Electrode assembly and secondary battery including the same

Abstract

The present invention relates to an electrode assembly and a secondary battery including the same. Specifically, in a core portion of an electrode assembly in which a negative electrode, a separator, and a positive electrode are sequentially stacked and wound, the negative electrode includes: a negative electrode coating portion including a negative electrode current collector and a negative electrode active material layer provided on at least one surface of the negative electrode current collector; and a negative electrode uncoated portion including a negative electrode current collector not provided with a negative electrode active material layer, in which the negative electrode uncoated portion does not include a negative electrode tab, and a longitudinal length of the negative electrode coated portion extending from a longitudinal end portion of the positive electrode is adjusted to a specific range.

Description

Technical Field

[0001] The present invention relates to an electrode assembly and a secondary battery including the electrode assembly, and more particularly to an electrode assembly in which the input amount of the negative electrode in the core part has been controlled and a cylindrical secondary battery including the electrode assembly. This application claims the priority and benefits of Korean Patent Application No. 10-2023-0088068, filed with the Korean Intellectual Property Office on July 7, 2023, the entire content of which is incorporated herein by reference. Background Art

[0002] For a cylindrical battery, a wound-type electrode assembly is manufactured by winding a long electrode having a predetermined width into a roll form. The cylindrical battery manufactured by inserting such an electrode assembly into a battery case undergoes repeated contraction / expansion of the electrodes during charging and discharging. In particular, when an in-tab is located in the core of the electrode assembly or the degree of contraction / expansion of the electrode assembly increases due to a silicon-based active material added to the negative electrode, the pressure acting on the core part of the electrode assembly increases significantly.

[0003] With the recent increase in low-resistance / high-capacity designs, in many cases, the electrode assembly includes a plurality of tabs or a silicon-based active material is added. Therefore, the possibility that the electrode assembly located in the core part is deformed due to the contraction / expansion of the electrode assembly increases. In particular, when the separator located between the negative electrode and the positive electrode is damaged, the negative electrode and the positive electrode come into direct contact with each other, causing heat generation and ignition due to an internal short circuit.

[0004] In order to solve the problems of separator damage and internal short circuit caused by the deformation of the electrode assembly, it is necessary to develop a technology capable of protecting the negative electrode and the separator in the corresponding area and suppressing the occurrence of an internal short circuit. Summary of the Invention

[0005] Technical Problem

[0006] The present invention is directed to providing an electrode assembly with a changed design and a secondary battery including the electrode assembly.

[0007] However, the problems to be solved by the present invention are not limited to the above problems, and other problems not mentioned will be clearly understood by those skilled in the art from the following description.

[0008] Technical Solution

[0009] An exemplary embodiment of the present invention provides an electrode assembly in which a negative electrode, a separator, and a positive electrode are sequentially stacked and wound. In the core portion of the electrode assembly, the negative electrode includes: a negative electrode coated portion including a negative electrode current collector and a negative electrode active material layer provided on at least one surface of the negative electrode current collector; and a negative electrode uncoated portion including the negative electrode current collector on which the negative electrode active material layer is not provided. The negative electrode uncoated portion does not include a negative electrode tab, and the length of the negative electrode coated portion extending from the longitudinal end portion of the positive electrode in the longitudinal direction is 2 turns or less from the longitudinal end portion of the positive electrode.

[0010] Another exemplary embodiment of the present invention provides a secondary battery including the above-described electrode assembly and a battery case for accommodating the electrode assembly.

[0011] Advantageous Effects

[0012] The electrode assembly according to the exemplary embodiment of the present invention can promote the sliding of the negative electrode during charging and discharging of the battery by controlling the input amount of the negative electrode in the core portion, and can reduce the relative sliding of the end portion of the positive electrode with respect to the negative electrode.

[0013] In addition, the secondary battery according to the exemplary embodiment of the present invention can prevent damage to the negative electrode and the separator due to the relative sliding of the end portion of the positive electrode, and prevent an internal short circuit between the positive electrode and the negative electrode, thereby improving the battery stability and life characteristics.

[0014] The effects of the present invention are not limited to the foregoing effects, and those skilled in the art will clearly understand the effects not mentioned from this specification and the drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 Schematically shows an electrode assembly including a negative electrode tab in the core portion.

[0016] Figure 2 and Figure 3 Schematically shows an electrode assembly according to an exemplary embodiment of the present invention.

[0017] Figure 4 is a CT image showing the results of the cyclic stability evaluation of secondary batteries according to Reference Example 1, Comparative Reference Example 1, and Comparative Reference Example 2.

[0018] Figure 5 is a CT image showing the results of the cyclic stability evaluation of secondary batteries according to Example 1, Example 2, and Comparative Example 1.

[0019] Figure 6Disclosed is a method for evaluating whether a separator in the core part of an electrode assembly according to an exemplary embodiment of the present invention is damaged.

[0020] Figure 7 FIG. is a diagram showing the results of evaluating whether a separator in the core part of a secondary battery according to Reference Example 1 and Comparative Reference Example 2 is damaged.

[0021] Figure 8 and Figure 9 FIG. shows an electrode assembly according to an exemplary embodiment of the present invention and a secondary battery including the electrode assembly. Detailed Description

[0022] Throughout the specification, when a part "includes", "comprises" or "has" a component, unless otherwise specifically described, this does not mean excluding another component, but means that another component may also be included.

[0023] Throughout the specification, when a member is referred to as being "on" another member, the member may be in direct contact with the other member, or there may also be an intermediate member.

[0024] Throughout this specification, the "winding axis of the electrode assembly" may refer to an imaginary line located at the center of the hollow part H of the core part of the wound electrode assembly 1. The hollow part H of the core part may be formed at the position of the wound core (mandrel) C, which is removed after winding the components included in the electrode assembly.

[0025] Therefore, the components included in the wound electrode assembly can respectively define the direction of the winding axis of the electrode assembly, that is, the direction parallel to the winding axis of the electrode assembly (Z-axis direction).

[0026] In addition, based on the cross-section (X-Y plane) perpendicular to the winding axis of the electrode assembly, the components included in the wound electrode assembly can respectively define the direction opposite to the winding axis of the electrode assembly, that is, the direction toward the center of the hollow part H of the core part of the wound electrode assembly 1.

[0027] Hereinafter, the present invention will be described in detail with reference to the drawings. However, it should be noted that the drawings are provided for illustrating the present invention, and the scope of the present invention is not limited by the drawings.

