Electrode assembly and secondary battery including same

Abstract

The present invention relates to a jelly roll type electrode assembly in which a first separator; a negative electrode; a second separator; and a positive electrode are sequentially stacked and wound up, the positive electrode having a first surface in a winding axis direction of the jelly roll type electrode assembly and a second surface opposite to the first surface, a core portion of the electrode assembly including a separator overlap portion in which the first separator and the second separator are overlapped three or more times between the positive electrode and the negative electrode facing the first surface of the positive electrode, and an adhesive tape is positioned between the positive electrode and the first separator facing the second surface of the positive electrode, or between the negative electrode adjacent to the second surface of the positive electrode and the first separator.

Description

[Technical field]

[0001] This application claims the benefit of the filing date of Korean Patent Application No. 10-2022-0165667 filed with the Korean Intellectual Property Office on December 1, 2022, and Korean Patent Application No. 10-2023-0171927 filed with the Korean Intellectual Property Office on December 1, 2023, the entire contents of which are incorporated herein by reference.

[0002] The present invention relates to an electrode assembly and a secondary battery including the same, and more particularly, to an electrode assembly capable of preventing damage to a separator located at an end of a positive electrode and an anode due to swelling.

[0003] Also, a secondary battery including the electrode assembly may be provided. [Background technology]

[0004] In general, a secondary battery is a battery that can be charged and discharged, unlike a primary battery that cannot be charged. Such secondary batteries are widely used in the field of advanced electronic devices such as phones, laptops, and video cameras.

[0005] The stability of the secondary battery can be measured by a stability test in which one side of the secondary battery is compressed with a press to measure internal short circuits.

[0006] Depending on the shape of the battery case, secondary batteries are classified into cylindrical batteries and prismatic batteries, in which the electrode assembly is housed in a cylindrical or prismatic metal battery case, and pouch-type batteries, in which the electrode assembly is housed in a pouch-type battery case made of an aluminum laminate sheet.

[0007] The electrode assembly built into the battery case is a power generating element that can be charged and discharged and has a laminated structure of a positive electrode / separator / negative electrode, and is classified into a folded type electrode assembly (jelly roll type electrode assembly) in which a separator is interposed between a long sheet-like positive electrode and a negative electrode coated with an active material and wound up, and a stack type electrode assembly in which a number of positive electrodes and negative electrodes of a certain size are stacked in sequence with a separator interposed between them. Among them, the jelly roll type electrode assembly has the advantage of being easy to manufacture and having a high energy density per weight.

[0008] The jelly roll type electrode assembly is formed by winding a positive electrode and a negative electrode, with a separator interposed between the positive electrode and the negative electrode. However, as charge / discharge cycles are repeated hundreds to thousands of times, the jelly roll type electrode assembly contracts and expands, which causes bending deformation at the end of the positive electrode at the center, eventually causing cracks, which can lead to disconnection or short circuit, significantly compromising the safety of the secondary battery. Summary of the Invention [Problem to be solved by the invention]

[0009] In view of the above-mentioned problems in the related art, the present invention provides an electrode assembly and a secondary battery including the same, which prevent the electrode ends from cracking a separator and other electrode surfaces when the electrodes contract and expand due to charging / discharging of the secondary battery. [Means for solving the problem]

[0010] One embodiment of the present invention provides a jelly roll type electrode assembly in which a first separator, a negative electrode, a second separator, and a positive electrode are sequentially stacked and wound up, the positive electrode having a first surface in a winding axis direction of the jelly roll type electrode assembly and a second surface opposite to the first surface, a core part of the electrode assembly includes a separator overlap part in which the first separator and the second separator are overlapped three or more times between the positive electrode and the negative electrode facing the first surface of the positive electrode, and an adhesive tape is located between the positive electrode and the first separator facing the second surface of the positive electrode, or between the negative electrode adjacent to the second surface of the positive electrode and the first separator.

[0011] One embodiment of the present invention provides a secondary battery comprising: the electrode assembly; a battery case having at least one open surface and accommodating the electrode assembly; and a cap assembly coupled to the open surface of the battery case.

[0012] One embodiment of the present invention provides a battery pack including the secondary battery.

[0013] One embodiment of the present invention provides a means of transportation including the battery pack. Effect of the Invention

[0014] In the electrode assembly and the secondary battery including the same according to the embodiment of the present invention, a separator is provided in three or more layers at a portion corresponding to an end of a portion where a positive electrode is wound toward a center of a jelly roll structure, and the separator prevents cracks in the negative electrode at a portion in contact with the end of the positive electrode, thereby preventing disconnection or short circuit, thereby improving the safety of the secondary battery.

[0015] In addition, in the electrode assembly and secondary battery including the same according to the embodiment of the present invention, a separator is provided on one side of a positive electrode in three or more layers, and a separator and an adhesive tape are disposed on the other side of the positive electrode in two layers, thereby preventing damage to the separator due to slipping of the positive electrode and preventing an internal short circuit in the secondary battery.

[0016] An adhesive tape having a porous structure is disposed between the separator and the negative electrode on the other side of the positive electrode, so that lithium ions of the negative electrode can move smoothly through the separator and the adhesive tape, thereby preventing a decrease in capacity of the secondary battery due to the adhesive tape. [Brief description of the drawings]

[0017] [Figure 1] 1 is a perspective view showing an electrode assembly according to an embodiment of the present invention; [Diagram 2] 1 is a plan view of a jelly roll-type electrode assembly including a separator overlapping portion according to an embodiment of the present invention. [Diagram 3] FIG. 3 is an enlarged plan view of a portion of the assembly of FIG. 2. [Figure 4] 1 is a schematic diagram illustrating a separator overlapping portion of a jelly roll type electrode assembly according to an embodiment of the present invention. [Diagram 5] 1 is a schematic diagram illustrating a separator overlapping portion of a jelly roll type electrode assembly according to an embodiment of the present invention. [Figure 6] 1 is a cross-sectional view showing a secondary battery according to an embodiment of the present invention. [Figure 7] 1 is a perspective view showing a battery pack according to an embodiment of the present invention. [Figure 8] FIG. 1 is a perspective view showing a moving means according to an embodiment of the present invention. [Figure 9] 1 shows CT images showing cycle stability evaluation results depending on the thickness of the adhesive tape of the secondary batteries according to Example 1 and Comparative Example 1. [Figure 10] 1 shows CT images showing the results of evaluating the cycle stability of secondary batteries according to Examples 1 to 4 and Comparative Example 2 depending on the length of the adhesive tape. [Figure 11] 10A to 10C are diagrams illustrating a method for evaluating whether or not a separation membrane of a core portion of a jelly roll-type electrode assembly according to an embodiment of the present invention is damaged. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0018] The detailed description of the present invention is intended to fully explain the present invention to those skilled in the art. Throughout the specification, when a part is described as "including" a certain element, or when a certain structure and shape are described as "featuring", this does not mean that other elements are excluded, or that other structures and shapes are excluded, but that other elements, structures and shapes may be included, unless otherwise specified to the contrary.

[0019] Since the present invention can be modified in various ways and can have various embodiments, specific embodiments are presented and described in detail in the detailed description. However, this is not intended to limit the content of the invention by the examples, and it is understood that the present invention includes all modifications, equivalents, or alternatives within the spirit and technical scope of the present invention.

[0020] Hereinafter, the present invention will be described in detail with reference to the drawings. However, the drawings are for illustrating the present invention, and the scope of the present invention is not limited by the drawings.

[0021] The electrode assembly 100 according to the present invention is a chargeable and dischargeable power generating element including a positive electrode 110, a negative electrode 120, and separators 130, 140. The separators 130, 140 may be located between the positive electrode 110 and the negative electrode 120. The separators 130, 140 may be located on one side of the positive electrode 110 or one side of the negative electrode 120.

[0022] In one embodiment, the electrode assembly 100 may have a jelly roll structure in which the positive electrode 110, the first separator 130, the negative electrode 120, and the second separator 140 are stacked and then wound up. That is, the electrode assembly 100 may have the positive electrode 110, the first separator 130, the negative electrode 120, and the second separator 140 stacked in this order before being wound up.

[0023] One end 110a of the positive electrode may extend in the longitudinal direction of the positive electrode, and may have a free-edge shape, which can reduce the area of ​​the unnecessary uncoated portion of the positive electrode current collector to ensure economy, and the slitting process can be performed after the active material layer is formed on the electrode, so that the roll-to-roll process including the slitting process and the winding process can be performed more efficiently.

[0024] The slitting process is a process of cutting the electrode width according to the designed battery specifications using a slitter or cutter. For example, a slitter can cut a sheet-shaped electrode to correspond to the height of the electrode assembly 100.

[0025] The roll-to-roll process may include any process in which a flexible material is moved using a roll. For example, when manufacturing an electrode assembly, an electrode and a separator are provided in a rolled state. Then, the electrode and the separator can be moved and fed to a winding core while being loosened from the roll, and wound around the winding core. In this case, one end of the electrode and the separator can be moved and fed to the winding core via another roll.

[0026] The winding process refers to a process in which the electrodes and the separator are wound around a winding core.

[0027] The positive electrode 110 may include a positive electrode current collector 111, a positive electrode active material layer, and a positive electrode uncoated portion. The positive electrode current collector 111 is not particularly limited as long as it is conductive and does not induce a chemical change in the battery. Specifically, the positive electrode current collector 111 may be stainless steel, aluminum, nickel, titanium, baked carbon, or aluminum or stainless steel whose surface is surface-treated with carbon, nickel, titanium, silver, or the like. That is, the positive electrode current collector 111 may be provided in the form of surface-treated stainless steel, aluminum foil, or the like.

[0028] The positive electrode current collector 111 may have a thickness of typically 3 to 50 μm, and may have fine irregularities formed on the surface of the current collector to enhance the adhesive strength of the positive electrode active material. For example, the positive electrode current collector 111 may be used in various forms, such as a film, sheet, foil, net, porous body, foam, nonwoven fabric, etc.

[0029] The positive electrode 110 is formed by coating a positive electrode active material on at least one of both sides of a positive electrode current collector 111, the area coated with the positive electrode active material being a positive electrode active material layer 112, and the area not coated with the positive electrode active material being a positive electrode uncoated portion. Since the positive electrode uncoated portion is not coated with the positive electrode active material layer 112, a first electrode tab 150 can be joined to the positive electrode current collector 111.

[0030] The positive electrode active material may include lithium cobalt oxide having a high working voltage and excellent capacity characteristics, lithium nickel oxide having a high reversible capacity and facilitating the realization of a large-capacity battery, lithium nickel cobalt oxide in which nickel is partially substituted with cobalt, lithium nickel cobalt metal oxide in which nickel is partially substituted with manganese, cobalt or aluminum, lithium manganese-based oxide having excellent thermal stability and being inexpensive, and lithium iron phosphate having excellent stability.

