Secondary battery and method for producing the same

Abstract

To provide a secondary battery with high volume energy density.SOLUTION: In a secondary battery, an electrode body having a positive electrode tab group at one end terminal unit is accommodated in a battery case. A positive electrode terminal and the positive electrode tab group are electrically connected to each other via a second positive electrode current collector. The positive electrode tab group is connected to a tab connection portion of the second positive electrode current collector in a bent state. A tape as fixing means is attached across a first main surface of the electrode body, a tab connection portion of the second positive electrode current collector, and a second main surface of the electrode body.SELECTED DRAWING: Figure 10

Description

Technical Field

[0001] The present disclosure relates to a secondary battery and a method for manufacturing the same.

Background Art

[0002] In driving power sources such as electric vehicles (EVs) and hybrid electric vehicles (HEVs, PHEVs), secondary batteries such as alkaline secondary batteries and non-aqueous electrolyte secondary batteries are used.

[0003] In these secondary batteries, a battery case is constituted by a bottomed cylindrical exterior body having an opening and a sealing plate that seals the opening. Inside the battery case, an electrode body composed of a positive electrode plate, a negative electrode plate, and a separator is accommodated together with an electrolyte. A positive electrode terminal and a negative electrode terminal are attached to the sealing plate. The positive electrode terminal is electrically connected to the positive electrode plate via a positive electrode current collector, and the negative electrode terminal is electrically connected to the negative electrode plate via a negative electrode current collector.

[0004] As such a secondary battery, there has been proposed a secondary battery having an electrode group in which a positive electrode and a negative electrode are wound with a separator interposed therebetween, current collecting tabs are formed at both ends of the electrode group, and the current collecting tabs are welded to leads in a state of being refracted with respect to the direction in which the winding axis of the electrode group extends (Patent Document 1 below).

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Summary of the Invention

[0006] A secondary battery according to one embodiment of the present disclosure is an electrode body including a positive electrode plate and a negative electrode plate, a rectangular exterior body having an opening and accommodating the electrode body, a sealing plate that seals the opening, and a terminal attached to the sealing plate, and is a secondary battery provided with The electrode body has a positive tab group at one end and a negative tab group at the other end. The electrode body has a first main surface and a second main surface arranged to face each other. The rectangular exterior body has a bottom, a pair of first side walls arranged to face each other, and a pair of second side walls arranged to face each other. The positive tab group is arranged on one of the first side wall sides. The negative tab group is arranged on the other first side wall side. The positive tab group or the negative tab group and the terminal are electrically connected by a current collector. The positive tab group or the negative tab group is connected to the current collector in a bent state. Fixing means is attached across the first main surface - the current collector - the second main surface.

[0007] According to the configuration of the secondary battery according to one embodiment of the present disclosure, a secondary battery having a higher volume energy density and an easily assembled structure is obtained.

[0008] In the width direction of the current collector, the joint portion of the current collector and the positive tab group or the negative tab group can be configured to be eccentric toward the root side of the positive tab group or the negative tab group.

[0009] The positive tab group or the negative tab group can be configured to have a contact region in contact with the current collector, a root region arranged on the root side of the positive tab group or the negative tab group rather than the contact region, and a tip region arranged on the tip side of the positive tab group or the negative tab group rather than the contact region.

[0010] The fixing means can be configured to contact the tip region.

[0011] The fixing means can be a tape.

[0012] The end portion of the fixing means on the sealing plate side is located closer to the sealing plate side than the end portion of the positive tab group or the negative tab group on the sealing plate side. The end portion of the fixing means on the bottom side can be configured to be located closer to the bottom side than the end portion of the positive tab group or the negative tab group on the bottom side.

[0013] The end portion of the current collector on the bottom side can be configured to be located closer to the bottom side than the end portion of the positive tab group or the negative tab group on the bottom side.

[0014] A method for manufacturing a secondary battery according to an embodiment of the present disclosure is as follows. An electrode body including a positive electrode plate and a negative electrode plate, A rectangular exterior body having an opening and accommodating the electrode body, A sealing plate for sealing the opening, Terminals attached to the sealing plate, and includes: The electrode body has a positive tab group at one end and a negative tab group at the other end, The electrode body has a first main surface and a second main surface arranged in opposite directions, The rectangular exterior body has a bottom, a pair of first side walls arranged in opposite directions, and a pair of second side walls arranged in opposite directions, A method for manufacturing a secondary battery, in which the positive tab group or the negative tab group and the terminals are electrically connected by a current collector, and includes: A step of connecting the positive tab group or the negative tab group and the current collector; A step of bending the positive tab group or the negative tab group and changing the direction of the current collector connected to the positive tab group or the negative tab group; A step of fixing the positive tab group or the negative tab group in a bent state by attaching fixing means across the first main surface - the current collector - the second main surface.

[0015] According to the method for manufacturing a secondary battery according to an embodiment of the present disclosure, a secondary battery with a higher volume energy density can be easily manufactured.

[0016] In the width direction of the current collector, the joint portion between the current collector and the positive tab group or the negative tab group can be formed eccentrically toward the root side of the positive tab group or the negative tab group.

