Secondary battery manufacturing method

Abstract

To suppress deposition of a lithium in an electrode body inner part while preferably holding an impregnation property of an electrolyte against an electrode body.SOLUTION: In a step of manufacturing an electrode body 20 by performing a press processing of a winding body in a flat shape, the winding body is nipped by a first fixture 3 having a first press surface F1 containing a first elastic part 7 and a second fixture 4 that includes a second press surface F2 containing a second elastic part 8. The winding body is depressed by the first press surface F1 and the second press surface F2 while elastically deforming at least one part of the first press surface F1 and the second press surface F2. In the step of manufacturing the electrode body 20 by performing the press processing of the winding body, a flat part 22, a first curvature part 24, and a second curvature part 25 are formed to the electrode body 20. In the step of manufacturing the electrode body 20 by performing the press processing of the winding body, each of the first curvature part 24 and the second curvature part 25 are heated to a temperature that is higher than a room temperature via at least one of the first press surface F1 and the second press surface F2.SELECTED DRAWING: Figure 7

Description

[Technical Field]

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

[0002] Japanese Patent Laid-Open Publication No. 2013-084445 (Patent Document 1) is a prior art document disclosing the configuration of an electrode body forming apparatus. The electrode body forming apparatus described in Patent Document 1 includes a first press head and a second press head. The first press head and the second press head clamp and press the electrode body, which is wound into a hollow cylindrical shape, from both sides in the diameter direction, thereby forming flat and curved portions on the outer peripheral surface of the electrode body and forming the electrode body into a flat shape. The first press head and the second press head are provided with a pressing surface and an R pressing surface. The pressing surfaces correspond to the flat portions of the outer peripheral surface of the electrode body when pressed. The R pressing surfaces are located at both ends of the pressing surface and protrude in the height direction from the pressing surface at least when pressed, and press the curved portions of the outer peripheral surface of the electrode body.

[0003] Furthermore, a prior art document similar to Patent Document 1 is Japanese Patent Application Laid-Open No. 2022-050088 (Patent Document 2). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2013-084445 [Patent Document 2] Japanese Patent Publication No. 2022-050088 Summary of the Invention [Problem to be solved by the invention]

[0005] In the electrode body forming device described in Patent Document 1, the curved portion of the electrode body is formed by aligning the wound body with the jig shape of the device, which may result in uneven inter-plate distances between the positive and negative plates at the curved portion. This may lead to lithium precipitation on the negative plate. Furthermore, if the curved portion of the electrode body is pressed strongly to optimize the inter-plate distance between the positive and negative plates, the positive and negative plates and the separator at the inner portions of the stack may be strongly bonded, which may result in poor impregnation of the electrode body with the electrolyte.

[0006] The present technology has been made to solve the above-mentioned problems, and aims to provide a method for manufacturing a secondary battery and a secondary battery that can suppress lithium precipitation inside the electrode body while maintaining good impregnation of the electrode body with an electrolyte solution. [Means for solving the problem]

[0007] The present technology provides the following method for manufacturing a secondary battery. [1] preparing a wound body in which a separator is sandwiched between a positive electrode plate and a negative electrode plate, and the positive electrode plate, the negative electrode plate, and the separator are wound around a winding axis that is aligned in a first direction; a step of sandwiching the wound body between a first jig having a first press surface including a first elastic portion and a second jig having a second press surface including a second elastic portion in a second direction perpendicular to the first direction, and pressing the wound body with the first press surface and the second press surface while elastically deforming at least a portion of the first press surface and the second press surface, thereby producing an electrode body by pressing the wound body into a flat shape; and housing the electrode body and the electrolyte in a case, In the step of producing the electrode body by press-forming the wound body, the electrode body is formed with a flat portion located on the central side in a third direction orthogonal to the first direction and the second direction and having a flat outer surface, a first curved portion located on one end side of the flat portion in the third direction and having a curved outer surface, and a second curved portion located on the other end side of the flat portion in the third direction and having a curved outer surface, a step of pressing the wound body to fabricate the electrode body, wherein each of the first curved portion and the second curved portion is heated to a temperature higher than room temperature via at least one of the first press surface and the second press surface. The room temperature refers to the ambient temperature when the electrode body is pressed. [2] The method for producing a secondary battery according to [1], wherein the temperature higher than room temperature is 50°C or higher and 110°C or lower. [3] The method for manufacturing a secondary battery according to [1] or [2], wherein the first press surface and the second press surface abut on the outer surface of 50% or more of the area that will become the first curved portion and the second curved portion after the wound body is press-processed. [4] The method for manufacturing a secondary battery according to any one of [1] to [3], wherein each of the first elastic portion and the second elastic portion is made of a porous material.

[0008] The present technology provides the following secondary battery. [5] an electrode assembly in which a separator is sandwiched between a positive electrode plate and a negative electrode plate, and the positive electrode plate, the negative electrode plate, and the separator are wound around a winding axis that is aligned in a first direction; a case that accommodates the electrode assembly and an electrolyte; the electrode body has a flat shape with a short side in a second direction perpendicular to the first direction and a long side in a third direction perpendicular to the first direction and the second direction, The electrode body is a flat portion located on the central side in the third direction and having a flat outer surface; a first curved portion located on one end side of the flat portion in the third direction and having a curved outer surface; a second curved portion located on the other end side of the flat portion in the third direction and having a curved outer surface, In the first curved portion, the adhesive strength between the surface of each of the positive electrode plates in the first to third layers counting from the positive electrode plate located at the outermost periphery among the stacked positive electrode plates and each of the separators adjacent to the outer periphery side is 1.0 N / m or more and 1.9 N / m or less, a secondary battery in which, in the first curved portion, the adhesive strength between the surface of the positive electrode plate located on the outer periphery of 50% of the total number of stacked positive electrode plates, counting from the innermost positive electrode plate among the stacked positive electrode plates, and the separator adjacent to that outer periphery is 0.6 N / m or more and 1.5 N / m or less. Note that "each of the positive electrode plates up to the third layer counting from the outermost positive electrode plate" refers to each of the positive electrode plates located in the first layer on the outermost periphery, the second layer one layer inward from the first layer, and the third layer one layer inward from the second layer. Furthermore, when the total number of stacked positive electrode plates is an even number, "50% of the total number of stacked plates" refers to the total number of stacked plates divided in half. Furthermore, when the total number of stacked positive electrode plates is an odd number, "50% of the total number of stacked plates" means the total number of stacked plates divided in half and rounded off to the nearest whole number. [6] [5] The secondary battery according to [5], wherein in the flat portion, the adhesive strength between the surface of each of the positive electrode plates from the outermost positive electrode plate to the third layer counting from the outermost positive electrode plate among the stacked positive electrode plates and each of the separators adjacent to the outer periphery side is 1.5 N / m or more and 1.9 N / m or less. [7] [5] or [6]. The secondary battery according to [5] or [6], wherein in the flat portion, the adhesive strength between the surface of the positive electrode plate located on the outer periphery of 50% of the total number of stacked positive electrode plates, counting from the innermost positive electrode plate among the stacked positive electrode plates, and the separator adjacent to that outer periphery is 1.5 N / m or more and 1.9 N / m or less. [Effects of the Invention]

