Secondary battery and method for manufacturing the same

Abstract

The present application relates to a secondary battery and a manufacturing method thereof. A secondary battery (1) is provided with an electrode body (200) including a first electrode (210) and a second electrode (220), and an exterior can (100) that houses the electrode body (200). A separator (230) of the electrode body (200) has, in the vicinity of at least one of a pair of first end edges (101) of a first face (111) of the exterior can (100), a turn-back portion (231, 232) that extends in a belt shape in a first direction, the turn-back portion overlapping the first electrode (210) and the second electrode (220) of the electrode body (200) in a first region on a first main face (251) or a second main face (252) of the electrode body (200) in a manner facing the first face (111) of the exterior can (100), and a thickness of the electrode body (200) in the first region is greater than a thickness of the electrode body (200) in a second region that is juxtaposed with the first region in a second direction.

Description

Technical Field

[0001] This technology relates to secondary batteries and their manufacturing methods. Background Technology

[0002] Japanese Patent Application Publication No. 2013-084387 discloses a battery in which a limiting portion is provided on the separator to contact the end of the positive or negative electrode, thereby limiting the movement of the positive or negative electrode in a direction perpendicular to the stacking direction. Summary of the Invention

[0003] The requirement is to suppress metal deposition in secondary batteries. When a battery pack is constructed from secondary batteries in a square-shaped outer can, the pressure load tends to be relatively small near the end edges of the roughly rectangular outer can. This deviation in pressure load creates a resistance difference within the electrode body, easily leading to metal deposition. Therefore, it is necessary to effectively suppress metal deposition in areas with relatively small pressure loads. From this perspective, there is still room for improvement in conventional secondary batteries.

[0004] The purpose of this technology is to provide a secondary battery with suppressed metal deposition and a method for manufacturing the same.

[0005] This technology provides the following secondary batteries and their manufacturing methods.

[0006] [1] A secondary battery, comprising: an electrode body including a first electrode, a second electrode having a polarity different from the first electrode, and a separator disposed between the first electrode and the second electrode; and an outer can having a square shape for housing the electrode body, the outer can having a pair of first surfaces, a pair of second surfaces substantially orthogonal to the first surfaces, and a pair of third surfaces substantially orthogonal to the first and second surfaces, the area of ​​the first surface being larger than the area of ​​the second surface and the area of ​​the third surface, the first surface having a pair of first end edges extending along a first direction and a pair of first end edges extending along a first direction. The electrode body has a generally rectangular shape including a pair of second end edges extending in a second direction that is generally orthogonal to the first direction. The electrode body has a first main surface and a second main surface facing the pair of first surfaces, respectively. The diaphragm has a folded portion extending in a strip shape along the first direction near at least one of the pair of first end edges. The folded portion overlaps with the first electrode and the second electrode in a first region on the first main surface or the second main surface, such that it faces the first surface of the outer can. The thickness of the electrode body in the first region is greater than the thickness of the electrode body in the second region that is parallel to the first region in the second direction.

[0007] [2] According to the secondary battery of [1], the foldback portion is disposed near both of the pair of first end edges.

[0008] [3] According to the secondary battery of [1] or [2], wherein, in the second direction, the second electrode is formed to be shorter than the first electrode, and the folded-back portion is formed to overlap with the second electrode.

[0009] [4] A secondary battery according to any one of [1] to [3], wherein an adhesive tape for fixing the end of the diaphragm is provided on the first main surface of the electrode body, and the fold-back portion is provided on the first main surface.

[0010] [5] A secondary battery according to any one of [1] to [4], wherein the separator includes an outer peripheral portion disposed outside the first electrode and the second electrode, the outer peripheral portion having an excess portion extending from the edge of the first main surface of the electrode body to the edge of the second main surface, and having 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 orthogonal to the first direction and the second direction, the foldback portion being formed by bending the excess portion.

[0011] [6] The secondary battery according to any one of [1] to [5], wherein the pair of first end sides are long sides.

[0012] [7] A secondary battery according to any one of [1] to [6], wherein the electrode body has electrode tabs at a position facing the pair of second end edges.

[0013] [8] The secondary battery according to any one of [1] to [7], wherein the electrode body is a stacked electrode body.

[0014] [9] The secondary battery according to [8], wherein the separator is folded.

