JP2014116180A - Method for manufacturing nonaqueous electrolyte secondary battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress, while performing aging, the melting and deposition of a cathode active material which occurs during manufacture of a nonaqueous electrolyte secondary battery.SOLUTION: A method of the present invention for manufacturing a nonaqueous electrolyte secondary battery comprises a lamination step, a winding step, an assembly step, and an aging step. In the lamination step, a cathode 1 is provided with a cathode collector 7 and cathode mixture layers 3 and 5 positioned on both sides of the cathode collector 7, and an anode 2 is provided with an anode collector 8, anode mixture layers 4 and 6 positioned on both sides of the anode collector 8, and an anode end face 22 in which an end face of the anode collector 8 and end faces of the anode mixture layers 4 and 6 are substantially flush with each other. In the winding step, the laminate is wound in a manner that the anode mixture layer 4 on the outer circumferential side does not face the cathode mixture layers 3 and 5 on the outermost circumference of the anode positioned on the outer circumferential side of the outermost circumference of the cathode. In the aging step, the laminate is held in place while kept in storage by covering at least part of a side end portion of the cathode mixture layer 5 facing the anode mixture layer 6 in proximity to the anode end face 22 with a nonaqueous electrolyte.

Description

  The present invention relates to a method for producing a nonaqueous electrolyte secondary battery.

  In the manufacturing process of a non-aqueous electrolyte secondary battery such as a lithium ion secondary battery, it is necessary to charge and discharge after accommodating the electrode group in a battery case and further injecting the non-aqueous electrolyte. Furthermore, as shown in Patent Document 1, in the manufacturing process, in addition to charging and discharging, the battery can be subjected to an aging treatment in a temperature range of 60 ° C. or higher.

JP 2000-340262 A

  The invention described in Patent Document 1 is excellent in improving the initial discharge capacity or charge / discharge cycle characteristics of the nonaqueous electrolyte secondary battery. However, when the aging treatment is performed, the metal in the positive electrode active material of the battery may be eluted. Such metal elution causes a short circuit inside the battery, and the battery may not exhibit the desired performance.

  An object of the present invention is to provide a method for producing a non-aqueous electrolyte secondary battery that suppresses dissolution and precipitation of a positive electrode active material that occurs during the production of a non-aqueous electrolyte secondary battery while performing an aging treatment. It is.

  The method for producing a nonaqueous electrolyte secondary battery of the present invention includes a lamination step of laminating a positive electrode, a separator, and a negative electrode to create a laminate, and a winding step of winding the laminate to create a wound body. A battery is assembled by housing the wound body in a case, an assembling step, an injecting step of injecting a nonaqueous electrolyte into the case, an initial charging step of charging the battery, and a voltage between the positive electrode and the negative electrode. And an aging step of storing the charged battery in a temperature range of 30 ° C. or higher without applying.

  In the stacking step, the positive electrode includes a positive electrode current collector and a positive electrode mixture layer located on both surfaces of the positive electrode current collector, and the negative electrode is located on both sides of the negative electrode current collector and the negative electrode current collector. And a negative electrode end face in which the end face of the negative electrode current collector and the end face of the negative electrode mixture layer are substantially flush with each other. In the winding step, in the outermost negative electrode outer periphery located on the outer peripheral side of the positive electrode outermost periphery, the negative electrode mixture layer on the outer peripheral side does not face the positive electrode mixture layer, and the laminate is wound, and the aging step Then, during storage, at least a part of the side end portion of the positive electrode mixture layer facing the end portion of the negative electrode mixture layer adjacent to the negative electrode end surface is held in a state of being covered with the nonaqueous electrolyte.

  The temperature range is preferably 60 ° C. or higher. After the winding step, before the assembly step, the winding body is further deformed by pressing and deforming into a flat shape, and the aging step further includes a deformation step of the flat-shaped winding body during storage. In the nonaqueous electrolyte, at least a part of the side end portion of the positive electrode mixture layer on the outermost periphery, which is located at the curved portion at both ends in the positive electrode direction and in the winding direction and faces the negative electrode on the outer periphery, is immersed in the nonaqueous electrolyte. It is preferable to hold in the state.

  In the aging step, it is preferable that all of the side end portions are held in a state of being immersed in the nonaqueous electrolyte. In the aging step, it is preferable that all of the sagging portions of the side end portions are kept in a state of being immersed in the nonaqueous electrolyte during storage.

  In the aging step, it is preferable that the entire side end portion of the positive electrode mixture layer is held in a state immersed in the nonaqueous electrolyte. In the aging step, it is preferable that a side end portion of the positive electrode mixture layer is positioned below in a direction of a winding axis of the wound body.

  In the aging step, a planar member fitted to one opening surface of a square case, a positive terminal and a negative terminal connected to the planar member, a winding shaft substantially parallel to the opening surface, The battery comprising: a positive electrode direction end connected to the positive electrode terminal; and the wound body having a negative electrode direction end connected to the negative electrode terminal and located on the opposite side of the winding axis direction with respect to the positive electrode direction end. It is preferable that the positive electrode end is held in a state located below the negative electrode end.

  According to the production method of the present invention, dissolution / deposition of the positive electrode active material that occurs during the production of the nonaqueous electrolyte secondary battery can be suppressed while performing the aging treatment.

It is a flowchart concerning the manufacturing method of an embodiment. It is the figure after the assembly of the battery concerning the manufacturing method of embodiment and an Example. It is a schematic diagram of the press after the injection | pouring process concerning the manufacturing method of embodiment. It is an installation figure of the battery concerning the manufacturing method of an embodiment. It is a schematic diagram of the winding body cross section of the battery concerning the manufacturing method of embodiment. It is an installation figure of the battery concerning the manufacturing method of a comparison object. It is a schematic diagram showing the mechanism of the short circuit generation | occurrence | production by a positive electrode elution. It is the figure after the aging of the battery concerning the manufacturing method of an Example. 6 is a view after aging of a battery according to the manufacturing method of Comparative Example 1. FIG. 6 is a view after aging of a battery according to a manufacturing method of Comparative Example 2. FIG. 10 is a view after aging of a battery according to a manufacturing method of Comparative Example 3. FIG. 10 is a view after aging of a battery according to a manufacturing method of Comparative Example 4. FIG. FIG. 10 is a view after aging of the battery according to the manufacturing method of Comparative Example 5. FIG. 10 is a view after aging of the battery according to the manufacturing method of Comparative Example 5. 10 is a view after aging of a battery according to a manufacturing method of Comparative Example 6. FIG. 10 is a view after aging of a battery according to a manufacturing method of Comparative Example 4. FIG. 10 is a diagram after conditioning of a battery according to the manufacturing method of Comparative Example 5. FIG. FIG. 10 is a diagram before conditioning a battery according to the manufacturing method of Comparative Example 5; 10 is a diagram after conditioning of a battery according to the manufacturing method of Comparative Example 5. FIG. 10 is a view after aging of a battery according to a manufacturing method of Comparative Example 4. FIG.

