Method for manufacturing non-aqueous electrolyte secondary battery and non-aqueous electrolyte secondary battery

Abstract

In a method for producing a nonaqueous electrolyte secondary battery according to the present invention, a wound electrode body is formed (S10); and a flat wound electrode body is formed by pressing (S12). The flat wound electrode body and a cover member are connected to each other (S14); a battery case and the cover member are integrated with each other (S16); and a nonaqueous electrolyte solution is injected using a liquid injection port of the cover member, and the liquid injection port is sealed after the liquid injection, thereby forming a nonaqueous electrolyte secondary battery before inspection (S18). Subsequently, the nonaqueous electrolyte secondary battery before inspection is pressed into a predetermined pressed state (S20). A predetermined charge / discharge inspection is performed on the nonaqueous electrolyte secondary battery in the predetermined pressed state (S22). If predetermined inspection specifications are satisfied in the predetermined charge / discharge inspection, the nonaqueous electrolyte secondary battery is considered as a product that is ready for shipment (S24).

Description

[Technical field]

[0001] The present disclosure relates to a method for manufacturing a nonaqueous electrolyte secondary battery and a nonaqueous electrolyte secondary battery, and more particularly to a method for manufacturing a nonaqueous electrolyte secondary battery including a flat wound electrode body and the nonaqueous electrolyte secondary battery. [Background technology]

[0002] Lithium-ion batteries are being used not only for consumer applications such as mobile phones and laptops, but also for in-vehicle applications such as electric vehicles and hybrid vehicles. In particular, prismatic lithium-ion batteries, which have excellent volumetric efficiency when modularized, are used, and in these batteries, flat wound electrode bodies with no space on the inner circumference are used as electrode bodies to increase capacity, i.e., to increase the electrode occupancy rate per volume.

[0003] When a flat wound electrode body is used as the electrode body, the electrode body expands and contracts repeatedly during charging and discharging, causing the flat part of the electrode body to bend due to undulation, and the winding tension to decrease, causing the winding to become loose. When the flat wound electrode body is bent or loosened, the performance of the secondary battery is reduced.

[0004] Patent Document 1 states that bending and loosening of the flat wound electrode body in a rectangular lithium-ion battery can be suppressed by setting the length of the flat wound electrode body in the winding direction as L and its thickness as W, and making (L / W) 1.7 or more and 3.8 or less.

[0005] Patent Document 2 states that the deflection of the flat wound electrode body in a prismatic lithium ion battery is suppressed by pressing the flat wound electrode body in the thickness direction by a battery case or the like. Here, the ratio of the outer dimension of the "thickness direction of the flat wound electrode body housed in the battery case during discharge" to the inner dimension of the "battery case before housing the flat wound electrode body" is defined as the electrode body thickness ratio, and experimental results of eight examples and four comparative examples are described. If the electrode body thickness ratio is smaller than 1.01, sufficient restraining force is not applied to the flat wound electrode body during discharge, causing the flat wound electrode body to deflect, and cycle capacity maintenance characteristics are reduced. If the electrode body thickness ratio is larger than 1.03, the dimensions of the battery case relative to the flat wound electrode body during discharge are too small, causing the deflection of the flat wound electrode body and the swelling of the battery case to increase. Therefore, it is stated that the electrode body thickness ratio is preferably in the range of 1.01 to 1.03.

[0006] As a technique related to the present disclosure, Patent Document 3 points out that when a sealed lithium-ion battery is initially charged, a small amount of water and part of the electrolyte components contained in the battery material decompose on the electrode surface, generating gas and increasing the internal pressure of the battery. Here, a battery case containing an electrode body and an electrolyte is sealed under reduced pressure, and then pressure is applied to the battery case with a restraining plate or the like when the battery is initially charged. This causes part of the electrolyte to decompose, generating gas, and a coating is formed on the surface of the negative electrode active material, stabilizing the interface between the negative electrode surface and the electrolyte. It also states that the generated gas is smoothly released from the electrode surface by the reduced pressure during sealing and the pressure load during the initial charge, thereby suppressing the rise in internal pressure. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] JP 2013-115033 A [Patent Document 2] JP 2014-082157 A [Patent Document 3] JP 2013-125650 A Summary of the Invention

[0008] In order to suppress the bending that may occur due to the expansion and contraction of the flat wound electrode body during charging and discharging in a nonaqueous electrolyte secondary battery, it is effective to press the flat wound electrode body from the outside of the battery case, but if the pressing force is too strong, the battery case and the pressing tool will be deformed. If the pressing force is too weak, the bending cannot be effectively suppressed. Therefore, there is a demand for a method for manufacturing a nonaqueous electrolyte secondary battery that can effectively suppress the bending that may occur due to the expansion and contraction of the flat wound electrode body.

[0009] The method for manufacturing a nonaqueous electrolyte secondary battery according to the present disclosure includes a step of manufacturing a nonaqueous electrolyte secondary battery including a step of preparing a flat wound electrode body using a positive electrode plate, a negative electrode plate, and an ion-permeable separator disposed between the positive electrode plate and the negative electrode plate, a step of housing an insert including the flat wound electrode body in a battery case having an opening, a step of closing the opening of the battery case with a lid, and a step of injecting a nonaqueous electrolyte into the battery case, and then a step of pressing a predetermined pressing area on the outside of the battery case with a pressing tool, and setting a predetermined pressing state of 0.92≦N1<0.98, where N1 is the occupancy rate of the insert in the battery case, where N1 is the ratio (E1 / T1) of the total thickness E1 of the insert into the battery case including the flat wound electrode body along a direction parallel to the thickness direction of the flat wound electrode body in the pressed battery case to an inner dimension T1 of the battery case, and performing a charge / discharge test under the predetermined pressing state.

[0010] The nonaqueous electrolyte secondary battery according to the present disclosure is a nonaqueous electrolyte secondary battery in which a flat wound electrode body including a positive electrode plate, a negative electrode plate, and an ion-permeable separator disposed between the positive electrode plate and the negative electrode plate is housed in a battery case together with a nonaqueous electrolyte, wherein C1 is the actual length of the flat wound electrode body along the locus path of the innermost winding locus connecting both ends of the innermost winding portion, and S1 is the straight-line distance connecting both ends of the innermost winding locus, where 1.000<(C1 / S1)<1.001.

