Secondary batteries

Abstract

W1 / T1 is set to be 5 or more for W1 (mm) as the width of an electrode body in a direction perpendicular to its winding axis direction and thickness direction and T1 (mm) as the thickness of the electrode body 3.

Description

[Technical Field]

[0001] The present disclosure relates to a secondary battery including a flat electrode assembly 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 technology]

[0002] Patent Document 1 discloses a secondary battery including an outer casing having a pair of first side walls arranged parallel to and facing each other and a pair of second side walls arranged parallel to and facing each other, and a flat electrode assembly having a strip-shaped positive electrode plate and a strip-shaped negative electrode plate wound with a strip-shaped separator interposed therebetween, the flat electrode assembly housed in the casing with its winding axis oriented perpendicular to the first side wall and parallel to the second side wall. In this secondary battery, where W (mm) is the width of the electrode assembly in the direction perpendicular to the winding axis and thickness direction, X (mm) is the thickness of the electrode assembly, and Y (mm) is the thickness of the separator layer at the center, W / (XY) is set to be 1.7 to 3.8. This suppresses bending and loosening of the positive and negative electrode plates. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2016-105415 Summary of the Invention

[0004] In Patent Document 1, the ratio of the thickness of the electrode body to the width in the direction perpendicular to the winding axis and the thickness direction of the electrode body is high, and the ratio of the volume of the space formed between the curved surfaces at both ends of the electrode body in the width direction and the second side wall of the outer casing to the volume of the outer casing is large, resulting in a low energy density.

[0005] The secondary battery according to the present disclosure is a secondary battery comprising: an outer casing having a pair of first side walls arranged parallel to and facing each other and a pair of second side walls arranged parallel to and facing each other; and a flat electrode body having a strip-shaped positive electrode plate and a strip-shaped negative electrode plate wound with a strip-shaped separator interposed therebetween, the flat electrode body being housed in the outer casing with its winding axis direction oriented perpendicular to the first side wall and parallel to the second side wall; a sealing plate; and a terminal attached to the sealing plate; the outer casing has an opening sealed by the sealing plate, and one end edge in the winding axis direction of the positive electrode plate of the electrode body and one end edge in the winding axis direction of the negative electrode plate of the electrode body are disposed adjacent to each other; a current collecting tab protruding from the other end edge of the electrode body, and the current collecting tab 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 first side walls and the electrode body; the current collecting tab is connected to the second current collector in a bent state; the second current collector is welded to the second region of the first current collector; and when W1 (mm) is the width of the electrode body in a direction perpendicular to the winding axis direction and the thickness direction, and T1 (mm) is the thickness of the electrode body, W1 / T1 is 5 or more.

[0006] According to the present disclosure, in the novel battery structure described above, when the width of the electrode body in the direction perpendicular to the winding axis and thickness direction is W1 (mm) and the thickness of the electrode body is T1 (mm), by making W1 / T1 5 or more, the effective volume of the electrode body that contributes to power generation in the internal space of the outer casing can be increased, thereby further increasing the energy density of the secondary battery. [Brief explanation of the drawings]

[0007] [Figure 1] FIG. 1 is a perspective view showing a nonaqueous electrolyte secondary battery according to an embodiment of the present disclosure. [Figure 2] FIG. 2 is a cross-sectional view taken along line II-II in FIG. [Figure 3] FIG. 3 is a diagram showing an electrode assembly including a plurality of electrode bodies. [Figure 4] FIG. 4 is a schematic plan view showing the electrode assembly in an unfolded state. [Figure 5] FIG. 5 is a cross-sectional view taken along line VV in FIG. [Figure 6] FIG. 6 is a schematic cross-sectional view taken along line VI-VI in FIG. [Figure 7] FIG. 7 is a schematic cross-sectional view taken along line VII-VII in FIG. [Figure 8A] FIG. 8A is a perspective view of the sealing plate to which the positive electrode terminal, the first positive electrode current collector, the negative electrode terminal, and the first negative electrode current collector are attached, as viewed from the outer surface side of the battery. [Figure 8B] FIG. 8B is a perspective view of the sealing plate to which the positive electrode terminal, the first positive electrode current collector, the negative electrode terminal, and the first negative electrode current collector are attached, as viewed from the inner surface side of the battery. [Figure 9] FIG. 9 is a view equivalent to FIG. 5 showing the tip region of the positive electrode tab before bending. [Figure 10] FIG. 10 is a perspective view of the electrode assembly before the tip region of the positive electrode tab is bent. [Figure 11A] FIG. 11A is a diagram showing a state in which a first positive electrode current collector and a first negative electrode current collector are disposed between a second positive electrode current collector and a second negative electrode current collector. [Figure 11B] FIG. 11B is a diagram showing a state in which the distance between the second positive electrode current collector and the second negative electrode current collector is reduced. [Figure 11C] FIG. 11C is a diagram showing the state after the first positive electrode current collector and the second positive electrode current collector are connected, and the first negative electrode current collector and the second negative electrode current collector are connected. [Figure 12] FIG. 12 is a development view of the electrode holder. DETAILED DESCRIPTION OF THE INVENTION