[0028] Exemplary embodiments of the present invention provide an electrode assembly in which a negative electrode, a separator, and a positive electrode are sequentially stacked and wound. In the core portion of the electrode assembly, the negative electrode includes: a negative electrode coated portion including a negative electrode current collector and a negative electrode active material layer provided on at least one surface of the negative electrode current collector; and a negative electrode uncoated portion including the negative electrode current collector on which the negative electrode active material layer is not provided. The negative electrode uncoated portion does not include a negative electrode tab, and the length of the negative electrode coated portion extending from the longitudinal end portion of the positive electrode in the longitudinal direction is 2 turns or less from the longitudinal end portion of the positive electrode.

[0029] The electrode assembly according to the exemplary embodiments of the present invention can promote the sliding of the negative electrode during charging and discharging of the battery by controlling the input amount of the negative electrode in the core portion, and can reduce the relative sliding of the end portion of the positive electrode with respect to the negative electrode. In addition, the electrode assembly can reduce the relative sliding of the end portion of the positive electrode with respect to the negative electrode during charging and discharging of the battery, prevent damage to the negative electrode and the separator due to deformation of the electrode assembly caused by contraction / expansion of the electrode, and prevent an internal short circuit between the positive electrode and the negative electrode, thereby improving battery stability and life characteristics. Specifically, when the negative electrode tab is not included, the effect of reducing the relative sliding of the end portion of the positive electrode due to controlling the input amount of the negative electrode in the core portion within the foregoing range may be better.

[0030] Herein, the "core portion" is a region including a hollow portion located on the winding axis of the electrode assembly and a part of the laminated structure of the wound negative electrode / separator / positive electrode, and may refer to a region within 2 turns of the positive electrode starting from one end portion in the longitudinal direction of the positive electrode located on the innermost side of the electrode assembly.

[0031] Figure 1 is a reference diagram schematically showing an electrode assembly that includes a negative electrode tab in the core portion, and Figure 2 and Figure 3 schematically shows an electrode assembly according to an exemplary embodiment of the present invention.

[0032] Refer to Figures 1 to 3, the electrode assembly according to an exemplary embodiment of the present invention may be an electrode assembly in which the negative electrodes 100, 100', the separators 20, 20' and the positive electrode 300 are stacked and wound. In the core part of the electrode assembly, the negative electrode 100 may include: a negative electrode current collector 101; and negative electrode active material layers 102 and 103 provided on at least one surface of the negative electrode current collector 101. Specifically, the negative electrode 100 may include: a negative electrode coated portion 10 that includes the negative electrode current collector 101 and the negative electrode active material layers 102 and 103 provided on at least one surface of the negative electrode current collector 101; and a negative electrode uncoated portion 12 that includes the negative electrode current collector 101 on which no negative electrode active material layer is provided.

[0033] According to an exemplary embodiment of the present invention, the positive electrode 300 may include a first surface in the direction of the winding axis of the electrode assembly and a second surface opposite to the first surface, and the negative electrode 100 in contact with the first surface of the positive electrode may include a negative electrode coated portion 10 and a negative electrode uncoated portion 12 extending from a longitudinal end portion 310 of the positive electrode.

[0034] According to an exemplary embodiment of the present invention, the negative electrode coated portion 10 extends from the longitudinal end portion 310 of the positive electrode, and may refer to a region within a range from the longitudinal end portion 310 of the positive electrode to a point where the negative electrode coated portion contacts the negative electrode uncoated portion extending from the negative electrode coated portion and having a predetermined length L1 in the longitudinal direction.

[0035] According to an exemplary embodiment of the present invention, the negative electrode uncoated portion 12 extends from the negative electrode coated portion 10, and may refer to a region within a range from the point where it contacts the longitudinal end portion of the negative electrode coated portion to the longitudinal end portion of the negative electrode and having a predetermined length L2 in the longitudinal direction.

[0036] According to an exemplary embodiment of the present invention, the length of the negative electrode coated portion extending from the longitudinal end portion of the positive electrode in the longitudinal direction may be 2 turns or less from the longitudinal end portion of the positive electrode. Specifically, the length of the negative electrode coated portion extending from the longitudinal end portion of the positive electrode in the longitudinal direction may be 1.8 turns or less, 1.6 turns or less, 1.4 turns or less, 1.2 turns or less, or 1 turn or less from the longitudinal end portion of the positive electrode. Additionally, the length of the negative electrode coated portion extending from the longitudinal end portion of the positive electrode in the longitudinal direction may be more than 0.5 turns, 0.6 turns or more, 0.7 turns or more, or 0.8 turns or more from the longitudinal end portion of the positive electrode.

[0037] Here, "one (1) turn" may refer to the length required to wind the positive electrode or the negative electrode included in the electrode assembly 360° from a reference point, and this length may be determined according to the outer diameter of the winding core (mandrel) C used to wind the electrode assembly, the thickness of the electrode, and the number of turns of the electrode wound on the inner side. For example, one turn of the negative electrode 100 in contact with the first surface of the positive electrode 300 may refer to the length required to wind the negative electrode 100 360° from the longitudinal end portion 310 of the positive electrode in the direction of the end portion where the winding of the negative electrode 100 starts.

[0038] According to an exemplary embodiment of the present invention, the uncoated portion of the negative electrode may not include a tab.

[0039] Generally, in the core portion of the electrode assembly, the negative electrode may include: a negative electrode coated portion including a negative electrode current collector and a negative electrode active material layer provided on at least one surface of the negative electrode current collector; and an uncoated portion of the negative electrode including a negative electrode current collector on which no negative electrode active material layer is provided, and may further include a tab located on the uncoated portion of the negative electrode as needed.

[0040] Specifically, referring to Figure 1 , the negative electrode 100 may include an uncoated portion 12 of the negative electrode and a negative electrode tab 50 provided on the uncoated portion of the negative electrode. That is, the electrode assembly may include one or more negative electrode tabs, and the electrode assembly may include negative electrode tabs according to design requirements, and may further include a protective tape 40 to prevent short circuits caused by the thickness of the negative electrode tab.

[0041] On the other hand, referring to Figure 2 and Figure 3 , the electrode assembly according to an exemplary embodiment of the present invention may not include a negative electrode tab, and the length of the negative electrode coated portion in the longitudinal direction may be controlled within a different length range from the case including a negative electrode tab as described above.

[0042] According to an exemplary embodiment of the present invention, the length of the negative electrode extending from the longitudinal end portion of the positive electrode in the longitudinal direction may be 0.5 turns or more and 2.3 turns or less from the longitudinal end portion of the positive electrode. Specifically, referring to Figure 2 and Figure 3 , the length L1 of the negative electrode coated portion extending from the longitudinal end portion 310 of the positive electrode in the longitudinal direction may be 0.6 turns or more, 0.7 turns or more, or 0.8 turns or more and 2.2 turns or less, 2.1 turns or less, or 2 turns or less from the longitudinal end portion 310 of the positive electrode.

