Manufacturing method of non-aqueous electrolyte secondary battery

Abstract

To provide a manufacturing method capable of promoting the impregnation of a non-aqueous electrolyte into a wound electrode body.SOLUTION: A manufacturing method disclosed herein includes a construction step of housing a wound electrode body and a nonaqueous electrolyte in a battery case to construct a battery assembly, and a pressurizing step of, after the construction step, placing the battery assembly in a chamber with the battery case open, changing the pressure in the chamber to increase the pressure in the battery case to 0.4 MPa or more, and maintaining the state in which the pressure in the battery case is 0.4 MPa or more for 20 minutes or more.SELECTED DRAWING: Figure 9

Description

[Technical Field]

[0001] The present invention relates to a method for manufacturing a non-aqueous electrolyte secondary battery. [Background technology]

[0002] In the manufacture of a non-aqueous electrolyte secondary battery including an electrode assembly, a non-aqueous electrolyte, and a battery case that houses the electrode assembly and the non-aqueous electrolyte, studies have been conducted to efficiently inject the non-aqueous electrolyte into the battery case and to rapidly permeate the non-aqueous electrolyte into the electrode assembly. Related prior art documents include Patent Documents 1 to 3.

[0003] For example, Patent Document 1 describes that in a liquid injection step of injecting a nonaqueous electrolyte into a battery case, the pressure inside the battery case is reduced to a low pressure state and maintained for a certain period of time, and then the pressure is gradually increased to a high pressure state, thereby enabling the nonaqueous electrolyte to be filled in a short period of time. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2002-033114 [Patent Document 2] Japanese Patent Application Laid-Open No. 2007-165170 [Patent Document 3] Patent No. 5683938 Summary of the Invention [Problem to be solved by the invention]

[0005] However, according to the inventors' investigations, there is still room for improvement when applying the above technology to non-aqueous electrolyte secondary batteries equipped with recent high-capacity electrode assemblies, particularly wound electrode assemblies. That is, since the wound electrode assemblies are only open at both ends in the winding axis direction, non-aqueous electrolyte is only supplied to the interior from these ends. Furthermore, in recent high-capacity wound electrode assemblies, the length (width) in the winding axis direction is significantly longer than conventional ones, for example, 20 cm or more. For this reason, the central part of the wound electrode assemblies in the winding axis direction is particularly difficult to impregnate with non-aqueous electrolyte. This poses a problem that the time required for impregnation during manufacturing may be excessively long or impregnation may be insufficient, resulting in a deterioration in battery characteristics.

[0006] The present invention has been made in view of the above circumstances, and has an object to provide a method for manufacturing a nonaqueous electrolyte secondary battery that can promote impregnation of a nonaqueous electrolyte into a wound electrode body. [Means for solving the problem]

[0007] The present invention provides a method for producing a non-aqueous electrolyte secondary battery comprising: a wound electrode assembly including a positive electrode and a negative electrode, a non-aqueous electrolyte, and a battery case containing the wound electrode assembly and the non-aqueous electrolyte, wherein the positive electrode comprises a positive electrode current collector and a positive electrode active material layer formed on the positive electrode current collector, and the negative electrode comprises a negative electrode current collector and a negative electrode active material layer formed on the negative electrode current collector, and the width of the negative electrode active material layer in the direction of the winding axis is 20 cm or more. This production method includes: a construction step of constructing a battery assembly by containing the wound electrode assembly and the non-aqueous electrolyte in the battery case; and a pressurization step of, after the construction step, placing the battery assembly in an internal pressure-adjustable chamber with the battery case open, and changing the pressure in the chamber to pressurize the battery case until the pressure in the battery case is 0.4 MPa or more, and maintaining the pressure in the battery case at 0.4 MPa or more for 20 minutes or more.

[0008] The inclusion of the pressurizing step can promote impregnation of the nonaqueous electrolyte into the wound electrode body. Therefore, even with the recent high-capacity wound electrode bodies, the nonaqueous electrolyte can penetrate to the center in the winding axis direction in a relatively short time compared to when the pressurizing step is not included. Therefore, batteries can be manufactured efficiently and deterioration of battery characteristics due to insufficient impregnation of the nonaqueous electrolyte can be suppressed. [Brief explanation of the drawings]

[0009] [Figure 1] FIG. 1 is a perspective view schematically showing a nonaqueous electrolyte secondary battery according to one embodiment. [Figure 2] FIG. 2 is a schematic vertical cross-sectional view taken along line II-II in FIG. [Figure 3] FIG. 3 is a schematic cross-sectional view taken along line III-III in FIG. [Figure 4] FIG. 4 is a perspective view that schematically shows an electrode assembly attached to a sealing plate. [Figure 5] FIG. 5 is a perspective view that schematically shows a wound electrode body. [Figure 6] FIG. 6 is a schematic diagram showing the configuration of a wound electrode body. [Figure 7] FIG. 7 is a flowchart of a manufacturing method according to one embodiment. [Figure 8] FIG. 8 is a schematic diagram of a pressure adjusting device according to one embodiment. [Figure 9] FIG. 9 is a graph showing the transition of pressure in the pressurizing step according to one embodiment. [Figure 10] FIG. 10 is a graph showing the relationship between the impregnation rate and the applied pressure in Test Example I. [Figure 11] FIG. 11 is a graph showing the relationship between the impregnation rate and the pressure holding time in Test Example I. DETAILED DESCRIPTION OF THE INVENTION

[0010] Hereinafter, some preferred embodiments of the technology disclosed herein will be described with reference to the drawings. It should be noted that matters necessary for carrying out the present invention other than those specifically mentioned in this specification (e.g., the general configuration and manufacturing process of non-aqueous electrolyte secondary batteries that do not characterize the present invention) can be understood as design matters for those skilled in the art based on the prior art in the relevant field. The present invention can be carried out based on the contents disclosed in this specification and the technical common sense in the relevant field. In this specification, the expression "A to B" indicating a range includes not only the meaning of A or more but also the meaning of "greater than A" and "smaller than B." In addition, in this specification, "pressure" refers to gauge pressure based on atmospheric pressure (i.e., the difference obtained by subtracting atmospheric pressure from absolute pressure).

[0011] In this specification, the term "nonaqueous electrolyte secondary battery" refers to a general electricity storage device that can be repeatedly charged and discharged by the movement of charge carriers between a positive electrode and a negative electrode via a nonaqueous electrolyte. The term "nonaqueous electrolyte secondary battery" encompasses storage batteries such as lithium ion secondary batteries and capacitors such as lithium ion capacitors and electric double layer capacitors.

[0012] <Battery 100> First, the configuration of a nonaqueous electrolyte secondary battery manufactured by the technology disclosed herein will be described. FIG. 1 is a perspective view of a nonaqueous electrolyte secondary battery (hereinafter simply referred to as a battery) 100. FIG. 2 is a schematic longitudinal sectional view taken along line II-II in FIG. 1. FIG. 3 is a schematic transverse sectional view taken along line III-III in FIG. 1. In the following description, the symbols L, R, F, Rr, U, and D in the drawings represent left, right, front, rear, top, and bottom, and the symbols X, Y, and Z in the drawings represent the short side direction, long side direction perpendicular to the short side direction, and height direction perpendicular to the short side and long side directions, respectively, of the battery 100. However, these directions are merely used for convenience of description and do not limit the installation form of the battery 100 in any way.

[0013] 2, the battery 100 includes a battery case 10, an electrode assembly 20, a positive electrode terminal 30, a negative electrode terminal 40, and a non-aqueous electrolyte (not shown). The battery 100 here is a lithium ion secondary battery. The battery 100 is preferably a lithium ion secondary battery.

[0014] The battery case 10 is a housing that houses the electrode assembly 20 and the nonaqueous electrolyte. As shown in FIG. 1, the battery case 10 has a flat, bottomed, rectangular parallelepiped (rectangular) outer shape. The material of the battery case 10 may be the same as that conventionally used, and is not particularly limited. The battery case 10 is preferably made of metal, and more preferably made of, for example, aluminum, an aluminum alloy, iron, an iron alloy, or the like. As shown in FIG. 2, the battery case 10 has an exterior body 12 having an opening 12h and a sealing plate (lid) 14 that closes the opening 12h. The battery case 10 preferably has an exterior body 12 and a sealing plate 14.

