Electrode assembly and secondary battery including the same

Abstract

The present invention provides an electrode assembly having a jelly-roll structure in which a cathode, a separator, and a cathode are wound around a core portion, the cathode including an active material portion in which a cathode active material is laminated on one or both sides of a cathode current collector, and a cathode uncoated portion in which the cathode active material portion is not laminated, the cathode including a protective tape covering at least a portion of the cathode uncoated portion adjacent to the core portion, and a cross-sectional area of ​​the protective tape in the longitudinal direction of the cathode being 0.3 mm 2 ~0.47mm 2 The present invention relates to an electrode assembly in which

Description

[Technical Field]

[0001] The present invention relates to an electrode assembly and a secondary battery including the same. [Background technology]

[0002] Generally, 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 cutting-edge electronic devices such as telephones, laptops, and video cameras.

[0003] To ensure the stability of a secondary battery, one side is crimped with a crimping machine and a stability test is carried out to measure internal short circuits.

[0004] 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 batteries, in which the electrode assembly is housed in a pouch battery made of an aluminum-laminated sheet.

[0005] The electrode assembly housed in the battery case is a power generating element that can be charged and discharged and has a laminated structure of anode / separator / cathode. It is classified into a folding type electrode assembly (jelly roll) in which a long sheet-like anode and cathode coated with an active material are wound up with a separator between them, and a stack type electrode assembly in which multiple anodes and cathodes of a predetermined size are stacked one after the other with a separator between them. Of these, the jelly roll has the advantages of being easy to manufacture and having a high energy density per weight.

[0006] In addition, in a secondary battery, the portion where the electrode tab is welded to the electrode plate is a portion where dissimilar metals are connected, which increases internal resistance (IR) and causes heat to be concentrated. Therefore, a protective tape is attached to the portion where the electrode tab is provided to protect the portion where the electrode plate and the electrode tab are electrically connected.

[0007] In conventional jelly roll-type electrode assemblies, the core portion at the center has an open structure regardless of whether the outer diameter is large or small, and this open structure reduces the electrode adhesion between the anode and cathode in the core portion.

[0008] The protective tape attached to the electrode tab corresponds to a part of the core and cannot support the core. Therefore, in the conventional electrode assembly, there is no support and the adhesion strength is reduced. As a result, the electrode reaction rate in the core is relatively low, and there is a high possibility of core collapse when the core deteriorates. [Prior art documents] [Patent documents]

[0009] [Patent Document 1] Republic of Korea Publication No. 10-2023-0086616 Summary of the Invention [Problem to be solved by the invention]

[0010] SUMMARY OF THE INVENTION In order to solve the above-mentioned problems of the prior art, an object of the present invention is to provide an electrode assembly and a secondary battery including the same, in which collapse of the core portion is prevented. [Means for solving the problem]

[0011] In one embodiment of the present invention, there is provided an electrode assembly having a jelly roll structure in which a cathode, a separator, and a cathode are wound around a core portion. The cathode includes an active material portion in which a cathode active material is laminated on one or both sides of a cathode current collector, and a cathode uncoated portion in which the cathode active material portion is not laminated. The cathode also includes a protective tape extending in a length direction of the cathode from the cathode uncoated portion adjacent to the core portion, and the cross-sectional area of ​​the protective tape in the length direction of the cathode is 0.3 mm 2 ~0.47mm 2 The present invention provides an electrode assembly comprising:

[0012] One embodiment of the present invention provides a secondary battery including the electrode assembly, a battery case including a space for accommodating the electrode assembly and an electrolyte and having an opening with at least one side open, and a cap assembly coupled to the opening. [Effects of the Invention]

[0013] According to an embodiment of the electrode assembly and a secondary battery including the same, the length and thickness of the protective tape are controlled to support the core portion, thereby preventing the core portion from collapsing and improving the safety of the secondary battery. [Brief explanation of the drawings]

