JP2013164967A - Square secondary battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a configuration capable of protecting an electrode body disposed inside a battery case even when the battery case is subjected to impacts in a square secondary battery having the electrode body stored in the battery case, the electrode body being formed by stacking and winding a positive electrode, a negative electrode and a separator which are respectively formed in a sheet shape.SOLUTION: A square secondary battery includes: an electrode body formed by stacking and winding a positive electrode (31), a negative electrode (32) and a separator (33), each being formed in a sheet shape; and a flat columnar-shaped battery case configured to store the electrode body therein. The separator (33) has a larger area than the positive electrode (31) and the negative electrode (32). A projected portion (33a) of the separator (33) located on a bottom surface side of the battery case and projecting from the positive electrode (31) and the negative electrode (32) constitutes a buffer part that absorbs impacts exerted on the bottom surface side of the battery case.

Description

  The present invention relates to a prismatic secondary battery in which an electrode body formed by winding a positive electrode, a negative electrode, and a separator, each formed in a sheet shape, is housed in a flat columnar battery case.

  2. Description of the Related Art Conventionally, a prismatic secondary battery is known that is configured by storing an electrode body that is wound in a state where a positive electrode, a negative electrode, and a separator, each formed in a sheet shape, are stacked in a flat columnar battery case. ing. As such a rectangular secondary battery, for example, as disclosed in Patent Document 1, a laminate of a separator, a positive electrode, a separator, and a negative electrode in this order is wound into a bobbin shape and then pressed into a flat shape. A configuration stored in a rectangular tube-shaped metal container is known.

JP 2003-151615 A

  By the way, in the configuration in which the electrode body formed by stacking the positive electrode, the negative electrode, and the separator, each formed in a sheet shape, is stored in the battery case as in the configuration of Patent Document 1, When an impact is applied, a large impact is also applied to the electrode body in the battery case.

  In particular, in an impact resistance test, which is one of battery performance tests, the battery is dropped and impact is applied to the bottom surface of the battery case, so that a large impact is likely to be applied to the bottom surface side of the battery case in the electrode body. When the positive electrode and the negative electrode move with respect to the separator due to impact, the positional relationship between the positive electrode and the negative electrode may change, resulting in performance degradation, or the positive electrode and the negative electrode may contact to cause a short circuit.

  Therefore, an object of the present invention is to provide a prismatic secondary battery in which an electrode body formed by winding a positive electrode, a negative electrode, and a separator, each formed in a sheet shape, in a stacked state, is housed in the battery case. The object is to obtain a configuration capable of protecting the internal electrode body even under impact.

  A prismatic secondary battery according to an embodiment of the present invention includes an electrode body configured by winding a positive electrode, a negative electrode, and a separator formed in a sheet shape in an overlapped state, and the electrode body inside. The separator is larger than the positive electrode and the negative electrode so as to protrude outward from the positive electrode and the negative electrode in a state of being superimposed on the positive electrode and the negative electrode. The protruding portion that has an area and is located on the bottom surface side of the battery case and protrudes from the positive electrode and the negative electrode of the separator absorbs an impact applied to the bottom surface side of the battery case. (First configuration).

  In the above configuration, since the separator has a larger area than the positive electrode and the negative electrode, the separator protrudes outward from the positive electrode and the negative electrode. Thereby, the occurrence of a short circuit between the positive electrode and the negative electrode can be prevented by the separator. In addition, in such a separator, a protruding portion located on the bottom surface side of the battery case and protruding from the positive electrode and the negative electrode constitutes a buffer portion that absorbs an impact applied to the bottom surface side of the battery case. Therefore, the impact applied to the portion where the positive electrode and the negative electrode are arranged in the electrode body can be reduced.

  In the first configuration, it is preferable that the protruding portion of the separator has a protruding length that is equal to or greater than an interval between inner surfaces facing in the thickness direction in the battery case (second configuration).

