Non-aqueous electrolyte secondary battery

Abstract

This non-aqueous electrolyte secondary battery is provided with: an electrode body; a rectangular exterior body housing the electrode body; a sealing plate; an electrode terminal provided to the sealing plate; a first collector that is disposed between the electrode body and the sealing plate and that is connected to the electrode terminal; a second collector that is disposed between the electrode body and a lateral wall of the rectangular exterior body and that is connected to the first collector; and a tab group that extends from the electrode body to the lateral wall side and that is connected to the second collector. The second collector has a fuse part that is formed of a flat plate having a surface parallel to the lateral wall and that has provided therein a slit along the width direction of the flat plate. The tab group is connected to the second collector by being disposed close to one side of the width direction, and is folded, on the side of a part of connection to the second collector, so as to be parallel to the lateral wall. In the fuse part, a section having a cross-sectional area larger than the slit is unevenly present on the other side of the width direction.

Description

[Technical field]

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

[0002] In a non-aqueous electrolyte secondary battery such as a lithium ion battery, an electrode assembly is housed in a rectangular exterior body having an opening, and the opening is sealed with a sealing plate. An electrode terminal provided on the sealing plate and a group of tabs extending from the electrode assembly are electrically connected to each other by a current collector.

[0003] Here, as shown in Patent Document 1, a configuration is known in which a fuse portion is provided on a current collector of a nonaqueous electrolyte secondary battery. The fuse portion is configured as a portion of the current collector having a smaller cross-sectional area than other portions. When an overcurrent occurs, the fuse portion melts as the temperature reaches its melting point due to current concentration. This makes it possible to prevent overheating and ignition due to overcurrent. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2011-258550 A Summary of the Invention

[0005] Since the fuse portion has a small cross-sectional area, its strength is weaker than other portions, and therefore if the stress applied to the fuse portion is unevenly distributed, the fuse portion may be deformed in the areas where the stress is strong.

[0006] a first current collector arranged between the electrode body and the sealing plate and connected to the electrode terminal; a second current collector arranged between the electrode body and a side wall of the rectangular exterior body and connected to the first current collector; and a tab group extending from the electrode body toward the side wall and connected to the second current collector, the second current collector being made of a flat plate having a surface parallel to the side wall and having a fuse portion in which a slit is provided along a width direction of the flat plate, the tab group being connected to the second current collector near one width side of the flat plate and being bent parallel to the side wall at a connection portion side with the second current collector, and the fuse portion having a portion having a larger cross-sectional area than the slit is biased toward the other width side of the flat plate.

[0007] According to the present disclosure, in a nonaqueous electrolyte secondary battery, deformation of a fuse portion provided on a current collector can be suppressed. [Brief description of the drawings]

[0008] [Figure 1] FIG. 1 is a perspective view showing a nonaqueous electrolyte secondary battery according to an embodiment of the present disclosure. [Diagram 2] FIG. 2 is a cross-sectional view taken along line II-II in FIG. [Diagram 3] FIG. 3 is a diagram showing a second current collector according to the previous application. [Figure 4] FIG. 4 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. [Diagram 5] FIG. 5 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. [Figure 6] FIG. 6 is a diagram showing a second current collector according to the present embodiment. [Figure 7] FIG. 7 is a perspective view showing an electrode assembly in which the tab group is connected to a second current collector before the tab group is folded. [Figure 8]FIG. 8 is a diagram showing an electrode assembly group including a plurality of electrode bodies. [Figure 9] FIG. 9 is a diagram showing an electrode assembly group connected to each other by a first current collector and a second current collector, and a sealing plate. [Figure 10] FIG. 10 is a view corresponding to FIG. 6 according to the first modified example of the present embodiment. [Figure 11] FIG. 11 is a view corresponding to FIG. 6 according to the second modified example of the present embodiment. [Figure 12] FIG. 12 is a view corresponding to FIG. 6 according to the third modified example of this embodiment. [Figure 13] FIG. 13 is a diagram showing a second current collector according to another embodiment. [Figure 14] FIG. 14 is a contour diagram showing the distribution of stress applied to the fuse portion. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] 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 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] The tab group 40 extends from the electrode body 3 towards the side wall 1b and is connected to a second current collector 62. As shown in Fig. 3, the second current collector 62 has a fuse portion 66 in which a fuse hole (slit) 66c is provided along the width direction of the plate. The fuse portion 66 is a portion of the second current collector 62 having a smaller cross-sectional area than other portions.