  A non-aqueous electrolyte secondary battery (hereinafter sometimes simply referred to as a battery) according to an embodiment of the present invention is a lithium ion secondary battery. Hereinafter, the manufacturing method of the present embodiment will be described with emphasis on aging processing.

[Manufacture of batteries]
<From laminate production to aging>
The manufacturing process of each member of the battery such as the positive electrode, the separator, and the negative electrode will be described later. As shown in FIG. 1, in the present embodiment, in the stacking step (step S <b> 11), a positive electrode, a separator, and a negative electrode are stacked to produce a stacked body.

  In step S11, for example, as shown in FIG. 2, the laminate is prepared so that the negative electrode direction end 24 is positioned on the opposite side of the positive electrode direction end 23 in the direction to be the winding shaft 25 of the winding body 13. To do. The positive electrode direction end 23 is a side where a portion of the positive electrode current collector 7 which is a terminal connection surface with the positive electrode terminal 11 on the wound body 13 is exposed. As shown in FIG. 5 to be described later, at the positive electrode direction end 23, the portion of the positive electrode mixture layer 5 close to the terminal connection surface of the positive electrode terminal 11 and the portion of the negative electrode mixture layer 6 close to the negative electrode end surface 22 to be described later are opposed. doing.

  Similarly, the negative electrode direction end 24 is a side where a part of the negative electrode current collector 8 which is a terminal connection surface with the positive electrode terminal 12 on the wound body 13 is exposed. At the negative electrode end 24, the portion of the negative electrode mixture layer 6 that is close to the terminal connection surface of the positive electrode terminal 12 faces the portion of the positive electrode mixture layer 5 that is close to the positive electrode end surface 21 described later. By separating the positive electrode and the negative electrode in this manner, a short circuit between the lead or the terminal between the positive electrode and the negative electrode can be prevented while having a simple structure.

  Next, in the winding step (step S12), the negative electrode mixture layer on the outer peripheral side does not face the positive electrode mixture layer on the outer periphery of the negative electrode located on the outer peripheral side of the positive electrode outermost periphery. Create a circular body. That is, the laminated body is wound so that the outermost periphery of the positive and negative electrodes is the negative electrode, thereby creating a wound body. If it is wound on the contrary, the outermost positive electrode surface without the opposing negative electrode surface is generated. Therefore, the supply of lithium at the end in the negative electrode direction becomes excessive, and lithium may be deposited. The winding method is performed so as not to cause such a short circuit due to lithium deposition. After the winding process, a deforming process may be provided, and the wound body may be pressed and deformed to have a flat shape.

  Next, as shown in FIG. 2, in the assembly process (step S <b> 13), the wound body 13 is housed in a case and the battery 10 is assembled. In the present embodiment, the rectangular battery 10 is manufactured by housing the flat wound body 13 in the rectangular case 15. In the assembly process, the positive electrode terminal 11 and the negative electrode terminal 12 are joined to the wound body 13 (the inside is not shown). The wound body 13 is housed in the case 15 so that the flat direction is the vertical direction in the figure. After storage, the opening of the case 15 is closed with a planar member such as the sealing body 19. The mixture layer closest to the surface layer of the wound body 13 is a negative electrode mixture layer 4 described later.

  In step S <b> 13, the flat wound body 13 is accommodated in the rectangular case 15 so that the winding shaft 25 of the wound body 13 is substantially parallel to the opening surface of the rectangular case 15. Can do. Moreover, the positive electrode terminal 11 can be connected to the positive electrode end of the sealing body 19 fitted to one opening surface through the terminal connection surface of the positive electrode current collector 7. Similarly, the negative electrode terminal 12 can be connected to the negative electrode direction end of the sealing body 19 through the terminal connection surface of the negative electrode current collector 8. The configuration of the positive electrode terminal 11 and the negative electrode terminal 12 will be described in detail in Examples.

  Thus, the sealing body connected to the positive electrode terminal and the negative electrode terminal is prepared, and the battery can be made a simple structure by drawing the positive electrode terminal and the negative electrode terminal. Further, the positive electrode terminal and the negative electrode terminal can be caulked into holes provided in the sealing body or the case. Such a caulking surface is preferably the same surface for the positive electrode terminal and the negative electrode terminal because the structure of the battery becomes simple.

  In the injection step in step 14, the nonaqueous electrolyte is injected into the case from the inlet of the sealing body. As described above, the amount of the non-aqueous electrolyte to be injected is preferably equal to or larger than the amount capable of immersing at least a part of the positive electrode end in the winding axis direction of the wound body during aging. The amount of the non-aqueous electrolyte can be adjusted in consideration of the amount that the wound body can hold, the amount necessary for immersion in the positive electrode direction end, the volatilization amount after long-term use, and the like.

  In addition, the amount of non-aqueous electrolyte that the wound body can hold may change before and after conditioning. For this reason, it can also adjust in consideration of the part by which the nonaqueous electrolyte which the winding body hold | maintained before conditioning is extruded by conditioning. These quantities can be determined experimentally.

  After the injection, the wound body is immersed in the non-aqueous electrolyte in a dipping process in step 14 for a predetermined time. The wound body absorbs the non-aqueous electrolyte by a capillary phenomenon generated in a separator or the like. By immersing the wound body as described above, the positive electrode and the negative electrode are in contact with the non-aqueous electrolyte without any defects, and thus can be charged.

  As shown in FIG. 3, when the flat wound body is inserted into the square case, the immersed wound body 13 may be pressed in the pressing step in step 14. The pressing step is performed by pressing the case 15 that houses the wound body 13. The flat wound body 13 is restrained in a square case 15. The battery 10 includes a wound body 13 including the positive electrode 1 and the negative electrode 2, an insulator 9 that surrounds the wound body 13, and a case 15 that houses the wound body 13 and the insulator 9.

  The pressing is performed in order to make the case 15 have a desired shape when the wound body 13 is inflated by pushing the case 15 from the inside with a force that causes the wound body 13 to swell by itself. The desired shape refers to a rectangular shape such as a rectangular parallelepiped that the case 15 originally had. In addition, the relationship between the short-circuit occurrence location and the press of the wound body according to FIG. 3 will be described in detail in the description of the effect.

