Disassembly method for electrode body

Abstract

To provide a disassembly method for an electrode body capable of reducing an active material layer, which is transferred to a separator, and suppressing collapse, etc., of the active material later when peeling an outermost separator from the active material layer.SOLUTION: Provided is a disassembly method for an electrode body 2 in which a positive electrode body 21 and a negative electrode body 22 coating metal foils 21K and 22K with active material layers KT1 and KT2 are held between separators 23, laminated / crimped and used for a power storage device 10. The disassembly method includes: a separator dividing step S1 of extending an outermost separator 23S in the separators in such a manner that an extension position NP continuously moves along a boundary surface KM with the active material layer KT2, thereby dividing the separator and the active material layer on the boundary surface; a separator peeling step S2 of peeling the separator, which is divided from the active material layer in the separator dividing step, from the active material layer; and a disassembly step S3 of disassembling a laminated state of the electrode bodies for each partial electrode 2XR including the active material layer from which the separator is peeled in the separator peeling step.SELECTED DRAWING: Figure 4

Description

Technical Field

[0001] The disclosed technology relates to a method for disassembling an electrode body used in an energy storage device.

Background Art

[0002] For example, the electrode body of a lithium-ion battery (energy storage device) is wound flat in a state where a positive electrode body and a negative electrode body, each having an active material layer coated on a metal foil, are sandwiched between separators and laminated and pressed. For recycling or performance evaluation of this electrode body, it was necessary to disassemble the laminated state of the electrode body while peeling off the outermost separator from the active material layer.

[0003] However, since the active material layer is generally only bonded to the surface of the metal foil via a binder that binds the composite materials together, if the outermost separator is directly peeled off from the active material layer, the active material layer may detach from the metal foil and be transferred to the separator.

[0004] In this regard, for example, Patent Document 1 discloses a method for peeling a surface material from a laminate in which a surface material is laminated on a base material via an adhesive layer. The method includes bringing a tool horn into contact with the surface material and applying ultrasonic vibration through the tool horn to break the adhesive layer or reduce the adhesive force, and then separating the surface material from the base material.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0006] Therefore, when disassembling the laminated state of the electrode body, a method of separating the separator and the active material layer by applying ultrasonic vibration to the outermost separator is also conceivable. However, in this case, there are problems such as the ultrasonic vibration applied to the separator separating the composite materials bound by the binder in the active material layer and deforming or collapsing the active material layer of the electrode body to be disassembled.

[0007] The present disclosure technology has been made in view of such problems, and in an electrode body used in a power storage device, when peeling the outermost separator from the active material layer, it is possible to reduce the active material layer transferred to the separator and suppress deformation, collapse, etc. of the active material layer. An object is to provide a method for disassembling an electrode body.

Means for Solving the Problems

[0008] (1) One aspect of the present disclosure technology for solving the above problems is a method for disassembling an electrode body used in a power storage device, in which a positive electrode body and a negative electrode body having an active material layer coated on a metal foil are sandwiched between separators and laminated and pressed. A separator cutting step of stretching the outermost separator among the separators so that the stretching position continuously moves along the interface with the active material layer, thereby separating the separator and the active material layer at the interface; a separator peeling step of peeling the separator separated from the active material layer in the separator cutting step from the active material layer; and a disassembly step of disassembling the laminated state of the electrode body for each partial electrode including the active material layer from which the separator has been peeled in the separator peeling step.

[0009] (2) In the method for disassembling an electrode body according to (1) above, it is preferable that in the separator cutting step, a rotating buff rotating at a predetermined peripheral speed is advanced while being in frictional contact with the surface of the outermost separator, and the separator is stretched in the tangential direction of the rotating buff.

[0010] (3) In the method for disassembling the electrode body described in (1) or (2), the separator is an extruded resin film, and in the separator dividing step, it is preferable that the outermost separator is stretched in a transverse direction perpendicular to the extrusion direction of the resin film. Here, the transverse direction means the TD direction (TD: transverse direction) perpendicular to the MD direction (MD: machine direction) in which the resin material of the resin film is extruded.