[0011] According to the manufacturing method for a nonaqueous electrolyte secondary battery and the nonaqueous electrolyte secondary battery configured as described above, bending that may occur due to expansion and contraction of the flat wound electrode body can be effectively suppressed. [Brief description of the drawings]

[0012] [Figure 1] 1 is an external view of a nonaqueous electrolyte secondary battery manufactured by a method for manufacturing a nonaqueous electrolyte secondary battery according to an embodiment; [Diagram 2] FIG. 2 is an exploded view of the nonaqueous electrolyte secondary battery of FIG. [Diagram 3] 3 is a flowchart showing the steps of a method for manufacturing a nonaqueous electrolyte secondary battery according to the embodiment. [Figure 4] FIG. 4(a) shows a wound electrode body, and FIG. 4(b) shows a flat wound electrode body. [Diagram 5] FIG. 5 is a cross-sectional view of the flat wound electrode body of FIG. 4(b). [Figure 6] FIG. 6 is an enlarged view of a portion VI in FIG. 5. [Figure 7] FIG. 1 is a cross-sectional view of a nonaqueous electrolyte secondary battery. [Figure 8] FIG. 2 is a diagram showing a nonaqueous electrolyte secondary battery being pressed using a pressing jig. [Figure 9] FIG. 9 is a cross-sectional view taken along the pressing direction in FIG. 8. [Figure 10] 11A and 11B are diagrams showing an example of measuring the deflection of a flat wound electrode body using an X-ray CT. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0013] Hereinafter, the embodiments of the present disclosure will be described in detail with reference to the drawings. The materials, dimensions, shapes, etc. described below are examples for the purpose of explanation, and can be appropriately changed according to the specifications of the non-aqueous electrolyte secondary battery. In the following, the same reference numerals are used for corresponding elements in all drawings, and duplicated explanations will be omitted.

[0014] 1 is an external perspective view of a nonaqueous electrolyte secondary battery 10. Hereinafter, unless otherwise specified, the nonaqueous electrolyte secondary battery 10 will be referred to as a secondary battery 10. The secondary battery 10 is a prismatic lithium ion battery having a battery case 12 in the form of a cylindrical rectangular parallelepiped with a bottom and a rectangular opening on the ceiling side, and a lid 14 that closes the rectangular opening of the battery case 12.

[0015] 2 is a cross-sectional view showing the internal structure of the secondary battery 10 with the battery case 12 and the lid 14 separated. The inside of the secondary battery 10 contains a flat wound electrode body 16 in which a positive electrode and a negative electrode are laminated and wound with a separator interposed therebetween and wound into a flat shape. Hereinafter, unless otherwise specified, the flat wound electrode body 16 will be referred to as the electrode body 16. In addition to the electrode body 16, the inside of the secondary battery 10 contains a nonaqueous electrolyte 18 impregnated in the electrode body 16, and an electrode body holder 20 which is an insulator for electrically insulating the electrode body 16 from the battery case 12.

[0016] 1 shows a first direction, a second direction, and a third direction as three orthogonal directions. The first direction is a direction from the bottom of the battery case 12 toward the lid 14, and corresponds to the height direction of the battery case 12. The second direction is a direction in which the long sides of the rectangular opening of the battery case 12 extend, and corresponds to the width direction of the battery case 12. The third direction is a direction in which the short sides of the rectangular opening of the battery case 12 extend, and corresponds to the external thickness direction of the battery case 12. The same applies to the following figures.

[0017] The battery case 12 is a square can with a rectangular opening, and is made by integrally molding a suitable metal material into a predetermined shape. The outer dimension of the battery case 12 alone along the first direction is indicated as H12, the outer dimension of the battery case 12 along the second direction is indicated as W12, and the outer dimension of the battery case 12 along the third direction is indicated as D12. The outer dimensions of the battery case 12 alone refer to the outer dimensions of the battery case 12 in a state where nothing is housed in the bottomed cylindrical rectangular parallelepiped having a rectangular opening on the ceiling side.

[0018] The length of the long side of the rectangular opening of the battery case 12 as a single unit is W12 in terms of the outer dimension along the second direction. The length of the short side of the rectangular opening of the battery case 12 is D12 in terms of the outer dimension along the third direction. The outer dimensions of the five side surfaces of the battery case 12 are (W12×H12) for the two side surfaces having the long sides of the rectangular opening, (D12×H12) for the two side surfaces having the short sides of the rectangular opening, and (W12×D12) for one side surface consisting of the long side and short side of the rectangular opening. The size of the battery case 12 as a single unit is set according to the battery capacity (Ah) of the secondary battery 10.

[0019] The thickness t12 of each wall of the battery case 12 may be set appropriately according to the overall size of the battery case 12, but it is necessary to make the thickness appropriately thin so that the electrode body 16 is in a predetermined pressed state when pressed during a charge / discharge test described below. Aluminum or an aluminum alloy is often used as the material for the battery case 12 of the secondary battery 10 for vehicle mounting, and in that case, the thickness of each wall is set to t12≦1.0 mm. The charge / discharge test and the predetermined pressed state will be described later.

[0020] The lid 14 includes a rectangular plate portion 15 having a size capable of liquid-tightly closing the rectangular opening of the battery case 12. The material of the rectangular plate portion 15 is selected from a material that can be integrated with the battery case 12 by joining such as welding. The rectangular plate portion 15 can be made of the same material as the battery case 12.

[0021] The lid body 14 includes, on the rectangular plate portion 15, two external terminals, a positive electrode external terminal 22 and a negative electrode external terminal 24, which protrude outward in the first direction of the secondary battery 10 when integrated with the battery case 12, a liquid injection port 26, and a gas exhaust port 28. The positive electrode external terminal 22 is electrically insulated from the rectangular plate portion 15 via an insulating member. The negative electrode external terminal 24 is electrically insulated from the rectangular plate portion 15 via an insulating member.

[0022] The positive electrode external terminal 22 and the negative electrode external terminal 24 are connected to the electrode body positive electrode 34 and the electrode body negative electrode 36 of the electrode body 16 via the positive electrode current collector 30 and the negative electrode current collector 32, respectively. Through these connections, the electrode body 16 and the lid body 14 are mechanically and electrically integrated to form an electrode body-attached lid body 38. The electrode body-attached lid body 38 does not yet contain the nonaqueous electrolyte 18 immediately after being mechanically and electrically integrated.

[0023] The electrode body holder 20 is an insulating sheet formed into a shape that covers the portion of the electrode body 16 so that the electrode body 16 portion of the electrode body-attached lid body 38 does not come into electrical contact with the inner wall portion of the battery case 12 when the electrode body-attached lid body 38 and the battery case 12 are integrated. The material used for the electrode body holder 20 is an electrically insulating resin that is resistant to the nonaqueous electrolyte 18. In FIG. 2, the thickness of the electrode body holder 20 is indicated as t1. An example of t1 is about 0.15 mm.

[0024] The liquid inlet 26 is an opening for injecting the nonaqueous electrolyte 18 into the battery case 12 after the electrode body 16 portion of the electrode body-attached lid body 38 is inserted into the battery case 12 in which the electrode body holder 20 is arranged, and the battery case 12 and the lid body 14 are integrated by welding or the like. When the nonaqueous electrolyte 18 is injected and the electrode body 16 is immersed, the liquid inlet 26 is sealed, thereby forming a nonaqueous electrolyte secondary battery 40 before inspection. The nonaqueous electrolyte secondary battery 40 before inspection undergoes a prescribed charge / discharge inspection to become a secondary battery 10 as a product.