[0043] When the length of the negative electrode extending from the longitudinal end portion of the positive electrode in the longitudinal direction satisfies the above range, the negative electrode can have an appropriate length of the uncoated portion of the negative electrode when no negative electrode tab is provided. For example, when no negative electrode tab is provided, the length L2 of the uncoated portion of the negative electrode can be approximately 3 mm.

[0044] According to an exemplary embodiment of the present invention, based on the circumference of the inner peripheral surface of the electrode assembly being 100%, the length of the coated portion of the negative electrode extending from the longitudinal end portion of the positive electrode in the longitudinal direction can be less than 200%. Specifically, based on the circumference of the inner peripheral surface of the electrode assembly being 100%, the length of the coated portion of the negative electrode extending from the longitudinal end portion of the positive electrode in the longitudinal direction can be 180% or less, 160% or less, 140% or less, or 120% or less.

[0045] Here, the "circumference of the inner peripheral surface" can refer to the circumference of a virtual circle with the maximum value among the distances from the winding axis of the electrode assembly to the innermost layer in contact with the hollow portion H of the core portion of the electrode assembly as the radius, and its length can be determined according to the outer diameter of the winding core C used for winding the electrode assembly. For example, the circumference of the inner peripheral surface can have a value of about 10 mm.

[0046] According to an exemplary embodiment of the present invention, in the core portion of the electrode assembly, the negative electrode and the separator can extend longer than the longitudinal end portion of the positive electrode. Specifically, referring to Figure 3 , the negative electrode 100' and the separators 20 and 20' can extend longer than the longitudinal end portion 310 of the positive electrode. In other words, the negative electrode and the separator are wound first, and then the negative electrode and the separator can be wound together with the positive electrode. For example, the negative electrode and the separator can be wound around the winding core by 0.5 turns or more, and then the negative electrode and the separator can be wound together with the positive electrode. That is, in the core portion of the electrode assembly, the longitudinal end portions of the negative electrode and the separator can be located more inward than the longitudinal end portion of the positive electrode.

[0047] According to an exemplary embodiment of the present invention, based on the length of the uncoated portion of the negative electrode extending from the end portion of the coated portion of the negative electrode in the longitudinal direction being 100%, the length of the coated portion of the negative electrode extending from the longitudinal end portion of the positive electrode in the longitudinal direction can be 150% or more and 650% or less. Specifically, referring to Figure 2 and Figure 3 , based on the length L2 of the uncoated portion of the negative electrode extending from the end portion of the coated portion of the negative electrode in the longitudinal direction being 100%, the length L1 of the coated portion of the negative electrode extending from the longitudinal end portion 310 of the positive electrode in the longitudinal direction can be 155% or more, 160% or more, or 165% or more and 500% or less, 400% or less, 300% or less, or 250% or less.

[0048] When the length of the negative electrode coating portion extending from the longitudinal end portion of the positive electrode in the longitudinal direction satisfies the above range, even without including the negative electrode tab, it is possible to promote the sliding of the negative electrode during charging and discharging of the battery by controlling the input amount of the negative electrode in the core portion, and reduce the relative sliding of the end portion of the positive electrode with respect to the negative electrode. Specifically, when the negative electrode tab is not included, the effect of reducing the relative sliding of the end portion of the positive electrode may be better due to controlling the length of the negative electrode coating portion in the longitudinal direction within the above range.

[0049] According to an exemplary embodiment of the present invention, based on the weight of the uncoated negative electrode portion extending from the end portion of the negative electrode coating portion and additionally wound being 100%, the weight of the negative electrode coating portion extending from the longitudinal end portion of the positive electrode and additionally wound can be 500% or more and 2000% or less. Specifically, referring to Figure 2 and Figure 3 , based on the weight of the uncoated negative electrode portion 12 extending from the end portion of the negative electrode coating portion being 100%, the weight of the negative electrode coating portion 10 extending from the longitudinal end portion 310 of the positive electrode can be 500% or more, 550% or more, or 600% or more and 1500% or less, 1000% or less, 900% or less, or 700% or less.

[0050] When the above weight range of the negative electrode coating portion is satisfied, it is possible to promote the sliding of the negative electrode during charging and discharging of the battery by controlling the input amount of the negative electrode in the core portion, and reduce the relative sliding of the end portion of the positive electrode with respect to the negative electrode. Specifically, when the negative electrode tab is not included, the effect of reducing the relative sliding of the end portion of the positive electrode may be better due to controlling the weight of the negative electrode coating portion in the core portion within the above range.

[0051] According to an exemplary embodiment of the present invention, the length of the negative electrode coating portion extending from the longitudinal end portion of the positive electrode in the longitudinal direction can be 5 mm or more and 15 mm or less. Specifically, referring to Figure 2 and Figure 3 , the length L1 of the negative electrode coating portion extending from the longitudinal end portion 310 of the positive electrode in the longitudinal direction can be 5 mm or more, 5.5 mm or more, or 6 mm or more and 9.5 mm or less, 9 mm or less, or 8.5 mm or less.

[0052] When the length range of the negative electrode coating portion extending from the longitudinal end portion of the positive electrode in the longitudinal direction is satisfied, the input amount of the negative electrode into the core portion can be controlled to promote the sliding of the negative electrode during charging and discharging of the battery, and reduce the relative sliding of the end portion of the positive electrode with respect to the negative electrode. Specifically, when the negative electrode tab is not included, the effect of reducing the relative sliding of the end portion of the positive electrode may be better due to controlling the length of the negative electrode coating portion in the longitudinal direction within the above range.

[0053] According to an exemplary embodiment of the present invention, the length of the negative electrode in the longitudinal direction may be greater than the length of the positive electrode in the longitudinal direction. In addition, the length of the separator located on one surface and the opposite side of the negative electrode in the longitudinal direction may be greater than the length of the positive electrode in the longitudinal direction.

[0054] When the negative electrode and the separator extend longer than the longitudinal end portion of the positive electrode, lithium ions can be more easily transferred from the positive electrode to the negative electrode in the chemical reaction of the lithium ion battery. When the length or width of the negative electrode is formed larger, the area of the negative electrode for receiving lithium ions increases, thereby preventing a decrease in charge / discharge efficiency and improving the stability and life characteristics of the battery.

[0055] According to an exemplary embodiment of the present invention, the negative electrode coating portion 10 may include a single-sided coating portion 11, and the single-sided coating portion 11 includes one surface of the negative electrode current collector provided with the negative electrode active material layer and the other surface on which the negative electrode active material layer is not provided and the negative electrode current collector is directly exposed. Specifically, the single-sided coating portion 11 may have one surface facing the winding axis of the negative electrode current collector and provided with the negative electrode active material layer and the other surface on which the negative electrode active material layer is not provided and the negative electrode current collector is directly exposed. When the single-sided coating portion is included, the amount of the negative electrode active material applied to the region not facing the positive electrode can be minimized to ensure economic efficiency. In addition, when the negative electrode active material layer is provided on one surface of the single-sided coating portion facing the winding axis of the negative electrode current collector, the step formed due to the thickness of the negative electrode active material can be minimized.

