JP4400289B2 - Disassembly method of wound battery - Google Patents

Description

The present invention relates to a method for disassembling a wound battery, and in particular, a wound group in which a first separator, a negative electrode, a second separator, and a positive electrode are stacked and wound in this order, and the first separator is disposed on the outermost periphery. Relates to a method of disassembling a wound battery housed in a battery container.

  In the automobile industry, in order to respond to environmental problems, the development of hybrid (electric) vehicles using both an internal combustion engine and a battery as the power source, as well as an electric vehicle with no exhaust gas, which uses only a battery as the power source. Has been accelerated and has reached the stage of practical application.

  A battery serving as a power source for an electric vehicle is naturally required to have high output and high energy characteristics, and at the same time, high reliability that can withstand long-term use (maintain battery performance). In order to reduce the economic burden on vehicle-related personnel, including vehicle users, the battery must not be replaced (no need to be replaced) during the period from the registration of a new vehicle to the end of the vehicle's life and the disuse of the vehicle. Is desirable. In order to improve battery reliability, there is no deterioration in battery performance due to repeated charging / discharging corresponding to vehicle use and parking for a long period of time, and when multiple batteries are installed per vehicle. Various items such as the absence of variation in battery performance between batteries and the expansion of variation in battery performance during vehicle use have been studied. Conversely, there are various factors that reduce the reliability of the battery.

  One factor that reduces the reliability of the battery is that foreign matter is mixed between the positive and negative electrodes and the separator from the battery manufacturing environment. In particular, in a lithium ion battery, in order to obtain a high output, the charging / discharging area is expanded by forming a winding group in which the positive and negative electrodes are wound through a separator, and the lithium ion battery is disposed between the positive and negative electrodes. As the separator, an ultrathin polyethylene or polypropylene film having a thickness of several tens of μm is used. Since the battery mounted on the vehicle is subject to external factors such as charging / discharging in the vehicle, vibration during traveling, and temperature changes in the surrounding environment, the stacking pressure between the positive and negative electrodes / separator (winding) Depending on the situation where the pressure is applied, there is a possibility that the foreign matter mixed in the battery itself penetrates the ultrathin separator and causes an internal short circuit. In particular, when the foreign matter is a conductive foreign matter such as a metal, it may be said that an internal short circuit is always caused when it passes through the separator.

  In addition, in the case of metals such as copper and iron that are easily dissolved and deposited electrochemically, the foreign matter that adheres to the positive electrode and enters the battery is easily charged with the high potential positive electrode that is in a charged state. Dissolve. The dissolved metal ions diffuse in the electrolytic solution and eventually reach the low potential negative electrode and precipitate as metal on the negative electrode surface. The deposited metal grows the electrolyte phase in the separator, and the growth tip reaches the positive electrode to cause an internal short circuit. In this case, the deposition growth pattern of the metal on the negative electrode surface reflects the concentration distribution during diffusion of the metal ions dissolved in the positive electrode, so that the deposition trace is small on the positive electrode side of the separator, and conversely, the deposition on the negative electrode side of the separator. Large marks will remain.

  Regardless of whether the foreign material itself penetrates the separator or whether the foreign material has melted or deposited, the separator always leaves traces of the foreign material mixed in. Therefore, the observation of the separator grasps the foreign material contamination status. It is extremely important to do so. In battery manufacturers, it is common to observe the surfaces of positive and negative electrodes and separators taken apart by disassembling batteries in order to confirm the state of foreign matter contamination from the manufacturing environment. At this time, the wound group is taken out from the battery container, and the taken-out wound group is unwound and observed on a flat plate such as a mounting table, for example.

  On the other hand, in order to inspect the contamination of metal foreign matter, the positive and negative electrodes facing each other through the separator are infiltrated into the electrolyte, and a predetermined voltage is applied between the positive and negative electrodes to deposit the mixed metal as black spots on the separator. The technique to make is disclosed (for example, refer patent document 1).

JP 2001-345094 A

  However, when removing the wound group from the battery container and disassembling it, foreign substances may be mixed in from the surrounding environment. Sometimes it is not possible to distinguish it from foreign matter. In order to avoid this, even if the disassembly work is performed in a clean room environment that is free from contamination from the surrounding environment, the ultrathin separator should come into contact with the mounting table when the winding group is unwound on the mounting table. May damage the accurate observation of traces of foreign matter.