[0017] The current collector includes a first current collector and a second current collector. The positive tab group or the negative tab group is connected to the second current collector. A step of connecting the second current collector to which the positive tab group or the negative tab group is connected and to which the fixing means is attached to the first current collector attached to the sealing plate can be included.

[0018] The fixing means can be a tape.

[0019] According to the present disclosure, a secondary battery with a higher volume energy density can be provided.

Brief Description of the Drawings

[0020]

Figure 1

Figure 2

Figure 3A

Figure 3B

Figure 4

Figure 5

Figure 6

Figure 7A

Figure 7B

Figure 8

Figure 9

Figure 10

Figure 11

Figure 12A

Figure 12B

Figure 12C

Figure 13

Figure 14

Figure 15

Figure 16

Figure 17

Figure 18

Embodiment for Carrying Out the Invention

[0021] The configuration of the secondary battery 20 according to the embodiment will be described below. Note that the present disclosure is not limited to the following embodiments.

[0022] As shown in FIGS. 1 and 2, the 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 has a bottom 1a, a pair of first side walls 1b and 1c, and a pair of second side walls 1d and 1e. The pair of first side walls 1b and 1c are arranged facing each other, and the pair of second side walls 1d and 1e are arranged facing each other. The area of the pair of first side walls 1b and 1c is smaller than the area of the pair of second side walls 1d and 1e. The rectangular outer case 1 and the sealing plate 2 are preferably each made of metal, and more preferably made of aluminum or iron. Inside the rectangular outer case 1, an electrode body 3 including a positive electrode plate 4 and a negative electrode plate 5 is accommodated together with an electrolyte. The electrode body 3 according to the embodiment is a flat wound electrode body in which a strip-shaped positive electrode plate 4 and a strip-shaped negative electrode plate 5 are wound via a strip-shaped separator. In the electrode body 3, a positive electrode tab group 40 is provided at one end in the direction in which the winding axis extends, and a negative electrode tab group 50 is provided at the other end in the direction in which the winding axis extends.

[0023] A positive electrode terminal 8 and a negative electrode terminal 9 are attached to the sealing plate 2. The positive electrode tab group 40 is electrically connected to the positive electrode terminal 8 via a positive electrode current collector 6. The positive electrode current collector 6 includes a first positive electrode current collector 61 and a second positive electrode current collector 62. The negative electrode tab group 50 is electrically connected to the negative electrode terminal 9 via a negative electrode current collector 7. The negative electrode current collector 7 includes a first negative electrode current collector 71 and a second negative electrode current collector 72.

[0024] The positive electrode tab group 40 includes a plurality of positive electrode tabs 4b. The second positive electrode current collector 62 has a region arranged along the first side wall 1b of the rectangular exterior body 1. The positive electrode tab group 40 is connected in a bent state to the region arranged along the first side wall 1b in the second positive electrode current collector 62. The second positive electrode current collector 62 has a plate-shaped region arranged along the first side wall 1b of the rectangular exterior body 1, and the positive electrode tab group 40 is connected to the surface on the electrode body 3 side of the plate-shaped region. The inclination of the plate-shaped region with respect to the first side wall 1b is preferably less than ±30°, more preferably less than ±15°, and even more preferably less than ±10°. The plate-shaped region is more preferably substantially parallel to the first side wall 1b (for example, the inclination of the plate-shaped region with respect to the first side wall 1b is within ±5°).

[0025] The negative electrode tab group 50 includes a plurality of negative electrode tabs 5b. The second negative electrode current collector 72 has a region arranged along the first side wall 1c of the rectangular exterior body 1. The negative electrode tab group 50 is connected in a bent state to the region arranged along the first side wall 1c in the second negative electrode current collector 72. The second negative electrode current collector 72 has a plate-shaped region arranged along the first side wall 1c of the rectangular exterior body 1, and the negative electrode tab group 50 is connected to the surface on the electrode body 3 side of the plate-shaped region. The inclination of the plate-shaped region with respect to the first side wall 1c is preferably less than ±30°, more preferably less than ±15°, and even more preferably less than ±10°. The plate-shaped region is more preferably substantially parallel to the first side wall 1c (for example, the inclination of the plate-shaped region with respect to the first side wall 1b is within ±5°).

[0026] An external side insulating member 10 made of resin is arranged between the sealing plate 2 and the positive electrode terminal 8. An internal side insulating member 11 made of resin is arranged between the sealing plate 2 and the first positive electrode current collector 61. An external side insulating member 12 made of resin is arranged between the sealing plate 2 and the negative electrode terminal 9. An internal side insulating member 13 made of resin is arranged between the sealing plate 2 and the first negative electrode current collector 71.

[0027] The electrode body 3 is arranged inside an electrode body holder 14 formed by bending a resin insulating sheet into a box shape or a bag shape.

[0028] The sealing plate 2 is provided with an electrolytic solution injection hole 15, and the electrolytic solution injection hole 15 is sealed by a sealing member 16. The sealing plate 2 is provided with a gas discharge valve 17 that breaks when the pressure in the battery case 100 becomes a predetermined value or more and discharges the gas in the battery case 100.

