Secondary battery and manufacturing method thereof

Abstract

According to one embodiment of the present invention, a method for manufacturing a secondary battery includes: a step of manufacturing an electrode assembly in which electrodes and separators are alternately stacked, and an adhesive is applied to at least one surface of the electrodes and the separators to bond the electrodes and the separators to each other; and a step of manufacturing a battery cell in which the electrode assembly is placed in a pouch case together with an electrolyte and the pouch case is sealed, and at least a portion of the adhesive dissolves in the electrolyte, forming an adhesive mark on the separator.

Description

[Technical Field]

[0001] [Cross-reference to related applications] This application claims the benefit of priority based on Korean Patent Application No. 10-2020-0155000 filed on November 18, 2020, and Korean Patent Application No. 10-2021-0124053 filed on September 16, 2021, and all contents disclosed in the documents of said Korean patent applications are incorporated herein by reference.

[0002] The present invention relates to a secondary battery and a manufacturing method thereof, which is a method for preventing electrodes or separators from coming off from their designated positions when manufacturing a unit cell by laminating electrodes and separators. In particular, the present invention relates to a secondary battery and a manufacturing method thereof, which can reduce production costs compared to conventional methods for manufacturing basic unit cells by lamination, reduce process defects caused by high heat and pressure, and prevent battery performance degradation. [Background technology]

[0003] Generally, secondary batteries are classified into nickel-cadmium batteries, nickel-metal hydride batteries, lithium-ion batteries, and lithium-ion polymer batteries. These secondary batteries are used not only in small products such as digital cameras, DVD players, MP3 players, mobile phones, PDAs, portable game devices, power tools, and e-bikes, but also in large products that require high output, such as electric vehicles and hybrid vehicles, as well as in power storage devices and backup power storage devices that store surplus generated power and renewable energy.

[0004] To manufacture such a secondary battery, electrode active material slurry is first applied to a positive electrode current collector and a negative electrode current collector to form a positive electrode and a negative electrode, which are then stacked on both sides of a separator to form an electrode assembly of a predetermined shape, and the electrode assembly is then placed in a battery case, an electrolyte is injected, and the battery case is sealed.

[0005] Electrode assemblies are classified into various types, such as the simple stack type, in which positive electrodes, separators, and negative electrodes are simply stacked alternately without manufacturing unit cells; the lamination and stack (L&S) type, in which unit cells are first manufactured using positive electrodes, separators, and negative electrodes and then stacked; the stack and folding (S&F) type, in which multiple electrodes or unit cells are attached at a distance to one side of a long separator sheet and the separator sheet is repeatedly folded from one end in the same direction; and the Z-folding type, in which multiple electrodes or unit cells are alternately attached to one side and the other side of a long separator sheet and the separator sheet is repeatedly folded from one end in a specific direction and then in the opposite direction.

[0006] Among these, to manufacture a lamination-and-stack type, stack-and-fold type, or Z-fold type electrode assembly, a unit cell can be manufactured first. Generally, to manufacture a unit cell, a separator is laminated on each of the top and bottom surfaces of a central electrode, and then a top electrode is laminated on the topmost end. Then, a lamination process is performed in which heat and pressure are applied to the laminate in which the electrodes and separator are laminated. By performing this lamination process, the electrodes and separator are bonded to each other, and the unit cell can be firmly formed.

[0007] However, in the past, the electrodes and separators were not bonded to each other but merely in contact with each other before the lamination process was performed on the laminated body in which the electrodes and separators were stacked. Therefore, there was a problem that the electrodes would come off their fixed positions during the process of transporting the laminate to perform the lamination process. Furthermore, the lamination process requires the application of high heat and pressure to the laminate, which can cause damage to the electrodes. Furthermore, while separators that can be bonded to electrodes even with low heat and pressure have recently been developed, they have had problems such as excessively high manufacturing costs, making them uneconomical, and reducing process efficiency.

[0008] On the other hand, one possible way to solve this problem is to fabricate unit cells using an adhesive, but in this case, the adhesive is present on the electrode surface, preventing the electrode from performing its intended function in that area, resulting in a problem of reduced battery performance. Summary of the Invention [Problem to be solved by the invention]

[0009] The present invention has been devised to solve the above problems, and an object of the present invention is to provide a secondary battery and a manufacturing method thereof that prevents electrodes or separators from coming off from their designated positions when electrodes and separators are stacked to manufacture a unit cell.

[0010] In particular, the present invention aims to provide a secondary battery and a manufacturing method thereof that can reduce production costs compared to conventional methods for manufacturing basic unit cells by lamination, reduce the rate of defects in the process caused by high heat and pressure, and prevent deterioration of battery performance. [Means for solving the problem]

[0011] According to one embodiment of the present invention, a method for manufacturing a secondary battery includes: a step of manufacturing an electrode assembly in which electrodes and separators are alternately stacked, and an adhesive is applied to at least one surface of the electrodes and the separators to bond the electrodes and the separators to each other; and a step of manufacturing a battery cell in which the electrode assembly is placed in a pouch case together with an electrolyte and the pouch case is sealed, and at least a portion of the adhesive dissolves in the electrolyte, forming an adhesive mark on the separator.

[0012] The manufacturing step of the battery cell may further include a formation process of activating the battery cell by charging it at a temperature higher than room temperature, and at least a portion of the adhesive may be dissolved in the electrolyte during the formation process.

[0013] The formation process may be carried out at a temperature of 50 degrees Celsius or more and 70 degrees Celsius or less.

[0014] The formation process may include a jig pressing process of pressing both sides of the battery cell (initial cell) using a jig.

[0015] The formation process may be performed at a temperature of 55°C or more and 65°C or less, and the adhesive may be completely dissolved in the electrolyte during the formation process, thereby removing the adhesive located on the electrode surface.

[0016] The adhesive may be an acrylate adhesive, and the electrolyte may be an organic solvent.

[0017] The method for manufacturing a secondary battery may further include manufacturing a radical unit, which is a laminated unit of the electrode and the separator, and the electrode assembly may be manufactured by attaching a fixing tape to a periphery of an electrode laminate formed by stacking a plurality of the radical units.

[0018] The manufacturing step of the basic unit may include the steps of unwinding a lower separation membrane from a lower separation membrane reel; applying adhesive to at least a portion of an upwardly facing surface of the unwound lower separation membrane using a first nozzle; installing a first electrode on the adhesive-applied surface of the lower separation membrane; unwinding an upper separation membrane from an upper separation membrane reel; applying adhesive to at least a portion of an upwardly facing surface of the unwound upper separation membrane using a second nozzle; applying adhesive to at least a portion of an upwardly facing surface of the upper separation membrane using a third nozzle; and installing a second electrode on the adhesive-applied surface of the upper separation membrane after the third nozzle has applied the adhesive.

[0019] The first nozzle, the second nozzle, and the third nozzle may apply adhesive in the form of a plurality of dots.

[0020] The method for manufacturing a secondary battery may further include a step of manufacturing a radical unit in which the separator is folded to cover the electrode and the electrode and the separator are stacked, and the electrode assembly may be manufactured by repeatedly forming the radical unit.

[0021] The manufacturing step of the basic unit body includes the steps of unwinding an electrode sheet from an electrode reel and forming a plurality of electrodes from the electrode sheet; unwinding a separation membrane to be laminated with the electrodes from a separation membrane reel; placing the separation membrane on an upper surface of a table; and applying adhesive to at least a portion of the separation membrane and the electrodes placed on the table using a nozzle, and the electrodes may include a first electrode and a second electrode.

