Non-aqueous electrolyte secondary battery

Abstract

This secondary battery comprises: an electrode body including an electrode plate; a square exterior body containing the electrode body; a sealing plate; an electrode terminal provided to the sealing plate; a first current collector disposed between the electrode body and the sealing plate and connected to the electrode terminal; a second current collector disposed between the electrode body and a side wall of the square exterior body and connected to the first current collector; and a tab group that is formed by stacking a plurality of tabs extending from the electrode plate toward the side wall and is connected to the second current collector. The tab group is connected to the second current collector and bent in parallel with a side wall on the side of the connection part with the second current collector. The radius of curvature of a first rounded part of the base part of each tab is greater than the radius of curvature of a second rounded part of the tip part of each tab.

Description

[Technical field]

[0001] The present disclosure relates to a non-aqueous electrolyte secondary battery. [Background technology]

[0002] 2. Description of the Related Art In non-aqueous electrolyte secondary batteries such as lithium ion batteries, a configuration is known in which a group of tabs extending from an electrode assembly housed in a rectangular outer casing are connected, via a current collector, to external terminals provided on a sealing plate.

[0003] Patent Document 1 discloses a current collector that is composed of a base portion disposed between a sealing plate and an electrode assembly, and legs that extend from the end of the base portion toward the bottom along the side wall of the exterior body. The base portion is connected to an external terminal, and the legs are connected to an electrode plate stack (a group of tabs) that is pulled out from the electrode assembly. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2016-85875 A Summary of the Invention

[0005] In the current collector disclosed in Patent Document 1, the legs are disposed between the electrode body and the side wall of the exterior body, and the space in which the legs are disposed becomes dead space that does not contribute to power generation, which causes a decrease in the volumetric energy density of the battery.

[0006] A secondary battery according to the present disclosure includes an electrode body including an electrode plate, a rectangular exterior body having an opening and housing the electrode body, a sealing plate that seals the opening, an electrode terminal provided on the sealing plate, a first current collector disposed between the electrode body and the sealing plate and connected to the electrode terminal, a second current collector disposed between the electrode body and a side wall of the rectangular exterior body and connected to the first current collector, and a plurality of electrode tabs extending from the electrode plate towards the side wall and connected to the second current collector. the second current collector is made of a flat plate having a surface parallel to the side wall, the tab group is bent parallel to the side wall at the connection portion side with the second current collector, and each of the electrode tabs has a first rounded portion having a rounded shape provided at each corner on both sides in the width direction of a base portion with the electrode plate, and a second rounded portion having a rounded shape provided at each corner on both sides in the width direction of a tip portion in an extension direction, and a radius of curvature of the first rounded portion is greater than a radius of curvature of the second rounded portion.

[0007] According to the present disclosure, it is possible to provide a secondary battery that has a high volumetric energy density, and that alleviates current concentration while ensuring the welding stability between the tab group and the current collector. [Brief description of the drawings]

[0008] [Figure 1] FIG. 1 is a perspective view showing a nonaqueous electrolyte secondary battery. [Diagram 2] FIG. 2 is a cross-sectional view showing the internal structure of the nonaqueous electrolyte secondary battery. [Diagram 3] FIG. 3 is a view showing the vicinity of the connection portion between the second current collector and the tab group before the tab group is folded. [Figure 4] FIG. 4 is a view showing the vicinity of the connection portion between the second current collector and the tab group after the tab group is folded. [Diagram 5] FIG. 5 is a diagram showing electrode tabs extending from the electrode plate according to this embodiment. [Figure 6] FIG. 6 is a diagram showing the second current collector. [Figure 7] FIG. 7 is a diagram showing an electrode assembly group including a plurality of electrode bodies. [Figure 8] FIG. 8 is a diagram showing details of the electrode tab according to this embodiment. [Figure 9] FIG. 9 is a diagram showing a schematic diagram of a flow of a current flowing from an electrode plate to an electrode tab according to the present embodiment. [Figure 10] FIG. 10 shows electrode tabs extending from an electrode plate according to the earlier application. [Figure 11] FIG. 11 is a diagram showing details of the electrode tab according to the previous application. [Figure 12] FIG. 12 is a diagram showing a schematic diagram of a current flow from an electrode plate to an electrode tab according to the previous application. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] (Non-aqueous electrolyte secondary battery related to the previous application) The applicant of the present application has disclosed the structure of a non-aqueous electrolyte secondary battery in the specification of a previous application (Patent Application No. 2019-174878).