[0056] According to an exemplary embodiment of the present invention, the length of the negative electrode single-sided coating portion in the longitudinal direction may be 0 mm or more and 2 mm or less. Specifically, referring to Figure 3, the length L1' of the single-sided coated portion of the negative electrode in the longitudinal direction may be 0.1 mm or greater, 0.3 mm or greater, 0.5 mm or greater, or 0.7 mm or greater and 1.9 mm or less, 1.7 mm or less, 1.5 mm or less, or 1.3 mm or less, and may be, for example, 1 mm. When the above length range of the single-sided coated portion of the negative electrode in the longitudinal direction is satisfied, the input amount of the negative electrode in the core portion can be controlled to promote the sliding of the negative electrode during charging and discharging of the battery, and reduce the relative sliding of the end portion of the positive electrode with respect to the negative electrode. Specifically, when the negative electrode tab is not included, the effect of reducing the relative sliding of the end portion of the positive electrode by controlling the length of the single-sided coated portion of the negative electrode in the longitudinal direction within the above range may be better.

[0057] According to an exemplary embodiment of the present invention, the negative electrode active material layer may include a negative electrode active material including one or more selected from the group consisting of a silicon-based material and a carbon-based material. In addition, the negative electrode active material layer may further include a negative electrode conductive material and a negative electrode binder, and there is no limitation on the materials used for the negative electrode active material, the negative electrode conductive material, and the negative electrode binder, which may be materials used in the art.

[0058] According to an exemplary embodiment of the present invention, the negative electrode current collector is not particularly limited as long as it has conductivity and does not cause chemical changes in the battery. For example, for the negative electrode current collector, copper, stainless steel, aluminum, nickel, titanium, sintered carbon, aluminum or stainless steel whose surfaces are treated with carbon, nickel, titanium, silver, etc. can be used. Specifically, transition metals that adsorb carbon well, such as copper and nickel, can be used for the negative electrode current collector. The thickness of the negative electrode current collector may be 6 μm or greater and 80 μm or less. However, the thickness of the negative electrode current collector is not limited thereto.

[0059] According to an exemplary embodiment of the present invention, the negative electrode binder may include at least one selected from the group including the following: polyvinylidene fluoride-hexafluoropropylene copolymer (PVDF-co-HFP), polyvinylidene fluoride, polyacrylonitrile, polymethyl methacrylate, 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 the above materials in which hydrogen is replaced by Li, Na, Ca, etc., and may further include various copolymers thereof.

[0060] According to an exemplary embodiment of the present invention, the negative electrode conductive material is not particularly limited as long as it has conductivity and does not cause chemical changes in the battery. For example, the following can be used: graphite, such as natural graphite or artificial graphite; carbon black, such as acetylene black, Ketjen black, channel black, furnace black, lamp black, and thermal cracking carbon black; conductive fibers, such as carbon fibers and metal fibers; conductive tubes, such as carbon nanotubes; metal powders, such as carbon fluorides, aluminum, and nickel powders; conductive whiskers, such as zinc oxide and potassium titanate; conductive metal oxides, such as titanium oxide; conductive materials, such as polyphenylene derivatives, etc.

[0061] According to an exemplary embodiment of the present invention, the electrode assembly may include a plurality of separators. For example, the electrode assembly may have a structure in which a separator / negative electrode / separator / positive electrode are stacked in sequence. The separator is used to separate the negative electrode and the positive electrode and provide a migration path for lithium ions. Any separator can be used as this separator without particular limitation as long as it is commonly used in secondary batteries. In particular, a separator having high moisture retention capacity for the electrolyte and low resistance to the migration of electrolyte ions can be preferably used. Specifically, a porous polymer membrane can be used. For example, a porous polymer membrane made of a polyolefin-based polymer, and the polyolefin-based polymer is, for example, ethylene homopolymer, propylene homopolymer, ethylene / butene copolymer, ethylene / hexene copolymer, and ethylene / methacrylate copolymer, or a stacked structure having two or more layers thereof. In addition, a general porous nonwoven fabric can be used. For example, a nonwoven fabric formed of high melting point glass fibers, polyethylene terephthalate fibers, etc. In addition, the separator generally may have a thickness of 10 μm or more and 20 μm or less. The following separator can be used: in this separator, the above-mentioned separator material is used as a base layer, and a slurry containing a ceramic component or a polymer material to ensure heat resistance or mechanical strength is coated on the base layer. A separator having a single-layer or multi-layer structure can be selectively used.

[0062] According to an exemplary embodiment of the present invention, the positive electrode may include a positive electrode current collector and a positive electrode active material layer provided on the positive electrode current collector. Specifically, referring to Figure 1 , the positive electrode 300 may include a positive electrode current collector 301 and positive electrode active material layers 302 and 303 formed on one surface or two surfaces of the positive electrode current collector 301 and including positive electrode active materials. In other words, the positive electrode active material layer is formed on the positive electrode coating portion of the positive electrode current collector, and the surface where the positive electrode active material layer is not provided can be referred to as the positive electrode uncoated portion.

[0063] According to an exemplary embodiment of the present invention, the positive electrode current collector may include a positive electrode coated portion coated with a positive electrode active material and a positive electrode uncoated portion not coated with the positive electrode active material, and may include a tab located on the positive electrode uncoated portion. Specifically, the positive electrode current collector may include the positive electrode uncoated portion and a positive electrode tab formed on the positive electrode uncoated portion.

[0064] According to an exemplary embodiment of the present invention, in the core portion of the electrode assembly, the positive electrode may include a positive electrode current collector and a positive electrode active material layer, and the positive electrode active material layer is disposed on at least one surface of the positive electrode current collector and has a longitudinal end portion at the same position as the positive electrode current collector. Specifically, referring to Figure 1 , in the core portion of the electrode assembly, the positive electrode 300, the separators 20 and 20', and the negative electrode 100 are stacked and wound, and the positive electrode 300 may include a positive electrode current collector 301 and positive electrode active material layers 302 and 303, and the positive electrode active material layers 302 and 303 are disposed on at least one surface of the positive electrode current collector 301 and each have a longitudinal end portion 310 at the same position as the positive electrode current collector 301. That is, one end portion 310 of the positive electrode in the longitudinal direction may have a free edge form.

