Battery cell

Abstract

To obtain a battery cell capable of suppressing an internal short circuit due to breakage of a separator.SOLUTION: A battery cell 20 comprises an electrode body 40 constructed by alternately laminating a plurality of electrode sheets 50 and separators 60. The plurality of electrode sheets 50 comprises: a plurality of first electrode sheets 50 which has one end part of a width direction as projection end parts 50A projected from one end part of the width direction of the separator, the projection end parts 50A are collected at a predetermined position in a lamination direction with the other projection end parts 50A to constitute a collector part 56; and a plurality of second electrodes as non-projection end parts 50B opposite the first electrode sheets 50 via the separator 60, and in which the one end part of the width direction is arranged in an opposite region to the separators 60, and in which a direction of burrs 70 formed in the non-projection end parts 50B is aligned to a direction directed to the collector part 56 with the burrs of the other non-projection end parts 50B.SELECTED DRAWING: Figure 3

Description

[Technical field]

[0001] The present invention relates to a battery cell. [Background technology]

[0002] The following Patent Document 1 describes an electricity storage device having a current collecting element (electrode body) in which multiple electrodes and separators are alternately stacked, and in which a tab terminal is fixed between the bottom layer of the stacked electrodes and a lower laminate film. In this electricity storage device, the ends of the multiple stacked electrodes are assembled at a predetermined position in the stacking direction to form a current collecting part that is connected to the tab terminal. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2013-196930 A Summary of the Invention [Problem to be solved by the invention]

[0004] Incidentally, the electrodes of the electrode body are cut into a sheet shape in a cutting process during manufacturing. At this time, the cut surfaces are plastically deformed, and minute burrs (protrusions) are formed on the ends of the electrodes cut into the sheet shape.

[0005] As in Patent Document 1, the electrode body is formed by alternately stacking a plurality of electrode sheets and separators. The stacked electrode sheets include a first electrode sheet having one end in the width direction protruding from the separator and constituting a current collector, and a second electrode sheet facing the first electrode sheet via the separator and having one end in the width direction disposed in a region facing the separator.

[0006] The first electrode sheet is bent in an R shape by drawing out one end in the width direction toward the current collector. Therefore, one end in the width direction of the separator interposed between the electrode sheets is also bent along the R direction of the first electrode sheet. Therefore, if the direction of the burr formed on the end of the second electrode sheet in the opposing region with the separator is different from the direction toward the current collector, there is a risk that local stress will occur at the end of the separator due to interference from the burr. If the separator is damaged due to the occurrence of local stress, the risk of an internal short circuit occurring due to physical contact between the electrode sheets increases.

[0007] In consideration of the above, an object of the present invention is to provide a battery cell that can suppress internal short circuits caused by separator damage. [Means for solving the problem]

[0008] The battery cell of the first aspect is a battery cell having an electrode body formed by alternately stacking a plurality of electrode sheets and separators, and the plurality of electrode sheets comprise a plurality of first electrode sheets, one widthwise end of which is a protruding end that protrudes from one widthwise end of the separator, and the protruding end is assembled together with the other protruding end at a predetermined position in the stacking direction to form a current collecting portion, and a plurality of second electrode sheets, which face the first electrode sheets via the separator, one widthwise end of which is a non-protruding end that is positioned in an opposing area with the separator, and the direction of burrs formed on the non-protruding end is aligned toward the current collecting portion together with the burrs of the other non-protruding end.

[0009] In the battery cell of the first aspect, a plurality of electrode sheets and separators are alternately stacked. The plurality of electrode sheets are composed of a plurality of first electrode sheets and a plurality of second electrode sheets opposed to the plurality of first electrode sheets via separators. The first electrode sheets have one end in the width direction as a protruding end protruding from one end in the width direction of the separator. The protruding end is assembled together with the protruding end of the other first electrode sheets at a predetermined position in the stacking direction to form a current collector. On the other hand, the second electrode sheet has one end in the width direction as a non-protruding end arranged in an area facing the separator. Here, the direction of the burrs formed on the non-protruding end of the second electrode sheet is aligned in the direction toward the current collector together with the burrs on the non-protruding end of the other second electrode sheet. Therefore, damage to the separator caused by interference of the burrs on the end of the second electrode sheet in the area facing the separator is suppressed. As a result, internal short circuit of the battery cell due to damage to the separator is suppressed. Effect of the Invention

