Secondary batteries and methods for separating and recovering electrode active materials of secondary batteries

Abstract

To provide a secondary battery in which electrode active materials can be individually and easily separated and recovered. [Solution] The secondary battery comprises a multi-layer cell 10 in which multiple layers of first electrode layers, each having a first active material layer on the surface of a first current collector foil, and second electrode layers, each having a second active material layer on the surface of a second current collector foil, are alternately stacked via separators 4, and an outer casing 11 that houses the multi-layer cell 10. The multi-layer cell 10 is substantially rectangular in plan view, and multiple first current collector foils are joined together along one or more sides of the multi-layer cell 10, and multiple second current collector foils are joined together along at least the sides of the multi-layer cell 10 other than the sides to which the first current collector foils are joined together. In addition, multiple separators 4 are joined together along the sides of the multi-layer cell 10 other than the sides to which at least one of the first current collector foils and the second current collector foils are joined together.

Description

Technical Field

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

Background Art

[0002] As a secondary battery, one having a configuration in which a positive electrode layer and a negative electrode layer are arranged so as to sandwich a separator is known. In the present invention, a laminated structure including a positive electrode layer, a separator, and a negative electrode layer may be referred to as a single-layer cell.

[0003] By the way, expensive materials or materials with a large environmental load may be used for the positive electrode active material and the negative electrode active material (hereinafter, both are collectively referred to as the electrode active material) contained in each electrode layer of the secondary battery. Therefore, for the purpose of reusing the electrode active material, etc., it is desired to separate and recover the electrode active material from the secondary battery.

[0004] Patent Document 1 discloses a separation and recovery method in which a power storage element including a first electrode having a first electrode active material layer, a second electrode having a second electrode active material layer, and a separator disposed between the first electrode active material layer and the second electrode active material layer is heated to separate one of the electrode active materials. According to this method, one of the positive electrode active material or the negative electrode active material can be recovered from the battery.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0006] However, the method described in Patent Document 1 involves separating and recovering electrode active material from a secondary battery composed of single-layer cells. Therefore, in a secondary battery having a multi-layer cell in which multiple positive and negative electrode layers are alternately stacked with separators in between, each electrode active material layer is sandwiched between current collector foil and separators, making it difficult to easily separate and recover the electrode active material.

[0007] Therefore, the object of the present invention is to provide a secondary battery in which electrode active materials can be individually and easily separated and recovered. [Means for solving the problem]

[0008] According to one aspect of the present invention, a secondary battery is provided comprising a multi-layer cell in which a plurality of first electrode layers, each having a first active material layer on the surface of a first current collector foil, and a second electrode layer, each having a second active material layer on the surface of a second current collector foil, are alternately stacked via separators, and an outer casing for housing the multi-layer cell. The multi-layer cell is substantially rectangular in plan view, and a plurality of first current collector foils are joined together along one or more sides of the multi-layer cell, and a plurality of second current collector foils are joined together along at least the sides of the multi-layer cell other than the sides to which the first current collector foils are joined together. Furthermore, a plurality of separators are joined together along the sides of the multi-layer cell other than the sides to which at least one of the first current collector foils and the second current collector foils are joined together. [Effects of the Invention]

[0009] According to the present invention, a secondary battery is provided in which the first active material and the second active material can be individually and easily separated and recovered. [Brief explanation of the drawing]

[0010] [Figure 1] Figure 1 is a plan view of the secondary battery 1 according to this embodiment, viewed from above. [Figure 2] Figure 2 is a longitudinal cross-sectional view showing the XX' section of Figure 1. [Figure 3A]Figure 3A is a schematic diagram of the electrode active material separation and recovery method according to this embodiment, and is a diagram illustrating the first cutting step, the first impregnation step, and the first recovery step. [Figure 3B] Figure 3B is a schematic diagram of the electrode active material separation and recovery method according to this embodiment, and is a diagram illustrating the second cutting step, the second impregnation step, and the second recovery step. [Figure 4] Figure 4 is a longitudinal cross-sectional view showing the XX' section of Figure 1, illustrating the state in which the current collector foil and separator 4 are bonded to the outer casing 11. [Figure 5A] Figure 5A is a plan view of the secondary battery 1 according to the modified example 1. [Figure 5B] Figure 5B is a plan view of the secondary battery 1 according to Modification 1, and is a diagram illustrating an example of the position in which the negative electrode current collector foil and separator are integrated. [Figure 5C] Figure 5C is a plan view of the secondary battery 1 according to Modification 1, and is a diagram illustrating another example of the position in which the negative electrode current collector foil and separator are integrated. [Figure 6] Figure 6 is a plan view of the secondary battery 1 according to modified example 2. [Figure 7] Figure 7 is a plan view of the secondary battery 1 according to the modified example 3. [Modes for carrying out the invention]

[0011] The present invention will be described below with reference to the drawings.

[0012] Figure 1 is a plan view of the secondary battery 1 according to this embodiment, viewed from above. As shown in Figure 1, the secondary battery 1 has a multi-layer cell 10 and an outer casing 11 that are substantially rectangular in plan view. The multi-layer cell 10 is a battery element housed inside the outer casing 11.

