Secondary battery

Abstract

In the present invention, for each winding circumference of a positive electrode plate of an electrode body, two positive electrode tabs are projectingly formed at an end edge of the positive electrode plate on one side in the winding axis direction. For each winding circumference of a negative electrode plate of the electrode body, two negative electrode tabs are projectingly formed at an end edge of the negative electrode plate on the other side in the winding axis direction. The positive electrode tabs projectingly formed on the positive electrode plate include a plurality of types of positive electrode tabs having mutually different projection lengths and base end widths, and the negative electrode tabs projectingly formed on the negative electrode plate include a plurality of types of negative electrode tabs having mutually different projection lengths and base end widths.

Description

Technical Field

[0001] The present disclosure relates to a secondary battery including an electrode body in which a strip-shaped positive electrode plate and a strip-shaped negative electrode plate are wound with a strip-shaped separator interposed therebetween.

Background Art

[0002] Patent Document 1 discloses a secondary battery including an electrode body in which a strip-shaped positive electrode plate and a strip-shaped negative electrode plate are wound with a strip-shaped separator interposed therebetween. In this secondary battery, one current collector tab projects from each of one edge of the positive electrode plate in the winding axis direction of the electrode body and the other edge of the negative electrode plate in the winding axis direction for each turn.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

[0004] In Patent Document 1, only one current collector tab is provided for each turn of the positive electrode plate and the negative electrode plate, and the variation in the distance from each part in the electrode plate to the current collector tab is large, so the potential difference in the electrode plate becomes large and the deterioration of the electrode plate tends to progress. Therefore, the durability of the secondary battery is reduced.

[0005] There is also a desire to increase the output current of the secondary battery.

[0006] The secondary battery according to the present disclosure is a secondary battery including an electrode body in which a strip-shaped positive electrode plate and a strip-shaped negative electrode plate are wound with a strip-shaped separator interposed therebetween, wherein at least two current collector tabs project from each of one edge of the positive electrode plate in the winding axis direction of the electrode body and the other edge of the negative electrode plate in the winding axis direction for each turn, and the plurality of current collector tabs projecting from the positive electrode plate include a plurality of types of current collector tabs in which at least one of the protruding length and the width of the base end is different from each other. The plurality of current collecting tabs protruding from the negative electrode plate include a plurality of types of current collecting tabs in which at least one of the protruding length and the width of the base end is different from each other.

[0007] According to the present disclosure, the durability of the secondary battery can be enhanced, and the output current of the secondary battery can be increased.

Brief Description of the Drawings

[0008]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7A

Figure 7B

Figure 8

Figure 9

Figure 10A

Figure 10B

Figure 10C

Figure 11

Embodiments for Carrying Out the Invention

[0009] Hereinafter, embodiments of the present disclosure will be described in detail with reference to the drawings. The following description of the preferred embodiments is merely illustrative in nature and is in no way intended to limit the present disclosure, its applications, or its uses.

[0010] FIG. 1 is a perspective view showing a non-aqueous electrolyte secondary battery 20 according to the present disclosure. FIG. 2 is a cross-sectional view taken along line II-II in FIG. 1. As shown in FIGS. 1 and 2, the non-aqueous electrolyte secondary battery 20 includes a battery case 100 composed of a bottomed rectangular outer case 1 having an opening and a sealing plate 2 that seals the opening of the rectangular outer case 1. The rectangular outer case 1 and the sealing plate 2 are preferably each made of metal, more preferably made of aluminum or iron.

[0011] The rectangular outer case 1 has a bottom 1a, a pair of first side walls 1b and 1c, and a second front side wall 1d and a second rear side wall 1e. The pair of first side walls 1b and 1c are arranged facing each other in parallel. The second front side wall 1d and the second rear side wall 1e are arranged facing each other in parallel. The pair of first side walls 1b and 1c are perpendicular to the longitudinal direction of the sealing plate 2, and the area of the pair of first side walls 1b and 1c is smaller than the area of the second front side wall 1d and the second rear side wall 1e.

[0012] As shown in FIG. 3, three electrode bodies 3 including a positive electrode plate 4 and a negative electrode plate 5 are housed together with an electrolyte inside the rectangular outer case 1. As shown in FIG. 4, the electrode body 3 is a flat electrode body in which the positive electrode plate 4 and the negative electrode plate 5 are wound with a separator SP interposed therebetween. The winding axis of the electrode body 3 extends perpendicular to the first side walls 1b and 1c and parallel to the second front side wall 1d and the second rear side wall 1e. The thickness TH of the electrode body 3 is set to 12 mm.

[0013] As shown in FIGS. 4 to 6, at one edge of the positive electrode plate 4 of the electrode body 3 in the winding axis direction, two positive electrode tabs 40a as current collecting tabs are integrally protruded for each circumference and overlap each other. The positive electrode tab 40a is formed in a trapezoidal plate shape whose width gradually increases from the tip toward the base end side. These plurality of positive electrode tabs 40a are laminated to form a positive electrode tab group 40. In FIG. 5, the center of the rounded portion where the positive electrode plate 4 is curved is indicated by reference numeral R.