[0031] In detail, the positive electrode active material is lithium cobalt oxide (LiCoO 2 ), lithium nickel oxide (LiNiO 2 ), or compounds substituted with one or more transition metals; LiFe 3 O 4 Lithium iron oxide, etc.; chemical formula Li 1+x Mn 2-x O 4 (0≦x≦0.33), LiMnO 3 , LiMn 2 O 3 , LiMnO 2 Lithium manganese oxides such as lithium copper oxide (Li 2 CuO 2 );LiV 3 O 8 , V 2 O 5, Cu 2 V 2 O 7 Vanadium oxides such as LiNi 1-y M y O 2 (wherein M is at least one selected from the group consisting of Co, Mn, Al, Cu, Fe, Mg, B and Ga, and 0.01≦y≦0.3 is satisfied); 2-z MzO 2 (wherein M is at least one selected from the group consisting of Co, Ni, Fe, Cr, Zn and Ta, and satisfies 0.01≦z≦0.1.) or Li 2 Mn 3 MO 8 Lithium manganese composite oxide represented by the formula LiMn (wherein M is at least one selected from the group consisting of Fe, Co, Ni, Cu and Zn) 2 O 4 The positive electrode may be Li metal, but is not limited to these.

[0032] According to one embodiment of the present invention, the positive electrode active material layer 112 may further include a positive electrode conductive material and a positive electrode binder. The positive electrode conductive material is used to impart electrical conductivity to the electrode, and can be used without any particular limitation as long as it has electronic conductivity without causing a chemical change in the battery to be 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, and carbon fibers; metal powder or metal fibers such as copper, nickel, aluminum, and silver; conductive whiskers such as zinc oxide and potassium titanate; conductive metal oxides such as titanium oxide; or conductive polymers such as polyphenylene derivatives, and the like. Any combination of such materials as well as other materials similar to those described above may be used as the positive electrode conductive material.

[0033] The positive electrode binder plays a role in improving the adhesion between the positive electrode active material particles and the adhesive strength 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, carboxymethyl cellulose (CMC), starch, hydroxypropyl cellulose, regenerated cellulose, polyvinylpyrrolidone, tetrafluoroethylene, polyethylene, polypropylene, ethylene-propylene-diene monomer (EPDM), sulfonated EPDM, styrene butadiene rubber (SBR), fluororubber, or various copolymers thereof, and one or more of these may be used alone or in combination.

[0034] The negative electrode 120 may include a negative electrode current collector 121, a negative electrode active material layer, and a negative electrode uncoated portion. The negative electrode current collector 121 may include a metal thin plate having excellent electrical conductivity, such as a copper (Cu) or nickel (Ni) foil.

[0035] The negative electrode 120 is formed by coating one or both sides of a negative electrode current collector 121 with a negative electrode active material, the negative electrode active material layer 122 is formed by coating or spreading the negative electrode active material, and the negative electrode uncoated portion is a region where the negative electrode current collector is exposed without being coated or spread with the negative electrode active material. Since the negative electrode uncoated portion is not coated with the negative electrode active material, a second electrode tab 160 can be joined to the negative electrode current collector 121.

[0036] The negative electrode active material may be, for example, a carbon material such as crystalline carbon, amorphous carbon, carbon composite, or carbon fiber, lithium metal, or a lithium alloy, etc. In this case, the negative electrode active material may further include, for example, non-graphite-based SiO (silica) or SiC (silicon carbide) for high capacity design.

[0037] The negative electrode active material layer 122 may include a negative electrode active material including at least one selected from the group consisting of a silicon-based material and a carbon-based material. The negative electrode active material layer 122 may further include a negative electrode conductive material and a negative electrode binder, and the negative electrode active material, the negative electrode conductive material, and the negative electrode binder may be materials used in the art without any restrictions.

[0038] According to an embodiment of the present invention, the negative electrode current collector 121 may be any material that is conductive and does not induce chemical changes in the battery, and is not particularly limited. For example, the negative electrode current collector 121 may be made of copper, stainless steel, aluminum, nickel, titanium, baked carbon, or aluminum or stainless steel that has been surface-treated with carbon, nickel, titanium, silver, or the like. Specifically, a transition metal that effectively adsorbs carbon, such as copper or nickel, may be used as the negative electrode current collector 121. The thickness of the negative electrode current collector 121 may be 6 μm or more and 80 μm or less, but the thickness of the negative electrode current collector 121 is not limited thereto.

[0039] According to one embodiment of the present invention, the negative electrode binder may include at least one selected from the group consisting of polyvinylidene fluoride-hexafluoropropylene copolymer (PVDF-co-HFP), polyvinylidene fluoride, polyacrylonitrile, polymethylmethacrylate, polyvinyl alcohol, carboxymethyl cellulose (CMC), starch, hydroxypropyl cellulose, 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 hydrogen is substituted with Li, Na, Ca, or the like, or may include various copolymers thereof.

[0040] According to one embodiment of the present invention, the negative electrode conductive material is not particularly limited as long as it has conductivity without inducing a chemical change in the battery, and examples thereof include graphite such as natural graphite and artificial graphite; carbon black such as acetylene black, ketjen black, channel black, furnace black, lamp black, and thermal black; conductive fibers such as carbon fibers and metal fibers; conductive tubes such as carbon nanotubes; metal powders such as fluorocarbon, aluminum, and nickel powder; conductive whiskers such as zinc oxide and potassium titanate; conductive metal oxides such as titanium oxide; and conductive materials such as polyphenylene derivatives.

[0041] The first electrode tab 150 and the second electrode tab 160 transfer electrons collected by the current collector to an external circuit, and may protrude in opposite directions from the electrode assembly of the jelly roll structure.

[0042] The separators 130 and 140 can prevent an internal short circuit that may occur due to contact between the positive electrode 110 and the negative electrode 120. The separators 130 and 140 separate the negative electrode 120 and the positive electrode 110 to provide a path for lithium ion movement, and any separator that is generally used as a separator in a secondary battery may be used without any particular limitation. In particular, a separator that has low resistance to ion movement of the electrolyte and excellent electrolyte moisture absorption capacity is preferable.

[0043] The separators 130 and 140 may include a porous material to facilitate the movement of ions between the electrodes. In one embodiment, the separators 130 and 140 may include a base layer made of a porous material. The base layer 131 and 141 may include, for example, any one selected from the group consisting of polyethylene (PE), polystyrene (PS), polypropylene (PP), and a copolymer of polyethylene (PE) and polypropylene (PP).

[0044] Alternatively, the substrate layers 131 and 141 may be porous polymer films, for example, porous polymer films made of polyolefin-based polymers such as ethylene homopolymers, propylene homopolymers, ethylene / butene copolymers, ethylene / hexene copolymers, and ethylene / methacrylate copolymers, or laminated structures of two or more layers thereof. Ordinary porous nonwoven fabrics, for example, nonwoven fabrics made of high-melting-point glass fibers, polyethylene terephthalate fibers, etc. may be used. The separation membrane may have a thickness of typically 10 μm to 20 μm, and a separation membrane may be used in which the above-mentioned separation membrane material is used as a substrate layer and a slurry containing a ceramic component or a polymeric substance is coated on the substrate layer to ensure heat resistance or mechanical strength, and may be used selectively in a single layer or multilayer structure.

[0045] In another embodiment, the separation membranes 130, 140 may include a safety reinforced separator (SRS) separation membrane. That is, the separation membranes 130, 140 may include a substrate layer 131, 141 made of a porous material and a coating layer 132, 142 formed by applying a mixed slurry of inorganic particles and a binder polymer onto the substrate layer. Preferably, the coating layer 132, 142 has a uniform pore structure formed by the interstitial volume between the ceramic particles, which are active layer components, as well as the pore structure contained in the separation membrane substrate itself, including ceramic particles.

[0046] The coating layers 132 and 142 are made of alumina, silica, TiO 2 , SiC and MgAl 2 O 4 The coating layer may further include a ceramic particle including at least one selected from the group consisting of: By including such a coating layer, the safety of the electrode assembly can be enhanced. The coating layer may further include a lithium salt.

[0047] In another embodiment, the separators 130, 140 may each include a coating layer 132, 142 provided on at least one surface, and the coating layer 132, 142 may include an inorganic component, a binder component, and a lithium salt. Since the separator includes the above components, the separator may have excellent cell stability because the separator does not increase in internal resistance due to elution of the lithium salt included in the coating layer, despite including a binder for improving adhesion to the electrode and an inorganic component for improving the mechanical strength of the separator.

[0048] In addition, the electrolyte impregnation level of the electrodes facing the separators 130 and 140 can be increased, which is advantageous in terms of long life. Specifically, the coating layers 132 and 142 may include the inorganic component, and since the coating layers 132 and 142 including the inorganic component have an advantage in terms of thermal shrinkage rate compared to separators made of simple polymer materials, the separators 130 and 140 including the inorganic component may have better safety at high temperatures.

[0049] Specifically, the lithium salt may be substantially the same as that contained in the electrolyte of a lithium secondary battery, for example, LiCl, LiBr, LiI, LiClO 4 , LiBF 4 , LiB 10 Cl 10 , LiPF 6 , LiCF 3 SO 3 , LiCF 3 CO 2 , LiAsF 6 , LiSbF 6 , LiAlCl 4 , C.H. 3 SO 3 Li, C.F. 3 SO 3 Li, (CF 3 SO 2 ) 2 It may be one or more selected from the group consisting of NLi, lithium chloroborane, lithium lower aliphatic carboxylate, and lithium 4-phenylborate.

[0050] The inorganic component is not particularly limited as long as it does not undergo an oxidation and / or reduction reaction, i.e., an electrochemical reaction, with the positive or negative electrode current collector in the operating voltage range of the battery (e.g., 0 to 5 V based on Li / Li+) and does not impair electrical conductivity. For example, BaTiO 3 , Pb(Zr,Ti)O 3 (PZT), Pb 1-x La x Zr 1-y Ti y O 3 (PLZT), Pb(Mg 3 Nb 2 / 3 )O 3 -PbTiO 3 (PMN-PT), hafnia (HfO 2 ), SrTiO 3 , SnO 2 , CEO 2 , MgO, NiO, CaO, ZnO, ZrO 2 , Y 2 O 3 , Al 2 O 3 , and TiO 2 It may be one or more selected from the group consisting of:

[0051] The binder is not particularly limited as long as it exhibits binding strength with the electrodes laminated on the separator and alternate binding strength between the inorganic component and the lithium salt in the mixed coating layer and is not easily dissolved by the electrolyte. For example, polyvinylidene fluoride (PVdF), polyvinylidene fluoride-hexafluoropropylene, polyvinylidene fluoride-trichloroethylene, polyvinylidene fluoride-chlorotrifluoroethylene (PVdF-CTFE), polymethylmethacrylate, polyacrylonitrile, polyvinylpyrrolidone, polyvinylacetate, polyethylene-co-vinyl acetate, polyethylene oxide, cellulose acetate, cellulose acetate butyrate, cellulose acetate propionate The polyvinyl alcohol may be one or a mixture of two or more selected from the group consisting of PVdF, cyanoethyl pullulan, cyanoethyl polyvinyl alcohol, cyanoethyl cellulose, cyanoethyl sucrose, pullulan, carboxyl methyl cellulose, acrylonitrile-styrene-butadiene copolymer, and polyimide, and may be preferably PVdF or PVdF-CTFE.