  Thus, by making the protruding length of the battery case on the bottom side of the separator to be equal to or greater than the distance between the inner surfaces facing in the thickness direction in the battery case, the protruding portion of the separator that functions as a buffer portion can be easily deformed. be able to. Therefore, even when an impact is applied to the bottom surface side of the battery case, the impact can be more effectively absorbed by the protruding portion of the separator.

  Moreover, as described above, by making the protruding length of the protruding portion of the separator equal to or greater than the distance between the inner surfaces facing in the thickness direction in the battery case, the protruding portion can be easily bent or welded. Can do. This eliminates the need for a member such as a tape for collecting the protruding portions in a state where a plurality of layers of separators are stacked, and when the protruding portions are bent, the bent portions are more reliably subjected to impact. It is possible to function as a buffering part that absorbs water.

  In the second configuration, it is preferable that the protruding portion of the separator is bent in the thickness direction of the battery case (third configuration). Thereby, in a separator, the protrusion part located in the bottom face side of a battery case functions as a buffer part which absorbs an impact more reliably. That is, by bending the protruding portion of the separator, the bent portion easily deforms with respect to the impact applied to the bottom surface of the battery case, so that the impact can be absorbed more reliably.

  In addition, by bending the protruding portions in the thickness direction of the battery case, the protruding portions in a state where a plurality of layers of separators are stacked can be collected without using a tape or the like. Therefore, the number of parts can be reduced, and the manufacturing cost can be reduced.

  In the second configuration, it is preferable that the protruding end portions of the separator are integrated with each other by welding (fourth configuration). By doing so, the protruding portions in a state where a plurality of separators are stacked can be collected without using a tape or the like. Therefore, the number of parts can be reduced, and the manufacturing cost can be reduced.

  In any one of the first to fourth configurations, the protruding portion of the separator has a protruding length located on an upper surface side of the battery case of the separator, and the positive electrode and the positive electrode It is preferable that it is larger than the protrusion length of the protrusion part protruded from the negative electrode (5th structure).

  Thereby, it is possible to protect the electrode body in the battery case against an impact applied to the bottom surface side of the battery. That is, in general, since components other than the electrode body are also arranged on the upper surface side of the battery, the electrode body is not easily subjected to a large impact by the impact applied to the upper surface side of the battery. However, when a large impact is applied to the bottom surface side of the battery, the electrode body is likely to receive a large impact.

  On the other hand, as described above, in the separator, the protruding length of the protruding portion positioned on the bottom surface side of the battery case is set longer than the protruding length of the protruding portion positioned on the upper surface side, thereby positioning on the bottom surface side. The protruding portion functions more reliably as a buffer portion. Thereby, even when a large impact is applied to the bottom surface side of the battery, it is possible to prevent the positive electrode and the negative electrode from moving with respect to the separator in the electrode body in the battery case.

  In any one of the first to fifth configurations, the protruding portion of the separator located on the upper surface side of the battery case and protruding from the positive electrode and the negative electrode has a protruding length, In the battery case, it is preferable that the distance is greater than or equal to the distance between the inner surfaces facing each other in the thickness direction (sixth configuration).

  In this way, since the buffer part is formed by the protruding portion of the separator on the upper surface side of the battery case in the electrode body, even if an impact is applied to either the upper surface side or the lower surface side of the battery case, It can be absorbed at the end of the electrode body. Thereby, it can prevent that a positive electrode and a negative electrode move with respect to a separator within an electrode body.

  According to the prismatic secondary battery according to the embodiment of the present invention, the protruding portion of the separator that protrudes from the sheet-like positive electrode and the negative electrode on the battery case bottom surface side of the electrode body has an impact applied to the bottom surface side. The buffer part to absorb is comprised. Thereby, even if an impact is received on the bottom side of the battery case, the electrode body in the battery case can be protected.