[0010] As described above, in a battery cell according to the present invention, internal short circuits caused by breakage of the separator can be suppressed. [Brief description of the drawings]

[0011] [Figure 1] 2 is a schematic diagram of a battery cell according to an embodiment, viewed from a thickness direction. FIG. [Diagram 2] FIG. 2 is a schematic diagram of a battery cell according to an embodiment, viewed from the height direction in an exploded state. [Diagram 3] 3 is an enlarged schematic view of a region P in FIG. 2. FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0012] A battery cell 20 according to one embodiment of the present invention will be described below with reference to Figures 1 to 3. In each of Figures 1 to 3, the direction indicated by arrow W is the width direction of the battery cell 20, the direction indicated by arrow H is the height direction (vertical direction) of the battery cell 20, and the direction indicated by arrow D is the thickness direction of the battery cell 20. The width direction W of the battery cell 20 coincides with the width directions of an electrode sheet 50 and a separator 60, which will be described later.

[0013] (Overall composition) Fig. 1 is a schematic diagram of a battery cell viewed from a thickness direction D. As shown in Fig. 1, the battery cell 20 is formed into a flat and long rectangular plate shape with the width direction W as the longitudinal direction, and constitutes a secondary battery capable of charging and discharging.

[0014] The battery cell 20 has an electrode body 40 and a laminate film 22 that seals the electrode body 40. The electrode body 40 is connected to electrode leads 26 protruding in the width direction W at one end and the other end in the width direction W. The electrode lead 26 has a first electrode lead 26A connected to the positive electrode of the electrode body 40 at one end in the width direction W, and a second electrode lead 26B connected to the negative electrode of the electrode body 40 at the other end in the width direction W. The first electrode lead 26A and the second electrode lead 26B are formed in a rectangular plate shape that is long in the width direction W. The laminate film 22 is embossed on at least one side in the thickness direction. By embossing, a concave housing portion 221 in which the electrode body 40 is housed is formed on the side surface.

[0015] 2 is a schematic diagram of the battery cell 20 in an exploded state, as viewed from the height direction H. As shown in FIG. 2, the laminate film 22 has a first laminate film 22A arranged on one side of the thickness direction D of the electrode body 40, and a second laminate film 22B arranged on the other side of the thickness direction D of the electrode body 40. The first laminate film 22A and the second laminate film 22B are overlapped in the thickness direction D on both sides of the electrode body 40, and the outer peripheries are thermally welded to each other to form a storage space for the electrode body 40. In this embodiment, one side of the second laminate film 22B is embossed to form a storage section 221. The laminate film 22 may have either a single cup embossed structure in which one portion is embossed, or a double cup embossed structure in which two portions are embossed. In this embodiment, however, a single cup embossed structure is adopted in which a storage portion 221 having a drawing depth of approximately 8 mm to 10 mm is formed on one side of the second laminate film 22B.

[0016] On one side in the width direction W of the battery cell 20, one end of the first electrode lead 26A protrudes in the width direction W from an end of the laminate film 22. On the other side in the width direction W of the battery cell 20, one end of the second electrode lead 26B protrudes in the width direction W from the end of the laminate film 22.

[0017] On one side and the other side in the width direction W of the battery cell 20, one end of the electrode lead 26 protruding from the exterior material 22 is welded to a bus bar (not shown).

[0018] The length CW1 of the battery cell 20 in the vehicle width direction is, for example, 530 mm to 600 mm, 600 mm to 700 mm, 700 mm to 800 mm, 800 to 900 mm, 1000 mm or more, the length CW2 of the region in which the electrode body is housed is, for example, 500 mm to 520 mm, 600 mm to 700 mm, 700 mm to 800 mm, 800 to 900 mm, 1000 mm or more, and the height CH of the battery cell 20 is, for example, 80 mm to 110 mm, 110 mm to 140 mm. The thickness of the battery cell 20 is 5.0 mm to 7.0 mm, 7.0 mm to 9.0 mm, 9.0 mm to 11.0 mm, and the height TH of the electrode lead (terminal) 26 is 40 mm to 50 mm, 50 mm to 60 mm, 60 mm to 70 mm.

