Method for manufacturing nonaqueous electrolyte secondary battery

Abstract

Provided is a nonaqueous electrolyte secondary battery in which plastic deformation of a battery case resulting from constraint during initial charging is suppressed, and a method for manufacturing the same. The method for manufacturing the nonaqueous electrolyte secondary battery, which includes a wound electrode body, a nonaqueous electrolyte, and a battery case, includes an assembly step of housing the wound electrode body and the nonaqueous electrolyte in the battery case to form a secondary battery assembly, and an initial charging step of initially charging the secondary battery assembly. In the initial charging step, initial charging is started while the secondary battery assembly is constrained or unconstrained in a thickness direction of the wound electrode body, and a constraint force (P1) greater than a constraint force before a negative electrode potential of the secondary battery assembly reaches 0.6 V is applied to the secondary battery assembly when the negative electrode potential reaches 0.6 V, and the constraint force (P1) is maintained to be applied to the secondary battery assembly until the negative electrode potential reaches at least 0.3 V.

Description

TECHNICAL FIELD

[0001] The present application relates to a nonaqueous electrolyte secondary battery and a manufacturing method of a nonaqueous electrolyte secondary battery. BACKGROUND

[0002] Currently, secondary batteries such as lithium ion secondary batteries are widely used in various fields such as vehicles, portable terminals, and the like. As a typical example of such a secondary battery, a nonaqueous electrolyte secondary battery having an electrode body having a positive electrode plate and a negative electrode plate, a nonaqueous electrolyte, and a battery case that houses the electrode body and the nonaqueous electrolyte can be cited.

[0003] In the manufacturing of a nonaqueous electrolyte secondary battery, generally, an initial charge is performed on a secondary battery assembly in which the electrode body and the nonaqueous electrolyte are housed in the battery case. By performing the initial charge, a so-called SEI coating film can be formed on the surface of the negative electrode plate. On the other hand, at the time of the initial charge, gas from components included in the secondary battery assembly can be generated in the electrode body. In this regard, in Patent Literature 1, a manufacturing method of a secondary battery is proposed, which includes a step of vertically disposing a secondary battery precursor so as to have an opening portion at the uppermost position in the vertical direction, and performing an initial charge while releasing the generated gas from the opening portion.

[0004] In addition, as the electrode body provided in the above-described nonaqueous electrolyte secondary battery, a flat-shaped wound electrode body in which a strip-shaped positive electrode plate and a strip-shaped negative electrode plate are wound with a strip-shaped separator interposed therebetween is sometimes adopted. In this regard, in Patent Literature 2, a scheme is proposed in which the above-described wound electrode body is put in a rectangular parallelepiped-shaped battery case having a pair of wide faces, and a charging step, an aging step, and the like are performed in a state where the battery case is pressed from both sides of the pair of wide faces. Thereby, it is described that it is possible to prevent the effects caused by gas generation.

[0005] PRIOR ART DOCUMENTS

[0006] PATENT LITERATURE

[0007] Patent Literature 1: International Publication No. 2019 / 044560

[0008] Patent Literature 2: Japanese Patent Application Publication No. 2010-21104

[0009] In addition, for a secondary battery assembly provided with a flat-shaped wound electrode body, in order to suppress the stagnation of gas in the electrode body, if the secondary battery assembly is restrained at the time of the initial charge, plastic deformation of the battery case can occur. Therefore, in the restraint at the time of the initial charge, it is also necessary to find a way to suppress the plastic deformation of the battery case. SUMMARY

[0010] Problem to be solved by the Invention

[0011] The present invention has been achieved in order to solve the above-described problems, and has an object to provide a technology for suppressing plastic deformation of a battery case resulting from constraint at the time of initial charging.

[0012] Technical Solution for Solving the Problem

[0013] The present inventors have focused on swelling of the wound electrode body resulting from gas generation at the time of initial charging and reduction of a gap (a gap between the wound electrode body and an inner wall of the case) in the battery case accompanying the swelling. That is, before the start of initial charging, the wound electrode body is not swollen, and thus a gap exists in the battery case. When the secondary battery assembly is constrained in this state, the constrained faces (for example, a pair of wide faces) of the battery case are easily depressed inward, and the non-constrained faces (for example, a bottom face, other side faces) of the battery case are easily swollen. On the other hand, when the wound electrode body swells due to gas generation and the gap becomes small, it is difficult to cause plastic deformation of the battery case resulting from constraint. Furthermore, the present inventors have considered that the constraint force applied to the secondary battery assembly varies depending on the gas generation state in the wound electrode body at the time of initial charging. Furthermore, the present inventors have conducted intensive studies, and as a result, have found that gas is generated when the negative electrode potential is within a predetermined range, and thus have completed the present invention.

[0014] The manufacturing method disclosed herein is a manufacturing method of a nonaqueous electrolyte secondary battery provided with a flat-shaped wound electrode body in which a strip-shaped positive electrode plate and a strip-shaped negative electrode plate are wound with a strip-shaped separator interposed therebetween, a nonaqueous electrolyte, and a battery case that houses the wound electrode body and the nonaqueous electrolyte. The manufacturing method has an assembly process in which the wound electrode body and the nonaqueous electrolyte are housed in the battery case to construct a secondary battery assembly, and an initial charging process in which the secondary battery assembly is subjected to initial charging. Here, in the initial charging process, the initial charging is started in a state in which the secondary battery assembly is constrained or not constrained in the thickness direction of the wound electrode body, and when the negative electrode potential of the secondary battery assembly reaches 0.6 V, a greater constraint force P1 than the constraint force before the negative electrode potential reaches 0.6 V is applied to the secondary battery assembly, and the state in which the constraint force P1 is applied to the secondary battery assembly is maintained until the negative electrode potential reaches at least 0.3 V.

[0015] Here, the negative electrode potential refers to a negative electrode potential with respect to a lithium metal reference (vs. Li / Li + ).

[0016] In the manufacturing method of the above structure, by applying a greater restraining force to the secondary battery assembly when the negative electrode potential is within a predetermined range (i.e., during generation of gas in the wound electrode body), plastic deformation of the battery case can be suppressed. In addition, by the restraining, gas stagnation in the wound electrode body can be suppressed.

[0017] In a preferred embodiment of the manufacturing method disclosed herein, the restraining force P1 is 3 kN or greater and 15 kN or less. When the restraining force P1 is within the above range, the effects of the technology disclosed herein can be appropriately exerted.

[0018] In another preferred embodiment of the manufacturing method disclosed herein, the initial charging step includes a step of applying a restraining force P2 to the secondary battery assembly when the negative electrode potential reaches 0.3 V. The ratio of the restraining force P1 to the restraining force P2 (P2 / P1) is 0.8 or greater and 1.2 or less. As a result of studies by the present inventors and others, when the negative electrode potential reaches 0.3 V, gas generation is less, and the degree of expansion of the wound electrode body due to gas generation is small. Therefore, by applying a restraining force P2 that satisfies the above range, plastic deformation of the battery case at the time of initial charging can be suppressed, and gas stagnation in the wound electrode body can be suppressed.

[0019] In another preferred embodiment of the manufacturing method disclosed herein, both ends in the thickness direction of the wound electrode body are composed of wide flat portions. The flat portions have a central portion including a center line in the winding axis direction of the wound electrode body and two end portions sandwiching the central portion in the winding axis direction. In the initial charging step, a restraining force is applied to the central portion, and no restraining force is applied to the two end portions. Gas is likely to stagnate in the central portion of the wound electrode body. Therefore, by selectively applying a restraining force to this portion, gas stagnation can be more effectively suppressed.

