Fomation method and fomation device for lithium secondary battery

Abstract

The method for activating a lithium secondary battery according to the present invention comprises: a pre-aging process of aging the assembled lithium secondary battery at room temperature; a formation process of charging the lithium secondary battery; and a roll-pressing process of pressing the lithium secondary battery using a pressure roller, wherein the roll-pressing process applies pressure from the center of the lithium secondary battery toward the edge where the electrode lead is located. Accordingly, even a sliding part with a relatively thin thickness can be pressed with uniform force, preventing internal gas from getting trapped and improving the performance of the battery.

Description

Technology Field

[0001] The present invention relates to a method for activating a lithium secondary battery and an activation device for preventing localized non-uniform charging. Background Technology

[0003] Generally, secondary batteries can be classified into cylindrical, prismatic, and pouch types based on their shape. Among these, pouch-type secondary batteries are attracting significant attention because their exterior is constructed using a pouch casing consisting of a metal layer (foil) and a multilayer synthetic resin film coated on the upper and lower surfaces of the metal layer. This allows for a significant reduction in battery weight compared to cylindrical or prismatic types that use metal cans, thereby enabling lightweight design and allowing for variations in shape.

[0004] In these pouch-type secondary batteries, electrode assemblies are housed in a stacked form. Electrode tabs and electrode leads are connected to the electrode assemblies, and the electrode leads protrude from the pouch outer casing. These electrode leads are electrically connected to an external device through contact, thereby receiving power from the external device.

[0005] Pouch-type secondary batteries are manufactured through a process of cell assembly and battery activation. During the activation stage, secondary battery cells are mounted on a charge / discharge device, and charging and discharging are performed under the conditions necessary for activation. This process of conducting predetermined charges and discharges using a charge / discharge device to activate the battery is called the formation process.

[0007] FIGS. 1 and 2 illustrate a device for a formation process. Referring to FIG. 1, the formation device includes a frame (1), a pressure plate (2), and a drive unit (3: 3a, 3b). The drive unit (3) includes a drive shaft (3a) and a drive motor (3b).

[0008] A plurality of pressure plates (2) are arranged inside the frame (1), and a secondary battery (B) to perform a formation process is arranged between the pressure plates (2).

[0009] As shown in FIG. 1, when the drive shaft (3a) rotates due to the rotation of the drive motor (3b) and the plurality of pressure plates (2) engaged therewith move in one direction, the pressure plates (2) press both sides of the secondary battery (B) as shown in FIG. 2. These pressure plates (2) are formed of a rigid material such as aluminum.

[0010] Meanwhile, the electrode assembly housed inside the secondary battery to perform the formation process has a stacked structure of a positive electrode, a separator, and a negative electrode. These positive and negative electrodes are manufactured by applying an electrode slurry onto an electrode current collector, followed by drying and rolling. Since this electrode slurry is applied in a fluid state, the electrode slurry coating part flows down due to the characteristics of the fluid, and the end of the electrode takes on an inclined shape, which is called a sliding part.

[0011] FIG. 3 is a diagram illustrating a problem that occurs when a battery is pressed using a pressure plate included in the formation device of FIG. 1 and FIG. 2. Referring to FIG. 3, a pair of opposing pressure plates (2) press the two sides of a secondary battery (B) in which a negative electrode (10) has a negative active material layer (12) stacked on both sides of a negative electrode current collector (11), a positive electrode (20) has a positive active material layer (22) stacked on both sides of a positive electrode current collector (21), and a separator (30) is interposed between the negative electrode (10) and the positive electrode (20). In addition, the positive active material layer (22) and the negative active material layer (12) each include a sliding portion (S) in an inclined shape at their respective ends.

[0012] The end of the electrode coating portion coated with electrode slurry may include a sliding portion (S) that is inclined with respect to the plane of the current collector, as the electrode slurry is a fluid and flows down to the current collector. Since the thickness of the electrode active material layer in this sliding portion (S) is relatively thin compared to the thickness of the electrode active material layer in the flat portion, it is difficult to pressurize the sliding portion (S) with a flat pressure plate (2), and consequently, a gas trap phenomenon may occur in which gas generated during charging is trapped in the space between the sliding portion (S) and the separator (30). Furthermore, the trapped gas in this way may be in the form of bubbles, which restricts the impregnation of the electrolyte and hinders the movement of lithium ions, thereby deteriorating the quality of the battery, such as localized charging non-uniformity and lithium precipitation.

[0013] Therefore, there is a need to develop technology for activation methods and activation devices that can solve such problems. Prior art literature

[0015] Republic of Korea Published Patent Application No. 10-2013-0134242 The problem to be solved

[0016] The present invention aims to solve the problems of the prior art described above by providing a method for activating a secondary battery and an activation device that prevent gas trapping in the electrode sliding portion, thereby reducing the risk of localized charging non-uniformity and lithium precipitation. means of solving the problem

[0018] A method for activating a lithium secondary battery according to one embodiment of the present invention comprises: a pre-aging process of aging an assembled lithium secondary battery at room temperature; a formation process of charging the lithium secondary battery; and a roll-pressing process of pressing the lithium secondary battery using a pressure roller, wherein the roll-pressing process applies pressure from the center of the lithium secondary battery toward the edge where the electrode lead is located.

[0019] In an activation method according to one embodiment of the present invention, the roll-pressing process may be performed prior to the formation process.

[0020] In an activation method according to one embodiment of the present invention, the roll-pressing process may be performed during the formation process.

[0021] In an activation method according to one embodiment of the present invention, the roll-pressing process may be performed prior to and during the formation process.

[0022] In an activation method according to one embodiment of the present invention, the roll-pressing process may be performed 2 to 5 times.

[0023] In an activation method according to one embodiment of the present invention, the roll-pressing process can pressurize the lithium secondary battery with a linear pressure of 20 kgf / cm to 60 kgf / cm.

[0024] In an activation method according to one embodiment of the present invention, the pressure roller is composed of an upper pressure roller and a lower pressure roller, and the lithium secondary battery can be pressured while passing between the upper pressure roller and the lower pressure roller.

[0025] In an activation method according to one embodiment of the present invention, the formation process may include a process of applying surface pressure to a lithium secondary battery that is being charged.

[0026] In an activation method according to one embodiment of the present invention, the formation process may be composed of a plurality of formation steps in which the charge end SOC is set differently, and each of the formation steps may have one or more conditions selected from each charging speed and surface pressure applied to the lithium secondary battery set differently.

[0027] In an activation method according to one embodiment of the present invention, an aging process for maturing a battery in which formation is completed may be further included.