[0022] The method may further include a folding step after the adhesive application step, wherein, in the folding step, when the first electrode is installed on the separator, one side of the separator may be folded to cover the first electrode, and when the second electrode is installed on the separator, the other side of the separator may be folded to cover the second electrode.

[0023] The nozzle may apply the adhesive in the form of multiple dots.

[0024] According to another embodiment of the present invention, a secondary battery includes an electrode assembly in which electrodes and separators are alternately stacked; and a pouch case that contains both the electrode assembly and an electrolyte, wherein the separator has at least one adhesive trace remaining on a surface that contacts the electrode, and the adhesive trace may be a trace of a first adhesive layer formed between the electrode and the separator dissolved in the electrolyte.

[0025] The first adhesive layer may be formed by applying an adhesive in the form of a plurality of dots, and the adhesive application marks may be formed in the form of dots at positions where the first adhesive layer is formed.

[0026] The adhesive may be an acrylate adhesive, and the electrolyte may be an organic solvent.

[0027] The electrodes may include a first electrode and a second electrode, the separator may include an upper separator and a lower separator, and the electrode assembly may have a structure in which the lower separator, the first electrode, the upper separator, and the second electrode are alternately stacked.

[0028] The electrode may include a first electrode and a second electrode, and the electrode assembly may include the first electrode installed on the separator, one side of the separator folded to cover the first electrode, and the second electrode installed on the separator, the other side of the separator folded to cover the second electrode.

[0029] An electrode tab may be formed at one end of the electrode, and a second adhesive layer may be formed between the electrode tab and the separator, and the second adhesive layer may include an adhesive component that is insoluble in the electrolyte solution.

[0030] The second adhesive layer may be formed by applying adhesive in the form of a plurality of dots. [Effects of the Invention]

[0031] The secondary battery and its manufacturing method according to the present invention are a secondary battery and a manufacturing method thereof, which include an electrode assembly in which electrodes and separators are alternately stacked and an adhesive is applied to at least one surface of the electrodes and the separators to bond the electrodes and the separators to each other, and which is housed in a pouch case together with an electrolyte, wherein at least a portion of the adhesive dissolves in the electrolyte to form an adhesive application mark on the separator, and the adhesive application mark does not contain components of the adhesive.

[0032] Therefore, when manufacturing an electrode assembly by stacking electrodes and a separator, the adhesive can prevent the electrodes or separator from coming off from their designated positions. Furthermore, a secondary battery and a manufacturing method thereof can be provided in which the adhesive dissolves in an electrolyte in a battery cell, preventing the adhesive from deteriorating battery performance. [Brief explanation of the drawings]

[0033] [Figure 1] 2 is a flowchart illustrating a method for manufacturing a secondary battery according to an embodiment of the present invention. [Figure 2] 3 is a perspective view illustrating a step of manufacturing a radical unit in a method of manufacturing a secondary battery according to an embodiment of the present invention; [Figure 3] 3A and 3B are front views illustrating a step of manufacturing a radical unit in a method of manufacturing a secondary battery according to an embodiment of the present invention; [Figure 4] 4 is a cross-sectional view illustrating an electrode assembly formed by stacking radical units manufactured in a step of manufacturing a radical unit in a method of manufacturing a secondary battery according to an embodiment of the present invention; [Figure 5] 10 is a cross-sectional view illustrating an electrode assembly formed by stacking radical units manufactured in a step of manufacturing a radical unit in a method of manufacturing a secondary battery according to another embodiment of the present invention. [Figure 6] 4 is a schematic view illustrating a step of manufacturing a radical unit in a method of manufacturing a secondary battery according to another embodiment of the present invention; [Figure 7] 4 is a schematic view illustrating a step of manufacturing a radical unit in a method of manufacturing a secondary battery according to another embodiment of the present invention; [Figure 8] 4 is a schematic view illustrating a step of manufacturing a radical unit in a method of manufacturing a secondary battery according to another embodiment of the present invention; [Figure 9] 4 is a schematic view illustrating a step of manufacturing a radical unit in a method of manufacturing a secondary battery according to another embodiment of the present invention; [Figure 10] 10 is a cross-sectional view illustrating an electrode assembly manufactured by repeatedly forming radical units manufactured in a step of manufacturing a radical unit in a method of manufacturing a secondary battery according to another embodiment of the present invention; [Figure 11] 10 is a cross-sectional view illustrating an electrode assembly manufactured by repeatedly forming radical units manufactured in a step of manufacturing a radical unit in a method of manufacturing a secondary battery according to another embodiment of the present invention; [Figure 12] 10 is an exploded perspective view of a radical unit manufactured in a manufacturing step of a radical unit in a manufacturing method of a secondary battery according to another embodiment of the present invention; [Figure 13] 10 is an exploded perspective view of a radical unit manufactured in a manufacturing step of a radical unit in a manufacturing method of a secondary battery according to another embodiment of the present invention; [Figure 14] 10 is a perspective view illustrating a manufacturing step of an initial cell in a method for manufacturing a secondary battery according to another embodiment of the present invention; [Figure 15] FIG. 10 is a front view illustrating a formation process of a method for manufacturing a secondary battery according to another embodiment of the present invention. [Figure 16] FIG. 10 is a diagram showing adhesive application marks remaining on the surface of the separation membrane. DETAILED DESCRIPTION OF THE INVENTION

[0034] The present invention will be described in detail below with reference to the accompanying drawings, so that those skilled in the art can easily understand the preferred embodiments of the present invention. However, the present invention may be embodied in various different forms and is not limited to the following embodiments.

[0035] In order to clearly explain the present invention, detailed descriptions of parts that are not relevant to the description or related known technologies that 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 for the same or similar components.

[0036] Furthermore, the terms and words used in this specification and claims should not be interpreted in a limited way to their ordinary or dictionary meanings, but should be interpreted in a way that is consistent with the technical idea of ​​the present invention, in accordance with the principle that the inventor himself can appropriately define the concept of terms in order to best explain the invention.

[0037] FIG. 1 is a flowchart showing a method for manufacturing a secondary battery according to an embodiment of the present invention.

[0038] Referring to FIGS. 1 to 3, a method for manufacturing a secondary battery according to an embodiment of the present invention may include a step of manufacturing a basic unit body, a step of manufacturing an electrode assembly, a step of manufacturing an initial cell, and a step of manufacturing a final cell.

[0039] Hereinafter, a method for manufacturing a secondary battery according to an embodiment of the present invention will be described, focusing on a step of manufacturing a radical unit and a step of manufacturing an electrode assembly.

[0040] 2 and 3 are perspective and front views illustrating steps of manufacturing a radical unit in a method for manufacturing a secondary battery according to an embodiment of the present invention.

[0041] First, in this embodiment, the radical unit 10 may be a laminated unit of an electrode and a separator 13. That is, an electrode and a separator 13 are laminated in order to form one radical unit 10, and a plurality of the radical units 10 are stacked to form an electrode laminate 20.

[0042] In the method for manufacturing a secondary battery according to this embodiment, the step of manufacturing a radical unit may be a step of manufacturing a radical unit 10 in which an adhesive 14 is applied to the surface of at least one of an electrode and a separator 13, and the electrode and the separator 13 are adhered to each other.