[0008] Hereinafter, embodiments of the present disclosure will be described with reference to the drawings. 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 exemplary in nature and is not intended to limit the present disclosure, its applications, or its uses in any way.

[0009] Fig. 1 is a perspective view showing a nonaqueous 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 nonaqueous electrolyte secondary battery 20 includes a battery case 100 made of a prismatic outer casing 1 in the shape of a bottomed rectangular cylinder having an opening, and a sealing plate 2 that seals the opening of the prismatic outer casing 1. The prismatic outer casing 1 and the sealing plate 2 are each preferably made of metal, more preferably aluminum or iron.

[0010] The rectangular outer casing 1 has a bottom 1a, a pair of first side walls 1b, 1c, a second front side wall 1d, and a second rear side wall 1e. The pair of first side walls 1b, 1c are arranged parallel to and facing each other. The second front side wall 1d and the second rear side wall 1e are arranged parallel to and facing each other. The pair of first side walls 1b, 1c are perpendicular to the longitudinal direction of the sealing plate 2, and the area of ​​the pair of first side walls 1b, 1c is smaller than the area of ​​the second front side wall 1d and the second rear side wall 1e. Here, the distance between the first side walls 1b, 1c in the opposing direction is defined as DI1 (mm), the distance between the second front side wall 1d and the second rear side wall 1e in the opposing direction is defined as DI2 (mm), and the distance between the bottom 1a and the sealing plate 2 is defined as DI3 (mm). DI1 is set to 300, and DI2 is set to 40. In other words, DI1 / DI2 is 6 or greater. DI3 is set to 95.

[0011] As shown in Fig. 3, two electrode assemblies 3 are housed within the rectangular exterior housing 1 together with an electrolyte. The electrode assemblies 3 have a strip-shaped positive electrode plate 4 and a strip-shaped negative electrode plate 5 wound with a strip-shaped separator SP interposed therebetween, and have a flat shape. The electrode assemblies 3 are housed within the rectangular exterior housing 1 with their winding axis oriented 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.

[0012] As shown in Figures 4 and 5, a plurality of positive electrode tabs 40a as current collecting tabs are integrally provided and overlap one end edge in the winding axis direction of the positive electrode plate 4 of the electrode assembly 3. The positive electrode tabs 40a are formed in the shape of a trapezoidal plate whose width gradually increases from the tip to the base end. These multiple positive electrode tabs 40a are stacked to form a positive electrode tab group 40. In Figure 4, the center of the curved portion of the positive electrode plate 4 is indicated by the symbol RC.

[0013] The protruding length of the positive electrode tabs 40a gradually increases toward the second rear side wall 1e (one side in the thickness direction of the electrode body 3). In FIG. 4, of all the positive electrode tabs 40a, the positive electrode tab 40a that protrudes the furthest from the second rear side wall 1e is indicated by reference symbol 401a, and of all the positive electrode tabs 40a, the positive electrode tab 40a that protrudes the furthest from the second front side wall 1d is indicated by reference symbol 402a. In addition, the width TW of the base end of the positive electrode tab 40a increases as the protruding length of the positive electrode tab 40a increases.

[0014] The vicinity of the tips of all the positive electrode tabs 40a are connected to one another by welding with their plate surfaces facing in approximately the same direction, thereby constituting the connection portion 63. Note that in this embodiment, the connection portion 63 is formed at locations slightly distant from the tips of all the positive electrode tabs 40a, but the tips of all the positive electrode tabs 40a may also constitute the connection portion 63.

