Electrode body disassembling method

Abstract

This method for disassembling an electrode body (2) is provided with: a separator breaking step (S1) in which an outermost separator (23S) among separators is stretched so that an extension position (NP) continuously moves along a boundary surface (KM) between the separator and an active material layer (KT2), thereby breaking the separator and the active material layer at the boundary surface; a separator separation step (S2) in which the separator separated from the active material layer in the separator separation step is separated from the active material layer; and a disassembly step (S3) for disassembling the laminated state of the electrode body for each partial electrode (2XR) including the active material layer from which the separator has been peeled in the separator peeling step.

Description

Technical Field

[0001] The disclosed technology relates to a method for disassembling an electrode body of an electrical storage device. Background Art

[0002] For example, in the case of an electrode body of a lithium-ion battery (electrical storage device), a positive electrode body and a negative electrode body in which an active material layer is coated on a metal foil are respectively sandwiched by a separator and wound into a flat shape in a stacked and crimped state. For the purpose of reusing or evaluating the performance of the electrode body, it is necessary to peel the outermost separator from the active material layer and disassemble the stacked state of the electrode body.

[0003] However, generally, the active material layer is only adhered to the surface of the metal foil via an adhesive material that bonds composite materials to each other. Therefore, if an attempt is made to directly peel the outermost separator from the active material layer, the active material layer may detach from the metal foil and be transferred to the separator.

[0004] In response to this, for example, Patent Document 1 discloses a method for peeling a surface material, which is 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, characterized in that a tool die is brought into contact with the surface material, and ultrasonic vibration is applied through the tool die, thereby breaking the adhesive layer or reducing the adhesive force, and then separating the surface material from the base material.

[0005] Patent Document 1: Japanese Patent Application Laid-Open No. 2005-282165

[0006] Therefore, when disassembling the stacked state of the above electrode body, a method of applying ultrasonic vibration to the outermost separator to separate the separator from the active material layer can also be considered. However, in this case, there is a problem that the ultrasonic vibration applied to the separator separates the composite materials bonded by the adhesive material in the active material layer and deforms or damages the active material layer of the disassembled electrode body. Summary of the Invention

[0007] The disclosed technology has been completed in view of this problem, and its object is to provide a method for disassembling an electrode body that can reduce the active material layer transferred to the separator and can suppress deformation and damage of the active material layer when peeling the outermost separator from the active material layer in an electrode body for an electrical storage device.

[0008] (1) One aspect of the present disclosure technology for solving the above problems is a method for disassembling an electrode body for a power storage device, in which a positive electrode body and a negative electrode body, each having an active material layer coated on a metal foil, are sandwiched by a separator, laminated, and pressed. The method for disassembling the electrode body includes: a separator cutting step of stretching the outermost separator in the separator so that the extension position continuously moves along the boundary surface with the active material layer, thereby disconnecting the separator and the active material layer at the boundary surface; a separator peeling step of peeling the separator disconnected from the active material layer in the separator cutting step from the active material layer; and 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.

[0009] (2) According to the method for disassembling an electrode body described in (1), it is preferable that: in the separator cutting step, a rotating grinding wheel rotating at a prescribed peripheral speed is brought into frictional contact with the surface of the outermost separator and advanced, so as to stretch the separator in the tangential direction of the rotating grinding wheel.

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

[0011] (4) According to the method for disassembling an electrode body described in any one of (1) to (3), it is preferable that: the separator cutting step, the separator peeling step, and the disassembling step are performed in a water-free and inert environment. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] Figure 1 is a schematic cross-sectional view of a power storage device including a former electrode body disassembled by the method for disassembling an electrode body according to one aspect of the present embodiment.

[0013] Figure 2 is a schematic perspective view showing Figure 1 a state during winding in which the positive electrode body and the negative electrode body of the electrode body shown are respectively sandwiched by a separator and further wound.

[0014] Figure 3 is Figure 1 a cross-sectional view taken along line A-A of the one shown.

