Energy storage module and method for dismantling the energy storage module

Abstract

To minimize the number of steps involved in recycling and to facilitate dismantling. [Solution] A power storage module comprising a bipolar electrode having a positive electrode active material on one side of the current collector foil and a negative electrode active material on the other side of the current collector foil, an electrode laminate formed by stacking a plurality of bipolar electrodes, and a resin sealing portion provided on the periphery of the current collector foil that seals the spaces between adjacent bipolar electrodes in the stacking direction of the electrode laminate, wherein the sealing portion has a recess that forms a gap between the periphery portions of adjacent current collector foils in the stacking direction.

Description

Technical Field

[0001] The present invention relates to a power storage module and a method for disassembling the power storage module.

Background Art

[0002] Patent Document 1 discloses, as a method for disassembling a power storage module, disassembling the power storage module to separate bipolar electrodes, and cooling the entire bipolar electrodes to separate a current collector, a substrate, and an adhesive. In the configuration described in Patent Document 1, the cooling temperature of the bipolar electrodes is set to a temperature at which the current collector and the substrate are peeled off from the adhesive according to the difference in the linear expansion coefficients of the current collector, the substrate, and the adhesive.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] When recycling a power storage module, the cell is disassembled for the purpose of recovering the electrolytic solution or bipolar electrodes inside the cell. At this time, it is conceivable to remove the resin sealing portion forming the outer frame of the power storage module to open the cell. In this case, if the inside of the power storage module is cut more inward than the outer frame so as to cut off the sealing portion, the peripheral portion of the current collector foil will be cut as well, and a part of the current collector foil will be included in the cut piece. In order to recover the current collector foil from this cut piece, combustion or separation is required, which increases the number of steps.

[0005] The present invention has been made in view of the above circumstances, and an object thereof is to provide a power storage module and a method for disassembling the power storage module that can suppress an increase in steps and can be easily disassembled during recycling or the like.

Means for Solving the Problems

[0006] The present invention relates to an energy storage module comprising: a bipolar electrode having a positive electrode active material on one side of a current collector foil and a negative electrode active material on the other side of the current collector foil; an electrode laminate formed by stacking a plurality of the bipolar electrodes; and a resin sealing portion provided on the periphery of the current collector foil, which seals the spaces between adjacent bipolar electrodes in the stacking direction of the electrode laminate, wherein the sealing portion has a recess that forms a gap between the periphery portions of the current collector foils that are adjacent in the stacking direction. [Effects of the Invention]

[0007] This invention suppresses the increase in processes during recycling and allows for easy dismantling. [Brief explanation of the drawing]

[0008] [Figure 1] This is an external view showing an energy storage module in an embodiment. [Figure 2] This is a cross-sectional view showing a structure in which the current collector foil and the sealing portion are laminated. [Figure 3] This is a diagram illustrating the components that make up an energy storage module. [Figure 4] This figure shows the uneven surface of the sealant film. [Figure 5] This is a flowchart illustrating how to dismantle an energy storage module. [Figure 6] This diagram illustrates the state of a cracked seal. [Figure 7] This diagram illustrates the state in which the resin in the sealing area is crushed during the cooling press process. [Figure 8] This is a diagram illustrating an example of the cooling and dismantling process. [Modes for carrying out the invention]

[0009] The following describes in detail the energy storage module and the method for disassembling the energy storage module in the embodiments of the present invention. However, the present invention is not limited to the embodiments described below.

[0010] Figure 1 shows a power storage module in an embodiment. The power storage module 1 is used in the battery of a vehicle such as a plug-in hybrid vehicle or an electric vehicle. The power storage module 1 is a lithium-ion battery and constitutes a bipolar battery. A bipolar battery is a battery pack in which multiple power storage modules 1 are stacked. A bipolar battery including the power storage modules 1 is a bipolar lithium-ion battery.

[0011] The energy storage module 1 has a structure in which multiple cells are stacked. The energy storage module 1 comprises an electrode stack 2 in which multiple electrodes are stacked, and a sealing part 3 that seals the electrode stack 2. The sealing part 3 is formed in a frame that forms the outer frame of the energy storage module 1.

