Battery cell manufacturing method

Abstract

A battery manufacturing method according to one embodiment of the present invention includes a battery cell assembly step of attaching an electrode assembly including a positive electrode, a negative electrode, and a separation membrane interposed between the positive electrode and the negative electrode to a housing 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 applying pressure only to the battery cell after charging and discharging; and an aging step of storing the pressurized battery cell at a second temperature, wherein the second temperature may be in a range of or greater than the first temperature.

Description

[Technical Field]

[0001] [Cross-reference of related applications] This application claims priority rights based on Korean Patent Application No. 10-2023-0164672 dated November 23, 2023, and Korean Patent Application No. 10-2024-0163999 dated November 18, 2024, and all content disclosed in the documents of said Korean Patent Applications is incorporated herein as part of this specification.

[0002] The present invention relates to a battery cell manufacturing method, and more specifically, to a battery cell manufacturing method that prevents the bending phenomenon of battery cells without requiring a separate manual pressing process. [Background technology]

[0003] As technological development and demand for mobile devices increase, the demand for rechargeable batteries as an energy source is rapidly growing. Among these rechargeable batteries, lithium-ion batteries, which have high energy density and voltage, long cycle life, and low self-discharge rate, have been commercialized and are widely used.

[0004] Such secondary batteries are classified into cylindrical and rectangular batteries, in which the electrode assembly is housed in a cylindrical or rectangular metal can, and pouch 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. The electrode assembly housed in the battery case is a power generation element capable of charging and discharging, comprising a positive electrode, a negative electrode, and a separation membrane structure interposed between the positive and negative electrodes. It is classified into a jelly roll type, in which a long sheet-type positive electrode coated with an active material is wound with a separation membrane interposed between the positive and negative electrodes, and a stack type, in which a number of positive and negative electrodes are sequentially stacked with a separation membrane interposed between them.

[0005] Among these, pouch-type batteries, in particular, which have a structure in which stacked or stacked / folding electrode assemblies are housed in a pouch-type battery case made of aluminum laminate sheet, are seeing a gradual increase in usage due to their low manufacturing costs, small weight, and easy deformation.

[0006] When manufacturing pouch-type batteries, if the wet adhesion force at the interface between the separation membrane and the electrode is uneven, cell bending may occur after the activation process. Here, cell bending can be defined as the phenomenon in which the battery cell bends in a predetermined direction. Battery cells that have experienced such cell bending may cause problems such as cell transfer failures in the subsequent battery cell manufacturing process.

[0007] Consequently, conventionally, to resolve the cell bending phenomenon, it was necessary to perform a manual press process to manually pressurize the battery cells 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 battery cells that have already experienced cell bending, it is difficult to completely return the cell to its original state, and there is a problem that the process efficiency decreases as a result of performing the separate pressurization process.

[0008] Therefore, 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. [Overview of the project] [Problems that the invention aims to solve]

[0009] The problem that this invention aims to solve is to provide a battery cell manufacturing method that prevents the bending phenomenon of battery cells without requiring a separate manual pressing process.

[0010] The problems that this invention aims to solve are not limited to those described above, and any problems not mentioned should be clearly understood by a person with ordinary skill in the art to which this invention pertains from this specification and the accompanying drawings. [Means for solving the problem]

[0011] A battery cell manufacturing method according to one embodiment of the present invention includes a battery cell assembly step of attaching an electrode assembly including a positive electrode, a negative electrode, and a separation membrane interposed between the positive electrode and the negative electrode to a housing 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 applying pressure only to the battery cell after charging and discharging; and an aging step of storing the pressurized battery cell at a second temperature, wherein the second temperature may be in a range of or greater than the first temperature.

[0012] The aforementioned second formation step is 1 kgf / cm 2 From the above, 10 kgf / cm² 2 It may be carried out at the following pressures.

[0013] The second formation step may be performed at a temperature that is the same as or higher than the temperature of the first formation step.

[0014] The first and second formation steps may be performed at a temperature between 30 degrees Celsius and 80 degrees Celsius.

