Secondary battery

Abstract

The invention relates to a secondary battery. Provided is a secondary battery in which problems existing in the prior art are eliminated. A secondary battery according to the present disclosure includes: an electrode body including a plurality of first electrode plates, a plurality of second electrode plates, and a separator disposed between the first electrode plates and the second electrode plates; an electrolyte; and a housing for accommodating the same. The separator is bent into a zigzag shape and includes a first bent portion folded at an end portion of the first electrode plate and a second bent portion folded at an end portion of the second electrode plate. A plurality of first bent portions are disposed on one side of a pair of opposing side surfaces of the electrode body, and a plurality of second bent portions are disposed on the other side of the pair of opposing side surfaces of the electrode body. The partition body includes a covering portion covering an outer surface of the plurality of first bent portions, and an outer surface of the second bent portion is not covered by the partition body. In the electrode body, the separators are located on both outermost surfaces in the stacking direction of the first electrode plate and the second electrode plate.

Description

Technical Field

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

[0002] As one form of the 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 into a zigzag (repeatedly folded) shape so as to be interposed between the positive electrode and the negative electrode is known (for example, refer to Patent Document 1). Patent Document 1 discloses various schemes for an electrode body in which a separator is folded into a zigzag.

[0003] Prior Art Documents

[0004] Patent Documents

[0005] Patent Document 1: International Publication No. 2019 / 064740 Summary of the Invention

[0006] However, the various schemes disclosed in the above prior art have at least one of the problems of the possibility of short circuit caused by debris detached from the negative electrode active material layer and poor impregnation property (impregnation property) of the electrolyte into the electrode body.

[0007] Therefore, the present disclosure provides a secondary battery that eliminates the problems existing in the prior art.

[0008] The secondary battery of the present disclosure includes: an electrode body 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 separator disposed between the first electrode plates and the second electrode plates; an electrolyte; and a case housing the electrode body and the electrolyte. The separator is in a strip shape and is bent into a zigzag shape. The separator includes a first bent portion that is turned up at an end of the first electrode plate and a second bent portion that is turned up at an end of the second electrode plate. A plurality of the first bent portions are disposed on one side surface side of a pair of opposite side surfaces of the electrode body. A plurality of the second bent portions are disposed on the other side surface side of the pair of opposite side surfaces of the electrode body. The separator includes a covering portion that covers an outer surface of the plurality of first bent portions. The outer surface of the second bent portion is not covered by the separator. In the electrode body, the separator is located on the outermost two sides in the lamination direction of the first electrode plate and the second electrode plate.

[0009] According to such a configuration, a secondary battery that eliminates the problems existing in the prior art can be provided. That is, according to such a configuration, a secondary battery that suppresses short circuit caused by debris detached from the negative electrode active material layer and has excellent impregnation property of the electrolyte into the electrode body can be provided. Brief Description of the Drawings

[0010] Figure 1 A perspective view of a secondary battery according to an embodiment schematically showing an example of the secondary battery of the present disclosure.

[0011] Figure 2 To Figure 1 A perspective view of the secondary battery with the top and bottom reversed.

[0012] Figure 3 To schematically show Figure 1 A cross-sectional view along the main surface of the battery case of the secondary battery, showing the internal structure of the secondary battery.

[0013] Figure 4 For Figure 1 A perspective view of the secondary battery, showing the housing main body in a perspective and schematic manner.

[0014] Figure 5 To schematically show Figure 1 A cross-sectional view showing the configuration of the electrode body of the secondary battery.

[0015] Figure 6 To schematically show Figure 1 A cross-sectional view of the internal configuration of the secondary battery, perpendicular to the long side surface and the bottom surface of the battery case of the secondary battery.

[0016] Figure 7 For Figure 1 A developed view of the insulating sheet for the secondary battery. Detailed Embodiments

[0017] The embodiments related to the present disclosure will be described below with reference to the accompanying drawings. Moreover, matters not mentioned in this specification and 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 this field. The present disclosure can be implemented based on the content disclosed in this specification and the common technical knowledge in this field. In addition, in the following drawings, components and parts that perform the same function are denoted by the same reference numerals for description. Also, the dimensional relationships (length, width, thickness, etc.) in each figure do not reflect the actual dimensional relationships. Moreover, in this specification, the numerical range expressed as "A to B" includes A and B.

[0018] Moreover, in this specification, a "secondary battery" refers to a storage device that can be repeatedly charged and discharged. In addition, in this specification, a "lithium-ion secondary battery" refers to a secondary battery that uses lithium ions as charge carriers and realizes charge and discharge through the movement of charges accompanied by lithium ions between the positive and negative electrodes.

[0019] Figure 1 A perspective view of the secondary battery 100 according to the present embodiment, which is an example of the secondary battery of the present disclosure. Figure 2 To makeFigure 1 A perspective view of the secondary battery 100 inverted vertically. Figure 3 Shows Figure 1 The internal structure of the secondary battery 100. Further, in the following description, the reference numerals L, R, F, Rr, U, and D in the drawings represent left, right, front, back, up, and down, respectively, and the reference numerals 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.

[0020] It should be noted that U (up) and D (down) in the drawings are consistent with up and down in the normal usage form of the secondary battery 100 (especially the installation state in in-vehicle batteries), but the usage form of the secondary battery 100 is not limited thereto. For example, in another embodiment, the secondary battery 100 can be installed upside down.

