Jelly roll type electrode assembly, method for manufacturing a jelly roll type electrode assembly, and secondary battery containing the same

Abstract

The present invention relates to a jelly-roll type electrode assembly, a method for manufacturing the jelly-roll type electrode assembly, and a secondary battery including the same.

Description

[Technical Field]

[0001] The present invention relates to a jelly roll type electrode assembly, a method for manufacturing a jelly roll type electrode assembly, and a secondary battery including the same; more specifically, to a jelly roll type electrode assembly including a sweeping tape, a method for manufacturing a jelly roll type electrode assembly, and a cylindrical secondary battery including the same. This application claims the benefit as of the filing date of Korean Patent Application No. 10-2022-0121663, filed with the Korean Intellectual Property Office on September 26, 2022, and all contents disclosed in the documents of said Korean Patent Application are incorporated herein by reference. [Background technology]

[0002] In the case of cylindrical batteries, a jelly roll-shaped electrode assembly is manufactured by rolling up elongated electrodes of a defined width. Cylindrical batteries manufactured by inserting such jelly roll-shaped electrode assemblies into a battery case undergo repeated contraction and expansion of the electrodes during charging and discharging. In particular, if a tab is located in the core of the jelly roll-shaped electrode assembly, or if a silicon-based active material is added to the negative electrode, increasing the degree of contraction and expansion of the electrode assembly, the pressure acting on the core of the electrode assembly increases significantly.

[0003] In recent years, with the increasing demand for low-resistance / high-capacitance designs, jelly roll electrode assemblies increasingly contain multiple tabs or have silicon-based active materials added. This increases the possibility of deformation of the electrode assembly located in the core due to contraction / expansion of the electrode assembly. In particular, if the separator located between the negative and positive electrodes is damaged, the negative and positive electrodes can come into direct contact, causing a short circuit, heat generation, and ignition.

[0004] To solve the problem of separator damage and internal short circuits caused by deformation of such electrode assemblies, there is a need to develop technologies that can protect the positive electrode and separator in the affected area and suppress the occurrence of internal short circuits. [Overview of the project] [Problems that the invention aims to solve]

[0005] The present invention aims to provide a jelly roll type electrode assembly with a modified design, a method for manufacturing a jelly roll type electrode assembly, and a secondary battery containing the same.

[0006] However, the problems that this invention aims to solve are not limited to those described above, and other problems not mentioned can be clearly understood by those skilled in the art from the following description. [Means for solving the problem]

[0007] One embodiment of the present invention provides a jelly roll type electrode assembly comprising a first electrode; a first separator; a second electrode; and a second separator, which are sequentially laminated and wound together, and which includes a sweeping tape attached to at least one side of the first electrode, wherein the first electrode includes a first end along its length where winding begins and a second end where winding ends, and the sweeping tape is attached such that the first end and one end of the first electrode coincide.

[0008] Another embodiment of the present invention provides a method for manufacturing a jelly roll type electrode assembly in which a first electrode; a first separator; a second electrode; and a second separator are sequentially stacked and wound, comprising the steps of (a) transporting the first electrode in a roll-to-roll manner; (b) attaching a sweeping tape to at least one side of a slitting region included in the first electrode; and (c) slitting the longitudinal center of the slitting region of the first electrode, wherein step (b) is performed by attaching the sweeping tape such that its longitudinal center coincides with the longitudinal center of the slitting region of the first electrode, and step (c) is performed by slitting the longitudinal center of the slitting region to provide a first end where winding of the first electrode begins along its length; and a second end where winding ends, and provides a method for manufacturing a jelly roll type electrode assembly and a jelly roll type electrode assembly manufactured by the method.

[0009] Another embodiment of the present invention provides a secondary battery comprising the jelly roll-type electrode assembly and a battery case for housing the electrode assembly. [Effects of the Invention]

[0010] A jelly roll-type electrode assembly according to one embodiment of the present invention includes a swelling tape that expands when impregnated with an electrolyte and is attached to surround one end of the positive electrode in the longitudinal direction. This prevents damage to the positive electrode and separator from deformation of the electrode assembly due to contraction / expansion of the electrodes during battery charging and discharging. Even if the separator is damaged, the swelling tape prevents internal short circuits between the positive and negative electrodes, thereby improving the battery's stability and lifespan characteristics.

[0011] The manufacturing method of the jelly roll type electrode assembly according to an embodiment of the present invention enables the production of a jelly roll type electrode assembly including a swelling tape that swells during impregnation with the electrolytic solution and is attached so as to surround one end portion in the length direction of the positive electrode by a continuous process using conventional roll-to-roll process equipment, thereby ensuring productivity and economy.

[0012] In addition, the secondary battery according to the present invention can improve the stability and life characteristics of the battery by preventing an internal short circuit between the positive electrode and the negative electrode even when the electrode assembly is deformed due to contraction / expansion of the electrodes during charging and discharging of the battery.

[0013] The effects of the present invention are not limited to the effects described above, and the effects not mentioned are clearly understandable to those skilled in the art from the specification of the present application and the attached drawings.

Brief Description of the Drawings

[0014] [Figure 1] It shows a jelly roll type electrode assembly including a swelling tape according to an embodiment of the present invention. [Figure 2] It shows a schematic diagram of a manufacturing method of a jelly roll type electrode assembly including a swelling tape according to an embodiment of the present invention, and a manufacturing method of a jelly roll type electrode assembly including a PET tape. [Figure 3] It is an image showing an embodiment of a manufacturing method of a jelly roll type electrode assembly according to an embodiment of the present invention. [Figure 4] It shows the swelling test results of the swelling tape included in the jelly roll type electrode assembly according to an embodiment of the present invention. [Figure 5] It is an image showing the first end portion of the first electrode of the jelly roll type electrode assembly before and after activation according to Example 1. [Figure 6] It is an image showing the first end portion of the first electrode of the jelly roll type electrode assembly before and after activation according to Comparative Example 1. [Figure 7]This shows the changes in Coulomb efficiency as the cycle progresses and the evaluation results of room temperature-voltage tracking over time for the secondary batteries manufactured in Example 1 and Comparative Example 2. [Figure 8] This image shows the state of the first electrode-facing portion of the separator contained in the secondary batteries manufactured in Example 1 and Comparative Example 2. [Figure 9] This image shows the evaluation results of the roundness of the secondary batteries manufactured in Example 1 and Comparative Example 3. [Modes for carrying out the invention]

[0015] Throughout this specification, when a part of it is said to "include" a certain component, this means, unless otherwise stated, that it may include other components rather than excluding them.

[0016] Throughout this specification, when a member is described as being "on top of" another member, this includes not only cases where one member is in contact with another member, but also cases where another member exists between the two members.

[0017] One embodiment of the present invention provides a jelly roll type electrode assembly comprising a first electrode; a first separator; a second electrode; and a second separator, which are sequentially laminated and wound together, and which includes a sweeping tape attached to at least one side of the first electrode, wherein the first electrode includes a first end along its length where winding begins and a second end where winding ends, and the sweeping tape is attached such that the first end and one end of the first electrode coincide.

[0018] A jelly roll-type electrode assembly according to one embodiment of the present invention includes a swelling tape that expands when impregnated with an electrolyte and is attached to surround one end of the positive electrode in the longitudinal direction. This prevents damage to the positive electrode and separator from deformation of the electrode assembly due to contraction / expansion of the electrodes during battery charging and discharging. Even if the separator is damaged, the swelling tape prevents internal short circuits between the positive and negative electrodes, thereby improving the battery's stability and lifespan characteristics.

[0019] According to one embodiment of the present invention, the jelly roll type electrode assembly may include a sweeping tape attached to at least one side of the first electrode. Specifically, the sweeping tape may be attached to one side of the first electrode facing the winding shaft, or to the opposite side of the side facing the winding shaft, or to both sides of the first electrode.

[0020] As will be described later, the swelling tape may expand and increase in length when impregnated with the electrolyte, and when the swelling tape is attached to one side of the first electrode, the expanded swelling tape surrounds one end of the first electrode in the longitudinal direction, thereby preventing the first electrode and the second electrode, which face each other with the separator in between, from coming into direct contact even if the separator is damaged.

[0021] Therefore, when the swelling tape is attached to one side of the first electrode facing the winding shaft, it can more efficiently prevent internal short circuits between the positive and negative electrodes in the event of separator damage. Furthermore, when the swelling tape is attached to both sides of the first electrode, the expanded ends of the swelling tape surround the ends of the first electrode and come into contact with each other, thus providing even better protection for the longitudinal ends of the first electrode. Additionally, when the expanded swelling tape surrounds the longitudinal ends of the first electrode, the porous material properties of the swelling tape provide excellent relief of internal stress and improvement of the roundness of the core.

