Secondary battery manufacturing method and secondary battery

Abstract

To provide a secondary battery manufacturing method capable of preventing deposition from occurring in an end of a folded cell, and a secondary battery.SOLUTION: The present invention relates to a secondary battery manufacturing method and a secondary battery. The secondary battery manufacturing method comprises: a folded cell formation process of seating unit cells, each of which comprises at least one electrode and at least one separator, on one surface of a separation film to sequentially fold the unit cells, thereby forming a folded cell; a tape attachment process of attaching a pressing tape to an end of the folded cell; an accommodation process of accommodating the folded cell, to which the pressing tape is attached, and an electrolyte in a battery case; and a pressing process of pressing an outer surface of the battery case to press the folded cell.SELECTED DRAWING: Figure 3

Description

[Technical field]

[0001] This application claims the benefit of priority based on Korean Patent Application No. 10-2020-0123363 filed on September 23, 2020, and Korean Patent Application No. 10-2021-0071815 filed on June 2, 2021, the entire contents of which are incorporated herein by reference. The present invention relates to a method for manufacturing a secondary battery and a secondary battery. [Background technology]

[0002] Unlike primary batteries, secondary batteries are rechargeable and have the potential to be small and have large capacity, and as such, they have been the subject of much research and development in recent years. As technological development and demand for mobile devices increases, the demand for secondary batteries as an energy source is rapidly increasing.

[0003] Secondary batteries are classified into coin type batteries, cylindrical type batteries, prismatic type batteries, and pouch type batteries according to the shape of the battery case. In secondary batteries, the electrode assembly attached inside the battery case is a chargeable and dischargeable power generating element having a laminated structure of electrodes and separators.

[0004] Electrode assemblies can be broadly classified into a jelly-roll type in which a separator is interposed between a sheet-like positive electrode and a negative electrode coated with an active material and the electrode is wound up; a stack type in which a plurality of positive electrodes and negative electrodes are sequentially stacked with a separator interposed therebetween; and a stack / folding type in which a stack type unit cell is wound up with a long separating film.

[0005] In recent years, pouch-type batteries, which have a structure in which a stack / folding type electrode assembly is built into a pouch-type battery case made of an aluminum laminate sheet, have been attracting much attention due to their low manufacturing cost, small weight, and easy shape modification, and their usage is gradually increasing.

[0006] As the demand for rapid charging of lithium pouch batteries increases, cells are being designed to have higher energy, longer life, and lower swelling.

[0007] As the rate of fast charging increases, lithium deposition occurs in the cell, which occurs locally at first, but ultimately causes problems such as worsening cell retention and swelling.

[0008] In recent years, rapid charging issues have led to the problem of precipitation occurring at the top of the cell, and in order to meet rapid charging and long life cycles, the problem of precipitation at the top must be solved. That is, the top of the cell is weakly laminated, causing electrolyte to accumulate, which causes lithium precipitation and causes many problems. [Prior art documents] [Patent documents]

[0009] [Patent Document 1] Korean Patent Publication No. 10-2018-0051072 Summary of the Invention [Problem to be solved by the invention]

[0010] An aspect of the present invention is to provide a method for manufacturing a secondary battery capable of preventing precipitation from occurring at the ends of a folding cell, and the secondary battery. [Means for solving the problem]

[0011] A method for manufacturing a secondary battery according to an embodiment of the present invention may include a folding cell forming step of placing a plurality of unit cells, each including at least one electrode and at least one separator, on one side of a separator film and folding the unit cells sequentially to form a folded cell; a tape attaching step of attaching a pressure tape to an end of the folded cell; a housing step of housing the folded cell with the pressure tape attached and an electrolyte inside a battery case; and a pressurizing step of pressurizing the folded cell by applying pressure to an outer surface of the battery case.