[0013] The exterior body 11 is composed of two exterior body films, and these exterior body films are formed as substantially rectangular films. The multi-layer cell 10 is housed within the exterior body film such that it is sandwiched between the two exterior body films, and the outer edges that form the sides of the exterior body film are sealed. Thereby, the multi-layer cell 10 is housed inside the exterior body 11. However, for the secondary battery 1, the positive electrode tab 23 and the negative electrode tab 33 that function as input / output terminals are configured to protrude from the inside of the exterior body 11 to the outside at one side surface of the exterior body 11 (the upper end of the exterior body 11 in FIG. 1). The secondary battery 1 is provided as a so-called laminate cell.

[0014] FIG. 2 is a longitudinal sectional view showing the XX' cross-section of FIG. 1. As shown in FIG. 2, the multi-layer cell 10 has a configuration in which a plurality of positive electrode layers 2 and negative electrode layers 3 are alternately laminated via a separator 4. The positive electrode layer 2 is a layer in which a positive electrode active material layer 22 is disposed on the surface of a positive electrode current collector foil 21. Also, the negative electrode layer 3 is a layer in which a negative electrode active material layer 32 is disposed on the surface of a negative electrode current collector foil 31.

[0015] More specifically, in the layers excluding the outermost layer of the multi-layer cell 10 (the layers at the upper and lower ends of the multi-layer cell 10 in FIG. 2), the positive electrode active material layer 22 is disposed on both sides of the positive electrode current collector foil 21, and the negative electrode active material layer 32 is disposed on both sides of the negative electrode current collector foil 31. On the other hand, the outermost layer of the multi-layer cell 10 has the positive electrode layer 2 disposed therein, and in the thus disposed positive electrode layer 2, the positive electrode active material layer 22 is provided only on one surface of the positive electrode current collector foil 21.

[0016] In FIG. 2, a multi-layer cell 10 having 4 positive electrode layers 2 and 3 negative electrode layers 3 is illustrated, but the number of each layer is not limited to this and can be adjusted as appropriate.

[0017] In this specification, the positive electrode layer 2, the positive electrode current collector foil 21, the positive electrode active material layer 22, the positive electrode active material, the positive electrode binder, and the positive electrode tab 23 may be respectively referred to as the first electrode layer, the first current collector foil, the first active material layer, the first active material, the first binder, and the first electrode tab. Further, the negative electrode layer 3, the negative electrode current collector foil 31, the negative electrode active material layer 32, the negative electrode active material, the negative electrode binder, and the negative electrode tab 33 may be respectively referred to as the second electrode layer, the second current collector foil, the second active material layer, the second active material, the second binder, and the second electrode tab.

[0018] The positive electrode current collector foil 21 is integrally gathered at the side where at least the positive electrode tab 23 protrudes, and the above-mentioned positive electrode tab 23 is connected to the tip portion thereof. Similarly, the negative electrode current collector foil 31 is integrally gathered at the side where at least the negative electrode tab 33 protrudes, and the above-mentioned negative electrode tab 33 is connected to the tip portion thereof.

[0019] 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. Further, as the negative electrode current collector foil 31, for example, thin films such as copper, copper alloy, nickel, and nickel alloy can be used.

[0020] 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. Further, 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.

[0021] The positive electrode tab 23 and the negative electrode tab 33 are metal plates. The positive electrode tab 23 is connected to the positive electrode current collector foil 21, and the negative electrode tab 33 is connected to the negative electrode current collector foil 31. As the positive electrode tab 23 and the negative electrode tab 33, for example, a nickel plate or a copper alloy plate can be used.

[0022] In this secondary battery 1, multiple positive electrode current collector foils 21 are bundled together along one or more sides of a multi-layer cell 10. Multiple negative electrode current collector foils 31 are bundled together along at least one side of the multi-layer cell 10 other than the side on which the positive electrode current collector foils 21 are bundled together. Furthermore, multiple separators 4 are bundled together along the sides of the multi-layer cell 10 other than the side on which at least one of the positive electrode current collector foils 21 and the negative electrode current collector foils 31 are bundled together.

[0023] The details will be explained with reference to Figures 1 and 2. In Figure 1, the four sides of the multi-layer cell 10 are designated as the first side 101, the second side 102, the third side 103, and the fourth side 104, respectively. The thick solid lines, thick dashed lines, and double lines drawn near these four sides schematically indicate that the positive electrode current collector foil 21, the negative electrode current collector foil 31, and the separator 4 are integrated together at those sides, respectively. This point is also the same in the configuration described below.

[0024] As shown in Figure 1, the multiple positive electrode current collector foils 21 of the secondary battery 1 are joined together, for example, along the first side 101. In other words, the positive electrode current collector foils 21 are joined together along one or more sides of the multi-layer cell 10.

[0025] Furthermore, as shown in Figure 1, multiple negative electrode current collector foils 31 are joined together, for example, on the first side 101 and the second side 102. In other words, the negative electrode current collector foils 31 are joined together on at least one side of the multi-layer cell 10 other than the side on which the positive electrode current collector foils 21 are joined together (the first side 101 in Figure 1).