[0015] The second formation step may be performed at a temperature higher than that of the first formation step.

[0016] The first formation step is performed while the battery cell is pressurized, and the second formation step may be performed at the same or a higher pressure than that of the first formation step.

[0017] The first forming step may be performed with the battery cell positioned between a pair of jigs and the upper and lower portions of the battery cell being pressed by the pair of jigs.

[0018] The second forming step may be performed without releasing the pressure applied in the first forming step.

[0019] The first forming step is performed at a pressure of 0.01 kgf / cm 2 or more and 10 kgf / cm 2 or less, and the second forming step may be performed at a pressure of 1 kgf / cm 2 or more and 10 kgf / cm 2 or less.

[0020] The second forming step may be performed at a pressure higher than the pressure of the first forming step.

[0021] The second forming step may be performed for a time of 0.5 hours or more and 5 hours or less. <…>0000096

[0022] The first temperature is 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.

[0023] A degassing step may be further performed after the aging step.

[0024] A secondary battery according to another embodiment of the present invention may include a battery cell manufactured by the battery cell manufacturing method described above.

Advantages of the Invention

[0025] The battery cell manufacturing method according to an embodiment of the present invention can prevent the bending phenomenon of the battery cell without requiring a separate manual press process.

[0026] The effects of the present invention are not limited to those described above, and any effects not mentioned should be clearly understood by a person with ordinary skill in the art to which the present invention pertains from this specification and the accompanying drawings. [Brief explanation of the drawing]

[0027] [Figure 1] This flowchart shows a battery cell manufacturing method according to one embodiment of the present invention. [Figure 2] Figure 1 is a perspective view showing the battery cells assembled in the battery cell assembly step. [Figure 3] Figure 2 is a disassembled perspective view of a battery cell. [Figure 4] This is a flowchart showing a battery cell manufacturing method related to a comparative example. [Figure 5(a)] These are the results regarding the comparative example related to Experimental Example 1. [Figure 5(b)] This figure shows the results related to the example of Experimental Example 1. [Figure 6] This figure shows the results for comparative examples and examples related to Experimental Example 2. [Figure 7(a)] This is the result regarding the negative electrode of the comparative example related to Experimental Example 3. [Figure 7(b)] This figure shows the results regarding the negative electrode in the example related to Experimental Example 3. [Figure 8(a)] This is the result regarding the positive electrode of the comparative example related to Experimental Example 3. [Figure 8(b)] This figure shows the results regarding the positive electrode in the example related to Experimental Example 3. [Modes for carrying out the invention]

[0028] The following describes in detail, with reference to the attached drawings, various embodiments of the present invention so that those with ordinary skill in the art to which the present invention pertains can easily implement them. The present invention can be embodied in a variety of different forms and is not limited to the embodiments described herein.

[0029] To clearly explain the present invention, unnecessary explanatory parts have been omitted, and the same or similar reference numerals are used throughout the specification for identical or similar components.

[0030] Furthermore, when a specification states that a certain part "includes" a certain component, unless otherwise stated, this means that it may include other components rather than excluding them.

[0031] Figure 1 is a flowchart illustrating a battery cell manufacturing method according to one embodiment of the present invention. Figure 2 is a perspective view showing the battery cell assembled in the battery cell assembly step of Figure 1. Figure 3 is an exploded perspective view of the battery cell of Figure 2.

[0032] Referring to Figures 1 and 2, a battery cell manufacturing method according to one embodiment of the present invention includes a battery cell assembly step (S100) in which an electrode assembly 200 including a positive electrode, a negative electrode, and a separation membrane interposed between the positive electrode and the negative electrode is attached to a housing portion 300R of a battery case 300; a pre-aging step (S200) in which the battery cell 100 is stored at a first temperature; a first formation step (S300) in which the battery cell 100 is charged and discharged; a second formation step (S400) in which only pressurization is applied to the battery cell 100 that has been charged and discharged; and an aging step (S500) in which the pressurized battery cell 100 is stored at a second temperature, wherein the second temperature may be in a range of or greater than the first temperature.