[0022] According to one embodiment of the present invention, the first electrode may include a first end along the length direction from which winding begins, and a second end from which winding ends. In other words, the first electrode may begin winding from the first end and proceed toward the second end. That is, the first end may mean a longitudinal end located in the core portion of the jelly roll-type electrode assembly after winding, and the second end may mean a longitudinal end located on the outer portion of the jelly roll-type electrode assembly after winding.

[0023] According to one embodiment of the present invention, the sweeping tape may be attached so that one end of the first electrode in the longitudinal direction coincides with the other end. Specifically, the sweeping tape may be attached so that the first end of the first electrode coincides with the other end. In other words, the sweeping tape may be attached so that one end coincides with the longitudinal end located in the core portion of the first electrode.

[0024] As a result, the swelling tape can prevent deformation of the electrode assembly due to the contraction / expansion of the electrodes during battery charging and discharging, and in particular damage to the separator due to sliding of the first end of the core portion first electrode. Specifically, one end of the swelling tape after expansion surrounds the end of the first electrode, or the ends of the swelling tape attached to both sides of the first end of the first electrode surround the end of the first electrode and are in contact with each other, so that even if damage to the separator occurs, it can efficiently prevent internal short circuits between the positive and negative electrodes.

[0025] According to one embodiment of the present invention, the widthwise length of the sweeping tape may be 60% or more and 100% or less based on 100% of the width of the first electrode. Specifically, the widthwise length of the sweeping tape may be 70% or more and 100%, 80% or more and 100%, 60% or more and 90%, 60% or more and 80%, 60% or more and 70%, or 70% or more and 90% or less based on 100% of the width of the first electrode. When the widthwise length of the sweeping tape satisfies the above range, the length of the sweeping tape after expansion can correspond to the widthwise length of the first electrode, and one end of the sweeping tape effectively surrounds one end of the first electrode in the longitudinal direction, thereby more efficiently preventing internal short circuits between the positive and negative electrodes even if the separator is damaged.

[0026] If the widthwise length of the sweeping tape is less than the range described above, the protective effect on the first end of the first electrode will be inferior, and the exposure of one end of the first electrode may cause damage to the separator, and when the separator is damaged, an internal short circuit may occur due to direct contact between the first electrode and the second electrode. On the other hand, if the widthwise length of the sweeping tape exceeds the range described above, the manufacturing cost will increase due to the use of excessive material, and one end of the sweeping tape after expansion will be excessively exposed in the widthwise direction of the jelly roll type electrode assembly, causing defects during the insertion process into the battery case, and local problems such as lithium deposition due to the formation of steps in the area where the sweeping tape is superimposed may occur. On the other hand, the preferred widthwise length of the sweeping tape may be adjusted according to the physical properties of the sweeping tape, in particular the length change rate before / after expansion.

[0027] According to one embodiment of the present invention, the length of the sweeping tape in the longitudinal direction may be 250% or more and 3500% or less based on 100% of the thickness of the first electrode. Specifically, the length of the sweeping tape in the longitudinal direction may be 300% or more, 350% or more, 400% or more, 450% or more, or 500% or more based on 100% of the thickness of the first electrode, and the length of the sweeping tape in the longitudinal direction may be 3000% or less, 2500% or less, 2000% or less, or 1500% or less based on 100% of the thickness of the first electrode, preferably 1000% or less, 850% or less, or 700% or less.

[0028] If the length of the sweeping tape in the longitudinal direction satisfies the range described above, the length of the sweeping tape in the longitudinal direction after expansion can correspond to the thickness of the first electrode, and one end of the sweeping tape will effectively surround one end of the first electrode in the longitudinal direction, thereby more efficiently preventing internal short circuits between the positive and negative electrodes even if the separator is damaged.

[0029] Specifically, the sweeping tape may expand by 40% or more on both sides in the width direction and length direction, and by 20% or more on one side. That is, if the length of the sweeping tape attached to both sides of the first electrode is 250% or more with respect to 100% of the thickness of the first electrode, the sum of the length of the expanded sweeping tape can correspond to the thickness of the first electrode, and one end of the sweeping tape attached to both sides of the first electrode can touch each other and effectively surround one end of the first electrode in the length direction.

[0030] Furthermore, if the length of the sweeping tape in the longitudinal direction is 500% or more of the thickness of the first electrode (100%), even if the sweeping tape is attached only to one side of the first electrode facing the winding shaft, the length of the expanded sweeping tape in the longitudinal direction can correspond to the thickness of the first electrode, and it can efficiently perform its role in preventing internal short circuits between the positive and negative electrodes when the separator is damaged.

[0031] In contrast, if the length of the sweeping tape in the longitudinal direction is less than 250% of the thickness of the first electrode (100%), the expanded sweeping tape may not be able to completely surround one end of the first electrode, leaving a portion exposed. This can result in a reduced effectiveness in preventing damage to the separator and in preventing internal short circuits between the positive and negative electrodes when the separator is damaged.

[0032] On the other hand, if the length of the sweeping tape attached to both sides of the first electrode is 1000% or less of the thickness of the first electrode, defects caused by the overlapping area of ​​the sweeping tape, which may occur when one end of the sweeping tape is excessively exposed in the longitudinal direction of the first electrode, can be minimized.

[0033] Furthermore, if the length of the sweeping tape in the longitudinal direction is 700% or less of the thickness of the first electrode (100%), the inactivation region that may be formed in the sweeping tape application area can be adjusted to an appropriate level, minimizing the impact on the electrochemical properties of the battery, including the sweeping tape, such as the rate of capacity reduction, while also achieving the aforementioned effect of preventing separator damage and internal short circuits.

[0034] According to one embodiment of the present invention, the first end of the first electrode may have its end formed at the same position as the current collector of the first electrode and the active material layer of the first electrode. In other words, the first end of the first electrode may be in a free-edge form. This reduces the area of ​​the blank portion of the first electrode current collector, thereby ensuring economic efficiency, and allows the slitting process to be performed after the active material layer is formed on the electrode, thus enabling the roll-to-roll process, including the slitting and winding processes, to be performed more efficiently. Here, "same position" means that the ends in the longitudinal direction are the same, and may include cases where the ends are formed at substantially the same position due to process errors that may occur in the slitting process, etc.

[0035] According to one embodiment of the present invention, the swelling tape may swell or become flexible due to the electrolyte. Specifically, the swelling tape may include a portion made of a polymer substance, as described later, and when the swelling tape is impregnated with an electrolyte, the portion made of the polymer substance may absorb the electrolyte and swell or become flexible. More specifically, as one of the properties of the polymer substance, solvent molecules may penetrate between the chains of the polymer substance, increasing its volume. As a result, the swelling tape can swell or become flexible when it absorbs an electrolyte.

[0036] According to one embodiment of the present invention, the swelling tape expands due to the electrolyte, and after expansion, the swelling tape may surround the first end of the first electrode. Specifically, as will be described later, the swelling tape may expand by absorbing an electrolyte containing an organic solvent, and its length in the longitudinal direction may increase, and one end of the swelling tape in the longitudinal direction may extend and be folded to surround the first end of the first electrode. In other words, after expansion, the swelling tape may increase in length and be folded to cover at least one edge of the first end of the first electrode.

[0037] This prevents the sharp free edge of the positive electrode from directly contacting the separator or negative electrode, thereby preventing damage to the positive electrode and separator from deformation of the electrode assembly due to the contraction / expansion of the electrodes during battery charging and discharging. Furthermore, even if the separator is damaged, the swelling tape prevents internal short circuits between the positive and negative electrodes, improving the battery's stability and lifespan.

[0038] Figure 1 shows a jelly roll type electrode assembly including a sweeping tape according to one embodiment of the present invention.

[0039] Specifically, Figure 1(a) shows the first electrode including the sweeping tape attached to both sides of the first electrode before impregnation with the electrolyte, Figure 1(b) shows the first electrode including the sweeping tape attached to both sides of the first electrode after impregnation with the electrolyte, and Figure 1(c) shows the first electrode including the sweeping tape attached to one side of the first electrode after impregnation with the electrolyte.

[0040] Referring to Figure 1(a), the swelling tape may be attached to both sides of the first electrode so that the first end and one end of the first electrode coincide. Referring to Figure 1(b), the swelling tape may expand due to the electrolyte when impregnated with the electrolyte, and the expanded swelling tape may surround the first end of the first electrode. On the other hand, referring to Figure 1(c), the swelling tape may be attached to one side of the first electrode so that the first end and one end of the first electrode coincide. The swelling tape may expand due to the electrolyte when impregnated with the electrolyte, and the expanded swelling tape may surround the first end of the first electrode.