[0052] In one embodiment of the present invention, the cathode 110 includes a first surface facing toward the center (C or core) of the jelly roll structure and a second surface facing away from the center C in the diametric direction of the jelly roll. Here, the center C of the jelly roll structure refers to the center of the circular structure when the jelly roll structure is viewed from above, and is an imaginary area corresponding to the part where winding begins.

[0053] In detail, the "core part" may refer to a hollow portion located on the winding shaft of the electrode assembly and a part of the wound laminated structure of the first separator / negative electrode / second separator / positive electrode, and may refer to a region within two turns of the positive electrode from one end of the positive electrode in the longitudinal direction located at the innermost corner of the electrode assembly. The "one turn" may refer to a length required for winding an electrode or separator included in the electrode assembly 360° from a reference point, and may be determined according to the outer diameter of the winding core used for winding the electrode assembly, the thickness of the electrode or separator, and the number of windings of the electrode or separator located inside. For example, one turn of the positive electrode may refer to a length required for winding the positive electrode 360° from the end of the longitudinal direction of the positive electrode in the direction in which the jelly roll type electrode assembly is wound, which may be either clockwise or counterclockwise when viewed from above.

[0054] 3, the electrode assembly 100 includes a separator overlapping portion S in which three or more separators 130, 140 are overlapped between one surface of the positive electrode 110 and the negative electrode 120, specifically, the negative electrode current collector (or the negative electrode uncoated portion, 121), at the innermost end of the positive electrode 110, i.e., an edge portion of the positive electrode adjacent to the center C of the jelly roll structure. That is, three or more separators 130, 140 are disposed between a first surface of the positive electrode 110 and the negative electrode 120 facing the first surface of the positive electrode 110. An adhesive tape 180 is disposed between a second surface of the positive electrode 110 and the negative electrode 120.

[0055] The electrode assembly 100 according to one embodiment of the present invention includes a separator overlapping portion S, which suppresses sliding of the electrodes during charging and discharging of the battery and prevents damage to the negative electrode and separator due to deformation of the electrode assembly caused by contraction / expansion of the electrodes. Even if the separator is damaged, the separator overlapping portion prevents an internal short circuit between the positive and negative electrodes, thereby improving battery stability and life characteristics.

[0056] The length of the separation membrane overlapping part S may be 50% based on 100% of the circumferential length of the electrode assembly 100. That is, the separation membrane overlapping part S may extend 180° around the electrode assembly. Preferably, the length of the separation membrane overlapping part S may be more than half the circumference of the core part C of the electrode assembly 100. More preferably, the length of the separation membrane overlapping part S may be 6 mm or more from the end of the positive electrode 110 adjacent to the core part C in the opposite direction to the direction in which the core part C of the electrode assembly 100 is located.

[0057] The electrode assembly 100 may be formed by fixing the separators 130 and 140 to a winding core, and supplying and winding the negative electrode 120 and the positive electrode 110 in that order around the winding core (not shown). Thus, the first separator 130, the second separator 140, and the negative electrode 120 may be located at the front end of the positive electrode 110. In other words, the first separator 130, the second separator 140, and the negative electrode current collector 121 may be formed extending to the front end of the positive electrode 110, and the first separator 130 and the second separator 140 may be formed extending to the front end of the negative electrode current collector 121. Here, the ends of the positive electrode 110 and the negative electrode 120 refer to the ends of the positive electrode 110 and the negative electrode 120 adjacent to the winding core in the longitudinal direction.

[0058] After the negative electrode 120, the positive electrode 110, and the separators 130 and 140 are wound, the core of the electrode assembly 100 is removed, so that a core part C may be formed at the center of the electrode assembly 100.

[0059] In other words, in the core part C of the electrode assembly, the first separator 130, the negative electrode 120, and the second separator 140 may extend longer than the longitudinal end portion of the positive electrode 110 and be further wound up. Specifically, the first separator 130, the negative electrode 120, and the second separator 140 may extend longer than the longitudinal end portion 110a of the positive electrode and be further wound up.

[0060] The first separator 130, the negative electrode 120, and the second separator 140 may be first wound together, and then the positive electrode 110 may be wound together with the first separator 130, the negative electrode 120, and the second separator 140 starting from the longitudinal end 110a of the positive electrode. For example, the first separator 130, the negative electrode 120, and the second separator 140 may be wound together around a winding core for at least one turn, and then wound together with the positive electrode 110. That is, in the core part C of the jelly roll type electrode assembly, the longitudinal ends 120a, 133, and 143 of the first separator 130, the negative electrode 120, and the second separator 140 may be located inside the longitudinal end 110a of the positive electrode.

[0061] The length and width of the negative electrode 120 may be greater than that of the positive electrode 110, and the length and width of the first separator 130 and the second separator 140 located on one side and the opposite side of the negative electrode 120 may also be greater than that of the positive electrode. When the first separator 130, the negative electrode 120, and the second separator 140 extend longer than the longitudinal end 110a of the positive electrode and are further wound up, lithium ions from the positive electrode may be more easily transferred to the negative electrode in a chemical reaction of a lithium ion battery. When the negative electrode is formed to be wider in length or width, the area of ​​the negative electrode that receives lithium ions increases, preventing a decrease in charge / discharge efficiency and improving battery stability and life characteristics.

[0062] The separators 130 and 140 located at the front ends of the ends of the negative electrode 120 and the positive electrode 110 may be bent one or more times at the front end of the negative electrode 120 located at the center of the jelly roll structure. In other words, the separators 130 and 140 may be bent one or more times at the core part C of the electrode assembly 100.

[0063] The separators 130, 140 that have been bent one or more times to change the winding direction may be laminated on one side of the positive electrode 110. The separators 130, 140 extending from the negative electrode end may be folded in a direction opposite to the direction facing the winding shaft of the negative electrode and laminated on one side of the positive electrode 110. Thus, the separators 130, 140 may be laminated in triplicate on one side of an edge portion of the positive electrode 110 adjacent to the center of the electrode assembly 100 in the order of the second separator 140, the second separator 140', and the first separator 130'.

[0064] That is, the separation membranes 130, 140 are positioned in a circumferential direction around the core portion C of the electrode assembly 100, and the first separation membrane 130 and the second separation membrane 140 are bent toward each other at the bending portion B so as to extend from the bending portion B in both a clockwise direction and a counterclockwise direction.

[0065] The separation membranes 130, 140 are warped at least once each, and therefore have different winding directions (clockwise and counterclockwise directions, or opposite winding directions and winding directions) for at least a portion of the electrode assembly 100. The separation membranes 130, 140 may be laminated on one side of the positive electrode 110. The separation membranes 130, 140 extending in a first direction in the clockwise direction from the longitudinal end 120a of the negative electrode may be warped and extended in the counterclockwise direction. They may be laminated on one side of the positive electrode 110 based on the winding axis. Thus, the separation membranes 130, 140 are overlapped to form four layers, and the first separation membrane 130 is divided into two layers with the positive electrode 110 at the center, and three separation membrane layers can be formed within the separation membrane overlapping portion S.

[0066] In this case, the second separator 140' located between the second separator 140 and the first separator 130' is a second separator 140' located on one side of the negative electrode 120 as the second separator 140 is bent at least once at the front end of the positive electrode edge portion. That is, the separator overlapping portion S may directly contact the second separator 140' located closest to the positive electrode 110 and the second separator 140' extending from the longitudinal end of the negative electrode 120 in the core portion of the electrode assembly 100. That is, the separator overlapping portion S may directly contact the portion of the second separator 140 closest to the radial inside of the positive electrode 110 and the portion of the second separator 140' located farther away from the positive electrode 110 in the radial direction.

[0067] The core portion C of the electrode assembly may include a separation membrane overlap portion between the positive electrode and the negative electrode facing a first surface of the positive electrode, and the separation membrane overlap portion may have a separation membrane arranged in three or more overlapping layers.

[0068] The core part C of the electrode assembly includes a separation membrane overlap part S between the positive electrode 110 and the negative electrode 120 facing the first surface of the positive electrode, and the separation membrane overlap part S may refer to a part of a region in which the separation membrane is arranged in three or more layers, based on the longitudinal end 110a of the positive electrode. Here, the separation membrane overlap part S may refer to an end of a region in which the separation membrane is arranged in three or more layers, based on the longitudinal end 110a of the positive electrode, that is, a region having the same length in the core part direction of the electrode assembly as the region up to the longitudinal end of the separation membrane overlap part S. In other words, the separation membrane overlap part S may refer to a region in which one circumferential end Sa is defined at a position where three or more adjacent layers of the separation membrane end. The separation membrane overlap portion S can extend along three adjacent layers of the separation membrane from a circumferential end Sa to an opposing circumferential end Sb, with the circumferential end Sb opposing the circumferential end Sa being defined by a position spaced from the longitudinal end 110a of the positive electrode 110 the same distance as the circumferential end Sa is spaced from the longitudinal end 110a.

[0069] 4 illustrates various relationships between the electrodes and the separators disclosed herein. As shown in the figure, the separator overlapping portion S may refer to a region from the longitudinal end of the separator overlapping portion S to a length L' that is the same as the separation distance L between the longitudinal end of the separator overlapping portion and the longitudinal end of the positive electrode, based on the longitudinal end 110a of the positive electrode, or may refer to a region having a length of L+L'=L+L=2L from the longitudinal end of the separator overlapping portion S.

[0070] According to one embodiment of the present invention, the separation membrane overlapping portion may be a portion in which the first separation membrane 130 and the second separation membrane 140 extending from the longitudinal end 120a of the negative electrode are overlapped at the core portion C of the electrode assembly. Specifically, the separation membrane overlapping portion S may be a portion in which the first separation membrane 130 and the second separation membrane 140 extending from the longitudinal end 120a of the negative electrode are overlapped at the core portion C of the electrode assembly, and the first separation membrane 130 and the second separation membrane 140 may include a region extending from the longitudinal end 120a of the negative electrode. That is, the first separation membrane 130 and the second separation membrane 140 may extend longer than the longitudinal end 120a of the negative electrode and be further wound up.

[0071] In other words, the first and second separation membranes 130 and 140 may be wound together with the negative electrode 120 after a predetermined length of winding has been performed. The first and second separation membranes 130 and 140 extending from the longitudinal end 120a of the negative electrode may be a part of the first and second separation membranes 130 and 140 that have been wound before the negative electrode 120. The first and second separation membranes 130 and 140 extending from the longitudinal end 120a of the negative electrode may include a first separation membrane 130' and a second separation membrane 140' that extend in the opposite direction to the winding direction. A separation membrane overlapping portion S is formed by folding and overlapping the separation membranes in this manner.

