Secondary battery

Abstract

To provide a secondary battery which is suppressed in occurrence of a short circuit due to a fragment detached from a negative electrode active material layer and excellent in impregnation of an electrolytic solution into an electrode body.SOLUTION: A secondary battery includes: an electrode body 20 that includes a plurality of first electrode plates 23, a plurality of second electrode plates 24, and a separator 25 disposed therebetween; an electrolytic solution; and a housing case. The separator is bent in a zigzag manner, and includes a first bent part 25a folded at an end part of the first electrode plate and a second bent part 25b folded at an end part of the second electrode plate. A plurality of the first bent parts are disposed on one side of a pair of side surfaces of the electrode body that face each other, and a plurality of the second bent parts are disposed on the other side thereof. A first end part 25d located at one end part of the separator in a longitudinal direction and a second end part 25f located at the other end part thereof are disposed at one side surface of the pair of side surfaces of the electrode body that face each other. The separator is located on both outermost surfaces in a stacking direction of the first and second electrode plates.SELECTED DRAWING: Figure 5

Description

Technical Field

[0001] The present disclosure relates to a secondary battery.

Background Art

[0002] As one form of an electrode body included in a secondary battery, a laminated electrode body in which a plurality of positive electrodes and a plurality of negative electrodes are alternately laminated via a separator is known. In this laminated electrode body, a form in which the separator is folded ninety times so as to be interposed between the positive electrode and the negative electrode is known (see, for example, Patent Documents 1 to 4).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Patent Document 2

Patent Document 3

Patent Document 4

Summary of the Invention

Problems to be Solved by the Invention

[0004] However, in the above prior art, it has at least one of the problems of the possibility of short circuit due to fragments detached from the negative electrode active material layer and poor impregnation of the electrolyte into the electrode body.

[0005] Therefore, the present disclosure provides a secondary battery that solves the problems of the prior art.

Means for Solving the Problems

[0006] The secondary battery of the present disclosure includes an electrode assembly including a plurality of first electrode plates, a plurality of second electrode plates having polarities different from those of the first electrode plates, and a separator disposed between the first electrode plates and the second electrode plates; an electrolytic solution; and a case for housing the electrode assembly and the electrolytic solution. The separator is in a strip shape and is bent in a ninety-nine fold shape. The separator includes a first bent portion folded back at an end of the first electrode plate and a second bent portion folded back at an end of the second electrode plate. A plurality of the first bent portions are disposed on one side surface of a pair of opposing side surfaces of the electrode assembly. A plurality of the second bent portions are disposed on the other side surface of the pair of opposing side surfaces of the electrode assembly. A first end portion located at one end in the longitudinal direction of the separator and a second end portion located at the other end in the longitudinal direction of the separator are disposed on one side surface of the pair of opposing side surfaces of the electrode assembly. In the electrode assembly, the separator is located on both outermost surfaces in the stacking direction of the first electrode plate and the second electrode plate. [[ID=!]]

[0007] According to such a configuration, it is possible to provide a secondary battery that solves the problems of the prior art. That is, according to such a configuration, it is possible to provide a secondary battery in which a short circuit due to fragments detached from the negative electrode active material layer is suppressed and the impregnation property of the electrolytic solution into the electrode assembly is excellent.

Brief Description of the Drawings

[0008]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Figure 9

Figure 10

Embodiments for Carrying Out the Invention

[0009] Hereinafter, embodiments according to the present disclosure will be described with reference to the drawings. Matters not mentioned in this specification but necessary for the implementation of the present disclosure can be grasped as design matters of those skilled in the art based on the prior art in the relevant field. The present disclosure can be implemented based on the content disclosed in this specification and the common general knowledge in the relevant field. Also, in the following drawings, members and parts having the same function are denoted by the same reference numerals for explanation. Also, the dimensional relationships (length, width, thickness, etc.) in each figure do not reflect the actual dimensional relationships. In this specification, the numerical range expressed as "A to B" includes A and B.

[0010] In this specification, the "secondary battery" refers to a rechargeable power storage device. Also, in this specification, the "lithium ion secondary battery" refers to a secondary battery that uses lithium ions as charge carriers and realizes charge and discharge by the movement of charges associated with lithium ions between the positive and negative electrodes.

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

[0012] Note that U (top) and D (bottom) in the drawings correspond to the top and bottom in the normal usage form of the secondary battery 100 (particularly the installation state in an in-vehicle battery), but the usage form of the secondary battery 100 is not limited thereto. For example, in other embodiments, the secondary battery 100 may be installed upside down.

[0013] The secondary battery 100 according to the present embodiment is a lithium-ion secondary battery. Thereby, the secondary battery 100 can 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] As shown in FIGS. 1 to 3, the secondary battery 100 includes a battery case 10, an electrode body 20, and an electrolytic solution (not shown). The secondary battery 100 further includes a positive electrode terminal 30, a negative electrode terminal 40, and an insulating sheet 50.

[0015] <Battery case> The battery case 10 is a housing that houses the electrode body 20 and the electrolytic solution. As shown in FIGS. 1 and 2, the battery case 10 here has an outer shape of a flat and bottomed rectangular parallelepiped. That is, the battery case 10 is rectangular. Therefore, the secondary battery 100 in the illustrated example is a prismatic lithium-ion secondary battery. However, the shape of the battery case 10 is not limited thereto. Since the space efficiency is high when configuring a battery module using a plurality of secondary batteries 100, the battery case 10 is preferably rectangular.