[0043] 2 and 3, the manufacturing step of the basic unit includes unwinding a lower separator sheet 111 from a lower separator reel 110. Then, a first nozzle 211 applies adhesive 14 to at least a portion of an upwardly facing surface of the unwound lower separator sheet 111. The first nozzle 211 applies the adhesive 14 in the form of a plurality of dots. Next, a first electrode 11 is installed on the surface of the lower separator sheet 111 on which the adhesive 14 has been applied by the first nozzle 211. The first electrode 11 is installed on one surface of the lower separator sheet 111 by cutting the first electrode 11 sheet unwound from the first electrode reel 11-1 to a predetermined size using a first cutter 221. The first electrode 11 and the lower separator can be bonded together by the adhesive 14 applied by the first nozzle 211.

[0044] The method for manufacturing a secondary battery according to this embodiment may include unwinding the upper separator sheet 121 from the upper separator reel 120. When the upper separator sheet 121 is unwound, the second nozzle 212 applies the adhesive 14 to at least a portion of one surface of the unwound upper separator sheet 121 that contacts the first electrode 11. The second nozzle 212 applies the adhesive 14 in the form of a plurality of dots.

[0045] 2, after the second nozzle 212 applies the adhesive 14 to one side of the upper separator sheet 121, one side and the other side of the upper separator sheet 121 are inverted. This is because the adhesive 14 is applied from the top side down, but the side of the upper separator sheet 121 that contacts the first electrode 11 faces downward to contact the first electrode 11, so the state when the adhesive 14 is applied and the state when it is bonded to the first electrode 11 may be upside down.

[0046] Once the upper separator sheet 121 is turned upside down and bonded to the first electrode 11, the third nozzle 213 applies adhesive 14 to at least a portion of the other surface facing upward of the upper separator sheet 121. That is, the third nozzle 213 applies adhesive 14 to the top of the stack in which the lower separator sheet 111, the first electrode 11, and the upper separator sheet 121 are stacked in this order from bottom to top. In this case, the third nozzle 213 applies adhesive 14 in the form of a plurality of dots.

[0047] After the third nozzle 213 applies the adhesive 14, the manufacturing step of the radical unit in the method of manufacturing a secondary battery according to embodiment 1 of the present invention may include a step of installing a second electrode 12 on the other side of the upper separator sheet 121 on which the adhesive 14 is applied. The second electrode 12 may be formed by cutting the second electrode 12 sheet, which is unwound from the second electrode reel 12-1, using the second cutter 222. This allows for a four-layer structure to be formed. That is, after the step of installing the second electrode 12, a four-layer structure laminate 130 may be formed by sequentially stacking the lower separator sheet 111, the first electrode 11, the upper separator sheet 121, and the second electrode 12.

[0048] The method may further include a step of rotating pressure nip rolls 230 disposed on both the upper and lower surfaces of the four-layer laminate 130 to apply pressure to the four-layer laminate 130. The pressure application by the pressure nip rolls 230 can prevent any floating portions from being formed in the four-layer laminate 130. As a result, the electrodes and the separator 13 can be closely bonded to each other.

[0049] 2 and 3, after the step of applying pressure to the four-layered laminate 130, a step of cutting the four-layered laminate 130 at regular intervals with a cutter to form the radical units 10 may be further included. This may involve cutting the upper separator sheet 121 and the lower separator sheet 111 located in the gaps between the electrodes with a third cutter 223 to manufacture the radical units 10.

[0050] According to the step of manufacturing a basic unit in the method for manufacturing a secondary battery according to this embodiment, when electrodes and separators are stacked to manufacture a unit cell (i.e., a basic unit), adhesive 14 is applied in advance each time the electrodes are placed on separator sheets 111 and 121, thereby preventing the electrodes from being displaced without using an expensive separator.

[0051] In addition, since there is no need for a lamination process, the defect rate in the process caused by high heat and pressure can be reduced, and since the laminator can be eliminated, the volume of the unit cell manufacturing equipment can be reduced, simplifying the manufacturing process.

[0052] 4 is a cross-sectional view showing an electrode assembly 1 formed by stacking radical units 10 manufactured in a step of manufacturing a radical unit in a method for manufacturing a secondary battery according to an embodiment of the present invention. FIG. 5 is a cross-sectional view showing an electrode assembly formed by stacking radical units manufactured in a step of manufacturing a radical unit in a method for manufacturing a secondary battery according to another embodiment of the present invention.

[0053] 4, in the method for manufacturing a secondary battery according to the present embodiment, the step of manufacturing an electrode assembly may be a step of manufacturing an electrode assembly 1 by attaching a fixing tape 50 to the periphery of an electrode stack 20 formed by stacking a plurality of radical units 10. Here, the step of manufacturing the electrode assembly may be performed separately from the step of manufacturing the radical units described above, or the step of manufacturing the electrode assembly may include the step of manufacturing the radical units described above.

[0054] Within the basic unit 10, the electrodes 11, 12 and the separator 13 are adhered to one another by the adhesive 14, and therefore the electrodes 11, 12 and the separator 13 can maintain their alignment due to the adhesive strength of the adhesive 14. The stacked basic units 10 can be fixed in relative position by the fixing tape 50 attached to their outer surfaces. That is, the stacked alignment of the basic units 10 can be maintained due to the fixing strength of the fixing tape 50. For reference, the stack state before the fixing tape 50 is attached can be referred to as the electrode stack 20, and the stack state after the fixing tape 50 is attached can be referred to as the electrode assembly 1.

[0055] In addition, in the electrode assembly 1 manufactured in this embodiment, the adhesive 14 is disposed at the same position between each of the electrodes 11 and 12 and the separator 13. For example, as shown in Fig. 4, in the electrode assembly 1 of this embodiment, the adhesive 14 disposed between the lower part of the first electrode 11 and the separator 13 and the adhesive 14 between the upper part of the first electrode 11 and the separator 13 are disposed on the same vertical line based on the bottom surface, and the intervals at which the adhesives 14 are disposed may be the same. This can be similarly explained for the adhesive 14 disposed between the second electrode 12 and the separator 13.

[0056] Therefore, in the electrode assembly 1 manufactured in this embodiment, the adhesive 14 is disposed at the same position between each of the electrodes 11 and 12 and the separator 13, which is advantageous in that the process time and efficiency are increased.

[0057] In an electrode assembly 2 manufactured by a method for manufacturing a secondary battery according to another embodiment of the present invention, adhesives 14 are disposed between the electrodes 11 and 12 and the separator 13, and the adhesives 14 disposed in adjacent layers are disposed in a crossed configuration. For example, as shown in FIG. 5, in the electrode assembly 2 of this embodiment, a first adhesive 14-1 disposed between the lower part of the first electrode 11 and the separator 13 and a second adhesive 14-2 disposed between the upper part of the first electrode 11 and the separator 13 are disposed in a crossed configuration. In this case, the first adhesive 14-1 and the second adhesive 14-2 are simply disposed in crossed positions, and the spacing between them may be the same. This can be similarly explained for the adhesive 14 (14-1) disposed between the second electrode 12 and the separator 13.

[0058] As an example, in the manufacturing step of the basic unit body described above, by adjusting the position of at least one of the first nozzle 211, the second nozzle 212, and the third nozzle 213, the first adhesive 14-1 and the second adhesive 14-2 can be arranged to intersect with each other.

