of the prismatic secondary battery.

  The insulating protective film 2 shown in FIG. 13 is provided with a notch 51h along the adhesive tape 20a at the side end 51g of the front facing portion 51c. The cutout portion 51h is formed by cutting out the side end portion 51g of the front facing portion 51c into a rectangular shape. The cutout portion 51h is disposed at a position away from the adhesive tape 20a that fastens the winding end portion 33a of the separator 33 of the wound electrode body 3, and avoids overlapping with each other.

  According to the insulating protective film 2 shown in FIG. 13, the gap d1 between the side end portion 51f of the front facing portion 51b and the side end portion 51g of the front facing portion 51c is narrower than that in the second embodiment. ing. Accordingly, the surface of the wound electrode body 3 can be covered as much as possible while preventing the dimension in the thickness direction of the battery from increasing, and the area where the flat surface 3a of the wound electrode body 3 is exposed is reduced. Can do.

  Therefore, for example, when inserted into the battery can 1, it is possible to prevent the separator 33 of the wound electrode body 3 from being damaged. Further, the contact area between the separator 33 having a higher friction coefficient than the insulating protective film 2 and the battery can 1 can be reduced, and the battery can 1 can be easily inserted.

  In the above-described embodiment, the case where the cutout portion 51h is provided only at the side end portion 51g of the front facing portion 51c has been described, but the cutout portion may be provided only at the side end portion 51f of the front facing portion 51b. Moreover, you may provide a notch in both the side edge parts 51g and 51f.

  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 prismatic secondary battery 1 battery can 1a opening 2 insulating protective film 3 wound electrode body 3a flat surface on the front side (one flat surface)
4A Positive current collector 4B Negative current collector 5 Gasket 6 Lid 6A Positive side through hole 6B Negative 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 portion 12B Negative electrode connection portion 20a Adhesive tape (separator fixing tape)
20b Adhesive tape (second insulating protective film fixing tape)
20c Adhesive tape (first insulating protective film fixing tape)
20d Adhesive tape (first insulating protective film fixing tape)
21 Side wall part 22 Can bottom 31 Positive electrode body 31a Positive electrode foil 31b Positive electrode mixture 31c Positive electrode foil exposed part 31d Positive electrode foil connection part 32 Negative electrode body 32a Negative electrode foil 32b Negative electrode mixture 32c Negative electrode foil exposed part 32d Negative electrode foil connection part 33 Separator 33a End part 51 Side cover part 51a Flat surface facing part 51b, 51c Front facing part 51f, 51g Side edge part 52 Bottom face cover part 52a Curved surface facing part 52b Folding piece part 52c Flap part 52d Tip part

Claims (11)

A flat wound electrode body in which a positive electrode body and a negative electrode body are wound with a separator interposed therebetween, a bottomed battery can that accommodates the wound electrode body, and a bottom of the battery can. A prismatic secondary battery having a lid that seals the opening that opens, and an insulating protective film interposed between the battery can and the wound electrode body,
In the wound electrode body, the pair of curved surfaces of the wound electrode body are arranged separately on the lid side and the can bottom side, and the winding end of the separator wound around the outermost periphery is the wound electrode. Accommodated in the battery can in a posture state arranged in a direction from the lid side to the can bottom side on one flat surface of the body,
The insulation protective film includes a first flat surface facing portion that faces the other flat surface of the wound electrode body, and a curved surface on the can bottom side of the wound electrode body that is continuous with the first flat surface facing portion. A curved surface facing portion that faces the curved surface facing portion, and a folded piece portion that is continuous with the curved surface facing portion and faces one flat surface of the wound electrode body. A prismatic secondary battery, wherein the prismatic secondary battery is disposed at a position spaced toward the bottom of the can with respect to the end of the separator.   The insulating protective film includes a side cover portion that is attached to the wound electrode body by covering the side surface of the wound electrode body with a direction orthogonal to the wound axis direction of the wound electrode body as a central axis direction; A bottom surface cover portion that covers the curved surface on the bottom side of the can by being attached to the wound electrode body with the direction along the winding axis direction of the wound electrode body as a central axis direction continuously to the side surface cover portion. 2. The square according to claim 1, wherein the side surface cover portion has the first flat surface facing portion, and the bottom surface cover portion has the curved surface facing portion and the folded piece portion. Secondary battery.   The side cover portion has a pair of second flat surface facing portions that respectively face one flat surface of the wound electrode body continuously in a direction away from the first flat surface facing portion. 3. The prismatic secondary battery according to claim 2, wherein the side end portions of the pair of second flat surface facing portions are arranged at positions spaced from each other in the winding axis direction of the wound electrode body. .   The pair of second flat surface facing portions are overlapped on one flat surface of the wound electrode body, and the folded piece portion is overlapped on the pair of second flat surface facing portions. The prismatic secondary battery according to 3. A separator fixing tape that is attached to the bottom side of the separator from the lid end side of the separator on the one flat surface of the wound electrode body, and fixes the separator end end of the separator;
A first part that is adhered to the second flat surface facing portion of at least one of the pair of second flat surface facing portions from the folded piece portion to fix the folded piece portion to the second flat surface facing portion. An insulation protective film fixing tape, and
The separator fixing tape and the first insulating protective film fixing tape are provided at positions separated from each other in a direction along one flat surface of the wound electrode body. Square secondary battery. A second insulating protective film fixing tape that is attached to one side end portion of the pair of second flat surface facing portions and that fixes the pair of second flat surface facing portions; ,
The separator fixing tape, the first insulating protective film fixing tape, and the second insulating protective film fixing tape are provided at positions separated from each other in a direction along one flat surface of the wound electrode body. The prismatic secondary battery according to claim 5.   The prismatic secondary battery according to claim 6, wherein the separator fixing tape is disposed between one side end portion and the other side end portion of the pair of second flat surface facing portions. .   8. The square secondary according to claim 7, wherein a cutout portion that is separated from the separator fixing tape is provided at a side end portion of at least one of the pair of second flat surface facing portions. battery.   The first insulating protective film fixing tape is adhered to the pair of second flat surface facing portions from the folded piece portion to fix the folded piece portions and the pair of second flat surface facing portions to each other. The prismatic secondary battery according to claim 5, wherein:   2. The prismatic secondary battery according to claim 1, wherein the insulating protective film is thicker than a thickness of one of the separators and thinner than a thickness of three.   2. The separator according to claim 1, wherein the winding end portion of the separator is disposed at a position biased in a direction closer to the curved surface on the can bottom side than the center position of the flat surface of the wound electrode body. The described prismatic secondary battery.

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