  An object of the present invention is to provide a method for disassembling a wound battery that can prevent the separator from being damaged during disassembly.

In order to solve the above problems, the present invention provides a winding group in which a first separator, a negative electrode, a second separator, and a positive electrode are stacked and wound in this order, and the first separator is disposed on the outermost periphery. A method for disassembling a wound battery housed in a container, wherein the wound group is taken out from the battery container, and the taken-up wound group is removed from a lower layer which is a layer in contact with a mounting table , the positive electrode and the negative electrode Unwinding so that any one of the first and second separators, the other of the positive and negative electrodes, and the other of the first and second separators are stacked in order. It is characterized by including.

In the method for disassembling the wound battery of the present invention, the wound group housed in the battery container is taken out from the battery container, and the taken-up wound group is removed from the lower layer, which is a layer in contact with the mounting table, from either the positive electrode or the negative electrode On the other hand, in order to unravel the stacking order of either one of the first and second separators, either the positive electrode or the negative electrode, or the other of the first or second separator, When placed, either one of the lowermost positive electrode and the negative electrode comes into contact with the mounting table, and the first and second separators do not come into contact with the mounting table. Damage to the second separator can be prevented.

  In this case, after the step of unwinding the wound group first unravels approximately one turn of the first separator from the taken-up wound group, the wound group is removed from the lower layer by the negative electrode, the second separator, the positive electrode If the first separator is unrolled in the stacking order, the negative electrode becomes the lowest layer and comes into contact with the mounting table, so that contact with the mounting table of the first and second separators can be prevented. Further, the step of unwinding the wound group is to first unravel the first separator, the negative electrode, and the second separator from the taken-up wound group for about one turn, and then remove the wound group from the lower layer to the positive electrode, If the first separator, the negative electrode, and the second separator are unwound in the stacking order, the positive electrode becomes the lowest layer and comes into contact with the mounting table, thereby preventing the first and second separators from contacting the mounting table. Can do.

According to the present invention, the wound group accommodated in the battery container is taken out from the battery container, and the taken-up wound group is removed from the lower layer which is a layer in contact with the mounting table , either the positive electrode or the negative electrode, In order to unravel the stacking order of either one of the second separator, the other of the positive electrode and the negative electrode, or the other of the first and second separators, for example, when placed on the mounting table, Since either the lowermost positive electrode or the negative electrode is in contact with the mounting table, and the first and second separators are not in contact with the mounting table, the first and second separators are damaged when the wound battery is disassembled. The effect that can be prevented can be obtained.

  Hereinafter, an embodiment in which a decomposition method according to the present invention is applied to a cylindrical lithium ion secondary battery will be described with reference to the drawings.

<Battery configuration>
As shown in FIG. 1, a cylindrical lithium ion secondary battery 20 of the present embodiment is described later around a stainless steel bottomed cylindrical battery can 8 and a resin-made cylindrical core 7 serving as a battery container. The strip-shaped positive electrode and negative electrode that are wound are provided with a wound group 5 wound through a separator.

  On the upper side of the winding group 5, a ring-shaped positive current collecting ring 14 for collecting the potential from the positive electrode is disposed. The positive electrode current collector ring 14 is fixed to the upper end portion of the winding core 7 via a positive electrode current collector ring support that supports the positive electrode current collector ring 14. The edge of the positive electrode lead piece 12 extending from the positive electrode is welded to the periphery of the positive electrode current collecting ring 14. Above the positive electrode current collecting ring 14, a disk-shaped battery lid 9 having a central portion formed in a convex shape is disposed. The upper part of the positive electrode current collecting ring 14 is electrically connected to the lower part of the battery lid 9 through a positive electrode lead plate. On the other hand, a ring-shaped negative electrode current collecting ring 15 for collecting a potential from the negative electrode is disposed below the winding group 5, and the negative electrode current collecting ring 15 is a negative electrode that supports the negative electrode current collecting ring 15. It is fixed to the lower end of the winding core 7 via a current collecting ring support. The edge of the negative electrode lead piece 13 extending from the negative electrode is welded to the peripheral edge of the negative electrode current collecting ring 15, and the lower part of the negative electrode current collecting ring 15 is welded to the inner bottom portion of the battery can 8 via the negative electrode lead plate. Has been.

