JP2017139085A - Sealed battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To achieve a configuration capable of preventing a positive electrode and a negative electrode from being damaged by an impact applied to a battery case.SOLUTION: A separator (33) has a resin porous layer and an adhesive resin layer. An electrode body (30) has a flat shape that is crushed in a radial direction while wound, and has a pair of bent portions (30a, 30b) projecting to both the sides in the width direction and outwards in the width direction. The adhesive resin layer of the separator (33) adheres to at least one of the positive electrode (31) and the negative electrode (32). A protective sheet (37) for protecting the electrode body (30) is adhesively attached onto the outer peripheral surface of the electrode body (30) so as to cover only the bent portion (30b).SELECTED DRAWING: Figure 4

Description

  The present invention relates to a sealed battery in which an electrode body is enclosed in a battery case.

  Conventionally, a sealed battery in which an electrode body is enclosed in a battery case is known. As such a sealed battery, for example, Patent Document 1 discloses an oval wound electrode body (electrode) in which a positive electrode, a negative electrode, and a separator, each formed in a sheet shape, are wound in a spiral shape in a stacked state. Is disclosed in a battery case.

  Further, Patent Document 1 discloses a configuration in which the separator includes an adhesive resin. In the configuration of Patent Document 1, an electrode body formed by winding a positive electrode, a negative electrode, and a separator is heated and pressed, whereby at least one of the positive electrode and the negative electrode and the separator are integrated.

  That is, in the configuration disclosed in Patent Document 1, an electrode body in which a separator and at least one of a positive electrode and a negative electrode are integrated is enclosed in a battery case.

JP 2011-54503 A

  By the way, the electrode body in which the separator and at least one of the positive electrode and the negative electrode are integrated as described above has higher rigidity than the electrode body that is not integrated. Therefore, when an impact is applied to the battery case in a state enclosed in the battery case, a large impact is likely to be locally applied to the electrode body.

  That is, in an electrode body in which the separator and at least one of the positive electrode and the negative electrode are not integrated, even when an impact is applied to the battery case in which the electrode body is stored, the impact is applied to the positive electrode, the negative electrode, and the separator of the electrode body. Can be absorbed by the deformation of. On the other hand, in an electrode body in which a separator and at least one of a positive electrode and a negative electrode are integrated, deformation of each member is difficult to allow, so that an impact applied to the battery case is easily transmitted to the inside of the electrode body.

  Then, depending on the strength of the positive electrode and the negative electrode, the positive electrode or the negative electrode may be damaged inside the electrode body. Generally, the positive electrode located on the outermost peripheral side of the electrode body is easily damaged when an impact is applied to the electrode body.

  In the present invention, a separator having an adhesive layer is wound in a state of being overlapped with a positive electrode and a negative electrode, an electrode body integrated with at least one of the positive electrode and the negative electrode, and a battery case enclosing the electrode body In such a sealed battery, the positive electrode is prevented from being damaged by an impact applied to the battery case.

  As a result of the inventors' diligent research, in the electrode body wound in a state where the positive electrode, the negative electrode, and the separator are overlapped in the thickness direction, when the separator is integrated with at least one of the positive electrode and the negative electrode, the battery It was found that the electrode body is easily damaged by the impact applied to the case.

  As described above, the present inventors have a configuration in which the separator and at least one of the positive electrode and the negative electrode are integrated, and the thickness of the current collector of the positive electrode located on the outermost peripheral side of the electrode body is 11 μm or less. And found that the electrode body is easily damaged by the impact applied to the battery case. That is, as shown in Table 1 of Examples described later, if the thickness of the current collector is larger than 11 μm, the current collector has a sufficient thickness. Therefore, even when an impact is applied to the battery case, the electrode body Can prevent damage. On the other hand, when the thickness of the current collector is 11 μm or less, the strength of the current collector is reduced. Therefore, when an impact is applied to the battery case, the electrode body is easily damaged.

  As described above, the present inventors are concerned with the reason why the electrode body is damaged when the thickness of the current collector of the positive electrode is 11 μm or less in the configuration in which the separator and at least one of the positive electrode and the negative electrode are integrated. We studied diligently. As a result, the present inventors have found that when the current collector is thin, the electrode layer formed on the current collector is more susceptible to damage than the current collector alone. . That is, the present inventors have found that forming an electrode layer on a thin current collector reduces the strength compared to the current collector alone.

  Specifically, when the electrode layer is formed on the current collector, the strength per unit area is lower than that in the case of the current collector alone. For example, when a tensile strength test (in accordance with JIS Z 2241) is performed for each of the current collector and the electrode layer formed on the current collector, When the electrode layer is formed on the electric body, the tensile strength is about 80%.

  Generally, when an electrode layer is formed on a current collector, a coating film is formed on the current collector, and then a pressure is applied to the coating film by a roller or the like. Thus, an electrode layer is obtained by increasing the density of the coating film on the current collector. As described above, the reason why the strength is reduced by forming the electrode layer on the current collector as described above is that the electrode layer obtained by applying pressure to the coating film has the strength of the electrode (positive electrode). Is considered to be partly due to the fact that it is lower than the strength of the current collector.

  In view of the above points, the present inventors have conceived the following configuration.

  A sealed battery according to an embodiment of the present invention includes an electrode body wound in a state in which a positive electrode, a negative electrode, and a separator, each formed in a sheet shape, are stacked in a thickness direction, and the electrode body is enclosed therein. A battery case. The positive electrode and the negative electrode each have a current collector made of a metal foil and an electrode layer formed on at least one surface of the current collector. The separator has a porous layer and an adhesive layer formed on at least one side in the thickness direction of the porous layer. The electrode body has a flat shape crushed in the radial direction in the wound state, and has a pair of bent portions that protrude outward in the width direction on both sides in the width direction. The adhesive layer of the separator is bonded to at least one of the positive electrode and the negative electrode. In the positive electrode, the current collector has a thickness of 11 μm or less. On the outer peripheral surface of the electrode body, a protective sheet for protecting the electrode body is attached so as to cover only at least one of the pair of bent portions (first configuration).

