Electrode assembly and secondary battery including the same

Abstract

The present disclosure relates to an electrode assembly having a wound structure in which a negative electrode, a separator, and a positive electrode are wound around a core, in which the negative electrode includes an active material portion in which a negative electrode active material is laminated on one or both sides of a negative electrode current collector, and a negative electrode uncoated portion in which the negative electrode active material is laminated on one or both sides of the negative electrode current collector. The negative electrode active material is not laminated, the negative electrode includes a protective tape covering at least a portion of the uncoated portion of the negative electrode adjacent to the core, and the protective tape has a cross-sectional area of 0.3 mm2 to 0.47 mm2 in a longitudinal direction of the negative electrode.

Description

Technical Field

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

[0002] Generally, unlike a primary battery that cannot be recharged, a secondary battery is a battery that can be charged and discharged. Such secondary batteries are widely used in advanced electronic devices such as mobile phones, laptop computers, and portable video cameras.

[0003] The stability of a secondary battery can be tested by measuring internal short circuits by compressing one side with a press to ensure stability.

[0004] According to the shape of the battery case, secondary batteries can be classified into cylindrical batteries and square batteries in which the electrode assembly is built into a cylindrical or square metal battery case, and pouch-type batteries in which the electrode assembly is built into a pouch-type battery case made of aluminum laminate.

[0005] In addition, the electrode assembly built into the battery case is a power generating element capable of charging and discharging, and the electrode assembly includes a stacked structure of a positive electrode / separator / negative electrode, and is classified into: a folded-type electrode assembly (wound body), in which a long strip-shaped negative electrode and a positive electrode coated with an active material are wound with a separator interposed between the negative electrode and the positive electrode; and a stacked-type electrode assembly, in which a plurality of negative electrodes and positive electrodes having a predetermined size are sequentially stacked with a separator interposed therebetween. Among them, the advantage of the wound body is that it is easy to manufacture and has a high energy density per unit weight.

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

[0007] In a conventional wound-type electrode assembly, regardless of whether the outer diameter is large or small, the core portion at the center has an empty structure, and due to this empty structure, the electrode adhesion of the negative electrode and the positive electrode in the core portion is reduced.

[0008] Since the protective tape attached to the electrode tab corresponds to a part of the core portion, the protective tape does not support the core portion, and thus the conventional electrode assembly does not have a supporting portion and has low adhesion. Therefore, the electrode reaction rate of the core portion is relatively low, and there is a problem that the possibility of core collapse and the like increases when the core portion deteriorates.

[0009] (Prior Art Document)

[0010] (Patent Document)

[0011] (Patent Document 1) Korean Patent Publication No. 10-2023-0086616. Summary of the Invention

[0012] Technical Problem

[0013] In view of the problems of the above prior art, the present disclosure provides an electrode assembly that prevents core collapse and a secondary battery including the electrode assembly.

[0014] Technical Solution

[0015] One aspect of the present disclosure provides a wound-shaped electrode assembly in which a negative electrode, a separator, and a positive electrode are wound around a core. The negative electrode includes an active material portion and an uncoated portion of the negative electrode. In the active material portion, a negative electrode active material is laminated on one or both sides of a negative electrode current collector. In the uncoated portion of the negative electrode, no negative electrode active material is laminated. The negative electrode includes a protective band extending along the longitudinal direction of the negative electrode from the uncoated portion of the negative electrode adjacent to the core, and the protective band has a cross-sectional area of 0.3 mm 2 to 0.47 mm 2 in the longitudinal direction of the negative electrode.

[0016] One aspect of the present disclosure provides a secondary battery including an electrode assembly, a battery case, and a lid assembly. The battery case has a space for accommodating the electrode assembly and an electrolyte and includes at least one open side opening, and the lid assembly is coupled to the opening.

[0017] Advantageous Effects of the Invention

[0018] The electrode assembly and the secondary battery including the electrode assembly according to an embodiment of the present disclosure can prevent core collapse by controlling the length and thickness of the protective band to support the core, thereby improving the safety of the secondary battery. Brief Description of the Drawings

[0019] Figure 1 is a cross-sectional view showing a cross-section of an end portion of an electrode assembly according to an embodiment of the present disclosure before the electrode assembly is wound.