[0065] Thereby, the area of the unnecessary uncoated portion on the positive electrode current collector can be reduced to ensure economic efficiency, and the slitting process can be performed after forming the active material layer on the electrode, so that the slitting process and the roll-to-roll process including the winding process can be performed more effectively. Here, the description of "the same position" means that the end portions in the longitudinal direction are the same, and may include the case where the end portions are formed at substantially the same position due to process errors that may occur in the slitting process or the like.

[0066] According to an exemplary embodiment of the present invention, the positive electrode current collector is not particularly limited as long as it has conductivity and does not cause chemical changes in the battery. Specifically, for the positive electrode current collector, stainless steel, aluminum, nickel, titanium, sintered carbon, aluminum or stainless steel whose respective surfaces are treated with carbon, nickel, titanium, silver, etc. can be used. That is, the positive electrode current collector may be provided in the form of surface-treated stainless steel, aluminum foil, etc.

[0067] In addition, the positive electrode current collector generally may have a thickness of 3 μm to 50 μm, and microscopic irregularities may be formed on the surface of the current collector to enhance the adhesion force of the positive electrode active material. For example, the positive electrode current collector may be used in various forms such as a film, a sheet, a foil, a net, a porous body, a foam body, and a non-woven fabric body.

[0068] According to an exemplary embodiment of the present invention, the positive electrode active material may be a commonly used positive electrode active material. Specifically, the positive electrode active material may be a layered compound, such as: lithium cobalt oxide (LiCoO2) and lithium nickel oxide (LiNiO2), or a compound substituted by one or more transition metals; lithium iron oxide, such as LiFe3O4; lithium manganese oxide, such as a chemical formula of Li 1+x Mn 2-x O4 (0≤x≤0.33), LiMnO3, LiMn2O3 and LiMnO2; lithium copper oxide (Li2CuO2); vanadium oxide, such as LiV3O8, V2O5 and Cu2V2O7; nickel-site type lithium nickel oxide represented by the chemical formula LiNi 1-y M y O2 (where M is at least one selected from the group including the following: Co, Mn, Al, Cu, Fe, Mg, B and Ga, and 0.01≤y≤0.3); lithium manganese composite oxide represented by the chemical formula LiMn 2-z M z O2 (where M is at least one selected from the group including the following: Co, Ni, Fe, Cr, Zn and Ta, and 0.01≤z≤0.1) or Li2Mn3MO8 (where M is at least one selected from the group including the following: Fe, Co, Ni, Cu and Zn); LiMn2O4, in which a part of Li in the chemical formula is replaced by an alkaline earth metal ion, etc., but not limited thereto. The positive electrode may be lithium metal.

[0069] According to an exemplary embodiment of the present invention, the positive electrode active material layer may further include a positive electrode conductive material and a positive electrode binder. The positive electrode conductive material is used to impart conductivity to the electrode and may be used without particular limitation as long as it does not cause a chemical change in the battery being formed and has electronic conductivity. Specific examples of the positive electrode conductive material may include: 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 cracking carbon black and carbon fiber; metal powder or metal fiber, 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, etc., and any one of them or a mixture of two or more of them may be used.

[0070] In addition, the positive electrode binder is used to improve the adhesion between the particles of the positive electrode active material and the adhesion between the positive electrode active material and the positive electrode current collector. Specific examples may 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 polymer (EPDM), sulfonated EPDM, styrene-butadiene rubber (SBR), fluororubber, or various copolymers thereof, etc., and any one of them or a mixture of two or more of them may be used.

[0071] According to an exemplary embodiment of the present invention, based on the winding axis of the electrode assembly, the angle between the initial position of the longitudinal end portion of the negative electrode and the position of the longitudinal end portion of the negative electrode after an additional charge and discharge of 200 times or more at a temperature of 40 °C or higher may be 5° or greater. Specifically, based on the winding axis of the electrode assembly, the angle between the initial position of the longitudinal end portion of the negative electrode and the position of the longitudinal end portion of the negative electrode after an additional charge and discharge of 200 times or more at a temperature of 40 °C or higher may be 5° or greater, 10° or greater, 15° or greater, or 20° or greater and 45° or less, 40° or less, 35° or less, 30° or less, or 25° or less, and for example, it may be 5° or greater and 30° or less. More specifically, the initial position of the longitudinal end portion of the negative electrode can be measured after activation. Here, the term "after activation" may refer to after a predetermined number of cycles for manufacturing the secondary battery and completing the product. Specifically, "after activation" may include the state before the start of effective use including a plurality of cycles for power supply purposes, that is, the storage state before and after sales and the state in which self-discharge has occurred during storage.

[0072] When the above angle range is satisfied, the sliding of the negative electrode during the charge and discharge of the battery can be promoted by controlling the input amount of the negative electrode in the core portion, and the relative sliding of the end portion of the positive electrode with respect to the negative electrode can be reduced.

[0073] According to an exemplary embodiment of the present invention, when 200 or more additional charge and discharge cycles are performed at a temperature of 40 °C or higher after activation, the angle between the positive electrode and the negative electrode may be 25° or less. Specifically, the positive electrode may include a first surface in the direction of the winding axis of the electrode assembly and a second surface opposite to the first surface, and a first extension line is drawn by extending a straight line connecting two points that change the curvature direction at a distance of 5 mm from the longitudinal end portion of the positive electrode on the first surface of the positive electrode, and a second extension line is drawn by extending a straight line connecting two points at a distance of 5 mm from the longitudinal end of the positive electrode on the surface of the negative electrode facing the first surface of the positive electrode. The first extension line and the second extension line may form an angle of 25° or less. When the above angle range is satisfied, damage to the negative electrode and the separator due to relative sliding of the end portion of the positive electrode can be prevented, and an internal short circuit between the positive electrode and the negative electrode can be prevented, thereby improving battery stability and life characteristics.

[0074] Figure 8 and Figure 9 FIGS. show an electrode assembly according to an exemplary embodiment of the present invention and a secondary battery including the electrode assembly.

[0075] An exemplary embodiment of the present invention provides a secondary battery including the above electrode assembly and a battery case for accommodating the electrode assembly. Specifically, referring to Figure 8 and Figure 9 , the secondary battery 2 may include the electrode assembly 1 according to the above exemplary embodiment and a battery case 60 for accommodating the electrode assembly 1. More specifically, the electrode assembly 1 may or may not include a negative electrode tab 50.

[0076] The secondary battery according to an exemplary embodiment of the present invention can prevent damage to the negative electrode and the separator due to relative sliding of the end portion of the positive electrode, and prevent an internal short circuit between the positive electrode and the negative electrode, thereby improving battery stability and life characteristics.