  With the above configuration, in the flat electrode body in which the separator and at least one of the positive electrode and the negative electrode are integrated, even when the thickness of the current collector of the positive electrode is 11 μm or less, due to the impact applied to the battery case, The positive electrode can be prevented from being damaged.

  That is, on the outer peripheral surface of the electrode body, there is a protective sheet for protecting the electrode body so as to cover only at least one of the bent parts located on both sides in the width direction of the electrode body. It is pasted. The protective sheet functions as a cushioning material that protects the bent portion when the bent portion to which the protective sheet is applied receives an impact. Thereby, it can prevent that the positive electrode located in the outermost peripheral side of an electrode body in a bending part is damaged by the impact which this electrode body receives.

  Therefore, even when an impact is applied to the battery case at a position corresponding to the bent portion of the electrode body, it is possible to prevent the positive electrode located on the outermost peripheral side of the electrode body from being damaged.

  In the first configuration, the sealed battery further includes an anti-winding tape that stops a winding end portion of the electrode body. The protective sheet is affixed on the outer peripheral surface of at least one of the pair of bent portions separately from the winding tape (second configuration).

  Thereby, a protective sheet can be stuck on the outer peripheral surface of the at least one bending part in an electrode body irrespective of the sticking position etc. of the winding stop tape for stopping the winding end part of an electrode body. That is, even if the winding end portion of the electrode body is not around the bent portion of the electrode body, the protective sheet can be stuck on the bent portion of the electrode body by stopping the winding end portion with a winding tape. Therefore, the bent part of the electrode body can be more reliably protected by the protective sheet.

  In the first or second configuration, the separator is wound in a state of being stacked with the positive electrode and the negative electrode so as to be positioned on the outermost periphery of the electrode body (third configuration).

  As described above, by positioning the separator on the outermost periphery of the electrode body, the separator acts as a buffer material that cushions the impact applied to the electrode body, and also suppresses the electrode body from moving in the battery case. can do. That is, it is possible to suppress the electrode body from moving in the battery case due to the elastic restoring force of the separator and surface friction.

  Thereby, when a sealed battery receives an impact, it can prevent that an electrode body moves within a battery case, and this electrode body receives a big impact. Therefore, it can prevent more reliably that a positive electrode is damaged.

  In the third configuration, the adhesive layer of the separator is formed on a surface located on the outer surface of the electrode body (fourth configuration). Thereby, it can prevent more reliably that a separator moves within a battery case. Therefore, it is possible to more reliably prevent the electrode body from moving in the battery case when the sealed battery receives an impact. Therefore, it can prevent more reliably that a positive electrode is damaged.

  In any one of the first to fourth configurations, the positive electrode is most outward in the width direction at the outermost peripheral side of the electrode body and at least one of the pair of bent portions. An electrode layer non-formation region where the electrode layer is not formed on the current collector is provided at a position corresponding to the protruding portion (fifth configuration).

  With the above configuration, in the flat electrode body in which the separator and at least one of the positive electrode and the negative electrode are integrated, the positive electrode can be more reliably prevented from being damaged by an impact applied to the battery case.

  That is, the positive electrode is at a position corresponding to a portion that protrudes most outward in the width direction in at least one of the pair of bent portions located on the outermost peripheral side of the electrode body and on both sides in the width direction of the electrode body. And an electrode layer non-formation region in which no electrode layer is formed on the current collector. Thereby, the strength reduction of the positive electrode can be suppressed at a position corresponding to the outermost circumferential side of the electrode body and a portion that protrudes most outward in the width direction in the bent portion of the electrode body.

  Therefore, in addition to the protective sheet that protects the bent portion of the electrode body, the electrode layer non-formation region is provided on the positive electrode at a position corresponding to the most protruding portion of the bent portion outward in the width direction. Thus, even when an impact is applied to the position corresponding to the bent portion, it is possible to more reliably prevent the positive electrode located on the outermost peripheral side of the electrode body from being damaged.

  Here, the position corresponding to the portion that protrudes most outward in the width direction in the bent portion means the position inside the electrode body of the most protruding portion in the positive electrode. That is, the electrode layer non-formation region is provided at a position of the positive electrode that constitutes a portion that protrudes most outward in the width direction of the bent portion.

  In the fifth configuration, the electrode layer non-formation region is formed on the positive electrode in a range corresponding to at least one of the pair of bent portions on the outermost peripheral side of the electrode body ( Sixth configuration).

  As a result, no electrode layer is formed on the positive electrode current collector on the outermost peripheral side of the electrode body and in a range corresponding to the bent portion. Therefore, even when an impact is applied to the position corresponding to the bent portion with respect to the battery case, the positive electrode can be prevented from being damaged.

  Here, the range corresponding to the bent portion means a range inside the electrode body of the bent portion in the positive electrode. That is, the electrode layer non-formation region is provided in a range constituting a bent portion in the positive electrode.

  In any one of the first to sixth configurations, the bent portion is formed in a semicircular shape protruding outward in the width direction (seventh configuration). In the bent portion having such a shape, when an impact is applied to the battery case at a position corresponding to the bent portion, a portion that protrudes most outward in the width direction of the electrode body receives the greatest impact.

  Therefore, when the bent part of the electrode body has the shape as described above, it is preferable to apply the first to sixth configurations described above to the positive electrode.

  According to the sealed battery of one embodiment of the present invention, in the flat electrode body in which the separator and at least one of the positive electrode and the negative electrode are integrated, the positive electrode has a current collector of 11 μm or less. And the protective sheet for protecting the said electrode body is stuck on the outer peripheral surface of the said electrode body so that only at least one bending part may be covered among a pair of bending parts. Thereby, it is possible to prevent the positive electrode from being damaged by an impact applied to the battery case.

FIG. 1 is a perspective view showing a schematic configuration of a sealed battery according to an embodiment of the present invention. 2 is a cross-sectional view taken along line II-II in FIG. FIG. 3 is a diagram schematically showing a state in which the positive electrode, the negative electrode, and the separator are wound in a state where they are overlapped in the thickness direction. FIG. 4 is a perspective view showing a schematic configuration of the electrode body. FIG. 5 is a diagram schematically showing the winding structure of the electrode body.