[0015] As shown in Fig. 1, the exterior body 12 includes a substantially rectangular bottom wall 12a, a pair of long side walls 12b extending from the long sides of the bottom wall 12a and facing each other, and a pair of short side walls 12c extending from the short sides of the bottom wall 12a and facing each other. The long side walls 12b and the short side walls 12c are examples of side walls extending from the edges of the bottom wall toward the opening. The area of ​​the long side walls 12b is larger than the area of ​​the short side walls 12c. In this specification, the term "substantially rectangular" is intended to encompass not only a perfect rectangular shape (rectangular shape) but also shapes in which the corners connecting the long and short sides of the rectangle are rounded or have notches at the corners.

[0016] As shown in Fig. 1, the sealing plate 14 has a substantially rectangular shape in a plan view. As shown in Fig. 2, the sealing plate 14 is attached to the exterior body 12 so as to close the opening 12h of the exterior body 12. The sealing plate 14 faces the bottom wall 12a of the exterior body 12. The battery case 10 is integrated by joining (for example, welding) the sealing plate 14 to the periphery of the opening 12h of the exterior body 12. The battery case 10 is hermetically sealed (sealed).

[0017] As shown in FIG. 2, the sealing plate 14 is provided with a liquid inlet 15, a gas release valve 17, and two terminal holes 18 and 19. The liquid inlet 15 is a through-hole that penetrates the sealing plate 14 in the thickness direction (height direction Z). The liquid inlet 15 is used to inject non-aqueous electrolyte after the sealing plate 14 is assembled to the exterior body 12. The sealing plate 14 preferably has the liquid inlet 15. The liquid inlet 15 is sealed with a sealing member 16 after the non-aqueous electrolyte is injected. The gas release valve 17 is configured to rupture when the pressure inside the battery case 10 reaches or exceeds a predetermined value, thereby releasing gas inside the battery case 10 to the outside. The terminal holes 18 and 19 are formed at both ends of the sealing plate 14 in the long side direction Y (the left and right ends in FIG. 2). The terminal holes 18 and 19 penetrate the sealing plate 14 in the thickness direction (height direction Z). The terminal pull-out holes 18, 19 have inner diameters large enough to allow the positive electrode terminal 30 and the negative electrode terminal 40 to be inserted therethrough before being attached to the sealing plate 14 (before being crimped).

[0018] The positive electrode terminal 30 and the negative electrode terminal 40 are each fixed to the sealing plate 14 of the battery case 10. The positive electrode terminal 30 is disposed on one side of the sealing plate 14 in the long side direction Y (the left side in FIGS. 1 and 2). The negative electrode terminal 40 is disposed on the other side of the sealing plate 14 in the long side direction Y (the right side in FIGS. 1 and 2). As shown in FIG. 2, the positive electrode terminal 30 extends from the inside to the outside of the sealing plate 14 through the terminal lead-out hole 18. The negative electrode terminal 40 extends from the inside to the outside of the sealing plate 14 through the terminal lead-out hole 19. The positive electrode terminal 30 and the negative electrode terminal 40 are preferably attached to the sealing plate 14. Here, the positive electrode terminal 30 and the negative electrode terminal 40 are crimped to the peripheral portions of the sealing plate 14 surrounding the terminal lead-out holes 18 and 19 by crimping. The positive electrode terminal 30 and the negative electrode terminal 40 have crimped portions 30c, 40c formed at their ends on the exterior body 12 side (lower ends in FIG. 2).

[0019] As shown in Fig. 2, the positive electrode terminal 30 is electrically connected to the positive electrode 22 (see Fig. 6, specifically, the positive electrode tab group 23) of the electrode body group 20 inside the battery case 10 via the positive electrode current collecting portion 50. The positive electrode terminal 30 is insulated from the sealing plate 14 by an insulating member 80 and a gasket 90. The positive electrode terminal 30 is preferably made of metal, and more preferably made of, for example, aluminum or an aluminum alloy.

[0020] The negative electrode terminal 40 is electrically connected to the negative electrode 24 (see FIG. 6 , specifically, the negative electrode tab group 25) of the electrode body group 20 via the negative electrode current collector 60 inside the battery case 10. The negative electrode terminal 40 is insulated from the sealing plate 14 by an insulating member 80 and a gasket 90. The negative electrode terminal 40 is preferably made of metal, and more preferably made of copper or a copper alloy, for example. The negative electrode terminal 40 may be formed by joining two conductive members together. For example, the portion of the negative electrode terminal 40 that is connected to the negative electrode current collector 60 may be made of copper or a copper alloy, and the portion that is exposed on the outer surface of the sealing plate 14 may be made of aluminum or an aluminum alloy.

[0021] A plate-shaped positive electrode external conductive member 32 and a plate-shaped negative electrode external conductive member 42 are attached to the outer surface of the sealing plate 14. The positive electrode external conductive member 32 and the plate-shaped negative electrode external conductive member 42 are members to which bus bars are attached when electrically connecting multiple batteries 100 to each other. The positive electrode external conductive member 32 is electrically connected to the positive electrode terminal 30. The negative electrode external conductive member 42 is electrically connected to the negative electrode terminal 40. The positive electrode external conductive member 32 and the plate-shaped negative electrode external conductive member 42 are insulated from the sealing plate 14 by an external resin member 92. The positive electrode external conductive member 32 and the plate-shaped negative electrode external conductive member 42 are preferably made of metal, more preferably aluminum or an aluminum alloy. However, the positive electrode external conductive member 32 and the plate-shaped negative electrode external conductive member 42 are not essential and may be omitted in other embodiments.

[0022] As shown in FIG. 2, the electrode assembly group 20 is housed inside the battery case 10 (more specifically, inside the exterior body 12). FIG. 4 is a perspective view schematically showing the electrode assembly group 20 attached to the sealing plate 14. Here, the electrode assembly group 20 has three wound electrode assemblies 20a, 20b, and 20c. When multiple wound electrode assemblies 20a, 20b, and 20c are arranged inside one battery case 10, it may be difficult for the wound electrode assembly 20b, located in the center in the short side direction X, to be impregnated with the nonaqueous electrolyte. Therefore, it is particularly effective to apply the technology disclosed herein. However, the number of wound electrode assemblies arranged inside one battery case 10 is not particularly limited and may be two or more (plural), or may be one. The electrode assembly group 20 may be arranged inside the battery case 10 while covered with an insulating electrode assembly holder. In other words, an electrode assembly holder may be interposed between the electrode assembly group 20 and the battery case 10 (specifically, the exterior body 12). The electrode assembly holder is preferably made of resin.

[0023] FIG. 5 is a perspective view schematically showing the wound electrode body 20a. FIG. 6 is a schematic diagram showing the configuration of the wound electrode body 20a. Note that the wound electrode body 20a will be described in detail below as an example, but the wound electrode bodies 20b and 20c can also have a similar configuration. The wound electrode body 20a includes a positive electrode 22 and a negative electrode 24. As shown in FIG. 6, the wound electrode body 20a is preferably configured by stacking a strip-shaped positive electrode 22 and a strip-shaped negative electrode 24 with a strip-shaped separator 26 interposed therebetween and winding them around a winding axis WL. Although not particularly limited, the number of windings (number of turns) of the wound electrode body 20a is preferably 20 turns or more, more preferably 30 turns or more, and even more preferably 50 turns or more, and can be, for example, 150 turns or less, or 100 turns or less. As the number of windings increases, it becomes more difficult for the nonaqueous electrolyte to penetrate into the central portion of the wound electrode body 20a (the central portion in the short side direction X and the central portion in the long side direction Y). Therefore, applying the technology disclosed herein is particularly effective.

[0024] As can be seen from FIGS. 2 and 6, the wound electrode body 20a is disposed inside the battery case 10 with the winding axis WL oriented along the bottom wall 12a (in other words, oriented approximately parallel to the long side direction Y). The direction of the winding axis WL coincides with the long side direction Y. The wound electrode body 20a is disposed inside the battery case 10 with the winding axis WL oriented perpendicular to the short side wall 12c. A pair of end faces (opening ends) of the wound electrode body 20a in the winding axis WL direction face the pair of short side walls 12c of the exterior body 12, respectively. The end faces of the wound electrode body 20a in the winding axis WL direction serve as inlets through which the nonaqueous electrolyte flows in. In such cases, it is particularly effective to apply the technology disclosed herein.

