Battery cell manufacturing method

Abstract

A battery manufacturing method according to one embodiment of the present invention comprises: a battery cell assembly step of mounting, in a storage part of a battery case, an electrode assembly including a positive electrode, a negative electrode and a separator interposed between the positive electrode and the negative electrode; a pre-aging step of storing a battery cell at a first temperature; a first formation step of charging / discharging the battery cell; a second formation step of only pressing the battery cell having undergone charging / discharging; and an aging step of storing the pressed battery cell at a second temperature, wherein the second temperature can be in a range of at least that of the first temperature.

Description

Battery cell manufacturing method

[0001] Cross-citation with related application(s)

[0002] This application claims the benefit of priority to Korean Patent Application No. 10-2023-0164672, filed November 23, 2023, and Korean Patent Application No. 10-2024-0163999, filed November 18, 2024, the entire contents of which are incorporated herein by reference.

[0003] The present invention relates to a method for manufacturing a battery cell, and more specifically, to a method for manufacturing a battery cell that prevents the bending phenomenon of a battery cell without requiring a separate manual pressing process.

[0004] As technological development and demand for mobile devices increase, the demand for secondary batteries as an energy source is rapidly increasing. Among these secondary batteries, lithium secondary batteries, which have high energy density and voltage, long cycle life, and low self-discharge rate, are being commercialized and widely used.

[0005] These secondary batteries are classified into cylindrical and prismatic batteries, in which the electrode assembly is housed in a cylindrical or prismatic metal can, and pouch-type batteries, in which the electrode assembly is housed in a pouch-type case made of aluminum laminate sheet, depending on the shape of the battery case. Here, the electrode assembly housed in the battery case is a power plant capable of charging and discharging, consisting of a positive electrode, a negative electrode, and a separator structure interposed between the positive electrode and the negative electrode, and is classified into a jelly-roll type in which a separator is interposed between long sheet-shaped positive and negative electrodes coated with an active material and wound, and a stack type in which a plurality of positive electrodes and negative electrodes are sequentially stacked while interposing the separator between them.

[0006] Among these, pouch-type batteries, which have a structure in which a stack-type or stack / folding-type electrode assembly is built into a pouch-type battery case made of aluminum laminate sheet, are gradually increasing in usage due to reasons such as low manufacturing cost, small weight, and easy deformation.

[0007] When manufacturing such pouch-type batteries, if the wet adhesion between the separator and the electrode interface is uneven, cell bending may occur after the activation process. Here, cell bending may refer to a phenomenon in which the battery cell bends in a predetermined direction. Battery cells that exhibit this cell bending phenomenon may cause issues such as poor cell transport during the subsequent battery cell manufacturing process.

[0008] Accordingly, in the past, to resolve the cell bending phenomenon, it was necessary to perform a manual press process to manually pressurize the battery cell after the battery cell manufacturing process, or to perform a separate pressurization process, such as a rolling press. However, when a separate pressurization process is performed on a battery cell in which the cell bending phenomenon has already occurred, it is difficult to completely return the battery cell in which the cell bending has occurred to its original state, and there is the problem of a decrease in process efficiency due to performing a separate pressurization process.

[0009] Accordingly, there is a need to develop a battery cell manufacturing method that can prevent the bending phenomenon of battery cells without requiring a separate manual pressing process.

[0010] The problem to be solved by the present invention is to provide a method for manufacturing a battery cell that prevents the bending phenomenon of the battery cell without requiring a separate manual pressing process.

[0011] The problems to be solved by the present invention are not limited to the problems described above, and problems not mentioned can be clearly understood by a person having ordinary skill in the technical field to which the present invention pertains from this specification and the attached drawings.

[0012] A battery cell manufacturing method according to one embodiment of the present invention comprises a battery cell assembly step of mounting an electrode assembly including a positive electrode, a negative electrode, and a separator interposed between the positive electrode and the negative electrode into a receiving portion of a battery case; a pre-aging step of storing the battery cell at a first temperature; a first formation step of charging and discharging the battery cell; a second formation step of only performing pressurization on the battery cell on which charging and discharging have been performed; and an aging step of storing the battery cell on which pressurization has been performed at a second temperature, wherein the second temperature may be in a range equal to or higher than the first temperature.