[0028] An activation device for a lithium secondary battery according to the present invention comprises: a formation part configured to charge and discharge the battery and enable pressurization; and a roll-pressing part comprising an upper pressurization roller and a lower pressurization roller, wherein the battery is interposed between the upper pressurization roller and the lower pressurization roller and pressurizes the battery.

[0029] In one embodiment of the present invention, a transfer unit for extracting and bringing in / out of a battery between the formation unit and the roll-pressing unit is further included, and the transfer unit may include a pickup unit for bringing in or taking out a battery received in the formation unit or the roll-pressing unit; a driving unit for moving the pickup unit; and a control unit for controlling the operation of the pickup unit and the driving unit.

[0030] In one embodiment of the present invention, the roll-pressing unit may include an upper pressure roller and a lower pressure roller; a driving unit that drives the upper pressure roller and the lower pressure roller to rotate; and a pressure cylinder that causes the upper pressure roller to move in the direction of the lower pressure roller or the opposite direction.

[0031] In one embodiment of the present invention, the formation unit may include a frame accommodating a plurality of battery cells; a charging / discharging unit connected to the electrode leads of the battery to charge / discharge the battery; a plurality of pressure plates that press both sides of the battery; and a driving unit that moves the plurality of pressure plates. Effects of the invention

[0033] The activation method and activation device of the present invention have the effect of preventing gas from being trapped in the sliding part by applying pressure through roll pressing, so that the sliding part, which has a relatively thin thickness, is also pressed with the same force as the electrode flat part. Brief explanation of the drawing

[0035] Figures 1 and 2 are schematic diagrams showing a formation device. Figure 3 is a drawing illustrating a problem that occurs when pressurizing a battery with a pressure plate included in the formation device of Figure 1. FIG. 4 is a schematic diagram showing a roll-pressing process according to one embodiment of the present invention. FIG. 5 is a conceptual diagram illustrating the effects of a roll-pressing process according to one embodiment of the present invention. FIG. 6 is a flowchart of an activation method according to one embodiment of the present invention. FIG. 7 is a flowchart of an activation method according to another embodiment of the present invention. FIG. 8 is a flowchart of an activation method according to another embodiment of the present invention. FIG. 9 is a conceptual diagram of the lithium secondary battery activation device of the present invention. FIG. 10 is a perspective view of a roll-pressing section according to one embodiment of the present invention. Figure 11 is an upper view of the roll-pressing section. FIG. 12 is a front view of the roll-pressing section. Figure 13 is a photograph of the negative electrode taken after disassembling the battery following a long-term cycle of the secondary batteries of the example and comparative example. FIG. 14 is a flowchart of an activation method according to another embodiment of the present invention. Specific details for implementing the invention

[0036] Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the attached drawings. Prior to this, terms and words used in this specification and claims should not be interpreted as being limited to their ordinary or dictionary meanings, but should be interpreted in a meaning and concept consistent with the technical spirit of the present invention, based on the principle that the inventor can appropriately define the concept of the terms to best describe his invention.

[0037] Therefore, the embodiments described in this specification and the configurations illustrated in the drawings are merely the most preferred embodiments of the present invention and do not represent all of the technical ideas of the present invention; thus, it should be understood that various equivalents and modifications that can replace them may exist at the time of filing this application.

[0039] The present invention will be described in more detail below.

[0041] Activation method of a secondary battery according to the first embodiment

[0042] A method for activating a lithium secondary battery according to one embodiment of the present invention comprises: a pre-aging process for aging an assembled lithium secondary battery at room temperature; a formation process for charging the lithium secondary battery; and a roll-pressing process for pressing the lithium secondary battery using a pressure roller, wherein the roll-pressing process is characterized by applying pressure from the center of the lithium secondary battery toward the edge where the electrode lead is located.

[0043] FIG. 4 is a schematic diagram showing the roll-pressing process of the present invention, and FIG. 5 is a conceptual diagram explaining the effect of the roll-pressing process according to one embodiment of the present invention. Referring to these figures, in the roll-pressing process of the present invention, the pressure roller includes an upper pressure roller (121) and a lower pressure roller (122), and a lithium secondary battery (B) is pressed by the rolling of the roller while interposed between the upper pressure roller (121) and the lower pressure roller (122) facing each other.

[0044] The pressure applied by these rollers (121, 122) applies pressure to the battery (B) in the form of linear pressure, and the pair of upper pressure rollers (121) and lower pressure rollers (122) rotate and travel from the center of the battery (B) toward the edge where the electrode leads (13, 23) are located, thereby applying pressure sequentially from the center of the battery to the edge where the electrode leads are located.

[0045] Due to this sequential pressurization, the internal gas moves in a directional manner from the center of the battery to the edge region. In addition, since the pressurizing surface of the roller is not flat but curved, the sliding part (S), which is relatively thin compared to the center of the battery, can be pressurized with the same load as the center of the battery, thereby preventing gas from being trapped in that area and thus preventing localized undercharging and lithium deposition in the sliding part (S).

[0046] Thus, the activation method according to the present invention includes a roll-pressing process for applying linear pressure to the battery, wherein the roll-pressing process involves rolling a pressure roller from the center of the battery toward the edge of the battery where the sliding part (S) is located, thereby allowing gas inside the electrode assembly to be discharged to the outside of the electrode assembly and pressurizing the sliding part (S), which is relatively thin, so as to prevent gas from being trapped in the sliding part.

[0048] The above pre-aging process is a process of aging the battery after assembly so that the electrolyte is sufficiently impregnated into the electrode assembly. Once the assembly of the secondary battery is complete, a pre-aging process may be performed to stabilize the secondary battery by leaving it at room temperature for a certain period of time so that the electrolyte injected into the secondary battery is sufficiently wetted inside the electrode assembly.

[0049] More specifically, when a secondary battery is charged, electrons travel along the wire to the negative electrode and become charged; subsequently, lithium ions are absorbed into the negative electrode to achieve charge neutrality. At this time, lithium ions can be absorbed in the electrolyte-impregnated area—that is, the area where the ion movement path is maintained (wetting area)—but absorption becomes relatively difficult in the electrolyte-non-impregnated area (non-wetting area). Therefore, through a pre-aging process, the battery can be aged in an environment with specific humidity and temperature conditions to allow the electrolyte to permeate well into the positive and negative electrodes.

[0050] In one specific example, the time required for the pre-aging process may be, specifically, 3 to 72 hours, 6 to 60 hours, or 12 to 48 hours, and this can be appropriately adjusted depending on the materials of the anode, cathode, and electrolyte, the design capacity of the secondary battery, etc.

