Electrode assembly and secondary battery including the same

Abstract

The present invention relates to an electrode assembly and a secondary battery including the same. The electrode assembly according to one embodiment of the present invention includes a positive electrode, a negative electrode, and a separator disposed between the positive electrode and the negative electrode. An avoidance recess may be formed in one of the positive electrode and the negative electrode, and the avoidance recess may be recessed in a region overlapping an end of the other of the positive electrode and the negative electrode.

Description

[Technical Field]

[0001] This application claims the benefit of priority based on Korean Patent Application No. 10-2022-0110314, filed on August 31, 2022, and all contents disclosed in the documents of that Korean patent application are incorporated herein by reference.

[0002] The present invention relates to an electrode assembly and a device including the same, and more particularly to an electrode assembly capable of improving stability and a secondary battery including the same. [Background technology]

[0003] In recent years, the demand for portable electronic products such as laptops, video cameras, and mobile phones has increased sharply, and the development of electric vehicles, energy storage batteries, robots, satellites, and other products has progressed in earnest. As a result, much research has been conducted on secondary batteries, which are used as the driving power sources for these products.

[0004] Secondary batteries are classified into coin-type batteries, cylindrical batteries, prismatic batteries, and pouch-type batteries depending on the shape of the battery case. The electrode assembly installed inside the battery case is a power generating element that can be charged and discharged and has a structure in which electrodes and a separator are stacked.

[0005] When a secondary battery including such an electrode assembly is repeatedly charged and discharged, stress caused by expansion and contraction of the electrodes accumulates inside the electrode assembly. If the accumulated stress exceeds a certain limit, deformation of the electrode assembly occurs, which may result in a decrease in the stability and performance defects of the battery. Summary of the Invention [Problem to be solved by the invention]

[0006] SUMMARY OF THE INVENTION An embodiment of the present invention provides an electrode assembly capable of improving stability and a secondary battery including the same.

[0007] The technical problems of the present invention are not limited to the technical problems mentioned above, and other technical problems not mentioned will be clearly understood by those skilled in the art from the following description. [Means for solving the problem]

[0008] An electrode assembly according to an embodiment of the present invention includes a positive electrode, a negative electrode, and a separator disposed between the positive electrode and the negative electrode. An avoidance recess may be formed in one of the positive electrode and the negative electrode, and the avoidance recess may be recessed in a region overlapping an end of the other of the positive electrode and the negative electrode.

[0009] According to one embodiment, the negative electrode has an avoidance recess formed in a region that overlaps with the winding longitudinal end portion of the positive electrode, and the avoidance recess may be recessed from an inner surface of the negative electrode facing the winding center portion of the electrode assembly toward an outer surface of the negative electrode facing the winding outer casing portion of the electrode assembly.

[0010] According to one embodiment, the negative electrode may include a first negative electrode active material layer facing the winding center, a second negative electrode active material layer facing the winding outer periphery, and a negative electrode current collector disposed between the first negative electrode active material layer and the second negative electrode active material layer, and the avoidance recess may be formed in the first negative electrode active material layer.

[0011] According to one embodiment, the avoidance recess may be formed in a recessed shape surrounded by the first negative electrode active material layer and the negative electrode current collector.

[0012] According to one embodiment, the negative electrode may include a first negative electrode active material layer facing the winding center and having a multilayer structure including a plurality of active material layers, a second negative electrode active material layer facing the winding outer periphery, and a negative electrode current collector disposed between the first negative electrode active material layer and the second negative electrode active material layer, and the avoidance recess may be formed in at least one of the plurality of active material layers.

[0013] According to one embodiment, the thickness of at least one of the plurality of active material layers may be thinner than the thickness of the second negative electrode active material layer.

[0014] According to one embodiment, the first negative electrode active material layer may include a first active material layer and a second active material layer, and the avoidance recess may be formed in at least one of the first active material layer and the second active material layer.

[0015] According to one embodiment, the avoidance recess may be formed in a recessed shape surrounded by the first active material layer and the second active material layer.

[0016] According to one embodiment, the avoidance recess may be formed in a recessed shape surrounded by a second active material layer formed on the negative electrode current collector and a second active material layer formed on the first active material layer.

[0017] According to one embodiment, the negative electrode has a concave avoidance recess formed along the width direction of the negative electrode so as to overlap with the winding longitudinal end portion of the positive electrode, and the concave avoidance recess may extend parallel to the width direction of the negative electrode.

[0018] According to one embodiment, the avoidance recess may include a first avoidance recess formed in the negative electrode located outside the winding vertical end portion of the positive electrode, and a second avoidance recess formed in the negative electrode located inside the winding vertical end portion of the positive electrode.

[0019] According to one embodiment, the first avoidance recess may be recessed from an inner surface of the negative electrode facing the winding center of the electrode assembly toward an outer surface of the negative electrode facing the winding outer casing of the electrode assembly, and the second avoidance recess may be recessed from the outer surface of the negative electrode toward the inner surface of the negative electrode.