  The battery lid 9 is fixed by being crimped to the upper part of the battery can 8 via an insulating and heat resistant gasket. For this reason, the inside of the lithium ion secondary battery 20 is sealed. A predetermined amount of non-aqueous electrolyte solution (not shown) is injected into the battery can 8, and the wound group 5 is infiltrated with the non-aqueous electrolyte solution (not shown).

  As shown in FIG. 2, the wound group 5 includes a separator 1, a negative electrode N, a separator 2, and a positive electrode through two separators 1 and 2 each having a positive electrode P and a negative electrode N made of polyethylene and having a thickness of about 40 μm. Laminated in the order of P and wound around the core 7. For this reason, the positive electrode P is disposed on the innermost periphery on the winding core 7 side of the wound group 5, and the separator 1 is disposed on the outermost periphery of the wound group 5. Further, the separator 1 is disposed on the outer peripheral side of the negative electrode N, and the separator 2 is disposed on the outer peripheral side of the positive electrode P. An insulating film that electrically insulates the winding group 5 and the battery can 8 is wound on the outer peripheral surface of the winding group 5 (the outer periphery of the separator 1). The winding end of the insulating film is fixed with a squeeze-off adhesive tape or the like.

  The positive electrode P constituting the wound group 5 described above has a strip-shaped aluminum foil having a thickness of about 15 to 30 μm as a positive electrode current collector. On both surfaces of the aluminum foil, a lithium transition metal double oxide powder of a positive electrode active material is applied together with a binder (binder). On the side edge on one side in the longitudinal direction of the positive electrode P, an uncoated portion where the both surfaces of the positive electrode active material are not applied is formed, and a positive electrode lead piece 12 is formed in the uncoated portion. On the other hand, the negative electrode N has a strip-shaped copper foil having a thickness of about 10 to 20 μm as a negative electrode current collector. A carbon material powder of a negative electrode active material is coated on both sides of the copper foil together with a binder. An uncoated portion where both sides of the negative electrode active material are not applied is formed on the side edge on one side in the longitudinal direction of the negative electrode N, and a negative electrode lead piece 13 is formed in the uncoated portion.

<Battery disassembly>
Next, a procedure for disassembling the lithium ion secondary battery 20 after use will be described.

(Take out the group)
When the lithium ion secondary battery 20 is disassembled, first, the caulking portion at the top of the battery can 8 is cut to remove the gasket, and then the positive electrode lead plate is cut to remove the battery lid 9. Next, after draining the nonaqueous electrolyte in the battery can 8, the bottom of the battery can 8 is cut. Next, the wound group 5 is taken out from the battery can 8. At this time, work carefully so as not to damage the wound group 5 at the cutting portion of the battery can 8 or the like. Subsequently, the positive electrode lead piece 12 and the negative electrode lead piece 13 are cut, and current collecting members such as the positive electrode current collecting ring 14 and the negative electrode current collecting ring 15 which are obstructed when the winding group 5 is unrolled are also removed in advance. Next, the peeling adhesive tape or the like fixing the insulating film wound around the wound group 5 is peeled off, and the insulating film is removed. In particular, the separator 1 wound inside the insulating film is carefully removed so as not to be damaged. By these operations, the wound group 5 is in a state where the positive electrode P, the negative electrode N, the separator 1 and the separator 2 can be unwound.

(Unraveling)
As shown in FIG. 3, in the winding group 5 in a state where it can be unwound, since the separator 1 is wound on the outermost periphery, only the separator 1 is unrolled in advance in the direction of the arrow B by one turn and the negative electrode N on the outermost periphery. To expose. The unrolled separator 1 is positioned on the inner peripheral side of the positive electrode P. Next, as shown in FIG. 4, for example, the wound group 5 is placed on a flat work table 25 (preferably longer than the length of the separator 1 and separator 2) such as a long desk. Place. At this time, the negative electrode N exposed to the outermost periphery is placed on the lower side (working table 25 side). Next, the winding group 5 is unwound while rolling in the direction of arrow A opposite to the winding direction of the winding group 5 on the work table 25. In the stacking order after unraveling, the lowermost layer on the work table 25 side is the negative electrode N, the upper layer is the separator 2 and the positive electrode P, and the uppermost layer is the separator 1. For this reason, the lower surface of the negative electrode N is in contact with the work table 25. In addition, it is preferable that the operation | work which unwinds the winding group 5 is performed in clean room | chamber interior, such as a clean room, so that it may not be influenced by the dust from the circumference | surroundings.