[0015] Figure 4 is a schematic perspective view showing Figure 1Flow chart of the disassembly method of the electrode body shown

[0016] Figure 5 is with Figure 1 The B-B cross-section shown indicates the situation in Figure 4 The schematic cross-sectional view of the diaphragm cutting process shown uses a rotary grinding wheel to cut the outermost diaphragm and the active material layer at their boundary surface

[0017] Figure 6 is Figure 5 The C-C cross-sectional view shown

[0018] Figure 7 is with Figure 1 The B-B cross-section shown indicates the situation in Figure 4 The schematic cross-sectional view of the diaphragm peeling process shown peels the outermost diaphragm from the active material layer

[0019] Figure 8 is with Figure 1 The B-B cross-section shown indicates the situation in Figure 4 The schematic cross-sectional view of the disassembly process shown disassembles the stacked state of the electrode body for each partial electrode from which the outermost diaphragm has been peeled

[0020] Explanation of reference numerals

[0021] 1... Battery case; 2... Electrode body; 2X, 2XR... Partial electrodes; 6... Rotary grinding wheel; 10... Power storage device; 21... Positive electrode body; 22... Negative electrode body; 23, 23S, 23N... Diaphragm; 23J... Resin film; 21K, 22K... Metal foil; 231... Surface; KM... Boundary surface; KT1, KT2... Active material layer; NP... Extension position; S1... Diaphragm cutting process; S2... Diaphragm peeling process; S3... Disassembly process; VQ... Peripheral speed Detailed implementation mode

[0022] <Explanation of this power storage device>

[0023] Next, with reference to the drawings, the structure of a power storage device having a previous electrode body disassembled by the disassembly method of the electrode body according to the embodiment of the above disclosed technology will be described in detail. In Figure 1 A simplified cross-sectional view of a power storage device having a previous electrode body disassembled by the disassembly method of the electrode body according to one aspect of this embodiment is shown. In Figure 2 is shown to represent Figure 1 The schematic perspective view of the state during winding in which the positive electrode body and the negative electrode body of the electrode body shown are respectively sandwiched and wound by a diaphragm. In Figure 3 is shown Figure 1The cross-sectional view taken along the line A-A as shown. In addition, the X direction represents the long side direction of the battery case that houses the electrode body, the Y direction represents the short side direction of the battery case, and the Z direction represents the up-and-down direction of the battery case.

[0024] As Figures 1 to 3 shown, the power storage device 10 having the previous electrode body 2 disassembled by the disassembly method of the present electrode body includes a battery case 1, an electrode body 2, a current collecting terminal 4, and an electrolytic solution 5. One outer 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 penetrates into the electrode body 2 and a part of it accumulates near the bottom of the battery case 1. The accumulated electrolytic solution 5 can be replenished into the electrode body 2. In addition, one outer case wall portion 12 is provided with a safety valve 124 formed to be able to open the valve as the pressure inside the battery case 1 rises. In addition, the present power storage device 10 refers to all power storage devices capable of extracting electric energy, for example, including primary batteries, secondary batteries, electric double layer capacitors, etc.

[0025] Here, the battery case 1 includes a bottomed square tube-shaped case main body 11 having a rectangular opening 111 and a long and flat sealing body 12 for sealing the opening 111. The sealing body 12 corresponds to one outer case wall portion 12. The case main body 11 corresponds to the other outer case wall portion 11 (including long side wall portions 11A, 11B, short side wall portions 11C, 11D, and a bottom wall portion 11E). The battery case 1 is, for example, made of aluminum or an aluminum alloy. In addition, the battery case 1 only needs to be hermetically formed inside the battery case 1 and is not limited to the above form.

[0026] In addition, for the electrode body 2, the positive electrode body 21 and the negative electrode body 22 are respectively sandwiched by a separator 23 and laminated and pressed and housed in the battery case 1. In order to improve the insulation with respect to the battery case 1, the outermost separator 23S covers at least the outer peripheral surfaces of the long side wall portions 11A, 11B of the electrode body 2 close to the battery case 1. The positive electrode body 21 and the negative electrode body 22 each have an active material coating portion 212, 222 in which an active material layer KT1, KT2 is coated on a metal foil 21K, 22K and an active material non-coating portion 211, 221 in which the active material layer KT1, KT2 is not coated on one end portions 21K1, 22K1 of the metal foil 21K, 22K.

[0027] The non-coated portions 211 of the positive electrode body 21 and the non-coated portions 221 of the negative electrode body 22 are arranged on opposite sides in the longitudinal direction (X direction) of the battery case 1. The active material coated 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, the positive electrode body 21 and the negative electrode body 22 of the electrode body 2 are respectively sandwiched by the separator 23 and laminated, and wound into a flat shape. However, the sheet-like positive electrode body 21 and negative electrode body 22 may also be sandwiched by the sheet-like separator 23 and laminated into a planar shape.

[0028] For example, in a lithium-ion secondary battery as an example of the present 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 on the metal foil 21K can use, for example, a lithium transition metal oxide (LiNi 1 / 3 Co 1 / 3 Mn 1 / 3 O 2 , LiNiO 2 etc.). In addition, the metal foil 22K of the negative electrode body 22 uses, for example, a copper foil, and the active material layer KT2 coated on the metal foil 22K can use, for example, graphite, hard carbon, soft carbon, etc.

