Secondary battery and method for manufacturing the same

Abstract

The present invention provides a secondary battery in which metal deposition is suppressed and a method for manufacturing the same. [Solution] The secondary battery comprises an electrode body including a first electrode and a second electrode, and an outer casing that houses the electrode body. The separator of the electrode body has a folded portion that extends in a strip shape in a first direction near at least one of a pair of first end edges on the first surface of the outer casing, and the folded portion is superimposed on the first electrode and the second electrode of the electrode body in a first region on the first main surface or second main surface of the electrode body so as to face the first surface of the outer casing, and the thickness of the electrode body in the first region is greater than the thickness of the electrode body in the second region which is adjacent to the first region in a second direction.

Description

Technical Field

[0001] The present technology relates to a secondary battery and a method for manufacturing the same.

Background Art

[0002] Japanese Unexamined Patent Application Publication No. 2013-084387 (Patent Document 1) discloses a battery in which a separator is provided with a regulating portion that comes into contact with an end portion of a positive electrode or a negative electrode so as to regulate movement of the positive electrode or the negative electrode in a direction perpendicular to the stacking direction.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] It is required to suppress metal deposition in secondary batteries. When an assembled battery is configured from secondary batteries each having a prismatic outer can, the pressurizing load tends to be relatively small in the vicinity of the edge of the surface of the substantially rectangular outer can. Due to variations in the pressurizing load, a resistance difference occurs in the electrode body, which makes metal deposition likely to occur. It is required to effectively suppress metal deposition in a portion where the pressurizing load is relatively small. From this viewpoint, conventional secondary batteries still have room for improvement.

[0005] An object of the present technology is to provide a secondary battery in which metal deposition is suppressed and a method for manufacturing the same.

Means for Solving the Problems

[0006] The present technology provides the following secondary battery and method for manufacturing the same.

[0007] [1] An electrode body including a first electrode, a second electrode having a different polarity from the first electrode, and a separator provided between the first electrode and the second electrode, and an outer can having a rectangular shape for housing the electrode body, the outer can having a pair of first faces, a pair of second faces substantially perpendicular to the first faces, and a pair of third faces substantially perpendicular to the first and second faces, the area of ​​the first faces being larger than the area of ​​the second faces and the area of ​​the third faces, the first faces including a pair of first edges extending in a first direction and a pair of second edges extending in a second direction substantially perpendicular to the first direction A secondary battery having a substantially rectangular shape, wherein the electrode body has a first main surface and a second main surface facing each of the pair of first surfaces, the separator has a folded portion extending in a strip shape in the first direction near at least one of the pair of first end edges, the folded portion overlapping the first electrode and the second electrode in a first region on the first main surface or the second main surface so as to face the first surface of the outer casing, and the thickness of the electrode body in the first region is greater than the thickness of the electrode body in the second region which is adjacent to the first region in the second direction.

[0008] [2] The secondary battery according to [1], wherein the folded portion is provided near both of the pair of first end edges.

[0009] [3] The secondary battery according to [1] or [2], wherein in the second direction the second electrode is formed to be shorter than the first electrode, and the folded portion is formed to overlap with the second electrode.

[0010] [4] A secondary battery according to any one of [1] to [3], wherein a tape for fixing the end of the separator is provided on the first main surface of the electrode body, and the folded portion is provided on the first main surface.

[0011] [5] The separator includes an outer peripheral portion provided outside the first electrode and the second electrode, the outer peripheral portion having an excess portion that extends from the edge of the first main surface of the electrode body to the edge of the second main surface and has a creepage distance longer than the shortest distance from the edge of the first main surface to the edge of the second main surface in a third direction perpendicular to the first and second directions, the folded portion being formed by folding the excess portion, the secondary battery according to any one of [1] to [4].

[0012] [6] The secondary battery according to any one of [1] to [5], wherein the pair of first ends are the longer sides.

[0013] [7] The secondary battery according to any one of [1] to [6], wherein the electrode body has electrode tabs positioned facing the pair of second end edges.

[0014] [8] The electrode body is a stacked electrode body, as described in any one of [1] to [7].

[0015] [9] The separator is folded in a zigzag pattern, as described in [8].

[0016]

[10] The electrode body comprises the steps of preparing an electrode body having a first main surface and a second main surface, a first electrode, a second electrode having a different polarity from the first electrode, and a separator provided between the first electrode and the second electrode, and housing the electrode body in an outer can, the outer can having a rectangular shape, a pair of first surfaces, a pair of second surfaces substantially perpendicular to the first surfaces, and a pair of third surfaces substantially perpendicular to the first and second surfaces, the area of ​​the first surfaces being larger than the area of ​​the second surfaces and the area of ​​the third surfaces, the first surfaces having a pair of first end edges extending in a first direction, and substantially perpendicular to the first direction A method for manufacturing a secondary battery, comprising: having a substantially rectangular shape including a pair of second end edges extending in a second orthogonal direction, the step of preparing the electrode body comprising bending the separator in the vicinity of at least one of the pair of first end edges so as to form a folded portion that extends in a strip in the first direction and overlaps the first electrode and the second electrode in a first region on the first main surface or the second main surface, and the step of housing the electrode body in the outer casing comprising inserting the electrode body into the outer casing so as to the first main surface and the second main surface facing the pair of first surfaces, respectively.

