Method for separating and recovering electrode active material of secondary battery, and secondary battery

Abstract

This invention provides a method for individually and easily separating and recovering the electrode active material of a secondary battery. [Solution] The separation and recovery method comprises a first cutting step of cutting the outer casing 11 containing the secondary battery 1, a first impregnation step of impregnating the secondary battery 1 in a first solvent 5 in which the first active material can be dispersed after the first cutting step, and a first recovery step of recovering the first active material from the first solvent 5 after the first impregnation step. Furthermore, the method comprises a second cutting step of cutting a bag-shaped separator 4 after the first recovery step, a second impregnation step of impregnating the secondary battery 1 in a second solvent 6 in which the second active material can be dispersed after the second cutting step, and a second recovery step of recovering the second active material from the second solvent 6 after the second impregnation step.

Description

Technical Field

[0001] The present invention relates to a method for separating and recovering electrode active materials of a secondary battery and a secondary battery.

Background Art

[0002] As a secondary battery, one having a positive electrode layer, a separator, and a negative electrode layer is known.

[0003] <00​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​According to one aspect of the present invention, a separation and recovery method is provided for separating and recovering first and second active materials from a secondary battery comprising a first electrode layer having a first active material, a second electrode layer having a second active material, and a bag-shaped separator enclosing the first or second electrode layer. The separation and recovery method comprises a first cutting step of cutting an outer casing containing the secondary battery, a first impregnation step of impregnating the secondary battery in a first solvent in which the first active material can be dispersed after the first cutting step, and a first recovery step of recovering the first active material from the first solvent after the first impregnation step. Furthermore, the method comprises a second cutting step of cutting the bag-shaped separator after the first recovery step, a second impregnation step of impregnating the secondary battery in a second solvent in which the second active material can be dispersed after the second cutting step, and a second recovery step of recovering the second active material from the second solvent after the second impregnation step. [Effects of the Invention]

[0008] According to the present invention, a method is provided that allows for the individual and easy separation and recovery of the first active material and the second active material. [Brief explanation of the drawing]

[0009] [Figure 1] Figure 1 is a schematic longitudinal cross-sectional view of the secondary battery according to this embodiment. [Figure 2] Figure 2 is a diagram illustrating the separation and recovery method according to this embodiment. [Figure 3] Figure 3 is a diagram illustrating the vibration of the secondary battery during the impregnation step of the separation and recovery method according to this embodiment. [Figure 4] Figure 4 is a diagram illustrating how a load is applied to the secondary battery in the impregnation step of the separation and recovery method according to this embodiment, so that it remains immersed in the solvent. [Modes for carrying out the invention]

[0010] The present invention will be described below with reference to the drawings.

[0011] (Secondary battery) First, a secondary battery 1 capable of separating and recovering electrode active material by the separation and recovery method according to this embodiment will be described.

[0012] Figure 1 is a schematic longitudinal cross-sectional view of a secondary battery 1. As shown in Figure 1, the secondary battery 1 comprises a multi-layer cell 10 formed in a rectangular shape in plan view, and an outer casing 11 that houses the multi-layer cell 10. The multi-layer cell 10 has a configuration in which multiple positive electrode layers 2 and negative electrode layers 3 are alternately stacked with separators 4 in between. The positive electrode layer 2 is a layer in which a positive electrode active material layer 22 is arranged on the surface of a positive electrode current collector foil 21. The negative electrode layer 3 is a layer in which a negative electrode active material layer 32 is arranged on the surface of a negative electrode current collector foil 31.

[0013] As shown in Figure 1, in the layers of the multi-layer cell 10, excluding the outermost layer (the layers at the top and bottom ends of the multi-layer cell 10 in Figure 1), the positive electrode active material layer 22 is arranged on both sides of the positive electrode current collector foil 21, and the negative electrode active material layer 32 is arranged on both sides of the negative electrode current collector foil 31. On the other hand, the outermost layer of the multi-layer cell 10 is the positive electrode layer 2, and in this arrangement of the positive electrode layer 2, the positive electrode active material layer 22 is provided on only one surface of the positive electrode current collector foil 21.

[0014] Furthermore, while Figure 1 shows a multi-layer cell 10 having four positive electrode layers 2 and three negative electrode layers 3, the number of each layer is not limited to this and can be adjusted as appropriate.

[0015] In this specification, the positive electrode layer 2 and the positive electrode active material may be referred to as the first electrode layer and the first active material, respectively. Furthermore, the negative electrode layer 3 and the negative electrode active material may be referred to as the second electrode layer and the second active material, respectively.