[0059] As another example, in the manufacturing step of the above-described radical unit, another nozzle may be additionally disposed in addition to the first nozzle 211, the second nozzle 212, and the third nozzle 213, so that the first adhesive 14-1 and the second adhesive 14-2 are disposed to cross each other. More specifically, the another nozzle may be disposed at a different position from the first nozzle 211, the second nozzle 212, and the third nozzle 213, so that one of the first adhesive 14-1 and the second adhesive 14-2 is dispensed from the first nozzle 211, the second nozzle 212, and the third nozzle 213, and the other of the first adhesive 14-1 and the second adhesive 14-2 is dispensed from the another nozzle, so that the first adhesive 14-1 and the second adhesive 14-2 are disposed to cross each other.

[0060] However, the present invention is not limited thereto, and the structure in which the first adhesive 14-1 and the second adhesive 14-2 are arranged to cross each other can be manufactured by applying them in various ways.

[0061] Therefore, in the electrode assembly 2 manufactured in this embodiment, the adhesives 14 are disposed between the electrodes 11 and 12 and the separator 13, and the adhesives 14 disposed in adjacent layers are disposed in a crossed shape, thereby minimizing an increase in the thickness of the electrode assembly 2 due to the adhesives 14. In addition, because the adhesives 14 disposed in adjacent layers cross each other, the adhesives 14 can be more easily dissolved in the electrolyte contained in the initial cell 0, which will be described later.

[0062] Hereinafter, a method for manufacturing a secondary battery according to another embodiment of the present invention will be described, focusing on a step of manufacturing a radical unit and a step of manufacturing an electrode assembly.

[0063] 6 to 9 are schematic views showing steps of manufacturing a radical unit in a method of manufacturing a secondary battery according to another embodiment of the present invention.

[0064] First, in this embodiment, the radical unit 30 may be a unit in which the separator 322 is folded to cover the electrode 31, and the electrode 31 and the separator 322 are stacked together. That is, the radical unit 30 has one side and the other side of the separator 322 folded in sequence to cover the electrode 31, and the electrode 31 and the separator 322 are stacked together in sequence. An electrode stack 40 can be manufactured by repeatedly forming such radical units 30 a plurality of times.

[0065] 6 to 9, the method for manufacturing a secondary battery according to this embodiment includes the steps of unwinding electrode sheets 3111, 3121 from electrode reels 311, 312 to form a plurality of electrodes 31 from the electrode sheets 3111, 3121; unwinding a separator 322 to be laminated with the electrodes 31 from the separator reel 321; placing the separator 322 on the upper surface of a table 36; and using a nozzle 37 to apply adhesive to at least a portion of the separator 322 and electrode 31 placed on the table 36, where the electrode 31 includes a first electrode 3112 and a second electrode 3112.

[0066] 6, in the method of manufacturing a secondary battery according to this embodiment, when a first electrode sheet 3111 is unwound from a first electrode reel 311, a first cutter 331 cuts the first electrode sheet 3111 to form a plurality of first electrodes 3112. Thereafter, a first transfer device 341 transfers the first electrode 3112, and a first header 351 adsorbs the first electrode 3112.

[0067] 6, when the separation membrane 322 is unwound from the separation membrane reel 321, the first region 3221 of the separation membrane 322 is placed on the upper surface of the table 36. Then, as shown in FIG. 6, the first nozzle 371 may apply adhesive to at least a portion of the first region 3221 of the separation membrane 322. Here, the first nozzle 371 may apply the adhesive in the form of a plurality of dots.

[0068] Thereafter, the table 36 moves toward the first transfer device 341, and the first header 351 adsorbing the first electrode 3112 also moves toward the table 36. However, this is not limited to this, and the table 36 may be fixed. When the first header 351 is positioned above the table 36, as shown in FIG. 6, the first header 351 may install the first electrode 3112 in the first region 3221 of the separator 322 coated with the adhesive.

[0069] 6, adhesive may not be applied to the first region 3221 of the separation membrane 322, and adhesive may be applied in advance to the lower portion of the first electrode 3112. That is, the first electrode 3112 may be installed in the first region 3221 of the separation membrane 322 by the first header 351 with adhesive applied in advance to the lower portion of the first electrode 3112.

[0070] In addition, the method for manufacturing a secondary battery according to this embodiment may further include a folding step after the adhesive application step, in which, when the first electrode 3112 is installed on the separator 322, one side of the separator 322 may be folded to cover the first electrode 3112, and when the second electrode 3122 is installed on the separator 322, the other side of the separator 322 may be folded to cover the second electrode 3122.

[0071] 7, after the first electrode 3112 is installed in the first region 3221, the table 36 moves toward the second transfer device 342 that transfers the second electrode 3122. Then, one side of the separation membrane 322 is folded, and the second region 3222 of the separation membrane 322 can cover the first electrode 3112. Here, before the first electrode 3112 is covered by the second region 3222 of the separation membrane 322, an adhesive may be applied in advance to the top of the first electrode 3112 or the second region 3222 of the separation membrane 322 by the first nozzle 371.

[0072] Meanwhile, when the second electrode sheet 3121 is unwound from the second electrode reel 312, the second cutter 332 cuts the second electrode sheet 3121 to form a plurality of second electrodes 3122. Thereafter, the second transport device 342 transports the second electrode 3122, and the second header 352 adsorbs the second electrode 3122.

[0073] 7 and 8, when the second region 3222 covers the first electrode 3112, the second nozzle 372 positioned above the second region 3222 applies adhesive to at least a portion of the second region 3222 of the separation membrane 322. Here, the second nozzle 372 may apply the adhesive in the form of a plurality of dots.

[0074] 8, the table 36 moves toward the second transfer device 342, and the second header 352 adsorbing the second electrode 3122 also moves toward the table 36. However, this is not limited to this, and the table 36 may be fixed. When the second header 352 is positioned above the table 36, as shown in FIG. 8, the second header 352 may install the second electrode 3122 in the second region 3222 of the separator 322 on which the adhesive is applied.

[0075] However, the present invention is not limited thereto, and unlike Fig. 8, adhesive may not be applied to the second region 3222 of the separation membrane 322, and adhesive may be applied in advance to the lower portion of the second electrode 3122. In other words, the second electrode 3122 may be installed in the second region 3222 of the separation membrane 322 by the second header 352 with adhesive applied in advance to the lower portion of the second electrode 3122.

[0076] 9, after the second electrode 3122 is installed in the second region 3222, the table 36 moves toward the first transfer device 341 that transfers the first electrode 3112. However, this is not limited to this, and the table 36 may be fixed. Then, the other side of the separation membrane 322 is folded, and the first region 3221 of the separation membrane 322 can cover the second electrode 3122. Here, before the second electrode 3122 is covered by the first region 3221 of the separation membrane 322, an adhesive may be applied in advance to the top of the second electrode 3122 or the first region 3221 of the separation membrane 322 by the second nozzle 372.

[0077] 9, when the first region 3221 covers the second electrode 3122, the first nozzle 371 positioned above the first region 3221 applies adhesive to at least a portion of the first region 3221 of the separation membrane 322. Here, the first nozzle 371 may apply the adhesive in the form of a plurality of dots.

[0078] That is, by repeating the above process, a basic unit can be manufactured using the method for manufacturing a secondary battery according to the present embodiment.