[0014] The plurality of positive electrode tabs 40a protruding from the positive electrode plate 4 include a plurality of types of positive electrode tabs 40a having different protruding lengths and widths at the base ends. Specifically, the protruding length of the positive electrode tab 40a gradually increases toward the second rear side wall 1e side (one side in the thickness direction of the electrode body 3). Therefore, among all the positive electrode tabs 40a, the protruding length L2 of the positive electrode tab 40a that protrudes most from the second rear side wall 1e side is longer than the protruding length L1 of the positive electrode tab 40a that protrudes most from the second front side wall 1d side (the other side in the thickness direction of the electrode body 3). In FIGS. 4 and 5, the positive electrode tab 40a that protrudes most from the second rear side wall 1e side among all the positive electrode tabs 40a is denoted by reference numeral 401a, and the positive electrode tab 40a that protrudes most from the second front side wall 1d side among all the positive electrode tabs 40a is denoted by reference numeral 402a. Also, the width TW of the base end of the positive electrode tab 40a increases as the protruding length of the positive electrode tab 40a is longer. The protruding length L1 of the positive electrode tab 40a with the shortest protruding length, that is, the positive electrode tab 402a located closest to the second front side wall 1d side, is set to 12 mm, and the protruding length L2 of the positive electrode tab 401a with the longest protruding length, that is, the positive electrode tab 40a located closest to the second rear side wall 1e side, is set to 21 mm.

[0015] Near the tips of all the positive electrode tabs 40a, their plate surfaces are connected to each other by welding in substantially the same direction to form a connection portion 63. In the present embodiment, a portion slightly separated from the tips of all the positive electrode tabs 40a forms the connection portion 63, but the tips of all the positive electrode tabs 40a may form the connection portion 63.

[0016] The positive electrode plate 4 has regions where positive electrode active material layers 4a are formed on both sides of the positive electrode core. The positive electrode tab 40a consists of an exposed portion of the positive electrode core. A positive electrode protective layer 4b with lower conductivity than the positive electrode active material layer 4a is provided at the root of the positive electrode tab 40a. The positive electrode protective layer 4b can be a resin insulating layer, a layer containing ceramic and a resin binder, etc. Also, the positive electrode protective layer 4b may contain a conductive material such as a carbon material. Note that the positive electrode protective layer 4b may not be provided.

[0017] On the edge of the negative electrode plate 5 of the electrode body 3 on the other side (the side opposite to the positive electrode tab 40a) in the winding axis direction, two negative electrode tabs 50a as current collecting tabs are provided protruding for each circumference. These negative electrode tabs 50a have a shape that is symmetric with respect to the positive electrode tab 40a about the cross-section at the center in the winding axis direction of the electrode body 3. Therefore, the plurality of negative electrode tabs 50a protruding from the negative electrode plate 5 include a plurality of types of negative electrode tabs 50a with different protruding lengths and widths at the base ends. These plurality of negative electrode tabs 50a are laminated to form a negative electrode tab group 50.

[0018] The negative electrode plate 5 has regions where negative electrode active material layers are formed on both sides of the negative electrode core. The negative electrode tab 50a consists of an exposed portion of the negative electrode core.

[0019] A positive electrode terminal 8 and a negative electrode terminal 9 as electrode terminals are attached to the sealing plate 2. The positive electrode terminal 8 is electrically connected to the positive electrode tab group 40 via the positive electrode current collector 6. The positive electrode current collector 6 is composed of one first positive electrode current collector 61 and three second positive electrode current collectors 62. The three second positive electrode current collectors 62 correspond to each electrode body 3 respectively. The negative electrode terminal 9 is electrically connected to the negative electrode tab group 50 via the negative electrode current collector 7. The negative electrode current collector 7 is composed of one first negative electrode current collector 71 having the same shape as the first positive electrode current collector 61 and three second negative electrode current collectors 72 having the same shape as the second positive electrode current collectors 62. The three second negative electrode current collectors 72 correspond to each electrode body 3 respectively.

[0020] The first positive electrode current collector 61 has a substantially L-shaped cross-section and is disposed between the electrode body 3 and the sealing plate 2. The first positive electrode current collector 61 is connected to the positive electrode terminal 8.

[0021] The second positive current collector 62 is disposed between the electrode body 3 and the first side wall 1b of the rectangular exterior body 1. Specifically, the second positive current collector 62 has a substantially flat plate shape parallel to the first side wall 1b and extends along the first side wall 1b toward the bottom 1a side. The second positive current collector 62 is connected to the first positive current collector 61.

[0022] As shown in FIG. 3, the second positive current collector 62 has a current collector connection portion 62a, an inclined portion 62b, and a tab joint portion 62c. The current collector connection portion 62a is connected to the first positive current collector 61. The positive tab group 40 is connected to the tab joint portion 62c. The inclined portion 62b connects the current collector connection portion 62a and the tab joint portion 62c such that the current collector connection portion 62a is located on the inner side in the winding axis direction of the electrode body 3 than the tab joint portion 62c, and is inclined with respect to both of them. A step is formed between the current collector connection portion 62a and the tab joint portion 62c by the inclined portion 62b. The current collector connection portion 62a and the tab joint portion 62c have their plate surfaces facing the winding axis direction of the electrode body 3. As shown in FIG. 6, the width W1 in the thickness direction of the electrode body 3 of the tab joint portion 62c of the second positive current collector 62 is set to 10 mm.

[0023] A recess 62d is provided in the current collector connection portion 62a. The portion where the recess 62d is provided is thinner than its surroundings. A through hole 62e is provided in the recess 62d. In the recess 62d, the current collector connection portion 62a is joined to the first positive current collector 61.

[0024] Similar to the second positive current collector 62, the second negative current collector 72 has a current collector connection portion 72a, an inclined portion 72b, and a tab joint portion 72c as shown in FIG. 9. A recess 72d and a through hole 72e are provided in the current collector connection portion 72a.