[0010] As shown in FIGS. 1 and 2 , in the nonaqueous electrolyte secondary battery 20 disclosed in the above specification, a tab group 40 of an electrode body 3 including electrode plates (positive electrode plate 4 and negative electrode plate 5) housed in a rectangular outer casing 1 and an electrode terminal 8 provided on a sealing plate 2 are electrically connected to each other by a first current collector 61 and a second current collector 62.

[0011] The first current collector 61 is disposed between the electrode body 3 and the sealing plate 2, and is connected to the electrode terminal 8. The second current collector 62 is disposed between the electrode body 3 and the side wall 1b of the rectangular exterior body 1, and is made of a flat plate having a surface parallel to the side wall 1b.

[0012] 10 and 11, the tab group 40 is formed by stacking a plurality of electrode tabs (e.g., positive electrode tabs 41) extending from an end side 4a on one side in the short direction of an electrode plate (e.g., positive electrode plate 4). As shown in Fig. 3, the tab group 40 extends from the electrode body 3 toward the side wall 1b and is connected to the second current collector 62. As shown in Fig. 4, the tab group 40 is bent parallel to the side wall 1b on the side of a connection portion 63 with the second current collector 62.

[0013] According to this configuration, the tab group 40 can be folded without bending the second current collector 62. This makes it possible to fabricate a nonaqueous electrolyte secondary battery with high volumetric energy density by a simple method.

[0014] The present inventors further improved the nonaqueous electrolyte secondary battery by making the radius of curvature of the corners on both sides in the width direction of the base portion of each electrode tab where it is joined to the electrode plate larger than the radius of curvature of the corners on both sides in the width direction of the tip portion of each electrode tab, thereby making it possible to alleviate current concentration and stress concentration at the corners on both sides in the width direction of the base portion of the electrode tab where it is joined to the electrode plate while ensuring the welding stability between the tab group and the second current collector.

[0015] (Overall configuration of non-aqueous electrolyte secondary battery) Hereinafter, the embodiments of the present disclosure will be described in detail with reference to the drawings. The following description of the preferred embodiment is essentially merely illustrative and is not intended to limit the present disclosure, its applications, or its uses. Note that the basic configuration of the nonaqueous electrolyte secondary battery in this embodiment is the same as that of the previous application, and therefore Figures 1, 2, 3, and 4 used in the description of the previous application will be used as is.

[0016] Fig. 1 is a perspective view showing a nonaqueous electrolyte secondary battery 20 according to an embodiment of the present disclosure. Fig. 2 is a cross-sectional view showing the internal structure of the nonaqueous electrolyte secondary battery 20. As shown in Figs. 1 and 2, the nonaqueous electrolyte secondary battery 20 includes a battery case 100 including a rectangular exterior body 1 having an opening and a bottomed rectangular cylinder shape, and a sealing plate 2 that seals the opening of the rectangular exterior body 1.

[0017] The rectangular exterior body 1 has a bottom 1a, a pair of first side walls 1b, 1c, and a pair of second side walls 1d, 1e. The pair of first side walls 1b, 1c are arranged facing each other. The pair of second side walls 1d, 1e are arranged 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 pair of second side walls 1d, 1e.

[0018] The rectangular exterior housing 1 contains an electrode body 3 including a positive electrode plate 4 and a negative electrode plate 5 as electrode plates together with an electrolyte. In this embodiment, the electrode body 3 is a flat electrode body in which the positive electrode plate 4 and the negative electrode plate 5 are wound with a separator interposed therebetween. The winding axis of the electrode body 3 extends perpendicular to the first side walls 1b, 1c and parallel to the second side walls 1d, 1e. Note that the electrode body 3 is not limited to a wound electrode body, and may be, for example, a laminated electrode body in which the positive electrode plate 4 and the negative electrode plate 5 are laminated with a separator interposed therebetween.