[0013] The second formation stage above is 1 kgf / cm 2 More than 10 kgf / cm 2 It can be performed with the following pressures:

[0014] The second formation step may be performed at a temperature equal to or higher than the temperature of the first formation step.

[0015] The first formation step and the second formation step may be performed at a temperature of 30 degrees Celsius or higher and 80 degrees Celsius or lower.

[0016] The second formation step may be performed at a temperature greater than the temperature of the first formation step.

[0017] The first formation step may be performed while the battery cell is pressurized, and the second formation step may be performed at a pressure equal to or greater than the pressure of the first formation step.

[0018] The above first formation step can be performed in a state where the battery cell is positioned between a pair of jigs and the upper and lower parts of the battery cell are pressed by the pair of jigs.

[0019] The above second formation step can be performed without releasing the pressure in the above first formation step.

[0020] The above first formation stage is 0.01 kgf / cm 2 More than 10 kgf / cm 2 It is performed at a pressure below, and the second formation step is 1 kgf / cm 2 More than 10 kgf / cm 2 It can be performed with the following pressures:

[0021] The second formation step may be performed at a pressure greater than the pressure of the first formation step.

[0022] The second formation step may be performed for a period of time of 0.5 hours or more and 5 hours or less.

[0023] The first temperature may be a temperature of 10 degrees Celsius or more and 50 degrees Celsius or less, and the second temperature may be a temperature of 30 degrees Celsius or more and 100 degrees Celsius or less.

[0024] A degassing step may be further performed after the above aging step.

[0025] A secondary battery according to another embodiment of the present invention may include a battery cell manufactured by the above-described battery cell manufacturing method.

[0026] A battery cell manufacturing method according to an embodiment of the present invention can prevent the bending phenomenon of a battery cell without requiring a separate manual pressing process.

[0027] The effects of the present invention are not limited to the effects described above, and effects not mentioned can be clearly understood by a person having ordinary skill in the art to which the present invention pertains from this specification and the attached drawings.

[0028] FIG. 1 is a flowchart showing a battery cell manufacturing method according to one embodiment of the present invention.

[0029] Fig. 2 is a perspective view showing a battery cell assembled in the battery cell assembly step of Fig. 1.

[0030] Figure 3 is an exploded perspective view of the battery cell of Figure 2.

[0031] Figure 4 is a flowchart showing a battery cell manufacturing method according to a comparative example.

[0032] Figure 5 (a) is a drawing showing the results for a comparative example according to Experimental Example 1, and (b) is a drawing showing the results for an example according to Experimental Example 1.

[0033] Figure 6 (a) is a drawing showing the results of comparative examples and examples according to Experimental Example 2.

[0034] Figure 7 (a) is a drawing showing the results for the cathode of the comparative example according to Experimental Example 3, and (b) is a drawing showing the results for the cathode of the example according to Experimental Example 3.

[0035] Figure 8 (a) is a drawing showing the results for the anode of the comparative example according to Experimental Example 3, and (b) is a drawing showing the results for the anode of the example according to Experimental Example 3.

[0036] Hereinafter, various embodiments of the present invention will be described in detail with reference to the attached drawings so that those skilled in the art can easily implement the invention. The present invention may be implemented in various different forms and is not limited to the embodiments described herein.

[0037] In order to clearly explain the present invention, parts that are not related to the description are omitted, and the same reference numerals are used for identical or similar components throughout the specification.

[0038] Additionally, throughout the specification, whenever a part is said to “include” a component, this does not mean that it excludes other components, but rather that it may include other components, unless otherwise specifically stated.

[0039] FIG. 1 is a flowchart illustrating a method for manufacturing a battery cell according to one embodiment of the present invention. FIG. 2 is a perspective view illustrating a battery cell assembled in the battery cell assembly step of FIG. 1. FIG. 3 is an exploded perspective view of the battery cell of FIG. 2.

[0040] Referring to FIGS. 1 and 2, a battery cell manufacturing method according to one embodiment of the present invention includes a battery cell assembly step (S100) of mounting an electrode assembly (200) including a positive electrode, a negative electrode, and a separator interposed between the positive electrode and the negative electrode into a receiving portion (300R) of a battery case (300); a pre-aging step (S200) of storing a battery cell (100) at a first temperature; a first formation step (S300) of charging and discharging the battery cell (100); a second formation step (S400) of only performing pressurization on the battery cell (100) on which charge and discharge have been performed; and an aging step (S500) of storing the battery cell (100) on which pressurization has been performed at a second temperature, wherein the second temperature may be in a range equal to or greater than the first temperature.