[0016] The material of the battery case 10 may be the same as those conventionally used (e.g., metal, resin, etc.), and there is no particular limitation. From the viewpoints of strength, thermal conductivity, etc., the material of the battery case 10 is preferably metal, more preferably aluminum, an aluminum alloy, iron, or an iron alloy. Note that the battery case 10 may 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 has a rectangular tube shape. 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 the first sealing plate 14 and the second sealing plate 16 being joined (e.g., by welding) 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 long side surfaces 12b extending from the long sides of the bottom surface 12a and facing each other, 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 are the pair of first surfaces, and the pair of long side surfaces 12b are the pair of second surfaces. Note that the area of the long side surface 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 be the pair of short side surfaces. The case body 12 is formed, for example, by bending a single metal plate into a tubular shape and joining (e.g., by welding) the seams. In the illustrated example, a welded joint 12d is located on the top surface 12c. Note that 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 discharge valve 13 is provided on the bottom surface 12a of the case body 12. The gas discharge valve 13 is configured to break when the pressure in the battery case 10 reaches a predetermined value or more and discharge the gas in the battery case 10 to the outside. In the present embodiment, the number of gas discharge valves 13 is one, but it may be two or more. Also, in the present embodiment, the gas discharge valve 13 is provided on the bottom surface 12a, but it is not limited thereto. In other embodiments, the gas discharge valve 13 may be provided on a surface other than the bottom surface 12a, for example, a long side surface 12b, a top surface 12c, a sealing plate 14, etc. Alternatively, in other embodiments, the secondary battery 100 may be installed upside down with respect to the drawing, the bottom surface 12a may be changed to the top surface 12c, and the gas discharge valve may be directed upward. Also, the area of the gas discharge valve 13 is arbitrary.

[0020] In the present embodiment, the gas discharge valve 13 is a cross-shaped notch, but the shape of the gas discharge valve 13 is not particularly limited. In other embodiments, the gas discharge valve 13 may be, for example, a linear (vertical or horizontal line only) notch, or a conventionally known elliptical valve (with a notch inside) or a circular valve (with a notch inside), etc. Also, the dimensions of the notch (e.g., length, depth, etc.) are arbitrary and can be appropriately determined, for example, in consideration of 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 are a pair of third surfaces.

[0022] The first sealing plate 14 is provided with a liquid injection hole 17. The liquid injection hole 17 is for injecting electrolyte into the inside of 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 injection hole 17 is provided below the positive electrode terminal 30, but the position where the liquid injection hole 17 is provided on the first sealing plate 14 is not limited to this. After the injection of the electrolyte, the liquid injection hole 17 is sealed with a sealing member 18. In this embodiment, the liquid injection hole 17 is provided on the first sealing plate 14, but the liquid injection hole 17 may be provided on the second sealing plate 16 or on the case body 12. Also, in this embodiment, the liquid injection hole 17 is provided on a surface different from the gas discharge valve 13, but the liquid injection hole 17 may be provided on the same surface as the gas discharge 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 respectively fixed to the opposing surfaces of the battery case 10. 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 (see FIG. 4) are attached to each of the through holes. The positive electrode terminal 30 is attached to the first sealing plate 14 via the insulating member 63, and the positive electrode terminal 30 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 the negative electrode terminal 40 is insulated from the second sealing plate 16. Also, the insulating member 63 insulates the first sealing plate 14 and the electrode body 20 inside the battery case 10. The insulating member 64 insulates the second sealing plate 16 and the electrode body 20 inside the battery case 10.

[0025] In this embodiment, the positive electrode terminal 30 and the negative electrode terminal 40 are respectively provided on the first sealing plate 14 and the second sealing plate 16. 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. Also, in this embodiment, the positive electrode terminal 30 and the negative electrode terminal 40 are provided on a surface different from that of the gas discharge valve 13. However, the positive electrode terminal 30 and the negative electrode terminal 40 may be provided on the same surface as the gas discharge valve 13.

[0026] However, when the positive electrode terminal 30 and the negative electrode terminal 40 are respectively provided on the first sealing plate 14 and the second sealing plate 16 as in this embodiment, the height of the secondary battery 100 (that is, the dimension in the Z direction of the drawing) can be reduced, and it becomes easy to obtain a battery with a high volumetric energy density. Also, in this case, it becomes easy to configure 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 respectively exposed on the outer surfaces of the first sealing plate 14 and the second sealing plate 16. Here, the positive electrode terminal 30 and the negative electrode terminal 40 are arranged on an axis extending in the long side direction Y and passing through the centers of the first sealing plate 14 and the second sealing plate 16. However, in other embodiments, the axis may be displaced, for example, in the short side direction X from the centers of the first sealing plate 14 and the second sealing plate 16. Also, 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 displaced to one side in the short side direction X and the other may be displaced to the other side in the short side direction X.

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

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

[0030] In this way, the positive terminal 30 is electrically connected to the positive electrode 23 of the electrode body 20 via the positive current collector tab and the positive current collector member 32 inside the battery case 10. The negative terminal 40 is electrically connected to the negative electrode 24 of the electrode body 20 via the negative current collector tab and the negative current collector member 42 inside the battery case 10. Note that the structure for electrically connecting the positive terminal 30 and the negative terminal 40 to the positive electrode 23 and the negative electrode 24 of the electrode body 20 respectively is not limited to the one 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, schematically showing the case body 12 in a perspective manner. FIG. 5 is a schematic cross-sectional view of the electrode body 20 along the thickness direction of the electrode body 20, described in a simplified manner while changing the orientation of the electrode body 20. FIG. 6 is a side view of the electrode body 20, specifically, a view showing the upper side surface of the electrode body 20 (that is, the second side surface 20c of the electrode body 20). FIG. 7 is a cross-sectional view of the electrode body 20 schematically showing the internal structure of the battery case 10 in a simplified manner, and is a cross-sectional view 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.

[0032] Note that since these drawings are schematic diagrams, the main surface of the positive electrode 23 and the separator 25 are shown separately, and the main surface of the negative electrode 24 and the separator 25 are also shown separately. This is for ease of visual recognition of each member. In reality, the main surface of the positive electrode 23 is in contact with the separator 25, and the main surface of the negative electrode 24 is in contact with the separator 25. Also, in reality, the portions of the separator 25 can be in contact with each other. Furthermore, although the tape 26 is shown separately from the separator 25, in reality, the tape 26 is in contact with the separator 25.