[0009] According to the present technology, it is possible to suppress the deposition of lithium inside the electrode body while maintaining good impregnation of the electrode body with an electrolyte solution. [Brief explanation of the drawings]

[0010] [Figure 1] 1 is a perspective view showing a configuration of a secondary battery according to an embodiment of the present technology; [Figure 2] 1 is a perspective view showing an internal configuration of a secondary battery according to an embodiment of the present technology; [Figure 3] 1 is a perspective view showing a configuration of an electrode assembly and a current collector included in a secondary battery according to an embodiment of the present technology; [Figure 4] 4 is a cross-sectional view of the electrode body of FIG. 3 as seen from the direction of the arrows along line IV-IV. [Figure 5] 1 is a flowchart illustrating a method for manufacturing a secondary battery according to an embodiment of the present technology. [Figure 6] FIG. 2 is a schematic view showing a state before the wound body is press-formed. [Figure 7] FIG. 10 is a schematic diagram showing a state in which an electrode body is produced by pressing a wound body. [Figure 8] FIG. 2 is a schematic diagram showing the positions at which the adhesive strength between the positive electrode plate and the separator in the electrode assembly was measured. [Figure 9] FIG. 2 is a schematic diagram showing a method for measuring the adhesive strength between a positive electrode plate and a separator in an electrode assembly. [Figure 10] FIG. 10 is a schematic view showing a state in which an electrode body is produced by pressing a wound body according to a comparative example. [Figure 11] FIG. 4 is a cross-sectional view showing the configuration of an electrode body included in a secondary battery according to a comparative example. DETAILED DESCRIPTION OF THE INVENTION

[0011] Hereinafter, embodiments of the present technology will be described. Note that the same or corresponding parts are denoted by the same reference characters, and description thereof may not be repeated.

[0012] In the embodiments described below, when numbers, amounts, etc. are mentioned, the scope of the present technology is not necessarily limited to those numbers, amounts, etc., unless otherwise specified. Furthermore, in the following embodiments, each component is not necessarily essential to the present technology, unless otherwise specified. Furthermore, the present technology is not necessarily limited to those that achieve all of the effects and advantages mentioned in the present embodiments.

[0013] In this specification, the terms "comprise," "include," and "have" are open-ended. That is, when a certain feature is included, other features may or may not be included.

[0014] Furthermore, when geometric terms and terms expressing positional and directional relationships are used in this specification, such as "parallel," "orthogonal," "45° diagonal," "coaxial," and "along," these terms allow for manufacturing errors and slight variations. When terms expressing relative positional relationships, such as "upper side" and "lower side," are used in this specification, these terms are used to indicate relative positional relationships in a single state, and the relative positional relationships can be reversed or rotated to any angle depending on the installation direction of each mechanism (for example, by turning the entire mechanism upside down).

[0015] In this specification, the term "secondary battery" is not limited to lithium ion batteries, but may include other secondary batteries such as nickel-metal hydride batteries and sodium ion batteries. In this specification, the term "electrode" may collectively refer to a positive electrode and a negative electrode.

[0016] Furthermore, a "battery module" including a secondary 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 the "battery module" is not limited to in-vehicle use.

[0017] In the drawings, the direction along the winding axis of the electrode body provided in the secondary battery is the X direction as a first direction, the Y direction as a second direction which is perpendicular to the first direction and the short side direction of the electrode body as seen from the first direction, and the Z direction as a third direction which is perpendicular to the first direction and the long side direction of the electrode body as seen from the first direction. Also, to make the invention easier to understand, the dimensions of each component in the drawings may be shown differently from the actual dimensions.

[0018] Fig. 1 is a perspective view showing a configuration of a secondary battery according to an embodiment of the present technology. Fig. 2 is a perspective view showing an internal configuration of a secondary battery according to an embodiment of the present technology. Fig. 3 is a perspective view showing the configuration of an electrode assembly and a current collector included in a secondary battery according to an embodiment of the present technology.

[0019] 1 to 3, the secondary battery 1 is a prismatic secondary battery. It includes a case 10, an electrode assembly 20, a positive electrode current collector 30, a negative electrode current collector 40, a positive electrode terminal 50, a negative electrode terminal 60, a positive electrode external conductive member 70, a negative electrode external conductive member 80, and an insulating sheet (not shown).

[0020] The case 10 includes an exterior body 100 and a sealing plate 110 .

[0021] The exterior body 100 is a rectangular cylinder with a bottom and an opening 101. The exterior body 100 is made of metal. Specifically, the exterior body 100 is made of aluminum, an aluminum alloy, iron, an iron alloy, or the like.

[0022] Exterior body 100 has a bottom 102, a pair of first side walls 103a and 103b, and a pair of second side walls 104a and 104b.

[0023] The bottom 102 faces the opening 101. A pair of first side walls 103a, 103b stand upright from the edge of the bottom 102 and face each other in parallel. A pair of second side walls 104a, 104b stand upright from the edge of the bottom 102 and face each other in parallel. Each of the pair of second side walls 104a, 104b connects the first side walls 103a, 103b to each other. The area of ​​each of the pair of first side walls 103a, 103b is larger than the area of ​​each of the pair of second side walls 104a, 104b.

[0024] Sealing plate 110 seals opening 101 of exterior body 100. Sealing plate 110 is made of, for example, aluminum, an aluminum alloy, iron, or an iron alloy.

[0025] The sealing plate 110 has an electrolyte injection hole 111. The electrolyte injection hole 111 is sealed with a sealing member 112. The sealing plate 110 has a gas release valve 113. The gas release valve 113 breaks when the pressure inside the case 10 reaches or exceeds a predetermined value, and releases gas inside the case 10 to the outside.

