Secondary battery

Abstract

To provide a secondary battery in which the problems of conventional arts are solved.SOLUTION: A secondary battery according to the present disclosure includes a stacked type electrode body including a plurality of first electrode plates, a plurality of second electrode plates with a polarity different from that of the first electrode plate, and a band-shaped separator, a battery case, and an insulating sheet. The separator includes a zig-zag bent part that is bent in a zig-zag manner so as to be disposed between the first electrode plate and the second electrode plate, and a wound part that is wound on an outer periphery of a part where the first electrode plates, the second electrode plates, and the zig-zag bent part are stacked. The zig-zag bent part includes a first bent part that is disposed on one side in a direction perpendicular to a stacking direction of the first electrode plates and the second electrode plates, and a second bent part that is disposed on the other side in the direction perpendicular to the stacking direction of the first electrode plates and the second electrode plates. Outside the first bent part, a separator overlap part where the wound part is overlapped twice or more is provided. On an outer surface side of the separator overlap part, the insulating sheet is provided.SELECTED DRAWING: Figure 5

Description

[Technical Field]

[0001] The present disclosure relates to secondary batteries. [Background technology]

[0002] As one form of electrode assembly provided in a secondary battery, a stacked electrode assembly is known in which a plurality of positive electrodes and a plurality of negative electrodes are alternately stacked with separators interposed therebetween. In this stacked electrode assembly, a form in which the separator is zigzag folded so as to be interposed between the positive electrode and the negative electrode is known (see, for example, Patent Document 1). Patent Document 1 discloses various forms of electrode assemblies in which the separator is zigzag folded. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] International Publication No. 2019 / 064740 Summary of the Invention [Problem to be solved by the invention]

[0004] In recent years, there has been a demand for extending the driving range of electric vehicles (BEVs) and the like, and the secondary batteries used in these vehicles are becoming larger. The increase in the size of the secondary battery is accompanied by an increase in the weight of the electrode assembly. When the weight of the electrode assembly increases, it is increasingly necessary to suppress damage to the electrodes due to impact, vibration, and the like, from the viewpoint of the reliability of the secondary battery.

[0005] Therefore, the present disclosure provides a secondary battery that solves the problems of the conventional technology. [Means for solving the problem]

[0006] The secondary battery disclosed herein includes a stacked electrode assembly including multiple first electrode plates, multiple second electrode plates having a polarity opposite to that of the first electrode plates, and a strip-shaped separator; a battery case that houses the stacked electrode assembly; and an insulating sheet. The separator includes a zigzag fold portion folded zigzag to be positioned between the first electrode plates and the second electrode plates, and a wound portion wound around the outer periphery of the portion of the separator where the zigzag fold portion is stacked. The separator includes a starting end that is an end on one side of the separator in the longitudinal direction, and a terminal end that is an end on the other side. The terminal end is located at the end where the winding of the wound portion ends. The zigzag fold portion includes a first folded portion that is positioned on one side in a direction perpendicular to the stacking direction of the first electrode plates and the second electrode plates, and a second folded portion that is positioned on the other side in the direction perpendicular to the stacking direction of the first electrode plates and the second electrode plates. A separator overlapping portion is provided on the outer side of the first bent portion, where the wound portion overlaps two or more times. The insulating sheet is disposed on the outer surface side of the separator overlapping portion.

[0007] According to this configuration, it is possible to provide a secondary battery that solves the problems of the conventional technology, that is, according to this configuration, it is possible to provide a secondary battery in which damage to the electrodes is suppressed to a high level. [Brief explanation of the drawings]

[0008] [Figure 1] FIG. 1 is a perspective view schematically illustrating a secondary battery according to an embodiment of an example of a secondary battery of the present disclosure. [Figure 2] FIG. 2 is a perspective view of the secondary battery of FIG. 1 turned upside down. [Figure 3] FIG. 3 is a cross-sectional view taken along a main surface of a battery case of the secondary battery, schematically showing the internal structure of the secondary battery of FIG. [Figure 4] FIG. 4 is a perspective view of the secondary battery of FIG. 1, showing a schematic perspective view of the case body. [Figure 5]FIG. 5 is a cross-sectional view schematically showing the configuration of the electrode body of the secondary battery of FIG. [Figure 6] FIG. 6 is a cross-sectional view, perpendicular to the long side surface and perpendicular to the bottom surface, of the battery case of the secondary battery, schematically showing the internal configuration of the secondary battery of FIG. [Figure 7] FIG. 7 is a development view of an insulating sheet used in the secondary battery of FIG. [Figure 8] FIG. 8 is a view of the insulating sheet used in the secondary battery of FIG. 1, viewed from the bottom of the battery case of the secondary battery. DETAILED DESCRIPTION OF THE INVENTION

[0009] Hereinafter, embodiments of the present disclosure will be described with reference to the drawings. Matters not mentioned in this specification but necessary for implementing the present disclosure can be understood as design matters for a person skilled in the art based on the prior art in the relevant field. The present disclosure can be implemented based on the contents disclosed in this specification and the common general technical knowledge in the relevant field. In the following drawings, components and parts that perform the same function are denoted by the same reference numerals. Dimensional relationships (length, width, thickness, etc.) in each drawing do not reflect actual dimensional relationships. In this specification, a numerical range expressed as "A to B" includes A and B.

[0010] In this specification, the term "secondary battery" refers to an electricity storage device that can be repeatedly charged and discharged. In addition, in this specification, the term "lithium ion secondary battery" refers to a secondary battery that uses lithium ions as charge carriers and achieves charging and discharging by the transfer of charge associated with the lithium ions between the positive and negative electrodes.

[0011] Fig. 1 is a perspective view of a secondary battery 100 according to this embodiment, which is an example of a secondary battery of the present disclosure. Fig. 2 is a perspective view of the secondary battery 100 of Fig. 1 turned upside down. Fig. 3 shows the internal structure of the secondary battery 100 of Fig. 1. In the following description, the symbols L, R, F, Rr, U, and D in the drawings represent left, right, front, rear, top, and bottom, and the symbols X, Y, and Z in the drawings represent the short side direction of the secondary battery 100, the long side direction perpendicular to the short side direction, and the up-down direction perpendicular to the short side direction and the long side direction, respectively.

[0012] It should be noted that U (top) and D (bottom) in the drawings correspond to the top and bottom of the secondary battery 100 in a normal usage state (particularly when installed in an automotive battery), but the usage state of the secondary battery 100 is not limited to this. For example, in other embodiments, the secondary battery 100 may be installed upside down.