[0011] (4) In the method for disassembling the electrode body according to any one of (1) to (3), it is preferable that the separator dividing step, the separator peeling step, and the disassembling step are performed under water prohibition and an inert atmosphere.

Brief Description of the Drawings

[0012]

Figure 1

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Mode for Carrying Out the Invention

[0013] <Description of This Power Storage Device> Next, the configuration of a power storage device including an electrode body before being disassembled by the method for disassembling the electrode body according to the embodiment of the above-disclosed technology will be described in detail with reference to the drawings. FIG. 1 shows a schematic cross-sectional view of a power storage device including an electrode body before being disassembled by the method for disassembling the electrode body according to one aspect of the present embodiment. FIG. 2 shows a schematic perspective view representing a state during winding in which the positive electrode body and the negative electrode body of the electrode body shown in FIG. 1 are respectively sandwiched between separators and wound. FIG. 3 shows an A-A cross-sectional view of the electrode body shown in FIG. 1. Note that the X direction indicates the longitudinal direction of the battery case that houses the electrode body, the Y direction indicates the short-side direction of the battery case, and the Z direction indicates the vertical direction of the battery case.

[0014] As shown in FIGS. 1 to 3, a power storage device 10 including an electrode body 2 before being disassembled by the method for disassembling the present electrode body includes a battery case 1, an electrode body 2, a current collecting terminal 4, and an electrolytic solution 5. One case wall portion 12 constituting the battery case 1 has an injection port 121 for injecting the electrolytic solution 5 into the battery case 1 and a plug body 122 for sealing the injection port 121 by welding. The electrolytic solution 5 injected from the injection port 121 is impregnated into the electrode body 2, and a part of it is stored near the bottom of the battery case 1. The stored electrolytic solution 5 can be replenished into the electrode body 2. In addition, one case wall portion 12 is provided with a safety valve 124 formed to be able to open the valve as the pressure in the battery case 1 rises. Note that the present power storage device 10 means a general power storage device capable of extracting electrical energy, and includes, for example, a primary battery, a secondary battery, an electric double layer capacitor, and the like.

[0015] Here, the battery case 1 includes a bottomed rectangular tube-shaped case body 11 having a rectangular opening 111, and a long and flat sealing body 12 that seals the opening 111. The sealing body 12 corresponds to one case wall portion 12. The case body 11 corresponds to the other case wall portions 11 (including the long side wall portions 11A and 11B, the short side wall portions 11C and 11D, and the bottom wall portion 11E). The battery case 1 is made of, for example, aluminum or an aluminum alloy. Note that the battery case 1 only needs to have an airtight interior and is not limited to the above form.

[0016] Further, in the electrode body 2, the positive electrode body 21 and the negative electrode body 22 are each sandwiched between separators 23, laminated and pressure-bonded, and housed in the battery case 1. The outer peripheral surface of the electrode body 2 that is close to at least the long side wall portions 11A and 11B of the battery case 1 is covered by the outermost separator 23S in order to enhance the insulation with respect to the battery case 1. The positive electrode body 21 and the negative electrode body 22 each have an active material coating portion 212 and 222 in which an active material layer KT1 and KT2 are coated on metal foils 21K and 22K, and an active material non-coating portion 211 and 221 in which the active material layers KT1 and KT2 are not coated on one end portions 21K1 and 22K1 of the metal foils 21K and 22K.

[0017] The active material non-coating portion 211 of the positive electrode body 21 and the active material non-coating portion 221 of the negative electrode body 22 are arranged to face each other in the longitudinal direction (X direction) of the battery case 1. The active material coating portions 212 and 222 are formed at the other end portions 21K2 and 22K2 and the intermediate portions 21K3 and 22K3 of the metal foils 21K and 22K. Here, in the electrode body 2, the positive electrode body 21 and the negative electrode body 22 are each sandwiched between separators 23, laminated, and wound flat, but the sheet-shaped positive electrode body 21 and negative electrode body 22 may be sandwiched between sheet-shaped separators 23 and laminated in a planar shape.