[0026] Furthermore, as shown in Figure 1, multiple separators 4 are joined together, for example, at the third side 103 and the fourth side 104. In other words, the separators 4 are joined together at the sides of the multi-layer cell 10 other than the sides (in Figure 1, the first side 101 and the second side 102) where at least one of the positive electrode current collector foil 21 and the negative electrode current collector foil 31 are joined together.

[0027] In this invention, "integrally bundled" means that the current collector foils and separators 4 are stacked and bundled together as a single unit. For example, in Figure 2, which shows the XX' cross-section of Figure 1, it can be seen that the right outer edges of the multiple negative electrode current collector foils 31 are stacked and bundled together as a single unit in the right-hand portion of the multi-layer cell 10. This state is referred to as "integrally bundled".

[0028] 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.

[0029] However, in secondary batteries having a multi-layer cell in which multiple positive electrode layers and negative electrode layers are stacked with separators in between, the positive electrode active material layer and the negative electrode active material layer are sandwiched between current collector foil and separators, making it difficult to easily separate and recover the electrode active material.

[0030] In contrast, according to the secondary battery 1 of this embodiment, the positive electrode active material and the negative electrode active material can be separated and recovered individually and easily, as shown below.

[0031] Figures 3A and 3B are schematic diagrams of the electrode active material separation and recovery method according to this embodiment, illustrating each step of separating and recovering the positive electrode active material and negative electrode active material from the secondary battery 1 described in Figure 1.

[0032] In general terms, in this separation and recovery method, the positive electrode active material is first separated and recovered by the first cutting step, first impregnation step, and first recovery step shown in Figure 3A. Subsequently, the negative electrode active material is separated and recovered by the second cutting step, second impregnation step, and second recovery step shown in Figure 3B.

[0033] In Figure 3A, the upper section shows a plan view of the secondary battery 1 before and after the first cutting process, and the lower section shows a longitudinal section of these plan views, specifically the SS' cross-section. Similarly, in Figure 3B, the upper section shows a plan view of the secondary battery 1 before and after the first cutting process, and the lower section shows a longitudinal section of these plan views, specifically the TT' cross-section. Each process will be explained in detail below.

[0034] (1st cutting process) First, as shown in Figure 3A, in the first cutting step, the side of the outer casing 11 from which the positive electrode tab 23 and negative electrode tab 33 protrude (the side on the first side 101) is cut together with the positive electrode tab 23 and negative electrode tab 33 by a cutter or the like. At this time, the positive electrode current collector foil 21 and the negative electrode current collector foil 31, which are bundled together at the first side 101, are also cut at the same time.

[0035] As a result, the positive electrode current collector foil 21 is not bundled together on any side of the multi-layer cell 10. In other words, the positive electrode layer 2 is not fixed to any other components inside the outer casing 11. To put it another way, the positive electrode current collector foil 21 and the positive electrode active material layer 22 can be removed from the secondary battery 1.

[0036] If there are other sides where the positive electrode current collector foil 21 is bundled together, then in the first cutting step, all sides where the positive electrode current collector foil 21 is bundled together are cut.

[0037] (First impregnation process) After the first cutting step, as shown in Figure 3A, the secondary battery 1 is impregnated in the first solvent 5 in the first impregnation step. Since the positive electrode layer 2 is not fixed to the other components of the secondary battery 1 in the first cutting step, when the secondary battery 1 is impregnated in the first solvent 5, the positive electrode current collector foil 21 and the positive electrode active material layer 22 are easily removed into the first solvent 5.

[0038] The first solvent 5 is a solvent capable of dissolving the positive electrode binder contained in the positive electrode layer 2. Since the positive electrode active material layer 22 is adhered to the positive electrode current collector foil 21 by the positive electrode binder, if the first solvent 5 is capable of dissolving the positive electrode binder, the positive electrode active material layer 22 will peel off from the positive electrode current collector foil 21 in the first solvent 5, and the positive electrode active material will be dispersed.

[0039] At this time, the negative electrode current collector foil 31 is still held together as a single unit along the second side 102. Therefore, when impregnating the secondary battery 1 with the first solvent 5, for example, if the single unit portion of the negative electrode current collector foil 31 is grasped with a gripping jig or the like while impregnating, the negative electrode layer 3 will not be removed and mixed with the first solvent 5.

[0040] Furthermore, the separator 4 is still held together by its third side 103 and fourth side 104. Therefore, when impregnating the secondary battery 1 with the first solvent 5, if the grouped portion of the separator 4 is also grasped with a gripping jig or the like during impregnation, the separation of the separator 4 from being removed and mixed with the first solvent 5 is suppressed.

[0041] The first solvent 5 used in the first impregnation step is not particularly limited in type, as long as it can dissolve the positive electrode binder. Preferably, the first solvent 5 is one that can dissolve the positive electrode binder used in the positive electrode layer 2 and disperse the positive electrode active material. For example, when PVDF (polyvinylidene fluoride) is used as the positive electrode binder, the first solvent 5 may be TEP (triethyl phosphate) or NMP (N-methylpyrrolidone) that can dissolve PVDF and disperse the positive electrode active material.

[0042] (First recovery process) After the first impregnation step, as shown in Figure 3A, the positive electrode active material dispersed in the first solvent 5 is separated and 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, positive electrode binder, and positive electrode current collector foil 21 are dispersed. For filtration, for example, natural filtration, vacuum filtration, and pressure filtration can be employed.

