2 and the first negative electrode current collector 71. Reference numeral 14 indicates a box-shaped or bag-shaped insulating sheet which is arranged inside the rectangular exterior body 1 and houses the electrode body 3. Reference numeral 15 indicates an electrolyte injection hole provided in the sealing plate 2. Reference numeral 16 indicates a sealing member sealing the electrolyte injection hole 15. Reference numeral 17 indicates a gas discharge valve provided at the sealing plate 2.

Next, the method for manufacturing the non-aqueous electrolyte secondary battery 20 and each configuration thereof will be described in detail.

[Attachment of Terminals and First Current Collectors to Sealing Plate]

The sealing plate 2 has a positive electrode terminal attachment hole in the vicinity of one end portion, and has a negative electrode terminal attachment hole in the vicinity of the other end portion. The external insulating member 10 is arranged on an outer surface side of the periphery of 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 arranged on an inner surface side of the periphery of the positive electrode terminal attachment hole of the sealing plate 2. Then, the positive electrode terminal 8 is inserted, from the outer side of the battery, into a through-hole of the external insulating member 10, the positive electrode terminal attachment hole of the sealing plate 2, a through-hole of the internal insulating member 11, and a through-hole of the first positive electrode current collector 61. Then, the positive electrode terminal 8 is crimped onto the first positive electrode current collector 61. Further, the crimped portion of the positive electrode terminal 8 is welded to the first positive electrode current collector 61 in a more preferred embodiment.

The external insulating member 12 is arranged on an outer surface side of the periphery of 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 arranged on an inner surface side of the periphery of the negative electrode terminal attachment hole of the sealing plate 2. Then, the negative electrode terminal 9 is inserted, from the outer side of the battery, into a through-hole of the external insulating member 12, the negative electrode terminal attachment hole of the sealing plate 2, a through-hole of the internal insulating member 13, and a through-hole of the first negative electrode current collector 71. Then, the negative electrode terminal 9 is crimped onto the first negative electrode current collector 71. Further, the crimped portion of the negative electrode terminal 9 is welded to the first negative electrode current collector 71 in a more preferred embodiment.

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 outer side of the battery, and FIG. 7B shows the inner side of the battery.

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 portion 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 to 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.

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 portion 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 to 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.

In the second region 61b of the first positive electrode current collector 61, cutout portions 61c are provided at both end portions in the width direction in a preferred embodiment. When the second positive electrode current collectors 62, which will be described later, are connected to the second region 61b, the cutout portions 61c are gripped so that welding can be more stably performed and a higher-quality connection portion can be stably formed. In the second region 61b, the cutout portion 61c is arranged closer to the bottom 1a of the rectangular exterior body 1 than the internal insulating member 11 is to the bottom 1a in a preferred embodiment. In the second region 61b, the cutout portion 61c is provided in the vicinity of an end portion on a first region 61a side in a preferred embodiment. In the second region 71b of the first negative electrode current collector 71, cutout portions 71c are also provided at both end portions in the width direction in a preferred embodiment. In a case where the internal insulating member 11 has a wall portion covering part of the second region 61b, the cutout portion 61c has a region not covered with the wall portion of the internal insulating member 11 in a preferred embodiment.

The positive electrode terminal 8 and the first positive electrode current collector 61 are made of metal in a preferred embodiment and aluminum in a more preferred embodiment. The negative electrode terminal 9 and the first negative electrode current collector 71 are made of metal in a preferred embodiment and copper in a more preferred embodiment. The negative electrode terminal 9 may include a region made of aluminum and a region made of copper. In this case, the region made of copper is connected to the first negative electrode current collector 71 made of copper and the region made of aluminum is exposed on the outer side of the battery in a preferred embodiment.

[Positive Electrode Plate]

First, the method for manufacturing the positive electrode plate will be described.

[Preparation of Positive Electrode Active Material Layer Slurry]

Lithium nickel cobalt manganese composite oxide as a positive electrode active material, polyvinylidene fluoride (PVdF) as a binder, a carbon material as an electroconductive material, and N-methyl-2-pyrrolidone (NMP) as a dispersion medium are kneaded at a mass ratio of the lithium nickel cobalt manganese composite oxide:the PVdF:the carbon material of 97.5:1:1.5. In this manner, a positive electrode active material layer slurry is prepared.

[Preparation of Positive Electrode Protective Layer Slurry]

An alumina powder, a carbon material as an electroconductive material, polyvinylidene fluoride (PVdF) as a binder, and N-methyl-2-pyrrolidone (NMP) as a dispersion medium are kneaded at a mass ratio of the alumina powder:the carbon material:the PVdF of 83:3:14. In this manner, a protective layer slurry is prepared.