[0015] 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 is made of an exposed portion of the positive electrode core. A positive electrode protective layer 4b having lower conductivity than the positive electrode active material layer 4a is provided at the base portion of the positive electrode tab 40a. The positive electrode protective layer 4b may be a resin insulating layer, a layer containing ceramic and a resin binder, or the like. The positive electrode protective layer 4b may also contain a conductive material such as a carbon material. Note that the positive electrode protective layer 4b does not necessarily have to be provided.

[0016] A plurality of negative electrode tabs 50a as current collecting tabs are provided to protrude and overlap the other end edge of the negative electrode plate 5 of the electrode assembly 3 in the other direction of the winding axis (the side opposite to the positive electrode tab 40a). These negative electrode tabs 50a have shapes that are bilaterally symmetrical to the positive electrode tab 40a with respect to the cross section at the center of the direction of the winding axis of the electrode assembly 3. These multiple negative electrode tabs 50a are stacked to form a negative electrode tab group 50.

[0017] The negative electrode plate 5 has a region where a negative electrode active material layer is formed on both sides of the negative electrode core. The negative electrode tab 50a is made up of an exposed portion of the negative electrode core.

[0018] Here, the width of the electrode assembly 3 in the direction perpendicular to the winding axis and thickness direction is defined as W1 (mm), and the thickness of the electrode assembly 3 is defined as T1 (mm). W1 is set to 90, and T1 is set to 18. In other words, W1 / T1 is 5 or greater and 10 or less. If the length of the non-protruding portions of the positive electrode tab 40a and the negative electrode tab 50a in the electrode assembly 3 in the winding axis direction is defined as L1 (mm), then L1 is set to 270.

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

[0020] The first positive electrode current collector 61 has a generally 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 electrode current collector 62 is disposed between the electrode assembly 3 and the first side wall 1b of the rectangular exterior body 1. Specifically, the second positive electrode current collector 62 has a generally flat plate shape parallel to the first side wall 1b and extends along the first side wall 1b toward the bottom 1a. The second positive electrode current collector 62 is connected to the first positive electrode current collector 61.

[0022] As shown in FIG. 3 , the second positive electrode 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 electrode current collector 61. The tab joint portion 62c is connected to the positive electrode tab group 40. The inclined portion 62b connects the current collector connection portion 62a and the tab joint portion 62c so that the current collector connection portion 62a is located more inward in the direction of the winding axis of the electrode body 3 than the tab joint portion 62c, and is inclined relative to both. The inclined portion 62b forms a step between the current collector connection portion 62a and the tab joint portion 62c. The plate surfaces of the current collector connection portion 62a and the tab joint portion 62c face the direction of the winding axis of the electrode body 3.

[0023] The current collector connection portion 62a has a recess 62d. The portion where the recess 62d is provided is thinner than the surrounding area. A through-hole 62e is provided in the recess 62d. The current collector connection portion 62a is joined to the first positive electrode current collector 61 at the recess 62d.

[0024] 10, the second negative electrode current collector 72 also has a current collector connection portion 72a, an inclined portion 72b, and a tab joint portion 72c, similar to the second positive electrode current collector 62. The current collector connection portion 72a is provided with a recess 72d and a through-hole 72e.

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

[0026] 6, the tip regions including the connection portions 63 of all of the positive electrode tabs 40a configured as described above are bent toward the second rear side wall 1e (one side in the thickness direction of the electrode assembly 3) so that their plate surfaces face in the plate thickness direction of the tab joint portion 62c of the second positive electrode current collector 62. In other words, the tips of all of the positive electrode tabs 40a constituting the connection portions 63 face toward the second rear side wall 1e. In addition, the connection portions 63 are welded to the surface of the tab joint portion 62c of the second positive electrode current collector 62 facing the electrode assembly 3.

[0027] Furthermore, 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.

[0028] The negative electrode tab group 50 is also welded to the second negative electrode current collector 72 in the same manner as the positive electrode tab group 40 .

[0029] 2 and 6, the distance between the positive electrode tab 40a non-protruding region on the end face of the electrode assembly 3 on the protruding side (one side in the winding axis direction) of the positive electrode tab 40a and the first side wall 1b on the positive electrode tab 40a side is defined as DP (mm), and the distance between the negative electrode tab 50a non-protruding region on the end face of the electrode assembly 3 on the protruding side (the other side in the winding axis direction) of the negative electrode tab 50a and the first side wall 1c on the negative electrode tab 50a side is defined as DN (mm). DP and DN are set to 15. Therefore, (DP + DN) / DI1 is approximately 1 / 10. In other words, (DP + DN) / DI1 is 1 / 10 or less.