[0079] 10 is a cross-sectional view showing an electrode assembly manufactured by repeatedly forming radical units manufactured by a method for manufacturing a secondary battery according to another embodiment of the present invention, and FIG. 11 is a cross-sectional view showing an electrode assembly manufactured by repeatedly forming radical units manufactured by a method for manufacturing a secondary battery according to another embodiment of the present invention.

[0080] 10, in the method for manufacturing a secondary battery according to this embodiment, the step of manufacturing an electrode assembly may be a step of manufacturing an electrode assembly 3 by attaching fixing tape 50 around an electrode stack 40 formed by repeating radical units 30 a plurality of times, as in the electrode stack 20 of FIG. 4. Also, unlike the electrode assembly 1 of FIG. 4, the electrode assembly 3 may omit fixing tape 50 as in FIG. 10. Also, instead of fixing tape 50 of FIG. 4, one end of the separator 322 of the electrode assembly 3 may enclose a portion of the outer surface of the electrode stack 40. Here, the step of manufacturing the electrode assembly may be performed separately from the step of manufacturing the radical units described above, or the step of manufacturing the electrode assembly may include the step of manufacturing the radical units described above.

[0081] 4, the radical unit 30 of this embodiment may be in a state in which the electrodes 3112, 3122 and the separator 322 are adhered to each other by the adhesive 34. Therefore, the electrodes 3112, 3122 and the separator 322 can maintain their alignment due to the adhesive force of the adhesive 34.

[0082] In the electrode stack 40 of this embodiment, the separator 322 covers the top, bottom, and one side of the electrodes 3112 and 3122, and the stacked alignment of the radical units 30 can be maintained without a separate fixing tape 50 as shown in Fig. 4. Furthermore, when the fixing tape 50 of Fig. 4 is attached to the outside of the electrode stack 40 of this embodiment or when one end of the separator 322 is wrapped around it, the stacked alignment of the radical units 30 can be maintained more stably.

[0083] In addition, in the electrode assembly 3 manufactured in this embodiment, the adhesive 34 is disposed at the same position between each of the electrodes 3112, 3122 and the separator 322. For example, as shown in Fig. 10, in the electrode assembly 3 of this embodiment, the adhesive 34 disposed between the lower part of the first electrode 3112 and the separator 322 and the adhesive 34 between the upper part of the first electrode 3112 and the separator 322 are disposed on the same vertical line based on the bottom surface, and the intervals at which the adhesives 34 are disposed may be the same. This can be similarly explained in the case of the adhesive 34 disposed between the second electrode 3122 and the separator 322.

[0084] Therefore, in the electrode assembly 3 manufactured in this embodiment, the adhesive 34 is disposed at the same position between each of the electrodes 3112, 3122 and the separator 322, which is advantageous in that it increases process time and efficiency.

[0085] In an electrode assembly 4 manufactured using a method for manufacturing a secondary battery according to another embodiment of the present invention, adhesives 34 are disposed between the electrodes 3112 and 3122 and the separator 322, with the adhesives 34 disposed in adjacent layers being disposed in a crossed configuration. For example, as shown in FIG. 11 , in the electrode assembly 4 of this embodiment, the second adhesive 34-2 disposed between the lower part of the first electrode 3112 and the separator 322 and the first adhesive 34-1 disposed between the upper part of the first electrode 3112 and the separator 322 are disposed in a crossed configuration. Here, the first adhesive 34-1 and the second adhesive 34-2 are merely disposed in crossed positions, and the spacing between them may be the same. This can be similarly explained for the adhesive 14 disposed between the second electrode 3122 and the separator 322.

[0086] For example, in the manufacturing step of the above-mentioned basic unit, the first adhesive 34-1 and the second adhesive 34-2 can be arranged to cross each other by adjusting the position of at least one of the first nozzle 371 and the second nozzle 372.

[0087] As another example, in the manufacturing step of the above-described radical unit, another nozzle may be additionally disposed in addition to the first nozzle 371 and the second nozzle 372, so that the first adhesive 34-1 and the second adhesive 34-2 are disposed to cross each other. More specifically, the another nozzle may be disposed at a different position from the first nozzle 371 and the second nozzle 372, so that one of the first adhesive 34-1 and the second adhesive 34-2 is dispensed from the first nozzle 371 and the second nozzle 372, and the other of the first adhesive 34-1 and the second adhesive 34-2 is dispensed from the another nozzle, so that the first adhesive 34-1 and the second adhesive 34-2 are disposed to cross each other.

[0088] However, the present invention is not limited thereto, and the structure in which the first adhesive 34-1 and the second adhesive 34-2 are arranged to cross each other can be manufactured by applying them in various ways.

[0089] Therefore, in the electrode assembly 4 manufactured in this embodiment, the adhesive 34 is disposed between each of the electrodes 3112, 3122 and the separator 322, and the adhesives 34 disposed in adjacent layers are disposed in a crossed shape, thereby minimizing an increase in the thickness of the electrode assembly 4 due to the adhesive 34. In addition, because the adhesives 34 disposed in adjacent layers are disposed in a crossed shape, the adhesives 34 can be more easily dissolved in the electrolyte contained in the initial cell 0, which will be described later.

[0090] The following description will focus on the basic units 10 and 30 described above.

[0091] 12 and 13 are exploded perspective views of a radical unit manufactured in a manufacturing step of a radical unit in a manufacturing method of a secondary battery according to another embodiment of the present invention.

[0092] 12, the radical unit 10 may have a structure in which a separator 13, a first electrode 11, a separator 13, and a second electrode 12 are alternately stacked, as described with reference to FIGS. 2 to 5. Here, the separator 13 located below the first electrode 11 is called an upper separator, and the separator 13 located below the second electrode 12 is called an upper separator.

[0093] 6 to 11, the basic unit 30 may also have a structure in which the first electrode 3112, the separation membrane 322, and the second electrode 3122 are alternately stacked in a zigzag shape in which the separation membrane 322 is folded to cover the electrodes 3112 and 3122. However, for the sake of convenience, the folded surface of the separation membrane 322 is not shown in FIG.

[0094] In the basic unit 10, 30, a first electrode tab 11t, 3112t is formed at one end of the first electrode 11, 3112, and a second electrode tab 12t, 3122t is formed at one end of the second electrode 12, 3122. Here, the first electrode 11, 3112 and the second electrode 12, 3122 may be arranged such that the first electrode tab 11t, 3112t and the second electrode tab 12t, 3122t face in different directions.

[0095] Here, adhesive layers 14, 34 are formed between the first electrode 11, 3112 and the separator 13, 322 and between the second electrode 13, 3122 and the separator 12, 322. For example, the adhesive layers 14, 34 may be formed by applying an adhesive in the form of a plurality of dots as shown in FIG. 12. The dots are arranged at regular intervals. The adhesive layers 14, 34 may include an adhesive component that dissolves in the electrolyte contained in the initial cell 0, which will be described later.

[0096] Therefore, in the basic unit 10, 30 of this embodiment, the adhesive layer 14, 34 is arranged in a dot pattern, which can be easily dissolved by the electrolyte. In addition, the adhesive layer 14, 34 contains an adhesive component that dissolves in the electrolyte, so that the adhesive layer 14, 34 does not remain on the surfaces of the first electrode 11, 3112 and the second electrode 12, 3122 in the final battery cell, preventing a decrease in cell performance due to the adhesive layer 14, 34.