[0033] As shown in FIGS. 4 and 7, the electrode body 20 is disposed inside the battery case 10 in a state covered with an insulating sheet 50 described later. In the present embodiment, a plurality of electrode bodies 20 are accommodated inside one battery case 10. In the example shown in FIGS. 4 and 7, two electrode bodies 20 are accommodated inside one battery case 10. When there are a plurality of electrode bodies 20 in this way, a flow path for the electrolytic solution and the generated gas can be formed between the electrode body 20 and the adjacent electrode body 20. Note that the number of electrode bodies 20 accommodated inside one battery case 10 is not particularly limited. In other embodiments, the number of electrode bodies 20 accommodated inside one battery case 10 may be three or more, or may be one.

[0034] The electrode body 20 includes a plurality of positive electrodes 23 (positive electrode plates 23) as the first electrode plate, a plurality of negative electrodes 24 (negative electrode plates 24) as the second electrode plate having a polarity different from that of the first electrode plate, and a single separator 25. The single separator 25 is disposed between the plurality of positive electrodes 23 and the plurality of negative electrodes 24, thereby insulating the positive electrode 23 and the negative electrode 24. Note that in other embodiments, the first electrode plate can be configured as the negative electrode 24 and the second electrode plate can be configured as the positive electrode 23. The electrode body 20 is a laminated electrode body, and has higher impregnation properties of the electrolytic solution than a wound electrode body, and is particularly advantageous in terms of the injection property of the electrolytic solution during manufacturing. Also, according to the laminated electrode body, it is easy to configure a battery having a high volumetric energy density.

[0035] 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 number of positive electrodes 23 and negative electrodes 24 is not particularly limited and can be appropriately determined according to 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 laminate structure of the positive electrode 23 and the negative electrode 24, the outermost layers are both the negative electrode 24. In this case, the lithium contained in the positive electrode active material of the positive electrode 23 can be fully utilized, and the precipitation of lithium in the negative electrode 24 can be highly prevented. 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 more than the number of negative electrodes 24. For example, the number of positive electrodes 23 and negative electrodes 24 can be 20 or more, respectively.

[0036] In the present embodiment, the size of the negative electrode 24 is larger than the size of the positive electrode 23. In FIG. 5, the width of the negative electrode 24 (that is, the dimension in the Z direction of the drawing) is larger than the width of the positive electrode 23. Thereby, the precipitation of lithium in the negative electrode 24 can be highly prevented. In other embodiments, the width of the negative electrode 24 may be the same as the width of the positive electrode 23, or may be smaller.

[0037] 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 facing the bottom surface 12a of the case body 12. The electrode body 20 has a second side surface 20c facing the top surface 12c of the case body 12. The first side surface 20a and the second side surface 20c are a pair of side surfaces facing each other. In addition to this, the electrode body 20 has a pair of main surfaces facing the pair of long side surfaces 12b of the case body 12. The electrode body 20 has a pair of side surfaces facing the first sealing plate 14 and the second sealing plate 16.

[0038] The separator 25 is strip-shaped. That is, the separator 25 is long. The separator 25 is bent in a ninety-nine-fold shape. Specifically, the separator 25 is folded back alternately at the ends of the positive electrode 23 and the negative electrode 24. Therefore, as shown in FIG. 5, the separator 25 has a flat portion along the electrode and a bent portion folded back at the end of the electrode. As a result, each of the plurality of positive electrodes 23 is sandwiched by the separator 25, and each of the plurality of negative electrodes 24 is sandwiched by the separator 25. Since the separator 25 is in a ninety-nine-fold shape, the manufacturing efficiency of the laminated electrode body can be increased.

[0039] Therefore, as shown in FIG. 5, regarding the bent portion of the separator 25, it is defined as the first bent portion 25a folded back at the end of the positive electrode 23, and the second bent portion 25b folded back at the end of the negative electrode 24. As shown in FIG. 7, the plurality of first bent portions 25a are arranged on the side of the second side surface 20c facing the top surface 12c of the case body 12. The portion facing the top surface 12c of the plurality of first bent portions 25a faces the outside of the electrode body 20 and constitutes the outer surface of the plurality of first bent portions 25a. The plurality of second bent portions 25b are arranged on the side of the first side surface 20a facing the bottom surface 12a of the case body 12. The portion facing the bottom surface 12a of the plurality of second bent portions 25b faces the outside of the electrode body 20 and constitutes the outer surface of the plurality of second bent portions 25b.

[0040] In this embodiment, in the electrode body 20, separators 25 are positioned on both outermost surfaces in the stacking direction of the positive electrode 23 and the negative electrode 24. According to such a configuration, since the negative electrode 24, which is the outermost electrode in the electrode body 20, is covered by the separator 25, that is, it is not exposed, damage to the negative electrode 24 can be suppressed. Further, even when the negative electrode 24 is damaged and a part of the negative electrode active material layer peels off, the separator 25 can suppress the fragments peeled off from the negative electrode active material layer from moving within the secondary battery 100. Thus, in the secondary battery 100 according to this embodiment, in the electrode body 20, damage and peeling of the active material layer (negative electrode active material layer in the illustrated example) of the outermost electrode plate (negative electrode 24 in the illustrated example) in the stacking direction of the positive electrode 23 and the negative electrode 24 can be suppressed, and even when peeling of the active material layer occurs, a short circuit due to the peeled active material layer can be suppressed. Particularly in a lithium-ion secondary battery, the negative electrode active material layer is more likely to peel off than the positive electrode active material layer. Therefore, the secondary battery 100 according to this embodiment is a lithium-ion secondary battery, and since the outermost layers of the electrode stacking structures of the positive electrode 23 and the negative electrode 24 are both the negative electrode 24, the benefits of the peeling suppression effect are greater.

[0041] On the other hand, in a secondary battery, improvement in the impregnation property of the electrolyte into the electrode body is required. Particularly in an in-vehicle battery, when the secondary battery is enlarged to extend the cruising range of the vehicle, the time required to impregnate the electrode body with the electrolyte during the manufacture of the secondary battery becomes long (that is, the liquid injection property becomes low), and there is a problem that the production efficiency decreases. Further, when the secondary battery is repeatedly charged and discharged at a high rate, the electrolyte is discharged from the electrode body due to the expansion / contraction of the active material layer, and there is also a problem that the lithium ion concentration in the electrode body tends to become non-uniform. Therefore, in an in-vehicle battery, it is desirable to improve the impregnation property of the electrolyte into the electrode body.

