Electrode assembly and secondary battery including the same

Abstract

The present invention relates to an electrode assembly and a secondary battery including the same. An electrode assembly according to one embodiment of the present invention comprises a positive electrode and a negative electrode; and a separator disposed between the positive electrode and the negative electrode. An avoidance depression is formed in either the positive electrode or the negative electrode, and the avoidance depression may be formed to be depressed in an area that overlaps with the end of the other electrode among the positive electrode and the negative electrode.

Description

Technology Field

[0001] The present invention relates to an electrode assembly and a device including the same, and more specifically, to an electrode assembly capable of improving stability and a secondary battery including the same. Background Technology

[0002] Recently, as the demand for portable electronic products such as laptops, video cameras, and mobile phones has increased rapidly, and the development of electric vehicles, energy storage batteries, robots, and satellites has accelerated, much research is being conducted on secondary batteries used as their power sources.

[0003] Secondary batteries are classified into coin batteries, cylindrical batteries, prismatic batteries, and pouch batteries according to the shape of the battery case. The electrode assembly mounted inside the battery case is a rechargeable power generation device consisting of a stacked structure of electrodes and separators.

[0004] When charge and discharge cycles of a secondary battery containing such an electrode assembly are repeatedly performed, stress caused by the expansion and contraction of the electrodes may accumulate within the electrode assembly. If the stress accumulation exceeds a certain limit, deformation of the electrode assembly occurs, which may lead to reduced battery stability and performance defects. The problem to be solved

[0005] An embodiment of the present invention aims to provide an electrode assembly capable of improving stability and a secondary battery including the same.

[0006] The technical problems of the present invention are not limited to those mentioned above, and other unmentioned technical problems will be clearly understood by a person skilled in the art from the description below. means of solving the problem

[0007] An electrode assembly according to one embodiment of the present invention comprises an anode and a cathode; and a separator disposed between the anode and the cathode, wherein an avoidance depression is formed in either of the anode and the cathode, and the avoidance depression may be formed to be depressed in an area overlapping with the end of the other electrode among the anode and the cathode.

[0008] According to one embodiment, the cathode has a recessed area formed therein that overlaps with the winding end portion of the anode, and the recessed area may be recessed from the inner surface of the cathode facing the winding center of the electrode assembly toward the outer surface of the cathode facing the winding outer portion of the electrode assembly.

[0009] According to one embodiment, the cathode comprises a first cathode active material layer facing the center of the winding; a second cathode active material layer facing the outer edge of the winding; and a cathode current collector disposed between the first cathode active material layer and the second cathode active material layer, and the avoidance depression may be formed in the first cathode active material layer.

[0010] According to one embodiment, the avoidance depression may be formed in the shape of a groove surrounded by the first cathode active material layer and the cathode current collector.

[0011] According to one embodiment, the cathode is oriented toward the center of the winding and comprises a first cathode active material layer having a multilayer structure including a plurality of active material layers; a second cathode active material layer oriented toward the outer edge of the winding; and a cathode current collector disposed between the first cathode active material layer and the second cathode active material layer, wherein the avoidance depression may be formed in at least one of the plurality of active material layers.

[0012] 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 active material layer.

[0013] According to one embodiment, the first negative electrode active material layer includes a first active material layer and a second active material layer, and the avoidance depression may be formed in at least one of the first active material layer and the second active material layer.

[0014] According to one embodiment, the avoidance depression may be formed in the shape of a groove surrounded by the first active material layer and the second active material layer.

[0015] According to one embodiment, the avoidance depression may be formed in the shape of a groove surrounded by a second active material layer formed on the negative current collector and a second active material layer formed on the first active material layer.

[0016] According to one embodiment, the avoidance recess is formed in a groove shape along the width direction of the cathode so as to overlap with the winding end portion of the anode, and the groove-shaped avoidance recess can extend parallel to the width direction of the cathode.

[0017] According to one embodiment, the avoidance depression may include a first avoidance depression formed on the cathode located outside the winding end of the anode, and a second avoidance depression formed on the cathode located inside the winding end of the anode.

[0018] According to one embodiment, the first avoidance depression is depressed from the inner surface of the cathode facing the center of the winding of the electrode assembly toward the outer surface of the cathode facing the outer part of the winding of the electrode assembly, and the second avoidance depression can be depressed from the outer surface of the cathode toward the inner surface of the cathode.

[0019] According to one embodiment, the cathode may be formed with different thicknesses in the region overlapping with the winding end of the anode and in the region not overlapping with the winding end of the anode.