[0041] Referring to FIGS. 2 and 3, a battery cell (100) assembled in a battery cell assembly step (S100) is a pouch battery cell and includes an electrode assembly (200) inside a battery case (300). In addition, the battery cell (100) has a structure in which electrode leads (400) connected to electrode tabs of the electrode assembly (200) are exposed to the outside, and lead films (600) are attached to the upper and lower portions of the electrode leads (400).

[0042] The electrode assembly (200) includes a positive electrode, a negative electrode, and a separator. More specifically, the electrode assembly (200) may be configured such that the positive electrode and the negative electrode are sequentially stacked with a separator interposed therebetween and are insulated from each other. Here, the electrode assembly (200) may be a stack-type electrode assembly or a stack / folding-type electrode assembly. However, the shape of the electrode assembly (200) is not limited thereto, and any electrode assembly including a positive electrode, a negative electrode, and a separator may be included in the present embodiment. In addition, the positive electrode, the negative electrode, and the separator may be formed of a material generally included in a battery cell.

[0043] The electrode lead (400) may include a positive lead connected to the positive tabs (not shown) of the electrode assembly (200) and a negative lead connected to the negative tabs (not shown) of the electrode assembly (200). However, as shown in FIG. 2, the position of the electrode lead (400) is not limited to being located at both ends of the electrode assembly (200), and the positive lead and the negative lead may be located together at one end of the electrode assembly (200).

[0044] In the battery cell assembly step (S100), the assembled battery cell (100) can have an electrolyte injected into the battery case (300) while the electrode assembly (200) is mounted in the concave receiving portion (300R) formed in the battery case (300). In addition, a first outer circumferential surface (311) formed on the upper surface (310) of the battery case (300) and a second outer circumferential surface (321) formed on the lower surface (320) of the battery case (300) can be heat-sealed to form a sealing portion (300S). However, the sealing portion (300S) in the battery cell assembly step (S100) can be in a semi-sealed state, and when the degassing step (S600) described below is performed, the sealing of the battery cell (100) is released again, and then a re-sealed sealing portion (300S) can be formed.

[0045] Here, the electrolyte may include, but is not limited to, an organic liquid electrolyte, an inorganic liquid electrolyte, a solid polymer electrolyte, a gel-type polymer electrolyte, a solid inorganic electrolyte, a molten inorganic electrolyte, etc. that can be used in the manufacture of a lithium secondary battery.

[0046] Specifically, the electrolyte may include an organic solvent and a lithium salt. Any organic solvent capable of acting as a medium through which ions involved in the electrochemical reaction of the battery can move may be used without particular limitation. The lithium salt may be used without particular limitation as long as it is a compound capable of providing lithium ions used in a lithium secondary battery.

[0047] Referring to FIG. 1, the pre-aging step (S200) may be a step of storing the battery cell (100) assembled in the battery cell assembly step (S100) at a first temperature. More specifically, the pre-aging step (S200) may be a step of storing the battery cell (100) at a temperature of 10 degrees Celsius or more to 50 degrees Celsius or less, a temperature of 15 degrees Celsius or more to 40 degrees Celsius or less, or a temperature of 20 degrees Celsius or more to 30 degrees Celsius or less. In addition, the pre-aging step (S200) may be a step of storing the battery cell (100) in the first temperature range for a time of 24 hours or more to 96 hours or less, a time of 36 hours or more to 90 hours or less, or a time of 48 hours or more to 84 hours or less.

[0048] Referring to FIG. 1, the first formation step (S300) may be a step of activating the battery cell (100) by charging and discharging the battery cell (100) in which the pre-aging step (S200) has been performed within a predetermined SOC (State of Charging) range. For example, the first formation step (S300) may be a step of charging in a range of 20% or more to 100% or less, in a range of 30% or more to 100% or less, in a range of 50% or more to 100% or less, or in a range of 80% or more to 100% or less. For example, the first formation step (S300) may be a step of discharging in a range of 50% or less to 0% or more, in a range of 40% or less to 0% or more, in a range of 30% or less to 0% or more, or in a range of 20% or less to 0% or more. However, the charge / discharge conditions of the first formation step (S300) are not limited to this, and other charge / discharge conditions of the first formation step (S300) may be set to an appropriate range or condition depending on the electrode active material, battery type, battery characteristics, etc.