[0012] Meanwhile, a secondary battery according to an embodiment of the present invention includes a folding cell including a plurality of unit cells, each including at least one electrode and at least one separator, and a separation film folded to be positioned between the plurality of unit cells, a pressure tape attached to the folding cell, and a battery case in which the folding cell and an electrolyte are contained therein, and the pressure tape may be attached to an end of the folding cell such that the end of the folding cell is pressurized when an outer surface of the battery case is pressurized. Effect of the Invention

[0013] According to the present invention, a pressure tape is attached to the end of the folding cell, and pressure is applied to the end of the folding cell, so that the electrolyte accumulated at the end is pushed out of the unit cell, preventing precipitation, and abnormal swelling and retention fading during long-term cycles can be prevented. [Brief description of the drawings]

[0014] [Figure 1] 4 is a plan view illustrating a folding cell forming step in the method for manufacturing a secondary battery according to the embodiment of the present invention. FIG. [Diagram 2]3 is a front view showing a unit cell in a method for manufacturing a secondary battery according to an embodiment of the present invention; FIG. [Diagram 3] 1 is a perspective view showing a first example of a tape attachment step in a method for manufacturing a secondary battery according to an embodiment of the present invention. [Figure 4] FIG. 2 is a perspective view showing a housing step in the manufacturing method of the secondary battery according to the embodiment of the present invention. [Diagram 5] FIG. 4 is a front view showing a pressing step in the method for manufacturing a secondary battery according to the embodiment of the present invention. [Figure 6] FIG. 4 is a perspective view showing a second example of a tape attachment step in the manufacturing method of the secondary battery according to the embodiment of the present invention. [Figure 7] FIG. 11 is a perspective view showing a third example of a tape attachment step in the method for manufacturing a secondary battery according to an embodiment of the present invention. [Figure 8] FIG. 11 is a perspective view showing a fourth example of a tape attachment step in the method for manufacturing a secondary battery according to an embodiment of the present invention. [Figure 9] 4 is a graph showing the performance of a secondary battery manufactured by a method for manufacturing a secondary battery according to an embodiment of the present invention and a secondary battery according to the related art. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0015] The object, particular advantages, and novel features of the present invention will become more apparent from the following detailed description and preferred embodiments in conjunction with the accompanying drawings. In this specification, when referring to components in each drawing, it should be noted that the same components have the same numbers as much as possible when they are displayed in other drawings. In addition, the present invention may be realized in various different forms, and is not limited to the embodiments described herein. In addition, in describing the present invention, detailed descriptions of related known technologies that may unnecessarily obscure the gist of the present invention will be omitted.

[0016] Method for manufacturing a secondary battery according to an embodiment FIG. 1 is a plan view showing a folding cell forming process in a manufacturing method for a secondary battery according to an embodiment of the present invention, FIG. 2 is a front view showing a unit cell in a manufacturing method for a secondary battery according to an embodiment of the present invention, and FIG. 3 is a perspective view showing a first example of a tape attachment process in a manufacturing method for a secondary battery according to an embodiment of the present invention.

[0017] Moreover, FIG. 4 is a perspective view showing a housing step in the manufacturing method for a secondary battery according to an embodiment of the present invention, and FIG. 5 is a front view showing a pressurizing step in the manufacturing method for a secondary battery according to an embodiment of the present invention.

[0018] 1 to 5, a method for manufacturing a secondary battery according to an embodiment of the present invention may include a folding cell forming process of placing a unit cell 110 on one side of a separation film 120 and folding the unit cell 110 to form a folded cell 100, a tape attachment process of attaching a pressure tape 300 to the folded cell 100, an accommodating process of accommodating the folded cell 100 and an electrolyte solution inside a battery case 200, and a pressurizing process of pressurizing the battery case 200.

[0019] Hereinafter, a method for manufacturing a secondary battery according to an embodiment of the present invention will be described in more detail. Referring to Figs. 1 and 2, in a folding cell forming process, a plurality of unit cells 110, each including at least one electrode 113 and at least one separator 114, may be placed on one side of a separation film 120 and folded sequentially to form a folded cell 100. In this case, the separation film 120 may be folded so as to be positioned between the plurality of unit cells 110. Herein, referring to Fig. 1, the separation film 120 may be folded in the X-axis direction to form the folded cell 100.

[0020] The unit cell 110 is a power generating element capable of charging and discharging, and is configured by assembling at least one electrode 113 and at least one separator 114 and stacking them alternately.

[0021] The electrodes 113 may include a positive electrode 111 and a negative electrode 112. The separator 114 separates and electrically insulates the positive electrode 111 and the negative electrode 112. The separator 114 is made of an insulating material, and is laminated alternately with the positive electrode 111 and the negative electrode 112.