[0020] According to one embodiment, the cathode may be formed such that the region overlapping with the winding end of the anode has a thinner thickness than the region not overlapping with the winding end of the anode.

[0021] According to one embodiment, the cathode comprises a first cathode active material layer facing the center of the winding of the electrode assembly; a second cathode active material layer facing the outer edge of the winding of the electrode assembly; and a cathode current collector disposed between the first cathode active material layer and the second cathode active material layer, wherein the cathode is formed by the cathode current collector in an area overlapping with the end of the winding of the anode, and may be formed by at least one of the first cathode active material layer and the second cathode active material layer and the cathode current collector in an area not overlapping with the end of the winding of the anode.

[0022] A secondary battery according to one embodiment of the present invention may include the aforementioned electrode assembly. Effects of the invention

[0023] According to embodiments of the present invention, an avoidance depression may be formed on either the positive electrode or the negative electrode. Contact between the end of the positive electrode and the negative electrode may be avoided by the avoidance depression. Accordingly,

[0024] Accordingly, the present invention can reduce the direct contact stress applied by the winding end of the anode to the cathode, thereby preventing cracking and disconnection of the cathode, and thus can improve cell performance degradation and ensure stability.

[0025] In addition, various effects that can be identified directly or indirectly through this document may be provided. Brief explanation of the drawing

[0026] FIG. 1 is a perspective view showing a secondary battery including an electrode assembly according to a first embodiment of the present invention. FIG. 2 is an exploded perspective view showing the electrode assembly illustrated in FIG. 1 in an unfolded state before being wound. FIG. 3 is a cross-sectional view showing in detail the winding end portion of the negative electrode and the winding end portion of the positive electrode after the electrode assembly shown in FIG. 2 is wound. FIG. 4a is a perspective view showing the unfolded state of the cathode shown in FIG. 3 before it is wound, and FIG. 4b is a cross-sectional view showing the cathode included in region A of FIG. 4a and the state after the anode is wound. FIG. 5 is a cross-sectional view showing in detail the winding end portion of the negative electrode and the winding end portion of the positive electrode after the electrode assembly according to the second embodiment of the present invention is wound. FIG. 6a is a perspective view showing the unfolded state of the cathode shown in FIG. 5 before it is wound, and FIG. 6b is a cross-sectional view showing the cathode included in region B of FIG. 6a and the state after the anode is wound. FIG. 7 is a cross-sectional view showing in detail the winding end portion of the negative electrode and the winding end portion of the positive electrode after the electrode assembly according to the third embodiment of the present invention is wound. FIG. 8 is a cross-sectional view showing in detail the winding end portion of the negative electrode and the winding end portion of the positive electrode after the electrode assembly according to the fourth embodiment of the present invention is wound. Specific details for implementing the invention

[0027] Hereinafter, preferred embodiments of the present invention are described in detail with reference to the attached drawings so that those skilled in the art can easily implement the present invention. However, the present invention may be embodied in various different forms and is not limited or restricted by the following embodiments.

[0028] In order to clearly explain the present invention, detailed descriptions of related prior art that are irrelevant to the explanation or that may unnecessarily obscure the essence of the invention have been omitted. Furthermore, when assigning reference numerals to the components of each drawing in this specification, identical or similar reference numerals are assigned to identical or similar components throughout the entire specification.

[0029] Furthermore, terms and words used in this specification and claims should not be interpreted as being limited to their ordinary or dictionary meanings, but should be interpreted in a meaning and concept consistent with the technical spirit of the invention, based on the principle that the inventor can appropriately define the concept of the terms to best describe his invention.

[0031] A secondary battery comprising an electrode assembly according to the first embodiment

[0032] 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.

[0033] Referring to FIGS. 1 and FIGS. 2, a secondary battery (10) according to the present invention may include an electrode assembly (100) and a battery case (180).

[0034] An electrode assembly (100) may be accommodated within a battery case (180). The battery case (180) may include a battery can (182) and a cap assembly (181).

[0035] The battery can (182) may include a receiving portion (183) in which an electrode assembly (100) can be received. Electrolyte may be injected into the receiving portion (183) so that the electrode assembly (100) is completely immersed within the battery can (182). The top of the battery can (182) may be open so as to be used as an inflow passage for the electrode assembly (100). The battery can (182) may include metal. For example, the battery can (182) may include stainless steel.