  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.

(overall structure)
FIG. 1 is a perspective view showing a schematic configuration of a sealed battery 1 according to an embodiment of the present invention. 2 is a cross-sectional view taken along line II-II in FIG. The sealed battery 1 includes a bottomed cylindrical outer can 10, a lid 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 welding (connecting) the opening and the outer periphery of the cover plate 20 with the opening of the outer can 10 covered with the cover plate 20, a columnar battery case 2 having a space inside is formed. The battery case 2 is formed in a flat shape in which the dimension in the width direction (left-right direction in FIG. 1) is larger than the dimension in the thickness direction (paper surface direction in FIG. 1).

  In addition to the electrode body 30, a nonaqueous electrolytic solution (hereinafter simply referred to as an electrolytic solution) or the like is also enclosed in the battery case 2.

  As shown in FIG. 3, the electrode body 30 includes a positive electrode 31 and a negative electrode 32 formed in a sheet shape, for example, with the positive electrode 31 sandwiched therebetween so that the separator 33 is positioned between the positive electrode 31 and the negative electrode 32. In the combined state, it is a wound electrode body formed by winding in a spiral around the central axis P. FIG. 3 is a diagram schematically illustrating a state in which the electrode body is configured by winding the positive electrode 31, the negative electrode 32, and the separator 33 in a state of being overlapped in the thickness direction.

  The electrode body 30 is formed in a flat shape by winding in a state where the positive electrode 31, the negative electrode 32, and the separator 33 are overlapped and then being crushed by hot pressing. A detailed configuration of the electrode body 30 will be described later.

  As shown in FIGS. 2 and 3, a positive electrode lead 34 is connected to the positive electrode 31 of the electrode body 30, while a negative electrode lead 35 is connected to the negative electrode 32. The positive electrode lead 34 and the negative electrode lead 35 are drawn out of the electrode body 30. The tip end side of the positive electrode lead 34 is connected to the lid plate 20. On the other hand, the distal end side of the negative electrode lead 35 is connected to the negative electrode terminal 22 via the connection plate 27 as described later.

  FIG. 2 shows only a few layers on the outer peripheral side of the electrode body 30. 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 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 sealed battery 1.

  As shown in FIG. 2, a polyethylene sheet for preventing a short circuit from occurring between the positive electrode 31 and the negative electrode 32 of the electrode body 30 through the outer can 10 is formed on the bottom inside the outer can 10. The bottom insulator 15 is arranged. The above-described electrode body 30 is disposed on the bottom insulator 15 so that one end thereof is positioned.

  The cover plate 20 covers the opening of the outer can 10, and the outer peripheral portion is connected to the opening of the outer can 10 by welding. The cover plate 20 is made of an aluminum alloy member, like the outer can 10, and has a rectangular short side formed in an arc shape so as to fit inside the opening of the outer can 10.

  The cover plate 20 has a through hole 20a formed at the center in the longitudinal direction thereof, and a cleavage vent 40 and an injection port 24 formed in the longitudinal direction of the cover plate 20 with the through hole 20a interposed therebetween. That is, the lid plate 20 is provided with the cleavage vent 40, the through hole 20 a, and the injection port 24 side by side in the longitudinal direction of the lid plate 20.

  As shown in FIG. 2, an insulating packing 21 made of polypropylene and a negative electrode terminal 22 (terminal) made of stainless steel are inserted into the through hole 20 a of the lid plate 20. Specifically, a substantially cylindrical insulating packing 21 into which a substantially columnar negative electrode terminal 22 is inserted is fitted to the peripheral edge of the through hole 20a.

  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.

  The negative electrode terminal 22 is electrically connected to the connecting plate 27 by passing through the connecting plate 27 made of nickel at the shaft portion. The connection plate 27 is a rectangular plate member, and is connected to the negative electrode terminal 22 so as to extend in the longitudinal direction of the cover plate 20, that is, from the negative electrode terminal 22 toward the cleavage vent 40. Thereby, the negative electrode terminal 22 is electrically connected to the negative electrode 32 of the electrode body 30 via the connection plate 27 and the negative electrode lead 35.

  Between the connection plate 27 and the lid plate 20, a rectangular insulating plate 26 is disposed in plan view for electrically insulating the two. Similarly to the connection plate 27, the insulating plate 26 is also penetrated by the shaft portion of the negative electrode terminal 22 and is disposed so as to extend toward the cleavage vent 40. That is, the shaft portion of the negative electrode terminal 22 penetrates the cover plate 20 and penetrates the insulating plate 26 and the connection plate 27.

  The inlet 24 formed in the lid plate 20 is a through hole for injecting the electrolyte into the battery case 2. The injection port 24 is formed in a substantially circular shape in plan view. As shown in FIG. 2, the injection port 24 is sealed by a sealing plug 25 having a T-shaped cross section. After injecting the electrolytic solution into the battery case 2, the outer peripheral portion of the flange portion of the sealing plug 25 and the lid plate 20 are formed so that no gap is formed between the sealing plug 25 and the peripheral edge of the injection port 24. Are joined by laser welding.

  As shown in FIG. 1, the cleavage vent 40 is formed in an oval shape that is long in the longitudinal direction of the lid plate 20 in a plan view of the lid plate 20, that is, when the battery case 2 is viewed from above. The cleavage vent 40 has an oblong thin valve element 41 having a thickness smaller than the thickness of the other part of the cover plate 20, and the upper surface side of the cover plate 20 so as to surround the outer periphery of the thin valve element 41. And a thin portion 42 provided with a groove.

  As described above, by providing the thin portion 42 so as to surround the thin valve body 41, when the pressure in the battery case 2 rises, due to the deformation and internal pressure of the battery case 2 due to the increase in the internal pressure of the battery case 2, In the lid plate 20, the thinned portion 42 having the smallest thickness is broken. Then, since the thin valve body 41 is pushed upward with respect to the cover plate 20, the gas or the like in the battery case 2 is released to the outside. Thereby, it can prevent that the battery case 2 is damaged by the internal pressure rise.