[0025] The first negative current collector 71 and the second negative current collector 72 are arranged to be symmetric with respect to the first positive current collector 61 and the second positive current collector 62 about the cross section at the center in the winding axis direction of the electrode body 3.

[0026] As shown in FIG. 6, the interval DI1 in the winding axis direction of the electrode body 3 and the tab joint portion 62c of the second positive current collector 62 is set to 5.0 mm which is 1 / 2 or less of the thickness TH of the electrode body 3.

[0027] As shown in FIG. 6, the tip region including the connection portion 63 of all the positive tabs 40a configured as described above is bent toward the second rear wall 1e side (one side in the thickness direction of the electrode body 3) so that its plate surface faces in the plate thickness direction of the tab joint portion 62c of the second positive current collector 62. That is, the tips of all the positive tabs 40a constituting the connection portion 63 face the second rear wall 1e side. Also, the connection portion 63 is welded to the surface on the electrode body 3 side of the tab joint portion 62c of the second positive current collector 62. The width W2 in the thickness direction of the electrode body 3 of the connection portion 63 is set to 3.0 mm.

[0028] The tips of all the positive tabs 40a constituting the connection portion 63 overlap the tab joint portion 62c in the plate thickness direction of the tab joint portion 62c. That is, the tips of all the positive tabs 40a do not protrude from the tab joint portion 62c in the plate thickness direction of the tab joint portion 62c. Also, among the tips of all the positive tabs 40a constituting the connection portion 63, the displacement in the thickness direction of the electrode body 3 between the tip located most on one side in the thickness direction of the electrode body 3 and the tip located most on the other side in the thickness direction of the electrode body 3 is 2.0 mm or less. It is preferable that the positions of the tips of all the positive tabs 40a in the thickness direction of the electrode body 3 coincide.

[0029] Also, the connection portion 63 is located closer to the second front wall 1d (the other side in the thickness direction of the electrode body 3) than the center in the thickness direction of the electrode body 3.

[0030] The negative tab group 50 is also welded to the second negative current collector 72 in the same manner as the positive tab group 40.

[0031] In FIG. 2, reference numeral 10 denotes an external insulating member disposed between the sealing plate 2 and the positive electrode terminal 8. Reference numeral 11 denotes an internal insulating member disposed between the sealing plate 2 and the first positive electrode current collector 61. Reference numeral 12 denotes an external insulating member disposed between the sealing plate 2 and the negative electrode terminal 9. Reference numeral 13 denotes an internal insulating member disposed between the sealing plate 2 and the first negative electrode current collector 71. Reference numeral 14 denotes a box-shaped or bag-shaped insulating sheet disposed inside the rectangular exterior body 1 and accommodating the electrode body 3. Reference numeral 15 denotes an electrolyte injection hole provided in the sealing plate 2. Reference numeral 16 denotes a sealing member for sealing the electrolyte injection hole 15. Reference numeral 17 denotes a gas discharge valve provided in the sealing plate 2.

[0032] Next, a method for manufacturing the non-aqueous electrolyte secondary battery 20 and details of each component will be described.

[0033] [Attachment of Terminals and First Current Collectors to the Sealing Plate] The sealing plate 2 has a positive electrode terminal attachment hole near one end and a negative electrode terminal attachment hole near the other end. The external insulating member 10 is disposed on the outer surface side around the positive electrode terminal attachment hole of the sealing plate 2, and the internal insulating member 11 and the first positive electrode current collector 61 are disposed on the inner surface side around the positive electrode terminal attachment hole of the sealing plate 2. Then, the positive electrode terminal 8 is inserted from the outside of the battery through the through hole of the external insulating member 10, the positive electrode terminal attachment hole of the sealing plate 2, the through hole of the internal insulating member 11, and the through hole of the first positive electrode current collector 61, and the positive electrode terminal 8 is caulked onto the first positive electrode current collector 61. Further, it is more preferable to weld the caulked portion of the positive electrode terminal 8 to the first positive electrode current collector 61.

[0034] The external insulating member 12 is disposed on the outer surface side around the negative electrode terminal attachment hole of the sealing plate 2, and the internal insulating member 13 and the first negative electrode current collector 71 are disposed on the inner surface side around the negative electrode terminal attachment hole of the sealing plate 2. Then, the negative electrode terminal 9 is inserted from the outside of the battery through the through hole of the external insulating member 12, the negative electrode terminal attachment hole of the sealing plate 2, the through hole of the internal insulating member 13, and the through hole of the first negative electrode current collector 71, and the negative electrode terminal 9 is caulked onto the first negative electrode current collector 71. Further, it is more preferable to weld the caulked portion of the negative electrode terminal 9 to the first negative electrode current collector 71.

[0035] FIGS. 7A and 7B are perspective views of the sealing plate 2 to which the positive electrode terminal 8, the first positive electrode current collector 61, the negative electrode terminal 9, and the first negative electrode current collector 71 are attached. FIG. 7A shows the outside of the battery, and FIG. 7B shows the inside of the battery.

[0036] The first positive electrode current collector 61 has a first region 61a arranged along the sealing plate 2 and a second region 61b bent from an end of the first region 61a. In the state of the non-aqueous electrolyte secondary battery 20, the first region 61a is arranged between the sealing plate 2 and the electrode body 3. The second region 61b extends from the first region 61a toward the bottom 1a of the rectangular exterior body 1. The second region 61b is arranged between the first side wall 1b of the rectangular exterior body 1 and the electrode body 3.