[0072] The separator overlapping part may be formed by a folded structure extending integrally from the first separator and the second separator without providing a separate auxiliary separator. This allows the number of separators constituting the separator overlapping part to be adjusted to three or more with a simpler structure. In addition, when the separator overlapping part is formed by overlapping the first separator and the second separator extending from the longitudinal end of the negative electrode, damage to the negative electrode and the separator due to deformation of the electrode assembly caused by contraction / expansion of the electrode can be prevented, and even if the separator is damaged, the separator overlapping part can prevent an internal short circuit between the positive electrode and the negative electrode, thereby improving the stability and life characteristics of the battery.

[0073] According to one embodiment of the present invention, the first separator and the second separator may extend from the longitudinal end of the negative electrode in the core of the electrode assembly, be folded together in a direction opposite to the direction facing the winding shaft of the negative electrode, and be arranged to overlap between the positive electrode and the second separator facing the first surface of the positive electrode. Specifically, the first separator 130 and the second separator 140 extending from the longitudinal end 120a of the negative electrode may be folded together in a direction opposite to the direction facing the winding shaft of the negative electrode, i.e., toward the longitudinal end 110a of the positive electrode, and may be arranged to overlap between the positive electrode 110 and the negative electrode 120 facing the first surface of the positive electrode to form a separator overlap portion S. This allows the separators constituting the separator overlap portion to be three or more times by a simpler folding structure, while making it easier to adjust the facing direction of the separators constituting the separator overlap portion.

[0074] As described above, the separation membrane overlapping portion S may be stacked in the order of the first separation membrane 130', the second separation membrane 140', and the second separation membrane 140 with respect to one surface of the positive electrode 110. The separation membrane overlapping portion S may include a first interface and a second interface. The first interface refers to a surface where the second separation membranes 140, 140' are in direct contact with each other, and the second interface refers to a surface where the second separation membrane 140' and the first separation membrane 130' are in direct contact with each other.

[0075] Specifically, the separation membrane overlapping portion S may have three or more overlapping separation membranes, may include one or more of the first separation membrane 130 and the second separation membrane 140, 140', and may include a first interface S1 where the second separation membrane 140 and the second separation membrane 140' are in direct contact with each other; and a second interface S2 where the second separation membrane 140' and the first separation membrane 130 are in direct contact with each other. In other words, the separation membrane overlapping portion may include a structure of overlapping a first separation membrane and a second separation membrane, which are multiple separation membranes, instead of a structure of overlapping a single separation membrane, and may include interfaces where the first separation membrane and the second separation membrane are in contact with each other. By including multiple interfaces in the separation membrane overlapping portion, it may be easier to adjust the facing direction of the separation membranes and the friction coefficient of each interface by a simpler folding structure.

[0076] According to an embodiment of the present invention, the friction coefficients of the first interface and the second interface may be 0.4 or more. Specifically, the friction coefficients of the first interface S1 and the second interface S2 may be 0.42 or more, 0.44 or more, or 0.46 or more, respectively. That is, the separator overlapping portion includes a first separator and a second separator, which are multiple separators, rather than a single separator overlapping portion, and includes multiple interfaces where the first and second separators are in contact with each other, and the friction coefficients of the multiple interfaces may be adjusted to be greater than or equal to a specific range. When the friction coefficients of the first interface and the second interface satisfy the above-mentioned range, the first separator and the second separator formed integrally with the separator overlapping portion can suppress sliding of the positive electrode during charging and discharging of the battery, and damage to the negative electrode and the separator due to deformation of the electrode assembly caused by contraction / expansion of the electrode can be prevented. Here, the friction coefficient (μ) means a static friction coefficient measured according to the ASTM D1894 standard. The friction coefficient may be measured by a dry method, and may have a larger value when measured by a wet method by immersing a test piece in distilled water or an electrolyte.

[0077] In another embodiment, the electrode assembly 100 may have different friction coefficients between the first interface and the second interface. Preferably, the friction coefficient of the first interface may be greater than the friction coefficient of the second interface. More preferably, the friction coefficient of the first interface may be 0.6 or more, and the friction coefficient of the second interface may be 0.4 or more. Specifically, the friction coefficients of the first interface S1 and the second interface S2 may be different from each other depending on the types and facing directions of the first separator 130, 130' and the second separator 140, 140' that face each other. More specifically, the friction coefficient of the first interface S1 may be 0.62 or more or 0.66 or more, and the friction coefficient of the second interface S2 may be 0.42 or more, 0.44 or more, or 0.46 or more. When the friction coefficient of the interface of the separator included in the separator overlap portion is adjusted within the above range, sliding of the electrodes during charging and discharging of the battery is suppressed, and damage to the negative electrode and separator due to deformation of the electrode assembly caused by contraction / expansion of the electrodes is prevented. Even if the separator is damaged, the separator overlap portion prevents an internal short circuit between the positive and negative electrodes, thereby improving the stability and life characteristics of the battery.

[0078] According to one embodiment of the present invention, the first separation membrane and the second separation membrane may each include a coating layer provided on at least one surface.

[0079] Specifically, the first separator 130, 130' and the second separator 140, 140' each include the coating layer 132, 132', 142, 142' and the substrate layer 131, 131', 141, 141' provided on at least one surface, and may have a friction coefficient in a specific range depending on the components, content and particle size of the coating layer. Here, 130, 130', 140 and 140' indicate that the same separator extends in the opposite direction to the winding direction due to the bending structure of the separator at the bending portion B. Specifically, the friction coefficient between the coating layers of the separator and the friction coefficient between the substrate layers of the separator may be greater than the friction coefficient between the coating layers and the substrate layers. Also, the friction coefficient may be measured in a dry manner, but may have a more significant difference when it is measured by a wet manner, i.e., when it is immersed in distilled water or an electrolyte.

[0080] In the case where a coating layer is provided on at least one surface of the first separator and the second separator, the friction coefficient of the interface of the separator included in the separator overlapping portion can be adjusted within a specific range by adjusting the facing direction of the coating layer provided on at least one surface of the first separator and the second separator, thereby suppressing sliding of the electrodes during charging and discharging of the battery and preventing damage to the negative electrode and the separator due to deformation of the electrode assembly caused by contraction / expansion of the electrodes.

[0081] According to an embodiment of the present invention, the first separator 130, 130' and the second separator 140, 140' may each include a coating layer provided on at least one surface. Specifically, referring to FIG. 4, the first separator 130, 130' and the second separator 140, 140' may each include a coating layer 132, 132', 142, 142' provided on one surface, and the surface of the first separator and the second separator on which the coating layer is provided may have a higher friction coefficient than the surface of the first separator and the second separator on which the coating layer is not provided. That is, when the coating layer is provided on the separator, it can increase the friction coefficient of the interface. By adjusting the facing direction of the coating layers provided on one side of the first separator and the second separator, the friction coefficient of the separator interface included in the separator overlapping portion S can be adjusted within a specific range, thereby suppressing sliding of the electrodes during charging and discharging of the battery and preventing damage to the negative electrode and separator due to deformation of the electrode assembly caused by contraction / expansion of the electrodes.

[0082] According to an embodiment of the present invention, the first separator 130, 130' and the second separator 140, 140' may have a friction coefficient within a specific range by controlling the components, content and particle size of the coating layer.

[0083] According to one embodiment of the present invention, the first separator 130, 130' and the second separator 140, 140' may each include a coating layer provided on one surface, and the first interface S1 may be a direct contact between the coating layer of the second separator 140, 140' and the coating layer of the second separator. Specifically, referring to Fig. 4, the first separator 130, 130' and the second separator 140, 140' may each include coating layers 132, 132', 142, 142' provided on one surface, and the first interface S1 may be a direct contact between the coating layer 142 of the second separator and the coating layer 142' of the second separator. When the coating layer 142 of the second separator and the coating layer 142' of the second separator are in direct contact with each other, that is, the coefficient of friction between the coating layers of the separator may be greater than the coefficient of friction between a substrate layer and a substrate layer or between a coating layer and a substrate layer, and the coefficient of friction at the first interface may be greater. When the coating layer 142 of the second separator and the coating layer 142' of the second separator are in direct contact with each other, the coefficient of friction at the interface of the separator included in the separator overlapping portion S increases, suppressing sliding of the electrodes during charging and discharging of the battery, thereby preventing damage to the negative electrode and the separator due to deformation of the electrode assembly caused by contraction / expansion of the electrodes.

[0084] According to one embodiment of the present invention, the first separation membrane 130, 130' and the second separation membrane 140, 140' may each include a coating layer provided on one surface, and the second interface may be a surface of the second separation membrane on which the coating layer is not provided and a surface of the first separation membrane on which the coating layer is not provided that are in direct contact with each other. Specifically, referring to Fig. 4, the first separation membrane 130, 130' and the second separation membrane 140, 140' may each include coating layers 132, 132', 142, 142' provided on one surface, and the second interface S2 may be a surface of the second separation membrane on which the coating layer is not provided, i.e., the second separation membrane substrate layer 141', and a surface of the first separation membrane on which the coating layer is not provided, i.e., the first separation membrane substrate layer 131', that are in direct contact with each other. When the surface of the second separator not provided with a coating layer and the surface of the first separator not provided with a coating layer are in direct contact with each other, i.e., the coefficient of friction between the substrate layers of the separators may be greater than the coefficient of friction between the coating layers and the substrate layers, and the coefficient of friction at the second interface may be greater. When the surface of the second separator not provided with a coating layer and the surface of the first separator not provided with a coating layer are in direct contact with each other at the second interface, the coefficient of friction at the interface of the separator included in the separator overlapping portion increases, suppressing sliding of the electrodes during charging and discharging of the battery, thereby preventing damage to the negative electrode and the separator due to deformation of the electrode assembly caused by contraction / expansion of the electrodes.

[0085] According to an embodiment of the present invention, the first interface may be directly contacted with the second separator facing the first surface of the positive electrode; and the second separator extending from the longitudinal end of the negative electrode at the core of the electrode assembly. Specifically, referring to FIG. 2 to FIG. 4, the second separator 140' extending from the longitudinal end 120a of the negative electrode may be overlapped between the positive electrode 110 and the negative electrode 120 facing the first surface of the positive electrode to form a separator overlapping portion S. In this case, since the second separator 140 is located between the positive electrode 110 and the negative electrode 120 facing the first surface of the positive electrode, the extended second separator 140' may be directly contacted with the second separator 140 located between the positive electrode 110 and the negative electrode 120. That is, a first interface S1 may be formed where the second separator 140' extending from the longitudinal end 120a of the negative electrode at the core of the electrode assembly is in direct contact with the second separator 140. This allows the separators constituting the separator overlapping portion to be three or more layers with a simpler folding structure, and also makes it easier to adjust the facing direction of the separators constituting the separator overlapping portion and the frictional force of the interface.