[0049] The first formation step (S300) may be performed while pressurizing the battery cell (100). For example, the first formation step (S300) may be a jig formation performed while a jig pressurizes the upper and lower parts of the battery cell (100).

[0050] More specifically, the first formation step (S300) applies 0.01 kgf / cm to the battery cell (100). 2 More than 10 kgf / cm 2 , or 0.02 kgf / cm 2 More than 5 kgf / cm 2It can be performed under the following pressure conditions. In addition, the first formation step (S300) can be performed at a high temperature. For example, the first formation step (S300) can be performed at a temperature of 30 degrees Celsius or higher to 80 degrees Celsius or lower, 40 degrees Celsius or higher to 70 degrees Celsius or lower, or 50 degrees Celsius or higher to 60 degrees Celsius or lower.

[0051] Referring to FIG. 1, in the battery cell manufacturing method according to the present embodiment, the second formation step (S400) may be a step of pressurizing the battery cell (100) in which the first formation step (S300) has been performed at a predetermined temperature and pressure range.

[0052] Referring to FIG. 1, the second formation step (S400) may be performed at a temperature and pressure condition exceeding the temperature and pressure conditions of the first formation step (S300). More specifically, the second formation step (S400) may be performed at a temperature of 30 degrees Celsius or more to 100 degrees Celsius or less, a temperature of 40 degrees Celsius or more to 90 degrees Celsius or less, or a temperature of 50 degrees Celsius or more to 80 degrees Celsius or less. In addition, the second formation step (S400) may be performed at a temperature of 1 kgf / cm 2 More than 10 kgf / cm 2 Pressure below 1.5 kgf / cm 2 Above 7kgf / cm 2 Pressure below 2kgf / cm 2 More than 4 kgf / cm 2 It can be performed at the pressure below. In addition, the second formation step (S400) can be performed for a time of 0.5 hours or more and 5 hours or less in the temperature and pressure ranges above.

[0053] Accordingly, the second formation step (S400) is performed after the first formation step (S300) is performed, so that the degree of wet adhesion between the interfaces between the components in the first formation step (S300) may not be taken into consideration, and the temperature and pressure ranges in the second formation step (S400) may be set relatively higher than those in the first formation step (S300). In particular, the second formation step (S400) can effectively prevent cell bending of the battery cell (100) by increasing the wet adhesion between the interfaces between the components of the battery cell (100) through pressurization performed on the battery cell (100) sufficiently activated in the first formation step (S300) at a relatively high temperature and pressure range.

[0054] In contrast, in the case where the pressurizing step (S30) is performed before the formation step (S40), as in the battery cell manufacturing method according to the comparative example (see FIG. 4), since the wet adhesive force between the interfaces between the components is increased by the pressurizing step (S30), there is a problem that a porous space is not sufficiently secured at the interface between the components of the battery cell (100) in the formation step (S40). In this way, when a porous space is not sufficiently secured at the interface between the components in the formation step (S40), there is a problem that the wettability of the electrode is reduced and lithium (Li) precipitation and the dog-bone phenomenon are aggravated. In this way, in the case of a battery cell manufacturing method such as the comparative example, the temperature and pressure ranges in the pressurizing step (S30) cannot but be set relatively low in consideration of the wet adhesive force between the interfaces between the components of the battery cell (100) in the formation step (S40), and it is difficult to effectively prevent the cell bending phenomenon of the battery cell (100).

[0055] Additionally, the second formation step (S400) may be performed without releasing the pressurization in the first formation step (S300). In other words, the second formation step (S400) may be a step in which the battery cell (100) in the first formation step (S300) is maintained in a pressurized state without performing separate charging and discharging, unlike the first formation step (S300).

[0056] Accordingly, in the battery cell manufacturing method according to the present embodiment, the second formation step (S400) uses the same pressurizing equipment as the first formation step (S300), so that the process can be prevented from becoming complicated due to the addition of the second formation step (S400), while there is an advantage in that the pressurizing environment for the battery cell (100) can be maintained constant.