(Action etc.)
Next, the operation and the like of the decomposition method of this embodiment will be described.

  If foreign matter is mixed in the battery during production of the lithium ion secondary battery 20, the lithium ion secondary battery 20 cannot be used at an early stage because it penetrates the separator due to dissolution or precipitation of the foreign matter itself or foreign matter. Become. Since the traces of the mixed foreign matter always remain in the separator of the lithium ion secondary battery 20 in which the internal short circuit has occurred, it is possible to grasp the mixed state of the foreign matter by taking out and observing the separator. However, in the lithium ion secondary battery 20, the separator 1, the negative electrode N, the separator 2, and the positive electrode P are stacked and wound in this order to form the wound group 5. Is arranged. When the winding group 5 is unwound from this state, the separator 1 becomes the lowest layer. The separator 1 is extremely thin and very easily damaged. When the winding group 5 is unwound, the weight of the winding group 5 is applied to the lower side of the winding group 5. For this reason, if there is a foreign substance on the work table 25, for example, even a very small foreign substance of about several μm to several tens of micrometers, the foreign substance is easily pierced and damaged by the separator 1 as the lowermost layer. This will prevent accurate observation of traces.

  In this embodiment, when disassembling the lithium ion secondary battery 20, the stacking order after the winding group 5 is unwound by previously unwinding the separator 1 for one turn is changed from the lower layer to the negative electrode N, the separator. 2, positive electrode P and separator 1. For this reason, since the negative electrode N becomes the lowest layer and contacts the work table 25, the separator 1 and the separator 2 can be unwound without contacting the work table 25. Thereby, since the separator 1 and the separator 2 are not damaged at the time of decomposition | disassembly operation | work, the trace of the foreign material when a foreign material mixes in the lithium ion secondary battery 20 at the time of manufacture can be observed correctly.

  Further, in the disassembling method of the present embodiment, the outer peripheral surface of the winding group 5 in the middle of unwinding becomes the negative electrode N. Therefore, by observing the outer peripheral surface of the winding group 5 while unwinding the winding group 5. In addition, the presence or absence of foreign matter adhering to and adhering to the surface of the negative electrode N can be confirmed. Thus, when the winding group 5 is unwound, the negative electrode N can be observed before the lowermost negative electrode N comes into contact with the workbench 25. Can be prevented from being erroneously determined as foreign matter mixed in the wound group 5 during manufacture. Therefore, it is possible to accurately check the foreign matters mixed during the manufacturing.

  Furthermore, in the disassembling method of the present embodiment, the separator 1 is the uppermost layer in the stacking order after the winding group 5 is unwound, so that the upper surface of the uppermost layer is the surface in contact with the negative electrode N of the separator 1. . On this surface, since traces of precipitation due to dissolved and precipitated metal foreign matter are likely to remain, by observing the surface of the separator 1 in contact with the negative electrode N while unwinding the winding group 5, the dissolved and precipitated metal It is possible to easily check for contamination.

  In the present embodiment, the example in which the lowermost layer is the negative electrode N is shown in the stacking order after the winding group 5 is unwound, but the present invention is not limited to this, and the lowermost layer is the positive electrode. P may be used. In this case, in addition to unwinding the separator 1 by one turn from the outer periphery of the wound group 5 taken out from the battery can 8 (see FIG. 3), the negative electrode N and the separator 2 are previously wound by one turn. Unwind and expose the positive electrode P on the outermost periphery. The unrolled separator 1, the negative electrode N, and the separator 2 are positioned on the inner peripheral side of the positive electrode P in this order. Next, as shown in FIG. 5, the wound group 5 is placed on the work table 25 with the exposed positive electrode P facing down, and the wound group 5 is unrolled. As a result, the stacking order unwound from the wound group 5 becomes the positive electrode P, the separator 1, the negative electrode N, and the separator 2 in order from the lower layer. Even in this case, since the positive electrode P is in contact with the work table 25, both the separator 1 and the separator 2 can unroll the wound group 5 without contacting the work table 25. Further, the surface of the positive electrode N can be observed while the winding group 5 is being unwound (before contacting the work table 25). Further, the surface that has been in contact with the positive electrode of the separator 2 that becomes the upper surface of the uppermost layer after unraveling can also be observed while unrolling the wound group 5.

