Apparatus for impregnating secondary battery with electrolyte, method for impregnating secondary battery with electrolyte, and method for activating secondary battery

Abstract

An electrolyte impregnation device for a secondary battery according to one embodiment of the present invention includes a transfer unit configured to transfer a secondary battery in a first direction, and a magnetic field application unit that applies a magnetic field in a second direction to the secondary battery transferred by the transfer unit. A magnetic field is applied to the electrolyte flowing in a first direction to induce a magnetohydrodynamic convection flow in the electrolyte, generating a minute magnetohydrodynamic convection flow, particularly near the electrode. The synergistic effect of this flow force and the buoyancy force exerted on the bubbles causes the bubbles on the electrode surface to move to the gas pocket, eliminating the bubbles within the electrode assembly and improving the impregnation performance of the electrolyte.

Description

[Technical Field]

[0001] This application claims the benefit of priority based on Korean Patent Application No. 10-2023-0027833, filed on March 2, 2023.

[0002] The present invention relates to an electrolyte impregnation device for a secondary battery for improving the wetting performance of the electrolyte, an electrolyte impregnation method for a secondary battery, and a method for activating a secondary battery using the same. [Background technology]

[0003] A secondary battery capable of repeated charging and discharging includes an electrode assembly, a battery case in which the electrode assembly is housed, and an electrolyte that is poured into the battery case to activate the electrode assembly. The electrode assembly is formed by interposing a separator between a positive electrode plate formed by coating a positive electrode current collector with a positive electrode active material and a negative electrode plate formed by coating a negative electrode current collector with a negative electrode active material. Depending on the type of battery case, the electrode assembly may be manufactured in a jelly roll type, stack type, or the like and housed inside the battery case.

[0004] The battery case serves as an exterior material that maintains the shape of the battery and protects it from external impacts, and secondary batteries can be classified into cylindrical, prismatic, and pouch types depending on the type of battery case.

[0005] A secondary battery is manufactured by placing an electrode assembly in a battery case and injecting an electrolyte into the battery case. In order for a secondary battery to have high capacity, high energy density, and a long lifespan, an electrolyte appropriate for the designed capacity must be injected into the battery case. The electrode assembly must be completely impregnated with the electrolyte through an aging process at a predetermined temperature and humidity for a certain period of time to ensure active electrode reactions between the electrodes.

[0006] If the electrolyte content does not reach the designed amount, not only will the desired electrochemical performance not be achieved, but the lifespan of the secondary battery will also be significantly reduced. Furthermore, if the electrode assembly is incompletely impregnated with the electrolyte, the reaction between the electrodes will not proceed smoothly, resulting in increased resistance and a significant decrease in output characteristics and battery capacity, resulting in reduced battery performance and a shortened lifespan. Furthermore, the high resistance may cause battery degradation or explosion. Therefore, injecting the electrolyte in the exact designed amount and ensuring that the electrolyte is sufficiently impregnated into the electrode assembly is one of the key issues that determine the performance and lifespan of a secondary battery.

[0007] In particular, in recent years, as the demand for batteries with high energy density increases, the electrode loading amount tends to increase, and as the electrode loading amount increases, it may become difficult to impregnate the rolled electrodes with an electrolyte.

[0008] Patent Document 1 discloses a technique for vibrating a battery case to remove air bubbles from the electrolyte in order to improve the impregnation performance of the electrolyte. However, this method applies a physical external force to the battery to remove air bubbles from the electrolyte, and although it can remove large air bubbles, the application of vibration can instead generate small air bubbles, and is not sufficient to remove air bubbles formed on the electrode surface.

[0009] When bubbles are present on the electrode surface, the bubbles hinder the impregnation of the electrolyte. Therefore, it is necessary to develop a technology to effectively remove bubbles from the electrode surface and improve the impregnation performance of the electrolyte. Summary of the Invention [Problem to be solved by the invention]

[0010] An object of the present invention is to provide an electrolyte impregnation device and method for a secondary battery that effectively removes air bubbles from the electrode surface to improve the electrolyte impregnation performance, and a method for activating a secondary battery using the same. [Means for solving the problem]

[0011] According to one embodiment of the present invention, there is provided an electrolyte impregnation device for a secondary battery, the electrolyte impregnation device including a storage unit that stores an electrode assembly and an electrolyte, and a gas pocket unit disposed on one side of the storage unit. The electrolyte impregnation device includes a transfer unit configured to transfer a secondary battery in a first direction, and a magnetic field application unit that applies a magnetic field in a second direction to the secondary battery transferred by the transfer unit.

