How to disassemble a lithium-ion rechargeable battery

Abstract

A method for disassembling lithium-ion secondary batteries that can quickly deactivate the discharge function of the electrode body. [Solution] A method for disassembling a lithium-ion secondary battery is a method for disassembling a lithium-ion secondary battery cell 10 comprising a positive electrode sheet 31 on which a positive electrode active material layer 31b containing lithium ions is formed on a positive electrode current collector foil 31a, a negative electrode sheet 32 ​​on which a negative electrode active material layer 32b is formed on a negative electrode current collector foil 32a, an outer casing 20 that houses the positive electrode sheet 31 and the negative electrode sheet 32, and an electrolyte 40 containing LiPF6 and housed in the outer casing 20, the method comprising the steps of making a hole H1 in the outer casing 20, injecting water or hydrofluoric acid into the outer casing 20 through the hole H1, exposing the cell 10 into which water or hydrofluoric acid has been injected to a cycle of a reduced pressure atmosphere and a pressurized atmosphere, and cutting the outer casing 20 after the cell 10 has been exposed to the cycle.

Description

Technical Field

[0001] The present invention relates to a method for disassembling a lithium-ion secondary battery.

Background Art

[0002] For example, Patent Document 1 discloses a method for disassembling a lithium-ion battery cell in which a laminated electrode in which a positive electrode plate and a negative electrode plate are laminated via a separator is sealed with an exterior of a laminate film. In the method described in Patent Document 1, the lithium-ion battery cell is cut open at the end of the laminate film, and then the laminate film is separated from the laminated electrode.

[0003] In a battery in which an electrode body is housed in an exterior body such as a laminate film, it is preferable to deactivate the discharging function of the electrode body before cutting open the exterior body. For example, Patent Document 2 discloses a method of completely discharging a power generation element (electrode body) by injecting salt water into a battery case.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0005] Even if water is injected into the exterior body of a lithium-ion secondary battery, it is difficult for water to enter between the positive electrode sheet and the negative electrode sheet of the electrode body, and the reaction for deactivating the discharging function of the electrode body hardly proceeds. Here, a method for disassembling a lithium-ion secondary battery that can more rapidly deactivate the discharging function of the electrode body is proposed.

Means for Solving the Problems

[0006] The method for disassembling a lithium-ion secondary battery proposed herein is a method for disassembling a lithium-ion secondary battery cell comprising: a positive electrode sheet having a positive electrode active material layer containing lithium ions formed on a positive electrode current collector foil; a negative electrode sheet having a negative electrode active material layer formed on a negative electrode current collector foil; an outer casing housing the positive electrode sheet and the negative electrode sheet; and an electrolyte containing LiPF6 and housed in the outer casing, the method comprising: making holes in the outer casing; injecting water or hydrofluoric acid into the outer casing through the holes; exposing the cell into which the water or hydrofluoric acid has been injected to a cycle of reduced pressure and pressurized atmospheres; and cutting the outer casing after the cell has been exposed to the cycle.

[0007] According to the above method, hydrofluoric acid is generated by the reaction of the electrolyte with water, and the generated hydrofluoric acid causes the positive electrode active material layer and the negative electrode active material layer to peel off from the positive electrode current collector foil and the negative electrode current collector foil, respectively. If hydrofluoric acid is injected, the injected hydrofluoric acid and the generated hydrofluoric acid cause the positive electrode active material layer and the negative electrode active material layer to peel off from the positive electrode current collector foil and the negative electrode current collector foil, respectively. This can deactivate the discharge function of the electrode body. Furthermore, by exposing the cell to a cycle of reduced pressure and pressurized atmospheres, the intrusion of water or hydrofluoric acid between the positive electrode sheet and the negative electrode sheet is promoted, and peeling is accelerated. Therefore, according to the above method for decomposing lithium-ion secondary batteries, the discharge function of the electrode body can be deactivated more quickly. [Brief explanation of the drawing]

[0008] [Figure 1] This is a schematic longitudinal cross-sectional view of a lithium-ion secondary battery according to one embodiment. [Figure 2] This is a flowchart showing the disassembly process for lithium-ion secondary battery cells. [Figure 3] This is a schematic diagram of a pressure / vacuum device. [Modes for carrying out the invention]

[0009] The following describes one embodiment of a method for disassembling a lithium-ion secondary battery. It should be noted that the embodiment described herein is not intended to limit the present invention. Furthermore, the figures are schematic diagrams and do not necessarily faithfully reflect actual implementations. In the following, components and parts that perform the same function are denoted by the same reference numerals, and redundant explanations are omitted or simplified as appropriate.