[0013] The secondary battery 100 according to this embodiment is a lithium-ion secondary battery. This allows the secondary battery 100 to have excellent battery characteristics such as high energy density and high capacity. However, in other embodiments, the secondary battery may be a secondary battery other than a lithium-ion secondary battery (e.g., a sodium-ion secondary battery, etc.).

[0014] 1 to 3, the secondary battery 100 includes a battery case 10, an electrode assembly 20, and an insulating sheet 50. The secondary battery 100 also includes a positive electrode terminal 30, a negative electrode terminal 40, and an electrolyte (not shown).

[0015] <Battery case> The battery case 10 is a housing that houses the electrode assembly 20 and the electrolyte. As shown in FIGS. 1 and 2, the battery case 10 here has a flat, bottomed, rectangular parallelepiped outer shape. That is, the battery case 10 is rectangular. Therefore, the secondary battery 100 in the illustrated example is a rectangular lithium-ion secondary battery. However, the shape of the battery case 10 is not limited to this. A rectangular battery case 10 is preferable because it improves space efficiency when a battery module is constructed using multiple secondary batteries 100.

[0016] The material of the battery case 10 may be the same as that conventionally used (e.g., metal, resin, etc.) and is not particularly limited. From the viewpoint of strength, thermal conductivity, etc., the material of the battery case 10 is preferably metal, and more preferably aluminum, aluminum alloy, iron, or iron alloy. The battery case 10 may also be made of a laminate film.

[0017] As shown in FIGS. 1 to 3, the battery case 10 includes a case body 12, a first sealing plate 14, and a second sealing plate 16. The case body 12 is rectangular tubular. As shown in FIG. 3, the case body 12 has a first opening 12e at one end and a second opening 12f at the other end. The first sealing plate 14 seals the first opening 12e, and the second sealing plate 16 seals the second opening 12f. The battery case 10 is integrated by joining (e.g., welding) the first sealing plate 14 and the second sealing plate 16 to the case body 12 at the first opening 12e and the second opening 12f, respectively. The battery case 10 is hermetically sealed. Therefore, the secondary battery 100 is a sealed battery.

[0018] The battery case 10 has a pair of first surfaces, a pair of second surfaces, and a pair of third surfaces. As shown in FIG. 1 , the case body 12 includes a substantially rectangular bottom surface 12a, a pair of opposing long side surfaces 12b extending from the long sides of the bottom surface 12a, and a top surface 12c connecting the upper ends of the pair of long side surfaces 12b. The top surface 12c is substantially rectangular. The top surface 12c faces the bottom surface 12a. Here, the top surface 12c and the bottom surface 12a form a pair of first surfaces, and the pair of long side surfaces 12b form a pair of second surfaces. The area of ​​the long side surfaces 12b is preferably larger than the area of ​​the bottom surface 12a and larger than the area of ​​the top surface 12c. For example, the bottom surface 12a and the top surface 12c can form a pair of short side surfaces. The case body 12 is formed, for example, by bending a single metal plate into a cylindrical shape and joining (e.g., welding) the seams. In the illustrated example, the welded joint 12d is located on the top surface 12c. The welded joint 12d may be located on the bottom surface 12a or on the long side surface 12b.

[0019] As shown in FIG. 2 , a gas release valve 13 is provided on the bottom surface 12a of the case body 12. The gas release valve 13 is configured to break when the pressure inside the battery case 10 reaches a predetermined value or higher, thereby releasing gas inside the battery case 10 to the outside. While the present embodiment includes one gas release valve 13, the number of gas release valves 13 may be two or more. Although the present embodiment includes the gas release valve 13 on the bottom surface 12a, the present embodiment is not limited to this. In other embodiments, the gas release valve 13 may be provided on a surface other than the bottom surface 12a, such as the long side surface 12b, the top surface 12c, or the sealing plate 14. Alternatively, in other embodiments, the secondary battery 100 may be installed upside down relative to the drawing, with the bottom surface 12a replaced by the top surface 12c, and the gas release valve facing upward. The area of ​​the gas release valve 13 is optional.

[0020] In this embodiment, the gas release valve 13 is a cross-shaped notch, but the shape of the gas release valve 13 is not particularly limited. In other embodiments, the gas release valve 13 may be, for example, a linear notch (only vertical or horizontal lines), or may be a conventionally known oval valve (with an internal notch) or circular valve (with an internal notch). The dimensions of the notch (e.g., length, depth, etc.) are arbitrary and can be determined appropriately taking into consideration, for example, the pressure resistance of the battery case 10.

[0021] The first sealing plate 14 and the second sealing plate 16 are plate-like members that seal the first opening 12e and the second opening 12f of the case body 12. The first sealing plate 14 and the second sealing plate 16 are substantially rectangular in plan view. Here, the first sealing plate 14 and the second sealing plate 16 form a pair of third surfaces.

[0022] A liquid inlet 17 is provided in the first sealing plate 14. The liquid inlet 17 is used to inject an electrolyte into the battery case 10 after the first sealing plate 14 and the second sealing plate 16 are assembled to the case body 12. The liquid inlet 17 is provided below the positive electrode terminal 30, but the position at which the liquid inlet 17 is provided in the first sealing plate 14 is not limited to this. The liquid inlet 17 is sealed with a sealing member 18 after the electrolyte is injected. Note that, although the liquid inlet 17 is provided in the first sealing plate 14 in this embodiment, the liquid inlet 17 may be provided in the second sealing plate 16 or the case body 12. Furthermore, although the liquid inlet 17 is provided on a different surface from the gas release valve 13 in this embodiment, the liquid inlet 17 may be provided on the same surface as the gas release valve 13.

[0023] <Electrode terminal> The positive electrode terminal 30 and the negative electrode terminal 40 are each fixed to the battery case 10. Here, the positive electrode terminal 30 and the negative electrode terminal 40 are each fixed to opposing surfaces of the battery case 10. More specifically, the positive electrode terminal 30 is attached to the first sealing plate 14, and the negative electrode terminal 40 is attached to the second sealing plate 16.

[0024] Specifically, the first sealing plate 14 and the second sealing plate 16 have through holes, and insulating members 63, 64 are attached to the through holes, respectively. The positive electrode terminal 30 is attached to the first sealing plate 14 via the insulating member 63, and is insulated from the first sealing plate 14. The negative electrode terminal 40 is attached to the second sealing plate 16 via the insulating member 64, and is insulated from the second sealing plate 16. The insulating member 63 also insulates the first sealing plate 14 from the electrode assembly 20 inside the battery case 10. The insulating member 64 also insulates the second sealing plate 16 from the electrode assembly 20 inside the battery case 10.