[0026] The electrode assembly 20 in this embodiment is a flat electrode assembly having a positive electrode plate, a negative electrode plate, and a separator, which will be described later. Specifically, the electrode assembly 20 is a wound electrode assembly in which a strip-shaped positive electrode plate and a strip-shaped negative electrode plate are wound together with a strip-shaped separator interposed therebetween.

[0027] The thickness T of the electrode body 20 is, for example, 12 mm. The width W of the electrode body 20 is, for example, 290 mm. The height H of the electrode body is, for example, 95 mm. The width of the positive electrode plate in the electrode body 20 is preferably 140 mm or more and 500 mm or less, and more preferably 280 mm or more and 400 mm or less.

[0028] As shown in Fig. 1, case 10 houses electrode assemblies 20. Case 10 in the present embodiment houses three electrode assemblies 20. Electrode assemblies 20 are housed in exterior body 100 with their winding axes A1 parallel to bottom 102 and oriented along the longitudinal direction of case 10. The number of electrode assemblies 20 arranged in exterior body 100 is not limited to three.

[0029] Case 10 also contains an electrolyte solution, which is a liquid in which a lithium salt is dissolved in a non-aqueous solvent.

[0030] In the electrode body 20, a tab portion 21 is provided on at least one of the positive electrode plate and the negative electrode plate, and extends to the side of the electrode body 20. In the electrode body 20 of the present embodiment, a positive electrode tab group 201 including multiple positive electrode tabs is provided as one tab portion 21 at one end of the electrode body 20 in the direction in which the winding axis A1 of the electrode body 20 extends. A negative electrode tab group 211 including multiple negative electrode tabs is provided as the other tab portion 21 at the other end of the electrode body 20 in the direction in which the winding axis A1 of the electrode body 20 extends.

[0031] The electrode body 20 is preferably placed in the outer casing 100 with an insulating sheet sandwiched between them, with one second side wall 104a facing the positive electrode tab group 201 and the other second side wall 104b facing the negative electrode tab group 211.

[0032] The positive electrode current collector 30 has a plate-like shape. The positive electrode current collector 30 is connected to one of the tab portions 21. In this embodiment, the positive electrode current collector 30 is connected to a positive electrode tab group 201. The positive electrode current collector 30 is preferably made of metal, and more preferably made of aluminum or an aluminum alloy.

[0033] The negative electrode current collector 40 has a plate shape. The negative electrode current collector 40 is connected to the other tab portion 21. In the present embodiment, the negative electrode current collector 40 is connected to the negative electrode tab group 211. The negative electrode current collector 40 is preferably made of metal, and more preferably made of copper or a copper alloy.

[0034] A positive electrode terminal 50 and a negative electrode terminal 60 are attached to the sealing plate 110. The positive electrode terminal 50 is electrically connected to a positive electrode tab group 201 in each of the plurality of electrode bodies 20 via a positive electrode current collector 30. A positive electrode external conductive member 70 is connected to the positive electrode terminal 50. Note that the secondary battery 1 does not necessarily have to include the positive electrode external conductive member 70.

[0035] Each of the positive electrode terminal 50 and the positive electrode external conductive member 70 is preferably made of metal, and more preferably made of aluminum or an aluminum alloy.

[0036] The negative electrode terminal 60 is electrically connected to the negative electrode tab group 211 in each of the plurality of electrode bodies 20 via the negative electrode current collector 40. A negative electrode external conductive member 80 is connected to the negative electrode terminal 60. Note that the secondary battery 1 does not necessarily have to include the negative electrode external conductive member 80.

[0037] The negative electrode terminal 60 is preferably made of metal, more preferably copper or a copper alloy. The negative electrode external conductive member 80 is preferably made of metal, more preferably aluminum or an aluminum alloy. Note that the region of the negative electrode terminal 60 that is connected to the negative electrode current collector 40 may be made of copper or a copper alloy, and the region that protrudes outward from the sealing plate 110 may be made of aluminum or an aluminum alloy.

[0038] Fig. 4 is a cross-sectional view of the electrode assembly of Fig. 3 as viewed from the direction of the arrows along line IV-IV. As shown in Fig. 4, the electrode assembly 20 of this embodiment includes a positive electrode plate 200, a negative electrode plate 210, and a separator 220.

[0039] The positive electrode plate 200 is manufactured by processing a positive electrode blank. The positive electrode blank includes a positive electrode core, a positive electrode active material layer, and a positive electrode protective layer. The positive electrode core is an aluminum foil or an aluminum alloy foil.

[0040] A positive electrode active material layer is formed on both surfaces of the positive electrode core, except for one end. The positive electrode active material layer is preferably a lithium transition metal composite oxide layer. The transition metal preferably contains at least nickel. The positive electrode active material layer is formed on the positive electrode core by applying a positive electrode active material layer slurry using a die coater.

[0041] The positive electrode active material layer slurry is prepared by kneading lithium nickel cobalt manganese composite oxide as the positive electrode active material, polyvinylidene fluoride (PVDF) as a binder, a carbon material as a conductive material, and N-methyl-2-pyrrolidone (NMP) as a dispersion medium so that the mass ratio of lithium nickel cobalt manganese composite oxide:PVdF:carbon material is 97.5:1:1.5.

[0042] The positive electrode protective layer is formed on one end of the positive electrode active material layer in the width direction while being in contact with the positive electrode core by applying a positive electrode protective layer slurry using a die coater.

[0043] The positive electrode protective layer slurry is prepared by kneading alumina powder, a carbon material as a conductive material, PVdF as a binder, and NMP as a dispersion medium so that the mass ratio of alumina powder:carbon material:PVdF is 83:3:14.

[0044] The positive electrode core coated with the positive electrode active material layer slurry and the positive electrode protective layer slurry is dried, and the NMP contained in the positive electrode active material layer slurry and the positive electrode protective layer slurry is removed. This forms a positive electrode active material layer and a positive electrode protective layer. The positive electrode active material layer is then compressed to form a positive electrode base plate including the positive electrode core, the positive electrode active material layer, and the positive electrode protective layer. The positive electrode base plate is cut into a predetermined shape to form a positive electrode plate. The positive electrode base plate can be cut by laser processing using energy beam irradiation, mold processing, cutter processing, or the like.

[0045] The thickness of the positive electrode plate 200 is preferably 5 μm or more and 30 μm or less, and more preferably 8 μm or more and 20 μm or less.