[0019] (electrode body) The electrode body 40 is configured by alternately stacking a plurality of electrode sheets 50 and separators 60. The plurality of electrode sheets 50 includes a plurality of positive electrode sheets 52 and a plurality of negative electrode sheets 54, and in the electrode body 40, the positive electrode sheets 52 and the negative electrode sheets 54 are alternately stacked with the separators 60 interposed therebetween. The positive electrode sheet 52 is an example of a "first electrode sheet," and the negative electrode sheet 54 is an example of a "second electrode sheet."

[0020] (Positive electrode sheet) The positive electrode sheet 52 has a sheet-shaped positive electrode collector (electrode collector) 521 and a positive electrode active material layer (electrode active material layer) 522 coated on the surface of the positive electrode collector 521 (see FIG. 3). The positive electrode collector 521 is made of a metal foil such as an aluminum foil. The positive electrode active material layer 522 contains a positive electrode active material and a positive electrode binder. The positive electrode active material is a material capable of absorbing and releasing ions, and in the case of a lithium ion secondary battery, it can be made of, for example, a lithium nickel oxide, a lithium cobalt oxide (e.g., LiCoO2, etc.), a lithium manganese oxide (e.g., LiMn2O4), etc.

[0021] One end of the positive electrode sheet 52 in the width direction W is a protruding end 50A protruding from one end of the separator in the width direction. This protruding end 50A is an uncoated portion where the positive electrode active material layer 522 is not coated, and the positive electrode current collector 521 is exposed. The protruding end 50A is assembled with the protruding ends 50A of other positive electrode sheets 52 at a predetermined position in the stacking direction (thickness direction D in FIG. 2) of the electrode body 40, and constitutes a positive electrode side current collector 56 (see FIG. 3). In this embodiment, the protruding ends 50A of multiple positive electrode sheets 52 are assembled on the first laminate film 22A side, and a first electrode lead 26A is disposed between the positive electrode side current collector 56 and the first laminate film 22A. As a result, the first electrode lead 26A is connected to the positive electrode side current collector 56.

[0022] Meanwhile, the other end of the positive electrode sheet 52 in the width direction W is a non-protruding end 50B that is disposed in a region facing the separator 60. This non-protruding end 50B is configured as a coated portion on which the positive electrode active material layer 522 is coated, and is configured not to protrude from the other end of the separator 60 in the width direction W, and to face the second electrode sheet 50 via the separator 60.

[0023] (Negative electrode sheet) The negative electrode sheet 54 has a sheet-like negative electrode current collector (electrode current collector) 541 and a negative electrode active material layer (electrode active material layer) 542 coated on the surface of the negative electrode current collector 541 (see FIG. 3). The negative electrode current collector 541 is composed of a metal foil such as copper foil. The negative electrode active material layer 542 contains a negative electrode active material and a negative electrode binder. The negative electrode active material is a material capable of absorbing and releasing ions, and in the case of a lithium ion secondary battery, it can be composed of, for example, a carbon material, a fluororesin (for example, polyvinylidene fluoride, tetrafluoroethylene-hexafluoropropylene copolymer, etc.), polyvinyl acetate, etc.

[0024] One end of the negative electrode sheet 54 in the width direction W is a non-protruding end 50B that is disposed in a region facing the separator 60. This non-protruding end 50B is configured as a coated portion on which the negative electrode active material layer 542 is coated, and is configured not to protrude from one end of the separator 60 in the width direction W, and to face the second electrode sheet 50 via the separator 60.