[0016] The plurality of positive electrode current collector foils 21 are integrated on one side (the right side in the figure) of the multi-layer cell 10, and the plurality of negative electrode current collector foils 31 are also integrated on one side (the right side in the figure) of the multi-layer cell 10. Positive electrode tabs 23 and negative electrode tabs 33 are respectively connected to the tip portions of the integrated positive electrode current collector foil 21 and negative electrode current collector foil 31. The positive electrode tab 23 and the negative electrode tab 33 protrude from one side surface of the exterior body 11 to the outside of the secondary battery 1 and function as input / output terminals for electrically connecting to an external device.

[0017] The positive electrode active material layer 22 is a layer containing a positive electrode active material and a positive electrode binder, and is adhered to the positive electrode current collector foil 21 by the positive electrode binder. Also, the negative electrode active material layer 32 is a layer containing a negative electrode active material and a negative electrode binder, and is adhered to the negative electrode current collector foil 31 by the negative electrode binder.

[0018] Here, the separator 4 of the secondary battery 1 has a bag-like structure with each side closed. And the negative electrode layer 3 is accommodated inside the bag-like separator 4. More specifically, the bag-like separator 4 is composed of two separator sheets, and these separator sheets are formed as substantially rectangular films. One negative electrode layer 3 is accommodated in the separator sheet so as to be sandwiched between the two separator sheets, and the outer edges that become the respective sides of the separator sheet are sealed. Thereby, the negative electrode layer 3 is accommodated inside the bag-like separator 4. However, the bag-like separator 4 is configured such that a part of the negative electrode current collector foil 31 of the negative electrode layer 3 is drawn out from the inside of the separator 4 to the outside, and the above-mentioned negative electrode tab 33 is provided at the tip portion of the negative electrode current collector foil 31 exposed to the outside.

[0019] In the secondary battery 1, among the positive electrode layer 2 and the negative electrode layer 3 that constitute the multi-layer cell 10, the positive electrode layer 2 is accommodated in the exterior body 11 but not in the bag-like separator 4. On the other hand, the negative electrode layer 3 is accommodated in the exterior body 11 and also in the bag-like separator 4. Thereby, inside the exterior body 11 of the secondary battery 1, the spaces where the positive electrode layer 2 and the negative electrode layer 3 are provided are separated from each other via the separator 4.

[0020] According to the secondary battery 1 having such a configuration, the electrode active materials can be separated and recovered individually and easily by the separation and recovery method described later. Although details will be described later, since the spaces where the positive electrode layer 2 and the negative electrode layer 3 are provided are separated from each other via the separator 4, when recovering one electrode active material, it is suppressed that the other electrode active material is recovered in a mixed state. As a result, easy separation and recovery of the electrode active materials are realized.

[0021] In addition, the secondary battery 1 has an electrolytic solution (not shown) inside the exterior body 11. The electrolytic solution may be held so as to penetrate into the separator 4, or may be filled so as to fill the inside of the exterior body 11. Further, as long as the electrolytic solution has ion conductivity, its type is not particularly limited. As the electrolytic solution, for example, LiPF6 / EC-based, sulfonamide-based, and aqueous electrolytic solutions can be used.

[0022] Also, the positive electrode current collector foil 21 and the negative electrode current collector foil 31 are film-like metal foils. As the positive electrode current collector foil 21, for example, an aluminum foil or the like can be used. As the negative electrode current collector foil 31, for example, thin films such as copper, copper alloy, nickel, and nickel alloy can be used.

[0023] Also, as the positive electrode active material, preferably, a lithium metal composite oxide having a layered structure represented by the chemical formula LiMO2 is used. Examples of the lithium metal composite oxide include layered rock salt-type compounds such as LiCoO2, LiMnO2, LiNiO2, LiVO2, and Li(Ni-Mn-Co)O2, spinel-type compounds such as LiMn2O4 and LiNi 0.5 Mn 1.5 O4, olivine-type compounds such as LiFePO4 and LiMnPO4, or Si-containing compounds such as Li2FeSiO4 and Li2MnSiO4. Also, Li4Ti5O 12 and the like can also be used.

[0024] Furthermore, as the negative electrode active material, for example, lithium metal, silicon materials, tin materials, compounds containing silicon or tin (oxides, nitrides, alloys with other metals), and carbon materials (graphite, etc.) can be used.