[0020] In another preferred embodiment of the manufacturing method disclosed herein, the negative electrode plate has a negative electrode core and a negative electrode active material layer formed on the negative electrode core. The length of the negative electrode active material layer in the winding axis direction of the wound electrode body is at least 20 cm. The technology disclosed herein is suitable for manufacturing a nonaqueous electrolyte secondary battery having such a wound electrode body.

[0021] In another preferred embodiment of the manufacturing method disclosed herein, an adhesive layer is provided on at least one surface of the separator, and the adhesive layer is adhered to the positive electrode plate or the negative electrode plate. When a separator having an adhesive layer is used, the inter-electrode distance between the positive electrode plate and the negative electrode plate can be reduced. Therefore, the restraining force at the time of initial charging can be reduced, and plastic deformation of the battery case can be more effectively suppressed.

[0022] In another preferred embodiment of the manufacturing method disclosed herein, the battery case has: an outer body including an opening and a bottom portion facing the opening; and a sealing plate sealing the opening. The wound electrode body is arranged in the outer body with the winding axis parallel to the bottom portion. According to this structure, gas is easily discharged to the outside of the wound electrode body, and thus gas retention in the wound electrode body can be more effectively suppressed.

[0023] In another preferred embodiment of the manufacturing method disclosed herein, the battery case has a pair of large-area side walls facing each other and a pair of small-area side walls facing each other and having an area smaller than that of the large-area side walls. The distance between the pair of large-area side walls is at least 3 cm. A plurality of the wound electrode bodies are housed in the battery case. According to this structure, the effects of the technology disclosed herein can be more effectively achieved. In addition to this, when the nonaqueous electrolyte secondary battery has a plurality of wound electrode bodies, energy can be more efficiently extracted from the secondary battery.

[0024] When the manufacturing method disclosed herein is used, a nonaqueous electrolyte secondary battery having the following structure can be manufactured. The nonaqueous electrolyte secondary battery has: a positive electrode current collector and a negative electrode current collector electrically connected to the wound electrode body; a positive electrode tab group including a plurality of tabs protruding toward one end portion of the wound electrode body in the winding axis direction; and a negative electrode tab group including a plurality of tabs protruding toward the other end portion of the wound electrode body in the winding axis direction. The positive electrode current collector is connected to the positive electrode tab group, and the negative electrode current collector is connected to the negative electrode tab group.

[0025] According to the technology disclosed herein, a nonaqueous electrolyte secondary battery is provided that includes a flat-shaped wound electrode body having a strip-shaped positive electrode plate and a strip-shaped negative electrode plate wound with a strip-shaped separator interposed therebetween, a nonaqueous electrolyte, and a battery case that houses the wound electrode body and the nonaqueous electrolyte. The negative electrode plate has a negative electrode core and a negative electrode active material layer formed on the negative electrode core. The length of the negative electrode active material layer in the winding axis direction of the wound electrode body is at least 20 cm. Here, the negative electrode plate has a plurality of tabs that protrude toward one end portion in the winding axis direction. In the negative electrode plate, in the tab closest to the winding start end portion, when one end portion of the root of the tab in a direction orthogonal to the winding axis is set as an end portion B, another end portion of the root different from the end portion B is set as an end portion C, a midpoint of a line segment BC connecting the end portion B and the end portion C is set as a midpoint E, and a straight line passing through the midpoint E and along the winding axis is set as a straight line A, when phosphorus (P) contained in the negative electrode active material layer collected by laser ablation ICP mass spectrometry from the straight line A at the following (1) to (3) points: (1) the center of the negative electrode active material layer in the winding axis direction; (2) a point that is 5 mm or more and 15 mm or less away from the center toward the tab side; and (3) a point that is 5 mm or more and 15 mm or less away from the center toward the side opposite to the tab, the intensity of phosphorus (P) in (1) is lower than the intensity of phosphorus (P) in (2) and lower than the intensity of phosphorus (P) in (3).

[0026] In the nonaqueous electrolyte secondary battery having the above structure, plastic deformation of the battery case is suppressed. In addition to this, generation of coating film formation unevenness in the negative electrode plate is suppressed. Therefore, reduction in battery performance is suppressed.

[0027] In a preferred embodiment of the nonaqueous electrolyte secondary battery disclosed herein, characterized in that when the intensity of phosphorus (P) in (1) is set as I1, the intensity of phosphorus (P) in (2) is set as I2, and the intensity of phosphorus (P) in (3) is set as I3, the ratio of I1 to I2 (I2 / I1) and the ratio of I1 to I3 (I3 / I1) are each 1 or more and 2.5 or less. In the nonaqueous electrolyte secondary battery, the intensity of phosphorus (P) in (1) to (3) is such that the ratio (I2 / I1) and the ratio (I3 / I1) satisfy the above range.

[0028] Furthermore, according to the technology disclosed herein, a non-aqueous electrolyte secondary battery is provided, comprising a flat wound electrode body formed by winding a strip-shaped positive electrode plate and a strip-shaped negative electrode plate separated by a strip-shaped separator, a non-aqueous electrolyte, and a battery casing housing the wound electrode body and the non-aqueous electrolyte. The negative electrode plate has a negative electrode core and a negative electrode active material layer formed on the negative electrode core. The length of the negative electrode active material layer in the winding axis direction of the wound electrode body is at least 20 cm. Here, the negative electrode plate has a plurality of tabs protruding towards one end in the winding axis direction. In the tab closest to the starting end of the winding in the negative electrode plate, if one end of the root of the tab in the direction orthogonal to the winding axis is designated as end B, and the other end of the root that is different from end B is designated as end C, and the midpoint of the line segment BC connecting end B and end C is designated as midpoint E, and the straight line passing through midpoint E and along the winding axis is designated as straight line A, then the following three points (1), (4), and (5) on straight line A are analyzed by laser ablation ICP mass spectrometry:

[0029] (1) The center of the winding axis direction of the negative electrode active material layer;

[0030] (4) A point located 10 mm or more but less than 20 mm away from the center toward the tab side; and

[0031] (5) A point located 10 mm to 20 mm away from the center on the side opposite to the tab.

[0032] When the phosphorus (P) contained in the collected negative electrode active material layer is detected, the intensity of phosphorus (P) in (1) is lower than that of phosphorus (P) in (4) and lower than that of phosphorus (P) in (5).

[0033] In the non-aqueous electrolyte secondary battery with the above structure, plastic deformation of the battery casing is suppressed. Furthermore, uneven coating formation in the negative electrode plate is suppressed. Therefore, degradation of battery performance is prevented.

[0034] In a preferred embodiment of the non-aqueous electrolyte secondary battery disclosed herein, it is characterized in that, when the strength of phosphorus (P) in (1) is set to I1, the strength of phosphorus (P) in (4) is set to I4, and the strength of phosphorus (P) in (5) is set to I5, the ratio of I1 to I4 (I4 / I1) and the ratio of I1 to I5 (I5 / I1) are both 1 or more and 2.7 or less. In the non-aqueous electrolyte secondary battery, the ratios (I4 / I1) and (I5 / I1) satisfy the above-mentioned ranges regarding the strength of phosphorus (P) in (1), (4), and (5). Attached Figure Description

[0035] Figure 1 FIG. 1 is a perspective view schematically showing a nonaqueous electrolyte secondary battery manufactured by a manufacturing method of a first embodiment.

[0036] Figure 2 is a schematic cross-sectional view along the line II-II of Figure 1 FIG. 2.

[0037] Figure 3 FIG. 3 is a perspective view schematically showing a wound electrode body used in the manufacturing method of the first embodiment.