  The pressing force 17 can be selected based on the material and shape of the case, the size of the electrode, the number of turns of the electrode during winding, and other factors. For example, when a wound body is produced by winding an electrode having a width of 10 cm and a length of 5 m and winding it 50 times, the case (rolled body) is preferably 100 to 1000 kg weight, more preferably 500 kg weight. Press. The pressing can be performed for a desired time. If it is an example of said winding body, it can be made a desired flat shape by performing for 20 seconds.

  The direction of the force 17 for pressing the case is preferably a direction substantially perpendicular to the direction in which the wound body should be flattened and the winding axis direction. Here, “substantially vertical” refers to an angle within a range in which an error from the vertical can be allowed. The allowable range means, for example, that there is no possibility that the case 15 is deformed, a device that presses the case 15 is displaced, or the structure of the other battery 10 is not hindered.

  The pressing may be divided into a plurality of times. Moreover, the magnitude | size of the force 17 to press each time may differ. In the pressing step, the entire case may be pressed evenly. In the pressing step, the portion 18 that overlaps the winding axis of the wound body may be pressed with priority. By the pressing step, the case and the wound body have a desired shape. For this reason, the battery manufactured by the method of the present embodiment can obtain preferable space utilization efficiency as a prismatic battery.

  In the conditioning process (step S15), a desired voltage is applied to the charged battery to charge and discharge. The amount of the non-aqueous electrolyte that can be held by the wound body described above depends on step S15. In step S15, since the electrode expands, the nonaqueous electrolyte oozes out. In step S15, the lithium ion secondary battery is first charged to a predetermined capacity (initial charging step). Charging is preferably performed by constant current constant voltage charging (CCCV charging).

  For example, at room temperature, the battery can be charged for 2 hours from 0 V (discharged state) to 4 V (SOC 100%, fully charged state) at a current value of 3 A. Further, for example, at room temperature, the battery can be discharged from 4 V (fully charged state) to 3 V over 2 hours at a current value of 3 A.

  In the aging process (step S16), the battery is stored in a predetermined temperature range. In step S16, it is preferable not to apply a voltage to the positive electrode and the negative electrode, or to charge / discharge the battery. In step S16, it is preferable to store in a temperature range of 30 ° C. or higher according to the composition of the nonaqueous electrolyte. As long as the composition of the non-aqueous electrolyte permits, the temperature range is preferably 45 ° C. or higher, more preferably 50 ° C. or higher, and particularly preferably 60 ° C. or higher. It is preferable that a temperature range is 80 degrees C or less.

  The higher the temperature, the less time is required for aging and the battery manufacturing efficiency is improved. On the other hand, as described later, since there is a high possibility that a short circuit occurs between the electrodes due to the high temperature, the method of the present embodiment is particularly suitable for high-temperature storage at 60 ° C. or higher. High temperature storage is preferably performed for about 0 to 500 hours. For example, when aging at 85 ° C., it is preferably performed for about 20 hours. Moreover, it is preferable to store at high temperature under normal pressure.

  FIG. 4 shows a battery installation method in step S16 in the present embodiment. The configuration of the battery 10 of FIG. 4 is the same as that of FIG. During high-temperature storage, at least a part of the positive electrode direction end 23 in the direction of the winding axis 25 of the wound body 13 is held in a state of being immersed in a nonaqueous electrolyte. Preferably, the side edge part of the positive mix layer facing the negative mix layer which adjoins the negative electrode end surface mentioned later is hold | maintained in the state covered with the nonaqueous electrolyte. As shown in FIG. 4, the method of the present embodiment is a method in which a square battery is placed sideways in the terminal mounting direction and aged. In general, such a battery may be aged while being installed vertically in the terminal mounting direction as shown in FIG.

  Before step S16, the wound body 13 impregnates the nonaqueous electrolyte, so that the wound body 13 absorbs a part of the nonaqueous electrolyte. The nonaqueous electrolyte other than that which can be held by the wound body 13 is located in the gap in the case 15 as an excess electrolyte. In the figure, the excess electrolyte fills the case 15 up to the height of the interface 14.

  A state in which the inside of the case 15 is viewed from below in FIG. 4 will be described with reference to FIG. The insulator 9 surrounds the wound body 13 and prevents the wound body 13 from being short-circuited with the case 15. The wound body 13 includes a positive electrode 1, a negative electrode 2, and a separator (not shown). The positive electrode 1 includes a positive electrode mixture layer (not shown) on both surfaces of a positive electrode current collector 7 (not shown). The negative electrode 2 includes a negative electrode mixture layer on both surfaces of a negative electrode current collector 8 (not shown). The outermost periphery of the negative electrode 2 is located on the outer periphery of the outermost periphery of the positive electrode 1.

  Since the negative electrode 2 is arranged as shown in FIG. 3, the negative electrode mixture layer 4 located on the surface layer of the wound body in FIG. 4 does not face the positive electrode. In order to prevent a short circuit during aging caused by the negative electrode mixture layer 4, it is preferable that the positive electrode ends of the curved portions 16 at both ends in the flat direction of the wound body 13 are immersed in a nonaqueous electrolyte. The short circuit caused by the negative electrode mixture layer 4 will be described later. As shown in FIG. 4, by holding the winding shaft 25 of the winding body 13 substantially in parallel with the vertical direction, the positive electrode direction end 23 of the winding body 13 is located below the interface 14, and the nonaqueous electrolyte Immerse in.

  FIG. 5 schematically shows a cross section of the positive electrode 1 and the negative electrode 2 near the outermost periphery of the wound body 13 and the separator 20 positioned between them. The positive electrode 1 and the negative electrode 2 in FIG. 5 represent the outermost peripheral layers. As described above, the negative electrode 2 is on the outer peripheral side, and the positive electrode 1 is located on the inner peripheral side. In addition, the sheet-like positive electrode 1 and the negative electrode 2 are laminated such that both terminal connection surfaces are divided into a positive electrode direction end 23 and a negative electrode direction end 24 through the separator 20 and are alternately arranged. In order to prevent a short circuit during aging, the outermost positive electrode 1 of the wound body 13 is preferably immersed in a nonaqueous electrolyte as described below.

  The positive electrode current collector 7 is not in contact with the positive electrode mixture layer 3 and the positive electrode mixture layer 5 on the positive electrode direction end 23 side of the wound body 13 corresponding to the lower side in the figure, and is exposed as an uncoated part. The positive electrode mixture layer 3 is located on the inner peripheral side of the positive electrode 1. The positive electrode mixture layer 5 is located on the outer peripheral side of the positive electrode 1 and faces the negative electrode mixture layer 6 located on the inner peripheral side of the negative electrode 2.