[0025] Furthermore, PVDF (polyvinylidene fluoride) is preferably used as the positive electrode binder. A water-soluble resin is preferably used as the negative electrode binder. Examples of water-soluble resins include water-soluble epoxy resins and water-soluble phenolic resins.

[0026] Furthermore, the positive electrode tab 23 and the negative electrode tab 33 are metal plates, and for example, nickel plates or copper alloy plates can be used.

[0027] Furthermore, the separator sheet is a porous film having electrical insulation and ion conductivity, and for example, a nonwoven fabric can be used.

[0028] Furthermore, the outer casing 11 is a sheet-like film, and for example, a metal laminate film can be used.

[0029] (Method for separating and recovering electrode active material) Next, with reference to Figures 2 to 4, the method for separating and recovering the electrode active material according to this embodiment will be described.

[0030] The electrode active materials contained in each electrode layer of secondary batteries may include expensive or environmentally harmful materials. Therefore, there is a need to easily separate and recover the electrode active materials from secondary batteries, for purposes such as reuse.

[0031] However, conventional separation and recovery methods involved crushing the positive electrode layer, negative electrode layer, separator, and outer casing all together before separating the positive and negative electrode layers. This made it difficult to easily separate only the positive electrode active material or only the negative electrode active material.

[0032] Therefore, in this embodiment, each step is designed to enable the individual and easy separation and recovery of the positive electrode active material and the negative electrode active material.

[0033] Figure 2 is a diagram illustrating the separation and recovery method according to this embodiment. As shown in Figure 2, this separation and recovery method comprises a first cutting step, a first impregnation step, a first recovery step, a second cutting step, a second impregnation step, and a second recovery step. Each step will be described in detail below.

[0034] (1st cutting process) First, in the first cutting step, as shown in Figure 2(A), the end of the outer casing 11 of the secondary battery 1 that houses the multi-layer cell 10 is cut with a cutter or the like. Preferably, the end that is different from the end on which the positive electrode tab 23 and negative electrode tab 33 protrude is cut. More preferably, the end opposite to the end on which the positive electrode tab 23 and negative electrode tab 33 protrude is cut. Note that the individual components of the multi-layer cell 10 housed in the outer casing 11 are not cut; only the outer casing 11 is cut.

[0035] (First impregnation process) Following the first cutting step in Figure 2(A), as shown in Figure 2(B), the secondary battery 1 is impregnated in a first solvent 5 in which the positive electrode active material can be dispersed during the first impregnation step. This extracts the positive electrode active material into the first solvent 5. In other words, by impregnating the secondary battery 1 into the first solvent 5, the positive electrode active material layer 22 is peeled off from the positive electrode current collector foil 21, and the positive electrode active material is dispersed in the first solvent 5. At this time, the negative electrode layer 3 is contained in a bag-shaped separator 4 and therefore does not become impregnated in the first solvent 5. As a result, the dispersion of the negative electrode active material together with the positive electrode active material in the first solvent 5 is suppressed.

[0036] The type of the first solvent 5 is not particularly limited, as long as the positive electrode active material can be dispersed in it. Preferably, the first solvent 5 is one that can disperse the positive electrode active material and dissolve the positive electrode binder used in the positive electrode layer 2. For example, when PVDF (polyvinylidene fluoride) is used as the positive electrode binder, the first solvent 5 can be TEP (triethyl phosphate) or NMP (N-methylpyrrolidone), which can disperse the positive electrode active material and dissolve the PVDF.

[0037] In the first impregnation step, the first solvent 5 may be heated to a predetermined temperature below the melting point of the positive electrode binder in order to promote the dispersion of the positive electrode active material. For example, if PVDF is used as the positive electrode binder, the first solvent 5 is heated to 70-150°C.

[0038] Furthermore, in the first impregnation step, the secondary battery 1 being impregnated in the first solvent 5 may be vibrated for the purpose of promoting the dispersion of the positive electrode active material. For example, as shown in Figure 3, after the secondary battery 1 is impregnated in the first solvent 5, the upper end of the secondary battery 1 is connected to a vibration generator, and the entire secondary battery 1 is vibrated from left to right in the figure by the vibration generator.

[0039] Furthermore, in the first impregnation step, a load may be applied to the secondary battery 1 to maintain its immersion in the first solvent 5, with the aim of promoting the dispersion of the positive electrode active material. For example, as shown in Figure 4, after impregnating the secondary battery 1 with the first solvent 5, a weight may be placed on the secondary battery 1 to apply a load, thereby maintaining the state in which the secondary battery 1 remains immersed in the first solvent 5.