[0022] On the other hand, the separator 114 may be, for example, a multilayer film made of microporous polyethylene, polypropylene, or a combination thereof, or a polymer film for a solid polymer electrolyte or a gel-type polymer electrolyte, such as polyvinylidene fluoride, polyethylene oxide, polyacrylonitrile, or polyvinylidene fluoride-hexafluoropropylene copolymer.

[0023] Meanwhile, the unit cell 110 may further include an electrode tab 130 provided at an end of the electrode 113. In this case, the electrode tab 130 may be provided at an upper portion of the electrode 113. Here, the upper portion of the electrode 113 may be an upper side of the folded cell 100 in a direction parallel to the folding axis direction of the folded cell 100. In this case, referring to FIG. 1, the folding axis direction of the folded cell 100 may be a Y-axis direction. Meanwhile, in the manufacturing method of the secondary battery of the present invention, the electrode tab 130 is not necessarily limited to being provided at the upper portion of the electrode 113. For example, it goes without saying that the electrode tab 130 may be provided at both sides of the electrode 113, that is, at the upper side and the lower side. The electrode tab 130 may include a positive electrode tab 131 provided at an end of the positive electrode 111 and a negative electrode tab provided at an end of the negative electrode 112. Here, for example, the positive electrode tab 131 may be provided on the top of the positive electrode 111 , and the negative electrode tab 132 may be provided on the top of the negative electrode 112 .

[0024] Meanwhile, the folding cell 100 may further include an electrode lead 140 having one side connected to the electrode tab 130 and the other side protruding out of the battery case 200 to be connected to an external terminal. The electrode lead 140 may include a positive electrode lead 141 connected to the positive electrode tab 131 and a negative electrode lead 142 connected to the negative electrode tab 132 .

[0025] 3, in the tape attachment process, the pressure tape 300 may be attached to an end of the folding cell 100. Also, in the tape attachment process, as a first embodiment, the pressure tape 300 may be attached to an end of the folding cell 100 where the electrode tab 130 is located. Here, in the tape attachment process, as a first specific embodiment, the pressure tape 300 may be attached to an upper part of the folding cell 100 where the electrode tab 130 is located. At this time, in the tape attachment process, the pressure tape 300 may be further attached to a lower part of the folding cell 100.

[0026] Furthermore, in the tape attachment process, the pressure tape 300 may be attached to the outermost surface of the separation film 120. Here, in the tape attachment process, as a first embodiment, the pressure tape 300 may be attached to at least one of the front and rear surfaces of the folding cell 100 in a direction perpendicular to the folding axis when the folding cell 100 is folded. In this case, referring to FIG. 3, the folding axis direction may be the Y-axis direction, and the perpendicular direction to the folding axis may be the Z-axis direction.

[0027] Here, the thickness t1 of the pressure tape 300 can be 10 to 300 μm. Thus, when the thickness t1 of the pressure tape 300 is 10 μm or more, a stronger pressure can be applied to the end portion of the folded cell 100 through the pressure tape 300 when applying pressure to the outer surface of the battery case 200, and when the thickness t1 is 300 μm or less, it does not occupy an excessive space, and the separator located on the outer surface of the folded cell 100 is not damaged by an excessive pressure.

[0028] The length L1 of the pressure tape attached to the folded cell 100 in the folding axis direction of the folded cell 100 may be 5 to 300 mm. Thus, when the length L1 of the pressure tape 300 is 5 mm or more, a pressure force can be effectively applied to the end portion of the folded cell 100 that may be filled with electrolyte via the pressure tape 300 when pressing the outer surface of the battery case 200, and when the length L1 is 300 mm or less, it is possible to prevent the pressure tape 300 from occupying an excessive space and being excessively removed from the portion of the folded cell 100 that may be filled with electrolyte, thereby preventing a decrease in the effect of pushing the electrolyte out of the folded cell 100.