[0020] According to one embodiment, the negative electrode may be formed to have different thicknesses in a region overlapping with the winding longitudinal end portion of the positive electrode and a region not overlapping with the winding longitudinal end portion of the positive electrode.

[0021] According to one embodiment, the negative electrode may be formed so that a region overlapping with the winding longitudinal end portion of the positive electrode has a smaller thickness than a region not overlapping with the winding longitudinal end portion of the positive electrode.

[0022] According to one embodiment, the negative electrode may include a first negative electrode active material layer facing a winding center of the electrode assembly, a second negative electrode active material layer facing a winding outer periphery of the electrode assembly, and a negative electrode current collector disposed between the first negative electrode active material layer and the second negative electrode active material layer. The negative electrode may include the negative electrode current collector in a region overlapping with a winding longitudinal end portion of the positive electrode, and may include at least one of the first negative electrode active material layer and the second negative electrode active material layer and the negative electrode current collector in a region not overlapping with the winding longitudinal end portion of the positive electrode.

[0023] A secondary battery according to an embodiment of the present invention may include the above-described electrode assembly. [Effects of the Invention]

[0024] According to an embodiment of the present invention, an avoidance recess may be formed in either the positive electrode or the negative electrode, which can prevent contact between the end of the positive electrode and the negative electrode.

[0025] Therefore, the present invention can reduce the direct contact stress that the winding longitudinal end of the positive electrode applies to the negative electrode, and can prevent cracks and breaks in the negative electrode, thereby improving cell performance degradation and ensuring stability.

[0026] In addition, various other effects can be provided that can be understood directly or indirectly through this document. [Brief explanation of the drawings]

[0027] [Figure 1] 1 is a perspective view showing a secondary battery including an electrode assembly according to a first embodiment of the present invention; [Figure 2] 2 is an exploded perspective view showing the electrode assembly shown in FIG. 1 in an unfolded state before being wound up. FIG. [Figure 3] 3 is a cross-sectional view showing in detail the winding longitudinal end portion regions of the negative electrode and the positive electrode after the electrode assembly shown in FIG. 2 has been wound. [Figure 4a]FIG. 4 is a perspective view showing the negative electrode shown in FIG. 3 in an unfolded state before being wound up. [Figure 4b] 4b is a cross-sectional view showing the state after the negative electrode and positive electrode included in region A of FIG. 4a have been wound up. FIG. [Figure 5] 10 is a cross-sectional view showing in detail the winding longitudinal end portion regions of a negative electrode and a positive electrode after the electrode assembly according to the second embodiment of the present invention has been wound. FIG. [Figure 6a] FIG. 6 is a perspective view showing the negative electrode shown in FIG. 5 in an unfolded state before being wound up. [Figure 6b] 6b is a cross-sectional view showing the state after the negative electrode and positive electrode included in region B of FIG. 6a have been wound up. FIG. [Figure 7] FIG. 10 is a cross-sectional view showing in detail the winding longitudinal end portion regions of the negative electrode and the positive electrode after the electrode assembly according to the third embodiment of the present invention has been wound. [Figure 8] 10 is a cross-sectional view showing in detail the winding longitudinal end portion regions of the negative electrode and the positive electrode after the electrode assembly according to the fourth embodiment of the present invention has been wound. FIG. DETAILED DESCRIPTION OF THE INVENTION

[0028] The present invention will be described in detail below with reference to the accompanying drawings, so that those skilled in the art can easily understand the preferred embodiments of the present invention. However, the present invention can be realized in various different forms and is not limited to the following embodiments.

[0029] In order to clearly explain the present invention, detailed descriptions of parts that are not relevant to the explanation or related known technologies that may obscure the gist of the present invention will be omitted, and when assigning reference symbols to components in each drawing in this specification, the same or similar reference symbols will be assigned to the same or similar components throughout the specification.

[0030] Furthermore, the terms and words used in this specification and claims should not be interpreted in a limited way to their ordinary or dictionary meanings, but should be interpreted in a way that is consistent with the technical idea of ​​the present invention, in accordance with the principle that an inventor can appropriately define the concept of a term in order to best explain his or her invention.

[0031] Secondary battery including electrode assembly according to first embodiment FIG. 1 is a perspective view showing a secondary battery including an electrode assembly according to a first embodiment of the present invention, and FIG. 2 is an exploded perspective view showing the electrode assembly shown in FIG. 1 in an unfolded state before being wound up.

[0032] Referring to FIGS. 1 and 2, a secondary battery 10 according to the present invention may include an electrode assembly 100 and a battery case 180.

[0033] The electrode assembly 100 can be housed inside the battery case 180. The battery case 180 may include a battery can 182 and a cap assembly 181.

[0034] The battery can 182 may include a receiving portion 183 that can receive the electrode assembly 100. An electrolyte may be poured into the receiving portion 183 so that the electrode assembly 100 is completely immersed in the battery can 182. The top of the battery can 182 may be open so that it can be used as an inlet passage for the electrode assembly 100. The battery can 182 may include a metal. For example, the battery can 182 may include stainless steel.