[0010] [Composition of a lithium-ion secondary battery] Figure 1 is a longitudinal cross-sectional view of a lithium-ion secondary battery cell 10. In this embodiment, the lithium-ion secondary battery is a prismatic battery having a substantially rectangular parallelepiped external shape. However, lithium-ion secondary batteries are not limited to prismatic batteries. Figure 1 is a view of the substantially rectangular parallelepiped case 20 facing its wide surface 21a, and is drawn with the inside of the case 20 exposed. As shown in Figure 1, the lithium-ion secondary battery cell 10 comprises a case 20, an electrode body 30, an electrolyte 40, and electrode terminals 50.

[0011] Case 20 houses the electrode body 30 and the electrolyte 40. Case 20 is a roughly rectangular, flat, rectangular container. Case 20 comprises a case body 21, a lid 22, and a liquid injection stopper 23. The case body 21 comprises a pair of opposing wide surfaces 21a, a pair of opposing narrow surfaces 21b, a bottom surface 21c, and an opening 21d that is located opposite the bottom surface 21c. The case body 21 is made of, for example, aluminum or an aluminum alloy.

[0012] The lid 22 is fitted over the opening 21d of the case body 21, closing the opening 21d. The lid 22 is a plate-shaped component. The lid 22 is also made of, for example, aluminum or an aluminum alloy. The lid 22 is welded to the case body 21. There is one through hole 22a at each end of the lid 22 along its longitudinal direction. Electrode terminals 50 are inserted through each of the two through holes 22a. One of the two electrode terminals 50 is the positive terminal 51, and the other is the negative terminal 52.

[0013] The lid 22 is equipped with an injection port 22b into which the electrolyte 40 is injected. The injection port 22b is located between a pair of through holes 22a and penetrates the lid 22 in the vertical direction (the thickness direction of the lid 22). The injection port 22b is sealed by an injection plug 23. The injection plug 23 closes the injection port 22b after the electrolyte 40 has been injected. The injection port 22b and the injection plug 23 are located above the liquid level of the electrolyte 40 and the electrode body 30. The injection plug 23 is made of, for example, aluminum or an aluminum alloy. The injection plug 23 is welded to the lid 22.

[0014] The lid 22 further includes a thin-walled section 22c that is thinner than the surrounding area. The thin-walled section 22c ruptures when the internal pressure of the case 20 rises, acting as a safety valve to release the internal pressure. The thin-walled section 22c is located in the longitudinal center of the lid 22. The thin-walled section 22c is located above the liquid level of the electrolyte 40 and the electrode body 30.

[0015] The electrode body 30 is housed inside the case body 21. In this case, the electrode body 30 is a wound electrode body in which a positive electrode sheet 31 and a negative electrode sheet 32 ​​are wound with a separator 33 in between. However, the electrode body 30 may also be a laminated electrode body in which multiple positive electrode sheets 31 and multiple negative electrode sheets 32 are stacked with a separator 33 in between each.

[0016] The positive electrode sheet 31 is a component in which a positive electrode active material layer 31b containing a positive electrode active material is formed on both sides of a positive electrode current collector foil 31a (e.g., aluminum foil) of a predetermined width and thickness. The positive electrode active material is a material that can release lithium ions during charging and absorb lithium ions during discharging, such as a lithium transition metal composite material. Various materials other than lithium transition metal composite materials have been proposed for the positive electrode active material, and it is not particularly limited. An unformed portion 31c is provided at one end of the positive electrode current collector foil 31a where the positive electrode active material layer 31b is not formed.

[0017] The negative electrode sheet 32 ​​is a component in which a negative electrode active material layer 32b containing a negative electrode active material is formed on both sides of a negative electrode current collector foil 32a (e.g., copper foil) of a predetermined width and thickness. The negative electrode active material is a material that can absorb lithium ions during charging and release the lithium ions absorbed during charging during discharge, such as natural graphite. Various negative electrode active materials other than natural graphite have been proposed and are not particularly limited. An unformed portion 32c is provided at one end of the negative electrode current collector foil 32a where the negative electrode active material layer 32b is not formed.

[0018] For example, the separator 33 can be made of a porous resin sheet that has the required heat resistance and through which the electrolyte can pass. The material of the separator 33 is not particularly limited. The separator 33 is sandwiched between the positive electrode sheet 31 and the negative electrode sheet 32, and insulates the positive electrode sheet 31 and the negative electrode sheet 32.