FIG. 1 is a perspective view showing a schematic configuration of a prismatic secondary battery according to Embodiment 1 of the present invention. 2 is a cross-sectional view taken along line II-II in FIG. FIG. 3 is a diagram showing the arrangement of the separator and the positive electrode. FIG. 4 is a perspective view showing a schematic configuration of the electrode body. FIG. 5 is a diagram showing only the lower part of the cross section taken along the line VV in FIG. FIG. 6 is a perspective view illustrating a schematic configuration of an electrode body of the prismatic secondary battery according to the second embodiment. FIG. 7 is a perspective view illustrating a schematic configuration of the electrode body of the prismatic secondary battery according to the third embodiment. FIG. 8 is a diagram illustrating an arrangement of the separator and the positive electrode in the prismatic secondary battery according to the fourth embodiment.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. The same or corresponding parts in the drawings are denoted by the same reference numerals and description thereof will not be repeated.

<Embodiment 1>
(overall structure)
FIG. 1 is a perspective view showing a schematic configuration of a prismatic secondary battery 1 according to Embodiment 1 of the present invention. The prismatic secondary battery 1 includes a bottomed cylindrical outer can 10, a cover plate 20 that covers an opening of the outer can 10, and an electrode body 30 that is accommodated in the outer can 10. By attaching the cover plate 20 to the outer can 10, the columnar battery case 2 having a space inside is formed. In addition to the electrode body 30, a non-aqueous electrolyte (hereinafter simply referred to as an electrolyte) is also enclosed in the battery case 2.

  The outer can 10 is a bottomed cylindrical member made of an aluminum alloy, and constitutes the battery case 2 together with the cover plate 20. As shown in FIG. 1, the outer can 10 is a bottomed cylindrical member having a bottom surface 11 in which a rectangular short side is formed in an arc shape. Specifically, the outer can 10 includes a bottom surface 11 and a flat cylindrical side wall 12 having a smooth curved surface. That is, the outer can 10 has a dimension in the thickness direction corresponding to the short side direction of the bottom surface 11 smaller than the width direction corresponding to the long side direction of the bottom surface 11 (for example, the thickness is about 1/10 of the width). ) As shown in FIG. Further, since the outer can 10 is joined to the lid plate 20 connected to the positive electrode lead 34 as will be described later, it also serves as the positive electrode terminal of the rectangular secondary battery 1.

  The cover plate 20 is joined to the opening of the outer can 10 by welding so as to cover the opening of the outer can 10. Thereby, the upper surface of the battery case 2 is formed by the cover plate 20. Similar to the outer can 10, the lid plate 20 is made of an aluminum alloy member, and has a rectangular short side formed in an arc shape so as to be fitted inside the opening of the outer can 10. Moreover, the through-hole is formed in the center part of the longitudinal direction in the cover board 20. As shown in FIG. An insulating packing 21 made of polypropylene and a negative electrode terminal 22 made of stainless steel are inserted into the through hole. Specifically, a substantially cylindrical insulating packing 21 into which a substantially columnar negative electrode terminal 22 is inserted is fitted to the peripheral portion of the through hole. The negative electrode terminal 22 has a configuration in which flat portions are integrally formed at both ends of a cylindrical shaft portion. The negative electrode terminal 22 is disposed with respect to the insulating packing 21 so that the flat surface portion is exposed to the outside and the shaft portion is positioned in the insulating packing 21. A stainless steel lead plate 27 is connected to the negative terminal 22. Thereby, the negative electrode terminal 22 is electrically connected to the negative electrode 32 of the electrode body 30 via the lead plate 27 and the negative electrode lead 35 described later. An insulator 26 is disposed between the lead plate 27 and the insulating packing 21.

  An insulating plate 36 is disposed between the negative electrode terminal 22 attached to the lid plate 20 and the electrode body 30. The insulating plate 36 can prevent a short circuit from occurring between the negative electrode terminal 22 and the electrode body 30.