[0029] Next, the manufacturing method of the secondary battery 20 and the details of each component will be described. [Attachment of Terminals and First Current Collectors to the Sealing Plate]

[0030] 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. An external side insulating member 10 is disposed on the outer surface side around the positive electrode terminal attachment hole of the sealing plate 2, and an internal side insulating member 11 and a 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 side insulating member 10, the positive electrode terminal attachment hole of the sealing plate 2, the through hole of the internal side 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.

[0031] An external side insulating member 12 is disposed on the outer surface side around the negative electrode terminal attachment hole of the sealing plate 2, and an internal side insulating member 13 and a 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 side insulating member 12, the negative electrode terminal attachment hole of the sealing plate 2, the through hole of the internal side 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.

[0032] FIG. 3A and FIG. 3B 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. 3A shows the outside of the battery, and FIG. 3B shows the inside of the battery.

[0033] The first positive 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 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.

[0034] The first negative 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 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.

[0035] In the second region 61b of the first positive current collector 61, it is preferable to provide notches 61c at both ends in the width direction. When connecting the second positive current collector 62 described later to the second region 61b, by gripping the notches 61c, welding can be performed more stably, and a higher-quality joint can be formed stably. The notches 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 notches 61c are preferably provided near the end on the first region 61a side in the second region 61b. Regarding the second region 71b of the first negative current collector 71, it is also preferable to provide notches 71c at both ends in the width direction. When the inner side insulating member 11 has a wall portion covering a part of the second region 61b, the notches 61c preferably have a region not covered by the wall portion of the inner side insulating member 11.

[0036] The positive electrode terminal 8 and the first positive electrode current collector 61 are preferably made of metal, more preferably made of aluminum. The negative electrode terminal 9 and the first negative electrode current collector 71 are preferably made of metal, more preferably made of copper. Note that the negative electrode terminal 9 can be made to 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. [Positive electrode plate]

[0037] First, a method for manufacturing a positive electrode plate will be described. [Preparation of positive electrode active material layer slurry]

[0038] 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 the lithium nickel cobalt manganese composite oxide:PVdF:carbon material is 97.5:1:1.5 to prepare a positive electrode active material layer slurry. [Preparation of positive electrode protective layer slurry]

[0039] 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 the alumina powder:carbon material:PVdF is 83:3:14 to prepare a protective layer slurry. [Formation of positive electrode active material layer and positive electrode protective layer]

[0040] 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.

[0041] 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 the 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, etc.

[0042] FIG. 4 is a plan view of the positive electrode plate 4. The positive electrode plate 4 has regions where the positive electrode active material layers 4a are formed on both sides of the positive electrode core body. A plurality of positive electrode tabs 4b are provided at one end in the width direction of the positive electrode plate 4. The positive electrode tabs 4b are composed of exposed portions of the positive electrode core body. A positive electrode protective layer 4c having lower conductivity than the positive electrode active material layer 4a is provided at the root portion of the positive electrode tabs 4b. As the positive electrode protective layer 4c, an insulating layer made of resin, a layer containing ceramic and a resin binder, etc. can be used. Further, the positive electrode protective layer 4c may contain a conductive material such as a carbon material. Note that the positive electrode protective layer 4c may not be provided. [Negative electrode plate]

[0043] Next, a method for manufacturing the negative electrode plate will be described. [Preparation of negative electrode active material layer slurry]

[0044] Graphite as the negative electrode active material, styrene-butadiene rubber (SBR) and carboxymethyl cellulose (CMC) as the binder, and water as the 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. [Formation of negative electrode active material layer]

[0045] The negative electrode active material layer slurry prepared by the above method is applied to both sides of a copper foil with a thickness of 8 μm as the negative electrode core body by a die coater.

[0046] The negative electrode core body coated with the negative electrode active material layer slurry is dried to remove the 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.

[0047] FIG. 5 is a plan view of the negative electrode plate 5. The negative electrode plate 5 has regions where negative electrode active material layers 5a are formed on both surfaces of the negative electrode core body. A plurality of negative electrode tabs 5b are provided at one end in the width direction of the negative electrode plate 5. The negative electrode tabs 5b are composed of exposed portions of the negative electrode core body. [Fabrication of the electrode body]

[0048] The strip-shaped positive electrode plate 4 and the strip-shaped negative electrode plate 5 fabricated by the above method are wound through a strip-shaped separator made of polyolefin to fabricate 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. One outer surface of the flat region is the first main surface 3a, and the other outer surface of the flat region is the second main surface 3b.

[0049] FIG. 6 is a plan view of the electrode body 3. 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 4b 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 5b are stacked is provided. Note that the centers of the positive electrode tab group 40 and the negative electrode tab group 50 are displaced to one side (the upper side in FIG. 6) from the winding axis 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 vertical direction in FIG. 6).