[0046] The number of layers of the positive electrode plate 200 is preferably 10 or more, more preferably 20 or more, and even more preferably 30 or more. The number of layers of the positive electrode plate 200 is preferably 150 or less, and more preferably 100 or less. In this embodiment, the number of layers of the positive electrode plate 200 is, for example, 33.

[0047] The negative electrode plate 210 is manufactured by processing a negative electrode blank. The negative electrode blank includes a negative electrode core and a negative electrode active material layer. The negative electrode core is a copper foil or a copper alloy foil.

[0048] A negative electrode active material layer is formed on both surfaces of the negative electrode substrate except for one end portion by applying a negative electrode active material layer slurry using a die coater.

[0049] The negative electrode active material layer slurry is prepared by kneading graphite or a silicon-containing compound as the negative electrode active material, styrene butadiene rubber (SBR) and carboxymethyl cellulose (CMC) as binders, and water as a dispersion medium so that the mass ratio of graphite:SBR:CMC is 98:1:1.

[0050] The negative electrode substrate coated with the negative electrode active material layer slurry is dried to remove water contained in the negative electrode active material layer slurry. The negative electrode active material layer is then compressed to form a negative electrode master plate including the negative electrode substrate and the negative electrode active material layer. The negative electrode master plate is cut into a predetermined shape to form a negative electrode plate. The negative electrode master plate can be cut by laser processing using energy beam irradiation, die processing, cutter processing, or the like.

[0051] The thickness of the negative electrode plate 210 is preferably 5 μm or more and 30 μm or less, and more preferably 8 μm or more and 20 μm or less.

[0052] The number of layers of the negative electrode plates is preferably 10 or more, more preferably 20 or more, and even more preferably 30 or more. In this embodiment, the number of layers of the negative electrode plates is, for example, 35.

[0053] The separator 220 is provided to insulate the positive electrode plate 200 from the negative electrode plate 210. The separator 220 preferably includes a substrate layer and a functional layer. The substrate layer is preferably made of polyethylene or polyolefin. The substrate layer is preferably a microporous film. Note that the substrate layer is not limited to being made of polyethylene or polyolefin, and may be made of other resins.

[0054] The functional layer is preferably formed on at least one surface of the base material layer. The functional layer is, for example, a heat-resistant layer or an adhesive layer. Separator 220 in this embodiment preferably has adhesive layers on both surfaces of the base material layer.

[0055] The adhesive layer is, for example, an acrylic adhesive layer. The adhesive layer is arranged over the entire surface of the base material layer in a dotted or striped pattern. The adhesive layer is preferably composed of a layer containing PVDF. The PVDF may be arranged in a mesh pattern in the adhesive layer. The adhesive layer may contain ceramic particles such as alumina.

[0056] The separator 220 may have a configuration in which only an adhesive layer is arranged on the surface of the base material layer, a configuration in which a heat-resistant layer and an adhesive layer are arranged as multiple layers, or a configuration in which a single layer having heat-resistant and adhesive functions is arranged.

[0057] The thickness of the separator 220 is, for example, 16 μm. The thickness of the base layer is, for example, 12 μm. The thickness of the adhesive layer as a functional layer is, for example, 2 μm for a single layer located on one side of the base layer. Note that the thickness of the separator 220 is not limited as long as it can insulate the positive electrode plate 200 and the negative electrode plate 210.

[0058] The separators 220 are disposed at the innermost and outermost peripheries between the positive electrode plates 200 and the negative electrode plates 210. In this embodiment, the number of stacked separators 220 is, for example, 78 layers.

[0059] The electrode assembly 20 has a separator 220 sandwiched between a positive electrode plate 200 and a negative electrode plate 210. The electrode assembly 20 has the positive electrode plate 200, the negative electrode plate 210, and the separator 220 wound around a winding axis A1 that extends along a first direction (X direction).

[0060] The electrode body 20 has a short side in a second direction (Y direction) perpendicular to the first direction (X direction). The electrode body 20 also has a long side in a third direction (Z direction) perpendicular to the first direction (X direction) and the second direction (Y direction). That is, the electrode body 20 is flat when viewed from the first direction (X direction).

[0061] The electrode body 20 includes a flat portion 22 and a curved portion 23. The flat portion 22 has one flat portion 22a and the other flat portion 22b on both sides in the second direction (Y direction).

[0062] The flat portion 22 is located on the central side in the third direction (Z direction). The flat portion 22 has a flat outer surface. Note that the "flat" of the flat portion 22 does not only mean that it is on the same plane. The "flat" also includes a surface shape that includes steps at the winding end portions of the positive electrode plate 200, the negative electrode plate 210, and the separator 220, as well as steps such as the winding stop tape of the electrode body 20.

[0063] The curved portion 23 has a first curved portion 24 and a second curved portion 25. The first curved portion 24 is located on one end side of the flat portion 22 in the third direction (Z direction). The first curved portion 24 has a curved outer surface. The second curved portion 25 is located on the other end side of the flat portion 22 in the third direction (Z direction). The second curved portion 25 has a curved outer surface.

[0064] The positive electrode plate 200 and the separator 220 are pressure-bonded to each other at the flat portion 22 and the curved portion 23. The negative electrode plate 210 and the separator 220 are also pressure-bonded to each other at the flat portion 22 and the curved portion 23. This ensures that there is no gap between the positive electrode plate 200 and the separator 220, and between the negative electrode plate 210 and the separator 220, and that there is no gap between the positive electrode plate 200 and the separator 220.

[0065] A method for manufacturing a secondary battery according to an embodiment of the present technology will be described below. Fig. 5 is a flowchart showing a method for manufacturing a secondary battery according to an embodiment of the present technology.

[0066] As shown in FIG. 5, in the method for manufacturing the secondary battery 1 according to the present embodiment, first, a separator 220 is sandwiched between a positive electrode plate 200 and a negative electrode plate 210, and a wound body 20A is prepared in which the positive electrode plate 200, the negative electrode plate 210, and the separator 220 are wound around a winding axis A1 along a first direction (X direction) (step S1).

[0067] Next, the wound body 20A is pressed while being heated to form a flattened shape, thereby producing the electrode body 20 (step S2). Details of this step will be described later.

[0068] Next, the electrode assembly 20 and the electrolyte are housed in a case (step S3). The electrode assembly 20 is placed in a bag- or box-shaped insulating sheet. The electrode assembly 20 covered with the insulating sheet is inserted into the exterior body 100. As a result, the electrode assembly 20 is housed in the case 10.