[0012] In one specific example, the second direction may be determined so that a third direction from the storage portion toward the gas pocket portion is perpendicular to a plane formed by the first direction and the second direction.

[0013] In one specific example, the transport unit may include a carrier having a storage space capable of storing secondary batteries, a conveyor belt for transporting the carrier, and a drive unit for driving the conveyor belt in the first direction.

[0014] In one specific example, the magnetic field applying unit may include a permanent magnet or an electromagnet.

[0015] According to another embodiment of the present invention, there is provided a method for impregnating a secondary battery with an electrolyte, the method including: transferring a secondary battery in a first direction; and applying a magnetic field to the transferred secondary battery in a second direction.

[0016] In one specific example, during the process of applying the magnetic field, the second direction can be determined so that a third direction from the storage section toward the gas pocket section is perpendicular to the plane formed by the first direction and the second direction.

[0017] In one specific example, the magnitude of the magnetic field applied in the process of applying the magnetic field may be in the range of 0.1T to 100T.

[0018] According to another embodiment of the present invention, there is provided a method for activating a secondary battery including a housing containing an electrode assembly and an electrolyte, and a gas pocket disposed on one side of the housing. The method for activating the secondary battery includes a pre-aging process for immersing the electrode assembly of the secondary battery in the electrolyte, an initial charging process for charging the pre-aged secondary battery until it reaches a predetermined depth of charge (SOC), and an aging process for aging the secondary battery. The pre-aging process includes a process for transporting the secondary battery in a first direction and a process for applying a magnetic field to the transported secondary battery in a second direction.

[0019] In one specific example, during the process of applying the magnetic field, the second direction can be determined so that a third direction from the storage section toward the gas pocket section is perpendicular to the plane formed by the first direction and the second direction.

[0020] In one specific example, the initial charging process may be set such that the charging depth at which the charging of the secondary battery is terminated is within the range of SOC 20% to SOC 80%.

[0021] In one specific example, the initial charging process may include charging the secondary battery under pressure.

[0022] In one specific example, the aging process may include a high-temperature aging process in which the secondary battery is aged in a temperature range of 50°C to 80°C, and a room-temperature aging process in which the secondary battery is aged in a temperature range of 18°C ​​to 30°C. [Effects of the Invention]

[0023] The electrolyte impregnation device and method according to the present invention apply a magnetic field to an electrolyte flowing in a first direction, inducing a magnetohydrodynamic convection flow in the electrolyte, particularly generating a minute magnetohydrodynamic convection flow near the electrode. The synergistic effect of this flow force and the buoyancy force exerted on the bubbles causes the bubbles on the electrode surface to move to a gas pocket, removing the bubbles within the electrode assembly and improving the impregnation performance of the electrolyte.

[0024] The activation method according to the present invention induces such magnetohydrodynamic convection flow during the pre-aging process to remove bubbles on the electrode surface, thereby improving the electrolyte impregnation efficiency and shortening the time required for the pre-aging process. [Brief explanation of the drawings]

[0025] [Figure 1] 1 is a block diagram illustrating an electrolyte impregnation device for a secondary battery according to an embodiment. [Figure 2] 1 is an exploded perspective view of a pouch-type secondary battery according to an embodiment; [Figure 3] 1 is a schematic diagram of a pouch-type secondary battery according to an embodiment. [Figure 4] 1 is a diagram showing an electrolyte impregnation device for a secondary battery according to an embodiment; [Figure 5] 1 is a top view of an electrolytic solution impregnation device for a secondary battery according to one embodiment. [Figure 6] 1 is a flowchart illustrating an electrolyte impregnation method for a secondary battery according to an embodiment. [Figure 7] 1 is a flowchart illustrating a method for activating a secondary battery according to an embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0026]

[0033] The present invention will now be described in detail with reference to the accompanying drawings, in which:

[0034] A preferred embodiment of the present invention will be described in detail so that those skilled in the art can easily implement the present invention; however, the present invention may be embodied in various different forms and is not limited to the following embodiments.