[0038] Figure 4 FIG. 4 is a schematic view showing the structure of the wound electrode body used in the manufacturing method of the first embodiment.

[0039] Figure 5 FIG. 5 is a process diagram of the manufacturing method of the first embodiment.

[0040] Figure 6 FIG. 6 is a block diagram illustrating control in the initial charging process in the manufacturing method of the first embodiment.

[0041] Figure 7 FIG. 7 is a perspective view illustrating a restrained state of a secondary battery assembly in the manufacturing method of the first embodiment.

[0042] Figure 8 FIG. 8 is a control flowchart of the initial charging process in the manufacturing method of the first embodiment.

[0043] Figure 9 FIG. 9 is a graph showing the results of test examples.

[0044] Figure 10 FIG. 10 is a partial plan view showing a negative electrode plate of a nonaqueous electrolyte secondary battery manufactured using the manufacturing method of the first embodiment.

[0045] Figure 11 FIG. 11 is a perspective view illustrating a restrained state of a secondary battery assembly in the manufacturing method of the second embodiment.

[0046] Figure 12 FIG. 12 is a plan view illustrating a restrained state of a secondary battery assembly in the manufacturing method of the third embodiment.

[0047] BRIEF DESCRIPTION OF THE DRAWINGS

[0048] 10 cell case

[0049] 12 outer case

[0050] 14 sealing plate (cover)

[0051] 15 injection hole

[0052] 16 sealing member

[0053] 17 gas discharge valve

[0054] 20 wound electrode body

[0055] 22 positive electrode plate

[0056] 23 positive electrode tab group

[0057] 24 negative electrode plate

[0058] 25 negative electrode tab group

[0059] 26 separator

[0060] 30 positive electrode terminal

[0061] 40 negative electrode terminal

[0062] 50 positive electrode current collector

[0063] 60 negative electrode current collector

[0064] 70 electrode body holder

[0065] 500 control device

[0066] 800, 820, 830 restraining jig

[0067] 100 nonaqueous electrolyte secondary battery

[0068] 101 secondary battery assembly DETAILED DESCRIPTION

[0069] Hereinafter, several preferred embodiments of the technology disclosed herein will be described with reference to the accompanying drawings. Note that matters other than those specifically mentioned in this specification, which are required for the implementation of the present application (e.g., general structure and manufacturing process of a secondary battery that does not characterize the technology disclosed herein) can be understood as design matters of those skilled in the art based on the existing technology in the field. The technology disclosed herein can be implemented based on the content disclosed in this specification and the technical common sense in the field.

[0070] In the present specification, "secondary battery" refers to a term including all of the power storage devices capable of repeated charge and discharge, and is a concept including so-called storage batteries (chemical cells) such as lithium-ion secondary batteries and capacitors (physical cells) such as electric double layer capacitors. In the present specification, "active material" refers to a material capable of reversibly absorbing and discharging a charge carrier (for example, lithium ion). In the present specification, "charge depth" refers to a state in which the full charge of a secondary battery assembly (non-aqueous electrolyte secondary battery) is set to 100% of the charge rate (amount of charge from the initial state / cell capacity of the secondary battery assembly x 100), and is also referred to as SOC (state of charge).

[0071] In the drawings referred to in the present specification, reference sign X represents "depth direction", reference sign Y represents "width direction", and reference sign Z represents "height direction". In addition, F in the depth direction X represents "front", and Rr represents "rear". L in the width direction Y represents "left", and R represents "right". Furthermore, U in the height direction Z represents "upper", and D represents "lower". However, these are merely directions for convenience of explanation, and do not limit the arrangement of the secondary battery in any way. In addition, the expression "A to B" indicating a numerical range in the present specification includes not only the meaning of "A or more and B or less", but also the meaning of "more than A and less than B".

[0072] <First Embodiment>

[0073] Figure 1 、 Figure 2 An example of a non-aqueous electrolyte secondary battery manufactured in the manufacturing method disclosed herein is shown. The non-aqueous electrolyte secondary battery 100 is provided with a wound electrode body 20, a non-aqueous electrolyte not shown, and a battery case 10 that houses the wound electrode body and the non-aqueous electrolyte. The non-aqueous electrolyte secondary battery 100 is a lithium-ion secondary battery in this case.

[0074] The non-aqueous electrolyte can include a non-aqueous solvent and a supporting salt. As the non-aqueous solvent, various organic solvents such as carbonates used in general lithium-ion secondary batteries can be used without particular limitation. As specific examples, chain carbonates such as dimethyl carbonate (DMC), ethyl methyl carbonate (EMC), diethyl carbonate (DEC), and the like; cyclic carbonates such as ethylene carbonate (EC), propylene carbonate (PC), butylene carbonate (BC), methyl ethylene carbonate, ethyl ethylene carbonate, and the like; fluorinated chain carbonates such as methyl 2,2,2-trifluoroethyl carbonate (MTFEC); fluorinated cyclic carbonates such as monofluoroethylene carbonate (FEC), difluoroethylene carbonate (DFEC), and the like can be listed. Such non-aqueous solvents can be used alone or in combination of two or more. The non-aqueous solvent is preferably a cyclic carbonate. Among them, ethylene carbonate (EC) can be preferably used.

[0075] As the supporting salt, LiPF6or the like can be exemplified. The concentration of the supporting salt in the nonaqueous electrolyte solution can be set in the range of 0.7 mol / L to 1.3 mol / L. As the component other than the above-mentioned components, the nonaqueous electrolyte solution can contain, for example, a film-forming agent such as an oxalate complex compound containing a boron (B) atom and / or a phosphorus (P) atom (for example, lithium bis(oxalato)borate (LiBOB)), vinylene carbonate (VC), lithium difluorophosphate, or the like; a gas generating agent such as biphenyl (BP), cyclohexylbenzene (CHB), or the like. In addition, as long as the effects of the technology disclosed herein are not significantly impaired, a tackifier, a dispersant, or the like, a hitherto known additive can be contained. The film-forming agent is preferably an oxalate complex compound or lithium difluorophosphate.

[0076] The battery case 10 is provided with an outer body 12 having an opening and a sealing plate (cover body) 14 that seals the opening. The battery case 10 is integrated and hermetically sealed (closed) by joining the sealing plate 14 to the periphery of the opening of the outer body 12. The outer body 12 is a bottomed square cylindrical outer body including the opening, a rectangular bottom portion 12a facing the opening, a pair of large-area side walls 12b that stand from long sides of the bottom portion 12a, and a pair of small-area side walls 12c that stand from short sides of the bottom portion 12a. The small-area side walls 12c have an area smaller than that of the large-area side walls 12b. The sealing plate 14 is provided with a liquid injection hole 15, a gas discharge valve 17, a positive electrode terminal 30, and a negative electrode terminal 40 of the nonaqueous electrolyte solution. The liquid injection hole 15 is sealed by a sealing member 16. The positive electrode terminal 30 and the negative electrode terminal 40 are electrically connected to the wound electrode body 20 housed in the battery case 10. The battery case 10 is, for example, made of metal. As a metal material constituting the battery case 10, for example, aluminum, an aluminum alloy, iron, an iron alloy, or the like can be exemplified.

[0077] The size of the battery case 10 is not particularly limited. As described later, in a case where a plurality of wound electrode bodies 20 are housed in the outer body 12 in several modes, the distance between the pair of large-area side walls 12b can be appropriately set according to the number, size, or the like of the wound electrode bodies 20 housed. The distance can be, for example, at least 3 cm, can be 3 cm or more, can be 4 cm or more, and can be 5 cm or more. In addition, the distance can be, for example, 10 cm or less, can be 8 cm or less, and can be 6 cm or less.