  The positive electrode terminal 11 and the positive electrode 1 are in contact with each other with the uncoated portion exposed to the positive electrode current collector 7 as a terminal connection surface. The side ends of the positive electrode mixture layer 3 and the positive electrode mixture layer 5 on the lower positive electrode direction end 23 (+) side in the drawing are below the interface 14 of the nonaqueous electrolyte. The side end portion on the negative electrode direction end 24 (−) side in the upper side in the drawing is above the interface 14 of the nonaqueous electrolyte.

  The negative electrode current collector 8 is not in contact with the negative electrode mixture layer 4 and the negative electrode mixture layer 6 on the negative electrode direction end 24 side of the winding body 13 corresponding to the upper side in the drawing, and is exposed as an uncoated portion. The negative electrode mixture layer 4 is located on the outer peripheral side of the positive electrode 1 and does not face the positive electrode mixture layer. For this reason, there is very little opportunity to absorb lithium during charging. The negative electrode mixture layer 6 faces the positive electrode mixture layer 5.

  The negative electrode terminal 12 and the negative electrode 2 are in contact with each other with the uncoated portion exposed at the negative electrode current collector 8 as the terminal connection surface. The side ends of the negative electrode mixture layer 4 and the negative electrode mixture layer 6 on the lower positive electrode direction end 23 (+) side in the figure are below the interface 14 of the nonaqueous electrolyte. The side end portion on the negative electrode direction end 24 (−) side in the upper side in the drawing is above the interface 14 of the nonaqueous electrolyte.

  During high-temperature storage, it is preferable to immerse at least a part, preferably all, of the portion located on the outermost periphery of the positive electrode among the portions surrounded by the circles at the side end of the positive electrode mixture layer 5 in FIG. Such a portion is located at the positive electrode direction end 23 of the flat wound body. The part is more preferably located at the curved portions at both ends in the flat direction. The part is more preferably opposed to the outer peripheral negative electrode. This part is particularly preferably located on the outermost periphery of the positive electrode.

  By dipping such a part, a short circuit can be prevented particularly effectively. In addition, as a method for immersing the part, all of the outer peripheral positive electrode mixture layer or the inner peripheral and outer peripheral positive electrode mixture layer at the end in the positive electrode direction may be immersed in the nonaqueous electrolyte. By such a method, it is possible to suppress most of the short circuit that occurs at the end in the positive electrode direction due to metal elution from the positive electrode mixture layer.

  The said side edge part shall have a sagging part which arises in the positive electrode formation process mentioned later. Since such a sag part is likely to be a part that causes a short circuit, it is preferable to hold the entire sag part in a state of being immersed in a nonaqueous electrolyte. Such a method further enhances the short-circuit prevention effect.

  In the aging process, it is preferable that the positive electrode end is located below the end of the winding body on the opposite side of the winding axis direction with respect to the positive electrode direction end. In such a case, the nonaqueous electrolyte can prevent a short circuit without immersing the entire wound body during aging. In the present embodiment, the amount of nonaqueous electrolyte to be injected may be smaller than the amount capable of immersing the entire outermost periphery of the positive electrode during aging.

  Further, as described above, in a battery having a negative electrode direction end opposite to the winding axis direction with respect to the positive electrode direction end, for example, the battery is held in a state where the positive electrode direction end is positioned below the negative electrode direction end. ,be able to. In such a case, the operator can effectively prevent the occurrence of a short circuit in the aging process by simply arranging the battery in the direction shown in FIG. 4 without being aware of the portion of the wound body to be immersed.

  Since the method of this embodiment is a very simple method of placing a battery in a specific direction during aging, the battery design and configuration are not limited in implementation. Therefore, it can be applied to batteries in a wide range of fields.

  After step S16 is completed, it can be determined in the final inspection step whether the capacity and electric resistance of the battery are within a desired range. Although the produced battery is used after the final inspection process, the method of using the battery is not particularly limited. For example, a plurality of batteries can be assembled into a battery pack, and the battery pack can be mounted on an automobile and used as a driving power source. Specifically, it can be mounted on a power machine such as an electric vehicle (EV) or a plug-in hybrid vehicle (PHV) and used as an operating power source.

<Manufacture of battery components>
In the positive electrode forming step, the positive electrode mixture layer is laminated on the positive electrode current collector to form the positive electrode. For example, a positive electrode active material is applied to a positive electrode current collector such as an aluminum foil to produce a positive electrode. In the present embodiment, the positive electrode active material is not particularly limited.

As the positive electrode active material, for _{example, LiCoO 2, LiMnO 2, LiMn} 2 O 4, LiNiO 2, LiNi x Co (1-x) O 2, and _{LiNi x Mn y Co (1-} x-y) O 2 , etc. Lithium-containing composite oxides can be used (0 <x <1, 0 <y <1). As a ternary active material represented by LiNi _x Co _y Mn _(1-xy) O ₂ , LiNi _1/3 Co _1/3 Mn _1/3 O ₂ is preferable.

  As a method for applying the positive electrode active material, first, using a dispersant such as N-methyl-2-pyrrolidone, the above positive electrode active material, a conductive auxiliary agent such as acetylene black (AB), and polyvinylidene fluoride (PVDF) A binder like slurry is mixed to obtain a slurry-like paste. This paste is applied onto a positive electrode current collector such as an aluminum foil, dried, and pressed to obtain a positive electrode mixture layer.

  Since the positive electrode mixture paste has a predetermined fluidity, a sagging portion is generated at the side end portion during application. In FIG. 5, a slanted sagging portion appears on the positive electrode mixture layers 3 and 5 on the lower positive electrode direction end 23 side in the drawing. In the present embodiment, the side end portions of the positive electrode mixture layers 3 and 5 on the negative electrode direction end 24 side are formed by cutting a laminate composed of the positive electrode mixture layer and the positive electrode current collector. For this reason, the cut surfaces of the positive electrode mixture layers 3 and 5 are aligned with the cut surface of the positive electrode current collector 7. That is, the positive electrode 1 includes a positive electrode end surface 21 in which the end surface of the positive electrode current collector 7 and the end surfaces of the positive electrode mixture layers 3 and 5 are substantially flush. With this configuration, the exposed portion of the positive electrode current collector 7 does not appear on the negative electrode direction end 24 side.