[0025] In the present embodiment, the positive electrode terminal 30 and the negative electrode terminal 40 are provided on the first sealing plate 14 and the second sealing plate 16, respectively; however, the arrangement of the positive electrode terminal 30 and the negative electrode terminal 40 is not limited to this. In other embodiments, both the positive electrode terminal 30 and the negative electrode terminal 40 may be provided on one of the first sealing plate 14 or the second sealing plate 16. The first sealing plate 14 and the second sealing plate 16 may be provided on the case body 12. In the present embodiment, the positive electrode terminal 30 and the negative electrode terminal 40 are provided on a different surface from the gas release valve 13; however, the positive electrode terminal 30 and the negative electrode terminal 40 may be provided on the same surface as the gas release valve 13.

[0026] However, when the positive electrode terminal 30 and the negative electrode terminal 40 are provided on the first sealing plate 14 and the second sealing plate 16, respectively, as in the present embodiment, the height of the secondary battery 100 (i.e., the dimension in the Z direction in the drawing) can be reduced, making it easier to obtain a battery with a high volumetric energy density. In this case, it is also easier to construct a battery module with a high volumetric energy density, particularly for in-vehicle applications.

[0027] The positive electrode terminal 30 and the negative electrode terminal 40 are exposed on the outer surfaces of the first sealing plate 14 and the second sealing plate 16, respectively. Here, the positive electrode terminal 30 and the negative electrode terminal 40 are arranged on an axis that extends in the long side direction Y and passes through the center of the first sealing plate 14 and the second sealing plate 16. However, in other embodiments, the axis may be offset from the center of the first sealing plate 14 and the second sealing plate 16, for example, in the short side direction X. Furthermore, the positive electrode terminal 30 and the negative electrode terminal 40 do not have to be arranged on the axis. For example, one of the positive electrode terminal 30 and the negative electrode terminal 40 may be offset to one side in the short side direction X, and the other may be offset to the other side in the short side direction X.

[0028] The positive electrode terminal 30 is preferably made of a metal, more preferably aluminum or an aluminum alloy, and the negative electrode terminal 40 is preferably made of a metal, more preferably copper or a copper alloy.

[0029] The electrode body 20 has, at one end, a positive electrode current collecting tab electrically connected to the positive electrode 23, and the positive electrode current collecting tabs are gathered and attached to a positive electrode current collecting member 32. The electrode body 20 has, at the other end, a negative electrode current collecting tab electrically connected to the negative electrode 24, and the negative electrode current collecting tabs are gathered and attached to a negative electrode current collecting member 42. Inside the battery case 10, the positive electrode current collecting member 32 is attached to the first sealing plate 14 and electrically connected to the positive electrode terminal 30. Inside the battery case 10, the negative electrode current collecting member 42 is attached to the second sealing plate 16 and electrically connected to the negative electrode terminal 40.

[0030] In this way, the positive electrode terminal 30 is electrically connected to the positive electrode 23 of the electrode assembly 20 inside the battery case 10 via the positive electrode current collecting tab and the positive electrode current collecting member 32. The negative electrode terminal 40 is electrically connected to the negative electrode 24 of the electrode assembly 20 inside the battery case 10 via the negative electrode current collecting tab and the negative electrode current collecting member 42. Note that the structure for electrically connecting the positive electrode terminal 30 and the negative electrode terminal 40 to the positive electrode 23 and the negative electrode 24 of the electrode assembly 20, respectively, is not limited to that shown in the figure.

[0031] <Electrode body> The electrode body 20 is housed inside the battery case 10. FIG. 4 is a perspective view of the secondary battery 100, showing a schematic view seen through the case body 12. FIG. 5 is a schematic cross-sectional view of the electrode body 20 taken along the thickness direction of the electrode body 20. FIG. 6 is a cross-sectional view of the electrode body 20 showing a simplified schematic view of the internal structure of the battery case 10, taken along the X direction (the thickness direction of the electrode body 20, in other words, the stacking direction of the positive electrode 23 and the negative electrode 24) and the Z direction in FIG. 1. FIG. 6 is a cross-sectional view of a cross section parallel to the first opening 12e of the case body 12.

[0032] As shown in FIGS. 4 and 6, the electrode body 20 is placed inside the battery case 10 while being covered with an insulating sheet 50, which will be described later. In this embodiment, a plurality of electrode bodies 20 are housed inside one battery case 10. In the example shown in FIGS. 4 and 6, two electrode bodies 20 are housed inside one battery case 10. When there are a plurality of electrode bodies 20 in this manner, a flow path for the electrolyte solution and generated gas can be formed between an electrode body 20 and an adjacent electrode body 20. The number of electrode bodies 20 housed inside one battery case 10 is not particularly limited. In other embodiments, the number of electrode bodies 20 housed inside one battery case 10 may be three or more, or may be one.

[0033] The electrode assembly 20 includes a plurality of negative electrodes 24 (negative electrode plates 24) as first electrode plates, a plurality of positive electrodes 23 (positive electrode plates 23) as second electrode plates having a polarity opposite to that of the first electrode plates, and a single separator 25. Thus, in this embodiment, the electrode assembly 20 is a stacked electrode assembly, in which the positive electrodes 23 and the negative electrodes 24 are alternately stacked. A single separator 25 is disposed between the plurality of positive electrodes 23 and the plurality of negative electrodes 24, thereby insulating the positive electrodes 23 from the negative electrodes 24. Note that in another embodiment, the second electrode plate may be the negative electrode 24, and the first electrode plate may be the positive electrode 23. The electrode assembly 20 is a stacked electrode assembly, which has a higher electrolyte impregnation capability than a wound electrode assembly, and is particularly advantageous in terms of electrolyte injection during manufacturing. Furthermore, a stacked electrode assembly facilitates the construction of a battery with a high volumetric energy density.

[0034] In the example shown in FIG. 5, the number of positive electrodes 23 is two, and the number of negative electrodes 24 is three. However, the numbers of positive electrodes 23 and negative electrodes 24 are not particularly limited and can be determined appropriately depending on the battery design. In the illustrated example, the number of negative electrodes 24 is one more than the number of positive electrodes 23. Therefore, in the electrode stacking structure of the positive electrodes 23 and the negative electrodes 24, the outermost layers are both negative electrodes 24. In this case, lithium contained in the positive electrode active material of the positive electrode 23 can be fully utilized, and lithium precipitation in the negative electrode 24 can be highly prevented. Note that in other embodiments, the number of positive electrodes 23 and the number of negative electrodes 24 may be the same, or the number of positive electrodes 23 may be greater than the number of negative electrodes 24. Note that, for example, the number of positive electrodes 23 and the number of negative electrodes 24 can each be 20 or more.