[0035] The battery can 182 accommodates the electrode assembly 100 and may be formed in a shape corresponding to the shape of the electrode assembly 100. For example, the battery can 182 may be formed in a cylindrical shape so as to accommodate the electrode assembly 100 formed in a jelly roll shape.

[0036] The cap assembly 181 may be mounted on the battery can 182 to cover the open top of the battery can 182 and coupled to the battery can 182. The cap assembly 181 may be formed by sequentially stacking a safety vent, a current interruption device, a positive temperature coefficient (PTC) device, a top cap, etc. The top cap is attached and coupled to the top of the cap assembly 181 and transmits current generated from the secondary battery to the outside.

[0037] One of the battery can 182 and the cap assembly 181 may be electrically connected to the positive electrode tab 250 of the electrode assembly 100, and the other of the battery can 182 and the cap 181 may be electrically connected to the negative electrode tab 260. As an example, the cap assembly 181 may be electrically connected to the positive electrode tab 250 by a welding process, and the bottom surface of the battery can 182 may be electrically connected to the negative electrode tab 260 by a welding process. As another example, one of the battery can 182 and the cap assembly 181 may be electrically connected to the positive electrode tab 250 and the negative electrode tab 260.

[0038] The electrode assembly 100 may be a chargeable / dischargeable power generating element. The electrode assembly 100 has a structure in which electrodes 130 and separators 160 are assembled and alternately stacked. The electrode assembly 100 may be formed in a form in which the electrodes 130 and separators 160 are assembled and wound up. The electrode assembly 100 may have a structure in which the diameter radially expands in proportion to the number of winding rotations. Here, the electrode assembly 100 may be wound up in a cylindrical shape around a winding center (or central axis) C. For example, the electrode 130 may include a positive electrode 110 and a negative electrode 120, and the separator 160 may include a first separator 140 and a second separator 150. The electrode assembly 100 may be a jelly-roll-shaped electrode assembly in which the positive electrode 110, the first separator 140, the negative electrode 120, and the second separator 150 are sequentially stacked and wound up in a cylindrical shape.

[0039] The positive electrode 110 may include a positive electrode current collector 113, a first positive electrode active material layer 111 formed on an inner surface of the positive electrode current collector 113 (e.g., a surface facing the winding center C), and a second positive electrode active material layer 112 formed on an outer surface of the positive electrode current collector 113 (e.g., a surface facing the winding outer shell portion O). The positive electrode 110 may not have a positive electrode non-coating portion formed on the winding outer shell portion O. At the winding outer shell portion O, the positive electrode current collector 113 may not protrude beyond the first positive electrode active material layer 111 and the second positive electrode active material layer 112.

[0040] For example, the positive electrode current collector 113 may be made of aluminum foil. At least one of the first positive electrode active material layer 111 and the second positive electrode active material layer 112 may be made of, for example, lithium manganese oxide, lithium cobalt oxide, lithium nickel oxide, lithium iron phosphate, or a compound or mixture containing one or more of these.

[0041] The negative electrode 120 may include a negative electrode current collector 123, a first negative electrode active material layer 121 formed on an inner surface 123a (e.g., a surface facing the winding center C) of the negative electrode current collector 123, and a second negative electrode active material layer 122 formed on an outer surface 123b (e.g., a surface facing the winding outer shell O) of the negative electrode current collector 123. The negative electrode 120 may be divided into a negative electrode coated portion (or coated portion) 125 and a negative electrode uncoated portion (or uncoated portion) depending on the positions where the first negative electrode active material layer 121 and the second negative electrode active material layer 122 are formed. The negative electrode coated portion 125 may be a region where the first negative electrode active material layer 121 and the second negative electrode active material layer 122 are formed. The negative electrode uncoated portion 126 may be a region where at least one of the first negative electrode active material layer 121 and the second negative electrode active material layer 122 is not formed. At least one negative electrode tab 260 may be fused onto the negative electrode current collector 123 of the negative electrode uncoated portion 126 by a method such as welding.

[0042] The negative electrode current collector 123 may be made of, for example, a foil containing copper (Cu) and / or nickel (Ni). At least one of the first negative electrode active material layer 121 and the second negative electrode active material layer 122 may be made of artificial graphite, lithium metal, a lithium alloy, carbon, petroleum coke, activated carbon, graphite, a silicon compound, a tin compound, a titanium compound, or an alloy thereof. At least one of the first negative electrode active material layer 121 and the second negative electrode active material layer 122 may contain, for example, non-graphite-based silica (SiO2) or silicon carbide (SiC).