[0029] FIG. 6 is a perspective view showing a second embodiment of a tape attachment process in a method for manufacturing a secondary battery according to an embodiment of the present invention. Meanwhile, referring to FIG. 6, in the tape attachment process, as a second embodiment, a pressure tape 300' may be attached to surround the upper part of the folding cell 100 so that the end of the folding cell 100 is pressurized. At this time, as a specific second embodiment of the tape attachment process, the pressure tape 300' may be attached to surround the upper part of the folding cell 100 in the folding direction of the folding cell 100. That is, the pressure tape 300' may be attached to surround the upper part of the folding cell 100 in the full width direction of the folding cell 100. As a result, the upper part of the folding cell 100 may be easily pressurized to maintain the pressure.

[0030] At this time, tension of the pressure tape 300' can be maintained so that the upper part of the folding cell 100 is pressed through the pressure tape 300'. Here, the thickness of the pressure tape 300' can be 1 to 300 μm. Thus, since the thickness of the pressure tape 300' is 1 μm or more, a pressure force can be applied to the end part of the folding cell 100 through the pressure tape 300' that surrounds and presses the upper part of the folding cell 100 so that the upper part of the folding cell 100 is pressed, and since the thickness is 300 μm or less, it does not occupy an excessive space, and the separator located on the outer surface of the folding cell 100 is not damaged by an excessive pressure force.

[0031] The length L2 of the pressure tape 300' attached to the folding cell 100 in the folding axis direction of the folding cell 100 may be 0.5 to 300 mm. As a result, when the length L2 of the pressure tape 300' is 0.5 mm or more, the pressure can be effectively applied to the end portion of the folding cell 100 that may be filled with electrolyte through the pressure tape 300 that surrounds and presses the upper portion of the folding cell 100 so that the upper portion of the folding cell 100 is pressurized, and when the length L2 is 300 mm or less, it is possible to prevent the effect of pushing the electrolyte out of the folding cell 100 from being reduced by not occupying excessive space and being excessively deviated from the portion of the folding cell 100 that may be filled with electrolyte.

[0032] FIG. 7 is a perspective view showing a third example of a tape attachment process in a method for manufacturing a secondary battery according to an embodiment of the present invention. Meanwhile, referring to FIG. 7, in the tape attachment process, as a third example, pressure tapes 300', 300'' are attached to surround the upper and lower parts of the folding cell 100 so that the upper and lower parts of the folding cell 100 are pressurized, and the pressure tapes 300', 300'' can be attached to surround the folding cell 100 in the folding direction of the folding cell 100. That is, one pressure tape 300' can be attached to surround the upper part of the folding cell 100 in the full width direction of the folding cell 100, and another pressure tape 300'' can be attached to surround the lower part of the folding cell 100 in the full width direction of the folding cell 100. As a result, the upper and lower parts of the folding cell 100 can be easily pressurized to maintain the pressurizing force. Here, the pressure tapes 300', 300'' are formed to have a thickness of 1 to 300 μm, and the lengths L2, L3 of the pressure tapes 300', 300'' attached to the folding cell 100 in the folding axis direction of the folding cell 100 may be 0.5 to 300 mm.

[0033] 8 is a perspective view showing a fourth embodiment of a tape attachment process in a method for manufacturing a secondary battery according to an embodiment of the present invention. Referring to FIG. 8, in the tape attachment process, as a fourth embodiment, a pressure tape 300''' may be attached to surround the upper part of the folding cell 100 so that an end of the folding cell 100 is pressurized. Here, as a specific fourth embodiment of the tape attachment process, the pressure tape 300''' may be attached to surround the upper part of the folding cell 100 so that the upper part of the folding cell 100 is pressurized, and may be attached to the front and rear parts of the folding cell 100 in a direction perpendicular to the folding axis and to surround the upper part of the folding cell 100 in the folding axis direction of the folding cell 100 when the folding cell 100 is folded. That is, the pressure tape 300''' may include a first portion P1 attached to the front and rear surfaces of the folding cell 100 in a direction perpendicular to the folding axis of the folding cell 100, and a second portion P2 attached to surround the upper portion of the folding cell 100 in the folding axis direction of the folding cell 100. Therefore, by attaching the pressure tape 300''' to surround the upper portion of the folding cell 100 in the full length direction of the folding cell 100, it is possible to prevent the overall width of the folding cell 100 from increasing, prevent the folding cell 100 from unwinding, and suppress excessive swelling. In addition, since the end portion of the electrode 113 is thinner than the center portion, it is possible to prevent the bond with the separator 114 from coming apart. Here, the thickness of the pressure tape 300''' may be 10 to 300 μm. In addition, the length L4 of the pressure tape 300''' attached to the folding cell 100 in the folding axis direction of the folding cell 100 may be 5 to 300 mm. That is, the length of the first portion P1 of the pressure tape 300''' attached to the folding cell 100 may be 5 to 300 mm.

