Jelly-roll type electrode assembly and manufacturing method thereof

Abstract

The present invention relates to a jelly roll type electrode assembly in which a first separator sheet, a first electrode sheet, a second separator sheet, and a second electrode sheet are sequentially stacked and wound up with the first separator sheet positioned at the innermost position and the first electrode sheet positioned at the outermost position, and a corner at an inner end of the second electrode sheet that contacts the first separator sheet and the second separator sheet has a curved shape, thereby preventing damage to the separator sheet due to a positive electrode sheet that expands during charging and discharging of the electrode assembly.

Description

[Technical Field]

[0001] This application claims the benefit of priority based on Korean Patent Application No. 10-2022-0103626 filed on August 18, 2022, and Korean Patent Application No. 10-2023-0107460 filed on August 17, 2023, and all contents disclosed in the Korean patent applications are incorporated herein by reference.

[0002] The present invention relates to a jelly roll electrode assembly including an electrode sheet with an adhesive and a manufacturing method thereof, and more particularly, to a jelly roll electrode assembly and a manufacturing method thereof in which an end portion of a winding start portion of an electrode sheet that is relatively far from the winding start point among electrode sheets constituting the jelly roll electrode assembly is curved to prevent damage to a separator sheet. [Background technology]

[0003] Depending on the shape of the battery case, lithium secondary batteries can be classified into cylindrical or prismatic secondary batteries in which an electrode assembly is housed in a cylindrical or prismatic metal can, and pouch-type secondary batteries in which an electrode assembly is housed in a pouch-type case made of an aluminum laminate sheet.

[0004] A cylindrical secondary battery uses a jelly-roll type electrode assembly in which an electrode sheet and a separator sheet are wound together. The electrode sheet repeatedly expands and contracts during charging and discharging, which may cause the periphery of the jelly-roll type electrode assembly to expand or the front and rear ends of the electrode sheet to elongate.

[0005] The electrode sheet is unwound from the electrode roll and then cut to a predetermined length to form an electrode assembly, but the cut surface of the electrode sheet may be uneven and sharp, which may damage the separator sheet and cause the insulation of the electrode assembly to be destroyed.

[0006] FIG. 1 is a cross-sectional view of a jelly roll type electrode assembly according to the prior art, and FIG. 2 is an enlarged view of a portion of the center of FIG.

[0007] 1 and 2, the jelly roll electrode assembly 100 is wound up in a stacked state of a first separator sheet 130, a first electrode sheet 110, a second separator sheet 140, and a second electrode sheet 120. At the start of winding the jelly roll electrode assembly 100, the inner edge of the first electrode sheet 110 extends further than the inner edge of the second electrode sheet 120. As the jelly roll electrode assembly 100 is charged and discharged, the second electrode sheet 120 may expand or contract in the direction of the arrow in FIG. 2.

[0008] For reference, although FIGS. 1 and 2 show the first separator sheet 130 as extending beyond the first electrode sheet 110, the edges of the first separator sheet 130 and the first electrode sheet 110 may coincide, and this can be changed as needed.

[0009] Here, the cut surface of the inner edge of the second electrode sheet 120 is sharp due to cutting, and this may damage the first separator sheet 130 and the second separator sheet 140 that come into contact with the cut surface, gradually reducing the thickness of the first separator sheet 130 and the second separator sheet 140. Furthermore, as charging and discharging continues, the first electrode sheet 110 and the second electrode sheet 120 repeatedly expand and contract, and the damaged separator sheet gradually becomes thinner and may then be perforated, which may cause the inner edge of the second electrode sheet 120 to come into contact with the first electrode sheet 110, resulting in a short circuit.

[0010] Since the inner end portion, which is the starting point for winding the first electrode sheet 110, extends further inward than the inner end portion, which is the starting point for winding the second electrode sheet 120, there is no problem of a short circuit between the inner end portion of the first electrode sheet 110 and the second electrode sheet 120 even if the first electrode sheet 110 contracts and expands due to charging and discharging.

[0011] Figure 3 is a photograph of the start of rewinding a wound jelly-roll electrode assembly, and Figure 4 is a 200x magnified photograph of the cut edge of the positive electrode. Figures 3 and 4 show that the above-mentioned problems occur in wound jelly-roll electrode assemblies.

[0012] Figure 4 is a photograph of the edge of a cut cathode taken from above. Referring to the coordinates and reference numerals in Figure 8, the cut surface 112 was photographed from above the Z axis. The boundary displayed in a different color in the center corresponds to the cut surface 112, with the right side being a simple background and the left side being the cathode. As can be seen from Figure 4, the cut surface of the cathode is very sharp.