[0014] [Figure 1] FIG. 2 is a cross-sectional view showing a cross section of an end portion of an electrode assembly according to an embodiment of the present invention before being wound up. [Figure 2] FIG. 10 is a cross-sectional view showing a cross section of an end portion of a cathode according to another embodiment of the present invention before being wound up. [Figure 3] 10 is a CT image showing the evaluation results of core collapse according to an example and a comparative example. [Figure 4] 10A and 10B are diagrams illustrating a method for evaluating whether or not a core separator of a jelly roll-type electrode assembly according to an embodiment of the present invention is damaged. [Figure 5] 1 is a cross-sectional view showing a secondary battery according to an embodiment of the present invention. [Figure 6] 1 is a perspective view showing a battery pack including a secondary battery according to an embodiment of the present invention; [Figure 7] 1 is a perspective view showing a vehicle including a battery pack according to an embodiment of the present invention; DETAILED DESCRIPTION OF THE INVENTION

[0015] The detailed description of the present invention is intended to fully explain the present invention to those skilled in the art. In the specification, when a part "comprises" a certain element or "features" a certain structure and shape, it does not mean that other elements are excluded or that other structures and shapes are not included, but rather that other elements, structures, and shapes can be included, unless otherwise specified.

[0016] The present invention can be modified in various ways and can have various embodiments, so a detailed description will be given by presenting specific embodiments, but this is not intended to limit the content of the invention according to the embodiments, and it should be understood that the present invention includes all modifications, equivalents, and alternatives included in the spirit and technical scope of the present invention.

[0017] The present invention will be described in detail below with reference to the drawings. However, the drawings are for illustrative purposes only and the scope of the present invention is not limited by the drawings.

[0018] The electrode assembly 100 includes a positive electrode 110, a negative electrode 120, and separators 130, 140 positioned between the positive electrode 110 and the negative electrode 120, and is a power generating element that can be charged and discharged.

[0019] The electrode assembly 100 may have a jelly roll structure in which the first separator 130, the cathode 120, the second separator 140, and the anode 110 are stacked and wound in this order, and include a core portion (C).

[0020] The "core portion" of the electrode assembly 100 according to the present invention refers to a hollow region located on the winding shaft of the electrode assembly 100 and a portion of the laminated structure consisting of the wound first separator 130, cathode 120, second separator 140, and anode 110. The "core portion" may refer to a region within two turns of the anode 110 from one longitudinal end of the anode 110 located at the innermost shell of the electrode assembly 100. The term "one turn" refers to the length required to wind an electrode or separator included in the electrode assembly 100 360° from a reference point, and the length may be determined based on the outer diameter of the winding core used to wind the electrode assembly 100, the thickness of the electrode or separator, and the number of innermost electrode or separator windings. For example, one turn of the anode may refer to the length required to wind the anode 110 360° from the longitudinal end of the anode 110 in the direction of winding the jelly roll-type electrode assembly.

[0021] In one embodiment, the first turn of the cathode, i.e., the length at which the cathode 120 is first wound around the core portion (C), may be 10.5 mm, the second turn may be 12 mm, and the third turn may be 12.5 mm.

[0022] The anode 110 may include a cathode current collector, an anode active material portion, and an anode uncoated portion. The anode current collector may be a thin metal plate having excellent conductivity, such as aluminum (Al) foil.

[0023] The anode 110 is formed by coating a cathode active material on at least one of both surfaces of an anode current collector. The area coated with the anode active material is the anode active material portion, and the area not coated with the anode active material is the anode uncoated portion. Since the anode uncoated portion is not coated with the anode active material, a first electrode tab, i.e., an anode tab, can be bonded thereto.

[0024] Examples of the positive electrode active material include lithium cobalt oxide, which has a high working voltage and excellent capacity characteristics; lithium nickel oxide, which has a high reversible capacity and can easily realize 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 oxide, which is inexpensive and has excellent thermal stability; and lithium iron phosphate, which has excellent stability.