[0033] Referring to Figures 2 and 3, the battery cell 100 assembled in the battery cell assembly step (S100) is a pouch battery cell and includes an electrode assembly 200 inside the battery case 300. The battery cell 100 also has an external structure in which electrode leads 400 connected to electrode tabs of the electrode assembly 200 are exposed, and lead films 600 are attached to the upper and lower parts of the electrode leads 400.

[0034] The electrode assembly 200 includes a positive electrode, a negative electrode, and a separator membrane. More specifically, the electrode assembly 200 may be constructed by sequentially stacking the positive electrode and the negative electrode with a separator membrane in between, and insulating them from each other. Here, the electrode assembly 200 may be a stacked electrode assembly or a stack / folding electrode assembly. However, the form of the electrode assembly 200 is not limited to this, and any form of electrode assembly including a positive electrode, a negative electrode, and a separator membrane may be included in this embodiment. Furthermore, the positive electrode, negative electrode, and separator membrane may be made of materials generally included in battery cells.

[0035] The electrode leads 400 may include a positive lead connected to a positive tab (not shown) of the electrode assembly 200 and a negative lead connected to a negative tab (not shown) of the electrode assembly 200. However, as shown in Figure 2, the position of the electrode leads 400 is not limited to being located at both ends of the electrode assembly 200, and both the positive and negative leads may be located at one end of the electrode assembly 200.

[0036] In the battery cell assembly step (S100), the battery cell 100 is assembled with the electrode assembly 200 attached to a recessed housing portion 300R formed in the battery case 300, and the electrolyte may be injected into the battery case 300. Alternatively, the first outer peripheral surface 311 formed on the upper surface 310 of the battery case 300 and the second outer peripheral surface 321 formed on the lower surface 320 of the battery case 300 may be heat-fused to each other to form a sealing portion 300S. However, the sealing portion 300S in the battery cell assembly step (S100) may be in a temporarily sealed state, and when the degassing step (S600), described later, is performed, the sealing portion 300S may be resealed after the battery cell 100 is released again.

[0037] Here, the electrolyte can be, but is not limited to, organic liquid electrolytes, inorganic liquid electrolytes, solid polymer electrolytes, gel-type polymer electrolytes, solid inorganic electrolytes, or molten inorganic electrolytes that can be used in the manufacture of lithium secondary batteries.

[0038] Specifically, the electrolyte may include an organic solvent and a lithium salt. The organic solvent is not particularly limited as long as it can serve as a medium through which ions involved in the electrochemical reaction of the battery can move. The lithium salt is not particularly limited as long as it is a compound that can provide lithium ions used in a lithium secondary battery.

[0039] Referring to Figure 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 between 10 degrees Celsius and 50 degrees Celsius, between 15 degrees Celsius and 40 degrees Celsius, or between 20 degrees Celsius and 30 degrees Celsius. Alternatively, the pre-aging step (S200) may be a step of storing the battery cell 100 at the first temperature for a period of time between 24 hours and 96 hours, between 36 hours and 90 hours, or between 48 hours and 84 hours.

[0040] Referring to FIG. 1, the first formation step (S300) may be a step of charging and discharging the battery cell 100 on which the pre-aging step (S200) has been performed within a predetermined state of charge (SOC) range to activate the battery cell 100. As an example, the first formation step (S300) may be a step of charging within a range of 20% or more to 100% or less, a range of 30% or more to 100% or less, a range of 50% or more to 100% or less, or a range of 80% or more to 100% or less. As an example, the first formation step (S300) may be a step of discharging within a range of 50% or less to 0% or more, a range of 40% or less to 0% or more, a range of 30% or less to 0% or more, or a range of 20% or less to 0% or more. However, the charging and discharging conditions of the first formation step (S300) are not limited to this, and the charging and discharging conditions of other first formation steps (S300) may be set to an appropriate range or conditions according to the electrode active material, the type of battery, the battery characteristics, and the like.