[0021] The secondary battery 100 according to this embodiment is a lithium-ion secondary battery. Thus, the secondary battery 100 can have excellent battery characteristics such as high energy density and high capacity. However, in another embodiment, the secondary battery can be a secondary battery other than a lithium-ion secondary battery (such as a sodium-ion secondary battery, etc.).

[0022] As Figures 1 - 3 shown, the secondary battery 100 includes a battery case 10, an electrode body 20, and an electrolytic solution (not shown). In addition, the secondary battery 100 further includes a positive electrode terminal 30, a negative electrode terminal 40, and an insulating sheet 50.

[0023] <Battery Case>

[0024] The battery case 10 is a case for housing the electrode body 20 and the electrolytic solution. As Figure 1 and Figure 2 shown, the battery case 10 has an outer shape of a flat and bottomed rectangular parallelepiped shape here. That is, the battery case 10 is square. Therefore, the illustrated secondary battery 100 is a square lithium-ion secondary battery. However, the shape of the battery case 10 is not limited thereto. Since the space efficiency is improved when using a plurality of secondary batteries 100 to form a battery module, the battery case 10 is preferably square.

[0025] The material of the battery case 10 can be the same as the materials used in the past (such as metals, resins, etc.), and there is no particular limitation. From the viewpoints of strength, heat conductivity, etc., the material of the battery case 10 is preferably a metal, more preferably aluminum, aluminum alloy, iron, or iron alloy. Further, the battery case 10 can be made of a laminated film.

[0026] As Figures 1 - 3 shown, the battery case 10 includes: a case main body 12, a first sealing plate 14, and a second sealing plate 16. The case main body 12 is in a square tube shape. AsFigure 3 As shown, the housing main 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 housing 10 is joined (e.g., welded) to the housing main body 12 at the first opening 12e and the second opening 12f by the first sealing plate 14 and the second sealing plate 16 respectively, thereby being integrated. The battery housing 10 is hermetically sealed. Thus, the secondary battery 100 is a sealed type battery.

[0027] The battery housing 10 has a pair of first surfaces, a pair of second surfaces, and a pair of third surfaces. As Figure 1 shown, the housing main 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 opposite to each other, and a top surface 12c connecting between the upper end portions of the pair of long side surfaces 12b. The top surface 12c is substantially rectangular. The top surface 12c is opposite to the bottom surface 12a. Among them, 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. Further, preferably, the area of the long side surface 12b is 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 housing main body 12 is formed, for example, by bending a single metal plate into a cylindrical shape and joining the seams (e.g., welding). In the illustrated example, the welding joint 12d is located on the top surface 12c. Further, the welding joint 12d can be located on the bottom surface 12a or on the long side surface 12b.

[0028] As Figure 2 shown, a gas discharge valve 13 is provided on the bottom surface 12a of the housing main body 12. The gas discharge valve 13 is configured to break when the pressure inside the battery housing 10 becomes a specified value or more and discharge the gas inside the battery housing 10 to the outside. Further, in the present embodiment, the number of the gas discharge valves 13 is one, and it can also be two or more. In addition, in the present embodiment, the gas discharge valve 13 is provided on the bottom surface 12a, but it is not limited thereto. In another embodiment, the gas discharge valve 13 can be provided on a surface other than the bottom surface 12a, such as the long side surface 12b, the top surface 12c, the sealing plate 14, etc. Or, in another embodiment, the secondary battery 100 can be arranged upside down compared with the drawing, changing the bottom surface 12a to the top surface 12c and making the gas discharge valve face upward. In addition, the area of the gas discharge valve 13 is arbitrary.

[0029] In this embodiment, the gas discharge valve 13 is a cross-shaped cut, and the shape of the gas discharge valve 13 is not particularly limited. In another embodiment, the gas discharge valve 13 can be, for example, a linear (only vertical or horizontal) cut, and can be a conventionally known elliptical valve (with a cut inside), a circular valve (with a cut inside), etc. In addition, the size of the cut (such as length, depth, etc.) is arbitrary, and can be appropriately determined, for example, considering the pressure resistance of the battery case 10.

[0030] The first sealing plate 14 and the second sealing plate 16 are plate-shaped members that seal the first opening 12e and the second opening 12f of the housing body 12. The first sealing plate 14 and the second sealing plate 16 are substantially rectangular in plan view. Among them, the first sealing plate 14 and the second sealing plate 16 form a pair of third surfaces.

[0031] A liquid injection hole 17 is provided in the first sealing plate 14. The liquid injection hole 17 is used to inject electrolyte into the inside of the battery case 10 after the first sealing plate 14 and the second sealing plate 16 are installed on the housing 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 in 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. Further, in this embodiment, the liquid injection hole 17 is provided in the first sealing plate 14, but the liquid injection hole 17 can also be provided in the second sealing plate 16, or can be provided in the housing body 12. In addition, 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 can also be provided on the same surface as the gas discharge valve 13.

[0032] <Electrode terminals>

[0033] The positive electrode terminal 30 and the negative electrode terminal 40 are respectively fixed to the battery case 10. The positive electrode terminal 30 and the negative electrode terminal 40 are respectively fixed to opposite surfaces of the battery case 10 here. Specifically, the positive electrode terminal 30 is installed on the first sealing plate 14, and the negative electrode terminal 40 is installed on the second sealing plate 16.