[0025] The cathode 120 may include a cathode current collector, a cathode active material portion, and a cathode uncoated portion. The cathode current collector may include a highly conductive thin metal plate, such as a copper (Cu) or nickel (Ni) foil.

[0026] The cathode 120 is formed by coating one or both surfaces of a cathode current collector with a cathode active material, and the cathode active material portion is formed by coating or spreading the cathode active material, while the cathode uncoated portion is a region of the cathode current collector where the cathode active material is not coated or spread and the cathode active material is not applied. Since the cathode uncoated portion is not coated with the cathode active material, a second electrode tab 160, i.e., the cathode tab 160, can be bonded thereto.

[0027] Examples of the negative electrode active material include carbon materials such as crystalline carbon, amorphous carbon, carbon composites, and carbon fibers, lithium metal, lithium alloys, etc. In this case, the negative electrode active material may further include non-graphite-based materials such as SiO (silica) or SiC (silicon carbide) for high capacity design.

[0028] The separators 130 and 140 prevent an internal short circuit caused by contact between the anode 110 and the cathode 120, and may include a porous material to facilitate the movement of ions between the electrodes.

[0029] In one embodiment, the separators 130 and 140 may include a substrate layer of a porous material, which 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).

[0030] In another embodiment, the separators 130 and 140 may include a safety-reinforced separator (SRS). That is, the separators 130 and 140 may include a substrate layer of a porous material and a coating layer formed by applying a mixed slurry of inorganic particles and a binder polymer onto the substrate layer. Preferably, the coating layer contains ceramic particles and has a uniform pore structure formed by the pore structure contained in the separator substrate itself and the interstitial space between the ceramic particles, which are the active layer components.

[0031] The coating layer may include ceramic particles including at least one selected from the group consisting of alumina, silica, TiO2, SiC, and MgAl2O4. The inclusion of such a coating layer can improve the safety of the electrode assembly. The coating layer may further include a lithium salt.

[0032] The anode tab and the cathode tab 160 transfer electrons collected in the current collector to an external circuit, and may protrude in opposite directions from the electrode assembly 100 of the jelly roll structure.

[0033] In addition, the cathode 120 may have a protective tape 170 disposed on one surface of the cathode current collector plate or the cathode uncoated portion 121 where the cathode tab 160 is located. The protective tape 170 may wrap the cathode tab 160 or the starting end of the cathode active material portion 122.

[0034] In detail, the cathode 120 may have the cathode uncoated portion 121 and the cathode active material portion 122 arranged in this order from the core portion (C), and the cathode tab 160 may be located on one surface of the cathode uncoated portion 121. In one embodiment, the cathode tab 160 may be fixed to the cathode uncoated portion 121 by welding.

[0035] Alternatively, the cathode uncoated portion 121 may be wound around the core portion (C) for two turns, and the cathode active material portion 122 may be wound around the core portion (C) from the third turn onwards.

[0036] Protective tape 170 is attached to cover the outer surface of the welded portion of cathode tab 160 and cathode uncoated portion 121. Therefore, protective tape 170 prevents separators 130 and 140 from being damaged by the portion of cathode tab 160 protruding from cathode uncoated portion 121.

[0037] Alternatively, the protective tape 170 may wrap one end adjacent to the core portion (C) of both ends of the negative electrode active material portion 122 facing each other in the longitudinal direction, thereby preventing the separator from being damaged by a step between the negative electrode uncoated portion 121 and the negative electrode active material portion 122 due to volumetric expansion of the negative electrode active material portion 122.

[0038] Furthermore, the protective tape 170 according to the present invention has a cross-sectional area in the longitudinal direction of the cathode, i.e., the area of ​​the protective tape 170 in a cross section perpendicular to the winding axis of the electrode assembly 100, which satisfies the above-mentioned range, so that not only the separators 130 and 140 but also a certain length (L) and thickness (d) of the protective tape 170 can be wound around the core portion (C) to support the core portion.