[0043] (2nd cutting process) In the first recovery step, after separating and recovering the positive electrode active material, in the second cutting step, as shown in Figure 3B, the side of the outer casing 11 to which the negative electrode current collector foil is integrally bundled (the side on the first side 101) is cut by a cutter or the like. At this time, the negative electrode current collector foil 31, which is integrally bundled on the second side 102, is also cut simultaneously.

[0044] As a result, the negative electrode current collector foil 31 is not bundled together on any side of the multi-layer cell 10. In other words, the negative electrode layer 3 is not fixed to any other components inside the outer casing 11. To put it another way, the negative electrode current collector foil 31 and the negative electrode active material layer 32 can be removed from the secondary battery 1.

[0045] Furthermore, if there are multiple sides on which the negative electrode current collector foil 31 is bundled together, all of those multiple sides are cut in the second cutting step.

[0046] (Second impregnation process) After the second cutting step, as shown in Figure 3B, the secondary battery 1 is impregnated in the second solvent 6 in the second impregnation step. Since the negative electrode layer 3 is not fixed to the other components of the secondary battery 1 in the second cutting step, when the secondary battery 1 is impregnated in the second solvent 6, the negative electrode current collector foil 31 and the negative electrode active material layer 32 are easily removed into the second solvent 6.

[0047] The second solvent 6 is a solvent capable of dissolving the negative electrode binder contained in the negative electrode layer 3. Since the negative electrode active material layer 32 is adhered to the negative electrode current collector foil 31 by the negative electrode binder, if the second solvent 6 is capable of dissolving the negative electrode binder, the negative electrode active material layer 32 will peel off from the negative electrode current collector foil 31 in the second solvent 6, and the negative electrode active material will be dispersed.

[0048] At this point, the components of the positive electrode layer 2, including the positive electrode active material, have already been recovered in the first recovery step and are therefore difficult to mix with the second solvent 6. Furthermore, the separator 4 is still held together as a single unit along its third side 103. For this reason, when impregnating the secondary battery 1 with the second solvent 6, for example, by grasping the unitally assembled portion of the separator 4 with a gripping jig or the like while impregnating, the separation of the separator 4 into the second solvent 6 and subsequent mixing can be suppressed.

[0049] The type of the second solvent 6 used in the second impregnation step is not particularly limited, as long as it can dissolve the negative electrode binder. Preferably, the second solvent 6 is one that can dissolve the negative electrode binder used in the negative electrode layer 3 and disperse the negative electrode active material. For example, if a water-soluble resin such as a water-soluble epoxy resin is used as the negative electrode binder, the second solvent 6 is water that can dissolve the water-soluble resin and disperse the negative electrode active material.

[0050] (Second recovery process) After the second impregnation step, as shown in Figure 3B, the negative electrode active material dispersed in the second solvent 6 is separated and recovered in the second recovery step. For example, the negative electrode active material is separated and recovered from the second solvent 6 by filtering the second solvent 6 in which the negative electrode active material, negative electrode binder, and negative electrode current collector foil 31 are dispersed. As with the first recovery step, filtration methods such as natural filtration, vacuum filtration, and pressure filtration can be employed.

[0051] As described above, the secondary battery 1 and the electrode active material separation and recovery method according to this embodiment enable the individual and easy separation and recovery of the positive electrode active material and the negative electrode active material.

[0052] In this embodiment, in order to more easily remove the positive electrode layer 2 and the negative electrode layer 3, it is preferable that at least one of the positive electrode current collector foil 21 and the negative electrode current collector foil 31 of the secondary battery 1 has a portion of it that is integrated with the outer casing 11 on an edge other than the edge on which the positive electrode tab 23 and the negative electrode tab 33 are provided. Furthermore, it is preferable that the separator 4 also has a portion of it that is integrated with the outer casing 11 on an edge other than the edge on which the positive electrode tab 23 and the negative electrode tab 33 are provided.

[0053] Please refer to Figure 4 for a detailed explanation. Figure 4 is a longitudinal cross-sectional view showing the XX' section of Figure 1, illustrating the state in which the current collector foil and separator 4 are bonded to the outer casing 11.

[0054] As shown in Figure 4, the end of the integrated portion of the negative electrode current collector foil 31 is bonded to the outer casing 11 on the right side of the multi-layer cell 10. Similarly, the end of the integrated portion of the separator 4 is bonded to the outer casing 11 on the left side of the multi-layer cell 10.

[0055] The current collector foil and separator 4 can be bonded to the outer casing 11 using a resin-based adhesive. Examples of resins that can be used include thermoplastic resins and thermosetting resins.

[0056] With this configuration, when removing the positive electrode layer 2 in the first impregnation step, the mixing of the negative electrode layer 3 and separator 4 with the first solvent 5 is more reliably suppressed compared to when the combined portion of the negative electrode current collector foil 31 and separator 4 is grasped with a gripping jig or the like. Similarly, when removing the negative electrode layer 3 in the second impregnation step, the mixing of the separator 4 with the second solvent 6 is more reliably suppressed. As a result, the positive electrode layer 2 and the negative electrode layer 3 can be removed more easily.