[0041] The first formation step (S300) may be performed in a state where the battery cell 100 is pressurized. As an example, the first formation step (S300) may be a jig formation in which the upper and lower parts of the battery cell 100 are pressurized by a jig.

[0042] More specifically, the first formation step (S300) may be performed in a state where a pressure of 0.01 kgf / cm 2 or more to 10 kgf / cm 2 or less, or 0.02 kgf / cm 2 or more to 5 kgf / cm 2 or less is applied to the battery cell 100. Also, the first formation step (S300) may be performed at a high temperature. As an example, the first formation step (S300) may be performed at a temperature of 30 degrees Celsius or more to eighty degrees Celsius or less, 40 degrees Celsius or more to seventy degrees Celsius or less, or 50 degrees Celsius or more to sixty degrees Celsius or less.

[0043] Referring to Figure 1, in the battery cell manufacturing method according to this embodiment, the second formation step (S400) may be a step of pressurizing the battery cell 100 that has undergone the first formation step (S300) within a predetermined temperature and pressure range.

[0044] Referring to Figure 1, the second formation step (S400) may be performed within a range of temperature and pressure conditions greater than or equal to those of the first formation step (S300). More specifically, the second formation step (S400) may be performed at temperatures between 30 degrees Celsius and 100 degrees Celsius, between 40 degrees Celsius and 90 degrees Celsius, or between 50 degrees Celsius and 80 degrees Celsius. Also, the second formation step (S400) may be performed at a pressure of 1 kgf / cm². 2 From the above, 10 kgf / cm² 2 The following pressure: 1.5 kgf / cm² 2 From the above, 7 kgf / cm² 2 The following pressure: 2 kgf / cm² 2 From the above, 4 kgf / cm² 2 The following pressures may be used. The second formation step (S400) may also be performed for a period of 0.5 hours or more and 5 hours or less within the aforementioned temperature and pressure range.

[0045] As a result, the second formation step (S400) is performed after the first formation step (S300), eliminating the need to consider the degree of wet adhesion at the interfaces between the components in the first formation step (S300), and the temperature and pressure range in the second formation step (S400) may be set relatively higher than that of the first formation step (S300). In particular, the second formation step (S400) can effectively prevent the cell bending phenomenon of the battery cell 100 by increasing the wet adhesion at the interfaces between the components of the battery cell 100 through pressurization applied to the battery cell 100, which has been sufficiently activated in the first formation step (S300), at a relatively high temperature and pressure range.

[0046] In contrast, in the battery cell manufacturing method described in the comparative example (see Figure 4), when the pressurizing step (S30) is performed before the formation step (S40), the pressurizing step (S30) increases the wet adhesion force at the interfaces between the components, which leads to the problem that sufficient porous space is not secured at the interfaces between the components of the battery cell 100 during the formation step (S40). Thus, when sufficient porous space is not secured at the interfaces between the components during the formation step (S40), problems arise such as a decrease in electrode wettability, lithium (Li) deposition, and a worsening of the dogbone phenomenon. In this way, in the case of a battery cell manufacturing method like the comparative example, the temperature and pressure range in the pressurizing step (S30) must be set relatively low to account for the wet adhesion force at the interfaces between the components of the battery cell 100 during the formation step (S40), making it difficult to effectively prevent the cell bending phenomenon of the battery cell 100.

[0047] Furthermore, the second formation step (S400) may be performed without releasing the pressure applied in the first formation step (S300). In other words, unlike the first formation step (S300), the second formation step (S400) may be a step that maintains the state in which the battery cell 100 is pressurized in the first formation step (S300) without any separate charging or discharging taking place.

[0048] As a result, in the battery cell manufacturing method according to this embodiment, the second formation step (S400) uses the same pressurizing equipment as in the first formation step (S300), thus preventing the process from becoming more complex due to the addition of the second formation step (S400), and also has the advantage of maintaining a constant pressurized environment for the battery cell 100.