[0051] In addition, the temperature during pre-aging can be performed at room temperature conditions of 18°C ​​to 28°C, specifically at 19°C to 27°C, more specifically at 20°C to 26°C, and even more specifically at 21°C to 25°C, but is not necessarily limited thereto and can be appropriately changed according to the characteristics of the battery to be designed.

[0053] The above formation process is a step of charging a secondary battery to form a SEI (Solid Electrolyte Interface, hereinafter referred to as "SEI") film layer of the negative electrode, and is a process of charging the assembled secondary battery to a predetermined range of SOC level of full charge capacity (SOC 100, SOC; State Of Charge). Here, the predetermined range of SOC may be 20% to 80%, and preferably 40% to 70%.

[0054] When the formation process is performed in a lithium secondary battery, lithium ions originating from lithium transition metal oxides, such as the cathode active material and cathode additive contained in the cathode, move to the carbon electrode of the anode. Since these lithium ions are highly reactive, they react with the carbon anode to produce compounds such as Li2CO3, LiO, and LiOH, and an SEI film is formed on the surface of the anode by these compounds. The SEI film is an insulator that forms when the amount of ion movement in the battery increases. Once the SEI film is formed, it prevents lithium ions from reacting with other substances at the anode during subsequent charging of the secondary battery, and it functions as a kind of ion tunnel to allow only lithium ions to pass through. Since lithium ions do not react with the anode or other substances once this SEI film is formed, the amount of lithium ions is reversibly maintained, and the charging and discharging of the secondary battery are maintained reversibly, thereby improving the lifespan of the secondary battery. Furthermore, because it does not easily collapse even when left at high temperatures or subjected to repeated charging and discharging, changes in the battery thickness occur less frequently.

[0055] The charging conditions of this formation process may be performed according to conditions known in the art. Specifically, the charging method may be performed in a constant current manner until the charging termination voltage is reached. At this time, the charging rate (c-rate) may be 0.01C to 2C, 0.1C to 1.5C, or 0.2C to 1C, but is not necessarily limited thereto and can be appropriately changed according to the characteristics of the positive and negative electrode materials.

[0056] In addition, the temperature conditions of the above initial charging process can be carried out at 18°C ​​to 28°C, specifically 19°C to 27°C, and more specifically 20°C to 26°C.

[0057] In one specific example, the formation process may include a process of applying surface pressure to a lithium secondary battery that is being charged. When surface pressure is applied to the lithium secondary battery during the formation process, excessive volume expansion of the electrode due to charging and discharging can be prevented, chemical reactions of the battery can be promoted to induce gas generation, and the generated gas can be moved to a gas pocket.

[0058] In order to apply surface pressure to a lithium secondary battery that is being charged. A formation process according to one embodiment of the present invention can be performed while mounted on a jig formation device capable of pressurizing a lithium secondary battery, and this is referred to as a jig formation process. Referring to FIGS. 1 and 2, the formation device used for formation includes a frame (1), a pressure plate (2), and a driving unit (3: 3a, 3b). The driving unit (3) includes a driving shaft (3a) and a driving motor (3b).

[0059] A plurality of pressure plates (2) are arranged inside the frame (1), and a secondary battery (B) to perform a formation process is arranged between the pressure plates (2).

[0060] As shown in FIG. 1, when the drive shaft (3a) rotates due to the rotation of the drive motor (3b) and the plurality of pressure plates (2) engaged therewith move in one direction, the pressure plates (2) press both sides of the secondary battery (B) as shown in FIG. 2. Thus, the formation device is configured to press the battery while the lithium secondary battery is interposed between a pair of pressure plates.

[0061] As described above, since such a pressure plate is formed of a rigid material and is plate-shaped, and the surface for pressurizing the battery is flat, it cannot pressurize areas of the battery to be pressurized where the thickness is relatively thin. Consequently, with conventional formation devices, the sliding portion area where the thickness is relatively thin cannot be pressurized, resulting in a problem where internal gas is trapped in that area. However, the activation method of the present invention includes a roll-pressing process in which the battery is pressurized by a pressure roller, thereby enabling the pressurization of the sliding portion and preventing the risk of localized undercharging and lithium precipitation caused by gas in the sliding portion.

[0062] In one embodiment of the present invention, the surface pressure applied during the formation process can be set in the range of 0.1 kgf / ㎠ to 7.5 kgf / ㎠, preferably 0.2 kgf / ㎠ to 7.0 kgf / ㎠, and more preferably 0.3 kgf / ㎠ to 6.5 kgf / ㎠.

[0063] In an activation method according to one embodiment of the present invention, the formation process may be composed of a plurality of formation processes in which the charge termination SOC is set differently. For example, the formation process according to the present invention may be composed of: a first formation step of charging a secondary battery to an SOC of less than 10%; a second formation step of charging the lithium secondary battery that performed the first formation step to a charging depth set in the range of 10% to 30% SOC; a third formation step of charging the lithium secondary battery that performed the second formation step to a charging depth set in the range of 35% to 50% SOC; and a fourth formation step of charging the lithium secondary battery that performed the third formation step to a charging depth set in the range of more than 50% to 70% SOC. Although the above example describes an embodiment in which the formation process consists of four steps, it is not limited thereto, and the formation process may consist of two to five steps.

[0064] In addition, each of the multiple formation stages may have one or more selected from the charging speed and the surface pressure applied to the secondary battery set differently.

[0065] Specifically, the cell can be pressurized with a weak surface pressure during the initial stage of the formation process, and then pressurized with a stronger surface pressure after the initial formation process.

[0066] At this time, the initial stage of the formation process may be when the secondary battery is charged to a state where the charge depth is 3% to 30%.

[0067] Specifically, in the initial formation process, pressure can be applied at a surface pressure of 0.1 kgf / ㎠ to 1.0 kgf / ㎠, preferably 0.2 kgf / ㎠ to 0.8 kgf / ㎠, more preferably 0.3 kgf / ㎠ to 0.7 kgf / ㎠, and in the subsequent formation process, pressure can be applied at a surface pressure of 2.5 kgf / ㎠ to 7.5 kgf / ㎠, preferably 3.0 kgf / ㎠ to 7.0 kgf / ㎠, more preferably 3.5 kgf / ㎠ to 6.5 kgf / ㎠.