[0050] In addition, the shape of the positive tab 4b and / or the negative tab 5b in plan view can be a shape in which the width gradually increases from the tip toward the root. With such a configuration, even when an impact or vibration is applied to the secondary battery 20, the positive tab 4b and / or the negative tab 5b are less likely to be damaged, resulting in the secondary battery 20. Further, it is more effective to form the corner portion at the root into an R shape. In addition, by providing the positive electrode protective layer 4c at the root portion of the positive tab 4b as described above, damage to the positive tab 4b can be suppressed. Further, by providing the negative electrode active material layer 5a at the root portion of the negative tab 5b, damage to the negative tab 5b can be suppressed. [Second Positive Current Collector and Second Negative Current Collector]

[0051] FIG. 7A is a plan view of the second positive current collector 62. FIG. 7B is a cross-sectional view taken along line VIIB-VIIB in FIG. 7A. The second positive current collector 62 has a second region connection portion 62a, an inclined portion 62b, and a tab connection portion 62c. The second region connection portion 62a is connected to the second region 61b of the first positive current collector 61. The positive tab group 40 is connected to the tab connection portion 62c. The inclined portion 62b is disposed inclined with respect to each of the second region connection portion 62a and the tab connection portion 62c, and connects the second region connection portion 62a and the tab connection portion 62c. A step is formed between the second region connection portion 62a and the tab connection portion 62c by the inclined portion 62b. Note that the angle of the inclined portion 62b with respect to the second region connection portion 62a and the angle of the inclined portion 62b with respect to the tab connection portion 62c are not particularly limited. Note that the shape of the second positive current collector 62 is not limited. The second positive current collector 62 can also be formed into a flat plate shape.

[0052] A recess 62d is provided in the second region connection portion 62a. The portion where the recess 62d is provided is thinner than its surroundings. A through hole 62e is provided inside the recess 62d. Inside the recess 62d, the second region 61b and the second region connection portion 62a are joined.

[0053] A fuse portion 62f is provided in the second region connection portion 62a. The fuse portion 62f is a portion that melts when an excessive current flows through the secondary battery 20. The fuse portion 62f is a portion with a reduced cross-sectional area by forming a fuse hole 62g in the second region connection portion 62a. The fuse portion 62f is preferably provided between the position where the second region 61b is joined and the position where the positive tab group 40 is joined in the second positive current collector 62. The fuse portion 62f only needs to be a portion with a reduced cross-sectional area, and may be a portion provided with a notch or a thin portion.

[0054] The shape of the second negative current collector 72 can be the same as that of the second positive current collector 62. The second positive current collector 62 is preferably made of metal, and more preferably made of aluminum. The second negative current collector 72 is preferably made of metal, and more preferably made of copper, nickel, or iron.

[0055] It is not necessary to provide the fuse portion 62f on the second positive current collector 62. Also, it is not necessary to provide a fuse portion on the second negative current collector 72. [Connection between the first current collector and the tab group]

[0056] As shown in FIG. 8, the positive tab group 40 is arranged on the tab connection portion 62c of the second positive current collector 62, and the tab connection portion 62c and the positive tab group 40 are joined to form a joint portion 63. For the joining, ultrasonic welding (ultrasonic bonding), resistance welding, welding by irradiation with high energy rays such as a laser, etc. can be used. The tab connection portion 72c of the second negative current collector 72 and the negative tab group 50 can also be joined in the same manner.

[0057] In the tab connection portion 62c of the second positive electrode current collector 62, it is preferable that the joint portion 63 is eccentrically arranged on the root side (the right side in FIG. 8) of the positive tab group 40 in the width direction of the tab connection portion 62c (the left - right direction in FIG. 8). With such a configuration, when the positive tab group 40 is bent, a curved shape can be more reliably and stably formed in the vicinity of the root of the positive tab group 40. Thereby, damage to the positive tab group 40 can be suppressed. Also, even if there is a displacement in the positive tab 4b, the positive tab group 40 and the tab connection portion 62c can be stably joined.

[0058] As shown in FIG. 8, it is preferable to join the positive tab group 40 and the tab connection portion 62c in a state where the tip of the positive tab group 40 protrudes outward (the left side in FIG. 8) from the tab connection portion 62c of the second positive electrode current collector 62. Thereby, the positive tab group 40 and the tab connection portion 62c can be joined more stably.

[0059] FIG. 9 is a perspective view of the electrode body 3 to which the second positive electrode current collector 62 and the second negative electrode current collector 72 are attached. The lower end portion of the second positive electrode current collector 62 (the portion that becomes the end on the bottom 1a side of the rectangular exterior body 1) is preferably located below the lower end portion of the positive tab group 40 (the portion that becomes the end on the bottom 1a side of the rectangular exterior body 1). With such a configuration, in the process of bending the positive tab group 40 described later, the positive tab group 40 can be bent more reliably and stably. The same applies to the second negative electrode current collector 72 and the negative tab group 50. [Bending of the tab group]

[0060] As shown in FIG. 10, the positive electrode tab group 40 is in a bent state. The tab connection portion 62c of the second positive electrode current collector 62, which was arranged substantially parallel to the first main surface 3a and the second main surface 3b of the electrode body 3 as shown in FIG. 9, is bent by bending the positive electrode tab group 40 so as to be in a direction substantially perpendicular to the winding axis of the electrode body 3 (for example, the inclination of the tab connection portion 62c with respect to the winding axis is less than ±15°). Then, a tape 80 as a fixing means is attached so as to straddle the first main surface 3a - tab connection portion 62c - second main surface 3b of the electrode body 3. With such a configuration, the positive electrode tab group 40 can be more stably maintained in a curved state. Further, the curved positive electrode tab group 40 can be given elasticity, and when the second positive electrode current collector 62 is pressed toward the electrode body 3 side, the second positive electrode current collector 62 can move in a direction approaching the electrode body 3. When bending the positive electrode tab group 40, the second positive electrode current collector 62 itself is not bent.