[0025] Here, the battery 100 has a so-called horizontal tab structure in which the positive electrode tab group 23 and the negative electrode tab group 25 are located at both ends of the wound electrode body 20a in the winding axis WL direction (left and right in FIGS. 2 and 4). However, in other embodiments, the battery 100 may have a so-called top tab structure in which the positive electrode tab group 23 and the negative electrode tab group 25 are located at one end of the wound electrode body 20a in the winding axis WL direction (for example, the top end in FIGS. 2 and 4). In this case, the winding axis WL direction may coincide with the height direction Z.

[0026] The wound electrode body 20a preferably has a flat outer shape, as shown in Fig. 5. The wound electrode body 20a has a pair of flat portions 20f extending along the long side direction Y (winding axis WL direction) and a pair of curved portions (R portions) 20r connecting the pair of flat portions 20f. The flat portions 20f have a flat outer surface (the YZ plane in Fig. 5). The curved portions 20r have a curved outer surface. Note that in this specification, the term "flat outer surface" is not limited to a completely flat surface, and includes cases where, for example, when viewed microscopically, there are slight steps, curves, recesses, protrusions, etc.

[0027] 2 and 5, the pair of flat portions 20f face the pair of long side walls 12b of the exterior body 12. The flat portions 20f extend along the long side walls 12b. The pair of curved portions 20r face the bottom wall 12a and the sealing plate 14 of the exterior body 12. As in this embodiment, the wound electrode body 20a is preferably disposed inside the battery case 10 such that the stacking direction (thickness direction) of the positive electrode 22 (see FIG. 6) and the negative electrode 24 (see FIG. 6) in the flat portions 20f coincides with the short side direction X (the direction perpendicular to the long side walls 12b).

[0028] Although not particularly limited, as shown in FIG. 5, in a high-capacity battery 100 used in a vehicle or the like, the height Ta of the wound electrode body 20a (the length from the lower end of the curved portion 20r on the bottom wall 12a side to the upper end of the curved portion 20r on the sealing plate 14 side) is preferably 12 cm or less, more preferably 6 to 12 cm, even more preferably 8 to 11 cm, and particularly preferably 9 to 10 cm.

[0029] The positive electrode 22 may be the same as a conventional one and is not particularly limited. As shown in FIG. 6, the positive electrode 22 has a positive electrode current collector 22c, a positive electrode active material layer 22a and a positive electrode protective layer 22p adhered to at least one surface of the positive electrode current collector 22c. However, the positive electrode protective layer 22p is not essential and may be omitted in other embodiments. The positive electrode current collector 22c is strip-shaped. The positive electrode current collector 22c is made of a conductive metal such as aluminum, an aluminum alloy, nickel, or stainless steel. In this example, the positive electrode current collector 22c is a metal foil, specifically, an aluminum foil.

[0030] A plurality of positive electrode tabs 22t are provided at one end of the positive electrode current collector 22c in the long side direction Y (the left end in FIG. 6). The plurality of positive electrode tabs 22t each protrude toward one side in the long side direction Y (the left side in FIG. 6). The plurality of positive electrode tabs 22t protrude further in the long side direction Y than the separator 26. The plurality of positive electrode tabs 22t are provided at intervals (intermittently) along the longitudinal direction of the positive electrode 22. Providing a plurality of positive electrode tabs 22t can reduce the resistance of the battery 100. Here, the positive electrode tab 22t is part of the positive electrode current collector 22c and is made of metal foil (aluminum foil). Preferably, the positive electrode tab 22t is a current collector exposed portion where the positive electrode active material layer 22a and the positive electrode protective layer 22p are not formed on at least a portion of the positive electrode tab 22t and the positive electrode current collector 22c is exposed.

[0031] As shown in FIG. 3, the positive electrode tabs 22t are stacked at one end in the long side direction Y (the left end in FIG. 3) to form a positive electrode tab group 23. The positive electrode tabs 22t are stacked and bent so that their outer ends are aligned. This improves the fitment into the battery case 10 and allows the battery 100 to be miniaturized. It also improves the volumetric energy density of the battery 100. A positive electrode current collector 50 is attached (more specifically, joined) to the positive electrode tab group 23. The positive electrode tab group 23 is electrically connected to the positive electrode terminal 30 via the positive electrode current collector 50. The positive electrode current collector 50 may be made of the same metal as the positive electrode current collector 22c, such as a conductive metal such as aluminum, an aluminum alloy, nickel, or stainless steel. A joint J between the positive electrode current collector 50 and the positive electrode tab group 23 is formed on the positive electrode current collector 50. The joint J is, for example, a welded joint formed by welding such as ultrasonic welding, resistance welding, or laser welding in a state where a plurality of positive electrode tabs 22t are stacked.

[0032] As shown in Fig. 6, the positive electrode active material layer 22a is provided in a strip shape along the longitudinal direction of the strip-shaped positive electrode current collector 22c. The positive electrode active material layer 22a contains a positive electrode active material (e.g., lithium transition metal composite oxide) that can reversibly store and release charge carriers. The positive electrode active material layer 22a may further contain optional components other than the positive electrode active material, such as a conductive material, a binder, and various additive components. As the conductive material, for example, a carbon material such as acetylene black (AB) can be used. As the binder, for example, polyvinylidene fluoride (PVdF) can be used.

[0033] Although not particularly limited, in a high-capacity battery 100 used in a vehicle or the like, the width of the positive electrode active material layer 22a in the direction of the winding axis WL (average value, excluding the portion formed on the positive electrode tab 22t), in other words, the length Lc in the long side direction Y, is preferably 15 cm or more, more preferably 20 cm or more, and even more preferably 25 cm or more.

[0034] As shown in FIG. 6, the positive electrode protective layer 22p is provided between the positive electrode current collector 22c and the positive electrode active material layer 22a in the long side direction Y. Here, the positive electrode protective layer 22p is provided at one end of the positive electrode current collector 22c in the long side direction Y (the left end in FIG. 6). The positive electrode protective layer 22p is provided in a strip shape along the positive electrode active material layer 22a. The positive electrode protective layer 22p contains an inorganic filler (e.g., alumina). The positive electrode protective layer 22p may contain optional components other than the inorganic filler, such as a conductive material, a binder, various additive components, etc. The conductive material and binder may be the same as those exemplified as those that may be contained in the positive electrode active material layer 22a.

[0035] The negative electrode 24 may be the same as a conventional negative electrode 24 and is not particularly limited. As shown in FIG. 6, the negative electrode 24 has a negative electrode current collector 24c and a negative electrode active material layer 24a fixed to at least one surface of the negative electrode current collector 24c. The negative electrode current collector 24c is strip-shaped. The negative electrode current collector 24c is made of a conductive metal such as copper, a copper alloy, nickel, or stainless steel. In this example, the negative electrode current collector 24c is a metal foil, specifically a copper foil.

[0036] A plurality of negative electrode tabs 24t are provided at one end of the negative electrode current collector 24c in the long side direction Y (the right end in FIG. 6). The plurality of negative electrode tabs 24t each protrude toward one side in the long side direction Y (the right side in FIG. 6). The plurality of negative electrode tabs 24t protrude further in the long side direction Y than the separator 26. The plurality of negative electrode tabs 24t are provided at intervals (intermittently) along the longitudinal direction of the negative electrode 24. Providing a plurality of negative electrode tabs 24t can reduce the resistance of the battery 100. Here, the negative electrode tab 24t is part of the negative electrode current collector 24c and is made of metal foil (copper foil). The negative electrode tab 24t is preferably a current collector exposed portion where the negative electrode active material layer 24a is not formed on at least a portion and the negative electrode current collector 24c is exposed.