[0078] The wound electrode body 20 is a power generating element of the nonaqueous electrolyte secondary battery 100 and is provided with a positive electrode plate, a negative electrode plate, and a separator. In the present embodiment, as shown in FIG. 1, a plurality of (for example, two or more, three or more, or four or more, and three in the present embodiment) wound electrode bodies 20 are housed in the battery case 10 (the outer body 12) in a state of being arranged in the depth direction X. As shown in FIG. 1, the wound electrode bodies 20 are arranged in the depth direction X in the battery case 10 (the outer body 12) in a state of being arranged in the depth direction X. Figure 2 Figure 2 Figures 1-4 ​​As shown, the wound electrode body 20 is disposed inside the outer casing 12 with the winding axis WL parallel to the bottom 12a. The wound electrode body 20 is housed in the battery casing 10 in a state of being housed within the electrode body holder 70. Furthermore, the materials used to construct the various components constituting the wound electrode body 20 (positive electrode plate, negative electrode plate, and separator, etc.) can be materials that are generally used in non-aqueous electrolyte secondary batteries without particular limitation, and the technology disclosed herein is not limited; therefore, detailed descriptions are sometimes omitted.

[0079] The length L1 of the winding axis WL of the wound electrode body 20 is at least 20 cm, and can be set to more than 20 cm, more than 25 cm, or more than 30 cm. Alternatively, the length L1 can be less than 60 cm, less than 50 cm, or less than 40 cm. It should be noted that the length L1 does not include either the length of the positive electrode tab 22t or the length of the negative electrode tab 24t, which will be described later.

[0080] like Figure 4 As shown, the wound electrode body 20 has a positive electrode plate 22 and a negative electrode plate 24. The wound electrode body 20 is a flat-shaped wound electrode body formed by winding a long strip of positive electrode plate 22 and a long strip of negative electrode plate 24, separated by a long strip of diaphragm 26, around a winding axis WL orthogonal to the length direction. Figure 3 As shown, the two ends of the wound electrode body 20 in the width direction Y are formed by the laminated surface 20b of the positive electrode plate 22, the negative electrode plate 24, and the separator 26. The laminated surface 20b is open to the outside of the wound electrode body 20.

[0081] The two ends of the wound electrode body 20 in the thickness direction (depth direction X) are formed by wide flat portions 20a. Each flat portion 20a has a central portion 201 that includes the center line C of the flat portion 20a in the winding axis direction of the wound electrode body 20, and two end portions 202 and 203 sandwiching the central portion 201 in the winding axis direction. Gas generated within the wound electrode body 20 is released out of the wound electrode body via the lamination surface 20b, and therefore tends to remain in the central portion 201. The ratio (L2 / L1) of the length L1 of the flat portion 20a in the winding axis direction to the length L2 of the central portion 201 can be, for example, 1 / 6 or more, 1 / 4 or more, or 1 / 2 or less, 1 / 3 or less. "Including the center line C" simply means that the center line C is included in the central portion 201; for example, the distance between the center line of the central portion 201 and the center line C is 1 / 4L2 or less. The lengths of the end portions 202 and 203 in the winding axis direction can be appropriately set according to the length L2.

[0082] The positive electrode sheet 22 has a long, strip-shaped positive electrode core 22c and a positive electrode active material layer 22a that is fixed to at least one surface (preferably both surfaces) of the positive electrode core 22c (for example, an aluminum foil, an aluminum alloy foil, or the like) and contains a positive electrode active material (for example, a lithium nickel cobalt manganese composite oxide (NCM) or the like). Although not particularly limited, a positive electrode protective layer 22p can be provided on one side edge portion in the width direction Y of the positive electrode sheet 22 as needed. A plurality of positive electrode tabs 22t are provided on one end portion in the width direction Y (left end portion) of the positive electrode core 22c. The plurality of positive electrode tabs 22t each protrude toward one side in the width direction Y (left side) of the positive electrode core 22c. The plurality of positive electrode tabs 22t are provided at intervals (intermittently) along the length direction of the positive electrode sheet 22. The positive electrode tabs 22t are portions of the positive electrode core 22c and are portions (core exposed portions) on which the positive electrode active material layer 22a and the positive electrode protective layer 22p of the positive electrode core 22c are not formed. The plurality of positive electrode tabs 22t are laminated on one end portion in the width direction Y (left end portion) to constitute a positive electrode tab group 23 including the plurality of positive electrode tabs 22t. The positive electrode tab group 23 is joined to a positive electrode current collector 50 (see FIG. 1). Figure 4 Figure 4 Figure 4 Figures 2-4

[0083] The size of the positive electrode sheet 22 can be set to achieve the length LI of the wound electrode body 20. The length of the positive electrode sheet 22 in the winding axis WL direction can be set to, for example, 20 cm or more, 25 cm or more, or 30 cm or more. In addition, the length can be, for example, 60 cm or less, 50 cm or less, or 40 cm or less. Note that the length does not include the length of the positive electrode tabs 22t.

[0084] The negative electrode sheet 24 has a long, strip-shaped negative electrode core 24c (for example, a copper foil, a copper alloy foil, or the like) and a negative electrode active material layer 24a that is fixed to at least one surface (preferably both surfaces) of the negative electrode core 24c and contains a negative electrode active material (for example, graphite or the like). A plurality of negative electrode tabs 24t are provided on one end portion in the width direction Y (right end portion) of the negative electrode core 24c. The plurality of negative electrode tabs 24t protrude toward one side in the width direction Y (right side) of the negative electrode core 24c. The plurality of negative electrode tabs 24t are provided at intervals (intermittently) along the length direction of the negative electrode sheet 24. Here, the negative electrode tabs 24t are portions of the negative electrode core 24c and are portions (core exposed portions) on which the negative electrode active material layer 24a of the negative electrode core 24c is not formed. The plurality of negative electrode tabs 24t are laminated on one end portion in the width direction Y (right end portion) to constitute a negative electrode tab group 25 including the plurality of negative electrode tabs 24t. The negative electrode tab group 25 is joined to a negative electrode current collector 60 (see FIG. 1). Figure 4 Figure 4 Figure 4 Figures 2-4 ​​​​​​​​

[0085] The dimensions of the negative electrode plate 24 can be set to achieve the length L1 of the wound electrode body 20. The length of the negative electrode plate 24 in the winding axis WL direction (e.g., the length of the negative electrode active material layer 24a) is at least 20 cm, and can be set to more than 20 cm, more than 25 cm, or more than 30 cm. Alternatively, this length can be less than 60 cm, less than 50 cm, or less than 40 cm. It should be noted that the length does not include the length of the negative electrode tab 24t.

[0086] As the separator 26, conventionally known separators composed of microporous sheets can be used without particular limitation. Examples include porous sheets (membranes, nonwoven fabrics, etc.) composed of polyolefin resins such as polyethylene (PE) and polypropylene (PP). An adhesive layer can be provided on at least one surface of the separator 26. By providing the adhesive layer, the positive electrode plate 22 and the negative electrode plate 24 can be tightly adhered to the separator 26. Therefore, the inter-electrode distance between the positive electrode plate 22 and the negative electrode plate 24 can be reduced, and their positional displacement can be prevented. The material constituting the adhesive layer is not particularly limited as long as it is a resin material with suitable adhesive properties; for example, it can be a fluorinated resin, acrylic resin, polyamide resin, polyimide resin, polyurethane resin, or other resin materials.