[0049] Referring to Figure 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 greater 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 between 40 degrees Celsius and 80 degrees Celsius, between 50 degrees Celsius and 70 degrees Celsius, or between 55 degrees Celsius and 65 degrees Celsius. Alternatively, the aging step (S500) may be a step of storing the battery cell 100 at the second temperature range for a period of 12 hours to 48 hours or between 18 hours and 36 hours.

[0050] As a result, in the battery cell manufacturing method according to this embodiment, by performing the aging step (S500) within the aforementioned temperature and time range, the electrolyte can be uniformly dispersed inside the battery cell 100, and the SEI film can be formed more stably.

[0051] Referring to Figure 1, in the battery cell manufacturing method according to this embodiment, a degassing step (S600) may be performed after the aging step (S500). More specifically, the degassing step (S600) may be a step to release the seal of the sealing portion 300S formed in the aforementioned battery cell assembly step (S100) and discharge the gas generated inside the battery cell 100 to the outside. Alternatively, the battery case 300 opened in the degassing step (S600) may be sealed again by forming the sealing portion 300S again, thereby sealing the battery cell 100.

[0052] Figure 4 is a flowchart showing a battery cell manufacturing method according to a comparative example.

[0053] Referring to Figure 4, the battery cell manufacturing method according to the 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 much the same way as the battery cell manufacturing method according to one embodiment of the present invention described above, with the difference being that the pressurizing step (S30) is performed before the formation step (S40), and this difference will be explained in detail.

[0054] Referring to Figure 4, unlike in Figure 1, the pressurizing step (S30) may be performed before the formation step (S40). In this case, the pressurizing step (S30) may be a step in which the battery cell 100 that has undergone the pre-aging step (S20) is pressurized.

[0055] In particular, the pressurizing step (S30) can increase the wet adhesion at the interfaces between the components of the battery cell 100 by pressurizing the battery cell 100 within a predetermined temperature and pressure range, thereby preventing the cell bending phenomenon of the battery cell 100.

[0056] However, as mentioned above, in the battery cell manufacturing method relating to the comparative example, the pressurizing step (S30) is performed before the formation step (S40), resulting in a relatively high wet adhesion force at the interfaces between the components of the battery cell 100. When the formation step (S40) is performed with a relatively high wet adhesion force at the interfaces between the components of the battery cell 100, sufficient porous space cannot be secured at the interfaces between the components during the formation step (S40), which may lead to a decrease in electrode wettability, lithium (Li) deposition, and a worsening of the dogbone phenomenon.

[0057] As shown in Figure 4, in the case of a battery cell manufacturing method like the comparative example, the temperature and pressure range in the pressurizing step (S30) must be set relatively low in the formation step (S40) to take into account the wet adhesion force at the interfaces between the components of the battery cell 100, making it difficult to effectively prevent the cell bending phenomenon of the battery cell 100.

[0058] In contrast, as shown in Figures 1 to 3, in the battery cell manufacturing method according to this embodiment, the second formation step (S400) is performed after the first formation step (S300), eliminating the need to consider the wet adhesion force at the interfaces between the components of the battery cell 100 in the first formation step (S300), and the temperature and pressure range in the second formation step (S400) may be set to an extent that effectively prevents the cell bending phenomenon of the battery cell 100. In other words, by performing the second formation step (S400) after the first formation step (S300), it is possible to effectively prevent the cell bending phenomenon that may occur in the first formation step (S300), as well as prevent a decrease in electrode wettability (Wetting), lithium (Li) deposition, and the dogbone phenomenon.

[0059] Another embodiment of the present invention may include a secondary battery manufactured by the battery cell manufacturing method described above. The battery cells may be included in a battery module in a stacked configuration, and one or more of these battery modules may be packaged in a pack case to form a battery pack. Alternatively, the battery cells may be directly packaged in a pack case in a stacked configuration to form a battery pack, and some of the components of the battery module unit may be omitted.

[0060] The aforementioned battery pack can be applied to a variety of devices. Such devices can be used as means of transport, such as electric bicycles, electric vehicles, and hybrid vehicles. However, the present invention is not limited thereto and is applicable to a variety of devices that use battery modules and battery packs containing them, and this also falls within the scope of the present invention.