[0077] According to an exemplary embodiment of the present invention, the battery case may have a cylindrical shape. Specifically, depending on the use application, the battery case may have a cylindrical, prismatic, or pouch shape. However, a battery case having a cylindrical shape may be more suitable for accommodating the electrode assembly. When the battery case has a cylindrical shape, the secondary battery including the electrode assembly and the battery case for accommodating the electrode assembly may have a cylindrical shape.

[0078] According to an exemplary embodiment of the present invention, an electrolyte may be included in the battery case. Specifically, the electrolyte may include an organic liquid electrolyte, an inorganic liquid electrolyte, a solid polymer electrolyte, a gel-type polymer electrolyte, a solid inorganic electrolyte, or a molten-type inorganic electrolyte that can be used to manufacture a lithium secondary battery, but is not limited thereto. Specifically, the electrolyte may include a non-aqueous organic solvent and a metal salt.

[0079] According to an exemplary embodiment of the present invention, as the non-aqueous organic solvent, for example, an aprotic organic solvent such as N-methyl-2-pyrrolidone, acrylate, ethylene carbonate, butylene carbonate, dimethyl carbonate, diethyl carbonate, γ-butyrolactone, 1,2-dimethoxyethane, tetrahydrofuran, 2-methyltetrahydrofuran, dimethyl sulfoxide, 1,3-dioxolane, formamide, dimethylformamide, dioxolane, acetonitrile, nitromethane, methyl formate, methyl acetate, triphosphate, trimethoxymethane, dioxolane derivatives, sulfolane, methylsulfolane, 1,3-dimethyl-2-imidazolidinone, propylene carbonate derivatives, tetrahydrofuran derivatives, diethyl ether, methyl propionate, or ethyl propionate may be used.

[0080] According to an exemplary embodiment of the present invention, a lithium salt may be used as the metal salt, and the lithium salt is a material that is easily soluble in a non-aqueous electrolyte solution. Among them, for example, one or more selected from the group including the following may be used as the anion of the lithium salt: F - , Cl - , I - , NO3 - , N(CN) 2- , BF4 - , ClO4 - , PF6 - , (CF3)2PF4 - , (CF3)3PF3 - , (CF3)4PF2 - , (CF3)5PF - , (CF3)6P - , CF3SO3 - , CF3CF2SO3 - , (CF3SO2)2N - , (FSO2)2N - , CF3CF2(CF3)2CO - , (CF3SO2)2CH - , (SF5)3C - , (CF3SO2)3C - , CF3(CF2)7SO3 - , CF3CO2 - , CH3CO2 - , SCN- and (CF3CF2SO2)2N - 。

[0081] According to an exemplary embodiment of the present invention, for the purpose of improving the life characteristics of the battery, suppressing the decrease in battery capacity, increasing the discharge capacity of the battery, etc., in addition to the above electrolyte components, the electrolyte may further include one or more additives, for example, halogenated alkylene carbonate compounds such as diethyl difluorocarbonate, pyridine, triethyl phosphite, triethanolamine, cyclic ethers, ethylenediamine, n-glyme, hexaphosphoric triamide, nitrobenzene derivatives, sulfur, quinone imine dyes, N-substituted oxazolidinone, N,N-substituted imidazolidine, ethylene glycol dialkyl ether, ammonium salts, pyrrole, 2-methoxyethanol or aluminum trichloride, etc.

[0082] Hereinafter, examples will be described in detail to specifically describe the present invention. However, the examples according to the present invention can be modified in other forms, and the scope of the present invention should not be construed as being limited to the following examples. The examples of this specification are provided to more fully explain the present invention to those skilled in the art.

[0083] Embodiments of the invention

[0084] Preparation Example

[0085] Reference Example 1

[0086] Preparation of Electrode Assembly

[0087] A positive electrode current collector was prepared by making an Al foil with a thickness of 15 μm and a length of 63.9 mm in the width direction, and a positive electrode active material layer was formed by coating and drying a positive electrode active material slurry on the positive electrode current collector, thereby preparing a positive electrode with a thickness of 154 μm. Among them, the positive electrode active material slurry includes an NMCA (Ni-Mn-Co-Al) composite with a Ni content of 92% or higher as the positive electrode active material and CNT as the conductive material.

[0088] Next, a negative electrode current collector was prepared by making a copper foil with a thickness of 8 μm and a length of 65.1 mm in the width direction, and a negative electrode active material layer was formed by coating and drying a negative electrode active material slurry on the negative electrode current collector, thereby preparing a negative electrode with a thickness of 187 μm. Among them, the negative electrode active material slurry contains 50 parts by weight each of artificial graphite and natural graphite as the negative electrode active material.

[0089] Note that two sheet-like separators made of polyethylene were prepared.

[0090] Then, the negative electrode and the positive electrode are sequentially added to fabricate the electrode assembly. In this case, the core part of the electrode assembly is provided with a negative electrode coating part having a length of 6 mm in the longitudinal direction (the length of the negative electrode single-sided coating part in the longitudinal direction is 1 mm) and a non-coated part of the negative electrode having a length of 19 mm in the longitudinal direction, and it is made to have the conditions according to Table 1 below and according to Figure 1 the structure of

[0091] Preparation of Secondary Battery

[0092] The secondary battery is prepared through the following steps: The electrode assembly is inserted into a cylindrical battery case, an electrolyte solution is injected, in which ethylene carbonate (EC), dimethyl carbonate (EMC), and ethyl methyl carbonate (DMC) are mixed at a volume ratio (vol%) of 20:5:75, and LiPF6 is dissolved to 0.7 M, and the cylindrical battery case is sealed with a lid assembly.

[0093] Compare Comparative Reference Example 1 and Comparative Reference Example 2

[0094] The electrode assembly and the secondary battery are prepared in the same manner as in Reference Example 1, except that the lengths of the negative electrode coating part and the non-coated part of the negative electrode that extend from the longitudinal end part of the positive electrode and are further wound are adjusted to the conditions according to Table 1 below.

[0095] Table 1

[0096]

[0097]

[0098]

[0099] Example 1 and Example 2

[0100] The electrode assembly and the secondary battery are prepared in the same manner as in Reference Example 1, except that the lengths of the negative electrode coating part and the non-coated part of the negative electrode that extend from the longitudinal end part of the positive electrode and are further wound are adjusted to the conditions according to Table 2 below to have the structure according to Figure 2 the structure of

[0101] Comparative Example 1

[0102] The electrode assembly and the secondary battery are prepared in the same manner as in Example 1, except that the lengths of the negative electrode coating part and the non-coated part of the negative electrode that extend from the longitudinal end part of the positive electrode and are further wound are adjusted to the conditions according to Table 2 below.