[0019] The electrolyte 40 is a liquid obtained by dissolving an ionic substance in a solvent, and mediates the transfer of charge between the positive electrode sheet 31 and the negative electrode sheet 32. The electrolyte 40 is housed in the case 20. The electrolyte 40 contains LiPF6. The solvent of the electrolyte 40 is not particularly limited, but for example, it may be a mixed solvent of ethylene carbonate (EC), dimethyl carbonate (DMC), and ethyl methyl carbonate (EMC). However, various electrolytes 40 have been proposed, and are not particularly limited as long as they contain LiPF6.

[0020] The positive electrode terminal 51 includes a current collecting terminal 51a and an external terminal 51b. The current collecting terminal 51a is inserted into the inside of the case body 21 through the through hole 22a of the lid 22 and is connected to the unformed portion 31c of the positive electrode sheet 31. The external terminal 51b is provided along the upper surface of the lid 22 and is connected to the current collecting terminal 51a. A gasket 61 made of an insulator is sandwiched between the lid 22 and the current collecting terminal 51a. The gasket 61 electrically insulates between the lid 22 and the current collecting terminal 51a and seals the through hole 22a. An insulator 62 made of an insulator is sandwiched between the lid 22 and the external terminal 51b. The insulator 62 electrically insulates between the lid 22 and the external terminal 51b.

[0021] The negative electrode terminal 52 is also configured in the same manner as the positive electrode terminal 51. The negative electrode terminal 52 includes a current collecting terminal 52a connected to the unformed portion 32c of the negative electrode sheet 32 and an external terminal 52b disposed outside the lid 22. The negative-side gasket 61 electrically insulates between the lid 22 and the current collecting terminal 52a and seals the negative-side through hole 22a. The negative-side insulator 62 electrically insulates between the lid 22 and the external terminal 52b. However, the configuration of the cell 10 of the lithium ion secondary battery described above is merely an example and is not particularly limited.

[0022] [Disassembly Procedure of Lithium Ion Secondary Battery] Hereinafter, an example of the procedure for disassembling the cell 10 of a lithium-ion secondary battery will be described. FIG. 2 is a flowchart related to the disassembly of the cell 10 of a lithium-ion secondary battery. As shown in FIG. 2, in step S10 of disassembling the cell 10, a positive electrode sheet 31 in which a positive electrode active material layer 31b containing lithium ions is formed on a positive electrode current collector foil 31a, a negative electrode sheet 32 in which a negative electrode active material layer 32b is formed on a negative electrode current collector foil 32a, a case 20 that houses the positive electrode sheet 31 and the negative electrode sheet 32, and an electrolytic solution 40 containing LiPF6 and housed in the case 20 are prepared. The cell 10 to be prepared is typically a cell of a used lithium-ion secondary battery. However, the cell 10 to be disassembled is not limited to a cell of a used lithium-ion secondary battery.

[0023] In step S20, a hole H1 (see FIG. 3) is made in the case 20. Specifically, in this embodiment, the hole H1 is made in the thin portion 22c of the lid 22. The hole H1 is formed, for example, by cutting the thin portion 22c with an end mill. However, the location where the hole H1 is made and the tool for forming the hole H1 are not particularly limited.

[0024] In step S3, hydrofluoric acid (aqueous hydrogen fluoride solution HF + H2O, see FIG. 3) is injected into the case 20 through the hole H1 formed in step S20. The hydrogen fluoride concentration of the hydrofluoric acid is, for example, 5% by weight. However, the hydrogen fluoride concentration of the hydrofluoric acid is not particularly limited. Instead of hydrofluoric acid, water (H2O) may be injected into the case 20. By injecting water (including water which is the solvent of hydrofluoric acid) into the case 20, LiPF6 contained in the electrolytic solution 40 and water react according to the following reaction formula. LiPF6 + 2H2O = POF2(OH) + 2HF

[0025] Hydrogen fluoride (HF) is generated by this reaction between LiPF6 and water. This reaction continues while both the electrolytic solution 40 and water are present in the case 20 and they are in contact with each other. The hydrofluoric acid injected into the case 20 contains hydrogen fluoride (HF) in advance.