[0019] 2, reference numeral 14 denotes a box- or bag-shaped insulating sheet that is disposed inside the rectangular exterior body 1 and houses the electrode body 3. Reference numeral 15 denotes an electrolyte injection hole provided in the sealing plate 2. Reference numeral 16 denotes a sealing member that seals the electrolyte injection hole 15. Reference numeral 17 denotes a gas release valve provided in the sealing plate 2.

[0020] In the nonaqueous electrolyte secondary battery 20, one side is a positive electrode side and the other side is a negative electrode side in the extension direction of the winding axis of the electrode body 3. Below, the positive electrode side will be mainly described, and a description of the negative electrode side may be omitted.

[0021] A positive electrode tab group 40 is provided at one end of the electrode body 3 in the direction in which the winding axis extends. Specifically, the positive electrode tab group 40 extends from one end of the electrode body 3 toward the first side wall 1b. The positive electrode tab group 40 is formed by stacking positive electrode tabs 41, 41, ... as a plurality of electrode tabs.

[0022] As shown in FIG. 5, the positive electrode plate 4 is a long strip formed in a substantially rectangular shape. The positive electrode plate 4 has an area in which a positive electrode active material layer 4b is formed on both sides of a positive electrode core. A plurality of positive electrode tabs 41, 41, ... extend from one end side 4a in the short direction of the substantially rectangular positive electrode plate 4. The positive electrode tab 41 is made of a positive electrode core exposed portion. A positive electrode protective layer having a lower conductivity than the positive electrode active material layer 4b is provided at the base portion of the positive electrode tab 41, i.e., the base portion 42 with the positive electrode plate 4. It is not necessary to provide a positive electrode protective layer. The shape of the positive electrode tab (electrode tab) 41 will be described in detail later.

[0023] The short side direction of the positive electrode plate 4 coincides with the winding axis direction of the wound electrode body 3. That is, each positive electrode tab 41 extends from the positive electrode plate 4 towards the first side wall 1b.

[0024] 2, a positive electrode terminal 8 is provided on the sealing plate 2 as an electrode terminal. The positive electrode terminal 8 is electrically connected to the positive electrode tab group 40 via a positive electrode current collector 6. The positive electrode current collector 6 is composed of a first positive electrode current collector 61 and a second positive electrode current collector 62.

[0025] 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. Specifically, the first positive electrode current collector 61 has a first region disposed along the sealing plate 2 and a second region bent from an end of the first region. The second region extends along the first side wall 1b toward the bottom 1a. The first positive electrode current collector 61 is connected to the positive electrode terminal 8.

[0026] The second positive electrode current collector 62 is disposed between the electrode body 3 and the first side wall 1b of the rectangular exterior body 1. Specifically, the second positive electrode current collector 62 is made of a flat plate having a surface 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.

[0027] 6 shows the second positive electrode current collector 62. The second positive electrode current collector 62 has a current collector connection portion 62a, an inclined portion 62b, and a tab connection portion 62c. The current collector connection portion 62a is connected to the first positive electrode current collector 61. The tab connection 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 connection portion 62c, and is inclined with respect to both of them.

[0028] The current collector connection portion 62a is provided with a recess 62d. The recess 62d is provided with a through hole 62e. The current collector connection portion 62a is joined to the first positive electrode current collector 61 at the recess 62d.

[0029] The second positive electrode current collector 62 is provided with a fuse portion 66 .

[0030] Next, there will be described the bending of the positive electrode tab group 40 and the connection between the positive electrode tab group 40 and the second positive electrode current collector 62. Fig. 3 shows the vicinity of the connection between the second positive electrode current collector 62 and the positive electrode tab group 40 before the positive electrode tab group 40 is folded.

[0031] The positive electrode tab group 40 is connected to the tab connection portion 62c of the second positive electrode current collector 62. Specifically, as shown in Fig. 3, before bending the positive electrode tab group 40, in a state in which the positive electrode tab group 40 is disposed on the tab connection portion 62c of the second positive electrode current collector 62, the tab connection portion 62c and the positive electrode tab group 40 are joined (welded) to each other, thereby forming the connection portion 63.