[0057] However, regardless of the above configuration, note that the negative electrode current collector foil 31 has a portion of it that is integrated with the negative electrode tab 33 and is bonded to the outer casing 11. Similarly, note that the positive electrode current collector foil 21 also has a portion of it that is integrated with the positive electrode tab 23 and is bonded to the outer casing 11. This is also true for the configuration described below.

[0058] Furthermore, the secondary battery 1 in this embodiment has an electrolyte (not shown) inside the outer casing 11. The electrolyte may be held by soaking into the separator 4, or it may be filled to fill the inside of the outer casing 11. Also, the type of electrolyte is not particularly limited as long as it has ionic conductivity. For example, LiPF6 / EC-based, sulfonamide-based, and aqueous-based electrolytes can be used.

[0059] Furthermore, as the positive electrode active material, for example, a lithium metal composite oxide having a layered structure, represented by the chemical formula LiMO2, is used. Examples of lithium metal composite oxides include layered rock salt type compounds such as LiCoO2, LiMnO2, LiNiO2, LiVO2, and Li(Ni-Mn-Co)O2, as well as LiMn2O4 and LiNi 0.5 Mn 1.5 Examples include spinel-type compounds such as O4, olivine-type compounds such as LiFePO4 and LiMnPO4, or Si-containing compounds such as Li2FeSiO4 and Li2MnSiO4. Also, Li4Ti5O 12 Other options can also be used.

[0060] 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.

[0061] Furthermore, PVDF (polyvinylidene fluoride) can be used as the positive electrode binder. For the negative electrode binder, a water-soluble resin can be used. Examples of water-soluble resins include water-soluble epoxy resins and water-soluble phenolic resins.

[0062] Furthermore, the separator 4 is a porous film having electrical insulation and ion conductivity, and for example, a nonwoven fabric can be used.

[0063] Furthermore, the outer casing film is a sheet-like film, and for example, a metal laminate film can be used.

[0064] The secondary battery 1 and the method for separating and recovering the electrode active material according to this embodiment have been described above. Next, a secondary battery 1 with a configuration different from that shown in Figures 1 and 2 will be described with reference to a modified example. Details will be omitted regarding aspects where the same configuration as the previously described embodiment can be adopted.

[0065] (Variation 1) Figure 5A is a plan view of the secondary battery 1 according to Modification 1. In this modification, the separator 4 of the secondary battery 1 is integrally assembled along the sides other than those on which the positive electrode tab 23 and the negative electrode tab 33 are provided.

[0066] For example, as shown in Figure 5A, the positive electrode tab 23 and the negative electrode tab 33 are provided so as to protrude from the end of the outer casing 11 on the first side 101 to the outside of the secondary battery 1. In this case, the separator 4 is integrally bound together at the second side 102, where the positive electrode tab 23 and the negative electrode tab 33 are located at a position 90° offset from the sides other than the first side 101 when viewed from above.

[0067] With this configuration, the positive electrode current collector foil 21 and the positive electrode active material layer 22 can be easily removed. In the first cutting step described above, the positive electrode current collector foil 21 and the negative electrode current collector foil 31, which are bundled together, are cut at the first edge 101 from which the positive electrode tab 23 and the negative electrode tab 33 protrude. As a result, since the separator 4 is not bundled at that edge, the positive electrode current collector foil 21 and the positive electrode active material layer 22 can be easily removed from the cut portion.

[0068] On the other hand, the negative electrode current collector foil 31 is still integrally bound together at the second side 102. Therefore, it is not possible to remove the negative electrode current collector foil 31. However, it is possible to remove the negative electrode active material layer 32. For example, after removing the positive electrode layer 2 in the first recovery step described above, if the secondary battery 1 is impregnated with a second solvent 6 capable of dissolving the negative electrode binder, the negative electrode active material layer 32 will peel off from the negative electrode current collector foil 31 and be removed into the second solvent 6.

[0069] In this modified example, as shown in Figure 5A, it is preferable that the separator 4 is integrally assembled at the same edge where at least one of the positive electrode current collector foil 21 and the negative electrode current collector foil 31 is integrally assembled.

[0070] At this time, as shown in Figure 5B, the portion where the negative electrode current collector foil 31 and the separator 4 are integrated together may overlap in a plan view. In other words, as shown by the thick dashed line and double line on the second side 102 in Figure 5B, the portion where the negative electrode current collector foil 31 and the separator 4 are integrated together may overlap. In this case, when viewed along the stacking direction of the multi-layer cell 10, the multiple negative electrode current collector foils 31 and the multiple separators 4 are stacked so that they overlap alternately one by one.

[0071] Alternatively, as shown in Figure 5C, the portion where the negative electrode current collector foil 31 and the separator 4 are integrated may be located at positions offset from each other in a plan view. For example, in Figure 5C, as indicated by the thick dashed line and double line on the second side 102, the integrated portion of the negative electrode current collector foil 31 may be provided in the upper half and the integrated portion of the separator 4 may be provided in the lower half along the direction of the second side 102.

[0072] With this configuration, when removing the positive electrode layer 2 in the first impregnation step described above, the negative electrode current collector foil 31 and the separator 4, which are integrally bound together at the second side 102, can be simultaneously grasped with a gripping jig or the like. Therefore, the mixing of the negative electrode layer 3 and the separator 4 during removal is more reliably suppressed.