[0036] Since the battery can (182) accommodates the electrode assembly (100), it can be formed in a shape corresponding to the shape of the electrode assembly (100). For example, the battery can (182) can be formed in a cylindrical shape so as to accommodate the electrode assembly (100) formed in a jelly-roll shape.

[0037] A cap assembly (181) can be mounted on a battery can (182) to cover the open top of the battery can (182) and combined with the battery can (182). The cap assembly (181) may be formed by sequentially stacking a safety vent, a current cutoff element, a positive temperature coefficient (PTC) element, and a top cap. The top cap is seated and combined on the top of the cap assembly (181) and transmits the current generated from the secondary battery to the outside.

[0038] Either one of the battery can (182) and the cap assembly (181) may be electrically connected to the positive 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 tab (260). For example, the cap assembly (181) may be electrically connected to the positive tab (250) through a welding process, and the bottom surface of the battery can (182) may be electrically connected to the negative tab (260) through a welding process. As another example, either one of the battery can (182) and the cap assembly (181) may be electrically connected to the positive tab (250) and the negative tab (260).

[0039] The electrode assembly (100) may be a power generation device capable of charging and discharging. The electrode assembly (100) forms a structure in which electrodes (130) and separators (160) are assembled and alternately stacked. The electrode assembly (100) may be formed in a wound form in which electrodes (130) and separators (160) are alternately assembled. The electrode assembly (100) may have a structure in which the diameter expands radially in proportion to the number of winding rotations. At this time, the electrode assembly (100) may be wound in a cylindrical shape centered on the 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 an anode (110), a first separator (140), a cathode (120), and a second separator (150) are sequentially stacked and wound into a cylindrical shape.

[0040] The positive electrode (110) may include a positive electrode current collector (113), a first positive electrode active material layer (111) formed on the inner surface of the positive electrode current collector (113) (e.g., the surface facing the center of the winding (C)), and a second positive electrode active material layer (112) formed on the outer surface of the positive electrode current collector (113) (e.g., the surface facing the outer part of the winding (O). The positive electrode (110) may not have a positive electrode-free portion formed on the outer part of the winding (O). On the outer part of the winding (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 (111).

[0041] For example, the positive current collector (113) may be made of aluminum foil. At least one of the first positive active material layer (111) and the second positive 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 and mixture containing one or more of these.

[0042] The cathode (120) may include a cathode current collector (123), a first cathode active material layer (121) formed on the inner surface (e.g., the surface facing the center of the winding (C)) (123a) of the cathode current collector (123), and a second cathode active material layer (122) formed on the outer surface (e.g., the surface facing the outer edge of the winding (O)) (123b) of the cathode current collector (123). The cathode (120) may be divided into a cathode coated portion (or retaining portion) (125) and a cathode uncoated portion (or uncoated portion) depending on the formation location of the first cathode active material layer (121) and the second cathode active material layer (122). The cathode coated portion (125) may be an area where the first cathode active material layer (121) and the second cathode active material layer (122) are formed. The negative electrode unoccupied portion (126) may be an area 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 unoccupied portion (126) by a method such as welding.

[0043] The negative electrode current collector (123) may be made of a foil, for example, a copper (Cu) or / and nickel (Ni) material. 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, lithium alloy, carbon, petroleum coke, activated carbon, graphite, silicon compound, tin compound, 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 SiO (silica) or SiC (silicon carbide).

[0044] Since the negative electrode (120) is formed to surround the positive electrode (110) during winding, the negative electrode (120) can be formed longer than the positive electrode (110). At the outer winding portion (O) of the electrode assembly (100), the first negative active material layer (121) formed on the inner surface (123a) of the negative current collector (123) faces the positive electrode (110), whereas the second negative active material layer (122) formed on the outer surface (123b) of the negative current collector (123) may not face the positive electrode (110). Accordingly, at the outer winding portion (O) of the electrode assembly, the first negative active material layer (121) can be formed longer than the second negative active material layer (122). At the outer winding portion (O) of the electrode assembly, the end (e.g., winding end) of the first negative active material layer (121) may be positioned closer to the end (e.g., winding end) of the negative current collector (123) than to the end (e.g., winding end) of the second negative active material layer (122).