[0068] Thus, when the pressure applied to the battery increases as the charging depth increases during the formation process, a low surface pressure is applied during the initial formation process when the amount of gas generated is low, thereby allowing the electrolyte to be sufficiently impregnated into the electrode assembly within the lithium secondary battery, and a high surface pressure is applied during the mid / late formation process when a large amount of internal gas is generated, thereby removing the internal gas, so that an appropriate amount of electrolyte is impregnated into the electrode assembly, and at the same time, the internal gas can be efficiently removed.

[0069] In addition, during the initial formation process, low-speed charging of 0.01 C to 0.5 C may be performed, and during the mid / late formation process, charging at a rate of 0.6 C to 1.5 C may be performed. Since the electrolyte may not be sufficiently impregnated into the electrode during the initial formation process, the risk of undercharging can be reduced by performing low-speed charging.

[0071] In this specification, the roll-pressing process is described as one roll-pressing process by combining the process of rolling a pair of pressure rollers from the center of the battery toward one edge and the process of rolling from the center of the battery toward the other edge.

[0072] This roll-pressing process may be performed once, or two to five times. The number of pressurizations may be appropriately adjusted depending on the thickness of the battery and the degree of sliding in the sliding part.

[0073] In one specific example, the roll-pressing process may involve applying pressure to the cell with a linear pressure of 20 kgf / cm to 60 kgf / cm, preferably 25 kgf / cm to 50 kgf / cm.

[0075] FIG. 6 is a flowchart of a method for activating a lithium secondary battery according to a first embodiment of the present invention. Referring to FIG. 6, the activation method according to the first embodiment may sequentially perform a pre-aging process of aging the assembled lithium secondary battery at room temperature, a roll-pressing process of pressing the secondary battery using a pressure roller, and a formation process of charging the lithium secondary battery. That is, the method for activating a secondary battery according to the first embodiment performs the roll-pressing process before the formation process.

[0076] Even before performing the formation process, bubbles may be generated during the electrolyte injection process, and a small amount of gas may be generated as the electrolyte impregnates the electrode during the pre-aging process. Therefore, by performing a roll-pressing process prior to the formation process, these bubbles or gases can be discharged to the outside of the electrode assembly.

[0078] FIG. 7 is a flowchart of a method for activating a lithium secondary battery according to an embodiment of the present invention. Referring to FIG. 7, the method for activating a lithium secondary battery according to an embodiment of the present invention may proceed in the order of a pre-aging process of aging the assembled lithium secondary battery at room temperature - a roll-pressing process of pressing the secondary battery using a pressure roller - a formation process of charging the lithium secondary battery - and an aging process of aging the formed lithium secondary battery.

[0079] The above aging process is a process of aging a secondary battery under various conditions to accelerate the stabilization of the SEI film formed through the above formation process.

[0080] The above aging process may undergo a room temperature aging process in which the secondary battery is aged for a predetermined period of time under room temperature / atmospheric pressure conditions, and depending on the purpose, a high temperature aging process may be performed instead of room temperature aging, or both room temperature aging and high temperature aging may be performed.

[0081] The above high-temperature aging involves aging the battery in a high-temperature environment, which can accelerate the stabilization of the SEI film, and allows for the sequential execution of high-temperature aging and room-temperature aging processes on an initially charged battery.

[0082] In one specific example, the high-temperature aging may be carried out at a temperature of 50°C to 100°C, preferably 50°C to 80°C. The high-temperature aging may be carried out for 1 hour to 30 hours, preferably 2 hours to 24 hours.

[0083] In one specific example, the room temperature aging may be carried out at a temperature of 18°C ​​to 28°C, more specifically 19°C to 27°C, more specifically 20°C to 26°C, and even more specifically 21°C to 25°C. The room temperature aging may be carried out for 12 to 120 hours, or 18 to 72 hours.

[0085] In addition, the activation method according to one embodiment of the present invention may further include a degas process for discharging gas trapped inside the secondary battery to the outside. The degas process is a process of discharging gas trapped inside the secondary battery to the outside of the secondary battery, wherein gas trapped inside the battery case or in the gas pocket by the roll-pressing process is discharged to the outside of the battery.

[0086] For this degassing process, various degassing techniques known at the time of filing of the present invention may be employed. For example, in a pouch-type secondary battery in which one side is extended, the degassing process may be performed by cutting the extended portion and sealing the cut portion. However, since such degassing techniques are widely known to those skilled in the art, a more detailed description is omitted.

[0088] In addition, the activation method according to one embodiment of the present invention may further perform a full discharge and full charge process in which the secondary battery is completely discharged to near SOC 0 and then charged to 95% (SOC 95%) or more of the discharged secondary battery's design capacity. The full discharge and full charge process may be performed once or repeated two or more times.

[0089] In one specific example, the method for activating a secondary battery according to the present invention may further perform an additional aging process after the full discharge and full charge processes. The additional aging process is a process for stabilizing the secondary battery and can be performed at room temperature or high temperature, specifically for 1 to 21 days. The additional aging process may include a monitoring (OCV tracking) process that includes measuring the open circuit voltage (OCV) of the battery at regular time intervals to identify low-voltage defective batteries in which a voltage drop occurs to a range exceeding the battery's self-discharge.

[0091] Activation method of a secondary battery according to a second embodiment

[0092] In the method for activating a secondary battery according to the second embodiment, the roll-pressing process may be performed during the formation process.

[0093] FIG. 8 is a flowchart of a method for activating a lithium secondary battery according to a second embodiment of the present invention. Referring to FIG. 8, the activation method according to the second embodiment may sequentially perform a pre-aging process of aging the assembled lithium secondary battery at room temperature, a first formation step of charging the lithium secondary battery, a roll-pressing process of pressing the secondary battery using a pressure roller, and a second formation step of charging the lithium secondary battery.

[0094] In the formation process, as the secondary battery is charged, a large amount of gas is generated due to the full-scale chemical reaction between the electrode and the electrolyte. Since the method for activating a secondary battery according to the second embodiment performs a roll-pressing process in the middle of the formation process, it has the effect of effectively preventing the gas generated during the formation process from being trapped in the electrode assembly.

[0095] The activation method according to the second embodiment may be such that the formation process consists of a plurality of formation steps in which the charge end SOC is set differently, and the roll-pressing process is performed between the formation steps.

[0096] For example, the above formation process may consist of a first formation stage in which the charge end SOC is set in the range of 10% to 40% and a second formation stage in which the charge end SOC is set in the range of 45% to 60%, and the above roll-pressing process may be performed between the first formation stage and the second formation stage.

[0097] And, when performing a formation process with the battery mounted in the formation device shown in FIGS. 1 and FIGS. 2 capable of pressurizing the battery, after the first formation step is completed, the battery is removed from the formation device and a roll-pressing process is performed, and when the roll-pressing process is completed, the battery is mounted back into the formation device and a second formation step can be performed.