[0020] Figure 2 is a cross-sectional view showing a cross-section of an end portion before the negative electrode is wound according to another embodiment of the present disclosure.

[0021] Figure 3 is a CT image showing the result of evaluating core collapse according to an embodiment and a comparative example.

[0022] Figure 4 Illustrates a method of evaluating whether a core separator of a wound-shaped electrode assembly according to an embodiment of the present disclosure is damaged.

[0023] Figure 5 is a cross-sectional view showing a secondary battery according to an embodiment of the present disclosure.

[0024] Figure 6 is a perspective view showing a battery pack including a secondary battery according to an embodiment of the present disclosure.

[0025] Figure 7 is a perspective view showing a vehicle including a battery pack according to an embodiment of the present disclosure. Detailed Embodiments

[0026] The detailed description of the present disclosure aims to fully explain the present disclosure to those skilled in the art. Throughout the specification, when a part is referred to as "including" a certain component or "characterized by" a certain structure and shape, this does not mean excluding other components or excluding other structures and shapes, but other components, structures and shapes can be included unless otherwise specifically stated.

[0027] The present disclosure can be modified in various ways and has various embodiments, and thus specific embodiments are presented and described in detail in the detailed description. However, this is not intended to limit the content of the present disclosure to the embodiments, and it should be understood that all modifications, equivalents or alternatives included in the spirit and technical scope of the present disclosure are included.

[0028] The present disclosure will be described in detail below with reference to the accompanying drawings. However, the drawings are intended to illustrate the present disclosure, and the scope of the present disclosure is not limited by the drawings.

[0029] The electrode assembly 100 includes a positive electrode 110, a negative electrode 120, and separators 130 and 140 disposed between the positive electrode 110 and the negative electrode 120, and is a power generating element capable of charging and discharging.

[0030] The electrode assembly 100 may include a wound structure in which a first separator 130, a negative electrode 120, a second separator 140, and a positive electrode 110 are sequentially laminated and wound to form a core C.

[0031] The "core part" of the electrode assembly 100 according to the present disclosure is a region including a hollow part located on the winding axis of the electrode assembly 100 and a part of the laminated structure of the wound first separator 130 / negative electrode 120 / second separator 140 / positive electrode 110, and may mean a region within two turns of the positive electrode 110 along the length direction of the positive electrode 110 starting from one end of the positive electrode 110 located at the innermost side of the electrode assembly 100. Additionally, "one turn" may mean the length required for the electrode or separator included in the electrode assembly 100 to be wound 360° starting from a reference point, and may be determined by the outer diameter of the winding core used for winding the electrode assembly 100, the thickness of the electrode or separator, and the number of turns of the electrode or separator located inside. For example, one turn of the positive electrode may mean the length required to wind the positive electrode 360° along the direction in which the wound electrode assembly is wound from the end of the positive electrode 110 in the longitudinal direction.

[0032] In an embodiment, the length of the first turn of the negative electrode, i.e., the length of the first circle of the negative electrode 120 wound around the core part C, may be 10.5 mm, the second turn may be 12 mm, and the third turn may be 12.5 mm.

[0033] The positive electrode 110 may include a positive electrode current collector, a positive electrode active material part, and a positive electrode uncoated part. The positive electrode current collector may include a metal thin plate with excellent electrical conductivity, such as aluminum (Al) foil.

[0034] The positive electrode 110 is formed by coating the positive electrode active material on at least one of the two sides of the positive electrode current collector. The region coated with the positive electrode active material is the positive electrode active material part, and the region not coated with the positive electrode active material is the positive electrode uncoated part. The positive electrode uncoated part can be coupled to the first electrode tab, i.e., the positive electrode tab, because the positive electrode active material is not applied to the positive electrode uncoated part.

[0035] The positive electrode active material may include: lithium cobalt oxide with a high working voltage and excellent capacity characteristics, lithium nickel oxide with a high reversible capacity and easy to achieve a large-capacity battery, lithium nickel cobalt oxide in which some nickel is replaced by cobalt, lithium nickel cobalt metal oxide in which a part of nickel is replaced by manganese, cobalt, or aluminum, lithium manganese oxide with excellent thermal stability and low cost, lithium iron phosphate oxide with excellent stability, etc.