[0015]

[10] A method for manufacturing a secondary battery, wherein the method comprises: a step of preparing an electrode body, the electrode body having a first main surface and a second main surface, and including a first electrode, a second electrode having a polarity different from the first electrode, and a separator disposed between the first electrode and the second electrode; and a step of housing the electrode body in an outer packaging can, the outer packaging can having a square shape and having a pair of first surfaces, a pair of second surfaces substantially orthogonal to the first surfaces, and a pair of third surfaces substantially orthogonal to the first surfaces and the 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 generally rectangular shape including a pair of first end edges extending along a first direction and a pair of second end edges extending along a second direction generally orthogonal to the first direction, the process of preparing the electrode body includes: bending the diaphragm to form a folded portion, the folded portion extending in a strip shape along the first direction near at least one of the pair of first end edges, and overlapping with the first electrode and the second electrode in a first region on the first main surface or the second main surface; the process of housing the electrode body in the outer can includes: inserting the electrode body into the outer can such that the first main surface and the second main surface face the pair of first surfaces respectively.

[0016]

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

[10] further includes a 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.

[0017]

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

[11] further includes a step of bending the diaphragm before bending the insulating component.

[0018] The above and other objects, features, aspects and advantages of the present invention will become clear from the following detailed description relating to the invention, which will be understood in conjunction with the accompanying drawings. Attached Figure Description

[0019] Figure 1 This is a front view showing the structure of the secondary battery according to the embodiment.

[0020] Figure 2 This indicates viewing from the direction of arrow II. Figure 1 The diagram shows the state of the secondary battery.

[0021] Figure 3 This indicates viewing from the direction of arrow III. Figure 1 The diagram shows the state of the secondary battery.

[0022] Figure 4 This indicates viewing from the direction of arrow IV. Figure 1The diagram shows the state of the secondary battery.

[0023] Figure 5 This indicates viewing from the direction of arrow V. Figure 1 The diagram shows the state of the secondary battery.

[0024] Figure 6 yes Figure 1 The image shows a front cross-sectional view of a secondary battery.

[0025] Figure 7 This is a cross-sectional view of the negative electrode plate.

[0026] Figure 8 This is the front view of the negative electrode plate.

[0027] Figure 9 This is a cross-sectional view of the positive electrode plate.

[0028] Figure 10 This is the front view of the positive electrode plate.

[0029] Figure 11 It is a three-dimensional diagram showing the state where a sealing plate is installed on the current collector on the positive side.

[0030] Figure 12 It is a three-dimensional diagram showing the structure of a secondary battery.

[0031] Figure 13 This is a diagram showing the secondary battery and the battery spacer adjacent to it, viewed from the stacking direction.

[0032] Figure 14 This is a cross-sectional view of the electrode body before the diaphragm is bent.

[0033] Figure 15 This is a cross-sectional view of the electrode body after the diaphragm has been bent.

[0034] Figure 16 This is a cross-sectional view showing a deformed example of an electrode body after the diaphragm has been bent.

[0035] Figure 17 It means Figure 15 A cross-sectional view of the first stage of the diaphragm bending process in the manufacturing process of the electrode body shown.

[0036] Figure 18 It means to continue Figure 17 A cross-sectional view of the second stage of the diaphragm bending process.

[0037] Figure 19 It means Figure 16 A cross-sectional view of the first stage of the diaphragm bending process in the manufacturing process of the modified electrode body shown.

[0038] Figure 20 It means to continue Figure 18 A cross-sectional view of the second stage of a modified example of the diaphragm bending process.

[0039] Figure 21 This is a graph used to illustrate the relationship between the thickness of the electrode body and the creepage distance of the diaphragm. Detailed Implementation

[0040] The following describes the implementation of this technology. It should be noted that the same or equivalent parts are labeled with the same reference numerals, and sometimes the description is not repeated.

[0041] It should be noted that, in the embodiments described below, when numbers, quantities, etc., are mentioned, the scope of this technology is not necessarily limited to those numbers, quantities, etc., unless specifically stated otherwise. Furthermore, in the embodiments described below, each constituent element is not necessarily essential to this technology, unless specifically stated otherwise. Additionally, this technology is not limited to technologies that must achieve all the effects mentioned in this embodiment.

[0042] It should be noted that in this specification, the terms "comprise," "include," and "have" are open-ended. That is, when a structure is included, other structures besides that structure may be included, or they may not be included.