[0042] In addition, in a secondary battery, if gas generated in the electrode body remains in the electrode body for a long time, lithium metal precipitation may occur. Therefore, it is desirable that the gas generated in the electrode body be quickly discharged from the electrode body. Further, when a large amount of gas is generated in the electrode body when an abnormality occurs in the secondary battery, it is desirable that the gas be quickly released from the electrode body so that a region where the pressure is excessively high locally is not generated.

[0043] Therefore, in the present embodiment, a first end portion 25d located at one end portion in the longitudinal direction of the separator 25 and a second end portion 25f located at the other end portion in the longitudinal direction of the separator 25 are disposed on one side surface of a pair of opposing side surfaces of the electrode body 20. In the illustrated example, this one side surface of the electrode body 20 is a second side surface 20c facing the top surface 12c of the case main body 12 of the battery case 10.

[0044] On the other hand, the other side surface of the electrode body 20 is a first side surface 20a facing the bottom surface 12a of the case main body 12 of the battery case 10. At the first side surface 20a of the electrode body 20, the end portion of the positive electrode active material layer of the positive electrode 23 is exposed between adjacent second bent portions 25b.

[0045] Therefore, by disposing the first end portion 25d and the second end portion 25f of the separator 25 on the second side surface 20c (i.e., one side surface) of the electrode body 20 as described above, on the first side surface 20a (i.e., the other side surface) of the electrode body 20, the electrolytic solution easily penetrates into the electrode body 20 from the end portion of the exposed positive electrode active material layer. Thereby, in the secondary battery 100 according to the present embodiment, the impregnation property of the electrolytic solution into the electrode body 20 is extremely enhanced.

[0046] Similarly, at the first side surface 20a of the electrode body 20, the gas generated in the electrode body 20 is easily discharged from the electrode body 20 through the end portion of the exposed positive electrode active material layer. Therefore, in the secondary battery 100 according to the present embodiment, the gas discharge property of the electrode body 20 is extremely enhanced.

[0047] In consideration of the above, on the first side surface 20a of the electrode body 20, it is preferable that the second bent portion 25b is not covered by the separator 25.

[0048] Further, when the first end portion and the second end portion of the separator are arranged on the outermost surface in the stacking direction of the electrode body, a step is generated by the end portion of the separator on the outermost surface. Due to this step, the surface pressure in the stacking direction of the electrode body becomes uneven. When the first end portion 25d and the second end portion 25f of the separator 25 are arranged on the second side surface 20c (that is, one side surface) of the electrode body 20 as in the present embodiment, the above-mentioned step does not occur on the outermost surface in the stacking direction of the electrode body 20, so that the surface pressure can be applied to the electrode body 20 evenly.

[0049] Also, in the example shown in FIG. 7, a gas discharge valve 13 is provided on the side of the second bent portion 25b of the electrode body 20, in other words, on the bottom surface 12a side of the case body 12. In this case, when the amount of gas generated in the electrode body 20 is large, it is particularly advantageous because a large amount of gas generated by the gas discharge valve 13 can be easily discharged outside the battery case 10.

[0050] In the illustrated example, the second side surface 20c of the electrode body 20 on the side where the first bent portion 25a is arranged faces the top surface 12c of the case body 12, and the first side surface 20a of the electrode body 20 on which the second bent portion 25b is arranged faces the bottom surface 12a of the case body 12, so that the electrode body 20 is accommodated in the battery case 10. However, the orientation of the electrode body 20 when it is accommodated in the battery case 10 is not limited to that in the illustrated example. The above-mentioned effects can be obtained even when the first end portion 25d and the second end portion 25f of the separator 25 are arranged on the first side surface 20a side of the electrode body 20.

[0051] However, the electrolytic solution includes the one impregnated in the electrode body 20 and the surplus solution not impregnated in the electrode body 20. The surplus solution is located between the battery case 10 and the electrode body 20. Therefore, the surplus solution is located on the first side surface 20a side of the electrode body 20 facing the bottom surface 12a of the case body 12. Thus, as in the example shown in FIG. 7, when the first side surface 20a of the electrode body 20 is on the side where the first bending portion 25a is disposed, since the surplus solution is likely to impregnate from the end portion of the positive electrode active material layer of the exposed positive electrode 23, the impregnation property of the electrolytic solution into the electrode body 20 becomes particularly high.

[0052] Further, when the first end portion 25d and the second end portion 25f of the separator 25 are disposed on the second side surface 20c of the electrode body 20 (that is, on the top surface 12c side of the case body 12 of the battery case 10), the electrolytic solution can be held on the second side surface 20c of the electrode body 20. In particular, since the surplus solution of the electrolytic solution is located on the first side surface 20a side of the electrode body 20 facing the bottom surface 12a of the case body 12, liquid shortage (so-called liquid depletion) of the electrolytic solution may occur in the upper part of the electrode body 20. Therefore, in this case, the occurrence of liquid depletion can be suppressed. For the holding on the second side surface 20c of the electrode body 20, the first surplus portion 25e and the second surplus portion 25g of the separator 25 described later, the tape 26 described later, and the like contribute.

[0053] Also, as shown in FIGS. 5 and 6, the separator 25 has a first surplus portion 25e that includes the first end portion 25d and is located on the second side surface 20c of the electrode body 20, and a second surplus portion 25g that includes the second end portion 25f and is located on the second side surface 20c of the electrode body 20. Therefore, the first surplus portion 25e of the separator 25 is a portion on the second side surface 20c of the electrode body 20 from the first end portion 25d to the end portion of the electrode body 20 (in FIG. 5, the upper end in the thickness direction of the electrode body 20). Therefore, the second surplus portion 25g of the separator 25 is a portion on the second side surface 20c of the electrode body 20 from the second end portion 25f to the end portion of the electrode body 20 (in FIG. 5, the lower end in the thickness direction of the electrode body 20).

[0054] In this embodiment, in the thickness direction of the electrode body 20 (i.e., the stacking direction of the positive electrode 23 and the negative electrode 24), the first end portion 25d and the second end portion 25f are arranged apart from each other, and there is a region between the first end portion 25d and the second end portion 25f where the first surplus portion 25e and the second surplus portion 25g are not arranged.