[0025] Gas exhaust port 28 is a gas vent hole for releasing gas to the outside of secondary battery 10 when gas is generated during charging and discharging of secondary battery 10 and the internal pressure of secondary battery 10 exceeds a predetermined value.

[0026] Next, a method for manufacturing the secondary battery 10 having the above configuration will be described.

[0027] 3, the process starts with the formation of a wound electrode body 42 (see FIG. 4) (S10). The formed wound electrode body 42 is flattened by pressing to become the electrode body 16 (S12).

[0028] Fig. 4(a) shows a perspective view of the wound electrode body 42, and (b) shows a development of the electrode body 16. Explaining using the development of Fig. 4(b), the wound electrode body 42 is a winding body in which one separator 46, one positive electrode plate 48, one separator 50, and one negative electrode plate 52 are stacked in this order in the thickness direction and wound into a cylindrical shape around a winding axis RR. In Fig. 4(a), d is the inner diameter of the wound electrode body 42, and corresponds to, for example, the outer diameter of the winding shaft.

[0029] The electrode body 16 is obtained by compressing a cylindrical roll of the wound electrode body 42 to a predetermined electrode body thickness M0 by pressing. The electrode body 16 is obtained by applying a press pressure to the wound electrode body 42 in the PP direction perpendicular to the winding axis RR using a press machine to form the cylindrical shape of the wound electrode body 42 into a flat shape. In the example of Fig. 4, the inner diameter d of the wound electrode body 42 is crushed by pressing, resulting in an electrode body 16 with almost no gap in the inner periphery and with a dimension S0 of the linear innermost wound part.

[0030] FIG. 4(b) shows three orthogonal directions, RR, PP, and FF, of the electrode body 16. Referring to FIG. 4(a), the RR direction is the direction of the winding axis, and the PP direction is the direction of pressing in the press process to flatten the electrode body. The FF direction is orthogonal to both the RR and PP directions, and is the direction in which the flattened flat portion extends by the press process, so it is called the flattening direction. Referring to FIG. 2, when the electrode body 16 is housed in the battery case 12 of the secondary battery 10, the FF direction in the flattening direction is parallel to the first direction, the RR direction in the direction of the winding axis is parallel to the second direction, and the PP direction in the pressing direction is parallel to the third direction.

[0031] 4 shows the outermost side in development. That is, the outermost side is a separator 46, a positive electrode plate 48 is stacked on the separator 46, a separator 50 is stacked on the positive electrode plate 48, and a negative electrode plate 52 is stacked on the separator 50. In this example, the innermost side is the negative electrode plate 52, but this is an example for the purpose of explanation, and the outermost side may be the negative electrode plate 52 and the innermost side may be the positive electrode plate 48.

[0032] The positive electrode plate 48 is formed by applying a positive electrode active material mixture layer 48b as a positive electrode slurry to both sides of an aluminum-based metal foil 48a, which is a positive electrode core as a metal current collector plate having electrical conductivity, and then drying the layer. The positive electrode active material mixture layer 48b contains a positive electrode active material. The aluminum-based metal is aluminum or an aluminum alloy mainly composed of aluminum. The positive electrode active material contains a lithium transition metal composite oxide capable of absorbing and releasing lithium ions.

[0033] The negative electrode plate 52 is formed by applying a negative electrode active material mixture layer 52b as a negative electrode slurry to both sides of a copper-based metal foil 52a, which is a negative electrode core as a metal current collector plate having electrical conductivity, and drying the layer. The negative electrode active material mixture layer 52b contains a negative electrode active material. The copper-based metal is copper or a copper alloy mainly composed of copper. The negative electrode active material is a carbonaceous material.

[0034] Separators 46, 50 are disposed between positive plate 48 and negative plate 52 and are films made of an ion-permeable material.

[0035] 4(b) shows the dimensions of the positive electrode plate 48, the negative electrode plate 52, and the separators 46, 50 along the winding axis direction of the electrode body 16. The width dimension of the aluminum-based metal foil 48a of the positive electrode plate 48 is indicated as the positive electrode core width w48a, and the width dimension of the positive electrode active material mixture layer 48b is indicated as the positive electrode coating width w48b. The width dimension of the copper-based metal foil 52a of the negative electrode plate 52 is indicated as the negative electrode core width w52a, and the width dimension of the negative electrode active material mixture layer 52b is indicated as the negative electrode coating width w52b. The width dimension of the separators 46, 50 is indicated as the separator width w4650. These width dimensions are dimensions along the winding axis direction.

[0036] In the positive electrode plate 48, the positive electrode coating width w48b is set narrower than the positive electrode core width w48a, and the positive electrode coating width w48b is disposed closer to the other end of the widthwise ends of the positive electrode core width w48a. In the example of FIG. 4(b), in the positive electrode plate 48, a width region is formed at one end side along the winding axis direction in which the positive electrode active material mixture layer 48b is not applied and the aluminum-based metal foil 48a is exposed. This width region where the aluminum-based metal foil 48a is exposed is used as the electrode body positive electrode 34 at one end along the winding axis of the electrode body 16.

[0037] In the negative electrode plate 52, the negative electrode coating width w52b is set narrower than the negative electrode core width w52a, and the negative electrode coating width w52b is disposed close to one of the two widthwise ends of the negative electrode core width w52a. In the example of FIG. 4(b), in the negative electrode plate 52, a width region is formed on the other end side along the winding axis direction, where the negative electrode active material mixture layer 52b is not applied and the copper-based metal foil 52a is exposed. This width region where the copper-based metal foil 52a is exposed is used as the electrode body negative electrode 36 at the other end along the winding axis of the electrode body 16.

[0038] FIG. 5 is a cross-sectional view of the electrode body 16 perpendicular to the winding axis direction. The thickness M0 of the electrode body 16 is a thickness dimension parallel to the pressing direction, and when the electrode body 16 is housed in the battery case 12, it is a thickness dimension parallel to the third direction, which is the thickness direction of the battery case 12. When the electrode body 16 is housed in the battery case 12, the total length L0 of the electrode body 16 along the flattening direction is a dimension parallel to the first direction, which is the height direction of the battery case 12. The dimension F0 of the flat part of the electrode body 16 extending in the flattening direction is shorter than the total length L0 and longer than the dimension S0 of the innermost wound part along the flattening direction. That is, the relationship is L0>F0>S0.

[0039] Fig. 6 is an enlarged view of part VI in Fig. 5. The positive electrode plate 48 has a positive electrode active material mixture layer 48b applied to both sides of an aluminum-based metal foil 48a, and the negative electrode plate 52 has a negative electrode active material mixture layer 52b applied to both sides of a copper-based metal foil 52a. The separators 46, 50 are disposed between the positive electrode active material mixture layer 48b and the negative electrode active material mixture layer 52b. Since the separators 46, 50 have ion permeability, when the electrode body 16 is immersed in the nonaqueous electrolyte 18, ions can flow between the positive electrode plate 48 and the negative electrode plate 52, and the electrode body 16 is in a state in which it can be charged and discharged.