[0032] Here, as shown in Fig. 3, the positive electrode tab group 40 is connected to the tab connection portion 62c of the second positive electrode current collector 62, closer to one width direction side of the flat plate (the right side in Fig. 3). That is, the connection portion 63 between the positive electrode tab group 40 and the tab connection portion 62c is closer to the base side of the positive electrode tab group 40 in the width direction of the flat plate (one width direction side, the right side in Fig. 3). This makes it possible to more reliably form a curved shape near the base of the positive electrode tab group 40 when the positive electrode tab group 40 is bent.

[0033] The positive electrode tab group 40 may be connected to the tab connection portion 62c of the second positive electrode current collector 62 at the center in the width direction of the flat plate.

[0034] 4 shows the vicinity of the connection part between the second positive electrode current collector 62 and the positive electrode tab group 40 after the positive electrode tab group 40 is folded. The tab connection part 62c of the second positive electrode current collector 62, which was disposed substantially parallel to the first main surface 3a and the second main surface 3b of the electrode body 3 (see FIG. 3), is oriented substantially perpendicular to the winding axis of the electrode body 3 by folding the positive electrode tab group 40. That is, the positive electrode tab group 40 is folded parallel to the first side wall 1b on the side of the connection part 63 with the second positive electrode current collector 62. The positive electrode tab group 40 in the folded state is fixed to the electrode body 3 by the tape 80.

[0035] 7, the nonaqueous electrolyte secondary battery 20 includes a plurality of electrode bodies 3. A second positive electrode current collector 62 is connected to the positive electrode tab group 40 of each electrode body 3. The electrode bodies 3 are arranged and fixed together with tape to form an electrode body group 300. The second positive electrode current collector 62 provided on each electrode body 3 is connected to one first positive electrode current collector 61 provided on the sealing plate 2.

[0036] (Detailed structure of electrode tab) The configuration of the electrode tab according to this embodiment will be described in detail below. Note that the positive electrode tab 41 on the positive electrode side will be described as an example, and a description of the negative electrode tab on the negative electrode side will be omitted.

[0037] FIG. 8 shows the details of the positive electrode tab 41 according to this embodiment. As shown in FIG. 8, each positive electrode tab 41 extends from one end side 4a in the short side direction (winding axis direction) of the approximately rectangular positive electrode plate 4. Each positive electrode tab 41 extends perpendicular to the end side 4a of the positive electrode plate 4. Each positive electrode tab 41 is approximately rectangular. Specifically, each positive electrode tab 41 is approximately trapezoidal in shape with a side 42a (lower base) on the side of the base portion 42 with the positive electrode plate 4 as the long side and a side 45a (upper base) on the side of the tip portion 45 in the extension direction as the short side. The side 45a on the tip side of each positive electrode tab 41 is parallel to the end side 4a of the positive electrode plate 4.

[0038] Each of the corners 43, 43 on both sides in the width direction of the base portion 42 of each positive electrode tab 41 where the positive electrode plate 4 is joined is provided with a first rounded portion 44, 44 having a rounded shape. The first rounded portion 44 is formed in a circular arc shape that protrudes toward the positive electrode plate 4 side. The first rounded portion 44 is provided to relieve current concentration and stress concentration at the corners 43. It is preferable that the radius of curvature R1 of the first rounded portion 44 is, for example, 5 mm or more.

[0039] Meanwhile, second rounded portions 47, 47 having a rounded shape are provided at each of corners 46, 46 on both sides in the width direction of a tip portion 45 in the extension direction of each positive electrode tab 41. The second rounded portion 47 is formed in a convex arc shape on the side opposite to the positive electrode plate 4. Providing the second rounded portion 47 to smooth the corners 46 is essential from the viewpoint of safety when an operator comes into contact with the corners 46. The radius of curvature R2 of the second rounded portion 47 is preferably, for example, 1 mm or more and 2 mm or less.

[0040] In this embodiment, the radius of curvature R1 of the first rounded portion 44 is larger than the radius of curvature R2 of the second rounded portion 47.

[0041] In the previous application, as shown in FIG. 11, the radius of curvature R1' on the base portion 42 side and the radius of curvature R2' on the tip portion 45 side are substantially the same size.