[0017]

[11] A method for manufacturing a secondary battery according to

[10] , further comprising the step of bending an insulating member disposed on the outside of the electrode body, wherein the folded portion is formed when the insulating member is bent.

[0018]

[12] The method for manufacturing a secondary battery according to

[11] , further comprising the step of bending the separator before bending the insulating member. [Effects of the Invention]

[0019] This technology makes it possible to provide a secondary battery in which metal deposition is suppressed, and a method for manufacturing the same. [Brief explanation of the drawing]

[0020] [Figure 1] This is a front view showing the configuration of a secondary battery according to an embodiment. [Figure 2]This is a diagram showing the secondary battery illustrated in Figure 1, viewed from the direction of arrow II. [Figure 3] This is a diagram showing the secondary battery illustrated in Figure 1, viewed from the direction of arrow III. [Figure 4] This is a diagram showing the secondary battery illustrated in Figure 1, viewed from the direction of arrow IV. [Figure 5] This is a diagram showing the secondary battery illustrated in Figure 1, viewed from the direction of arrow V. [Figure 6] This is a front cross-sectional view of the secondary battery illustrated in Figure 1. [Figure 7] This is a cross-sectional view of the negative electrode plate. [Figure 8] This is a front view showing the negative electrode plate. [Figure 9] This is a cross-sectional view of the positive electrode plate. [Figure 10] This is a front view showing the positive electrode plate. [Figure 11] This is a perspective view showing a state where a sealing plate is attached to the positive electrode-side current collector. [Figure 12] This is a perspective view showing the configuration of the secondary battery. [Figure 13] This is a diagram of the secondary battery and the inter-cell separator adjacent to the secondary battery, viewed from the stacking direction. [Figure 14] This is a cross-sectional view showing the electrode body before the separator is folded. [Figure 15] This is a cross-sectional view showing the electrode body with the separator folded. [Figure 16] This is a cross-sectional view showing a modified example of the electrode body with the separator folded. [Figure 17] This is a cross-sectional view showing the first stage of the separator folding step in the manufacturing process of the electrode body illustrated in Figure 15. [Figure 18] This is a cross-sectional view showing the second stage of the separator folding step that follows Figure 17. [Figure 19] This is a cross-sectional view showing the first stage of a modified example of the separator folding step in the manufacturing process of the modified example of the electrode body illustrated in Figure 16. [Figure 20] This is a cross-sectional view showing the second stage of the modified example of the separator folding step that follows Figure 18. [Figure 21] This diagram illustrates the relationship between the thickness of the electrode body and the creepage distance of the separator. [Modes for carrying out the invention]

[0021] Embodiments of this technology are described below. Note that the same or corresponding parts may be denoted by the same reference numerals, and their descriptions may not be repeated.

[0022] In the embodiments described below, when referring to the number, quantity, etc., unless otherwise specified, the scope of this technology is not necessarily limited to that number, quantity, etc. Also, in the embodiments described below, each component is not necessarily essential to this technology unless otherwise specified. Furthermore, this technology is not necessarily limited to achieving all of the effects and advantages mentioned in these embodiments.

[0023] In this specification, the terms "comprise," "include," and "have" are in open-ended form. That is, if a configuration includes one configuration, it may also include other configurations, or it may not.

[0024] Furthermore, where geometric terms and terms describing positional and directional relationships are used in this specification, such as "parallel," "orthogonal," "45° oblique," "coaxial," and "alongside," these terms allow for manufacturing tolerances or slight variations. Where terms describing relative positional relationships, such as "upper" and "lower," are used in this specification, these terms are used to indicate the relative positional relationship in a single state, and the relative positional relationship may be reversed or rotated to any angle depending on the installation direction of each mechanism (for example, by inverting the entire mechanism upside down).

[0025] Furthermore, the dimensions of each component illustrated in this specification, such as width, length, and diameter, are not limited to those shown and may be changed as appropriate. In this specification, each component may be assigned an ordinal number such as "1st" or "2nd," but these ordinal numbers do not limit priority, order, etc., unless explicitly specified.

[0026] In this specification, "battery" is not limited to lithium-ion batteries, but may include other batteries such as nickel-metal hydride batteries and sodium-ion batteries. In this specification, "electrode" may refer collectively to the positive electrode and the negative electrode. Also, "electrode plate" may refer collectively to the positive electrode plate and the negative electrode plate.