  The lid plate 20 is formed with an electrolyte solution inlet 24 along with the negative electrode terminal 22. The injection port 24 is formed in a substantially circular shape in plan view. The injection port 24 has a small diameter portion and a large diameter portion so that the diameter changes in two steps in the thickness direction of the lid plate 20. The injection port 24 is sealed by a sealing plug 25 formed in a step shape corresponding to a change in the diameter of the injection port 24. The outer peripheral portion on the large diameter side of the sealing plug 25 and the peripheral portion of the injection port 24 are joined by laser welding so that no gap is generated between the sealing plug 25 and the peripheral portion of the injection port 24. Has been.

  Although not particularly illustrated, a circuit board, a resin cover, and the like are disposed on the lid plate 20. That is, the cover plate 20 is not exposed because it is covered with other members. Thereby, even when an impact is applied to the prismatic secondary battery 1 from the cover plate 20 side, the impact can be reduced. Therefore, it is possible to suppress the impact applied to the lid plate 20 side from being transmitted to the electrode body 30.

(Electrode body)
As shown in FIG. 3, the electrode body 30 is a state in which the positive electrode 31 and the negative electrode 32 each formed in a sheet shape are overlapped so that the separator 33 is positioned between the two and the lower side of the negative electrode 32, for example. Thus, it is a wound electrode body formed by winding in a spiral shape as shown in FIG. The electrode body 30 is formed in a flat shape after being wound in a state where the positive electrode 31, the negative electrode 32, and the separator 33 are overlapped with each other. That is, the electrode body 30 is obtained by crushing a cylindrical wound body extending in the axial direction to make it flat.

  Here, in FIG. 2, only a few layers on the outer peripheral side of the electrode body 30 are illustrated. However, in FIG. 2, the illustration of the inner peripheral side portion of the electrode body 30 is omitted, and naturally, the positive electrode 31, the negative electrode 32, and the separator 33 are also present on the inner peripheral side of the electrode body 30. .

The positive electrode 31 is obtained by providing positive electrode active material layers containing a positive electrode active material on both surfaces of a positive electrode current collector made of a metal foil such as aluminum. Specifically, the positive electrode 31 is coated with a positive electrode mixture containing a positive electrode active material that is a lithium-containing oxide capable of occluding and releasing lithium ions, a conductive additive, and a binder on a positive electrode current collector made of aluminum foil or the like. And then dried. As the lithium-containing oxide as the positive electrode active material, for example, a lithium composite oxide such as lithium cobalt oxide such as LiCoO ₂ , lithium manganese oxide such as LiMn ₂ O ₄ , lithium nickel oxide such as LiNiO ₂ is used. Is preferred. Note that only one type of material may be used as the positive electrode active material, or two or more types of materials may be used. Further, the positive electrode active material is not limited to the above-described materials.

  In the negative electrode 32, negative electrode active material layers containing a negative electrode active material are provided on both sides of a negative electrode current collector made of a metal foil such as copper. Specifically, the negative electrode 32 is obtained by applying and drying a negative electrode mixture containing a negative electrode active material capable of inserting and extracting lithium ions, a conductive additive, a binder, and the like on a negative electrode current collector made of copper foil or the like. It is formed. As the negative electrode active material, for example, it is preferable to use a carbon material (such as graphite, pyrolytic carbon, coke, or glassy carbon) that can occlude and release lithium ions. The negative electrode active material is not limited to the above-described materials.

  That is, as shown in FIG. 3, the positive electrode 31 and the negative electrode 32 are formed by providing an active material layer in addition to the end on one side in the longitudinal direction of the metal strip-shaped current collector. FIG. 3 shows only the positive electrode 31, and the hatched portion in the drawing is a portion where the positive electrode active material layer is provided.