[0034] Specifically, the first sealing plate 14 and the second sealing plate 16 have through holes, and insulating members 63, 64 (refer to Figure 4 ) are respectively installed in the through holes. The positive electrode terminal 30 is installed on 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 installed on the second sealing plate 16 via the insulating member 64, and the negative electrode terminal 40 is insulated from the second sealing plate 16. In addition, inside the battery case 10, 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.

[0035] Furthermore, in the present embodiment, the positive terminal 30 and the negative terminal 40 are respectively provided on the first sealing plate 14 and the second sealing plate 16, but the arrangement of the positive terminal 30 and the negative terminal 40 is not limited thereto. In another embodiment, both the positive terminal 30 and the negative terminal 40 may be provided on one of the first sealing plate 14 or the second sealing plate 16. The positive terminal 30 and the negative terminal 40 may be provided on the housing main body 12. In addition, in the present embodiment, the positive terminal 30 and the negative terminal 40 are provided on a surface different from the gas discharge valve 13, but the positive terminal 30 and the negative terminal 40 may also be provided on the same surface as the gas discharge valve 13.

[0036] However, as in the present embodiment, when the positive terminal 30 and the negative terminal 40 are respectively provided on the first sealing plate 14 and the second sealing plate 16, the height of the secondary battery 100 (i.e., the dimension in the Z direction of the drawing) can be reduced, and it is easy to obtain a battery with a high volume energy density. In addition, in this case, especially in in-vehicle applications, it is easy to form a battery module with a high volume energy density.

[0037] The positive terminal 30 and the negative terminal 40 are respectively exposed on the outer surfaces of the first sealing plate 14 and the second sealing plate 16. The positive terminal 30 and the negative terminal 40 are arranged on the axis passing through the centers of the first sealing plate 14 and the second sealing plate 16 extending in the long side direction Y. However, in another embodiment, the axis may deviate from the centers of the first sealing plate 14 and the second sealing plate 16, for example, in the short side direction X. In addition, the positive terminal 30 and the negative terminal 40 may not be arranged on the axis. For example, one of the positive terminal 30 and the negative terminal 40 may deviate to one side in the short side direction X, and the other may deviate to the other side in the short side direction X.

[0038] The positive terminal 30 is preferably made of metal, and more preferably made of aluminum or an aluminum alloy. The negative terminal 40 is preferably made of metal, and more preferably made of copper or a copper alloy.

[0039] The electrode body 20 has a positive electrode current collector tab electrically connected to the positive electrode 23 at one end, and the positive electrode current collector tab is collectively mounted on the positive electrode current collecting member 32. The electrode body 20 has a negative electrode current collector tab electrically connected to the negative electrode 24 at the other end, and the negative electrode current collector tab is collectively mounted on the negative electrode current collecting member 42. Inside the battery case 10, the positive electrode current collecting member 32 is mounted on the first sealing plate 14 and electrically connected to the positive terminal 30. Inside the battery case 10, the negative electrode current collecting member 42 is mounted on the second sealing plate 16 and electrically connected to the negative terminal 40.

[0040] Thus, inside the battery case 10, the positive terminal 30 is electrically connected to the positive electrode 23 of the electrode body 20 via the positive electrode current collector sheet and the positive electrode current collecting 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 electrode current collector sheet and the negative electrode current collecting member 42. Furthermore, the structure in which the positive terminal 30 and the negative terminal 40 are electrically connected to the positive electrode 23 and the negative electrode 24 of the electrode body 20 respectively is not limited to the structure shown in the figure.

[0041] <Electrode body>

[0042] The electrode body 20 is housed inside the battery case 10. Figure 4 FIG. is a perspective view of the secondary battery 100, schematically showing the housing main body 12 in a perspective manner. Figure 5 FIG. is a schematic cross-sectional view of the electrode body 20 along the thickness direction of the electrode body 20, with the direction of the electrode body 20 changed and simplified for description. Figure 6 FIG. is a cross-sectional view of the electrode body 20 schematically showing the internal structure of the battery case 10 simplified, and is a cross-sectional view along the Figure 1 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.

[0043] Furthermore, since these drawings are schematic views, the main surface of the positive electrode 23 and the separator 25 are shown separately, and in addition, the main surface of the negative electrode 24 and the separator 25 are shown separately. This is to make it easier to recognize each component. In reality, the main surface of the positive electrode 23 abuts (comes into contact) with the separator 25, and the main surface of the negative electrode 24 abuts (comes into contact) with the separator 25. In addition, in reality, parts of the separator 25 may also abut (come into contact) with each other.

[0044] As Figure 4 and Figure 6 shown, the electrode body 20 is disposed inside the battery case 10 in a state covered by an insulating sheet 50 described later. In the present embodiment, a plurality of electrode bodies 20 are housed inside one battery case 10. In Figure 4 and Figure 6 the example shown, two electrode bodies 20 are housed inside one battery case 10. Thus, when there are a plurality of electrode bodies 20, a flow path for the electrolyte or the generated gas can be formed between the electrode body 20 and the adjacent electrode body 20. Furthermore, the number of electrode bodies 20 housed inside one battery case 10 is not particularly limited. In another embodiment, the number of electrode bodies 20 housed inside one battery case 10 can be three or more, or can also be one.