[0055] According to such a configuration, in the portion between the first end portion 25d and the second end portion 25f of the separator 25, the inflow and outflow of the electrolytic solution are facilitated. Therefore, the impregnation property of the electrolytic solution into the electrode body 20 in the secondary battery 100 according to this embodiment can be further enhanced. Also, in the portion between the first end portion 25d and the second end portion 25f of the separator 25, the gas generated in the electrode body 20 can be easily discharged to the outside of the electrode body 20. The distance between the first end portion 25d and the second end portion 25f is not particularly limited, but is preferably 5% to 95% of the thickness of the electrode body 20, more preferably 10% to 90% of the thickness of the electrode body 20, and even more preferably 20% to 60% of the thickness of the electrode body 20.

[0056] In this embodiment, a tape 26 (typically, for example, an adhesive tape) is affixed across the first surplus portion 25e and the second surplus portion 25g. In this case, the first surplus portion 25e and the second surplus portion 25g can be firmly fixed to the electrode body 20.

[0057] Note that in the thickness direction of the electrode body 20 (i.e., the stacking direction of the positive electrode 23 and the negative electrode 24), the first surplus portion 25e and the second surplus portion 25g may overlap each other. In this case, it is easy to join and fix the first surplus portion 25e and the second surplus portion 25g. This joining is possible not only by the method of joining the first surplus portion 25e and the second surplus portion 25g using the tape 26, but also by a method of joining without using the tape 26. As an example thereof, a method of providing an adhesive layer on the separator 25 and adhering the first surplus portion 25e and the second surplus portion 25g with this adhesive layer, a method of applying an adhesive to one of the first surplus portion 25e and the second surplus portion 25g and adhering them, a method of using a double-sided tape, etc. can be adopted.

[0058] When fixing the first surplus part 25e and the second surplus part 25g with the tape 26, as shown in FIG. 6, in the direction in which the first end part 25d extends (the Y direction in the drawing), it is preferable that a plurality of tapes 26 are arranged at intervals. According to such a configuration, on the second side surface 20c of the electrode body 20, an area where the electrolytic solution can enter and exit can be provided between adjacent tapes 26. Therefore, it is possible to improve the overall permeability of the electrolytic solution on the second side surface 20c of the electrode body 20. In addition, it becomes easy to control the balance between the strength of fixing the first surplus part 25e and the second surplus part 25g of the separator 25 and the impregnation property of the electrolytic solution into the electrode body 20, and the degree of freedom in the design of the electrode body 20 is increased. When using a plurality of tapes 26, the number of tapes 26 is not particularly limited, but is preferably two or three. In the example shown in FIG. 6, three tapes 26 are used.

[0059] At least one of the first surplus part 25e and the second surplus part 25g is preferably adhered to the first bending part 25a. That is, the first bending part 25a covered by the first surplus part 25e is preferably adhered to the first surplus part 25e, and / or the first bending part 25a covered by the second surplus part 25g is preferably adhered to the second surplus part 25g. Particularly preferably, it is both. By adhering at least one of the first surplus part 25e and the second surplus part 25g to the first bending part 25a, the first surplus part 25e and / or the second surplus part 25g can be firmly fixed to the electrode body 20. Examples of the adhesion method include a method using an adhesive, a method of press adhesion, a method of heat welding, etc. When performing press adhesion, it is preferable that the separator 25 has an adhesive layer described later. Press adhesion may be performed at room temperature or at a high temperature (for example, 50°C to 100°C).

[0060] Note that the method of fixing the first surplus portion 25e and the second surplus portion 25g with a tape is not limited to the above. Two modified examples with changed tape attachment forms are shown in FIGS. 8 and 9 respectively. FIGS. 8 and 9 are cross-sectional views schematically showing the electrode bodies 120 and 220 of each modified example, and correspond to FIG. 5. In FIGS. 8 and 9, for convenience of explanation, the number of positive electrodes 23 and negative electrodes 24 is increased, and three positive electrodes 23 and four negative electrodes 24 are laminated. However, the number of positive electrodes 23 and negative electrodes 24 is not limited to this. Also, since the modified examples shown in FIGS. 8 and 9 have a different tape attachment form from the example shown in FIG. 5, other points are the same as the example shown in FIG. 5, and the description thereof is simplified or omitted.

[0061] In the modified examples shown in FIGS. 8 and 9, tapes 126 and 226 are attached to at least one of the first surplus portion 25e and the second surplus portion 25g. The tapes 126 and 226 are also attached to the first bent portion 25a that is not covered by either the first surplus portion 25e or the second surplus portion 25g.

[0062] As shown in FIGS. 8 and 9, the separator 25 has a first bent portion 25a that is not covered by the first surplus portion 25e and the second surplus portion 25g, and tapes 126 and 226 are attached to the first surplus portion 25e, the second surplus portion 25g, and this first bent portion 25a.

[0063] In the case of the modified example shown in FIG. 8, in the electrode body 120, a tape 126 is attached from the first surplus portion 25e to the first bent portion 25a, while a tape 126 is attached from the second surplus portion 25g to another first bent portion 25a. In this way, one tape 126 is not attached to both the first surplus portion 25e and the second surplus portion 25g, but is attached from one of the first surplus portion 25e and the second surplus portion 25g to the first bent portion 25a. Therefore, the tape 126 attached to the first surplus portion 25e and the tape 126 attached to the second surplus portion 25g are separate bodies.

[0064] When the secondary battery is charged, the electrode body 120 expands as the active material expands. Due to this expansion, tension is generated in the tape 126 in the thickness direction of the electrode body 120. However, according to the modification example of FIG. 8, since the dimension (i.e., length) of the tape 126 in the thickness direction of the electrode body 120 can be shortened, the tension applied to each tape can be reduced.

[0065] Further, in the first bent portion 25a of the separator 25, there may be a margin for folding back the separator 25. Since the tape 126 is attached to the first bent portion 25a, this margin can absorb the stress caused by the expansion of the electrode body 120.