  Moreover, in this embodiment, although the bottomed cylindrical lithium ion secondary battery 20 was illustrated, this invention is not specifically limited to a battery structure or a shape. For example, the battery structure can be applied to a battery having a structure in which positive and negative external terminals are pressed together via a winding core. Moreover, as a shape, if the positive and negative electrodes are wound through a separator, the effect of the present invention can be exhibited. For example, the present invention is also applied to a battery in which a wound group is accommodated in a rectangular battery can. be able to. Further, in the present embodiment, an example in which the positive and negative electrodes are wound around the winding core 7 is shown, but the present invention can also be applied to a battery in which the positive and negative electrodes are wound without using the winding core 7.

  Furthermore, although the polyethylene separators 1 and 2 are illustrated in the present embodiment, the present invention is not limited to the material of the separator. Regardless of the material of the separator, it is unraveled without damaging the separator, so that traces of contamination can be accurately observed. As a separator other than the present embodiment, for example, a polyolefin-based material such as polypropylene may be used, or a separator of a type in which films of different materials are laminated.

  Furthermore, in the present embodiment, the lithium transition metal double oxide is exemplified as the positive electrode active material and the carbon material is exemplified as the negative electrode active material, but the present invention is not limited to these. Examples of the positive electrode active material for a lithium ion secondary battery include lithium manganate, lithium cobaltate, lithium nickelate, and materials obtained by substituting or doping some of lithium and manganese in crystals with other elements. it can. Moreover, as a negative electrode active material, carbon materials, such as graphite and amorphous carbon, can be mentioned, for example. Furthermore, the present invention is not limited to a lithium ion secondary battery, and it is needless to say that the present invention can be applied to any winding type battery in which positive and negative electrodes are wound.

  Next, an example in which the lithium ion secondary battery 20 is disassembled and foreign matter traces of the positive and negative electrodes and the separator are observed according to the present embodiment will be described. In addition, for comparison, a comparative example in which the stacking order after unraveling is changed to be disassembled is also shown. In the examples and comparative examples shown below, the battery was disassembled not in a clean room but in a room at normal temperature and humidity in order to clarify the effect of foreign object observation.

Example 1
In Example 1, the stacking order after unwinding the wound group 5 was set as the negative electrode N, the separator 2, the positive electrode P, and the separator 1 from the lower layer (see FIG. 4). The positive electrode P is formed to be relatively thicker than the negative electrode N due to the difference in the lithium ion occlusion ability between the positive electrode active material and the negative electrode active material, and has properties that are harder than the negative electrode N due to the difference in constituent material and thickness. For this reason, after the wound state is forced for a long time, the wound shape (curvature) tends to remain. For this reason, when the winding group 5 is unwound, the habit of the positive electrode P becomes stronger as the curvature becomes closer to the winding center side (in the vicinity of the winding core 7), and the positive electrode P on the winding center side rises. It becomes. In particular, in Example 1, since only the lightweight separator 1 is stacked on the upper layer of the positive electrode P after being unwound, the positive electrode P is likely to be lifted. For this reason, when observing the separator 1 and the positive electrode P, the separator 1 is pressed from above the separator 1 with an appropriate weight or the like as necessary so as not to be damaged.

  After unwinding the wound group 5, the uppermost separator 1 was turned off from the laminated body, and the surface of the separator 1 that was in contact with the positive electrode P and both surfaces of the positive electrode P were observed. Next, the positive electrode P was turned off, and the surface of the separator 2 that appeared was in contact with the positive electrode P was observed. Then, the separator 2 was turned off, and the surface of the peeled separator 2 that was in contact with the negative electrode N and the surface of the negative electrode N (the lower surface of the negative electrode N was observed while being unwound) were observed. In Example 1, both the separator 1 and the separator 2 can unravel the wound group 5 without being brought into contact with the work table 25, and accurately and easily observe scratches, precipitation traces, and the like due to foreign matters mixed during manufacturing. I was able to.

(Example 2)
In Example 2, the stacking order after unwinding the wound group 5 was set as the positive electrode P, the separator 1, the negative electrode N, and the separator 2 from the lower layer (see FIG. 5). In the case of Example 2, similarly to Example 1, the laminated body after being unwound was sequentially turned up and each surface was observed. Also in Example 2, it is possible to unwind the wound group 5 without bringing the separator 1 and the separator 2 into contact with the work table 25, and it is possible to accurately and easily observe scratches, precipitation traces, and the like due to foreign matters mixed during manufacturing. did it. Moreover, in Example 2, the separators 1 and 2 and the negative electrode N are laminated | stacked on the upper layer of the positive electrode P after unraveling. For this reason, even if there is a habit on the winding center side of the positive electrode P, the two separators and the negative electrode N play the role of the press used in Example 1, so that the positive electrode P is not lifted or lifted. As a result, the secondary separator could be prevented from being damaged by pressing the weight or the like.

