Reform device and reform method for electrode assembly

Abstract

Provided are a reforming device and a reforming method capable of improving defects in a reforming process. The reforming device according to the present invention includes a reforming pin that can be inserted into a hollow portion of an electrode assembly, and a driving unit that performs a forward and backward movement and a rising and falling movement of the reforming pin, and includes a reforming pin unit, and a rotating unit that can rotate the electrode assembly about the axial direction of the hollow portion.

Description

Technical Field

[0001] The present invention relates to a reforming apparatus and a reforming method for an electrode assembly, and more particularly, to a reforming apparatus and a reforming method for a jelly roll type electrode assembly for a cylindrical secondary battery.

[0002] This application claims priority based on Korean Patent Application Nos. 10-2022-0179765 and 10-2023-0186226 filed on December 20, 2022, and all of the contents disclosed in the specifications and drawings of the applications are incorporated herein.

Background Art

[0003] The recent development of technologies related to mobile devices and the increasing demand are remarkable. Along with this, the demand for secondary batteries as an energy source is rapidly increasing. Among such secondary batteries, research on lithium secondary batteries having a high energy density and a discharge potential has been actively conducted and has reached the commercialization level and is widely used.

[0004] Secondary batteries can be broadly classified into cylindrical batteries and prismatic batteries in which the electrode assembly is built into a cylindrical or prismatic metal can according to the shape of the battery case, and pouch-type batteries in which the electrode assembly is built into a pouch-type case of an aluminum laminate sheet.

[0005] In addition, the electrode assembly built into the battery case is a charge-dischargeable power generation element having a laminated structure of a positive electrode / separator / negative electrode. Generally, a jelly roll type in which a separator is interposed between a long sheet-shaped positive electrode and a negative electrode coated with an active material and wound up, a stack type in which a plurality of positive electrodes and negative electrodes of a predetermined size are laminated in this order with a separator interposed therebetween, and a stack / folding type in which a unit cell of the stack type is wound up with a long separation film. Among them, the jelly roll type electrode assembly has the advantages of being the easiest to manufacture and having a high energy density per unit weight.

[0006] FIG. 1 is a diagram showing a state in which a separator is interposed between a core and wound in the winding process of a conventional jelly roll type electrode assembly, and FIG. 2 is a diagram showing an electrode assembly in a state where the core has been removed after winding of the conventional jelly roll type electrode assembly, with emphasis on the separator.

[0007] Referring to FIG. 1, the jelly roll type electrode assembly is manufactured by winding a separator 1 between a positive electrode 2 in which a positive electrode active material is coated on an aluminum foil and a negative electrode 3 in which a negative electrode active material is coated on a copper foil, and then winding it into a cylindrical shape. In particular, the winding process is carried out by first winding the separator 1 with a core 4 separated into two parts, then winding the positive electrode 2 and the negative electrode 3 together into a cylindrical shape, and then removing the core 4.

[0008] After being wound into a cylindrical jelly roll shape and the core 4 is removed and discharged, a hollow portion 11 is formed at the central portion from which the core 4 has been removed in the electrode assembly 10. However, as shown in FIG. 1, since the separator 1 is first wound around the core 4 and then wound up to the positive electrode 2 and the negative electrode 3, the separator 1 remains in the hollow portion 11 in the shape shown in FIG. 2. The separator 1 remains in the center of the hollow portion 11 so as to divide the hollow portion 11. The separator 1 remaining in the hollow portion 11 of the electrode assembly 10 hinders the insertion of a resistance welding rod during the subsequent assembly process. Therefore, after the winding process, a reforming process is carried out to dispose of the separator 1 in the hollow portion 11.

[0009] FIGS. 3 and 4 are diagrams for explaining the reforming process of the jelly roll type electrode assembly.

[0010] Referring to FIGS. 3 and 4, conventionally, a reforming process has been carried out in which a heated reforming pin 20 is inserted into the hollow portion 11 of the electrode assembly 10 to extrude the separator 1 remaining inside the hollow portion 11 toward the inner wall of the hollow portion 11. That is, the conventional reforming process is of a method in which the heated reforming pin 20 is inserted into the hollow portion 11 to displace the separator 1 remaining in the hollow portion 11 toward the inner wall of the hollow portion 11.

[0011] In particular, the specific process is carried out in the order of heating the reforming pin 20 (step 1), advancing the reforming pin 20 and pushing it into the hollow portion 11 to proceed with the reforming (step 2), and retracting the reforming pin 20 (step 3).

[0012] However, if the outer diameter R_20 of the reforming pin 20 used in the conventional reforming process is increased, there is a problem that the frictional force with the separator 1 increases during the insertion and removal processes of the reforming pin 20, and the separator 1 is damaged. As a result, in the existing reforming process, as shown in FIG. 4, when the reforming pin 20 is inserted into the hollow portion 11, a gap d has to be opened between the reforming pin 20 and the inner wall of the hollow portion 11. That is, the reforming is carried out in a state where the reforming pin 20 and the inner wall of the hollow portion 11 are not in contact.