[0039] Preferably, the cross-sectional area of ​​the protective tape 170 is 0.37 mm 2 ~0.47mm 2 The ratio of the thickness to the length of the protective tape 170 may be 0.015:9 to 0.08:20, and more preferably 0.02:9 to 0.05:17.

[0040] Within the above range, the thickness of the protective tape 170 according to the present invention may decrease as the length of the protective tape 170 increases, and may increase as the length decreases.

[0041] For example, if the length of the protective tape 170 is 17 mm and the thickness is 0.022 mm, the cross-sectional area of ​​the protective tape 170 is 0.374 mm 2 If the protective tape 170 has the same cross-sectional area and a length of 11 mm, the thickness can be increased to 0.034 mm.

[0042] When the cathode 120 according to the present invention is arranged in this order from the core portion (C) to the cathode uncoated portion 121 and the cathode active material portion 122, the attachment position of the protective tape 170 is not limited as long as the ratio of the cross-sectional area, length, and thickness satisfies the above range. Preferably, the protective tape 170 may be positioned to cover the end of the cathode active material portion 122 adjacent to the core portion (C). That is, the protective tape 170 according to the present invention may be positioned anywhere on one side of the cathode uncoated portion 121 or one side of the cathode active material portion 122. Furthermore, the protective tape 170 may cover all or part of the cathode uncoated portion 121, and may cover only a certain length of the cathode active material portion 122 from the end in the length direction.

[0043] For example, the protective tape 170 may be attached from one end of the negative electrode active material portion 122 to a position corresponding to the tip of the end of the positive electrode 110 .

[0044] Alternatively, the protective tape 170 may be applied to one side of the negative electrode active material part 122, and the length of the protective tape 170 may be 5 mm to 50 mm.

[0045] Preferably, the protective tape 170 may be unattached to the negative electrode tab 160. In other words, the protective tape 170 may extend from the negative electrode uncoated portion 121 between the negative electrode tab 160 and the negative electrode active material portion 122 to one surface of the negative electrode active material portion 122.

[0046] In the electrode assembly 100, as the secondary battery 1 is charged and discharged, the positive electrode 110 and the negative electrode 120 expand at the portions where the positive electrode active material portion and the negative electrode active material portion 122 face each other. Due to the expansion of the positive electrode 110 and the negative electrode 120, the electrodes 110 and 120 slide toward the core portion (C), causing core impingement.

[0047] The protective tape 170 according to the present invention extends from the cathode uncoated portion 121 to one side of the cathode active material portion 122, in other words, extends adjacent to the portion where the cathode active material portion and the cathode active material portion 122 face each other. This increases the rigidity of the cathode facing the cathode active material portion, which causes core impingement, and prevents the electrodes 110 and 120 from slipping, thereby preventing core impingement and improving the safety of the secondary battery 1.

[0048] In another embodiment, the cathode 120 may further include an auxiliary tape 180 .

[0049] That is, the cathode 120 according to this embodiment includes a protective tape 170 and an auxiliary tape 180. The protective tape 170 is positioned adjacent to a portion where the positive electrode active material portion and the negative electrode active material portion 122 face each other and is not attached to the cathode tab 160. Therefore, the auxiliary tape 180 is attached to the cathode tab 160 to completely cover the cathode tab and thereby fix the cathode tab 160 to the cathode uncoated portion 121.

[0050] Furthermore, the area or thickness of protective tape 170 and auxiliary tape 180 laminated on cathode uncoated portion 121 wound around core portion (C) increases, and the shape of core portion (C) is supported by cathode uncoated portion 121, separators 130 and 140, protective tape 170, and auxiliary tape 180, increasing the strength and providing the effect of preventing core collapse and core deformation.