[0098] After the formation process is completed in this way, the aforementioned aging process can be performed.

[0099] The activation method according to the second embodiment differs from the activation method according to the first embodiment only in that the roll-pressing process is performed in the middle of the formation, and the specific details of the pre-aging process, roll-pressing process, and formation process are as described above, so a detailed description thereof is omitted.

[0101] In addition, in an activation method according to another embodiment of the present invention, the roll-pressing process may be performed before and during the formation process, respectively. Referring to FIG. 14, an activation method according to another embodiment of the present invention may sequentially perform a pre-aging process, a roll-pressing process, a first formation step, a roll-pressing process, and a second formation step.

[0103] Hereinafter, a lithium secondary battery manufactured according to the activation method of the present invention will be described in detail.

[0104] The lithium secondary battery of the present invention is manufactured by housing an electrode assembly having a positive electrode / separator / negative electrode structure in a battery case, injecting an electrolyte, and sealing it.

[0105] Specifically, an electrode mixture containing an electrode active material and a binder is applied to an electrode current collector to manufacture an anode and a cathode, respectively, and then a separator is interposed between the anode and the cathode to prepare an electrode assembly.

[0106] After placing the prepared electrode assembly into the battery case, the electrolyte is injected, and the battery case is sealed to assemble the battery.

[0107] The steps for assembling such batteries are not particularly limited and can be performed according to known methods.

[0108] In addition, the electrode assembly is not particularly limited as long as it has a structure including an anode, a cathode, and a separator interposed between the anode and the cathode, and may be, for example, a jelly-roll type, a stack type, or a stack / folding type.

[0109] The above battery case is not particularly limited as long as it is used as an outer material for packaging batteries, and cylindrical, prismatic, or pouch-type cases may be used.

[0110] In the case where the battery case is of the pouch type, an aluminum laminated pouch including an aluminum layer may be used. After injecting the electrolyte, the opened portion of the aluminum laminated pouch can be sealed by heat welding or heat fusion.

[0111] The lithium secondary battery of the present invention comprises an electrode assembly including a positive electrode, a negative electrode, and a separator disposed between the positive electrode and the negative electrode, and an electrolyte.

[0112] The above-mentioned anode comprises an anode current collector and an anode active material layer prepared by applying, drying, and pressing an anode composite slurry onto the anode current collector. The anode composite comprises an anode active material and a binder, and may further comprise an anode additive, a conductive material, and a filler as needed.

[0113] The above-mentioned cathode active material is a compound capable of reversible intercalation and deintercalation of lithium, and specifically, may include a lithium composite metal oxide comprising lithium and one or more metals such as cobalt, manganese, nickel, or aluminum. More specifically, the lithium composite metal oxide is a lithium-manganese-based oxide (e.g., LiMnO2, LiMn2O4, etc.), a lithium-cobalt-based oxide (e.g., LiCoO2, etc.), a lithium-nickel-based oxide (e.g., LiNiO2, etc.), or a lithium-nickel-manganese-based oxide (e.g., LiNi 1-Y Mn Y O2(here, 0 <Y<1), LiMn 2-z Ni z O4 (where 0 < Z < 2), etc.), lithium-nickel-cobalt oxides (e.g., LiNi 1-Y1 Co Y1 O2(here, 0 <Y1<1) 등), 리튬-망간-코발트계 산화물(예를 들면, LiCo 1-Y2 Mn Y2 O2(here, 0 <Y2<1), LiMn 2-z1 Co z1O4 (where 0 < Z1 < 2), etc.), lithium-nickel-manganese-cobalt oxides (e.g., Li(Ni p Co q Mn r1 )O2(where, 0<p<1, 0<q<1, 0<r1<1, p+q+r1=1) or Li(Ni p1 Co q1 Mn r2 )O4 (where 0<p1<2, 0<q1<2, 0<r2<2, p1+q1+r2=2), etc.), or lithium-nickel-cobalt-transition metal (M) oxide (e.g., Li(Ni p2 Co q2 Mn r3 M S2 Examples include )O2 (wherein M is selected from the group consisting of Al, Fe, V, Cr, Ti, Ta, Mg, and Mo, and p2, q2, r3, and s2 are each atomic fractions of independent elements, such that 0 < p2 < 1, 0 < q2 < 1, 0 < r3 < 1, 0 < s2 < 1, p2 + q2 + r3 + s2 = 1), etc.), and any one or more of these compounds may be included. Among these, the lithium composite metal oxides are LiCoO2, LiMnO2, LiNiO2, and lithium nickel manganese cobalt oxide (for example, Li(Ni 0.6 Mn 0.2 Co 0.2 )O2, Li(Ni 0.5 Mn 0.3 Co 0.2 )O2, or Li(Ni 0.8 Mn 0.1 Co 0.1 )O2, etc.), or lithium nickel-cobalt-aluminum oxide (e.g., Li(Ni 0.8 Co 0.15 Al 0.05 It may be )O2, etc., and considering the significant improvement effect resulting from controlling the type and content ratio of constituent elements forming the lithium composite metal oxide, the lithium composite metal oxide is Li(Ni 0.6 Mn 0.2 Co0.2 )O2, Li(Ni 0.5 Mn 0.3 Co 0.2 )O2, Li(Ni 0.7 Mn 0.15 Co 0.15 )O2 or Li(Ni 0.8 Mn 0.1 Co 0.1 It may be O2, etc., and any one or more of these may be used.

[0114] In addition, the content of the above-mentioned positive active material may be 85 to 99 parts by weight per 100 parts by weight of the positive composite, and specifically, may be 88 to 98 parts by weight, 90 to 97 parts by weight, or 92 to 95 parts by weight.

[0115] The above conductive material may be used to improve performance such as the electrical conductivity of the anode, and one or more selected from the group consisting of natural graphite, artificial graphite, carbon black, acetylene black, Ketjen black, and carbon fiber may be used. For example, the above conductive material may include acetylene black.

[0116] In addition, the conductive material may be included in an amount of 1 to 10 parts by weight per 100 parts by weight of the composite layer, specifically 2 to 8 parts by weight; or 2 to 6 parts by weight of the conductive material.

[0117] In addition, the binder may include one or more resins selected from the group consisting of polyvinylidene fluoride-hexafluoropropylene copolymer (PVDF-co-HFP), polyvinylidene fluoride, polyacrylonitrile, polymethylmethacrylate, and copolymers thereof. As one example, the binder may include polyvinylidene fluoride.