(Electrode body)
Next, the configuration of the electrode body 30 will be described in detail below with reference to FIGS. 3 to 5. FIG. 4 is a perspective view showing a schematic configuration of the electrode body 30. FIG. 5 is a diagram schematically showing the winding structure of the electrode body 30. That is, FIG. 5 schematically shows a state where the positive electrode 31, the negative electrode 32, and the separator 33 are wound for explanation.

  As described above, the electrode body 30 is formed by being spirally wound around the central axis P in a state where the positive electrode 31, the negative electrode 32, and the separator 33 formed in a sheet shape are stacked in the thickness direction. Has been.

  In the present embodiment, the electrode body 30 includes a pair of separators 33 that are longer than the positive electrode 31 and the negative electrode 32 in the longitudinal direction. The pair of separators 33 sandwich the positive electrode 31 and overlap the positive electrode 31 and the negative electrode 32 in the thickness direction so as to be positioned between the positive electrode 31 and the negative electrode 32.

  In the present embodiment, the positive electrode 31, the negative electrode 32, and the pair of separators 33 overlapped in the thickness direction are separated from the separator 33 that is not located between the positive electrode 31 and the negative electrode 32. It is wound so that it may be located in. Thereby, the separator 33 is positioned on the outer surface of the electrode body 30.

  In the present embodiment, the electrode body 30 is formed in a flat shape by hot pressing in the radial direction. As will be described later, in this embodiment, since the separator 33 has an adhesive resin layer, the adhesive resin layer is melted and bonded to at least one of the positive electrode 31 and the negative electrode 32 by hot pressing. Thus, the electrode body 30 is formed in a substantially rectangular parallelepiped shape in which the positive electrode 31, the negative electrode 32, and the separator 33 are integrated.

  Since the electrode body 30 is formed in a flat shape as described above, as shown in FIG. 4, a pair of bent portions 30a projecting outward in the width direction on both sides in the width direction (left-right direction in FIG. 4). , 30b. The pair of bent portions 30a and 30b are formed in an arc shape that protrudes outward in the width direction when the electrode body 30 is viewed from the axial direction of the central axis P when the positive electrode 31, the negative electrode 32, and the separator 33 are wound. Has been. That is, the pair of bent portions 30 a and 30 b are R portions formed on both sides of the electrode body 30 in the width direction.

  A part of the winding stop tape 36 for stopping the winding end of the separator 33 of the electrode body 30 is attached to one of the bent portions 30a and 30b. This winding tape 36 is made of PP (polypropylene) or the like.

  A protective sheet 37 is attached to the other bent portion 30b of the pair of bent portions 30a and 30b. Specifically, the protective sheet 37 is affixed on the outer peripheral surface of the electrode body 30 so as to cover the bent portion 30b. The protective sheet 37 is made of polypropylene (PP), polyethylene terephthalate resin (PET), or the like.

  Thus, by attaching the protective sheet 37 to the bent portion 30b, the protective sheet 37 functions as a buffer material when an impact is applied to the bent portion 30b side of the sealed battery 1 as will be described later. Thereby, it can prevent that the positive electrode 31 located in the outer peripheral side of the bending part 30b of the electrode body 30 receives damage.

  In addition, by attaching a protective sheet 37 other than the winding tape 36 to the bent portion 30 b of the electrode body 30, the bent portion 30 b can be protected by the protective sheet 37 regardless of the winding end position of the separator 33. Therefore, the positive electrode 31 located on the outer peripheral side of the bent portion 30b of the electrode body 30 can be more reliably prevented from being damaged.

  Here, as described above, the positive electrode 31, the negative electrode 32, and the separator 33 of the electrode body 30 have a longer length in the longitudinal direction than the positive electrode 31 and the negative electrode 32. That is, the length of the separator 33 in the longitudinal direction is long enough to cover the outer surface of the electrode body 30 while being wound together with the positive electrode 31 and the negative electrode 32. Thereby, the outer surface of the electrode body 30 is covered with the separator 33.

  In the positive electrode 31, a positive electrode active material layer 31b (electrode layer) containing a positive electrode active material is provided on a positive electrode current collector 31a (current collector) made of a metal foil such as aluminum. Specifically, the positive electrode 31 has a positive electrode mixture containing a positive electrode active material, a conductive auxiliary, and a binder, which is a lithium-containing oxide capable of inserting and extracting lithium ions, on a positive electrode current collector 31a made of aluminum foil or the like. After being applied and dried, it is formed by pressing in the thickness direction with a roller or the like. The thickness of the positive electrode current collector 31a is, for example, 10 μm.

  That is, the positive electrode 31 includes a positive electrode current collector 31a and a positive electrode active material layer 31b formed on the positive electrode current collector 31a. The positive electrode active material layer 31b is formed on at least one surface of the positive electrode current collector 31a.

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.

  As shown in FIG. 5, in the positive electrode 31, the positive electrode active material layer 31b is not formed on the positive electrode current collector 31a on the winding start side (center side) and winding end side (outer peripheral side) of the electrode body 30. . In particular, the positive electrode 31 has an electrode layer non-formation region in which the positive electrode active material layer 31b is not formed on the positive electrode current collector 31a on the winding end side of the electrode body 30 corresponding to the bent portion 30b of the electrode body 30. 31c. The electrode layer non-formation region 31c is formed from at least a portion of the positive electrode 31 constituting the bent portion 30b of the electrode body 30 to the end portion on the winding end side.

  Here, “corresponding to the bent portion 30 b of the electrode body 30” means a portion of the electrode body 30 constituting the bent portion 30 b. That is, the electrode layer non-formation region 31 c is provided in a portion of the positive electrode 31 located on the outer peripheral side of the electrode body 30 that constitutes the bent portion 30 b. In addition, the bending part 30b means the part which has produced the displacement in the thickness direction so that the planar positive electrode 31 may be return | folded.