[0027] In order to clearly explain the present invention, detailed descriptions of parts that are not relevant to the description or related known technologies that may unnecessarily obscure the gist of the present invention will be omitted, and in this specification, when adding reference symbols to components in each drawing, the same or similar reference symbols will be used throughout the specification to refer to the same or similar components.

[0028] Furthermore, the terms and words used in this specification and claims should not be interpreted as being limited to their ordinary or dictionary meanings, but rather as meanings and concepts that are consistent with the technical idea of ​​the present invention, based on the principle that the inventor can appropriately define the concepts of the terms in order to best explain his own invention.

[0029] <Secondary battery electrolyte impregnation device>

[0030] (First embodiment) FIG. 1 is a block diagram illustrating an electrolyte impregnation device for a secondary battery according to one embodiment.

[0031] 1, the electrolyte impregnation apparatus 100 for a secondary battery may include a transfer unit 110 configured to transfer a secondary battery in a first direction, and a magnetic field application unit 120 configured to apply a magnetic field in a second direction to the secondary battery transferred by the transfer unit. According to one embodiment of the present invention, the electrolyte impregnation apparatus 100 for a secondary battery may generate magnetic field-induced magnetohydrodynamic (MHD) convection in the electrolyte, thereby removing bubbles on the electrode surface, by applying a magnetic field formed by the magnetic field application unit to the electrolyte of the secondary battery transferred within the magnetic field.

[0032] When air bubbles are present on the electrode surface of a secondary battery, the air bubbles prevent the electrolyte from wetting the electrode. However, when magnetic field-induced magnetohydrodynamic convection is formed in the electrolyte, the force of the magnetohydrodynamic convection acts on the air bubbles, causing them to fall from the electrode surface, allowing the electrolyte to be successfully impregnated into the electrode.

[0033] The transport unit 110 is not particularly limited as long as it can transport the secondary battery in one direction. The transport unit 110 transports the secondary battery and generates a kinetic electromotive force in the electrolyte flowing in the same direction as the secondary battery when a magnetic field is applied.

[0034] The magnetic field applying unit 120 applies a magnetic field to the secondary battery being transported, generating magnetohydrodynamic convection due to interaction with the electromotive force of the electrolyte. Air bubbles on the electrode surface are removed by magnetohydrodynamic convection. When a magnetic field is applied to the flowing electrolyte, the electric and magnetic fields induce magnetohydrodynamic convection flow due to the Lorentz force, and micro-magnetohydrodynamic convection flow occurs near the electrode. Small air bubbles can be effectively removed by the magnetohydrodynamic convection flow. In addition, the magnetic field applying unit can increase the mean free path of ions near the electrode surface, thereby increasing the amount of charge.

[0035] According to an embodiment of the present invention, the magnetic field applying unit 120 may include a permanent magnet or an electromagnet, preferably an electromagnet, which is preferable because it can periodically change the direction of the magnetic field and increase the flow in the electrolyte.

[0036] According to one embodiment of the present invention, the secondary battery may be a lithium secondary battery, specifically a pouch-type secondary battery. Figure 2 is an exploded perspective view of a pouch-type secondary battery according to one embodiment, and Figure 3 is a schematic diagram of a pouch-type secondary battery according to one embodiment.

[0037] Referring to these drawings, a pouch-type secondary battery 10 according to an embodiment may have an electrode assembly 11 sealed within a storage space 12a of a pouch-type battery case 12. The pouch-type secondary battery 10 according to an embodiment may include a storage portion 13 that stores the electrode assembly 11 and an electrolyte (not shown), and a gas pocket portion 14 disposed on one side of the storage portion.

[0038] The gas pocket portion 14 of the secondary battery is a space where gas generated during the activation process of the secondary battery is collected.

[0039] The electrode assembly 11 is formed by alternately stacking electrodes and separators. First, electrodes such as a positive electrode and a negative electrode are manufactured by coating a positive electrode current collector and a negative electrode current collector with an electrode slurry, which is a mixture of an electrode active material, a binder, a conductive material, and a solvent. Then, a separator is laminated between the electrodes to manufacture the electrode assembly 11. The manufactured electrode assembly 11 is inserted into a pouch-type battery case 12, an electrolyte is injected, and the case is sealed, thereby manufacturing the pouch-type secondary battery 10.