[0069] Next, the case 10 is sealed (step S4). The sealing plate 110 is joined to the opening 101 of the exterior body 100 by laser welding or the like.

[0070] Next, an electrolyte solution is poured into the case 10 (step S5). A non-aqueous electrolyte solution is poured through an electrolyte solution pouring hole 111 provided in the sealing plate 110, and the electrolyte solution pouring hole 111 is sealed with a sealing member 112. In this way, the secondary battery 1 is completed.

[0071] The press working of the electrode body 20 according to an embodiment of the present technology will be described in detail below. Fig. 6 is a schematic diagram showing a state before the wound body is press worked. Fig. 7 is a schematic diagram showing a state in which the wound body is press worked to produce the electrode body.

[0072] As shown in FIGS. 6 and 7, the wound body 20A is pressed by a press jig 2 to form the electrode body 20.

[0073] Before being pressed, wound body 20A may have a cylindrical shape with a substantially circular cross section as viewed from the first direction (X direction) or an elliptical cross section. When wound body 20A has an elliptical cross section, wound body 20A is formed into an elliptical shape by performing another press process in advance before being pressed.

[0074] The press jig 2 is provided in a press machine (not shown). The press jig 2 is provided with a heater (not shown). The press jig 2 includes a first jig 3 and a second jig 4. The first jig 3 is provided opposite a portion of the wound body 20A where one flat portion 22a is to be formed. The second jig 4 is provided opposite a portion of the wound body 20A where the other flat portion 22b is to be formed.

[0075] The first jig 3 has a first head portion 5. The first head portion 5 has a first press surface F1 that includes a first elastic portion 7. The second jig 4 has a second head portion 6. The second head portion 6 has a second press surface F2 that includes a second elastic portion 8.

[0076] Each of the first elastic portion 7 and the second elastic portion 8 is made of a porous material. In this embodiment, each of the first elastic portion 7 and the second elastic portion 8 is made of foamed silicone. Each of the first elastic portion 7 and the second elastic portion 8 may be made of a thermosetting elastomer such as natural rubber, urethane rubber, silicone rubber, or fluororubber. Each of the first elastic portion 7 and the second elastic portion 8 is preferably made of a material that undergoes large elastic deformation during press processing.

[0077] Each of the first elastic portion 7 and the second elastic portion 8 preferably has a thickness for shaping the electrode body 20 so as to press the wound body 20A while elastically deforming. The thickness of each of the first elastic portion 7 and the second elastic portion 8 in the second direction (Y direction) is preferably at least half, and more preferably at least two-thirds, of the thickness of the electrode body 20 in the short direction.

[0078] When the wound body 20A is pressed, the wound body 20A is sandwiched between a first jig 3 and a second jig 4 in a second direction (Y direction) perpendicular to the first direction (X direction). The wound body 20A is pressed by the first press surface F1 and the second press surface F2 while elastically deforming at least a portion of the first press surface F1 and the second press surface F2, thereby pressing the wound body 20A into a flat shape to produce the electrode body 20. In this embodiment, the wound body 20A is pressed by the first press surface F1 and the second press surface F2 while elastically deforming both the first press surface F1 and the second press surface F2.

[0079] In the electrode body 20, the first pressed surface F1 and the second pressed surface F2 abut on 50% or more of the outer surface of the region that will become the first curved portion 24 and the second curved portion 25 after the wound body 20A is pressed. In this embodiment, the first pressed surface F1 and the second pressed surface F2 abut on the entire outer surface of the region that will become the first curved portion 24 and the second curved portion 25.

[0080] By pressing the wound body 20A into a flat shape, the electrode body 20 produced has a flat portion 22 and curved portions 23, which are a first curved portion 24 and a second curved portion 25. The positive electrode plate 200 and the separator 220 in each of the flat portion 22 and the curved portion 23 are pressed and bonded together by the press jig 2. The negative electrode plate 210 and the separator 220 in each of the flat portion 22 and the curved portion 23 are also pressed and bonded together by the press jig 2.

[0081] The pressing pressure of wound body 20A is preferably, for example, 50 kN or more, more preferably 80 kN or more, and even more preferably 90 kN or more. The pressing pressure of wound body 20A is preferably, for example, 200 kN or less, and more preferably 150 kN or less. In this embodiment, the pressing pressure of wound body 20A is, for example, 110 kN.

[0082] When the wound body 20A is pressed to produce the electrode body 20, each of the first curved portion 24 and the second curved portion 25 is heated to a temperature higher than room temperature. Specifically, when the wound body 20A is pressed to produce the electrode body 20, each of the first curved portion 24 and the second curved portion 25 is heated to a temperature higher than room temperature via at least one of the first press surface F1 and the second press surface F2. In the present embodiment, each of the first curved portion 24 and the second curved portion 25 is heated to a temperature higher than room temperature via both the first press surface F1 and the second press surface F2 by a heater built into the press jig 2.

[0083] Room temperature refers to the ambient temperature when press working is performed on electrode body 20. The temperature higher than room temperature is, for example, preferably 50°C or higher and 110°C or lower, more preferably 60°C or higher and 100°C or lower, and even more preferably 70°C or higher and 90°C or lower. In this embodiment, the heating temperature of each of first curved portion 24 and second curved portion 25 is, for example, 70°C.

[0084] The heating time for each of first bending portion 24 and second bending portion 25 is preferably, for example, 1 second to 30 seconds, more preferably 3 seconds to 20 seconds, and even more preferably 5 seconds to 10 seconds. In this embodiment, the heating time for each of first bending portion 24 and second bending portion 25 is, for example, 10 seconds.

[0085] 7, the flat portion 22 is formed by being pressed simultaneously with the curved portion 23. In this embodiment, the flat portion 22 is also heated during the press working, but the flat portion 22 does not necessarily have to be heated during the press working.

[0086] The adhesive strength between the positive electrode plate 200 and the separator 220 inside the electrode assembly 20 will be described below. Fig. 8 is a schematic diagram showing the measurement positions for the adhesive strength between the positive electrode plate and the separator in the electrode assembly. Fig. 8 shows only the positive electrode plate of the electrode assembly.

[0087] One of the properties required for the electrode assembly 20 is the adhesive strength between the positive electrode plate 200 or the negative electrode plate 210 and the separator 220. The positive electrode plate 200 or the negative electrode plate 210 and the separator 220 are bonded by pressure during press processing. The adhesive strength increases as the pressure during press processing increases. Furthermore, the adhesive strength increases when heated.