[0012] The electrode laminate 2 has a structure in which multiple bipolar electrodes, a positive electrode end electrode, a negative electrode end electrode, and multiple separators are laminated. Each bipolar electrode comprises a current collector foil 10, a positive electrode active material, and a negative electrode active material. In the bipolar electrode, the positive electrode active material is provided on one side of the current collector foil 10, and the negative electrode active material is provided on the other side of the current collector foil 10. The positive electrode end electrode includes a terminal positive electrode foil and a terminal positive electrode active material provided on one side of the terminal positive electrode foil. The negative electrode end electrode includes a terminal negative electrode foil and a terminal negative electrode active material provided on one side of the terminal negative electrode foil. Bipolar electrodes and separators are alternately laminated between the positive electrode end electrode and the negative electrode end electrode. Between adjacent bipolar electrodes in the lamination direction, the positive electrode active material of one bipolar electrode is laminated with the negative electrode active material of the other bipolar electrode, with a separator in between.

[0013] As shown in Figure 2, the current collector foil 10 is a current collector in which aluminum foil 11 and copper foil 12 are bonded together via an adhesive layer 13. In other words, the current collector foil 10 is a laminated foil. The aluminum foil 11 is the positive electrode substrate (positive electrode foil). The copper foil 12 is the negative electrode substrate (negative electrode foil). The adhesive layer 13 is a resin layer that bonds the aluminum foil 11 and the copper foil 12. The adhesive layer 13 contains epoxy resin.

[0014] One side of the aluminum foil 11 is bonded to the copper foil 12 via an adhesive layer 13. The other side of the aluminum foil 11 is provided with a positive electrode active material. The outer shape of the positive electrode active material is smaller than the outer shape of the aluminum foil 11. The other side of the aluminum foil 11 includes an uncoated area. This uncoated area is a region where no positive electrode active material is provided and is located at the periphery of the aluminum foil 11. The periphery of the aluminum foil 11 is the periphery of the current collector foil 10.

[0015] One side of the copper foil 12 is bonded to the aluminum foil 11 via an adhesive layer 13. The other side of the copper foil 12 is provided with a negative electrode active material. The outer shape of the negative electrode active material is smaller than the outer shape of the copper foil 12. The other side of the copper foil 12 includes an uncoated area. This uncoated area is a region where no negative electrode active material is provided and is located at the periphery of the copper foil 12. The periphery of the copper foil 12 is the periphery of the current collector foil 10.

[0016] Each cell consists of an electrode stack 2, a sealing portion 3, and an electrolyte. Adjacent cells in the stacking direction share one bipolar electrode and are electrically connected in series via that bipolar electrode. The electrolyte is contained in a space partitioned by adjacent current collector foils 10 in the stacking direction and the sealing portion 3 located between these current collector foils 10. The electrolyte is also contained in a space partitioned by the bipolar electrode, the positive terminal electrode, and the sealing portion 3 located between them. Similarly, the electrolyte is contained in a space partitioned by the bipolar electrode, the negative terminal electrode, and the sealing portion 3 located between them.

[0017] The sealing portion 3 is a seal member provided at the peripheral edge of the current collector foil 10 and arranged so as not to touch the positive electrode active material and the negative electrode active material. The sealing portion 3 is made of an insulating resin. As the material constituting the sealing portion 3, resin materials such as polypropylene (PP), polyethylene (PE), polyphenylene sulfide (PPS), polystyrene (PS), ABS resin, and AS resin can be used. For example, the sealing portion 3 is composed of a composite of polypropylene, polyethylene, and polyphenylene sulfide.

[0018] The power storage module 1 has a structure in which the peripheral edge of the current collector foil 10 is laminated with a plurality of resins. That is, the sealing portion 3 is composed of a plurality of seal members. And, as shown in FIG. 2, the sealing portion 3 has a recess 4 that forms a gap between the peripheral edges of the current collector foils 10 adjacent to each other in the lamination direction.

[0019] The recess 4 is formed in a shape recessed in the lamination direction, and a plurality of recesses 4 are provided in the sealing portion 3. The recesses 4 are provided in plurality along the peripheral edge of the current collector foil 10 at a position overlapping the peripheral edge of the current collector foil 10. A plurality of recesses 4 are provided over the entire circumference of the frame body formed by the sealing portion 3.