[0013] As a result, in a non-contact state, the heat of the reforming pin 20 is transferred, and the process proceeds so that the separator 1 remaining in the hollow portion 11 is displaced toward the inner wall of the hollow portion 11 and does not float. However, in the non-contact method, it is difficult to form the remaining separator 1 so that it is in complete contact with the inner wall of the hollow portion 11 and the shape of the hollow portion 11 is close to a cylindrical shape. Thus, conventionally, due to the non-contact reforming process being carried out, there is a problem that situations where it is judged as defective and insufficient frequently occur as a result of the process. SUMMARY OF THE INVENTION PROBLEMS TO BE SOLVED BY THE INVENTION

[0014] The present invention was conceived in view of the above circumstances, and the problem to be solved by the present invention is to provide a reforming device capable of improving defects in the reforming process.

[0015] Another problem to be solved by the present invention is to provide a reforming method capable of improving defects in the reforming process.

[0016] However, the technical problems to be solved by the present invention are not limited to the above-mentioned problems at all, and other problems not mentioned should be clearly understood by those skilled in the art from the description of the invention described below.

Means for Solving the Problems

[0017] The reforming device according to the present invention for solving the above-mentioned problems includes a reforming pin unit and a rotating unit.

[0018] The reforming pin unit includes a reforming pin that can be inserted into the hollow portion of the electrode assembly, and a driving unit that performs the forward and backward movements and the upward and downward movements of the reforming pin.

[0019] The rotating unit is configured to be able to rotate the electrode assembly around the axial direction of the hollow portion.

[0020] In the present invention, the outer diameter of the reforming pin is smaller than the inner diameter of the hollow portion.

[0021] Preferably, the electrode assembly is a long sheet-like laminate including a structure of a positive electrode, a separator, and a negative electrode wound up and having the hollow portion at the central portion, the separator protruding from the inner wall of the hollow portion, and the reforming pin being inserted into the hollow portion in a state separated from the inner wall of the hollow portion.

[0022] After being inserted into the hollow portion, the reforming pin is raised and lowered to bring the separator into close contact with the inner wall of the hollow portion for reforming.

[0023] After the completion of the reforming, the reforming pin is lowered and raised to move away from the inner wall of the hollow portion and then pulled out from the hollow portion.

[0024] In one embodiment, the driving unit includes a first actuator connected to one side of the reforming pin to perform a forward movement and a backward movement, and a second actuator connected to the first actuator to perform a lifting movement.

[0025] And the rotating unit is a turntable structure that is rotated by motor drive.

[0026] The reforming method of the present invention includes a heating step of the reforming pin, a forward movement step of the reforming pin into the hollow portion of the jelly roll type electrode assembly, a raising and lowering step of the reforming pin in the hollow portion, a rotating step of the jelly roll type electrode assembly with the reforming pin positioned in the hollow portion, a lowering and raising step of the reforming pin in the hollow portion, and a backward movement step of the reforming pin from the hollow portion.

[0027] Another reforming method of the present invention includes a step of non - contact insertion of a heated reforming pin into the hollow portion of the electrode assembly, a step of moving the reforming pin to bring it into close contact with the inner wall of the hollow portion and then rotating the electrode assembly around the axial direction of the hollow portion, and a step of moving the reforming pin to move away from the inner wall of the hollow portion.

[0028] These reforming methods can be performed using the reforming apparatus according to the present invention.

Advantages of the Invention

[0029] In the present invention, a reforming pin heated with heat is inserted into the hollow portion of the electrode assembly to move the reforming pin, and after bringing a separator into close contact with the wall surface of the hollow portion, a method of moving the electrode assembly to fix the separator is proposed. Thus, in the present invention, the conventional non-contact heating reforming process can be improved. According to such a present invention, there is an effect of improving the reforming quality.

[0030] The reforming apparatus of the present invention is configured to be able to perform forward movement and backward movement of the reforming pin, and to be able to perform upward and downward movement of the reforming pin, rotation of the electrode assembly, and downward and upward movement of the reforming pin between the forward movement and the backward movement of the reforming pin. In the reforming method using such a reforming apparatus, after inserting the reforming pin into the hollow portion of the electrode assembly without interference, the separator can be brought into close contact with the inner wall of the hollow portion, and with the reforming pin in a state of bringing the separator into close contact with the inner wall of the hollow portion, even if the reforming pin does not move, the electrode assembly rotates, so that reforming is performed in a contact manner along the inner diameter of the hollow portion. Then, the reforming pin can be pulled out of the hollow portion without interference. According to such a present invention, since the inner wall of the hollow portion of the electrode assembly is not contacted when the reforming pin is inserted or removed, defects such as damage to the separator or a part of the separator being pulled out of the electrode assembly do not occur.

[0031] When the present invention is applied, reforming defects can be reduced, and batch reforming becomes possible, so that the productivity of the electrode assembly can be increased.