[0034] 4, in the accommodation step, the folded cell 100 with the pressure tape 300 attached and the electrolyte can be accommodated inside the battery case 200. At this time, an accommodation portion 210 is formed inside the battery case 200 to accommodate the folded cell 100 and the electrolyte.

[0035] In addition, in the housing step, after the folding cell 100 and the electrolyte are housed inside the battery case 200, the outer periphery of the battery case 200 can be sealed by heat fusion. At this time, the upper and lower parts of the battery case 200 can be joined to each other by applying heat and pressure along the outer edge of the housing part 210 of the battery case 200.

[0036] 5, in the pressurizing step, the outer surface of the battery case 200 can be pressed to pressurize the folded cell 100. In the pressurizing step, pressure can be applied to both sides of the battery case 200 from both sides of the battery case 200 via a pair of pressurizing jigs 30.

[0037] The pair of pressurizing jigs 30 may include an upper jig 10 and a lower jig 20. Here, in the pressurizing process, pressure may be applied to the upper and lower sides of the battery case 200 in which the folded cell 100 is accommodated between the upper jig 10 and the lower jig 20.

[0038] Therefore, when the secondary battery E is pressurized through the pressurizing jig 30, the pressurizing tape 300 attached to the top of the folded cell 100 applies stronger pressure to the top of the folded cell 100, so that the electrolyte remaining at the top of the folded cell 100 can be easily pushed out to the outside of the folded cell 100. This prevents precipitation from occurring, and can prevent abnormal swelling and retention fading during long-term cycles.

[0039] 9 is a graph showing the performance of a secondary battery manufactured by the method for manufacturing a secondary battery according to an embodiment of the present invention and a secondary battery according to the related art. The graph shown in Fig. 9 shows the cycle performance of secondary battery A of the present invention in which a pressure tape is attached to the folding cell, and a conventional secondary battery B in which a pressure tape is not attached to the folding cell.

[0040] Referring to the graph shown in FIG. 9, it can be seen that secondary battery A manufactured by the manufacturing method of a secondary battery according to an embodiment of the present invention shows almost no change in retention as the charge / discharge cycle progresses, whereas conventional secondary battery B shows a rapid retention fading after 210 cycles as the charge / discharge cycle progresses.

[0041] Therefore, it can be seen that the secondary battery A manufactured by the manufacturing method of a secondary battery according to an embodiment of the present invention can prevent the electrolyte from being pushed out and precipitated on the top of the folding cell when pressure is applied through the pressure tape attached to the top of the folding cell.

[0042] Secondary battery according to an embodiment Hereinafter, a secondary battery according to an embodiment of the present invention will be described. Referring to Fig. 1 to Fig. 5, a secondary battery E according to an embodiment of the present invention includes a folded cell 100 including a plurality of unit cells 110 and a separator film 120 folded to be positioned between the plurality of unit cells 110, a pressure tape 300 attached to the folded cell 100, and a battery case 200 in which the folded cell 100 and an electrolyte are contained.

[0043] The secondary battery E according to the embodiment of the present invention relates to a secondary battery manufactured by the method for manufacturing a secondary battery according to the above-described embodiment. Therefore, in this embodiment, the overlapping content with the above-described embodiment will be omitted or briefly described, and the description will focus on the differences.

[0044] 1 and 2, the folding cell 100 may include a unit cell 110 and a separation film 120. The unit cell 110 may include at least one electrode 113 and at least one separator 114. The unit cell 110 is a power generating element capable of being charged and discharged, and may form a structure in which the at least one electrode 113 and the at least one separator 114 are assembled together to be alternately stacked.

[0045] The electrode 113 may include a positive electrode 111 and a negative electrode 112. The separator 114 separates and electrically insulates the positive electrode 111 and the negative electrode 112. The separator film 120 may be folded so as to be positioned between the unit cells 110.