[0088] Even if the electrode body 20 is pressed so as not to create a gap between the positive electrode plate 200 or the negative electrode plate 210 and the separator 220 at the curved portion 23 as described above, if the adhesive strength is too high, the impregnation of the electrolyte into the inside of the electrode body 20 will decrease. For this reason, it is desirable that the adhesive strength between the positive electrode plate 200 or the negative electrode plate 210 and the separator 220 in the electrode body 20 be within an appropriate range.

[0089] The required adhesive strength is preferably measured on the outer and inner sides of the electrode body 20, since the pressing forces applied to the outer and inner sides of the electrode body 20 during press processing are different.

[0090] Therefore, in the electrode body 20 of the present embodiment, the adhesive strength is specified at the following four locations: a first outer location 240, a first inner location 241, a second outer location 250, and a second inner location 251.

[0091] The first outer regions 240 are the positive electrode plates 200 in the first curved portion 24, from the positive electrode plate 200 located at the outermost periphery among the stacked positive electrode plates 200 to the third layer counting from the positive electrode plate 200 located at the outermost periphery. "Each positive electrode plate in the first to third layer counting from the positive electrode plate located at the outermost periphery" refers to each positive electrode plate located at the first layer at the outermost periphery, the second layer one layer inward from the first layer, and the third layer one layer inward from the second layer.

[0092] The first outer region 240 is located outside the stacked electrode assembly 20 of the first curved portion 24. In the first outer region 240 of the first curved portion 24, the adhesive strength between the surface of each of the first to third positive electrode plates 200, counting from the outermost positive electrode plate 200, and each separator 220 adjacent to the outer periphery, is 1.0 N / m or more and 1.9 N / m or less. The adhesive strength is more preferably 1.5 N / m or more and 1.9 N / m or less. Note that if the adhesive strength is less than 1.0 N / m, lithium may precipitate. Furthermore, if the adhesive strength is 1.9 N / m or more, the impregnation of the electrode assembly 20 with the electrolyte may be impaired.

[0093] It is preferable that the adhesive strength between the surface of the positive electrode plate 200 and the separator 220 adjacent to its outer periphery at the first outer location 240 of the first curved portion 24 is also the same in the portion corresponding to the first outer location of the second curved portion 25.

[0094] The first inner region 241 is located inside the stacked electrode assemblies 20 of the first curved portion 24. In the first inner region 241 of the first curved portion 24, the adhesive strength between the surface of the positive electrode plate 200 located on the outer periphery of 50% of the total number of stacked positive electrode plates 200, counting from the innermost positive electrode plate 200, and the separator 220 adjacent to that outer periphery, is 0.6 N / m or more and 1.5 N / m or less. Note that an adhesive strength of 1.5 N / m or more may deteriorate the impregnation of the electrode assembly 20 with the electrolyte. Note that when the total number of stacked positive electrode plates is an even number, "50% of the total number of stacked positive electrode plates" refers to the number of plates obtained by dividing the total number in half. Note that when the total number of stacked positive electrode plates is an odd number, "50% of the total number of stacked positive electrode plates" refers to the number of plates obtained by dividing the total number in half and rounding off to the nearest whole number.

[0095] It is preferable that the adhesive strength between the surface of the positive electrode plate 200 and the separator 220 adjacent to its outer periphery at the first inner location 241 of the first curved portion 24 is similar to that at the portion corresponding to the first inner location in the second curved portion 25.

[0096] The second outer region 250 is located outside the stacked electrode body 20 of the flat portion 22. In the second outer region 250 of the flat portion 22, the adhesive strength between the surface of each of the first to third positive electrode plates 200, counting from the positive electrode plate 200 located at the outermost periphery among the stacked positive electrode plates 200, and each separator 220 adjacent to that outer periphery side is 1.5 N / m or more and 1.9 N / m or less.

[0097] The second inner portion 251 is located inside the stacked electrode bodies 20 of the flat portion 22. In the second inner portion 251 of the flat portion 22, the adhesive strength between the surfaces of the positive electrode plates 200 located on the outer periphery for 50% of the total number of stacked positive electrode plates 200, counting from the positive electrode plate 200 located at the innermost periphery, and the separators 220 adjacent to the outer periphery is 1.5 N / m or more and 1.9 N / m or less.

[0098] FIG. 9 is a schematic diagram showing a method for measuring the adhesive strength between the positive electrode plate and the separator in the electrode assembly.

[0099] When measuring the adhesive strength between the positive electrode plate 200 and the separator 220 in the electrode assembly 20, the electrode assembly 20 is measured after it has cooled to room temperature after being pressed. The electrode assembly 20 is disassembled in a state in which the positive electrode plate 200 and the separator 220 are stuck together.

[0100] Test pieces are obtained by cutting a portion from the laminated portion of the positive electrode plate 200 and separator 220. The test piece for the curved portion 23 is cut to a size of 70 mm in the direction of the winding axis and 8 mm in the direction perpendicular to the winding axis. The test piece for the flat portion 22 is cut to a size of 70 mm in the direction of the winding axis and 20 mm in the direction perpendicular to the winding axis.

[0101] Thereafter, the test specimen is fixed to a plate (not shown) with double-sided tape so that the positive electrode plate 200 is in contact with the plate. The separator 220 is pulled in a direction perpendicular to the direction in which the positive electrode plate 200 extends. During the test, the plate is moved so that the direction in which the separator 220 is peeled is always perpendicular. The adhesive strength is measured when the separator 220 is peeled at a rate of 50 mm / min.

[0102] A method for manufacturing a secondary battery according to a comparative example will be described below. The method for manufacturing a secondary battery according to this comparative example differs from the method for manufacturing an electrode body by pressing in secondary battery 1 according to an embodiment of the present technology, and therefore, description of the same configuration as secondary battery 1 according to an embodiment of the present technology will not be repeated.

[0103] FIG. 10 is a schematic diagram showing a state in which an electrode body is produced by pressing a wound body according to a comparative example.

[0104] 10, an electrode body 90 according to the comparative example is formed by a press jig 9. The press jig 9 includes a first jig 9a and a second jig 9b.

[0105] The first jig 9a has a first head portion 9c. The first head portion 9c has a first press surface F91. The second jig 9b has a second head portion 9d. The second head portion 9d has a second press surface F92. The first head portion 9c and the second head portion 9d are each made of, for example, steel. Therefore, the first press surface F91 and the second press surface F92 are not substantially elastically deformed during the press process to form the electrode body 90.