[0026] The injected or generated hydrofluoric acid reduces (dissolves) the oxide film on the surfaces of the positive electrode current collector foil 31a and the negative electrode current collector foil 32a. As a result, the positive electrode active material layer 31b formed on the positive electrode current collector foil 31a peels off from the positive electrode current collector foil 31a. Similarly, the negative electrode active material layer 32b formed on the negative electrode current collector foil 32a peels off from the negative electrode current collector foil 32a. The peeling of the positive electrode active material layer 31b from the positive electrode current collector foil 31a and the peeling of the negative electrode active material layer 32b from the negative electrode current collector foil 32a disables the discharge function of the lithium-ion secondary battery.

[0027] In step S40, the cell 10 injected with hydrofluoric acid is subjected to a cycle of reduced pressure and increased pressure. The pressure-reducing cycle facilitates the penetration of hydrofluoric acid between the wound positive electrode sheet 31, negative electrode sheet 32, and separator 33 of the electrode body 30. This promotes the reaction between the electrolyte impregnated between the positive electrode sheet 31, negative electrode sheet 32, and separator 33 of the electrode body 30 and water. In this embodiment, the cell 10 is heated in step S40, when the cell 10 is subjected to the pressure-reducing cycle. Heating the cell 10 increases the reaction rate between the electrolyte 40 and water.

[0028] Step S40 is performed by housing the cell 10 in a pressure / depressurization device 100 that can create a reduced pressure atmosphere and a pressurized atmosphere. Figure 3 is a schematic diagram of the pressure / depressurization device 100. As shown in Figure 3, the pressure / depressurization device 100 includes a chamber 110, an air compressor 120, pressurized side piping 125, a pressure pump 130, a reduced pressure side piping 135, and a heater 140.

[0029] Chamber 110 is a container that can be opened to house the cell 10 and can be sealed. Chamber 110 is provided with an air supply port 111 and an exhaust port 112. An air compressor 120 is connected to the air supply port 111 via a pressurizing pipe 125. A valve 126 is provided on the pressurizing pipe 125. A pressure reducing pump 130 is connected to the exhaust port 112 via a pressure reducing pipe 135. A valve 136 is provided on the pressure reducing pipe 135. When creating a pressurized atmosphere inside Chamber 110, the valve 126 on the pressurizing pipe 125 is opened, the valve 136 on the pressure reducing pipe 135 is closed, and the air compressor 120 is driven. When creating a pressure reducing atmosphere inside Chamber 110, the valve 126 on the pressurizing pipe 125 is closed, the valve 136 on the pressure reducing pipe 135 is opened, and the pressure reducing pump 130 is driven.

[0030] The heater 140 is located inside the chamber 110. The heater 140 heats the lithium-ion secondary battery cell 10 inside the chamber 110.

[0031] As shown in Figure 2, step S40 includes step S41 of housing cell 10 in chamber 110, step S42 of heating cell 10, a first depressurization step S43, a first pressurization step S44, a second depressurization step S45, a second pressurization step S46, a third depressurization step S47, and a third pressurization step S48. However, the number of pressurization / depressurization cycles is not limited to three. The number of pressurization / depressurization cycles may be one, two, or four or more.

[0032] In a preferred example, in step S42, the cell 10 is heated to a temperature of 55°C or higher and 65°C or lower. In the depressurization steps S43, S45, and S47, the pressure inside the chamber 110 is reduced to 2 kPa or lower. In the pressurization steps S44, S46, and S48, the pressure inside the chamber 110 is increased to 0.3 MPa or higher. However, the heating temperature of the cell 10 is not particularly limited as long as it is higher than room temperature. The pressure during depressurization is not particularly limited as long as it is lower than 1 atmosphere. The pressure during pressurization is not particularly limited as long as it is higher than 1 atmosphere.

[0033] In step S50, cell 10 is removed from chamber 110 and left to stand. During step S50, peeling of the positive electrode active material layer 31b from the positive electrode current collector foil 31a and peeling of the negative electrode active material layer 32b from the negative electrode current collector foil 32a proceed. In a preferred example, the time in step S50 is 24 hours or more. However, the standing time of cell 10 is not particularly limited.

[0034] In step S60, the case 20 is cut. Step S60 is performed, for example, using a band saw. By the time of steps S50, the discharge function of the lithium-ion secondary battery cell 10 has been lost. Therefore, even if the positive electrode sheet 31 (positive electrode current collector foil 31a) and the negative electrode sheet 32 ​​(negative electrode current collector foil 32a) are short-circuited through a cutting tool such as a band saw during cutting, no current will flow between the positive electrode current collector foil 31a and the negative electrode current collector foil 32a. Thus, the cell 10 can be cut safely.