[0032] According to the present invention, the shape of the hollow portion of the electrode assembly is improved, and the occurrence of defects such as damage to the separator can be suppressed as much as possible.

[0033] Further, since the reforming pin of the present invention can be realized in a form that maintains the basic specifications of the conventional reforming pin as it is, there is no need to separately design the reforming pin, and workability equivalent to or higher than that of the existing one can be ensured.

[0034] The drawings attached to this specification illustrate desirable embodiments of the present invention and are for the purpose of further understanding the technical idea of the present invention together with the content of the invention. Therefore, the present invention should not be construed as being limited only to the matters described in the drawings.

Brief Description of the Drawings

[0035]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Figure 9

Embodiments for Carrying Out the Invention

[0036] Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. Prior to this, the terms and words used in this specification and the claims are not to be construed as being limited to ordinary or dictionary meanings. The inventor interprets them in accordance with the meaning and concept corresponding to the technical idea of the present invention in accordance with the principle that the inventor can appropriately define the concept of the terms in order to explain the invention in the best way. Therefore, it should be understood that the embodiments described in this specification and the configurations shown in the drawings are merely preferred embodiments of the present invention and do not represent all of the technical ideas of the present invention. At the time of this application, there may be various equivalents and modified embodiments that can replace them.

[0037] The same reference numerals indicate the same components. Also, the thickness, ratio, and dimensions of the components are exaggerated for an effective explanation of the technical content.

[0038] FIG. 5 is a schematic diagram of a reforming device according to an embodiment of the present invention.

[0039] In the present invention, a method is proposed in which a reforming pin heated is inserted into the hollow portion of an electrode assembly and a separator is brought into close contact with the wall surface of the hollow portion, and then the separator is fixed. The reforming device shown in FIG. 5 is configured to realize such a method.

[0040] Referring to FIG. 5, the reforming device 200 includes a reforming pin unit 300 and a rotating unit 400. The reforming device 200 is for reforming a cylindrical jelly roll type electrode assembly A.

[0041] FIG. 6 is a diagram showing the laminated state before winding and the winding process of the jelly roll type electrode assembly to be reformed in the present invention. FIG. 7 shows the structure of the electrode plate shown in FIG. 6.

[0042] Referring to FIG. 6, the electrode assembly A can be manufactured by winding a laminate formed by laminating at least once a separator 112, a positive electrode plate 110, the separator 112, and a negative electrode plate 111 in this order in one direction (X).

[0043] At this time, as shown in FIG. 7, the positive electrode plate 110 and the negative electrode plate 111 have a structure in which an active material layer 121 is formed on a long sheet-shaped current collector 120, and may include a blank portion 122 where the active material layer 121 is not formed in a part of the region of the current collector 120.

[0044] Referring to FIG. 7, the positive electrode plate 110 and the negative electrode plate 111 have a structure in which an active material layer 121 is coated on a sheet-shaped current collector 120, and include a blank portion 122 where the active material is not coated on one long side along the winding direction X. In the direction (X direction) along the long side of the current collector 120, one side becomes the core and the other side becomes the outer periphery.

[0045] The electrode assembly A is manufactured by laminating the positive electrode plate 110 and the negative electrode plate 111 next together with two separators 112 as shown in FIG. 6, and then winding them in one direction X from the core. At this time, the blank portions of the positive electrode plate 110 and the negative electrode plate 111 are arranged in opposite directions along the direction (Y direction) along the short side of the current collector 120.

[0046] At the central part of the electrode assembly A produced by the method of FIG. 6, that is, in the inner core, a hollow part B is formed like the hollow part 11 shown in FIG. 2. After the winding process, the plain parts of the positive electrode plate 110 and the negative electrode plate 111 can be bent toward the core side. Thereafter, a current collector plate can be connected to the plain part. The current collector plate has a larger cross-sectional area compared to a strip-type electrode tab, and since the resistance is inversely proportional to the cross-sectional area of the path through which the current flows, when the secondary battery is formed in the above structure, the resistance of the cell can be significantly reduced. As described above, when the positive electrode plate 110 and the negative electrode plate 111 including the plain part 122 are used, a tab-less structure battery can be realized in which at least a part of the plain parts 122 of the positive electrode plate 110 and the negative electrode plate 111 limit the electrode tab without providing a separate electrode tab.

[0047] In the hollow part B, a residual separator 112 can be formed in the shape shown in FIG. 2. In the present invention, a reforming process and a reforming device 200 for disposing of the residual separator 112 that divides the hollow part B and deforming the hollow part B into a cylindrical shape are proposed.

[0048] Returning to FIG. 5, the reforming pin unit 300 includes a reforming pin 310 that can be inserted into the hollow part B of the electrode assembly A, and a driving part 320 that performs the forward and backward movements and the upward and downward movements of the reforming pin 310.