[0040] Returning to Fig. 3, once the electrode body 16 is molded, the electrode body-attached lid body 38 is formed (S14). The electrode body 16 has an electrode body positive electrode 34 at one end in the winding direction, and an electrode body negative electrode 36 at the other end. The electrode body positive electrode 34 of the electrode body 16 is connected to the positive external terminal 22 of the lid body 14 via a positive electrode current collector 30, and the electrode body negative electrode 36 of the electrode body 16 is connected to the negative external terminal 24 of the lid body 14 via a negative electrode current collector 32, to form the electrode body-attached lid body 38 (see Fig. 2).

[0041] Next, the battery case 12 and the lid body 14 are integrated (S16). Here, the electrode body holder 20 is placed in the rectangular cylindrical internal space of the battery case 12. Then, the electrode body-attached lid body 38 is positioned so that the winding axis direction of the electrode body 16 is parallel to the second direction of the battery case 12 and the periphery of the electrode body 16 of the electrode body-attached lid body 38 is covered by the electrode body holder 20. Then, the electrode body-attached lid body 38 is inserted into the internal space of the battery case 12 along the first direction of the battery case 12. When the electrode body-attached lid body 38 is arranged without any gaps, covering the ceiling side opening of the battery case 12, the battery case 12 and the lid body 14 are integrated at the joint between the battery case 12 and the lid body 14 by using a joining means such as welding.

[0042] After the battery case 12 and the lid 14 are integrated, a predetermined amount Q of non-aqueous electrolyte 18 is injected through the inlet 26 of the lid 14. The non-aqueous electrolyte 18 is made by adding lithium hexafluorophosphate (LiPF6) as an electrolyte salt to ethylene carbonate (EC), ethyl methyl carbonate (EMC), dimethyl carbonate (DMC), or the like as a non-aqueous solvent. This is an example for explanation, and other compositions can be used depending on the specifications of the non-aqueous electrolyte secondary battery 10. After the injection, a provisional charge is performed after a time period during which the electrode body 16 is sufficiently immersed in the non-aqueous electrolyte 18, and the inlet 26 is sealed. This forms a non-aqueous electrolyte secondary battery 40 before inspection (S18). FIG. 7 is a cross-sectional view of the non-aqueous electrolyte secondary battery 40 before inspection.

[0043] When the non-aqueous electrolyte secondary battery 40 before inspection is formed, a charge / discharge inspection is performed before shipping it as a product, the non-aqueous electrolyte secondary battery 10. The charge / discharge inspection is performed under a predetermined pressure state so that bending does not occur in the electrode body 16 due to charge / discharge. For this reason, the non-aqueous electrolyte secondary battery 40 is pressed under a predetermined pressure state before the charge / discharge inspection (S20).

[0044] The pressure is applied from the outside of the battery case 12 to two side surfaces 56, 58 that are perpendicular to the third direction of the battery case 12, include the long sides of the rectangular opening of the battery case 12, and have an outer area of ​​(W12 × H12) using pressing tools 60, 62. Fig. 8 shows a state in which pressing tool 60 is applied to side surface 56, pressing tool 62 is applied to side surface 58, and pressure J is applied in opposing directions.

[0045] The pressing jigs 60, 62 are applied to predetermined pressing areas of the side surfaces 56, 58. The predetermined pressing areas are set in accordance with the accommodation position of the electrode body 16 in the battery case 12. The length of the predetermined pressing areas in the second direction may be the entire length of the electrode body 16 in the second direction. The length L1 of the predetermined pressing areas in the first direction is set in accordance with the shape of the flat wound shape of the electrode body 16.

[0046] FIG. 9 is a cross-sectional view taken along the pressing direction of the press J in FIG. 8. Using FIG. 9, the setting of the length L1 along the first direction of the predetermined pressing region will be described. In FIG. 9, the length along the first direction of the flat flat portion of the electrode body 16 is L2. Also, the overall length of the electrode body 16 along the first direction is L3. And the length between both ends along the first direction of the innermost circumferential winding portion of the electrode body 16 is L4. The length L4 between both ends of the innermost circumferential winding portion of the electrode body 16 is such that the position of the bending portion closest to the start of winding in the innermost circumferential winding portion of the electrode body 16 is defined as the first bending portion A, and the position of the first bending portion on the side opposite to the first bending portion A along the first direction is defined as the second bending portion B, and it is the length between A and B. Using the above L2, L3, and L4, the length L1 along the first direction of the predetermined pressing region is set so as to satisfy L1≦L2, L1<L3, and L1≧L4.

[0047] The predetermined pressing state is a state in which the press J is set so that the ratio of the total thickness E1 of the insert disposed in the battery case 12 to the inner dimension T1 of the battery case 12 is defined as the occupancy rate N1 of the insert in the battery case, and 0.92≦N1<0.98. T1 and E1 for determining N1 are values in the pressing state. The total thickness E1 of the insert is the sum of the thickness M0 of the electrode body 16 and twice the wall thickness t1 of the electrode body holder 20, and E1=(M0 + 2×t1). FIG. 9 shows the relationship among T1, M0, and t1 in the pressing state.

[0048] The inner dimension T1 of the battery case 12 is the inner dimension of the short side of the rectangular opening when the press J is applied in a state where the insert and the non-aqueous electrolyte 18 are disposed in the internal space of the battery case 12. The inner dimension T1 is different from the inner dimension of the short side of the rectangular opening in the battery case 12 as a single unit described in FIG. 1.

[0049] The thickness M0 of the electrode body 16 is the thickness M0 of the electrode body 16 as a single unit described in FIG. 5. Since the wall thickness t1 of the electrode body holder 20 is a small value compared to T1 and M0, the influence of the non-aqueous electrolyte 18 and the press J can be ignored.

[0050] Returning to FIG. 3, when the nonaqueous electrolyte secondary battery 40 before inspection is pressed in a predetermined pressing state, a predetermined charge / discharge inspection is performed on the nonaqueous electrolyte secondary battery 40 in the predetermined pressing state (S22). The predetermined charge / discharge inspection may include, for example, an initial charging step, a high-temperature aging step, and a characteristic confirmation step. The initial charging step is, for example, charging to an SOC of 40 to 80% in an environment at 25° C. The high-temperature aging step is, for example, leaving the battery in an environment at 60° C. or higher for 12 to 24 hours. The characteristic confirmation step is, for example, charging to an SOC of 100% in an environment at 25° C., and then discharging to 0%.

[0051] If the predetermined test specifications are met in a given charge / discharge test, the nonaqueous electrolyte secondary battery 10 is ready for shipment as a product (S24).