[0029] In addition, the separator 23 can use, for example, a porous resin film made of a polypropylene (PP) resin, a polyethylene (PE) resin, etc. It is preferable to have a ceramic layer such as alumina and an adhesive layer such as polyvinylidene fluoride (PVDF) on both sides of the separator 23. Furthermore, it is more preferable that the adhesive is coated less on the surface side than on the back side of the outermost separator 23S close to the battery case 1. This is because, in this case, it is easy to avoid the problem that the electrode body 2 adheres to the inner wall of the battery case 1 during the process of housing the electrode body 2 into the battery case 1. In addition, 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)).

[0030] In addition, the current collecting terminal 4 has a positive current collecting terminal 4A and a negative current collecting terminal 4B. The positive current collecting terminal 4A is made of aluminum, for example, and the negative current collecting terminal 4B is made of copper, for example. The positive and negative current collecting terminals 4 (4A, 4B) respectively have a base portion 41, a base adjacent portion 42, and a lead portion 43 formed integrally. Here, the base portion 41 is combined with the back side of the two end portions 12R in the longitudinal direction (X direction) of the sealing body (one outer shell wall portion) 12 with the insulating member 3 interposed therebetween, but it is not limited thereto. For example, the base portion 41 may also be combined with the back side of the two end portions in the longitudinal direction (X direction) of the outer shell main body (the other outer shell wall portion) 11 with the insulating member 3 interposed therebetween.

[0031] Further, a base adjacent portion 42 is adjacent to the base portion 41 and abuts against the insulating member 3. Here, at the position of the upper end portion 43a of the lead wire above the outer casing, the lead wire portion 43 is bent downward in the Z direction from the base adjacent portion 42 toward the outer casing. The metal foils 21K and 22K of the non-coated active material portions 211 and 221 of the electrode body 2 are welded and joined in an overlapping state (foil collecting state) to the lower end portion 43b of the lead wire below the outer casing of the lead wire portion 43 and are electrically connected.

[0032] In addition, the base portion 41 is coupled to the external connection portions 45 located at both ends 12R in the long side direction on the surface 12a side of the sealing body (one outer casing wall portion) 12, for example, by means of riveting pins 46 or the like. An insulating member 3 that also serves as a sealing member is interposed between the riveting pins 46 and the external connection portions 45 and the sealing body (one outer casing wall portion) 12. The insulating member 3 can use, for example, polyphenylene sulfide (PPS) resin. In the case of connecting a plurality of the power storage devices 10, a connecting bus bar (not shown) is connected to the external connection portion 45. Alternatively, the external connection portion 45 may be integrally formed with the base portion 41. In this case, the sealing body (one outer casing wall portion) 12, the external connection portion 45, and the base portion 41 may be insert-molded in the insulating member 3.

[0033] <Method for disassembling the present electrode body>

[0034] Next, with reference to the drawings, a method for disassembling the electrode body according to the embodiment of the above-disclosed technology will be described in detail. In Figure 4 shows a flowchart representing Figure 1 the method for disassembling the electrode body shown. In Figure 5 is shown in Figure 1 the B-B cross-sectional view shown represents a schematic cross-sectional view of a case where, in the separator cutting step shown in Figure 4 , a rotary grinding wheel is used to cut the outermost separator from the active material layer at their interface. In Figure 6 shows Figure 5 the C-C cross-sectional view shown. In Figure 7 , in Figure 1 the B-B cross-sectional view shown represents a schematic cross-sectional view of a case where, in the separator peeling step shown in Figure 4 , the outermost separator is peeled from the active material layer. In Figure 8 , in Figure 1 the B-B cross-sectional view shown represents a schematic cross-sectional view of a case where, in the disassembly step shown in Figure 4 , for each partial electrode from which the outermost separator has been peeled, the stacked state of the electrode body is disassembled.

[0035] The disassembling method of this 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 coated with the active material layers KT1 and KT2 on the metal foils 21K and 22K are sandwiched by the separator 23 and laminated and pressed, as Figure 4 shown, and includes a separator cutting step S1, a separator peeling step S2, and a disassembling step S3. In addition, after the disassembled electrode body 2 is taken out from the battery case 1, the positive and negative current collecting terminals 4 (4A, 4B) are separated from the metal foils 21K and 22K in advance.