[Formation of Positive Electrode Active Material Layer and Positive Electrode Protective Layer]

To both surfaces of aluminum foil as a positive electrode core, the positive electrode active material layer slurry and the positive electrode protective layer slurry prepared by the above-described method are applied using a die coater. At this time, the positive electrode active material layer slurry is applied to the center of the positive electrode core in the width direction thereof. Further, the positive electrode protective layer slurry is applied to end portions of a region in the width direction thereof. The positive electrode active material layer slurry is applied to the region.

The positive electrode core with the positive electrode active material layer slurry and the positive electrode protective layer slurry applied thereon is dried to remove NMP contained in the positive electrode active material layer slurry and the positive electrode protective layer slurry. Accordingly, a positive electrode active material layer and a positive electrode protective layer are formed. Then, the positive electrode active material layer is compressed, thereby obtaining a positive electrode original plate. The positive electrode original plate is cut into a predetermined shape, thereby obtaining the positive electrode plate 4. The cutting of the positive electrode original plate may be performed by irradiation with energy rays such as laser, a die, a cutter, or the like.

[Negative Electrode Plate]

Next, the method for manufacturing the negative electrode plate will be described.

[Preparation of Negative Electrode Active Material Layer Slurry]

Graphite as a negative electrode active material, styrene-butadiene rubber (SBR) and carboxymethyl cellulose (CMC) as a binder, and water as a dispersion medium are kneaded at a mass ratio of graphite:SBR:CMC of 98:1:1. In this manner, a negative electrode active material layer slurry is prepared.

[Formation of Negative Electrode Active Material Layer]

To both surfaces of copper foil as a negative electrode core, the negative electrode active material layer slurry prepared by the above-described method is applied using a die coater.

The negative electrode core with the negative electrode active material layer slurry applied thereon is dried to remove water in the negative electrode active material layer slurry. In this manner, a negative electrode active material layer is formed. Thereafter, the negative electrode active material layer is compressed, thereby obtaining a negative electrode original plate. The negative electrode original plate is cut into a predetermined shape, thereby obtaining the negative electrode plate 5. The cutting of the negative electrode original plate may be performed by irradiation with energy rays such as laser, a die, a cutter, or the like.

[Preparation of Electrode Body]

The strip-like positive electrode plate 4 and the strip-like negative electrode plate 5 prepared by the above-described method are wound with the strip-like separator SP made of polyolefin interposed therebetween, thereby preparing the flat wound electrode body 3. The electrode body 3 has a flat region at the center, and has curved portions at both ends of the flat region.

The positive electrode tab group 40 including the multiple positive electrode tabs 40a stacked on each other is provided at one end of the electrode body 3 in a direction in which the winding axis extends. The negative electrode tab group 50 including the multiple negative electrode tabs 50a stacked on each other is provided at the other end of the electrode body 3 in the direction in which the winding axis extends. In the direction perpendicular to the direction in which the winding axis of the electrode body 3 extends and 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 arranged shifted from the winding axis to one side.

The shape of the positive electrode tab 40a and/or the negative electrode tab 50a in plan view is set to a shape having a width gradually increasing from a distal end to a base, and with this shape, damage to the positive electrode tab 40a and/or the negative electrode tab 50a can be reduced even in a case where impact or vibration is applied to the non-aqueous electrolyte secondary battery 20. In addition, it is more effective to form the corner portion of the base portion in a rounded shape.

The positive electrode protective layer 4b is provided at the base portion of the positive electrode tab 40a as described above so that damage to the positive electrode tab 40a can be reduced. In addition, the negative electrode active material layer is provided at the base portion of the negative electrode tab 50a so that damage to the negative electrode tab 50a can be reduced.

[Connection Between First Current Collector and Tab Group]

In order to manufacture the non-aqueous electrolyte secondary battery 20 configured as described above, welding is performed with a welding tool T in contact with a position slightly lower than the tip ends of all of the positive electrode tabs 40a, with the distal end regions of all of the positive electrode tabs 40a overlaid on the tab joint portion 62c of the second positive electrode current collector 62, as shown in FIG. 8. In this manner, all of the positive electrode tabs 40a are joined to each other, and are welded to the second positive electrode current collector 62. Accordingly, the portion slightly lower than the distal ends of all of the positive electrode tabs 40a form the connection portion 63. The connection portion 63 may be formed at the tip end portions of all of the positive electrode tabs 40a by welding performed with the welding tool T in contact with the distal end portions of all of the positive electrode tabs 40a. In this case, the tab joint portion 62c of the second positive electrode current collector 62 is provided such that the plate surfaces thereof face the thickness direction of the electrode body 3, as shown in FIG. 9. In addition, the distal end regions of all of the positive electrode tabs 40a overlap with each other with the plate surfaces of all of the positive electrode tabs 40a face the thickness direction of the electrode body 3 and the positive electrode tabs 40a gathered toward the positive electrode tab 40a (one end side in the thickness direction of the electrode body 3) with the shortest protrusion length. In this case, an interval 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 of the positive electrode tabs 40a are bent.