[0027] In this specification, "battery" can be installed in hybrid electric vehicles (HEVs), plug-in hybrid electric vehicles (PHEVs), and battery electric vehicles (BEVs), etc. However, the use of "battery" is not limited to in-vehicle applications.

[0028] In this specification, the X direction (first direction) may be referred to as the "width direction" of the secondary battery, electrode body and case body, the Z direction (second direction) may be referred to as the "height direction" of the secondary battery, electrode body and case body, and the Y direction (third direction) may be referred to as the "thickness direction" of the secondary battery, electrode body and case body.

[0029] (Overall configuration of a secondary battery) The overall configuration of the secondary battery 1 will be described with reference to Figures 1 to 6. The secondary battery 1 includes a case 100 (outer casing), an electrode body 200, electrode terminals 300, and a current collector 400. The case 100 includes a case body 110, a sealing plate 120, and a sealing plate 130.

[0030] When a battery pack including a secondary battery 1 is constructed, multiple secondary batteries 1 are stacked in the thickness direction. The stacked secondary batteries 1 may be constrained in the stacking direction (Y direction) by a restraining member to form a battery module, or the battery pack may be directly supported on the side of the battery pack case without using a restraining member.

[0031] The case body 110 is made of a cylindrical, preferably rectangular, member. This provides a secondary battery 1 equipped with a rectangular case 100. The case body 110 is made of metal. Specifically, the case body 110 is made of aluminum, aluminum alloy, iron, or iron alloy.

[0032] As shown in Figures 1 and 2, sealing plates 120 and 130 are provided at both ends of the case body, respectively. The case body 110 can be formed into a rectangular tube shape by, for example, bringing together the ends of bent plate-like members (joint portion 115 as illustrated in Figure 2) and joining them together (for example, by energy ray irradiation such as laser welding). The corners of the "rectangular tube" may have a rounded shape.

[0033] In this embodiment, the case body 110 is formed to be longer in the width direction (X direction) of the secondary battery 1 than in the thickness direction (Y direction) and height direction (Z direction) of the secondary battery 1. The dimension (width) of the case body 110 in the X direction is preferably about 300 mm or more. This makes it possible to construct a relatively large (high capacity) secondary battery 1. The dimension (height) of the case body 110 in the Z direction is preferably about 100 mm or less. This makes it possible to construct a relatively low-height secondary battery 1, for example, improving its mountability in a vehicle. However, the dimensions of the secondary battery 1 are not limited to the above ranges.

[0034] The case body 110 includes a first side portion 111 (first surface) and a second side portion 112 (second surface). The first side portion 111 consists of a pair of first side portions 111A and 111B, and the second side portion 112 consists of a pair of second side portions 112A and 112B. The first side portions 111A and 111B constitute a part of the side surface of the case 100. The pair of second side portions 112A and 112B constitute the bottom surface and top surface of the case 100. The first side portion 111 and the second side portion 112 are arranged to intersect (approximately perpendicular to) each other. The first side portion 111 and the second side portion 112 are connected at their respective ends.

[0035] As shown in Figure 5, a gas exhaust valve 150 is provided on one of the second side portions 112A of the second side portion 112. The gas exhaust valve 150 extends in the width direction (X direction) of the secondary battery 1. The gas exhaust valve 150 extends in the X direction to the extent that it does not reach the ends of the case body 110 from the center in the X direction. The shape of the gas exhaust valve 150 can be changed as appropriate.

[0036] The thickness of the plate-shaped member in the gas discharge valve 150 is thinner than the thickness of the other plate-shaped members in the case body 110. As a result, when the pressure inside the case 100 exceeds a predetermined value, the gas discharge valve 150 preferentially ruptures compared to other parts of the case body 110, and discharges the gas inside the case 100 to the outside.

[0037] As shown in Figure 2, a joint portion 115 is formed on the other second side portion 112B of the second side portion 112. The joint portion 115 extends in the width direction (X direction) of the secondary battery 1. At the joint portion 115, the ends of the plate-shaped members constituting the case body 110 are joined together.

[0038] As shown in Figure 3, an opening 113 (first opening) is provided at one end of the case body 110 in the first direction (X direction). The opening 113 is sealed by a sealing plate 120 (first sealing plate). A joint 115 is formed in the opening 113 to seal it. The opening 113 and the sealing plate 120 have a substantially rectangular shape with the Y direction being the short side and the Z direction being the long side. The substantially rectangular shape includes a rectangular shape, or a rectangular shape with rounded corners, etc.

[0039] A negative terminal 300A is provided on the sealing plate 120. The position of the negative terminal 300A can be changed as appropriate.