[0036] The negative electrode 120 may include a negative electrode current collector, a negative electrode active material part, and a negative electrode uncoated part. The negative electrode current collector may include a metal thin plate with excellent electrical conductivity, such as copper (Cu) or nickel (Ni) foil.

[0037] The negative electrode 120 is formed by coating a negative electrode active material on one or both sides of a negative electrode current collector. The negative electrode active material portion is formed by coating or applying a negative electrode active material, and the uncoated portion of the negative electrode is an area where no negative electrode active material is coated or applied and the negative electrode current collector is exposed. The uncoated portion of the negative electrode can be bonded to the second electrode tab 160, i.e., the negative electrode tab 160, because no negative electrode active material is applied to the uncoated portion of the negative electrode.

[0038] The negative electrode active material can be, for example, a carbon material such as crystalline carbon, amorphous carbon, a carbon composite material, or carbon fiber, a lithium metal, or a lithium alloy. The negative electrode active material can also include, for example, non-graphite SiO (silicon dioxide) or SiC (silicon carbide) for a high-capacity design.

[0039] The separators 130 and 140 prevent an internal short circuit that may occur when the positive electrode 110 and the negative electrode 120 come into contact with each other, and can include a porous material to facilitate the movement of ions between the electrodes.

[0040] In an embodiment, the separators 130 and 140 can include a substrate layer made of a porous material. The substrate layer can include, for example, one selected from the group consisting of polyethylene (PE), polystyrene (PS), polypropylene (PP), and a copolymer of polyethylene (PE) and polypropylene (PP).

[0041] In another embodiment, the separators 130 and 140 can include a safety-reinforced separator (SRS). That is, the separators 130 and 140 can include a substrate layer made of a porous material and a coating layer formed by coating a mixed slurry of inorganic particles and a binder polymer on the substrate layer. Preferably, the coating layer includes ceramic particles and has a uniform pore structure formed by the interstitial volume between the ceramic particles as active layer components in addition to the pore structure included in the separator substrate.

[0042] The coating layer can include ceramic particles, and the ceramic particles include at least one selected from the group consisting of alumina, silica, TiO2, SiC, and MgAl2O4. By including such a coating layer, the safety of the electrode assembly can be enhanced. In addition, the coating layer can also include a lithium salt.

[0043] The positive electrode tab and the negative electrode tab 160 can protrude in opposite directions with respect to the wound electrode assembly 100 to transfer the electrons collected in the current collector to an external circuit.

[0044] The negative electrode 120 can have a protective tape 170 located on the side of the negative electrode current collector or the uncoated portion 121 of the negative electrode where the negative electrode tab 160 is positioned. The protective tape 170 can be wrapped around the starting end portion of the negative electrode tab 160 or the negative electrode active material portion 121.

[0045] Specifically, in the negative electrode 120, the uncoated portion 121 of the negative electrode and the negative electrode active material portion 122 may be positioned in sequence starting from the core C, and the negative electrode tab 160 may be positioned on one surface of the uncoated portion 121 of the negative electrode. In an embodiment, the negative electrode tab 160 may be fixed to the uncoated portion 121 of the negative electrode by welding.

[0046] In addition, the uncoated portion 121 of the negative electrode may be wound around the core C for two turns, and the negative electrode active material portion 122 may start to be wound around the core C from the third turn.

[0047] The protective tape 170 is attached to wrap the outer surface of the welded portion of the negative electrode tab 160 and the uncoated portion 121 of the negative electrode. Therefore, the protective tape 170 prevents the separators 130 and 140 from being damaged by the following part: the portion where the negative electrode tab 160 protrudes from the uncoated portion 121 of the negative electrode.

[0048] Alternatively, the protective tape 170 may wrap one end of the negative electrode active material portion 122 adjacent to the core C between two ends facing each other in the longitudinal direction of the negative electrode active material portion 122, thereby preventing the separator from being damaged by the step portion between the uncoated portion 121 of the negative electrode and the negative electrode active material portion 122 due to the volume expansion of the negative electrode active material portion 122.