[0049] The driving part 320 provides the driving force for the forward and backward movements and the upward and downward movements of the reforming pin 310. Such a driving part 320 may include a motor or a cylinder that operates by a supplied power source and an applied signal. When it consists of a motor, power transmission means (bearings, gears, belts, chains, etc.) for transmitting the power of the motor to the reforming pin 310 may be further provided. More preferably, it includes a cylinder that operates by a supplied power source and an applied signal but can finely adjust the moving distance, and the end of the rod provided on the cylinder is removably connected to the reforming pin 310.

[0050] For example, the drive unit 320 may include a first actuator 330 and a second actuator 340. The first actuator 330 and the second actuator 340 may include a hydraulic cylinder or a pneumatic cylinder. As another example, the first actuator 330 and the second actuator 340 may be an electric configuration that moves a rod forward and backward by an electric signal. As yet another example, the first actuator 330 and the second actuator 340 may include a servo motor and a linear motion conversion mechanism. The linear motion conversion mechanism may be a rack / pinion that switches a rotational motion to a linear motion.

[0051] The first actuator 330 is connected to one side of the reform pin 310 and performs a forward and backward movement. The first actuator 330 is capable of reciprocating movement. When the first actuator 330 operates, the reform pin 310 can move forward and backward.

[0052] The second actuator 340 is connected to the first actuator 330 and performs a lifting and lowering operation. The second actuator 340 can reciprocate. When the second actuator 340 operates, the first actuator 330 and the reform pin 310 connected to the first actuator 330 can be moved up and down.

[0053] The first actuator 330 and the second actuator 340 preferably include a pneumatic cylinder that can be controlled with high precision by air pressure. If the drive unit 320 is of such a drive method of an air device, it may further include an air compressor that supplies air pressure to the air cylinders of the first actuator 330 and the second actuator 340, and the air cylinders of the first actuator 330 and the second actuator 340 may be connected to such an air compressor to hold or discharge air pressure. The air cylinder operates by the operating air pressure whose supply is interrupted via an air pressure pipeline by a control signal of a controller, and can perform a forward and backward movement of a rod and a forward and backward movement and an upward and downward movement of a reforming pin 310 connected to an end of the rod.

[0054] On the other hand, the reforming pin unit 300 may further include a sensor that senses the forward and backward movement and the upward and downward movement states of the reforming pin 310. The sensor senses the forward and backward movement and the upward and downward movement states of the reforming pin 310 and outputs a signal to the controller, and the controller may control the operations of the first actuator 330 and the second actuator 340 based on the input signal.

[0055] The rotation unit 400 is configured to rotate the electrode assembly A about the axial direction of the hollow portion B. While the electrode assembly A is rotated by the rotation unit 400, the center of the hollow portion B of the electrode assembly A remains in its original position. The rotation unit 400 may be in the structure of a turntable 420 that is rotated by the drive of a motor 410. By mounting the electrode assembly A on the turntable 420 and driving the motor 410, the rotation unit 400 can rotate the electrode assembly A. In particular, with the reforming pin 310 positioned within the hollow portion B, the electrode assembly A can be rotated in place. The rotation unit 400 may further include a jig (not shown) so that when the electrode assembly A is fixed on the turntable 420, the electrode assembly A can also rotate accordingly when the turntable 420 rotates. For example, a motor 410, which is a servo motor, may be mounted on a base (not shown), and the turntable 420 may be connected to the main shaft of this motor 410. The turntable 420 can control the motor 410 to vary the rotation speed in a wide variety of ways.

[0056] On the other hand, the rotation unit 400 may further include a sensor that senses the mounting state of the electrode assembly A and implements the drive of the motor 410. The drive of the motor 410 can be started only after sensing that the reforming pin 310 has abutted against the inner wall of the hollow portion B, so that the reforming process can be carried out stably.

[0057] The reforming pin unit 300 may further include heating means 350 for heating the reforming pin 310 to a temperature at which reforming can be performed. The heating means 350 may include a heating element within the reforming pin 310 and a power source. Alternatively, the heating means 350 may include a heating element that heats the reforming pin 310 by a heat contact method with the reforming pin 310.

[0058] The reforming pin 310 is a long bar shape in one direction. The center axis of the reforming pin 310 is linear along its longitudinal direction and cannot be bent. The longitudinal cross-section perpendicular to the longitudinal direction of the reforming pin 310 can be generally circular. And at any part, the center of the longitudinal cross-section can be constant without displacement along the longitudinal direction. That is to say, it can be said that the shape around the reforming pin 310 substantially presents a circular shape so as to make the hollow part B of the electrode assembly A cylindrical.

[0059] The tip of the reforming pin 310 is formed in a pointed shape, and the remaining body part following the tip can be cylindrical. For example, the front transverse cross-section in the cross-section along the longitudinal direction of the reforming pin 310 can be provided with an inclined cut surface. Needless to say, the tip of the reforming pin 310 may have a shape different from the shape described and illustrated here.