[0061] As shown in FIG. 10, the positive electrode tab group 40 has a contact region 40b that contacts the tab connection portion 62c, a root region 40a arranged on the root side of the positive electrode tab group 40 rather than the contact region 40b, and a tip region 40c arranged on the tip side of the positive electrode tab group 40 rather than the contact region 40b. By fixing the tip region 40c in a state bent from the contact region 40b with the tape 80, the assemblability in subsequent processes is improved. By providing the tip region 40c, the contact region 40b can be provided wider, and when joining the positive electrode tab group 40 and the tab connection portion 62c, they can be joined more stably. Note that the tip region 40c does not necessarily need to be provided.

[0062] Note that the negative electrode tab group 50 is also fixed in a bent state in the same manner as the positive electrode tab group 40. [Electrode body group]

[0063] 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 collectively fixed by an electrode body fixing means 90 such as a tape to form an electrode body group 300. FIG. 11 is a perspective view of the electrode body group 300. 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. Further, 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. The electrode body group 300 according to the embodiment includes two electrode bodies 3. Note that the number of electrode bodies 3 included in the electrode body group 300 is not limited to two.

[0064] As the tape 80 as a fixing means that is attached across the first main surface 3a of the electrode body 3 - the tab connection portion 62c - the second main surface 3b of the electrode body 3, it is preferable to include a first tape 80a and a second tape 80b. As shown in FIG. 11, at the tab connection portion 62c of the second positive electrode current collector 62, it is preferable to attach the first tape 80a above the joint portion 63 between the tab connection portion 62c and the positive electrode tab group 40, and attach the second tape 80b below the joint portion 63 between the tab connection portion 62c and the positive electrode tab group 40. With such a configuration, the curved state of the positive electrode tab group 40 can be stably maintained. The same applies to the tab connection portion 72c of the second negative electrode current collector 72.

[0065] As shown in FIG. 11, it is preferable that the upper end of the first tape 80a arranged on the upper side is arranged above the upper end of the positive electrode tab group 40, and the lower end of the second tape 80b arranged on the lower side is arranged below the lower end of the positive electrode tab group 40. With such a configuration, the curved shape of the positive electrode tab group 40 can be more reliably maintained.

[0066] As shown in FIG. 11, 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.

[0067] In the electrode body 3 according to the embodiment, a joint portion 63 between the positive electrode tab group 40 and the tab connection portion 62c is disposed between the lower end of the first tape 80a and the upper end of the second tape 80b.

[0068] In the embodiment, the first tape 80a and the second tape 80b are divided into two tapes in the vertical direction, but they can also be made into one tape. In this case, it is preferable to dispose the upper end of the one tape above the upper end of the positive electrode tab group 40 and the lower end of the one tape below the lower end of the positive electrode tab group 40. The tape 80 may cover the portion where the joint portion 63 is formed at the tab connection portion 62c. The same configuration can be applied to the second negative electrode current collector 72 and the negative electrode tab group 50 side. [Connection between the first current collector and the second current collector]

[0069] The second region 61b of the first positive electrode current collector 61 is disposed inside the second region connection portion 62a of the second positive electrode current collector 62, and the second region 71b of the first negative electrode current collector 71 is disposed inside the second region connection portion 72a of the second negative electrode current collector 72. Then, the second region 61b of the first positive electrode current collector 61 is connected to the second region connection portion 62a of the second positive electrode current collector 62. Further, the second region 71b of the first negative electrode current collector 71 is joined to the second region connection portion 72a of the second negative electrode current collector 72. As the joining method, ultrasonic welding (ultrasonic bonding), resistance welding, welding by irradiation with a high energy beam such as a laser, or the like can be used. In particular, it is preferable to use welding by irradiation with a high energy beam such as a laser.

[0070] Figs. 12A to 12C are cross-sectional views along the winding axis of the electrode body 3 of the second region 61b of the first positive electrode current collector 61, the second region 71b of the first negative electrode current collector 71, the second region connection portion 62a of the second positive electrode current collector 62, and the second region connection portion 72a of the second negative electrode current collector 72 at each stage.

[0071] As shown in FIG. 12A, between the second region connection part 62a of the second positive electrode current collector 62 and the second region connection part 72a of the second negative electrode current collector 72, the second region 61b of the first positive electrode current collector 61 and the second region 71b of the first negative electrode current collector 71 are arranged. At this time, the distance D1 between the inner surfaces of the second region connection part 62a and the second region connection part 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.