[0043] Furthermore, in this specification, when using geometric terms and terms indicating positional / directional relationships, such as "parallel," "orthogonal," "tilted at 45°," "coaxial," and "along," these terms are permissible with manufacturing errors or slight variations. In this specification, when using terms indicating relative positional relationships such as "upper side" and "lower side," these terms are used to indicate the relative positional relationship in a given state. Depending on the orientation of each mechanism (e.g., flipping the entire mechanism upside down), the relative positional relationship can be flipped or rotated to any angle.

[0044] Furthermore, the dimensions of the components illustrated in this specification, such as width, length, and diameter, are not limited to those shown in the illustrations and may be appropriately changed. In this specification, structures are sometimes labeled with ordinal numbers such as "first" or "second," but these ordinal numbers, except where explicitly specified, do not imply priority or order.

[0045] In this instruction manual, "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 instruction manual, "electrode" can be collectively referred to as the positive electrode and the negative electrode. Additionally, "electrode plate" can be collectively referred to as the positive plate and the negative plate.

[0046] In this manual, "battery" can be used in hybrid electric vehicles (HEVs), plug-in hybrid electric vehicles (PHEVs), and battery electric vehicles (BEVs). However, the use of "battery" is not limited to vehicle applications.

[0047] In this specification, the X direction (first direction) is sometimes referred to as the "width direction" of the secondary battery, electrode body and housing body, and similarly, the Z direction (second direction) is sometimes referred to as the "height direction" of the secondary battery, electrode body and housing body, and similarly, the Y direction (third direction) is sometimes referred to as the "thickness direction" of the secondary battery, electrode body and housing body.

[0048] (The overall structure of a secondary battery)

[0049] Reference Figures 1 to 6 The overall structure of the secondary battery 1 is described below. The secondary battery 1 includes a casing 100 (outer can), electrode bodies 200, electrode terminals 300, and current collector 400. The casing 100 includes a casing body 110, a sealing plate 120, and a sealing plate 130.

[0050] When constructing a battery pack including secondary batteries 1, multiple secondary batteries 1 are stacked in their thickness direction. The stacked secondary batteries 1 can be constrained in the stacking direction (Y direction) by a limiting member to form a battery module, or the battery pack can be directly supported on the side of the battery pack housing without using a limiting member.

[0051] The casing body 110 is composed of a cylindrical, preferably square-cylindrical, component. This allows for the production of a secondary battery 1 with a square-shaped casing 100. The casing body 110 is made of metal. Specifically, it is made of aluminum, aluminum alloy, iron, or an iron alloy.

[0052] like Figure 1 as well as Figure 2 As shown, sealing plates 120 and 130 are respectively provided at both ends of the housing body. The housing body 110 is constructed, for example, by having the end edges of a bent plate-like component abut against each other. Figure 2 The illustrated joint 115 is joined together (e.g., by energy line irradiation such as laser welding) to form a square tube shape. The corners of the "square tube" may also have an R-shape (rounded corner shape).

[0053] In this embodiment, the housing body 110 is formed such that its width (X direction) is longer than its thickness (Y direction) and height (Z direction) of the secondary battery 1. The width of the housing body 110 in the X direction is preferably 300 mm or more. This allows for the construction of a relatively large (high-capacity) secondary battery 1. The height of the housing body 110 in the Z direction is preferably 100 mm or less. This allows for the construction of a relatively low-height (low-height) secondary battery 1, for example, improving vehicle mounting capability. However, the size of the secondary battery 1 is not limited to the above-described range.

[0054] The housing body 110 includes a first side surface 111 (first surface) and a second side surface 112 (second surface). The first side surface 111 is composed of a pair of first side surface portions 111A and 111B, and the second side surface 112 is composed of a pair of second side surface portions 112A and 112B. The first side surface portions 111A and 111B form part of the side surface of the housing 100. The pair of second side surface portions 112A and 112B form the bottom surface and the top surface of the housing 100. The first side surface portions 111 and 112 are arranged to intersect each other (approximately orthogonal). The first side surface portions 111 and 112 are connected at their respective ends.

[0055] like Figure 5 As shown, a gas discharge valve 150 is provided on one of the second side surfaces 112A. The gas discharge valve 150 extends along the width direction (X direction) of the secondary battery 1. The gas discharge valve 150 extends along the X direction to a degree that it does not extend from the center of the housing body 110 in the X direction to both ends. The shape of the gas discharge valve 150 can be appropriately modified.

[0056] The thickness of the plate-shaped component at the gas discharge valve 150 is thinner than the thickness of the plate-shaped components other than the gas discharge valve 150 in the housing body 110. As a result, when the pressure inside the housing 100 reaches a predetermined value or higher, the gas discharge valve 150 breaks first compared to other parts in the housing body 110, venting the gas inside the housing 100 to the outside.