  In the negative electrode forming step, the negative electrode mixture layer is laminated on the negative electrode current collector to form the negative electrode. As a negative electrode formation process of a negative electrode, a negative electrode active material is apply | coated to negative electrode collectors, such as copper foil, for example, and a negative electrode is manufactured. Negative electrode active materials include metallic lithium, lithium alloys, transition metal oxides / transition metal nitrides / transition metal sulfides capable of doping / dedoping lithium ions, and carbon-based materials such as graphite, etc. And the like.

  As a method for applying the negative electrode active material, first, using a dispersant such as water, graphite, a binder such as modified styrene-butadiene copolymer latex (SBR), carboxymethylcellulose Na salt (CMC), etc. Mix with thickener to obtain slurry. This slurry is applied onto a negative electrode current collector such as a copper foil, dried, and pressed to obtain a negative electrode mixture layer. The side end portion of the negative electrode mixture layer also has the same configuration as the side end portion of the positive electrode mixture layer. For this reason, the cut surfaces of the negative electrode mixture layers 4 and 6 are aligned with the cut surface of the negative electrode current collector 8. That is, the negative electrode 2 includes a negative electrode end surface 22 in which the end surface of the negative electrode current collector 8 and the end surfaces of the negative electrode mixture layers 4 and 6 are substantially flush.

  The non-aqueous electrolyte includes a mixed solvent of a high dielectric constant carbonate solvent such as propylene carbonate or ethylene carbonate and a low viscosity carbonate solvent such as diethyl carbonate, methyl ethyl carbonate, or dimethyl carbonate, and a lithium-containing electrolyte. A non-aqueous electrolyte in which is dissolved is preferable. As the mixed solvent, a mixed solvent of ethylene carbonate (EC) / dimethyl carbonate (DMC) / ethyl methyl carbonate (EMC) is preferable.

As the supporting salt, a lithium-containing electrolyte is preferable. Examples of the lithium-containing electrolyte include LiPF ₆ , LiBF ₄ , LiClO ₄ , LiAsF ₆ , Li ₂ SiF ₆ , LiOSO ₂ C _k F _{(2k + 1)} (k = 1 to 8), LiPF _n {C _k F _{(2k + 1) )} (6-n) (} n = 1~5 integer, k = 1 to 8 integer) lithium salts, and the like, and combinations thereof are preferred. LiPF ₆ is preferred as the lithium salt.

  The separator may be a film that electrically insulates the positive electrode and the negative electrode and is permeable to lithium ions. As the separator, a porous polymer film is preferable. The separator is preferably a polyolefin porous film such as a PP (polypropylene) porous film, a PE (polyethylene) porous film, or a laminated porous film of PP (polypropylene) -PE (polyethylene).

  Secondary battery types include cylindrical, coin, rectangular, and film types. The case can be selected according to the desired mold. The square battery is superior in space utilization efficiency when the batteries are assembled to form a battery pack as compared with, for example, a cylindrical battery. In addition, an insulating layer for insulating the case and the wound body can be provided.

  Moreover, the thing which can be fitted to the said case can be selected as a sealing body. In the present embodiment, the sealing body has a hole through which a positive electrode terminal connected to the positive electrode and a negative electrode terminal connected to the negative electrode can pass. The sealing body has one or a plurality of injection ports.

  When the sealing body has such a structure, the wound body, the positive electrode and the negative electrode terminal, and the nonaqueous electrolyte can be accommodated and sealed from one opening provided in the case. In addition, only the sealing body needs to be processed, and processing such as perforation is unnecessary on the side of the case, so that the production efficiency is improved.

  The positive electrode terminal and the negative electrode terminal have a desired shape so as to conform to the structure of the battery, that is, the shape of the case, the direction in which the wound body is inserted into the case, and the positions where both terminals on the surface of the case and the sealing body should be provided. You can choose one. As the structure of the battery, the structure shown in FIG. 4 is preferable because the structure of the prismatic battery is simple. As a more specific structure, the thing of FIG. 2 demonstrated in the following Example is mentioned.

  Such a battery includes a negative electrode direction end 24 positioned opposite to the positive electrode direction end in the direction of the winding axis, and a winding body having a winding axis direction substantially parallel to the opening surface of the rectangular case. And a positive electrode terminal and a negative electrode terminal connected to the one sealing member fitted to the opening surface.

As a feature thereof, the winding axis of the winding body has a direction substantially parallel to the opening surface of the case. Moreover, a positive electrode and a negative electrode terminal are respectively connected to both ends of the wound body in the winding axis direction. Moreover, both terminals penetrate the hole provided in the both ends of the direction parallel to the winding axis | shaft of a sealing body, or both sides.

  With such a battery structure, there is no need to route the positive electrode and the negative electrode terminal within the case. For this reason, the shape of both terminals can be as simple as a short rod shape, and the production efficiency of the battery is improved. The method of the present embodiment can be particularly suitably used for a battery having the above structure.

<Modification of Embodiment>
The present invention is not limited to the above-described embodiment, and can be changed as appropriate without departing from the spirit of the present invention. In the present embodiment, in the aging process, the installation direction of the battery is maintained so that the positive electrode end of the wound body is immersed in the nonaqueous electrolyte. On the other hand, you may hold | maintain the direction of a battery similarly in any other processes, such as an injection | pouring process, an immersion process, a press process, or a conditioning process. Alternatively, the assembled battery may be installed so that the end in the positive electrode direction is downward until the aging process is completed. In such a case, the work of changing the installation direction of the battery can be reduced.

  In this embodiment, the battery is installed horizontally in the terminal mounting direction. This is because it is preferable from the viewpoint of easy installation and prevention of battery overturn. As a modification of the present embodiment, as long as the above-described part is immersed in the nonaqueous electrolyte, the battery can be inclined to a desired angle. In this case, by supporting the inclined side with the support member, the entire battery can be stably supported rather than placing it on a flat surface.

[Description of effects]
<Overview>
The battery 10 shown in FIG. 6 is the same as that shown in FIG. The positive electrode terminal 11 and the negative electrode terminal 12 are located above in the figure. In the drawing, the surface on the side opposite to the opening surface side or the sealing body side where the positive electrode terminal 11 and the negative electrode terminal 12 are provided is the bottom surface. The nonaqueous electrolyte is accumulated up to the height of the interface 14 on the bottom surface. Since the wound body 13 is located higher than the interface 14, it is not immersed in the nonaqueous electrolyte.

  6 is a general method for placing a prismatic battery having the structure shown in the figure. For example, a battery pack can be made by stacking and putting the rectangular batteries placed in such a direction on a plane parallel to the winding axis direction and the vertical direction.