[0106] Fig. 11 is a cross-sectional view showing the configuration of an electrode assembly included in a secondary battery according to a comparative example. As shown in Fig. 11, an electrode assembly 90 according to the comparative example includes a positive electrode plate 900, a negative electrode plate 910, and a separator 920. In a flat portion 92, the positive electrode plate 900, the negative electrode plate 910, and the separator 920 are each pressure-bonded.

[0107] At the curved portion 93, a gap G is formed between each of the positive electrode plate 900, the negative electrode plate 910, and the separator 920. This increases the inter-electrode distance between the positive electrode plate 900 and the negative electrode plate 910, which may increase the concentration of lithium in the gap G and cause lithium to deposit on the negative electrode plate 910.

[0108] On the other hand, in the electrode body 20 according to the present embodiment, the curved portion 23 is formed by pressing the wound body 20A with the first press surface F1 and the second press surface F2 while elastically deforming the first press surface F1 and the second press surface F2. The curved portion 23 is formed by applying a pressing force of the press process along the shape of the electrode body 20 due to the elastic deformation of the first press surface F1 and the second press surface F2, thereby suppressing the formation of gaps between the positive electrode plate 200, the negative electrode plate 210, and the separator 220 at the curved portion 23. This maintains an appropriate inter-electrode plate distance between the positive electrode plate 200 and the negative electrode plate 210, thereby suppressing lithium deposition at the curved portion 23.

[0109] The manufacturing conditions of the electrode assemblies according to the present embodiment and the comparative examples and the test results of the battery characteristics are described below. Table 1 shows the adhesive strength between the positive electrode plate and the separator and the battery characteristics when the electrode assemblies were press-processed under each manufacturing condition in the examples and the comparative examples.

[0110] [Table 1]

[0111] As shown in Table 1, the electrode body was produced by changing the press processing conditions when pressing the wound body to produce the electrode body, such as whether or not the wound body was heated, whether or not the wound body was pressed using the elastic part, and the press pressure.

[0112] The adhesive strength of the electrode assemblies produced under the production conditions of Experimental Examples 1 to 3 and Comparative Examples 1 and 2 was measured, and the battery characteristics were evaluated. The battery characteristics were evaluated in terms of the impregnation of the electrode assembly with the electrolyte solution and lithium deposition in the electrode assembly.

[0113] To evaluate the impregnation of the electrode assembly with the electrolyte, the secondary battery was first fabricated to the state before the electrolyte was poured in, and then the electrolyte was poured in. 24 hours, 48 ​​hours, and 72 hours after the electrolyte was poured in, the secondary battery was disassembled, and the impregnation of the electrolyte between the positive electrode plate and the separator was visually confirmed.

[0114] To evaluate whether or not lithium was deposited in the electrode assembly, a secondary battery containing the electrode assembly was first prepared. Then, the secondary battery was connected to an external power source in a restrained state, and a lithium deposition durability test was performed in which charge / discharge cycles were repeated.

[0115] The lithium deposition durability test was conducted under the following conditions: charging the battery at a current of 37 A for 10 seconds at a temperature of −30° C. until the charge rate reached 80%, and then discharging the battery. This charge-discharge cycle was repeated 500 times.

[0116] After the lithium deposition durability test, the secondary battery was disassembled and the state of the electrode assembly was visually inspected. Visual inspection was performed on all layers of the laminated electrode assembly. In the curved portion of the electrode assembly, the first, second, and third layers counting from the outermost periphery were carefully inspected to see if lithium had been generated.

[0117] As a result of the test, in Examples 1 to 3, the adhesive strength was neither too low nor too high at each measurement point. In addition, good results were obtained in terms of impregnation of the electrolyte solution and lithium deposition.

[0118] In Comparative Example 1, results regarding adhesive strength were comparable to those in Examples 1 to 3. However, in Comparative Example 1, the wound body was not heated during press processing, and the wound body was pressed with high pressure. As a result, the adhesive strength was high on the inner circumferential side where the electrode body was stacked, and the impregnation of the electrolyte was poor.

[0119] In Comparative Example 2, since the pressing was not performed using an elastic portion, the curved portion was not pressed sufficiently, and the adhesive strength at the curved portion could not be ensured between the positive electrode plate 200 or the negative electrode plate 210 and the separator 220. Furthermore, in Comparative Example 2, although the impregnation of the electrolyte was good, gaps were formed at the curved portion, causing lithium deposition.

[0120] In the manufacturing method of the secondary battery 1 according to one embodiment of the present technology, the curved portion 23 of the electrode assembly 20 is formed while the first press surface F1 and the second press surface F2 are elastically deformed. This prevents the inter-electrode plate distance between the positive electrode plate 200 and the negative electrode plate 210 from increasing at the curved portion 23 of the electrode assembly 20, thereby suppressing lithium precipitation. Furthermore, by applying heat when pressing the curved portion 23, the adhesive strength of the outer periphery of the electrode assembly 20, which is susceptible to heat, is ensured. This prevents excessive load from being applied to the inner periphery of the electrode assembly 20 compared to when the electrode assembly 20 is pressed without heating, and prevents the adhesive strength between the positive electrode plate 200 or the negative electrode plate 210 on the inside of the electrode assembly 20 and the separator 220 from being too high, thereby maintaining good electrolyte impregnation. This prevents lithium precipitation within the electrode assembly 20 while maintaining good electrolyte impregnation.

[0121] In the case of a relatively large electrode body, the adhesive strength between the separator and the positive or negative electrode plate on the outer periphery of the electrode body is likely to be low. Therefore, by pressing the electrode body using the elastic portion and heating the electrode body during pressing, the effect of suppressing lithium precipitation inside the electrode body while ensuring impregnation with the electrolyte is more effective in secondary batteries equipped with a relatively large electrode body.

[0122] In the manufacturing method of the secondary battery 1 according to the embodiment of the present technology, the curved portion 23 is heated at a temperature of 50° C. or higher and 110° C. or lower when being press-formed. This makes it easier to keep the adhesive strength between the positive electrode plate 200 or the negative electrode plate 210 and the separator 220 at the outer periphery of the curved portion 23 within an appropriate range, and also makes it easier to maintain good impregnation with the electrolyte by preventing the adhesive strength between the positive electrode plate 200 or the negative electrode plate 210 and the separator 220 on the inner side of the electrode body 20 from becoming too high.