[0046] The unit cell 110 may further include an electrode tab 130 provided at an end of the electrode 113. In this case, the electrode tab 130 may be provided on an upper portion of the electrode 113. Here, the upper portion of the electrode 113 may be on the upper side of the folded cell 100 in a direction parallel to the folding axis direction of the folded cell 100. In this case, referring to FIG. 1, the folding axis direction of the folded cell 100 may be the Y-axis direction. Meanwhile, in the secondary battery of the present invention, the electrode tab 130 is not necessarily limited to being provided on the upper portion of the electrode 113, and it goes without saying that the electrode tab 130 may be provided on both sides of the electrode 113, that is, on the upper side and the lower side, respectively.

[0047] The electrode tabs 130 may include a positive electrode tab 131 provided at an end of the positive electrode, and a negative electrode tab 132 provided at an end of the negative electrode 112. Here, for example, the positive electrode tab 131 may be provided on an upper portion of the positive electrode 111, and the negative electrode tab 132 may be provided on an upper portion of the negative electrode 112.

[0048] Meanwhile, the folding cell 100 may further include an electrode lead 140 having one side connected to the electrode tab 130 and the other side protruding outside the battery case 200 to be connected to an external terminal. The electrode lead 140 may include a positive electrode lead 141 connected to the positive electrode tab 131 and a negative electrode lead 142 connected to the negative electrode tab 132.

[0049] The battery case 200 may have a folding cell 100 and a receiving portion 210 for receiving an electrolyte formed therein. Here, the battery case 200 may be a pouch-type battery case made of a flexible material. In this case, the battery case 200 may include, for example, an aluminum sheet and resin layers provided on both sides of the aluminum sheet.

[0050] 3, the pressure tape 300 may be attached to the folding cell 100. In this case, the pressure tape 300 may be attached to the end of the folding cell 100 such that the end of the folding cell 100 is pressurized when the outer surface of the battery case is pressurized.

[0051] In addition, the pressure tape 300 includes a heat dissipating material, and when the electrode tab 130 located at the end of the folding cell 100 generates heat, the pressure tape 300 can dissipate heat from the end of the folding cell 100 and prevent damage to the folding cell 100 including the separator.

[0052] The pressure tape 300 may include a substrate and an adhesive layer provided on one surface of the substrate. Here, the substrate may be made of a polymer resin film. In this case, the substrate may include any one of polypropylene, polyethylene, polyimide, and polyethylene terephthalate. In particular, polyimide and polyethylene terephthalate are materials with excellent heat dissipation properties.

[0053] Also, the pressure tape 300 may be attached to the outermost surface of the separation film 120. Furthermore, the pressure tape 300 may be attached to an end portion of the folding cell 100 where the electrode tab 130 is located. Here, in the first embodiment, the pressure tape 300 may be attached to an upper portion of the folding cell 100 where the electrode tab 130 is located. In this case, the pressure tape 300 may be further attached to a lower portion of the folding cell 100.

[0054] More specifically, referring to FIG. 3, the pressure tape 300 may be attached to at least one of the front and rear surfaces of the folding cell 100 in a direction perpendicular to the folding axis of the folding cell 100 as a first embodiment. Here, the pressure tape 300 may be attached to the front and rear surfaces of the folding cell 100 in a direction perpendicular to the folding axis of the folding cell 100 as a specific first embodiment. In this case, referring to FIG. 3, the folding axis direction may be the Y-axis direction, and the perpendicular direction to the folding axis may be the Z-axis direction. Here, the thickness t1 of the pressure tape 300 may be 10 to 300 μm. Thus, when the thickness t1 of the pressure tape 300 is 10 μm or more, a stronger pressure force can be applied to the end portion of the folding cell 100 through the pressure tape 300 when the outer surface of the battery case 200 is pressed, and when the thickness t1 is 300 μm or less, it does not occupy an excessive space, and the separator located on the outer surface of the folding cell 100 is not damaged by excessive pressure.

[0055] The length L1 of the pressure tape attached to the folded cell 100 in the folding axis direction of the folded cell 100 may be 5 to 300 mm. Thus, when the length L1 of the pressure tape 300 is 5 mm or more, a pressure force can be effectively applied to the end portion of the folded cell 100 that may be filled with electrolyte via the pressure tape 300 when pressing the outer surface of the battery case 200, and when the length L1 is 300 mm or less, it is possible to prevent the pressure tape 300 from occupying an excessive space and being excessively removed from the portion of the folded cell 100 that may be filled with electrolyte, thereby preventing a decrease in the effect of pushing the electrolyte out of the folded cell 100.