[0052] The above is a description of the manufacturing method for the nonaqueous electrolyte secondary battery 10. Next, the effect of performing a predetermined charge / discharge test under a predetermined pressure condition will be described by actually producing nine secondary batteries and examining the state of bending of the electrode body 16 after the predetermined charge / discharge test.

[0053] Immediately after being formed by press working, the electrode body 16 has almost no gaps in the inner periphery, and the innermost wound portion extends linearly with a dimension S0, as shown in Fig. 5. When this electrode body 16 is stored in the battery case 12 and immersed in the non-aqueous electrolyte 18 for charging and discharging, the innermost wound portion is not linear and is warped. The deformation from a linear shape to a non-linear shape can be considered as a type of buckling. Therefore, the bending of the electrode body 16 due to charging and discharging is evaluated using the buckling index value described below.

[0054] After a predetermined charge / discharge test is performed, the actual length along the path of the innermost winding locus connecting both ends of the innermost winding portion of the electrode body 16 is C1, and the straight-line distance connecting both ends of the innermost winding locus is S1. If there is no bending at all in the innermost winding portion, (C1 / S1)=1.000. If bending occurs in the innermost winding portion, C1>S1, (C1 / S1) exceeds 1.000, and the larger the bending, the larger (C1 / S1). Therefore, (C1 / S1) is set as the buckling index value.

[0055] The innermost winding locus of the electrode assembly 16 after the charge / discharge test can be measured using an X-ray CT method. FIG. 10 shows an example of an X-ray CT image of the electrode assembly 16 after the charge / discharge test. Images of the positive electrode plate 48, the negative electrode plate 52, and the multiple windings of the separators 46, 50 are omitted here. In the example of FIG. 10, considerable bending has occurred in the innermost winding locus 70. Compared to the distance S1 between both ends of the straight line 72 connecting both ends of the innermost winding locus 70, the actual length C1 along the locus path of the innermost winding locus 70 is quite long, and (C1 / S1) is a value significantly exceeding 1.000.

[0056] Here, a total of nine secondary batteries were produced, four as examples and five as comparative examples, and the relationship between the occupancy rate N1 of the insert in the battery case and the buckling index value (C1 / S1) along with various parameters of each battery are summarized in Table 1. The vertical axis of Table 1 lists various parameters of the secondary batteries, and the horizontal axis lists Examples 1 to 4 and Comparative Examples 1 to 5.

[0057] [Table 1]

[0058] The various parameters on the vertical axis of Table 1 are listed from top to bottom as follows: The unit of dimensions is mm, the unit of injected amount is g, and the unit of battery capacity is Ah.

[0059] The first five rows counting from the top are the positive electrode core width w48a, the positive electrode coating width w48b, the negative electrode core width w52a, the negative electrode coating width w52b, and the separator width w4650. The sixth row counting from the top is the thickness M0 of the electrode body 16 after pressing. The seventh to tenth rows counting from the top are the outer dimension thickness D12 along the third direction of the battery case 12 as a single unit, the outer dimension width W12 along the second direction, the outer dimension height H12 along the first direction, and the wall thickness t12 of the battery case 12. The eleventh row counting from the top is the pouring amount Q of the nonaqueous electrolyte 18.

[0060] The twelfth row counting from the top is the inner dimension T1 of the battery case 12 along the third direction in a pressed state before a charge / discharge test. The thirteenth row counting from the top is the calculated value of the occupancy rate N1 of the inserted object in the battery case, N1=(E1 / T1). The total thickness E1 of the inserted object in the battery case 12 is calculated by adding twice the thickness (t1=0.15 mm) of the electrode body holder 20 to the thickness M0 of the electrode body 16.

[0061] The 14th to 17th rows counting from the top are the length L1 of the predetermined pressing area along the first direction, and the lengths L2, L3, and L4 described in Fig. 9. The 18th row counting from the top is the buckling index value (C1 / S1). The 19th row counting from the top is the battery capacity.

[0062] The horizontal axis of Table 1 lists the secondary batteries from left to right on the page, with the first three batteries counting from the leftmost side being Example 1, Comparative Example 1, and Example 2, which are examples in which the outer thickness D12 of the battery case 12 along the third direction is less than 17 mm. The fourth and subsequent batteries counting from the leftmost side being Comparative Example 2, Example 3, Comparative Example 3, Comparative Example 4, Comparative Example 5, and Example 4, which are examples in which the outer thickness D12 of the battery case 12 along the third direction is 17 mm or more and 27 mm or less. The details of these nine secondary batteries are as follows:

[0063] In Example 1, a positive electrode plate 48 was formed with a positive electrode core width w48a = 121 mm and a positive electrode coating width w48b = 105 mm, and a negative electrode plate 52 was formed with a negative electrode core width w52a = 123 mm and a negative electrode coating width w52b = 110 mm. Then, a wound electrode body 42 was formed using separators 46, 50 with a separator width w4650 = 115 mm, and an electrode body 16 was formed by pressing. The thickness M0 of the electrode body 16 after pressing is 11.2 mm. This is covered with an electrode body holder 20 with a thickness of 0.15 mm, and inserted into a battery case 12 with an outer dimension thickness D12 = 13.4 mm, an outer dimension width W12 = 137 mm, an outer dimension height H12 = 63.3 mm, and a wall thickness t12 = 0.4 mm. Then, a quantity Q of 50 g of nonaqueous electrolyte 18 was poured and the pouring port 26 was closed to form a pre-test nonaqueous electrolyte secondary battery 40. The battery capacity was 4 Ah.

[0064] A predetermined charge / discharge test was performed on the nonaqueous electrolyte secondary battery 40 of Example 1. Before the charge / discharge test, the battery was pressed with pressing tools 60, 62. Unless otherwise specified below, pressing tools 60, 62 were used to press the entire sides 56, 58 of the nonaqueous electrolyte secondary battery 40. The inner dimension T1 of the battery case 12 when pressed before the charge / discharge test was 12.3 mm, and the occupancy rate N1 of the inserted object in the battery case was 0.93. The buckling index value (C1 / S1) after the charge / discharge test was 1.0005, which was less than 1.001.

[0065] In Comparative Example 1, a positive electrode plate 48 was formed with a positive electrode core width w48a = 105 mm and a positive electrode coating width w48b = 90 mm, and a negative electrode plate 52 was formed with a negative electrode core width w52a = 107 mm and a negative electrode coating width w52b = 95 mm. Then, a wound electrode body 42 was formed using separators 46, 50 with a separator width w4650 = 100 mm, and an electrode body 16 was formed by pressing. The thickness M0 of the electrode body 16 after pressing is 10.3 mm. This is covered with an electrode body holder 20 with a thickness of 0.15 mm, and inserted into a battery case 12 with an outer dimension thickness D12 = 12.5 mm, an outer dimension width W12 = 120 mm, an outer dimension height H12 = 85 mm, and a wall thickness t12 = 0.5 mm. Then, a quantity Q of 50 g of nonaqueous electrolyte 18 was poured and the pouring port 26 was closed to form a pre-test nonaqueous electrolyte secondary battery 40. The battery capacity was 5 Ah.