[0040] The electrode assembly 11 includes electrode tabs 15a and 15b. The electrode tabs 15a and 15b are connected to the positive and negative electrodes of the electrode assembly 11, respectively, and protrude from the electrode assembly 11 to provide a path for electrons to move between the inside and outside of the electrode assembly 11. The electrode current collector of the electrode assembly 11 is composed of a portion coated with an electrode active material and an end portion, i.e., a plain portion, where the electrode active material is not coated. The electrode tabs 15a and 15b may be formed by cutting the plain portion or by connecting a separate conductive member to the plain portion using ultrasonic welding or the like. The electrode tabs 15a and 15b may protrude in different directions from the electrode assembly 11, but are not limited thereto and may protrude in various directions, such as protruding side by side in the same direction from one side.

[0041] Electrode leads 16a and 16b, which supply electricity to the outside of the secondary battery 10, may be connected to the electrode tabs 15a and 15b of the electrode assembly 11 by spot welding or the like. Portions of the electrode leads 16a and 16b may be surrounded by insulating portions 17a and 17b. The insulating portions 17a and 17b are located only on the side S where the upper and lower cases of the battery case 12 are thermally fused together, and may bond the electrode leads 16a and 16b to the battery case 12. These insulating portions 17a and 17b prevent electricity generated by the electrode assembly 11 from flowing to the battery case 12 through the electrode leads 16a and 16b, thereby maintaining the sealing of the battery case 12. Therefore, the insulating portions 17a and 17b are made of a non-conductor that does not allow electricity to pass through easily. Generally, insulating tape, which is easy to attach to the electrode leads 16a and 16b and is relatively thin, is often used as the insulating parts 17a and 17b. However, the present invention is not limited to this, and various materials can be used as long as they can insulate the electrode leads 16a and 16b.

[0042] The electrode leads 16a, 16b may have one end connected to the electrode tabs 15a, 15b and the other end protruding out of the battery case 12. That is, the electrode leads 16a, 16b may include a positive electrode lead 16a connected at one end to the positive electrode tab 15a and extending in the protruding direction of the positive electrode tab 15a, and a negative electrode lead 16b connected at one end to the negative electrode tab 15b and extending in the protruding direction of the negative electrode tab 15b. Meanwhile, the other ends of the positive electrode lead 16a and the negative electrode lead 16b may protrude out of the battery case 12. This allows electricity generated inside the electrode assembly 11 to be supplied to the outside. In addition, since the positive electrode tab 15a and the negative electrode tab 15b protrude in various directions, the positive electrode lead 16a and the negative electrode lead 16b may also extend in various directions.

[0043] According to one embodiment, the second direction may be determined such that a third direction (z-axis direction) from the storage section 13 toward the gas pocket section 14 is perpendicular to a plane formed by the first direction (x-axis direction) and the second direction (y-axis direction). Here, the first direction is the direction in which the secondary battery is transported, and the second direction is the direction in which a magnetic field is applied.

[0044] When a magnetic field is formed around the secondary battery moving in the first direction (x-axis direction), a kinetic electromotive force is generated in the electrolyte fluid inside the secondary battery, causing it to become charged. The charged electrolyte is subjected to the electromotive force and the magnetic field, and magnetohydrodynamic convection is generated in the direction of the Lorentz force. Considering the mechanism by which this magnetohydrodynamic convection is generated, it is preferable to determine the second direction so that the direction of magnetohydrodynamic convection is the third direction from the storage section 13 toward the gas pocket section 14.

[0045] In particular, bubbles in the electrolyte are subjected to a buoyancy force in the direction opposite to gravity, and when the direction of the buoyancy force coincides with the third direction, the bubbles on the electrode surface can be more effectively moved to the gas pocket portion 14 due to the synergistic effect of the magnetohydrodynamic convection acting in the third direction and the buoyancy force.

[0046] (Second embodiment) 4 and 5 are diagrams showing an electrolyte impregnation apparatus for a secondary battery according to one embodiment. A transfer unit 110' can be employed in the electrolyte impregnation apparatus 100 for a secondary battery in place of the transfer unit 100 of FIG.