[0061] The present invention will be described below through more specific examples, but these examples are for illustrative purposes only and do not limit the scope of the present invention.

[0062] <Manufacturing example> LiRing 1 / 3 Mn 1 / 3 Co 1 / 3 O4, conductive material (carbon black), and binder (SBR / CMC, 70:30 weight ratio) were added to DI water in a weight ratio of 90:5:5 and mixed to produce a positive electrode mixture. The produced positive electrode mixture was used as a positive electrode current collector, coated to a thickness of 60 μm on 20 μm thick aluminum foil, and then dried to produce the positive electrode. A lithium metal thin film (160 μm thick) was used as the negative electrode.

[0063] A stacked electrode assembly was manufactured by interposing a separation membrane (polyethylene material separation membrane, thickness: 20 μm) between the negative electrode and the positive electrode. Here, the electrode assembly was manufactured by sequentially stacking and laminating the manufactured positive electrode / separation membrane / negative electrode.

[0064] After the manufactured electrode assembly was placed inside the pouch-type battery case, an electrolyte solution was injected to produce a temporarily sealed battery cell. The electrolyte solution was an organic solvent mixture of ethyl carbonate (EC) and ethyl methyl carbonate (EMC) in a 3:7 (volume ratio) composition, in which 1M LiPF6 was dissolved.

[0065] <Examples> The battery cells manufactured according to the above manufacturing example were subjected to a pre-aging step in which they were stored at a temperature of 25 degrees Celsius for 72 hours.

[0066] Subsequently, a first formation step was performed in which the battery cells that had undergone the pre-aging step were charged and discharged to a C-rate of 0.2 to 1.0 and a SOC of 60%. Here, the first formation step was performed at a temperature of 55 degrees Celsius and a load of 0.2 kgf / cm². 2 From 5 kgf / cm² 2 This is a jig formation step in which jig pressurization is simultaneously performed on the battery cells with the specified pressure.

[0067] Subsequently, the battery cells that underwent the first formation step were subjected to a temperature of 70 degrees Celsius at 3 kgf / cm². 2 The second formation step, which involves applying pressure, was performed for one hour.

[0068] Subsequently, the battery cells that underwent the second formation step were subjected to an aging step, in which they were stored at a temperature of 60 degrees Celsius for 24 hours.

[0069] Afterward, a degassing step was performed to release the seal from the battery cell, and then it was resealed to manufacture the battery cell.

[0070] <Comparative Example> The comparative battery cells can be manufactured in the same manner as the examples, except that a pressurizing step is performed to pressurize the battery cells that have undergone the pre-aging step, an aging step is performed to store the pressurized battery cells, and an additional manual pressurizing step is performed after the aging step and before the degassing step.

[0071] <Experimental Example 1: Confirmation of the presence or absence of bending in battery cells> Magnified images of parts of the battery cells manufactured in the examples and comparative examples are shown in Figures 5(a) and 5(b). Figure 5(a) shows the results for the comparative example related to Experimental Example 1, and (b) shows the results for the example related to Experimental Example 1.

[0072] Referring to Figure 5(a), it can be seen that the battery cell manufactured in the comparative example exhibits cell bending, as the center of the battery cell is curved towards the bottom. In contrast, referring to Figure 5(b), it can be seen that the battery cell manufactured in the example does not exhibit cell bending, or at least the cell bending phenomenon is relatively suppressed, as the center of the battery cell is not curved towards the bottom.

[0073] As a result, as in Experimental Example 1, when the presence or absence of bending is checked based on the outer surface of the battery cells of the Example and the Comparative Example, it can be confirmed that, unlike the Comparative Example, the cell bending phenomenon does not occur or is relatively suppressed in the battery cell of the Example.

[0074] <Experimental Example 2: Confirmation of the degree of battery cell bending> 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 Figure 6. Figure 6 shows the results for the comparative examples and examples related to Experimental Example 2.