[0066] A predetermined charge / discharge test was performed on the nonaqueous electrolyte secondary battery 40 of Comparative Example 1. Before the charge / discharge test, the battery case 12 was pressed with pressing jigs 60 and 62. The inner dimension T1 of the battery case 12 when pressed before the charge / discharge test was 11.8 mm, and the occupancy rate N1 of the inserted object in the battery case was 0.90. The buckling index value (C1 / S1) after the charge / discharge test was 1.0171, which was greater than 1.001.

[0067] In Example 2, a positive electrode plate 48 was formed with a positive electrode core width w48a = 105 mm, a positive electrode coating width w48b = 90 mm, and a negative electrode plate 52 was formed with a negative electrode core width w52a = 107 mm, and a negative electrode coating width w52b = 95 mm. Then, a wound electrode body 42 was formed using separators 46, 50 with a separator width w4650 = 100 mm. These conditions are the same as those of Comparative Example 1. Then, an electrode body 16 was formed by pressing. The thickness M0 of the electrode body 16 after pressing is 10.6 mm. This was covered with an electrode body holder 20 with a thickness of 0.15 mm, and inserted into a battery case 12 with an outer dimension thickness D12 = 12.5 mm, an outer dimension width W12 = 120 mm, an outer dimension height H12 = 85 mm, and a wall thickness t12 = 0.5 mm. The conditions of the battery case 12 were the same as those of Comparative Example 1. Then, a quantity Q of 60 g of nonaqueous electrolyte 18 was poured and the pouring port 26 was closed to form a pre-test nonaqueous electrolyte secondary battery 40. The battery capacity was 5 Ah.

[0068] A predetermined charge / discharge test was performed on the nonaqueous electrolyte secondary battery 40 of Example 2. Before the charge / discharge test, the battery case 12 was pressed with pressing jigs 60 and 62. The inner dimension T1 of the battery case 12 when pressed before the charge / discharge test was 11.8 mm, which is the same as that of Comparative Example 2, but the occupancy rate N1 of the inserted object in the battery case was 0.92. The buckling index value (C1 / S1) after the charge / discharge test was 1.0006, which was less than 1.001.

[0069] In Comparative Example 2, a positive electrode plate 48 was formed with a positive electrode core width w48a = 127 mm and a positive electrode coating width w48b = 108 mm, and a negative electrode plate 52 was formed with a negative electrode core width w52a = 130 mm and a negative electrode coating width w52b = 113 mm. Then, a wound electrode body 42 was formed using separators 46, 50 with a separator width w4650 = 119 mm, and an electrode body 16 was formed by pressing. The thickness M0 of the electrode body 16 after pressing is 15.5 mm. This is covered with an electrode body holder 20 with a thickness of 0.15 mm, and inserted into a battery case 12 with an outer dimension thickness D12 = 17.5 mm, an outer dimension width W12 = 148 mm, an outer dimension height H12 = 65 mm, and a wall thickness t12 = 0.5 mm. Then, a quantity Q of 60 g of nonaqueous electrolyte 18 was poured and the pouring port 26 was closed to form a pre-test nonaqueous electrolyte secondary battery 40. The battery capacity was 8 Ah.

[0070] For the non-aqueous electrolyte secondary battery 40 of Comparative Example 2, a predetermined charge-discharge test was performed. It was pressed with the pressing jigs 60 and 62 before the charge-discharge test. The inner dimension T1 of the battery case 12 during pressing before the charge-discharge test was 16.8 mm, and the occupancy rate N1 of the insert in the battery case was 0.94. The buckling index value (C1 / S1) after the charge-discharge test was 1.0052, which was 1.001 or more.

[0071] In Example 3, the positive electrode plate 48 was formed with a positive electrode core width w48a = 127 mm and a positive electrode coating width w48b = 108 mm, and the negative electrode plate 52 was formed with a negative electrode core width w52a = 130 mm and a negative electrode coating width w52b = 113 mm. Then, using separators 46 and 50 with a separator width w4650 = 119 mm, a wound electrode body 42 was formed, and the electrode body 16 was formed by pressing. The thickness M0 of the electrode body 16 after pressing was 15.5 mm. This was covered with an electrode body holder 20 having a thickness of 0.15 mm and inserted into a battery case 12 having an outer dimension thickness D12 = 17.5 mm, an outer dimension width W12 = 148 mm, an outer dimension height H12 = 65 mm, and a wall thickness t12 = 0.5 mm. Then, a non-aqueous electrolyte 18 with a liquid injection amount Q = 60 g was injected and the liquid injection port 26 was closed to form a non-aqueous electrolyte secondary battery 40 before inspection. The battery capacity was 8 Ah. These were the same conditions as in Comparative Example 2.

[0072] For the non-aqueous electrolyte secondary battery 40 of Example 3, a predetermined charge-discharge test was performed. It was pressed with the pressing jigs 60 and 62 before the charge-discharge test. The inner dimension T1 of the battery case 12 during pressing before the charge-discharge test was 16.42 mm, and the occupancy rate N1 of the insert in the battery case was 0.96.

[0073] Here, the predetermined pressing region described in FIG. 9 for compressing more than the outer dimension of the battery case 12 during pressing was H12 = 65 mm, L1 = 41.4 mm, L2 = 42.0 mm, L3 = 57.5 mm, L4 = 40.1 mm. Here, L1 ≦ L2, L1 < L3, L1 ≧ L4. Pressing was performed in this predetermined pressing region so that the occupancy rate N1 of the insert in the battery case was 0.96. The buckling index value (C1 / S1) after the charge-discharge test was 1.0007, which was 1.001 or less.

[0074] In Comparative Example 3, a positive electrode plate 48 was formed with a positive electrode core width w48a=132 mm and a positive electrode coating width w48b=117 mm, and a negative electrode plate 52 was formed with a negative electrode core width w52a=134 mm and a negative electrode coating width w52b=122 mm. Then, a wound electrode body 42 was formed using separators 46, 50 with a separator width w4650=127 mm, and an electrode body 16 was formed by pressing. The thickness M0 of the electrode body 16 after pressing is 23.0 mm. These conditions are larger than any of Examples 1, 2, 3, Comparative Example 1, and Comparative Example 2. This was covered with an electrode body holder 20 with a thickness of 0.15 mm, and inserted into a battery case 12 with an outer dimension thickness D12=26.5 mm, an outer dimension width W12=148 mm, an outer dimension height H12=91 mm, and a wall thickness t12=0.7 mm. Then, a quantity Q of 150 g of nonaqueous electrolyte 18 was poured and the pouring port 26 was closed to form a pre-test nonaqueous electrolyte secondary battery 40. The battery capacity was 25 Ah.