[0045] A separator (160) may be disposed between an anode (110) and a cathode (120) to separate the anode (110) and the cathode (120) and to electrically insulate them. The separator (160) may include a first separator (140) and a second separator (150). The first separator (140) may be laminated on the outside of either the anode (110) or the cathode (120). The second separator (150) may be laminated on the outside of the other of the anode (110) and the cathode (120). For example, when the first separator (140) is laminated on the outside of the anode (110), the first separator (140) may be disposed between the second anode active material layer (112) and the first cathode active material layer (121). When the second separator (150) is laminated on the outside of the cathode (120), the second separator (150) may be placed between the first positive active material layer (111) and the second negative active material layer (122). Meanwhile, when a laminate in which the positive electrode (110), the first separator (140), the cathode (120), and the second separator (150) are laminated in order is wound, a jelly roll type electrode assembly (100) in which the second separator (150) is formed on the outermost surface may be formed.

[0046] At least one of the first separator (140) and the second separator (150) may be a multilayer film made of, for example, 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.

[0047] In the electrode assembly (100) according to the present invention, an avoidance recess (or, first avoidance recess) (200), which is an empty space, may be formed in at least one of the cathode (120) and the anode (110). The avoidance recess (200) may be formed in either the cathode (120) or the anode (110). The avoidance recess (200) may be formed to be recessed in an area that overlaps with the end of the other one of the cathode (120) and the anode (110). For example, the avoidance recess (200) may be formed in a part of the cathode (120) corresponding to the winding end of the anode (110).

[0048] FIG. 3 is a cross-sectional view showing in detail the winding end portion (CE) of the cathode and the winding end portion (AE) of the anode after the electrode assembly shown in FIG. 2 is wound; FIG. 4a is a perspective view showing the unfolded state of the cathode shown in FIG. 3 before it is wound; FIG. 4b is a cross-sectional view showing the state of the cathode included in region A of FIG. 4a and the anode after it is wound. Meanwhile, in FIG. 3, the wound anode (110), the first separator (140), the cathode (120), and the second separator (150) are shown as being spaced apart, but the wound anode (110), the first separator (140), the cathode (120), and the second separator (150) can be in close contact with each other.

[0049] Referring to FIGS. 3 to 4b, the cathode (120) may be formed with different thicknesses in the region overlapping with the winding end (AE) of the anode (110) and in the region not overlapping with the winding end (AE) of the anode (110). The cathode (120) may be formed with a thinner thickness in the region overlapping with the winding end (AE) of the anode (110) than in the region not overlapping with the winding end (AE) of the anode.

[0050] The cathode (120) may be composed of at least one of a first cathode active material layer (121) and a second cathode active material layer (122) and a cathode current collector (123) in an area that does not overlap with the winding end (AE) of the anode (110). The cathode (120) may have a maximum thickness corresponding to the sum of the thicknesses of the first cathode active material layer (121), the second cathode active material layer (122), and the cathode current collector (123) in at least a portion of the area that does not overlap with the winding end (AE) of the anode (110).

[0051] The cathode (120) may be composed of a cathode current collector (123) in an area overlapping with the winding end (AE) of the anode (110). The cathode (120) may have a thickness thinner than the maximum thickness in an area overlapping with the winding end (AE) of the anode (110). The cathode (120) may have a thickness corresponding to the thickness of the cathode current collector (123) in an area overlapping with the winding end (AE) of the anode (110). An avoidance depression (200) may be formed in the cathode (120) that overlaps with the winding end (AE) of the anode (110). The avoidance depression (200) may be recessed from the inner surface of the cathode (120) facing the winding center (C) toward the outer surface of the cathode (120) facing the winding outer portion (O). The avoidance recess (200) can be formed by the first negative active material layer (121) facing outwardly with the winding end portion (AE) of the anode (110) being recessed. Since the first negative active material layer (121) is not formed in the avoidance recess (200), the negative current collector (123) may face the first separator (140) that overlaps with the avoidance recess (200). The avoidance recess (200) can be formed in the shape of a groove surrounded by the first negative active material layer (121) and the negative current collector (123). A part of the avoidance recess (200) is open toward the first separator (140), and the remaining part of the avoidance recess (200) may be surrounded by the negative current collector (123) and the first negative active material layer (121). In the avoidance depression (200), the negative current collector (123) can form a step with the first negative active material layer (121).

[0052] The avoidance recess (200) may be formed in a groove shape along the width direction of the cathode (120) so as to overlap with the winding end of the anode (110) as shown in FIG. 4a. The groove-shaped avoidance recess (200) may extend parallel to the width direction of the cathode (120).