[0040] As shown in Figure 4, an opening 114 (second opening) is provided at the other end of the case body 110 in the X direction. That is, the opening 114 is located at the end opposite to the opening 113, and the openings 113 and 114 face each other. The opening 114 is sealed by a sealing plate 130 (second sealing plate). A joint 115 is formed in the opening 114 to seal it. The opening 114 and the sealing plate 130 have a substantially rectangular shape with the Y direction being the short side and the Z direction being the long side.

[0041] A positive electrode terminal 300B and an injection hole 140 are provided on the sealing plate 130. The positions of the positive electrode terminal 300B and the injection hole 140 can be changed as appropriate. The injection hole 140 is sealed by a sealing member (not shown). As the sealing member, for example, a blind rivet or other metal member can be used.

[0042] The sealing plates 120 and 130 are made of metal. Specifically, the sealing plates 120 and 130 are made of aluminum, aluminum alloy, iron, or iron alloy.

[0043] The sealing plates 120 and 130 (third surface) constitute a part of the case 100. The sealing plates 120 and 130 are provided so as to intersect (approximately perpendicular to) the first side portion 111 and the second side portion 112.

[0044] In case 100, the area of ​​each of the pair of first side surfaces 111 (first surface) (first area) is larger than the area of ​​each of the pair of second side surfaces 112 (second surface) (second area) and the area of ​​each of the sealing plates 120, 130 (third surface) (third area).

[0045] The negative terminal 300A is electrically connected to the negative electrode of the electrode body 200. The negative terminal 300A is attached to the sealing plate 120, i.e., the case 100. The positive terminal 300B is electrically connected to the positive electrode of the electrode body 200. The positive terminal 300B is attached to the sealing plate 130, i.e., the case 100.

[0046] The negative terminal 300A is made of a conductive material (more specifically, a metal), such as copper or a copper alloy. The positive terminal 300B is made of a conductive material (more specifically, a metal), such as aluminum or an aluminum alloy.

[0047] In this embodiment, the electrode body 200 is a flat-shaped electrode body in which a negative electrode plate 210 and a positive electrode plate 220, which will be described later, are stacked. Specifically, the electrode body 200 is a laminated electrode body in which a plurality of negative electrode plates 210 and a plurality of positive electrode plates 220 are alternately stacked with a separator in between. The separator is made by folding a strip-shaped insulating sheet material in a zigzag pattern.

[0048] As shown in Figure 6, the case 100 houses the electrode body 200. The electrode body 200 is housed in the case 100 such that its longitudinal direction is parallel to the X direction. Specifically, one or more stacked electrode bodies are housed in the case 100 together with an electrolyte (not shown). As the electrolyte (non-aqueous electrolyte), for example, a solution of LiPF6 dissolved in a non-aqueous solvent can be used. A solid electrolyte may be used instead of an electrolyte.

[0049] The electrode body 200 includes a roughly rectangular main body, a negative electrode tab group 200A, and a positive electrode tab group 200B.

[0050] The main body is composed of a negative electrode plate 210 and a positive electrode plate 220, which will be described later. The negative electrode tab group 200A is located at one end of the electrode body 200 (the sealing plate 120 side) in the X direction relative to the main body. The positive electrode tab group 200B is located at the other end of the electrode body 200 (the sealing plate 130 side) in the X direction relative to the main body.

[0051] The negative electrode tab group 200A and the positive electrode tab group 200B are formed to protrude from the central portion of the electrode body 200 toward the sealing plate 120 or the sealing plate 130, respectively.

[0052] The current collector 400 includes a negative electrode current collector 400A and a positive electrode current collector 400B. The negative electrode current collector 400A and the positive electrode current collector 400B are each made of plate-shaped members. The electrode body 200 is electrically connected to the negative electrode terminal 300A and the positive electrode terminal 300B via the current collector 400.

[0053] The negative electrode current collector 400A is positioned on the sealing plate 120 via a resin insulating member. The negative electrode current collector 400A is electrically connected to the negative electrode tab group 200A and the negative electrode terminal 300A. The negative electrode current collector 400A is made of a conductive material (more specifically, a metal), which may be made of copper or a copper alloy, for example.

[0054] The positive electrode current collector 400B is positioned on the sealing plate 130 via a resin insulating member. The positive electrode current collector 400B is electrically connected to the positive electrode tab group 200B and the positive electrode terminal 300B. The positive electrode current collector 400B is made of a conductive material (more specifically, a metal), such as aluminum or an aluminum alloy. The positive electrode tab group 200B may be electrically connected to the sealing plate 130 directly or via the positive electrode current collector 400B. In this case, the sealing plate 130 may also function as the positive electrode terminal 300B.