[0037] The first negative electrode current collector 71 has a first region 71a arranged along the sealing plate 2 and a second region 71b bent from an end of the first region 71a. In the state of the non-aqueous electrolyte secondary battery 20, the first region 71a is arranged between the sealing plate 2 and the electrode body 3. The second region 71b extends from the first region 71a toward the bottom 1a of the rectangular exterior body 1. The second region 71b is arranged between the first side wall 1c of the rectangular exterior body 1 and the electrode body 3.

[0038] In the second region 61b of the first positive electrode current collector 61, it is preferable to provide cutout portions 61c at both ends in the width direction. When connecting the second positive electrode current collector 62 described later to the second region 61b, by gripping the cutout portions 61c, welding can be performed more stably, and a higher-quality connection portion can be formed stably. The cutout portions 61c are preferably arranged on the bottom 1a side of the rectangular exterior body 1 from the inner side insulating member 11 in the second region 61b. The cutout portions 61c are preferably provided near the end on the first region 61a side in the second region 61b. Note that it is also preferable to provide cutout portions 71c at both ends in the width direction for the second region 71b of the first negative electrode current collector 71. When the inner side insulating member 11 has a wall portion covering a part of the second region 61b, the cutout portions 61c preferably have a region not covered by the wall portion of the inner side insulating member 11.

[0039] The positive electrode terminal 8 and the first positive electrode current collector 61 are preferably made of metal, and more preferably made of aluminum. The negative electrode terminal 9 and the first negative electrode current collector 71 are preferably made of metal, and more preferably made of copper. Note that the negative electrode terminal 9 can include a region made of aluminum and a region made of copper. In this case, it is preferable to connect the region made of copper to the first negative electrode current collector 71 made of copper and expose the region made of aluminum to the outside of the battery.

[0040] [Positive electrode plate] First, the manufacturing method of the positive electrode plate will be described.

[0041] [Preparation of positive electrode active material layer slurry] A lithium nickel cobalt manganese composite oxide as a positive electrode active material, polyvinylidene fluoride (PVdF) as a binder, a carbon material as a conductive material, and N-methyl-2-pyrrolidone (NMP) as a dispersion medium are kneaded so that the mass ratio of lithium nickel cobalt manganese composite oxide:PVdF:carbon material is 97.5:1:1.5 to prepare a positive electrode active material layer slurry.

[0042] [Preparation of positive electrode protective layer slurry] Alumina powder, a carbon material as a conductive material, polyvinylidene fluoride (PVdF) as a binder, and N-methyl-2-pyrrolidone (NMP) as a dispersion medium are kneaded so that the mass ratio of alumina powder:carbon material:PVdF is 83:3:14 to prepare a protective layer slurry.

[0043] [Formation of positive electrode active material layer and positive electrode protective layer] The positive electrode active material layer slurry and the positive electrode protective layer slurry prepared by the above method are applied to both sides of an aluminum foil as a positive electrode core by a die coater. At this time, the positive electrode active material layer slurry is applied to the center in the width direction of the positive electrode core. Also, the positive electrode protective layer slurry is applied to the end in the width direction of the region where the positive electrode active material layer slurry is applied.

[0044] The positive electrode core body coated with the positive electrode active material layer slurry and the positive electrode protective layer slurry is dried to remove NMP contained in the positive electrode active material layer slurry and the positive electrode protective layer slurry. Thereby, the positive electrode active material layer and the positive electrode protective layer are formed. Then, the positive electrode active material layer is compressed to obtain a positive electrode raw plate. This positive electrode raw plate is cut into a predetermined shape to obtain a positive electrode plate 4. Note that the cutting of the positive electrode raw plate can be performed by irradiation with an energy beam such as a laser, a mold, or a cutter.

[0045] [Negative electrode plate] Next, a method for manufacturing a negative electrode plate will be described.

[0046] [Preparation of negative electrode active material layer slurry] Graphite as a negative electrode active material, styrene-butadiene rubber (SBR) and carboxymethyl cellulose (CMC) as binders, and water as a dispersion medium are kneaded so that the mass ratio of graphite:SBR:CMC is 98:1:1 to prepare a negative electrode active material layer slurry.

[0047] [Formation of negative electrode active material layer] The negative electrode active material layer slurry prepared by the above method is applied to both sides of a copper foil as a negative electrode core body by a die coater.

[0048] The negative electrode core body coated with the negative electrode active material layer slurry is dried to remove water contained in the negative electrode active material layer slurry. Thereby, the negative electrode active material layer is formed. Then, the negative electrode active material layer is compressed to obtain a negative electrode raw plate. This negative electrode raw plate is cut into a predetermined shape to obtain a negative electrode plate 5. Note that the cutting of the negative electrode raw plate can be performed by irradiation with an energy beam such as a laser, a mold, or a cutter.

[0049] [Manufacture of electrode body] The strip-shaped positive electrode plate 4 and the strip-shaped negative electrode plate 5 manufactured by the above method are wound through a strip-shaped separator SP made of polyolefin to manufacture a flat wound type electrode body 3. The electrode body 3 has a flat region in the center and curved portions at both ends of the flat region.

[0050] At one end in the direction in which the winding axis of the electrode body 3 extends, a positive electrode tab group 40 in which a plurality of positive electrode tabs 40a are stacked is provided. At the other end in the direction in which the winding axis of the electrode body 3 extends, a negative electrode tab group 50 in which a plurality of negative electrode tabs 50a are stacked is provided. Note that, in a direction perpendicular to the direction in which the winding axis of the electrode body 3 extends and in a direction perpendicular to the thickness direction of the electrode body 3, the center of the positive electrode tab group 40 and the center of the negative electrode tab group 50 are displaced to one side from the winding axis.