[0087] like Figure 5 As shown, the manufacturing method disclosed herein includes an assembly step S1, an initial charging step S2, and a high-temperature aging step S3. In the assembly step S1, a secondary battery assembly is constructed by housing a wound electrode body and a non-aqueous electrolyte in a battery casing. First, a wound electrode body 20 is fabricated using the aforementioned materials and a conventionally known method. Next, a positive current collector 50 is installed on the positive electrode tab group 23 of the wound electrode body 20, and then a negative current collector 60 is installed on the negative electrode tab group 25, preparing a composite of the wound electrode body and the electrode current collector (first composite) (see reference). Figure 3 In this embodiment, three first composite objects are prepared.

[0088] Next, the three first composite components are integrated with the sealing plate 14 to prepare the second composite component. Specifically, for example, the positive terminal 30 pre-installed on the sealing plate 14 is joined to the positive current collector 50 of the first composite component. Similarly, the negative terminal 40 pre-installed on the sealing plate 14 is joined to the negative current collector 60 of the first composite component. As a joining method, ultrasonic joining, resistance welding, laser welding, etc., can be used, for example.

[0089] Next, the second assembly is housed in the outer casing 12. Specifically, for example, three wound electrodes 20 are housed in an electrode holder 70 made by bending an insulating resin sheet (such as polyethylene (PE) or other polyolefins) into a bag or box shape. Then, the wound electrodes 20 covered by the electrode holder 70 are inserted into the outer casing 12. In this state, the sealing plate 14 is overlapped with the opening of the outer casing 12, and the outer casing 12 and the sealing plate 14 are welded to seal the outer casing 12. Then, a non-aqueous electrolyte is injected into the battery housing 10 through the injection hole 15 using a conventionally known method. The wound electrodes 20 are immersed in the injected non-aqueous electrolyte. In this way, a secondary battery assembly is constructed in which the wound electrodes 20 and the non-aqueous electrolyte are housed in the battery housing 10.

[0090] In the initial charging step S2, the secondary battery assembly is initially charged. This step includes the process of constraining and controlling the secondary battery assembly into a predetermined shape. Figure 6 As shown, the constraint of the constraint fixture 800 on the secondary battery assembly 101 is controlled by the control device 500. The type of constraint fixture 800 is not particularly limited; for example, it can be any type of fixture. Figure 7 The constraint clamp 800, as shown, comprises a pair of constraint plates 80 and constraint members (e.g., springs, bolts, belts, etc.) (not shown). While not particularly limited, for example, an elastic body such as a spring can be mounted on the constraint plates 80, and the distance between the pair of constraint plates 80 can be changed by the elastic force of the elastic body, thereby applying a constraint force to the secondary battery assembly 101. Alternatively, a belt or the like can be used to support the constraint between the pair of constraint plates 80. The constraint can be performed with multiple constraint bodies 180 arranged along the depth direction X.

[0091] The control device 500 is configured to evaluate the state of charge of the secondary battery assembly 101 and, based on this, control the constraints on the secondary battery assembly 101 imposed by the constraint fixture 800. The control device 500 includes a CPU for executing a processing program, a ROM for storing the processing program, RAM for temporarily storing data, input / output ports and communication ports, and various sensors. The various structures and processes of the control device 500 can be embodied as a database storing computer-specific data in a pre-set format, a data structure, a processing module performing predetermined calculations according to a pre-set program, or as part of such a module. The processing of the control device 500 can also be performed in cooperation with an external computer. For example, the external computer can store information or a portion of the information stored in the control device 500, and can also execute the processing performed by the control device 500 or a portion of the processing.

[0092] The control device 500 includes, for example, a detection unit, a map information storage unit, a storage unit, a battery information acquisition unit, a negative electrode potential estimation unit, and a control unit as functional blocks for evaluating the state of charge of the secondary battery assembly 101 and controlling the restraint of the secondary battery assembly 101 by the restraint jig 800 on the basis of the evaluation.

[0093] The detection unit is configured to be able to detect the current value (Ib) and the voltage value (Vb) of the secondary battery assembly 101, and can include a current detection unit 501 and a voltage detection unit 502. The current detection unit 501 is connected to a current meter (not shown) connected in series with the secondary battery assembly 101 to detect the current value (Ib). The voltage detection unit 502 is connected to a voltage meter (not shown) connected in parallel with the secondary battery assembly 101 to detect the voltage value (Vb).

[0094] The map information storage unit 503 stores a negative electrode potential estimation map configured to be able to estimate the negative electrode potential on the basis of the voltage value (Vb) of the secondary battery assembly 101. In the negative electrode potential estimation map, the correlation between the cell voltage of the secondary battery assembly 101 and the negative electrode potential is recorded. In the present specification, the "negative electrode potential" refers to the negative electrode potential on the lithium metal basis (vs. Li / Li +

[0095] The storage unit can include, for example, a basic information storage unit 504 that stores basic information of the secondary battery assembly 101 and a voltage storage unit 505 that temporarily stores the voltage (Vb) of the secondary battery assembly 101 during initial charging. As the basic information, for example, the types of positive and negative electrode active materials included in the secondary battery assembly 101, the size of the wound electrode body, and the like can be listed.

[0096] The negative electrode potential estimation unit 506 is configured to estimate the negative electrode potential in the secondary battery assembly 101 during initial charging with reference to the negative electrode potential estimation map stored in the map information storage unit 503. At this time, the negative electrode potential estimation unit 506 refers to the voltage (Vb) of the secondary battery assembly 101 detected by the voltage detection unit 502.

[0097] ​The control unit 507 is configured to cooperate with the voltage detection unit 502, the mapping information storage unit 503, the basic information storage unit 504, the voltage storage unit 505, and the negative electrode potential estimation unit 506 to control the constraint of the secondary battery assembly 101 formed by the constraint fixture 800. Furthermore, the control unit 507 is configured to control a series of charging and discharging operations of the secondary battery assembly 101 in the initial charging step S2 and other steps. The control unit 507 is connected to a charging / discharging mechanism (not shown) and a constraint force control mechanism. The charging / discharging mechanism is a conventionally known charging / discharging mechanism used in the manufacturing method disclosed herein for performing a series of charging and discharging operations of the secondary battery assembly 101.

[0098] The constraint force control mechanism is also connected to the constraint clamp 800, as described later, and is configured to acquire this information when the negative electrode potential of the secondary battery assembly 101 reaches 0.6V and 0.3V. Based on this information, the constraint force control mechanism controls the constraint force applied to the secondary battery assembly 101 from the constraint clamp 800. As an example, the constraint force control mechanism is a hydraulic supply pipe.

[0099] The constraint control of the control unit 507 will be explained below. When the initial charging of the secondary battery assembly 101 begins, the basic information of the secondary battery assembly 101 is input to the control device 500, and a reference negative electrode potential estimation mapping is selected. Furthermore, as... Figure 7 As shown, a constraint body 180 is constructed, consisting of a secondary battery assembly 101 and a constraint fixture 800. Specifically, a constraint body 180 is constructed with a large-area sidewall 12b (refer to the battery casing 10 (outer body 12) of the secondary battery assembly 101) as the constraint body. Figure 1 The battery casing 10 is clamped between a pair of opposing constraint plates 80. Then, the distance between the pair of constraint plates 80 is adjusted to apply a constraint force P0 to the secondary battery assembly 101. The constraint force P0 is set to be between 0 kN and 12 kN. That is, initial charging begins either when the secondary battery assembly 101 is constrained along the thickness direction (depth direction Y) of the wound electrode body 20 (constraint force P0 > 0 kN) or when the secondary battery assembly 101 is not constrained along the thickness direction (depth direction Y) of the wound electrode body 20 (constraint force P0 = 0 kN). The charging rate used for initial charging is not particularly limited and can be set appropriately, for example, to 1C or less.