  As shown in FIG. 3, a positive electrode lead 34 is connected to the positive electrode 31 of the electrode body 30 at a portion where the positive electrode active material layer is not formed. On the other hand, the negative electrode lead 35 is connected to the negative electrode 32 at a portion where the negative electrode active material layer is not formed. The positive electrode lead 34 and the negative electrode lead 35 are connected to the belt-like positive electrode 31 and the negative electrode 32 so as to extend in the short direction thereof. The positive electrode lead 34 and the negative electrode lead 35 are drawn outward from the positive electrode 31 and the negative electrode 32. As shown in FIG. 2, the tip end side of the positive electrode lead 34 is connected to the lid plate 20. On the other hand, the tip end side of the negative electrode lead 35 is connected to the negative electrode terminal 22 via the lead plate 27 described above.

  The separator 33 is a porous film made of a resin material such as polyolefin. As shown in FIG. 3, like the positive electrode 31 and the negative electrode 32, the separator 33 is formed in a band shape and has a larger area than the positive electrode 31 and the negative electrode 32.

  As shown in FIG. 3, the positive electrode 31 and the negative electrode 32 are superimposed on both surfaces of the separator 33 so that only one side in the longitudinal direction of the separator 33 is exposed. That is, the positive electrode 31 and the negative electrode 32 are arranged so that the end portions in the longitudinal direction overlap the opposite end portions in the longitudinal direction of the separator 33 with respect to both surfaces of the separator 33. Thereby, one side of the separator 33 in the longitudinal direction protrudes with respect to the positive electrode 31 and the negative electrode 32.

  Further, as shown in FIG. 3, the positive electrode 31 and the negative electrode 32 are in a range in which one side (lower side in FIG. 3) of the separator 33 is exposed from the other side (upper side in FIG. 3). The separators 33 are overlapped with each other so that the projecting length is increased. That is, the positive electrode 31 and the negative electrode 32 are arranged so as to be biased toward the other side (upper side in FIG. 3) in the lateral direction with respect to the separator 33. As a result, a protruding portion 33 a protruding from the positive electrode 31 and the negative electrode 32 is formed on one side of the separator 33 in the short direction.

  Further, as shown in FIGS. 3 and 5, the positive electrode 31 and the negative electrode 32 are formed so that the protruding length X of the protruding portion 33 a on the other side in the short direction of the separator 33 is the inner surface facing the thickness direction in the battery case 2. Is overlaid on the separator 33 so as to be equal to or greater than the interval Y.

  For example, the positive electrode 31 and the negative electrode 32 are arranged so that the protruding length of the separator 33 on one side in the short direction is about 2 mm and the protruding length of the separator 33 on the other side is about 3 to 5 mm with respect to the separator 33. Is done. In the battery case 2, the distance between the inner surfaces facing each other in the thickness direction is equal to the protruding length of the separator 33 on the other side.

  The positive electrode 31, the negative electrode 32, and the separator 33 that are superposed as described above are wound and then flattened to form an electrode body 30 having a shape as shown in FIG. In FIG. 4, the broken lines indicate the positive electrode 31 and the negative electrode 32. Therefore, the positive electrode 31 and the negative electrode 32 are not disposed on the lower portion 30a located on the bottom surface 11 side of the battery case 2 in the electrode body 30, and only a plurality of separators 33 are stacked.

  Although not particularly illustrated, the lower portion 30a of the electrode body 30 is integrated with a tape or the like. That is, the lower portion 30a is integrated by winding a tape or the like around the lower portion 30a of the electrode body 30.

  Thereby, even when an impact is applied to the bottom surface 11 of the battery case 2, the separator 33 located in the lower portion 30a of the electrode body 30 is deformed and absorbs the impact. Therefore, the impact applied to the bottom surface 11 of the battery case 2 can be prevented from being transmitted to the upper portion of the electrode body 30.