[0053] The distance between the winding end portion (AE) of the anode (110) and the cathode (120) can be increased by the avoidance depression (200). In the case of a comparative example where the avoidance depression (200) is not formed, the winding end portion (AE) of the anode (110) and the cathode (120) can be separated by a distance (S1) between the first cathode active material layer (121) and the winding end portion (AE) of the anode (110) (e.g., the thickness of the first separator (140)). On the other hand, in the embodiment in which the avoidance recess (200) is formed, the winding end (AE) of the anode (110) and the cathode (120) may be separated by a distance (S2) between the first current collector (123) and the winding end (AE) of the anode (110) (e.g., the sum of the thickness of the first separator (140) and the thickness of the first cathode active material layer (121). Accordingly, in the embodiment in which the avoidance recess (200) is formed, the distance between the winding end (AE) of the anode (110) and the cathode (120) may be greater by the thickness of the first cathode active material layer (121) compared to the comparative example in which the avoidance recess (200) is not formed.

[0054] Contact between the winding end portion (AE) of the anode (110) and the cathode (120) can be avoided by such avoidance recess (200). That is, the winding end portion (AE) of the wound anode (110) can avoid direct contact with the first cathode active material layer (121) as shown in FIG. 4b by the avoidance recess (200). In the wound electrode assembly, the winding end portion (AE) of the anode (110) and the cathode (120) can be kept out of contact with each other. Accordingly, the present invention can reduce direct contact stress caused by the winding end portion (AE) of the anode (110), thereby preventing cracks and disconnections of the cathode (120).

[0056] Electrode assembly according to the second embodiment

[0057] FIG. 5 is a cross-sectional view showing in detail the winding end portion of the cathode and the winding end portion of the anode after the electrode assembly according to the second embodiment of the present invention is wound, FIG. 6a is a perspective view showing the unfolded state of the cathode shown in FIG. 5 before it is wound, and FIG. 6b is a cross-sectional view showing the state of the cathode included in region B of FIG. 6a and the anode after it is wound. Meanwhile, in FIG. 5, the wound anode (110), the first separator (140), the cathode (120), and the second separator (150) are shown as being spaced apart, but the wound anode (110), the first separator (140), the cathode (120), and the second separator (150) can be in close contact with each other.

[0058] Referring to FIGS. 5 to 6b, an electrode assembly according to a second embodiment of the present invention may include a cathode (120), an anode (110), a first separator (140), and a second separator (150). The cathode (120) may include a first cathode active material layer (121), a cathode current collector (123), and a second cathode active material layer (122).

[0059] The first negative active material layer (121) may be formed such that its inner surface faces the center of the winding (C) and its outer surface faces the outer part of the winding (O). The first negative active material layer (121) may be formed as a multilayer structure including a plurality of active material layers. An avoidance depression (200) may be formed in at least one of the plurality of active material layers.

[0060] For example, the first negative 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 a negative current collector (123). The first active material layer (121a) may be formed with a first thickness (d1) that is thinner than the second negative active material layer (122). The first active material layer (121a) may be formed of the same or a different material as the second active material layer (121b).

[0061] The second active material layer (121b) can be formed by coating the first active material layer (121a) with a larger area than the first active material layer (121a). The second active material layer (121b) can be formed with a second thickness (d2) that is thinner than the second negative 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 similar to the thickness (T2) of the second negative active material layer (122).

[0062] In either the first active material layer (121a) or the second active material layer (121b), an avoidance recess (200) corresponding to the winding end portion (AE) of the anode (110) may be formed. The avoidance recess (200) may be formed concavely to have an empty space in the area corresponding to the winding end portion (AE) of the anode (110).

[0063] The avoidance recess (200) can be formed by the recess of the first active material layer (121a) facing outwardly toward the winding end (AE) and winding outer portion (O) of the anode (110). The first active material layer (121a) can be formed in at least a portion of the area excluding the avoidance recess (200). The first active material layer (121a) may not be formed in the avoidance recess (200). A portion of the second active material layer (121b) can be formed on the negative current collector (123) corresponding to the avoidance recess (200). At least a portion of the remainder of the second active material layer (121b) can be formed on the first active material layer (121a). The second active material layer (121b) can face the first separator (140) that overlaps with the avoidance recess (200). The avoidance recess (200) may be formed in the shape of a groove surrounded by a second active material layer (121b) formed on a negative current collector (123) and a second active material layer (121b) formed on a first active material layer (121a). A portion of the avoidance recess (200) is open toward the first separator (140), and the remaining portion of the avoidance recess (200) may be surrounded by the second active material layer (121b). The second active material layer (121b) placed in the avoidance recess (200) may have a step difference with the second active material layer (121b) placed on the first active material layer (121a).