[0100] like Figure 8As shown, after the start of initial charging (START), first, the voltage detection section 502 detects the voltage (Vb) (step Sll), and the voltage storage section 505 stores the voltage (Vb). Next, the negative electrode potential estimation section 506 refers to the negative electrode potential estimation map of the map information storage section 503 and the voltage (Vb) stored in the voltage storage section 505, and estimates the negative electrode potential of the secondary battery assembly 101 (step S12). Here, the control section 507 determines whether the negative electrode potential has reached 0.6 V (step S13). In the case where it is determined that the negative electrode potential has not reached 0.6 V (No), the process returns to step Sll.

[0101] In the case where it is determined that the negative electrode potential has reached 0.6 V (Yes), the restraint force control mechanism switches the restraint force P0 to the restraint force PI, and applies the restraint force PI to the secondary battery assembly 101 (step S14). The restraint force PI is greater than the restraint force P0 before the negative electrode potential reaches 0.6 V, and can be appropriately set within a range of 1 kN or more and 15 kN or less (preferably, 3 kN to 15 kN, more preferably, 6 kN to 10 kN). The ratio (P0 / PI) of the restraint force P0 to the restraint force PI is, for example, 0.3 or more, can be 0.5 or more, and can be 0.8 or more. The upper limit of the ratio can be, for example, 0.9 or less.

[0102] Next, the control section 507 determines whether the negative electrode potential has reached 0.3 V (step S15). In the case where it is determined that the negative electrode potential has not reached 0.3 V (No), the process returns to step S14. In the case where it is determined that the negative electrode potential has reached 0.3 V (Yes), the restraint force control mechanism switches the restraint force PI to the restraint force P2, and applies the restraint force P2 to the secondary battery assembly 101 (step S16). That is, the state in which the restraint force PI is applied to the secondary battery assembly 101 is maintained until the negative electrode potential reaches at least 0.3 V. From the viewpoint of suppressing plastic deformation of the battery case 10, the ratio (P2 / PI) of the restraint force PI to the restraint force P2 is preferably 0.8 or more and 1.2 or less, more preferably 0.9 or more and 1.1 or less, and further preferably 1.0 or more and 1.1 or less. Note that, as shown in the test example described later, the amount of gas generation decreases after the negative electrode potential reaches 0.3 V. Therefore, the switching to the restraint force P2 in step S16 is not necessarily required. Alternatively, in step S16, the restraint of the secondary battery assembly 101 can be released.

[0103] The initial charging temperature is preferably below 45°C, more preferably between 15°C and 35°C, and even more preferably between 20°C and 30°C. Furthermore, the depth of charge of the secondary battery assembly 101 after the initial charging is preferably 5% or more, more preferably 10% or more, and even more preferably 15% or more. The depth of charge is preferably below 50%, more preferably below 40%, and even more preferably below 30%. In addition, although not particularly limited, in order to release the gas generated during the initial charging, the initial charging process S2 is preferably performed with the injection hole 15 open (i.e., with the battery casing 10 open).

[0104] Although not specifically limited, the secondary battery assembly can be placed for a predetermined time after the initial charging step S2 and before the high-temperature aging described below, as needed. This better suppresses gas retention within the wound electrode body 20 after the initial charging step S2. The predetermined time can be appropriately set within a range of 24 hours to 336 hours. The temperature conditions at this time can be appropriately set, for example, within a range of 5°C to 45°C. Furthermore, although not specifically limited, the secondary battery assembly 101 can also be placed with the injection hole 15 open (i.e., with the battery casing 10 open). Additionally, during this placement, the secondary battery assembly can be constrained or not.

[0105] like Figure 5 As shown, after the initial charging step S2, a high-temperature aging step S3 is performed. First, the charging and discharging mechanism is used to charge the secondary battery assembly to a depth of charge of, for example, 5% or more and 50% or less (preferably 15% or more and 40% or less). The temperature conditions at this time can be set to, for example, 45°C or less (preferably 20°C or more and 30°C or less). The charging rate at this time is not particularly limited and can be appropriately set, for example, to 1C or less. Furthermore, if the secondary battery assembly is constrained, it can be pre-released at the start of charging in this step.

[0106] Next, the secondary battery assembly is placed in a high-temperature environment at its depth of charge to begin high-temperature aging. The temperature conditions are not particularly limited at this time; for example, they can be set to 50°C or higher and 70°C or lower (e.g., around 60°C). Furthermore, the high-temperature aging time can be set to 5 hours or more and 20 hours or less. As described above, by implementing the manufacturing method disclosed herein, a usable non-aqueous electrolyte secondary battery can be manufactured.

[0107] [Experimental Example]

[0108] The following describes test examples related to the present application. Note that the contents of the test examples described below are for explaining the origins of the idea of the present application conceived by the present inventors and are not intended to limit the present application.

[0109] -Construction of secondary battery assembly-

[0110] A lithium nickel cobalt manganese composite oxide (NCM) as a positive electrode active material, polyvinylidene fluoride (PVdF) as a binder, and acetylene black (AB) as a conductive material were weighed in a mass ratio of NCM:PVdF:AB = 98:1:1, mixed in N-methyl-2-pyrrolidone (NMP), and prepared into a positive electrode slurry. The positive electrode slurry was applied to both surfaces of a long strip-shaped positive electrode core (aluminum foil, thickness 18 μm) and dried. This was cut into a predetermined size and rolled to obtain a positive electrode sheet having positive electrode active material layers on both surfaces of the positive electrode core. Note that the density of the positive electrode active material layers was 3.4 g / cm 3 , and the thickness was 110 μm on one side. In addition, the length in the length direction of the positive electrode sheet was 72 m, and the length in the width direction was 242 mm.

[0111] A graphite powder (C) as a negative electrode active material, styrene butadiene rubber (SBR) as a binder, and carboxymethyl cellulose (CMC) as a tackifier were weighed in a mass ratio of C:SBR:CMC = 98:1:1, mixed in water, and prepared into a negative electrode slurry. The negative electrode slurry was applied to both surfaces of a long strip-shaped negative electrode core (copper foil, 12 μm) and dried. This was cut into a predetermined size and rolled to obtain a negative electrode sheet having negative electrode active material layers on both surfaces of the negative electrode core. Note that the density of the negative electrode active material layers was 1.4 g / cm 3 , and the thickness was 200 μm on one side. In addition, the length in the length direction of the negative electrode sheet was 80 m, and the length in the width direction was 252 mm.

[0112] Next, the above-described positive electrode sheet and negative electrode sheet were stacked with a separator (separator sheet) interposed therebetween. By winding this in the sheet length direction, a wound electrode body as shown in FIG. 1 was prepared. Figure 4 Note that the separator had a base material composed of a porous layer made of polyolefin and a heat-resistant layer containing alumina and a resin binder. The thickness of the base material was 16 μm, and the thickness of the heat-resistant layer was 4 μm. In addition, the heat-resistant layer was formed on the side of the positive electrode sheet. In addition, the length in the length direction of the separator was 82 m, and the length in the width direction was 260 mm.

[0113] The dimensional relationship of the wound electrode body prepared as described above was as follows:

[0114] W: 8 mm;

[0115] L1: 260mm; and

[0116] H: 82mm

[0117] In addition, the reference numerals in the accompanying drawings are as follows: Figure 3 As described above. Specifically, W is the thickness of the wound electrode body 20. L1 is the width of the wound electrode body 20. H is the height of the wound electrode body 20.