[0020] The recess 4 is provided in at least one of the plurality of seal members constituting the sealing portion 3. For example, the recess 4 is provided in the first seal member that contacts the surface of the peripheral edge of the current collector foil 10 among the plurality of seal members. In the example shown in FIG. 2, the recess 4 is provided in the first seal member that contacts the aluminum foil 11. This recess 4 is provided on the surface of the first seal member that contacts the peripheral edge of the aluminum foil 11.

[0021] The sealing portion 3 has an uneven surface on a portion of the resin at the periphery of the current collector foil 10, and has a structure in which stress concentrates in the recessed area 4 during cooling press, making the resin prone to cracking. Because the sealing portion 3 includes the recessed area 4, stress concentrates in the thin part of the resin during cooling press, causing cracks to form from that point and the resin to slide off. The heating and lamination is performed on the outer edge of the current collector foil 10, and heat is not transferred inside this edge, so the uneven structure remains. The remaining void in the sealing portion 3 ensures that a starting point for cracking is secured during cooling press.

[0022] As shown in Figure 3, in the energy storage module 1, multiple resins such as a seal, a spacer, a sealant film 21, and a terminal housing are provided on the periphery of the current collector foil 10, and these resins are welded together with a laminate film 22. The sealing portion 3 includes a seal (first sealing member), a spacer, a sealant film 21, a terminal housing, and a laminate film 22.

[0023] The sealant film 21 is made of polypropylene resin. The sealant film 21 is arranged to cover the entire circumference of the peripheral edge of the current collector foil 10 on all four sides. As shown in Figure 4, one surface of the sealant film 21 is formed with an uneven shape. The sealant film 21 includes an uneven surface 21b with recesses 21a and a flat surface 21c. It is possible to adopt a structure in which only a part of the sealant film 21 has an uneven surface.

[0024] The laminate film 22 contains polypropylene resin. The laminate film 22 is welded to the sealant film 21. The laminate film 22 is provided on the outside of the sealant film 21 in a direction perpendicular to the lamination direction.

[0025] Figure 5 is a flowchart showing the dismantling method for the energy storage module. The dismantling method for energy storage module 1 includes a detoxification step (step S1), a pack dismantling step (step S2), a cooling dismantling step (step S3), and a recovery step (step S4).

[0026] The detoxification process involves discharging the battery pack to make it safe to handle (step S1). The detoxification process includes a discharge step to discharge the battery pack. The battery pack is a bipolar battery equipped with multiple energy storage modules 1.

[0027] The pack dismantling process is the process of dismantling the battery pack and separating the energy storage module 1 from the components of the battery pack (step S2). This dismantling process dismantles the structure in which multiple energy storage modules 1 are stacked and separates the energy storage module 1 into individual units.

[0028] The cooling and dismantling process is a process in which stress is applied to the sealing part 3 while it is cooled, causing it to pulverize (step S3). The cooling and dismantling process is carried out by cooling and dismantling each energy storage module 1 so that each bipolar electrode can be separated from the energy storage module 1. In the cooling and dismantling process, the energy storage module 1 is cooled and the sealing parts 3 provided on all four sides of the energy storage module 1 are removed. The cooling and dismantling process includes a cooling process to concentrate on cooling the sealing part 3, a pressing process to apply stress to the sealing part 3 in a cooled environment, and a recovery process to recover the pulverized sealing part 3.

[0029] The cooling step of the cooling dismantling process cools the energy storage module 1 so that the resin of the sealing part 3 becomes brittle at low temperatures. In this cooling step, the energy storage module 1 is cooled to below -60°C. The pressing step of the cooling dismantling process presses the cooled energy storage module 1 in the stacking direction to freeze-pulverize the sealing part 3. In the pressing step, stress is intentionally applied to the sealing part 3, which has become brittle at low temperatures due to cooling, causing the sealing part 3 to freeze-pulverize. As shown in Figure 6, during cooling and pressing, stress concentrates in the thin parts of the resin of the sealing part 3, causing cracks to form starting from there. With the sealing part 3 cracked starting from the void created by the recess 4, pressing the sealing part 3 in the stacking direction causes the resin of the sealing part 3 to crack, and the broken resin 30 falls off, as shown in Figure 7. Note that Figure 7 shows the cooling environment and arrows indicating the direction in which the pressing load from the pressing step acts.