[0051] Cathode uncoated region 121 may be entirely covered by at least one of protective tape 170 and auxiliary tape 180. In one embodiment, protective tape 170 and auxiliary tape 180 are positioned such that one end thereof contacts with one another, and the sum of the area of ​​protective tape 170 and the area of ​​auxiliary tape 180 may be the same as the area of ​​cathode uncoated region 121.

[0052] Alternatively, the protective tape 170 and the auxiliary tape 180 may be overlapped to cover the entire surface of the cathode uncoated region 121. In this case, the sum of the area of ​​the protective tape 170 and the area of ​​the auxiliary tape 180 may be greater than the area of ​​the cathode uncoated region 121.

[0053] The area of ​​protective tape 170 , the area of ​​auxiliary tape 180 , and the area of ​​cathode uncoated portion 121 refer to the product of the length and width of protective tape 170 , auxiliary tape 180 , and cathode uncoated portion 121 .

[0054] Therefore, in the electrode assembly 100 according to the present invention, the protective tape 170 and the auxiliary tape 180 are positioned on the cathode uncoated portion 121, thereby reducing the step between the cathode uncoated portion 121 and the cathode active material portion 122, thereby reducing the influence of the step caused by the two ends during charging and discharging of the secondary battery 1 and preventing a short circuit.

[0055] The protective tape 170 and the auxiliary tape 180 may be any one selected from the group consisting of polyethylene terephthalate (PET), polypropylene (PP), polyester (PE), polycarbonate (PC), polyimide (PI), polyethylene naphthalene (PEN), polyether ether ketone (PEEK), polyacrylate (PAR), polycycloolefin (PCO), polynorbornene, polyethersulfone (PES), and cycloolefin polymer (COP).

[0056] The protective tape 170 and the auxiliary tape 180 may be made of the same material or different materials. Preferably, the protective tape 170 and the auxiliary tape 180 may be made of different materials. For example, the protective tape 170 may be made of PI, and the auxiliary tape 180 may be made of PET.

[0057] The secondary battery 1 may include the above-described electrode assembly 100. Specifically, the secondary battery 1 may include a battery case 200 having an open surface and a space for accommodating the electrode assembly 100 and an electrolyte, and a cap assembly 300 coupled to the open surface of the battery case.

[0058] 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 electrodes and a separator, and an electrolyte (not shown) in the space. The battery case 200 may have a structure in which one side is open (hereinafter referred to as an opening) and the other side is sealed. Here, the terms "one side" and "other side" refer to the ends located at the top and bottom along the direction of gravity or the central axis of the battery case 200.

[0059] The upper side of the opened battery case 200 may be provided with a beading portion 210 folded toward the center of the secondary battery 1. The battery case 200 may also be provided with a crimping portion 220 above the beading portion 210. That is, the crimping portion 220 may be located at the top of the battery case 200. Here, the upper portion refers to the region from the center of the battery case 200 toward the opening.

[0060] The battery case 200 may be made of a lightweight conductive metal material such as aluminum or an aluminum alloy, or may be made of a nickel-plated steel sheet material. Preferably, the battery case 200 is made of a nickel-plated steel sheet material.

[0061] The cap assembly 300 is coupled to the open surface of the battery case 200 and can include a top cap 310 , a safety vent 320 and a current interrupting device 330 .

[0062] 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 terminal.

[0063] The top cap 310 may have a sealing gasket 340 coupled to the edge of the top cap 310, or the sealing gasket 340 may be located inside the crimping portion 220 of the battery case 200. The sealing gasket 340 can increase the sealing force between the top cap 310 and the battery case 200.

[0064] The top cap 310 may include a protrusion protruding upward, a rim that contacts and is coupled with the sealing gasket 340, and a first connecting portion that connects the protrusion and the rim.

[0065] The safety vent 320 is located at the bottom of the top cap 310 and is electrically connected to the top cap 310. At least a portion of the 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 its end, and the portion excluding the contact length may be located a certain distance away from the top cap 310. In addition, the portion of the safety vent 320 that is in contact with the top cap 310 may be coupled to a sealing gasket 340.