[0051] Note that, by forming the shape of the positive electrode tab 40a and / or the negative electrode tab 50a in a plan view such that the width gradually increases from the tip toward the root, it is possible to make it difficult to damage the positive electrode tab 40a and / or the negative electrode tab 50a even when an impact or vibration is applied to the non-aqueous electrolyte secondary battery 20. Further, it is more effective to form the corner portion of the root portion into an R shape.

[0052] Note that, by providing the positive electrode protective layer 4b at the root portion of the positive electrode tab 40a as described above, damage to the positive electrode tab 40a can be suppressed. Further, by providing a negative electrode active material layer at the root portion of the negative electrode tab 50a, damage to the negative electrode tab 50a can be suppressed.

[0053] [Connection between the first current collector and the tab group] To manufacture the non-aqueous electrolyte secondary battery 20 configured as described above, as shown in FIG. 8, with the tip regions of all the positive electrode tabs 40a overlapped with the tab joint portion 62c of the second positive electrode current collector 62, a welding jig T is applied at a position slightly below the tips of all the positive electrode tabs 40a to perform welding, thereby joining all the positive electrode tabs 40a to each other and welding them to the second positive electrode current collector 62. As a result, a portion slightly below the tips of all the positive electrode tabs 40a constitutes the connection portion 63. Note that the connection portion 63 may be formed at the tip portions of all the positive electrode tabs 40a by applying the welding jig T to the tip portions of all the positive electrode tabs 40a and performing welding. At this time, as also shown in FIG. 9, the tab joint portion 62c of the second positive electrode current collector 62 has its plate surface directed in the thickness direction of the electrode body 3. Also, the tip regions of all the positive electrode tabs 40a have their plate surfaces directed in the thickness direction of the electrode body 3 and are overlapped in a state where they are shifted toward the side of the positive electrode tab 40a with the shortest protruding length (one end side in the thickness direction of the electrode body 3). Also, at this time, the distance DI2 between the electrode body 3 and the tab joint portion 62c of the second positive electrode current collector 62 is set to 6 mm, and all the positive electrode tabs 40a are bent.

[0054] At this time, in the tab joint portion 62c of the second positive electrode current collector 62, it is preferable that the connection portion 63 be arranged closer to the root side (the left side in FIG. 8) of the positive electrode tab group 40 in the width direction of the tab joint portion 62c (the left-right direction in FIG. 8). With such a configuration, when the positive electrode tab group 40 is bent, a stable curved shape can be more reliably formed in the vicinity of the root of the positive electrode tab group 40. Thereby, damage to the positive electrode tab group 40 can be suppressed. Also, even if there is a displacement in the positive electrode tab 40a, the positive electrode tab group 40 and the tab joint portion 62c can be stably joined.

[0055] Also, it is preferable that the lower end portion of the second positive electrode current collector 62 (the portion that becomes the end portion on the bottom 1a side of the rectangular exterior body 1) be located below the lower end portion of the positive electrode tab group 40 (the portion that becomes the end portion on the bottom 1a side of the rectangular exterior body 1). With such a configuration, in the process of bending the positive electrode tab group 40 described later, it becomes possible to more reliably and stably bend the positive electrode tab group 40.

[0056] From this state, as shown in FIG. 6, the tip regions of all the positive electrode tabs 40a are bent with their plate surfaces facing in the substantially winding axis direction of the electrode body 3 (for example, in a state where the inclination of the tab joint portion 62c with respect to the winding axis is less than ±15°). As a result, the tab joint portion 62c of the second positive electrode current collector 62 is in a state where its plate surface faces in the substantially winding axis direction of the electrode body 3. In this way, the positive electrode tab group 40 can be bent without bending the second positive electrode current collector 62.

[0057] The negative electrode tab 50a is also attached to the second negative electrode current collector 72 in the same manner as the positive electrode tab 40a.

[0058] [Electrode body group] As shown in FIG. 3, a plurality of electrode bodies 3 in a state where the positive electrode tab group 40 and the negative electrode tab group 50 are each bent are stacked and fixed by an electrode body fixing means such as a tape. Each positive electrode tab group 40 is arranged on the same side, and each negative electrode tab group 50 is arranged on the same side. Also, in each electrode body 3, the positive electrode tab groups 40 are each bent in the same direction. In each electrode body 3, the negative electrode tab groups 50 are each bent in the same direction.

[0059] In the stacking direction of the electrode bodies 3, the second positive electrode current collectors 62 attached to each electrode body 3 are arranged at intervals and connected on the second region 61b of the first positive electrode current collector 61. The same applies to each second negative electrode current collector 72.

[0060] [Connection between the first current collector and the second current collector] The second region 61b of the first positive current collector 61 is disposed inside the current collector connection portion 62a of the second positive current collector 62, and the second region 71b of the first negative current collector 71 is disposed inside the current collector connection portion 72a of the second negative current collector 72. Then, the second region 61b of the first positive current collector 61 and the current collector connection portion 62a of the second positive current collector 62 are joined. Also, the second region 71b of the first negative current collector 71 is joined to the current collector connection portion 72a of the second negative current collector 72. As the joining method, ultrasonic welding (ultrasonic bonding), resistance welding, welding by irradiation with high energy rays such as a laser, or the like can be used. In particular, it is preferable to use welding by irradiation with high energy rays such as a laser.