[0030] As shown in Figure 7, if the distance between the electrode body 3 and the bottom 1a is DL (mm) and the distance between the electrode body 3 and the sealing plate 2 is DU (mm), DL is set to 1 and DU is set to 4.

[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- or bag-shaped insulating sheet disposed inside the rectangular outer casing 1 and accommodating the electrode assembly 3. Reference numeral 15 denotes an electrolyte injection hole provided in the sealing plate 2. Reference numeral 16 denotes a sealing member that seals the electrolyte injection hole 15. Reference numeral 17 denotes a gas release valve provided in the sealing plate 2.

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

[0033] [Attaching the terminal and first current collector to the sealing plate] The sealing plate 2 has a positive electrode terminal mounting hole near one end and a negative electrode terminal mounting hole near the other end. An external insulating member 10 is arranged on the outer surface of the sealing plate 2 around the positive electrode terminal mounting hole, and an internal insulating member 11 and a first positive electrode current collector 61 are arranged on the inner surface of the sealing plate 2 around the positive electrode terminal mounting hole. Then, from the outside of the battery, a positive electrode terminal 8 is inserted through the through hole in the external insulating member 10, the positive electrode terminal mounting hole in the sealing plate 2, the through hole in the internal insulating member 11, and the through hole in the first positive electrode current collector 61, and the positive electrode terminal 8 is crimped onto the first positive electrode current collector 61. More preferably, the crimped portion of the positive electrode terminal 8 is welded to the first positive electrode current collector 61.

[0034] An external insulating member 12 is arranged on the outer surface of the sealing plate 2 around the negative terminal mounting hole, and an internal insulating member 13 and a first negative electrode current collector 71 are arranged on the inner surface of the sealing plate 2 around the negative terminal mounting hole. Then, a negative electrode terminal 9 is inserted from the outside of the battery through the through hole in the external insulating member 12, the negative electrode terminal mounting hole in the sealing plate 2, the through hole in the internal insulating member 13, and the through hole in the first negative electrode current collector 71, and the negative electrode terminal 9 is crimped onto the first negative electrode current collector 71. It is more preferable to further weld the crimped portion of the negative electrode terminal 9 to the first negative electrode current collector 71.

[0035] 8A and 8B 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. 8A shows the outside of the battery, and Fig. 8B shows the inside of the battery.

[0036] The first positive electrode current collector 61 has a first region 61a that is arranged along the sealing plate 2, and a second region 61b that is folded from an end of the first region 61a. In the state of the nonaqueous 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 outer casing 1. The second region 61b is arranged between the first side wall 1b of the rectangular outer casing 1 and the electrode body 3.

[0037] The first negative electrode current collector 71 has a first region 71a that is arranged along the sealing plate 2, and a second region 71b that is folded from an end of the first region 71a. In the state of the nonaqueous 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 outer casing 1. The second region 71b is arranged between the first side wall 1c of the rectangular outer casing 1 and the electrode body 3.

[0038] It is preferable to provide notches 61c at both widthwise ends of the second region 61b of the first positive electrode current collector 61. When connecting the second region 61b to the second positive electrode current collector 62 (described later), gripping the notches 61c enables more stable welding, resulting in the stable formation of a higher-quality connection. It is preferable that the notches 61c are located closer to the bottom 1a of the rectangular outer casing 1 than the inner insulating member 11 in the second region 61b. It is preferable that the notches 61c are located near the end of the second region 61b on the first region 61a side. It is also preferable that the second region 71b of the first negative electrode current collector 71 also have notches 71c at both widthwise ends. When the inner insulating member 11 has a wall portion covering a portion of the second region 61b, it is preferable that the notches 61c have an area that is not covered by the wall portion of the inner insulating member 11.

[0039] The positive electrode terminal 8 and the first positive electrode current collector 61 are preferably made of metal, more preferably aluminum. The negative electrode terminal 9 and the first negative electrode current collector 71 are preferably made of metal, more preferably copper. The negative electrode terminal 9 may include an area made of aluminum and an area made of copper. In this case, it is preferable that the area made of copper is connected to the first negative electrode current collector 71 made of copper, and the area made of aluminum is exposed to the outside of the battery.