[0072] Next, as shown in FIG. 12B, the second region connection part 62a and / or the second region connection part 72a is displaced inward so that the distance between the second region connection part 62a and the second region connection part 72a becomes smaller. Thereby, the distance D1 between the inner surfaces of the second region connection part 62a and the second region connection part 72a is changed to D1'. At this time, the difference between D2 and D1' is preferably 0 to 0.2 mm.

[0073] In the state shown in FIG. 12B, high energy rays such as a laser are irradiated onto each of the second region connection part 62a and the second region connection part 72a. Thereby, the second region 61b of the first positive electrode current collector 61 and the second region connection part 62a of the second positive electrode current collector 62 are joined by welding, and the second region 71b of the first negative electrode current collector 71 and the second region connection part 72a of the second negative electrode current collector 72 are joined by welding.

[0074] As shown in FIG. 12C, a joint part 64, which is a welded part of the second region 61b and the second region connection part 62a, is formed in the concave part 62d. Also, a joint part 74, which is a welded part of the second region 71b and the second region connection part 72a, is formed in the concave part 72d.

[0075] By adopting the procedures of FIGS. 12A to 12C, the first positive electrode current collector 61 and the second positive electrode current collector 62, and the first negative electrode current collector 71 and the second negative electrode current collector 72 can be welded more stably by a simpler method. Therefore, highly reliable joint parts 64 and 74 can be formed.

[0076] The portions where the concave portions 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. Thus, a secondary battery with higher reliability is obtained. Also, by using the through holes 62e to measure the presence or absence or the size of the gap between the second region 61b and the second region connection portion 62a, the second region 61b and the second region connection portion 62a can be joined more stably by welding. The same applies to the through hole 72e.

[0077] FIG. 13 is a perspective view showing the state after connecting the first positive electrode current collector 61 and the second positive electrode current collector 62, and the first negative electrode current collector 71 and the second negative electrode current collector 72, respectively. [Electrode body holder]

[0078] FIG. 14 is a developed view of the electrode body holder 14. By bending the insulating sheet constituting the electrode body holder 14 at the broken line portions in FIG. 14, a box-shaped electrode body holder 14 is formed. 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.

[0079] 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.

[0080] With the electrode body group 300 arranged inside the box-shaped electrode body holder 14, the electrode body group 300 is 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. Thus, a secondary battery 20 is obtained. [Secondary battery]

[0081] In the secondary battery 20 according to the embodiment, the positive electrode current collector 6 has a configuration including a first positive electrode current collector 61 and a second positive electrode current collector 62. With such a configuration, when bending the positive electrode tab group 40, the positive electrode tab group 40 can be bent without bending the positive electrode current collector 6, and a secondary battery with a higher volumetric energy density can be obtained in a simpler way and more stably. When the number of electrode bodies 3 accommodated in the battery case 100 is two or more, the effect is more remarkable. According to the present disclosure, the degree of freedom regarding the number of electrode bodies 3 accommodated in the battery case 100 is improved. According to the present disclosure, even when the number of electrode bodies 3 accommodated in the battery case 100 is more than two, a highly reliable secondary battery can be stably manufactured without making the positive electrode current collector 6 have a complicated shape. The present disclosure is particularly effective when the number of electrode bodies 3 accommodated in the battery case 100 is more than two and an odd number.

[0082] In the secondary battery 20, the tab connection 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 second region 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 volumetric 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 eccentric toward the sealing plate 2 side. Thereby, the conductive path from the positive electrode tab group 40 to the positive electrode terminal 8 can be shortened, resulting in a secondary battery 20 with a small internal resistance. In the electrode body 3, it is preferable that the negative electrode tab group 50 is eccentric toward the sealing plate 2 side. Thereby, the conductive path from the negative electrode tab group 50 to the negative electrode terminal 9 can be shortened, resulting in a secondary battery 20 with a small internal resistance.

[0084] It is preferable to dispose an insulating member (not shown) different from the electrode body holder 14 between the region where the second region 61b of the first positive electrode current collector 61 overlaps with the connection portion 62a of the second region of the second positive electrode current collector 62 and the first side wall 1b of the rectangular exterior body 1. Further, it is preferable to dispose an insulating member (not shown) different from the electrode body holder 14 between the region where the second region 71b of the first negative electrode current collector 71 overlaps with the connection portion 72a of the second region 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 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] FIG. 15 is a cross-sectional view in the vicinity of the joint portion 63 between the tab connection portion 62c of the second positive electrode current collector 62 and the positive electrode tab group 40 in another embodiment, and shows a state in which the positive electrode tab group 40 is bent and fixed. As shown in FIG. 15, the portion of the tab connection portion 62c of the second positive electrode current collector 62 where the joint portion 63 is formed can be covered with a tape 80. Even if there are burrs or metal powder generated when the joint portion 63 is formed in the portion of the tab connection portion 62c of the second positive electrode current collector 62 where the joint portion 63 is formed, the tape 80 can suppress the movement of the burrs or metal powder.