[0047] 4 and 5, the transport section 110' may include a carrier 111, a conveyor belt 112, and a drive roller 113a.

[0048] The carrier 111 may have a storage space 111a capable of storing the secondary battery 10. The storage space 111a may have a volume large enough to accommodate the secondary battery 10, and as shown in Fig. 4, the carrier may be configured so that the secondary battery 10 is transported in an upright state with the storage section 13 of the secondary battery 10 positioned downward and the gas pocket section 14 positioned upward.

[0049] The carrier 111 is configured to allow the secondary battery 10 to be transported in an upright position, thereby maximizing the area of ​​the electrode assembly 11 and electrolyte (not shown) located in the storage section 13 exposed to the magnetic field, thereby improving the efficiency of removing air bubbles.

[0050] According to a preferred embodiment, the length of the accommodating space 111a in the vertical direction (y-axis direction) may correspond to the thickness of the storage section for the secondary battery 10, and the length of the accommodating space 111a in the horizontal direction (x-axis direction) may correspond to the length of the secondary battery in the width direction (x-axis direction). In addition, in order to increase the magnetic field exposure area of ​​the electrode assembly and the electrolyte solution located in the storage section, it is preferable that the length of the secondary battery inserted into the accommodating space 111a is not long.

[0051] The conveyor belt 112 may be configured to transport the carrier 111. The carrier 111 may be attached to the upper surface of the conveyor belt or may be configured to be detachable.

[0052] The drive unit 113 may be configured to drive the conveyor belt 112 in a first direction (x-axis direction). Such a drive unit may include a drive roller 113a disposed below the conveyor belt 112 at a position where it can come into contact with the conveyor belt 112, and a motor (not shown) that applies a rotational force to the drive roller 113a.

[0053] According to one embodiment of the present invention, in the electrolyte impregnation device 100 for a secondary battery, a magnetic field MF formed by a magnetic field application unit 120 acts on the electrolyte of the secondary battery 10 transported within the magnetic field, generating magnetic field-induced magnetohydrodynamic (MHD) convection in the electrolyte. Gas bubbles on the electrode surface are moved to gas pockets by such MHD convection and removed from the electrode.

[0054] Referring to FIG. 5, the magnetic field applying unit 120; 121, 122 according to the exemplary embodiment may include a first electromagnet 121 and a second electromagnet 122 respectively arranged in front of and behind a carrier 111 that houses the secondary battery 10.

[0055] The electrolyte impregnation device for such a secondary battery is configured to apply a magnetic field MF in a second direction to a secondary battery moving in a first direction, thereby generating magnetohydrodynamic convection in the electrolyte due to the Lorentz force. Such magnetohydrodynamic convection can move gas bubbles on the electrode surface in a third direction, effectively removing the gas bubbles from the electrode surface.

[0056] In addition, due to the synergistic effect of the flow force of the magnetohydrodynamic convection generated near the electrode and the buoyancy force exerted on the bubbles, the bubbles on the electrode surface can move to the gas pocket, removing the bubbles within the electrode assembly and improving the impregnation performance of the electrolyte.

[0057] <Method for impregnating secondary batteries with electrolyte>

[0058] FIG. 6 is a flowchart illustrating a method for impregnating an electrolyte solution into a secondary battery according to one embodiment.

[0059] Referring to Figures 1 to 6, a method for impregnating a secondary battery with an electrolyte may include a step (P10) of transporting a secondary battery in a first direction and a step (P20) of applying a magnetic field in a second direction to the transported secondary battery.

[0060] The secondary battery has been described in detail above, so a duplicate description thereof will be omitted.

[0061] Referring to Figures 1 and 4 to 6, the transferring process (P10) may be performed by the transferring unit 110, 110', and the magnetic field applying process (P20) may be performed by the magnetic field applying unit 120, and redundant explanations regarding these will be omitted.

[0062] As described above, when determining the second direction in the process of applying a magnetic field (P20), the second direction is determined so that the third direction from the storage section toward the gas pocket section is perpendicular to the plane formed by the first direction and the second direction.