[0055] (Configuration of electrode body 200) As shown in Figures 7 and 8, the negative electrode plate 210 (first electrode) includes a negative electrode core 211 and a negative electrode active material layer 212. A negative electrode tab 200A0 made of the negative electrode core 211 is provided at one end of the negative electrode plate 210 in the width direction. When the negative electrode plates 210 are stacked, multiple negative electrode tabs 200A0 are stacked to form a negative electrode tab group 200A. The negative electrode tab group 200A is electrically connected to the negative electrode. The length of each negative electrode tab 200A0 in the protruding direction in the multiple negative electrode plates 210 is appropriately adjusted considering the state in which the negative electrode tab group 200A is connected to the negative electrode current collector 400A. The shape of the negative electrode tab 200A0 is not limited to that illustrated in Figure 8.

[0056] As shown in Figures 9 and 10, the positive electrode plate 220 (second electrode) includes a positive electrode core 221, a positive electrode active material layer 222, and a positive electrode protective layer 223. A positive electrode tab 200B0 made of the positive electrode core 221 is provided at one end of the positive electrode plate 220 in the width direction. When the positive electrode plates 220 are stacked, multiple positive electrode tabs 200B0 are stacked to form a positive electrode tab group 200B. The positive electrode tab group 200B is electrically connected to the positive electrode. The length of each positive electrode tab 200B0 in the protruding direction on the multiple positive electrode plates 220 is appropriately adjusted considering the state in which the positive electrode tab group 200B is connected to the positive electrode current collector 400B. The shape of the positive electrode tab 200B0 is not limited to that illustrated in Figure 10.

[0057] A positive electrode protective layer 223 is provided at the base of the positive electrode tab 200B0. However, the positive electrode protective layer 223 is not necessarily required at the base of the positive electrode tab 200B0.

[0058] (Housing of electrode body 200) The electrode body 200 is inserted into the case body 110 through the opening 113, with the positive electrode tab group 200B side leading. As shown in Figure 11, a spacer 500 is provided between the electrode body 200 and the sealing plate 130 on the positive electrode side. A spacer 500 is also provided between the electrode body 200 and the sealing plate 120 on the negative electrode side, similar to the positive electrode side.

[0059] Before inserting the electrode body 200 into the case body 110, the electrode body 200 may be electrically connected to the negative terminal 300A. After inserting the electrode body 200 into the case body 110, the electrode body 200 is electrically connected to the positive terminal 300B.

[0060] After inserting the electrode body 200 into the case body 110, the sealing plates 120 and 130 are joined to the case body 110 as shown in Figure 12. The sealing plate 120 seals the opening 113 of the case body 110, and the sealing plate 130 seals the opening 114 of the case body 110. This houses the electrode body 200 in the case 100.

[0061] (Battery pack configuration) As shown in Figure 13, the first side portion 111 of the case body 110 has a substantially rectangular shape including a pair of first end sides 101 extending in the X direction and a pair of second end sides 102 extending in the Z direction. Here, the pair of first end sides 101 are longer than the pair of second end sides 102. That is, the first side portion 111 has a substantially rectangular shape with the X direction being the longer side direction and the Z direction being the shorter side direction.

[0062] When a battery pack is constructed, multiple secondary batteries 1 are arranged so as to be aligned in the Y direction. Intercellular separators 2 are placed between the multiple secondary batteries 1. As shown in Figure 13, when viewed from the Y direction, the area of ​​the intercellular separator 2 is smaller than the area of ​​the first side portion 111 of the case body 110. The height of the intercellular separator 2 is lower than the height of the main body portion 200C of the electrode body 200 (the roughly rectangular portion excluding the electrode tabs).

[0063] Therefore, portions of the electrode body 200 that do not overlap with the inter-cell separator 2 are created at the upper and lower ends (near the pair of first end edges 101), and the pressurizing load by the inter-cell separator 2 tends to be relatively small. In this embodiment, the electrode body 200 has a separator 230 configuration that suppresses the decrease in pressurizing load near the first end edges 101, as will be described later.

[0064] (Configuration of separator 230) As shown in Figure 14, the electrode body 200 includes a negative electrode plate 210 and a positive electrode plate 220 with opposite polarities, a separator 230, and a tape 240. The separator 230 is provided between the negative electrode plate 210 and the positive electrode plate 220.

[0065] The separator 230 is a component for insulating the negative electrode plate 210 and the positive electrode plate 220. The separator 230 is made of a porous resin sheet made of polyolefin resin such as polyethylene (PE) or polypropylene (PP). The porous resin sheet may have a single-layer structure or a multi-layer structure (for example, a three-layer structure of PP / PE / PP).

[0066] It is preferable that an adhesive layer is provided on the surface of the separator 230. The adhesive layer contains, for example, an adhesive resin such as an acrylic resin or polyvinylidene fluoride. By having an adhesive layer on the separator 230, misalignment of the lamination between the negative electrode plate 210 and the positive electrode plate 220 and the separator 230 can be easily suppressed. The adhesive layer may be provided on the entire surface of the separator 230, or it may be pattern-coated on the surface of the separator 230.