[0037] As shown in FIG. 3 , multiple negative electrode tabs 24t are stacked at one end in the long side direction Y (the right end in FIG. 3 ) to form a negative electrode tab group 25. The multiple negative electrode tabs 24t are stacked and bent and curved so that their outer ends are aligned. This improves the fitment into the battery case 10 and allows the battery 100 to be miniaturized. It also improves the volumetric energy density of the battery 100. A negative electrode current collector 60 is attached (more specifically, joined) to the negative electrode tab group 25. The negative electrode tab group 25 is electrically connected to the negative electrode terminal 40 via the negative electrode current collector 60. The negative electrode current collector 60 may be made of the same metal as the negative electrode current collector 24c, such as a conductive metal such as copper, a copper alloy, nickel, or stainless steel. A joint J with the negative electrode tab group 25 is formed on the negative electrode current collector 60. The joint J is a welded joint formed by welding such as ultrasonic welding, resistance welding, or laser welding in a state where a plurality of negative electrode tabs 24t are stacked, as in the case of the positive electrode side.

[0038] As shown in Fig. 6, the negative electrode active material layer 24a is provided in a strip shape along the longitudinal direction of a strip-shaped negative electrode current collector 24c. The negative electrode active material layer 24a contains a negative electrode active material (e.g., a carbon material such as graphite, or a silicon-containing material) that can reversibly store and release charge carriers. The negative electrode active material layer 24a may further contain optional components other than the negative electrode active material, such as a binder and various additive components. Examples of binders that can be used include rubbers such as styrene butadiene rubber (SBR) and celluloses such as carboxymethyl cellulose (CMC).

[0039] The width of the negative electrode active material layer 24a in the winding axis WL direction (average value, excluding the portion formed on the negative electrode tab 24t), in other words, the length La in the long side direction Y, is typically the same as or longer than the length Lc in the long side direction Y of the positive electrode active material layer 22a. From the viewpoint of achieving high capacity, the length La is 20 cm or more here. The length La is more preferably 25 cm or more. In the wound electrode body 20a, the nonaqueous electrolyte is supplied only from both ends in the long side direction Y (winding axis WL direction). Therefore, the longer the length La, the more difficult it is for the nonaqueous electrolyte to penetrate into the center portion in the long side direction Y. Therefore, applying the technology disclosed herein is particularly effective. The length La may be, for example, 100 cm or less, or 50 cm or less. This allows the effects of the technology disclosed herein to be exerted to a high level.

[0040] As shown in FIG. 6 , the separator 26 is a member that insulates the positive electrode active material layer 22 a of the positive electrode 22 from the negative electrode active material layer 24 a of the negative electrode 24. The width of the separator 26 in the winding axis WL direction, in other words, the length Ls of the long side direction Y, is typically equal to or longer than the length La of the negative electrode active material layer 24 a in the long side direction Y. The separator 26 is preferably a porous resin sheet made of a polyolefin resin such as polyethylene (PE) or polypropylene (PP). The separator 26 may have a functional layer, such as an adhesive layer or a heat-resistant layer (HRL), on the surface of the substrate portion made of a porous resin sheet. The adhesive layer and the heat-resistant layer may have the same configuration as conventional ones. The adhesive layer is a layer containing a binder. The heat-resistant layer is a layer containing, for example, an inorganic filler such as alumina, silica, boehmite, magnesia, or titania, and a binder such as PVdF. The heat-resistant layer may also serve as an adhesive layer.

[0041] The non-aqueous electrolyte typically contains a non-aqueous solvent and a supporting salt (electrolyte salt). As the non-aqueous solvent, one or more of those known to be usable in non-aqueous electrolyte secondary batteries can be used. Examples of the non-aqueous solvent include organic solvents such as carbonates, ethers, esters, nitriles, sulfones, and lactones. The non-aqueous solvent preferably contains a carbonate. Examples of the carbonate include linear carbonates such as ethylene carbonate (EC), dimethyl carbonate (DMC), diethyl carbonate (DEC), and ethyl methyl carbonate (EMC), and cyclic carbonates such as propylene carbonate (PC).

[0042] The supporting salt is not particularly limited as long as it contains a charge carrier (typically lithium ion), and one or more salts known to be usable in non-aqueous electrolyte secondary batteries can be used. Examples of the supporting salt include fluorine-containing lithium salts such as LiPF6 and LiBF4. The supporting salt preferably contains LiPF6. The non-aqueous electrolyte may further contain additional components (additives).

[0043] <Method of manufacturing the battery 100> FIG. 7 is a flowchart of a manufacturing method according to one embodiment. As shown in FIG. 7, the manufacturing method according to this embodiment includes the following steps, in this order: a construction step (step S10); a pressurization step (step S20); a depressurization step (step S30); an initial charging step (step S40); and a sealing step (step S50). However, the depressurization step (step S30) is optional and may be omitted in other embodiments. The order of the initial charging step (step S40) and the sealing step (step S50) may also be reversed. Furthermore, other steps may be included at any stage.

[0044] The construction step (step S10) is a step of constructing a battery assembly 100A by housing an electrode body group 20 (wound electrode assemblies 20a, 20b, 20c) and a non-aqueous electrolyte solution in a battery case 10. This step is typically performed in a glove box under atmospheric pressure and at room temperature (for example, approximately 25°C ± 10°C or 25°C ± 5°C). In this specification, the term "battery assembly" refers to an intermediate product assembled to a state prior to the initial charging step (step S40) in the manufacturing process of the battery 100. The order in which the electrode body group 20 and the non-aqueous electrolyte solution are housed in the battery case 10 is not particularly limited. This step here includes an arrangement step (step S11) and a liquid injection step (step S12), in this order.

[0045] The arrangement step (step S11) is a step of arranging the electrode assembly group 20 (wound electrode assemblies 20a, 20b, 20c) inside the battery case 10. In this step, for example, first, as shown in FIG. 4, an assembly is produced in which the sealing plate 14 and the electrode assembly group 20 are integrated. Next, the sealing plate 14 is fitted into the opening 12h of the exterior body 12, thereby accommodating the electrode assembly group 20 inside the exterior body 12. As a result, the wound electrode assemblies 20a, 20b, 20c are accommodated inside the exterior body 12 with the winding axis WL oriented along the bottom wall 12a, as shown in FIG. 2. Next, the sealing plate 14 is welded to the periphery of the opening 12h of the exterior body 12, thereby integrating the exterior body 12 and the sealing plate 14.

[0046] Before or after integrating the exterior body 12 and the sealing plate 14, moisture may be removed from the interior of the exterior body 12 (particularly from the interior of the electrode assembly 20) using a heating and drying device, a vacuum drying device, or the like, with the liquid injection hole 15 open. In this case, the heating temperature is preferably set to approximately 200°C or less, for example, within the range of 50 to 200°C.

[0047] The liquid injection step (step S12) is a step of injecting nonaqueous electrolyte through the liquid injection hole 15 provided in the sealing plate 14 after the arrangement step (step S11). In this step, for example, first, a nonaqueous electrolyte is prepared. Then, a predetermined amount of nonaqueous electrolyte is injected through the liquid injection hole 15 into the inside of the battery case 10 containing the electrode body group 20 (wound electrode bodies 20a, 20b, 20c). The predetermined amount of nonaqueous electrolyte may be injected all at once, or may be dispensed in multiple stages, divided into two or more stages (for example, two or three stages). When dispensing in multiple stages, it is preferable to provide a certain period of time between the first liquid injection and the second liquid injection. By providing a period of time of time of time of leaving, the nonaqueous electrolyte can be suitably impregnated into the inside of the wound electrode bodies 20a, 20b, 20c, so the liquid level of the nonaqueous electrolyte drops, and a larger amount of nonaqueous electrolyte can be injected in the liquid injection (second liquid injection) after leaving. This step may be carried out under atmospheric pressure, or may be carried out under a pressure reduced below atmospheric pressure within the battery case 10, for example, for the purpose of improving the impregnation of the electrode assembly 20 with the non-aqueous electrolyte solution.

[0048] The amount of nonaqueous electrolyte injected is preferably an amount that ensures excess electrolyte between the battery case 10 and the wound electrode bodies 20a, 20b, and 20c. It is more preferable that the amount of nonaqueous electrolyte injected is an amount that, when performing the pressurizing step (step S20) described below, the liquid level of the excess electrolyte falls within an area A1 (see FIG. 2) that satisfies the following: between a height of 1 / 8 Ta from the end of the wound electrode bodies 20a, 20b, and 20c on the bottom wall 12a side to a height of 7 / 8 Ta from the end of the wound electrode bodies 20a, 20b, and 20c on the bottom wall 12a side, where Ta is the height of the wound electrode bodies 20a, 20b, and 20c (the length in the direction from the bottom wall 12a toward the sealing plate 14).