[0123] In the manufacturing method of the secondary battery 1 according to the embodiment of the present technology, the first press surface F1 and the second press surface F2 abut on 50% or more of the outer surface of the region that will become the first curved portion 24 and the second curved portion 25 after the wound body 20A is pressed. This allows the shape of the curved portion 23 to be formed more uniformly compared to when the curved portion 23 is pressed locally, making it easier to obtain the required adhesive strength between the positive electrode plate 200 or the negative electrode plate 210 and the separator 220. Furthermore, by increasing the contact area between the first press surface F1 and the second press surface F2 and the curved portion 23, it is possible to more easily transfer heat due to heating from the press jig 2 to the curved portion 23.

[0124] In a manufacturing method of a secondary battery 1 according to one embodiment of the present technology, by constructing each of the first elastic portion 7 and the second elastic portion 8 from a porous material, it is possible to easily obtain the elastic modulus of the first press surface F1 and the second press surface F2 required to form the curved portion 23.

[0125] In the secondary battery 1 according to one embodiment of the present technology, the adhesive strength between the surface of each of the first three positive electrode plates 200, counting from the outermost positive electrode plate 200 among the stacked positive electrode plates 200, and each separator 220 adjacent to that outer periphery is 1.0 N / m or more and 1.9 N / m or less in the first curved portion 24. Furthermore, the adhesive strength between the surface of each of the positive electrode plates 200 located on the outer periphery of 50% of the total number of stacked positive electrode plates 200, counting from the innermost positive electrode plate 200 among the stacked positive electrode plates 200, and each separator 220 adjacent to that outer periphery is 0.6 N / m or more and 1.5 N / m or less in the first curved portion 24. This allows the adhesive strength between the positive electrode plate 200 and the separator 220 to be within an appropriate range in the vicinity of the outermost periphery of the first curved portion 24, thereby maintaining a normal inter-electrode plate distance between the positive electrode plate 200 and the negative electrode plate 210. As a result, the impregnation of the electrolyte in the curved portion 23 can be maintained in a good condition, and deposition of lithium in the curved portion 23 can be suppressed.

[0126] In the secondary battery 1 according to one embodiment of the present technology, in the flat portion 22, the adhesive strength between the surface of each of the positive electrode plates 200 from the outermost positive electrode plate 200 to the third layer among the stacked positive electrode plates 200 and each separator 220 adjacent to the outer periphery is 1.5 N / m or more and 1.9 N / m or less. This ensures the necessary adhesive strength in the outer periphery of the flat portion 22 and prevents the electrode plate distance between the positive electrode plate 200 and the negative electrode plate 210 from increasing. This makes it possible to suppress lithium deposition while maintaining good impregnation of the electrolyte in the flat portion 22.

[0127] In the secondary battery 1 according to the embodiment of the present technology, in the flat portion 22, the adhesive strength between the surface of the positive electrode plate 200 located on the outer periphery side for 50% of the total number of stacked positive electrode plates 200, counting from the innermost positive electrode plate 200, and the separator 220 adjacent to that outer periphery side is 1.5 N / m or more and 1.9 N / m or less. This ensures the necessary adhesive strength in the inner peripheral part of the flat portion 22 and prevents the electrode plate distance between the positive electrode plate 200 and the negative electrode plate 210 from widening, thereby suppressing lithium deposition while maintaining good impregnation of the electrolyte in the flat portion 22.

[0128] Although the embodiments of the present technology have been described above, the embodiments disclosed herein should be considered to be illustrative and not restrictive in all respects. The scope of the present technology is defined by the claims, and it is intended to include all modifications within the meaning and scope of the claims. [Explanation of symbols]

[0129] 1 secondary battery, 2, 9 press jig, 3, 9a first jig, 4, 9b second jig, 5, 9c first head portion, 6, 9d second head portion, 7 first elastic portion, 8 second elastic portion, 10 case, 20, 90 electrode body, 20A wound body, 21 tab portion, 22, 22a, 22b, 92 flat portion, 23, 93 curved portion, 24 first curved portion, 25 second curved portion, 30 positive electrode current collector, 40 negative electrode current collector, 50 positive electrode terminal, 60 negative electrode terminal, 70 positive electrode external conductive member, 80 negative electrode external conductive member, 100 outer casing, 101 opening, 102 bottom, 103a, 103b first side wall, 104a, 104b second side wall, 110 sealing plate, 111 liquid injection hole, 112 Sealing member, 113 gas exhaust valve, 200,900 positive electrode plate, 201 positive electrode tab group, 210,910 negative electrode plate, 211 negative electrode tab group, 220,920 separator, 240 first outer portion, 241 first inner portion, 250 second outer portion, 251 second inner portion, A1 winding shaft, F1,F91 first press surface, F2,F92 second press surface.

Claims

1. preparing a wound body in which a separator is sandwiched between a positive electrode plate and a negative electrode plate, and the positive electrode plate, the negative electrode plate, and the separator are wound around a winding axis that is aligned in a first direction; a step of sandwiching the wound body between a first jig having a first press surface including a first elastic portion and a second jig having a second press surface including a second elastic portion in a second direction perpendicular to the first direction, and pressing the wound body with the first press surface and the second press surface while elastically deforming at least a portion of the first press surface and the second press surface, thereby press-forming the wound body into a flat shape to produce an electrode body; and housing the electrode body and the electrolyte in a case, In the step of fabricating the electrode body by press-forming the wound body, the electrode body is formed with a flat portion located on the central side in a third direction orthogonal to the first direction and the second direction and having a flat outer surface, a first curved portion located on one end side of the flat portion in the third direction and having a curved outer surface, and a second curved portion located on the other end side of the flat portion in the third direction and having a curved outer surface, a step of pressing the wound body to fabricate the electrode body, wherein each of the first curved portion and the second curved portion is heated to a temperature of 50°C or higher and 110°C or lower for a time of 1 second or higher and 30 seconds or lower via at least one of the first press surface and the second press surface, and the flat portion is not heated.

2. 2. The method for manufacturing a secondary battery according to claim 1, wherein the first press surface and the second press surface abut on the outer surface of 50% or more of an area that will become the first curved portion and the second curved portion after the wound body is press-formed.

3. 3. The method for manufacturing a secondary battery according to claim 1, wherein the first elastic portion and the second elastic portion are each made of a porous material.

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