[0040] [Positive electrode] First, a method for manufacturing 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 mixed and 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, carbon material as a conductive material, polyvinylidene fluoride (PVdF) as a binder, and N-methyl-2-pyrrolidone (NMP) as a dispersion medium are mixed together 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-described method are applied to both sides of an aluminum foil serving as a positive electrode core 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. In addition, the positive electrode protective layer slurry is applied to the widthwise end portions of the region where the positive electrode active material layer slurry is applied.

[0044] The positive electrode substrate coated with the positive electrode active material layer slurry and the positive electrode protective layer slurry is dried to remove the NMP contained in the positive electrode active material layer slurry and the positive electrode protective layer slurry. This forms the positive electrode active material layer and the positive electrode protective layer. The positive electrode active material layer is then compressed to form a positive electrode base plate. This positive electrode base plate is cut into a predetermined shape to form the positive electrode plate 4. The positive electrode base plate can be cut by irradiation with an energy beam such as a laser, using a mold, a cutter, or the like.

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

[0046] [Preparation of negative electrode active material layer slurry] Graphite as the negative electrode active material, styrene butadiene rubber (SBR) and carboxymethyl cellulose (CMC) as binders, and water as a dispersion medium are kneaded together 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 serving as a negative electrode substrate using a die coater.

[0048] The negative electrode substrate coated with the negative electrode active material layer slurry is dried to remove water contained in the negative electrode active material layer slurry. This forms the negative electrode active material layer. The negative electrode active material layer is then compressed to form a negative electrode base plate. This negative electrode base plate is cut into a predetermined shape to form the negative electrode plate 5. The negative electrode base plate can be cut by irradiation with energy rays such as a laser, using a mold, a cutter, or the like.

[0049] [Preparation of electrode body] The strip-shaped positive electrode plate 4 and strip-shaped negative electrode plate 5 prepared by the above-mentioned method are wound with a strip-shaped polyolefin separator SP interposed therebetween to prepare a flat wound electrode body 3. The electrode body 3 has a flat region in the center and curved portions on both ends of the flat region.

[0050] A positive electrode tab group 40, in which multiple positive electrode tabs 40a are stacked, is provided at one end in the direction in which the winding axis of the electrode body 3 extends. A negative electrode tab group 50, in which multiple negative electrode tabs 50a are stacked, is provided at the other end in the direction in which the winding axis of the electrode body 3 extends. Note that in a 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 shifted to one side from the winding axis.

[0051] Furthermore, by forming the positive electrode tab 40a and / or the negative electrode tab 50a in a shape in plan view that gradually increases in width from the tip to the base, the positive electrode tab 40a and / or the negative electrode tab 50a can be made less susceptible to damage even when an impact or vibration is applied to the nonaqueous electrolyte secondary battery 20. Furthermore, forming the corners of the base portion into an R-shape is more effective.

[0052] As described above, by providing the positive electrode protective layer 4b at the base of the positive electrode tab 40a, damage to the positive electrode tab 40a can be suppressed. Also, by providing the negative electrode active material layer at the base 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 nonaqueous electrolyte secondary battery 20 configured as described above, as shown in FIG. 9 , the tip regions of all the positive electrode tabs 40a are overlapped with the tab joints 62c of the second positive electrode current collector 62, and a welding jig T is applied to a position slightly lower than the tips of all the positive electrode tabs 40a to perform welding, thereby joining all the positive electrode tabs 40a to each other and to the second positive electrode current collector 62. As a result, the portions slightly lower than the tips of all the positive electrode tabs 40a form the connection portions 63. Alternatively, the connection portions 63 may be formed 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. 10 , the plate surfaces of the tab joints 62c of the second positive electrode current collector 62 are oriented in the thickness direction of the electrode assembly 3. The tip regions of all the positive electrode tabs 40a are stacked with their plate surfaces facing the thickness direction of the electrode body 3 and close to the positive electrode tab 40a with the shortest protruding length (one end side in the thickness direction of the electrode body 3). At this time, 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, the connection portion 63 is preferably disposed closer to the base side (left side in FIG. 9) of the positive electrode tab group 40 in the width direction of the tab joint portion 62c (left-right direction in FIG. 9). With this configuration, when the positive electrode tab group 40 is bent, a curved shape can be more reliably formed in a stable manner near the base of the positive electrode tab group 40. This makes it possible to suppress damage to the positive electrode tab group 40. Furthermore, even if the positive electrode tab 40a is misaligned, the positive electrode tab group 40 and the tab joint portion 62c can be stably joined.