[0045] The electrode body 20 includes: a plurality of positive electrodes 23 (positive electrode plates 23) as the first electrode plates, a plurality of negative electrodes 24 (negative electrode plates 24) as the second electrode plates having a polarity different from that of the first electrode plates, 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 electrodes 23 and the negative electrodes 24. Further, in another embodiment, the first electrode plate can be formed as the negative electrode 24 and the second electrode plate can be formed as the positive electrode 23. The electrode body 20 is a laminated electrode body, which has a high impregnation property of the electrolyte as compared with a wound electrode body, and is particularly advantageous in terms of the liquid injection property of the electrolyte during manufacturing. In addition, according to the laminated electrode body, it is easy to form a battery having a high volumetric energy density.

[0046] In Figure 5 the example shown, the number of the positive electrodes 23 is three, and the number of the negative electrodes 24 is four. However, the numbers of the positive electrodes 23 and the negative electrodes 24 are not particularly limited and can be appropriately determined according to the battery design. In the illustrated example, the number of the negative electrodes 24 is one more than the number of the positive electrodes 23. Therefore, in the electrode lamination structure of the positive electrodes 23 and the negative electrodes 24, the outermost layers are both the negative electrodes 24. In this case, the lithium contained in the positive active material of the positive electrodes 23 can be fully utilized, and at the same time, the precipitation of lithium in the negative electrodes 24 can be highly prevented. Further, in another embodiment, the number of the positive electrodes 23 can be the same as the number of the negative electrodes 24, or the number of the positive electrodes 23 can be more than the number of the negative electrodes 24. For example, the numbers of the positive electrodes 23 and the negative electrodes 24 can be each 20 or more.

[0047] In the present embodiment, the size of the negative electrode 24 is larger than the size of the positive electrode 23. In Figure 5 it, the width of the negative electrode 24 (i.e., 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. Further, in another embodiment, the width of the negative electrode 24 can be the same as the width of the positive electrode 23 or smaller than it.

[0048] The electrode body 20 has a substantially rectangular parallelepiped shape. As Figure 3 and Figure 4 shown, the electrode body 20 has a first side surface 20a facing the bottom surface 12a of the housing main body 12. The electrode body 20 has a second side surface 20c facing the top surface 12c of the housing main 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 housing main body 12. The electrode body 20 has a pair of side surfaces facing the first sealing plate 14 and the second sealing plate 16.

[0049] The separator 25 is strip-shaped. That is, the separator 25 is long and strip-shaped. The separator 25 is bent in a zigzag manner (repeatedly folded). Specifically, the separator 25 is alternately folded at the ends of the positive electrode 23 and the negative electrode 24. Therefore, as Figure 5 shown, the separator 25 has a flat portion along the electrode and a bent portion that is folded at the end of the electrode. Thus, while the plurality of positive electrodes 23 are each held by the separator 25, the plurality of negative electrodes 24 are each held by the separator 25. By the separator 25 being zigzag-shaped, the manufacturing efficiency of the laminated electrode body can be improved.

[0050] Therefore, as Figure 5 shown, for the bent portion of the separator 25, a first bent portion 25a that is folded at the end of the positive electrode 23 is defined, and a second bent portion 25b that is folded at the end of the negative electrode 24 is defined. As Figure 6 shown, the plurality of first bent portions 25a are arranged on the second side surface 20c side opposite to the top surface 12c of the housing main body 12. The portions of the plurality of first bent portions 25a that are opposite to the top surface 12c face the outside of the electrode body 20 and constitute the outer surfaces of the plurality of first bent portions 25a. The plurality of second bent portions 25b are arranged on the first side surface 20a side opposite to the bottom surface 12a of the housing main body 12. The portions of the plurality of second bent portions 25b that are opposite to the bottom surface 12a face the outside of the electrode body 20 and constitute the outer surfaces of the plurality of second bent portions 25b.

[0051] In the present embodiment, in the electrode body 20, the separator 25 is located on the two outermost sides in the stacking direction of the positive electrode 23 and the negative electrode 24. According to such a configuration, the outermost electrode in the electrode body 20, that is, the negative electrode 24, is covered by the separator 25, that is, it is not exposed. Therefore, damage to the negative electrode 24 can be suppressed. In addition, even when the negative electrode 24 is damaged and a part of the negative electrode active material layer detaches, the separator 25 can be used to suppress the movement of the fragments detached from the negative electrode active material layer within the secondary battery 100. Thus, in the secondary battery 100 according to the present embodiment, in the electrode body 20, damage and detachment of the active material layer (the negative electrode active material layer in the illustrated example) of the outermost electrode plate (the 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 at the same time, even when the active material layer has detached, a short circuit caused by the detached active material layer can be suppressed.

[0052] On the other hand, in a secondary battery, it is necessary to improve the impregnation property of the electrolyte into the electrode body. Especially in in-vehicle batteries, when the secondary battery is enlarged to extend the driving range of the vehicle, the time for impregnating (impregnating) the electrode body with the electrolyte is prolonged during the manufacture of the secondary battery (that is, the liquid injection property is reduced), and there is a problem of reduced production efficiency. In addition, when the secondary battery is repeatedly charged and discharged at a high rate, due to the expansion / contraction of the active material layer, the electrolyte is discharged from the electrode body, and thus, there is also a problem that the lithium ion concentration in the electrode body easily becomes uneven. Therefore, in in-vehicle batteries, it is desired to improve the impregnation property of the electrolyte into the electrode body.