[0041] According to one embodiment of the present invention, the length of the swelling tape after being impregnated for 60 minutes in an electrolyte containing 45% by weight of dimethyl carbonate, 20% by weight of ethylene carbonate, 15% by weight of ethyl methyl carbonate, and 15% by weight of LiPF6 as an electrolyte may be 120% or more and 160% or less based on 100% of the length of the swelling tape before expansion. Specifically, the length of the swelling tape after expansion may be 120% or more and 150%, 120% or more and 140%, 120% or more and 130%, 130% or more and 160%, 140% or more and 160%, 150% or more and 160%, or 130% or more and 150%, based on 100% of the length of the swelling tape before expansion.

[0042] Here, the length of the swelling tape after expansion may include both the length and width directions. That is, the ratio of the length of the swelling tape after expansion to the length of the swelling tape before expansion may be the same in both the length and width directions. Furthermore, the length of the swelling tape may mean the length measured from one end to the other in a specific direction of the swelling tape. For example, if the length measured from one end to the other in the length direction of the swelling tape after expansion is measured, it may be between 120% and 160%, and if the length measured from the center of the length direction of the swelling tape before expansion to one end in the length direction after expansion is measured, it may be between 110% and 130%.

[0043] If the length of the swelling tape after expansion meets the range described above, even if the swelling tape is attached to at least one side of the first electrode so that its first end and one end coincide, subsequent impregnation with the electrolyte allows the swelling tape to expand to a length suitable for effectively surrounding the first end of the first electrode. This provides excellent protection for the first end of the first electrode, further improving the prevention of internal short circuits and the stability of the battery.

[0044] According to one embodiment of the present invention, the swelling tape may include a portion made of a polymeric substance that absorbs an electrolyte and expands or becomes flexible, and an adhesive portion for attaching the swelling tape to the first electrode.

[0045] According to one embodiment of the present invention, the sweeping tape includes a base layer and an adhesive layer, the adhesive layer may be provided on at least one side of the base layer. Specifically, the sweeping tape may include a multilayer structure of a base layer that absorbs the electrolyte and expands when impregnated with the electrolyte, and an adhesive layer for attaching the sweeping tape to the first electrode, the adhesive layer may be provided on one or both sides of the base layer.

[0046] According to one embodiment of the present invention, the adhesive layer may include a pressure-sensitive adhesive containing a polyacrylic resin. That is, the adhesive strength of the adhesive layer may be affected by the magnitude of the pressure acting on the surface of the sweeping tape.

[0047] According to one embodiment of the present invention, the adhesive layer may contain one or more comonomers selected from the group consisting of PMMA (poly methyl methacrylate), PEMA (poly ethyl methacrylate), and PBMA (poly butyl methacrylate). Specifically, the adhesive layer may contain a polyacrylic resin produced by copolymerizing a monomer such as EA (Ethyl acrylate), BA (Butyl acrylate), or 2-EHA (2-Ethylhexyl acrylate) with a comonomer selected from the group consisting of PMMA (poly methyl methacrylate), PEMA (poly ethyl methacrylate), and PBMA (poly butyl methacrylate). When the adhesive layer contains the above-mentioned materials, the influence on the electrochemical properties of the battery including the sweeping tape can be minimized, and the adhesive strength of the sweeping tape can be maintained at an appropriate level.

[0048] According to one embodiment of the present invention, the base layer may contain a urethane resin. For example, the base layer may contain a polyurethane resin or the like. When the base layer contains the above-mentioned material, the absorption of the electrolyte by the sweeping tape is further facilitated, and when impregnated with the electrolyte, the sweeping tape can expand to a length suitable for effectively surrounding the first end of the first electrode.

[0049] According to one embodiment of the present invention, the electrolyte may contain an organic solvent. Specifically, the organic solvent may contain 70% by weight or more of any one of ethylene carbonate (EC), propylene carbonate (PC), dimethyl carbonate (DMC), ethyl methyl carbonate (EMC), and mixtures thereof. Specifically, the electrolyte may contain a mixed organic solvent containing 45% by weight or more of dimethyl carbonate. For example, the electrolyte may contain a mixed organic solvent containing 45% by weight of dimethyl carbonate, 20% by weight of ethylene carbonate, and 15% by weight of ethyl methyl carbonate.

[0050] Specifically, if the base layer contains a urethane resin, the base layer can absorb the electrolyte and expand, and if the electrolyte contains the aforementioned type of organic solvent, the expansion of the base layer containing the urethane resin becomes even easier. That is, the expansion of the swelling tape containing the base layer becomes even easier, and the expanded swelling tape effectively surrounds the first end of the first electrode, thereby preventing damage to the separator.

[0051] According to one embodiment of the present invention, the electrolyte may further contain an electrolyte. Examples of the electrolyte include, but are not limited to, solid polymer electrolytes, gel-type polymer electrolytes, solid inorganic electrolytes, or molten inorganic electrolytes that can be used in the manufacture of lithium secondary batteries.

[0052] Specifically, the electrolyte may contain a metal salt such as LiPF6 as the electrolyte. For example, an electrolyte containing 45% by weight of dimethyl carbonate, 20% by weight of ethylene carbonate, 15% by weight of ethyl methyl carbonate, and 15% by weight of LiPF6 as the electrolyte may be used. When the electrolyte further contains the aforementioned type of electrolyte, the swelling characteristics of the swelling tape can be further improved compared to when the electrolyte is not present, and the expanded swelling tape effectively surrounds the first end of the first electrode, thereby preventing damage to the separator.

[0053] According to one embodiment of the present invention, the first electrode may be a positive electrode and the second electrode may be a negative electrode. That is, the jelly roll type electrode assembly according to one embodiment of the present invention may be a jelly roll type electrode assembly in which a positive electrode; a first separator; a negative electrode; and a second separator are sequentially laminated and wound, and includes a sweeping tape attached to at least one side of the positive electrode, the positive electrode including a first end along the length direction where winding begins and a second end where winding ends, and the sweeping tape may be attached so that the first end and one end of the positive electrode coincide.

[0054] According to one embodiment of the present invention, the first electrode may include a current collector and an active material layer provided on the current collector. That is, the positive electrode may include a positive electrode current collector and a positive electrode active material layer provided on the positive electrode current collector. Specifically, the positive electrode may include a positive electrode current collector and a positive electrode active material layer formed on one or both sides of the positive electrode current collector and containing positive electrode active material. In other words, the positive electrode active material layer is formed on the positive electrode active material coated portion of the positive electrode current collector, and the surface on which the positive electrode active material layer is not provided can be referred to as the positive electrode blank portion.

[0055] According to one embodiment of the present invention, the positive electrode current collector may include a positive electrode active material coated portion on which a positive electrode active material is applied, and a positive electrode blank portion on which the positive electrode active material is not applied, and may include a tab on the positive electrode blank portion. Specifically, the positive electrode current collector may include a positive electrode blank portion, and may include a positive electrode tab formed on the positive electrode blank portion.

[0056] According to one embodiment of the present invention, the positive electrode current collector is not particularly limited as long as it does not cause a chemical change in the battery and is conductive. Specifically, the positive electrode current collector may be stainless steel, aluminum, nickel, titanium, calcined carbon, or aluminum or stainless steel with a surface treatment of carbon, nickel, titanium, silver, etc. That is, the positive electrode current collector may be provided in the form of surface-treated stainless steel, aluminum foil, etc.

[0057] Furthermore, the positive electrode current collector may typically have a thickness of 3 to 50 μm, but is not limited to this, and fine irregularities may be formed on the surface of the current collector to enhance the adhesion of the positive electrode active material. For example, it may be used in various forms such as film, sheet, foil, mesh, porous material, foam, or nonwoven fabric.

[0058] According to one embodiment of the present invention, the positive electrode active material may be a commonly used positive electrode active material. Specifically, the positive electrode active material may be a layered compound such as lithium cobalt oxide (LiCoO2) or lithium nickel oxide (LiNiO2), or a compound substituted with one or more transition metals; lithium iron oxide such as LiFe3O4; or a compound with the chemical formula Li 1+x Mn 2-x Lithium manganese oxides such as O4 (0 ≤ x ≤ 0.33), LiMnO3, LiMn2O3, LiMnO2; lithium copper oxide (Li2CuO2); vanadium oxides such as LiV3O8, V2O5, Cu2V2O7; chemical formula LiNi 1-y M yNi-site type lithium nickel oxide represented by O2 (where M is at least one selected from the group consisting of Co, Mn, Al, Cu, Fe, Mg, B, and Ga, satisfying 0.01 ≤ y ≤ 0.3); chemical formula LiMn 2-z M z Lithium manganese composite oxides represented as O2 (where M is at least one selected from the group consisting of Co, Ni, Fe, Cr, Zn, and Ta, satisfying 0.01 ≤ z ≤ 0.1) or Li2Mn3MO8 (where M is at least one selected from the group consisting of Fe, Co, Ni, Cu, and Zn); examples include, but are not limited to, LiMn2O4 in which part of the Li in the chemical formula is substituted with alkaline earth metal ions. The positive electrode may also be Li-metal.