[0075] Referring to Figure 6, it can be seen that in the comparative example, when the pressurization step is performed before the formation step (J / F), the degree of bending in the formation step (J / F) and the aging step (Aging) is relatively high, with an average of 1.95 mm and 2.8 mm, respectively. In particular, it can be seen that the degree of bending in the aging step (Aging) in the comparative example is relatively high, with an average of 2.8 mm and a maximum of 4 mm. In other words, in the comparative example, it can be seen that a uniform wet adhesion force is not formed at the interface between the negative electrode and the separation membrane and / or the interface between the positive electrode and the separation membrane after the formation step (J / F) and the aging step (Aging).

[0076] Furthermore, if an additional manual pressurization process is performed prior to the degassing step (DGS), it can be confirmed that the degree of bending in the degassing step (DGS) is reduced to an average of 0.925 mm, as shown in Figure 6. However, this method has the drawbacks of requiring a considerable amount of processing time and carrying the risk of damaging the external shape of the battery cells.

[0077] In contrast, referring to Figure 6, as in the example, when pressurization is applied to the battery cell through the second formation step after the first formation step (J / F) and before the aging step (Aging), the degree of bending in the first formation step (J / F) and aging step (Aging) is 1.025 mm and 0.75 mm on average, respectively, indicating that the degree of bending of the battery cell is relatively low. In other words, in the example, it can be confirmed that after the first formation step (J / F) and aging step (Aging) are performed, a uniform wet adhesion force is sufficiently formed at the interface between the negative electrode and the separation membrane and / or the interface between the positive electrode and the separation membrane.

[0078] Furthermore, the degree of bending of the battery cells is confirmed to be even lower, as the average bending degree of the battery cells is 0.125 mm during the subsequent degassing step (DGS). In particular, in the example, it can be confirmed that the degree of bending of the battery cells is sufficiently small even without performing an additional manual pressurization step as in the comparative example. In other words, unlike the comparative example, the example can omit an additional manual pressurization step, thereby shortening the process time and preventing the risk of damage to the external shape of the battery cells.

[0079] As a result, as in Experimental Example 2, when the degree of bending is checked based on the outer surface of the battery cells of the Example and the Comparative Example, it can be confirmed that, unlike the Comparative Example, the battery cell of the Example does not exhibit cell bending, or the cell bending phenomenon is relatively suppressed, even without an additional manual pressurization process.

[0080] <Experimental Example 3: Confirmation of lithium (Li) deposition on electrodes and the occurrence of the dogbone phenomenon> After disassembling the battery cells manufactured in the examples and comparative examples, the presence or absence of lithium (Li) deposition and dogbone phenomenon on the electrodes was checked, with the positive and negative electrodes as references. The results are shown in Figures 7(a), 7(b), 8(a), and 8(b). Figure 7(a) shows the results for the negative electrode of the comparative example related to Experimental Example 3, and (b) shows the results for the negative electrode of the example related to Experimental Example 3. Figure 8(a) shows the results for the positive electrode of the comparative example related to Experimental Example 3, and (b) shows the results for the positive electrode of the example related to Experimental Example 3.

[0081] Referring to Figures 7(a) and 7(b), it can be seen that the battery cells manufactured in the comparative example do not differ significantly from those in the example in the case of the negative electrode.

[0082] In contrast, as can be seen by referring to Figures 8(a) and 8(b), in the case of the battery cell manufactured in the comparative example, a dogbone-like phenomenon appeared on the surface of the positive electrode, unlike in the example. In contrast, in the case of the battery cell manufactured in the example, unlike in the comparative example, no other phenomenon appeared on the surface of the positive electrode.

[0083] As a result, as in Experimental Example 3, when the presence or absence of Li deposition and the occurrence of the dogbone phenomenon are checked based on the positive and negative electrodes inside the battery cells of the Example and Comparative Example, it can be confirmed that, unlike the Comparative Example, the battery cell of the Example does not experience Li deposition and the dogbone phenomenon, or at least these phenomena are relatively suppressed.