[0053] Therefore, in the present embodiment, the outer surface of the second bent portion 25b is not covered by the separator 25. Therefore, between adjacent second bent portions 25b, the end portions of the positive electrode active material layer of the positive electrode 23 are exposed. Therefore, the electrolyte easily penetrates into the electrode body 20 from the end portions of the exposed positive electrode active material layer. Thus, in the secondary battery 100, the impregnation property of the electrolyte into the electrode body 20 is significantly improved.

[0054] In addition to this, there is also an advantage that the gas generated in the electrode body 20 can be easily discharged from the end portions of the exposed positive electrode active material layer to the outside of the electrode body 20. In addition, in Figure 6 In the example shown, a gas discharge valve 13 is provided on the outer surface side of the second bent portion 25b, that is, on the bottom surface 12a side of the housing main body 12. In this case, when the amount of gas generated in the electrode body 20 is large, it is easy to discharge the large amount of generated gas to the outside of the battery housing 10 by using the gas discharge valve 13, which is particularly advantageous.

[0055] Furthermore, in the illustrated example, the electrode body 20 is housed in the battery housing 10 such that the second side surface 20c of the electrode body 20 on the side where the first bent portion 25a is disposed faces the top surface 12c of the housing main body 12, and the first side surface 20a of the electrode body 20 where the second bent portion 25b is disposed faces the bottom surface 12a of the housing main body 12. However, the direction of the electrode body 20 when the electrode body 20 is housed in the battery housing 10 is not limited to the direction of the illustrated example.

[0056] However, the electrolyte includes the electrolyte impregnated in the electrode body 20 and the remaining liquid that is not impregnated in the electrode body 20. The remaining liquid is located between the battery housing 10 and the electrode body 20. Therefore, the remaining liquid is located on the first side surface 20a side of the electrode body 20 that faces the bottom surface 12a of the housing main body 12. Therefore, as Figure 6 In the example shown, when the first side surface 20a of the electrode body 20 is on the side where the first bent portion 25a is disposed, the remaining liquid easily impregnates from the end portions of the exposed positive electrode active material layer, and thus the impregnation property of the electrolyte into the electrode body 20 becomes particularly high.

[0057] As Figure 5 shown, in the present embodiment, in the longitudinal direction of the separator 25, the top end 25e on the covering portion 25c side is disposed on one of the pair of opposing main surfaces of the electrode body 20. In this case, it is possible to more reliably suppress the lamination deviation of the positive electrode 23, the negative electrode 24, and the separator 25 in the electrode body 20 as a whole. The top end 25e on the covering portion 25c side of the separator 25 is preferably located in the region where the positive electrode 23 and the negative electrode 24 face each other. In particular, in the illustrated example, since the width of the negative electrode 24 is larger than the width of the positive electrode 23, the negative electrode 24 has a region where it does not face the positive electrode 23 at its edge portion and a region where it faces the positive electrode 23 at its central portion. Therefore, by the top end 25e on the covering portion 25c side of the separator 25 being located in the region where the positive electrode 23 and the negative electrode 24 face each other, it is easier to suppress the lamination deviation.

[0058] In the present embodiment, in the separator 25, the region 25d of the separator 25 on the top end 25e side compared to the covering portion 25c (in other words, the region of the separator 25 that is folded along the main surface of the electrode body 20 from the end of the covering portion 25c) is bonded to the region existing inside the region 25d on the top end 25e side compared to the covering portion 25c (that is, the electrode body 20 side). Regarding the region existing inside, it is the region of the separator 25 on the inner layer side of the region 25d on the top end 25e side compared to the covering portion 25c in the electrode body 20. In other words, the region existing inside is a part of the separator 25 that covers the negative electrode 24 located in the outermost layer in the electrode layer lamination structure contained in the electrode body 20. In this case, the region 25d on the top end side compared to the covering portion 25c can be effectively fixed to the electrode body 20. That is, it is easy to fix the separator 25.

[0059] At this time, preferably, in the separator 25, the region 25d on the top end 25e side compared to the covering portion 25c is fixed to the inside of the region 25d on the top end 25e side without using a tape. Therefore, no tape is pasted on the main surface of the electrode body 20. In this case, it is possible to suppress the generation of a large step height difference due to the thickness of the tape. In the case where the electrode body 20 of the secondary battery 100 expands and the electrode body 20 comes into contact with the battery case 10, or in the case where the secondary battery 100 is used while being pressed in its thickness direction, a step height difference due to the thickness of the tape can generate a pressure difference applied to the electrode body 20. This pressure difference can be the main cause of uneven battery reaction and the main cause of lithium precipitation. Therefore, by not using a tape as described above, no step height difference caused by the thickness of the tape is generated, and it is possible to obtain effects such as an improvement in the uniformity of the battery reaction and suppression of lithium precipitation.

[0060] As a specific method for fixing the region 25d on the top 25e side of the separator 25 without using a tape, for example, a method using an adhesive, particularly a press bonding method, can be cited. In the case of press bonding, it is preferable that the separator 25 has an adhesive layer described later. Further, the adhesive can be applied only to the fixing portion of the separator 25. The press bonding can be performed at room temperature or at a high temperature (for example, 50°C to 100°C).