[0055] Furthermore, the lower end portion (the portion that becomes the end portion on the bottom 1a side of the rectangular outer casing 1) of the second positive electrode current collector 62 is preferably located lower than the lower end portion (the portion that becomes the end portion on the bottom 1a side of the rectangular outer casing 1) of the positive electrode tab group 40. With this configuration, it becomes possible to more reliably and stably bend the positive electrode tab group 40 in the step of bending the positive electrode tab group 40, which will be described later.

[0056] 5, the tip regions of all the positive electrode tabs 40a are bent so that their plate surfaces face approximately in the direction of the winding axis of the electrode assembly 3 (for example, so that the inclination of the tab joints 62c with respect to the winding axis is less than ±15°). This causes the plate surfaces of the tab joints 62c of the second positive electrode current collector 62 to face approximately in the direction of the winding axis of the electrode assembly 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 group] As shown in Fig. 3, multiple electrode assemblies 3 with their positive electrode tab groups 40 and negative electrode tab groups 50 folded are stacked and fixed with an electrode assembly fixing means such as 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. In each electrode assembly 3, the positive electrode tab groups 40 are all folded in the same direction. In each electrode assembly 3, the negative electrode tab groups 50 are all folded 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 onto 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 and second current collectors] The second region 61b of the first positive electrode current collector 61 is disposed 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 disposed inside the current collector connection portion 72a of the second negative electrode current collector 72. The second region 61b of the first positive electrode current collector 61 is then connected to the current collector connection portion 62a of the second positive electrode current collector 62. 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. Examples of joining methods that can be used include ultrasonic welding (ultrasonic bonding), resistance welding, and welding using high-energy rays such as lasers. Welding using high-energy rays such as lasers is particularly preferred.

[0061] 11A to 11C are cross-sectional views taken 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 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.

[0062] 11A, 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 disposed 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 case, 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 is preferably larger than the distance D2 between the outer surface of the second region 61b and the outer surface of the second region 71b. Note that D1 is preferably larger than D2 by 0.1 to 5 mm, and more preferably by 0.2 to 3 mm.

[0063] 11B, the current collector connection portion 62a and / or the current collector connection portion 72a are displaced inward to reduce the distance between the current collector connection portion 62a and the current collector connection portion 72a. This changes 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 to D1'. At this time, the difference between D2 and D1' is preferably 0 to 0.2 mm.

[0064] 11B, a high-energy beam such as a laser is irradiated onto each of the current collector connection portion 62a and the current collector connection portion 72a, thereby joining 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 by welding, and joining 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 by welding.

[0065] 11C, joint 64, which is a weld between second region 61b and current collector connection portion 62a, is formed in recess 62d. Also, joint 74, which is a weld between second region 71b and current collector connection portion 72a, is formed in recess 72d.

[0066] 11A to 11C, it is possible to more stably weld 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, by a simpler method, thereby forming highly reliable joints 64 and 74.

[0067] The portions where the recesses 62d, 72d are formed are thinner than the surrounding areas. By performing welding so that the joints 64, 74 are formed in these thinner portions, a higher quality joint can be formed more stably. This results in a more reliable secondary battery. Furthermore, by using the through-hole 62e to measure the presence or size of a 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 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 have been connected, respectively.

[0069] [Electrode holder] Figure 12 is a development view of the electrode holder 14. The insulating sheet that constitutes the electrode holder 14 is folded along the dashed lines in Figure 12 to form the box-shaped electrode holder 14. The electrode holder 14 has a holder bottom 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 holder 14 is box-shaped, it has an area where the holder first side 14d, the holder second side 14e, and the holder third side 14f overlap, and it has an area where the holder fourth side 14g, the holder fifth side 14h, and the holder sixth side 14i overlap.

[0071] With two electrode bodies 3 arranged in a box-shaped electrode body holder 14, these two electrode bodies 3 are inserted into a rectangular exterior body 1. Then, a 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. An electrolyte is poured through an electrolyte pouring hole 15 provided in the sealing plate 2, and the electrolyte pouring hole 15 is sealed with a sealing member 16. This completes a nonaqueous electrolyte secondary battery 20.