[0018] For example, in a lithium-ion secondary battery which is an example of the power storage device 10, the metal foil 21K of the positive electrode body 21 uses, for example, an aluminum foil, and the active material layer KT1 coated thereon uses, for example, a lithium transition metal oxide (LiNi 1 / 3 Co 1 / 3 Mn 1 / 3 O2 , LiNiO 2 , etc.) can be used. Also, the metal foil 22K of the negative electrode body 22 can use, for example, a copper foil, and the active material layer KT2 coated thereon can use, for example, graphite, hard carbon, soft carbon, etc.

[0019] Also, as the separator 23, a porous resin film made of, for example, polypropylene (PP) resin or polyethylene (PE) resin can be used. It is preferable that both surfaces of the separator 23 are provided with a ceramic layer such as alumina and an adhesive layer such as polyvinylidene fluoride (PVDF). In addition, it is more preferable that less adhesive is applied to the surface side of the outermost separator 23S close to the battery case 1 than the back side. This is because it is easy to avoid the problem that the electrode body 2 adheres to the inner wall of the battery case 1 when the electrode body 2 is being housed in the battery case 1. Note that the electrolytic solution 5 can use a known non-aqueous electrolytic solution (for example, an electrolytic solution containing LiPF 6 salt and composed of ethylene carbonate (EC), dimethyl carbonate (DMC), and ethyl methyl carbonate (EMC)).

[0020] Also, the current collector terminal 4 has a positive current collector terminal 4A and a negative current collector terminal 4B. The positive current collector terminal 4A is, for example, made of aluminum, and the negative current collector terminal 4B is, for example, made of copper. The positive and negative current collector terminals 4 (4A, 4B) each have a base portion 41, a base adjacent portion 42, and a lead portion 43 formed integrally. Here, the base portion 41 is coupled to the back side of both end portions 12R in the longitudinal direction (X direction) of the sealing body (one case wall portion) 12 with the insulating member 3 interposed therebetween, but it is not necessarily limited to this. For example, the base portion 41 may be coupled to the back side of both end portions in the longitudinal direction (X direction) of the case body (other case wall portion) 11 with the insulating member 3 interposed therebetween.

[0021] Further, the base adjacent portion 42 is adjacent to the base portion 41 and is in contact with the insulating member 3. Here, the lead portion 43 is bent downward in the Z direction from the base adjacent portion 42 at the position of the upper end portion 43a of the lead above the case. The metal foils 21K and 22K of the non-active material coated portions 211 and 221 of the electrode body 2 are welded and joined to the lower end portion 43b of the lead portion 43 below the case in a superposed state (foil stacking state) and are electrically connected.

[0022] Note that the base portion 41 is coupled to the external connection portions 45 located at both longitudinal ends 12R on the surface 12a side of the sealing body (one case wall portion) 12 by, for example, caulking pins 46 or the like. An insulating member 3 also serving as a sealing material is interposed between the caulking pins 46 and the external connection portions 45 and the sealing body (one case wall portion) 12. For example, a polyphenylene sulfide (PPS) resin can be used for the insulating member 3. When a plurality of the power storage devices 10 are connected, a connecting bus bar (not shown) is connected to the external connection portion 45. Further, the external connection portion 45 may be integrally formed with the base portion 41. In this case, the sealing body (one case wall portion) 12, the external connection portion 45, and the base portion 41 may be insert-molded with the insulating member 3.