(Effect of Embodiment 1)
In the present embodiment, in a state where the positive electrode 31, the negative electrode 32, and the separator 33 are overlapped, a portion of the separator 33 that is located on the bottom side of the battery case 2 protrudes from the positive electrode 31 and the negative electrode 32. Thereby, in the electrode body 30, since the lower part 30a located on the bottom surface 11 side of the battery case 2 is configured by the separator 33, it functions as a buffer portion that absorbs an impact applied to the bottom surface 11 of the battery case 2. Therefore, it is possible to prevent the positive electrode 31 and the negative electrode 32 of the electrode body 30 from moving with respect to the separator 33 when an impact is applied to the bottom surface 11 of the battery case 2.

  In particular, in the present embodiment, the positive electrode 31, the negative electrode 32, and the separator 33 are such that the protruding length of the separator 33 with respect to the positive electrode 31 and the negative electrode 32 is larger on the bottom surface 11 side of the battery case 2 than on the lid portion 20 side. Are superimposed on each other. Thereby, in the electrode body 30, the bottom face 11 side of the battery case 2 is likely to be deformed, and the impact can be absorbed more reliably.

  Furthermore, in the above-described configuration, the protruding length X of the protruding portion 33a located on the bottom surface 11 side of the battery case 2 in the separator 33 is equal to or larger than the interval Y between the inner surfaces facing in the thickness direction in the battery case 2. The positive electrode 31 and the negative electrode 32 are superimposed on the separator 33. Thereby, the lower part 30 a located on the bottom surface 11 side of the battery case 2 in the electrode body 30 is more likely to be deformed in the vertical direction of the electrode body 30. Therefore, the impact applied to the bottom surface 11 of the battery case 2 can be more reliably absorbed by the lower portion 30a of the electrode body 30.

  Note that the impact applied to the lid 20 side of the battery case 2 is reduced by other components disposed on the lid 20 and members disposed on the lid 20 side of the electrode body 20. However, the impact received from the bottom surface 11 side cannot be reduced with other components or the like arranged on the lid 20 side. In the present embodiment, the above-described configuration can suppress the impact received from the bottom surface 11 side from being transmitted to the electrode body 30.

<Embodiment 2>
FIG. 6 shows a schematic configuration of the electrode body 40 of the prismatic secondary battery according to the second embodiment. This embodiment differs from Embodiment 1 in that the lower portion 40a of the electrode body 40 is welded. In the following description, parts having the same configurations and functions as those of the first embodiment are denoted by the same reference numerals as those of the first embodiment, and description thereof is omitted.

  Specifically, as shown in FIG. 6, in the electrode body 40, the lower portion 40 a (the net-like hatched portion in FIG. 5) located on the bottom surface 11 side of the battery case 2 has a positive electrode as in the first embodiment. Only the separator 33 is laminated in a plurality of layers without the 31 and the negative electrode 32. In the present embodiment, the separators 33 of the lower portion 40a are connected to each other by welding. Thereby, the lower part 40a of the electrode body 40 is integrated.

  In addition, all the separators 33 of the lower part 40a may be welded, or only a part of the separators 33 of the lower part 40a may be welded. Similar to the first embodiment, the lower portion 40a of the electrode body 40 functions as a buffer portion that absorbs an impact.

(Effect of Embodiment 2)
In the present embodiment, in the electrode body 40, the separators 33 of the lower portion 40a located on the bottom surface 11 side of the battery case 2 are connected to each other by welding. Thereby, the lower part 40a of the electrode body 40 can be integrated. Therefore, a member such as a tape for collecting the end portions of the electrode body 40 becomes unnecessary.

<Embodiment 3>
FIG. 7 shows a schematic configuration of the electrode body 50 of the prismatic secondary battery according to the third embodiment. This embodiment differs from the first embodiment in that the lower part of the electrode body 50 is bent. In the following description, parts having the same configurations and functions as those of the first embodiment are denoted by the same reference numerals as those of the first embodiment, and description thereof is omitted.