[0035] In this embodiment, the dimensions of the negative electrode 24 are larger than the dimensions of the positive electrode 23. In FIG. 5, the width of the negative electrode 24 (i.e., the dimension in the Z direction in the drawing) is larger than the width of the positive electrode 23. This makes it possible to highly prevent lithium deposition in the negative electrode 24. Note that in other embodiments, the width of the negative electrode 24 may be the same as or smaller than the width of the positive electrode 23.

[0036] The electrode body 20 has a substantially rectangular parallelepiped shape. As shown in FIGS. 3 and 4, the electrode body 20 has a first side surface 20a that faces the bottom surface 12a of the case body 12. The electrode body 20 has a second side surface 20c that faces the top surface 12c of the case body 12. The first side surface 20a and the second side surface 20c form a pair of side surfaces that face each other. In addition, the electrode body 20 has a pair of main surfaces that face the pair of long side surfaces 12b of the case body 12. The electrode body 20 has a pair of side surfaces that face the first sealing plate 14 and the second sealing plate 16.

[0037] The separator 25 is strip-shaped. That is, the separator 25 is elongated. The separator 25 has a zigzag fold portion 25a folded zigzag so that the separator 25 is disposed between the positive electrode 23 and the negative electrode 24. In the zigzag fold portion 25a, the separator 25 is folded back alternately at the end of the positive electrode 23 and the end of the negative electrode 24. Thus, the zigzag fold portion 25a has a first fold portion 25aa folded back at the end of the negative electrode 24 and a second fold portion 25ab folded back at the end of the positive electrode 23. The first fold portion 25aa is disposed on one side in a direction perpendicular to the stacking direction of the positive electrode 23 and the negative electrode 24, and the second fold portion 25ab is disposed on the other side in a direction perpendicular to the stacking direction of the positive electrode 23 and the negative electrode 24. In the illustrated example, the first bent portion 25aa faces the bottom surface 12a of the case body 12, and the second bent portion 25ab faces the top surface 12c of the case body 12. However, the first bent portion 25aa may face the top surface 12c of the case body 12, and the second bent portion 25ab may face the bottom surface 12a of the case body 12.

[0038] In the illustrated example, the first bent portion 25aa is spaced apart from the end face of the negative electrode 24. Thus, there is a distance between the end face of the negative electrode 24 and the first bent portion 25aa. However, the first bent portion 25aa may be located along the end of the negative electrode 24 and in contact with the end face of the negative electrode 24.

[0039] Similarly, in the illustrated example, the second bent portion 25ab is spaced apart from the end face of the positive electrode 23. Therefore, there is a distance between the end face of the positive electrode 23 and the second bent portion 25ab. However, the second bent portion 25ab may be located along the end of the positive electrode 23 and in contact with the end face of the positive electrode 23.

[0040] Furthermore, the zigzag fold portion 25a has a flat portion 25ac sandwiched between the positive electrode 23 and the negative electrode 24. The flat portion 25ac is also present on the outermost surface of the negative electrode 24, which is the outermost layer where the zigzag fold portion 25a begins. In this manner, each of the multiple positive electrodes 23 is sandwiched between the flat portions 25ac of the separator 25, and each of the multiple negative electrodes 24 is sandwiched between the flat portions 25ac of the separator 25. This insulates adjacent positive electrodes 23 and negative electrodes 24 from each other via the flat portions 25ac. It is not necessary for all of the positive electrodes 23 and negative electrodes 24 to be sandwiched between the flat portions 25ac of the zigzag fold portion 25a. For example, zigzag folding may begin with the separator 25 sandwiched between the positive electrode 23 and the negative electrode 24, and there may be no flat portion 25ac on the outermost surface of the negative electrode 24, which is the outermost layer where the zigzag fold portion 25a begins. However, from the viewpoint of protecting the negative electrode 24, it is preferable that the outermost surface of the negative electrode 24, which is the outermost layer where the zigzag fold portion 25a starts, is covered with the flat portion 25ac. By folding the separator 25 in a zigzag shape, the manufacturing efficiency of the stacked electrode body can be improved.

[0041] In addition, the separator 25 has a wound portion 25b wound around the outer periphery of the portion where the positive electrode 23, the negative electrode 24, and the zigzag portion 25a (more specifically, the flat portion 25ac) are stacked. The wound portion 25b ensures that the outermost surface of one electrode positioned in the outermost layer in the electrode stack structure of the positive electrode 23 and the negative electrode 24 and the outermost surface of the other electrode are covered by the separator 25. This makes it possible to suppress the intrusion of foreign matter into the electrode assembly 20 or the generation of foreign matter in the electrode assembly 20.

[0042] Separator 25 has first end 25c, which is one end in the longitudinal direction of separator 25, and second end 25d, which is the other end. First end 25c is the starting end, and therefore continues to zigzag fold portion 25a, and is located inside (in other words, on the inner circumferential side of) wound portion 25b. Second end 25d is the ending end, and therefore second end 25d is located at the end of winding of wound portion 25b.

[0043] The position of the first end 25c, which is the starting end, is not particularly limited. As shown in the illustrated example, the first end 25c may be located on a side surface of the electrode stack structure of the positive electrode 23 and the negative electrode 24, or on the main surface of the outermost electrode of the electrode stack structure. The first end 25c, which is the starting end, is located inside the wound portion 25b and does not need to be secured by tape or the like. Tape can create a step in the electrode body 20, which can lead to lithium deposition. When the first end 25c is not secured by tape, lithium deposition can be suppressed. For example, the first end 25c is secured by being sandwiched between the stack of the positive electrode 23, the negative electrode 24, and the zigzag portion 25a and the wound portion 25b. Alternatively, for example, if the separator 25 has an adhesive layer, the first end 25c is secured by the adhesive layer.

[0044] The position of the second end 25d, which is the terminal end, is not particularly limited. As in the illustrated example, the second end 25d may be located on the main surface of the outermost electrode plate (negative electrode 24 in the illustrated example) of the electrode laminate structure of the positive electrode 23 and the negative electrode 24, or may be located on a side surface of the electrode laminate structure. The second end 25d, which is the terminal end, is preferably fixed with tape. In the illustrated example, the second end 25d is fixed with a winding stop tape 26. The second end 25d may also be fixed to a part of the separator 25 on the inner circumferential side by adhesive, press bonding, heat welding, or the like.

[0045] 6, when multiple electrode bodies 20 are arranged in the battery case 10, it is preferable that at least one stop tape 26 is arranged between the multiple electrode bodies 20. When there are multiple electrode bodies 20, the adjacent electrode bodies 20 may be in contact with each other or may be spaced apart.