[0060] Also, the reforming pin 310 may be inserted into the hollow part B of the electrode assembly A with an insertion depth that is equal to or greater than the length L_B of the hollow part B of the electrode assembly A. Through this, the cylindrical body part of the reforming pin 310 can be positioned so as to extend from one end to the other end of the hollow part B. The tip of the reforming pin 310 is processed to be rounded so as not to cause indentations on the separator 112 in case of insertion into the hollow part B of the electrode assembly A. In order to be able to insert the reforming pin 310 into the hollow part B of the electrode assembly A with a sufficient insertion depth, the turntable 420 of the rotating unit 400 may be formed with a groove for accommodating the tip side of the reforming pin 310 or a through hole that penetrates from the beginning.

[0061] Here, the outer diameter R_310 of the reforming pin 310, specifically, the outer diameter of the body portion is smaller than the inner diameter R_B of the hollow portion B of the electrode assembly A. The outer diameter R_310 of the reforming pin 310 is such that when the reforming pin 310 is inserted into the hollow portion B, it can be inserted while being separated from the inner wall of the hollow portion B. That is, when the reforming pin 310 is inserted into the hollow portion B, it is a non-contact type. The reforming pin 310 can be inserted at a position generally corresponding to the central portion of the hollow portion B. Since the reforming pin 310 is inserted in a non-contact manner, there is no defect such that the separator 112 in the hollow portion B is caught along the reforming pin 310 or pushed out of the hollow portion B.

[0062] The reforming pin 310 can be made of a metallic material in order to transmit heat well and may include a surface coating layer for reducing friction. The surface coating layer can be made of, for example, a polyether ether ketone (PEEK) material, but the present invention is not limited thereto at all. When the surface coating layer is made of a PEEK material, since PEEK is a thermoplastic resin excellent in high strength, high rigidity, and heat resistance, it has the effect of increasing the durability of the reforming pin 310. Even if the residual separator 112 protrudes in a taiji pattern in the hollow portion B of the electrode assembly A, the reforming pin 310 can be inserted into the hollow portion B while suppressing the friction between the separator 112 and the reforming pin 310 as much as possible.

[0063] The tip of the reforming pin 310 is shaped to be pointed for smooth insertion. Even if the residual separator 112 protrudes in a taiji pattern in the hollow portion B of the electrode assembly A, the pointed tip can be inserted into the empty space between the separators 112 without encountering the separator 112. As the reforming pin 310 advances and enters the hollow portion B up to the cylindrical body portion, it will encounter the protruding separator 112, but since the separator 112 is pushed out into the surrounding empty space, it can be inserted without difficulty.

[0064] The reforming pin 310 advances and fits into the hollow portion B of the electrode assembly A. After coming into contact with the inner wall of the hollow portion B by ascending and descending within the hollow portion B, reforming can be performed while closely adhering the separator 112 remaining in the hollow portion B to the inner wall of the hollow portion B. That is, in the reforming step using the reforming pin 310, it is a contact type.

[0065] The reforming pin 310 is not deformed during use, but can contact the inner wall of the hollow portion B by the ascending operation and the descending operation of the driving unit 320. Thus, in the present invention, the reforming pin 310 is moved to bring the reforming pin 310 into contact with the inner wall of the hollow portion B.

[0066] The reforming pin 310 does not expand or bend to contact the separator 112. The reforming pin 310 contacts the separator 112 by ascending and descending. Since there is no deformation of the reforming pin 310, the consistency of the reforming process is excellent. Further, since the reforming pin 310 of the present invention can be realized in a shape that retains the basic specifications of the conventional reforming pin as it is, there is no need to separately design the reforming pin, and workability equivalent to or higher than that of the existing one can be ensured. Moreover, it is not necessary to provide reforming pins of various sizes according to the inner diameter of the hollow portion B of the electrode assembly A. Since the reforming pin 310 is fitted into the hollow portion B and contacts the inner wall of the hollow portion B by ascending and descending, if the inner diameter of the hollow portion B changes, the contact area may change due to the difference in the bending radius with the reforming pin 310, but it is not necessary to replace it with reforming pins of completely different sizes.

[0067] With the reform pin 310 in contact with the inner wall of the hollow portion B, the rotating unit 400 can rotate the electrode assembly A. By rotating at least once, the entire inner wall of the hollow portion B of the electrode assembly A can come into contact with the reform pin 310. During the rotation of the electrode assembly A, the reform pin 310 may be fixed in position. During the reforming process, the reform pin 310 is stopped and only the electrode assembly A moves. Even if the reform pin 310 does not move, since the electrode assembly A rotates, reforming can be performed in a contact manner along the inner diameter of the hollow portion B.

[0068] The method of moving the reform pin 310 is such that the movement of the reform pin 310 is complex, and moreover, the movement may vary depending on the circumstances at that time, so it is difficult to perform reforming all at once. According to the present invention, when performing contact-type reforming, the reform pin 310 does not move, so there is no change in movement, and only the electrode assembly A rotates around the axial direction of the hollow portion B. Such a rotation-based method always has a constant movement compared to movement in three axial directions, so it is easy to manage the reforming process and is excellent in terms of maintaining reform quality. Therefore, when applying the present invention, reforming defects can be reduced and reforming can be performed all at once, so the productivity of the electrode assembly can be increased. According to the present invention, the results of the reforming process are constant every time, and it is not difficult to set the process quality.