[0035] Step S60 is performed with hydrofluoric acid stored in case 20. Therefore, even if current flows between the positive electrode current collector foil 31a and the negative electrode current collector foil 32a, the heat generated by the short circuit can be cooled by the hydrofluoric acid (and its solvent, water). However, the cutting of case 20 may be performed after the hydrofluoric acid has been drained from inside case 20.

[0036] In step S70, the electrode body 30 is removed from the cut case 20. Subsequently, steps such as recovering rare earth elements from the removed electrode body 30 follow, but the explanation of those steps will be omitted.

[0037] [Effects of the Embodiment] The following describes the effects and benefits that can be achieved by the method for disassembling the lithium-ion secondary battery cell 10 according to this embodiment.

[0038] The present embodiment provides a method for disassembling a lithium-ion secondary battery cell 10 comprising a positive electrode sheet 31 having a positive electrode active material layer 31b containing lithium ions formed on a positive electrode current collector foil 31a, a negative electrode sheet 32 ​​having a negative electrode active material layer 32b formed on a negative electrode current collector foil 32a, a case 20 housing the positive electrode sheet 31 and the negative electrode sheet 32, and an electrolyte 40 containing LiPF6 and housed in the case 20, the method comprising: making a hole H1 in the case 20 S20; injecting water or hydrofluoric acid into the case 20 through the hole H1 S30; exposing the cell 10 into which water or hydrofluoric acid has been injected to a cycle of reduced pressure and pressurized atmosphere S40; and cutting the case 20 after the cell 10 has been exposed to the cycle S50.

[0039] According to this method, hydrofluoric acid is generated by the reaction of the electrolyte 40 with water, and the generated hydrofluoric acid causes the positive electrode active material layer 31b and the negative electrode active material layer 32b to peel off from the positive electrode current collector foil 31a and the negative electrode current collector foil 32a, respectively. If hydrofluoric acid is injected, the injected hydrofluoric acid and the generated hydrofluoric acid cause the positive electrode active material layer 31b and the negative electrode active material layer 32b to peel off from the positive electrode current collector foil 31a and the negative electrode current collector foil 32a, respectively. As a result, the discharge function of the electrode body 30 is deactivated, and it is possible to suppress the short circuit and heat generation between the positive electrode sheet 31 and the negative electrode sheet 32 ​​in step S50, in which the case 20 is cut. In addition, step S40, in which the cell 10 is subjected to a cycle of reduced pressure and pressurized atmosphere, promotes the intrusion of water or hydrofluoric acid between the positive electrode sheet 31 and the negative electrode sheet 32, and accelerates peeling. Therefore, the discharge function of the electrode body 30 can be deactivated more quickly.

[0040] In this embodiment, in step S40, in which cell 10 is subjected to an expansion-contraction cycle, cell 10 is heated. This method allows for a faster reaction rate in the hydrofluoric acid generation reaction and the reaction that peels the positive electrode active material layer 31b and the negative electrode active material layer 32b from the positive electrode current collector foil 31a and the negative electrode current collector foil 32a, respectively (reduction reaction of the surface oxide film of the positive electrode current collector foil 31a and the negative electrode current collector foil 32a). As a result, the time required for step S40 can be shortened.

[0041] In this embodiment, the step of cutting the case 20 is performed with water or hydrofluoric acid stored inside the case 20. With this method, when the positive electrode sheet 31 and the negative electrode sheet 32 ​​short-circuit and generate heat during the cutting step S50 of the case 20, the water or hydrofluoric acid inside the case 20 can cool the heat-generating area.

[0042] In this embodiment, the case 20 is a case that has a thin-walled portion 22c that is thinner than the surrounding area, and the hole H1 is made in the thin-walled portion 22c. By this method, the hole H1 can be made easily and quickly by forming it in the thin-walled portion 22c that is thinner than the surrounding area.

[0043] [Other embodiments] The above describes one embodiment of the method for disassembling a lithium-ion secondary battery cell 10 as proposed. However, the above embodiment is merely an example, and it can be implemented in other ways.

[0044] For example, hole H1 may be made in the injection plug 23 that seals the injection port 22b into which the electrolyte 40 is injected. There is sufficient space around the injection plug 23 to insert and seal it. Therefore, the risk of short-circuiting the positive electrode sheet 31 and the negative electrode sheet 32 ​​with the drilling tool when making hole H1 can be reduced. Note that hole H1 may be made in a location on the case 20 other than the thin-walled portion 22c or the injection plug 23. For example, hole H1 may be made in a location on the lid 22 other than the thin-walled portion 22c or the injection plug 23.