[0030] The recovery process is a process of recovering the electrolyte that fills the space between the bipolar electrodes by heating, vacuum drying, etc. (Step S4). The recovery process recovers the electrolyte contained in the components remaining after the cooling and dismantling process, namely the laminate, bipolar electrodes, and separator, by vacuum drying.

[0031] Figure 8 shows an example of the cooling and dismantling process. In the cooling and dismantling process, the energy storage module 1 obtained in the back dismantling process is transported by pinch rolls 41 while the cooling, pressing, and recovery processes are carried out.

[0032] The cooling process cools the entire energy storage module 1 by means of forced cooling or contact cooling. In the cooling process, the energy storage module 1 is cooled to -60°C or below. For example, the cooling process may include a step of spraying a refrigerant solvent such as liquid nitrogen (-196°C) or dry ice (-79°C) onto the energy storage module 1, or a step of bringing a cooled component into contact with the energy storage module 1. In the cooling process, the refrigerant solvent 43 is sprayed onto the entire energy storage module 1 by the cooling device 42. In the cooling process, it is not necessary to cool the inside of the energy storage module 1 uniformly; if the sealing portion 3 can be cooled over a predetermined range from the outer circumference to the inside, the resin constituting the sealing portion 3 can be made brittle at low temperatures.

[0033] The pressing process involves pressing the cooled energy storage module 1 in the stacking direction. In the pressing process, the entire energy storage module 1 is pressed by a press device 44 to freeze and pulverize the sealing portion 3. The pressing process uses a press device 44 that can press while cooling the contact area, using a press die shaped to press a part or all four sides of the sealing portion 3 simultaneously.

[0034] In the example shown in Figure 8, the press device 44 has a pair of press rollers. The press rollers are sufficiently cooled and press the energy storage module 1 so as to sandwich it in the stacking direction. For example, the press rollers are cooled by a cooling process. In the press device 44, the energy storage module 1 is transported using pinch rolls 41. The press device 44 presses the energy storage module 1 with the press rollers while transporting it. For example, the roller surface of the press roller is formed with an uneven shape in order to transmit stress to the inside of the sealing portion 3. The unevenness of the press roller surface can crush the sealing portion 3.

[0035] The recovery process recovers the resin 30 when the brittle sealing portion 3, weakened by cooling and stress, cracks and slides off. In the recovery process, external force is applied to the energy storage module 1 after the pressing process by means of air blowing using a blower 45 or by applying vibration, and the crushed resin 30 is recovered. In the example shown in Figure 8, the blower 45 and the receiving tray 46 are provided downstream of the press roller of the press device 44. The air blown by the blower 45 separates the resin 30 from the bipolar electrode and causes it to fall. In the recovery process, the fallen resin 30 is collected by the receiving tray 46. If liquid nitrogen is used in the cooling process, the liquid nitrogen will volatilize as the resin 30 falls. The crushed sealing portion 3 is returned to room temperature by the receiving tray 46 and washed with water (acid pickling) to remove electrolyte components, allowing only the carbon component to be recovered. At that time, the resin 30 can be recovered by submerging it in water with a screen or the like to remove salt. Furthermore, assuming that electrolyte solution adheres to the fallen resin 30, the resin can be recovered more safely by pre-filling the receiving tray 46 with an excess amount of water. In this case, if a weak acid solution is used instead of water, lithium carbonate and other substances generated after degradation can be dissolved, making it possible to separate only the resin 30 from the solid-liquid state.

[0036] The resin 30 obtained through the recovery process can be reused as a raw material for molding as resin fragments, making it recyclable as a material. Aluminum and copper do not break due to their metallic toughness, and the adhesive layer 13 of the current collector foil 10 is made of epoxy resin, which has a very low heat resistance temperature of -268°C, so only the electrodes can be efficiently recovered.