[0063] According to one embodiment of the present invention, the magnitude of the magnetic field applied in the step of applying a magnetic field (P20) may be in the range of 0.1T to 100T, preferably 0.1T to 50T, and more preferably 0.1T to 5T.

[0064] In this method of electrolyte impregnation for secondary batteries, when a magnetic field is applied in a second direction to an electrolyte flowing in a first direction, a magnetohydrodynamic convection flow is induced by the Lorentz force, generating a magnetohydrodynamic convection flow near the electrode and moving bubbles on the electrode surface in a third direction.

[0065] The flow force due to such magnetohydrodynamic convection and the buoyancy force exerted by the bubbles exert a synergistic effect, more effectively moving the bubbles on the electrode surface to the gas pocket, and as a result, removing the bubbles within the electrode assembly, improving the impregnation performance of the electrolyte.

[0066] <Method for activating secondary batteries>

[0067] FIG. 7 is a flowchart illustrating a method for activating a secondary battery according to an embodiment.

[0068] Referring to Figures 1 to 7, a method for activating a secondary battery may include a pre-aging process (P100) for immersing an electrode assembly of the secondary battery in an electrolyte, an initial charging process (P200) for charging the pre-aged secondary battery until it reaches a predetermined range of state of charge (SOC), and an aging process (P300) for aging the secondary battery. The pre-aging process (P100) may include a process (P10) for transferring the secondary battery in a first direction and a process (P20) for applying a magnetic field in a second direction to the transferred secondary battery.

[0069] The secondary battery has been described in detail above, so a duplicate description thereof will be omitted.

[0070] The pre-aging process (P100) may be a process of waiting for the electrolyte to be sufficiently impregnated into the electrode assembly 11 in the battery case 12, after which the secondary battery 10 is manufactured by injecting the electrolyte into the battery case 12 and sealing the battery case.

[0071] In order for an electrode reaction to occur during initial charging after the electrode assembly 11 and electrolyte are housed in the battery case 12, the electrolyte must be sufficiently impregnated into the positive electrode, negative electrode, and separator that make up the electrode assembly beforehand. If the initial charging process is performed without the electrolyte being impregnated, uncharged areas may occur, which may prevent the SEI film from forming uniformly, resulting in a decrease in battery performance.

[0072] Conventionally, the pre-aging process (P100) was performed by leaving the secondary battery at a constant temperature and humidity for a predetermined period of time. The electrolyte gradually seeps into the electrodes, and a chemical reaction occurs between the electrolyte and the electrodes, generating bubbles that can hinder the impregnation of the electrolyte.

[0073] The pre-aging process according to the present invention includes the transporting step (P10) and the magnetic field applying step (P20), thereby inducing magnetohydrodynamic convection in the electrolyte, and the bubbles are more effectively transported to the gas pocket portion 14, thereby removing the bubbles on the electrode surface. This improves the electrolyte impregnation efficiency and shortens the pre-aging time.

[0074] Such a pre-aging process may involve leaving the secondary battery at a temperature range of 18 to 27 degrees Celsius for 12 to 48 hours, and the temperature range may be 18 to 27 degrees Celsius, preferably 19 to 26 degrees Celsius, and more preferably 20 to 25 degrees Celsius. The duration of the pre-aging process may be 12 to 48 hours, and preferably 18 to 36 hours.

[0075] The pre-aging process may include a high-temperature pre-aging process to improve the electrolyte impregnation efficiency. Such a high-temperature pre-aging process may be a process of aging a spare lithium secondary battery at a temperature of 40 to 55 degrees Celsius for 12 to 24 hours.

[0076] When such a high-temperature pre-aging process is performed during the pre-aging process, the impregnation of the electrolyte is improved, an SEI film can be formed more uniformly during the initial charging process, and the occurrence of uncharged regions can be reduced, thereby preventing the risk of lithium deposition.

[0077] During the pre-aging process, the transferring process (P10) and the magnetic field application process (P20) may be performed at a suitable time point among the early stage, middle stage, or late stage of the pre-aging process, preferably at the early stage of the pre-aging process, where the early stage of the pre-aging process may be within 12 hours after the secondary battery is manufactured.

[0078] The transfer process (P10) and the magnetic field application process (P20) have been described in detail above, so a repeated description thereof will be omitted.