[0043] Since the negative electrode 120 is formed to cover the positive electrode 110 during winding, the negative electrode 120 may be formed longer than the positive electrode 110. In the wound outer shell O of the electrode assembly 100, the first negative electrode active material layer 121 formed on the inner surface 123a of the negative electrode current collector 123 faces the positive electrode 110, whereas the second negative electrode active material layer 122 formed on the outer surface 123b of the negative electrode current collector 123 does not need to face the positive electrode 110. Therefore, in the wound outer shell O of the electrode assembly, the first negative electrode active material layer 121 may be formed longer than the second negative electrode active material layer 122. In the winding outer shell portion O of the electrode assembly, the end portion (e.g., winding vertical end portion) of the first negative electrode active material layer 121 may be positioned closer to the end portion (e.g., winding vertical end portion) of the negative electrode current collector 123 than the end portion (e.g., winding vertical end portion) of the second negative electrode active material layer 122.

[0044] The separator 160 is disposed between the positive electrode 110 and the negative electrode 120 to separate and electrically insulate the positive electrode 110 and the negative electrode 120. The separator 160 may include a first separator 140 and a second separator 150. The first separator 140 may be stacked on the outside of one of the positive electrode 110 and the negative electrode 120. The second separator 150 may be stacked on the outside of the other of the positive electrode 110 and the negative electrode 120. For example, when the first separator 140 is stacked on the outside of the positive electrode 110, the first separator 140 may be disposed between the second positive electrode active material layer 112 and the first negative electrode active material layer 121. When the second separator 150 is stacked on the outside of the negative electrode 120, the second separator 150 may be disposed between the first positive electrode active material layer 111 and the second negative electrode active material layer 122. Meanwhile, when a stack in which the positive electrode 110, the first separator 140, the negative electrode 120, and the second separator 150 are sequentially stacked is wound up, a jelly-roll type electrode assembly 100 is formed in which the second separator 150 is formed on the outermost surface.

[0045] At least one of the first separation membrane 140 and the second separation membrane 150 may be, for example, a multilayer film made of polyethylene, polypropylene, or a combination thereof, or a polymer film for a solid polymer electrolyte or a gel-type polymer electrolyte, such as polyvinylidene fluoride, polyethylene oxide, polyacrylonitrile, or polyvinylidene fluoride-hexafluoropropylene copolymer.

[0046] In the electrode assembly 100 according to the present invention, an avoidance recess (or a first avoidance recess) 200, which is an empty space, may be formed in at least one of the negative electrode 120 and the positive electrode 110. The avoidance recess 200 may be formed in one of the negative electrode 120 and the positive electrode 110. The avoidance recess 200 may be recessed in an area overlapping the other end of the negative electrode 120 and the positive electrode 110. For example, the avoidance recess 200 may be formed in a partial area of ​​the negative electrode 120 corresponding to the winding longitudinal end of the positive electrode 110.

[0047] Fig. 3 is a cross-sectional view showing in detail the winding longitudinal end portion CE of the negative electrode and the winding longitudinal end portion AE of the positive electrode after the electrode assembly shown in Fig. 2 has been wound, Fig. 4a is a perspective view showing the unfolded state of the negative electrode shown in Fig. 3 before being wound, and Fig. 4b is a cross-sectional view showing the state of the negative electrode and positive electrode included in region A of Fig. 4a after being wound. Meanwhile, Fig. 3 shows that the wound positive electrode 110, first separator 140, negative electrode 120, and second separator 150 are spaced apart, but the wound positive electrode 110, first separator 140, negative electrode 120, and second separator 150 may be in close contact with each other.

[0048] 3 and 4b, the negative electrode 120 may be formed to have different thicknesses in a region overlapping with the winding longitudinal end portion AE of the positive electrode 110 and a region not overlapping with the winding longitudinal end portion AE of the positive electrode 110. The negative electrode 120 may be formed so that the region overlapping with the winding longitudinal end portion AE of the positive electrode 110 is thinner than the region not overlapping with the winding longitudinal end portion AE of the positive electrode.

[0049] The negative electrode 120 may include at least one of a first negative electrode active material layer 121 and a second negative electrode active material layer 122, and a negative electrode current collector 123, in a region that does not overlap with the winding longitudinal end portion AE of the positive electrode 110. The negative electrode 120 may have a maximum thickness equivalent to the sum of the thicknesses of the first negative electrode active material layer 121, the second negative electrode active material layer 122, and the negative electrode current collector 123, in at least a portion of the region that does not overlap with the winding longitudinal end portion AE of the positive electrode 110.

[0050] The negative electrode 120 may be composed of a negative electrode current collector 123 in a region overlapping with the winding longitudinal end portion AE of the positive electrode 110. The negative electrode 120 may have a thickness thinner than the maximum thickness in a region overlapping with the winding longitudinal end portion AE of the positive electrode 110. The negative electrode 120 may have a thickness corresponding to the thickness of the negative electrode current collector 123 in a region overlapping with the winding longitudinal end portion AE of the positive electrode 110. The negative electrode 120 may have an avoidance recess 200 formed therein that overlaps with the winding longitudinal end portion AE of the positive electrode 110. The avoidance recess 200 may be recessed from the inner surface of the negative electrode 120 facing the winding center portion C toward the outer surface of the negative electrode 120 facing the winding outer shell portion O. The avoidance recess 200 may be formed by recessing the first negative electrode active material layer 121 that faces the winding longitudinal end portion AE of the positive electrode 110 on the outside. Since the first anode active material layer 121 is not formed in the avoidance recess 200, the anode current collector 123 can face the first separator 140 overlapping the avoidance recess 200. The avoidance recess 200 may be formed in a concave shape surrounded by the first anode active material layer 121 and the anode current collector 123. A part of the avoidance recess 200 may be open toward the first separator 140, and the remaining part of the avoidance recess 200 may be surrounded by the anode current collector 123 and the first anode active material layer 121. In the avoidance recess 200, the anode current collector 123 may form a step with the first anode active material layer 121.