[0097] Referring to FIG. 13, the basic units 10' and 30' can be described in much the same way as the basic units 10 and 30 of FIG. 12, and the following description will focus on the adhesive layers 14 and .

[0098] In the basic unit 10', 30' according to this embodiment, the adhesive layer 14, 34 may include a first adhesive layer 1410, 3410 and a second adhesive layer 1420, 3420. Here, the first adhesive layer 1410, 3410 is located between the center of the first electrode 11, 3112 and the separator 13, 322, and between the center of the second electrode 12, 3122 and the separator 13, 322.

[0099] 13, the second adhesive layers 1420, 3420 are located at both ends of the first electrode tab 11t, 3112t or the second electrode tab 12t, 3122t and the adjacent separator 12, 322. More specifically, the second adhesive layers 1420, 3420 may be located between the first electrode tab 11t, 3112t and the separator 13, 322 and between the second electrode tab 12t, 3122t.

[0100] As another example, unlike FIG. 13, the second adhesive layer 1420, 3420 may be formed only in the portion between the first electrode tab 11t, 3112t and the separation membrane 13, 322 where the first electrode tab 11t, 3112t and the separation membrane 13, 322 face each other, or may be formed only in the portion between the second electrode tab 12t, 3122t and the separation membrane 13, 322 where the second electrode tab 12t, 3122t and the separation membrane 13, 322 face each other.

[0101] At this time, the first adhesive layers 1410 and 3410 and the second adhesive layers 1420 and 3420 may be formed by applying adhesive in the form of a plurality of dots.

[0102] 12, the first adhesive layers 1410 and 3410 may contain an adhesive component that dissolves in the electrolyte contained in the initial cell 0, which will be described later. In contrast, the second adhesive layers 1420 and 3420 may contain an adhesive component that does not dissolve in the electrolyte.

[0103] As an example, in the manufacturing step of the above-mentioned basic unit body, the first adhesive layer 1410, 3410 and the second adhesive layer 1420, 3420 can be formed, respectively, by changing the type of adhesive applied from at least one of the nozzles 210 in Figures 2 and 3 or at least one of the nozzles 37 in Figures 6 to 9 during the manufacturing process.

[0104] As another example, in the manufacturing step of the above-described radical unit, another nozzle may be additionally disposed in addition to the nozzle 210 of Figures 2 and 3 or the nozzle 37 of Figures 6 to 9, and the first adhesive layers 1410, 3410 and the second adhesive layers 1420, 3420 may be formed, respectively. More specifically, the other nozzle may be disposed adjacent to both ends of the separation membrane 12, 322, and the first adhesive layers 1410, 3410 may be formed from the nozzle 210 of Figures 2 and 3 or the nozzle 37 of Figures 6 to 9, and the second adhesive layers 1420, 3420 may be formed from the other nozzle.

[0105] However, the present invention is not limited thereto, and the first adhesive layers 1410 and 3410 and the second adhesive layers 1420 and 3420 may be formed by applying different adhesives in various ways.

[0106] Therefore, in the basic unit bodies 10', 30' of this embodiment, the first adhesive layers 1410, 3410 are located between the center of the first electrode 11, 3112 and the separator 13, 322 and between the center of the second electrode 12, 3122 and the separator 13, 322, and the first adhesive layers 1410, 3410 do not remain on the surfaces of the first electrode 11, 3112 and the second electrode 12, 3122 in the final battery cell, thereby preventing a decrease in cell performance due to the first adhesive layers 1410, 3410.

[0107] In addition, in the radical unit bodies 10′, 30′ of this embodiment, the second adhesive layers 1420, 3420 are positioned between the first electrode tabs 11t, 3112t and the separators 13, 322 and between the second electrode tabs 12t, 3122t, so that the second adhesive layers 1420, 3420 do not dissolve in the electrolyte in the final battery cell, preventing the separators 13, 322 facing the first electrode tabs 11t, 3112t and second electrode tabs 12t, 3122t from breaking. In addition, the second adhesive layers 1420, 3420 prevent the first electrodes 11, 3112 and second electrodes 12, 3122 from separating from the separators 13, 322 in the final battery cell.

[0108] The second adhesive layers 1420, 3420 are located between a pair of facing separation membranes 13, 322 and are formed in a portion excluding the portion where the separation membrane 13, 322 contacts the first electrode 11, 3112 and / or the second electrode 12, 3122. In other words, the second adhesive layers 1420, 3420 are located between a pair of facing separation membranes 13, 322 and do not necessarily need to contact the first electrode 11, 3112 and the second electrode 12, 3122.

[0109] Therefore, in the radical unit 10', 30' of this embodiment, the second adhesive layer 1420, 3420 is formed at a position that avoids the portion where the first electrode 11, 31112 and / or the second electrode 12, 3122 contacts the separator 13, 322, and the second adhesive layer 1420, 3420 does not hinder the movement of lithium ions between the first electrode 11, 31112 and / or the second electrode 12, 3122 and the separator 13, 322. In other words, the second adhesive layer 1420, 3420 does not reduce cell performance, and can prevent the separator 13, 322 from breaking as described above, and can prevent the first electrode 11, 3112 and the second electrode 12, 3122 from separating from the separator 13, 322.

[0110] 14 is a perspective view illustrating a manufacturing step of an initial cell in a method for manufacturing a secondary battery according to another embodiment of the present invention, and FIG. 15 is a front view illustrating a formation process in a method for manufacturing a secondary battery according to another embodiment of the present invention.

[0111] Referring to FIG. 14, the method for manufacturing a secondary battery according to this embodiment may include a step of manufacturing an initial cell after a step of manufacturing an electrode assembly.

[0112] The initial cell manufacturing step may be a step of manufacturing the initial cell 0 by placing the above-described electrode assemblies 1, 2, 3, and 4 in a pouch case 70, injecting electrolyte into the pouch case 70, and then sealing the pouch case edge 71. The pouch case 70 includes a gas pocket portion 75 extending to one side of the cup portion in which the electrode assemblies 1, 2, 3, and 4 are placed. After the electrode assemblies 1, 2, 3, and 4 and the electrolyte are placed in the cup portion, the pouch case edge 71 is sealed.

[0113] In this case, sealing is performed at the edge of the cup portion and the outer edge of the gas pocket portion 75. That is, the edge of the area where the cup portion and the gas pocket portion 75 are joined can be sealed to draw a closed curve, so that the area where the cup portion and the gas pocket portion 75 are joined can be sealed so that it is sealed from the outside. That is, although it is isolated from the outside, the cup portion and the gas pocket portion 75 can communicate with each other after sealing.

[0114] Once the initial cell 0 is manufactured in a sealed state, a step of manufacturing a final cell is performed by post-processing the initial cell 0. In the step of manufacturing the final cell, the adhesive applied to the surface of at least one of the electrode and separator 13, 322 in the previous step of manufacturing the basic unit body is dissolved. The electrolyte solution contained in the initial cell 0 may be an organic solvent, and dissolving the adhesive 14 means that the adhesive 14, 34 dissolves in the electrolyte solution, which is an organic solvent.

[0115] This means that the area of ​​the adhesive 14, 34 that was applied to the surface of the electrode or separator 13, 322 is reduced, or the applied adhesive 14, 34 is completely removed.