[0037] In the cooling and dismantling process, the brittle sealing portion 3 is crushed, but it is not a problem if not all of the resin constituting the sealing portion 3 is recovered. The cooling and dismantling process not only separates the electrodes for each current collector foil 10, but also secures an opening for recovering the electrolyte. Because an opening is formed by the cooling and dismantling process, the electrolyte can be recovered by vacuum drying in the next process.

[0038] Furthermore, the energy storage module 1 can be dismantled without roasting through the cooling dismantling process. By performing the cooling dismantling process, the resin constituting the sealing part 3 can be recovered in a pulverized state and used as a recycled material. Since the recovered resin 30 may have electrolyte attached to it, it is washed with weakly acidic water, and solid salts such as lithium carbonate are dissolved and washed with water again to make it easier to use as a raw material.

[0039] As described above, according to this embodiment, the recess 4 provided in the sealing portion 3 makes it easy to separate the resin forming the outer frame of the energy storage module 1 from the current collector foil 10. This allows the energy storage module 1 to be easily disassembled. Furthermore, the energy storage module 1 can be disassembled without affecting the current collector foil 10, the positive electrode, and the negative electrode, and the resin that can be recycled can be recovered.

[0040] Furthermore, in the current collector foil 10, the combination of metal foils constituting the positive electrode foil and the negative electrode foil is not limited to a combination of aluminum foil 11 and copper foil 12. The metal foil included in the current collector foil 10 may also be lead foil. The bipolar storage battery including the current collector foil 10 is not limited to a bipolar lithium-ion battery, but may also be a bipolar lead-acid battery or a bipolar nickel-metal hydride battery.

[0041] Furthermore, the surface on which the recess 4 is provided in the sealing member is not particularly limited. The recess 4 may be provided on either side of the sealing member, or on both sides of the sealing member. For example, if the first sealing member is provided with a recess 4, it may be provided not only on the side that contacts the current collector foil 10, but also on the side that does not contact the current collector foil 10.

[0042] Furthermore, the recess 4 is not limited to the sealing portion 3 positioned between adjacent current collector foils 10 in the stacking direction, but may also be provided in the sealing portion 3 positioned outside the positive terminal electrode in the stacking direction, or outside the negative terminal electrode in the stacking direction. For example, the energy storage module 1 may have a sealant film 21 formed in an uneven shape. In short, when the energy storage module 1 is viewed from the stacking direction, the recess 4 is provided in the resin of the portion of the sealing portion 3 that overlaps with the peripheral edge of the current collector foil 10. [Explanation of Symbols]

[0043] 1. Energy storage module 2-electrode stack 3. Sealing part 4 recesses 10 Current collector foil 11 Aluminum foil 12 Copper foil 13 Adhesive layer 30 resin 41 Pinch Roll 42 Cooling device 43. Cryogenic solvents 44 Pressing device 45 Blower 46. ​​Drip tray

Claims

1. A bipolar electrode in which a positive electrode active material is provided on one side of the current collector foil and a negative electrode active material is provided on the other side of the current collector foil, An electrode laminate comprising multiple bipolar electrodes stacked on top of each other, A resin sealing portion is provided on the periphery of the current collector foil and seals the space between adjacent bipolar electrodes in the stacking direction of the electrode laminate, A battery storage module equipped with, The sealing portion has recesses that form gaps between the peripheral edges of adjacent current collector foils in the stacking direction. A battery storage module characterized by the following features.

2. The sealing portion is composed of a plurality of sealing members, The recess is provided in at least one of the plurality of sealing members. The energy storage module according to claim 1.

3. The current collector foil is a current collector in which a positive electrode foil and a negative electrode foil are bonded together via an adhesive layer. The recess is provided in at least the first sealing member among the plurality of sealing members that contacts the peripheral edge of the current collector foil. The energy storage module according to claim 2.

4. The recess is formed in a shape that is recessed in the stacking direction and is provided on the surface of the first sealing member that contacts the peripheral edge of the current collector foil. The energy storage module according to claim 3.

5. A method for dismantling an energy storage module according to any one of claims 1 to 4, This includes a cooling and dismantling process in which the sealed portion is cooled to -60°C or below and pressed in the stacking direction to freeze-grind. A method for dismantling an energy storage module, characterized by the following features.

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