  The positive electrode 31 includes a single-sided formation region 31d in which the positive electrode active material layer 31b is formed only on one side of the positive electrode current collector 31a on the winding start side of the electrode body 30 relative to the electrode layer non-formation region 31c, and the single-sided formation region 31d. Furthermore, it has a double-sided formation region 31e in which a positive electrode active material layer 31b is formed on both sides of the positive electrode current collector 33 on the winding start side of the electrode body 30.

  In the present embodiment, the positive electrode 31 is located on the inner circumference side of the separator 33 located on the outermost circumference of the electrode body 30. That is, the end portion on the winding end side of the positive electrode 31 is located closer to the outer peripheral side of the electrode body 30 than the end portion on the winding end side of the negative electrode 32. Further, as described above, in the positive electrode 31, the electrode layer non-formation region 31 c is formed corresponding to the bent portion 30 b of the electrode body 30.

  Thereby, the positive electrode active material layer 31b is not formed on the positive electrode current collector 31a in the positive electrode 31 located on the outer peripheral side of the bent portion 30b among the positive electrode 31 and the negative electrode 32.

  Here, as a result of the inventors' diligent research, when the thickness of the positive electrode current collector 31a is thin (particularly 11 μm or less), the positive electrode active material layer 31b is formed on the positive electrode current collector 31a. It was found that the strength decreased compared to the strength of the positive electrode current collector 31a itself. This is because, when the positive electrode active material layer 31b is formed on the positive electrode current collector 31a, the positive electrode mixture applied and dried on the positive electrode current collector 31a is pressurized with a roller or the like, and the positive electrode active material layer This is probably because 31b and the positive electrode current collector 31a are integrated. Thus, when the positive electrode active material layer 31b and the positive electrode current collector 31a are integrated, the strength of the positive electrode 31 is affected by the strength of the positive electrode active material layer 31b. It is considered that the strength is lower than that of 31a.

  Therefore, if the positive electrode 31 located on the outer peripheral side of the bent portion 30b of the electrode body 30 has the positive electrode active material layer 31b, the strength is reduced at a portion corresponding to the bent portion 30b of the positive electrode 31. Then, when an impact is applied to the bent portion 30b side in the sealed battery 1, the positive electrode 31 located on the outer peripheral side of the bent portion 30b may be damaged.

  On the other hand, as described above, by providing the electrode layer non-formation region 31c on the positive electrode 31 located on the outer peripheral side of the bent portion 30b of the electrode body 30, the positive electrode active material layer 31b does not exist. Strength reduction can be suppressed. Therefore, even when the sealed battery 1 receives the impact as described above, the positive electrode 31 located on the outer peripheral side of the bent portion 30b of the electrode body 30 can be prevented from being damaged.

  Further, as described above, the protective sheet 37 functions as a buffer material by attaching the protective sheet 37 to the bent portion 30b of the electrode body 30. Therefore, even when the sealed battery 1 receives the impact as described above, the positive electrode 31 positioned on the outer peripheral side of the bent portion 30b of the electrode body 30 can be more reliably prevented from being damaged.

  Note that, as described above, the winding tape 36 is applied to the bent portion 30a of the electrode body 30. Therefore, when an impact is applied to the bent portion 30a side of the sealed battery 1, the winding tape 36 is Serves as a cushioning material. Therefore, even if the positive electrode active material layer 31b exists in the portion located on the outer peripheral side of the bent portion 30a in the positive electrode 31, the positive electrode 31 is damaged when the above-described impact is applied to the sealed battery 1. Not receive.

  In the negative electrode 32, a negative electrode active material layer 32b containing a negative electrode active material is provided on a negative electrode current collector 31a made of a metal foil such as copper. Specifically, in the negative electrode 32, a negative electrode mixture containing a negative electrode active material capable of occluding and releasing lithium ions, a conductive additive, a binder, and the like was applied onto a negative electrode current collector 31a made of copper foil and dried. Thereafter, it is formed by pressing in the thickness direction with a roller or the like.

  That is, the negative electrode 32 includes a negative electrode current collector 32a and a negative electrode active material layer 32b formed on the negative electrode current collector 32a. The negative electrode active material layer 32b is formed on at least one surface of the negative electrode current collector 32a.

  In the case of the present embodiment, as shown in FIG. 5, in the negative electrode 32, the negative electrode active material layer is formed on the negative electrode current collector 32 a on the winding start side (center side) and winding end side (outer peripheral side). 32b is not formed.

  The negative electrode 32 includes an electrode layer non-formation region 32c formed on the winding start side of the electrode body 30, a single-side formation region 32d located on the winding end side of the electrode body 20 with respect to the electrode layer non-formation region 32c, A double-sided formation region 32e positioned closer to the end of winding of the electrode body 20 than the single-sided formation region 32d.

  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.

  The separator 33 has a resin porous layer (porous layer) and an adhesive resin layer (adhesive layer). The adhesive resin layer is formed on both surfaces of the resin porous layer. The separator 33 has a thickness of 11 μm, for example.

  As the resin porous layer, a polyolefin microporous film that is used in electrochemical elements such as lithium secondary batteries that are conventionally known can be used. That is, the resin porous layer is made of the same material as the resin porous layer of a conventional general separator and has the same structure as the conventional resin porous layer, and thus detailed description thereof is omitted.

  The adhesive resin layer is made of a material that exhibits adhesiveness by a heat press and is in close contact with a counterpart material. That is, the material constituting the adhesive resin layer is a material that exhibits adhesiveness at a temperature lower than the melting point of the resin that is the main component of the resin porous layer. Specific examples of such materials include, for example, low density polyethylene (LDPE), poly-α-olefin [PP, polybutene-1, etc.], polyacrylate ester, polyvinyl acetate, monomers constituting these resins, and the like. [Ethylene-vinyl acetate copolymer (EVA), ethylene-methyl acrylate copolymer (EMA), ethylene-ethyl acrylate copolymer (EEA), ethylene-butyl acrylate copolymer (EBA) , Ethylene-methyl methacrylate copolymer (EMMA), ionomer resin, etc.].