[0061] FIGS. 10A to 10C are cross-sectional views along the winding axis of the electrode body 3 of the second region 61b of the first positive current collector 61, the second region 71b of the first negative current collector 71, the current collector connection portion 62a of the second positive current collector 62, and the current collector connection portion 72a of the second negative current collector 72 at each stage.

[0062] As shown in FIG. 10A, the second region 61b of the first positive current collector 61 and the second region 71b of the first negative current collector 71 are disposed between the current collector connection portion 62a of the second positive current collector 62 and the current collector connection portion 72a of the second negative current collector 72. At this time, the distance D1 between the inner surfaces of the current collector connection portion 62a and the current collector connection portion 72a is preferably larger than the distance D2 between the outer surfaces of the second region 61b and the second region 71b. Note that D1 is preferably 0.1 to 5 mm larger than D2, and more preferably 0.2 to 3 mm larger.

[0063] Next, as shown in FIG. 10B, the current collector connection portion 62a and / or the current collector connection portion 72a is displaced inward so that the distance between the current collector connection portion 62a and the current collector connection portion 72a becomes smaller. Thereby, the distance D1 between the inner surfaces of the current collector connection portion 62a and the current collector connection portion 72a is changed to D1'. At this time, the difference between D2 and D1' is preferably 0 to 0.2 mm.

[0064] In the state shown in FIG. 10B, a high-energy beam such as a laser is irradiated onto each of the current collector connection portions 62a and 72a. As a result, the second region 61b of the first positive current collector 61 and the current collector connection portion 62a of the second positive current collector 62 are joined by welding, and the second region 71b of the first negative current collector 71 and the current collector connection portion 72a of the second negative current collector 72 are joined by welding.

[0065] As shown in FIG. 10C, a joint portion 64, which is a welded portion of the second region 61b and the current collector connection portion 62a, is formed within the recess 62d. Further, a joint portion 74, which is a welded portion of the second region 71b and the current collector connection portion 72a, is formed within the recess 72d.

[0066] By following the procedures of FIGS. 10A to 10C, the first positive current collector 61 and the second positive current collector 62, and the first negative current collector 71 and the second negative current collector 72 can be welded more stably in a simpler method. Therefore, highly reliable joint portions 64 and 74 can be formed.

[0067] The portions where the recesses 62d and 72d are formed are thinner than their surroundings. By performing welding so that the joint portions 64 and 74 are formed in these thinner portions, higher-quality joint portions can be formed more stably. Therefore, a secondary battery with higher reliability is obtained. Further, by using the through-hole 62e to measure the presence or absence or the size of the gap between the second region 61b and the current collector connection portion 62a, the second region 61b and the current collector connection portion 62a can be joined by welding more stably. The same applies to the through-hole 72e.

[0068] FIG. 3 is a perspective view showing the state after the first positive current collector 61 and the second positive current collector 62, and the first negative current collector 71 and the second negative current collector 72 are connected respectively.

[0069] [Electrode body holder] FIG. 11 is a developed view of the electrode body holder 14. In FIG. 11, the insulating sheet constituting the electrode body holder 14 is bent at the dashed line portions to form a box-shaped electrode body holder 14. The electrode body holder 14 has a holder bottom portion 14a, a holder first main surface 14b, a holder second main surface 14c, a holder first side surface 14d, a holder second side surface 14e, a holder third side surface 14f, a holder fourth side surface 14g, a holder fifth side surface 14h, and a holder sixth side surface 14i.

[0070] When the electrode body holder 14 is box-shaped, it has a region where the holder first side surface 14d, the holder second side surface 14e, and the holder third side surface 14f overlap, and a region where the holder fourth side surface 14g, the holder fifth side surface 14h, and the holder sixth side surface 14i overlap.

[0071] With the three electrode bodies 3 arranged in the box-shaped electrode body holder 14, these three electrode bodies 3 are inserted into the rectangular exterior body 1. Then, the sealing plate 2 is joined to the rectangular exterior body 1, and the opening of the rectangular exterior body 1 is sealed with the sealing plate 2. Electrolyte is injected through the electrolyte injection hole 15 provided in the sealing plate 2, and the electrolyte injection hole 15 is sealed with the sealing member 16. Thereby, a non-aqueous electrolyte secondary battery 20 is obtained.

[0072] Therefore, according to the present embodiment, since two positive electrode tabs 40a are provided on each circumference of the positive electrode plate 4, compared with the case where only one positive electrode tab 40a is provided on each circumference of the positive electrode plate 4, the variation in the distance from each part in the positive electrode plate 4 to the positive electrode tab 40a is reduced, and the potential difference in the positive electrode plate 4 can be reduced. Therefore, deterioration of the positive electrode plate 4 can be suppressed, and the durability of the non-aqueous electrolyte secondary battery 20 can be enhanced.

[0073] Also, compared with the case where only one positive electrode tab 40a is provided on each circumference of the positive electrode plate 4, the current collection resistance of the positive electrode plate 4 can be reduced, so the output current of the non-aqueous electrolyte secondary battery 20 can be increased.

[0074] Similarly, since two negative electrode tabs 50a are provided on each circumference of the negative electrode plate 5, the variation in the distance from each part within the negative electrode plate 5 to the negative electrode tab 50a is reduced compared to the case where only one negative electrode tab 50a is provided on each circumference of the negative electrode plate 5, and the potential difference within the negative electrode plate 5 can be reduced. Therefore, deterioration of the negative electrode plate 5 can be suppressed, and the durability of the non-aqueous electrolyte secondary battery 20 can be enhanced.