[0046] A separator overlapping portion 25ba is provided on the outer side of the first folded portion 25aa of the separator 25, where the wound portion 25b overlaps two or more times (i.e., the separator layers of the wound portion 25b overlap two or more times). In a lithium-ion secondary battery, the negative electrode is more susceptible to damage than the positive electrode. The negative electrode is also more susceptible to damage at its end, particularly at the corners of the end of the negative electrode active material layer. Furthermore, in the illustrated example, as described above, the negative electrode 24 is larger than the positive electrode 23, and therefore the end of the negative electrode 24 protrudes from the side of the stack of the positive electrode 23 and the negative electrode 24. In this embodiment, the end of the negative electrode 24 can be protected by the first folded portion 25aa and the separator overlapping portion 25ba, i.e., by a total of three or more separator layers 25. This makes it possible to more effectively prevent damage to the negative electrode 24 (particularly the end of the negative electrode 24).

[0047] In the illustrated example, because the end of the negative electrode 24 is designed to be more susceptible to damage, the separator overlapping portion 25ba is provided on the outside of the first bent portion 25aa folded back at the end of the negative electrode 24. However, it is also possible to provide the separator overlapping portion 25ba on the outside of the second bent portion 25ab folded back at the end of the positive electrode 23. In this case, damage to the end of the positive electrode 23 can be suppressed. Therefore, whether the separator overlapping portion 25ba is provided at the first bent portion 25aa or the second bent portion 25ab may be determined depending on the battery design.

[0048] In the illustrated example, the number of negative electrodes 24 is one more than the number of positive electrodes 23, as described above. Therefore, in the electrode stacking structure of the positive electrodes 23 and the negative electrodes 24, both negative electrodes 24 form the outermost layers. Therefore, the negative electrode 24 located on one of the outermost surfaces in the stacking direction of the positive electrodes 23 and the negative electrodes 24 is referred to as the outermost negative electrode. This outermost negative electrode is the negative electrode 24 on the outermost layer on the right side of FIG. 5. This outermost negative electrode is disposed between the zigzag fold portion 25a and the wound portion 25b. When the separator 25 has a substrate and a heat-resistant layer on the main surface of the substrate facing the positive electrode 23 (in this case, an adhesive layer may be further provided on the heat-resistant layer), the positive electrode 23 contacts the heat-resistant layer, and the negative electrode contacts the substrate. When the outermost negative electrode is disposed between the zigzag fold portion 25a and the wound portion 25b, the substrate of the separator 25 is exposed on the outer surface (i.e., the exposed surface) of the electrode assembly 20. In this way, when the base material of the separator 25 is exposed on the outer surface of the electrode assembly 20, the heat-resistant layer of the separator 25 can be advantageously protected by the base material.

[0049] 3, in the electrode assembly 20, the negative electrode current collecting tab is located at the center of the negative electrode 24 in the direction connecting the first bent portion 25aa and the second bent portion ab of the separator 25 (the Z direction in the drawing). However, the negative electrode current collecting tab may be biased away from the separator overlapping portion 25ba in the direction connecting the first bent portion 25aa and the second bent portion ab of the separator 25 (the Z direction in the drawing). In other words, the negative electrode current collecting tab may be biased closer to the top surface 12c of the case body 12 than to the bottom surface 12a of the case body 12.

[0050] Similarly, in the electrode assembly 20, the positive electrode current collecting tab is located at the center of the positive electrode 23 in the direction connecting the first bent portion 25aa and the second bent portion ab of the separator 25 (the Z direction in the drawing). However, the positive electrode current collecting tab may be biased away from the separator overlapping portion 25ba in the direction connecting the first bent portion 25aa and the second bent portion ab of the separator 25 (the Z direction in the drawing). In other words, the positive electrode current collecting tab may be biased closer to the top surface 12c of the case body 12 than to the bottom surface 12a of the case body 12.

[0051] It is preferable that the surfaces of the electrode assembly 20 other than the surfaces from which the electrode current collecting tabs (i.e., the positive electrode current collecting tab and the negative electrode current collecting tab) protrude are covered with the separator 25. Furthermore, on the surface from which the electrode current collecting tabs protrude, the portions other than the electrode current collecting tabs may be covered with the separator 25.

[0052] 6 is also a cross-sectional view parallel to the first opening 12e of the case body 12. In the cross-section parallel to the first opening 12e of the case body 12, D1 is the internal dimension of the case body 12 in the direction in which the negative electrode 24 extends (i.e., the Z direction in FIG. 6), and W1 is the dimension of the negative electrode 24 along the internal dimension D1. D1 and W1 preferably satisfy W1 / D1 > 0.9, and more preferably W1 / D1 > 0.95. When W1 / D1 is greater than 0.9 (particularly greater than 0.95), large movement of the electrode assembly 20 inside the battery case 10 can be suppressed, and damage to the electrodes when the secondary battery 100 is subjected to vibration or impact can be further suppressed.

[0053] <Insulation sheet> As shown in FIGS. 4 and 6 , the insulating sheet 50 is housed inside the battery case 10 together with the electrode assembly 20. The insulating sheet 50 is disposed between the battery case 10 and the electrode assembly 20. In this embodiment, the insulating sheet 50 is disposed at least on the outer surface side of the overlapping portion 25ba of the separator 25. This further reduces damage to the electrode (negative electrode 24 in the illustrated example). Therefore, the secondary battery 100 according to this embodiment can highly effectively reduce damage to the electrode due to impact, vibration, etc., even when the electrode assembly is heavy. In the illustrated example, the insulating sheet 50 covers the periphery of the electrode assembly 20 (the four outer surfaces facing the inner surface of the case body 12). Therefore, the insulating sheet 50 has a portion disposed on the outer surface side of the separator overlapping portion 25ba.

[0054] The insulating sheet 50 is made of an insulating material, preferably a resin. Examples of resins include olefin-based resins such as polyethylene (PE), polypropylene (PP), and polymethylpentene (PMP / TPX™); polyester-based resins such as polyethylene terephthalate (PET) and polyethylene naphthalate (PEN); acrylic resin (PMMA); polyimide (PI); polyphenylene ether (PPE); triacetate (TAC); polyphenylene sulfide resin (PPS); polycarbonate (PC); nylon; and fluororesins such as polytetrafluoroethylene (PTFE). Of these, PE and PP are preferred. The thickness of the insulating sheet 50 is preferably greater than that of the separator 25.