[0040] (First recovery process) After the first impregnation step in Figure 2(B), the positive electrode active material dispersed in the first solvent 5 is recovered in the first recovery step. For example, the positive electrode active material is separated and recovered from the first solvent 5 by filtering the first solvent 5 in which the positive electrode active material is dispersed. For filtration, for example, natural filtration, vacuum filtration, and pressure filtration can be employed.

[0041] In the processes described above—the first cutting step, the first impregnation step, and the first recovery step—the positive electrode active material is separated and recovered from the secondary battery 1.

[0042] (2nd cutting process) Next, as shown in Figure 2(C), in the second cutting step, the end of the bag-shaped separator 4 containing the negative electrode layer 3 is cut by a cutter or the like. At this time, the end of the separator 4 on the same side as the end of the outer casing 11 that was cut in the first cutting step is cut. Furthermore, the individual components of the negative electrode layer 3 contained inside the separator 4 are not cut; only the separator 4 is cut.

[0043] (Second impregnation process) Next, as shown in Figure 2(D), in the second impregnation step, the secondary battery 1 is impregnated with a second solvent 6 in which the negative electrode active material can be dispersed. This extracts the negative electrode active material into the second solvent 6. In other words, by impregnating the secondary battery 1 with the second solvent 6, the negative electrode active material layer 32 is peeled off from the negative electrode current collector foil 31, and the negative electrode active material is dispersed in the second solvent 6. At this time, since the positive electrode active material has already been separated and recovered in the first recovery step, the dispersion of the positive electrode active material into the second solvent 6 together with the negative electrode active material is suppressed.

[0044] The type of the second solvent 6 is not particularly limited, as long as the negative electrode active material can be dispersed in it. Preferably, the second solvent 6 is one that can disperse the negative electrode active material and dissolve the negative electrode binder used in the negative electrode layer 3. For example, when a water-soluble resin such as a water-soluble epoxy resin is used as the negative electrode binder, water is used as the second solvent 6, which can disperse the negative electrode active material and dissolve the water-soluble resin.

[0045] In the second impregnation step, the second solvent 6 may be heated to a predetermined temperature below the melting point of the negative electrode binder in order to promote the dispersion of the negative electrode active material. Furthermore, the method of vibrating the secondary battery 1 while it is impregnated in the solvent, as described in the first impregnation step, and the method of applying a load to the secondary battery 1 to maintain its immersion in the second solvent 6, can also be similarly employed in the second impregnation step.

[0046] (Second recovery process) After the second impregnation step in Figure 2(D), the anode active material dispersed in the second solvent 6 is recovered in the second recovery step. For example, similar to the first recovery step, the anode active material is separated and recovered from the second solvent 6 by filtering or other means.

[0047] In the processes described above—the second cutting step, the second impregnation step, and the second recovery step—the negative electrode active material is separated and recovered from the secondary battery 1.

[0048] The above describes the separation and recovery method according to this embodiment. In this separation and recovery method, in the first impregnation step, the positive electrode layer 2 is impregnated with the first solvent 5, while the negative electrode layer 3 is contained within a bag-shaped separator 4 and therefore does not come into contact with the first solvent 5. As a result, the positive electrode active material is dispersed in the first solvent 5, but the negative electrode active material is not dispersed. In other words, since the negative electrode active material is not mixed with the first solvent 5, the positive electrode active material can be easily separated and recovered in the first recovery step.

[0049] Next, in the second impregnation step, the negative electrode layer 3 is impregnated with the second solvent 6, and the negative electrode active material is dispersed in the second solvent 6. At this time, since the positive electrode active material has already been recovered in the first recovery step, mixing of the positive electrode active material with the second solvent 6 is suppressed. Therefore, the negative electrode active material can be easily separated and recovered in the second recovery step. In this way, the positive electrode active material and the negative electrode active material can be easily separated and recovered individually.

[0050] The separation and recovery method according to this embodiment, and the effects of the secondary battery 1 capable of separating and recovering electrode active material by this separation and recovery method, will be described below.

[0051] The separation and recovery method according to this embodiment comprises a first cutting step of cutting the outer casing 11 containing the secondary battery 1, a first impregnation step of impregnating the secondary battery 1 in a first solvent 5 in which positive electrode active material can be dispersed after the first cutting step, and a first recovery step of recovering the positive electrode active material from the first solvent 5 after the first impregnation step. Furthermore, the method comprises a second cutting step of cutting a bag-shaped separator 4 after the first recovery step, a second impregnation step of impregnating the secondary battery 1 in a second solvent 6 in which negative electrode active material can be dispersed after the second cutting step, and a second recovery step of recovering the negative electrode active material from the second solvent 6 after the second impregnation step.