[0049] In addition, the area of the protective tape 170 according to the present disclosure satisfies the above range in the cross-sectional area of the negative electrode in the longitudinal direction of the negative electrode, that is, in the cross-section perpendicular to the winding axis of the electrode assembly 100, and thus not only the separators 130 and 140 but also the protective tape 170 having a predetermined length L and thickness d can be wound around the core C to support the core C.

[0050] Preferably, the cross-sectional area of the protective tape 170 may be 0.37 mm 2 to 0.47 mm 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.

[0051] According to the present disclosure, within the above range, when the length of the protective tape 170 increases, the thickness of the protective tape 170 may decrease, and when the length decreases, the thickness may increase.

[0052] 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 may be 0.374 mm 2 . If the length of the protective tape 170 is 11 mm under the same cross-sectional area, the thickness may increase to 0.034 mm.

[0053] When the uncoated portion 121 and the negative electrode active material portion 122 of the negative electrode 120 according to the present disclosure are positioned in order from the core portion C, the attachment position of the protective tape 170 is not limited as long as the cross-sectional area and the ratio of the length to the thickness of the protective tape 170 satisfy the above ranges. Preferably, the protective tape 170 may be positioned at a position covering the end portion of the negative electrode active material portion 122 adjacent to the core portion C. That is, the protective tape 170 according to the present disclosure may be located on both a side portion of the uncoated portion 121 of the negative electrode and a side portion of the negative electrode active material portion 122. In addition, the protective tape 170 may cover all or a part of the uncoated portion 121 of the negative electrode, and cover only a certain length of the negative electrode active material portion 122 in the longitudinal direction from the end portion.

[0054] For example, the protective tape 170 may be attached from one end portion of the negative electrode active material portion 122 to a position corresponding to the tip portion of the end portion of the positive electrode 110.

[0055] Alternatively, the protective tape 170 may be located on a side portion of the negative electrode active material portion 122, and its length may be 5 mm to 50 mm.

[0056] Preferably, the protective tape 170 may not be attached to the negative electrode tab 160. In other words, the protective tape 170 may extend from the uncoated portion 121 of the negative electrode between the negative electrode tab 160 and the negative electrode active material portion 122 to a side portion of the negative electrode active material portion 122.

[0057] When the secondary battery 1 is charged / discharged, the positive electrode 110 and the negative electrode 120 expand in the electrode assembly 100 in a region 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 positive electrode 110 and the positive electrode 120 slide toward the core portion C, resulting in a core impact.

[0058] The protective tape 170 according to the present disclosure extends from the uncoated portion 121 of the negative electrode to a side portion of the negative electrode active material portion 122, in other words, extends to be adjacent to the portion where the positive electrode active material portion and the negative electrode active material portion 122 face each other, thereby increasing the stiffness of the negative electrode facing the positive electrode active material portion that causes the core impact and preventing the positive electrode 110 and the negative electrode 120 from sliding, so as to prevent the core impact and improve the safety of the secondary battery 1.

[0059] In another embodiment, the negative electrode 120 may further include an auxiliary tape 180.

[0060] That is, the negative electrode 120 according to another embodiment includes a protective tape 170 and an auxiliary tape 180, and 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 negative electrode tab 160, such that the auxiliary tape 180 is attached to the negative electrode tab 160 to completely cover the negative electrode tab 160 and fix the negative electrode tab 160 to the uncoated portion 121 of the negative electrode.

[0061] In addition, the area or thickness of the protective tape 170 and the auxiliary tape 180 laminated on the uncoated portion 121 of the negative electrode wound around the core C increases, and thus the shape of the core C is supported, and the strength of the core C is increased by the uncoated portion 121 of the negative electrode, the separators 130 and 140, the protective tape 170, and the auxiliary tape 180, thereby preventing core collapse and core deformation.