[0061] Alternatively, the top 25e on the covering portion 25c side of the separator 25 can be disposed on one of the pair of opposite side surfaces of the electrode body 20. In this case, it is possible to suppress the step height difference caused by the separator 25 on the main surface of the electrode body 20.

[0062] In the present embodiment, the first bending portion 25a for folding the separator 25 is provided at the end of the positive electrode 23. Therefore, the separator 25 has a covering portion 25c that covers the outer surface of the first bending portion 25a. Thus, on the side surface 20c side of the electrode body 20, the outside of the portion where the end of the negative electrode active material layer of the negative electrode 24 is exposed is covered by the covering portion 25c of the separator 25. Thereby, even when a part of the negative electrode active material layer of the negative electrode 24 comes off, the covering portion 25c of the separator 25 can suppress the fragments of the detached negative electrode active material layer from moving significantly from the detached position. As a result, it is possible to effectively suppress the occurrence of a short circuit caused by the fragments of the detached negative electrode active material layer.

[0063] Further, in a lithium ion secondary battery, compared with the positive electrode, the negative electrode is more likely to significantly experience the detachment of a part of the active material layer. Therefore, by adopting this embodiment, even if a part of the negative electrode active material layer that is more likely to come off sometimes comes off, it is possible to more effectively suppress a short circuit caused by the detached negative electrode active material layer.

[0064] 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, or stainless steel. The positive electrode current collector is a metal foil here, 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 this exposed portion constitutes the current collector tab. However, the method of forming the current collector tab is not limited to this.

[0065] 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, oxides containing at least one of Ni, Co, and Mn are preferably used. Examples thereof include lithium transition metal composite oxides such as lithium cobalt oxide, lithium manganate, 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 molar amount of metals other than Li. Further, in the lithium transition metal composite oxide, a part of Ni, Co, and Mn may be replaced by Al, Ti, Zr, P, B, Si, Nb, C, etc. In addition, the positive electrode active material may be a product in which the surface of particles 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 of the replacement amount and the addition amount is about 0.1 to 7% by 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, etc. Further, as the conductive material, carbon materials such as carbon black and carbon nanotubes are preferably used. In addition, as the binder, a resin binder such as polyvinylidene fluoride is preferably used.

[0066] 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, for example. The negative electrode current collector is a metal foil here, specifically a copper foil. In the present embodiment, in the negative electrode 24, a portion where the negative electrode active material layer is not formed and the negative electrode current collector is exposed is formed, and this exposed portion constitutes the current collector tab. However, the method of forming the current collector tab is not limited to this.

[0067] 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; Sn-based negative electrode active materials such as Sn, etc. The negative electrode active material layer may contain a conductive material, a thickening material, a binder, etc. As the binder, styrene-butadiene rubber, carboxymethyl cellulose, etc. are preferably included.

[0068] The separator 25 is a member that insulates the positive electrode active material layer from 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 preferably used. The porous resin sheet may have a single-layer structure or a multilayer structure (for example, a three-layer structure of PP / PE / PP).

[0069] 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 deviation between the separator 25 and the electrode. The adhesive layer can be provided on the entire surface of the separator 25 or can be applied in a pattern.

[0070] On the surface of the separator 25, a heat resistance layer (HRL) containing ceramic particles can be provided. As the material of the ceramic particles, for example, alumina, boehmite, aluminum hydroxide, titanium dioxide, etc. can be cited. The heat resistance layer preferably further contains a resin binder. The resin binder can be an adhesive resin such as an acrylic resin or polyvinylidene fluoride. By adding an appropriate amount of resin binder to the heat resistance layer, the heat resistance layer can also function as an adhesive layer.

[0071] As one embodiment of the separator 25, the separator 25 includes: a base material of a porous resin sheet, and adhesive layers on both sides 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 side of the base material, and a heat resistance layer on the other side of the base material. In this embodiment, the heat resistance layer can have the function of an adhesive layer. As another embodiment of the separator 25, the separator 25 includes: a base material of a porous resin sheet, an adhesive layer on one side of the base material, and a heat resistance layer on the other side of the base material, and an adhesive layer is further included on the heat resistance layer.

[0072] <Insulating sheet>

[0073] As Figure 4 and Figure 6 shown, the insulating sheet 50 is housed together with the electrode body 20 inside the battery case 10. 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. The insulating sheet 50 preferably covers at least the main surface, the first side surface 20a, and the second side surface 20c of the electrode body 20.

[0074] The insulating sheet 50 is made of an insulating material and is preferably made of resin. As examples of the resin, 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; fluororesins such as polytetrafluoroethylene (PTFE), etc. can be cited. Among them, PE and PP are preferred.

[0075] In Figure 7The developed view of the insulating sheet 50 is shown. In the present embodiment, the insulating sheet 50 is composed of a single sheet-like member. The sheet-like member is bent in a manner corresponding to the shape of the electrode body 20 to form a square tube shape, thereby constituting the insulating sheet 50. As Figure 6 shown, at both ends in the circumferential direction of the electrode body 20, there is an overlapping portion 50a where the end portions of the bent sheet overlap. In the insulating sheet 50, at this overlapping portion 50a, both ends of the bent sheet are fixed by bonding or the like. Bonding can be performed, for example, by fusion such as heat fusion or ultrasonic fusion; bonding using an adhesive; fixing using an adhesive tape, etc. At this overlapping portion 50a, only a part of both ends of the bent sheet can be bonded. For example, a total of two places at both ends of the overlapping portion 50a are bonded, or a total of three places at both ends and the central portion of the overlapping portion 50a are bonded. At this overlapping portion 50a, it is also possible to bond over the entire length of the overlapping portion 50a (bond over the entire length of the overlapping portion 50a).