[0013] Figure 3 is a photograph of the start of winding after unwinding a wound jelly roll-type electrode assembly, and it can be seen that there is a bright or white area inside the central dotted circle. Figure 3 is a photograph taken with a light placed on the back of the unwound electrode assembly, and the bright or white area inside the dotted circle is where part of the separator sheet was cut open, allowing light to leak through. The dotted circle is the inner edge of the positive electrode sheet in the start of winding the electrode assembly. This shows that the separator sheet that contacts the inner edge of the positive electrode sheet in the start of winding the electrode assembly is essentially damaged.

[0014] Patent Document 1 relates to an electrode assembly having a structure in which a separator is interposed between a positive electrode sheet and a negative electrode sheet and the positive electrode sheet are wound up, and the separator and the positive electrode sheet are adhered to each other by attaching double-sided adhesive tape to the uncoated portion of the positive electrode sheet. This configuration enhances the mechanical rigidity of the separator located in the center of the jelly roll-type electrode assembly and prevents the positive or negative electrode sheet from slipping and coming into contact with the opposite electrode due to the low friction of the separator during the winding process, thereby preventing an internal short circuit.

[0015] Patent Document 2 discloses a configuration in which an electrode winding group is wound around a cylindrical shaft core, and the leading end of the winding of the separation membrane is adhered to the cylindrical shaft core with an acrylic adhesive.

[0016] In the cylindrical lithium-ion battery of Patent Document 2, the winding opening end of the separator is adhered to the shaft core with the acrylic adhesive, which improves winding workability and prevents internal short circuits due to lead breakage or damage to the electrode winding group even when vibration is applied to the cylindrical lithium-ion battery.

[0017] Patent Documents 1 and 2 only disclose a configuration in which the electrode sheet is fixed with an adhesive, and do not recognize the problem that the separator may be damaged if the cut surface of the electrode sheet is not smooth when it is wound up, and are unable to provide a solution to this problem.

[0018] In Patent Document 3, the edges of the negative electrode active material layer formed at the widthwise end of a wound electrode assembly are made to form an acute angle. This is intended to prevent damage due to shrinkage of the separator. Patent Document 3 only addresses the problem of uncoated areas that can be easily observed externally, and does not address the problem inside the winding recognized in the present invention. Furthermore, because the thickness of the electrode active material layer is very thin, it is virtually impossible to make the edges acute by separate processing. In Patent Document 3, the acute angle is achieved by a method in which compositions applied using a coating device with two coating ports flow in the width direction and come into contact with each other, but this is not applicable to continuous coating in the lengthwise direction as in the present invention.

[0019] The breakage of the separator due to a sharp cut on the electrode sheet at the center of the winding of the jelly roll electrode assembly and the resulting short circuit are problems that occur when charging and discharging are performed repeatedly. However, it was previously thought that the charge / discharge life was shortened due to the denaturation of the negative and positive electrode materials and the formation of lithium dendrites.

[0020] As a result of continued research, the present inventors have found that physical damage to the separator sheet, which is essentially located at the center of the winding of a jelly roll-type electrode assembly, can also shorten the charge / discharge life of a battery. Thus, in the past, the problem of separator sheet damage was not recognized, and no solution to this problem was proposed. [Prior art documents] [Patent documents]

[0021] [Patent Document 1] Korean Patent Publication No. 10-2009-0027314 [Patent Document 2] Japanese Patent Application Laid-Open No. 2001-126769 [Patent Document 3] Japanese Patent Application Laid-Open No. 2015-181112 Summary of the Invention [Problem to be solved by the invention]

[0022] It is analyzed that the above-mentioned problems occur when a battery is used for a long period of time, resulting in an increase in the number of charge / discharge cycles. Previous research has only focused on problems that occur during the initial charge / discharge cycle, and has simply attributed the above-mentioned problems that arise during long-term charge / discharge cycles to issues with the efficiency of the battery itself or the lifespan of different materials. The present invention analyzes each of the potential problems that can occur when a secondary battery, particularly a cylindrical secondary battery, is charged and discharged for a long period of time, and has found that tearing of the separator sheet during long-term charge / discharge cycles, particularly breakage of the separator sheet at the start of winding in a jelly roll-type electrode assembly, has a significant impact on the long-term lifespan of the battery. The present invention aims to solve these problems.