[0103] Table 2

[0104]

[0105]

[0106] Experimental Example

[0107] Experimental Example 1 - Cycle Stability Evaluation

[0108] The secondary batteries prepared in Reference Example 1, Comparative Reference Example 1, Comparative Reference Example 2, Example 1, Example 2, and Comparative Example 1 were each subjected to 3 cycles of 0.2C charging and 0.2C discharging from 4.2 V to 2.5 V and charged to 30% SOC, thereby preparing activated secondary batteries. Thereafter, the activated secondary batteries were subjected to 200 cycles under the conditions of 4.3 V to 2.85 V, 0.5C / 1C, and 55°C, thereby preparing the cycled secondary batteries. For the evaluation of cycle stability, computerized tomography (CT) was performed on the core portions of the activated secondary batteries and the cycled secondary batteries to check for the presence or absence of core shock, and the images are shown in Figure 4 and Figure 5 .

[0109] Experimental Example 2 - Anode Sliding Evaluation

[0110] Computerized tomography (CT) was performed on the core portions of the secondary batteries prepared in Reference Example 1 and Comparative Reference Example 2. Based on the winding axis of the electrode assembly, the change in the angle between the initial position of the longitudinal end portion of the negative electrode and the position of the longitudinal end portion of the negative electrode after cycling was measured, and the change in the angle was re-measured every 200 cycles, and the results are shown in the following Figure 7 .

[0111] Experimental Example 3 - Core Impact Evaluation

[0112] In the following method, the secondary batteries prepared in Reference Example 1, Comparative Reference Example 1, Comparative Reference Example 2, Example 1, Example 2, and Comparative Example 1 were each subjected to 3 cycles of 0.2C charging and 0.2C discharging from 4.2 V to 2.5 V and charged to 30% SOC, thereby preparing activated secondary batteries. Computerized tomography was performed on the core portions of the activated secondary batteries to evaluate whether core shock occurred according to the following method for evaluating whether core shock occurred, and whether core shock occurred was re-evaluated every 200 cycles, and the results are shown in Figure 6 .

[0113] Figure 6 A method for evaluating whether core shock occurs is schematically shown. Specifically, Figure 6(a) schematically shows a method for evaluating whether core impact occurs when deformation occurs in the negative electrode, and Figure 6 (b) schematically shows a method for evaluating whether core impact occurs when no deformation occurs in the negative electrode.

[0114] 1) On the first surface of the positive electrode 300, a first extension line E1 is drawn by extending a straight line connecting the longitudinal end portion 310 of the positive electrode and a point spaced 5 mm from the end portion.

[0115] 2-1) When the negative electrode is deformed

[0116] At the core portion of the electrode assembly, a second extension line E2 is drawn by extending a straight line connecting two points on the surface of the negative electrode 100 facing the first surface of the positive electrode, where the curvature direction changes within a spacing distance of 5 mm from the longitudinal end portion 310 of the positive electrode.

[0117] 2-2) When the negative electrode is not deformed

[0118] At the core portion of the electrode assembly, a second extension line E2 is drawn by extending a straight line connecting two points on the surface of the negative electrode 100 facing the first surface of the positive electrode and spaced 5 mm from the longitudinal end portion 310 of the positive electrode.

[0119] 3) When the angle from the first extension line E1 to the second extension line E2 in the counterclockwise direction with respect to the intersection point of the first extension line E1 and the second extension line E2 exceeds 25°, it is evaluated that core impact has occurred.

[0120] On the other hand, in the case of obtaining an unknown secondary battery (unknown battery), the above method for evaluating whether core impact has occurred can be applied in the following manner: evaluate whether core impact has occurred at the initial acquisition, re-evaluate whether core impact has occurred every 200 cycles, and compare and analyze the results with the core impact conditions of the secondary battery according to the exemplary embodiments of the present invention.

[0121] Referring to Table 1 and Figure 3 、 Figure 6 and Figure 7 , it is confirmed that when the negative tab is included in the core portion, in the cycle stability evaluation, no core impact occurred in the secondary battery prepared in Reference Example 1, but core impact occurred in both the secondary batteries prepared in Comparative Reference Example 1 and Comparative Reference Example 2. Specifically, it is confirmed that for the secondary batteries prepared in Comparative Reference Example 1 and Comparative Reference Example 2, no core impact occurred in the secondary battery after activation, but core impact occurred after 200 cycles at 55 °C, that is, after long-term high-temperature cycling.

[0122] Referring toFigure 7 It was confirmed that the secondary battery prepared in Reference Example 1 exhibited the following negative electrode core slippage: wherein, based on the winding axis of the electrode assembly, the change in the angle between the initial position of the longitudinal end portion of the negative electrode and the position of the longitudinal end portion of the negative electrode after cycling gradually decreased but was relatively high after 200 cycles, such as 5° or greater. However, comparing the secondary battery prepared in Comparative Reference Example 2 exhibited the following negative electrode core slippage: wherein, since the negative electrode core slippage was suppressed, even after 400 cycles, the change in the angle was relatively low, such as 5° or less. In addition, it was confirmed that in the secondary battery prepared in Comparative Reference Example 2, the angle formed between the positive electrode and the negative electrode increased significantly after 200 cycles, and the angle formed between the positive electrode and the negative electrode was 25° or greater after 400 cycles, indicating that core impact occurred.

[0123] Accordingly, it was confirmed that in the secondary battery according to Reference Example 1, in which the input amount of the negative electrode in the core portion was controlled within a specific range, particularly when the negative electrode tab was included in the core portion, compared with the secondary batteries according to Comparative Reference Example 1 and Comparative Reference Example 2, the damage to the negative electrode and the separator caused by the longitudinal end portion of the positive electrode was significantly reduced, that is, the occurrence frequency and degree of core impact caused by the shrinkage / expansion of the electrode assembly were significantly reduced. Specifically, it was confirmed that in the secondary batteries according to Comparative Reference Example 1 and Comparative Reference Example 2, in which the length of the negative electrode coating portion in the longitudinal direction was more than 0.5 turns away from the longitudinal end portion of the positive electrode, the battery stability and life characteristics were worse than those of the secondary battery according to Reference Example 1, in which the input amount of the negative electrode in the core portion satisfied a specific range.

[0124] Note that referring to Table 2 and Figure 5 and Figure 6 it was confirmed that when the negative electrode tab was not included in the core portion, no core impact occurred in the secondary batteries prepared in Example 1 and Example 2 during the cyclic stability evaluation, but core impact occurred in the secondary battery prepared in Comparative Example 1. Specifically, it was confirmed that with respect to the secondary batteries prepared in Example 1 and Example 2, no core impact occurred in the secondary batteries after activation and after 200 cycles at 55 °C, that is, after long-term high-temperature cycling. On the other hand, it was confirmed that with respect to the secondary battery prepared in Comparative Example 1, no core impact occurred in the secondary battery after activation, but core impact occurred after 200 cycles at 55 °C, that is, after long-term high-temperature cycling.