[0079] Furthermore, as described above, when determining the second direction in the process of applying a magnetic field (P20), the second direction is determined so that the third direction from the storage section toward the gas pocket section is perpendicular to the plane formed by the first direction and the second direction.

[0080] The first charging process (P200) is a process in which the secondary battery is charged at a predetermined voltage. Lithium secondary batteries are activated by first charging during the manufacturing process, and during this first charging, lithium ions released from the positive electrode move to and are inserted into the negative electrode, forming a solid electrolyte interface (SEI) film on the surface of the negative electrode.

[0081] Once formed, the SEI film acts as an ion tunnel, allowing only lithium ions to pass through. This ion tunnel effect solvates the lithium ions, preventing large-molecular-weight organic solvent molecules that migrate with lithium ions in the electrolyte, such as lithium salts, EC, DMC, or DEC, from co-inserting into the graphite anode and disrupting the anode structure. Once the SEI film is formed, the lithium ions no longer react with the graphite anode or other materials. The charge consumed in the formation of the SEI film is irreversible, meaning it does not reversibly react during discharge. Therefore, further decomposition of the electrolyte does not occur, and the amount of lithium ions in the electrolyte is reversibly maintained, allowing for stable charge and discharge.

[0082] In conclusion, once the SEI film is formed, the amount of lithium ions can be reversibly maintained, and the life characteristics of the battery are also improved.

[0083] In one specific example, the charge depth at which charging is terminated during the first charging process (P200) may be set within a range of 20% (SOC 20%) to 80% (SOC 80%) of the lithium secondary battery capacity (SOC 100%), or within a range of 30% to 80%, or within a range of 40% to 80%, or within a range of 50% to 75%. This may be suitably selected depending on the material characteristics, capacity, etc. of the secondary battery.

[0084] The charging conditions in the first charging step (P200) may be those known in the art. Specifically, the charging method may be a constant current charging method until the end-of-charge voltage is reached. The charging rate (c-rate) may be 0.01 C to 2 C, 0.1 C to 1.5 C, or 0.2 C to 1 C, but is not limited thereto and may be suitably changed depending on the material properties of the positive and negative electrodes.

[0085] The temperature condition for the first charging process (P200) may be 18°C ​​to 28°C, specifically 19°C to 27°C, and more specifically 20°C to 26°C.

[0086] The initial charging process (P200) may also include charging the secondary battery under pressure. Charging the secondary battery under pressure prevents gas generated during the charging process from being trapped inside the electrode assembly. This pressure may be applied using a pressure tool configured to apply pressure to both sides of the secondary battery.

[0087] In addition, the initial charging process (P200) can be performed in one step without a rest period until the charging depth is reached at which the charging is terminated. Alternatively, the initial charging process can be divided into multiple steps until the set charging end voltage is reached, and the charging conditions and pressure conditions can be changed for each step to perform the initial charging process.

[0088] The aging process (P300) may be a process of aging the secondary battery to stabilize the SEI film formed during the first charging process (P200).

[0089] According to one embodiment, the aging process (P300) may include a high-temperature aging process in which the secondary battery is aged in a temperature range of 50°C to 80°C, and a room-temperature aging process in which the secondary battery is aged in a temperature range of 18°C ​​to 30°C.

[0090] The high-temperature aging process has the effect of further accelerating the stabilization of the SEI film formed during the first charging process.

[0091] The high-temperature aging process may be carried out at a temperature ranging from 50 to 80 degrees Celsius, preferably from 55 to 80 degrees Celsius, and more preferably from 60 to 75 degrees Celsius. The high-temperature aging time may be from 10 to 40 hours, from 12 to 36 hours, or from 18 to 30 hours.

[0092] If the set temperature during high-temperature aging is too high or the high-temperature aging process is performed for too long, the durability of the SEI coating may be reduced, which is undesirable. Conversely, if the set temperature during high-temperature aging is too low or the high-temperature aging process is performed for too short a time, the life characteristics of the lithium secondary battery may be reduced.

[0093] The room temperature aging process may be a process of aging the secondary battery at a temperature range of 18 to 30 degrees for 24 to 80 hours.