[0073] Furthermore, in this modified example, the side on which both the negative electrode current collector foil 31 and the separator 4 are integrated is not limited to the second side 102. For example, both the negative electrode current collector foil 31 and the separator 4 may be integrated on the third side 103 or the fourth side 104. Alternatively, both the negative electrode current collector foil 31 and the separator 4 may be integrated on multiple sides of the second side 102, the third side 103, and the fourth side 104.

[0074] Furthermore, in this modified example, the positive electrode current collector foil 21 may be bundled together along multiple sides other than the first side 101, excluding the side on which both the negative electrode current collector foil 31 and the separator 4 are bundled together.

[0075] Furthermore, in this modified example, the positive electrode current collector foil 21, the negative electrode current collector foil 31, and the separator 4 may each be bonded to the outer casing 11 at a portion where they are integrated together.

[0076] (Modification 2) Figure 6 is a plan view of the secondary battery 1 according to Modification 2. In this modification, the secondary battery 1 has the positive electrode current collector foil 21 integrally bundled at least along the side on which the positive electrode tab 23 is provided, and the negative electrode current collector foil 31 integrally bundled at least along one or more sides other than the side on which the positive electrode tab 23 is provided. In addition, the separator 4 integrally bundled along one or more sides other than the side on which the positive electrode tab 23 is provided.

[0077] For example, as shown in Figure 6, the positive electrode current collector foil 21 is integrally assembled along the fourth side 104 in addition to the first side 101 on which the positive electrode tab 23 is provided. Similarly, the negative electrode current collector foil 31 is integrally assembled along the first side 101 on which the positive electrode tab 23 is provided, and the other second side 102 and fourth side 104. The separator 4 is integrally assembled along the third side 103 and fourth side 104, excluding the first side 101 on which the positive electrode tab 23 is provided. Although not shown, the integrally assembled parts of the positive electrode current collector foil 21, the negative electrode current collector foil 31, and the separator 4 are each bonded to the outer casing 11.

[0078] With this configuration, in the first cutting step described above, cutting the first side 101 and the fourth side 104 makes the positive electrode current collector foil 21 and the positive electrode active material layer 22 removable. At this time, the negative electrode current collector foil 31 is still attached to the outer casing 11 by the second side 102, so the removal and mixing of the negative electrode layer 3 with the positive electrode current collector foil 21 and the positive electrode active material layer 22 is suppressed. Similarly, the separator 4 is still attached to the outer casing 11 by the third side 103, so mixing is also suppressed.

[0079] Next, in the second cutting step described above, cutting the second side 102 makes the negative electrode current collector foil 31 and the negative electrode active material layer 32 removable. At this time, the separator 4 is still held together by the third side 103 and bonded to the outer casing 11, thus preventing mixing.

[0080] (Variation 3) Figure 7 is a plan view of the secondary battery 1 according to Modification 3. This modification shows the most preferred embodiment of the secondary battery 1 according to this embodiment.

[0081] In this modified example, the secondary battery 1 has the positive electrode current collector foil 21 bundled together on one side where the positive electrode tab 23 is provided, and the negative electrode current collector foil 31 bundled together on one side other than the side where the positive electrode tab 23 is provided. The separator 4 is bundled together on one side other than the side where the positive electrode current collector foil 21 is bundled together, and also on one side other than the side where the negative electrode current collector foil 31 is bundled together.

[0082] For example, as shown in Figure 7, the positive electrode current collector foil 21 is integrally assembled along the first side 101 on which the positive electrode tab 23 is provided, and the negative electrode current collector foil 31 is integrally assembled along the first side 101 on which the positive electrode tab 23 is provided and the other second side 102. The separator 4 is integrally assembled along the fourth side 104, which is the side other than the first side 101 on which the positive electrode current collector foil 21 is integrally assembled, and the side other than the first side 101 and the second side 102 on which the negative electrode current collector foil 31 is integrally assembled. Although not shown in the figure, the integrally assembled parts of the positive electrode current collector foil 21, the negative electrode current collector foil 31, and the separator 4 are each bonded to the outer casing 11.

[0083] With this configuration, in the first cutting step described above, only the first side 101, to which the positive electrode current collector foil 21 is integrally bundled, needs to be cut, and there is no need to cut the other sides. Therefore, the cutting efficiency in the first cutting step is improved compared to the case where multiple sides are cut. Similarly, in the second cutting step described above, only the second side 102, to which the negative electrode current collector foil 31 is integrally bundled, needs to be cut, and there is no need to cut the other sides. Therefore, the cutting efficiency in the second cutting step is improved compared to the case where multiple sides are cut.

[0084] The above describes modified versions of the secondary battery 1 according to this embodiment. Note that the above-described modifications are not independent of each other and can be combined within a reasonable range.

[0085] Next, the effects and advantages of the secondary battery 1 and the method for separating and recovering the electrode active material according to this embodiment will be explained.