[0057] like Figure 2 As shown, a joining portion 115 is formed on the other side of the second side portion 112, the second side portion 112B. The joining portion 115 extends along the width direction (X direction) of the secondary battery 1. At the joining portion 115, the end edges of the plate-shaped members constituting the housing body 110 are joined together.

[0058] like Figure 3As shown, an opening 113 (first opening) is provided at one end of the housing body 110 in a first direction (X direction). The opening 113 is sealed by a sealing plate 120 (first sealing plate). A joint portion 115 is formed in the opening 113, and the opening 113 is sealed. The opening 113 and the sealing plate 120 have a generally rectangular shape with the short side in the Y direction and the long side in the Z direction. The generally rectangular shape includes a rectangular shape or a shape with rounded corners, etc., that is substantially rectangular.

[0059] A negative terminal 300A is provided on the sealing plate 120. The position of the negative terminal 300A can be changed as appropriate.

[0060] like Figure 4 As shown, an opening 114 (second opening) is provided at the end of the housing body 110 on the opposite side in the X direction. That is, opening 114 is located at the end opposite to opening 113, and openings 113 and 114 face each other. Opening 114 is sealed by a sealing plate 130 (second sealing plate). A joint portion 115 is formed in opening 114, and opening 114 is sealed. Opening 114 and sealing plate 130 have a generally rectangular shape with the short side in the Y direction and the long side in the Z direction.

[0061] A positive terminal 300B and a liquid injection hole 140 are provided on the sealing plate 130. The positions of the positive terminal 300B and the liquid injection hole 140 can be changed as appropriate. The liquid injection hole 140 is sealed by a sealing component (not shown). As a sealing component, blind rivets and other metal components can be used, for example.

[0062] Sealing plates 120 and 130 are made of metal. Specifically, sealing plates 120 and 130 are made of aluminum, aluminum alloy, iron, or iron alloy.

[0063] Sealing plates 120 and 130 (third side) form part of housing 100. Sealing plates 120 and 130 are arranged in a manner that intersects (approximately orthogonal) with respect to the first side portion 111 and the second side portion 112.

[0064] In the housing 100, the area (first area) of each of the pair of first side portions 111 (first surfaces) is larger than the area (second area) of each of the pair of second side portions 112 (second surfaces) and the area (third area) of each of the sealing plates 120 and 130 (third surfaces).

[0065] The negative terminal 300A is electrically connected to the negative terminal of the electrode body 200. The negative terminal 300A is mounted on the sealing plate 120, i.e., the housing 100. The positive terminal 300B is electrically connected to the positive terminal of the electrode body 200. The positive terminal 300B is mounted on the sealing plate 130, i.e., the housing 100.

[0066] 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.

[0067] In this embodiment, the electrode body 200 is a flat electrode body having a negative electrode plate 210 and a positive electrode plate 220 (described later) stacked on top of each other. Specifically, the electrode body 200 is a stacked electrode body formed by alternately stacking multiple negative electrode plates 210 and multiple positive electrode plates 220 separated by a separator. The separator is formed by folding and bending a strip-shaped insulating sheet component.

[0068] like Figure 6 As shown, the housing 100 houses the electrode body 200. The electrode body 200 is housed within the housing 100 with its long side parallel to the X direction. Specifically, one or more stacked electrode bodies are housed in the housing 100 together with an electrolyte (not shown). As the electrolyte (non-aqueous electrolyte), for example, an electrolyte in which LiPF6 is dissolved in a non-aqueous solvent can be used. A solid electrolyte can also be used instead of the electrolyte.

[0069] The electrode body 200 includes a generally rectangular main body, a negative electrode tab group 200A, and a positive electrode tab group 200B.

[0070] 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 assembly 200A is located at the end of the main body on one side (the sealing plate 120 side) of the electrode body 200 in the X direction. The positive electrode tab assembly 200B is located at the end of the main body on the other side (the sealing plate 130 side) of the electrode body 200 in the X direction.

[0071] The negative electrode tab group 200A and the positive electrode tab group 200B are formed to protrude from the central part of the electrode body 200 toward the sealing plate 120 or the sealing plate 130, respectively.

[0072] The current collector 400 includes a negative current collector 400A and a positive current collector 400B. The negative current collector 400A and the positive current collector 400B are each composed of plate-shaped components. The electrode body 200 is electrically connected to the negative terminal 300A and the positive terminal 300B via the current collector 400.