[0066] The safety vent 320 may have a contact area with the top cap 310 such that the distance from the top cap 310 increases toward the center of the safety vent 320 .

[0067] 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 also 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.

[0068] In one embodiment, the safety vent 320 may have 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, just like the safety vent 320. That is, the safety vent 320 and the top cap 310 may be positioned horizontally.

[0069] In other embodiments, the safety vent 320 may have a folded end that wraps around the outer periphery of the top cap 310 .

[0070] 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, which causes an increase in internal pressure.

[0071] When the internal pressure of the secondary battery 1 increases, the safety vent 320 receives a force in the direction of the top cap 310, causing the bent portion to burst and releasing the internal gas of the secondary battery 1.

[0072] A current interruptive device (CID) 330 is located below the safety vent 320 and is at least partially connected to the safety vent 320 .

[0073] When the internal pressure of the secondary battery 1 increases and the safety vent 320 bursts, the current interrupting device 330 separates from the safety vent 320 to interrupt the current.

[0074] More specifically, the current interruption device 330 may include a central portion connected to the safety vent 320, a connecting portion protruding in the direction of the safety vent 320, an edge portion excluding the connecting portion, and a coupling portion connecting the connecting portion and the edge portion. A plurality of coupling portions may be provided, and the plurality of coupling portions may be spaced apart from one another.

[0075] When the safety vent 320 is deformed in the direction of the top cap 310, the joint may break and the connecting portion may be separated from the edge. That is, the connecting portion may be separated in the direction of the top cap 310 while still connected to the safety vent 320.

[0076] The CID gasket 350 wraps around the edge of the current interrupting element 330 and electrically isolates the edges and joints of the current interrupting element 330 other than the connecting portion from the safety vent 320 .

[0077] In one embodiment of the present invention, a battery pack 3 including any one of the above-described secondary batteries 1 is provided.

[0078] In relation to the above embodiment, as shown in FIG. 6, a battery pack 3 including a secondary battery 1 in a pack housing 2 is shown.

[0079] The battery pack according to the above embodiment has high output and high capacity.

[0080] According to one embodiment of the present invention, there is provided a means of transport including the battery pack described above.

[0081] In relation to the above embodiment, as shown in FIG. 7, a vehicle (V) including a battery pack 3 is shown.

[0082] The vehicle according to the above embodiment uses a battery pack with high output / high capacity, thereby achieving excellent stability and safety.

[0083] [Mode for carrying out the invention] Example 1 Electrode assembly manufacturing An Al foil with a thickness of 15 μm and a width direction length of 63.9 mm was prepared as an anode current collector. An anode active material part was formed by applying and drying an anode active material slurry containing an NMCA (Ni-Mn-Co-Al) composite with a Ni content of 92% or more as an anode active material and CNT as a conductive material onto the anode current collector, and an anode active material part was produced by applying and drying the slurry. An anode with a thickness of 154 μm was produced.

[0084] Next, a Cu foil having a thickness of 10 μm and a width direction length of 64.9 mm was prepared as a cathode current collector. A cathode active material slurry containing 50 parts by weight each of artificial graphite and natural graphite as cathode active materials was applied onto the cathode current collector and dried to form a cathode active material part, thereby producing a cathode having a thickness of 141 μm.

[0085] In addition, a protective tape having a thickness of 22 μm, a length of 17 mm, and a width of 63.5 mm and containing PI was attached to one surface of the negative electrode active material part in the direction where the negative electrode tab was located.

[0086] The first and second separators each consisted of two separators each having a coating layer formed on one surface of a sheet-like polyethylene substrate layer, the coating layer containing Al2O3 as an inorganic component and a PVdF-based binder and a lithium salt as binder components.