[0062] The front side portion of the uncoated portion 121 of the negative electrode may be covered by at least one of the protective tape 170 and the auxiliary tape 180. In an embodiment, one end of the protective tape 170 and one end of the auxiliary tape 180 are positioned to contact each other, and the sum of the width of the protective tape 170 and the width of the auxiliary tape 180 may be equal to the width of the uncoated portion 121 of the negative electrode.

[0063] Alternatively, the protective tape 170 and the auxiliary tape 180 may overlap to cover the front side portion of the uncoated portion 121 of the negative electrode. In this case, the sum of the width of the protective tape 170 and the width of the auxiliary tape 180 may be wider than the width of the uncoated portion 121 of the negative electrode.

[0064] Here, the width of the protective tape 170, the width of the auxiliary tape 180, and the width of the uncoated portion 121 of the negative electrode refer to the product of the length and width of the protective tape 170, the auxiliary tape 180, and the uncoated portion 121 of the negative electrode.

[0065] Therefore, since the protective tape 170 and the auxiliary tape 180 are located on the uncoated portion 121 of the negative electrode in the electrode assembly 100 according to the present disclosure, the step portion between the uncoated portion 121 of the negative electrode and the negative electrode active material portion 122 is reduced, thereby reducing the influence of the step portion caused by the end of the positive electrode during charging and discharging of the secondary battery 1, and preventing short circuit.

[0066] The protective tape 170 and the auxiliary tape 180 may be made of any one selected from the group consisting of polyethylene terephthalate (PET), polypropylene (PP), polyethylene (PE), polycarbonate (PC), polyimide (PI), polyethylene naphthalate (PEN), polyether ether ketone (PEEK), polyarylate (PAR), polycycloolefin (PCO), polynorbornene, polyethersulfone (PES), and cycloolefin polymer (COP).

[0067] The protective tape 170 and the auxiliary tape 180 may include the same material, or may have different materials. Preferably, the material forming the protective tape 170 and the material forming the auxiliary tape 180 may be different. For example, the protective tape 170 may be made of PI, while the auxiliary tape 180 may be made of PET.

[0068] The secondary battery 1 may include the above-described electrode assembly 100. Specifically, the secondary battery 1 may include a battery case 200 and a cover assembly 300. The battery case 200 has a space therein for accommodating the electrode assembly 100 and an electrolyte and has an open surface, and the cover assembly 300 is coupled to the open surface of the battery case.

[0069] The battery case 200 may be provided as a columnar structure having a space formed therein. The battery case 200 may accommodate the electrode assembly 100 including electrodes and separators and an electrolyte (not shown) in the internal space. The battery case 200 may have a structure in which one side thereof is open (hereinafter referred to as an "opening") and the other side is sealed. Here, one side and the other side of the battery case 200 refer to the upper end portion and the lower end portion positioned along the direction of gravity or along the central axis of the battery case 200.

[0070] A curled portion 210 that is folded toward the center of the secondary battery 1 may be provided at the open upper side portion of the battery case 200. In addition, the battery case 200 may be provided with a crimping portion 220 located on the upper side portion of the curled 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 direction.

[0071] 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 may be made of a nickel-plated steel sheet material.

[0072] The cover assembly 300 may be coupled to the open surface of the battery case 200 and may include a top cover 310, a safety vent 320, and a current interruption device 330.

[0073] The top cover 310 may be located at the top of the cover assembly 300 and may protrude in a direction opposite to the center of the battery case 200. The top cover 310 may serve as an electrode terminal such that the protruding portion is electrically connected to the outside. For example, the top cover 310 may serve as a positive electrode terminal.

[0074] The edge of the top cover 310 may be combined with a sealing gasket 340, and the sealing gasket 340 may be located within the crimping portion 220 of the battery case 200. The sealing gasket 340 may increase the sealing ability between the top cover 310 and the battery case 200.

[0075] The top cover 310 may include a protruding portion that protrudes upward, an edge that contacts and engages with the sealing gasket 340, and a first connecting portion that connects the protruding portion and the edge.