[0055] FIG. 7 shows a development view of the insulating sheet 50. FIG. 8 shows the insulating sheet 50 as viewed from the bottom surface 12a of the battery case 10. In this embodiment, the insulating sheet 50 is made of a single sheet-like member. The insulating sheet 50 is formed by folding this sheet-like member into a rectangular tube shape to match the shape of the electrode assembly 20. As shown in FIGS. 6 and 8, both circumferential end portions 50a of the electrode assembly 20 have overlapping portions 50b where the folded sheet ends 50a overlap. In the insulating sheet 50, the folded sheet ends 50a are fixed to each other at these overlapping portions 50b by bonding or the like. In the example shown in FIG. 8, the sheet ends 50a are fixed to each other using adhesive tape 52. The fixing method is not limited to using adhesive tape 52, and may be welding such as thermal welding or ultrasonic welding, or bonding with an adhesive.

[0056] As shown in Figure 8, both end portions 50a of the folded insulating sheet 50 may be fixed only in part at the overlapping portion 50b. In Figure 8, the sheet end portions 50a are fixed together at two locations near both ends of the overlapping portion 50b. The number of fixing locations is not limited to this. For example, the sheet end portions 50a may be fixed together at a total of three locations, including both ends and the center of the overlapping portion 50b. Alternatively, the sheet end portions 50a may be fixed together along the entire length of the overlapping portion 50b.

[0057] In the illustrated example, the overlapping portion 50b of the insulating sheet 50 is disposed outside the separator overlapping portion 25ba. For example, at least a portion of the overlapping portion 50b of the insulating sheet 50 faces a portion of the separator overlapping portion 25ba. In this case, since there are at least two layers of insulating sheet 50 in the overlapping portion 50b, the ends of the electrodes inside the separator overlapping portion 25ba can be protected to a higher degree. Therefore, damage to the ends of the electrodes inside the separator overlapping portion 25ba can be more effectively suppressed. Note that the position of the overlapping portion 50b of the insulating sheet 50 is not limited thereto, and the overlapping portion 50b of the insulating sheet 50 may be located in a position that does not face the separator overlapping portion 25ba.

[0058] In the illustrated example, the overlapping portion 50b of the insulating sheet 50 has a region through which the electrolyte and gas can pass. This is advantageous from the viewpoint of high electrolyte impregnation into the electrode assembly 20 and rapid gas discharge from the electrode assembly 20. The region through which the electrolyte and gas can pass can be provided by joining only a portion of the overlapping portion 50b. That is, the unjoined portion of the overlapping portion 50b becomes the region through which the electrolyte and gas can pass. Alternatively, the region through which the electrolyte and gas can pass can be provided by joining the entire length of the overlapping portion 50b and providing through-holes in the insulating sheet. When the entire length of the overlapping portion 50b is L, the region through which the electrolyte and gas can pass in the extension direction of the overlapping portion 50b preferably has a dimension of 1 / 5L or more, more preferably 1 / 3L or more, and even more preferably 1 / 2L or more. The area in the overlapping portion 50b of the insulating sheet 50 through which the electrolyte and gas can pass may be open all the way, or may be an area that opens under stress.

[0059] In the illustrated example, the bottom surface 12a of the case body 12 of the battery case 10 faces the overlapping portion 50b of the insulating sheet 50. That is, the overlapping portion 50b of the insulating sheet 50 is located on the bottom surface 12a side of the case body 12 of the battery case 10. Therefore, excess electrolyte not impregnated in the electrode assembly 20 is present on the bottom surface 12a side of the case body 12 within the battery case 10. Therefore, having the overlapping portion 50a facing the bottom surface 12a is advantageous for supplying this excess electrolyte to the electrode assembly 20. Therefore, in this embodiment, it is preferable that the overlapping portion 50b of the insulating sheet 50 is located on the side where excess electrolyte is present. In this case, it is more advantageous for the overlapping portion 50b of the insulating sheet 50 to have an area through which the electrolyte can pass. Furthermore, in the illustrated example, the overlapping portion 25ba of the separator 25 also faces the bottom surface 12a of the case body 12 of the battery case 10. This reduces or eliminates a decrease in the impregnation of the electrolyte into the electrode body 20 at the overlapping portion 25ba, which is caused by the presence of three or more separator layers. Note that the overlapping portion 50b of the insulating sheet 50 may face a surface other than the bottom surface 12a of the case body 12 of the battery case 10.

[0060] In the illustrated example, the bottom surface 12a of the case body 12 of the battery case 10 has a gas release valve 13. Therefore, the gas release valve 13 is provided on the surface of the battery case 10 facing the overlapping portion 25ba of the separator 25. In addition, the gas release valve 13 is provided on the surface of the battery case 10 facing the overlapping portion 50b of the insulating sheet 50. In this case, when gas is suddenly generated inside the electrode assembly 20, the gas can be easily released to the outside of the battery case 10 via the gas release valve 13. In this case, it is more advantageous that the overlapping portion 50b of the insulating sheet 50 has an area through which the gas can pass. Note that the overlapping portion 50b of the insulating sheet 50 may face the surface of the case body 12 of the battery case 10 that does not have the gas release valve 13.

[0061] Next, the materials constituting the positive electrode 23, negative electrode 24, and separator 25 will be described. The positive electrode 23 typically has a positive electrode current collector and a positive electrode active material layer fixed to at least one surface of the positive electrode current collector. The positive electrode current collector is made of a conductive metal such as aluminum, an aluminum alloy, nickel, or stainless steel. Here, the positive electrode current collector is a metal foil, specifically an aluminum foil. In this embodiment, the positive electrode 23 has an exposed portion of the positive electrode current collector without forming a positive electrode active material layer, and this exposed portion constitutes a current collecting tab. However, the method of forming the current collecting tab is not limited to this.

[0062] The positive electrode active material layer contains a positive electrode active material capable of reversibly absorbing and releasing charge carriers. The positive electrode active material is preferably an oxide containing at least one of Ni, Co, and Mn, and examples thereof include lithium transition metal composite oxides such as lithium cobalt oxide, lithium manganese oxide, lithium nickel oxide, lithium nickel manganese composite oxide, and lithium nickel cobalt manganese composite oxide. The positive electrode active material is more preferably a lithium composite oxide containing Ni (in other words, a Ni-containing lithium composite oxide). In the Ni-containing lithium composite oxide, the Ni content is preferably in the range of 70 to 100 mol% relative to the total number of moles of metals other than Li. In the lithium transition metal composite oxide, a portion of Ni, Co, and Mn may be substituted with Al, Ti, Zr, P, B, Si, Nb, C, or the like. Furthermore, the positive electrode active material may be a lithium transition metal composite oxide whose particle surfaces are coated with a compound containing Al, Ti, Zr, W, P, B, Si, Nb, C, or the like. The total amount of substitution and addition is about 0.1 to 7 mass %. Alternatively, a lithium transition metal phosphate compound such as lithium iron phosphate can also be used as the positive electrode active material. The positive electrode active material layer may contain a conductive material, a binder, and the like. The conductive material is preferably a carbon material such as carbon black or carbon nanotubes. The binder is preferably a resin binder such as polyvinylidene fluoride.