[0086] The secondary battery 1 according to this embodiment comprises a multi-layer cell 10 in which a plurality of positive electrode layers 2, each having a positive electrode active material layer 22 on the surface of a positive electrode current collector foil 21, and a negative electrode layer 3, each having a negative electrode active material layer 32 on the surface of a negative electrode current collector foil 31, are alternately stacked via separators 4, and an outer casing 11 that houses the multi-layer cell 10. The multi-layer cell 10 is substantially rectangular in plan view, and the plurality of positive electrode current collector foils 21 are bundled together along one or more sides of the multi-layer cell 10, and the plurality of negative electrode current collector foils 31 are bundled together along at least the sides of the multi-layer cell 10 other than the sides on which the positive electrode current collector foils 21 are bundled together. In addition, the plurality of separators 4 are bundled together along the sides of the multi-layer cell 10 other than the sides on which at least one of the positive electrode current collector foils 21 and the negative electrode current collector foils 31 are bundled together.

[0087] With this configuration, the positive electrode active material and the negative electrode active material can be easily and individually separated and recovered.

[0088] Furthermore, the secondary battery 1 according to this embodiment further includes a positive electrode tab 23 provided so as to protrude from one side of the edge on which the positive electrode current collector foil 21 is integrally assembled, and a negative electrode tab 33 provided so as to protrude from one side of the edge on which the negative electrode current collector foil 31 is integrally assembled, and the separator 4 is integrally assembled along the edges other than the edge on which at least one of the positive electrode tab 23 and the negative electrode tab 33 is provided.

[0089] With this configuration, the positive electrode current collector foil 21 and the positive electrode active material layer 22 can be easily removed from the secondary battery 1.

[0090] Furthermore, in the secondary battery 1 according to this embodiment, the separator 4 is integrated along the edge where at least one of the positive electrode current collector foil 21 and the negative electrode current collector foil 31 is integrated.

[0091] With this configuration, the positive electrode current collector foil 21 and the positive electrode active material layer 22 can be easily removed from the secondary battery 1. Furthermore, the negative electrode active material layer 32 can be easily removed from the negative electrode layer 3.

[0092] Furthermore, in the secondary battery 1 according to this embodiment, at least one of the positive electrode current collector foil 21 and the negative electrode current collector foil 31 and the separator 4 are bonded to the outer casing 11 at the edges other than the edges on which the positive electrode tab 23 and the negative electrode tab 33 are provided, where they are integrated together.

[0093] With this configuration, the positive electrode current collector foil 21 and the positive electrode active material layer 22 can be easily removed from the secondary battery 1. Furthermore, the negative electrode current collector foil 31 and the negative electrode active material layer 32 can also be easily removed.

[0094] Furthermore, in the secondary battery 1 according to this embodiment, the positive electrode current collector foil 21 is integrally bundled at least along the side on which the positive electrode tab 23 is provided, and the negative electrode current collector foil 31 is integrally bundled at least along one or more sides other than the side on which the positive electrode tab 23 is provided. The separator 4 is also integrally bundled along one or more sides other than the side on which the positive electrode tab 23 is provided. Moreover, the integrally bundled portions of the negative electrode current collector foil 31 and the separator 4 are each bonded to the outer casing 11.

[0095] With this configuration, the positive electrode current collector foil 21 and the positive electrode active material layer 22 can be easily removed from the secondary battery 1. The negative electrode current collector foil 31 and the negative electrode active material layer 32 can also be easily removed.

[0096] Furthermore, in the secondary battery 1 according to this embodiment, when the positive electrode tab 23 and the negative electrode tab 33 protrude side by side from one side of the outer casing 11, the positive electrode current collector foil 21 is integrally assembled on the side on which the positive electrode tab 23 is provided. The negative electrode current collector foil 31 is integrally assembled on the side other than the side on which the positive electrode tab 23 is provided. Moreover, the separator 4 is integrally assembled on the side other than the side on which the positive electrode current collector foil 21 is integrally assembled, and also on the side other than the side on which the negative electrode current collector foil 31 is integrally assembled.

[0097] With this configuration, the positive electrode current collector foil 21 and the positive electrode active material layer 22 can be easily and efficiently removed from the secondary battery 1. Furthermore, the negative electrode current collector foil 31 and the negative electrode active material layer 32 can also be easily and efficiently removed.

[0098] Furthermore, the separation and recovery method for separating and recovering electrode active material from the secondary battery 1 according to this embodiment includes: a first cutting step of cutting the edge of the outer casing 11 on which the positive electrode tab 23 protrudes; a first impregnation step of impregnating the secondary battery 1 in a first solvent 5 capable of dissolving the positive electrode binder contained in the positive electrode layer 2 after the first cutting step; and a first recovery step of recovering the positive electrode active material and positive electrode binder from the first solvent 5 after the first impregnation step. Furthermore, the method includes: a second cutting step of cutting the edge of the outer casing 11 on which the negative electrode current collector foil 31 is integrally bundled after the first recovery step; a second impregnation step of impregnating the secondary battery 1 in a second solvent 6 capable of dissolving the negative electrode binder contained in the negative electrode layer 3 after the second cutting step; and a second recovery step of recovering the negative electrode active material and negative electrode binder from the second solvent 6 after the second impregnation step.

[0099] With this configuration, the positive electrode active material and the negative electrode active material can be easily and individually separated from the secondary battery 1 described above.