[0069] Also, the reforming device 200 of the present invention can perform reforming by contact and can improve the conventional non-contact heating type reforming process. Since the reform pin 310 can contact the inner wall of the hollow portion B and directly contact the separator 112 to transfer heat, heat can reach all parts uniformly and reforming can be performed uniformly. According to such a present invention, there is an effect of improving reform quality.

[0070] After the reform process is completed, the reform pin 310 can be withdrawn from the hollow portion B after descending and ascending. For example, the reform pin 310 that has been ascending can be withdrawn by a retracting operation after descending to a position that generally coincides with the central portion of the hollow portion B, that is, returning to the original position. Conversely, the reform pin 310 that has been descending can be withdrawn by a retracting operation after ascending to a position that generally coincides with the central portion of the hollow portion B, that is, returning to the original position.

[0071] By using such a reforming device 200, damage to the separator 112 inside the hollow portion B of the electrode assembly A due to poor insertion can be prevented, reforming defects can be suppressed as much as possible, and the reforming quality can also be improved.

[0072] FIG. 8 is a flowchart of a reforming method according to an embodiment of the present invention.

[0073] Referring to FIG. 8, a reforming method according to an embodiment of the present invention includes a heating step (S1) of the reform pin, a forward movement step (S2) of the reform pin, an ascending and descending step (S3) of the reform pin, a rotation step (S4) of the electrode assembly, a descending and ascending step (S5) of the reform pin, and a retracting step (S6) of the reform pin.

[0074] When compared with the existing reform pin heating (step 1) - reform pin forward movement (step 2) - reform pin retraction (step 3) process described with reference to FIG. 3, in the reforming method according to the present invention, between the reform pin forward movement step (S2) and the reform pin retraction step (S6), there are differences in that it includes an ascending and descending step (S3) of the reform pin, a rotation step (S4) of the electrode assembly, and a descending and ascending step (S5) of the reform pin.

[0075] Such a reforming method can be performed using the reforming device 200 according to the present invention.

[0076] FIG. 9 is a diagram showing the state of the electrode assembly and the reforming pin for each step in the reforming apparatus according to the present invention when performing the method according to FIG. 8. FIG. 9 simultaneously shows the relative position of the reforming pin 310 as viewed from the side of the electrode assembly A in each step and the relative position of the reforming pin 310 as viewed from the end of the electrode assembly A during the reforming process. In some of the drawings, some reference numerals are omitted.

[0077] The reforming method of the present invention will be described with reference to FIGS. 8 and 9.

[0078] First, as shown in FIG. 9(a), the electrode assembly A is mounted on the turntable 420 of the rotating unit 400 and set in a ready state. Next, the reforming pin 310 is heated (step S1).

[0079] Thereafter, as shown in FIG. 9(b), the reforming pin 310 is advanced into the hollow portion B of the electrode assembly A (step S2). This can be achieved by driving the first actuator 330 of the driving unit 320. The reforming pin 310 can be generally inserted into the center of the hollow portion B.

[0080] As described above, the outer diameter R_310 of the reforming pin 310 is smaller than the inner diameter R_B of the hollow portion B of the electrode assembly A. Further, even if the separator 112 with a taiji pattern is formed on the inner wall of the hollow portion B, the reforming pin 310 can be inserted into the hollow portion B while being separated from the inner wall of the hollow portion B without putting too much stress on the separator 112 while advancing. Therefore, in the reforming pin advancement step (S2), the separator 112 does not protrude to the opposite side due to the reforming pin 310. Since no frictional force with the separator 112 occurs during the process of inserting the reforming pin 310, there is no risk of the separator 112 being damaged or torn off.

[0081] Next, rather than in the ascending and descending steps (S3) of the reforming pins, the reforming pin 310 can bring the separator 112 remaining at the center of the hollow portion B into close contact with the inner wall of the hollow portion B. In FIG. 9(c), an example of raising the reforming pin 310 within the hollow portion B is shown. Therefore, unlike the conventional reforming being carried out in a non-contact state, in the present invention, it can be carried out in a contact state.

[0082] Since the cylindrical body portion of the reforming pin 310 is located within the hollow portion B and the reforming pin 310 extends along the longitudinal direction of the hollow portion B without being bent, it can contact evenly without a portion where the reforming pin 310 does not contact the longitudinal wall surface of the hollow portion B.

[0083] After this, with the reforming pin 310 positioned within the hollow portion B, the rotation step (S4) of the electrode assembly A is carried out. In FIG. 9(d), an example of the electrode assembly A rotating in the clockwise direction is shown. By driving the motor 410 of the rotation unit 400, the electrode assembly A can be rotated.