[0023] <Disassembly Method of the Present Electrode Body> Next, a method for disassembling the electrode body according to the embodiment of the disclosed technology will be described in detail with reference to the drawings. FIG. 4 shows a flowchart representing the method for disassembling the electrode body shown in FIG. 1. FIG. 5 shows a schematic cross-sectional view representing a state in which the outermost separator and the active material layer are separated at their interface using a rotary buff in the separator cutting step shown in FIG. 4 in the B-B cross-section shown in FIG. 1. FIG. 6 shows the C-C cross-sectional view shown in FIG. 5. FIG. 7 shows a schematic cross-sectional view representing a state in which the outermost separator is peeled from the active material layer in the separator peeling step shown in FIG. 4 in the B-B cross-section shown in FIG. 1. FIG. 8 shows a schematic cross-sectional view representing a state in which the laminated state of the electrode body is disassembled for each partial electrode from which the outermost separator has been peeled in the disassembly step shown in FIG. 4 in the B-B cross-section shown in FIG. 1.

[0024] The method for disassembling the electrode body 2 is a method for disassembling the electrode body 2 used in the power storage device 10, in which the positive electrode body 21 and the negative electrode body 22, on which the active material layers KT1 and KT2 are coated on the metal foils 21K and 22K, are sandwiched between the separators 23 and laminated and pressed. As shown in FIG. 4, the method includes a separator cutting step S1, a separator peeling step S2, and a disassembly step S3. The electrode body 2 to be disassembled is taken out from the battery case 1, and then the positive and negative current collecting terminals 4 (4A, 4B) are separated from the metal foils 21K and 22K in advance.

[0025] Here, as shown in FIGS. 5, 6, and 8, the electrode body 2 includes the outermost separator 23S, the negative electrode body 22 with the active material layer KT2 of the negative electrode coated on both sides of the metal foil 22K, the intermediate separator 23N, and the positive electrode body 21 with the active material layer KT1 of the positive electrode coated on both sides of the metal foil 21K, which form a set of partial electrodes 2X and are laminated multiple times. However, the electrode body 2 does not necessarily have to be limited to the above configuration. For example, the outermost separator 23S, the positive electrode body 21 with the active material layer KT1 of the positive electrode coated on both sides of the metal foil 21K, the intermediate separator 23N, and the negative electrode body 22 with the active material layer KT2 of the negative electrode coated on both sides of the metal foil 22K may form a set of partial electrodes 2X and be laminated multiple times.

[0026] As shown in FIG. 6, in the separator cutting step S1, the outermost separator 23S within the separator 23 is stretched so that the stretching position NP continuously moves along the interface KM with the active material layer KT2 (KT1), thereby cutting the separator 23S and the active material layer KT2 (KT1) at the interface KM. In this case, within a minute range of the stretching position NP, a local misalignment occurs between the outermost separator 23S and the active material layer KT2 (KT1). Due to this local misalignment of the outermost separator 23S, the separator 23S and the active material layer KT2 (KT1) are cut at their joint part (such as an adhesive layer). And since the cutting of the joint part (such as an adhesive layer) gradually progresses along the interface KM, the burden on the active material layer KT2 (KT1) is small. Therefore, the outermost separator 23S and the active material layer KT2 (KT1) can be separated without imposing an excessive burden on the active material layer KT2 (KT1). Note that the amount of local misalignment of the outermost separator 23S does not exceed the stretching limit value of the separator 23S, and is larger than the stretching limit value of the joint part (such as an adhesive layer) connecting the separator 23S and the active material layer KT2 (KT1).

[0027] Also, as shown in FIG. 7, the separator peeling step S2 is a step of peeling the outermost separator 23S separated from the active material layer KT2 (KT1) in the separator cutting step S1 from the active material layer KT2 (KT1). In this case, since the outermost separator 23S and the active material layer KT2 (KT1) are already cut at the interface KM, when peeling the outermost separator 23S from the active material layer KT2 (KT1), the transfer of the active material layer KT2 (KT1) to the separator 23S can be reduced. Therefore, the state of the active material layer KT2 (KT1) can be maintained in the state before separator peeling, and deformation and damage of the active material layer KT2 (KT1) can be suppressed.