[0118] In addition, the binder may be included in an amount of 1 to 10 parts by weight per 100 parts by weight of the total mixture, specifically 1 to 8 parts by weight; or 1 to 6 parts by weight.

[0119] In addition, the average thickness of the above composite layer is not particularly limited, but specifically may be 50㎛ to 300㎛, and more specifically may be 100㎛ to 200㎛; 80㎛ to 150㎛; 120㎛ to 170㎛; 150㎛ to 300㎛; 200㎛ to 300㎛; or 150㎛ to 190㎛.

[0120] In addition, the above-mentioned positive electrode may be used as a current collector that has high conductivity without causing chemical changes in the battery. For example, stainless steel, aluminum, nickel, titanium, calcined carbon, etc. may be used, and in the case of aluminum or stainless steel, surface-treated materials such as carbon, nickel, titanium, silver, etc. may be used. Furthermore, the above-mentioned current collector may form fine irregularities on its surface to increase the adhesion of the positive electrode active material, and various forms such as films, sheets, foils, nets, porous bodies, foams, and nonwoven fabrics are possible. Moreover, the average thickness of the above-mentioned current collector may be appropriately applied in the range of 3 to 500 μm, taking into consideration the conductivity and total thickness of the manufactured positive electrode.

[0121] In addition, the negative electrode of the lithium secondary battery used in the present invention is manufactured by coating, drying, and pressing a negative electrode active material onto a negative electrode current collector, and, if necessary, a conductive material, an organic binder polymer, an additive, etc., as in the positive electrode may be optionally further included.

[0122] In addition, the above-mentioned cathode active material is, for example, carbon and graphite materials such as graphite having a completely formed layered crystal structure like natural graphite, soft carbon having a low-crystallinity layered crystal structure (graphene structure; a structure in which hexagonal honeycomb-shaped planes of carbon are arranged in layers), hard carbon in which such structures are mixed with amorphous parts, artificial graphite, expanded graphite, carbon fiber, non-graphitized carbon, carbon black, carbon nanotubes, fullerene, activated carbon, etc.; or LixFe2O3(0≤x≤1), LixWO2(0≤x≤1), SnxMe1-xMe'yOz (Me: Mn, Fe, Pb, Ge; Me', Al, B, P, Si, elements of Group 1, Group 2, and Group 3 of the periodic table, halogen; 0 <x≤1; 1≤y≤3; 1≤z≤8) 등의 금속 복합 산화물; 리튬 금속; 리튬 합금; 규소계 합금; 주석계 합금; SnO, SnO2, PbO, PbO2, Pb2O3, Pb3O4, Sb2O3, Sb2O4, Sb2O5, GeO, GeO2, Bi2O3, Bi2O4및 Bi2O5등의 금속 산화물; 폴리아세틸렌 등의 도전성 고분자; Li-Co-Ni계 재료; 티타늄 산화물; 리튬 티타늄 산화물 등을 사용할 수 있다.

[0123] As an example, the cathode active material may include graphite and silicon (Si) containing particles together, and the graphite may include one or more of natural graphite having a layered crystal structure and artificial graphite having an isotropic structure, and the silicon (Si) containing particles may include silicon (Si) particles, SiO particles, SiO2 particles, or a mixture of one or more of these particles, as particles containing silicon (Si) as a main component as a metal component.

[0124] In this case, the negative electrode active material may comprise 80 to 95 parts by weight of graphite and 1 to 20 parts by weight of silicon (Si) containing particles, based on 100 parts by weight of the total. By controlling the content of graphite and silicon (Si) containing particles included in the negative electrode active material to the above range, the present invention can improve the charge capacity per unit mass while reducing lithium consumption and irreversible capacity loss during the initial charge and discharge of the battery.

[0125] In addition, the cathode composite layer may have an average thickness of 100㎛ to 200㎛, and specifically, may have an average thickness of 100㎛ to 180㎛, 100㎛ to 150㎛, 120㎛ to 200㎛, 140㎛ to 200㎛, or 140㎛ to 160㎛.

[0126] In addition, the above-mentioned negative electrode current collector is not particularly limited as long as it has high conductivity without causing chemical changes in the battery, and for example, copper, stainless steel, nickel, titanium, calcined carbon, etc. may be used, and in the case of copper or stainless steel, surface-treated carbon, nickel, titanium, silver, etc. may be used. Furthermore, similar to the positive electrode current collector, the above-mentioned negative electrode current collector may form fine irregularities on its surface to strengthen the bonding force with the negative electrode active material, and various forms such as films, sheets, foils, nets, porous bodies, foams, and nonwoven fabrics are possible. In addition, the average thickness of the above-mentioned negative electrode current collector may be appropriately applied in the range of 3 to 500 μm, taking into consideration the conductivity and total thickness of the manufactured negative electrode.

[0127] In addition, the separator is interposed between the anode and the cathode, and an insulating thin film having high ion permeability and mechanical strength is used. The separator is not particularly limited as long as it is commonly used in the industry, but specifically, a sheet or nonwoven fabric made of chemically resistant and hydrophobic polypropylene; glass fiber; or polyethylene may be used, and in some cases, a composite separator in which inorganic particles / organic particles are coated by an organic binder polymer on a porous polymer substrate such as the sheet or nonwoven fabric may be used. When a solid electrolyte such as a polymer is used as the electrolyte, the solid electrolyte may also serve as the separator. Furthermore, the pore diameter of the separator may be an average of 0.01 to 10 μm, and the thickness may be an average of 5 to 300 μm.

[0128] The above electrolyte may include an organic solvent, a lithium salt, and an additive.

[0129] The above organic solvent is not limited as long as it minimizes decomposition due to oxidation reactions, etc. during the charging and discharging process of the battery, and may be, for example, cyclic carbonates, linear carbonates, esters, ethers, or ketones. These may be used alone or two or more may be used in combination.

[0130] Among the above organic solvents, carbonate-based organic solvents may be particularly preferred. Examples of cyclic carbonates include ethylene carbonate (EC), propylene carbonate (PC), and butylene carbonate (BC), while examples of linear carbonates include dimethyl carbonate (DMC), diethyl carbonate (DEC), dipropyl carbonate (DPC), ethylmethyl carbonate (EMC), methylpropyl carbonate (MPC), and ethylpropyl carbonate (EPC).

[0131] The above lithium salts may be used without limitation as lithium salts commonly used in the electrolytes of lithium secondary batteries, such as LiPF6, LiAsF6, LiCF3SO3, LiN(CF3SO2)2, LiBF4, LiBF6, LiSbF6, LiN(C2F5SO2)2, LiAlO4, LiAlCl4, LiSO3CF3, and LiClO4, and may be used individually or in combination of two or more types.