[0086] According to one embodiment of the present invention, the second interface may be directly contacted by the first separator extending from the longitudinal end of the negative electrode at the core of the electrode assembly and the second separator extending from the longitudinal end of the negative electrode at the core of the electrode assembly. Specifically, referring to FIG. 2 to FIG. 4, the first separator 130' extending from the longitudinal end 120a of the negative electrode and the second separator 140' extending from the longitudinal end of the negative electrode may be overlapped between the positive electrode 110 and the negative electrode 120 facing the first surface of the positive electrode to form a separator overlapping portion S. In this case, the first separator 130 extending from the longitudinal end 120a of the negative electrode and the second separator 140' extending from the longitudinal end 120a of the negative electrode may be directly contacted by forming a second interface S2. This makes it easier to adjust the facing direction of the separation membranes constituting the separation membrane overlapping portion and the frictional force at the interface while allowing the separation membranes constituting the separation membrane overlapping portion to be three or more layers with a simpler folding structure.

[0087] Fig. 5 is a schematic diagram of a separator overlapping portion of a jelly roll type electrode assembly according to an embodiment of the present invention. Specifically, Fig. 5(a) is a schematic diagram of a separator overlapping portion of a jelly roll type electrode assembly including a first separator and a second separator each having a coating layer on both sides, and Fig. 5(b) is a schematic diagram of a separator overlapping portion of a jelly roll type electrode assembly including a first separator and a second separator each not having a coating layer.

[0088] According to an embodiment of the present invention, the first separator and the second separator may each include a coating layer provided on at least one surface. Specifically, referring to FIG. 3 and FIG. 5(a), the first separator 130, 130' and the second separator 140, 140' each include the coating layer 132, 132', 142, 142' and the substrate layer 131, 131', 141, 141' provided on at least one surface, and may have a friction coefficient in a specific range according to the component, content and particle size control of the coating layer. Specifically, the friction coefficient between the coating layers of the separator and the friction coefficient between the substrate layers may be greater than the friction coefficient between the coating layers and the substrate layers. Also, the friction coefficient may be measured by a dry method, but may have a more significant difference when measured by a wet method, i.e., when immersed in distilled water or an electrolyte.

[0089] In the case where a coating layer is provided on at least one surface of the first separator and the second separator, the friction coefficient of the interface of the separator included in the separator overlapping portion can be adjusted within a specific range by adjusting the facing direction of the coating layer provided on at least one surface of the first separator and the second separator, thereby suppressing sliding of the electrodes during charging and discharging of the battery and preventing damage to the negative electrode and the separator due to deformation of the electrode assembly caused by contraction / expansion of the electrodes.

[0090] According to one embodiment of the present invention, the first separator and the second separator may each include a coating layer provided on at least one surface, and the coating layer may include an inorganic component, a binder component, and a lithium salt. Since the separator includes the above-mentioned components, the separator may have excellent cell stability because an increase in internal resistance is not caused by elution of the lithium salt included in the coating layer, despite including a binder for improving adhesion to an electrode and an inorganic component for improving the mechanical strength of the separator.

[0091] According to an embodiment of the present invention, the length of the separator overlapping portion S may be 30% or more based on 100% of the circumference of the electrode assembly, that is, the separator overlapping portion S may extend about 108° from the electrode assembly.

[0092] Specifically, the length of the separator overlapping portion may be 40% or more or 50% or more based on 100% of the circumference of the electrode assembly, that is, the separator overlapping portion S may extend at least 144° around the electrode assembly.

[0093] Alternatively, the separator layer may be folded to form a separator overlapping portion S of at least 1 / 3 turn or at least 1 / 2 turn of the inner circumferential surface of the core portion of the electrode assembly.

[0094] Here, the perimeter of the electrode assembly may refer to the perimeter of the inner perimeter of the electrode assembly, and the "perimeter of the inner perimeter" may refer to a virtual circumference having a radius of the largest value among the distances to the innermost stratum corneum that contacts the hollow of the electrode assembly based on the winding axis of the electrode assembly. For example, the perimeter of the inner perimeter of the electrode assembly may be about 10 mm, but is not limited thereto.

[0095] The longitudinal length of the separator overlapping part may be L+L'=L+L=2L. That is, the first separator extending from the longitudinal end of the negative electrode in the core part of the electrode assembly and the second separator extending from the longitudinal end of the negative electrode in the core part of the electrode assembly may be disposed between the positive electrode and the negative electrode facing the first surface of the positive electrode, at least 1 / 6 turn or at least 1 / 4 turn from the longitudinal end of the positive electrode, in which case the longitudinal length of the separator overlapping part may be at least 1 / 3 turn or at least 1 / 2 turn. When the longitudinal length range of the separator overlapping part is satisfied, the frictional force of the interface of the separator included in the separator overlapping part may be sufficient to prevent the electrode from sliding during charging and discharging of the battery, thereby preventing damage to the negative electrode and the separator from deformation of the electrode assembly due to contraction / expansion of the electrode.

[0096] According to one embodiment of the present invention, the separation distance between the longitudinal end of the separator overlapping part and the longitudinal end of the positive electrode may be 3 mm or more. Specifically, referring to Fig. 4, the separation distance L between the longitudinal end of the separator overlapping part and the longitudinal end of the positive electrode may be 4 mm or more, 5 mm or more, or 6 mm or more.

[0097] That is, the first separator 130' extending from the longitudinal end of the negative electrode in the core portion of the electrode assembly and the second separator 140' extending from the longitudinal end 120a of the negative electrode in the core portion of the electrode assembly may be disposed 3 mm or more from the longitudinal end 110a of the positive electrode between the positive electrode 110 and the negative electrode 120 facing the first surface of the positive electrode.

[0098] When the longitudinal length range of the separator overlapping part is satisfied, the separator overlapping part can be disposed between the positive electrode and the negative electrode facing the first surface of the positive electrode even if a process error exists when the first separator and the second separator are inserted. In addition, the frictional force of the interface of the separator included in the separator overlapping part can be sufficient to prevent the negative electrode and the separator from being damaged due to deformation of the electrode assembly caused by contraction / expansion of the electrode by suppressing sliding of the electrodes during charging / discharging of the battery.

[0099] The electrode assembly 100 according to the present invention may further include a third electrode tab 170 in the core portion C. The third electrode tab 170 may be located at a front end of a longitudinal end of the positive electrode 110. In other words, the third electrode tab 170 may contact a front end of an end of the pocket-shaped separators 130, 140 in the core portion C direction.

[0100] The adhesive tape 180 is located on one side of the first separator 130 facing the second side of the positive electrode 110 or one side of the negative electrode 120. In other words, the adhesive tape 180 may be laminated on one side of the first separator 130 or one side of the negative electrode 120 facing the edge portion of the positive electrode adjacent to the center of the jelly roll structure.

[0101] The adhesive tape 180 may include a base layer having a porous structure, like the separators 130 and 140 .

[0102] The electrode assembly 100 may have three or more layers of separators 130, 140 superimposed between the first surface 110 of the positive electrode 110 and the negative electrode 120, and two layers of the first separator 130 and the adhesive tape 180 superimposed between the second surface 110b of the positive electrode 110 and the negative electrode 120.

[0103] This configuration can prevent cracks and overheating that may occur from the end of the positive electrode 110. That is, as the design requirement for high energy density increases, an electrode tab (second electrode tab or in tap) is joined to the core part C of the electrode assembly 100, or SiO is further included in the negative electrode active material, which inevitably increases the density of the positive electrode and increases the stress at the positive electrode step. Here, the positive electrode step is a part where the thickness suddenly increases to 100 μm to 200 μm due to the presence of the positive electrode at the starting point of the positive electrode, and where a physical step is formed in the jelly roll electrode assembly, and corresponds to the edge part of the positive electrode 110 in the drawing.

[0104] For example, an in tap is an electrode tab located on one side of a negative electrode uncoated portion close to the core portion C. That is, an in tap refers to an electrode tab closest to an end of the negative electrode that constitutes the core portion C in the longitudinal direction.

[0105] In such a positive electrode step, stress is high, and therefore, if this part is continuously pressed during the process of contraction and expansion due to charging and discharging, the separator in the contacting part is damaged, and the risk of fire due to cracks and short circuit increases. However, according to one embodiment of the present invention, as described above, a triple separator is disposed on the first surface of the positive electrode 110 at the edge of the positive electrode, and a double separator and adhesive tape is disposed on the second surface of the positive electrode 110 at the edge of the positive electrode, thereby preventing damage to the separator at the positive electrode step and enabling a stable buffering effect, and preventing cracks and short circuit caused by repeated contraction and expansion at the end of the positive electrode where stress is high, thereby reducing the risk of fire.

[0106] That is, as the charge / discharge cycle proceeds several hundred to several thousand times, the electrode may shrink and expand, which may cause bending deformation at the edge of the positive electrode 110, which may cause cracks in the electrode. However, by disposing a triple separator on the first surface of the positive electrode 110 at the edge of the positive electrode, and a double separator and adhesive tape on the second surface of the positive electrode 110 at the edge of the positive electrode, it is possible to prevent cracks and short circuits caused by shrinkage and expansion of the edge of the positive electrode 110 and ignition due to this. In particular, in this embodiment, a triple separator is disposed on the first surface of the positive electrode, not on one surface of the positive electrode, and a double separator and adhesive tape is disposed on the second surface, so that cracks and short circuits in the electrode can be prevented on both surfaces.

[0107] An adhesive tape 180 according to one embodiment may include a porous base layer 181 and an adhesive layer 182 applied to one side of the porous base layer. The adhesive layer 182 may be laminated over the entire surface of the porous base layer 181, or the adhesive layer 182 may be provided in a pattern and laminated over only a portion of the surface of the porous base layer 181.

[0108] The porous substrate layer 181 of the adhesive tape 180 may be the separator substrate layers 131, 141 included in the first separator 130 and the second separator 140. When the adhesive tape 180 includes a porous substrate layer and an adhesive layer 182, the adhesive layer 182 may include a material through which ions, specifically lithium ions, can easily move, or the adhesive layer 182 may absorb an electrolyte solution and expand to form an ion migration path.

[0109] Therefore, like the separators 130 and 140, the adhesive tape 180 facilitates the movement of ions between the electrodes and can prevent the precipitation of lithium ions even when the secondary battery 1 is charged / discharged.

[0110] Alternatively, the porous substrate layer 181 may be, for example, one or more films selected from the group consisting of an acrylic film, a polyolefin film, a polyamide film, a polycarbonate film, a polyurethane film, a cellulose acetate film, and a polyester film, but is not limited thereto.

[0111] When a polyester film is used as the porous substrate layer 181, one or more films selected from the group consisting of a polyethylene terephthalate film, a polyethylene naphthalate film, and a polybutylene terephthalate film can be used, and when a cellulose-based porous substrate layer 181 is used as the porous substrate layer 181, for example, a porous substrate layer 181 containing a cellulose acetate resin or a cellulose alkylate resin can be used, which is manufactured by applying a mixture containing the resin to an extrusion or casting process. In the above, for example, cellulose acetate propionate or cellulose acetate butylate can be used as the cellulose alkylate.