[0063] The negative electrode 24 typically includes a negative electrode current collector and a negative electrode active material layer fixed to at least one surface of the negative electrode current collector. The negative electrode current collector is made of a conductive metal such as copper, a copper alloy, nickel, or stainless steel. The negative electrode current collector is a metal foil, specifically a copper foil. In this embodiment, the negative electrode 24 has an exposed portion of the negative electrode current collector without forming a negative electrode active material layer, and this exposed portion constitutes a current collecting tab. However, the method for forming the current collecting tab is not limited to this.

[0064] The negative electrode active material layer contains a negative electrode active material capable of reversibly absorbing and releasing charge carriers. Examples of the negative electrode active material include carbon-based negative electrode active materials such as graphite, hard carbon, and soft carbon; Si-based negative electrode active materials such as silicon and silicon oxide; silicon-carbon composite negative electrode active materials; and Sn-based negative electrode active materials such as Sn. The negative electrode active material layer may contain a conductive material, a thickener, a binder, and the like. Preferably, the binder contains styrene butadiene rubber, carboxymethyl cellulose, or the like.

[0065] The separator 25 is a member that insulates the positive electrode active material layer from the negative electrode active material layer. A porous resin sheet made of a polyolefin resin such as polyethylene (PE) or polypropylene (PP) is suitable as the separator 25. The porous resin sheet may have a single-layer structure or a multi-layer structure (e.g., a three-layer structure of PP / PE / PP).

[0066] An adhesive layer is preferably provided on the surface of the separator 25. The adhesive layer contains, for example, an adhesive resin such as an acrylic resin or polyvinylidene fluoride. When the separator 25 has an adhesive layer, it is easy to prevent the separator 25 and the electrodes from being misaligned when stacked. The adhesive layer may be provided on the entire surface of the separator 25, or may be coated in a pattern. The adhesive layer is bonded by, for example, applying pressure or heat.

[0067] A heat-resistant layer (HRL) containing ceramic particles may be provided on the surface of the separator 25. Examples of materials for the ceramic particles include alumina, boehmite, aluminum hydroxide, and titania. The heat-resistant layer preferably further contains a resin binder. The resin binder may be an adhesive resin such as an acrylic resin or polyvinylidene fluoride. By adding an appropriate amount of resin binder to the heat-resistant layer, the heat-resistant layer can also function as an adhesive layer.

[0068] In one advantageous embodiment of the separator 25, the separator 25 has a substrate made of a polyolefin microporous film, and a heat-resistant layer and an adhesive layer on the surface of the substrate facing the positive electrode 23. Specifically, the heat-resistant layer is laminated on the substrate, and the adhesive layer is laminated on the heat-resistant layer. On the other hand, the surface of the substrate facing the negative electrode 24 does not have any laminated layers. Therefore, the substrate and the negative electrode 24 are in direct contact with each other.

[0069] In another embodiment of separator 25, separator 25 comprises a porous resin sheet substrate and adhesive layers on both sides of the substrate. In yet another embodiment of separator 25, separator 25 comprises a porous resin sheet substrate, an adhesive layer on one side of the substrate, and a heat-resistant layer on the other side of the substrate. In this embodiment, the heat-resistant layer may also function as an adhesive layer. In yet another embodiment of separator 25, separator 25 comprises a porous resin sheet substrate, an adhesive layer on one side of the substrate, and a heat-resistant layer on the other side of the substrate, with an adhesive layer further provided on the heat-resistant layer.

[0070] <Electrolyte> The electrolyte solution is accommodated inside the battery case 10 together with the electrode assembly 20. The electrolyte solution may be the same as that used in general secondary batteries and is not particularly limited. The electrolyte solution is typically a non-aqueous liquid electrolyte (i.e., non-aqueous electrolyte solution) containing a non-aqueous solvent and a supporting salt. The non-aqueous solvent contains, for example, carbonates such as ethylene carbonate (EC), ethyl methyl carbonate (EMC), and dimethyl carbonate (DMC). The non-aqueous solvent is preferably a mixture of EC, EMC, and DMC in a range of 1 to 99% by volume, with the total ratio being 100% by volume. The non-aqueous solvent may further contain a carboxylic acid ester such as methyl acetate. The supporting salt is also called an electrolyte salt and is, for example, a fluorine-containing lithium salt. Examples of fluorine-containing lithium salts include LiPF6, LiBF4, and lithium bis(fluorosulfonyl)imide (LiFSI). The supporting salt preferably contains LiPF6. The concentration of the supporting electrolyte is not particularly limited, but is preferably 0.6 to 1.8 mol / L, and more preferably 0.7 mol / L to 1.3 mol / L. The electrolyte may further contain additives, specifically, for example, film-forming agents such as vinylene carbonate (VC) and oxalate complexes; gas generating agents; thickeners; etc.

[0071] The secondary battery 100 can highly suppress damage to the electrodes due to impact, vibration, and the like, even when the electrode body is heavy. The secondary battery 100 can be used for a variety of purposes. Suitable applications include in-vehicle applications, specifically, as a driving power source mounted on vehicles such as electric vehicles (BEVs), hybrid electric vehicles (HEVs), and plug-in hybrid electric vehicles (PHEVs). The secondary battery 100 can also be used as a storage battery for small-sized power storage devices and the like. The secondary battery 100 can also be used in the form of a battery module, typically consisting of a plurality of batteries connected in series and / or parallel.

[0072] Although specific examples of the present disclosure have been described in detail above, these are merely examples and do not limit the scope of the claims. The technology described in the claims includes various modifications and alterations of the specific examples exemplified above.