[0076] The safety vent 320 is located below the top cover 310 and may be electrically connected to the top cover 310. At least a part of the surface of the safety vent 320 facing the top cover 310 may contact the top cover 310. A portion of the safety vent 320 corresponding to a predetermined length from the end may contact the top cover 310, while the remaining portion may be located at a predetermined distance from the top cover 310. In addition, the portion of the safety vent 320 that contacts the top cover 310 may be combined with the sealing gasket 340.

[0077] The distance between the safety vent 320 and the top cover 310 may increase when the distance moves from the area in contact with the top cover 310 toward the center of the safety vent 320.

[0078] The safety vent 320 may include a contact portion that contacts the top cover 310, a central portion located at the center of the safety vent 320 and in contact with the current interruption device, and a second connecting portion that connects the contact portion and the central portion. In addition, the safety vent 320 may include bending portions (or notches) at the portions where the contact portion and the second connecting portion are connected and at the portions where the second connecting portion and the central portion are connected.

[0079] In an embodiment, the end portion of the safety vent 320 may be perpendicular to the axial direction of the battery case 200. In this case, the top cover 310 may similarly have an end portion perpendicular to the axial direction of the battery case 200 as the safety vent 320. That is, the safety vent 320 and the top cover 310 may be horizontally positioned.

[0080] In another embodiment, the end portion of the safety vent 320 may be bent and wrapped around the outer surface of the top cover 310.

[0081] In the secondary battery 1 according to the present disclosure, when the electrode assembly 100 and the electrolyte accommodated in the battery case 200 react with each other, gas is generated or heat is generated, thereby increasing the internal pressure.

[0082] When the pressure inside the secondary battery 1 increases, the safety vent 320 is pressed toward the top cover 310, and when the bending portion ruptures, the gas inside the secondary battery 1 is discharged.

[0083] The current interruption device (CID) 330 is located below the safety vent 320, and at least a part of the current interruption device 330 may be connected to the safety vent 320.

[0084] When the safety venting member 320 ruptures as the pressure inside the secondary battery 1 increases, the current interruption device 330 separates from the safety venting member 320 and interrupts the current.

[0085] More specifically, the current interruption device 330 may include a central portion connected to the safety venting member 320, a connecting portion protruding toward the safety venting member 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 positioned to be spaced apart from each other.

[0086] When the safety venting member 320 deforms in the direction of the top cover 310, the coupling portion ruptures, and thus the connecting portion may separate from the edge portion. That is, the connecting portion separates in the direction of the top cover 310 while being connected to the safety venting member 320.

[0087] The CID gasket 350 wraps around the edge of the current interruption device 330 and may electrically isolate the edge portion and the coupling portion of the current interruption device 330 other than the connecting portion from the safety venting member 320.

[0088] According to an embodiment of the present disclosure, a battery pack 3 including the above-described secondary battery 1 is provided.

[0089] Regarding the above embodiment, referring to Figure 6 , a battery pack 3 including the secondary battery 1 in the battery pack housing 2 is illustrated.

[0090] The battery pack according to the above embodiment has high output power / high capacity.

[0091] According to an embodiment of the present disclosure, a transportation means including the above-described battery pack is provided.

[0092] Regarding the above embodiment, referring to Figure 7 , a transportation means V including the battery pack 3 is illustrated.

[0093] The transportation means according to the above embodiment uses a battery pack having high output power / high capacity and is thus excellent in terms of stability and safety.

[0094] Modes for implementing the present invention

[0095] Embodiment 1

[0096] Manufacture of Electrode Assembly

[0097] An Al foil with a thickness of 15 μm and a length in the width direction of 63.9 mm is prepared as the positive current collector, and a positive active material slurry is coated on the positive current collector and the positive active material slurry is dried to form a positive active material portion, thereby manufacturing a positive electrode with a thickness of 154 μm. The positive active material slurry includes a Ni-Mn-Co-Al (NMCA) composite with a Ni content of 92% or higher as the positive active material and CNT as the conductive material.

[0098] Next, a copper foil with a thickness of 10 μm and a length in the width direction of 64.9 mm is prepared as the negative current collector, and a negative active material slurry is coated on the negative current collector and the negative active material slurry is dried to form a negative active material portion, thereby manufacturing a negative electrode with a thickness of 141 μm. The negative active material slurry includes 50 parts by weight of artificial graphite and natural graphite as the negative active material.