[0087] Secondary battery manufacturing The jelly-roll type electrode assembly was inserted into a cylindrical battery case, and then a main electrolyte solution was prepared by mixing ethylene carbonate (EC): dimethyl carbonate (DMC): ethyl methyl carbonate (EMC) in a weight ratio of 4:9:3 and dissolving LiPF6 to contain 15 wt% of LiPF6. The cylindrical battery case was then sealed with a cap assembly to manufacture a secondary battery.

[0088] Example 2 A jelly-roll type electrode assembly and a secondary battery were manufactured in the same manner as in Example 1, except that protective tapes with a thickness of 50 μm and a length of 9 mm were attached to the negative electrode active material portion and the negative electrode non-coating portion.

[0089] Comparative Example 1 A jelly-roll type electrode assembly and a secondary battery were manufactured in the same manner as in Example 1, except that a protective tape having a thickness of 22 μm and a length of 9 mm was attached to the negative electrode tab.

[0090] Comparative Example 2 A jelly-roll type electrode assembly and a secondary battery were manufactured in the same manner as in Example 1, except that a protective tape having a thickness of 30 μm and a length of 16 mm was attached to the negative electrode tab.

[0091] Experimental Example - Evaluation of Core Impingement Cycle stability evaluation The secondary batteries manufactured in Example 1, Example 2, Comparative Example 1, and Comparative Example 2 were each activated by two cycles of 4.2 V-2.5 V, 0.2 C charge, and 0.2 C discharge to prepare secondary batteries. Then, the activated secondary batteries were each subjected to 400 cycles under conditions of 4.25 V (0.3 C)-2.85 V (0.5 C) and 55°C, and the long-term cycle stability was evaluated by performing computed tomography (CT) of the core portion to check for the presence or absence of core impingement, and the image is shown in Figure 3.

[0092] Core impingement assessment The secondary batteries according to Example 1, Example 2, Comparative Example 1, and Comparative Example 2 were evaluated for the occurrence of core impingement by the following method.

[0093] Figure 4 is a diagram showing a method for evaluating whether or not core impingement has occurred. Specifically, (a) of Figure 4 is a diagram showing a method for evaluating whether or not core impingement has occurred when deformation has occurred in the cathode, and (b) of Figure 4 is a diagram showing a method for evaluating whether or not core impingement has occurred when deformation has not occurred in the cathode.

[0094] 1) On the first surface of the anode, a straight line connecting the end of the anode 110 in the length direction to a point 5 mm away from the end is extended to draw a first extension line (Eq).

[0095] 2-1) When deformation occurs in the cathode In the core portion of the jelly roll type electrode assembly, on the surface of the cathode 120 facing the first surface of the anode 110, 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 of the anode 110.

[0096] 2-2) When there is no deformation in the cathode In the core portion of the jelly roll type electrode assembly, on the surface of the cathode 120 facing the first surface of the anode 110, a second extension line (E2) is drawn by extending a straight line connecting two points spaced 5 mm apart from the longitudinal end of the anode 110.

[0097] 3) It was determined that core impingement occurred when the angle from the first extension line (E1) to the second extension line (E2) in a counterclockwise direction exceeds 25°, centered on the intersection of the first extension line (E1) and the second extension line (E2).

[0098] As shown in FIG. 3, it can be seen that the secondary batteries manufactured in Examples 1 and 2 have improved core impingement compared to Comparative Examples 1 and 2 in the evaluation of cycle safety.

[0099] Specifically, the cross-sectional area of ​​the protective tapes according to Example 1, Example 2, Comparative Example 1, and Comparative Example 2 was 0.374 mm 2 , 0.45mm 2 , 0.198mm 2 , 0.48mm 2 is.

[0100] The cross-sectional area of ​​the protective tape is 0.37 mm 2 ~0.47mm2 It can be seen that in Examples 1 and 2 which satisfy the above range, core impingement is improved compared to Comparative Examples 1 and 2.

[0101] Furthermore, when comparing Example 2 and Comparative Example 1, which have the same length but different thicknesses, it can be confirmed that Example 2, which has a thicker thickness, has improved core impingement more than Comparative Example 1.