[0045] The outer casing of the lithium-ion secondary battery does not have to be a fixed-shape case; for example, it may be a laminate film. The step of exposing the cell to an expansion / contraction cycle may be performed without heating the cell.

[0046] Furthermore, the technologies disclosed herein are subject to various modifications. Each component and each process referred to herein may be omitted or combined as appropriate, unless no particular problem arises. This specification includes the disclosures described in the following sections.

[0047] Section 1: A method for disassembling a lithium-ion secondary battery cell comprising: a positive electrode sheet having a positive electrode active material layer containing lithium ions formed on a positive electrode current collector foil; a negative electrode sheet having a negative electrode active material layer formed on a negative electrode current collector foil; an outer casing housing the positive electrode sheet and the negative electrode sheet; and an electrolyte containing LiPF6 and housed in the outer casing, The steps include making holes in the exterior body, The steps include injecting water or hydrofluoric acid into the outer casing through the aforementioned hole, The steps include: exposing the cell into which the water or hydrofluoric acid has been injected to a cycle of reduced pressure and pressurized atmospheres; The step of cutting the outer casing after exposing the cell to the cycle, How to disassemble a lithium-ion rechargeable battery.

[0048] Section 2: In the step of exposing the cell to the cycle, the cell is heated. The method for disassembling a lithium-ion secondary battery as described in item 1.

[0049] Section 3: The step of cutting the outer casing is performed while water or hydrofluoric acid is stored inside the outer casing. A method for disassembling a lithium-ion secondary battery as described in item 1 or 2.

[0050] Section 4: The aforementioned exterior body is a case having a thin-walled section that is thinner than the surrounding area. The aforementioned holes are made in the thin portion, The method for disassembling a lithium-ion secondary battery as described in any one of items 1 to 3.

[0051] Section 5: The aforementioned exterior body is a case equipped with a liquid injection plug that seals the liquid injection port into which the electrolyte is injected, The aforementioned hole is made in the injection plug. The method for disassembling a lithium-ion secondary battery as described in any one of items 1 to 3. [Explanation of symbols]

[0052] 10 cells 20 cases (outer casings) 21 Case body 21a Wide surface 21b narrow side 21c bottom 21d opening 22 Lid 22a Through hole 22b Liquid injection port 22c thin section 23 Injection plug 30 Electrode body 31 Positive electrode sheet 31a Positive electrode current collector foil 31b Positive electrode active material layer 31c Unformed part 32 Negative electrode sheets 32a Negative current collector foil 32b Negative electrode active material layer 32c Unformed part 33 Separator 40 Electrolyte 50 electrode terminal 51 Positive terminal 51a Current collector terminal 51b External terminal 52 Negative terminal 52a Current collector terminal 52b External terminals 61 Gasket 62 Insulators 100 Pressure / Vacuum Device 110 Chamber 111 Air supply port 112 Exhaust port 120 Air Compressor 125 Pressurized side piping 126 valves 130 Pressure Reducing Pump 135 Pressure-reducing piping 136 valves 140 Heater H1 hole

Claims

1. A positive electrode sheet having a positive electrode active material layer containing lithium ions formed on the positive electrode current collector foil, a negative electrode sheet having a negative electrode active material layer formed on the negative electrode current collector foil, an outer casing housing the positive electrode sheet and the negative electrode sheet, and LiPF ６ A method for disassembling a lithium-ion secondary battery cell comprising an electrolyte containing and housed in the outer casing, The steps include making holes in the exterior body, The steps include injecting water or hydrofluoric acid into the outer casing through the aforementioned hole, The steps include: exposing the cell into which the water or hydrofluoric acid has been injected to a cycle of reduced pressure and pressurized atmospheres; The step of cutting the outer casing after exposing the cell to the cycle, How to disassemble a lithium-ion rechargeable battery.

2. In the step of exposing the cell to the cycle, the cell is heated. A method for disassembling a lithium-ion secondary battery according to claim 1.

3. The step of cutting the outer casing is performed while water or hydrofluoric acid is stored inside the outer casing. A method for disassembling a lithium-ion secondary battery according to claim 1.

4. The aforementioned exterior body is a case having a thin-walled section that is thinner than the surrounding area. The aforementioned holes are made in the thin portion, A method for disassembling a lithium-ion secondary battery according to claim 1.

5. The aforementioned exterior body is a case equipped with a liquid injection plug that seals the liquid injection port into which the electrolyte is injected, The aforementioned hole is made in the injection plug. A method for disassembling a lithium-ion secondary battery according to claim 1.

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