[0072] Therefore, according to this embodiment, the ratio of the thickness T1 of the electrode body 3 to the width W1 in the direction perpendicular to the winding axis and thickness direction of the electrode body 3 is set to 1 / 5 or less, so that the ratio of the volume of the space S (see Figure 7) formed on both sides of the curved surfaces C (see Figure 7) at both ends of the width direction of the electrode body 3 to the volume of the rectangular outer casing 1 can be reduced, thereby increasing the energy density, compared to when this ratio is set to a value exceeding 1 / 5.

[0073] Furthermore, since the width W1 of the electrode body 3 in the direction perpendicular to the winding axis and thickness direction is set to 10 times or less the thickness T1 of the electrode body 3, it is possible to narrow the spacing between the positive electrode tab 40a and the negative electrode tab 50a and reduce the current collection resistance compared to when the width W1 is set to more than 10 times the thickness T1 of the electrode body 3. Furthermore, by ensuring the thickness T1 of the electrode body 3 and the number of windings, it is possible to reduce the volume proportion of the separator SP and the negative electrode plate 5 not used for charging and discharging in each electrode body 3, making it easier to increase the cell capacity.

[0074] Furthermore, the ratio of the sum of the distance DP between the non-protruding region of the positive electrode tab 40a at the protruding side end face of the electrode body 3 and the first side wall 1b on the positive electrode tab 40a side and the distance DN between the non-protruding region of the negative electrode tab 50a at the protruding side end face of the electrode body 3 and the first side wall 1c on the negative electrode tab 50a side to the distance DI1 in the opposing direction of the first side walls 1b, 1c is set to 1 / 10 or less. Therefore, compared to when this ratio is set to a value exceeding 1 / 10, the ratio of the volume of the electrode body 3 to the volume of the rectangular outer casing 1 can be increased, and the energy density can be increased.

[0075] Furthermore, because the positive electrode current collector 6 includes the first positive electrode current collector 61 and the second positive electrode current collector 62, the positive electrode tab group 40 can be folded without bending the positive electrode current collector 6, making it possible to more stably produce a secondary battery with a high volumetric energy density using a simpler method. Even when the number of electrode assemblies 3 housed 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 complex shape. This increases the degree of freedom in the number of electrode assemblies 3 housed in the battery case 100.

[0076] Furthermore, the tab joint 62c of the second positive electrode current collector 62 is positioned closer to the first side wall 1b of the rectangular exterior body 1 than the current collector connection part 62a of the second positive electrode current collector 62. With this configuration, the space between the first side wall 1b and the electrode body 3 can be used more effectively, allowing the power generation part of the electrode body 3 to 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.

[0077] In the electrode assembly 3, the positive electrode tab group 40 is preferably located closer to the sealing plate 2. This allows the conductive path from the positive electrode tab group 40 to the positive electrode terminal 8 to be short, resulting in a nonaqueous electrolyte secondary battery 20 with low internal resistance. In the electrode assembly 3, the negative electrode tab group 50 is preferably located closer to the sealing plate 2. This allows the conductive path from the negative electrode tab group 50 to the negative electrode terminal 9 to be short, resulting in a nonaqueous electrolyte secondary battery 20 with low internal resistance.

[0078] It is preferable to place an insulating member other than the electrode assembly holder 14 between the area where 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 overlap and the first side wall 1b of the rectangular outer casing 1. It is also preferable to place an insulating member other than the electrode assembly holder 14 between the area where 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 overlap and the first side wall 1c of the rectangular outer casing 1. With this configuration, even when the nonaqueous electrolyte secondary battery 20 is subjected to impact or vibration, damage to the joints between the respective members, the positive electrode tab group 40, and the negative electrode tab group 50 can be suppressed.

[0079] (Other embodiments) The above-described embodiments are merely examples of the present invention, and the present invention is not limited to these examples. These examples may be combined with well-known, commonly used, or publicly known technologies, or may be partially replaced. Modified inventions that would be easily conceived by a person skilled in the art are also included in the present invention.