  When a battery is placed in the manner shown in FIG. 6 and aging is performed, a short circuit of the battery indicated by a star may occur. The inventors have found a common feature in the location where such a short circuit occurs. Common features are local overcharge and high temperature and the presence of oxygen. The inventors considered that these caused dissolution / elution of the positive electrode active material. The mechanism of occurrence of a short circuit will be described later.

  The inventors have found that the local high potential is due to the local high amount of non-aqueous electrolyte during initial conditioning. Usually, in order to prevent conduction between the electrode and the case, a separator is located on the outermost layer of the wound body. Further, the curved portion of the wound body is less likely to be restrained as will be described later. For this reason, in the outermost layer of the curved portion, a separator that easily contains a non-aqueous electrolyte is more likely to store surplus non-aqueous electrolyte.

  From this, the inventors have found that the short circuit due to the high potential is due to the presence of a large amount of non-aqueous electrolyte at the place where the short circuit is likely to occur. However, since a non-aqueous electrolyte is indispensable for the conditioning treatment, it is necessary to devise appropriate measures to remove it from a place where a short circuit is likely to occur. The part where the short circuit is likely to occur will be described later.

  Aging is intended to improve battery characteristics at the initial use of the battery by storage at high temperature. The improvement of the battery characteristics means that the electric resistance inside the battery at the initial use is reduced and the capacity is improved. For this reason, it is difficult to remove the high temperature factor.

  Therefore, the inventors paid attention to oxygen mixed in the atmosphere in the case at the time of cell sealing. We paid attention to non-aqueous electrolytes as a method of preventing oxygen from touching places where short-circuiting is likely to occur. Usually, the non-aqueous electrolyte is injected into the case more than the amount that can be held in the wound body in consideration of volatilization after long-term use.

  In the method of the present embodiment, such excess electrolyte prevents oxygen from being in contact with a portion where local overcharge is likely to occur. It has been found that this method can prevent dissolution and elution of the positive electrode active material and prevent occurrence of a short circuit during high temperature storage.

  When the method of this embodiment is simply expressed, as shown in FIG. 4, the rectangular battery is aged by being placed horizontally with respect to a direction perpendicular to the terminal surface of the battery. From another viewpoint, the battery is placed vertically with respect to the longitudinal direction of the battery.

<Mechanism of short circuit occurrence>
FIG. 7 estimates the dissolution / deposition mechanism of the positive electrode active material described above. In FIG. 7, the positive electrode 1 and the negative electrode 2 face each other in the vicinity of the outermost periphery of the wound body. As in FIG. 5, the sheet-like positive electrode 1 and negative electrode 2 are divided into a positive electrode direction end on the positive electrode terminal 11 side and a negative electrode direction end on the negative electrode terminal 12 side through a separator (not shown). The layers are stacked in a staggered manner. The positive electrode mixture layer 3 faces the inner negative electrode mixture layer in the wound body. The positive electrode mixture layer 3 faces the negative electrode mixture layer 6.

  In these mixture layers, lithium ions are desorbed and absorbed, so that charging is performed. In FIG. 7, the positive electrode current collector 7 is located between the positive electrode mixture layer 3 and the positive electrode mixture layer 5. In FIG. 7, the positive electrode current collector 7 is left on the right side and is coupled to the positive electrode terminal 11. The negative electrode current collector 8 is positioned between the negative electrode mixture layer 4 and the negative electrode mixture layer 6. On the left side in FIG. 7, the negative electrode current collector 8 is left and is coupled to the negative electrode terminal 12.

In FIG. 7, the separator is omitted. The positive electrode active material is a material containing Mn such as LiNi _1/3 Co _1/3 Mn _1/3 O ₂ . Supporting salt is LiPF _6. Further, there is no positive electrode mixture layer facing the outermost negative electrode mixture layer 4. For this reason, the negative electrode mixture layer 4 cannot receive lithium ions and remains uncharged.

  The mechanism by which metal elution occurs is estimated as follows. That is, from the above configuration, the positive electrode active material is largely lacking with respect to the negative electrode active material at the right end portions of the positive electrode 1 and the negative electrode 2. Further, the lithium ions desorbed from the positive electrode mixture layer 5 may wrap around the right end of the negative electrode 2 in the drawing and reach the uncharged negative electrode mixture layer 4 in some cases.

  For this reason, many lithium ions are easily detached from the right end portion of the positive electrode mixture layer 5 as compared with the amount of the positive electrode active material. Such desorption of lithium ions during the initial charging step generates a local high potential at the right end of the positive electrode 1. It is estimated that the positive electrode metal is eluted by adding a high temperature environment such as an aging process to such a local high potential. As a metal in the positive electrode active material, it is estimated that manganese is particularly easily eluted. Moreover, it is estimated that such elution causes an internal short circuit.

<Locations where short circuits are likely to occur>
The inventors have found that the outermost periphery of the wound body is a place where a short circuit is likely to occur. As shown in FIG. 3, the outermost periphery of the negative electrode is located on the outer peripheral side of the outermost periphery of the positive electrode. As described above, the negative electrode mixture layer on the wound body surface layer is left uncharged. For this reason, there is a high possibility that lithium ions are extracted from the positive electrode facing inside. For this reason, the part located in the outermost periphery among the wound positive electrodes tends to be in an overcharged state, and a local high potential is generated and the positive electrode active material is easily eluted.

  The inventors have found that the end in the positive electrode direction is a place where a short circuit is likely to occur. The positive electrode elution location where a short circuit occurs will be described with reference to FIG. 7 are the same as those in FIG. As shown in FIG. 7, there is no uncoated portion of the negative electrode 2 at the end of the winding body on the outermost periphery, and the cut surfaces of the negative electrode mixture layers 4 and 6 and the negative electrode current collector 8 appear. For this reason, since there is nothing that hinders movement, lithium ions generated from the positive electrode 1 reach the uncharged negative electrode mixture layer 4 that does not face the positive electrode 1. On the other hand, lithium ions generated from the positive electrode mixture layer 5 at the negative electrode end are blocked by the uncoated portion of the negative electrode current collector 8 and cannot reach the negative electrode mixture layer 4.

  The inventors have found that, in a battery including a flat-shaped winding body in particular, a portion where no restraining load is applied becomes a place where a short circuit is likely to occur. As shown in FIG. 3, in the battery including the flat wound body, the flat end portion is restrained by the pressing of the force 17. On the other hand, in the upper and lower curved portions in the drawing, no restraint load is applied as shown by the broken line.

  Further, the wound body 13 is not in contact with the sealing body on the bottom surface or the opening surface of the case, and is generally suspended in the case 15. For this reason, it is rare that a restraint load is applied to the curved portion. Note that, in a cylindrical battery including a cylindrical winding body, it is common to apply a restraining load evenly to the winding body throughout the case.