[0076] Among them, in the present embodiment, in the overlapping portion 50a of the insulating sheet 50, there is a region through which the electrolyte and gas can pass. In this case, it is advantageous from the viewpoints of high impregnation of the electrolyte into the electrode body 20 and rapid discharge of gas from the electrode body 20. The region through which the electrolyte and gas can pass can be provided by bonding only a part of the overlapping portion 50a. That is, the unbonded part in the overlapping portion 50a becomes the region through which the electrolyte and gas can pass. Alternatively, the region through which the electrolyte and gas can pass can also be provided by bonding the entire length of the overlapping portion 50a and simultaneously providing through-holes in the insulating sheet. Regarding the region through which the electrolyte and gas can pass in the overlapping portion 50a, when the total length of the overlapping portion in the elongation direction of the overlapping portion 50a is set to L, it preferably has a size of 1 / 5L or more, more preferably has a size of 1 / 3L or more, and further preferably has a size of 1 / 2L or more. The region through which the electrolyte and gas can pass in the overlapping portion 50a of the insulating sheet 50 can be always open or can be a region that opens under stress.

[0077] In the present embodiment, the overlapping portion 50a of the insulating sheet 50 faces the first side surface 20a on the side where the second bent portion 25b of the electrode body 20 exists. In the second bent portion 25b, the positive electrode active material layer of the positive electrode 23 is exposed, and the impregnation property of the electrolyte into the electrode body is improved. Therefore, when the overlapping portion 50a faces the first side surface 20a, it is advantageous in terms of further improving the impregnation property of the electrolyte into the electrode body. At this time, it is more advantageous for the overlapping portion 50a of the insulating sheet 50 to have a region through which the electrolyte and gas can pass.

[0078] In the present embodiment, the overlapping portion 50a of the insulating sheet 50 is located on the bottom surface 12a side of the housing main body 12 of the battery housing 10. The remaining liquid of the electrolyte solution that has not impregnated the electrode body 20 exists inside the battery housing 10 on the bottom surface 12a side of the housing main body 12. Therefore, when the overlapping portion 50a faces the bottom surface 12a, it is advantageous for supplying the remaining liquid to the electrode body 20. Thus, in the present embodiment, it is preferred that the overlapping portion 50a of the insulating sheet 50 is located on the side where the remaining liquid of the electrolyte solution exists. At this time, it is more advantageous if there is a region through which the electrolyte solution can pass in the overlapping portion 50a of the insulating sheet 50. Further, the overlapping portion 50a of the insulating sheet 50 may also face a surface of the housing main body 12 of the battery housing 10 other than the bottom surface 12a.

[0079] In the present embodiment, the overlapping portion 50a faces the bottom surface 12a of the housing main body 12 having the gas discharge valve 13. Thus, it is preferred that the overlapping portion 50a faces the surface of the battery housing 10 having the gas discharge valve 13. In this case, when gas is rapidly generated inside the electrode body 20, it is easy to discharge the gas to the outside of the battery housing 10 through the gas discharge valve 13. At this time, it is more advantageous if there is a region through which the gas can pass in the overlapping portion 50a of the insulating sheet 50. Further, the overlapping portion 50a of the insulating sheet 50 may also face a surface of the housing main body 12 of the battery housing 10 that does not have the gas discharge valve 13.

[0080] <Electrolyte solution>

[0081] The electrolyte solution is housed together with the electrode body 20 inside the battery housing 10. The electrolyte solution may be the same as that of a general secondary battery and is not particularly limited. Typically, the electrolyte solution is a non-aqueous liquid electrolyte (i.e., non-aqueous electrolyte solution) 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 mixed solvent in which EC, EMC, and DMC are mixed 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 known as the 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. There is no particular limitation on the concentration of the supporting salt, and it is preferably 0.6 to 1.8 mol / L, more preferably 0.7 mol / L to 1.3 mol / L. The electrolyte solution may further contain additives, specifically, for example, film-forming agents such as vinylene carbonate (VC) and oxalic acid complexes; gas generators; thickeners, etc.

[0082] The secondary battery 100 can be used for various purposes. As preferred purposes, vehicle-mounted purposes can be cited. Specifically, it can be cited as a driving power source mounted in vehicles such as electric vehicles (BEVs), hybrid electric vehicles (HEVs), plug-in hybrid electric vehicles (PHEVs), etc. In addition, the secondary battery 100 can be used as a storage battery of a small power storage device or the like. The secondary battery 100 can typically also be used in the form of a battery module in which a plurality of secondary batteries 100 are connected in series and / or in parallel.

[0083] The specific examples of the present disclosure have been described in detail above, but these are merely examples and do not limit the claims. The technology described in the claims includes technical solutions obtained by various deformations and changes of the above-described specific examples.