[0023] The present invention has been made to solve the above problems, and an object of the present invention is to provide a jelly-roll type electrode assembly and a manufacturing method thereof that prevent a separator from being damaged by a sharp cut surface of an electrode sheet at the winding center of the jelly-roll type electrode assembly, thereby preventing a short circuit from occurring. [Means for solving the problem]

[0024] In order to achieve the above object, the electrode assembly according to the present invention includes a first separator sheet, a first electrode sheet, a second separator sheet, and a second electrode sheet stacked in this order, the first separator sheet being located at the innermost position, 2 The electrode sheets are wound to be positioned at the outermost side, and the corners of the inner end of the second electrode sheet that contact the first separator sheet and the second separator sheet may have a curved shape.

[0025] The outer surface of the protective resin applied to at least some of the corners and edges of the inner end portion of the second electrode sheet may be curved.

[0026] The protective resin may be one or more selected from the group consisting of an instant adhesive, a hot melt adhesive, and a pressure sensitive adhesive.

[0027] The protective resin may include an elastic material.

[0028] The inner end of the first electrode sheet may be configured to extend further toward the winding center than the inner end of the second electrode sheet.

[0029] The protective resin may further be applied to the cut surface of the winding start portion of the second electrode sheet.

[0030] The cut surface of the inner end of the second electrode sheet may have a curved shape.

[0031] At least a portion of the cut surface may be configured to have a thickness that decreases toward an inner end.

[0032] The protective resin does not have to be bonded to the first separation membrane sheet and the second separation membrane sheet.

[0033] The first electrode sheet may be a negative electrode sheet, and the second electrode sheet may be a positive electrode sheet.

[0034] The present invention provides a cylindrical battery cell in which the jelly-roll type electrode assembly is housed in a cylindrical battery case.

[0035] The present invention also provides a method for manufacturing the jelly-roll type electrode assembly.

[0036] Specifically, the jelly roll type electrode assembly may include the steps of: (a) preparing a first separator sheet, a first electrode sheet, a second separator sheet, and a second electrode sheet; (b) applying a protective resin to a winding start portion of the second electrode sheet; and (c) winding up the first separator sheet, the first electrode sheet, the second separator sheet, and the second electrode sheet.

[0037] The application of the protective resin can be carried out immediately after cutting the second electrode sheet.

[0038] The protective resin can be applied to the cut surface using a brush-type tool or by spraying the protective resin onto the cut surface.

[0039] After the protective resin has completely dried, step (c) can be carried out.

[0040] The method may further include cutting the first electrode sheet drawn from the first electrode roll and adding a first electrode tab or a first electrode lead, and cutting the second electrode sheet drawn from the second electrode roll and adding a second electrode tab or a second electrode lead.

[0041] In addition, the present invention can also be provided in the form of various combinations of the means for solving the above problems. [Effects of the Invention]

[0042] As described above, in the jelly roll-type electrode assembly according to the present invention, the corners at the inner ends of the winding start portion of the second electrode sheet that contact the first and second separator sheets are curved, thereby deforming sharp or pointed portions into a curved shape, thereby preventing the separator sheets from being damaged by sharp corners or edges of the second electrode sheet.

[0043] In addition, the electrode sheet and the separator sheet are wound up together after the protective resin applied to the inner edge of the second electrode sheet has completely dried, which prevents the second electrode sheet and the separator sheet from being adhered to each other by the protective resin, and therefore the separator sheet is not damaged even if the second electrode sheet expands.

[0044] The present invention solves structural problems that occur during long-term charge-discharge cycles, which were not previously recognized, and overcomes the limitations on charge-discharge cycles that arise due to structural problems rather than the lifespan of the positive and negative electrode materials themselves, and these configurations and effects were completely unknown in the past. [Brief explanation of the drawings]

[0045] [Figure 1] FIG. 1 is a cross-sectional view of a jelly roll-type electrode assembly according to the prior art. [Figure 2] FIG. 2 is a partially enlarged view of the central portion of FIG. [Figure 3] 10 is a photograph of the start of winding of a wound jelly roll-type electrode assembly after it has been unwound. [Figure 4] This is a 200x magnification of the edge of the cut cathode. [Figure 5] 1 is a perspective view of a jelly roll-type electrode assembly according to the present invention; [Figure 6] FIG. 6 is a cross-sectional view of FIG. 5. [Figure 7] FIG. 7 is a partially enlarged view of the central portion of FIG. 6. [Figure 8] FIG. 2 is a perspective view of a portion of a second electrode sheet. [Figure 9] 9A and 9B are perspective views of the second electrode sheets shown in FIGS. 7 and 8, respectively. [Figure 10] 9 is a partial enlarged view of the center of the jelly-roll type electrode assembly including the second electrode sheet of FIG. 8. FIG. [Figure 11] FIG. 10 is a perspective view of a second electrode sheet having a rounded inner end portion. [Figure 12] 1 is an exploded perspective view of a cylindrical battery cell according to the present invention. [Figure 13] FIG. 10 is a schematic diagram of a step of applying a protective resin to the winding start portion of the second electrode sheet. DETAILED DESCRIPTION OF THE INVENTION

[0046] Hereinafter, with reference to the accompanying drawings, a detailed description will be given of an embodiment of the present invention that will enable a person skilled in the art to easily carry out the present invention. However, in describing the operation principle of the preferred embodiment of the present invention in detail, detailed description of related well-known functions or configurations will be omitted if it is determined that such detailed description may unnecessarily obscure the gist of the present invention.