[0099] Then, a protective tape with a thickness of 22 μm, a length of 17 mm, a width of 63.5 mm and including PI is attached to one side of the negative electrode material portion in the direction where the negative electrode tab is located.

[0100] Meanwhile, two separators each having a coating layer are prepared as the first separator and the second separator. The coating layer includes Al2O3 as the inorganic component, a PVdF-based binder as the binder component, and a lithium salt and is formed on one side of a sheet-like polyethylene substrate layer.

[0101] Manufacture of Secondary Battery

[0102] After inserting the wound electrode assembly into a cylindrical battery case, an electrolyte solution is injected into the cylindrical battery case and the cylindrical battery case is sealed with a lid assembly to manufacture a secondary battery. The electrolyte solution includes 15 wt% of LiPF6 and is dissolved by mixing ethylene carbonate (EC), dimethyl carbonate (DMC), and ethyl methyl carbonate (EMC) in a weight ratio of 4:9:3.

[0103] Embodiment 2

[0104] A wound electrode assembly and a secondary battery are manufactured in the same manner as in Embodiment 1, except that a protective tape with a thickness of 50 μm and a length of 9 mm is attached to the negative active material portion and the uncoated portion of the negative electrode.

[0105] Comparative Example 1

[0106] A wound electrode assembly and a secondary battery are manufactured in the same manner as in Embodiment 1, except that a protective tape with a thickness of 22 μm and a length of 9 mm is attached to the negative electrode tab.

[0107] Comparative Example 2

[0108] The wound-type electrode assembly and the secondary battery are manufactured in the same manner as in Embodiment 1, except that a protective tape having a thickness of 30 μm and a length of 16 mm is attached to the negative electrode tab.

[0109] Experimental Example - Core Impact Evaluation

[0110] Cycle Stability Evaluation

[0111] The secondary batteries manufactured in Embodiments 1 and 2 and Comparative Examples 1 and 2 are activated by performing two cycles of 0.2C charge and 0.2C discharge at 4.2 V to 2.5 V, thereby preparing the secondary batteries. Thereafter, the activated secondary batteries are subjected to 400 cycles under the conditions of 4.25 V (0.3C) to 2.85 V (0.5C) at 55 °C, and computer tomography (CT) is performed on the core to check for core shock, thereby evaluating the long-term cycle stability evaluation, and Figure 3 An image of the results is shown in.

[0112] Core Impact Evaluation

[0113] The occurrence of core shock in the secondary batteries in Embodiments 1 and 2 and Comparative Examples 1 and 2 is evaluated by the following method.

[0114] Figure 4 A method for evaluating whether core shock occurs is schematically illustrated. Specifically, (a) of FIG. 9 schematically illustrates a method for evaluating whether core shock occurs when deformation occurs in the negative electrode, and (b) of FIG. 9 schematically illustrates a method for evaluating whether core shock occurs when no deformation occurs in the negative electrode.

[0115] 1) On the first surface of the positive electrode, a first extension line E1 is drawn by extending the following straight line: the straight line connects the longitudinal end of the positive electrode 110 and a point spaced 5 mm from the end.

[0116] 2-1) When deformation occurs in the negative electrode

[0117] In the core of the wound-type electrode assembly, on the surface of the negative electrode 120 facing the first surface of the positive electrode 110, a second extension line E2 is drawn by extending the following straight line: the straight line connects two points where the bending direction changes within a distance of 5 mm from the longitudinal end of the positive electrode 110.

[0118] 2-2) When no deformation occurs in the negative electrode

[0119] In the core of the wound electrode assembly, on the surface of the first surface of the negative electrode 120 facing the positive electrode 110, a second extension line E2 is drawn by extending the following straight line: the straight line connects two points spaced 5 mm from the longitudinal end of the positive electrode 110.

[0120] 3) When the angle from the first extension line E1 to the second extension line E2 along the counterclockwise direction based on the intersection point of the first extension line E1 and the second extension line E2 exceeds 25°, it is evaluated that a core impact has occurred.