[0028] Also, as shown in FIG. 8, the disassembly step S3 is a step of disassembling the laminated state of the electrode body 2 for each partial electrode 2XR including the active material layer KT2 (KT1) from which the outermost separator 23S has been peeled off in the separator peeling step S2. Here, for each set of partial electrodes 2XR including the negative electrode body 22 coated with the active material layer KT2 of the negative electrode, the intermediate separator 23N, and the positive electrode body 21 coated with the active material layer KT1 of the positive electrode, disassembly is performed. In this case, deformation, collapse, and mixing of the separator 23S into the active material layer KT2 of the negative electrode can be reduced. Further, since the active material layer KT2 of the negative electrode and the active material layer KT1 of the positive electrode are exposed in the disassembled partial electrode 2XR, it is easy to recover the respective active material layers KT2 and KT1, and performance evaluation of the active material layers KT2 and KT1 (for example, appearance evaluation or evaluation of charge and discharge performance by forming a small cell, etc.) can be easily performed. Note that the partial electrode 2XR to be disassembled is not limited to the above configuration, and for example, it may be disassembled into a partial electrode composed only of the negative electrode body 22 coated with the active material layer KT2 of the negative electrode from which the outermost separator 23S has been peeled off.

[0029] As described in detail above, according to the method for disassembling the electrode body 2, when peeling the outermost separator 23S from the active material layer KT2 (KT1) in the electrode body 2 used in the power storage device 10, the active material layer KT2 (KT1) transferred to the separator 23S can be reduced, and deformation, collapse, etc. of the active material layer KT2 (KT1) from which the separator 23S has been peeled off can be suppressed. Therefore, it is easy to recover the active material layers KT2 and KT1, and performance evaluation of the active material layers KT2 and KT1 can be easily performed.

[0030] Note that in the method for disassembling the electrode body 2, it is preferable that the separator cutting step S1, the separator peeling step S2, and the disassembly step S3 are performed under a water-free and inert atmosphere. When the electrode body 2 to be disassembled contains, for example, components of the electrolytic solution 5 (fluorine-based salts such as LiPF 6 salts), water reacts with LiPF 6This is to avoid reacting with fluorine-based salts such as salts to generate corrosive substances such as hydrofluoric acid, toxic substances, etc. Since a water-free and inert atmosphere can be formed, for example, in a glove box filled with an inert gas (e.g., Ar gas, etc.) with a dew point of -50°C or lower, the disassembly method of this electrode body 2 is preferably carried out in the above glove box.

[0031] Also, in the disassembly method of the above electrode body 2, as shown in FIGS. 5 and 6, in the separator cutting step S1, the rotating buff 6 rotating at a predetermined peripheral speed VQ is advanced while being in frictional contact with the surface 231 of the outermost separator 23S, and the separator 23S is stretched in the tangential direction (SS direction) of the rotating buff 6. Here, the P direction indicates the advancing direction of the rotating buff 6. The rotating buff 6 is preferably a buff made of a material (e.g., felt, etc.) that is less likely to damage the separator 23S. Specifically, the rotating buff 6 is more preferably one in which a disc-shaped felt fabric 62 laminated on the rotating shaft 61 is mounted, and abrasive grains 63 of about #100 to 120 are applied to the surface of the felt fabric 62. Also, the peripheral speed VQ is preferably the maximum speed at which the separator 23S does not tear.

[0032] In this separator cutting step S1, after the rotating buff 6 rotating at a predetermined peripheral speed VQ is advanced by a predetermined distance while being in frictional contact with the surface 231 of the separator 23S, the rotating buff 6 is moved in the axial direction by the buff width and this is repeated. As a result, since the separator 23S is stretched in the tangential direction (SS direction) of the rotating buff 6, while reducing the load in the vertical direction (ST direction) on the active material layer KT2 (KT1), the separator 23S with a predetermined width can be stretched along the surface of the interface KM. Therefore, the separation of the composite materials of the active material layer KT2 (KT1), the deformation, collapse, etc. of the active material layer KT2 (KT1) can be further reduced. Also, since the rotating buff 6 advances while being in frictional contact with the surface 231 of the separator 23S and does not stay in a fixed position, the temperature rise of the active material layer KT2 (KT1) can be suppressed and the deterioration of the active material layer KT2 (KT1) can be reduced.