[0047] Furthermore, the same reference numerals are used throughout the drawings for parts having similar functions and actions. Throughout the specification, when a part is said to be connected to another part, this includes not only a direct connection but also an indirect connection via another element therebetween. Furthermore, unless otherwise specified, "including a certain element" does not mean that other elements are excluded, but that other elements may also be included.

[0048] Furthermore, descriptions that specify or add elements are applicable to all inventions unless otherwise specified, and are not limited to a particular invention.

[0049] Furthermore, throughout the description of the present invention and the claims, the singular includes the plural unless otherwise stated.

[0050] Furthermore, throughout the description of the present invention and the claims, unless otherwise specified, "or" includes "and." Therefore, "including A or B" means the three cases of including A, including B, or including both A and B.

[0051] The invention will now be explained with reference to the drawings and in conjunction with detailed embodiments.

[0052] Fig. 5 is a perspective view of a jelly-roll type electrode assembly according to the present invention, Fig. 6 is a cross-sectional view of Fig. 5, and Fig. 7 is a partially enlarged view of the center of Fig. 6. Also, Fig. 8 is a perspective view of a portion of a second electrode sheet, Fig. 9 is a perspective view of the second electrode sheets shown in Figs. 7 and 8, respectively, and Fig. 10 is a partially enlarged view of the center of the jelly-roll type electrode assembly including the second electrode sheet of Fig. 8.

[0053] 5 to 10, the jelly roll type electrode assembly 100 according to the present invention includes a first separator sheet 130, a first electrode sheet 110, a second separator sheet 140, and a second electrode sheet 120 stacked in order. 2 The electrode sheet is wound so that it is positioned on the outermost side.

[0054] Although FIG. 6 shows the inner edges of the first separator sheet 130 and the second separator sheet 140 as being aligned, if necessary, one of the first separator sheet 130 and the second separator sheet 140 may be elongated more than the other, and one of the first separator sheet 130 and the second separator sheet 140 may be positioned closer to the winding center of the jelly roll-type electrode assembly 100 when wound up.

[0055] The first electrode sheet 110 is wound closer to the winding center, i.e., extended longer, than the second electrode sheet 120. The winding start point, which is the inner edge of the first electrode sheet 110, extends closer to the winding center than the winding start point, which is the inner edge of the second electrode sheet 120.

[0056] In general, to manufacture the jelly roll type electrode assembly 100, a first electrode sheet 110 wound around a first electrode roll and a second electrode sheet 120 wound around a second electrode roll are unwound and cut to a predetermined length, a first electrode tab 11 and a second electrode tab 12 are attached to uncoated portions of the surfaces of the first electrode sheet 110 and the second electrode sheet 120 that are not coated with an electrode mixture, respectively, and the first electrode sheet and the second electrode sheet are stacked together with a separator sheet and then rolled up to manufacture the jelly roll type electrode assembly.

[0057] During charging and discharging, the volume of the jelly roll electrode assembly may increase or decrease toward the winding center and the winding periphery, and therefore the length of the electrode sheet may also increase or decrease.

[0058] As a result of the electrode sheet's behavior, which changes in volume and length, the end of the electrode sheet's winding start portion may extend toward the separator sheet, damaging the separator sheet. It is expected that the lengths of both the winding start portion and the winding end portion will change during charging and discharging, and damage to the separator primarily occurs at the winding start portion due to the difference in curvature between the winding start portion and the winding end portion. This portion is commonly referred to as the core-free edge. The problem addressed by the present invention, which is to prevent the separator sheet from being pierced at the winding start portion, is also because problems primarily occur at the winding start portion.

[0059] In addition, when the first and second electrode sheets are cut with a blade, the cut surfaces of the first and second electrode sheets may become sharp. The sharp cut surfaces of the first and second electrode sheets may rub against the separator sheet during charging and discharging, damaging the separator sheet. Such damage to the separator sheet may cause a short circuit between different electrodes.