[0013] As shown in Fig. 4, the tab group 40 is connected to the second current collector 62 at one side in the width direction of the plate. Also, as shown in Fig. 5, the tab group 40 is bent in parallel to the side wall 1b (see Fig. 2) on the side of the connection portion 63 with the second current collector 62.

[0014] 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.

[0015] However, the above configuration has the following problems. Fig. 14 shows the results of a simulation of the stress distribution applied to the fuse portion 66 by the reaction force applied from the folded tab group 40 to the second current collector 62 when the tab group 40 is folded, and the darker the dots, the greater the stress. That is, because the connection portion 63 of the second current collector 62 with the tab group 40 is shifted to one side in the width direction of the plate (see Figs. 4 and 5), a bias occurs in the distribution of the stress applied to the fuse portion 66.

[0016] In particular, as shown in Fig. 14, strong stress is unevenly distributed on the other widthwise side of the plate (the left side in Fig. 14) of slit 66c in fuse portion 66. Fuse portion 66 originally has a small cross-sectional area and low strength, so there is a risk that fuse portion 66 will be deformed due to the uneven distribution of stress.

[0017] The present inventors believed that the above problem could be solved by distributing the portion of fuse portion 66 with a larger cross-sectional area toward the other widthwise side of the plate relative to slit 66c, and arrived at the present invention.

[0018] 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, 4, and 5 used in the description of the previous application will be used as is.

[0019] Fig. 1 is a perspective view showing a nonaqueous electrolyte secondary battery 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, a 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.

[0020] 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.

[0021] An electrode body 3 including a positive electrode plate 4 and a negative electrode plate 5 is housed in the rectangular exterior body 1 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.

[0022] 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 14 denotes a box- or bag-shaped insulating sheet disposed inside the rectangular exterior body 1 and accommodating the electrode body 3. Reference numeral 15 denotes an electrolyte injection hole provided in the sealing plate 2. Reference numeral 16 denotes a sealing member that seals the electrolyte injection hole 15. Reference numeral 17 denotes a gas exhaust valve provided in the sealing plate 2.

[0023] 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.

[0024] 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 side wall 1b. The positive electrode tab group 40 is formed by stacking a plurality of positive electrode tabs.

[0025] A positive electrode terminal 8 serving as an electrode terminal is provided on the sealing plate 2. 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.

[0026] 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.

[0027] 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.

[0028] 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.

[0029] 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.

[0030] The second positive electrode current collector 62 is provided with a fuse portion 66. The fuse portion 66 will be described in detail later.

[0031] Next, 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 will be described. Fig. 4 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. Fig. 7 shows the electrode assembly 3 in which the positive electrode tab group 40 is connected to the second positive electrode current collector 62 before the positive electrode tab group 40 is folded.

[0032] 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. 4, 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.

[0033] Here, as shown in Fig. 4, 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. 4). 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. 4). 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.

[0034] 5 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 FIGS. 4 and 7), 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] Next, the configuration of the fuse portion 66 will be described in detail with reference to Fig. 6. As described above, the fuse portion 66 is provided at the current collector connection portion 62a of the second positive electrode current collector 62. The fuse portion 66 is provided with a slit 66c along the width direction of the flat plate.

[0036] The fuse portion 66 is composed of a portion 66a located on one side in the width direction of the plate (the right side in FIG. 6) with respect to the slit 66c, and a portion 66b located on the other side in the width direction of the plate (the left side in FIG. 6). The portions 66a and 66b have smaller cross-sectional areas than the other portions of the plate, so that when an overcurrent flows through the second positive electrode current collector 62, the portion 66a and / or the portion 66b melts. Here, the cross-sectional area refers to the area in a cross section parallel to the width direction of the plate.