[0084] In the above-described step S3, the reforming pins 310 are in a state of being uniformly in close contact with the longitudinal direction of the hollow portion B without any portion where the reforming pins 310 do not contact the wall surface of the hollow portion B of the separator 112. Since the electrode assembly A is rotated in place in the current step S4, the separator 112 can be reformed all at once along the inner wall of the hollow portion B. The reforming pins 310 can press the separator 112 evenly over the entire circumference of the inner wall of the hollow portion B. The separator 112 is thermally deformed and displaced in the direction of the inner wall of the hollow portion B. Therefore, the taiji pattern as shown in FIG. 2 can be completely in close contact with the inner wall of the hollow portion B, and the shape of the hollow portion B can be formed to be close to a cylindrical shape. Moreover, due to the rotation of the electrode assembly A, the separator 112 on the inner wall of the hollow portion B can be properly wound around the inner wall while being bent without being forcibly folded. Thus, according to the present invention, process defects can be improved. Even with only a minimum of one rotation, reforming can be achieved, so a reduction in process time can also be expected.

[0085] Since the taiji pattern is sufficiently formed by the reforming process and no taiji pattern remains inside the hollow portion B, it does not prevent the insertion of the resistance welding rod in the subsequent process, and further, it does not cause the problem of defects when inserting the center pin. Through this, during the assembly process, the insertion of the resistance welding rod and the insertion of the center pin into the hollow portion B of the electrode assembly A can be smoothly performed, and the occurrence of secondary defects due to the shape defect of the hollow portion B can be suppressed as much as possible, and the yield of the next battery production process can be improved.

[0086] While the electrode assembly A is rotating, the reforming pins 310 can be fixed. Therefore, the miracle of the reforming pins 310 is not complicated, and there is no need to control the complicated miracle of the reforming pins 310.

[0087] Next, when performing the lowering / raising step (S5) of the reforming pin, the reforming pin 310 moves away from the inner wall of the hollow portion B of the electrode assembly A. In Fig. 9(e), an example of lowering the reforming pin 310 within the hollow portion B is shown.

[0088] After this, as shown in Fig. 9(f), the backward step (S6) of the reforming pin is performed. Since the outer diameter R_310 of the reforming pin 310 is smaller than the inner diameter R_B of the hollow portion B of the electrode assembly A, the reforming pin 310 can be withdrawn from within the hollow portion B without interference between the reforming pin 310 and the hollow portion B, and the process can be terminated. In the process of withdrawing the reforming pin 310, no frictional force with the separator 112 is generated, so there is no risk of the separator 112 being damaged or torn. In this way, even if the separator 112 protruded so as to divide the hollow portion B before reforming, the hollow portion B of the electrode assembly A after finishing the reforming molding not only completely adheres to and deforms on the inner wall of the hollow portion B due to reforming, but also the inner end of the electrode assembly is not damaged such as being pulled outwards, and it becomes possible to form a hollow portion B having a cylindrical shape.

[0089] The reforming device 200 according to the present invention, as described based on Fig. 3 as existing, was only able to move the reforming pin 20 forward and backward, whereas the upward and downward movements of the reforming pin 310 are added. The reforming device 200 according to the present invention includes a rotating unit 400, and such a rotating unit 400 was not provided in the existing reforming device.

[0090] In short, the reforming method of the present invention may include a heating step of the reforming pin, a forward movement step of the reforming pin, a rising step of the reforming pin, a rotating step of the electrode assembly, a descending step of the reforming pin, and a backward movement step of the reforming pin. The method may also be modified and performed by a method including a heating step of the reforming pin, a forward movement step of the reforming pin, a descending step of the reforming pin, a rotating step of the electrode assembly, a rising step of the reforming pin, and a backward movement step of the reforming pin.

[0091] In addition, another reforming method of the present invention is recognized to include a step of non - contact fitting of a heated reforming pin 310 into a hollow portion B of an electrode assembly A, a step of moving the reforming pin 310 to make it in close contact with the inner wall of the hollow portion B, and then a step of rotating the electrode assembly A with respect to the reforming pin 310, and a step of moving the reforming pin 310 away from the inner wall of the hollow portion B. Such a method can also be performed using the reforming device 200.

[0092] Thus, in the present invention, a method is proposed in which a heated reforming pin 310 is fitted into a hollow portion B of an electrode assembly A, the reforming pin 310 is moved (raised and lowered) to make a separator 112 in close contact with the wall surface of the hollow portion B, and then the electrode assembly A is moved (rotated) to fix the separator 112.

[0093] According to the present invention, without changing the shape of the reforming pin 310 or increasing the outer diameter of the reforming pin 310, it is possible to bring the reforming pin 310 into contact with the inner wall of the hollow portion B only by the upward and downward movement of the reforming pin 310 without deforming the reforming pin 310. Since the contact is controllably performed only by mechanical movement, it is easy to perform process management and predictable. In addition, since only the upward and downward movements need to be added to the existing forward and backward movements, the reforming device 200 can be easily realized, and the effect of process improvement is remarkable. Furthermore, by rotating the electrode assembly A, reforming can be performed while the reforming pin 310 is evenly abutted against the entire inner wall of the hollow portion B.