(Comparative Example 1 and Comparative Example 2)
Comparative Example 1 and Comparative Example 2 were the same as Example 1 except that the stacking order after the winding group 5 was unwound was changed. In Comparative Example 1, as shown in FIG. 6, the stacking order was set to separator 2, positive electrode P, separator 1, and negative electrode N in order from the lower layer. In Comparative Example 2, as shown in FIG. 7, the stacking order was set as separator 1, negative electrode N, separator 2, and positive electrode P in order from the lower layer. That is, in Comparative Example 2, it was unwound in the order in which the layers were stacked when the wound group 5 was manufactured (see also FIG. 2).

  In Comparative Example 1 and Comparative Example 2, since the separator 1 and the separator 2 are located in the lowermost layer, the separator 1 and the separator 2 are easily damaged by foreign matters on the work table 25, and scratches and precipitation due to foreign matters mixed during manufacturing. Traces etc. could not be observed accurately. Further, when unraveling, since the weight of the wound group 5 is applied to the lower side of the wound group 5, if there is a foreign substance on the work table 25, even the very small foreign substance of several μm to several tens of μm is the lowest layer. It was found that the foreign material was easily pierced and damaged by the separator located at.

  The present invention provides a method of disassembling a wound battery that can prevent the separator from being damaged during disassembly, and accurately and easily grasping the state of contamination from the observation of the separator and reflecting it in the improvement of the manufacturing environment. Therefore, it contributes to the manufacture and sale of wound batteries and can be used industrially.

It is sectional drawing which shows the cylindrical lithium ion secondary battery of embodiment which applied the decomposition | disassembly method based on this invention. It is explanatory drawing which shows typically the lamination | stacking order when producing the winding group of a cylindrical lithium ion secondary battery. It is explanatory drawing which shows typically the state in the middle when the separator of the outermost periphery of a winding group is previously unwound by one round. It is explanatory drawing which shows typically the order of lamination | stacking when unwinding a winding group by making a lowermost layer into a negative electrode. It is explanatory drawing which shows typically the order of lamination | stacking when unwinding a winding group by making the lowest layer into a positive electrode. In the comparative example 1, when unwinding the winding group of a cylindrical lithium ion secondary battery, it is explanatory drawing which shows typically the lamination | stacking order which made the separator located in the outer peripheral side of the positive electrode in the winding group the lowest layer. is there. In the comparative example 2, when unwinding the winding group of a cylindrical lithium ion secondary battery, it is explanatory drawing which shows typically the lamination | stacking order which made the separator located in the outer peripheral side of the negative electrode in the winding group the lowest layer. is there.

Explanation of symbols

P Positive electrode N Negative electrode 1 Separator (first separator)
2 Separator (second separator)
5 Winding group 7 Winding core 8 Battery can 20 Cylindrical lithium ion secondary battery (winding battery)

Claims (3)

A method for disassembling a wound battery in which a wound group in which a first separator, a negative electrode, a second separator, and a positive electrode are stacked and wound in this order and the first separator is disposed on the outermost periphery is accommodated in a battery container Because
Removing the wound group from the battery container;
From the lower layer, which is a layer in contact with the mounting table , the taken out winding group is either one of the positive electrode and the negative electrode, one of the first and second separators, one of the positive electrode and the negative electrode, Unravel so that either one of the first and second separators is in the stacking order,
A decomposition method comprising steps. Step solving Maki said winding assembly, after solving Maki substantially one rotation of said first separator above the winding group taken out above the winding group from the lower the negative electrode, the second The decomposition method according to claim 1, wherein the separator, the positive electrode, and the first separator are unrolled in order. Step solving Maki said winding assembly, said the winding group taken out of the first separator, the negative electrode, after solving plated approximately one rotation of the second separator before the said winding assembly 2. The decomposition method according to claim 1, wherein the positive electrode, the first separator, the negative electrode, and the second separator are unwound from the lower layer in the stacking order.