  For this reason, the method of the present embodiment has a particularly large short-circuit suppressing effect in a battery including a wound body having a portion that is not subjected to a restraining load or receives only a weak restraining load. A typical example of such a battery is a prismatic battery including a flat wound body.

  Summing up the above, the inventors are in the side of the positive electrode mixture layer belonging to the outermost periphery of the positive electrode of the curved portion at both ends of the flat-shaped wound body at the positive electrode end during high-temperature storage in the aging process. It was found that a short circuit is likely to occur at the end.

In the description of the embodiments, the aging process will be described. The positive electrode of the battery of this example contains LiNi _1/3 Co _1/3 Mn _1/3 O ₂ as a positive electrode active material, acetylene black as a conductive additive, and PVDF as a binder. The negative electrode contained graphite as a negative electrode active material, SBR as a binder, and CMC as a thickener. A positive electrode and a negative electrode mixture layer containing each of the above materials were formed on the positive electrode and the negative electrode current collector to form a positive electrode and a negative electrode.

  Next, the battery 10 was assembled as shown in FIG. A wound body 13 having a flat shape was accommodated in a rectangular case 15. The insertion direction of the wound body 13 is such that the winding shaft 25 of the wound body 13 is parallel to the opening surface above the case 15 in the drawing.

  Further, the positive electrode terminal 11 was attached to an uncoated portion of the positive electrode current collector 7. Further, the negative electrode terminal 12 was attached to an uncoated portion of the negative electrode current collector 8. Further, the sealing body 19 was fitted into the opening surface of the case 15 at the upper side in the figure.

  The positive terminal 11 includes an external positive terminal 40, an internal positive terminal 45, and the like. The external positive terminal 40 includes a bolt 41, a connecting member 42, a caulking member 43, and the like. The connecting member 42 includes a screw hole portion into which the bolt 41 is screwed. The bolt 41 and the connecting member 42 are connected by screwing the bolt 41 into the screw hole.

The connecting member 42, the sealing body 19, and the insulating member 60 were provided with a caulking hole. And the insulating member 60, the sealing body 19, and the connection member 42 were mutually connected by crimping the crimping member 43 in the crimping hole part of the insulating member 60, the sealing body 19, and the connection member 42. FIG. In addition, the external positive terminal 40 was connected to the sealing body 19 via an insulating member 60.

  The negative electrode terminal 12 includes an external negative electrode terminal 50, an internal negative electrode terminal 55, and the like. The external negative electrode terminal 50 includes a bolt 51, a connecting member 52, a caulking member 53, and the like. The connecting member 52 includes a screw hole portion into which the bolt 51 is screwed. The bolt 51 and the connecting member 52 are connected by screwing the bolt 51 into the screw hole.

The connecting member 52, the sealing body 19, and the insulating member 70 have crimped holes. The insulating member 70, the sealing body 19, and the connecting member 52 are connected to each other by caulking the caulking member 53 in the caulking hole portions of the insulating member 70, the sealing body 19, and the connecting member 52. The external negative electrode terminal 50 was connected to the sealing body 19 via an insulating member 70. After the battery was assembled as described above, a nonaqueous electrolyte was poured from an injection port (not shown) and injection was performed. Supporting salt in the nonaqueous electrolyte was LiPF _6.

  The battery was stored at room temperature for a predetermined time, and the wound body was impregnated with a nonaqueous electrolyte. After impregnation, the battery was pressed with a weight of 500 kg. The pressing direction was a direction in which the wound body should be flattened as shown in FIG. 3 and a direction perpendicular to the winding axis direction. After pressing, the non-aqueous electrolyte did not exude from the wound body. After pressing, conditioning treatment was performed. First, CCCV charge was performed. The battery was charged to a final voltage of about 4 V at a current value of about 5 A at room temperature.

  After charging and discharging, as shown in FIG. 8, the positive electrode terminal 11 and the negative electrode terminal 12 were opened, stored at a high temperature of 60 ° C. or higher under normal pressure for 20 hours, and subjected to an aging treatment. As shown in FIG. 8, the case 15 was placed sideways so that the positive electrode direction end was downward as shown in FIG. In FIG. 8, the same members as those in FIG. As shown by the interface 14, the nonaqueous electrolyte was immersed in the wound body to the upper side of the side end portion on the positive electrode direction end side of the positive electrode mixture layer 5 of the outermost positive electrode. In the wound body 13, a positive electrode current collector and the like are not shown. The wound body is fixed in a wound state by a winding tape 30.

  Finally, the presence or absence of a short circuit was confirmed. In particular, the correlation between the location of the short circuit and the positional relationship between the nonaqueous electrolyte interface and the wound body was investigated. The location where the short circuit occurred was examined as follows. First, the battery after aging was disassembled, and the wound body was taken out. Next, the wound body was confirmed, and when the deposition of the positive electrode active material was detected by elemental analysis at the location where the short circuit occurred, it was determined that the short circuit occurred. As shown in FIG. 8, no short circuit occurred in the example. In addition, the height of the interface was judged from the transmission image which image | photographed the battery of each step with the X-ray CT apparatus (FIGS. 14-20).

<Comparative Example 1>
A battery was assembled as in the example. As shown in FIG. 9, the battery was installed in the same manner as in the example except that the terminal side was turned upward and aging was performed. As shown in FIG. 9, it was found that a short circuit occurred at the outermost periphery of the curved portion at the positive electrode end of the wound body that was not in contact with the nonaqueous electrolyte.

<Comparative example 2>
A battery was assembled as in the example. As shown in FIG. 10, the battery was installed in the same manner as in the example except that the end in the negative electrode direction was lowered and aging was performed. As shown in FIG. 10, it was found that a short circuit occurred at the outermost periphery of the curved portions at both ends of the end in the positive electrode direction not in contact with the nonaqueous electrolyte of the wound body.

<Comparative Example 3>
A battery was assembled as in the example. As shown in FIG. 11, the battery was installed in the same manner as in Example except that the terminal side was lowered and aging was performed. As shown in FIG. 11, it was found that a short circuit occurred at the outermost periphery of the curved portions at both ends at the end in the positive electrode direction. In addition, since the space on the terminal side is large due to the structure of the case, in the comparative example 3, the curved portion that was on the lower side was not immersed in the nonaqueous electrolyte. For this reason, unlike Comparative Example 1, a short circuit occurred at the curved portions at both ends.