[0057] Referring to FIG. 1, the aging step (S500) may be a step of storing the battery cell (100) pressurized in the second formation step (S400) at a second temperature, and the second temperature may be in a range higher than or equal to the first temperature. More specifically, the aging step (S500) may be a step of storing the battery cell (100) at a temperature of 40 degrees Celsius or more to 80 degrees Celsius or less, a temperature of 50 degrees Celsius or more to 70 degrees Celsius or less, or a temperature of 55 degrees Celsius or more to 65 degrees Celsius or less. In addition, the aging step (S500) may be a step of storing the battery cell (100) at the second temperature range for a time of 12 hours or more to 48 hours or less, or a time of 18 hours or more to 36 hours or less.

[0058] Accordingly, in the battery cell manufacturing method according to the present embodiment, as the aging step (S500) is performed in the temperature and time range described above, the electrolyte is evenly distributed inside the battery cell (100), and the SEI film can be formed more stably.

[0059] Referring to Fig. 1, in the battery cell manufacturing method according to the present embodiment, a degassing step (S600) may be further performed after the aging step (S500). More specifically, the degassing step (S600) may be a step of releasing gas generated inside the battery cell (100) to the outside by releasing the seal of the sealing portion (300S) formed in the battery cell assembly step (S100) described above. In addition, in the degassing step (S600), the battery case (300) opened may be sealed as the sealing portion (300S) is formed again, thereby sealing the battery cell (100).

[0060] Figure 4 is a flowchart showing a battery cell manufacturing method according to a comparative example.

[0061] Referring to FIG. 4, a battery cell manufacturing method according to a comparative example includes a battery cell assembly step (S10); a pre-aging step (S20); a pressurizing step (S30); a formation step (S40); an aging step (S50); and a degassing step (S60). Here, the battery cell manufacturing method according to the comparative example can be described in most of the same way as the battery cell manufacturing method according to the above-described embodiment of the present invention, with the difference being that the pressurizing step (S30) is performed before the formation step (S40), and the description will focus on this difference.

[0062] Referring to FIG. 4, unlike FIG. 1, the pressurizing step (S30) may be performed before the formation step (S40). In this case, the pressurizing step (S30) may be a step of pressurizing a battery cell (100) in which the pre-aging step (S20) has been performed.

[0063] In particular, the pressurizing step (S30) can increase wet adhesiveness between interfaces between components of the battery cell (100) by pressurizing the battery cell (100) according to a predetermined temperature and pressure range, and can prevent cell bending of the battery cell (100).

[0064] However, as described above, in the battery cell manufacturing method according to the comparative example, since the pressurizing step (S30) is performed before the formation step (S40), the wet adhesive force between the interfaces between the components of the battery cell (100) is relatively high due to the pressurizing step (S30). If the formation step (S40) is performed in a state where the wet adhesive force between the interfaces between the components of the battery cell (100) is relatively high, sufficient porous space is not secured at the interfaces between the components in the formation step (S40), and thus the wettability of the electrode may be reduced, lithium (Li) precipitation, and the dog-bone phenomenon may be aggravated.

[0065] In this way, referring to FIG. 4, in the case of a battery cell manufacturing method such as a comparative example, the temperature and pressure ranges in the pressurizing step (S30) cannot but be set relatively low in consideration of the wet adhesive force between the interfaces between the components of the battery cell (100) in the formation step (S40), and it is difficult to effectively prevent the cell bending phenomenon of the battery cell (100).

[0066] In contrast, referring to FIGS. 1 to 3, in the battery cell manufacturing method according to the present embodiment, since the second formation step (S400) is performed after the first formation step (S300), there is no need to consider the wet adhesive force between the interfaces between the components of the battery cell (100) in the first formation step (S300), and the temperature and pressure ranges in the second formation step (S400) can be set to a level that can effectively prevent the cell bending phenomenon of the battery cell (100). That is, since the second formation step (S400) is performed after the first formation step (S300), the cell bending phenomenon that may occur in the first formation step (S300) can be effectively prevented, while preventing a decrease in the wetting of the electrode, lithium (Li) precipitation, and the dog-bone phenomenon.

[0067] A secondary battery according to another embodiment of the present invention may include a battery cell manufactured using the battery cell manufacturing method described above. In addition, the battery cells may be included in a battery module in a stacked form, and one or more of the battery modules may be packaged in a pack case to form a battery pack. In addition, the battery cells may be directly packaged in a pack case in a stacked form to form a battery pack, and some of the components of the battery module unit may be omitted.