[0060] For example, the first and second electrode sheets may be a positive electrode sheet and a negative electrode sheet, respectively, or may be a negative electrode sheet and a positive electrode sheet, respectively. However, considering that the lengths of the separator sheet, negative electrode sheet, and positive electrode sheet generally decrease in this order, in FIGS. 6 and 7, the first electrode sheet 110 may be a negative electrode sheet, and the second electrode sheet 120 may be a positive electrode sheet.

[0061] When the winding start point, which is the inner edge of the first electrode sheet 110, extends toward the winding center further than the winding start point, which is the inner edge of the second electrode sheet 120, and the first electrode sheet 110 is positioned closer to the winding center of the jelly roll-type electrode assembly, the first electrode sheet 110 is wound inward and outward based on the winding start point of the second electrode sheet 120. When the second electrode sheet 120 contracts and expands due to charging and discharging, if the edge 111 of the cut surface, which is the inner edge of the second electrode sheet 120, is sharp, the first separator sheet 130 and the second separator sheet 140 may be damaged. If such damage to the separator sheets is repeated, tears may occur, and a short circuit may occur between the second electrode sheet 120 and the first electrode sheet 110.

[0062] Therefore, in the present invention, as shown in Figures 7 and 9(a), a protective resin 201 is added to the corner 111 that contacts the first separator sheet 130 and the second separator sheet 140 at the inner end, which is the winding start portion of the second electrode sheet 120, so that the sharp corner 111 at the inner end of the second electrode sheet 120 can be deformed into a curved shape by the protective resin 201.

[0063] Therefore, as shown in FIG. 7, even if the second electrode sheet 120 extends in the direction of the arrow and comes into contact with the first separator sheet 130 and the second separator sheet 140 during charging and discharging of the jelly roll-type electrode assembly, damage to the first separator sheet 130 and the second separator sheet 140 can be minimized because the corners 111 of the second electrode sheet 120 have a curved shape.

[0064] The first electrode sheet 110 extends further than the second electrode sheet 120, and the second electrode sheet 120 does not exist in the extended portion, so there is no problem of short circuit even if the first electrode sheet 110 contracts or expands due to charging and discharging.

[0065] Meanwhile, when wound into the jelly roll-type electrode assembly according to the present invention, the electrode coating layers on both outer peripheries of the first electrode sheet 110 as well as the second electrode sheet 120 parallel to the circumferential direction may be configured in an angular shape rather than a curved shape.

[0066] Referring to Figures 8 and 9 (b), at the winding start portion, which is the inner end portion of the second electrode sheet 120, protective resin 201 is added to the four-way edges 113 of the cut surface 112, and further protective resin 201 can be added so as to extend from the cut surface 112 in the longitudinal direction Y of the second electrode sheet 120.

[0067] In the present invention, the expression "adhesive is applied to the edges" includes the case where adhesive is applied to at least one of the edges.

[0068] In this way, in the present invention, since the protective resin is applied to at least a part of the corners and edges of the inner end portion of the second electrode sheet, the angular or sharp portions can be deformed into a curved shape.

[0069] On the other hand, if the second electrode sheet 120 is bonded to the first separator sheet 130 and / or the second separator sheet 140 by the protective resin 201, the first separator sheet 130 and / or the second separator sheet 140 may be torn when deformation occurs due to expansion and stretching of the second electrode sheet 120. Therefore, it is preferable that the protective resin 201 is not bonded to the first separator sheet 130 and the second separator sheet 140.

[0070] In one specific example, the protective resin may have the property of maintaining the curved surface due to surface tension when applied to the start of winding of the electrode sheet, not being absorbed into the electrode mixture layer of the electrode sheet, and having a fast curing rate.

[0071] For example, the protective resin may be at least one selected from the group consisting of cyanoacrylate-based instant adhesives; hot-melt adhesives such as ethylene vinyl acetate-based, polyolefin-based, styrene block copolymer-based, polyamide-based, polyester-based, and urethane-based adhesives; and pressure-sensitive adhesives such as acrylic resin, butyl rubber, and vinyl acetate. However, considering that the protective resin applied to the edges of the winding start portion of the electrode sheet is completely dried before being wound into a jelly-roll electrode assembly, it is preferable to use a fast-curing instant adhesive to prevent the protective resin applied to the edges of the electrode sheet from adhering to the first separator sheet 130 and the second separator sheet 140.

[0072] Meanwhile, when the length of the second electrode sheet 120 expands or contracts with the protective resin 201 attached to the second electrode sheet 120, it is preferable that there is little friction with the first separator sheet 130 and / or the second separator sheet 140.

[0073] FIG. 10 is a partial enlarged view of the center of the jelly-roll type electrode assembly including the second electrode sheet of FIG.