In this case, at the tab joint portion 62c of the second positive electrode current collector 62, the connection portion 63 is arranged closer to the base side (the left side in FIG. 8) of the positive electrode tab group 40 in the width direction (the left-right direction in FIG. 8) of the tab joint portion 62c in a preferred embodiment. With this configuration, when the positive electrode tab group 40 is bent, a curved shape can be more reliably and stably formed in the vicinity of the base of the positive electrode tab group 40. This can reduce damage to the positive electrode tab group 40. In addition, even with displacement of the positive electrode tabs 40a, the positive electrode tab group 40 and the tab joint portion 62c can be stably joined to each other.

In a preferred embodiment, a lower end portion (an end portion closer to the bottom 1a of the rectangular exterior body 1) of the second positive electrode current collector 62 is positioned lower than a lower end portion (an end portion closer to the bottom 1a of the rectangular exterior body 1) of the positive electrode tab group 40. With this configuration, the positive electrode tab group 40 can be more reliably and stably bent in the process of bending the positive electrode tab group 40 as described later.

From this state, the distal end regions of all of the positive electrode tabs 40a are, as shown in FIG. 6, bent so that the plate surfaces thereof face the substantially winding axis direction of the electrode body 3 (e.g., the inclination of the tab joint portion 62c with respect to the winding axis is less than ±15°. Accordingly, the plate surfaces of the tab joint portion 62c of the second positive electrode current collector 62 face the substantially winding axis direction of the electrode body 3. As described above, the positive electrode tab group 40 can be bent without bending the second positive electrode current collector 62.

The negative electrode tabs 50a are also attached to the second negative electrode current collector 72 in a manner similar to that for the positive electrode tabs 40a.

[Electrode Body Group]

As shown in FIG. 3, the multiple electrode bodies 3 each provided with a positive electrode tab group 40 and a negative electrode tab group 50 being bent are stacked on each other, and are fixed by an electrode body fixer such as a tape. The positive electrode tab groups 40 are arranged on the same side, and the negative electrode tab groups 50 are arranged on the same side. In the electrode bodies 3, the positive electrode tab groups 40 are bent in the same direction. In the electrode bodies 3, the negative electrode tab groups 50 are bent in the same direction.

In the direction in which the electrode bodies 3 are stacked, the second positive electrode current collectors 62 attached to the respective electrode bodies 3 are arranged at an interval and connected to the second region 61b of the first positive electrode current collector 61. The same applies to the second negative electrode current collector 72.

[Connection Between First Current Collector and Second Current Collector]

The second region 61b of the first positive electrode current collector 61 is arranged inside the current collector 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 arranged inside the current collector connection portion 72a of the second negative electrode current collector 72. Then, 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 are joined to each other. In addition, the second region 71b of the first negative electrode current collector 71 is joined to the current collector connection portion 72a of the second negative electrode current collector 72. As the joining method, ultrasonic welding (ultrasonic joining), resistance welding, welding by irradiation with high-energy rays such as laser, and the like may be used. Particularly, welding by irradiation with high-energy rays such as laser is used in a preferred embodiment.

FIGS. 10A to 10C are cross-sectional views taken along the winding axis of the electrode body 3. FIGS. 10A to 10C show 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 current collector connection portion 62a of the second positive electrode current collector 62, and the current collector connection portion 72a of the second negative electrode current collector 72 at each stage.

As shown in FIG. 10A, 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 between the current collector connection portion 62a of the second positive electrode current collector 62 and the current collector connection portion 72a of the second negative electrode current collector 72. In this state, a distance D1 between an inner surface of the current collector connection portion 62a and an inner surface of the current collector connection portion 72a is greater than a distance D2 between an outer surface of the second region 61b and an outer surface of the second region 71b in a preferred embodiment. D1 is preferably greater than D2 by 0.1 mm to 5 mm and more preferably by 0.2 mm to 3 mm.

Next, as shown in FIG. 10B, the current collector connection portion 62a and/or the current collector connection portion 72a are displaced inwardly such that the distance between the current collector connection portion 62a and the current collector connection portion 72a decreases. Accordingly, the distance D1 between the inner surface of the current collector connection portion 62a and the inner surface of the current collector connection portion 72a changes to D1′. In this case, a difference between D2 and D1′ is preferably 0 mm to 0.2 mm.

In the state shown in FIG. 10B, each of the current collector connection portion 62a and the current collector connection portion 72a is irradiated with high-energy rays such as laser. Accordingly, 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 are joined to each other by welding, and 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 are joined to each other by welding.