[0068] The battery pack described above can be applied to various devices. These devices include electric bicycles, electric vehicles, hybrid vehicles, and other transportation vehicles. However, the present invention is not limited thereto, and can be applied to various devices that utilize battery modules and battery packs containing the same, which also fall within the scope of the present invention.

[0069]

[0070] Hereinafter, the present invention will be described through more specific examples. However, the following examples are provided to exemplify the present invention, and the scope of the present invention is not limited thereto.

[0071]

[0072] <Manufacturing Example>

[0073] LiNi1 / 3Mn1 / 3Co1 / 3O4, conductive agent (carbon black), and binder (SBR / CMC, 70:30 weight ratio) were added to DI water at a weight ratio of 90: 5: 5, respectively, and mixed to prepare a cathode mixture. The prepared cathode mixture was coated on a 20 μm thick aluminum foil as a cathode current collector to a thickness of 60 μm, and then dried to prepare a cathode. A lithium metal thin film (160 μm thick) was used as the anode.

[0074] A stack-type electrode assembly was manufactured by interposing a separator (polyethylene material separator, thickness: 20 μm) between the cathode and the anode. Here, the electrode assembly was manufactured by sequentially stacking and laminating the manufactured cathode / separator / cathode.

[0075] After placing the manufactured electrode assembly inside a pouch-type battery case, an electrolyte was injected and a sealed battery cell was manufactured. Here, the electrolyte is an electrolyte in which 1M LiPF6 is dissolved in an organic solvent containing ethyl carbonate (EC) and ethyl methyl carbonate (EMC) in a composition of 3:7 (volume ratio).

[0076]

[0077] <Example>

[0078] A pre-aging step was performed in which the battery cell manufactured according to the above manufacturing example was stored at a temperature of 25 degrees Celsius for 72 hours.

[0079] Afterwards, the first formation step was performed to charge and discharge the battery cells that had undergone the pre-aging step at a C-rate of 0.2 to 1.0 and an SOC of 60%. Here, the first formation step was performed at a temperature of 55 degrees Celsius and a pressure of 0.2 kgf / cm - 2 5kgf / cm - 2 This is a jig formation step in which jig pressurization of the battery cell is performed simultaneously with the pressure of the jig.

[0080] Afterwards, the battery cell on which the first formation step was performed was subjected to a temperature of 70 degrees Celsius and a pressure of 3 kgf / cm 2 The second formation stage, pressurized with pressure, was performed for 1 hour.

[0081] Afterwards, the battery cells on which the second formation step was performed were subjected to an aging step of storing them at a temperature of 60 degrees Celsius for 24 hours.

[0082] Afterwards, a degassing step was performed to unseal the battery cell, and then the battery cell was resealed to manufacture the battery cell.

[0083]

[0084] <Comparative Example>

[0085] The battery cell of the comparative example can be manufactured in the same manner as the embodiment, except that a pressurizing step is performed to pressurize the battery cell on which the pre-aging step has been performed, an aging step is performed to store the battery cell on which the pressurizing step has been performed, and a separate manual additional pressurizing process is performed after the aging step and before the degassing step.

[0086]

[0087] <Experimental Example 1: Checking for Bending of Battery Cells>

[0088] Some of the battery cells manufactured in the examples and comparative examples were photographed in an enlarged manner, and the results are shown in Fig. 5. Fig. 5 (a) is a drawing showing the results for the comparative example according to Experimental Example 1, and (b) is a drawing showing the results for the example according to Experimental Example 1.

[0089] Referring to Fig. 5(a), it can be confirmed that the battery cell manufactured in the comparative example has a shape in which the center of the battery cell is bent toward the floor, indicating that a cell bending phenomenon has occurred. In contrast, referring to Fig. 5(b), it can be confirmed that the battery cell manufactured in the example does not have a center of the battery cell bent toward the floor, indicating that the cell bending phenomenon does not occur or is relatively suppressed.

[0090] Accordingly, when bending was confirmed based on the outer surface of the battery cells of the examples and comparative examples as in Experimental Example 1, it was confirmed that, unlike the comparative examples, the battery cells according to the examples did not exhibit cell bending or that the cell bending phenomenon was relatively suppressed.