[0112] The method for manufacturing the porous substrate layer 181 using the resin is not particularly limited, and for example, a conventional film or sheet molding method such as extrusion or casting of a raw material containing the resin and, if necessary, known additives can be used.

[0113] When the porous base layer 181 is in the form of a sheet or film, the thickness of the porous base layer 181 is not particularly limited and may be, for example, about 10 to 200 μm, 10 to 100 μm, 10 to 50 μm, 15 to 30 μm, or 15 to 20 μm.

[0114] The adhesive layer may include polyethylene oxide (PEO, Polyethylene oxide, ether group). The polyethylene oxide acts with the electrolyte by electrostatic polar attraction, and the adhesive layer can attract the electrolyte that has flowed into the separator through the porous substrate layer and absorb the electrolyte into the adhesive layer.

[0115] Specifically, the adhesive layer 182 can be represented by the following chemical formula 1 (Chemical Formula 1).

[0116] [ka]

[0117] In the above Chemical Formula 1, R1 represents hydrogen or an alkyl group having 1 to 12 carbon atoms; R2 represents an alkylene group having 1 to 6 carbon atoms; R3 represents hydrogen, an alkyl group having 1 to 12 carbon atoms, an aryl group having 6 to 24 carbon atoms, or an arylalkyl group having 6 to 48 carbon atoms; n is 0 or greater.

[0118] In the above Chemical Formula 1, R1 is hydrogen or an alkyl group having 1 to 12 carbon atoms, 1 to 8 carbon atoms, or 1 to 4 carbon atoms, and examples thereof include hydrogen, a methyl group, an ethyl group, a propyl group, a butyl group, a pentyl group, and a hexyl group, and preferably hydrogen or a methyl group, but is not limited thereto.

[0119] In addition, in the above Chemical Formula 1, R2 is an alkylene group having 1 to 6, 1 to 4, or 1 to 2 carbon atoms, and may be, for example, ethylene or propylene, but is not limited thereto.

[0120] R3 represents hydrogen; an alkyl group having 1 to 12, 1 to 8, 1 to 6, or 1 to 4 carbon atoms; an aryl group having 6 to 24, 6 to 20, 6 to 18, or 6 to 12 carbon atoms; or an arylalkyl group having 6 to 48, 6 to 30, 6 to 24, or 6 to 18 carbon atoms, and examples thereof include hydrogen, a methyl group, an ethyl group, a propyl group, a phenyl group, a naphthalic group, a butylphenol group, a pentylphenol group, a hexylphenol group, a heptylphenol group, an octylphenol group, and a nonylphenol group, but is not limited thereto.

[0121] Moreover, the n may be 0 or more, for example, 1 or more, and preferably 2 or more.

[0122] Referring to FIG. 6, in the secondary battery 1 according to the present invention, a double layer consisting of a first separator 130 and an adhesive tape 180 is overlapped on the second surface of the positive electrode 110, which prevents damage to the separator due to a stepped portion of the positive electrode and an internal short circuit of the secondary battery 1. In addition, lithium ions of the positive electrode move to the negative electrode through the electrolyte absorbed in the porous substrate layer and the adhesive layer, so that the secondary battery 1 according to the present invention can improve the problem of capacity reduction caused by the adhesive layer.

[0123] The monomer represented by Chemical Formula 1 contains at least one oxygen atom, and the monomer has a very high polarity due to the high electronegativity of the oxygen atom, so that the adhesive layer containing the monomer has a high affinity with a polar electrolyte solution and can expand when in contact with the electrolyte. In addition, the term "electrolyte solution" in the above may mean, for example, an ion-conducting medium used in a secondary battery. As an example, the electrolyte may be an electrolyte solution that is a liquid medium, but is not limited thereto. In this specification, the electrolyte solution may be referred to as an electrolyte.

[0124] According to another embodiment, the adhesive tape 180 may include a porous base layer 181 and a coating layer (not shown) in which a slurry of a mixture of inorganic particles and a binder is applied to one side of the porous base layer 181. The adhesive tape 180 may have adhesive strength due to the binder contained in the coating layer. For example, the adhesive tape 180 may be made by mixing an organic solvent with a slurry of a mixture of inorganic particles and a binder, coating the slurry on one side of the porous base layer 181, and then adjusting process conditions immediately before drying to induce phase separation so that the binder acting as an adhesive is exposed to the surface.

[0125] An adhesive tape 180 according to another embodiment may include a porous base layer 181, a coating layer formed by applying a slurry of a mixture of inorganic particles and a binder to one side of the porous base layer 181, and an adhesive layer 182 applied to either one side of the coating layer or the other side of the porous base layer 181. Here, the one side of the coating layer to which the adhesive layer 182 is applied refers to the side opposite to the side directly in contact with the base layer. The adhesive layer may have the same structure as the adhesive layer of the adhesive tape 180 according to an embodiment.

[0126] The layering position of the adhesive tape 180 may be determined so that the base layer 181 of the adhesive tape 180 and the positive electrode 110 can be in direct contact with each other, or the adhesive layer 182 and the negative electrode 120 can be in direct contact with each other.

[0127] Such a configuration increases the frictional force between the positive electrode 110 and the negative electrode 120 and the adhesive tape 180, preventing the negative electrode 120 and the positive electrode 110 from sliding, and preventing the shape of the core portion C from collapsing (core deformation).

[0128] The adhesive tape 180 may be adhered such that the coating layer and the adhesive layer are in direct contact with the second surface of the positive electrode 110, or may be adhered to one surface of the negative electrode 120 facing the second surface of the positive electrode 110. Alternatively, the adhesive tape 180 may be adhered such that the coating layer and the adhesive layer are in direct contact with the second surface 110b of the positive electrode 110 and one surface of the first separator 130 located between the second surface 110b of the positive electrode 110 and the negative electrode 120.

[0129] The adhesive tape 180 has a porous structure in the base layer, coating layer, and adhesive layer, allowing lithium ions of the negative electrode 120 to pass through, thereby minimizing lithium deposition and ensuring the safety of the secondary battery even when the electrode assembly 100 is charged and discharged.

[0130] In the adhesive tape 180 according to the present invention, the thickness of the porous base layer 181 may be 13 μm or more, and the thickness of the adhesive layer 182 may be more than 0 μm and 4 μm or less. Preferably, the thickness of the porous base layer 181 may be 15 μm or more, and the thickness of the adhesive layer 182 may be more than 0 μm and 3 μm or less. When the thickness of the porous base layer 181 is 13 μm or more, the total thickness of the adhesive tape 180 becomes thick, and it is possible to prevent the end of the negative electrode or positive electrode from damaging or penetrating the separator during core impingement. And, since the thickness of the adhesive layer 182 is 4 μm or less, the permeability of the electrolyte is high, and therefore, the effect of increasing ion conductivity may be obtained.

[0131] The length of the adhesive tape 180 may be 5 mm or more. Preferably, the length of the adhesive tape 180 may be 10 mm or more. Furthermore, the length of the adhesive tape 180 that overlaps with the positive electrode may be 2 mm or more, preferably 5 mm or more.

[0132] In the adhesive tape 180, the porous base material layer 181 faces the base material layer 131 of the first separation membrane, and the length over which the porous base material layer 181 faces the base material layer 131 of the first separation membrane satisfies the above-mentioned range, so that electrode sliding is suppressed by the friction coefficient between the separation membranes, and therefore the shape of the core part C can be prevented from collapsing.

[0133] In addition, since the overlap length between the adhesive tape 180 and the positive electrode 110 satisfies the above range, the thickness of the area where the positive electrode edge portion is located increases, and when the electrode assembly 100 contracts and expands, the friction coefficient increases due to the pressure of the adhesive tape 180 and the first separator 130, preventing the electrodes from sliding.

[0134] The secondary battery 1 according to the present invention may include an electrode assembly 100, a battery case 200, and a cap assembly 300.

[0135] The secondary battery 1 may include an electrode assembly 100, a battery case 200, and a cap assembly 300.

[0136] The electrode assembly 100 is according to the embodiments described above.

[0137] The battery case 200 may have a columnar structure with a space formed therein. The battery case 200 may accommodate an electrode assembly 100 including an electrode and a separator, and an electrolyte (not shown) in the internal space. The battery case 200 may have a structure in which at least one side is open (hereinafter, referred to as an opening), and the other side may be sealed. Here, the one side and the other side of the battery case 200 refer to the ends located at the top and bottom along the direction of gravity or the central axis of the battery case 200.

[0138] A beading portion 210 folded toward the center of the secondary battery 1 may be provided on the upper side of the open battery case 200. The battery case 200 may have a crimping portion 220 on the upper side of the beading portion 210. That is, the crimping portion 220 may be located on the uppermost side of the battery case 200. Here, the upper portion refers to the region from the center of the battery case 200 toward the opening.

[0139] The battery case 200 may be made of a lightweight conductive metal material such as aluminum or an aluminum alloy, and may have a cylindrical shape.

[0140] Preferably, the battery case 200 according to the present invention may be cylindrical. Specifically, the battery case 200 may be cylindrical, square, or pouch-shaped depending on the application, and when the battery case is cylindrical, it may be more suitable for accommodating a jelly-roll type electrode assembly, and when the battery case is cylindrical, the shape of a secondary battery including the jelly-roll type electrode assembly and a battery case for accommodating the electrode assembly may be cylindrical.

[0141] According to an embodiment of the present invention, the inside of the battery case may contain an electrolyte. Specifically, the electrolyte may be an organic liquid electrolyte, an inorganic liquid electrolyte, a solid polymer electrolyte, a gel-type polymer electrolyte, a solid inorganic electrolyte, or a molten inorganic electrolyte that can be used in manufacturing a lithium secondary battery, but is not limited thereto. Specifically, the electrolyte may contain a non-aqueous organic solvent and a metal salt.

[0142] According to one embodiment of the present invention, the non-aqueous organic solvent may be, for example, an aprotic organic solvent such as N-methyl-2-pyrrolidinone, propylene carbonate, ethylene carbonate, butylene carbonate, dimethyl carbonate, diethyl carbonate, gamma-butyrolactone, 1,2-dimethoxyethane, tetrahydrofuran, 2-methyltetrahydrofuran, dimethylsulfoxide, 1,3-dioxolane, formamide, dimethylformamide, dioxolane, acetonitrile, nitromethane, methyl formate, methyl acetate, phosphoric acid triester, trimethoxymethane, dioxolane derivatives, sulfolane, methylsulfolane, 1,3-dimethyl-2-imidazolidinone, propylene carbonate derivatives, tetrahydrofuran derivatives, ether, methyl propionate, or ethyl propionate.