[0094] The temperature range for the room temperature aging process may be 18 to 30 degrees Celsius, preferably 19 to 27 degrees Celsius, and more preferably 20 to 25 degrees Celsius. The room temperature aging time may be 24 to 80 hours, preferably 30 to 72 hours, and more preferably 16 to 60 hours.

[0095] If the room temperature aging process is performed at an excessively low temperature outside the above range or for an excessively short time, the spare lithium secondary battery may not be sufficiently activated and its electrical performance may be reduced. Conversely, if the room temperature aging process is performed at an excessively high temperature or for an excessively long time, swelling may occur or the durability of the SEI film may be reduced.

[0096] On the other hand, the order of the high-temperature aging process and the room-temperature aging process is more preferably such that the high-temperature aging process is performed first and then the room-temperature aging process is performed in terms of stabilizing the SEI film.

[0097] According to one embodiment, after the first charging process (P200) and the aging process (P300), a degassing process may be further included in which gas inside the secondary battery is discharged to the outside of the secondary battery.

[0098] The above-described preferred embodiments of the present invention are for illustrative purposes only, and those skilled in the art may make various modifications, changes, substitutions and additions within the technical spirit and scope of the appended claims, and such modifications and variations should be understood as falling within the scope of the following claims. [Explanation of symbols]

[0099] 10: Secondary battery 100: Electrolyte impregnation device 110:Transfer section 120: Magnetic field application unit

Claims

1. An electrolyte impregnation device for a secondary battery, comprising: a storage section that stores an electrode assembly and an electrolyte; and a gas pocket section that is disposed on one side of the storage section, a transfer unit configured to transfer the secondary battery in a first direction; a magnetic field applying unit that applies a magnetic field in a second direction to the secondary battery being transported by the transporting unit.

2. 2. The electrolyte impregnation device for a secondary battery according to claim 1, wherein the second direction is determined so that a third direction extending from the storage section toward the gas pocket section is perpendicular to a plane formed by the first direction and the second direction.

3. The transfer unit is a carrier having a storage space for storing the secondary battery; a conveyor belt for transporting the carrier; 2. The electrolyte impregnation device for a secondary battery according to claim 1, further comprising: a drive unit that drives the conveyor belt in the first direction.

4. The electrolyte impregnation device for a secondary battery according to claim 1 , wherein the magnetic field application unit includes a permanent magnet or an electromagnet.

5. a step of transporting a secondary battery in a first direction, the secondary battery including a housing containing an electrode assembly and an electrolyte, and a gas pocket disposed on one side of the housing; and applying a magnetic field in a second direction to the secondary battery being transported.

6. 6. The method for impregnating a secondary battery with an electrolyte according to claim 5, wherein, in the process of applying the magnetic field, the second direction is determined so that a third direction from the storage portion toward the gas pocket portion is perpendicular to a plane formed by the first direction and the second direction.

7. 7. The method for impregnating a secondary battery with an electrolyte solution according to claim 5, wherein the magnitude of the magnetic field applied during the magnetic field application process is in the range of 0.1 T to 100 T.

8. A method for activating a secondary battery including a storage unit that stores an electrode assembly and an electrolyte, and a gas pocket unit disposed on one side of the storage unit, comprising: a pre-aging process for immersing the electrode assembly of the secondary battery in an electrolyte; an initial charging process in which the pre-aged secondary battery is charged until it reaches a predetermined depth of charge; an aging process of aging the secondary battery, The pre-aging process includes: transferring the secondary battery in a first direction; and applying a magnetic field in a second direction to the transported secondary battery.

9. 9. The method for activating a secondary battery according to claim 8, wherein, during the process of applying the magnetic field, the second direction is determined so that a third direction from the storage portion toward the gas pocket portion is perpendicular to a plane formed by the first direction and the second direction.

10. The first charging process is 9. The method for activating a secondary battery according to claim 8, wherein the state of charge at which charging of the secondary battery is terminated is set within a range of SOC 20% to SOC 80%.

11. The first charging process is The method for activating a secondary battery according to claim 8 , further comprising the step of charging the secondary battery under pressure.

12. The aging process includes: a high-temperature aging process of aging the secondary battery at a temperature range of 50°C to 80°C; The method for activating a secondary battery according to claim 8, further comprising: a room temperature aging step of aging the secondary battery at a temperature in the range of 18°C ​​to 30°C.

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