[0025] On the other hand, the other end of the negative electrode sheet 54 in the width direction W is a protruding end 50A protruding from one end of the separator in the width direction. This protruding end 50A is an uncoated portion where the negative electrode active material layer 542 is not coated, and the negative electrode current collector 541 is exposed. The protruding end 50A is assembled on the first laminate film 22A side together with the protruding end 50A of the other negative electrode sheet 54 to form a negative electrode side current collector 56. In this embodiment, the second electrode lead 26B is disposed between the negative electrode side current collector 56 and the first laminate film 22A. As a result, the second electrode lead 26B is connected to the negative electrode side current collector 56.

[0026] Fig. 3 shows an enlarged view of region P shown in Fig. 2. Region P shows one region in the width direction W of the electrode body 40.

[0027] As shown in FIG. 3, on one side of the width direction W of the electrode body 40, the protruding end 50A of the stacked positive electrode sheets 52 is drawn in the first direction D1 along the stacking direction toward the current collector 56. Therefore, the protruding end 50A of the multiple positive electrode sheets 52 is bent in an R shape. In addition, one end of the separator 60 interposed between the positive electrode sheet 52 and the negative electrode sheet 54 in the width direction W is also bent along the R direction of the positive electrode sheet 52. In this way, the end of the separator 60 bent in an R shape by the positive electrode sheet 52 is in contact with the edge of the non-protruding end 50B on one side of the width direction W of the negative electrode sheet 54. Therefore, if the non-protruding end 50B of the negative electrode sheet 54 and the separator 60 strongly interfere with each other, local stress concentration may occur.

[0028] Here, the positive electrode sheet 52 and the negative electrode sheet 54 are cut into sheets in a cutting process during manufacturing. At this time, the cut surfaces are plastically deformed, forming minute burrs 70 (protrusions) on the ends of the positive electrode sheet 52 and the negative electrode sheet 54 (see FIG. 3). Note that the "burrs" referred to here mainly refer to burrs formed by deformation of the cut surfaces of the electrode current collectors made of metal foil. If the direction of the burrs 70 differs from the bending direction of the separator 60, there is a risk that the burrs 70 and the separator 60 will strongly interfere with each other.

[0029] In this embodiment, in the protruding end 50A of the negative electrode sheet 54, the direction of the burrs 70 formed on the non-protruding end 50B is aligned with the direction toward the current collector 56 (toward the first direction D1 in FIG. 3 ) together with the burrs 70 on the non-protruding end 50B of the other negative electrode sheet 54. Therefore, the direction of the burrs 70 formed on the non-protruding end 50B is aligned with the R direction of the separator 60, so that strong interference between the burrs 70 on the non-protruding end 50B and the separator 60 can be suppressed.

[0030] The problem of local stress concentration on the separator 60 as described above is also the same at the other end of the width direction W of the electrode body 40 where the protruding end 50A of the negative electrode sheet 54 is pulled toward the negative electrode side current collector 56 and bent into an R shape. That is, at the other end of the width direction W of the electrode body 40, it is desirable to avoid strong interference between the non-protruding end 50B of the positive electrode sheet 52 and the separator 60. For this reason, although not shown, at the other protruding end 50A of the positive electrode sheet 52 in the width direction W, the direction of the burr 70 formed on the non-protruding end 50B is aligned with the burr 70 of the non-protruding end 50B of the other positive electrode sheet 52 in the direction toward the current collector 56 (the first direction D1 side in FIG. 3).

[0031] (Separator) The separator 60 is an insulating layer that maintains the distance between the positive electrode sheet 52 and the negative electrode sheet 54 to prevent contact short circuits, and also retains the non-aqueous electrolyte. The separator 60 is, for example, made of a porous resin plate. In this embodiment, the battery cell 20 has a plurality of separators 60 cut into sheets, and one separator 60 is disposed between the positive electrode sheet 52 and the negative electrode sheet 54. When viewed from the lamination direction of the electrode body 40, the protruding end 50A of the positive electrode sheet 52 protrudes from one end of the separator 60 in the width direction W. The protruding end 50A of the negative electrode sheet 54 protrudes from the other end of the separator 60 in the width direction W. In addition, the separator 60

[0032] (Battery cell manufacturing method) The battery cell 20 described above is manufactured through, by way of example, a source process, a burr orientation inspection process, a lamination process, a pressing process, a terminal welding process, a cell drying process, a liquid injection / sealing process, an activation process, and an evaluation process.