[0036] Here, as Figure 5 , Figure 6 , Figure 8 shown, for the electrode body 2, the outermost separator 23S, the negative electrode body 22 coated with the negative active material layer KT2 on both sides of the metal foil 22K, the intermediate separator 23N, and the positive electrode body 21 coated with the positive active material layer KT1 on both sides of the metal foil 21K form a set of partial electrodes 2X, and the partial electrodes 2X are laminated multiple times. However, the electrode body 2 is not necessarily limited to the above structure. For example, the outermost separator 23S, the positive electrode body 21 coated with the positive active material layer KT1 on both sides of the metal foil 21K, the intermediate separator 23N, and the negative electrode body 22 coated with the negative active material layer KT2 on both sides of the metal foil 22K can also form a set of partial electrodes 2X, and the partial electrodes 2X are laminated multiple times.

[0037] As Figure 6 shown, the separator cutting step S1 is a step of stretching the outermost separator 23S in the separator 23 in such a way that the extension position NP moves continuously along the boundary surface KM of the active material layer KT2 (KT1), so that the separator 23S and the active material layer KT2 (KT1) are disconnected at the boundary surface KM. In this case, the outermost separator 23S has a local position shift relative to the active material layer KT2 (KT1) within a minute range of the extension position NP. Due to this local position shift of the outermost separator 23S, the separator 23S and the active material layer KT2 (KT1) are disconnected at their connection part (adhesive layer, etc.). Moreover, the disconnection of the connection part (adhesive layer, etc.) proceeds slowly along the boundary surface KM, so the burden on the active material layer KT2 (KT1) is small. Therefore, the outermost separator 23S can be separated from the active material layer KT2 (KT1) without imposing an excessive burden on the active material layer KT2 (KT1). In addition, the amount of local position shift of the outermost separator 23S is not more than the extension limit value of the separator 23S but exceeds the extension limit value of the connection part (adhesive layer, etc.) that connects the separator 23S and the active material layer KT2 (KT1).

[0038] In addition, as Figure 7As shown, 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 disconnected at the boundary surface KM, when peeling the outermost separator 23S from the active material layer KT2 (KT1), the transfer of the active material layer KT2 (KT1) to this separator 23S can be reduced. Therefore, the state of the active material layer KT2 (KT1) can be maintained in the state before the separator peeling, and the deformation and damage of the active material layer KT2 (KT1) can be suppressed.

[0039] In addition, as Figure 8 shown, the disassembling 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 in the separator peeling step S2. Here, the disassembling is performed 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. In this case, the deformation, damage, and mixing of the separator 23S in the active material layer KT2 of the negative electrode can be reduced. In addition, since the peeled partial electrodes 2XR expose the active material layer KT2 of the negative electrode and the active material layer KT1 of the positive electrode, it is easy to recover the respective active material layers KT2 and KT1, and the performance evaluation of the active material layers KT2 and KT1 (for example, appearance evaluation, charge and discharge performance evaluation by forming a small-sized battery cell, etc.) can be simply performed. In addition, the disassembled partial electrode 2XR is not limited to the above structure. 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.

[0040] As described in detail above, according to the disassembling method of the present electrode body 2, in the electrode body 2 for the power storage device 10, when peeling the outermost separator 23S from the active material layer KT2 (KT1), the active material layer KT2 (KT1) transferred to the separator 23S can be reduced, and the deformation and damage of the active material layer KT2 (KT1) from which the separator 23S has been peeled can be suppressed. Therefore, it is easy to recover the active material layers KT2 and KT1, and the performance evaluation of the active material layers KT2 and KT1 can be simply performed.

[0041] In addition, in the disassembling method of the present electrode body 2, it is preferable to perform the separator cutting step S1, the separator peeling step S2, and the disassembling step S3 in a water-free and inert environment. This is to avoid, for example, the components of the electrolyte 5 (LiPF 6In the case of a fluorinated salt such as salt, water reacts with a fluorinated salt such as LiPF6 salt to generate corrosive substances and toxic substances such as hydrofluoric acid. An airtight and inert environment can be formed, for example, inside a glove box filled with an inert gas (e.g., Ar gas, etc.) with a dew point of -50°C or lower. Therefore, the disassembly method of the present electrode body 2 can be implemented inside the above-mentioned glove box.

[0042] In addition, in the disassembly method of the above electrode body 2, as Figure 5 , Figure 6 shown, it is preferable that in the separator cutting step S1, the rotary grinding wheel 6 rotating at a prescribed peripheral speed VQ is brought into frictional contact with the surface 231 of the outermost separator 23S and advanced, and the separator 23S is stretched in the tangential direction (SS direction) of the rotary grinding wheel 6. Here, the P direction indicates the advancing direction of the rotary grinding wheel 6. The rotary grinding wheel 6 is preferably made of a material (e.g., felt, etc.) that is not likely to damage the separator 23S. Specifically, it is more preferable that the rotary grinding wheel 6 is a disc-shaped felt texture 62 laminated on the rotary shaft 61, and abrasive grains 63 of about #100 to 120 are coated on the surface of the felt texture 62. In addition, the peripheral speed VQ is preferably the highest speed at which the separator 23S does not break.