[0049] More specifically, in one embodiment, the amount of non-aqueous electrolyte injected is preferably about 300 to 400 ml (e.g., 315 ml) per battery assembly 100 A. Alternatively, in another embodiment, the ratio (Vl / Va) of the volume Vl of the injected amount (total amount) of non-aqueous electrolyte to the internal volume Va of the battery case 10 at 25°C and 1 atmosphere is preferably about 0.2 to 0.4, more preferably 0.27 to 0.3, and in one example, 0.28.

[0050] In one embodiment, it is preferable to perform the pressurizing step (step S20) after the predetermined amount of nonaqueous electrolyte has been completely injected. In other words, it is preferable not to inject nonaqueous electrolyte after the pressurizing step (step S20). Having a sufficient amount of nonaqueous electrolyte in battery case 10 from the beginning of the pressurizing step allows the effects of the technology disclosed herein to be optimally exhibited.

[0051] In this manner, a battery assembly 100A (see FIG. 8 ) is constructed, in which the electrode body group 20 and the nonaqueous electrolyte are housed in the battery case 10. In one embodiment, after the construction step (step S10), typically after the liquid injection step (step S12), it is preferable to start the pressurization step (step S20) without reducing the pressure inside the battery case 10 to 0 MPa or less (atmospheric pressure or less). More specifically, it is preferable to start the pressurization step (step S20) without reducing the pressure inside the battery case 10 to preferably −0.05 MPa or less, more preferably −0.01 MPa or less, and even more preferably −0.02 MPa or less. This ensures a relatively long retention time in the pressurization step (step S20), which more effectively promotes impregnation of the nonaqueous electrolyte.

[0052] The battery assembly 100A is placed in a chamber 210 of a pressure adjustment device 200 (see FIG. 8 ) during the subsequent pressurization step (step S20) and depressurization step (step S30). FIG. 8 is a schematic diagram of the pressure adjustment device 200. The pressure adjustment device 200 of this embodiment includes a chamber 210 that houses the battery assembly 100A and a pressure adjustment unit 220 that adjusts the pressure within the chamber 210. The chamber 210 here has a cylindrical shape and is sized to accommodate one or more battery assemblies 100A directly therein. Note that, here, three battery assemblies 100A are housed in the chamber 210, but the number can, of course, be changed as appropriate. The chamber 210 is configured so that the internal pressure can be adjusted by the pressure adjustment unit 220. An exhaust passage 211 is provided in the chamber 210. An exhaust valve 212 is attached to the exhaust passage 211. The exhaust valve 212 is electrically connected to a control device (not shown) and is configured so that it can be switched between an open state and a closed state by the control device.

[0053] Here, the pressure adjusting unit 220 includes a gas flow path 230, a three-way valve 240, a gas supply source 250, a vacuum source 260, and a control device (not shown). The pressure adjusting unit 220 is configured such that the gas supply source 250 is connected to one of the branched gas flow paths 230, the vacuum source 260 is connected to the other, and the three-way valve 240 is disposed at the branch point.

[0054] The gas flow path 230 includes a first flow path 231, a second flow path 232, and a third flow path 233. One end of the first flow path 231 is connected to the chamber 210, and the other end is connected to a three-way valve 240. One end of the second flow path 232 is connected to the three-way valve 240, and the other end is connected to a gas supply source 250. One end of the third flow path 233 is connected to the three-way valve 240, and the other end is connected to a vacuum source 260. The three-way valve 240 is electrically connected to a control device, and is configured to be switchable by the control device between a state in which the first flow path 231 is connected to the second flow path 232 and a state in which the first flow path 231 is connected to the third flow path 233.

[0055] Here, the gas supply source 250 is an air compressor that generates compressed air. However, the gas supply source 250 may also be, for example, a gas cylinder filled with an inert gas or the like. The vacuum source 260 is a vacuum pump. The pressure adjustment unit 220 is configured to be able to pressurize the chamber 210 by switching the three-way valve 240 to a state in which the first flow path 231 and the second flow path 232 are connected so that the chamber 210 and the gas supply source 250 are in communication with each other. The pressure adjustment unit 220 is configured to be able to depressurize the chamber 210 by switching the three-way valve 240 to a state in which the first flow path 231 and the third flow path 233 are connected so that the chamber 210 and the vacuum source 260 are in communication with each other.

[0056] The pressurizing step (step S20) is a step of pressurizing the battery case 10 to a predetermined first pressure after the construction step (step S10) and maintaining that pressure for a predetermined time or longer. This step is typically performed in a room temperature environment (e.g., about 25°C ± 10°C, 25°C ± 5°C). In this step, for example, as shown in FIG. 8, the battery assembly 100A is first accommodated in the chamber 210 of the pressure adjustment device 200 with the battery case 10 in an open state (here, the liquid inlet 15 is open). Then, the pressure in the chamber 210 is changed with no pressure difference between the inside and outside of the battery case 10 (in other words, with no bulging or denting of the battery case 10). Specifically, the control device closes exhaust valve 212, switches three-way valve 240 to connect chamber 210 with gas supply source 250, supplies gas from gas supply source 250 into chamber 210, and pressurizes chamber 210 to a predetermined first pressure. This effectively promotes impregnation of the nonaqueous electrolyte solution.

[0057] 9 is a graph showing the transition of pressure in this step according to one embodiment. In this step, as shown in FIG. 9, it is preferable to continuously supply gas from the gas supply source 250 to pressurize the chamber until a predetermined first pressure is reached. That is, it is preferable to pressurize the chamber from, for example, 0 MPa (atmospheric pressure) to the predetermined first pressure in a single pressurization. Although not particularly limited, the rate at which the pressure inside the chamber 210 is increased (typically to the predetermined first pressure) (pressure increase speed) is preferably 0.0013 to 0.0133 MPa / sec.

[0058] When the battery assembly 100A includes large-sized wound electrode bodies 20a, 20b, 20c (specifically, wound electrode bodies 20a, 20b, 20c in which the length La of the negative electrode active material layer 24a in the long side direction Y is 20 cm or more) as in the present embodiment, it is necessary to pressurize the chamber 210 until the pressure inside the battery case 10 reaches 0.4 MPa or more. From the viewpoint of further improving work efficiency and productivity, it is preferable to pressurize the battery case 10 until the pressure inside the battery case 10 reaches 0.5 MPa or more, more preferably 0.6 MPa or more, and even more preferably 0.7 MPa or more. On the other hand, if the pressure becomes too high, the impregnation promotion effect levels off and it takes time to increase the pressure; therefore, it is preferable that the pressure inside the battery case 10 be, for example, 1 MPa or less, 0.9 MPa or less.

[0059] In this embodiment, the chamber 210 is maintained for a predetermined time under a pressurized state in which the pressure inside the battery case 10 is 0.4 MPa or higher. The time for maintaining the battery case 10 under such a pressurized state (pressurized holding time) is longer than that of the conventional techniques disclosed in, for example, Patent Documents 1 to 3, and must be 20 minutes or longer. This promotes impregnation with the nonaqueous electrolyte, allowing the large-sized wound electrode bodies 20a, 20b, and 20c to be thoroughly impregnated with the nonaqueous electrolyte, particularly up to the center portion in the long side direction Y. The pressurized holding time is preferably 30 minutes or longer, more preferably 40 minutes or longer, even more preferably 45 minutes or longer, or even more preferably 50 minutes or longer. From the viewpoint of improving work efficiency and productivity, the pressurized holding time is preferably, for example, 300 minutes (5 hours) or shorter, more preferably 250 minutes or shorter, and even more preferably, for example, 120 minutes (2 hours) or shorter, or 60 minutes (1 hour) or shorter. Note that the "pressurized holding time" referred to here typically refers to the time for continuous holding. That is, in this step, it is preferable to maintain the pressurized state continuously for 20 minutes or more, although it is also acceptable to reduce the pressure to less than 0.4 MPa for a very short period of time (for example, within a few seconds to a minute).