[0037] Specifically, slit 66c is offset toward one side in the width direction of the plate. As a result, portion 66b is wider than portion 66a. That is, in fuse portion 66, wider portion 66b is offset toward the other side in the width direction of the plate with respect to slit 66c.

[0038] As described above, the connection portion 63 of the second positive electrode current collector 62 with the positive electrode tab group 40 is located toward one side in the width direction of the flat plate. For this reason, strong stress is unevenly distributed toward the other side in the width direction of the flat plate with respect to the slit 66c in the fuse portion 66 (see FIG. 14). If the slit 66c is provided in the center in the width direction of the flat plate as shown in FIG. 3, there is a risk that the fuse portion 66 will be deformed due to the uneven distribution of stress.

[0039] Therefore, in this embodiment, in the fuse portion 66, the portion 66b having a large cross-sectional area is biased toward the other side in the width direction of the flat plate with respect to the slit 66c, thereby increasing the strength of the portion 66b where strong stress is biased.

[0040] Therefore, in the nonaqueous electrolyte secondary battery 20, deformation of the fuse portion 66 provided on the second current collector 62 can be suppressed.

[0041] In this embodiment, the cross-sectional area of ​​the portion 66b on the other widthwise side of the plate relative to the slit 66c in the fuse portion 66 is increased, and the cross-sectional area of ​​the portion 66a on one widthwise side is reduced accordingly. That is, by reducing the cross-sectional area of ​​the portion 66a on one widthwise side where stress is relatively weak, the cross-sectional area of ​​the fuse portion 66 as a whole is kept as small as possible. This ensures the function of the fuse portion 66.

[0042] In the fuse portion 66, the portion 66b on the other widthwise side of the flat plate relative to the slit 66c is made wider, so that the portion with the larger cross-sectional area is biased toward the other widthwise side of the flat plate, resulting in a simple structure.

[0043] In the fuse portion 66, by biasing the slit 66c to one side in the width direction of the flat plate, it is possible to easily bias the wide portion 66b to the other side in the width direction of the flat plate and also bias the narrow portion 66a to one side in the width direction of the flat plate.

[0044] In this embodiment, the fuse portion 66 is formed in the second positive electrode collector 62 with the wide portion 66b biased toward the other side of the flat plate in the width direction relative to the slit 66c. However, the specific configuration of the fuse portion 66 is not particularly limited and can be determined as appropriate depending on the processing of the slit 66c, the assembly of the second positive electrode collector 62, etc.

[0045] 10 shows a second positive electrode current collector 62 according to Modification 1 of the present embodiment. In this modification, a fuse portion 66 has a notch 66f provided on one side in the width direction of the plate (part 66a) with respect to the slit 66c.

[0046] When the slit 66c is opened by pressing, the portions 66a and 66b on both sides of the slit 66c need to have a certain width, and it may not be possible to make the width of the portion 66a as narrow as desired. According to this configuration, after pressing, the cross-sectional area of ​​the portion 66a can be reduced by forming the notch 66f in the portion 66a by cutting.

[0047] 11 shows a second positive electrode current collector 62 according to Modification 2 of the present embodiment. In this modification, the fuse portion 66 is provided with an extension portion 66g extending in the width direction on the other width direction side (part 66b) of the flat plate with respect to the slit 66c.

[0048] As in the first modification, when it is not possible to make the width dimension of the portion 66a as narrow as desired, it is possible to reduce the cross-sectional area of ​​the portion 66a by reducing the thickness of the flat plate. According to this configuration, the reduction in the cross-sectional area of ​​the portion 66b caused by reducing the thickness of the flat plate can be increased by providing the extension portion 66g.

[0049] 12 shows a second positive electrode current collector 62 according to Modification 3 of the present embodiment. In this modification, the fuse portion 66 is provided with a protruding portion 66h that protrudes in the thickness direction on the other width direction side (part 66b) of the flat plate relative to the slit 66c.

[0050] According to this configuration, by making the protruding portion 66h protrude in the thickness direction, it is possible to suppress interference with the terminal arranged adjacently in the width direction.