[0052] With this configuration, the positive electrode active material and the negative electrode active material can be easily and individually separated and recovered.

[0053] Furthermore, in the separation and recovery method according to this embodiment, the first solvent 5 is a solvent capable of dissolving the positive electrode binder.

[0054] With this configuration, the positive electrode active material can be dispersed more easily in the first solvent 5 during the first impregnation step. In other words, since the positive electrode active material layer 22 is adhered to the positive electrode current collector foil 21 by a positive electrode binder, the first solvent 5 dissolves the positive electrode binder, making it easier to peel off the positive electrode active material layer 22. This makes it possible to easily disperse the positive electrode active material in the first solvent 5.

[0055] Furthermore, in the separation and recovery method according to this embodiment, the first solvent 5 is heated to a predetermined temperature below the melting point of the positive electrode binder in the first impregnation step.

[0056] With this configuration, the solubility of the positive electrode binder is improved, making it easier to disperse the positive electrode active material in the first solvent 5.

[0057] Furthermore, in the separation and recovery method according to this embodiment, the positive electrode binder is PVDF, and the first solvent 5 is TEP or NMP.

[0058] With this configuration, since TEP or NMP can dissolve PVDF, it becomes possible to easily disperse the positive electrode active material in the first solvent 5 in a secondary battery 1 that uses PVDF as a positive electrode binder.

[0059] Furthermore, in the separation and recovery method according to this embodiment, the second solvent 6 is a solvent capable of dissolving the negative electrode binder.

[0060] With this configuration, the negative electrode active material can be dispersed more easily in the second solvent 6 during the second impregnation step. In other words, since the negative electrode active material layer 32 is adhered to the negative electrode current collector foil 31 by the negative electrode binder, the second solvent 6 dissolves the negative electrode binder, making it easier to peel off the negative electrode active material layer 32. This makes it possible to easily disperse the negative electrode active material in the second solvent 6.

[0061] Furthermore, in the separation and recovery method according to this embodiment, the second solvent 6 is heated to a predetermined temperature below the melting point of the negative electrode binder in the second impregnation step.

[0062] With this configuration, the solubility of the negative electrode binder is improved, making it easier to disperse the negative electrode active material in the second solvent 6.

[0063] Furthermore, in the separation and recovery method according to this embodiment, the negative electrode binder is water-soluble, and the second solvent 6 is water.

[0064] With this configuration, since water can dissolve water-soluble binders, in a secondary battery 1 that uses a water-soluble resin as the negative electrode binder, it becomes possible to easily disperse the negative electrode active material in the second solvent 6.

[0065] Furthermore, in the separation and recovery method according to this embodiment, the secondary battery 1 is vibrated while impregnated in the solvent during the first and second impregnation steps.

[0066] With this configuration, vibrating the secondary battery 1 in the solvent improves the solubility of the binder and also improves the dispersibility of the electrode active material. Therefore, it becomes possible to disperse the positive electrode active material and the negative electrode active material in the solvent more easily.

[0067] Furthermore, in the separation and recovery method according to this embodiment, a load is applied to the secondary battery 1 in the first impregnation step and the second impregnation step so as to maintain the state of being immersed in the solvent.

[0068] With this configuration, the secondary battery 1 is prevented from floating away from the solvent during each impregnation step, allowing the positive electrode layer 2 and the negative electrode layer 3 to be more reliably immersed in the solvent. This makes it possible to more reliably disperse the positive electrode active material and the negative electrode active material in the solvent.

[0069] Furthermore, in the secondary battery 1 in which electrode active material can be separated and recovered by the separation and recovery method according to this embodiment, either the positive electrode layer 2 or the negative electrode layer 3 is housed in a bag-shaped separator 4.

[0070] With this configuration, the separation and recovery method according to this embodiment makes it possible to easily and individually separate and recover the positive electrode active material and the negative electrode active material.

[0071] Furthermore, in the secondary battery 1 according to this embodiment, the positive electrode active material of the positive electrode layer 2 includes a compound having a layered structure represented by the chemical formula LiMO2.

[0072] Furthermore, in the secondary battery 1 according to this embodiment, the negative electrode binder of the negative electrode layer 3 is water-soluble.

[0073] Although embodiments of the present invention have been described above, the configurations described above represent only a part of the application examples of the present invention and are not intended to limit the technical scope of the present invention.