[0056] Meanwhile, referring to FIG. 6, the pressure tape 300' may be attached to surround the end of the folding cell 100 so that the upper portion of the folding cell 100 is pressurized as a second embodiment. Here, the pressure tape 300' may be attached to surround the upper portion of the folding cell 100 in the folding direction of the folding cell 100 so that the upper portion of the folding cell 100 is pressurized as a specific second embodiment. At this time, the tension of the pressure tape 300' may be maintained so that the upper portion of the folding cell 100 is pressurized through the pressure tape 300'. Here, the thickness of the pressure tape 300' may be 1 to 300 μm. As a result, since the thickness of the pressure tape 300 is 1 μm or more, pressure can be applied to the end portions of the folding cell 100 through the pressure tape 300 which surrounds and pressurizes the upper portion of the folding cell 100 so that the upper portion of the folding cell 100 is pressurized, and since the thickness is 300 μm or less, it does not occupy excessive space, and the separator located on the outer surface of the folding cell 100 is not damaged by excessive pressure.

[0057] The length L2 of the pressure tape 300' attached to the folding cell 100 in the folding axis direction of the folding cell 100 may be 0.5 to 300 mm. As a result, when the length L2 of the pressure tape 300' is 0.5 mm or more, the pressure can be effectively applied to the end portion of the folding cell 100 that may be filled with electrolyte through the pressure tape 300 that surrounds and presses the upper portion of the folding cell 100 so that the upper portion of the folding cell 100 is pressurized, and when the length L2 is 300 mm or less, it is possible to prevent the effect of pushing the electrolyte out of the folding cell 100 from being reduced by not occupying excessive space and being excessively deviated from the portion of the folding cell 100 that may be filled with electrolyte.

[0058] 7, in the third embodiment, the pressure tapes 300', 300'' may be attached to surround the upper portion of the folding cell 100 so that the upper portion of the folding cell 100 is pressurized, and may be attached to surround the lower portion of the folding cell 100 so that the lower portion of the folding cell 100 is pressurized. In this case, the pressure tapes 300', 300'' may be attached to the front and rear surfaces of the folding cell 100 in a direction perpendicular to the folding axis of the folding cell 100, and to surround the upper and lower portions of the folding cell 100 in the folding axis direction of the folding cell 100. Here, the thickness of the pressure tapes 300', 300'' may be formed to be 1 to 300 μm, and the lengths L2, L3 of the pressure tapes 300', 300'' attached to the folding cell 100 in the folding axis direction of the folding cell 100 may be 0.5 to 300 mm.

[0059] 8, the pressure tape 300''' may be attached to surround the top of the folding cell 100 so that the end of the folding cell 100 is pressurized as a fourth embodiment. Here, the pressure tape 300''' may be attached to surround the top of the folding cell 100 so that the top of the folding cell 100 is pressurized as a specific fourth embodiment, and may be attached to the front and rear surfaces of the folding cell 100 in a direction perpendicular to the folding axis of the folding cell 100 and to surround the top of the folding cell 100 in the folding axis direction of the folding cell 100. That is, the pressure tape 300''' may include a first portion P1 attached to the front and rear surfaces of the folding cell 100 in a direction perpendicular to the folding axis of the folding cell 100 and a second portion P2 attached to surround the top of the folding cell 100 in the folding axis direction of the folding cell 100 as the fourth embodiment. Here, the thickness of the pressure tape 300''' may be 10 to 300 μm. In addition, the length L4 of the pressure tape 300''' attached to the folding cell 100 in the folding axis direction of the folding cell 100 may be 5 to 300 mm. That is, the length of the first portion P1 of the pressure tape 300''' attached to the folding cell 100 may be 5 to 300 mm.