[0059] According to one embodiment of the present invention, the positive electrode active material layer may further include a positive electrode conductive material and a positive electrode binder. The positive electrode conductive material is used to impart conductivity to the electrode and can be used without particular limitation as long as it has electronic conductivity without causing a chemical change in the battery that is constructed. Specifically, the positive electrode conductive material may be graphite such as natural graphite or artificial graphite; carbon-based materials such as carbon black, acetylene black, Ketjen black, channel black, furnace black, lamp black, thermal black, or carbon fiber; metal powder or metal fiber such as copper, nickel, aluminum, or silver; conductive whiskers such as zinc oxide or potassium titanate; conductive metal oxides such as titanium oxide; or conductive polymers such as polyphenylene derivatives, and one of these alone or a mixture of two or more may be used.

[0060] Furthermore, the positive electrode binder plays a role in improving the adhesion between positive electrode active material particles and the adhesion between the positive electrode active material and the positive electrode current collector. Specific examples include polyvinylidene fluoride (PVDF), vinylidene fluoride-hexafluoropropylene copolymer (PVDF-co-HFP), polyvinyl alcohol, polyacrylonitrile, carboxymethylcellulose (CMC), starch, hydroxypropylcellulose, regenerated cellulose, polyvinylpyrrolidone, tetrafluoroethylene, polyethylene, polypropylene, ethylene-propylene-diene polymer (EPDM), sulfonated-EPDM, styrene-butadiene rubber (SBR), fluororubber, or various copolymers thereof, and one of these alone or a mixture of two or more may be used.

[0061] According to one embodiment of the present invention, the second electrode may include a current collector and an active material layer provided on the current collector. That is, the negative electrode may include a negative electrode current collector and a negative electrode active material layer provided on the negative electrode current collector. Specifically, the negative electrode may include a negative electrode current collector and a negative electrode active material layer formed on one or both sides of the negative electrode current collector and containing negative electrode active material. In other words, the negative electrode active material layer is formed on the negative electrode active material coated portion of the negative electrode current collector, and the surface on which the negative electrode active material layer is not provided can be referred to as the negative electrode blank portion.

[0062] According to one embodiment of the present invention, the negative electrode current collector may include a negative electrode active material coated portion on which a negative electrode active material layer is formed, and a negative electrode blank portion on which a negative electrode active material layer is not formed, and may include a tab on the negative electrode blank portion. Specifically, the negative electrode current collector may include a negative electrode blank portion, and may include a negative electrode tab formed on the negative electrode blank portion. As a result, the manufactured electrode assembly may include one or more negative electrode tabs.

[0063] According to one embodiment of the present invention, the negative electrode active material layer may include a negative electrode active material comprising one or more selected from the group consisting of silicon-based materials and carbon-based materials. Furthermore, the negative electrode active material layer may further include a negative electrode conductive material and a negative electrode binder, and the negative electrode active material, negative electrode conductive material, and negative electrode binder can be any material used in the industry without limitation.

[0064] According to one embodiment of the present invention, the negative electrode current collector is not particularly limited as long as it does not cause a chemical change in the battery and is conductive. For example, the negative electrode current collector may be made of copper, stainless steel, aluminum, nickel, titanium, calcined carbon, or aluminum or stainless steel with a surface treatment of carbon, nickel, titanium, silver, etc. Specifically, transition metals that readily adsorb carbon, such as copper and nickel, may be used as the negative electrode current collector. The thickness of the negative electrode current collector may be 6 μm or more and 80 μm or less, but is not limited thereto.

[0065] According to one embodiment of the present invention, the negative electrode binder may contain at least one selected from the group consisting of polyvinylidene fluoride-hexafluoropropylene copolymer (PVDF-co-HFP), polyvinylidene fluoride, polyacrylonitrile, polymethyl methacrylate, polyvinyl alcohol, carboxymethylcellulose (CMC), starch, hydroxypropylcellulose, regenerated cellulose, polyvinylpyrrolidone, tetrafluoroethylene, polyethylene, polypropylene, polyacrylic acid, ethylene-propylene-diene monomer (EPDM), sulfonated EPDM, styrene-butadiene rubber (SBR), fluororubber, polyacrylic acid, and substances in which the hydrogen atoms of these substances are substituted with Li, Na, or Ca, and may also contain various copolymers thereof.

[0066] According to one embodiment of the present invention, the negative electrode conductive material is not particularly limited as long as it does not cause a chemical change in the battery and is conductive, and may be used, for example, graphite such as natural graphite or artificial graphite; carbon black such as acetylene black, Ketjen black, channel black, furnace black, lamp black, or thermal black; conductive fibers such as carbon fibers or metal fibers; conductive tubes such as carbon nanotubes; metal powders such as fluorocarbon, aluminum, or nickel powder; conductive whiskers such as zinc oxide or potassium titanate; conductive metal oxides such as titanium oxide; or conductive materials such as polyphenylene derivatives.

[0067] One embodiment of the present invention provides a method for manufacturing a jelly roll type electrode assembly in which a first electrode; a first separator; a second electrode; and a second separator are sequentially stacked and wound, comprising: (a) a step of transporting the first electrode in a roll-to-roll manner; (b) a step of attaching a sweeping tape to at least one side of a slitting region included in the first electrode; and (c) a step of slitting the longitudinal center of the slitting region of the first electrode, wherein step (b) is performed by attaching the sweeping tape such that its longitudinal center coincides with the longitudinal center of the slitting region of the first electrode, and step (c) is performed by slitting the longitudinal center of the slitting region to provide a first end where winding of the first electrode begins along its length; and a second end where winding ends.

[0068] A method for manufacturing a jelly roll type electrode assembly according to one embodiment of the present invention enables the continuous production of a jelly roll type electrode assembly, which includes a swelling tape that expands when impregnated in the electrolyte and is attached to surround one end of the positive electrode in the longitudinal direction, using conventional roll-to-roll process equipment, thereby ensuring productivity and economic efficiency. Furthermore, the jelly roll type electrode assembly manufactured by this method includes a swelling tape that expands when impregnated in the electrolyte and is attached to surround one end of the positive electrode in the longitudinal direction, thereby preventing damage to the positive electrode and separator from deformation of the electrode assembly due to contraction / expansion of the electrodes during battery charging and discharging. Even if the separator is damaged, the swelling tape prevents internal short circuits between the positive and negative electrodes, thereby improving the battery's stability and lifespan characteristics.

[0069] According to one embodiment of the present invention, the method for manufacturing the jelly roll type electrode assembly may include the step of (a) transporting the first electrode in a roll-to-roll manner. Specifically, step (a) may be carried out in a roll-to-roll processing manner in which a plurality of bendable metal foils or the like are processed while being moved between rollers. Here, the roll-to-roll method may mean a method in which a roll winding a flexible, thin metal sheet-like electrode current collector is unwound to supply the electrode current collector, an electrode slurry containing an electrode active material is applied to at least one side of the electrode current collector and dried to form an electrode mixture layer, and then the electrode current collector processed by another roll is unwound again and recovered. That is, step (a) may be a step of transporting the first electrode for processing in the roll-to-roll manner, and can be referred to as the first electrode transport step (S11).

[0070] According to one embodiment of the present invention, the method for manufacturing the jelly roll type electrode assembly may include the step of (b) attaching a sweeping tape to at least one side of a slitting region included in the first electrode. Here, the slitting region means a region for cutting the first electrode by a slitting process that cuts the first electrode or the electrode assembly including it to a set length, and the slitting region may mean a part of the length direction including the first electrode current collector and the first electrode active material layer included in the first electrode, and the length of the slitting region may be adjusted according to the process conditions. Furthermore, the length and position of the slitting region may be changed according to the length and position of the sweeping tape to be attached. That is, the slitting region can be set by changing the length and position of the sweeping tape attached to one or both sides of the first electrode according to the process conditions.

[0071] According to one embodiment of the present invention, step (b) may be performed by attaching the sweeping tape such that its longitudinal center coincides with the longitudinal center of the slit region of the first electrode. Specifically, step (b) may be performed by attaching the sweeping tape on at least one side of the slit region included in the first electrode such that its longitudinal center coincides with the longitudinal center of the slit region of the first electrode. This allows the first electrode to provide a first end where winding begins along the length and a second end where winding ends in the subsequent step of slitting the longitudinal center of the slit region, and the first electrode can be provided after the slitting step with a predetermined length of sweeping tape attached to at least one side of the first and second ends.