[0067] A heat-resistant layer containing ceramic particles may be provided on the surface of the separator 230. Preferably, the heat-resistant layer contains a resin binder. This allows the heat-resistant layer to function as an adhesive layer.

[0068] The electrode body 200 has a main surface 250 facing the first side portion 111 (first surface) of the case body 110. The main surface 251 (first main surface) and the main surface 252 (second main surface) face the first side portions 111A and 111B, respectively.

[0069] The end of the separator 230 that is at the end of the winding (first end) is fixed onto the main surface 251 by the tape 240.

[0070] The separator 230 includes a zigzag folded portion between the negative electrode plate 210 and the positive electrode plate 220, and an outer peripheral portion (outer surface portion) provided to surround the outside of the negative electrode plate 210 and the positive electrode plate 220. However, the shape of the separator 230 is not limited to the above, and the portion provided between the negative electrode plate 210 and the positive electrode plate 220 and the outer peripheral portion surrounding the outside of the negative electrode plate 210 and the positive electrode plate 220 may be provided separately. The portion provided between the negative electrode plate 210 and the positive electrode plate 220 is not limited to a zigzag folded strip-shaped separator 230, but may be provided individually as rectangular separators.

[0071] As shown in Figure 14, the outer circumference of the separator 230 has excess portions 231A and 232A at both ends in the Z direction. The ends of the separator 230 in the X direction may be open or closed in a bag-like manner.

[0072] In the example shown in Figure 15, the separator 230 has folded portions 231 and 232 that extend in a band shape in the X direction near a pair of first end edges 101. The folded portions 231 and 232 shown in Figure 15 are formed by folding back the excess portions 231A and 232A shown in Figure 14. Preferably, the folded portions 231 and 232 are formed over the entire length of the main body portion 200C of the electrode body 200 in the X direction. However, the folded portions 231 and 232 may be formed over a part of the main body portion 200C of the electrode body 200 in the X direction. In this case, it is preferable that the folded portions 231 and 232 are formed over about 1 / 2 or more (more preferably about 2 / 3 or more) of the length of the main body portion 200C of the electrode body 200.

[0073] In the modified example shown in Figure 16, the separator 230 has a folded portion 231 that extends in a band shape in the X direction near the first end edge 101 on the -Z side of the pair of first end edges 101. The folded portion 231 shown in Figure 16 is formed by folding back the excess portion 231A in Figure 14.

[0074] The folded portions 231 and 232 are superimposed on the negative electrode plate 210 and the positive electrode plate 220 on the main surface 251 so as to face the first side surface 111 of the case body 110. The folded portions 231 and 232 may also be provided on the main surface 252. The folded portions 231 and 232 are provided on the same side of a pair of main surfaces 250 (either one of the main surfaces 251 or 252). It is preferable that the folded portions 231 and 232 are provided on the main surface 250 on the same side as the tape 240 (main surface 251 in the examples of Figures 15 and 16).

[0075] As shown in Figures 15 and 16, the electrode body 200 is thickened in the region where the folded portions 231 and 232 are formed on the main surface 251. The thickness of the electrode body 200 in the region where the folded portions 231 and 232 are formed (first region) is greater than the thickness of the electrode body 200 in the region located between the folded portions 231 and 232 in the Z direction (second region).

[0076] In the examples in Figures 15 and 16, the end of the separator 230 on the winding start side (second end) is located inside the folded portion 231. In the example in Figure 15, two roughly U-shaped portions (parts that are folded back by approximately 180°) are formed in the folded portion 232, with the other roughly U-shaped portion located inside one of them.

[0077] In the folded portions 231 and 232 shown in Figures 15 and 16, the electrode body 200 is thickened by the thickness of four layers of the separator 230. It is more preferable that the amount of thickness increase of the electrode body 200 corresponds to five or more layers of the sheet material constituting the separator 230. However, the amount of thickness increase of the electrode body 200 is not limited to the above range.

[0078] The amount of thickness increased by the folded portions 231 and 232 is preferably equivalent to the thickness of two to sixteen sheets of the sheet material constituting the separator 230. The ratio (ΔT / T2) of the amount of thickness increased by the folded portions 231 and 232 (ΔT) to the thickness of the electrode body 200 without the folded portions 231 and 232 (T2 in Figure 21) is preferably about 0.1% or more, more preferably about 0.2% or more, and even more preferably about 0.25% or more. Furthermore, ΔT / T2 is preferably about 2.0% or less, more preferably about 1.0% or less, and even more preferably about 0.5% or less.

[0079] In the example in Figure 15, folded portions 231 and 232 are provided near the pair of first edges 101. In the example in Figure 16, a folded portion 231 is formed only near the first edge 101 on the -Z side of the pair of first edges 101. Alternatively, a folded portion 232 may be formed only near the first edge 101 on the +Z side of the pair of first edges 101.