<Comparative example 4>
A battery was fabricated in the same manner as in Example except that the injection amount was 33 g. As shown in FIG. 12, the battery was installed in the same manner as in the example except that the terminal side was turned upward and aging was performed. The non-aqueous electrolyte after aging was all retained in the wound body as shown in FIGS. As shown in FIG. 12, it was found that a short circuit occurred at the outermost periphery of the curved portions at both ends at the end in the positive electrode direction.

<Comparative Example 5>
A battery was fabricated in the same manner as in Example except that the injection amount was 55 g. As shown in FIG. 13, the battery was disposed in the same manner as in the example except that the terminal side was turned upward and aging was performed. When the battery was installed with the terminals facing upwards, the interface of the non-aqueous electrolyte after aging was more than half the height of the wound body as shown in FIGS.

  As shown in FIG. 17, the interface of the nonaqueous electrolyte after conditioning was less than half the height of the wound body when the battery was installed with the end in the positive electrode direction down. Moreover, as shown in FIG. 18, all the nonaqueous electrolytes after pressing and before conditioning were held by the wound body. As shown in FIG. 19, the interface of the nonaqueous electrolyte after conditioning was less than half the height of the wound body when the battery was installed with the terminals facing upward.

  It is considered that the wound body expanded due to the conditioning process, and the nonaqueous electrolyte was pushed out of the wound body. For this reason, it turned out that it is preferable to adjust the quantity of the nonaqueous electrolyte which should be inject | poured as described in embodiment. As shown in FIG. 13, it was found that a short circuit occurred at the outermost periphery of the curved portion at the positive electrode end of the wound body that was not in contact with the nonaqueous electrolyte. The signs of short circuit were small.

<Comparative Example 6>
A battery was produced in the same manner as in Example except that the injection amount was 40 g. The treatment was performed in the same manner as in the example, including the direction of battery installation during aging. As shown in FIG. 15, the interface of the non-aqueous electrolyte after aging was less than half the height of the wound body when the battery was installed with the terminals facing upward. Further, as shown in FIG. 20, the interface of the non-aqueous electrolyte after aging did not reach the side edge of the positive electrode mixture layer when the battery was installed with the positive electrode end facing downward. When the occurrence of a short circuit was confirmed, it was found that a short circuit occurred at the outermost periphery of the curved portions at both ends at the positive electrode end of the wound body.

  As described above, the present invention is not limited to the configurations of the above-described embodiments or examples, and various modifications, corrections, and combinations that can be made by those skilled in the art within the scope of the invention of the claims of the claims of the present application. Of course.

DESCRIPTION OF SYMBOLS 1 Positive electrode 2 Negative electrode 3 Positive electrode mixture layer 4 Negative electrode mixture layer 5 Positive electrode mixture layer 6 Negative electrode mixture layer 7 Positive electrode collector 8 Negative electrode collector 10 Battery (nonaqueous electrolyte secondary battery) 11 Positive electrode terminal 12 Negative electrode terminal 13 Winding body 15 Case 19 Sealing body (planar member)
20 Separator 21 Positive End Face 22 Negative End Face 23 Positive Direction End 24 Negative Direction End 25 Winding Shaft S11 Lamination Process S12 Winding Process S13 Assembly Process S14 Injection Process (-Immersion Process / Pressing Process)
S15 Conditioning process S16 Aging process

Claims (8)

A lamination step of laminating a positive electrode, a separator, and a negative electrode to create a laminate; and
Winding the laminate to create a wound body, and a winding step;
Assembling a battery by storing the wound body in a case; and
An injection step of injecting a non-aqueous electrolyte into the case;
An initial charging step for charging the battery;
An aging step of storing the charged battery in a temperature range of 30 ° C. or higher without applying a voltage between the positive electrode and the negative electrode,
In the lamination step,
The positive electrode comprises a positive electrode current collector, and a positive electrode mixture layer located on both sides of the positive electrode current collector,
The negative electrode includes a negative electrode current collector, a negative electrode mixture layer positioned on both sides of the negative electrode current collector, and a negative electrode end surface in which an end surface of the negative electrode current collector and an end surface of the negative electrode mixture layer are substantially flush with each other With
In the winding step, in the negative electrode outermost periphery located on the outer peripheral side of the positive electrode outermost periphery, the negative electrode mixture layer on the outer peripheral side does not face the positive electrode mixture layer, and the laminate is wound,
In the aging step, during storage, it is held in a state in which at least a part of the side end portion of the positive electrode mixture layer facing the end portion of the negative electrode mixture layer adjacent to the negative electrode end surface is covered with the nonaqueous electrolyte.
A method for producing a non-aqueous electrolyte secondary battery.   The method for manufacturing a nonaqueous electrolyte secondary battery according to claim 1, wherein the temperature range is 60 ° C. or higher. After the winding step and before the assembly step, the winding body is pressed and deformed to have a flat shape, further comprising a deformation step,
In the aging process, during storage, the side ends of the positive electrode mixture layer on the outermost periphery of the positive electrode located at the curved portions at both ends in the flat direction of the flat wound body and facing the negative electrode on the outer periphery The method for producing a non-aqueous electrolyte secondary battery according to claim 1, wherein at least a part of the non-aqueous electrolyte is held in a state immersed in the non-aqueous electrolyte.   The manufacturing method of the non-aqueous electrolyte secondary battery according to claim 3, wherein in the aging step, all of the side end portions are held in a state of being immersed in the non-aqueous electrolyte.   The manufacturing method of the nonaqueous electrolyte secondary battery according to claim 3, wherein in the aging step, all of the sagging portions of the side end portions are held in a state of being immersed in the nonaqueous electrolyte during storage.   The method for producing a nonaqueous electrolyte secondary battery according to any one of claims 1 to 5, wherein in the aging step, all of the side end portions of the positive electrode mixture layer are held in a state of being immersed in the nonaqueous electrolyte. .   The method for producing a nonaqueous electrolyte secondary battery according to claim 6, wherein in the aging step, a side end portion of the positive electrode mixture layer is positioned below in a direction of a winding axis of the wound body. In the aging process,
A planar member that fits into one opening surface of the square case;
A positive electrode terminal and a negative electrode terminal connected to the planar member;
A winding axis substantially parallel to the opening surface, a positive electrode end connected to the positive electrode terminal, and a negative electrode end connected to the negative electrode terminal on the opposite side of the winding axis direction with respect to the positive electrode end. The wound body having
The manufacturing method of the nonaqueous electrolyte secondary battery according to claim 6 or 7, wherein the battery including the battery is held in a state where the positive electrode direction end is positioned below the negative electrode direction end.

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