[0051] 4a, the avoidance recess 200 may be formed in a concave shape along the width direction of the negative electrode 120 so as to overlap with the winding longitudinal end portion of the positive electrode 110. The concave avoidance recess 200 may extend parallel to the width direction of the negative electrode 120.

[0052] The avoidance recess 200 increases the separation distance between the winding vertical end portion AE of the positive electrode 110 and the negative electrode 120. In a comparative example in which the avoidance recess 200 is not formed, the winding vertical end portion AE of the positive electrode 110 and the negative electrode 120 may be separated by a separation distance S1 (e.g., the thickness of the first separator 140) between the first negative electrode active material layer 121 and the winding vertical end portion AE of the positive electrode 110. In contrast, in an embodiment in which the avoidance recess 200 is formed, the winding vertical end portion AE of the positive electrode 110 and the negative electrode 120 may be separated by a separation distance S2 (e.g., the sum of the thickness of the first separator 140 and the thickness of the first negative electrode active material layer 121) between the first current collector 123 and the winding vertical end portion AE of the positive electrode 110. As a result, in the embodiment in which the avoidance recess 200 is formed, the distance between the winding vertical end portion AE of the positive electrode 110 and the negative electrode 120 is further increased by the thickness of the first negative electrode active material layer 121 compared to the comparative example in which the avoidance recess 200 is not formed.

[0053] Such avoidance recess 200 can prevent contact between the winding longitudinal end portion AE of the positive electrode 110 and the negative electrode 120. That is, the winding longitudinal end portion AE of the wound positive electrode 110 can be prevented from directly contacting the first negative electrode active material layer 121 by the avoidance recess 200, as shown in FIG. 4b. In the wound electrode assembly, the winding longitudinal end portion AE of the positive electrode 110 can be prevented from contacting the negative electrode 120. As a result, the present invention can reduce direct contact stress caused by the winding longitudinal end portion AE of the positive electrode 110, and prevent cracks and breaks in the negative electrode 120.

[0054] Electrode assembly according to a second embodiment Fig. 5 is a cross-sectional view showing in detail the winding longitudinal end regions of the negative electrode and the positive electrode after the electrode assembly according to the second embodiment of the present invention has been wound, Fig. 6a is a perspective view showing the unfolded state of the negative electrode shown in Fig. 5 before being wound, and Fig. 6b is a cross-sectional view showing the state of the negative electrode and the positive electrode included in region B of Fig. 6a after being wound. Meanwhile, Fig. 5 shows that the wound positive electrode 110, first separator 140, negative electrode 120, and second separator 150 are spaced apart, but the wound positive electrode 110, first separator 140, negative electrode 120, and second separator 150 may be in close contact with each other.

[0055] 5 and 6b, the electrode assembly according to the second embodiment of the present invention may include a negative electrode 120, a positive electrode 110, a first separator 140, and a second separator 150. The negative electrode 120 may include a first negative electrode active material layer 121, a negative electrode current collector 123, and a second negative electrode active material layer 122.

[0056] The first negative electrode active material layer 121 may be formed so that its inner surface faces the winding center C and its outer surface faces the winding outer shell O. The first negative electrode active material layer 121 may be formed in a multi-layer structure including a plurality of active material layers. An avoidance recess 200 may be formed in at least one of the plurality of active material layers.

[0057] For example, the first negative electrode active material layer 121 may include a first active material layer 121a and a second active material layer 121b. The first active material layer 121a may be formed by coating on the negative electrode current collector 123. The first active material layer 121a may be formed to a first thickness d1 that is thinner than the second negative electrode active material layer 122. The first active material layer 121a may be formed of the same material as the second active material layer 121b, or may be formed of a different material.

[0058] The second active material layer 121b may be formed on the first active material layer 121a by coating it over an area larger than that of the first active material layer 121a. The second active material layer 121b may be formed to a second thickness d2 that is thinner than that of the second negative electrode active material layer 122. The second thickness d2 may be the same as or different from the first thickness d1. The sum T1 of the first thickness d1 of the second active material layer 121a and the second thickness d2 of the first active material layer 121b may be the same as or approximately the same as the thickness T2 of the second negative electrode active material layer 122.