[0042] In Fig. 8, reference symbol B1 denotes the width dimension including the first rounded portions 44, 44 of the base portion 42. Reference symbol b1 denotes the width dimension excluding the first rounded portions 44, 44 of the base portion 42. Reference symbol B2 denotes the width dimension including the second rounded portions 47, 47 of the tip portion 45. Reference symbol b2 denotes the width dimension excluding the second rounded portions 47, 47 of the tip portion 45.

[0043] 8, the hatched portion is the welded area 48 between the positive electrode tab group 40 and the second positive electrode current collector 62. The width dimension B3 of the welded area 48 is approximately equal to the width dimension b2 of the tip portion 45 excluding the second rounded portions 47, 47.

[0044] (Action and effect) As described above, according to this embodiment, the radius of curvature R1 of the first rounded portion 44 on the base portion 42 side and the radius of curvature R2 of the second rounded portion 47 on the tip portion 45 side are not made the same, but the radius of curvature R1 on the base portion 42 side is made larger than the radius of curvature R2 on the tip portion 45 side.

[0045] This makes it possible to make the radius of curvature R1 on the base portion 42 side larger than when the radius of curvature R1' on the base portion 42 side and the radius of curvature R2' on the tip portion 45 side are approximately the same as in the previous application (see Figure 11).

[0046] Here, when the radius of curvature R1' on the root portion 42 side is small (see FIG. 11) as in the previous application, as shown in FIG. 12, the current F' flowing along the edge 4a of the positive electrode plate 4 does not smoothly flow into the positive electrode tab 41. As a result, current concentration may occur at the corners 43 on both sides of the root portion 42 in the width direction.

[0047] In this embodiment, as shown in Fig. 8, the radius of curvature R1 on the side of the root portion 42 can be increased, so that the current F flowing along the edge 4a of the positive electrode plate 4 can be smoothly caused to flow into the positive electrode tab 41, as shown in Fig. 9. As a result, the occurrence of current concentration at the corners 43 on both sides of the root portion 42 in the width direction can be mitigated.

[0048] Moreover, by increasing the radius of curvature R1 on the side of the base portion 42, it is possible to alleviate stress concentration at the corners 43 on both sides of the base portion 42 in the width direction. This makes it possible to prevent the positive electrode tab 41 from breaking at the corners 43 when a load is applied to the positive electrode tab 41 due to vibration of the nonaqueous electrolyte secondary battery 20 during transportation, etc. In particular, the nonaqueous electrolyte secondary battery 20 according to this embodiment is heavy and the load applied to the positive electrode tab 41 is large because the dead space is reduced and the volumetric energy density is increased. Therefore, it is effective to adopt the above-mentioned stress concentration alleviation structure.

[0049] In this embodiment, only the radius of curvature R1 on the root portion 42 side is made large, and the radius of curvature R2 on the tip portion 45 side is not made large.

[0050] This makes it possible to prevent the width dimension b2 excluding the second rounded portions 47, 47 in the tip portion 45 from becoming smaller. That is, it is possible to prevent the width dimension B3 of the welding area 48 between the positive electrode tab group 40 and the second positive electrode current collector 62 from becoming smaller. This makes it possible to ensure a sufficient welding area between the positive electrode tab group 40 and the second positive electrode current collector 62. Therefore, it is possible to ensure sufficient welding stability between the positive electrode tab group 40 and the second positive electrode current collector 62.

[0051] As described above, it is possible to ensure the welding stability between the positive electrode tab group 40 and the second positive electrode collector 62 while mitigating current concentration and stress concentration at the corners 43 on both sides in the width direction of the base portion 42 between the positive electrode tab 41 and the positive electrode plate 4.

[0052] By setting the radius of curvature R1 of the first rounded portion 44 to 5 mm or more, it is possible to further reduce current concentration at the corners 43 on both sides in the width direction of the base portion 42. According to a simulation, when the radius of curvature R1 is 5 mm, the current density (mA / mm 2 ) is reduced by more than 10%.