[0121] Referring to Figure 3 , it can be confirmed that in the cyclic safety evaluation, compared with Comparative Examples 1 and 2, the secondary batteries manufactured in Embodiments 1 and 2 have improved core impact.

[0122] Specifically, the cross-sectional areas of the protective tapes in Embodiments 1 and 2 and Comparative Examples 1 and 2 are 0.374 mm 2 , 0.45 mm 2 , 0.198 mm 2 and 0.48 mm 2 .

[0123] It can be determined that compared with Comparative Examples 1 and 2, the core impact is improved in Embodiments 1 and 2, and in Embodiments 1 and 2, the cross-sectional area of the protective tape satisfies the range of 0.37 mm 2 to 0.47 mm 2 .

[0124] Furthermore, when comparing Embodiment 2 and Comparative Example 1 in which the protective tapes have the same length and different thicknesses, it can be confirmed that compared with Comparative Example 1, the core impact is improved in Embodiment 2 with a thicker protective tape.

[0125] When the protective tape is attached to a certain width, the stiffness of the core of the wound structure is improved, and thus core collapse and core impact can be improved.

[0126] Furthermore, by comparing Embodiment 1 and Embodiment 2, it can be determined that compared with Embodiment 2 having a larger cross-sectional area and a shorter length of the protective tape, the core impact is improved in Embodiment 1 having a smaller cross-sectional area and a longer length of the protective tape.

[0127] That is to say, even if the cross-sectional area of the protective tape satisfies the range of 0.37 mm 2 to 0.47 mm 2 , however, the longer the bonding length of the protective tape with respect to the uncoated portion of the negative electrode, the longer the length of supporting the core, thereby improving the core deformation.

[0128] The present disclosure has been described with reference to the above preferred embodiments, but the present disclosure is not limited to the above embodiments, and those skilled in the art can make various changes and modifications without departing from the spirit of the present disclosure.

[0129] Description of Reference Numerals

[0130] 1: Secondary battery

[0131] 2: Battery pack housing

[0132] 3: Battery pack

[0133] 100: Electrode assembly

[0134] 110: Positive electrode

[0135] 120: Negative electrode

[0136] 121: Uncoated portion of negative electrode

[0137] 122: Negative electrode active material portion

[0138] 130, 140: Separator

[0139] 160: Negative electrode tab

[0140] 170: Protection tape

[0141] 180: Auxiliary tape

[0142] 200: Battery case

[0143] 210: Crimped portion

[0144] 220: Pressing portion

[0145] 300: Cover assembly

[0146] 310: Top cover

[0147] 320: Safety vent

[0148] 330: Current interruption device

[0149] 340: Sealing gasket

[0150] 350: CID gasket

[0151] V: Vehicle

[0152] C: Core

[0153] Industrial Applicability

[0154] An electrode assembly according to an embodiment of the present disclosure and a secondary battery including the electrode assembly can improve the safety of the secondary battery by controlling the length and thickness of a protective tape that supports a core portion, thereby preventing the core portion from collapsing.

Claims

1. An electrode assembly having a wound structure, wherein, The negative electrode, the separator, and the positive electrode are wound around the core, wherein the negative electrode includes an active material portion and an uncoated portion of the negative electrode. In the active material portion, the negative electrode active material is laminated on one or both sides of the negative electrode current collector. In the uncoated portion of the negative electrode, the negative electrode active material is not laminated. The negative electrode includes a protective tape that covers at least a part of the uncoated portion of the negative electrode adjacent to the core, and The protective tape has a cross-sectional area of 0.3 mm 2 to 0.47 mm 2 in the longitudinal direction of the negative electrode.

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

20.

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

4. The electrode assembly according to claim 1, wherein, The uncoated portion of the negative electrode is located at the end portion of the negative electrode adjacent to the core. A negative tab is laminated on one side of the uncoated portion of the negative electrode, and the protective tape is not attached to the negative tab.

5. The electrode assembly according to claim 4, further comprising an auxiliary tape attached to the negative tab.

6. The electrode assembly according to claim 5, wherein, At least one of the protective tape and the auxiliary tape covers the front surface of the uncoated portion of the negative electrode.

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

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

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

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

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