[0059] An avoidance recess 200 may be formed in either the first active material layer 121a or the second active material layer 121b, corresponding to the winding longitudinal end portion AE of the positive electrode 110. The avoidance recess 200 may be formed in a concave shape so as to have an empty space in a region corresponding to the winding longitudinal end portion AE of the positive electrode 110.

[0060] The avoidance recess 200 may be formed by recessing the first active material layer 121a that faces the winding vertical end portion AE of the positive electrode 110 and the outer side facing the winding outer shell portion O. The first active material layer 121a may be formed in at least a portion of the region excluding the avoidance recess 200. The first active material layer 121a does not have to be formed in the avoidance recess 200. A portion of the second active material layer 121b may be formed on the negative electrode current collector 123 corresponding to the avoidance recess 200. At least a portion of the remainder of the second active material layer 121b may be formed on the first active material layer 121a. The second active material layer 121b may face the first separator 140 that overlaps the avoidance recess 200. The avoidance recess 200 may be formed in a concave shape surrounded by the second active material layer 121b formed on the negative electrode current collector 123 and the second active material layer 121b formed on the first active material layer 121a. A part of the avoidance recess 200 may be open toward the first separation membrane 140, and the remaining part of the avoidance recess 200 may be surrounded by the second active material layer 121b. The second active material layer 121b arranged in the avoidance recess 200 may form a step with the second active material layer 121b arranged on the first active material layer 121a.

[0061] Such avoidance recesses 200 increase the separation distance between the winding vertical end portion AE of the positive electrode 110 and the negative electrode 120. In a comparative example in which the avoidance recesses 200 are not formed, the winding vertical end portion AE of the positive electrode 110 and the negative electrode 120 may be separated by a separation distance S1 (e.g., at least the thickness of the first separator 140) between the first negative electrode active material layer 121 and the winding vertical end portion AE of the positive electrode 110. In contrast, in an embodiment in which the avoidance recesses 200 are formed, the winding vertical end portion AE of the positive electrode 110 and the negative electrode 120 may be separated by a separation distance S2 (e.g., the sum of the thickness of the first active material layer 121a or the second active material layer 121b and the thickness of the first separator 140) between the first active material layer 121a or the second active material layer 121b and the winding vertical end portion AE of the positive electrode 110. As a result, in the embodiment in which the avoidance recess 200 is formed, the distance between the winding vertical end portion AE of the positive electrode 110 and the negative electrode 120 is further increased by the thickness of the first active material layer 121a or the second active material layer 121b compared to the comparative example in which the avoidance recess 200 is not formed.

[0062] The avoidance recess 200, which increases the separation distance between the winding longitudinal end portion AE of the positive electrode 110 and the negative electrode 120, can prevent contact between the winding longitudinal end portion AE of the positive electrode and the negative electrode 120. That is, as shown in FIG. 6b, the winding recess 200 can prevent direct contact between the winding longitudinal end portion AE of the positive electrode 110 and the first negative electrode active material layer 121 in the wound electrode assembly. In the wound electrode assembly, the winding longitudinal end portion AE of the positive electrode 110 can be prevented from contacting the negative electrode 120. As a result, the present invention can reduce direct contact stress caused by the winding longitudinal end portion AE of the positive electrode 110 and prevent cracks and breaks in the negative electrode 120 due to the contact stress.

[0063] The second active material layer 121b and the negative electrode current collector 123 may be formed in a region overlapping with the winding longitudinal end portion AE of the positive electrode 110. The negative electrode 120 can stably supply an electric signal (e.g., current) in the region overlapping with the winding longitudinal end portion AE of the positive electrode 110 via the negative electrode current collector 123 and the second negative electrode active material layer 121b.

[0064] Electrode assembly according to a third embodiment 7 is a cross-sectional view showing in detail the winding longitudinal end portions of the negative electrode and the positive electrode after the electrode assembly according to the third embodiment of the present invention has been wound. In FIG. 7, the wound positive electrode 110, first separator 140, negative electrode 120, and second separator 150 are shown spaced apart, but the wound positive electrode 110, first separator 140, negative electrode 120, and second separator 150 may be in close contact with each other.

[0065] 7, the electrode assembly according to the third embodiment of the present invention may have the same components as the electrode assemblies shown in FIGS. 5 and 6b, except that the avoidance recesses 200 are formed in the second active material layer 121b. Therefore, detailed descriptions of the same components will be omitted.

[0066] As shown in FIG. 7 , the avoidance recess 200 may be formed by recessing the second active material layer 121b that faces the winding longitudinal end portion AE of the positive electrode 110 and the outer side facing the winding outer shell portion O. The first active material layer 121a may be formed on the negative electrode current collector 123 with a larger area than the second active material layer 121b. The second active material layer 121b may be formed on the first active material layer 121a except for the region corresponding to the avoidance recess 200. The second active material layer 121b may face the first separator 140 that overlaps with the avoidance recess 200. The avoidance recess 200 may be formed in a concave shape surrounded by the first active material layer 121a and the second active material layer 121b. A portion of the avoidance recess 200 may be open toward the first separator 140, and the remaining portion of the avoidance recess 200 may be surrounded by the first active material layer 121a and the second active material layer 121b. The first active material layer 121a disposed in the avoidance recess 200 may form a step with the second active material layer 121b disposed on the first active material layer 121a.