[0091]

[0092] <Experimental Example 2_Checking the Bending Degree of Battery Cells>

[0093] The degree of bending of the battery cells was calculated based on the outer surface of the battery cells manufactured in the examples and comparative examples, and the results are shown in Fig. 6. Fig. 6 (a) is a drawing showing the results for the comparative examples and examples according to Experimental Example 2.

[0094] Referring to FIG. 6, when the pressurizing step is performed before the formation step (J / F) in the comparative example, it can be confirmed that the bending degree of the battery cell is relatively high, as the bending degree in the formation step (J / F) and the aging step (Aging) is 1.95 mm and 2.8 mm on average. In particular, it can be confirmed that the bending degree is particularly high, as the bending degree of the battery cell in the aging step (Aging) in the comparative example is 2.8 mm on average, and the maximum value is 4 mm. That is, in the case of the comparative example, it can be confirmed that a uniform wet adhesive force is not formed at the interface between the negative electrode and the separator and / or the interface between the positive electrode and the separator after the formation step (J / F) and the aging step (Aging) are performed.

[0095] In addition, if an additional pressurizing process is performed through a separate manual operation before the degassing step (DGS), it can be confirmed that the bending degree is reduced to an average of 0.925 mm in the degassing step (DGS), as shown in Fig. 6. However, in this case, there is a problem in that it takes a considerable amount of process time and there is a risk that the appearance of the battery cell may be damaged.

[0096] In contrast, referring to FIG. 6, when pressurization of the battery cell is performed through the second formation step after the first formation step (J / F) and before the aging step (Aging) as in the embodiment, it can be confirmed that the bending degree of the battery cell is relatively low, as the bending degree in the first formation step (J / F) and the aging step (Aging) is 1.025 mm and 0.75 mm on average. That is, in the case of the embodiment, it can be confirmed that after the first formation step (J / F) and the aging step (Aging) are performed, a uniform wet adhesive force is sufficiently formed at the interface between the negative electrode and the separator and / or the interface between the positive electrode and the separator.

[0097] In addition, in the subsequent degassing step (DGS), it can be confirmed that the bending degree of the battery cell is lowered, with an average bending degree of 0.125 mm. In particular, in the case of the embodiment, it can be confirmed that the bending degree of the battery cell is sufficiently small even without performing a separate manual additional pressurization process like the comparative example. That is, unlike the comparative example, the embodiment can omit a separate manual additional pressurization process, thereby shortening the process time and preventing the risk of damage to the appearance of the battery cell.

[0098] Accordingly, when the degree of bending was confirmed based on the outer surface of the battery cells of the examples and comparative examples as in Experimental Example 2, it was confirmed that, unlike the comparative examples, the battery cells according to the examples did not experience cell bending or that the cell bending phenomenon was relatively suppressed without any additional manual pressing process.

[0099]

[0100] <Experimental Example 3_ Confirmation of lithium (Li) precipitation and dog-bone phenomenon on electrodes>

[0101] After disassembling the battery cells manufactured in the examples and comparative examples, the occurrence of lithium (Li) precipitation and dog-bone phenomenon in the electrodes was checked based on the positive and negative electrodes, and the results are shown in Figs. 7 and 8. Fig. 7 (a) is a drawing showing the results for the negative electrode of the comparative example according to Experimental Example 3, and (b) is a drawing showing the results for the negative electrode of the example according to Experimental Example 3. Fig. 8 (a) is a drawing showing the results for the positive electrode of the comparative example according to Experimental Example 3, and (b) is a drawing showing the results for the positive electrode of the example according to Experimental Example 3.

[0102] Referring to FIG. 7 (a) and FIG. 7 (b), it can be confirmed that in the battery cell manufactured in the comparative example, there is no significant difference from the embodiment in the case of the negative electrode.

[0103] In contrast, referring to FIGS. 8 (a) and 8 (b), in the battery cell manufactured in the comparative example, it can be confirmed that, unlike in the embodiment, a dog-bone-like shape appears on the surface of the positive electrode. In contrast, in the battery cell manufactured in the embodiment, it can be confirmed that, unlike in the comparative example, no separate shape appears on the surface of the positive electrode.