[0084] In other words, as in the comparative example, when the pressurization step is performed before the first formation step (J / F), it can be confirmed that the levels of wet adhesion at the interface between the negative electrode and the separation membrane and the interface between the positive electrode and the separation membrane differ, depending on whether or not Li deposition and the dogbone phenomenon occur. Furthermore, in the comparative example, it can be confirmed that bending of the battery cell occurs in the aging step performed after the formation step due to this difference in the level of wet adhesion.

[0085] In contrast, as in the example, when pressure is applied to the battery cell through the second formation step after the first formation step (J / F) and before the aging step (Aging), it can be confirmed that the wet adhesion strength at the interface between the negative electrode and the separation membrane and the wet adhesion strength at the interface between the positive electrode and the separation membrane are of similar levels, based on the presence or absence of Li deposition and the occurrence of the dogbone phenomenon. Furthermore, in the example, sufficient wet adhesion strength is exhibited at the interfaces between the negative electrode and the separation membrane and the interfaces between the positive electrode and the separation membrane, and it can be confirmed that bending of the battery cell does not occur in the aging step performed after the second formation step.

[0086] Although preferred embodiments of the present invention have been described in detail above, the scope of the present invention is not limited thereto. Various modifications and improvements by those skilled in the art, using the basic concepts of the present invention as defined in the following claims, also fall within the scope of the present invention.

Claims

1. A battery cell assembly step involves attaching an electrode assembly, including a positive electrode, a negative electrode, and a separator membrane interposed between the positive and negative electrodes, to the housing of a battery case; A pre-aging step in which the battery cell is stored at a first temperature; A first formation step of charging and discharging the aforementioned battery cell; A second formation step in which only pressure is applied to the battery cell that has been charged and discharged; and The process includes an aging step of storing the pressurized battery cell at a second temperature, A battery cell manufacturing method wherein the second temperature is in a range equal to or greater than the first temperature.

2. The second formation step is 1 kgf / cm ２ From the above, 10 kgf / cm² ２ The battery cell manufacturing method according to claim 1, performed at the following pressure.

3. The battery cell manufacturing method according to claim 1, wherein the second formation step is performed at a temperature that is the same as or higher than the temperature of the first formation step.

4. The battery cell manufacturing method according to claim 3, wherein the first formation step and the second formation step are performed at a temperature between 30 degrees Celsius and 80 degrees Celsius.

5. The battery cell manufacturing method according to claim 4, wherein the second formation step is performed at a temperature higher than the temperature of the first formation step.

6. The first formation step is performed with the battery cell under pressure. The battery cell manufacturing method according to claim 1, wherein the second formation step is performed at a pressure equal to or greater than the pressure of the first formation step.

7. The aforementioned first formation step is, The battery cell manufacturing method according to claim 6, wherein the battery cell is positioned between a pair of jigs, and the upper and lower parts of the battery cell are pressed against the pair of jigs.

8. The battery cell manufacturing method according to claim 7, wherein the second formation step is performed while the pressure applied in the first formation step has not been released.

9. The first formation step is 0.01 kgf / cm ２ From the above, 10 kgf / cm² ２ The following pressures are used: The second formation step is 1 kgf / cm ２ From the above, 10 kgf / cm² ２ The battery cell manufacturing method according to claim 6, performed at the following pressure.

10. The battery cell manufacturing method according to claim 9, wherein the second formation step is performed at a pressure greater than the pressure of the first formation step.

11. The battery cell manufacturing method according to claim 1, wherein the second formation step is performed for a period of time from 0.5 hours to 5 hours.

12. The first temperature is a temperature between 10 degrees Celsius and 50 degrees Celsius. The battery cell manufacturing method according to claim 1, wherein the second temperature is a temperature between 30 degrees Celsius and 100 degrees Celsius.

13. The battery cell manufacturing method according to claim 1, wherein a degassing step is further performed after the aging step.

14. A secondary battery comprising a battery cell manufactured by the battery cell manufacturing method described in any one of claims 1 to 13.

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