[0064] The distance between the winding end portion (AE) of the anode (110) and the cathode (120) can be increased by such avoidance depression (200). In the case of a comparative example where the avoidance depression (200) is not formed, the winding end portion (AE) of the anode (110) and the cathode (120) can be separated by a distance (S1) between the first cathode active material layer (121) and the winding end portion (AE) of the anode (110) (e.g., the thickness of the first separator (140)). On the other hand, in the embodiment in which the avoidance depression (200) is formed, the winding end portion (AE) of the anode (110) and the cathode (120) may be separated by a distance (S2) between the first active material layer (121a) or the second active material layer (121b) and the winding end portion (AE) of the anode (110) (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). Accordingly, in the embodiment in which the avoidance depression (200) is formed, the distance between the winding end portion (AE) of the anode (110) and the cathode (120) may be greater than that of 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 depression (200) is not formed.

[0065] Contact between the winding end portion (AE) of the anode (110) and the cathode (120) can be avoided by the avoidance recess (200) that increases the distance between the winding end portion (AE) of the anode (110) and the cathode (120). That is, the wound electrode assembly can avoid direct contact between the winding end portion (AE) of the anode (110) and the first cathode active material layer (121) by the avoidance recess (200) as shown in FIG. 6b. In the wound electrode assembly, the winding end portion (AE) of the anode (110) and the cathode (120) can be kept out of contact with each other. Accordingly, the present invention can reduce direct contact stress caused by the winding end portion (AE) of the anode (110), thereby preventing cracks and disconnections of the cathode (120) caused by contact stress.

[0066] Additionally, the second active material layer (121b) and the negative current collector (123) may be formed in an area overlapping with the winding end (AE) of the positive electrode (110). The negative electrode (120) can stably supply an electrical signal (e.g., current) through the negative current collector (123) and the second negative active material layer (121b) in the area overlapping with the winding end (AE) of the positive electrode (110).

[0068] Electrode assembly according to the third embodiment

[0069] FIG. 7 is a cross-sectional view showing in detail the winding end portion of the cathode and the winding end portion of the anode after the electrode assembly according to the third embodiment of the present invention is wound. In FIG. 7, the wound anode (110), the first separator (140), the cathode (120), and the second separator (150) are shown as being spaced apart, but the wound anode (110), the first separator (140), the cathode (120), and the second separator (150) can be in close contact with each other.

[0070] Referring to FIG. 7, the electrode assembly according to the third embodiment of the present invention may have the same components as the electrode assembly shown in FIG. 5 to 6b, except that an avoidance depression (200) is formed in the second active material layer (121b). Accordingly, a detailed description of the same components is omitted.

[0071] The avoidance recess (200) can be formed by the recess of the second active material layer (121b) facing outwardly toward the winding end (AE) and winding outer portion (O) of the anode (110), as shown in FIG. 7. The first active material layer (121a) can be formed on the negative current collector (123) with an area larger than that of the second active material layer (121b). The second active material layer (121b) can be formed on the first active material layer (121a) excluding the area corresponding to the avoidance recess (200). The second active material layer (121b) can face the first separator (140) that overlaps with the avoidance recess (200). The avoidance recess (200) can be formed in the shape of a groove surrounded by the first active material layer (121a) and the second active material layer (121b). A portion of the avoidance recess (200) is 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) placed in the avoidance recess (200) may have a step difference with the second active material layer (121b) placed on the first active material layer (121a).

[0072] Contact between the winding end portion (AE) of the anode and the cathode (120) can be avoided by such avoidance recess (200). That is, the wound electrode assembly can avoid direct contact between the winding end portion (AE) of the anode (110) and the first cathode active material layer (121) by the avoidance recess (200). In the wound electrode assembly, the winding end portion (AE) of the anode (110) and the cathode (120) can be kept out of contact with each other. Accordingly, the present invention can reduce direct contact stress caused by the winding end portion (AE) of the anode (110), thereby preventing cracks and disconnections of the cathode (120).

[0074] Electrode assembly according to the fourth embodiment

[0075] FIG. 8 is a cross-sectional view showing in detail the winding end portion of the cathode and the winding end portion of the anode after the electrode assembly according to the fourth embodiment of the present invention is wound. In FIG. 8, the wound anode (110), the first separator (140), the cathode (120), and the second separator (150) are shown as being spaced apart, but the wound anode (110), the first separator (140), the cathode (120), and the second separator (150) can be in close contact with each other.