[0033] In the burr direction inspection process, the positive electrode sheet 52, the negative electrode sheet 54, and the separator 60 constituting the electrode body 40 are formed. The positive electrode sheet 52 and the negative electrode sheet 54 are cut into sheets in a state in which the electrode active material is applied to the electrode current collector. In the burr direction inspection process, the burr direction of the end portion of the cut surface of the positive electrode sheet 52 and the negative electrode sheet 54 cut into sheets is inspected. In this burr direction inspection process, at least the burr direction of the end portion constituting the non-protruding end portion 50B in the electrode body 40 is inspected. In the stacking process, the positive electrode sheet 52 and the negative electrode sheet 54 are stacked alternately with the separator 60 interposed therebetween. At this time, the positive electrode sheet 52 and the negative electrode sheet 54 are aligned such that the burr direction of the non-protruding end portion is directed toward the current collector 56 (the first direction D1 side in FIG. 3). In the pressing process, the electrode body 40 is formed by pressing a laminate formed by alternately stacking positive electrode sheets 52 and negative electrode sheets 54 with separators 60 interposed therebetween in the stacking direction. In the terminal welding process, electrode leads 26 are welded to one side and the other side in the width direction W of the electrode body 40. In the cell drying process, the electrode body 40 is vacuum dried to remove moisture contained in the electrode body 40. In the electrolyte injection / sealing process, the electrode body 40 is sealed with a laminate film and electrolyte is injected inside to form a battery cell 20. In the activation process, the battery cell 20 is initially charged, and then a high-temperature aging process is performed. In the evaluation process, cell voltage, battery resistance, etc. are inspected, and battery cells 20 that exhibit predetermined performance are selected.

[0034] (Action and Effects) As described above, in the battery cell 20 according to this embodiment, a plurality of electrode sheets 50 and separators 60 are alternately stacked. The plurality of electrode sheets 50 are composed of a plurality of positive electrode sheets 52 and a plurality of negative electrode sheets 54 that face the plurality of positive electrode sheets 52 via the separator 60. The positive electrode sheets 52 have a protruding end 50A at one end in the width direction W that protrudes from one end in the width direction W of the separator 60. The protruding end 50A is assembled together with the protruding end 50A of the other positive electrode sheets 52 at a predetermined position in the stacking direction to form a positive electrode side current collector 56. On the other hand, the negative electrode sheets 54 have a non-protruding end 50B at one end in the width direction W that is disposed in an area facing the separator 60. Here, the direction of the burrs 70 formed on the non-protruding end portion 50B of the negative electrode sheet 54 is aligned with the direction toward the positive electrode side current collector 56 (first direction D1 in FIG. 3 ) together with the burrs 70 on the non-protruding end portions 50B of the other negative electrode sheets 54. This suppresses damage to the separator 60 caused by interference from the burrs 70 on the end portion of the negative electrode sheet 54 in the opposing region with the separator 60. As a result, internal short circuits in the battery cell 20 caused by damage to the separator 60 are suppressed. [Explanation of symbols]

[0035] 20 Battery Cells 40 Electrode body 50 Electrode Sheet 50A protruding end 50B Non-protruding end 52 Positive electrode sheet (first electrode sheet) 54 Negative electrode sheet (second electrode sheet) 56 Current collector 60 Separator 70 Bali W Width direction

Claims

[Claim 1] A battery cell including an electrode assembly formed by alternately stacking a plurality of electrode sheets and separators, The plurality of electrode sheets include a plurality of first electrode sheets each having one end in a width direction as a protruding end portion protruding from one end in the width direction of the separator, the protruding end portion being assembled together with other protruding end portions at a predetermined position in the stacking direction to form a current collecting portion; a plurality of second electrode sheets opposed to the first electrode sheet via the separator, each having one end in a width direction as a non-protruding end portion disposed in an opposing region with the separator, and a burr formed on the non-protruding end portion and a burr formed on the other non-protruding end portions are aligned in a direction toward the current collector portion; Battery cell.

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