[0080] In the Z direction, the positive electrode plate 220 is formed to be shorter than the negative electrode plate 210. The folded portions 231 and 232 are formed to overlap with the positive electrode plate 220. In the Z direction, the dimension of the portion where the folded portions 231 and 232 overlap with the positive electrode plate 220 (H in Figure 15) is preferably about 0.1 mm or more (more preferably about 0.5 mm or more), and about 3.0 mm or less (more preferably about 2.0 mm or less).

[0081] The method for forming the electrode body 200 shown in Figure 15 will be explained using Figures 17 and 18. An electrode body holder 600 (insulating member) is placed on the outside of the electrode body 200.

[0082] As shown in Figure 17, in the first step of bending the electrode holder 600, the bent portions 231B and 232B of the separator 230 are formed. As shown in Figure 18, in the second step of bending the electrode holder 600, the bent portions 231B and 232B are further bent to form the folded portions 231 and 232. In this way, the folded portions 231 and 232 of the separator 230 can be formed when bending the electrode holder 600.

[0083] A modified example of the electrode body 200 shown in Figure 16 will be explained using Figures 19 and 20. In this modified example as well, an electrode body holder 600 (insulating member) is placed on the outside of the electrode body 200.

[0084] As shown in Figure 19, in the first step of bending the electrode holder 600, the bent portion 231B of the separator 230 is formed. As shown in Figure 20, in the second step of bending the electrode holder 600, the bent portion 231B is further bent to form the folded portion 231. In this way, the folded portion 231 of the separator 230 can be formed when bending the electrode holder 600.

[0085] Before bending the electrode holder 600, the separator 230 may be bent to create a fold line.

[0086] The electrode holder 600 is made of, for example, resin. Preferably, polyethylene (PE) or polypropylene (PP) is used as the resin constituting the electrode holder 600. However, the resin constituting the electrode holder 600 is not limited to these; for example, olefin resins such as polymethylpentene (PMP), polyester resins such as polyethylene terephthalate (PET) and polyethylene naphthalate (PEN), fluororesins such as polytetrafluoroethylene (PTFE), acrylic resin (PMMA), polyimide (PI), polyphenylene ether (PPE), triacetate (TAC), polyphenylene sulfide resin (PPS), polycarbonate (PC), nylon, etc., can be used. The electrode holder 600 may be porous or non-porous.

[0087] The electrode holder 600 may be formed in the shape of a rectangular tube, a box, or a bag. Preferably, the electrode holder 600 is provided with a region through which the electrolyte and gas can pass. Preferably, the region through which the electrolyte and gas can pass faces the gas discharge valve 150. This makes it easier to discharge the gas generated in the electrode 200 to the outside of the case 100 via the gas discharge valve 150.

[0088] As shown in Figure 21, the excess portions 231A and 232A of the separator 230 reach from the edges 2511 and 2512 of the main surface 251 to the edges 2521 and 2522 of the main surface 252, respectively. The creepage distances (L1 and L2) of the excess portions 231A and 232A are longer than the shortest distances (T1 and T2) in the Y direction from the edges 2511 and 2512 of the main surface 251 to the edges 2521 and 2522 of the main surface 252. Preferably, (L1-T1) / T1 and (L2-T2) / T2 are approximately 0.1 or more (more preferably approximately 0.2 or more, and even more preferably approximately 0.4 or more), and approximately 1.5 or less (more preferably approximately 1.1 or less, and even more preferably approximately 0.7 or less).

[0089] The thickness (T2) of the electrode body 200 is, for example, about 11 mm or more (preferably about 13 mm or more) and about 16 mm or less (preferably about 14 mm or less).

[0090] As described above, when a battery pack is constructed by constraining the rectangular case 100 in the Y direction, the pressurized load tends to be relatively small, especially near the first end edge 101. If this variation in pressurized load causes variation in potential within the positive electrode plate 220 of the electrode body 200, metal deposition (lithium deposition in lithium-ion batteries) may occur.

[0091] In contrast, in the secondary battery 1 according to this embodiment, by providing folded portions 231 and 232 of the separator 230 on both ends in the Z direction, the thickness of the electrode body 200 is relatively increased in that region (first region), thereby suppressing a decrease in the pressurized load near the first end edge 101 of the case body 110. Therefore, lithium deposition (metal deposition) can be effectively suppressed in areas where the pressurized load tends to be relatively small.