[0132] In addition, the electrolyte may further include additives, for example, to stably form an SEI film, any one selected from the group consisting of vinylene carbonate, vinylethylene carbonate, fluoroethylene carbonate, cyclic sulfite, saturated sulfone, unsaturated sulfone, acyclic sulfone, lithium oxalyl difluoroborate (LiODFB), and derivatives thereof, or a mixture of two or more of these may be used as the additive, but is not limited thereto.

[0133] Examples of the above-mentioned cyclic sulfites include ethylene sulfite, methyl ethylene sulfite, ethyl ethylene sulfite, 4,5-dimethyl ethylene sulfite, 4,5-diethyl ethylene sulfite, propylene sulfite, 4,5-dimethyl propylene sulfite, 4,5-diethyl propylene sulfite, 4,6-dimethyl propylene sulfite, 4,6-diethyl propylene sulfite, 1,3-butylene glycol sulfite, etc. Examples of saturated sulfones include 1,3-propane sulfone, 1,4-butane sulfone, etc. Examples of unsaturated sulfones include ethene sulfone, 1,3-propene sulfone, 1,4-butene sulfone, 1-methyl-1,3-propene sulfone, etc. Examples of acyclic sulfones include divinyl sulfone, dimethyl sulfone, diethyl sulfone, methyl ethyl sulfone, methyl vinyl sulfone, etc. there is.

[0134] These additives are added to the electrolyte to improve low-temperature output characteristics by forming a robust SEI film on the cathode, as well as to suppress the decomposition of the anode surface that may occur during high-temperature cycle operation and to prevent oxidation reactions of the electrolyte.

[0136] secondary battery activation device

[0137] FIG. 9 is a conceptual diagram of an activation device for a lithium secondary battery according to the present invention. Referring to FIG. 9, the activation device (100) of the present invention includes: a formation part (110) configured to charge and discharge the battery and enable pressurization; and a roll-pressing part (120) that includes an upper pressurizing roller and a lower pressurizing roller, and pressurizes the battery while the battery is interposed between the upper pressurizing roller and the lower pressurizing roller.

[0138] Additionally, the activation device of the present invention further comprises a transfer unit (130) for taking out and bringing in / taking out a battery between the formation unit (110) and the roll-pressing unit (120), wherein the transfer unit (130) comprises: a pickup unit for taking out or bringing in a battery received in the formation unit (110) or the roll-pressing unit (120); a driving unit for moving the pickup unit; and a control unit for controlling the operation of the pickup unit and the driving unit.

[0139] In order to perform the roll-pressing of the present invention by means of a roll-pressing unit during the formation process, it is necessary to transfer the battery contained in the formation unit (110) to the roll-pressing unit (120), and the transfer unit (130) is configured to transfer the battery from the formation unit (110) to the roll-pressing unit (120), or to transfer the battery after roll-pressing is completed from the roll-pressing unit (120) to the formation unit (110).

[0140] The above pickup unit is configured to pick up and lift a battery so as to be ejected from a formation unit or a roll-pressing unit, move to the roll-pressing unit or the formation unit by means of a drive unit, and lower the battery to the roll-pressing unit or the formation unit. In one specific example, the above pickup unit may be a robot arm.

[0141] And, the above control unit controls the operation of the drive unit of these pickup units.

[0142] The above-described formation unit is configured to charge and discharge the battery and to pressurize the battery. In one specific example, the formation unit may include a frame accommodating a plurality of battery cells; a charge / discharge unit connected to the electrode leads of the battery to charge and discharge the battery; a plurality of pressure plates that pressurize both sides of the battery; and a driving unit that moves the plurality of pressure plates.

[0143] FIG. 10 is a perspective view of a roll-pressing unit according to one embodiment of the present invention, FIG. 11 is a top view of the roll-pressing unit, and FIG. 12 is a front view of the roll-pressing unit. Referring to these drawings, the roll-pressing unit of the present invention includes an upper pressure roller (121) and a lower pressure roller (122); a driving unit (123) that drives the upper pressure roller and the lower pressure roller to rotate; and a pressure cylinder (124) that causes the upper pressure roller to move in the direction of the lower pressure roller or the opposite direction.

[0144] Referring to FIGS. 3, FIGS. 4 and FIGS. 10 to 12, the upper pressure roller (121) and the lower pressure roller (122) are means for contacting the battery and pressing the battery, wherein the upper pressure roller (121) presses the upper surface of the battery (B), and the lower pressure roller (122) presses the lower surface of the battery (B).

[0145] The above driving unit (123) is located on one side of the upper pressure roller (121) and the lower pressure roller (122) and applies driving force to cause the upper pressure roller and the lower pressure roller to rotate.

[0146] The above-mentioned pressure cylinder (124) is a means for adjusting the load applied to the battery by adjusting the gap between the upper pressure roller (121) and the lower pressure roller (122), causing the upper pressure roller (121) to reciprocate in the direction of the lower pressure roller (122) or the opposite direction. As the gap between the upper pressure roller and the lower pressure roller narrows, the force applied to the battery increases, and as the gap widens, the force applied to the battery decreases.

[0147] The activation device of the present invention includes a roll-pressing section, so that a sliding section with a relatively thin thickness can be pressed with the same force as a flat section, thereby preventing gas from being trapped in that section and improving the performance of the battery.

[0149] The present invention will be described in more detail below through examples and the like. However, since the configurations described in the examples described in this specification are merely one embodiment of the present invention and do not represent all of the technical ideas of the present invention, it should be understood that various equivalents and modifications that can replace them may exist at the time of filing this application.

[0151] Manufacturing Example: Manufacturing of a lithium secondary battery

[0152] LiNi as a positive electrode active material 0.8 Co 0.1 Mn 0.1 O295 parts by weight, Li6Co as anode additive 0.7 Zn 0.3 0.9 parts by weight of O4, 1.6 parts by weight of PVdF as a binder, and 2.5 parts by weight of carbon black as a conductive material were weighed and mixed in an N-methylpyrrolidone (NMP) solvent to prepare a slurry for an anode composite layer. The slurry for the composite layer was applied to an aluminum foil, dried, and then rolled to form an anode having an anode composite layer (average thickness: 130 μm).