[0051] The fuse portion 66 may have a portion of the plate thickness that is biased toward the other side in the width direction of the plate (portion 66b) relative to the slit 66c.

[0052] 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.

[0053] Although the present invention has been described above with reference to the preferred embodiments, such description is not limiting and various modifications are possible.

[0054] It is not necessary to have the portion 66a on one widthwise side of the flat plate relative to the slit 66c in the fuse portion 66. In other words, the slit 66c may be a cutout extending from one widthwise end of the flat plate in the fuse portion 66 to the vicinity of the other widthwise end.

[0055] As shown in FIG. 13, the fuse portion 66 may be provided with a thin portion 66j, which is thinner than the other portions of the flat plate, along the width direction of the flat plate, instead of the slit 66c.

[0056] The nonaqueous electrolyte secondary battery 20 may include a plurality of electrode assemblies 3. Fig. 8 shows an electrode assembly group 300 including a plurality of electrode assemblies 3. As shown in Fig. 8, the nonaqueous electrolyte secondary battery 20 includes a plurality (two) of electrode assemblies 3. A second current collector 62 is connected to the positive electrode tab group 40 of each electrode assembly 3. The electrode assembly group 300 is formed by arranging the plurality of electrode assemblies 3, 3 and fixing them together with tape 90.

[0057] 9 shows an electrode assembly group 300 and a sealing plate 2 connected to each other by a first positive electrode current collector 61 and a second positive electrode current collector 62. As shown in FIG. 9, the second positive electrode current collector 62 provided on each electrode assembly 3 is connected to the first positive electrode current collector 61 provided on the sealing plate 2. [Explanation of symbols]

[0058] 1. Rectangular exterior body 1b 1st side wall (side wall) 2 Sealing plate 3 Electrode body 4 Positive plate 5 Negative plate 8 Positive terminal (electrode terminal) 20 Nonaqueous electrolyte secondary battery 40 Positive electrode tab group (tab group) 61 First positive electrode collector (first collector) 62 Second positive electrode collector (second collector) 63 Connection 66 Fuse section 66a Part 66b Part 66c slit 66f Cutout 66g extension 66h protrusion 66j Thin section

Claims

1. an electrode assembly including a positive electrode plate and a negative electrode plate; A rectangular exterior body having an opening and housing the electrode 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 group of tabs extending from the electrode body 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, and has a fuse portion having a slit provided along a width direction of the flat plate; the tab group is connected to the second current collector near one side in the width direction of the flat plate, and is bent in parallel to the side wall at a connection portion with the second current collector, the fuse portion has a portion having a larger cross-sectional area located on the other side in the width direction of the plate relative to the slit.

2. 2 . The nonaqueous electrolyte secondary battery according to claim 1 , wherein the fuse portion has a wider portion located toward the other side in the width direction of the plate with respect to the slit.

3. The nonaqueous electrolyte secondary battery according to claim 2 , wherein the slit is offset to one side in the width direction of the flat plate.

4. The nonaqueous electrolyte secondary battery according to claim 2 , wherein the fuse portion has a notch formed on one widthwise side of the flat plate with respect to the slit.

5. The nonaqueous electrolyte secondary battery according to claim 2 , wherein the fuse portion is provided with an extension portion extending in the width direction on the other width direction side of the flat plate with respect to the slit.

6. The nonaqueous electrolyte secondary battery according to claim 1 , wherein the fuse portion is provided with a protruding portion that protrudes in a thickness direction on the other widthwise side of the flat plate relative to the slit.

7. The nonaqueous electrolyte secondary battery according to claim 1 , wherein the fuse portion has a plate thickness that is biased toward the other side in the width direction of the plate with respect to the slit.

8. 2 . The nonaqueous electrolyte secondary battery according to claim 1 , wherein the fuse portion has a thin portion, instead of the slit, that is thinner than other portions of the flat plate along the width direction of the flat plate.

9. A plurality of the electrode bodies are provided, the second current collector is connected to the tab group of each of the electrode bodies, The nonaqueous electrolyte secondary battery according to claim 1 , wherein each of the second current collectors is connected to the first current collector.

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