  In addition, each of the above-mentioned resins and a resin having adhesiveness at room temperature such as SBR, nitrile rubber (NBR), fluorine rubber, and ethylene-propylene rubber are used as a core, and the melting point and softening point are within a range of 60 ° C. or higher and 120 ° C. or lower. A resin having a core-shell structure with the resin in the above as a shell may be used for the adhesive resin layer. In this case, various acrylic resins or polyurethane may be used for the shell. Further, for the adhesive resin layer, a material exhibiting adhesiveness in a range of 60 ° C. or higher and 120 ° C. or lower among one-pack type polyurethane, epoxy resin, and the like may be used.

  In the adhesive resin layer, one type of the resin exemplified above may be used alone, or two or more types may be used in combination.

  By using the separator 33 having the adhesive resin layer as described above, the separator 33 is bonded to the positive electrode 31 and the negative electrode 32 when the electrode body 30 is hot-pressed to be flat. As a result, the electrode body 30 has the positive electrode 31, the negative electrode 32, and the separator 33 integrated.

  As described above, the protective sheet 37 functions as a buffer material by sticking the protective sheet 37 to the bent portion 30b so as to cover the bent portion 30b formed on one side in the width direction of the electrode body 30. Thus, even when an impact is applied to the sealed battery 1 on the bent portion 30b side of the electrode body 20, it is possible to prevent the positive electrode 31 located on the outer peripheral side of the bent portion 30b from being damaged.

  In addition, by attaching a protective sheet 37 different from the winding tape 36 of the electrode body 30 to the bent portion 30b of the electrode body 30, regardless of the end position of the separator 33 of the electrode body 30 being wound, The bent portion 30 b can be protected by the protective sheet 37. Therefore, even when an impact is applied to the sealed battery 1 on the bent portion 30b side of the electrode body 20, it is possible to more reliably prevent the positive electrode 31 located on the outer peripheral side of the bent portion 30b from being damaged.

Furthermore, by attaching the protective sheet 37 only to the bent portion 30 b of the electrode body 30, the protective sheet 37 is not attached in the thickness direction of the electrode body 30. Thereby, it can prevent that the dimension of the thickness direction of the electrode body 30 becomes large by the protective sheet 37. FIG.

  Further, by forming an electrode layer non-formation region 31 c on the positive electrode 31 located on the outer peripheral side of the electrode body 30 so as to correspond to the bent part 30 b of the electrode body 30, the outer periphery of the bent part 30 b of the positive electrode 31 is formed. The strength reduction of the part located in the side can be suppressed. Thus, even when an impact is applied to the sealed battery 1 on the bent portion 30b side of the electrode body 20, it is possible to prevent the positive electrode 31 located on the outer peripheral side of the bent portion 30b from being damaged.

  Since the separator 33 is positioned on the outer surface of the electrode body 30, the separator 33 serves as a buffer material that cushions the impact applied to the electrode body 30, and the electrode body 30 moves in the battery case 2. Can be suppressed. That is, the electrode body 30 can be prevented from moving in the battery case 2 by the elastic restoring force of the separator 33 and the surface friction.

  Moreover, the separator 33 has an adhesive resin layer on the surface. Thereby, the electrode body 30 is less likely to move with respect to the inner surface of the battery case 2.

  When the thickness of the positive electrode current collector 31a of the positive electrode 31 is 11 μm or less, the strength of the positive electrode 31 is reduced by forming the positive electrode active material layer 31b on the positive electrode current collector 31a. Therefore, in the positive electrode 31 located on the outer peripheral side of the bent portion 30b of the electrode body 30, the sealed battery 1 is provided in the sealed battery 1 by providing an electrode layer non-formation region 31c that does not form the positive electrode active material layer 31b on the positive electrode collector 31a. On the other hand, it is possible to prevent the positive electrode 31 from being damaged when the impact as described above is applied.

  Further, as in the present embodiment, when the bent portion 30b is formed in a semicircular shape protruding outward in the width direction of the electrode body 30, the bent portion 30b is formed with respect to the sealed battery 1. When an impact is applied to the corresponding position, the portion of the electrode body 30 that protrudes most outward in the width direction receives the greatest impact. Therefore, by forming the electrode layer non-formation region 31c in the positive electrode 31 located on the outer peripheral side of the electrode body 30 in a range including the portion that protrudes most outward in the width direction of the bent portion 30b, a sealed battery is formed. 1 can be prevented from being damaged when the above-described impact is applied.

  In the present embodiment, the electrode layer non-formation region 31 c is formed from the portion corresponding to the bent portion 30 b of the electrode body 30 to the end portion on the winding end side in the positive electrode 31. Thereby, the electrode layer non-formation region 31c can be easily formed in the positive electrode 31.

  Thereby, when the sealed battery 1 receives an impact, the electrode body 30 can be prevented from moving within the battery case 2 and the electrode body 30 being subjected to a large impact. Therefore, the positive electrode 31 positioned on the outer peripheral side of the electrode body 30 can be more reliably prevented from being damaged.

(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 the embodiment, the bent portion 30 a of the electrode body 30 is covered with the winding tape 36, while the bent portion 30 b is covered with the protective sheet 37. However, the bent portion 30 a of the electrode body 30 may also be covered with the protective sheet 37. Thus, by covering the bent portions 30a and 30b with the protective sheet 37 different from the winding tape 36, the bent portions 30a and 30b can be protected regardless of the winding end position of the separator 33 of the electrode body 30. it can.

  Further, a tape may be attached to the bottom of the electrode body 30 (the side opposite to the extending direction of the positive electrode lead 34 and the negative electrode lead 35) so as to cover the bottom. Thereby, even when the bottom receives an impact or the like, the bottom can be protected.

  In the embodiment, the electrode layer non-forming region 31c is provided on the positive electrode 31 located on the outer peripheral side in the bent portion 30b of the electrode body 30 corresponding to the bent portion 30b. However, the electrode layer non-formation region 31c may be provided only in the portion of the bent portion 30b that protrudes most outward in the width direction of the electrode body 30. The portion of the bent portion 30b that protrudes most outward in the width direction of the electrode body 30 is most susceptible to an impact when the shock is applied to the sealed battery 1 on the bent portion 30b side. It is effective to provide the layer non-formation region 31c.