As shown in FIG. 10C, a joint portion 64 as a welding portion between the second region 61b and the current collector connection portion 62a is formed in the recess 62d. In addition, a joint portion 74 as a welding portion between the second region 71b and the current collector connection portion 72a is formed in the recess 72d.

According to the processes of FIGS. 10A to 10C, by a simpler method, the first positive electrode current collector 61 and the second positive electrode current collector 62 can be more stably welded to each other, and the first negative electrode current collector 71 and the second negative electrode current collector 72 can be more stably welded to each other. Thus, the joint portion 64 and the joint portion 74 can be formed with a high reliability.

The portion formed with the recess 62d, 72d is thinner than a peripheral portion thereof. Welding is performed such that the joint portion 64, 74 is formed at such a thin portion, and therefore, a higher-quality joint portion can be more stably formed. Thus, a secondary battery with a higher reliability is provided. Using the through-hole 62e, the presence or absence of a clearance between the second region 61b and the current collector connection portion 62a and the size of the clearance are measured. Thus, the second region 61b and the current collector connection portion 62a can be more stably joined to each other by welding. The same applies to the through-hole 72e.

FIG. 3 is a perspective view showing a state after the first positive electrode current collector 61 and the second positive electrode current collectors 62 have been connected to each other and the first negative electrode current collector 71 and the second negative electrode current collectors 72 have been connected to each other.

[Electrode Body Holder]

FIG. 11 is a development view of an electrode body holder 14. The box-shaped electrode body holder 14 is formed in such a manner that an insulating sheet forming the electrode body holder 14 is bent at portions indicated by broken lines in FIG. 11. The electrode body holder 14 has a holder bottom 14a, a holder first principal surface 14b, a holder second principal 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.

In a case where the electrode body holder 14 is in the box shape, the electrode body holder 14 has a region where the holder first side surface 14d, the holder second side surface 14e, and the holder third side surface 14f overlap with each other, and has a region where the holder fourth side surface 14g, the holder fifth side surface 14h, and the holder sixth side surface 14i overlap with each other.

In a state in which three electrode bodies 3 are 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 to seal the opening of the rectangular exterior body 1 with the sealing plate 2. An electrolyte is then injected from the electrolyte injection hole 15 provided in the sealing plate 2, and the electrolyte injection hole 15 is sealed with a sealing member 16. Thus, the non-aqueous electrolyte secondary battery 20 is obtained.

According to the present embodiment, two positive electrode tabs 40a are provided per turn of the positive electrode plate 4. Thus, as compared to a case where only one positive electrode tab 40a is provided per turn of the positive electrode plate 4, variation in a distance from each portion in the positive electrode plate 4 to the positive electrode tab 40a can be reduced and a potential difference in the positive electrode plate 4 can be reduced. Accordingly, deterioration of the positive electrode plate 4 is reduced, and the durability of the non-aqueous electrolyte secondary battery 20 is enhanced.

In addition, as compared to the case where only one positive electrode tab 40a is provided per turn of the positive electrode plate 4, the current collection resistance of the positive electrode plate 4 can be reduced. Thus, the output current of the non-aqueous electrolyte secondary battery 20 can be increased.

Similarly, two negative electrode tabs 50a are provided per turn of the negative electrode plate 5. Thus, as compared to a case where only one negative electrode tab 50a is provided per turn of the negative electrode plate 5, variation in a distance from each portion in the negative electrode plate 5 to the negative electrode tab 50a can be reduced and a potential difference in the negative electrode plate 5 can be reduced. Accordingly, deterioration of the negative electrode plate 5 is reduced, and the durability of the non-aqueous electrolyte secondary battery 20 is enhanced.

In addition, as compared to the case where only one negative electrode tab 50a is provided per turn of the negative electrode plate 5, the current collection resistance of the negative electrode plate 5 can be reduced. Thus, the output current of the non-aqueous electrolyte secondary battery 20 can be increased.

The distal ends of all of the positive electrode tabs 40a forming the connection portion 63 overlap with the tab joint portion 62c in the plate thickness direction thereof. This can prevent the distal ends of the positive electrode tabs 40a from protruding from the tab joint portion 62c and contacting the adjacent electrode body 3. A restriction member, such as a tape, for restricting contact of portions of the positive electrode tab 40a protruding from the tab joint portion 62c with the adjacent electrode body 3 is not necessarily provided, and therefore, the number of components can be reduced and the effort of assembling the restriction member can be eliminated as compared to a case where the restriction member is provided.

Among the distal ends of all of the positive electrode tabs 40a forming the connection portion 63, the displacement in the thickness direction of the electrode body