[0074] Referring to FIG. 10, protective resin 201 is applied not only to corner 111 at the winding start portion, which is the inner end of second electrode sheet 120, but also to the outer surface of cut surface 112.

[0075] In such a case, if the protective resin 201 cannot expand and contract together with the first electrode sheet 110 and the second electrode sheet 120 during the expansion and contraction process, it may become detached, so the adhesive may include an elastic material such as urethane, rubber, or an elastic polymer.

[0076] FIG. 11 is a perspective view of a second electrode sheet having a rounded inner edge.

[0077] 11, the cut surface 112 at the inner end of the second electrode sheet 120 is curved. Specifically, the cut surface 112 of the second electrode sheet 120 shown in Figures 11(a) and 11(b) is curved. Therefore, even if the length of the second electrode sheet 120 extends in the circumferential direction R, the corners 111 are curved and the cut surfaces 112 of the corners 111 are rounded, so there is little risk of the first separator sheet 130 and / or the second separator sheet 140 being damaged.

[0078] 11(a) and 11(b) show a configuration in which no protective resin is applied to the inner edge of the second electrode sheet 120. Even without the protective resin, the rounded shape of the inner edge of the second electrode sheet 120 reduces the risk of problems such as short circuits caused by damage to the separator sheet.

[0079] 11(b) shows a configuration in which the thickness of the inner end portion of the second electrode sheet 120 is not uniform. Specifically, at least a portion of the cut surface of the inner end portion of the second electrode sheet 120 may be configured to have a thickness that decreases toward the inner end and toward the center of the second electrode sheet 120 in the width direction x.

[0080] However, in the case of FIG. 11, a protective resin like that of FIGS. 7 to 10 can be further added.

[0081] When the cut surface of the inner end portion, which is the winding start point of the electrode sheet located relatively far from the winding center, of the first and second electrode sheets is curved as in the present invention, damage to the separator sheet caused by the electrode sheet expanding at the winding center of the jelly roll-type electrode assembly can be prevented without adding a separate member such as a protective resin, as compared to adding a protective resin to the inner end portion. However, since an additional process is required to curve the cut surface of the inner end portion of the electrode sheet, the manufacturing cost and the manufacturing process may be lengthened.

[0082] Meanwhile, when the separator and the positive electrode sheet are attached by attaching double-sided adhesive tape to the uncoated portion of the double-sided sheet as in Patent Document 1, if the separator cannot change its length in accordance with the change in length of the positive electrode sheet during charging and discharging, the separator may break. Also, when the outer end of the separator is fixed with an adhesive as in Patent Document 2, the separator can be stably fixed, but it cannot prevent the separator sheet from being damaged by the rough cut surface of the inner end of the electrode sheet when the electrode sheet expands and changes in length in a jelly roll electrode assembly.

[0083] FIG. 12 is an exploded perspective view of a cylindrical battery cell according to the present invention.

[0084] Referring to FIG. 12, the cylindrical battery cell according to the present invention is formed by housing the jelly-roll-type electrode assembly 100 described above in a cylindrical battery case 300, and sealing the cylindrical battery case 300 by combining a cap assembly 310 to the top of the cylindrical battery case 300.

[0085] The cap assembly 310 includes a top cap 311 located at the top end and having a gas release hole formed therein, a safety vent 312 that changes shape to release gas when the internal pressure of the cylindrical battery case 300 increases, and a gasket 313 that is disposed between the outer periphery of the top cap 311 and the safety vent 312 and the cylindrical battery case 300 for sealing.

[0086] It goes without saying that other components such as a current interrupting member that are conventionally included in the cap assembly 310 may be additionally provided as needed.

[0087] A first electrode tab 11 is attached to the jelly-roll type electrode assembly 100 so as to protrude upward, and a second electrode tab 12 is attached to the jelly-roll type electrode assembly 100 so as to protrude downward. The first electrode tab 11 is attached to the lower part of the cap assembly 310, and the second electrode tab 12 is attached to the inner bottom surface of the cylindrical battery case 300.

[0088] Although FIG. 12 shows one first electrode tab and one second electrode tab, the number of first electrode tabs and second electrode tabs may be increased in consideration of rate control and battery capacity, and their attachment positions may also be varied.

[0089] A method for manufacturing a jelly roll-type electrode assembly according to the present invention may include the steps of: (a) preparing a first separator sheet, a first electrode sheet, a second separator sheet, and a second electrode sheet; (b) applying a protective resin to a winding start portion of the second electrode sheet; and (c) winding up the first separator sheet, the first electrode sheet, the second separator sheet, and the second electrode sheet.