[0076] Referring to FIG. 8, the electrode assembly according to the fourth embodiment of the present invention may have the same components as the electrode assembly shown in FIG. 3 to FIG. 4b, except that it further comprises a second avoidance recess (300). Accordingly, a detailed description of the same components is omitted.

[0077] A first avoidance recess (200) and a second avoidance recess (300) may be formed in the cathode (120). The first avoidance recess (200) may be formed in the cathode (120) located outside the winding end portion (AE) of the anode (110). The first avoidance recess (200) may be recessed from the inner surface of the cathode (120) facing the winding center (C) toward the outer surface of the cathode (120) facing the winding outer portion (O). For example, the first avoidance recess (200) may be recessed from the inner surface of the first cathode active material layer (121) facing the winding center (C) toward the cathode current collector (123) facing the winding outer portion (O). The first avoidance recess (200) can be formed by the first negative active material layer (121) being recessed toward the negative current collector (123). By the first avoidance recess (200), contact between the second positive active material layer (112), which forms at least a portion of the outer side of the winding end (AE) of the positive electrode (110), and the negative electrode (120) can be avoided. That is, the wound electrode assembly can avoid direct contact between the outer side of the winding end (AE) of the positive electrode (110) and the negative electrode (120) by the first avoidance recess (200).

[0078] The second avoidance recess (300) may be formed on the cathode (120) located inward from the winding end portion (AE) of the anode (110). The second avoidance recess (300) may be recessed from the outer surface of the cathode (120) facing the winding outer portion (O) toward the inner surface of the cathode (120) facing the winding center (C). The second avoidance recess (300) may be recessed from the outer surface of the second cathode active material layer (122) facing the winding outer portion (O) toward the inner surface of the first cathode active material layer (121) facing the winding center (C). The second avoidance recess (300) may be formed by the second cathode active material layer (122) being recessed toward the cathode current collector (123). Contact between the first positive active material layer (111), which forms at least a portion of the inner side of the winding end portion (AE) of the positive electrode (110), and the negative electrode (120) can be avoided by the second avoidance recess (300). That is, the wound electrode assembly can avoid direct contact between the inner side of the winding end portion (AE) of the positive electrode (110) and the negative electrode (120) by the second avoidance recess (300).

[0079] In this way, in the wound electrode assembly, the inner and outer sides of the wound end portion (AE) of the anode (110) and the cathode (120) can be kept out of contact with each other. Accordingly, the present invention can reduce the direct contact stress applied by the wound end portion (AE) of the anode (110) to the cathode (120), thereby preventing cracking and disconnection of the cathode (120) caused by direct contact stress.

[0081] The aforementioned electrode assembly is not limited to the embodiments described in each figure, and the structures described in each figure may be applied in combination with one another. A secondary battery according to the present invention may employ multiple electrode assemblies only as described in FIG. 3, multiple electrode assemblies only as described in FIG. 5, multiple electrode assemblies only as described in FIG. 7, multiple electrode assemblies only as described in FIG. 8, or any one of the electrode assemblies described in FIG. 3, FIG. 5, FIG. 7, and FIG. 8, and at least one of the electrode assemblies described in the remainder may be employed in combination. The avoidance recess according to the present invention may be disposed not only in the outer winding portion but also in the middle winding portion and the winding portion located between the winding center and the outer winding portion. The avoidance recess according to the present invention may be employed in the negative electrode, employed in the positive electrode, or employed in combination in the positive electrode and the negative electrode. Although the electrode assembly according to the present invention has been described using a structure applied to a cylindrical secondary battery as an example, it is not limited thereto and may also be applied to pouch-type or prismatic batteries.

[0082] A secondary battery comprising the aforementioned electrode assembly can be applied to various devices. It can be applied to means of transportation such as electric bicycles, electric vehicles, and hybrids, but is not limited thereto and can be applied to various devices capable of using battery modules.