  In addition, if the electrode layer non-formation area | region 31c contains the part which protrudes most in the width direction outer side of the electrode body 30 among the bending parts 30b, an electrode layer will be from the said part to the edge part of the winding end side of the positive electrode 31 The non-formation region 31c may be provided, or the electrode layer non-formation region 31c may be provided only in a portion corresponding to the bent portion 30b.

  In the embodiment, the electrode layer is not formed on the positive electrode 31 positioned on the outer peripheral side of the electrode body 30 so as to correspond to the bent section 30b among the pair of bent sections 30a and 30b positioned on both sides in the width direction of the electrode body 30. A region 31c is provided. However, the electrode layer non-formation region 31c may be provided in the positive electrode 31 so as to correspond to both the pair of bent portions 30a and 30b. As described above, by providing the positive electrode 31 with the electrode layer non-formation region 31c so as to correspond to both the pair of bent portions 30a and 30b, on either side of the pair of bent portions 30a and 30b in the sealed battery 1. Even when an impact is applied, the positive electrode 31 located on the outer peripheral side of the electrode body 30 can be prevented from being damaged.

  In the embodiment, the electrode layer non-forming region 31c is provided on the positive electrode 31 located on the outer peripheral side in the bent portion 30b of the electrode body 30 corresponding to the bent portion 30b. However, the electrode layer non-formation region 31 c may not be provided in the positive electrode 31.

  In the embodiment, the pair of bent portions 30 a and 30 b are formed in a semicircular shape protruding outward in the width direction of the electrode body 30. However, the shape of the pair of bent portions 30a and 30b may be any shape as long as it can form a flat electrode body.

  In the embodiment, in the positive electrode 31 and the negative electrode 32, the positive electrode active material layer 31b and the negative electrode active material layer 32b are formed as shown in FIG. However, the positions where the positive electrode active material layer 31b and the negative electrode active material layer 32b are formed on one side and both sides of the positive electrode current collector 31a and the negative electrode current collector 32a may be positions other than those in the above embodiment. That is, as long as the electrode layer non-formation region is provided in the electrode located on the outer peripheral side in the bent portion 30b of the electrode body 30, the configuration of the electrode may be any configuration.

  In the embodiment, the electrode body 30 is wound in a state where the positive electrode 31, the negative electrode 32, and the separator 33 are overlapped in the thickness direction so that the separator 33 is positioned on the outer surface. However, the electrode body may be wound in a state where the positive electrode 31, the negative electrode 32, and the separator 33 are overlapped in the thickness direction so that the positive electrode 31 or the negative electrode 32 is positioned on the outer surface.

  In the said embodiment, the adhesive resin layer is formed on both surfaces of the resin porous layer of the separator 33. FIG. However, the adhesive resin layer may be formed only on one surface of the resin porous layer. In this case, the separator 33 is integrated with either the positive electrode 31 or the negative electrode 32. Moreover, while providing an adhesive resin layer on one side of the pair of separators 33, an adhesive resin layer may be provided only on the other side. Even in this case, an adhesive resin layer is provided on the surface of the separator 33 located on the outer surface of the electrode body 30 of the separator 33 from the viewpoint of effectively suppressing the movement of the electrode body 30 in the battery case 2. Is preferred.

  In the embodiment, the sealed battery 1 is a lithium ion battery. However, the sealed battery 1 may be a battery other than a lithium ion battery.

  A test for confirming the effect of the sealed battery 1 having the above-described configuration was performed. Specifically, lithium ion batteries of Examples 1 and 2 and Comparative Examples and Reference Examples as described below were prepared and subjected to a drop test of the lithium ion battery, and then the presence or absence of damage to the positive electrode was confirmed.

Example 1
<Preparation of positive electrode>
96 parts by mass of lithium cobaltate as a positive electrode active material, 20 parts by mass of an N-methyl-2-pyrrolidone (NMP) solution containing polyvinylidene fluoride (PVDF) as a binder at a concentration of 10% by mass, 1 part by mass of artificial graphite and 1 part by mass of ketjen black, which are agents, were kneaded using a biaxial kneader, and NMP was added to adjust the viscosity to prepare a positive electrode mixture-containing paste.

  The positive electrode mixture-containing paste was applied to both sides of an aluminum foil (positive electrode current collector) having a thickness of 10.3 μm, and then dried to form a positive electrode active material layer on both sides or one side of the aluminum foil. Thereafter, the positive electrode active material layer is pressed to adjust the thickness and density of the positive electrode active material layer, and a nickel lead body is welded to the exposed portion of the aluminum foil to obtain a length of 540 mm and a width of 70 mm. A belt-like positive electrode was prepared.

<Production of negative electrode>
97.5 parts by mass of graphite as a negative electrode active material in which 50% of the average particle diameter D is 16 μm, styrene butadiene rubber (SBR) as a binder: 1.5 parts by mass, and carboxymethyl cellulose (Thickener) CMC): Water was added to 1 part by mass and mixed to prepare a negative electrode mixture-containing paste.

  The negative electrode mixture-containing paste was applied to both sides of a copper foil (negative electrode current collector) having a thickness of 6 μm, and then dried to form a negative electrode mixture layer (negative electrode active material layer) on both sides of the copper foil. . Thereafter, the negative electrode active material layer is pressed to adjust the thickness and density of the negative electrode active material layer, and a nickel lead body is welded to the exposed portion of the copper foil to obtain a length of 530 mm, a width of A 74 mm strip-shaped negative electrode was produced.

<Preparation of non-aqueous electrolyte>
LiPF6 was dissolved at a concentration of 1.1 mol / L in a mixed solvent of ethylene carbonate (EC) and diethyl carbonate (DEC) in a volume ratio of 3: 7, and fluoroethylene carbonate (FEC) was 2.0% by mass. And vinylene carbonate (VC) in an amount of 2.0% by mass, respectively, to prepare a non-aqueous electrolyte.