[0075] A predetermined charge / discharge test was performed on the nonaqueous electrolyte secondary battery 40 of Comparative Example 3. Before the charge / discharge test, the battery case 12 was pressed with pressing jigs 60 and 62. The inner dimension T1 of the battery case 12 when pressed before the charge / discharge test was 25.4 mm, and the occupancy rate N1 of the inserted object in the battery case was 0.92. The buckling index value (C1 / S1) after the charge / discharge test was 1.0128, which was greater than 1.001.

[0076] In Comparative Example 4, a positive electrode plate 48 was formed with a positive electrode core width w48a = 132 mm and a positive electrode coating width w48b = 117 mm, and a negative electrode plate 52 was formed with a negative electrode core width w52a = 134 mm and a negative electrode coating width w52b = 122 mm. Then, a wound electrode body 42 was formed using separators 46, 50 with a separator width w4650 = 127 mm. These conditions were the same as those of Comparative Example 3. The electrode body 16 was formed by pressing, and the thickness M0 of the electrode body 16 after pressing was 23.1 mm, which was thicker than Comparative Example 3. This was covered with an electrode holder 20 having a thickness of 0.15 mm, and inserted into a battery case 12 having outer dimensions of thickness D12=26.5 mm, width W12=148 mm, height H12=91 mm, and thickness t12=0.7 mm, and a quantity of nonaqueous electrolyte 18 of Q=150 g was poured into the battery case 12. These conditions were the same as those in Comparative Example 3. Then, the pouring port 26 was closed to form a nonaqueous electrolyte secondary battery 40 before testing. The battery capacity was 35 Ah.

[0077] A predetermined charge / discharge test was performed on the nonaqueous electrolyte secondary battery 40 of Comparative Example 4. It was pressed with pressing jigs 60, 62 before the charge / discharge test. The inner dimension T1 of the battery case 12 when pressed before the charge / discharge test was 25.4 mm, and the occupancy rate N1 of the inserted object in the battery case was 0.92. These are the same as those of Comparative Example 3. The buckling index value (C1 / S1) after the charge / discharge test was 1.0148, which was greater than 1.001.

[0078] In Comparative Example 5, a positive electrode plate 48 was formed with a positive electrode core width w48a = 132 mm and a positive electrode coating width w48b = 117 mm, and a negative electrode plate 52 was formed with a negative electrode core width w52a = 134 mm and a negative electrode coating width w52b = 122 mm. Then, a wound electrode body 42 was formed using separators 46, 50 with a separator width w4650 = 127 mm. These conditions are the same as those of Comparative Example 3 and Comparative Example 4. The electrode body 16 was formed by pressing, and the thickness M0 of the electrode body 16 after pressing was 23.3 mm, which was thicker than Comparative Example 3 and Comparative Example 4. This was covered with an electrode body holder 20 with a thickness of 0.15 mm, and inserted into a battery case 12 with an outer dimension thickness D12 = 26.5 mm, an outer dimension width W12 = 148 mm, an outer dimension height H12 = 91 mm, and a wall thickness t12 = 0.7 mm. These conditions are the same as those in Comparative Example 3 and Comparative Example 4. Then, the nonaqueous electrolyte 18 was poured in an amount Q of 150 g. This is the same as in Comparative Example 3 and Comparative Example 4. Then, the pouring port 26 was closed to form a nonaqueous electrolyte secondary battery 40 before inspection. The battery capacity is 30 Ah.

[0079] A predetermined charge / discharge test was performed on the nonaqueous electrolyte secondary battery 40 of Comparative Example 5. Before the charge / discharge test, the battery case 12 was pressed with pressing jigs 60 and 62. When pressed before the charge / discharge test, the inner dimension T1 of the battery case 12 was 25.4 mm, and the occupancy rate N1 of the inserted object in the battery case was 0.93. This is larger than those of Comparative Examples 3 and 4. After the charge / discharge test, the buckling index value (C1 / S1) was 1.0079, which was greater than 1.001.

[0080] In Example 4, a positive electrode plate 48 was formed with a positive electrode core width w48a = 132 mm and a positive electrode coating width w48b = 117 mm, and a negative electrode plate 52 was formed with a negative electrode core width w52a = 134 mm and a negative electrode coating width w52b = 122 mm. Then, a wound electrode body 42 was formed using separators 46, 50 with a separator width w4650 = 127 mm. These conditions are the same as those of Comparative Example 3, Comparative Example 4, and Comparative Example 5. The electrode body 16 was formed by pressing, and the thickness M0 of the electrode body 16 after pressing was 24.0 mm, which is thicker than Comparative Example 3, Comparative Example 4, and Comparative Example 5. This was covered with an electrode holder 20 having a thickness of 0.15 mm, and inserted into a battery case 12 having outer dimensions of thickness D12=26.5 mm, width W12=148 mm, height H12=91 mm, and thickness t12=0.7 mm, and a quantity of nonaqueous electrolyte 18 of Q=150 g was poured into the battery case 12. These conditions were the same as those in Comparative Examples 3 to 5. Then, the pouring port 26 was closed to form a nonaqueous electrolyte secondary battery 40 before testing. The battery capacity was 25 Ah.

[0081] A predetermined charge / discharge test was performed on the nonaqueous electrolyte secondary battery 40 of Example 4. Before the charge / discharge test, the battery case 12 was pressed with pressing jigs 60 and 62. The inner dimension T1 of the battery case 12 when pressed before the charge / discharge test was 25.4 mm, and the occupancy rate N1 of the inserted object in the battery case was 0.96. This is larger than any of Comparative Examples 3, 4, and 5. The buckling index value (C1 / S1) after the charge / discharge test was 1.0004, which was less than 1.001.

[0082] The relationship between the occupancy rate N1 of the insert in the battery case and the buckling index value (C1 / S1) for four examples and five comparative examples is extracted from Table 1 and shown in Table 2. The outer thickness D12 of each battery case 12 is also shown.

[0083] [Table 2]

[0084] Regarding the results of FIG. 12 for four examples and five comparative examples in the range where the outer dimension thickness of the battery case 12 is 12 mm or more and 27 mm or less, when the buckling index value (C1 / S1) ≤ 1.001 is set as the pass criterion value for the deflection of the electrode body 16, the following can be understood.

[0085] Using the battery case internal occupancy rate N1 of the insert as a value indicating a predetermined pressing state, to make the buckling index value (C1 / S1) ≤ 1.001, when the outer dimension thickness of the battery case 12 is 12 mm or more and less than 17 mm, press so that 0.92 ≤ N1 < 0.98. When the outer dimension thickness of the battery case 12 is 17 mm or more and 27 mm or less, press so that 0.94 < N1 < 0.98. Thus, by appropriately pressing the battery case internal occupancy rate N1 of the insert according to the size of the battery case 12, the deflection of the electrode body 16 can be effectively suppressed.