[0118] Next, the wound electrode body is connected to the cover of the battery casing via the positive and negative current collectors. It is then inserted into the main body of the casing, and the main body is welded to the cover. Next, a non-aqueous electrolyte is injected through the injection hole of the battery casing (sealing plate). The non-aqueous electrolyte is prepared by dissolving LiPF6 as a supporting salt in a mixed solvent containing ethylene carbonate (EC), ethyl methyl carbonate (EMC), and dimethyl carbonate (DMC) at a volume ratio of EC:EMC:DMC = 30:40:30 (25°C, 1 atm), with a concentration of 0.3% by weight, and dissolving ethylene carbonate (VC) as an additive (coating forming agent). Thus, a test secondary battery assembly is constructed.

[0119] -Determination of residual gas content within the wound electrode body-

[0120] For the experimental secondary battery assembly constructed as described above, a non-aqueous electrolyte is further injected to fill the battery casing. In this state, a funnel is inserted into the injection hole of the battery casing. Next, a pair of restraining plates are used to restrain the experimental secondary battery assembly from both sides in the thickness direction (refer to...). Figure 7 The constraint force at this point is 0 kN (unconstrained), 6 kN, or 10 kN. Next, charging is initiated at 0.5 C under a nitrogen atmosphere and 1 atm. The liquid level in the funnel is observed from the start of charging until the depth of charge (SOC) reaches 12% of the specified capacity of the test secondary battery assembly. The volume of liquid level rise is then measured as the amount of gas remaining in the wound electrode body. The results are presented below. Figure 9 .

[0121] like Figure 9As shown, even with constraint forces of 0 kN, 6 kN, and 10 kN, gas is generated within the wound electrode body when the depth of charge of the test secondary battery assembly is at least 2% to 4%. In this test secondary battery assembly, the negative electrode potential is 0.6 V to 0.3 V when the depth of charge is 2% to 4%. Therefore, applying a larger constraint force to the secondary battery assembly when the negative electrode potential reaches 0.6 V than before it reaches 0.6 V, and maintaining this state until the negative electrode potential reaches at least 0.3 V, can better suppress plastic deformation of the battery casing. It should be noted that, as... Figure 9 As shown, the greater the constraint force, the less gas residue remains in the wound electrode body.

[0122] According to the technology disclosed herein, during the initial charging of a secondary battery assembly, when the negative electrode potential reaches 0.6V, a greater constraint force P1 than that before the negative electrode potential reaches 0.6V is applied to the secondary battery assembly, and the constraint force P1 is maintained on the secondary battery assembly until the negative electrode potential reaches at least 0.3V, thereby suppressing plastic deformation of the battery casing.

[0123] The non-aqueous electrolyte secondary battery 100 manufactured by the above method (refer to...) Figure 1 This suppresses plastic deformation of the battery casing. Specifically, in the non-aqueous electrolyte secondary battery 100, the expansion amount D1 of the bottom 12a of the outer casing 12 is less than 0.3% of the length of the outer casing 12 in the height direction Z. Here, the expansion amount D1 refers to the maximum deformation of the bottom 12a downwards in the height direction Z, with the periphery of the bottom 12a as a reference (zero). Furthermore, the indentation amount D2 of the large-area sidewall 12b is less than 5% of the length of the outer casing 12 in the depth direction X. Here, the indentation amount D2 refers to the maximum deformation of the large-area sidewall 12b in the depth direction X towards the inside of the outer casing 12, with the periphery of the large-area sidewall 12b as a reference (zero). Additionally, the expansion amount D3 of the small-area sidewall 12c is less than 0.1% of the length of the outer casing 12 in the width direction X. Here, expansion amount D3 refers to the maximum deformation of the small-area sidewall 12c in the width direction Y outward from the outer part of the outer body 12, with the periphery of the small-area sidewall 12c as the reference (zero).

[0124] Furthermore, according to the inventors' research, when the length of the negative electrode active material layer 24a in the winding axis direction of the wound electrode body 20 is at least 20 cm, gas retention in the central portion 201 of the wound electrode body 20 is more significant, which easily leads to uneven coating formation during initial charging. During initial charging, a high-quality coating (SEI coating) is formed on the surface of the negative electrode active material layer 24a. However, when gas exists between the negative electrode active material layer 24a and the separator 26, charging reaction is difficult to occur in that portion, hindering coating formation. The gas is released outside the wound electrode body 20 through subsequent high-temperature aging, etc. In the gas-released portion (the portion where coating formation is insufficient), for example, non-aqueous electrolyte components (e.g., LiPF6 as a supporting salt) react rapidly with the negative electrode active material due to high temperature. This results in the excessive formation of a non-high-quality coating with properties different from the original coating.

[0125] In the above manufacturing method, gas retention can be suppressed during initial charging through predetermined constraints, thus inhibiting the excessive formation of substandard coatings. This effect can be evaluated by laser ablation ICP-MS analysis of the negative electrode plate after high-temperature aging. Specifically, for example, the high-temperature aged non-aqueous electrolyte secondary battery is first charged to 100% depth of charge (full charge) at a current of approximately 0.5C. Then, it is discharged to 0% depth of charge at a current of approximately 0.5C. Next, the non-aqueous electrolyte secondary battery is disassembled, and the negative electrode plate is cleaned with a cleaning solution (e.g., 100 vol% dimethyl carbonate (DMC)) and dried.

[0126] For the dried negative electrode plate, LA-ICP-MS was used to... Figure 10 Linear analysis of phosphorus (P) is performed on line A as shown. (For example...) Figure 10 As shown, in the negative electrode tab 24t of the negative electrode plate 24, which is closest to the winding start end 24s, the winding shaft (refer to...) will be... Figure 4 One end of the root of the electrode in the orthogonal direction is designated as end B. The other end, different from end B, is designated as end C. The midpoint of the line segment BC connecting end B and end C is designated as midpoint E. The straight line passing through midpoint E and along the winding axis is designated as line A. It should be noted that the LA-ICP-MS device is not particularly limited. For example, ESI's NWR213 (LA) and Agilent Technologies' 7900 (ICP-MS) can be used in combination.

[0127] Furthermore, the following three points on line A were analyzed using LA-ICP-MS:

[0128] (1) The center P of the negative electrode active material layer 24a in the direction of its winding axis;

[0129] (2) a point Q that is 5 mm or more and 15 mm or less (for example, about 10 mm) from the center P toward the negative tab 24t side; and

[0130] (3) a point R that is 5 mm or more and 15 mm or less (for example, about 10 mm) from the center P toward the side opposite to the negative tab 24t

[0131] The phosphorus (P) contained in the negative electrode active material layer 24a collected is detected. In the nonaqueous electrolyte secondary battery 100 manufactured by the method disclosed herein, the intensity I1 of the phosphorus (P) in (1) is lower than the intensity I2 of the phosphorus (P) in (2) (I1≤I2) and is lower than the intensity I3 of the phosphorus (P) in (3) (I1≤I3). The ratio of I1 to I2 (I2 / I1) and the ratio of I1 to I3 (I3 / I1) are each preferably 1 or more (1.0 or more) and 2.5 or less, and more preferably 1 or more (1.0 or more) and 2.0 or less. Note that the center P is the intersection of the straight line A and the central line L of the negative electrode active material layer 24a in the winding axis direction.