<Battery assembly>
The strip-shaped positive electrode is wound in a state of being stacked on the strip-shaped negative electrode so as to sandwich a separator having a thickness of 11 μm (a separator having an adhesive layer of 1 μm provided on both sides of a 9 μm porous layer), 4 is attached to the bent portion, and then pressed (hot press) so as to be flattened, and then a protective sheet is attached to the other bent portion to form an electrode body having a structure as shown in FIG. Obtained. In the two bent portions, the positive electrode active material layer was present on any of the outermost positive electrodes. Next, the electrode body is inserted into an aluminum alloy prismatic battery case having an outer dimension of a thickness of 4.3 mm, a width of 39 mm, and a height of 79 mm, and the lead body is welded. It welded to the opening edge part of a battery case. Thereafter, the nonaqueous electrolyte was injected from the inlet provided in the lid plate, and allowed to stand for 1 hour, and then the inlet was sealed. Then, the lithium ion battery of the structure shown in FIG. 1 was obtained through the activation process.

(Example 2)
A positive electrode was produced in the same manner as in Example 1 except that the positive electrode current collector was changed to an aluminum foil having a thickness of 11 μm, and a lithium ion battery was produced in the same manner as in Example 1 except that this positive electrode was used.

(Comparative example)
A lithium ion battery was produced in the same manner as in Example 1 except that the protective sheet was not attached on the outer peripheral surface of the electrode body.

(Reference example)
A lithium ion battery was produced in the same manner as in Example 1 except that the positive electrode current collector was changed to an aluminum foil having a thickness of 12 μm and that the protective sheet was not attached to the outer peripheral surface of the electrode body.

(Drop test)
Five lithium ion batteries of Example 1, Example 2, Comparative Example, and Reference Example prepared as described above were prepared, and a drop test was performed on each lithium ion battery. In the drop test, each lithium ion battery was dropped on a flat surface from a position with a height of 1.5 m so that the six surfaces of the battery were impacted, and no winding tape was attached to the electrode body. The presence or absence of the fracture | rupture of the positive electrode located in the one bending part was confirmed. The presence or absence of breakage of the positive electrode was visually observed by disassembling the battery after the drop test. The test results are shown in Table 1.

  As shown in Table 1, when the thickness of the positive electrode current collector was larger than 11 μm (reference example: the thickness of the positive electrode current collector was 12 μm), the positive electrode was not broken. On the other hand, when the thickness of the positive electrode current collector is 11 μm or less, of the pair of bent portions of the electrode body, the positive electrode current collector of the positive electrode located on the outermost peripheral side in the bent portion where the winding tape is not attached. When the positive electrode active material layer was formed on the electric conductor, the positive electrode broke (comparative example).

  When the thickness of the positive electrode current collector is 11 μm or less, the positive electrode active material layer is formed on the positive electrode located on the outermost peripheral side in the bent portion on the side where the protective sheet is attached, of the pair of bent portions of the electrode body. However, the positive electrode did not break (Examples 1 and 2).

  Therefore, when the thickness of the positive electrode current collector was 11 μm or less, it was confirmed that the positive electrode could be prevented from being damaged even when an impact was applied to the lithium ion battery by applying a protective sheet to the bent portion of the electrode body. .

  INDUSTRIAL APPLICABILITY The present invention can be used for a flat sealed battery in which an electrode body formed by hot pressing in a state where a positive electrode and a negative electrode are wound together with a separator having an adhesive resin layer is enclosed in a battery case. .

DESCRIPTION OF SYMBOLS 1 Sealed battery 2 Battery case 30 Electrode bodies 30a and 30b Bending part 31 Positive electrode 31a Positive electrode current collector (current collector)
31b Positive electrode active material layer (electrode layer)
31c Electrode layer non-formation region 31d Single-sided formation region 31e Double-sided formation region 32 Negative electrode 32a Negative electrode current collector 32b Negative electrode active material layer 32c Electrode layer non-formation region 32d Single-sided formation region 32e Double-sided formation region 33 Separator 36 Winding tape 37 Protective sheet

Claims (7)

An electrode body wound in a state where a positive electrode, a negative electrode, and a separator, each formed in a sheet shape, are stacked in a thickness direction;
A battery case in which the electrode body is enclosed;
Each of the positive electrode and the negative electrode has a current collector made of a metal foil, and an electrode layer formed on at least one surface of the current collector.
The separator has a porous layer and an adhesive layer formed on at least one side in the thickness direction of the porous layer,
The electrode body is a flat shape crushed in the radial direction in the wound state, and has a pair of bent portions that protrude outward in the width direction on both sides in the width direction,
The adhesive layer of the separator is bonded to at least one of the positive electrode and the negative electrode,
In the positive electrode, the current collector has a thickness of 11 μm or less,
A sealed battery in which a protective sheet for protecting the electrode body is attached to the outer peripheral surface of the electrode body so as to cover only at least one of the pair of bent portions. The sealed battery according to claim 1,
Further comprising a winding tape for stopping the winding end portion of the electrode body,
The protective sheet is a sealed battery that is affixed on an outer peripheral surface of at least one of the pair of bent portions, separately from the winding tape. The sealed battery according to claim 1 or 2,
The separator is a sealed battery wound around the positive electrode and the negative electrode so as to be positioned on the outermost periphery of the electrode body. The sealed battery according to claim 3,
The said contact bonding layer of the said separator is a sealed battery formed in the surface located in the outer surface of the said electrode body. 5. The sealed battery according to claim 1, wherein the positive electrode is located on the outermost peripheral side of the electrode body and at the outermost side in the width direction at least one of the pair of bent portions. A sealed battery having an electrode layer non-formation region where the electrode layer is not formed on the current collector at a position corresponding to the protruding portion. The sealed battery according to claim 5,
The said electrode layer non-formation area | region is a sealed battery formed in the said positive electrode in the outermost peripheral side of the said electrode body, and the range corresponding to at least one bending part among a pair of said bending parts. The sealed battery according to any one of claims 1 to 6,
The bent portion is a sealed battery that is formed in a semicircular shape protruding outward in the width direction.

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