[0060] Although the present invention has been described in detail above with reference to specific embodiments, this is for the purpose of specifically explaining the present invention, and the present invention is not limited thereto. It is possible to carry out various embodiments within the technical concept of the present invention by a person having ordinary skill in the art. Moreover, the specific scope of protection of the invention will become apparent from the appended claims. [Explanation of symbols]

[0061] 10: Upper jig 20: Lower jig 30: Pressure jig 100: Folding cell 110: Unit cell 111: Positive electrode 112: Negative electrode 113: Electrode 114: Separator 120: Separation film 130: Electrode tab 131: Positive electrode tab 132: Negative electrode tab 140: Electrode lead 141: Positive lead 142: Negative lead 200: Battery case 210: Storage unit 300, 300', 300'', 300''': Pressure tape E: Secondary battery

Claims

1. a folding cell forming step of placing a plurality of unit cells, each of which includes at least one electrode and at least one separator, on one side of a separation film and folding the unit cells in sequence to form folded cells; a tape attachment step of attaching a pressure tape to an end of the folding cell; a housing step of housing the folding cell with the pressure tape attached thereto and an electrolyte solution inside a battery case; a pressurizing step of pressurizing the outer surface of the battery case to pressurize the folding cell; A method for manufacturing a secondary battery comprising the steps of:

2. The unit cell further includes an electrode tab provided on an upper portion of the electrode, The method of claim 1 , wherein in the tape attaching step, the pressure tape is attached to an upper portion of the folding cell where the electrode tab is located.

3. The method of claim 2 , wherein the pressure tape is further attached to a lower portion of the folding cell in the tape attaching step.

4. In the tape attachment step, The method for producing a secondary battery according to claim 2 , wherein the pressure tape is attached to an outermost surface of the release film.

5. In the tape attachment step, The method of claim 4, wherein the pressure tape is attached to at least one of a front surface and a rear surface of the folded cell in a direction perpendicular to a folding axis when the folded cell is folded.

6. In the tape attachment step, The method of claim 4 , wherein the pressure tape is attached to surround an upper portion of the folded cell such that the upper portion of the folded cell is pressurized.

7. In the tape attachment step, The method of claim 6 , wherein the pressure tape is attached to the folded cell in a folding direction of the folded cell so as to surround the folded cell.

8. In the tape attachment step, The method of claim 6 , wherein the pressure tape is attached to surround an upper portion of the folded cell in a folding axis direction of the folded cell.

9. a folding cell including a plurality of unit cells each including at least one electrode and at least one separator, and a separation film folded so as to be positioned between the plurality of unit cells; A pressure tape attached to the folding cell; a battery case in which the folding cell and an electrolyte are housed; Including, The pressure tape is attached to an end of the folding cell such that the end of the folding cell is pressurized when the outer surface of the battery case is pressurized.

10. The unit cell further includes an electrode tab provided on an upper portion of the electrode, The secondary battery of claim 9 , wherein the pressure tape is attached to an upper portion of the folding cell where the electrode tab is located.

11. The secondary battery according to claim 10 , wherein the pressure tape is further attached to a lower portion of the folding cell.

12. The secondary battery according to claim 10 , wherein the pressure tape is attached to an outermost surface of the release film.

13. The secondary battery of claim 12 , wherein the pressure tape is attached to at least one of a front surface and a rear surface of the folding cell in a direction perpendicular to a folding axis of the folding cell.

14. The secondary battery according to claim 13, wherein the pressure tape has a thickness of 10 to 300 μm.

15. The secondary battery of claim 13, wherein the length of the pressure tape attached to the folded cell in the folding axis direction of the folded cell is 5 to 300 mm.

16. The secondary battery of claim 12 , wherein the pressure tape is attached to surround an upper portion of the folding cell such that the upper portion of the folding cell is pressurized.

17. The secondary battery of claim 16 , wherein the pressure tape is attached to surround the folded cell in a folding direction of the folded cell.

18. The secondary battery according to claim 17, wherein the pressure tape has a thickness of 1 to 300 μm.

19. The secondary battery of claim 17, wherein the length of the pressure tape attached to the folded cell in the folding axis direction of the folded cell is 0.5 to 300 mm.

20. The secondary battery according to claim 16 , wherein the pressure tape is attached to surround an upper portion of the folding cell in a folding axis direction of the folding cell.

21. The pressure tape includes a substrate and an adhesive layer, The secondary battery of claim 9, wherein the substrate includes any one of polypropylene, polyethylene, polyimide, and polyethylene terephthalate.

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