[0073] The negative current collector 400A is disposed on the sealing plate 120 through a resin insulating component. The negative current collector 400A is electrically connected to the negative electrode tab assembly 200A and the negative terminal 300A. The negative current collector 400A is made of a conductive material (more specifically, a metal), such as copper or a copper alloy.

[0074] The positive current collector 400B is disposed on the sealing plate 130 through a resin insulating component. The positive current collector 400B is electrically connected to the positive electrode tab assembly 200B and the positive terminal 300B. The positive current collector 400B is made of a conductive material (more specifically, a metal), such as aluminum or an aluminum alloy. The positive electrode tab assembly 200B can also be electrically connected to the sealing plate 130 directly or via the positive current collector 400B. In this case, the sealing plate 130 can also function as the positive terminal 300B.

[0075] (Structure of electrode body 200)

[0076] like Figure 7 as well as Figure 8 As shown, the negative electrode plate 210 (first electrode) includes a negative electrode core 211 and a negative electrode active material layer 212. At one end of the negative electrode plate 210 in the width direction, a negative electrode tab 200A0 formed by the negative electrode core 211 is provided. When stacking the negative electrode plates 210, 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 of the multiple negative electrode plates 210 is appropriately adjusted considering the connection state between the negative electrode tab group 200A and the negative electrode current collector 400A. The shape of the negative electrode tab 200A0 is not limited to... Figure 8 The illustrated shape.

[0077] like Figure 9 as well as Figure 10 As shown, 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. At one end of the positive electrode plate 220 in the width direction, a positive electrode tab 200B0 composed of the positive electrode core 221 is provided. When stacking the positive electrode plates 220, 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 of the multiple positive electrode plates 220 is appropriately adjusted considering the connection state between the positive electrode tab group 200B and the positive current collector 400B. The shape of the positive electrode tab 200B0 is not limited to... Figure 10 The illustrated shape.

[0078] A positive electrode protection layer 223 is provided at the root of the positive electrode tab 200B0. However, it is not always necessary to provide a positive electrode protection layer 223 at the root of the positive electrode tab 200B0.

[0079] (Containment of electrode body 200)

[0080] The electrode body 200, with the positive electrode tab group 200B side as the front, is inserted into the housing body 110 through the opening 113. For example... Figure 11As shown, 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 one on the positive electrode side.

[0081] Alternatively, the electrode body 200 can be electrically connected to the negative terminal 300A before being inserted into the housing body 110. After the electrode body 200 is inserted into the housing body 110, it can be electrically connected to the positive terminal 300B.

[0082] After inserting the electrode body 200 into the housing body 110, as Figure 12 As shown, sealing plates 120 and 130 are joined to the housing body 110. Sealing plate 120 seals the opening 113 of the housing body 110, and sealing plate 130 seals the opening 114 of the housing body 110. Thus, the electrode body 200 is housed in the housing 100.

[0083] (Structure of the battery pack)

[0084] like Figure 13 As shown, the first side portion 111 of the housing body 110 has a generally rectangular shape including a pair of first end edges 101 extending in the X direction and a pair of second end edges 102 extending in the Z direction. Here, the pair of first end edges 101 are longer than the pair of second end edges 102. That is, the first side portion 111 has a generally rectangular shape with the X direction being the long side direction and the Z direction being the short side direction.

[0085] In the configuration of the battery pack, multiple secondary batteries 1 are arranged side-by-side in the Y direction. Battery spacers 2 are disposed between the multiple secondary batteries 1. For example... Figure 13 As shown, when viewed from the Y direction, the area of ​​the battery spacer 2 is smaller than the area of ​​the first side portion 111 of the housing body 110. The height of the battery spacer 2 is lower than the height of the main body portion 200C of the electrode body 200 (the generally rectangular portion excluding the electrode tabs).

[0086] Therefore, at the upper and lower ends of the electrode body 200 (near the pair of first end edges 101), portions are generated that do not overlap with the battery spacer 2, making it easier for the pressure load on the battery spacer 2 to be relatively smaller. As described later, the electrode body 200 in this embodiment has a structure of a separator 230 that suppresses the reduction of the pressure load near the first end edge 101.

[0087] (Structure of diaphragm 230)

[0088] like Figure 14As shown, the electrode body 200 includes a negative electrode plate 210 and a positive electrode plate 220 with different polarities, a diaphragm 230, and an adhesive tape 240. The diaphragm 230 is disposed between the negative electrode plate 210 and the positive electrode plate 220.