[0066] In another modification example shown in FIG. 9, the tape 226 is attached to both the first surplus portion 25e and the first surplus portion 25g, and is also attached to the first bent portion 25a that is not covered by either the first surplus portion 25e or the second surplus portion 25g. Also in the modification example shown in FIG. 9, since the tape 226 is attached to the first bent portion 25a of the separator 25, the stress caused by the expansion of the electrode body 220 can be absorbed by the above-mentioned margin.

[0067] Also, in the modification example shown in FIG. 9, since the first bent portion 25a together with the first surplus portion 25e and the second surplus portion 25g is fixed by the tape 226, the fixing of the separator 25 by the tape 226 is stronger.

[0068] Next, the materials constituting the positive electrode 23, the negative electrode 24, and the separator 25 will be described. The positive electrode 23 typically has a positive electrode current collector and a positive electrode active material layer fixed on 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, stainless steel, etc. Here, the positive electrode current collector is a metal foil, specifically an aluminum foil. In the present embodiment, in the positive electrode 23, a portion where the positive electrode current collector is exposed without forming a positive electrode active material layer is formed, and the exposed portion constitutes a current collecting tab. However, the method of configuring the current collecting tab is not limited to this.

[0069] The positive electrode active material layer contains a positive electrode active material capable of reversibly occluding and releasing charge carriers. As the positive electrode active material, an oxide containing at least one of Ni, Co, and Mn is preferable, and examples thereof include lithium transition metal composite oxides such as lithium cobalt oxide, lithium manganate, lithium nickelate, lithium nickel manganese composite oxide, and lithium nickel cobalt manganese composite oxide. It is more preferable that the positive electrode active material is 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% with respect to the total number of moles of metals other than Li. In the lithium transition metal composite oxide, a part of Ni, Co, and Mn may be substituted with Al, Ti, Zr, P, B, Si, Nb, C, etc. Further, the positive electrode active material may be one in which the particle surface of the lithium transition metal composite oxide is coated with a compound containing Al, Ti, Zr, W, P, B, Si, Nb, C, etc. The total substitution amount and addition amount are about 0.1 to 7 mass%. On the other hand, as the positive electrode active material, a lithium transition metal phosphate compound such as lithium iron phosphate can also be used. The positive electrode active material layer may contain a conductive material, a binder, and the like. As the conductive material, a carbon material such as carbon black or carbon nanotube is preferable. As the binder, a resin binder such as polyvinylidene fluoride is preferable.

[0070] The negative electrode 24 typically has a negative electrode current collector and a negative electrode active material layer fixed on 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. Here, the negative electrode current collector is a metal foil, specifically a copper foil. In the present embodiment, in the negative electrode 24, a portion where the negative electrode current collector is exposed without forming the negative electrode active material layer is formed, and the exposed portion constitutes a current collecting tab. However, the method of forming the current collecting tab is not limited to this.

[0071] The negative electrode active material layer contains a negative electrode active material capable of reversibly occluding 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 Si 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 thickening material, a binder, and the like. It is preferable to include styrene-butadiene rubber or carboxymethyl cellulose as the binder.

[0072] The separator 25 is a member that insulates the positive electrode active material layer and the negative electrode active material layer. As the separator 25, for example, a porous resin sheet made of a polyolefin resin such as polyethylene (PE) or polypropylene (PP) is suitable. 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).

[0073] Preferably, an adhesive layer is 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 suppress the lamination shift between the separator 25 and the electrode. The adhesive layer may be provided on the entire surface of the separator 25 or may be pattern-coated.

[0074] A heat resistance layer (HRL) containing ceramic particles may be provided on the surface of the separator 25. Examples of the material of the ceramic particles include alumina, boehmite, aluminum hydroxide, and titania. The heat resistance 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 the resin binder to the heat resistance layer, the heat resistance layer can also function as an adhesive layer.

[0075] As one embodiment of the separator 25, the separator 25 includes a base material of a porous resin sheet and adhesive layers on both surfaces of the base material. As another embodiment of the separator 25, the separator 25 includes a base material of a porous resin sheet, an adhesive layer on one surface of the base material, and a heat-resistant layer on the other surface of the base material. In this embodiment, the heat-resistant layer may have the function of the adhesive layer. As yet another embodiment of the separator 25, the separator 25 includes a base material of a porous resin sheet, an adhesive layer on one surface of the base material, and a heat-resistant layer on the other surface of the base material, and further includes an adhesive layer on this heat-resistant layer.

[0076] <Insulating sheet> As shown in FIGS. 4 and 7, the insulating sheet 50 is housed inside the battery case 10 together with the electrode body 20. The insulating sheet 50 is disposed between the battery case 10 and the electrode body 20. The insulating sheet 50 covers the periphery of the electrode body 20. Preferably, the insulating sheet 50 covers at least the main surface of the electrode body 20, the first side surface 20a, and the second side surface 20c.

[0077] The insulating sheet 50 is made of an insulating material and is preferably made of resin. Examples of the resin include olefin resins such as polyethylene (PE), polypropylene (PP), and polymethylpentene (PMP / TPX (trademark)); polyester 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 fluorine resins such as polytetrafluoroethylene (PTFE). Among them, PE and PP are preferred.

[0078] FIG. 10 shows a developed view of the insulating sheet 50. In the present embodiment, the insulating sheet 50 is composed of a single sheet-like member. By bending this sheet-like member to correspond to the shape of the electrode body 20 to form a square tube shape, the insulating sheet 50 is configured. As shown in FIG. 7, at both ends in the circumferential direction of the electrode body 20, there is an overlapping portion 50a where the bent sheet ends overlap. In the insulating sheet 50, at this overlapping portion 50a, both ends of the bent sheet are fixed by joining or the like. The joining can be performed, for example, by welding such as thermal welding or ultrasonic welding; adhesion with an adhesive; fixing with an adhesive tape, etc. At this overlapping portion 50a, only a part of both ends of the bent sheet may be joined. For example, a total of two locations at both ends of the overlapping portion 50a are joined, or a total of three locations at both ends and the central portion of the overlapping portion 50a are joined. At this overlapping portion 50a, it may be joined over the entire length of the overlapping portion 50a.