[0073] That is, the secondary battery of the present disclosure has the following features [1] to [9]. [1] A stacked electrode assembly including a plurality of first electrode plates, a plurality of second electrode plates having a polarity different from that of the first electrode plates, and a strip-shaped separator; a battery case that houses the stacked electrode body; An insulating sheet; A secondary battery comprising: the separator has a zigzag fold portion folded in a zigzag manner so as to be disposed between the first electrode plate and the second electrode plate; a winding portion wound around an outer periphery of a portion where the first electrode plate, the second electrode plate, and the zigzag folded portion of the separator are stacked, the separator includes a start end portion that is an end portion on one side in a longitudinal direction of the separator and a finish end portion that is an end portion on the other side, the terminal end portion is located at the end of the winding of the winding portion, The zigzag folding portion includes a first folding portion disposed on one side in a direction perpendicular to the stacking direction of the first electrode plate and the second electrode plate; a second bent portion disposed on the other side in a direction perpendicular to the stacking direction of the first electrode plate and the second electrode plate, a separator overlapping portion in which the winding portion overlaps two or more times is provided on the outer side of the first bent portion, The insulating sheet is disposed on the outer surface side of the separator overlapping portion. Secondary battery. [2] The laminated electrode body has a first electrode tab electrically connected to the first electrode plate at one end and a second electrode tab electrically connected to the second electrode plate at the other end, the case includes a case body having a first opening at one end and a second opening at the other end, a first sealing plate that seals the first opening, and a second sealing plate that seals the second opening; The secondary battery according to item [1], wherein a first electrode terminal electrically connected to the first electrode plate is provided on the first sealing plate, and a second electrode terminal electrically connected to the second electrode plate is provided on the second sealing plate. [3] The secondary battery according to item [2], wherein in a cross section of the case body parallel to the first opening, an internal dimension D1 of the case body in a direction in which the first electrode plate extends and a dimension W1 of the first electrode plate along the internal dimension D1 satisfy W1 / D1>0.9. [4] The insulating sheet has an insulating sheet overlapping portion in which the insulating sheet is overlapped two or more times, The secondary battery according to any one of items [1] to [3], wherein the insulating sheet overlapping portion is disposed outside the separator overlapping portion. [5] The secondary battery according to item [4], wherein the battery case has a gas release valve on the surface facing the separator overlapping portion, which ruptures when the pressure inside the battery case reaches or exceeds a predetermined value, and releases gas inside the battery case to the outside of the battery case. [6] The secondary battery according to any one of items [1] to [5], wherein one outermost first electrode plate, which is a first electrode plate located on one of the outermost surfaces in the stacking direction of the first electrode plate and the second electrode plate, is disposed between the zigzag fold portion and the winding portion. [7] The first electrode plate has a first electrode tab; The secondary battery according to any one of items [1] to [6], wherein the first electrode tab is biased in a direction away from the separator overlapping portion from the center of the first electrode plate in a direction connecting the first bent portion and the second bent portion. [8] A plurality of the electrode assemblies are disposed in the battery case, a stop tape is attached to the end of the separator on the outermost surface of the electrode body, The secondary battery according to any one of items [1] to [7], wherein at least one of the winding stop tapes is disposed between a plurality of the electrode assemblies. [9] The first electrode plate is a negative electrode plate, and the second electrode plate is a positive electrode plate; the separator has a substrate made of a polyolefin microporous film, and a heat-resistant layer and an adhesive layer on the surface of the substrate facing the positive electrode plate, The secondary battery according to any one of items [1] to [8], wherein the substrate and the negative electrode plate are in direct contact with each other. [Explanation of symbols]

[0074] 10 Battery case 12 Case body 12a Bottom 13 Gas exhaust valve 14 1st sealing plate 16 Second sealing plate 20 Electrode body 23 Positive electrode 24 Negative electrode 25 Separator 50 Insulation Sheet 100 Secondary battery

Claims

1. a stacked electrode assembly including a plurality of first electrode plates, a plurality of second electrode plates having a polarity different from that of the first electrode plates, and a strip-shaped separator; a battery case that houses the stacked electrode body; An insulating sheet; A secondary battery comprising: the separator has a zigzag fold portion folded in a zigzag shape so as to be disposed between the first electrode plate and the second electrode plate; a winding portion wound around an outer periphery of a portion where the first electrode plate, the second electrode plate, and the zigzag folded portion of the separator are stacked, the separator includes a start end portion that is an end portion on one side in a longitudinal direction of the separator and a finish end portion that is an end portion on the other side, the terminal end portion is located at the end of the winding of the winding portion, The zigzag folding portion includes a first folding portion disposed on one side in a direction perpendicular to a stacking direction of the first electrode plate and the second electrode plate; a second bent portion disposed on the other side in a direction perpendicular to the stacking direction of the first electrode plate and the second electrode plate, a separator overlapping portion in which the winding portion overlaps two or more times is provided on the outer side of the first bent portion, The insulating sheet is disposed on the outer surface side of the separator overlapping portion. Secondary battery.

2. the laminated electrode body has, at one end, a first electrode tab electrically connected to the first electrode plate, and at the other end, a second electrode tab electrically connected to the second electrode plate; the case includes a case body having a first opening at one end and a second opening at the other end, a first sealing plate that seals the first opening, and a second sealing plate that seals the second opening; 2. The secondary battery according to claim 1, wherein the first sealing plate is provided with a first electrode terminal electrically connected to the first electrode plate, and the second sealing plate is provided with a second electrode terminal electrically connected to the second electrode plate.

3. 3. The secondary battery according to claim 2, wherein in a cross section of the case body parallel to the first opening, an inner dimension D1 of the case body in a direction in which the first electrode plate extends and a dimension W1 of the first electrode plate along the inner dimension D1 satisfy W1 / D1 > 0.

9.

4. the insulating sheet has an insulating sheet overlapping portion in which the insulating sheet is overlapped two or more times, The secondary battery according to claim 1 , wherein the insulating sheet overlapping portion is disposed outside the separator overlapping portion.

5. 5. The secondary battery according to claim 4, wherein the battery case has a gas release valve on a surface facing the separator overlapping portion, the gas release valve being ruptured when pressure inside the battery case reaches or exceeds a predetermined value to release gas inside the battery case to the outside of the battery case.

6. 2. The secondary battery according to claim 1, wherein one outermost first electrode plate, which is a first electrode plate located on one of the outermost surfaces in the stacking direction of the first electrode plate and the second electrode plate, is disposed between the zigzag fold portion and the winding portion.

7. the first electrode plate has a first electrode tab; 2. The secondary battery according to claim 1, wherein the first electrode tab is located offset in a direction away from the separator overlapping portion from the center of the first electrode plate in a direction connecting the first bent portion and the second bent portion.

8. A plurality of the electrode assemblies are disposed in the battery case, a stop tape is attached to the end of the separator on the outermost surface of the electrode body, The secondary battery according to claim 1 , wherein at least one of the securing tapes is disposed between a plurality of the electrode bodies.

9. the first electrode plate is a negative electrode plate and the second electrode plate is a positive electrode plate; the separator has a substrate made of a polyolefin microporous film, and a heat-resistant layer and an adhesive layer on the surface of the substrate facing the positive electrode plate, The secondary battery according to claim 1 , wherein the substrate and the negative electrode plate are in direct contact with each other.

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