[0089] The diaphragm 230 is a component used to insulate the negative electrode plate 210 and the positive electrode plate 220. The diaphragm 230 is, for example, made of a porous resin sheet made of polyolefin resins such as polyethylene (PE) and polypropylene (PP). The porous resin sheet can have a single-layer structure or a multi-layer structure (e.g., a three-layer structure of PP / PE / PP).

[0090] Preferably, an adhesive layer is provided on the surface of the separator 230. The adhesive layer may include, for example, an acrylic resin or polyvinylidene fluoride (PVDF) and other adhesive resins. Because the separator 230 has an adhesive layer, it is easy to suppress the lamination misalignment of the negative electrode plate 210 and the positive electrode plate 220 with the separator 230. The adhesive layer may be provided on the entire surface of the separator 230, or a pattern may be applied to the surface of the separator 230.

[0091] Alternatively, a heat-resistant layer containing ceramic particles can be provided on the surface of the diaphragm 230. The heat-resistant layer preferably contains a resin adhesive. This allows the heat-resistant layer to function as an adhesive layer.

[0092] The electrode body 200 has a main surface 250 facing the first side surface 111 (first surface) of the housing body 110. The main surface 251 (first main surface) and the main surface 252 (second main surface) face the first side surface 111A and 111B respectively.

[0093] The end of the diaphragm 230 at the end of winding (first end) is fixed to the main surface 251 by tape 240.

[0094] The separator 230 includes a portion folded between the negative electrode plate 210 and the positive electrode plate 220, and an outer peripheral portion (outer surface portion) provided to surround the outer sides 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 shape, and the portion between the negative electrode plate 210 and the positive electrode plate 220 and the outer peripheral portion surrounding the outer sides of the negative electrode plate 210 and the positive electrode plate 220 may also be provided separately. The portion provided between the negative electrode plate 210 and the positive electrode plate 220 is not limited to folding the strip-shaped separator 230, and rectangular separators may also be provided individually.

[0095] like Figure 14 As shown, the outer periphery of the diaphragm 230 has excess portions 231A and 232A at both ends in the Z direction. The ends of the diaphragm 230 in the X direction can be open or closed into a bag shape.

[0096] exist Figure 15In the example, the diaphragm 230 has folded-back portions 231, 232 extending in a strip along the X direction near a pair of first end edges 101. Figure 15 The folding sections 231 and 232 shown are achieved by... Figure 14 The excess portions 231A and 232A shown are formed by folding back. The folded portions 231 and 232 are preferably formed along 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 also be formed in a portion of the main body portion 200C of the electrode body 200 in the X direction. In this case, the folded portions 231 and 232 are preferably formed to a extent that extends to more than 1 / 2 (more preferably more than 2 / 3) of the length of the main body portion 200C of the electrode body 200.

[0097] exist Figure 16 In a modified example, the diaphragm 230 has a folded portion 231 extending in a strip shape along the X direction near the first end edge 101 on the -Z side of a pair of first end edges 101. Figure 16 The folding section 231 shown here passes through... Figure 14 The excess portion 231A is formed by its return.

[0098] The fold-back portions 231 and 232 overlap with the negative electrode plate 210 and the positive electrode plate 220 on the main surface 251, facing the first side portion 111 of the housing body 110. The fold-back portions 231 and 232 may also be provided on the main surface 252. The fold-back portions 231 and 232 are provided on the same side of a pair of main surfaces 250 (either of main surfaces 251 and 252). The fold-back portions 231 and 232 are preferably provided on the main surface 250 on the same side as the tape 240 (on...). Figure 15 , Figure 16 In the example, the main face is 251.

[0099] like Figure 15 , Figure 16 As shown, by forming folded-back portions 231 and 232 on the main surface 251, the electrode body 200 is thickened in this region. The thickness of the electrode body 200 in the region where the folded-back portions 231 and 232 are formed (the first region) is greater than the thickness of the electrode body 200 in the region located between the folded-back portions 231 and 232 in the Z direction (the second region).

[0100] exist Figure 15 , Figure 16 In this example, the end (second end) of the diaphragm 230 on the winding start side is located inside the fold-back portion 231. Figure 15 In the example, two roughly U-shaped portions (parts that fold back approximately 180°) are formed in the folding section 232, with one roughly U-shaped portion located inside the other roughly U-shaped portion.