[0072] According to one embodiment of the present invention, step (b) may be a step of attaching a sweeping tape to at least one side of the slit region included in the first electrode, and more specifically, step (b) may be a step of attaching a sweeping tape to one or both sides of the slit region included in the first electrode, and can be referred to as the sweeping tape attachment step (S12).

[0073] According to one embodiment of the present invention, the method for manufacturing the jelly roll type electrode assembly may include the step of (c) slitting the longitudinal center of the slit region of the first electrode. Specifically, step (c) may be the step of cutting the first electrode or the electrode assembly containing it to a set length, and the cutting may be performed using a cutting knife or the like, but is not particularly limited.

[0074] According to one embodiment of the present invention, step (c) may slit the longitudinal center of the slit region to provide a first end from which winding of the first electrode begins along its length and a second end from which winding ends. Specifically, step (c) may slit the longitudinal center of the slit region to provide a first end from which winding of the first electrode or a first electrode included in the electrode assembly begins along its length and a second end from which winding ends. Step (c) may consist of multiple steps, and if performed during the first electrode preparation step (S10), step (c) may be referred to as the slitting step (S13).

[0075] According to one embodiment of the present invention, steps (a) and (b) may be performed during the first electrode preparation step (S10), and step (c) may be performed during or after the first electrode preparation step (S10). Specifically, step (c) may be performed before or after the winding step (S50). More specifically, step (c) may be performed after the winding step (S50).

[0076] When protective tape is used to protect the exposed ends of the electrodes after the slitting stage, a separate process is required to confirm the position of the slit ends of the electrodes after slitting and to properly apply the protective tape around them. Furthermore, after applying the protective tape to the ends of the electrodes, an inspection process, such as a vision inspection stage, is required to eliminate any adhesion defects. Additionally, if the winding process is performed only after the vision inspection stage to reduce defects in the electrode assemblies, the production speed of the jelly roll type electrode assemblies is significantly reduced, making a roll-to-roll process virtually impossible.

[0077] In contrast, a method for manufacturing a jelly roll type electrode assembly according to one embodiment of the present invention makes it possible to produce the jelly roll type electrode assembly including the swelling tape in a continuous process using conventional roll-to-roll process equipment. In other words, the method for manufacturing the jelly roll type electrode assembly includes a swelling tape application step (S12) in the first electrode preparation step (S10), so that step (c) is performed during or after the first electrode preparation step (S10), and therefore the entire process can be carried out by a roll-to-roll process used in the industry. That is, a method for manufacturing a jelly roll type electrode assembly according to one embodiment of the present invention makes it possible to produce a jelly roll type electrode assembly including a swelling tape that expands when impregnated in the electrolyte and is applied so as to surround one end in the longitudinal direction of the positive electrode in a continuous process using conventional roll-to-roll process equipment, thereby ensuring productivity and economic efficiency.

[0078] Figure 2 shows a schematic diagram of a method for manufacturing a jelly roll type electrode assembly including a sweeping tape, and a method for manufacturing a jelly roll type electrode assembly including a PET tape, according to one embodiment of the present invention.

[0079] Specifically, Figure 2(a) schematically shows a method for manufacturing a jelly roll type electrode assembly including a sweeping tape according to one embodiment of the present invention, which includes the step of attaching the sweeping tape (S12). Figure 2(b) schematically shows a method for manufacturing a jelly roll type electrode assembly including a PET tape, in which a PET protective tape is attached around the first end of the first electrode instead of the sweeping tape.

[0080] Referring to Figure 2(b), an additional step is required to apply protective tape around the first end of the first electrode, as in the jelly roll type electrode assembly including a sweeping tape according to one embodiment of the present invention. That is, if a protective tape (PET) application step (S12') is included instead of the sweeping tape application step (S12), an additional step is required to produce electrodes with a similar structure.

[0081] Specifically, if the process includes a protective tape (PET) application step (S12') instead of a sweeping tape application step (S12), then after the first electrode transfer step (S11), there is a step of slitting the first electrode (S11'), and a first electrode separation step (S11'') is required to separate the slit first electrode by a predetermined distance in order to apply the protective tape of PET material, and an additional slitting step (S13') is required to slit the applied protective tape so as to surround the longitudinal end of the first electrode.

[0082] More specifically, if the process includes a protective tape (PET) application step (S12') instead of a sweeping tape application step (S12), then a slitting step (S11') is required after stopping the winder of the first electrode while it is in motion, and further a step (S11'') is required to separate the first electrode, taking into account the thickness of the first electrode so as to sufficiently surround the first end of the slit first electrode. Subsequently, a step (S12') of applying protective tape to both sides of the separated first electrode is required; and further an additional slitting step (S13') of cutting the applied protective tape is required.

[0083] In other words, when using PET protective tape instead of sweeping tape, a certain additional process is required to manufacture a structure similar to the jelly roll type electrode assembly including sweeping tape according to one embodiment of the present invention.

[0084] In other words, a method for manufacturing a jelly roll type electrode assembly according to one embodiment of the present invention minimizes additional steps by including a swelling tape application step (S12), and provides a jelly roll type electrode assembly that includes a swelling tape applied so as to surround one end of the positive electrode in the longitudinal direction. Furthermore, it is possible to ensure productivity and economic efficiency by enabling production in a continuous process using conventional roll-to-roll process equipment.

[0085] Figure 3 is an image illustrating an embodiment of a method for manufacturing a jelly roll-type electrode assembly according to one embodiment of the present invention.

[0086] Specifically, Figure 3(a) shows the state after the swelling tape application step (S12) and the winding step (S50) where the swelling tape is applied to the slitting region included in the first electrode; Figure 3(b) shows the state after the slitting step (S13) where the swelling tape is applied so that the first end and one end of the first electrode coincide; and Figure 3(c) is an image showing the state after the winding step (S50) where the jelly roll type electrode assembly is disassembled and the swelling tape is applied.

[0087] Referring to Figure 2(a), a method for manufacturing a jelly roll type electrode assembly according to one embodiment of the present invention may further include a supply step (S20), a placement step (S30), a lamination step (S40), a winding step (S50), a taping step (S60), and an inspection step (S70).

[0088] Specifically, the supply step (S20) may be a step in which the first electrode and the second electrode are supplied together with the first separator and the second separator after the first electrode preparation step (S10), and the arrangement step (S30) may be a step in which the first electrode, the first separator, the second electrode, and the second separator supplied in the supply step (S20) are arranged sequentially to form a laminate.

[0089] Furthermore, the lamination step (S40) may involve pressurizing and heat-sealing the laminate manufactured in the arrangement step (S30), i.e., the laminate including the first electrode, the first separator, the second electrode, and the second separator, to provide an electrode assembly.

[0090] On the other hand, the winding step (S50) may involve winding the electrode assembly that has undergone the lamination step, and may further include a slitting step of cutting the electrode assembly to a set length before or after the winding step.

[0091] Next, the taping step (S60) may be a process in which the outer surface of the electrode assembly wound up by the winding step (S50) is finished with sealing tape, and the taping step can prevent defects such as the electrode assembly coming undone due to the separation of the longitudinal ends of the first electrode, first separator, second electrode, and second separator.

[0092] The inspection process (S70) may include a vision inspection step in which the shape, arrangement, damage, etc., of the first electrode, first separator, second electrode, and second separator included in the electrode assembly are inspected to determine if a defect exists, and a voltage withstand inspection step in which power is supplied to the electrode assembly and the voltage withstand is measured to determine if a defect exists.

[0093] According to one embodiment of the present invention, the sweeping tape used in the method for manufacturing the jelly roll type electrode assembly may be the same as the sweeping tape described above for the jelly roll type electrode assembly.

[0094] According to one embodiment of the present invention, the widthwise length of the sweeping tape may be 60% or more and 100% or less based on 100% of the width of the first electrode. Specifically, the widthwise length of the sweeping tape may be 70% or more and 100%, 80% or more and 100%, 60% or more and 90%, 60% or more and 80%, 60% or more and 70%, or 70% or more and 90% or less based on 100% of the width of the first electrode. When the widthwise length of the sweeping tape satisfies the above range, the length of the sweeping tape after expansion can correspond to the widthwise length of the first electrode, and one end of the sweeping tape effectively surrounds one end of the first electrode in the longitudinal direction, thereby more efficiently preventing internal short circuits between the positive and negative electrodes even if the separator is damaged.