[0143] 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 dissolved in the non-aqueous organic solvent. For example, the anion of the lithium salt is F - , Cl - , I - , NO 3- 、N(CN) 2- 、BF 4 - 、ClO 4 - 、PF 6 - 、(CF 3 ) 2 PF 4 - 、(CF 3 ) 3 PF 3 - 、(CF 3 ) 4 PF 2 - 、(CF 3 ) 5 PF - 、(CF 3 ) 6 P - 、CF 3 SO 3 - 、CF 3 CF 2 SO 3 - ,(CF 3 SO 2 ) 2 N - 、(FSO 2 ) 2 N - 、CF 3 CF 2 (CF 3 ) 2 CO - 、(CF 3 SO 2 ) 2 CH - 、(SF 5 ) 3 C - 、(CF 3 SO 2 ) 3 C - 、CF 3 (CF 2 ) 7 SO 3 - 、CF 3 CO 2 - 、CH 3 CO 2 -, SCN - and (CF 3 CF 2 SO 2 ) 2 N - One or more selected from the group consisting of:

[0144] According to one embodiment of the present invention, the electrolyte may further contain, in addition to the electrolyte constituents, one or more additives such as a haloalkylene carbonate compound such as difluoroethylene carbonate, pyridine, triethyl phosphite, triethanolamine, cyclic ether, ethylenediamine, n-glyme, hexaphosphoric acid triamide, nitrobenzene derivatives, sulfur, quinoneimine dyes, N-substituted oxazolidinones, N,N-substituted imidazolidines, ethylene glycol dialkyl ethers, ammonium salts, pyrrole, 2-methoxyethanol, or aluminum trichloride for the purpose of improving the life characteristics of the battery, suppressing a decrease in battery capacity, improving the discharge capacity of the battery, etc.

[0145] The cap assembly 300 can be coupled to the open side of the battery case 200 and can include a top cap 310 , a safety vent 320 , and a current interrupt device 330 .

[0146] The top cap 310 may be located at the top of the cap assembly 300 and may protrude in a direction opposite to the center of the battery case 200. The top cap 310 may serve as an electrode terminal such that the protruding portion is electrically connected to the outside, for example, the top cap 310 may serve as a positive electrode terminal.

[0147] The top cap 310 may have a sealing gasket 340 coupled to an edge of the top cap 310, and the sealing gasket 340 may be located inside the crimping portion 220 of the battery case 200. The sealing gasket 340 may increase the sealing force between the top cap 310 and the battery case 200.

[0148] The top cap 310 may include a protrusion protruding upward, a rim that contacts and couples with the sealing gasket 340, and a first connecting portion that connects the protrusion and the rim.

[0149] The safety vent 320 may be located at a lower portion of the top cap 310 and may be electrically connected to the top cap 310. At least a portion of a surface of the safety vent 320 facing the top cap 310 may be in contact with the top cap 310. The safety vent 320 may be in contact with the top cap 310 for a certain length from an end thereof, and a portion other than the contact length may be located at a certain distance from the top cap 310. The portion of the safety vent 320 in contact with the top cap 310 may be coupled to the sealing gasket 340.

[0150] The safety vent 320 may be spaced apart from the top cap 310 by an increasing distance toward the center of the safety vent 320 in the area where it contacts the top cap 310 .

[0151] The safety vent 320 may include a contact portion that contacts the top cap 310, a central portion that is located at the center of the safety vent 320 and that contacts the current interrupting element, and a second connecting portion that connects the contact portion and the central portion. The safety vent 320 may have bent portions (or notches) at the portions where the contact portion and the second connecting portion and the second connecting portion and the central portion contact each other.

[0152] In one embodiment, the safety vent 320 may be provided with an end perpendicular to the axial direction of the battery case 200. In this case, the top cap 310 may be provided perpendicular to the axial direction of the battery case 200, similar to the safety vent 320. That is, the safety vent 320 and the top cap 310 may be positioned horizontally.

[0153] In other embodiments, the safety vent 320 may be provided with a folded end that wraps around the outer periphery of the top cap 310 .

[0154] In the secondary battery 1 according to the present invention, the electrode assembly 100 housed inside the battery case 200 reacts with the electrolyte, generating gas and heat, resulting in an increase in internal pressure.

[0155] When the pressure inside the secondary battery 1 rises, the safety vent 320 receives a force in the direction of the top cap 310, causing the bent portion to burst and allowing the gas inside the secondary battery 1 to be discharged.

[0156] A current interruptive device (CID) 330 may be located below the safety vent 320 and at least a portion of the CID may be coupled to the safety vent 320 .

[0157] When the safety vent 320 bursts due to an increase in the internal pressure of the secondary battery 1, the current interrupting element 330 is separated from the safety vent 320 to interrupt the current.

[0158] The current interrupting element 330 may include a connecting portion connected to the safety vent 320 at a center portion and protruding upward toward a midpoint in a direction in which the safety vent 320 is located, i.e., along the length of the current interrupting element 330, an edge portion excluding the connecting portion, and a connecting portion connecting the connecting portion and the edge portion. A plurality of connecting portions may be provided, and the plurality of connecting portions may be located spaced apart from each other.

[0159] When the safety vent 320 is deformed in the direction in which the top cap 310 is positioned, the joint breaks and the connecting portion can be separated from the edge. That is, the connecting portion is separated in the direction of the top cap 310 while remaining connected to the safety vent 320.

[0160] The CID gasket 350 wraps around the edge of the current interrupting element 330 and can electrically isolate the edges and joints of the current interrupting element 330 other than the connection portion from the safety vent 320 .

[0161] According to an embodiment of the present invention, a battery pack 3 including any of the secondary batteries described above is provided.

[0162] With regard to the above embodiment, referring to FIG. 7, a battery pack 3 in which a secondary battery 1 is included in a pack housing 2 is shown.

[0163] The battery pack according to the embodiment has high output and high capacity.

[0164] According to an embodiment of the present invention, there is provided a vehicle including the battery pack described above.

[0165] With respect to the above embodiment, referring to FIG. 8, a vehicle V including a battery pack 3 is shown.

[0166] The vehicle according to the embodiment uses a battery pack having high output / capacity, and is therefore excellent in terms of stability and safety.

[0167] While the present invention has been described above with reference to preferred embodiments, it will be understood that those skilled in the art can make various modifications and variations to the present invention without departing from the spirit and scope of the present invention as set forth in the following claims.

[0168] Example 1 Electrode Assembly Manufacturing An Al foil having a thickness of 15 μm and a width length of 63.9 mm was prepared as a 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 a positive electrode active material and CNTs (carbon nanotubes) as a conductive material was applied onto the positive electrode current collector and dried to form a positive electrode active material layer, thereby producing a positive electrode having a thickness of 154 μm.

[0169] Next, a Cu foil having a thickness of 8 μm and a width direction length of 65.1 mm was prepared as a negative electrode current collector, and a negative electrode active material slurry containing 50 parts by weight each of artificial graphite and natural graphite as negative electrode active materials was applied to the negative electrode current collector and dried to form a negative electrode active material layer, thereby producing a negative electrode having a thickness of 187 μm.

[0170] On the other hand, the first and second separation membranes were prepared by depositing Al as an inorganic component on one side of a sheet-shaped polyethylene substrate layer. 2 O 3 Two separators each having a coating layer containing a PVdF binder and a lithium salt as binder components were prepared.

[0171] Before winding the jelly roll electrode assembly, the base layers of the first and second separators are overlapped such that the first and second base layers face each other, and the first and second separators are provided with an extension portion that extends long enough that the overlapping portion where the first and second base layers face each other wraps around the winding core of the electrode assembly by about three turns. The three turns extend in the opposite direction to the "winding direction," which is the direction in which the separator and the electrodes are wound outward from the winding core, and extend outward instead of inward toward the winding core. In the electrode assembly of FIG. 2, the winding direction is counterclockwise. The winding core may be a core of the jelly roll electrode assembly having a perimeter of about 10 mm.

[0172] After the first and second separators are wound toward the core part C for about three turns, the separators can be bent again and begin to be wound up so as to extend in the winding direction. The negative and positive electrodes were sequentially inserted into the first and second separators, and the negative electrode was inserted closer to the core part C to manufacture a jelly roll type electrode assembly. In this case, the core part of the jelly roll type electrode assembly had a separator overlapping part between one side of the positive electrode in the winding axis direction and the second separator located on one side of the negative electrode, with the extensions of the first and second separators interposed therebetween, and an adhesive tape was placed on the opposite side where the extensions are interposed, i.e., between the first separator and the negative electrode, to have the structure shown in Figs. 2 and 3.

[0173] In this case, the gap distance (L) between the longitudinal end of the separator overlapping part and the longitudinal end of the positive electrode was 3 mm, and the longitudinal length of the separator overlapping part (L+L'=2L) was adjusted to be 6 mm. The perimeter of the inner circumferential surface of the manufactured jelly-roll type electrode assembly was about 10 mm.

[0174] The adhesive tape had a porous base layer thickness of 16 μm, an adhesive layer thickness of 3 μm, and a length of 18 mm.

[0175] Secondary battery manufacturing The jelly-roll type electrode assembly was inserted into a cylindrical battery case, and then ethylene carbonate (EC): dimethyl carbonate (DMC): ethyl methyl carbonate (EMC) were mixed in a weight ratio of 4:9:3 to prepare LiPF 6 An electrolyte containing 15 wt % of the above was poured into the cylindrical battery case, and the cylindrical battery case was sealed with a cap assembly to prepare a secondary battery.

[0176] 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 10 mm adhesive tape was used.

[0177] 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 15 mm adhesive tape was used.

[0178] Example 4 A jelly-roll type electrode assembly and a secondary battery were manufactured in the same manner as in Example 1, except that a 5 mm adhesive tape was used.

[0179] 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 the thickness of the porous substrate layer of the adhesive tape was 11 μm and the thickness of the adhesive layer was 5 μm.

[0180] Comparative Example 2 A jelly-roll type electrode assembly and a secondary battery were fabricated in the same manner as in Example 1, except that no adhesive tape was attached between the first separator and the negative electrode.

[0181] Experimental Example Experimental Example 1 - Evaluation of Core Impingement Evaluation of cycle stability depending on thickness of adhesive tape The secondary batteries manufactured in Example 1 and Comparative Example 1 were activated by performing 2 cycles of 4.2V-2.5V, 0.2C charge, and 0.2C discharge to prepare secondary batteries. Then, the activated secondary batteries were each subjected to 50 cycles of 4.3V-2.5V, 1C / 1C@24°C to prepare secondary batteries, and the short-term cycle stability was evaluated by checking whether or not core impingement occurred by performing computed tomography (CT) of the core part, and the image is shown in FIG.

[0182] Evaluation of cycle stability by length of adhesive tape The secondary batteries manufactured in Example 1 and Comparative Example 2 were activated by performing 2 cycles of 4.2V-2.5V, 0.2C charge, and 0.2C discharge to prepare secondary batteries. Then, the activated secondary batteries were each subjected to 50 cycles of 4.3V-2.5V, 1C / 1C@24°C to prepare secondary batteries, and the short-term cycle stability was evaluated by checking whether or not core impingement occurred by performing computed tomography (CT) of the core part, and the image is shown in FIG. 10.