[0092] While embodiments of the present technology have been described above, the embodiments disclosed herein should be considered in all respects to be illustrative and not restrictive. The scope of the present technology is defined by the claims, and all modifications within the meaning and scope equivalent to the claims are intended to be included. [Explanation of symbols]

[0093] 1 Secondary battery, 2 Inter-cell separator, 100 Case, 101 First edge, 102 Second edge, 110 Case body, 111, 111A, 111B First side, 112, 112A, 112B Second side, 113, 114 Opening, 115 Joint, 120 Sealing plate, 130 Sealing plate, 140 Liquid injection hole, 150 Gas discharge valve, 200 Electrode body, 200A Negative electrode tab group, 200A0 Negative electrode tab, 200B Positive electrode tab group, 200B0 Positive electrode tab, 200C Main body, 210 Negative electrode plate, 211 Negative electrode core, 212 Negative electrode active material layer, 220 Positive electrode plate, 221 Positive electrode core, 222 Positive electrode active material layer, 223 Positive electrode protective layer, 230 Separator, 231, 232 Folded portion, 231A, 232A Excess portion, 231B, 232B Folded portion, 240 Tape, 250, 251, 252 Main surface, 300 Electrode terminal, 300A Negative electrode terminal, 300B Positive electrode terminal, 400 Current collector, 400A Negative electrode current collector, 400B Positive electrode current collector, 500 Spacer, 600 Electrode holder, 2511, 2512, 2521, 2522 Edge.

Claims

1. An electrode body including a first electrode, a second electrode having a different polarity from the first electrode, and a separator provided between the first electrode and the second electrode, It has a rectangular shape and comprises an outer container for housing the electrode body, The outer can has a pair of first surfaces, a pair of second surfaces substantially perpendicular to the first surfaces, and a pair of third surfaces substantially perpendicular to the first and second surfaces, wherein the area of ​​the first surfaces is larger than the area of ​​the second surfaces and the area of ​​the third surfaces. The first surface has a substantially rectangular shape including a pair of first edges extending in a first direction and a pair of second edges extending in a second direction substantially perpendicular to the first direction. The electrode body has a first main surface and a second main surface that are opposite to the pair of first surfaces, The separator has a folded portion extending in a strip-like manner in the first direction near at least one of the pair of first end edges, and the folded portion is superimposed on the first electrode and the second electrode in a first region on the first main surface or the second main surface so as to face the first surface of the outer can. A secondary battery wherein the thickness of the electrode body in the first region is greater than the thickness of the electrode body in the second region which is adjacent to the first region in the second direction.

2. The secondary battery according to claim 1, wherein the folded portion is provided near both of the pair of first end edges.

3. In the second direction, the second electrode is formed to be shorter than the first electrode. The secondary battery according to claim 1 or claim 2, wherein the folded portion is formed to overlap with the second electrode.

4. A tape for fixing the end of the separator is provided on the first main surface of the electrode body. The folded portion is provided on the first main surface, as described in claim 1 or claim 2.

5. The separator includes an outer peripheral portion provided outside the first electrode and the second electrode, The outer peripheral portion has an excess portion that extends from the edge of the first main surface of the electrode body to the edge of the second main surface and has a creepage distance longer than the shortest distance from the edge of the first main surface to the edge of the second main surface in a third direction perpendicular to the first and second directions. The secondary battery according to claim 1 or claim 2, wherein the folded portion is formed by folding the excess portion.

6. The secondary battery according to claim 1 or claim 2, wherein the pair of first end sides are the longer sides.

7. The secondary battery according to claim 1 or claim 2, wherein the electrode body has electrode tabs at positions facing the pair of second end edges.

8. The secondary battery according to claim 1 or claim 2, wherein the electrode body is a stacked electrode body.

9. The secondary battery according to claim 8, wherein the separator is folded in a zigzag pattern.

10. A step of preparing an electrode body having a first main surface and a second main surface, including a first electrode, a second electrode having a different polarity from the first electrode, and a separator provided between the first electrode and the second electrode, The process includes the step of housing the electrode body in an outer can, The outer can has a rectangular shape and comprises a pair of first surfaces, a pair of second surfaces substantially perpendicular to the first surfaces, and a pair of third surfaces substantially perpendicular to the first and second surfaces, wherein the area of ​​the first surfaces is larger than the area of ​​the second surfaces and the area of ​​the third surfaces. The first surface has a substantially rectangular shape including a pair of first edges extending in a first direction and a pair of second edges extending in a second direction substantially perpendicular to the first direction. The step of preparing the electrode body includes bending the separator so as to form a folded portion that extends in a strip shape in the first direction near at least one of the pair of first end edges and is superimposed on the first electrode and the second electrode in a first region on the first main surface or the second main surface, A method for manufacturing a secondary battery, comprising the step of housing the electrode body in the outer casing, which includes inserting the electrode body into the outer casing such that the first main surface and the second main surface face the pair of first surfaces, respectively.

11. The process further includes bending an insulating member arranged on the outside of the electrode body, The method for manufacturing a secondary battery according to claim 10, wherein the folded portion is formed when the insulating member is bent.

12. The method for manufacturing a secondary battery according to claim 11, further comprising the step of bending the separator before bending the insulating member.

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