[0090] When the second electrode sheet is cut, the cut surface may be sharp, and if such a second electrode sheet comes into contact with the separator sheet, the separator sheet may be damaged. Therefore, before the second electrode sheet damages the separator sheet, it is preferable to soften the corners of the cut surface by applying a protective resin to the corners of the inner edge of the second electrode sheet that come into contact with the first separator sheet and the second separator sheet. Alternatively, a protective resin may be applied to the edge of the cut surface or at least a portion of the outer surface of the cut surface.

[0091] Therefore, the step of applying the protective resin can be performed immediately after cutting the second electrode sheet that is pulled out from the second electrode roll.

[0092] FIG. 13 is a schematic diagram showing the application of protective resin to the winding start portion of the second electrode sheet.

[0093] 13, (a) shows a method of applying protective resin to the winding start portion of the second electrode sheet 120 being unwound from the second electrode roll 20 using a tool such as a brush 401, and (b) shows a method of spraying protective resin to the winding start portion of the second electrode sheet 120 being unwound from the second electrode roll 20 using a sprayer 402. By applying protective resin to the edge of the winding start portion of the second electrode sheet in this manner, the corners and / or edges of the cut surface of the second electrode sheet 120 can be deformed into a curved shape. Therefore, it is possible to prevent short circuits caused by damage to the separator sheet between the first and second electrode sheets due to expansion and stretching of the second electrode sheet.

[0094] The method for applying the protective resin is not limited to the method shown in FIG. 11, as long as the protective resin can be applied uniformly and quickly to the winding start portion of the second electrode sheet.

[0095] In the present invention, a protective resin is applied to the corners and / or edges of the cut surface of the inner end of the second electrode sheet, which extends relatively small toward the winding center of the jelly roll-type electrode assembly, and step (c) is performed after the protective resin is completely dried. This prevents the protective resin from being applied to the first and second separator sheets arranged adjacent to the second electrode sheet, and therefore prevents the first and second separator sheets from adhering to the second electrode sheet.

[0096] The method for manufacturing a jelly roll electrode assembly according to the present invention includes a process for manufacturing a jelly roll electrode assembly 100 having a first electrode tab 11 and a second electrode tab 12 attached thereto, as shown in Fig. 12. This process further includes the steps of cutting a first electrode sheet drawn out from a first electrode roll and attaching a first electrode tab thereto, and cutting a second electrode sheet drawn out from a second electrode roll and attaching a second electrode tab thereto.

[0097] The first and second electrode tabs serve as paths for electron transfer in the jelly roll electrode assembly, and the second electrode tab is a positive electrode tab that can be attached to the bottom of a cap assembly, allowing the top cap to function as a positive electrode terminal. The first electrode tab is a negative electrode tab that can be attached to the inner bottom surface of a cylindrical battery case, allowing the cylindrical battery case to function as a negative electrode terminal.

[0098] The present invention will be described below with reference to examples, but these are for easier understanding of the present invention and are not intended to limit the scope of the present invention.

[0099] <Reference example 1> Cut surface of the positive electrode sheet To manufacture a jelly roll-type electrode assembly, a positive electrode sheet was cut from a positive electrode roll, and a photograph of the cross section, magnified 200 times, is shown in Figure 4.

[0100] 4 shows a plan view of a cut surface of the positive electrode sheet. Specifically, it shows a portion of the cut surface when the positive electrode sheet is viewed from top to bottom in the z-axis direction of FIG. 8, as if looking at the second electrode sheet 120, and the remaining part excluding the positive electrode sheet corresponds to the background.

[0101] It can be seen that the cut surface of the positive electrode sheet shown in FIG. 4 is not an uneven or curved surface but is formed at right angles.

[0102] Therefore, if a jelly roll electrode assembly is assembled with the negative electrode sheet positioned at the center of the winding without any treatment such as adding a protective resin to the cut surface of the positive electrode sheet, there is a high risk of a short circuit occurring between the positive electrode sheet and the negative electrode sheet due to expansion and contraction of the positive electrode sheet.

[0103] <Reference example 2> The winding center of a jelly roll-type electrode assembly where a short circuit occurred The negative electrode sheet, the first separator sheet, the positive electrode sheet of Reference Example 1, and the second separator sheet were sequentially arranged so that the negative electrode sheet was positioned at the center of the winding, and then wound up. After pouring in the electrolyte, a cylindrical battery cell was assembled.

[0104] The cylindrical battery cell was charged and discharged until a short circuit occurred, and then the cylindrical battery cell was disassembled, the jelly-roll type electrode assembly was taken out, and the presence or absence of damage to the separator was confirmed.

[0105] Figure 3 is a photograph of the center of the winding of a jelly roll-type electrode assembly where a short circuit occurred.