[0074] In this embodiment of the secondary battery 1, it has been described that one negative electrode layer 3 is housed inside the separator 4 by being sandwiched between two separator sheets, but this is not the only way to do so. That is, as long as each negative electrode layer 3 can be housed inside the bag-shaped separator 4, one negative electrode layer 3 may be housed by folding a single separator sheet.

[0075] Furthermore, although the secondary battery 1 in which the electrode active material can be separated and recovered by the separation and recovery method according to this embodiment has been described as having the negative electrode layer 3 housed in a bag-shaped separator 4, it is not limited to this configuration. That is, even in a secondary battery having a configuration in which the positive electrode layer 2 is housed in a bag-shaped separator 4 instead of the negative electrode layer 3, the electrode active material can be individually and easily separated and recovered by the separation and recovery method according to this embodiment. In this case, the negative electrode layer 3 and the negative electrode active material become the first electrode layer and the first active material, respectively, and the positive electrode layer 2 and the positive electrode active material become the second electrode layer and the second active material, respectively.

[0076] Furthermore, although the positive electrode tab 23 and the negative electrode tab 33 have been described as protruding from one side of the outer casing 11 of the secondary battery 1, this is not limited to this configuration. In other words, the positive electrode tab 23 and the negative electrode tab 33 may protrude from different sides of the outer casing 11. [Explanation of symbols]

[0077] 1: Secondary battery, 2: Positive electrode layer, 21: Positive electrode current collector foil, 22: Positive electrode active material layer, 23: Positive electrode tab, 3: Negative electrode layer, 31: Negative electrode current collector foil, 32: Negative electrode active material layer, 33: Negative electrode tab, 4: Separator, 5: First solvent, 6: Second solvent, 10: Multilayer cell, 11: Outer casing

Claims

1. A separation and recovery method for separating and recovering the first and second active materials from a secondary battery comprising a first electrode layer having a first active material, a second electrode layer having a second active material, and a bag-shaped separator enclosing the first or second electrode layer, A first cutting step involves cutting the outer casing containing the secondary battery, A first impregnation step is performed in which the secondary battery is impregnated in a first solvent in which the first active material can be dispersed, after the first cutting step, A first recovery step is performed to recover the first active material from the first solvent after the first impregnation step, After the first recovery step, a second cutting step is performed to cut the bag-shaped separator, A second impregnation step is performed in which the secondary battery is impregnated in a second solvent in which the second active material can be dispersed, after the second cutting step, The process includes a second recovery step of recovering the second active material from the second solvent after the second impregnation step, Separation and recovery method.

2. A separation and recovery method according to claim 1, The aforementioned first electrode layer is a positive electrode layer, The first solvent is a solvent capable of dissolving the positive electrode binder of the first electrode layer. Separation and recovery method.

3. A separation and recovery method according to claim 2, In the first impregnation step, the first solvent is heated to a predetermined temperature below the melting point of the positive electrode binder. Separation and recovery method.

4. A separation and recovery method according to claim 2 or 3, The positive electrode binder is PVDF. The first solvent is TEP or NMP. Separation and recovery method.

5. A separation and recovery method according to claim 1, The aforementioned second electrode layer is a negative electrode layer, The second solvent is a solvent capable of dissolving the negative electrode binder of the second electrode layer. Separation and recovery method.

6. A separation and recovery method according to claim 5, In the second impregnation step, the second solvent is heated to a predetermined temperature below the melting point of the negative electrode binder. Separation and recovery method.

7. A separation and recovery method according to claim 5 or 6, The aforementioned negative electrode binder is water-soluble, The second solvent is water. Separation and recovery method.

8. A separation and recovery method according to claim 1, In the first impregnation step and the second impregnation step, the secondary battery is vibrated while being impregnated in the solvent. Separation and recovery method.

9. A separation and recovery method according to claim 1, In the first impregnation step and the second impregnation step, a load is applied to the secondary battery so as to maintain the state of being immersed in the solvent. Separation and recovery method.

10. A secondary battery capable of separating and recovering electrode active material by the separation and recovery method described in claim 1, Either the positive electrode layer or the negative electrode layer is housed in a bag-shaped separator. Secondary battery.

11. A secondary battery according to claim 10, The positive electrode active material of the positive electrode layer, which serves as the first electrode layer, has the chemical formula LiMO ２ A compound having a layered structure, represented by Secondary battery.

12. A secondary battery according to claim 10 or 11, The negative electrode binder of the negative electrode layer, which serves as the second electrode layer, is water-soluble. Secondary battery.

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