[0095] According to one embodiment of the present invention, the length of the sweeping tape in the longitudinal direction may be 500% or more and 7000% or less based on 100% of the thickness of the first electrode. Specifically, the length of the sweeping tape in the longitudinal direction may be 600% or more, 700% or more, 800% or more, or 1000% or more based on 100% of the thickness of the first electrode, and the length of the sweeping tape in the longitudinal direction may be 6000% or less, 5000% or less, 4000% or less, or 3000% or less based on 100% of the thickness of the first electrode, preferably 2000% or less, 1700% or less, or 1400% or less. If the length of the sweeping tape in the longitudinal direction satisfies the range described above, the length of the sweeping tape slit after step (c) can be in a suitable range, that is, 250% to 3500%, preferably 250% to 1000%, based on 100% of the thickness of the first electrode, so that the length of the sweeping tape in the longitudinal direction after expansion corresponds to the thickness of the first electrode, and one end of the sweeping tape effectively surrounds one end of the first electrode in the longitudinal direction, minimizing the impact on electrochemical properties such as the rate of capacity reduction of the battery including the sweeping tape, and further efficiently preventing internal short circuits between the positive and negative electrodes even if the separator is damaged.

[0096] According to one embodiment of the present invention, the length of the sweeping tape in the longitudinal direction may be 0.75 mm or more and 10 mm or less. Specifically, the length of the sweeping tape in the longitudinal direction may be 1 mm or more, 1.25 mm or more, 1.5 mm or more, 1.75 mm or more, or 2 mm or more, and the length of the sweeping tape in the longitudinal direction may be 2.75 mm or less, 2.5 mm or less, 2.25 mm or less, or 2 mm or less. When the length of the sweeping tape in the longitudinal direction satisfies the above range, it is easy to manufacture a sweeping tape in which the length in the longitudinal direction corresponds to the thickness of the first electrode, even if there is a certain process deviation.

[0097] According to one embodiment of the present invention, the first electrode may be a positive electrode and the second electrode may be a negative electrode. The positive electrode and negative electrode used in the method for manufacturing the jelly roll type electrode assembly may be the same as those described above for the jelly roll type electrode assembly.

[0098] One embodiment of the present invention provides a jelly roll type electrode assembly manufactured by the method for manufacturing a jelly roll type electrode assembly described above.

[0099] A jelly roll-type electrode assembly according to one embodiment of the present invention includes a swelling tape that expands when impregnated with an electrolyte and is attached to surround one end of the positive electrode in the longitudinal direction. This prevents damage to the positive electrode and separator from deformation of the electrode assembly due to contraction / expansion of the electrodes during battery charging and discharging. Even if the separator is damaged, the swelling tape prevents internal short circuits between the positive and negative electrodes, thereby improving the battery's stability and lifespan. Furthermore, when the swelling tape surrounds the longitudinal end of the first electrode, the porous material properties of the swelling tape provide excellent relief of internal stress and improvement of the roundness of the core.

[0100] One embodiment of the present invention provides a secondary battery comprising the jelly roll-type electrode assembly and a battery case for housing the electrode assembly. Specifically, the secondary battery may include the electrode assembly according to the above-described embodiment and a battery case for housing the electrode assembly.

[0101] The secondary battery according to the present invention can improve the stability and lifespan of the battery by preventing internal short circuits between the positive and negative electrodes even when the electrode assembly deforms due to the contraction / expansion of the electrodes during charging and discharging of the battery.

[0102] According to one embodiment of the present invention, the battery case may be cylindrical. Specifically, the battery case may be cylindrical, rectangular, or pouch-shaped depending on the application, but is not limited thereto.

[0103] According to one embodiment of the present invention, the inside of the battery case may contain an electrolyte. Specifically, examples of the electrolyte include, but are not limited to, organic liquid electrolytes, inorganic liquid electrolytes, solid polymer electrolytes, gel-type polymer electrolytes, solid inorganic electrolytes, or molten inorganic electrolytes that can be used in the manufacture of lithium secondary batteries. Specifically, the electrolyte may contain a non-aqueous organic solvent and a metal salt.

[0104] According to one embodiment of the present invention, examples of the non-aqueous organic solvent include, for example, N-methyl-2-pyrrolidinone, propylene carbonate, ethylene carbonate, butylene carbonate, dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, γ-butyrolactone, 1,2-dimethoxyethane, tetrahydrofuran, 2-methyltetrahydrofuran, dimethyl sulfoxide, 1,3-dioxolane, formamide, dimethylformamide, dioxolane, acetonitrile, nitromethane, methyl formate, methyl acetate, triphosphate ester, trimethoxymethane, dioxolane derivative, sulfolane, methyl sulfolane, 1,3-dimethyl-2-imidazolidinone, propylene carbonate derivative, tetrahydrofuran derivative, ether, methyl propionate, ethyl propionate and other aprotic organic solvents may be used.

[0105] According to one embodiment of the present invention, the metal salt may be a lithium salt, and the lithium salt is a substance that is easily soluble in the non-aqueous electrolyte solution. For example, as the anion of the lithium salt, F - , Cl - , I - , NO3 - , N(CN)2 - , BF4 - , ClO4 - , PF6 - , (CF3)2PF4 - , (CF3)3PF3 - , (CF3)4PF2 - , (CF3)5PF - , (CF3)6P - , CF3SO3 - , CF3CF2SO3- , (CF3SO2)2N - , (FSO2)2N - CF3CF2(CF3)2CO - (CF3SO2) 2CH - (SF5)3C - (CF3SO2)3C - CF3(CF2)7SO3 - CF3CO2 - CH3CO2 - SCN - , and (CF3CF2SO2)2N - You may use one or more selected from the group consisting of the following:

[0106] According to one embodiment of the present invention, in addition to the components of the electrolyte, the electrolyte may further contain one or more additives for the purpose of improving the battery life characteristics, suppressing the decrease in battery capacity, and improving the battery discharge capacity, such as haloalkylene carbonate compounds such as difluoroethylene carbonate, pyridine, triethyl phosphite, triethanolamine, cyclic ether, ethylenediamine, n-glyme, hexaphosphate triamide, nitrobenzene derivative, sulfur, quinone imine dye, N-substituted oxazolidinone, N,N-substituted imidazolidine, ethylene glycol dialkyl ether, ammonium salt, pyrrole, 2-methoxyethanol, or aluminum trichloride. [Examples]

[0107] The present invention will be described in detail below with reference to examples. However, the examples of the present invention may be modified into various different forms, and the scope of the present invention should not be construed as being limited to the examples described below. The examples in this specification are provided to give a more complete explanation of the present invention to a person of average skill in the industry.

[0108] [Example 1] <Manufacturing of electrode assemblies> An Al foil with a thickness of 15 μm and a width of 63.9 mm was prepared as the positive electrode current collector. A positive electrode active material slurry containing an NMCA (Ni-Mn-Co-Al) composite with a Ni content of 92% or more as the positive electrode active material and CNTs as the conductive material was applied to the positive electrode current collector and dried to form a positive electrode active material layer, thereby producing a positive electrode with a total thickness of 154 μm.

[0109] Subsequently, a 52 μm thick sweeping tape was prepared, having an adhesive layer containing a copolymer of ethyl acrylate (EA) and polyethyl methacrylate (PEMA) on one side of a polyurethane (PU) material base layer. The sweeping tape was then attached to one side of the slit region of the positive electrode so that it had a width of 62 mm and a length of 10 mm.

[0110] Next, a Cu foil with a thickness of 10 μm and a width of 62 mm was prepared as the negative electrode current collector. A negative electrode active material layer was formed by applying and drying a negative electrode active material slurry containing 50 parts by weight each of artificial graphite and natural graphite as the negative electrode active material onto the negative electrode current collector, thereby producing a negative electrode with a total thickness of 187 μm.

[0111] Meanwhile, two sheet-like polyethylene separators were prepared as the first and second separators.

[0112] Subsequently, the positive electrode, first separator, negative electrode, and second separator were arranged in sequence to form a laminate, which was then pressed and heat-sealed. The center of the slit region was slit, and the laminate was wound up so that the first end where the winding of the positive electrode begins was located in the core. A PET material seal tape was then applied to the second end where the winding ends, surrounding the outer circumferential surfaces of the upper and lower ends of the jelly roll, and the jelly roll type electrode assembly was manufactured. In this case, the seal tape used had a length of 62 mm in the longitudinal direction, a length of 10 mm in the width direction, and a thickness of 22 μm, and the length of the sweeping tape after slitting was 5 mm.

[0113] <Manufacturing of secondary batteries> After inserting the aforementioned jelly roll electrode assembly into a cylindrical battery case, an electrolyte solution prepared by mixing ethylene carbonate (EC), dimethyl carbonate (DMC), and ethyl methyl carbonate (EMC) in a weight ratio of 4:9:3 and dissolving LiPF6 to a concentration of 15% by weight was poured into the case, and the cylindrical battery case was sealed with a cap assembly to manufacture a secondary battery.