[0153] A slurry for a cathode composite layer was prepared by mixing 85 parts by weight of natural graphite as a carbon-based active material, 5 parts by weight of SiO (silicon oxide) as a silicon-based active material, 6 parts by weight of carbon black as a conductive material, and 4 parts by weight of PVDF as a binder in an N-methylpyrrolidone solvent, and the slurry was coated onto a copper foil to produce a cathode having a cathode composite layer (average thickness: 180 μm).

[0154] An electrode assembly was manufactured by laminating a separator (thickness: approximately 16 μm) made of a porous polyethylene (PE) film between each manufactured positive and negative electrode. After placing the electrode assembly inside a battery case, an electrolyte was injected into the case, and the battery was manufactured by leaving it at room temperature for 3 days to allow sufficient impregnation of the electrolyte. The battery was completed by injecting an electrolyte in which 1M LiPF6 was dissolved in an organic solvent mixed with ethyl methyl carbonate (EC) and ethyl methyl carbonate (EMC) in a composition of 3:7 (volume ratio).

[0156] Example 1

[0157] The assembled lithium secondary battery of the above manufacturing example was prepared and pre-aged by aging at room temperature of 25°C for 24 hours. The pre-aged secondary battery was then roll-pressed twice using the roll-pressing unit shown in FIG. 10, from the center of the battery toward the edge where the electrode leads are located. At this time, the linear pressure applied to the battery by the roll-pressing unit was set to 40 kfg / cm. Subsequently, the battery was mounted on the formation unit shown in FIG. 1, and the formation process was completed by pressing the battery and charging it until it reached a level of 60% SOC. At this time, the charging speed was 0.6C, and the surface pressure applied to the battery was 5.0 kgf / cm².

[0158] Subsequently, the secondary battery was high-temperature aged at 60°C for 24 hours and room-temperature aged at 23°C for 48 hours. The manufacturing of the secondary battery was completed by performing the process of fully charging and fully discharging the aged secondary battery.

[0160] Example 2

[0161] The assembled lithium secondary battery of the above manufacturing example was prepared and pre-aged by aging it at room temperature of 25°C for 24 hours. After mounting the pre-aged secondary battery in the formation section shown in Fig. 1, the battery was charged at a charging rate of 0.2C until the charge depth of the secondary battery reached 17% SOC, while the first formation step was performed by pressurizing the battery with a pressure of 0.5 kgf / ㎠ during charging. Subsequently, the secondary battery was removed from the formation section and, using the roll-pressing section shown in Fig. 10, was roll-pressed twice from the center of the battery toward the edge where the electrode lead is located. At this time, the linear pressure applied to the battery by the roll-pressing section was set to 40 kfg / cm. Afterwards, the secondary battery was removed from the roll pressing section, the secondary battery was mounted again in the formation section, and the secondary battery was charged at a charging rate of 1.0C until the charge depth of the secondary battery reached 60% SOC, while the battery was pressurized at a pressure of 5.0 kgf / ㎠ during charging and the second formation step was performed.

[0162] Subsequently, the secondary battery was high-temperature aged at 60°C for 24 hours and room-temperature aged at 23°C for 48 hours. The manufacturing of the secondary battery was completed by performing the process of fully charging and fully discharging the aged secondary battery.

[0164] Comparative example

[0165] In the above Example 1, a secondary battery was manufactured in the same manner as in Example 1, except that the roll-pressing process by the roll-pressing unit was omitted.

[0167] Experimental Example: Observation of lithium precipitation

[0168] Each secondary battery prepared in the above examples and comparative examples was charged with a constant current of 0.33C, cut off at 4.2V, charged with a constant voltage, then cut off at 0.05C, and discharged at 0.5C and 3.0V. After performing 100 cycles of charging and discharging with this as one cycle, the battery was disassembled to observe whether lithium had been deposited.

[0169] Whether lithium precipitates Example 1 X Example 2 X Comparative example O

[0170] In the battery of the example, lithium was not precipitated, but in the battery of the comparative example, lithium was precipitated. FIG. 13 is a photograph of the negative electrode taken after disassembling the secondary battery manufactured according to the comparative example and repeating the charging and discharging cycles according to the experimental example. Referring to FIG. 13, it can be confirmed that lithium was precipitated in the edge region of the negative electrode, that is, in the region where the sliding part is located. This is judged to be an effect resulting from applying pressure to the sliding part by performing a roll-pressing process before or during the formation process.

[0171] As described above, the activation method and activation device according to the present invention can prevent the trapping of internal gas in the sliding part, thereby preventing localized uneven charging and the risk of lithium precipitation. Explanation of the symbols

[0173] 1: Frame 2: Pressure plate 3: Driving unit 3a: Drive shaft, 3b: Drive motor B: Secondary battery 10: Cathode 11: Cathode current collector, 12: Cathode active material layer 20: Bipolar 21: Anode current collector, 22: Anode active material layer 30: Separator S: Sliding part 121,122: Pressure roller

Claims

Claim 1 A method for activating a lithium secondary battery, comprising: a pre-aging process for aging an assembled lithium secondary battery at room temperature; a formation process for charging the lithium secondary battery; and a roll-pressing process for pressing the lithium secondary battery using a pressure roller, wherein the roll-pressing process applies pressure from the center of the lithium secondary battery toward the edge where the electrode sliding part is located, the formation process charges the lithium secondary battery to a SOC level of 40~70%, and the roll-pressing process is performed during the formation process. Claim 2 delete Claim 3 delete Claim 4 A method for activating a lithium secondary battery according to claim 1, wherein the roll-pressing process is performed prior to and during the formation process. Claim 5 A method for activating a lithium secondary battery according to claim 1, wherein the roll-pressing process is performed 2 to 5 times. Claim 6 In claim 1, the roll-pressing process is a method for activating a lithium secondary battery by applying pressure to the lithium secondary battery with a linear pressure of 20 to 60 kgf / cm². Claim 7 A method for activating a lithium secondary battery according to claim 1, wherein the pressure roller is composed of an upper pressure roller and a lower pressure roller, and the lithium secondary battery is pressurized while passing between the upper pressure roller and the lower pressure roller. Claim 8 A method for activating a lithium secondary battery according to claim 1, wherein the formation process comprises a process of applying surface pressure to a lithium secondary battery being charged. Claim 9 A method for activating a lithium secondary battery according to claim 8, wherein the formation process comprises a plurality of formation steps in which the charge termination SOC is set differently, and each of the formation steps has one or more conditions selected from each charging speed and surface pressure applied to the secondary battery set differently. Claim 10 A method for activating a lithium secondary battery according to claim 1, further comprising an aging process for maturing the battery after formation is complete. Claim 11 delete Claim 12 delete Claim 13 delete Claim 14 delete

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