[0183] Core Impingement Evaluation The secondary batteries of Example 1 and Comparative Example 1 were evaluated for the occurrence of core impingement by the following method.

[0184] Fig. 11 is a schematic diagram showing a method for evaluating the occurrence of core impingement. Specifically, Fig. 11(a) is a schematic diagram showing a method for evaluating the occurrence of core impingement when deformation occurs in the negative electrode, and Fig. 11(b) is a schematic diagram showing a method for evaluating the occurrence of core impingement when deformation does not occur in the negative electrode.

[0185] 1) On the first surface of the positive electrode 110, a first extension line E1 is drawn by extending a straight line connecting the longitudinal end 110a of the positive electrode to a point 5 mm away from the end.

[0186] 2-1) When deformation occurs in the negative electrode In the core portion of the jelly roll type electrode assembly, on the surface of the negative electrode 120 facing the first surface of the positive electrode, a second extension line E2 is drawn by extending a straight line connecting two points where the curvature direction changes within a distance of 5 mm from the longitudinal end 110a of the positive electrode.

[0187] 2-2) When there is no deformation in the negative electrode A first extension line E1 is drawn on the radially inner surface of the positive electrode 110 by extending a straight line connecting the longitudinal end 110a of the positive electrode and a point 5 mm away from that end.

[0188] In the core portion of the jelly roll type electrode assembly, a second extension line E2 is drawn by extending a straight line connecting two points 5 mm apart from the longitudinal end 110a of the positive electrode on the surface of the negative electrode 120 facing the first surface of the positive electrode.

[0189] 3) Based on the intersection point of the first extension line E1 and the second extension line E2, if the angle from the first extension line E1 to the second extension line E2 in a counterclockwise direction exceeds 25°, it was evaluated that a core impingement occurred.

[0190] Meanwhile, the method of evaluating whether or not core impingement has occurred may be applied in the following manner: when an unknown cell is obtained, whether or not core impingement has occurred is evaluated at the time of initial acquisition, and whether or not core impingement has occurred is re-evaluated after 50 cycles, and the result is compared and analyzed with the core impingement conditions of the secondary battery of the embodiment of the present invention.

[0191] FIG. 9 is a set of CT images showing the results of cycle stability evaluation depending on the thickness of the adhesive tape of the secondary batteries of Example 1 and Comparative Example 1, and FIG. 10 is a set of CT images showing the results of cycle stability evaluation depending on the length of the adhesive tape of the secondary batteries of Examples 1 to 4 and Comparative Example 2.

[0192] 9 and 10, it was confirmed that the secondary battery manufactured in Example 1 did not suffer from core impingement in the cycle stability evaluation according to the thickness and length of the adhesive tape, and it was confirmed that the secondary batteries manufactured in Examples 2 to 4 did not suffer from core impingement in the cycle stability evaluation according to the length of the adhesive tape.

[0193] It was confirmed that the secondary battery manufactured in Comparative Example 1 had core impingement in the cycle stability evaluation based on thickness, and it was confirmed that the secondary battery manufactured in Comparative Example 2 had core impingement in the cycle stability evaluation based on length.

[0194] Specifically, it was confirmed that either no core impingement occurred after activation or minor core impingement occurred in both Comparative Examples 1 and 2. Also, it was confirmed that in Comparative Examples 1 and 2, after 50 cycles, the frequency and extent of core impingement due to damage to the negative electrode and separator caused by the longitudinal end of the positive electrode, i.e., contraction / expansion of the electrode assembly, significantly increased.

[0195] In Example 1, the puncture strength is higher than that of Comparative Example 1 due to the thicker porous substrate layer, and therefore, the first separator located between the positive and negative electrodes can be prevented from being punctured by the positive and negative electrodes.

[0196] In Example 1 and Comparative Example 1, a test piece that changes color when it comes into contact with the acidic component of the electrolyte was placed between the adhesive layer and the porous base layer to confirm electrolyte permeability. As a result, it was confirmed that in Example 1, the adhesive layer was thin, so there was ionic conductivity through the adhesive tape, and therefore the test piece between the porous base layer and the adhesive layer turned red.

[0197] In addition, in Example 1, the thickness of the adhesive tape can increase the frictional force between the negative electrode and the separator when the negative electrode moves due to the progress of cycles, thereby reducing core impingement.

[0198] It was confirmed that the difference in core impingement between after activation and after 50 cycles was negligible for the secondary batteries manufactured in Examples 2 to 4. In particular, it was confirmed that the core impingement was 89% or more when the overlap length between the adhesive tape and the positive electrode was 5 mm or more.

[0199] Through this, when the thickness of the adhesive tape between the first separator and the negative electrode is 19 μm or more and the length is 5 mm or more, a higher friction coefficient can be realized compared to when no adhesive tape is placed between the first separator and the negative electrode or when the thickness of the adhesive tape is less than 19 μm, and it can be seen that the sliding of the electrodes is suppressed and the effect of preventing damage to the negative electrode and separator even when the electrode contracts / expands can be excellent.

[0200] The above detailed description is illustrative and explanatory of the present invention. Moreover, the above content is merely representative and explanatory of preferred embodiments of the present invention, and as stated above, the present invention can be used in various other combinations, modifications and environments, and changes or modifications can be made within the scope of the inventive concept disclosed herein, the scope of the above disclosure, and / or the skill 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. Moreover, the appended claims should be construed to include other embodiments. [Explanation of symbols]

[0201] 1 Secondary battery 100 electrode assembly 110 Positive electrode 110a: longitudinal end of positive electrode 111 Positive electrode current collector 112 Cathode active material layer 120 negative electrode 120a: Longitudinal end of negative electrode 121 Negative electrode current collector 122 Negative electrode active material layer 130 First separation membrane 131 First separation membrane base layer 132 First separation membrane coating layer 140 Second separation membrane 141 Second separation membrane base material layer 142 Second membrane coating layer 143 Longitudinal end of second separation membrane 150 First electrode tab 160 Second electrode tab 170 3rd electrode tab 180 Adhesive Tape 181 Tape base layer 182 Adhesive layer 200 Battery Case 210 Beading section 220 Crimping section 300 Cap Assembly 310 Top Cap 320 Safety Vent 330 Current interruption element 340 Sealing gasket 350 CID gasket C Core S Separation membrane overlapping part B Bending part S1 1st interface S2 2nd interface S a One Circumference End S b Circumference end S a The end of the circumference facing L, L': Distance between the longitudinal end of the separator overlapping portion and the longitudinal end of the positive electrode E1 1st extension line E2 2nd extension line

Claims

1. A jelly-roll type electrode assembly in which a first separator, a negative electrode, a second separator, and a positive electrode are sequentially stacked and wound up to include a core portion, The positive electrode includes a first surface that is in a winding axis direction of the electrode assembly and a second surface that is opposite to the first surface, a core portion of the electrode assembly including a separator overlap portion, the separator overlap portion being disposed between the positive electrode and the negative electrode facing a first surface of the positive electrode, the first separator and the second separator being overlapped three or more times; an adhesive tape disposed between the positive electrode and the first separator facing the second surface of the positive electrode, or between the negative electrode adjacent to the second surface of the positive electrode and the first separator;

2. The electrode assembly of claim 1 , wherein a length of each of the first separator, the negative electrode, and the second separator is longer than a length of the positive electrode.

3. The electrode assembly according to claim 1 , wherein the separator overlapping portion extends from an end of the positive electrode in both a winding direction and an opposite winding direction, and the first separator and the second separator are disposed to overlap each other.

4. 2. The electrode assembly of claim 1, wherein the first separator and the second separator are folded together at the core portion and extend in a winding direction and an opposite direction to the winding direction to extend between a first surface of the positive electrode and an outer surface of the second separator.

5. The separation membrane overlapping portion is a first interface where the second separation membrane extending in the opposite direction to the winding direction and the second separation membrane extending in the winding direction are in direct contact with each other; and The second separation membrane extends in a direction opposite to the winding direction, and the first separation membrane extends in the winding direction. The second separation membrane and the first separation membrane directly contact each other at a second interface. The electrode assembly of claim 1 , wherein the first interface and the second interface each have a coefficient of friction of 0.4 or more.

6. The electrode assembly of claim 5 , wherein the first interface has a coefficient of friction of 0.6 or more and the second interface has a coefficient of friction of 0.4 or more.

7. The first separation membrane and the second separation membrane each include a coating layer on at least one of an inner surface and an outer surface, 6. The electrode assembly of claim 5, wherein a coefficient of friction of the coating layers of the first and second separators is greater than a coefficient of friction of at least one uncoated portion of the inner and outer surfaces of the first and second separators.

8. The first separation membrane and the second separation membrane are provided with a coating layer on at least one of their inner and outer surfaces, The electrode assembly according to claim 5 , wherein the coating layer comprises an inorganic component, a binder component, and a lithium salt.

9. The first separation membrane and the second separation membrane each include a coating layer on at least one of an inner surface and an outer surface, 6. The electrode assembly of claim 5, wherein the first interface is an interface where a coating layer of the second separator extending in a direction opposite to the winding direction and a coating layer of the second separator extending in a winding direction are in direct contact with each other.

10. The first separation membrane and the second separation membrane each include a coating layer on at least one of an inner surface and an outer surface, The electrode assembly of claim 5 , wherein the second interface is an interface where a surface of the second separator not provided with a coating layer and a surface of the first separator not provided with a coating layer are in direct contact with each other.

11. The electrode assembly of claim 5 , wherein the first interface is between one surface of the second separator in contact with the negative electrode and one surface of the second separator in contact with the first separator.

12. 6. The electrode assembly of claim 5, wherein the second interface is between one surface of the first separator that contacts the longitudinal end of the positive electrode and one surface of the second separator that is spaced from the longitudinal end of the positive electrode by a portion of the first separator.

13. The electrode assembly of claim 1 , wherein the separator overlapping portion extends at least 108° around a circumference of the electrode assembly.

14. The separator overlapping portion includes a first end extending in a direction opposite to the winding direction away from the longitudinal end of the positive electrode, and a second end extending in a winding direction opposite to the longitudinal end of the positive electrode, The electrode assembly of claim 1 , wherein at least one of the first end and the second end extends 3 mm or more from a longitudinal end of the positive electrode.

15. The electrode assembly of claim 1 , wherein the adhesive tape comprises a porous backing layer and an adhesive layer on the porous backing layer.

16. The electrode assembly of claim 15 , wherein the porous substrate layer has a thickness of 13 μm or more, and the adhesive layer has a thickness of more than 0 μm and not more than 4 μm.

17. The electrode assembly of claim 1 , wherein the adhesive tape has a length of 5 mm or more.

18. 18. An electrode assembly according to any one of claims 1 to 17, a battery case having at least one opening and housing the electrode assembly; and A cap assembly coupled to the opening surface of the battery case. A secondary battery including:

19. The secondary battery according to claim 18 , wherein the battery case is cylindrical.

Images