[0079] Here, in the present embodiment, in the overlapping portion 50a of the insulating sheet 50, there is a region through which the electrolytic solution and gas can pass. In this case, it is advantageous from the viewpoints of high impregnation of the electrolytic solution into the electrode body 20 and rapid discharge of gas from the electrode body 20. The region through which the electrolytic solution and gas can pass can be provided by joining only a part of the overlapping portion 50a. That is, the unjoined portion in the overlapping portion 50a becomes the region through which the electrolytic solution and gas can pass. Alternatively, by joining over the entire length of the overlapping portion 50a and providing through holes in the insulating sheet or the like, a region through which the electrolytic solution and gas can pass can also be provided. The region through which the electrolytic solution and gas can pass in the overlapping portion 50a preferably has a dimension of 1 / 5L or more, more preferably 1 / 3L or more, and even more preferably 1 / 2L or more in the extending direction of the overlapping portion 50a, where the total length of the overlapping portion is L. The region through which the electrolytic solution and gas can pass in the overlapping portion 50a of the insulating sheet 50 may be always open or may be a region that opens under stress.

[0080] In this embodiment, the overlapping portion 50a of the insulating sheet 50 faces the first side surface 20a, which is the side where the second bent portion 25b of the electrode body 20 is located. At the second bent portion 25b, the positive electrode active material layer of the positive electrode 23 is exposed, and the impregnation property of the electrolytic solution into the electrode body is enhanced. Therefore, when the overlapping portion 50a faces the first side surface 20a, it is advantageous in terms of further enhancing the impregnation property of the electrolytic solution into the electrode body. At this time, it is more advantageous that there is a region in the overlapping portion 50a of the insulating sheet 50 through which the electrolytic solution and gas can pass.

[0081] In this embodiment, the overlapping portion 50a of the insulating sheet 50 is on the side of the bottom surface 12a of the case body 12 of the battery case 10. Since the surplus liquid of the electrolytic solution not impregnated in the electrode body 20 exists on the bottom surface 12a side of the case body 12 in the battery case 10, when the overlapping portion 50a faces the bottom surface 12a, it is advantageous in supplying this surplus liquid to the electrode body 20. Therefore, in this embodiment, it is preferable that the overlapping portion 50a of the insulating sheet 50 is on the side where the surplus liquid of the electrolytic solution exists. At this time, it is more advantageous that there is a region in the overlapping portion 50a of the insulating sheet 50 through which the electrolytic solution can pass. Note that the overlapping portion 50a of the insulating sheet 50 may face a surface of the case body 12 of the battery case 10 other than the bottom surface 12a.

[0082] In this embodiment, the overlapping portion 50a faces the bottom surface 12a of the case body 12 having the gas discharge valve 13. Thus, it is preferable that the overlapping portion 50a faces the surface of the battery case 10 having the gas discharge valve 13. In this case, when gas rapidly generates in the electrode body 20, it is easy to discharge the gas to the outside of the battery case 10 through the gas discharge valve 13. At this time, it is more advantageous that there is a region in the overlapping portion 50a of the insulating sheet 50 through which the gas can pass. Note that the overlapping portion 50a of the insulating sheet 50 may face a surface of the case body 12 of the battery case 10 that does not have the gas discharge valve 13.

[0083] <Electrolytic solution> The electrolyte is housed inside the battery case 10 together with the electrode body 20. The electrolyte may be the same as that of a general secondary battery and is not particularly limited. Typically, the electrolyte is a non-aqueous liquid electrolyte (i.e., non-aqueous electrolyte) containing a non-aqueous solvent and a supporting salt. The non-aqueous solvent includes, 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 the range of 1 to 99% by volume respectively so that the total ratio is 100% by volume. The non-aqueous solvent may further contain carboxylic acid esters such as methyl acetate. The supporting salt, also called an electrolyte salt, is, for example, a fluorine-containing lithium salt. Examples of the fluorine-containing lithium salt include LiPF6, LiBF4, lithium bis(fluorosulfonyl)imide (LiFSI), etc. The supporting salt preferably contains LiPF6. The concentration of the supporting salt 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, specific examples such as film-forming agents such as vinylene carbonate (VC) and oxalate complexes; gas generators; thickeners, etc.

[0084] The secondary battery 100 can be used for various applications. Suitable applications include in-vehicle applications, specifically, power sources for driving mounted on vehicles such as battery electric vehicles (BEVs), hybrid electric vehicles (HEVs), plug-in hybrid electric vehicles (PHEVs), etc. Also, the secondary battery 100 can be used as a storage battery such as a small power storage device. The secondary battery 100 can typically also be used in the form of a battery module formed by connecting a plurality of them in series and / or in parallel.

[0085] As described above, specific examples of the present disclosure have been described in detail, but these are merely examples and do not limit the scope of the claims. The technology described in the claims includes various modifications and changes of the specific examples illustrated above.

[0086] That is, the secondary battery of the present disclosure is as follows in items [1] to