[0102] When the protective tape is applied only to a certain width, the rigidity of the core portion of the jelly roll type structure is improved, and core collapse and core impingement are improved.

[0103] Furthermore, when comparing Example 1 and Example 2, it can be seen that Example 1, in which the protective tape has a smaller cross-sectional area and a longer length, improves core impingement more than Example 2, in which the protective tape has a wider cross-sectional area and a shorter length.

[0104] That is, the protective tape has a cross-sectional area of ​​0.37 mm 2 ~0.47mm 2 Even if the above range is satisfied, the longer the bonding length with the cathode uncoated portion, the longer the length supporting the core portion, and the better the deformation of the core.

[0105] While the present invention has been described with reference to preferred embodiments thereof, it will be understood by those skilled in the art that various modifications and variations can be made to the present invention without departing from the spirit and scope of the present invention as defined in the appended claims. [Explanation of symbols]

[0106] 1: secondary battery, 2: pack housing, 3: battery pack, 100: electrode assembly, 110: anode, 120: cathode, 121: cathode uncoated portion, 122: cathode active material portion, 130, 140: separator, 160: cathode tab, 170: protective tape, 180: auxiliary tape, 200: battery case, 210: beading portion, 220: crimping portion, 300: cap assembly, 310: top cap, 320: safety vent, 330: current interrupting element, 340: sealing gasket, 350: CID gasket, V: moving means, C: core portion. [Industrial Applicability]

[0107] In the electrode assembly and the secondary battery including the same according to the embodiment of the present invention, the length and thickness of the protective tape are controlled to support the core portion, thereby preventing the core portion from collapsing and improving the stability of the secondary battery.

Claims

1. An electrode assembly having a jelly roll structure in which a cathode, a separator, and an anode are wound around a core, The negative electrode includes a negative electrode active material portion in which a negative electrode active material is laminated on one or both surfaces of a negative electrode current collector, and a negative electrode non-coating portion in which the negative electrode active material portion is not laminated, the cathode includes a protective tape covering at least a portion of the cathode uncoated portion adjacent to the core portion, The cross-sectional area of ​​the protective tape in the longitudinal direction of the cathode is 0.3 mm ２ ~0.47mm ２ An electrode assembly.

2. 2. The electrode assembly of claim 1, wherein the thickness-to-length ratio of the cross-sectional area of ​​the protective tape in the longitudinal direction of the cathode is 0.015:9 to 0.08:

20.

3. The electrode assembly of claim 1 , wherein the protective tape covers an end of the negative electrode active material portion adjacent to the core portion.

4. 2. The electrode assembly of claim 1, wherein the cathode uncoated portion is located at an end of the cathode adjacent to the core portion, a cathode tab is laminated on one surface of the cathode uncoated portion, and the protective tape is not attached to the cathode tab.

5. The electrode assembly of claim 4 , further comprising an auxiliary tape adhered to the cathode tab.

6. The electrode assembly of claim 5 , wherein the entire surface of the cathode uncoated region is covered with at least one of the protective tape and the auxiliary tape.

7. The electrode assembly according to claim 5 , wherein the protective tape and the auxiliary tape are overlapped.

8. The electrode assembly according to claim 5 , wherein the protective tape and the auxiliary tape are made of different materials.

9. 2. The electrode assembly of claim 1, wherein the protective tape is made of any one selected from the group consisting of polyethylene terephthalate, polypropylene, polyester, polycarbonate, polyimide, polyethylene naphthalene, polyether ether ketone, polyacrylate, polycycloolefin, polynorbornene, polyethersulfone, and cycloolefin polymer.

10. The electrode assembly according to at least one of claims 1 to 9. a battery case including a space for accommodating the electrode assembly and the electrolyte, the battery case having an opening with at least one side open; A secondary battery including a cap assembly coupled to the opening.

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