[0094] The reforming device 200 and the reforming method according to the present invention are particularly effectively applicable to the manufacturing process of small cylindrical secondary batteries having form factors of 18650 and 21700. Further, it is also applicable to the reforming of electrode assemblies for manufacturing cylindrical secondary batteries having an increased form factor. The cylindrical secondary battery having an increased form factor can be realized by a tabless cylindrical secondary battery as described with reference to FIGS. 6 and 7, and the increase in the form factor brings about an increase in energy density, an increase in safety against thermal runaway, and an improvement in cooling efficiency.

[0095] Preferably, the reforming apparatus 200 and the reforming method according to the present invention may be used, for example, in a reforming process of an electrode assembly for a cylindrical secondary battery having a form factor ratio (defined as a ratio of the diameter of the cylindrical secondary battery divided by the height, i.e., the ratio of the diameter (Φ) to the height (H)) greater than approximately 0.4. Such a secondary battery can be suitably used, for example, as a high-output and large-capacity secondary battery for a hybrid electric vehicle (HEV). Such secondary batteries can be, for example, 46110 cells, 48750 cells, 48110 cells, 48800 cells, 46800 cells. When assuming that the electrode assembly A is such an electrode assembly, the length L_B of the hollow portion B can be as long as 65 mm or more, and the inner diameter R_B of the hollow portion B can be 2 mm or more and 8 mm or less. The reforming pin 310 included in the reforming apparatus 200 of the present invention can have a length L_310 and an outer diameter R_310 that are fitted into the hollow portion B without interference, taking into account the length L_B and the inner diameter R_B of the hollow portion B that vary according to the form factor of the secondary battery.

[0096] As described above, although the present invention has been described with reference to limited embodiments and drawings, the present invention is not limited thereto, and it goes without saying that those having ordinary knowledge in the technical field to which the present invention pertains can make various modifications and variations within the equivalent scope of the technical idea of the present invention and the appended claims.

[0097] On the other hand, in this specification, directional terms such as up, down, front, and back are used, but these terms are merely used for ease of explanation and may vary depending on the position of the object and the position of the observer, etc., which is self-evident to those skilled in the art of the present invention.

Description of Reference Numerals

[0098] 200 Reforming apparatus 300 Reforming pin unit 310 Reforming pin 320 Driving unit 330 First actuator 340 Second actuator 350 Heating means 400 Rotating unit 410 Motor 420 Turntable

Claims

1. A reforming pin that can be inserted into the hollow portion of the electrode assembly, and a drive unit that performs a forward movement, a backward movement, an upward movement, and a downward movement of the reforming pin, a reforming pin unit (unit) including; A rotating unit that can rotate the electrode assembly about the axial direction of the hollow portion; A reforming apparatus including the above.

2. The reforming apparatus according to claim 1, wherein an outer diameter of the reforming pin is smaller than an inner diameter of the hollow portion.

3. The electrode assembly is a long sheet-like laminate including a structure of a positive electrode, a separator, and a negative electrode wound up and having the hollow portion at a central portion, and the separator protrudes from an inner wall of the hollow portion. The reforming apparatus according to claim 1 or 2, wherein the reforming pin is inserted into the hollow portion in a state of being separated from the inner wall of the hollow portion.

4. The reforming apparatus according to claim 3, wherein after the reforming pin is inserted into the hollow portion, the reforming pin is raised and lowered to bring the separator into close contact with the inner wall of the hollow portion for reforming.

5. The reforming apparatus according to claim 4, wherein after completion of the reforming, the reforming pin is lowered and raised to move away from the inner wall of the hollow portion and then pulled out from the hollow portion.

6. The drive unit includes: A first actuator connected to one side of the reforming pin to perform a forward movement and a backward movement; A second actuator connected to the first actuator to perform a lifting movement; The reforming apparatus according to claim 1 including the above.

7. The reforming apparatus according to claim 1, wherein the rotating unit has a turntable structure that is rotated by motor drive.

8. A heating step of the reforming pin; A forward step of the reforming pin into the hollow portion of the jelly roll type electrode assembly; A raising and lowering step of the reforming pin in the hollow portion; A rotating step of the jelly roll type electrode assembly with the reforming pin positioned in the hollow portion; A lowering and raising step of the reforming pin in the hollow portion; A backward step of the reforming pin from the hollow portion; A reforming method including the above.

9. A step of non - contact inserting a heat - applied reforming pin into the hollow portion of the electrode assembly; After moving the reforming pin to make it adhere to the inner wall of the hollow portion, rotating the electrode assembly about the axial direction of the hollow portion; Moving the reforming pin so as to move away from the inner wall of the hollow portion, the reforming method comprising the steps.

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