[0116] In the case of the electrodes 11, 12, and 31, this means that the adhesives 14 and 34 no longer remain on the electrode surfaces.

[0117] In addition, in the case of the separator 13, 322, since the separator 13, 322 is generally a porous sheet, some of the adhesive 14, 34 may have permeated into the separator 13, 322. In this case, in the final cell manufacturing stage described above, the adhesive 14, 34 that has permeated into the separator 13, 322 may dissolve in the electrolyte, and during this process, traces of the adhesive 14, 34 remain on the separator 13, 322.

[0118] Here, the trace of adhesive 14, 34 means that no components of adhesive 14, 34 remain, but a part of the outer surface of the separation membrane 13, 322 is deformed by the adhesive 14, 34. However, it is not limited thereto, and the trace of adhesive 14, 34 means a trace that can be confirmed by various methods as to whether or not the adhesive 14, 34 has been applied, such as a trace that can be confirmed with the naked eye as to whether or not the adhesive 14, 34 has been applied.

[0119] Therefore, the traces of the adhesives 14, 34 formed on the separation membranes 13, 322 are formed at the same positions as the positions where the adhesives 14, 34 are applied.

[0120] In particular, the adhesives 14 and 34 for bonding the electrodes and separator used in the method for manufacturing a secondary battery according to this embodiment may be acrylate adhesives. By using the acrylate adhesives 14 and 34, the adhesives 14 and 34 can be dissolved in the electrolyte.

[0121] In the method for manufacturing a secondary battery according to this embodiment, the final cell manufacturing step may include a formation process in which the initial cell 0 is activated by charging it at a temperature higher than room temperature. The formation process (activation process) is a process in which an SEI layer is formed on the surface of the electrode plate of the electrode assembly through a charging process, causing the electrode plate to carry an electric charge, thereby enabling the secondary battery to supply power.

[0122] In the final cell manufacturing stage, the formation process is performed at a temperature of 45°C or higher. The adhesives 14, 34 can be at least partially dissolved during the formation process. More preferably, in the final cell manufacturing stage, the formation process is performed at a temperature between 50°C and 70°C. At temperatures higher than 45°C, the adhesive 14 is more likely to dissolve. At temperatures higher than 70°C, the performance of the cell product may be reduced, which is undesirable.

[0123] 15, in the final cell manufacturing step of the secondary battery manufacturing method according to this embodiment, the formation process may include a jig pressurizing process in which both sides of the initial cell 0 are pressed using a jig 500. The left side of the initial cell 0 may be pressed using a left jig 510, and the right side of the initial cell 0 may be pressed using a right jig 520. When the initial cell 0 is pressed using the jig, gas generated inside the electrode assemblies 1, 2, 3, and 4 can smoothly move to the gas pocket 75. The gas that has moved to the gas pocket 75 is then smoothly discharged to the outside of the cell in a subsequent degassing process. Performing the jig pressurizing process during the formation process facilitates the dissolution of the adhesive 14 into the electrolyte.

[0124] Here, the jig pressurization process includes a process of applying and releasing pressure from the jig 500 that presses both sides of the initial cell 0. That is, one cycle of applying and releasing pressure from the jig 500 to press the initial cell 0 can be repeated at least twice.

[0125] The one cycle of applying and releasing pressure by the jig 500 can be a process of directly exerting physical force by alternately applying positive and negative pressure to the adhesive 14, 34 while it is melting, thereby achieving the effect of significantly improving the melting of the adhesive 14, 34.

[0126] In this case, a control device can be connected to the jig device for more systematic operation, allowing the positive pressure time and negative pressure time to be adjusted, and the magnitude of the positive pressure and negative pressure to be controlled, resulting in a more effective adhesive melting system.

[0127] In particular, in the final cell manufacturing step of the method for manufacturing a secondary battery according to embodiment 1 of the present invention, the formation process is performed at a temperature between 55°C and 65°C, and may include a jig pressing process of pressing both sides of the initial cell 0 using a jig 500. In this case, the adhesives 14 and 34 are completely dissolved in the formation process, and no adhesives 14 and 34 remain on the electrode surfaces. Also, as previously described, traces of the adhesives 14 and 34 remain on the separators 13 and 322.

[0128] If the adhesive 14, 34 remains on the electrode surface, the area where the adhesive 14, 34 remains becomes an unreacted area where no electrode reaction occurs, which can result in a decrease in battery performance. However, if the adhesive 14, 34 is completely dissolved and disappears on the surface of the electrode or separator 13, 322 as in the present invention, there is no unreacted area due to the adhesive 14, 34, preventing performance degradation and achieving excellent battery performance.

[0129] Meanwhile, the final cell manufacturing step of the secondary battery manufacturing method according to this embodiment may further include a pre-aging process of storing the initial cell 0 at room temperature before the formation process. The room temperature pre-aging process is performed for about 1.5 days. The pre-aging process may be a process of providing time for the electrolyte to sufficiently penetrate between the electrodes and the separators 13, 322. Of course, the adhesives 14, 34 may also be at least partially dissolved during the pre-aging process.

[0130] In addition, the final cell manufacturing step of the secondary battery manufacturing method according to this embodiment may further include a room temperature aging process in which the initial cell 0 is stored at room temperature after the formation process. The room temperature aging process is performed for about one day. In addition, the final cell manufacturing step may further include a high temperature aging process in which the initial cell 0 is stored at a temperature of 60 to 65 degrees Celsius after the room temperature aging process and before the degassing process.

[0131] In addition, the final cell manufacturing step of the secondary battery manufacturing method according to the present embodiment may include a degassing process after the high-temperature aging process. The degassing process may be a process of discharging internal gas of the initial cell 0 to the outside. The gas discharged in the degassing process may mainly be internal gas generated in the formation process and stored in the gas pocket 75. In the degassing process, through-holes may be formed in the gas pocket 75 so that the gas can be discharged to the outside.

[0132] The final cell manufacturing step includes a resealing process in which the initial cell 0 is resealed after the degassing process so that it is sealed from the outside again. This allows the final cell to be manufactured. The adhesives 14 and 34 have dissolved and no longer remain on the surfaces of the internal electrodes or separators 13 and 322 of the final cells manufactured in this manner. In particular, traces of the adhesives 14 and 34 remain on the separators 13 and 322, as previously described.

[0133] Meanwhile, the method for manufacturing a secondary battery according to the present embodiment may further include a final charge / discharge step of charging / discharging the final cell after the final cell manufacturing step. The final charge / discharge step may include a step of measuring the battery capacity of the final cell and a step of final charging the battery to a set voltage for shipping the final product.

[0134] The present invention will be explained below with more specific experimental examples. However, the following experimental examples are provided for illustrative purposes only and the scope of the present invention is not limited thereto.

[0135] <Experimental example - Checking adhesive marks> A battery cell was fabricated containing an electrode assembly in which positive electrodes, negative electrodes, and separators were alternately stacked, and an electrolyte. Adhesive dots were applied between the positive electrode and separator and between the negative electrode and separator. The separator was a ceramic coated separator (CCS), the adhesive included an acrylate adhesive, and the electrolyte was a standard electrolyte solution in which ethylene carbonate (EC) and ethylmethyl carbonate (EMC) were mixed in a 3:7 ratio.