[0101] exist Figure 15 , Figure 16 In the shown foldback portions 231 and 232, the electrode body 200 is thickened by four layers of the diaphragm 230. More preferably, the thickness increase of the electrode body 200 is equivalent to five or more layers of the sheet constituting the diaphragm 230. However, the thickness increase of the electrode body 200 is not limited to the above range.

[0102] The thickness increase based on the fold-back portions 231 and 232 is preferably equivalent to a thickness of two or more but less than 16 sheets of the sheet constituting the diaphragm 230. This is relative to the thickness of the electrode body 200 without the fold-back portions 231 and 232. Figure 21 The ratio (ΔT / T2) of the thickening amount (ΔT) of the folded-back portions 231 and 232 is preferably 0.1% or more, more preferably 0.2% or more, and even more preferably 0.25% or more. Furthermore, ΔT / T2 is preferably 2.0% or less, more preferably 1.0% or less, and even more preferably 0.5% or less.

[0103] exist Figure 15 In the example, foldback sections 231 and 232 are provided near a pair of first end edges 101. Figure 16 In the example, the folded portion 231 is formed only near the first end edge 101 on the -Z side of the pair of first end edges 101. It can also be configured such that the folded portion 232 is formed only near the first end edge 101 on the +Z side of the pair of first end edges 101.

[0104] In the Z-direction, the positive electrode plate 220 is formed to be shorter than the negative electrode plate 210. The fold-back portions 231 and 232 are formed to overlap with the positive electrode plate 220. The dimensions of the overlapping portions of the fold-back portions 231 and 232 with the positive electrode plate 220 in the Z-direction are (…). Figure 15 The H in the figure is preferably 0.1 mm or more (more preferably 0.5 mm or more) and 3.0 mm or less (more preferably 2.0 mm or less).

[0105] use Figure 17 as well as Figure 18 right Figure 15 The method of forming the electrode body 200 shown will be described. An electrode body holder 600 (insulating member) is disposed on the outside of the electrode body 200.

[0106] like Figure 17 As shown, in the first stage of the process of bending the electrode holder 600, the bent portions 231B and 232B of the diaphragm 230 are formed. Figure 18As shown, in the second stage of the process 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 diaphragm 230 can be formed when the electrode holder 600 is bent.

[0107] use Figure 19 as well as Figure 20 right Figure 16 The method of forming a modified example of the electrode body 200 shown will be described. In this modified example, an electrode body holder 600 (insulating member) is also disposed on the outside of the electrode body 200.

[0108] like Figure 19 As shown, in the first stage of the process of bending the electrode holder 600, the bent portion 231B of the diaphragm 230 is formed. Figure 20 As shown, in the second stage of the process of bending the electrode holder 600, the bent portion 231B is further bent to form a folded-back portion 231. In this way, the folded-back portion 231 of the diaphragm 230 can be formed when the electrode holder 600 is bent.

[0109] Alternatively, the diaphragm 230 can be bent to form a bend line before the electrode holder 600 is bent.

[0110] The electrode holder 600 is made of resin, for example. Polyethylene (PE) or polypropylene (PP) is preferably 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), fluoropolymers such as polytetrafluoroethylene (PTFE), acrylic resins (PMMA), polyimide (PI), polyphenylene ether (PPE), cellulose triacetate (TAC), polyphenylene sulfide resin (PPS), polycarbonate (PC), nylon, etc., can be used. The electrode holder 600 can be porous or non-porous.

[0111] The electrode holder 600 can be formed in a cylindrical shape, or in a box or bag shape. The electrode holder 600 preferably has an area through which electrolyte and gas can pass. This area is preferably opposite to the gas discharge valve 150. This allows gas generated within the electrode 200 to be easily discharged to the outside of the housing 100 via the gas discharge valve 150.

[0112] like Figure 21As shown, the excess portions 231A and 232A of the diaphragm 230 extend 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 preferably 0.1 or more (more preferably 0.2 or more, and even more preferably 0.4 or more) and 1.5 or less (more preferably 1.1 or less, and even more preferably 0.7 or less).

[0113] The thickness (T2) of the electrode body 200 is, for example, 11 mm or more (preferably 13 mm or more) and 16 mm or less (preferably 14 mm or less).

[0114] As described above, when a battery pack is constructed by constraining a square-shaped housing 100 in the Y direction, the pressure load tends to be relatively small, especially near the first end edge 101. If a deviation in the potential within the positive electrode plate 220 of the electrode body 200 occurs due to this deviation in pressure load, metal deposition (lithium deposition in lithium-ion batteries) may occur.