[0100] 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.

[0101] In this embodiment, the secondary battery 1 may have a positive electrode layer 2 and a negative electrode layer 3 with opposite configurations. That is, even if the positive electrode layer 2 is the second electrode layer and the negative electrode layer 3 is the first electrode layer, the positive electrode active material and the negative electrode active material can be easily separated and recovered individually. In this case, the positive electrode current collector foil 21, positive electrode active material layer 22, positive electrode active material, positive electrode binder, and positive electrode tab 23 become the second current collector foil, second active material layer, second active material, second binder, and second electrode tab, respectively. Also, the negative electrode current collector foil 31, negative electrode active material layer 32, negative electrode active material, negative electrode binder, and negative electrode tab 33 become the first current collector foil, first active material layer, first active material, first binder, and first electrode tab, respectively.

[0102] Furthermore, although the secondary battery 1 according to this embodiment has been described as having a positive electrode tab 23 and a negative electrode tab 33 protruding to the outside of the battery from one side of the outer casing 11, it is not limited to this. That is, the secondary battery 1 may have a positive electrode tab 23 protruding to the outside from one side of the outer casing 11 and a negative electrode tab 33 protruding to the outside from the other side of the outer casing 11.

[0103] Furthermore, the electrode active material separation and recovery method according to this embodiment may consist only of a first cutting step, a first impregnation step, and a first recovery step. In other words, the second cutting step, second impregnation step, and second recovery step may be omitted. In this case, only one of the electrode active materials can be separated and recovered individually and easily. [Explanation of symbols]

[0104] 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 secondary battery comprising a multi-layer cell in which a first electrode layer having a first active material layer disposed on the surface of a first current collector foil and a second electrode layer having a second active material layer disposed on the surface of a second current collector foil are alternately stacked with a separator in between, and an outer casing that houses the multi-layer cell, The aforementioned multi-layered cell is substantially rectangular in plan view, Multiple of the first current collector foils are joined together at one or more sides of the multi-layer cell. The multiple second current collector foils are joined together on at least one side of the multi-layer cell other than the side on which the first current collector foils are joined together. The multiple separators are joined together along the edges of the multi-layer cell, excluding the edges where at least one of the first current collector foil and the second current collector foil is joined together. Secondary battery.

2. A secondary battery according to claim 1, A first electrode tab is provided that protrudes from one of the sides of the first current collector foil, which is integrally bound together, so as to extend to the outside of the secondary battery, The second current collector foil is further provided with a second electrode tab that protrudes from one of the sides of the foil that is integrally bundled with the second current collector foil, so as to extend outward from the secondary battery. The separator is assembled together on an edge other than the edge on which at least one of the first electrode tab and the second electrode tab is provided. Secondary battery.

3. A secondary battery according to claim 1 or 2, The separator is formed at least at the edge where only one of the first current collector foil and the second current collector foil is formed together, Secondary battery.

4. A secondary battery according to claim 1 or 2, At least one of the first current collector foil and the second current collector foil and the separator are bonded together to the outer casing at the edges other than the edges on which the first electrode tab and the second electrode tab are provided. Secondary battery.

5. A secondary battery according to claim 4, The first current collector foil is assembled together at least along the side where the first electrode tab is provided. The second current collector foil is integrally assembled along at least one or more sides other than the side on which the first electrode tab is provided. The separator is integrally assembled along one or more sides other than the side on which the first electrode tab is provided. The second current collector foil and the separator are bonded together in a single unit, with each portion being adhered to the outer casing. Secondary battery.

6. A secondary battery according to claim 5, When the first electrode tab and the second electrode tab protrude side by side from one side of the outer casing, The first current collector foil is integrally assembled at one side on which the first electrode tab is provided. The second current collector foil is integrally assembled along one side other than the side on which the first electrode tab is provided. The separator is formed on one side other than the side on which the first current collector foil is formed, and on one side other than the side on which the second current collector foil is formed. Secondary battery.

7. A separation and recovery method for separating and recovering a first active material from a secondary battery according to claim 1 or 2, A cutting step of cutting the edge of the outer casing from which the first electrode tab protrudes, After the cutting step, an impregnation step is performed in which the secondary battery is impregnated with a first solvent capable of dissolving the first binder contained in the first electrode layer. The process includes a recovery step, after the impregnation step, in which the first active material and the first binder are recovered from the first solvent. Separation and recovery method.

8. A separation and recovery method for separating and recovering a first active material and a second active material from a secondary battery according to claim 1 or 2, A first cutting step involves cutting the edge of the outer casing on which the first electrode tab protrudes, Following the first cutting step, a first impregnation step is performed in which the secondary battery is impregnated with a first solvent capable of dissolving the first binder contained in the first electrode layer, A first recovery step is performed to recover the first active material and the first binder from the first solvent after the first impregnation step, After the first recovery step, a second cutting step is performed in which the side of the outer casing on which the second current collector foil is integrally bundled is cut, A second impregnation step is performed in which the secondary battery is impregnated with a second solvent capable of dissolving the second binder contained in the second electrode layer, after the second cutting step, The process includes a second recovery step, after the second impregnation step, in which the second active material and the second binder are recovered from the second solvent. Separation and recovery method.

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