[0086] Also, as shown in FIG. 15, the portion of the positive electrode tab group 40 where the joint portion 63 is formed can be covered with a tape 81. Even if there are burrs or metal powder generated when the joint portion 63 is formed in the portion of the positive electrode tab group 40 where the joint portion 63 is formed, the tape 81 can suppress the movement of the burrs or metal powder. The tape 81 is preferably attached before the positive electrode tab group 40 is bent.

[0087] In addition, an adhesive can be applied or pasted on the portion where the joint 63 is formed in the tab connection portion 62c of the second positive electrode current collector 62 and / or the portion where the joint 63 is formed in the positive electrode tab group 40. Further, the portion where the joint 63 is formed in the tab connection portion 62c of the second positive electrode current collector 62 and / or the portion where the joint 63 is formed in the positive electrode tab group 40 can be covered with a heat-sealing resin. Also, the tab connection portion 72c of the second negative electrode current collector 72 and the negative electrode tab group 50 can have the same configuration.

[0088] In the secondary battery 20 according to the above-described embodiment, one second positive electrode current collector 62 and one second negative electrode current collector 72 are attached to one electrode body 3. However, it is not limited thereto. A plurality of second positive electrode current collectors and / or a plurality of second negative electrode current collectors can be attached to one electrode body 3. Another embodiment in which a plurality of second positive electrode current collectors are attached to one electrode body 3 will be described below. Note that, in the same manner, a plurality of second negative electrode current collectors can be attached to one electrode body 3. In other embodiments, descriptions of portions common to the secondary battery 20 of the above-described embodiment will be omitted.

[0089] As shown in FIG. 16, the positive electrode tab group 40 is divided into two, and the tab connection portion 162c of the second positive electrode current collector 162 is connected to each of one divided positive electrode tab group 40A and the other divided positive electrode tab group 40B by welding to form a joint 163. It is preferable that one positive electrode tab group 40A is collected on the first main surface 3a side and the other positive electrode tab group 40B is collected on the second main surface 3b side. Note that the second positive electrode current collector 162 can have the same configuration as the second positive electrode current collector 62 according to the above-described embodiment.

[0090] As shown in FIG. 17, the positive electrode tab group 40A bundled on the first main surface 3a side is bent toward the center side in the thickness direction of the electrode body 3, and the positive electrode tab group 40B bundled on the second main surface 3b side is bent toward the center side in the thickness direction of the electrode body 3, and is fixed by a tape 80 as a fixing means.

[0091] As shown in FIG. 18, the second positive current collector 162 connected to the positive tab group 40A of one electrode body 3 and the second positive current collector 162 connected to the positive tab group 40B are connected to the first positive current collector 61 by welding. The second positive current collector 162 has a second region connection portion 162a, an inclined portion 162b, and a tab connection portion 162c. The second region connection portion 162a is connected to the second region 61b of the first positive current collector 61. Note that the configuration in other embodiments is particularly effective when the thickness of one of the electrode bodies 3 is increased. <Others>

[0092] In the above-described embodiment, an example in which the electrode body is a wound electrode body in which a positive electrode plate and a negative electrode plate are wound with a separator therebetween is shown, but the present invention is not limited to this. A stacked electrode body including a plurality of positive electrode plates and a plurality of negative electrode plates can also be used.

[0093] In the above-described embodiment, an example in which a wound electrode body is manufactured by winding a positive electrode plate having a plurality of positive tabs and a negative electrode plate having a plurality of negative tabs is shown, but the present invention is not limited to this. In the wound electrode body, a positive tab group or a negative tab group can also be formed by cutting the exposed portion of the positive electrode core or the exposed portion of the negative electrode core.

[0094] In the above-described embodiment, an example in which the positive current collector 6 and the negative current collector 7 each consist of two parts is shown, but the positive current collector 6 and the negative current collector 7 may each be composed of one part.

[0095] Regarding the positive electrode plate, negative electrode plate, separator, electrolyte, etc., known materials can be used.

[0096] The above-mentioned aluminum includes aluminum and aluminum alloys mainly composed of aluminum. The above-mentioned copper includes copper and copper alloys mainly composed of copper. The above-mentioned iron includes iron alloys mainly composed of iron. The above-mentioned nickel includes nickel alloys mainly composed of nickel.

[0097] As the tape, those having a base material and an adhesive layer formed on the base material are preferable. The base material is preferably composed of polyethylene, polypropylene, polyester, nylon, vinyl chloride, Teflon (registered trademark), polyimide, Kapton (registered trademark), polyphenylene sulfide, or polyethylene naphthalate, etc. The material of the adhesive layer is preferably composed of an acrylic adhesive, a silicone adhesive, a rubber adhesive, etc. However, it is not limited to these materials. Note that the adhesive layer preferably has adhesiveness at normal temperature.

[0098] As an embodiment, an example where the fixing means is a tape has been shown, but it is not limited thereto. As the fixing means, a resin frame, a metal frame, a ceramic frame, a clip-shaped member, etc. can be considered. Note that as the fixing means, a tape is more preferable.