[0060] This step is preferably performed in a state where the liquid level of the excess electrolyte injected in the injection step (step S12) is below the upper ends of the wound electrode assemblies 20a, 20b, and 20c, more preferably below the upper ends of the positive electrode tab group 23 and the negative electrode tab group 25. This makes it easier to degas the air that has replaced the nonaqueous electrolyte, and the impregnation of the nonaqueous electrolyte can be promoted to a higher level. Furthermore, this step is preferably performed in a state where the liquid level of the excess electrolyte is above the lower ends of the wound electrode assemblies 20a, 20b, and 20c, more preferably above the lower end of the flat portion 20f. This makes it easier for the nonaqueous electrolyte to flow into the wound electrode assemblies 20a, 20b, and 20c, and the impregnation of the nonaqueous electrolyte can be promoted to a higher level. In particular, this step is preferably carried out in a state in which the liquid level of the excess electrolyte is in the above-mentioned region A1 (see FIG. 2), and it is particularly preferable that the liquid level of the excess electrolyte is maintained in the above-mentioned region A1 from the start to the end of this step.

[0061] The depressurization step (step S30) is a step of reducing the pressure inside the battery case 10 to a predetermined second pressure after the pressurization step (step S20). This step is typically performed in a room temperature environment (e.g., approximately 25°C ± 10°C, 25°C ± 5°C). In this step, for example, while the battery assembly 100A continues to be housed in the chamber 210 of the pressure adjustment device 200, the pressure inside the chamber 210 is reduced to the predetermined second pressure. Specifically, the control device switches the three-way valve 240 to connect the chamber 210 to the vacuum source 260, and the vacuum source 260 exhausts gas from the chamber 210, reducing the pressure inside the chamber 210 to the predetermined second pressure. By reducing the pressure inside the chamber 210, residual air remaining inside, for example, the wound electrode bodies 20a, 20b, and 20c can be removed, effectively promoting impregnation with the nonaqueous electrolyte.

[0062] In this step, it is preferable to continuously drive the vacuum source 260 to reduce the pressure until the predetermined second pressure is reached. That is, it is preferable to reduce the pressure from, for example, the first pressure state adjusted in the previous pressurization step to the predetermined second pressure in a single depressurization. Although not particularly limited, it is preferable that the speed at which the pressure inside the chamber 210 is increased (typically to the predetermined second pressure) (pressure reduction speed) is 0.3 to 3 kPa / sec.

[0063] When the battery assembly 100A includes large-sized wound electrode bodies 20a, 20b, and 20c (specifically, wound electrode bodies 20a, 20b, and 20c in which the length La of the negative electrode active material layer 24a in the long side direction Y is 20 cm or more) as in the present embodiment, it is preferable to reduce the pressure inside the chamber 210 until the pressure inside the battery case 10 becomes −55 kPa or less. This effectively promotes impregnation with the nonaqueous electrolyte. From the viewpoint of further improving work efficiency and productivity, it is preferable to reduce the pressure inside the battery case 10 until the pressure becomes −60 kPa or less, and more preferably until the pressure becomes −80 kPa or less. On the other hand, if the pressure becomes too low, the impregnation promotion effect levels off and it takes time to reduce the pressure. Therefore, it is preferable that the pressure inside the battery case 10 be, for example, −95 kPa or more.

[0064] In this step, it is further preferable to maintain the chamber 210 in a reduced pressure state where the pressure inside the battery case 10 is −55 kPa or less for a predetermined time. The time for maintaining the reduced pressure inside the battery case 10 (reduced pressure maintaining time) is preferably 1 minute or more, more preferably 4 minutes or more, and more preferably 5 minutes or more when the battery assembly 100A includes large-sized wound electrode bodies 20a, 20b, 20c (specifically, wound electrode bodies 20a, 20b, 20c in which the length La in the long side direction Y of the negative electrode active material layer 24a is 20 cm or more). The reduced pressure maintaining time may typically be shorter than the pressurized maintaining time in the previous pressurizing step (step S20). From the viewpoint of improving work efficiency and productivity, the reduced pressure maintaining time is, for example, more preferably 150 minutes or less, even more preferably 125 minutes or less, and particularly preferably 120 minutes (2 hours) or less, 60 minutes (1 hour) or less, or 30 minutes or less.

[0065] In one embodiment, when the pressurized holding time in the previous pressurizing step (step S20) (i.e., the time during which the battery case 10 is held in a state of 0.4 MPa or higher) is T1 and the reduced pressure holding time in this step (i.e., the time during which the battery case 10 is held in a state of -55 kPa or lower) is T2, the ratio (T1 / T2) of the pressurized holding time T1 to the reduced pressure holding time T2 is preferably 2 to 40, and more preferably 3 to 8. By setting the ratio within this range, impregnation of the electrolyte can be effectively promoted.

[0066] This step is preferably carried out when excess electrolyte is still present between the battery case 10 and the wound electrode bodies 20a, 20b, and 20c, and more preferably when the liquid level of the excess electrolyte is above the lower ends of the wound electrode bodies 20a, 20b, and 20c, and even above the lower end of the flat portion 20f, particularly in the above-mentioned region A1 (see Figure 2).

[0067] After the depressurization step (step S30), for example, after a predetermined depressurization time has elapsed, the pressure inside the chamber 210 is typically returned to atmospheric pressure. Specifically, for example, the control device opens the exhaust valve 212 and exhausts the gas inside the chamber 210 through the exhaust passage 211, thereby returning the pressure inside the chamber 210 to atmospheric pressure. As a result, the pressure inside the battery case 10 also returns to near atmospheric pressure (for example, to -0.02 to 0.02 MPa).

[0068] In one embodiment, after the depressurization step (step S30), it is preferable to return the pressure inside the battery case 10 to near atmospheric pressure (for example, to -0.02 to 0.02 MPa), and then perform the initial charging step (step S40) without again pressurizing or depressurizing the chamber 210. More specifically, after the depressurization step (step S30), it is preferable to perform the initial charging step (step S40) without reducing the pressure inside the battery case 10 to a reduced pressure of -0.05 MPa or less, or a pressurized state of 0.1 MPa or more. This allows the battery 100 to be manufactured more efficiently than when large pressure increases and decreases are repeatedly performed.

[0069] In the initial charging step (step S40), after the decompression step (step S30), the battery assembly 100A is removed from the chamber 210 and charged at least once. The initial charging electrolyzes the nonaqueous electrolyte, and a coating (SEI film) containing decomposition products may be formed on the surface of the negative electrode active material layer 24a. This step may be performed in a room temperature environment (e.g., about 25°C ± 10°C, 25°C ± 5°C) or in a high-temperature environment, e.g., about 45°C. Performing the step in a high-temperature environment can promote the formation of the coating.

[0070] The battery assembly 100A can be charged in the same manner as conventional. Typically, an external power source is connected between the positive and negative terminals of the battery assembly 100A, and charging is continued until a predetermined voltage is reached between the positive and negative terminals. The battery assembly 100A is preferably charged until the state of charge (SOC) reaches 5% or more, more preferably 10% or more. The state of charge (SOC) of the battery assembly 100A in this step is preferably 50% or less, more preferably 40% or less, and even more preferably 30% or less. For example, when the negative electrode active material is a carbon material, the ultimate voltage may be set to approximately 3V or more, typically 3.5V or more, for example 4V or more. The charge rate may be set, for example, at about 0.1C to 2C. Charging may be performed once, or may be repeated two or more times, for example, with a discharge interval in between.

[0071] In this step, gas may be generated due to decomposition of the nonaqueous electrolyte solution. Therefore, after charging the battery assembly 100A at least once, the pressure inside the battery case 10 may be reduced again to a pressure below atmospheric pressure, for example, to exhaust the generated gas to the outside of the battery case 10.

[0072] In the sealing step (step S50), after the initial charging step (step S40), the liquid injection hole 15 is sealed with the sealing member 16 while the pressure inside the battery case 10 remains at atmospheric pressure or is reduced below atmospheric pressure. This causes the battery case 10 to be airtightly sealed (hermetically sealed). In this manner, the battery 100 can be suitably manufactured.

[0073] <Uses of Battery 100> The battery 100 can be used for various purposes. For example, the battery 100 includes large-sized wound electrode bodies 20a, 20b, and 20c (specifically, wound electrode bodies 20a, 20b, and 20c in which the length La in the long side direction Y of the negative electrode active material layer 24a is 20 cm or more) and has a high capacity. Therefore, the battery 100 can be suitably used as a power source (driving power source) for a motor mounted on a vehicle such as a passenger car or truck. The type of vehicle is not particularly limited, and examples include a plug-in hybrid electric vehicle (PHEV), a hybrid electric vehicle (HEV), and an electric vehicle (BEV). The battery 100 can also be suitably used as a battery pack in which a plurality of batteries 100 are arranged in a predetermined arrangement direction and a load is applied from the arrangement direction using a restraining mechanism.