  Specifically, as shown in FIG. 7, in the flat electrode body 50, the lower part 50a located on the bottom surface 11 side of the battery case 2 is bent in the thickness direction. In the example of FIG. 6, the lower portion 50 a of the electrode body 50 is bent so that the lower end portion of the electrode body 50 is located on the side of the electrode body 50 over the entire width direction of the electrode body 50. Yes. The lower portion 50a functions as a buffer portion that absorbs impact.

(Effect of Embodiment 3)
In the present embodiment, in the electrode body 50, the separator 33 constituting the lower portion 50 a located on the bottom surface 11 side of the battery case 2 is bent in the thickness direction of the electrode body 50. Thereby, the lower part 50a of the electrode body 50 can be integrated. Therefore, a member such as a tape for collecting the end portions of the electrode body 50 becomes unnecessary.

  Further, as described above, by bending the lower portion 50a of the electrode body 50 in the thickness direction of the electrode body 50, the bent lower portion 50a is likely to be deformed in the vertical direction. Thereby, the impact applied to the bottom surface 11 of the battery case 2 can be absorbed by the lower portion 50 a of the electrode body 50. Therefore, the impact applied to the bottom surface 11 side of the battery case 2 can be prevented from being transmitted to the upper portion of the electrode body 50, and the positive electrode 31 and the negative electrode 32 can be prevented from moving with respect to the separator 33.

  Moreover, the positive electrode 31 with respect to the separator 33 is such that the protruding length X of the portion protruding on the bottom surface 11 side of the battery case 2 in the separator 33 is equal to or greater than the interval Y between the inner surfaces facing in the thickness direction in the battery case 2. And the lower part 50a of the electrode body 50 is formed by overlapping the negative electrode 32. Thereby, the lower part 50 a can be easily bent in the thickness direction of the electrode body 50. Further, since the lower portion 50a bent in the thickness direction of the electrode body 50 can be disposed on the entire inner surface of the bottom surface 11 of the battery case 2, the impact transmitted to the electrode body 50 can be more reliably absorbed by the lower portion 50a. it can.

<Embodiment 4>
FIG. 8 shows an arrangement of the separator 33 and the positive electrode 31 in the electrode body of the prismatic secondary battery according to the fourth embodiment. In this embodiment, the positive electrode 31 and the negative electrode 32 are overlapped on the separator 33 so that projecting portions 33a and 33b having the same projecting length X as in the first embodiment are formed on the upper and lower portions of the electrode body, respectively. This is different from the first embodiment. In the following description, parts having the same configurations and functions as those of the first embodiment are denoted by the same reference numerals as those of the first embodiment, and description thereof is omitted.

  As shown in FIG. 8, the positive electrode 31 has a protruding length X of protruding portions 33 a and 33 b formed on both sides in the short direction of the separator 33 between the inner surfaces facing in the thickness direction in the battery case 2. They are overlaid so that the distance Y is greater than or equal to Y. That is, in the first embodiment, the protruding portion 33a having the protruding length X is formed only on one side of the separator 33 in the short direction (the bottom surface 11 side of the battery case 2). Protruding portions 33a and 33b having a protruding length X are formed on both sides of 33 in the short direction.

  Although not specifically shown in FIG. 8, the negative electrode 32 also has a protruding length X of a portion protruding on both sides in the short direction with respect to the separator 33, as in the case of the positive electrode 31. Are overlapped so as to be equal to or greater than the interval Y between the inner surfaces.

  The electrode body formed by winding and crushing the positive electrode 31, the negative electrode 32, and the separator 33 that are overlapped as described above has a buffer portion constituted by the separator 33 at both end portions in the axial direction. Thereby, even when an impact is applied from above and below the battery case 2, the impact can be absorbed at both end portions in the axial direction of the electrode body.