[0104] Accordingly, when the occurrence of Li precipitation and dog-bone phenomenon was confirmed based on the positive and negative electrodes inside the battery cells of the examples and comparative examples as in Experimental Example 3, it was confirmed that, unlike the comparative examples, the battery cells according to the examples did not cause Li precipitation and dog-bone phenomenon or that the phenomenon was relatively suppressed.

[0105] That is, in the case where the pressurization step is performed before the first formation step (J / F) as in the comparative example, it can be confirmed that the levels of adhesive strength between the negative electrode and the separator interface and the wet adhesive strength between the positive electrode and the separator interface are different based on whether Li precipitation and the dog-bone phenomenon occur. In addition, it can be confirmed that in the comparative example, bending of the battery cell occurs in the aging step that is performed after the formation step due to this difference in the level of wet adhesive strength.

[0106] In contrast, when pressurization of the battery cell is performed through the second formation step after the first formation step (J / F) and before the aging step (Aging) as in the embodiment, it can be confirmed that the wet adhesion between the negative electrode and the separator interface and the wet adhesion between the positive electrode and the separator interface are at similar levels based on whether Li precipitation and the dog-bone phenomenon occur. In addition, in the embodiment, it can be confirmed that sufficient wet adhesion is developed between the negative electrode and the separator interface and the positive electrode and the separator interface, so that bending of the battery cell does not occur in the aging step performed after the second formation step.

[0107]

[0108] Although the preferred embodiments of the present invention have been described in detail above, the scope of the present invention is not limited thereto, and various modifications and improvements made by those skilled in the art using the basic concept of the present invention defined in the following claims also fall within the scope of the present invention.

Claims

1. A battery cell assembly step of mounting an electrode assembly including a positive electrode, a negative electrode, and a separator interposed between the positive electrode and the negative electrode into a receiving portion of a battery case; A pre-aging step of storing the above battery cells at a first temperature; A first formation step of charging and discharging the above battery cells; A second formation step in which only pressurization is performed on the battery cell on which charging and discharging have been performed; and An aging step is included in which the pressurized battery cell is stored at a second temperature. A method for manufacturing a battery cell, wherein the second temperature is in a range higher than the first temperature.

2. In paragraph 1, The above second formation stage is 1kgf / cm 2 Above 10kgf / cm 2 A method for manufacturing a battery cell, the method comprising:

3. In paragraph 1, A method for manufacturing a battery cell, wherein the second formation step is performed at a temperature equal to or higher than the temperature of the first formation step.

4. In paragraph 3, A method for manufacturing a battery cell, wherein the first formation step and the second formation step are performed at a temperature of 30 degrees Celsius or higher and 80 degrees Celsius or lower.

5. In paragraph 4, A method for manufacturing a battery cell, wherein the second formation step is performed at a temperature greater than the temperature of the first formation step.

6. In paragraph 1, The above first formation step is performed while the battery cell is pressurized, A method for manufacturing a battery cell, wherein the second formation step is performed at a pressure equal to or greater than the pressure of the first formation step.

7. In paragraph 6, The above first formation stage is, A battery cell manufacturing method performed in a state where the battery cell is positioned between a pair of jigs and the upper and lower parts of the battery cell are pressurized by the pair of jigs.

8. In paragraph 7, A battery cell manufacturing method wherein the second formation step is performed without releasing the pressurization in the first formation step.

9. In paragraph 6, The above first formation step is 0.01 kgf / cm 2 Above 10kgf / cm 2 It is performed under the following pressures: The above second formation stage is 1kgf / cm 2 Above 10kgf / cm 2 A method for manufacturing a battery cell, the method comprising:

10. In Article 9, A method for manufacturing a battery cell, wherein the second formation step is performed at a pressure greater than the pressure of the first formation step.

11. In paragraph 1, A method for manufacturing a battery cell, wherein the second formation step is performed for a time period of 0.5 hours or more and 5 hours or less.

12. In paragraph 1, The above first temperature is a temperature of 10 degrees Celsius or more and 50 degrees Celsius or less, A method for manufacturing a battery cell, wherein the second temperature is a temperature of 30 degrees Celsius or more and 100 degrees Celsius or less.

13. In paragraph 1, A method for manufacturing a battery cell, wherein a degassing step is further performed after the above aging step.

14. A secondary battery including a battery cell manufactured by the battery cell manufacturing method of paragraph 1.

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