[0074] Hereinafter, several examples of the present invention will be described, but it is not intended that the present invention be limited to these examples.

[0075] <Test Example I: Examination of the pressurization process> In this test example, the impregnation rates were compared under different conditions (pressure and pressure holding time) for the pressurization step. Specifically, first, multiple battery assemblies with the same configuration were constructed. More specifically, first, in the placement step, a flat wound electrode body (total height Ta including curved portions was 9.4 cm, and length La in the long side direction of the negative electrode active material layer was 28.6 cm) was housed inside the exterior body. Next, a sealing plate was welded to the periphery of the opening of the exterior body to integrate the exterior body and the sealing plate. Next, in the liquid injection step, a predetermined amount of nonaqueous electrolyte was injected into the battery case through an injection hole provided in the sealing plate. In this manner, multiple battery assemblies with the same configuration (Examples 1 to 4, Comparative Examples 1 and 2) were constructed.

[0076] Next, after the liquid injection step, the battery assembly was moved into the chamber of the pressure adjustment device. Then, in the pressurization step, without reducing the pressure inside the battery case below atmospheric pressure, the chamber was pressurized from atmospheric pressure under the conditions (pressure and pressure holding time) shown in Table 1 while the liquid injection hole was left open.

[0077] After the pressurization step, the battery assembly was disassembled in a dry air atmosphere (e.g., with a dew point of approximately -50°C) without a depressurization step, and the wound electrode body was removed from the battery case. Next, when the wound electrode body was unwound, the portions not impregnated with the non-aqueous electrolyte (unimpregnated portions) were observed to have color unevenness. Therefore, the width Ln of the unimpregnated portions in the winding axis direction was measured visually, and the ratio of the impregnated portions to the width of the positive electrode active material layer, i.e., the impregnation rate (%) of the non-aqueous electrolyte, was calculated using the following formula (1). The results are shown in Table 1. Impregnation rate (%) = (Lc - Ln) / Lc × 100 Equation (1) (where Lc is the width of the positive electrode active material layer in the direction of the winding axis, and Ln is the width of the unimpregnated portion in the direction of the winding axis.)

[0078] [Table 1]

[0079] FIG. 10 is a graph showing the relationship between the impregnation rate and the applied pressure for Examples 1 to 3 and Comparative Example 2. As shown in FIG. 10 and Table 1, when the width of the negative electrode active material layer in the direction of the winding axis is 20 cm or more, a pressure of 0.4 MPa or more is required in the pressurizing step to achieve an impregnation rate of 75% or more, or even 80% or more. FIG. 11 is a graph showing the relationship between the impregnation rate and the applied pressure holding time for Examples 3 and 4 and Comparative Examples 1 and 2. As shown in FIG. 11 and Table 1, when the applied pressure holding time exceeded 15 minutes, the approximation curve rose sharply around 20 minutes, and the impregnation rate changed rapidly. Therefore, when the width of the negative electrode active material layer in the direction of the winding axis is 20 cm or more, it was found that a pressurized holding time of 20 minutes or more is effective, and that a pressurized holding time of 20 minutes or more can achieve an impregnation rate of 75% or more. Furthermore, it was found that a pressurized holding time of 30 minutes or more exhibits even more significant effects.

[0080] <Test Example II: Examination of the decompression process> In this test example, the time required for the nonaqueous electrolyte to be completely impregnated into the wound electrode body was compared with and without the depressurization step. Specifically, first, multiple battery assemblies (Examples 5 and 6) with the same configuration were constructed in the same manner as in Test Example I. Next, as in Test Example I, the battery assemblies were moved into a chamber, and the chamber was pressurized under the conditions (pressurization force and pressurization holding time) shown in Table 2. Next, for the battery assembly of Example 6, after the pressurization step, the chamber was subsequently depressurized under the conditions (depressurization force and depressurization holding time) shown in Table 2. On the other hand, the depressurization step was not performed for the battery assembly of Example 5.

[0081] Next, for each example, the battery assemblies were disassembled one by one at regular intervals after injection, and visually inspected to see if there was any unimpregnated area in the center of the separator in the winding axis direction. The time until no unimpregnated area was visible (the complete impregnation time required for complete impregnation) was then measured. The results are shown in Table 2. The complete impregnation time is expressed as a relative value, with the result of Example 5 being set as the reference (100).

[0082] [Table 2]

[0083] As shown in Table 2, by further including a decompression step after the pressurization step, it was found that the gas remaining in the wound electrode body could be efficiently degassed, thereby shortening the time required for complete impregnation and further improving the impregnation of the nonaqueous electrolyte.

[0084] <Test Example III: Examination of the decompression process> In this test example, the reduced pressure holding time during the depressurization step was varied to compare the time required for the wound electrode body to be completely impregnated with the nonaqueous electrolyte. Specifically, first, multiple battery assemblies (Examples 7 to 10) with the same configuration were constructed in the same manner as in Test Example II. Next, as in Test Example II, the battery assemblies were moved into a chamber, and the chamber was pressurized under the conditions (pressurizing force and pressurized holding time) shown in Table 3. Next, for the battery assemblies of Examples 8 to 10, after the pressurization step, the chamber was subsequently depressurized under the conditions (depressurizing force and depressurized holding time) shown in Table 3. Note that, for Examples 8 to 10, the total pressurized and depressurized holding times was standardized to 40.5 minutes. In other words, when the depressurized holding time was extended, the pressurized and depressurized holding time was shortened accordingly. On the other hand, the depressurization step was not performed for the battery assembly of Example 7.

[0085] Next, as in Test Example II, for each example, the battery assemblies were disassembled one by one at regular intervals after injection, and visually inspected for any unimpregnated areas in the center of the separator in the winding axis direction. The time until no unimpregnated areas were visible (the complete impregnation time required for complete impregnation) was then measured. The results are shown in Table 3. The complete impregnation time is expressed as a relative value, with the result of Example 7 set as the reference (100).

[0086] [Table 3]

[0087] As shown in Table 3, by setting the reduced pressure holding time in the reduced pressure step to 1 minute or more, the time required for complete impregnation can be shortened by about 20%, and the impregnation of the non-aqueous electrolyte can be further improved. In particular, by setting the reduced pressure holding time to around 5 minutes (for example, about 3 to 7 minutes), the impregnation of the non-aqueous electrolyte can be improved to an even higher level.

[0088] Although several embodiments of the present invention have been described above, the above embodiments are merely examples. The present invention can be implemented in various other forms. The present invention can be implemented based on the contents disclosed in this specification and the common general technical knowledge in the relevant field. The technology described in the claims includes various modifications and alterations of the above-exemplified embodiments. For example, it is possible to replace part of the above-described embodiments with other modifications, or to add other modifications to the above-described embodiments. Furthermore, if a technical feature is not described as essential, it may be deleted as appropriate.

[0089] For example, in the embodiment of FIG. 7 described above, the liquid injection step (step S12) is performed after the arrangement step (step S11), but this is not limited thereto. In other embodiments, for example, the arrangement step (step S11) can also be performed after the liquid injection step (step S12). Furthermore, when the nonaqueous electrolyte is injected into the battery case 10 before the sealing plate 14 is welded to the periphery of the opening 12h of the exterior body 12, in other words, when the exterior body 12 and the sealing plate 14 are integrated after the electrode body group 20 (wound electrode bodies 20a, 20b, 20c) are accommodated inside the battery case 10, the liquid injection hole 15 does not have to be provided in the sealing plate 14.