[0099] A pressure-sensitive current interruption mechanism can be provided in the conductive path between the positive electrode tab group and the positive electrode terminal, or in the conductive path between the negative electrode tab group and the negative electrode terminal. This current interruption mechanism operates when the pressure in the battery case becomes a predetermined value or more, and cuts the conductive path between the positive electrode tab group and the positive electrode terminal, or the conductive path between the negative electrode tab group and the negative electrode terminal, to interrupt the flow of current.

Explanation of Reference Numerals

[0100] 20 Secondary battery 100 Battery case 1 Square outer package 1a Bottom 1b, 1c First side wall 1d, 1e Second side wall 2 Sealing plate 3 Electrode body 3a First main surface 3b Second main surface 300 Electrode body group 4 Positive electrode plate 4a Positive electrode active material layer 4b Positive electrode tab 4c Positive electrode protective layer 40 Positive electrode tab group 40a Root region 40b Contact region 40c tip region 5 negative electrode plate 5a negative electrode active material layer 5b negative electrode tab 50 negative electrode tab group 6 positive electrode current collector 61 first positive electrode current collector 61a first region 61b second region 61c notch 62 second positive electrode current collector 62a second region connection part 62b inclined part 62c tab connection part 62d recess 62e through hole 62f fuse part 62g fuse hole 63,64 joint 7 negative electrode current collector 71 first negative electrode current collector 71a first region 71b second region 71c notch 72 second negative electrode current collector 72a second region connection part 72b inclined part 72c tab connection part 72d recess 72e through hole 74 joint 8 positive electrode terminal 9 negative electrode terminal 10,12 external side insulating member 11,13 internal side insulating member 14 electrode body holder 14a holder bottom 14b holder first main surface 14c holder second main surface 14d holder first side surface 14e holder second side surface 14f holder third side surface 14g holder fourth side surface 14h holder fifth side surface 14i holder sixth side surface 15 Electrolyte injection hole 16 Sealing member 17 Gas discharge valve 80 Tape 80a First tape 80b Second tape 81 Tape 90 Electrode body fixing means 40A, 40B Positive electrode tab group 162 Second positive current collector 162a Second region connection part 162b Inclined part 162c Tab connection part 163 Joint part

Claims

1. An electrode assembly including a positive electrode plate and a negative electrode plate; A rectangular exterior body having an opening and housing the electrode assembly; a sealing plate that seals the opening; A terminal attached to the sealing plate, the electrode assembly has a positive electrode tab group at one end and a negative electrode tab group at the other end; The electrode body has a first main surface and a second main surface arranged in a direction facing each other, The rectangular exterior body has a bottom, a pair of first side walls arranged in an opposing relationship to each other, and a pair of second side walls arranged in an opposing relationship to each other, The positive electrode tab group is disposed on one of the first side walls, the negative electrode tab group is disposed on the other first side wall side, the positive electrode tab group or the negative electrode tab group and the terminal are electrically connected by a current collector, the positive electrode tab group or the negative electrode tab group is connected to the current collector in a folded state, a joint portion between the current collector and the positive electrode tab group or the negative electrode tab group is eccentric toward a base side of the positive electrode tab group or the negative electrode tab group in a width direction of the current collector; secondary battery

2. An electrode assembly including a positive electrode plate and a negative electrode plate; A rectangular exterior body having an opening and housing the electrode assembly; a sealing plate that seals the opening; A terminal attached to the sealing plate, the electrode assembly has a positive electrode tab group at one end and a negative electrode tab group at the other end; The electrode body has a first main surface and a second main surface arranged in a direction facing each other, The rectangular exterior body has a bottom, a pair of first side walls arranged in an opposing relationship to each other, and a pair of second side walls arranged in an opposing relationship to each other, The positive electrode tab group is disposed on one of the first side walls, the negative electrode tab group is disposed on the other first side wall side, the positive electrode tab group or the negative electrode tab group and the terminal are electrically connected by a current collector, the positive electrode tab group or the negative electrode tab group is connected to the current collector in a folded state, The positive electrode tab group or the negative electrode tab group is a contact area in contact with the current collector; a root region disposed closer to the root of the positive electrode tab group or the negative electrode tab group than the contact region, and a tip region disposed closer to the tip of the positive electrode tab group or the negative electrode tab group than the contact region, Secondary battery.

3. An electrode assembly including a positive electrode plate and a negative electrode plate; A rectangular exterior body having an opening and housing the electrode assembly; a sealing plate that seals the opening; A terminal attached to the sealing plate, the electrode assembly has a positive electrode tab group at one end and a negative electrode tab group at the other end; The electrode body has a first main surface and a second main surface arranged in a direction facing each other, The rectangular exterior body has a bottom, a pair of first side walls arranged in an opposing relationship to each other, and a pair of second side walls arranged in an opposing relationship to each other, The positive electrode tab group is disposed on one of the first side walls, the negative electrode tab group is disposed on the other first side wall side, the positive electrode tab group or the negative electrode tab group and the terminal are electrically connected by a current collector, the positive electrode tab group or the negative electrode tab group is connected to the current collector in a folded state, an end portion on the bottom side of the current collector is located closer to the bottom side than an end portion on the bottom side of the positive electrode tab group or the negative electrode tab group; Secondary battery.

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