(Effect of Embodiment 4)
In the present embodiment, the protruding length X of the protruding portions 33 a and 33 b of the separator 33 protruding on both sides in the short direction with respect to the positive electrode 31 and the negative electrode 32 is the distance Y between the inner surfaces facing in the thickness direction in the battery case 2. As described above, the positive electrode 31 and the negative electrode 32 were overlapped with the separator 33. Thereby, the electrode body formed by winding and crushing the positive electrode 31, the negative electrode 32, and the separator 33 has a buffer portion constituted by the separators 33 on both sides in the axial direction. Therefore, the impact applied to the axial center portion of the electrode body can be reduced, and the positive electrode 31 and the negative electrode 32 can be prevented from moving with respect to the separator 33.

(Other embodiments)
While the embodiments of the present invention have been described above, the above-described embodiments are merely examples for carrying out the present invention. Therefore, the present invention is not limited to the above-described embodiment, and the above-described embodiment can be appropriately modified and implemented without departing from the spirit of the invention.

  In each of the above embodiments, the positive electrode 31 and the negative electrode 32 are each formed in a strip shape, and an active material layer is formed on the current collector except for one end in the longitudinal direction. However, the configuration of the positive electrode 31 and the negative electrode 32 may be any configuration as long as it functions as a positive electrode and a negative electrode.

  In the first embodiment, the positive electrode 31 and the negative electrode 32 each formed in a sheet shape are overlapped so that the separator 33 is positioned between the two and the lower side of the negative electrode 32, for example. However, the order of stacking the positive electrode 31, the negative electrode 32, and the separator 33 may be any order as long as the secondary battery can be configured.

  In each of the embodiments described above, the battery case 2 of the rectangular secondary battery 1 has a columnar shape having a bottom surface in which a rectangular short side is formed in an arc shape. However, the shape of the battery case may be other shapes such as a hexahedron.

  In each said embodiment, the square secondary battery 1 is comprised as a lithium ion battery. However, the prismatic secondary battery 1 may be a battery other than a lithium ion battery.

  The present invention can be used for a prismatic secondary battery in which an electrode body formed by winding a positive electrode, a negative electrode, and a separator is housed in a battery case.

1: Square secondary battery, 2: Battery case, 10: Exterior can, 11: Bottom surface, 12: Side wall, 20: Cover plate, 30: Electrode body, 31: Positive electrode, 32: Negative electrode, 33: Separator, 33a, 33b : Projecting portion, X: projecting length of projecting portion, Y: distance between inner surfaces facing each other in the battery case

Claims (6)

An electrode body constituted by winding a positive electrode, a negative electrode, and a separator, each formed in a sheet shape, in an overlapped state;
A flat columnar battery case in which the electrode body is housed;
The separator has a larger area than the positive electrode and the negative electrode so as to protrude outward from the positive electrode and the negative electrode in a state of being overlapped with the positive electrode and the negative electrode,
Of the separator, a protruding portion that is located on the bottom surface side of the battery case and protrudes from the positive electrode and the negative electrode constitutes a square secondary that absorbs an impact applied to the bottom surface side of the battery case. battery. The prismatic secondary battery according to claim 1,
The projecting portion of the separator is a prismatic secondary battery having a projecting length equal to or greater than a distance between inner surfaces facing in the thickness direction in the battery case. The prismatic secondary battery according to claim 2,
The protruding portion of the separator is a prismatic secondary battery that is bent in the thickness direction of the battery case. The prismatic secondary battery according to claim 2,
The protruding portion of the separator is a prismatic secondary battery in which the protruding end portions are integrated by welding. The prismatic secondary battery according to any one of claims 1 to 4,
The protruding portion of the separator has a protruding length that is larger than the protruding length of the protruding portion that is located on the upper surface side of the battery case and protrudes from the positive electrode and the negative electrode in the separator. . The prismatic secondary battery according to any one of claims 1 to 5,
Of the separator, the protruding portion located on the upper surface side of the battery case and protruding from the positive electrode and the negative electrode has a protruding length equal to or greater than the interval between the inner surfaces facing in the thickness direction in the battery case. Square secondary battery.

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