[0033] Note that, as described above, since an adhesive is slightly applied to the surface side of the outermost separator 23S close to the battery case 1 in an amount less than that on the back side, as shown in FIG. 8, after the first-layer partial electrode 2XR is disassembled, the positive electrode active material layer KT1 of the previously disassembled partial electrode 2XR may partially adhere to the surface side of the outermost separator 23S of the partial electrodes 2X from the second layer onward. In this case, in the separator cutting step S1, it is preferable that the rotating buff 6 scrapes off all of the positive electrode active material layer KT1 adhering to the surface side of the separator 23S. Thereby, the separator 23S can be uniformly stretched in the tangential direction (SS direction) of the rotating buff 6, and the separator 23S and the active material layer KT2 can be surely cut at the boundary surface KM.

[0034] Also, in the method for disassembling the electrode body 2, as shown in FIG. 2, the separator 23 is an extruded resin film 23J, and in the separator cutting step S1, as shown in FIG. 6, it is preferable that the outermost separator 23S is stretched in the transverse direction (TD direction) orthogonal to the extrusion direction (MD direction) of the resin film 23J. The extruded resin film 23J has a property of being more likely to extend in the transverse direction (TD direction) than in the extrusion direction (MD direction). In the separator cutting step S1, since the separator 23S is stretched in the transverse direction (TD direction) of the resin film 23J, the separator 23S can be stretched more with a smaller force. Therefore, the separator 23S and the active material layer KT2 (KT1) can be more easily cut along the boundary surface KM.

[0035] <Modification Example> The embodiment described in detail above is merely an example and does not limit the disclosed technology in any way. Therefore, the disclosed technology can be variously improved and modified without departing from its gist.

Description of Reference Numerals

[0036] 1 Battery case 2 Electrode body 2X, 2XR Partial electrodes 6 Rotating buff 10 Power storage device 21 Positive electrode body 22 Negative electrode body 23, 23S, 23N Separators 23J Resin film 21K, 22K Metal foils 231 Surface KM Interface KT1, KT2 Active material layers NP Elongation position S1 Separator cutting process S2 Separator peeling process S3 Disassembly process VQ Peripheral speed

Claims

1. A method for disassembling an electrode body used in a power storage device, wherein a positive electrode body and a negative electrode body, each having an active material layer coated on a metal foil, are laminated and pressed with each being sandwiched between separators, comprising: a separator cutting step of stretching the outermost separator among the separators so that the stretching position continuously moves along the interface with the active material layer, thereby separating the separator and the active material layer at the interface; a separator peeling step of peeling the separator separated from the active material layer in the separator cutting step from the active material layer; a disassembling step of disassembling the laminated state of the electrode body for each partial electrode including the active material layer from which the separator has been peeled in the separator peeling step. A method for disassembling an electrode body.

2. In the method for disassembling an electrode body according to Claim 1, the separator cutting step is performed by advancing a rotary buff rotating at a predetermined peripheral speed while frictionally contacting the surface of the outermost separator, so as to stretch the separator in the tangential direction of the rotary buff. A method for disassembling an electrode body.

3. In the method for disassembling an electrode body according to Claim 1, the separator is an extruded resin film, and the separator cutting step is performed by stretching the outermost separator in a transverse direction perpendicular to the extrusion direction of the resin film. A method for disassembling an electrode body.

4. In the method for disassembling an electrode body according to any one of Claims 1 to 3, the separator cutting step, the separator peeling step, and the disassembling step are performed under a water-free and inert atmosphere. A method for disassembling an electrode body.

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