[0080] In the above-described embodiment, the present disclosure is applied to a nonaqueous electrolyte secondary battery 20 having two electrode bodies 3, but the present disclosure can also be applied to a nonaqueous electrolyte secondary battery 20 having three or more electrode bodies 3, or only one electrode body 3. [Explanation of symbols]

[0081] 1. Rectangular exterior body 1b,1c 1st side wall 1d Second front wall 1e Second rear wall 2 Sealing plate 3 Electrode body 4 positive electrode plate 5 negative electrode plate 8 Positive terminal 9 Negative terminal 20 Nonaqueous electrolyte secondary battery 40a Positive electrode tab (current collecting tab) 50a Negative electrode tab (current collecting tab) 61 First positive electrode current collector 61a 1st area 61b 2nd area 62 Second positive electrode current collector 71 First negative electrode current collector 71a 1st area 71b 2nd area 72 Second negative electrode current collector SP Separator W1 width T1 Thickness DI1, DP, DN interval

Claims

1. an exterior body having a pair of first side walls arranged parallel to and facing each other and a pair of second side walls arranged parallel to and facing each other; a flat electrode assembly having a strip-shaped positive electrode plate and a strip-shaped negative electrode plate wound with a strip-shaped separator interposed therebetween, the flat electrode assembly being housed in the exterior body with the winding axis direction of the electrode assembly oriented perpendicular to the first side wall and parallel to the second side wall, A sealing plate, Further comprising a terminal attached to the sealing plate, the exterior body has an opening that is sealed by the sealing plate, a current collecting tab protruding from one end edge of the positive electrode plate of the electrode body in the winding axis direction and from the other end edge of the negative electrode plate of the electrode body in the winding axis direction; the current collecting tab 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 first side walls and the electrode body, a recess is provided in the second current collector, a recess-forming portion of the second current collector where the recess is provided is thinner than its surroundings, and a through hole is provided in the recess-forming portion; the second current collector is disposed between the first side wall and the electrode body, the current collecting tab is connected to the second current collector in a state where the plate surface of the tip region thereof is bent so as to face substantially in the direction of the winding axis of the electrode body, the recessed portion of the second current collector is welded to the second region of the first current collector; A secondary battery characterized in that W1 / T1 is 5 or more, where W1 (mm) is the width of the electrode body in a direction perpendicular to the winding axis direction and the thickness direction, and T1 (mm) is the thickness of the electrode body.

2. The secondary battery according to claim 1, A secondary battery characterized in that, when the width of the electrode body in a direction perpendicular to the winding axis direction and the thickness direction is W1 (mm) and the thickness of the electrode body is T1 (mm), W1 / T1 is 10 or less.

3. 3. The secondary battery according to claim 1, a positive electrode tab is provided to protrude from one end edge of the positive electrode plate of the electrode body in the winding axis direction; a negative electrode tab is provided to protrude from the other end edge of the negative electrode plate of the electrode body in the winding axis direction; a distance DP (mm) between a positive electrode tab non-protruding region at one end face of the electrode body in the winding axis direction and the first side wall on the positive electrode tab side, a distance DN (mm) between a negative electrode tab non-protruding region at the other end face of the electrode body in the winding axis direction and the first side wall on the negative electrode tab side, and a distance DI1 (mm) between the first side walls of the exterior bodies in an opposing direction.

4. The secondary battery according to any one of claims 1 to 3, A plurality of the electrode bodies are provided, A secondary battery characterized in that the collecting tabs of the plurality of electrode bodies and the terminals are electrically connected by one first collector and a plurality of second collectors, each corresponding to one electrode body.

5. The secondary battery according to any one of claims 1 to 4, a plurality of the current collecting tabs are provided to protrude from one end edge of the positive electrode plate of the electrode body in the winding axis direction and from the other end edge of the negative electrode plate of the electrode body in the winding axis direction, tip regions of the plurality of current collecting tabs protruding from one end edge of the positive electrode plate of the electrode body in the winding axis direction are joined to each other in an overlapping state, A secondary battery characterized in that the tip regions of the plurality of current collecting tabs protruding from the other end edge in the winding axis direction of the negative electrode plate of the electrode body are joined to each other in an overlapping state.

6. A method for producing a secondary battery according to any one of claims 1 to 5, a current collecting tab provided on one end edge of the positive electrode plate of the electrode body in the winding axis direction and on the other end edge of the negative electrode plate of the electrode body in the winding axis direction, the tip regions of the current collecting tabs being connected to the second current collector with their plate surfaces facing in the thickness direction of the electrode body, and then the current collecting tabs being bent so that the plate surface of their tip regions faces approximately in the winding axis direction of the electrode body.

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