[0067] Such avoidance recess 200 can prevent contact between the winding longitudinal end portion AE of the positive electrode and the negative electrode 120. That is, in the wound electrode assembly, the avoidance recess 200 can prevent direct contact between the winding longitudinal end portion AE of the positive electrode 110 and the first negative electrode active material layer 121. In the wound electrode assembly, the winding longitudinal end portion AE of the positive electrode 110 can be prevented from contacting the negative electrode 120. As a result, the present invention can reduce direct contact stress caused by the winding longitudinal end portion AE of the positive electrode 110, and prevent cracks and breaks in the negative electrode 120.

[0068] Electrode assembly according to a fourth embodiment 8 is a cross-sectional view showing in detail the winding longitudinal end portions of the negative electrode and the positive electrode after the electrode assembly according to the fourth embodiment of the present invention has been wound. In FIG. 8, the wound positive electrode 110, first separator 140, negative electrode 120, and second separator 150 are shown spaced apart, but the wound positive electrode 110, first separator 140, negative electrode 120, and second separator 150 may be in close contact with each other.

[0069] 8, the electrode assembly according to the fourth embodiment of the present invention may have the same components as the electrode assembly shown in Figures 3 and 4b, except that it further includes a second avoidance recess 300. Therefore, detailed description of the same components will be omitted.

[0070] The negative electrode 120 may have a first avoidance recess 200 and a second avoidance recess 300. The first avoidance recess 200 may be formed in a portion of the negative electrode 120 located outside the winding longitudinal end portion AE of the positive electrode 110. The first avoidance recess 200 may be recessed from the inner surface of the negative electrode 120 facing the winding center portion C toward the outer surface of the negative electrode 120 facing the winding outer shell portion O. For example, the first avoidance recess 200 may be recessed from the inner surface of the first negative electrode active material layer 121 facing the winding center portion C toward the negative electrode current collector 123 facing the winding outer shell portion O. The first avoidance recess 200 may be formed by recessing the first negative electrode active material layer 121 toward the negative electrode current collector 123. The first avoidance recess 200 can prevent contact between the negative electrode 120 and the second positive electrode active material layer 112 that forms at least a portion of the outside of the winding longitudinal end portion AE of the positive electrode 110. That is, in the wound electrode assembly, the first avoidance recess 200 can prevent direct contact between the outside of the winding longitudinal end portion AE of the positive electrode 110 and the negative electrode 120.

[0071] The second avoidance recess 300 may be formed in the negative electrode 120 located inside the winding longitudinal end portion AE of the positive electrode 110. The second avoidance recess 300 may be recessed from the outer surface of the negative electrode 120 facing the winding outer shell portion O toward the inner surface of the negative electrode 120 facing the winding central portion C. The second avoidance recess 300 may be recessed from the outer surface of the second negative electrode active material layer 122 facing the winding outer shell portion O toward the inner surface of the first negative electrode active material layer 121 facing the winding central portion C. The second avoidance recess 300 may be formed by recessing the second negative electrode active material layer 122 toward the negative electrode current collector 123. The second avoidance recess 300 can prevent contact between the negative electrode 120 and the first positive electrode active material layer 111 that forms at least a part of the inside of the winding longitudinal end portion AE of the positive electrode 110. That is, in the wound electrode assembly, the second avoidance recess 300 can prevent direct contact between the inside of the winding longitudinal end portion AE of the positive electrode 110 and the negative electrode 120.

[0072] In this way, in the wound electrode assembly, the inner and outer sides of the winding longitudinal end portion AE of the positive electrode 110 can be prevented from contacting the negative electrode 120. As a result, the present invention can reduce direct contact stress that the winding longitudinal end portion AE of the positive electrode 110 applies to the negative electrode 120, and prevent cracks and breaks in the negative electrode 120 due to the direct contact stress.

[0073] The electrode assembly described above is not limited to the embodiments shown in the drawings, and the structures shown in the drawings may be combined. A secondary battery according to the present invention may employ a plurality of electrode assemblies shown in FIG. 3, a plurality of electrode assemblies shown in FIG. 5, a plurality of electrode assemblies shown in FIG. 7, a plurality of electrode assemblies shown in FIG. 8, or a combination of any one of the electrode assemblies shown in FIGS. 3, 5, 7, and 8 and at least one of the electrode assemblies shown in the remaining drawings. The avoidance recess according to the present invention may be disposed not only in the outer winding portion but also in the intermediate winding portion and the winding portion located between the outer winding portion and the winding portion. The avoidance recess according to the present invention may be employed in the negative electrode, the positive electrode, or a combination of the positive and negative electrodes. While the electrode assembly according to the present invention has been described using a structure applied to a cylindrical secondary battery as an example, the present invention is not limited thereto and may also be applied to a pouch-type battery or a prismatic battery.