[0053] Moreover, by setting the radius of curvature R1 of the first rounded portion 44 to 5 mm or more, it is possible to further reduce the stress concentration at the corners 43 on both sides in the width direction of the base portion 42. According to a simulation, when the radius of curvature R1 is 5 mm, the stress (N / mm 2 ) is reduced by more than 20%.

[0054] By making the positive electrode tab 41 approximately trapezoidal, the current F flowing along the edge 4a of the positive electrode plate 4 can be made to flow more smoothly into the positive electrode tab 41 compared to, for example, when the positive electrode tab 41 is approximately rectangular.

[0055] The negative electrode side has the same configuration as the positive electrode side, and in Fig. 2, reference numeral 9 denotes a negative electrode terminal, reference numeral 50 denotes a negative electrode tab group, reference numeral 7 denotes a negative electrode current collector, reference numeral 71 denotes a first negative electrode current collector, reference numeral 72 denotes a second negative electrode current collector, reference numeral 12 denotes an outer insulating member, and reference numeral 13 denotes an inner insulating member. In Fig. 7, reference numeral 72a denotes a current collector connection portion, reference numeral 72b denotes an inclined portion, and reference numeral 72c denotes a tab connection portion.

[0056] (Other embodiments) Although the present disclosure has been described above with reference to the preferred embodiments, such description is not limiting, and various modifications are possible.

[0057] The above structure in which the radius of curvature R1 on the base portion 42 side is larger than the radius of curvature R2 on the tip portion 45 side may be used for both the positive electrode tab and the negative electrode tab, or may be used for only one of them.

[0058] In the above embodiment, each electrode tab is generally trapezoidal, but is not limited thereto. Each electrode tab may be, for example, generally square, generally rectangular, or other generally quadrangular. Furthermore, each electrode tab is not limited to a generally quadrangular shape, and may be generally polygonal, having pentagons or more sides, as long as corners are provided on both sides in the width direction of the base portion where the electrode tab is joined to the electrode plate, and corners are provided on both sides in the width direction of the tip portion in the extension direction. [Explanation of symbols]

[0059] R1 radius of curvature R2 radius of curvature B1 Width dimension b1 Width dimension B2 Width dimension b2 Width dimension B3 width F current F' current 1. Rectangular exterior body 1b 1st side wall (side wall) 2 Sealing plate 3 Electrode body 4 Positive electrode plate (electrode plate) 4a Edge 4b Positive electrode active material layer 8 Positive terminal (electrode terminal) 20 Nonaqueous electrolyte secondary battery 40 Positive electrode tab group (tab group) 41 Positive electrode tab (electrode tab) 42 Base Around 42a 43 Corner 44 1st Are Section 45 Tip part Around 45a 46 Corner 47 2nd Are Section 48 Welding range 61 First positive electrode collector (first collector) 62 Second positive electrode collector (second collector) 63 Connection

Claims

1. An electrode body including an electrode plate; A rectangular exterior body having an opening and housing the electrode body; a sealing plate that seals the opening; an electrode terminal provided on the sealing plate; a first current collector disposed between the electrode body and the sealing plate and connected to the electrode terminal; a second current collector disposed between the electrode body and a side wall of the rectangular exterior body and connected to the first current collector; a tab group formed by stacking a plurality of electrode tabs extending from the electrode plate toward the side wall and connected to the second current collector; Equipped with the second current collector is a flat plate having a surface parallel to the side wall, the tab group is bent in parallel to the side wall on a connection portion side with the second current collector, Each of the electrode tabs is a first rounded portion having a rounded shape provided at each of both corners in a width direction of a base portion of the electrode plate; and a second rounded portion having a rounded shape provided at each of the corners on both sides in the width direction of the tip portion in the extension direction, The radius of curvature of the first rounded portion is larger than the radius of curvature of the second rounded portion, a width dimension of a welded area between the tab group and the second current collector substantially coincides with a width dimension of the tip portion excluding the second rounded portion.

2. In claim 1, In the secondary battery, each of the electrode tabs is substantially trapezoidal in shape with a longer side on the base side and a shorter side on the tip side.

3. In claim 1 or 2, A secondary battery, wherein the first curved portion has a radius of curvature of 5 mm or more.

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