[0086] According to the manufacturing method of the non-aqueous electrolyte secondary battery 10 with the above configuration, according to the size of the battery case 12, press from the outside of the battery case 12 so that the battery case internal occupancy rate N1 of the insert becomes appropriate, and perform a charge and discharge inspection. As a result, the generation of strain accompanying the expansion and contraction of the electrode plate caused by charge and discharge can be suppressed, and the generation of deflection, which is buckling of the flat wound electrode body 16, can be suppressed. When deflection occurs in the flat wound electrode body 16, the inter-pole distance increases and the cell resistance increases. In addition, high stress parts are generated due to the deflection, and the reaction force increases. Further, due to the increase in the inter-pole distance caused by the deflection, the overvoltage increases, and irreversible deterioration such as decomposition of the electrolytic solution, Li precipitation, and elution of the positive electrode active material occurs, resulting in a decrease in durability. According to the manufacturing method of the non-aqueous electrolyte secondary battery 10 with the above configuration, these can be suppressed, and a non-aqueous electrolyte secondary battery 10 with low resistance, low reaction force, and excellent durability can be provided. Furthermore, when performing a charge and discharge inspection on the non-aqueous electrolyte secondary battery 40, by restraining the non-aqueous electrolyte secondary battery 40 before the inspection from the outside, the accumulation of gas generated during the charge and discharge inspection can be suppressed, enabling shortening of the charge and discharge inspection time and improvement of the accuracy of the voltage inspection.

Explanation of Signs

[0087] 10 (Non-aqueous electrolyte) secondary battery 12 Battery case 14 Lid 15 Rectangular plate section 16 (Flat wound type) electrode body 18 Nonaqueous electrolyte 20 Electrode holder (insulator) 22 Positive external terminal 24 Negative external terminal 26 Filling port 28 Gas exhaust port 30 Positive current collector 32 Negative current collector 34 Electrode body positive electrode 36 Electrode body negative electrode 38 Lid with electrode body 40 Non-aqueous electrolyte secondary battery (before inspection) 42 Wound electrode body 46,50 Separator 48 Positive plate 48a Aluminum-based metal foil 48b Positive electrode active material mixture layer 52 Negative plate 52a Copper metal foil 52b Negative electrode active material mixture layer 56,58 Side 60,62 Pressing tool 70 Innermost winding path 72 straight line

Claims

1. A step of preparing a flat wound electrode body using a positive electrode plate, a negative electrode plate, and a separator having ion permeability disposed between the positive electrode plate and the negative electrode plate; placing an insert including the flat wound electrode body in a battery case having an opening; closing the opening of the battery case with a lid; injecting a non-aqueous electrolyte into the battery case; After undergoing a manufacturing process for a non-aqueous electrolyte secondary battery including Pressing a predetermined pressing area on the outside of the battery case with a pressing tool; In the battery case in a pressed state, a ratio (E1 / T1) of a total thickness E1 of an insert into the battery case including the flat wound electrode body along a direction parallel to the thickness direction of the flat wound electrode body to an inner dimension T1 of the battery case is defined as an occupancy rate N1 of the insert in the battery case, and a predetermined pressed state is set such that 0.92≦N1<0.98; carrying out a charge / discharge test under the predetermined pressing state; the insert includes the flat wound electrode assembly and an electrode assembly holder between the battery case and the flat wound electrode assembly, The flat wound electrode body has a thickness of M0, The electrode holder has a wall thickness of t1, The E1 is (M0+2×t1), The occupancy rate N1 of the insert in the battery case is N1=(M0+2×t1) / T1, The electrode holder is an insulating sheet body, After the predetermined charge / discharge test is performed, an actual length along the locus path of the innermost winding locus connecting both ends of the innermost winding portion of the flat wound electrode body is C1, and a straight-line distance connecting both ends of the innermost winding locus is S1, and 1.000<(C1 / S1)<1.001 is satisfied; The outer thickness of the battery case is 12 mm or more and 27 mm or less, The predetermined pressing state is When the outer thickness of the battery case is 12 mm or more and less than 17 mm, 0.92≦N1<0.98; When the outer thickness of the battery case is 17 mm or more and 27 mm or less, 0.94<N1<0.98; The charge / discharge inspection includes an initial charging step, a high-temperature aging step of leaving the battery at a temperature higher than that at which the initial charging step was performed for 12 to 24 hours after the initial charging step, and a characteristic confirmation step of charging the battery after the high-temperature aging step and then discharging the battery.

2. A step of preparing a flat wound electrode body using a positive electrode plate, a negative electrode plate, and a separator having ion permeability disposed between the positive electrode plate and the negative electrode plate; placing an insert including the flat wound electrode body in a battery case having an opening; closing the opening of the battery case with a lid; injecting a non-aqueous electrolyte into the battery case; After undergoing a manufacturing process for a non-aqueous electrolyte secondary battery including Pressing a predetermined pressing area on the outside of the battery case with a pressing tool; In the battery case in a pressed state, a ratio (E1 / T1) of a total thickness E1 of an insert into the battery case including the flat wound electrode body along a direction parallel to the thickness direction of the flat wound electrode body to an inner dimension T1 of the battery case is defined as an occupancy rate N1 of the insert in the battery case, and a predetermined pressed state is set such that 0.92≦N1<0.98; carrying out a charge / discharge test under the predetermined pressing state; the insert includes the flat wound electrode assembly and an electrode assembly holder between the battery case and the flat wound electrode assembly, The flat wound electrode body has a thickness of M0, The electrode holder has a wall thickness of t1, The E1 is (M0+2×t1), The occupancy rate N1 of the insert in the battery case is N1=(M0+2×t1) / T1, The electrode holder is an insulating sheet body, After the predetermined charge / discharge test is performed, an actual length along the locus path of the innermost winding locus connecting both ends of the innermost winding portion of the flat wound electrode body is C1, and a straight-line distance connecting both ends of the innermost winding locus is S1, and 1.000<(C1 / S1)<1.001 is satisfied; In the flat wound electrode body, a direction perpendicular to the winding axis direction and in which a flat flat portion extends is defined as a first direction, The length of the flat portion of the flat wound electrode body along the first direction is L2, The overall length of the flat wound electrode body along the first direction is L3, The length between both ends of the innermost winding portion of the flat wound electrode body in the first direction is defined as L4, A length L1 of the predetermined pressing region along the first direction is set to L1≦L2, L1<L3, or L1≧L4, The charge / discharge inspection includes an initial charging step, a high-temperature aging step of leaving the battery at a temperature higher than that at which the initial charging step was performed for 12 to 24 hours after the initial charging step, and a characteristic confirmation step of charging the battery after the high-temperature aging step and then discharging the battery.

3. the battery case is made of aluminum or an aluminum alloy; 3 . The method for producing a nonaqueous electrolyte secondary battery according to claim 1 , wherein the thickness of the portion of the battery case corresponding to the predetermined pressing area is 1.00 mm or less.

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