[0106] In order to check for damage to the separator sheet at the winding center of the jelly roll type electrode assembly, a light was placed behind the separator sheet and the separator sheet was observed.

[0107] In Figure 3, a white area is observed within the dotted circle. This is observed when illumination light passes through the torn part of the separation membrane sheet. It was confirmed that tearing of the separation membrane sheet occurred as a result of using the positive electrode sheet of Reference Example 1, in which no treatment was performed on the cut surface.

[0108] Therefore, when a protective resin is applied to the corners and / or edges of the sharp cut surfaces of the electrode sheet or the cut surfaces are processed to be curved, the effect of preventing damage to the separator sheet can be significantly improved.

[0109] Those skilled in the art will be able to make various applications and modifications within the scope of the present invention based on the above content. [Explanation of symbols]

[0110] 11 First electrode tab 12 Second electrode tab 20 Second electrode roll 100 Jelly roll type electrode assembly 110 First electrode sheet 111 Corner 112 Cut surface 113 Edge 120 Second electrode sheet 130 First separation membrane sheet 140 Second separation membrane sheet 201 Protective resin 300 Cylindrical Battery Case 310 Cap Assembly 311 Top Cap 312 Safety Vent 313 Gasket 401 Brush 402 Injector

Claims

1. A first separation membrane sheet, a first electrode sheet, a second separation membrane sheet, and a second electrode sheet are sequentially stacked, The second electrode sheet is wound up so that the second electrode sheet is positioned on the outermost side. a corner of the inner edge of the second electrode sheet that contacts the first separator sheet and the second separator sheet has a curved shape; The cut surface of the inner end of the second electrode sheet has a curved shape.

2. The jelly-roll type electrode assembly of claim 1 , wherein the outer surface of the protective resin applied to at least some of the corners and edges of the inner end portion of the second electrode sheet is curved.

3. 3. The jelly roll type electrode assembly according to claim 2, wherein the protective resin is at least one selected from the group consisting of an instant adhesive, a hot melt adhesive, and a pressure sensitive adhesive.

4. The jelly roll type electrode assembly according to claim 2 , wherein the protective resin includes an elastic material.

5. The jelly-roll type electrode assembly according to claim 1 , wherein an inner end of the first electrode sheet extends closer to the center of the winding than the inner end of the second electrode sheet.

6. The jelly-roll type electrode assembly according to claim 2 , wherein the protective resin is further applied to the cut surface of the winding start portion of the second electrode sheet.

7. The jelly-roll type electrode assembly of claim 1 , wherein at least a portion of the cut surface is configured to have a thickness that decreases toward an inner end.

8. A first separation membrane sheet, a first electrode sheet, a second separation membrane sheet, and a second electrode sheet are sequentially stacked, The second electrode sheet is wound up so that the second electrode sheet is positioned on the outermost side. a corner of the inner edge of the second electrode sheet that contacts the first separator sheet and the second separator sheet has a curved shape; an outer surface of the protective resin applied to at least a portion of the corners and edges of the inner end portion of the second electrode sheet is configured in a curved shape; The protective resin is not bonded to the first separator sheet or the second separator sheet, in a jelly-roll type electrode assembly.

9. 9. The jelly-roll type electrode assembly of claim 1, wherein the first electrode sheet is a negative electrode sheet and the second electrode sheet is a positive electrode sheet.

10. A cylindrical battery cell, comprising the jelly roll-type electrode assembly according to claim 1 or 8 housed in a cylindrical battery case.

11. A method for manufacturing the jelly-roll type electrode assembly according to claim 1 or 8, comprising the steps of: (a) preparing a first separation membrane sheet, a first electrode sheet, a second separation membrane sheet, and a second electrode sheet; (b) applying a protective resin to a winding start portion of the second electrode sheet; (c) winding up the first separator sheet, the first electrode sheet, the second separator sheet, and the second electrode sheet; A method for manufacturing a jelly roll type electrode assembly, comprising:

12. The method of manufacturing a jelly-roll type electrode assembly according to claim 11 , wherein the application of the protective resin is performed immediately after cutting the second electrode sheet.

13. The method of claim 11, wherein the protective resin is applied to the cut surface using a brush-type tool or by spraying the protective resin.

14. 12. The method of claim 11, wherein step (c) is performed after the protective resin is completely dried.

15. cutting a first electrode sheet unwound from a first electrode roll and adding a first electrode tab or a first electrode lead; cutting the second electrode sheet unwound from the second electrode roll and adding a second electrode tab or a second electrode lead; The method for manufacturing a jelly roll type electrode assembly according to claim 11 , further comprising:

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