[0090] As described above, specific aspects of the technology disclosed herein include those described in the following sections. Item 1: A method for manufacturing a non-aqueous electrolyte secondary battery comprising: a wound electrode assembly including a positive electrode and a negative electrode; a non-aqueous electrolyte; and a battery case accommodating the wound electrode assembly and the non-aqueous electrolyte, wherein the positive electrode comprises a positive electrode current collector and a positive electrode active material layer formed on the positive electrode current collector; the negative electrode comprises a negative electrode current collector and a negative electrode active material layer formed on the negative electrode current collector; and the negative electrode active material layer has a width in the winding axis direction of 20 cm or more, a manufacturing method of a non-aqueous electrolyte secondary battery, comprising: a construction step of housing an electrode body and the non-aqueous electrolyte to construct a battery assembly; and a pressurizing step of, after the construction step, placing the battery assembly in a chamber whose internal pressure is adjustable with the battery case in an open state, changing the pressure in the chamber to increase the pressure in the battery case to 0.4 MPa or more, and maintaining the state in which the pressure in the battery case is 0.4 MPa or more for 20 minutes or more. Item 2: The method for producing a non-aqueous electrolyte secondary battery according to Item 1, further comprising, after the pressurizing step, a depressurizing step of depressurizing the pressure inside the battery case until the pressure inside the battery case becomes −55 kPa or less. Item 3: The method for producing a non-aqueous electrolyte secondary battery according to Item 2, wherein in the pressure reducing step, the pressure inside the battery case is maintained at -55 kPa or less for one minute or more. Item 4: The method for producing a nonaqueous electrolyte secondary battery according to Item 3, wherein, in the pressurizing step, a pressurized holding time T1 during which the pressure inside the battery case is maintained at 0.4 MPa or more and a reduced-pressure holding time T2 during which the pressure inside the battery case is maintained at -55 kPa or less are defined as T1 and T2, respectively, and a ratio (T1 / T2) of the pressurized holding time T1 to the reduced-pressure holding time T2 is 2 or more and 40 or less. Item 5: The method for producing a nonaqueous electrolyte secondary battery according to any one of Items 2 to 4, further comprising an initial charging step of charging the battery assembly for the first time after the depressurizing step, wherein the initial charging step is started without adjusting the pressure inside the battery case again to -0.05 MPa or less to 0.1 MPa or more once the pressure inside the battery case has been adjusted to -0.02 MPa or more and 0.02 MPa or less after the depressurizing step. Item 6: The method for producing a nonaqueous electrolyte secondary battery according to any one of Items 1 to 5, wherein after the assembly step, the pressurizing step is started without reducing the pressure inside the battery case to −0.05 MPa or less. Item 7: The method for manufacturing a nonaqueous electrolyte secondary battery according to any one of Items 1 to 6, wherein the battery case has an inlet, and the construction step includes an arrangement step of arranging the wound electrode body inside the battery case, and an injection step of injecting the nonaqueous electrolyte through the inlet after the arrangement step, and wherein the pressure in the chamber is changed in the pressurizing step with the inlet open. Item 8: The method for manufacturing a nonaqueous electrolyte secondary battery according to any one of Items 1 to 7, wherein the battery case has an opening, a bottom wall, and a side wall extending from an edge of the bottom wall toward the opening, an exterior body having the opening, and a sealing plate that seals the opening, and in the assembly step, the wound electrode body is housed in the battery case with the winding axis oriented along the bottom wall. Item 9: The method for manufacturing a nonaqueous electrolyte secondary battery according to Item 8, wherein in the assembly step, the nonaqueous electrolyte is injected between the battery case and the wound electrode body so as to contain excess electrolyte, and the pressurization step is performed in a state where the liquid level of the excess electrolyte is in an area A1 that satisfies the following: between a height of 1 / 8 Ta from the end of the wound electrode body on the bottom wall side to a height of 7 / 8 Ta from the end of the wound electrode body on the bottom wall side, where Ta is the length of the wound electrode body in the direction from the bottom wall toward the sealing plate. Item 10: The method for producing a nonaqueous electrolyte secondary battery according to any one of Items 1 to 9, wherein in the pressurizing step, the pressure inside the battery case is maintained at 0.4 MPa or higher for 30 minutes or longer. [Explanation of symbols]

[0091] 10 Battery case 15 Liquid injection hole 20 Electrode group 20a, 20b, 20c wound electrode body 22 Positive electrode 22a Cathode active material layer 22c Positive electrode current collector 24 Negative electrode 24a Negative electrode active material layer 24c negative electrode current collector 26 Separator 100 batteries 200 Pressure Regulator 210 Chamber 220 Pressure adjustment unit S10 construction process S11 Placement process S12 Liquid injection process S20 Pressurization process S30 Decompression process S40 initial charging process

Claims

1. a wound electrode assembly including a positive electrode and a negative electrode, a non-aqueous electrolyte, and a battery case that accommodates the wound electrode assembly and the non-aqueous electrolyte; the positive electrode comprises a positive electrode current collector and a positive electrode active material layer formed on the positive electrode current collector, the negative electrode comprises a negative electrode current collector and a negative electrode active material layer formed on the negative electrode current collector, The width of the negative electrode active material layer in the winding axis direction is 20 cm or more. A method for manufacturing a non-aqueous electrolyte secondary battery, a construction step of constructing a battery assembly by placing the wound electrode body in the battery case and injecting the nonaqueous electrolyte; a pressurizing step of, after the construction step, placing the battery assembly in a chamber whose internal pressure is adjustable with the battery case open, changing the pressure in the chamber to increase the pressure in the battery case (gauge pressure based on atmospheric pressure) to 0.4 MPa or more, and maintaining the state in which the pressure in the battery case is 0.4 MPa or more for 20 minutes or more; an initial charging step in which the battery assembly is removed from the chamber after the pressurizing step and charged for the first time; A method for manufacturing a non-aqueous electrolyte secondary battery, comprising:

2. the method further includes a depressurizing step of depressurizing the pressure in the chamber after the pressurizing step and before the initial charging step until the pressure in the battery case (gauge pressure based on atmospheric pressure) becomes −55 kPa or less. The method for producing the nonaqueous electrolyte secondary battery according to claim 1 .

3. In the decompression step, the pressure inside the battery case is maintained at −55 kPa or less for 1 minute or more. The method for producing the nonaqueous electrolyte secondary battery according to claim 2 .

4. a ratio (T1 / T2) of the pressurized holding time T1 to the reduced pressure holding time T2 is 2 or more and 40 or less, where T1 is a pressurized holding time during which the pressure inside the battery case is maintained at 0.4 MPa or more in the pressurizing step and T2 is a reduced pressure holding time during which the pressure inside the battery case is maintained at -55 kPa or less in the depressurizing step; The method for producing the nonaqueous electrolyte secondary battery according to claim 3 .

5. The initial charging step is started after the pressure in the battery case has been adjusted to between -0.02 MPa and 0.02 MPa after the depressurization step, without adjusting the pressure in the battery case to between -0.05 MPa and 0.1 MPa again.

5. A method for producing the nonaqueous electrolyte secondary battery according to claim 2.

6. After the construction step, the pressurization step is started without reducing the pressure inside the battery case to −0.05 MPa or less.

5. A method for producing the nonaqueous electrolyte secondary battery according to claim 1.

7. the battery case has a liquid injection hole, In the construction step, the nonaqueous electrolyte is poured through the pouring hole; In the pressurizing step, the pressure in the chamber is changed with the liquid injection hole being open.

5. A method for producing the nonaqueous electrolyte secondary battery according to claim 1.

8. The battery case is an exterior body having an opening, a bottom wall, and a side wall extending from an edge of the bottom wall toward the opening; a sealing plate that seals the opening, In the construction step, the wound electrode body is housed in the battery case with the winding axis oriented along the bottom wall.

5. A method for producing the nonaqueous electrolyte secondary battery according to claim 1.

9. In the construction step, the nonaqueous electrolyte is injected between the battery case and the wound electrode body so as to contain excess electrolyte, The pressurizing step is performed by adjusting the liquid level of the excess electrolyte to a region A1 that satisfies the following: When the length of the wound electrode body in the direction from the bottom wall toward the sealing plate is Ta, Between a height of 1 / 8 Ta from the end of the wound electrode body on the bottom wall side to a height of 7 / 8 Ta from the end of the wound electrode body on the bottom wall side; It is carried out in a state The method for producing the nonaqueous electrolyte secondary battery according to claim 8 .

10. In the pressurizing step, the pressure inside the battery case is maintained at 0.4 MPa or higher for 30 minutes or longer.

5. A method for producing the nonaqueous electrolyte secondary battery according to claim 1.

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