[0132] In addition, the phosphorus (P) contained in the negative electrode active material layer 24a collected is detected by LA-ICP-MS at the following 2 points on the straight line A:

[0133] (4) a point S that is 10 mm or more and 20 mm or less (for example, about 15 mm) from the center P toward the negative tab 24t side (where the point S is closer to the outer side of the negative plate 24 than the point Q); and

[0134] (5) a point T that is 10 mm or more and 20 mm or less (for example, about 15 mm) from the center P toward the side opposite to the negative tab 24t (where the point T is closer to the outer side of the negative plate 24 than the point R)

[0135] The phosphorus (P) contained in the negative electrode active material layer 24a collected is detected. At this time, with respect to the intensity I4 of the phosphorus (P) in (4) and the intensity I5 of the phosphorus (P) in (5), the ratio of I1 to I4 (I4 / I1) and the ratio of I1 to I5 (I5 / I1) are each preferably 1 or more (1.0 or more) and 2.7 or less, and more preferably 1 or more (1.0 or more) and 2.0 or less. Note that the positions of the points (2) to (5) can be appropriately set within the above ranges in accordance with the size of the negative plate 24.

[0136] The above describes one embodiment of the technology disclosed herein. In addition, the above first embodiment indicates one example of a manufacturing method and a nonaqueous electrolyte secondary battery to which the technology disclosed herein is applied, and is not intended to limit the technology disclosed herein. Hereinafter, other embodiments of the technology disclosed herein will be described. In addition, in the following description, the same structure as that of the manufacturing method of the above first embodiment can be employed except for aspects specifically mentioned.

[0137] <Second Implementation Method>

[0138] In the first embodiment described above, such as Figure 7 As shown, a pair of large-area sidewalls 12b (refer to) of the battery housing 10 (outer body 12) Figure 1 A pair of constraint plates 80 are arranged facing each other in an overall manner. However, the shape, size, etc. of the constraint fixture are not limited as long as the effect of the technology disclosed herein can be achieved. For example, a pair of constraint plates 80 can be used. Figure 11 A constraint fixture 820 having a constraint plate 82 as shown. Figure 11 As shown, the secondary battery assembly 101 (constraint body 280) is clamped in the battery housing 10 using a pair of constraint plates 82, so as to apply a predetermined constraint force to the central portion 201 of the wound electrode body 20 in the depth direction X of the battery housing 10. When the constraint clamp 820 is used, a predetermined constraint force is applied to the central portion 201 of the wound electrode body 20, but no constraint force is applied to the ends 202 and 203. By selectively applying a constraint force to the central portion 201, gas retention in the central portion 201 can be better suppressed. Furthermore, the manufacturing method of the second embodiment can be the same as the manufacturing method of the first embodiment, except that the constraint clamp 820 is used.

[0139] <Third Implementation Method>

[0140] Alternatively, you can also use Figure 12 The constraint fixture 830, as shown, has a constraint plate 83. Figure 12 As shown, a pair of constraint plates 83 can be used to clamp the secondary battery assembly 101 (constraint body 380) in the depth direction X of the battery casing 10. The constraint plate 83 has a flat wide surface 83a and a curved surface 83b facing the wide surface 83a. The curved surface 83b faces the large-area sidewall 12b of the battery casing 10 and bends towards the large-area sidewall 12b. The constraint portion 831, including the bend vertex 83t of the curved surface 83b, is in contact with the large-area sidewall 12b. The position of the bend vertex 83t and the length of the constraint portion 831 in the width direction Y are not particularly limited, and can be appropriately set in a way that a predetermined constraint force is applied to the central portion 201 of the wound electrode body 20 by constraint. The other parts of the curved surface 83b, except for the constraint portion 831, are not in contact with the large-area sidewall 12b. When the constraint jig 830 is used, a predetermined constraint force is applied to the central portion 201 of the wound electrode body 20, but no constraint force is applied to the ends 202 and 203. By selectively applying a constraint force to the central portion 201, gas retention in the central portion 201 can be better suppressed. Furthermore, the manufacturing method of the third embodiment can be the same as the manufacturing method of the first embodiment, except that the constraint jig 830 is used.

[0141] The above detailed description sets forth numerous specific details of the technology disclosed herein. However, these specifics are only intended to provide an overview of the technology disclosed herein. The technology disclosed herein includes all modifications and variations of the specific examples described herein as within the scope of the technology disclosed herein.

Claims

1. A method for manufacturing a nonaqueous electrolyte secondary battery, the nonaqueous electrolyte secondary battery having a flat-shaped wound electrode body in which a strip-shaped positive electrode plate and a strip-shaped negative electrode plate are wound with a strip-shaped separator interposed, a nonaqueous electrolyte, and a battery case that accommodates the wound electrode body and the nonaqueous electrolyte, wherein The manufacturing method has: an assembly step in which the wound electrode body and the nonaqueous electrolyte solution are housed in the battery case to construct a secondary battery assembly; and an initial charging step in which the secondary battery assembly is initially charged, Here, in the initial charging step, the initial charging is started in a state in which the secondary battery assembly is restrained or not restrained in a thickness direction of the wound electrode body, and at a potential of the negative electrode of the secondary battery assembly with respect to vs. Li / Li + at a potential of the negative electrode of the secondary battery assembly with respect to vs. Li / Li + at a potential of the negative electrode of the secondary battery assembly with respect to vs. Li / Li The initial charging step includes the following steps: applying a constraint force P1 to the secondary battery assembly when the negative electrode potential reaches 0.3 V vs. Li / Li + applying a constraint force P2 to the secondary battery assembly when the negative electrode potential reaches 0.3 V, P2 / P1, which is a ratio of the restraint force P1 to the restraint force P2, is 0.8 or greater and 1.2 or less.

2. The manufacturing method of the nonaqueous electrolyte secondary battery according to claim 1, wherein the restraint force P1 is 3 kN or greater and 15 kN or less.

3. The manufacturing method of the nonaqueous electrolyte secondary battery according to claim 1 or 2, wherein both ends in the thickness direction of the wound electrode body are constituted by wide flat portions, the flat portions have a central portion including a center line in a winding axis direction of the wound electrode body and two end portions sandwiching the central portion in the winding axis direction, in the initial charging step, a restraint force is applied to the central portion, and no restraint force is applied to the two end portions.

4. The manufacturing method of the nonaqueous electrolyte secondary battery according to claim 1 or 2, wherein the negative electrode plate has a negative electrode core and a negative electrode active material layer formed on the negative electrode core, a length of the negative electrode active material layer in the winding axis direction of the wound electrode body is at least 20 cm.

5. The manufacturing method of the nonaqueous electrolyte secondary battery according to claim 1 or 2, wherein an adhesive layer that is adhered to the positive electrode plate or the negative electrode plate is provided on at least one surface of the separator.

6. The manufacturing method of the nonaqueous electrolyte secondary battery according to claim 1 or 2, wherein the battery case has an outer body that includes an opening and a bottom portion facing the opening, and a sealing plate that seals the opening, the wound electrode body is disposed in the outer body in an orientation in which a winding axis is parallel to the bottom portion.

7. The manufacturing method of the nonaqueous electrolyte secondary battery according to claim 1 or 2, wherein the battery case has a pair of large-area side walls facing each other and a pair of small-area side walls facing each other and having an area smaller than that of the large-area side walls, a distance between the pair of large-area side walls is at least 3 cm, a plurality of the wound electrode bodies are housed in the battery case.

8. The manufacturing method of the nonaqueous electrolyte secondary battery according to claim 1 or 2, wherein the nonaqueous electrolyte secondary battery has a positive electrode current collector and a negative electrode current collector that are electrically connected to the wound electrode body, a positive electrode tab group including a plurality of tabs that project toward one end portion in a winding axis direction of the wound electrode body, and a negative electrode tab group including a plurality of tabs that project toward the other end portion in the winding axis direction, the positive electrode current collector is connected to the positive electrode tab group, and the negative electrode current collector is connected to the negative electrode tab group.

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