[0043] In this separator cutting step S1, after the rotary grinding wheel 6 rotating at a prescribed peripheral speed VQ is brought into frictional contact with the surface 231 of the separator 23S and advanced a prescribed distance, the rotary grinding wheel 6 is moved in the axial direction by the size of the grinding wheel width, and this operation is repeated. As a result, the separator 23S is stretched in the tangential direction (SS direction) of the rotary grinding wheel 6, so that the load in the vertical direction (ST direction) on the active material layer KT2 (KT1) can be reduced, and the separator 23S of a prescribed width can be stretched along the plane of the boundary surface KM. Therefore, the separation between the composite materials of the active material layer KT2 (KT1), the deformation, damage, etc. of the active material layer KT2 (KT1) can be further reduced. In addition, since the rotary grinding wheel 6 is in frictional contact with the surface 231 of the separator 23S and advances without staying at 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.

[0044] In addition, as described above, on the surface side of the outermost separator 23S close to the battery case 1, although the amount of the adhesive is less than that on the back side, the adhesive is slightly coated. Therefore, as Figure 8As shown, after disassembling a part of the electrode 2XR in the first layer, sometimes on the surface side of the outermost separator 23S of the part of the electrode 2X after the second layer, the active material layer KT1 of the positive electrode of the previously disassembled part of the electrode 2XR is partially attached. In this case, in the separator cutting step S1, it is preferable to wipe off all of the active material layer KT1 of the positive electrode attached to the surface side of the separator 23S by the rotary grinding wheel 6. Thereby, the separator 23S can be uniformly stretched in the tangential direction (SS direction) of the rotary grinding wheel 6, and the separator 23S and the active material layer KT2 can be reliably disconnected at the boundary surface KM.

[0045] In addition, in the method for disassembling the electrode body 2, it is preferable that: as Figure 2 shown, the separator 23 is an extruded resin film 23J, as Figure 6 shown, in the separator cutting step S1, 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 easily extended in the transverse direction (TD direction) than in the extrusion direction (MD direction). Since in the separator cutting step S1, the separator 23S is stretched in the transverse direction (TD direction) of the resin film 23J, the separator 23S can be extended more with a smaller force. Therefore, the separator 23S and the active material layer KT2 (KT1) can be more simply disconnected along the boundary surface KM.

[0046] <Variant Example>

[0047] The embodiments described in detail above are merely illustrative and do not limit the disclosed technology in any way. Therefore, the disclosed technology can be variously improved and modified without departing from its gist.

Claims

1. A method for disassembling an electrode body, wherein the electrode body is used for a power storage device, and is formed by sandwiching a positive electrode body and a negative electrode body coated with an active material layer on a metal foil with a separator, and then stacking and pressing them, wherein: The method for disassembling the electrode body comprises: A separator disconnection step of stretching the outermost separator among the separators so that the extension position moves continuously along the boundary surface between the separator and the active material layer, thereby disconnecting the separator and the active material layer at the boundary surface; a separator peeling step of peeling the separator, which has been cut from the active material layer in the separator cutting step, from the active material layer; as well as The disassembling step is to disassemble the stacked state of the electrode body for each partial electrode including the active material layer from which the separator is peeled off in the separator peeling step.

2. The method for disassembling an electrode assembly according to claim 1, wherein: In the separator breaking step, a rotating grinding wheel rotating at a predetermined peripheral speed is moved forward while being in frictional contact with the surface of the outermost separator, thereby stretching the separator in a tangential direction of the rotating grinding wheel.

3. The method for disassembling an electrode assembly according to claim 1 or 2, wherein: The diaphragm is an extruded resin film. In the separator cutting step, the outermost separator is stretched in a transverse direction perpendicular to the extrusion direction of the resin film.

4. The method for disassembling an electrode assembly according to claim 1, wherein: The diaphragm disconnection process, the diaphragm peeling process, and the disassembly process are performed in a water-free and inert environment.

5. The method for disassembling an electrode assembly according to claim 2, wherein: The diaphragm disconnection process, the diaphragm peeling process, and the disassembly process are performed in a water-free and inert environment.

6. The method for disassembling an electrode assembly according to claim 3, wherein: The diaphragm disconnection process, the diaphragm peeling process, and the disassembly process are performed in a water-free and inert environment.

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