[0083] Although the present invention has been described above with reference to limited embodiments and drawings, the present invention is not limited thereto, and various implementations are possible within the scope of the technical spirit of the present invention and the equivalent scope of the claims described below by those skilled in the art to which the present invention belongs. Explanation of the symbols

[0084] 100: Electrode assembly 110: Anode 120: Cathode 140: First separator 150: Second separator 200: Avoidance depression

Claims

Claim 1 The electrode assembly comprises an anode and a cathode; a separator disposed between the anode and the cathode, wherein an avoidance depression is formed in one of the anode and the cathode, wherein the avoidance depression is formed to be depressed in an area overlapping with the end of the other electrode among the anode and the cathode, and wherein the avoidance depression is formed in the cathode such that the area overlapping with the winding end of the anode is depressed, wherein the avoidance depression is depressed from the inner surface of the cathode facing the winding center of the electrode assembly toward the outer surface of the cathode facing the winding outer portion of the electrode assembly, and wherein the cathode comprises a first cathode active material layer facing the winding center; a second cathode active material layer facing the winding outer portion; and a cathode current collector disposed between the first cathode active material layer and the second cathode active material layer, wherein the avoidance depression is formed in the first cathode active material layer. Claim 2 delete Claim 3 delete Claim 4 In claim 1, the avoidance depression is an electrode assembly formed in the shape of a groove surrounded by the first cathode active material layer and the cathode current collector. Claim 5 An electrode assembly comprising an anode and a cathode; a separator disposed between the anode and the cathode, wherein an avoidance depression is formed in one of the electrodes of the anode and the cathode, wherein the avoidance depression is formed to be depressed in an area overlapping with the end of the other electrode of the anode and the cathode, and wherein the avoidance depression is formed in the cathode such that the area overlapping with the winding end of the anode is depressed, wherein the avoidance depression is depressed from the inner surface of the cathode facing the winding center of the electrode assembly toward the outer surface of the cathode facing the winding outer portion of the electrode assembly, wherein the cathode has a multilayer structure comprising a first cathode active material layer having a plurality of active material layers facing the winding center; a second cathode active material layer facing the winding outer portion; and a cathode current collector disposed between the first cathode active material layer and the second cathode active material layer, wherein the avoidance depression is formed in at least one of the plurality of active material layers. Claim 6 In claim 5, an electrode assembly in which the thickness of at least one of the plurality of active material layers is thinner than the thickness of the second negative active material layer. Claim 7 In claim 5, the first negative active material layer comprises a first active material layer and a second active material layer, and the avoidance depression is formed in at least one of the first active material layer and the second active material layer, forming an electrode assembly. Claim 8 In claim 7, the avoidance depression is an electrode assembly formed in the shape of a groove surrounded by the first active material layer and the second active material layer. Claim 9 In claim 7, the avoidance depression is an electrode assembly formed in the shape of a groove surrounded by a second active material layer formed on the negative current collector and a second active material layer formed on the first active material layer. Claim 10 In claim 1, the avoidance recess is formed in a groove shape along the width direction of the cathode so as to overlap with the winding end portion of the anode, and the avoidance recess in the groove shape extends parallel to the width direction of the cathode, forming an electrode assembly. Claim 11 In claim 1, the electrode assembly comprises a first avoidance depression formed on the cathode located outside the winding end of the anode, and a second avoidance depression formed on the cathode located inside the winding end of the anode. Claim 12 In claim 11, the first avoidance depression is recessed from the inner surface of the cathode facing the center of the winding of the electrode assembly toward the outer surface of the cathode facing the outer part of the winding of the electrode assembly, and the second avoidance depression is recessed from the outer surface of the cathode toward the inner surface of the cathode. Claim 13 In claim 1, the cathode is an electrode assembly formed with different thicknesses in a region overlapping with the winding end of the anode and a region not overlapping with the winding end of the anode. Claim 14 In claim 13, the cathode is an electrode assembly in which the region overlapping with the winding end of the anode is formed to have a thinner thickness than the region not overlapping with the winding end of the anode. Claim 15 An electrode assembly comprising an anode and a cathode; a separator disposed between the anode and the cathode, wherein an avoidance depression is formed in one of the electrodes of the anode and the cathode, wherein the avoidance depression is formed to be depressed in an area overlapping with the end of the other electrode of the anode and the cathode, wherein the cathode is formed with different thicknesses in an area overlapping with the winding end of the anode and an area not overlapping with the winding end of the anode, wherein the cathode comprises a first cathode active material layer facing the winding center of the electrode assembly; a second cathode active material layer facing the winding outer part of the electrode assembly; and a cathode current collector disposed between the first cathode active material layer and the second cathode active material layer, wherein the cathode is composed of the cathode current collector in an area overlapping with the winding end of the anode, and at least one of the first cathode active material layer and the second cathode active material layer and the cathode current collector in an area not overlapping with the winding end of the anode. Claim 16 A secondary battery comprising an electrode assembly described in any one of claims 1 and 4 to 15.

Images