[0125] Accordingly, it was confirmed that in the secondary batteries according to Example 1 and Example 2, especially when the negative electrode tab is not included, by controlling the input amount of the negative electrode in the core part, the sliding of the negative electrode during charging and discharging of the battery can be promoted, and the relative sliding of the end part of the positive electrode with respect to the negative electrode can be reduced. As a result, compared with the secondary battery according to Comparative Example 1, the damage to the negative electrode and the separator caused by the longitudinal end part of the positive electrode is significantly reduced, that is, the occurrence frequency and degree of the core impact caused by the contraction / expansion of the electrode assembly are significantly reduced.

[0126] Specifically, it was confirmed that when the length of the negative electrode coating part in the longitudinal direction is controlled within a length range different from that in the case including the negative electrode tab, the effect of reducing the relative sliding of the end part of the positive electrode with respect to the negative electrode is the most excellent.

[0127] That is, it can be seen that the electrode assembly according to the exemplary embodiment of the present invention can promote the sliding of the negative electrode during charging and discharging of the battery by controlling the input amount of the negative electrode in the core part, and can reduce the relative sliding of the end part of the positive electrode with respect to the negative electrode. Moreover, the secondary battery including the electrode assembly according to the exemplary embodiment of the present invention can prevent damage to the negative electrode and the separator due to the relative sliding of the end part of the positive electrode, and prevent an internal short circuit between the positive electrode and the negative electrode, thereby improving the battery stability and life characteristics.

[0128] The foregoing detailed description is intended to illustrate and explain the present invention. Additionally, the foregoing description is merely for the purpose of showing and describing the preferred embodiments of the present invention, and as described above, the present invention can be used in various other combinations, variations, and environments, and can be changed and modified within the scope of the concept of the present invention disclosed in this specification, within the scope equivalent to the above disclosure, and / or within the scope of the technology or knowledge in the art. Therefore, the foregoing detailed description of the present invention is not intended to limit the present invention to the disclosed embodiments. Moreover, the appended claims should be construed to also include other embodiments.

[0129] Description of Reference Numerals

[0130] C: Winding core

[0131] H: Hollow part of the core part

[0132] 100: Negative electrode

[0133] 101: Negative electrode current collector

[0134] 102, 103: Negative electrode active material layers

[0135] 10: Negative electrode coating part

[0136] 11: Negative electrode single-sided coating part

[0137] 12: Uncoated portion of the negative electrode

[0138] 20, 20': Separator

[0139] 300: Positive electrode

[0140] 301: Positive current collector

[0141] 302, 303: Positive active material layer

[0142] 310: Longitudinal end portion of the positive electrode

[0143] 40: Protection tape

[0144] 50: Negative tab

[0145] L1: Length of the coated portion of the negative electrode in the longitudinal direction

[0146] L1': Length of the single-sided coated portion of the negative electrode in the longitudinal direction

[0147] L2: Length of the uncoated portion of the negative electrode in the longitudinal direction

[0148] E1: First extension line

[0149] E2: Second extension line

[0150] 60: Battery case

[0151] 1: Electrode assembly

[0152] 2: Secondary battery

Claims

1. An electrode assembly, in which a negative electrode, a separator, and a positive electrode are sequentially stacked and wound, Among them, In the core part of the electrode assembly, The negative electrode includes: a negative electrode coating part, the negative electrode coating part includes a negative electrode current collector and a negative electrode active material layer provided on at least one surface of the negative electrode current collector; and a negative electrode uncoated part, the negative electrode uncoated part includes a negative electrode current collector on which the negative electrode active material layer is not provided, The negative electrode uncoated part does not include a negative electrode tab, and The length of the negative electrode coating part extending from the longitudinal end part of the positive electrode in the longitudinal direction is 2 turns or less from the longitudinal end part of the positive electrode.

2. The electrode assembly according to claim 1, wherein, The length of the negative electrode extending from the longitudinal end part of the positive electrode in the longitudinal direction is 0.5 turn or more and 2.3 turns or less from the longitudinal end part of the positive electrode.

3. The electrode assembly according to claim 1, wherein Based on the length of the negative electrode uncoated part extending from the end part of the negative electrode coating part being 100%, the length of the negative electrode coating part extending from the longitudinal end part of the positive electrode in the longitudinal direction is 150% or more and 650% or less.

4. The electrode assembly according to claim 1, wherein, Based on the weight of the negative electrode uncoated part extending from the end part of the negative electrode coating part being 100%, the weight of the negative electrode coating part extending from the longitudinal end part of the positive electrode is 500% or more and 2000% or less.

5. The electrode assembly according to claim 1, wherein The length of the negative electrode coating part extending from the longitudinal end part of the positive electrode in the longitudinal direction may be 5 mm or more and 15 mm or less.

6. The electrode assembly according to claim 1, wherein The negative electrode coating part includes a single-sided coating part, the single-sided coating part includes one surface of the negative electrode current collector provided with the negative electrode active material layer and another surface on which the negative electrode active material layer is not provided and the negative electrode current collector is directly exposed.

7. The electrode assembly according to claim 1, wherein, Based on the winding axis of the electrode assembly, the angle between the initial position of the longitudinal end part of the negative electrode and the position of the longitudinal end part of the negative electrode after additional charging and discharging 200 times or more at a temperature of 40 °C or higher is 5° or more.

8. The electrode assembly according to claim 1, wherein, Measure the initial position of the longitudinal end part of the negative electrode after activation.

9. The electrode assembly according to claim 1, wherein The positive electrode has a first surface in the direction of the winding axis of the electrode assembly and a second surface opposite to the first surface, and Wherein, a first extension line is drawn by extending a straight line connecting two points that change the curvature direction at a distance of 5 mm from the longitudinal end part of the positive electrode on the first surface of the positive electrode, and a second extension line is drawn by extending a straight line connecting two points at a distance of 5 mm from the longitudinal end part of the positive electrode on the surface of the negative electrode facing the first surface of the positive electrode, and an angle of 25° or less is formed between the first extension line and the second extension line.

10. The electrode assembly according to claim 1, wherein, In the core part of the electrode assembly, the positive electrode includes a positive electrode current collector and a positive electrode active material layer, and the positive electrode active material layer is disposed on at least one surface of the positive electrode current collector and has a longitudinal end portion at the same position as the positive electrode current collector.

11. A secondary battery, the secondary battery comprising: The electrode assembly according to any one of claims 1 to 10; And A battery case for housing the electrode assembly.

12. The secondary battery according to claim 11, wherein, The battery case has a cylindrical shape.

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