[0075] Also, since the current collecting resistance of the negative electrode plate 5 can be reduced compared to the case where only one negative electrode tab 50a is provided on each circumference of the negative electrode plate 5, the output current of the non-aqueous electrolyte secondary battery 20 can be increased.

[0076] Further, since the tips of all the positive electrode tabs 40a constituting the connection portion 63 are overlapped with the tab joint portion 62c in the plate thickness direction of the tab joint portion 62c, it is possible to prevent the tips of the positive electrode tabs 40a from protruding from the tab joint portion 62c and contacting the adjacent electrode body 3. Also, since it is not necessary to provide a restricting member such as a tape to restrict the portion of the positive electrode tab 40a protruding from the tab joint portion 62c from contacting the adjacent electrode body 3, the number of parts can be reduced and the labor of assembling the restricting member can be eliminated compared to the case where the restricting member is provided.

[0077] Moreover, the displacement in the thickness direction of the electrode body 3 between the tip located on one side in the thickness direction of the electrode body 3 and the tip located on the other side in the thickness direction of the electrode body 3 among the tips of all the positive electrode tabs 40a constituting the connection portion 63 is set to 2.0 mm or less. Thus, compared to the case where the displacement exceeds 2.0 mm, the welding operation for welding the positive electrode tab 40a to the second positive electrode current collector 62 becomes easier. Similarly, the welding operation for welding the negative electrode tab 50a to the second negative electrode current collector 72 also becomes easier.

[0078] Also, among all the positive electrode tabs 40a that make up the connection portion 63, the protruding length L2 of the positive electrode tab 40a that protrudes the most from the second rear side wall 1e side is made longer than the protruding length L1 of the positive electrode tab 40a that protrudes the most from the second front side wall 1d side. Therefore, even if the connection portion 63 is arranged closer to the second front side wall 1d than the center in the thickness direction of the electrode body 3, the deviation in the thickness direction of the electrode body 3 between the tip of the positive electrode tab 40a that protrudes the most from the second rear side wall 1e side and the tip of the positive electrode tab 40a that protrudes the most from the second front side wall 1d side can be reduced. The same effect can be obtained for the negative electrode tab 50a.

[0079] Also, since the protruding length of the positive electrode tab 40a that makes up the connection portion 63 is gradually increased toward the second rear side wall 1e side, even if the connection portion 63 is arranged closer to the second front side wall 1d of the electrode body 3 than the center in the thickness direction of the electrode body 3, the deviation in the thickness direction of the electrode body 3 at the tips of all the positive electrode tabs 40a can be reduced. The same effect can be obtained for the negative electrode tab 50a.

[0080] Also, since the width TW of the base end of the positive electrode tab 40a that makes up the connection portion 63 is made larger as the positive electrode tab 40a with a longer protruding length, compared to the case where the widths TW of the base ends of the positive electrode tabs 40a are made equal to each other, the resistance of the positive electrode tab 40a with a longer protruding length is not increased, and the current flowing through the positive electrode tab 40a can be made uniform regardless of the protruding length. The same effect can be obtained for the negative electrode tab 50a.

[0081] Also, since the positive current collector 6 is configured to include a first positive current collector 61 and a second positive current collector 62, when bending the positive electrode tab group 40, the positive electrode tab group 40 can be bent without bending the positive current collector 6, and a secondary battery with a higher volumetric energy density can be made more simply and stably. Even when the number of electrode bodies 3 housed in the battery case 100 is more than two, a highly reliable secondary battery can be stably manufactured without making the positive current collector 6 have a complicated shape. Therefore, the degree of freedom regarding the number of electrode bodies 3 housed in the battery case 100 is improved.

[0082] Further, the tab joint portion 62c of the second positive electrode current collector 62 is disposed closer to the first side wall 1b of the rectangular exterior body 1 than the current collector connection portion 62a of the second positive electrode current collector 62. With such a configuration, the space between the first side wall 1b and the electrode body 3 can be utilized more effectively, so that the power generation portion of the electrode body 3 can be made larger, resulting in a secondary battery with a higher volume energy density. The same applies to the second negative electrode current collector 72.

[0083] In the electrode body 3, it is preferable that the positive electrode tab group 40 is closer to the sealing plate 2 side. This can shorten the conductive path from the positive electrode tab group 40 to the positive electrode terminal 8, resulting in a non-aqueous electrolyte secondary battery 20 with a small internal resistance. In the electrode body 3, it is preferable that the negative electrode tab group 50 is closer to the sealing plate 2 side. This can shorten the conductive path from the negative electrode tab group 50 to the negative electrode terminal 9, resulting in a non-aqueous electrolyte secondary battery 20 with a small internal resistance.

[0084] It is preferable to dispose an insulating member different from the electrode body holder 14 between the overlapping region of the second region 61b of the first positive electrode current collector 61 and the current collector connection portion 62a of the second positive electrode current collector 62 and the first side wall 1b of the rectangular exterior body 1. Also, it is preferable to dispose an insulating member different from the electrode body holder 14 between the overlapping region of the second region 71b of the first negative electrode current collector 71 and the current collector connection portion 72a of the second negative electrode current collector 72 and the first side wall 1c of the rectangular exterior body 1. With such a configuration, even when an impact or vibration is applied to the non-aqueous electrolyte secondary battery 20, damage to the joint portions between the members, the positive electrode tab group 40, or the negative electrode tab group 50 can be suppressed.

[0085] (Other Embodiments) The above-described embodiments are examples of the present invention, and the present invention is not limited to these examples. Well-known techniques, conventional techniques, or known techniques may be combined with or partially replaced in these examples. Also, modified inventions that can be easily conceived by those skilled in the art are included in the present invention.