[0074] The secondary battery including the electrode assembly described above can be applied to various devices, including, but not limited to, transportation means such as electric bicycles, electric cars, and hybrid vehicles, and can be applied to various devices that can use a battery module.

[0075] Although the present invention has been described above using limited embodiments and drawings, the present invention is not limited thereto, and various implementations within the technical spirit of the present invention and the scope of equivalents of the appended claims can be made by a person having ordinary skill in the art to which the present invention pertains. [Explanation of symbols]

[0076] 100 electrode assembly 110 Positive electrode 120 negative electrode 140 First separation membrane 150 Second separation membrane 200 Avoidance recess

Claims

1. a positive electrode and a negative electrode; a separator disposed between the positive electrode and the negative electrode, an avoidance recess is formed in one of the positive electrode and the negative electrode; The avoidance recess is formed by being recessed in a region overlapping an end of the other of the positive electrode and the negative electrode.

2. The negative electrode has an avoidance recess formed in a region that overlaps with the winding longitudinal end portion of the positive electrode, The avoidance recess is The electrode assembly of claim 1 , wherein the negative electrode is recessed from an inner surface of the negative electrode facing the winding center of the electrode assembly to an outer surface of the negative electrode facing the winding outer shell of the electrode assembly.

3. The negative electrode is a first negative electrode active material layer facing the winding center; a second negative electrode active material layer facing the outer winding portion; a negative electrode current collector disposed between the first negative electrode active material layer and the second negative electrode active material layer, The electrode assembly of claim 2 , wherein the avoidance recess is formed in the first negative electrode active material layer.

4. The electrode assembly according to claim 3 , wherein the avoidance recess is formed in a recessed shape surrounded by the first negative electrode active material layer and the negative electrode current collector.

5. The negative electrode is a first negative electrode active material layer having a multilayer structure including a plurality of active material layers and facing the winding center; a second negative electrode active material layer facing the outer winding portion; a negative electrode current collector disposed between the first negative electrode active material layer and the second negative electrode active material layer, The electrode assembly according to claim 2 , wherein the avoidance recess is formed in at least one of the plurality of active material layers.

6. The electrode assembly of claim 5 , wherein at least one of the plurality of active material layers has a thickness smaller than a thickness of the second negative electrode active material layer.

7. the first negative electrode active material layer includes a first active material layer and a second active material layer, The avoidance recess is The electrode assembly of claim 5 , wherein the conductive layer is formed on at least one of the first active material layer and the second active material layer.

8. The avoidance recess is The electrode assembly according to claim 7 , wherein the first active material layer and the second active material layer form a recess surrounded by the first active material layer and the second active material layer.

9. The avoidance recess is The electrode assembly of claim 7 , wherein the negative electrode current collector is formed in a recessed shape surrounded by the second active material layer formed on the negative electrode current collector and the second active material layer formed on the first active material layer.

10. the negative electrode has an avoidance recess formed in a recessed shape along the width direction of the negative electrode so as to overlap with a winding longitudinal end portion of the positive electrode, The electrode assembly according to claim 1 , wherein the concave avoidance recess extends parallel to the width direction of the negative electrode.

11. The avoidance recess is a first avoidance recess formed in the negative electrode located outside a winding longitudinal end portion of the positive electrode; The electrode assembly according to claim 1 , further comprising: a second avoidance recess formed in the negative electrode located inside a winding longitudinal end portion of the positive electrode.

12. The first avoidance recessed portion is a recess from an inner surface of the negative electrode facing the winding center of the electrode assembly to an outer surface of the negative electrode facing the winding outer shell of the electrode assembly; The second avoidance recessed portion is The electrode assembly of claim 11 , wherein the negative electrode is recessed from an outer surface thereof toward an inner surface thereof.

13. The negative electrode is The electrode assembly according to claim 1 , wherein the electrode assembly is formed so that a region overlapping the winding longitudinal end portion of the positive electrode and a region not overlapping the winding longitudinal end portion of the positive electrode have different thicknesses.

14. The negative electrode is The electrode assembly according to claim 13 , wherein a region overlapping with the winding longitudinal end of the positive electrode is formed to have a thickness smaller than a region not overlapping with the winding longitudinal end of the positive electrode.

15. The negative electrode is a first negative electrode active material layer facing the winding center of the electrode assembly; a second negative electrode active material layer facing a wound outer shell of the electrode assembly; a negative electrode current collector disposed between the first negative electrode active material layer and the second negative electrode active material layer, The negative electrode is the negative electrode current collector in a region overlapping with a winding longitudinal end portion of the positive electrode, 14. The electrode assembly according to claim 13, comprising at least one of the first negative electrode active material layer and the second negative electrode active material layer and the negative electrode current collector in a region that does not overlap with a winding longitudinal end portion of the positive electrode.

16. A secondary battery comprising the electrode assembly according to any one of claims 1 to 15.

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