[0115] In contrast, in the secondary battery 1 of this embodiment, by providing folded-back portions 231 and 232 of the separator 230 at both ends in the Z direction, the thickness of the electrode body 200 is relatively increased in this region (first region). This suppresses the reduction of pressure load near the first end edge 101 of the housing body 110. Therefore, lithium deposition (metal deposition) can be effectively suppressed in the region where the pressure load tends to be relatively small.

[0116] Embodiments of the invention have been described, but the embodiments disclosed herein should be considered illustrative rather than limiting in all respects. The scope of the invention is set forth in the claims and is intended to include all modifications within the meaning and scope equivalent to the claims.

Claims

1. A secondary battery, wherein, The secondary battery has the following features: An electrode body, comprising a first electrode, a second electrode with a polarity different from that of the first electrode, and a diaphragm disposed between the first electrode and the second electrode; as well as An outer container, which is square in shape, is used to house the electrode body. The outer can has a pair of first faces, a pair of second faces substantially orthogonal to the first faces, and a pair of third faces substantially orthogonal to the first and second faces, wherein the area of ​​the first faces is larger than the area of ​​the second faces and the area of ​​the third faces. The first surface has a generally rectangular shape including a pair of first end edges extending along a first direction and a pair of second end edges extending along a second direction that is generally orthogonal to the first direction. The electrode body has a first main surface and a second main surface that face the pair of first surfaces respectively. The diaphragm has a folded portion extending in a strip along the first direction near at least one of the pair of first end edges. The folded portion overlaps with the first electrode and the second electrode in a first region on the first main surface or the second main surface, facing the first surface of the outer can. The thickness of the electrode in the first region is greater than the thickness of the electrode in the second region, which is parallel to the first region in the second direction.

2. The secondary battery as described in claim 1, wherein, The reversing section is located near both of the pair of first end edges.

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

4. The secondary battery as described in claim 1 or 2, wherein, An adhesive tape is provided on the first main surface of the electrode body to fix the end of the diaphragm. The turning-back section is disposed on the first main surface.

5. The secondary battery as described in claim 1 or 2, wherein, The diaphragm includes an outer peripheral portion disposed outside the first electrode and the second electrode. The outer peripheral portion has a redundant portion extending 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 orthogonal to the first and second directions. The folded-back section is formed by bending the excess portion.

6. The secondary battery as described in claim 1 or 2, wherein, The first end edge of the pair is the longer edge.

7. The secondary battery as described in claim 1 or 2, wherein, The electrode body has electrode tabs at the position facing the pair of second end edges.

8. The secondary battery as described in claim 1 or 2, wherein, The electrode body is a stacked electrode body.

9. The secondary battery as described in claim 8, wherein, The diaphragm is folded and bent.

10. A method for manufacturing a secondary battery, wherein, The method for manufacturing the secondary battery comprises: The process of preparing an electrode body, wherein the electrode body has a first main surface and a second main surface, and includes a first electrode, a second electrode with a polarity different from that of the first electrode, and a diaphragm disposed between the first electrode and the second electrode; as well as The process of storing the electrode body in the outer packaging can. The outer can has a square shape and has a pair of first faces, a pair of second faces that are substantially orthogonal to the first faces, and a pair of third faces that are substantially orthogonal to the first and second faces. The area of ​​the first face is larger than the area of ​​the second face and the area of ​​the third face. The first surface has a generally rectangular shape including a pair of first end edges extending along a first direction and a pair of second end edges extending along a second direction that is generally orthogonal to the first direction. The process of preparing the electrode body includes: bending the diaphragm to form a folded portion, the folded portion extending in a strip shape along the first direction near at least one of the pair of first end edges, and overlapping with the first electrode and the second electrode in a first region on the first main surface or the second main surface. The process of housing the electrode body in the outer can includes: inserting the electrode body into the outer can such that the first main surface and the second main surface face the pair of first surfaces respectively.

11. The method for manufacturing a secondary battery as described in claim 10, wherein, The method for manufacturing the secondary battery also includes a step of bending an insulating component disposed on the outside of the electrode body. The folded portion is formed when the insulating component is bent.

12. The method for manufacturing a secondary battery as described in claim 11, wherein, The method for manufacturing the secondary battery also includes a step of bending the diaphragm before bending the insulating component.

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