[0136] The fabricated battery cell was then charged, and the separator was separated from the charged battery cell. The separated separator was washed with acetone and dried to remove the electrolyte absorbed in the separated separator, and the surface of the separator was then observed. The results are shown in Figure 16. Figure 16(a) is an image observed with the naked eye, and Figure 16(b) is an image taken under a microscope.

[0137] <Analysis of Experimental Results - Confirmation of Adhesive Application Traces> 16(a) and 16(b), it can be seen that the adhesive leaves marks on the separator when it is separated from a charged battery cell. In particular, when the image is magnified using a microscope as in FIG. 16(b), it can be seen that the adhesive marks left on the separator are more easily observed.

[0138] That is, in the battery cell according to this embodiment, traces of adhesive remaining on the outer surface of the separator indicate that adhesive was applied between the positive electrode and the separator and between the negative electrode and the separator in the electrode assembly unit.

[0139] Although the present invention has been described above using limited embodiments and drawings, the present invention is not limited thereto, and various implementations are possible within the scope of the technical spirit of the present invention and the scope of equivalents of the claims set forth below by a person having ordinary skill in the art to which the present invention pertains. [Explanation of symbols]

[0140] 0 initial cell 1,2,3,4 electrode assembly 70 pouch cases 71 Pouch case edge 75 Gas pocket 10,30 base units 11,3112 1st electrode 11-1,311 First electrode reel 12,3122 2nd electrode 12-1,312 Second electrode reel 13,322 Separation membrane 14,34 Adhesive 20,40 Electrode stack 50 Fixing Tape 60 electrode leads 110 Lower separation membrane reel 111 Lower separation membrane sheet 120 Upper separation membrane reel 121 Upper separation membrane sheet 130 4-layer laminate 210,37 nozzle 211,371 No. 1 nozzle 212,372 No. 2 nozzle 213 Third Nozzle 221,331 First cutter 222,332 Second cutter 223 Third Cutter 230 Pressure nip roll 500 jig 510 Left side jig 520 Right side jig

Claims

1. An electrode assembly manufacturing step in which electrodes and separators are alternately stacked, and an adhesive is applied to a surface of at least one of the electrodes and the separators to bond the electrodes and the separators to each other; and a manufacturing step of a battery cell, which includes housing the electrode assembly together with an electrolyte in a pouch case and sealing the pouch case to manufacture a battery cell; At least a part of the adhesive dissolves in the electrolyte solution, forming an adhesive application mark on the separator; The method for manufacturing a secondary battery, wherein the adhesive application marks are portions of the outer surface of the separator that are deformed by the adhesive and do not contain components of the adhesive.

2. The manufacturing step of the battery cell further includes a formation process of activating the battery cell by charging it at a temperature higher than room temperature, The method for manufacturing a secondary battery according to claim 1 , wherein at least a part of the adhesive dissolves in the electrolyte solution in the formation step.

3. The method for manufacturing a secondary battery according to claim 2 , wherein the formation process is performed at a temperature of 50° C. to 70° C.

4. The method of manufacturing a secondary battery according to claim 3 , wherein the formation step includes a jig pressing step of pressing both side surfaces of the battery cell using a jig.

5. The formation step is carried out at a temperature of 55°C or more and 65°C or less, The method of manufacturing a secondary battery according to claim 4 , wherein the adhesive is completely dissolved in the electrolyte in the formation process, and the adhesive located on the surface of the electrode is removed.

6. the adhesive is an acrylate adhesive, The method for manufacturing a secondary battery according to claim 1 , wherein the electrolytic solution is an organic solvent.

7. The method for manufacturing a secondary battery further includes manufacturing a radical unit, which is a laminated unit of the electrode and the separator, The method of manufacturing a secondary battery according to claim 1 , wherein the electrode assembly is manufactured by attaching a fixing tape to a periphery of an electrode stack formed by stacking a plurality of the radical units.

8. The step of manufacturing the basic unit body includes: unwinding the lower separation membrane from the lower separation membrane reel; applying adhesive to at least a portion of an upwardly facing surface of the unwound lower separation film using a first nozzle; a step of providing a first electrode on one surface of the lower separator coated with the adhesive; unwinding the upper separation membrane from the upper separation membrane reel; applying adhesive to at least a portion of a surface of the unwound upper separation film that contacts the first electrode using a second nozzle; applying adhesive to at least a portion of the other surface of the upper separation film facing upward by a third nozzle; and The method of claim 7 , further comprising the step of: disposing an adhesive by a third nozzle; and then providing a second electrode on the other side of the upper separator where the adhesive is applied.

9. The method of claim 8 , wherein the first nozzle, the second nozzle, and the third nozzle apply the adhesive in the form of a plurality of dots.

10. The method for manufacturing a secondary battery further includes a step of manufacturing a radical unit in which the separator is folded to cover the electrode, and the electrode and the separator are stacked, The method of manufacturing a secondary battery according to claim 1 , wherein the electrode assembly is manufactured by repeatedly forming the basic unit bodies.

11. The step of manufacturing the basic unit body includes: unwinding an electrode sheet from an electrode reel to form a plurality of electrodes from the electrode sheet; unwinding the separator laminated with the electrode from a separator reel; placing the separation membrane on a table top; and applying adhesive to at least a portion of the separator and the electrode placed on the table using a nozzle; The method of manufacturing a secondary battery according to claim 10 , wherein the electrodes include a first electrode and a second electrode.

12. The method further includes a folding step after the adhesive applying step, The folding step comprises: When the first electrode is installed on the separator, one side of the separator is folded to cover the first electrode; The method of claim 11 , wherein when the second electrode is disposed on the separator, the other side of the separator is folded to cover the second electrode.

13. The method of claim 11 or 12, wherein the nozzle applies the adhesive in the form of a plurality of dots.

14. an electrode assembly in which electrodes and separators are alternately stacked; and a pouch case that accommodates both the electrode assembly and an electrolyte; the separator has at least one adhesive application mark remaining on a surface that contacts the electrode; the adhesive application trace is a trace of a first adhesive layer formed between the electrode and the separator dissolved in the electrolyte solution, A secondary battery in which the adhesive application marks are portions of the outer surface of the separator that have been deformed by the adhesive and do not contain components of the adhesive.

15. The first adhesive layer is formed by applying an adhesive in the form of a plurality of dots, The adhesive application marks are formed in the form of dots at the positions where the first adhesive layer is formed. The secondary battery according to claim 14.

16. the adhesive is an acrylate adhesive, The secondary battery according to claim 15 , wherein the electrolyte is an organic solvent.

17. the electrodes include a first electrode and a second electrode; The separation membrane includes an upper separation membrane and a lower separation membrane, The secondary battery of claim 14 , wherein the electrode assembly has a structure in which the lower separator, the first electrode, the upper separator, and the second electrode are alternately stacked.

18. the electrodes include a first electrode and a second electrode; The electrode assembly is The first electrode is installed on the separator, and one side of the separator is folded to cover the first electrode; The secondary battery according to claim 14 , wherein the second electrode is disposed on the separator, and the other side of the separator is folded to cover the second electrode.

19. An electrode tab is formed at one end of the electrode, a second adhesive layer is formed between the electrode tab and the separator; The secondary battery according to claim 17 or 18, wherein the second adhesive layer contains an adhesive component that is insoluble in the electrolyte solution.

20. The secondary battery of claim 19, wherein the second adhesive layer is formed by applying an adhesive in the form of a plurality of dots.

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