[0084] That is, the secondary battery of the present disclosure is as follows in items [1] to

[10] .

[0085] [1] A secondary battery, comprising: an electrode body 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 separator disposed between the first electrode plates and the second electrode plates; an electrolytic solution; and a case housing the electrode body and the electrolytic solution, wherein the separator is in a strip shape and bent into a zigzag shape, the separator includes a first bent portion folded at an end of the first electrode plate and a second bent portion folded 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 opposite side surfaces of the electrode body, a plurality of the second bent portions are disposed on the other side surface of the pair of opposite side surfaces of the electrode body, the separator includes a covering portion covering an outer surface of the plurality of first bent portions, an outer surface of the second bent portion is not covered by the separator, and in the electrode body, the separator is located at two outermost sides in a stacking direction of the first electrode plates and the second electrode plates.

[0086] [2] The secondary battery according to item [1], wherein the case includes a pair of opposite first surfaces, a pair of opposite second surfaces, and a pair of opposite third surfaces, the first bent portion and the covering portion are disposed on one side of the pair of first surfaces, and the second bent portion is disposed on the other side of the pair of first surfaces.

[0087] [3] The secondary battery according to item [2], wherein a gas discharge valve is provided on the other side of the pair of first surfaces, and the gas discharge valve breaks when the pressure in the case becomes a specified value or more and discharges the gas in the case to the outside of the case.

[0088] [4] The secondary battery according to item [2] or [3], wherein the electrolytic solution includes a remaining liquid located between the housing and the electrode body, and the remaining liquid is located on the other side of a pair of the first surfaces.

[0089] [5] The secondary battery according to any one of items [2] to [4], wherein an outer surface of the electrode body is covered with an insulating sheet, and the insulating sheet has an overlapping portion of the insulating sheet on the other side of a pair of the first surfaces, and a region through which the electrolytic solution and gas can pass exists in the overlapping portion.

[0090] [6] The secondary battery according to any one of items [1] to [5], wherein 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, and the housing includes a housing main 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, and 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.

[0091] [7] The secondary battery according to any one of items [1] to [6], wherein, in a longitudinal direction of the separator, a top end on the covering portion side is disposed on one of a pair of main surfaces of the electrode body that face each other.

[0092] [8] The secondary battery according to item [7], wherein, in the separator, a region on the top end side compared with the covering portion is bonded to a region existing inside the region on the top end side compared with the covering portion.

[0093] [9] The secondary battery according to item [8], wherein, in the separator, a region on the top end side compared with the covering portion is fixed to the inside of the region on the top end side compared with the covering portion without using a tape.

[0094]

[10] The secondary battery according to any one of items [1] to [6], wherein, in a longitudinal direction of the separator, a top end on the covering portion side is disposed on one of a pair of side surfaces of the electrode body that face each other.

Claims

1. A secondary battery, comprising: An electrode body 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 separator disposed between the first electrode plates and the second electrode plates; An electrolytic solution; And A case housing the electrode body and the electrolytic solution, wherein the separator is in a strip shape and is bent into a zigzag shape, the separator includes a first bent portion folded at an end of the first electrode plate and a second bent portion folded 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 opposite side surfaces of the electrode body, a plurality of the second bent portions are disposed on the other side surface of the pair of opposite side surfaces of the electrode body, the separator includes a covering portion covering an outer surface of the plurality of the first bent portions, the outer surface of the second bent portion is not covered by the separator, in the electrode body, the separator is located on two outermost sides in a stacking direction of the first electrode plates and the second electrode plates.

2. The secondary battery according to claim 1, wherein, The case includes a pair of opposite first surfaces, a pair of opposite second surfaces, and a pair of opposite third surfaces, the first bent portion and the covering portion are disposed on one side of the pair of first surfaces, the second bent portion is disposed on the other side of the pair of first surfaces.

3. The secondary battery according to claim 2, wherein, A gas discharge valve is provided on the other side of the pair of first surfaces, and the gas discharge valve breaks when the pressure in the case becomes a specified value or more and discharges the gas in the case to the outside of the case.

4. The secondary battery according to claim 2, wherein, The electrolytic solution includes a remaining liquid located between the case and the electrode body, and the remaining liquid is located on the other side of the pair of first surfaces.

5. The secondary battery according to claim 2, wherein, An outer surface of the electrode body is covered by an insulating sheet, the insulating sheet has an overlapping portion of the insulating sheet on the other side of the pair of first surfaces, a region through which the electrolytic solution and gas can pass exists in the overlapping portion.

6. The secondary battery according to claim 1, wherein, 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 sealing the first opening, and a second sealing plate sealing the second opening, 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.

7. The secondary battery according to claim 1, wherein, In a longitudinal direction of the separator, a top end on the covering portion side is disposed on one main surface of a pair of opposite main surfaces of the electrode body.

8. The secondary battery according to claim 7, wherein, In the separator, a region located on the top end side compared with the covering portion is bonded to a region existing inside the region located on the top end side compared with the covering portion.

9. The secondary battery according to claim 8, wherein In the separator, a region located on the top end side compared with the covering portion is fixed to the inside of the region located on the top end side compared with the covering portion without using a tape.

10. The secondary battery according to claim 1, wherein, In a longitudinal direction of the separator, a top end on the covering portion side is disposed on one side surface of a pair of opposite side surfaces of the electrode body.

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