[0114] [Example 2] A jelly roll-type electrode assembly and a secondary battery were manufactured in the same manner as in Example 1, except that sweeping tape was attached to both sides of the slit region of the positive electrode so that it had a width of 62 mm and a length of 5 mm.

[0115] [Comparative Example 1] A jelly roll-type electrode assembly and a secondary battery were manufactured in the same manner as in Example 1, except that a PET tape was attached to one side of the slit region of the positive electrode so that it had a width of 62 mm and a length of 10 mm.

[0116] [Comparative Example 2] A jelly roll-type electrode assembly and a secondary battery were manufactured in the same manner as in Example 1, except that a sweeping tape was not attached to the slit region of the positive electrode.

[0117] [Comparative Example 3] A jelly roll type electrode assembly and a secondary battery were manufactured in the same manner as in Example 1, except that a sweeping tape was not attached to the slit region of the positive electrode, the center of the slit region was slit, the slitted positive electrode was separated, and then PET tape was attached to both sides of the slit region so that it had a width of 62 mm and a length of 10 mm, and then the center was slit again to obtain the structure shown in Figure 1(b).

[0118] [Example of experiment] <Experimental Example 1 - Swelling Evaluation> Samples of the same material as the swelling tape used in Examples 1 and 2 (10 mm in length and 62 mm in width) were prepared, and an electrolyte solution was prepared by dissolving LiPF6 as the electrolyte in a mixed solvent of ethylene carbonate (EC), dimethyl carbonate (DMC), and ethyl methyl carbonate (EMC). Then, the swelling tape samples were impregnated in the electrolyte solution for 60 minutes, and the length of the swelling tape before and after expansion was measured. The composition of the electrolyte solution used for swelling evaluation is shown in Table 1 below. Except for the use of the electrolyte solution with the composition shown in Table 1 below, the swelling properties of the swelling tape samples were evaluated in the same manner in Experimental Examples 1-1 to 1-6.

[0119] [Table 1]

[0120] Subsequently, the ratio of the length of the swelling tape after expansion to the length of the swelling tape before expansion was calculated and is shown in Table 1 and Figure 4. Specifically, Figure 4 shows the ratio of the width direction (TD, Transverse Direction) and length direction (MD, Machine Direction) of the swelling tape after expansion to the length of the swelling tape after expansion, calculated after impregnating the swelling tape sample with an electrolyte having the composition of DMC and Experimental Example 1-1 for 60 minutes, respectively.

[0121] Referring to Table 1, it was confirmed that when the swelling tape was impregnated with the electrolytes having the compositions of Experimental Examples 1-1 to 1-6, the length in the longitudinal and lateral directions after expansion was approximately 140% of the length of the swelling tape before expansion. Specifically, referring to Experimental Examples 1-1 to 1-6, it was confirmed that when the presence and content of other solvent components in addition to dimethyl carbonate (DMC), namely ethylene carbonate (EC), propylene carbonate (PC), and ethyl methyl carbonate (EMC), were adjusted, there was a slight effect on the swelling characteristics of the swelling tape depending on the composition of the mixed solvent, but the difference was not significant. On the other hand, referring to Reference Example 1-1 and Experimental Examples 1-1 to 1-6, it was confirmed that when LiPF6 used as the electrolyte was added at approximately 7% by weight and approximately 15% by weight, i.e., when the electrolyte content was different from each other, the difference in the degree of expansion was not large, within approximately 3%. In contrast, when the electrolyte content was 0%, i.e., when no electrolyte was added, the difference in the degree of expansion was confirmed to be approximately 15%. This indicates that the presence or absence of electrolyte makes a relatively large difference in the swelling characteristics of the swelling tape.

[0122] Referring to Figure 4, it was confirmed that when the swelling tape was impregnated with the electrolyte having the composition of Experimental Example 1-1, the length in the longitudinal and width directions after expansion was approximately 140% of the length of the swelling tape before expansion. Specifically, it was confirmed that the length expansion of the swelling tape occurred at the same ratio in both the longitudinal and width directions, and that it expanded to approximately 120% on one side from the center of the swelling tape before expansion to one end. This allows us to determine the minimum length in the width and length directions of the swelling tape that should be attached to protect one end of the first electrode after expansion.

[0123] <Experimental Example 2 - Evaluation of Activation> The secondary batteries manufactured in Example 1 and Comparative Example 1 were activated by performing two cycles of charging at 4.2V-2.5V and 0.2C, respectively, and discharging at 0.2C. After that, they were disassembled to prepare jelly roll type electrode assemblies before and after activation. The ends of the positive electrodes of the jelly roll type electrode assemblies were observed with the naked eye, and the evaluation results are shown in Figures 5 and 6.

[0124] Specifically, Figure 5(a) shows the first end of the first electrode of the jelly roll type electrode assembly according to Example 1 before activation, Figure 5(b) shows the first end of the first electrode of the jelly roll type electrode assembly according to Example 1 after activation, Figure 6(a) shows the first end of the first electrode of the jelly roll type electrode assembly according to Comparative Example 1 before activation, and Figure 6(b) shows the first end of the first electrode of the jelly roll type electrode assembly according to Comparative Example 1 after activation.

[0125] Referring to Figure 5, in the case of the jelly roll type electrode assembly according to Example 1, it was confirmed that the swelling tape, which was attached so that the first end and one end of the first electrode coincided before activation, expanded after activation to surround the first end of the first electrode. At this time, the length 2L of the swelling tape attached to at least one side of the slitting region included in the first electrode was 10 mm, and after the step of slitting the longitudinal center of the slit region of the first electrode, the length of the swelling tape before expansion (L) was 5 mm, the length of the swelling tape after expansion (L') was 7 mm, and the expanded length of the swelling tape (L -s The total length was measured to be 2 mm. In other words, it was confirmed that the length of the swelling tape after expansion (L') expanded to approximately 140% of the length of the swelling tape before expansion (L), and that on one side, relative to the center of the swelling tape before expansion, it expanded by 1 mm to one end, i.e., to 120% of the length of the swelling tape before expansion (L). This confirmed that the jelly roll type electrode assembly including the swelling tape according to the present invention expands due to the electrolyte, and that the expanded swelling tape effectively surrounds the first end of the first electrode.

[0126] In contrast, as shown in Figure 6, in the case of the jelly roll type electrode assembly according to Comparative Example 1, the PET tape attached so that the first end and one end of the first electrode before activation coincided did not expand after activation, and it was confirmed that the first end of the first electrode remained exposed.

[0127] <Experimental Example 3 - Evaluation of Cycle Stability> The secondary batteries manufactured in Example 1 and Comparative Example 2 were tested for their battery characteristics in a cycle test at 25°C.

[0128] Specifically, after 500 cycles, the Coulomb efficiency was analyzed to confirm short-circuit behavior during the cycle, and room-temperature voltage tracking was performed to further evaluate abnormal behavior. The evaluation results are shown in Figure 7.

[0129] Specifically, Figure 7(a) shows the change in Coulomb efficiency as the cycle progresses for the secondary batteries manufactured in Example 1 and Comparative Example 2, and Figure 7(b) shows the evaluation results of room temperature-voltage tracking over time for the secondary batteries manufactured in Example 1 and Comparative Example 2.

[0130] Referring to Figure 7(a), the secondary battery according to Example 1 did not exhibit any abnormal behavior, but the secondary battery according to Comparative Example 2 showed abnormal behavior in Coulomb efficiency, specifically the occurrence of leakage current. Furthermore, referring to Figure 7(b), the secondary battery according to Example 1 maintained a voltage of 1.0V or higher even after 12 hours, but the secondary battery according to Comparative Example 2 was unable to maintain a constant voltage, and its voltage gradually decreased over time. This indicates that the separator was damaged and an internal short circuit occurred.

[0131] Subsequently, each of the secondary batteries from Example 1 was disassembled, and the presence or absence of separator damage was visually evaluated. The results are shown in Figure 8.

[0132] Specifically, Figure 8(a) is an image showing the state of the first electrode-facing portion of the separator contained in the secondary battery manufactured in Example 1, and Figure 8(b) is an image showing the state of the first electrode-facing portion of the separator contained in the secondary battery manufactured in Comparative Example 2.

[0133] Referring to Figure 8, it was confirmed that damage occurred to the separator of the secondary battery in Comparative Example 2, where the swelling tape was not applied.

[0134] This confirms that the secondary battery according to the present invention improves the battery's stability and lifespan characteristics by preventing internal short circuits between the positive and negative electrodes even when the electrode assembly deforms due to the contraction / expansion of the electrodes during charging and discharging.