[0086] In the above-described embodiment, the present invention is applied to the non-aqueous electrolyte secondary battery 20 including three electrode bodies 3. However, the present invention can also be applied to a non-aqueous electrolyte secondary battery 20 including a plurality of electrode bodies 3 other than three or only one electrode body 3.

[0087] In the above-described embodiment, two positive electrode tabs 40a are provided at each edge in the winding axis direction of one end of the positive electrode plate 4 of the electrode body 3 for each turn. However, at least two positive electrode tabs 40a may be provided for each turn, and three or more positive electrode tabs 40a may be provided for each turn. Similarly, at least two negative electrode tabs 50a may be provided at each edge in the other direction (the side opposite to the positive electrode tabs 40a) of the winding axis direction of the negative electrode plate 5 for each turn, and three or more negative electrode tabs 50a may be provided for each turn.

[0088] In the above-described embodiment, the plurality of positive electrode tabs 40a protruding from the positive electrode plate 4 include a plurality of types of positive electrode tabs 40a having different protruding lengths and widths of the base ends. However, the plurality of positive electrode tabs 40a protruding from the positive electrode plate 4 may include a plurality of types of positive electrode tabs 40a in which only one of the protruding length and the width of the base end is different from each other. For example, the widths of the base ends of all the positive electrode tabs 40a may be the same. Similarly, the plurality of negative electrode tabs 50a protruding from the negative electrode plate 5 may include a plurality of types of negative electrode tabs 50a in which only one of the protruding length and the width of the base end is different from each other.

Explanation of Reference Numerals

[0089] 1 Square outer package 1b, 1c First side wall 2 Sealing plate 3 Electrode body 4 Positive electrode plate 5 Negative electrode plate 8 Positive electrode terminal 9 Negative electrode terminal 20 Non-aqueous electrolyte secondary battery 40a Positive electrode tab (current collecting tab) 50a Negative electrode tab (current collecting tab) 61 First positive current collector 61a First region 61b Second region 62 Second positive current collector 62c Tab joint portion 63 Connection part 71 First negative electrode current collector 71a First region 71b Second region 72 Second negative electrode current collector 72c Tab joint SP Separator L1, L2 Protrusion length DI1 Interval TH Thickness TW Width

Claims

A secondary battery comprising an electrode body in which a strip-shaped positive electrode plate and a strip-shaped negative electrode plate are wound with a strip-shaped separator interposed therebetween, an exterior body having an opening and a pair of side walls arranged to face each other, a sealing plate for sealing the opening, and further comprising a terminal attached to the sealing plate, at least two current collecting tabs are provided projecting from each circumference at one edge of the positive electrode plate in the winding axis direction of the electrode body and at the other edge of the negative electrode plate in the winding axis direction, the plurality of current collecting tabs projecting from the positive electrode plate include a plurality of types of current collecting tabs at least one of the projecting length and the width of the base end of which is different from each other, the plurality of current collecting tabs projecting from the negative electrode plate include a plurality of types of current collecting tabs at least one of the projecting length and the width of the base end of which is different from each other, the electrode body has a flat shape and is accommodated in the exterior body with its winding axis direction perpendicular to the side walls, the current collecting tabs and the terminal are electrically connected by a first current collector and a second current collector, the first current collector includes a first region disposed between the sealing plate and the electrode body and a second region bent from an end of the first region and disposed between one of the side walls and the electrode body, the second current collector has a plate-shaped tab joint portion with its plate surface facing the winding axis direction of the electrode body, the tips or the vicinity of the tips of the plurality of current collecting tabs are joined to each other with their plate surfaces facing in substantially the same direction, and a connection portion welded to the surface on the electrode body side of the tab joint portion of the second current collector is formed, the tip region including the connection portions of the plurality of current collecting tabs is bent in one direction in the thickness direction of the electrode body so that its plate surface faces in the plate thickness direction of the tab joint portion of the second current collector, the tips of all the current collecting tabs constituting the connection portion overlap the tab joint portion and the plate thickness direction of the tab joint portion, the second current collector is welded to the second region of the first current collector. A secondary battery characterized by this.

2. In the secondary battery according to claim 1, the displacement in the thickness direction of the electrode body between the tip located most on one side in the thickness direction of the electrode body and the tip located most on the other side in the thickness direction of the electrode body among the tips of all the current collecting tabs constituting the connection portion is 2.0 mm or less. A secondary battery characterized by this.

3. In the secondary battery according to claim 1 or 2, Among all the current collecting tabs constituting the connection part, the protruding length of the current collecting tab that protrudes the most from one side in the thickness direction of the electrode body is longer than the protruding length of the current collecting tab that protrudes the most from the other side in the thickness direction of the electrode body among all the current collecting tabs constituting the connection part. The secondary battery is characterized in that the connection part is located closer to the other side in the thickness direction of the electrode body than the center in the thickness direction of the electrode body.

4. In the secondary battery according to claim 3, The secondary battery is characterized in that the protruding length of the current collecting tab constituting the connection part gradually increases toward one side in the thickness direction of the electrode body.

5. In the secondary battery according to claim 3 or 4, The secondary battery is characterized in that the width of the base end of the current collecting tab constituting the connection part is larger as the current collecting tab has a longer protruding length.

6. In the secondary battery according to any one of claims 3 to 5, The secondary battery is characterized in that the interval in the winding axis direction between the electrode body and the tab joint part of the second current collector is set to be 1 / 2 or less of the thickness of the electrode body.

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