[13] . [1] An electrode body including a plurality of first electrode plates, a plurality of second electrode plates having polarities different from those of the first electrode plates, and a separator disposed between the first electrode plates and the second electrode plates, An electrolytic solution, A case for housing the electrode body and the electrolytic solution, A secondary battery comprising: The separator is strip-shaped and is bent in a ninety-fold shape, The separator includes a first bent portion folded back at an end of the first electrode plate and a second bent portion folded back at an end of the second electrode plate, A plurality of the first bent portions are disposed on one side surface of a pair of opposing side surfaces of the electrode body, A plurality of the second bent portions are disposed on the other side surface of a pair of opposing side surfaces of the electrode body, A first end portion located at one end in the longitudinal direction of the separator and a second end portion located at the other end in the longitudinal direction of the separator are disposed on one side surface of a pair of opposing side surfaces of the electrode body, In the electrode body, the separator is located on both outermost surfaces in the stacking direction of the first electrode plate and the second electrode plate, A secondary battery. [2] The separator includes a first surplus portion including the first end portion and located on the first side surface, and a second surplus portion including the second end portion and located on the first side surface, In the stacking direction of the first electrode plate and the second electrode plate, the first end portion and the second end portion are disposed apart from each other, and there is a region between the first end portion and the second end portion where the first surplus portion and the second surplus portion are not disposed. The secondary battery according to item [1]. [3] A tape is attached across the first surplus portion and the second surplus portion. The secondary battery according to item [2]. [4] In the direction in which the first end portion extends, a plurality of the tapes are disposed at intervals. The secondary battery according to item [3]. [5] The secondary battery according to any one of items [2] to [4], wherein at least one of the first surplus portion and the second surplus portion is adhered to the first bending portion. [6] The secondary battery according to any one of items [2] to [5], wherein a tape is attached to at least one of the first surplus portion and the second surplus portion, and the tape is also attached to the first bending portion that is not covered by either the first surplus portion or the second surplus portion. [7] The case includes a pair of opposing first surfaces, a pair of opposing second surfaces, and a pair of opposing third surfaces. On one side of the pair of first surfaces, the first bending portion of the separator, the first end portion, and the second end portion are arranged. The secondary battery according to any one of items [1] to [6], wherein the second bending portion is arranged on the other side of the pair of first surfaces. [8] The secondary battery according to item [7], wherein a gas discharge valve is provided on the other side of the pair of first surfaces, which breaks when the pressure inside the case becomes a predetermined value or more and discharges the gas inside the case to the outside of the case. [9] The electrolytic solution includes a surplus liquid located between the case and the electrode body. The secondary battery according to item [7] or item [8], wherein the surplus liquid is located on the other side of the pair of first surfaces.

[10] The outer surface of the electrode body is covered with an insulating sheet. The insulating sheet has an overlapping portion on the other side of the pair of first surfaces. The secondary battery according to any one of items [7] to [9], wherein a region through which the electrolytic solution and gas can pass exists in the overlapping portion.

[11] The 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 for sealing the first opening, and a second sealing plate for sealing the second opening. 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. The secondary battery according to any one of items [1] to

[10] .

[12] The secondary battery according to any one of items [1] to

[11] , wherein the first end portion and the second end portion of the separator are disposed on the top surface side of the case.

[13] The secondary battery according to any one of items [1] to

[12] , wherein a plurality of the electrode bodies are accommodated in the case.

Explanation of reference numerals

[0087] 10 Battery case 12 Case body 12a Bottom surface 13 Gas discharge valve 14 First sealing plate 16 Second sealing plate 20 Electrode body 23 Positive electrode 24 Negative electrode 25 Separator 50 Insulating sheet 100 Secondary battery

Claims

1. An electrode body including a plurality of first electrode plates, a plurality of second electrode plates having polarities different from those of the first electrode plates, and a separator disposed between the first electrode plates and the second electrode plates; An electrolytic solution; A case for housing the electrode body and the electrolytic solution; A secondary battery comprising: The separator is strip-shaped and is bent in a ninety-fold shape. The separator includes a first bent portion folded back at an end portion of the first electrode plate and a second bent portion folded back at an end portion of the second electrode plate. A plurality of the first bent portions are disposed on one side surface of a pair of opposing side surfaces of the electrode body. A plurality of the second bent portions are disposed on the other side surface of a pair of opposing side surfaces of the electrode body. A first end portion located at one end in the longitudinal direction of the separator and a second end portion located at the other end in the longitudinal direction of the separator are disposed on one side surface of a pair of opposing side surfaces of the electrode body. In the electrode body, the separator is located on both outermost surfaces in the stacking direction of the first electrode plate and the second electrode plate. A secondary battery.

2. The separator includes a first surplus portion including the first end portion and located on the first side surface, and a second surplus portion including the second end portion and located on the first side surface. In the stacking direction of the first electrode plate and the second electrode plate, the first end portion and the second end portion are disposed apart from each other, and there is a region between the first end portion and the second end portion where the first surplus portion and the second surplus portion are not disposed. The secondary battery according to claim 1.

3. A tape is attached across the first surplus portion and the second surplus portion. The secondary battery according to claim 2.

4. In the direction in which the first end portion extends, a plurality of the tapes are disposed at intervals. The secondary battery according to claim 3.

5. At least one of the first surplus portion and the second surplus portion is adhered to the first bent portion. The secondary battery according to claim 2.

6. A tape is attached to at least one of the first surplus portion and the second surplus portion, and the tape is also attached to the first bent portion that is not covered by either the first surplus portion or the second surplus portion. The secondary battery according to claim 2.

7. The case includes a pair of opposing first surfaces, a pair of opposing second surfaces, and a pair of opposing third surfaces. On one side of one of the pair of the first surfaces, the first bent portion of the separator, the first end portion, and the second end portion are arranged. The secondary battery according to claim 1, wherein the second bent portion is arranged on the other side of the pair of the first surfaces.

8. The secondary battery according to claim 7, wherein on the other side of the pair of the first surfaces, a gas discharge valve is provided which breaks when the pressure in the case becomes a predetermined value or more and discharges the gas in the case to the outside of the case.

9. The electrolytic solution includes surplus liquid located between the case and the electrode body. The secondary battery according to claim 7, wherein the surplus liquid is located on the other side of the pair of the first surfaces.

10. The outer surface of the electrode body is covered with an insulating sheet. The insulating sheet has an overlapping portion of the insulating sheet on the other side of the pair of the first surfaces. The secondary battery according to claim 7, wherein in the overlapping portion, there is a region through which the electrolytic solution and gas can pass.

11. The electrode body has a first electrode tab electrically connected to the first electrode plate at one end portion, and has a second electrode tab electrically connected to the second electrode plate at the other end portion. The case includes a case body having a first opening at one end portion and a second opening at the other end portion, a first sealing plate for sealing the first opening, and a second sealing plate for sealing the second opening. The secondary battery according to claim 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.

12. The secondary battery according to claim 1, wherein the first end portion and the second end portion of the separator are arranged on the top surface side of the case.

13. The secondary battery according to claim 1, wherein a plurality of the electrode bodies are accommodated in the case.

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