[0135] <Experimental Example 4 - Evaluation of Roundness and Productivity> To confirm the degree of deformation improvement of the secondary batteries manufactured in Example 1 and Comparative Example 3, the circularity was evaluated after 20 cycles at 25°C, and the results are shown in Table 2 and Figure 9 below. Here, circularity (%) indicates the degree to which the shape of the electrode assembly is closer to a circle. The maximum and minimum isolation distances between the winding shaft and the positive electrode were measured from computed tomography (CT) images of the positive electrode, and the ratio (%) of the minimum isolation distance between the winding shaft and the positive electrode to the maximum isolation distance of 100% between the winding shaft and the positive electrode was calculated.

[0136] Furthermore, in order to evaluate the productivity of each jelly roll type electrode assembly, the time required to manufacture the jelly roll type electrode assembly, i.e., the cycle time, was measured and is shown in Table 2 below.

[0137] [Table 2]

[0138] Figure 9 is an image showing the evaluation results of the roundness of the secondary batteries manufactured in Example 1 and Comparative Example 3. Referring to Table 2, it was confirmed that in the case of the secondary battery of Comparative Example 3, which has a structure similar to the secondary battery of Example 1 that includes a swelling tape after expansion, by surrounding the longitudinal end of the positive electrode with PET protective tape, the cycle time increased to 3.0 s, approximately twice as much as the secondary battery of Example 1, and was inferior in productivity.

[0139] This demonstrates that a method for manufacturing a jelly roll-type electrode assembly according to one embodiment of the present invention minimizes additional steps by including a swelling tape application step, and provides a jelly roll-type electrode assembly that includes a swelling tape applied to surround one end of the positive electrode in the longitudinal direction. This allows for production in a continuous process using conventional roll-to-roll equipment, ensuring productivity and economic efficiency.

[0140] On the other hand, referring to Table 2 and Figure 9, it was confirmed that in the case of the secondary battery according to Comparative Example 3, the roundness was 90% or less, and the degree of improvement in safety was similar to or worse than that of the secondary battery according to Example 1.

[0141] As a result, the secondary battery according to the present invention includes a structure in which the expanded swelling tape surrounds the longitudinal end of the first electrode, thereby preventing internal short circuits between the positive and negative electrodes even when the electrode assembly deforms due to the contraction / expansion of the electrodes during charging and discharging of the battery, thereby improving the battery's stability and lifespan characteristics. Furthermore, the porous material properties of the swelling tape provide excellent effects in relieving internal stress and improving the roundness of the core.

[0142] The above detailed description is illustrative of the present invention. Furthermore, the foregoing merely illustrates preferred embodiments of the present invention, and as stated above, the present invention is usable in a variety of other combinations, modifications, and environments, and can be changed or modified within the scope of the concept of the invention disclosed herein, within the scope equivalent to the foregoing disclosures, and / or within the scope of the art or knowledge of the art. Therefore, the above detailed description of the invention is not intended to limit the present invention to the disclosed embodiments. Furthermore, the appended claims should be interpreted as including other embodiments. [Explanation of symbols]

[0143] 100...1st electrode 101 ···First electrode current collector 102, 103...first electrode active material layer 110 ···First end of the first electrode 20 ···Separator 30, 30' ··· Sweeping tape 40 ···PET tape L... Length of the swelling tape before expansion L' ···Length of the swelling tape after expansion Ls ···Swelling tape expansion length S10, S10'...First electrode preparation process S11 ···First electrode transfer stage S11' ... Slit stage S11'' ···First electrode separation stage S12... Sweeping tape application stage S12' ... Protective tape application stage S13, S13'... Slit stage S20...Supply process S30...Placement process S40 ···Laminating process S50 ···Winding process S60 ··Taping process S70 ··Inspection process TD...Width direction MD ···Length direction

Claims

1. A jelly roll type electrode assembly in which a first electrode; a first separator; a second electrode; and a second separator are sequentially stacked and wound together, The first electrode includes a sweeping tape that is attached to at least one side of the electrode, The first electrode includes a first end along the length direction where winding begins, and a second end where winding ends. The sweeping tape is attached so that the first end and one end of the first electrode coincide. The aforementioned swelling tape expands due to the electrolyte, The expanded swelling tape surrounds the first end of the first electrode. Jelly roll-type electrode assembly.

2. The widthwise length of the sweeping tape is 60% or more and 100% or less, based on 100% of the width of the first electrode. The jelly roll type electrode assembly according to claim 1.

3. The length of the sweeping tape in the longitudinal direction is 250% to 3500% of the thickness of the first electrode, based on 100% of the thickness of the first electrode. The jelly roll type electrode assembly according to claim 1.

4. The electrolyte contains 70% by weight or more of any one of ethylene carbonate (EC), propylene carbonate (PC), dimethyl carbonate (DMC), ethyl methyl carbonate (EMC), or a mixture thereof. The jelly roll type electrode assembly according to claim 1.

5. Dimethyl carbonate 45% by weight, ethylene carbonate 20% by weight, ethyl methyl carbonate 15% by weight, and LiPF as the electrolyte. ６ The length of the sweeping tape after being impregnated for 60 minutes in an electrolyte solution containing 15% by weight of is The length of the swelling tape before expansion is 100% or more, and 160% or less. The jelly roll type electrode assembly according to claim 1.

6. The aforementioned sweeping tape includes a base layer and an adhesive layer. The adhesive layer is provided on at least one side of the base layer. A jelly roll type electrode assembly according to any one of claims 1 to 3.

7. The adhesive layer includes a vacuum adhesive containing a polyacrylic resin. The jelly roll type electrode assembly according to claim 6.

8. A jelly roll type electrode assembly comprising a first electrode; a first separator; a second electrode; and a second separator, which are sequentially stacked and wound together, The first electrode includes a sweeping tape that is attached to at least one side of the electrode, The first electrode includes a first end along the length direction where winding begins, and a second end where winding ends. The sweeping tape is attached so that the first end and one end of the first electrode coincide. The aforementioned sweeping tape includes a base layer and an adhesive layer. The adhesive layer is provided on at least one side of the base material layer, The adhesive layer contains one or more comonomers selected from the group consisting of PMMA (polymethyl methyllate), PEMA (polymethyl methyllate), and PBMA (polybutyl methyllate). Jelly roll-type electrode assembly.

9. A jelly roll type electrode assembly comprising a first electrode; a first separator; a second electrode; and a second separator, which are sequentially stacked and wound together, The first electrode includes a sweeping tape that is attached to at least one side of the electrode, The first electrode includes a first end along the length direction where winding begins, and a second end where winding ends. The sweeping tape is attached so that the first end and one end of the first electrode coincide. The aforementioned sweeping tape includes a base layer and an adhesive layer. The adhesive layer is provided on at least one side of the base material layer, The aforementioned substrate layer contains a urethane resin, Jelly roll-type electrode assembly.

10. The first electrode is the positive electrode, and the second electrode is the negative electrode. A jelly roll type electrode assembly according to any one of claims 1 to 3.

11. The first electrode includes a current collector and an active material layer provided on the current collector. A jelly roll type electrode assembly according to any one of claims 1 to 3.

12. A method for manufacturing a jelly roll type electrode assembly in which a first electrode, a first separator, a second electrode, and a second separator are sequentially stacked and wound up, (a) Step of transporting the first electrode; (b) The step of attaching a sweeping tape to at least one side of the slitting region included in the first electrode; and (c) Step of slitting the longitudinal center of the slit region of the first electrode. Includes, The (b) step involves attaching the sweeping tape such that its longitudinal center coincides with the longitudinal center of the slit region of the first electrode. The (c) step involves slitting the longitudinal center of the slit region so that a first end along the longitudinal direction where winding begins and a second end where winding ends are provided to the first electrode. A method for manufacturing a jelly roll-type electrode assembly.

13. The widthwise length of the sweeping tape is 60% or more and 100% or less, based on 100% of the width of the first electrode. A method for manufacturing a jelly roll type electrode assembly according to claim 12.

14. The length of the sweeping tape in the longitudinal direction is 500% to 7000% of the thickness of the first electrode, based on 100% of the thickness of the first electrode. A method for manufacturing a jelly roll type electrode assembly according to claim 12.

15. The first electrode is the positive electrode, and the second electrode is the negative electrode. A method for manufacturing a jelly roll type electrode assembly according to claim 12.

16. A jelly roll type electrode assembly according to any one of claims 1 to 3; and A secondary battery, including a battery case for housing the electrode assembly.

17. The aforementioned battery case is cylindrical. The secondary battery according to claim 16.

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