Electrode assembly, secondary battery, and electrode assembly manufacturing method

Abstract

The present invention relates to an electrode assembly, a secondary battery, and an electrode assembly manufacturing method. The electrode assembly according to one aspect of the present invention comprises: a plurality of separators stacked in one direction; a first electrode and a second electrode alternately disposed between the plurality of separators with one separator interposed therebetween; a first electrode tab coupled to the first electrode; and a second electrode tab coupled to the second electrode, wherein ends of the plurality of separators are bent. According to the technical solution of the present invention, shorting between the first electrode and the second electrode can be prevented.

Description

Electrode assembly, secondary battery and method of manufacturing electrode assembly

[0001] This application claims priority to Korean Patent Application No. 10-2025-0009133 filed on January 21, 2025, the entire disclosure of said application is incorporated herein by reference.

[0002] The present invention relates to an electrode assembly, a secondary battery including the same, and a method for manufacturing the electrode assembly.

[0003] 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, research on high-performance secondary batteries capable of repeated charging and discharging is actively underway.

[0004] Currently commercialized rechargeable batteries include nickel-cadmium batteries, nickel-hydrogen batteries, nickel-zinc batteries, and lithium-ion batteries. Among these, lithium-ion batteries are gaining attention for their advantages, such as the ability to freely charge and discharge with almost no memory effect compared to nickel-based batteries, a very low self-discharge rate, and high energy density.

[0005] These lithium secondary batteries primarily use lithium-based oxides and carbon materials as the positive and negative active materials, respectively. Additionally, the lithium secondary battery comprises a positive plate and a negative plate coated with these positive and negative active materials, respectively; an electrode assembly in which the positive and negative plates are arranged with a separator in between; and an outer casing that seals and encloses the electrode assembly together with an electrolyte.

[0006] In an electrode assembly, a short circuit between the positive and negative plates can be prevented by a separator placed between them; however, if the positive and negative plates are exposed to the outside of the separator, there is a problem where a short circuit occurs due to the exposed plates coming into contact with each other.

[0007] To solve the above problem, the present invention aims to provide an electrode assembly capable of preventing short circuits between electrodes by preventing exposure of the positive plate and the negative plate in an electrode assembly housed inside an outer casing, and a secondary battery including the same.

[0008] An electrode assembly according to one aspect of the present invention comprises a plurality of separators stacked along one direction, a first electrode and a second electrode alternately arranged between the plurality of separators with one of the separators in between, a first electrode tab coupled to the first electrode, and a second electrode tab coupled to the second electrode, wherein the ends of the plurality of separators are bent.

[0009] At least some of the plurality of separators may have their ends bent in the aforementioned direction.

[0010] The remaining portion of the plurality of separators may be bent so that the end faces the one direction.

[0011] Among the plurality of separators mentioned above, the two separators located at both ends of the unidirectional portion may be folded so that their respective ends face each other.

[0012] The folded end of the above separator may come into contact with another above separator.

[0013] The folded ends of the plurality of separators can be joined together to seal at least one surface of the electrode assembly.

[0014] The above-mentioned bent end may be located at the bottom of the separator.

[0015] Each of the first electrode and the second electrode can be overlapped vertically with the bent end.

[0016] The above-mentioned bent end may be located at the side end of the separator.

[0017] The above-mentioned folded end may be located at the top of the separator.

[0018] The first electrode tab and the second electrode tab may protrude in the same direction.

[0019] The first electrode tab and the second electrode tab may each protrude upward from the first electrode and the second electrode.

[0020] A secondary battery according to one aspect of the present invention comprises a case, an electrode assembly according to the aforementioned aspect of the present invention accommodated in the case, a first current collector plate coupled to the first electrode tab, a second current collector plate coupled to the second electrode tab, and a cap assembly that seals the case and has a first electrode terminal and a second electrode terminal located thereon, which are respectively connected to the first current collector plate and the second current collector plate.

[0021] The folded end of the separator may be located between either the first electrode or the second electrode and the lower surface of the case.

[0022] The folded end of the separator may be located between either the first electrode or the second electrode and the side of the case.

[0023] The folded end of the separator may be located between either the first electrode or the second electrode and the cap assembly.

[0024] The first electrode tab and the second electrode tab may protrude toward the cap assembly.

[0025] The above electrode assembly may be of a stack type.

[0026] A method for manufacturing an electrode assembly according to one aspect of the present invention comprises a stacking step of stacking the separator, the first electrode, the separator, and the second electrode in sequence along one direction, and a bending step of bending the end of the separator.

[0027] The above bending step may include a first bending step in which a first roller rotates to bend at least some of the ends of the plurality of separators in the above one direction.

[0028] The above bending step may further include a second bending step, after the first bending step, in which a second roller rotates to bend the end of the remaining portion of the plurality of separators in a direction facing the one direction.

[0029] After the above folding step, a sealing step may be further included to seal at least one side of the electrode assembly by joining the folded ends of the plurality of separators.

[0030] The sealing step above may apply heat of 40°C or higher and 65°C or lower to the separator.

[0031] As described above, according to one aspect of the present invention, short circuits between electrodes can be prevented by preventing exposure of the positive plate and the negative plate in an electrode assembly housed inside an outer casing.

[0032] FIG. 1 is a perspective view illustrating a secondary battery according to a first embodiment of the present invention.

[0033] FIG. 2 is a perspective view showing a disassembled state of a part of the secondary battery of FIG. 1.

[0034] FIGS. 3a and FIGS. 3b are top views of an example of a stacked electrode assembly of FIG. 2.

[0035] FIG. 4 is a side view of the electrode assembly of FIG. 2 housed in a case, viewed from the longitudinal side.

[0036] Figure 5 is a modified example of the electrode assembly of Figure 4.

[0037] Figure 6 is another modified example of the electrode assembly of Figure 4.

[0038] FIG. 7 is a perspective view illustrating an electrode assembly of a secondary battery according to a second embodiment of the present invention.

[0039] Figure 8 is a top view of the electrode assembly of Figure 7.

[0040] Figure 9 is a modified example of the electrode assembly of Figure 8.

[0041] FIG. 10 is a perspective view illustrating an electrode assembly of a secondary battery according to a third embodiment of the present invention.

[0042] FIG. 11 is a side view of the electrode assembly of FIG. 10 housed in a case, viewed from the longitudinal side.

[0043] Figure 12 is a modified example of the electrode assembly of Figure 11.

[0044] FIG. 13 is a block diagram illustrating a method for manufacturing an electrode assembly according to a first embodiment of the present invention.

[0045] Figure 14 is a diagram illustrating the stacking steps.

[0046] FIGS. 15a, FIGS. 15b, and FIGS. 15c are drawings illustrating the first bending step in sequence.

[0047] FIGS. 16a, FIGS. 16b, and FIGS. 16c are drawings illustrating the first bending step and the second bending step in sequence.

[0048] FIGS. 17a, FIGS. 17b, and FIGS. 17c are drawings illustrating the sealing step.

[0049] FIG. 18 is a perspective view illustrating a battery module including the secondary battery of FIG. 1.

[0050] FIG. 19 is a perspective view illustrating a battery pack including the battery module of FIG. 18.

[0051] The present invention is capable of various modifications and may have various embodiments, and specific embodiments are illustrated and described in detail in the detailed description. However, this is not intended to limit the present invention to specific embodiments, and it should be understood that it includes all modifications, equivalents, and substitutions that fall within the spirit and scope of the invention.

[0052] The terms used in this invention are used merely to describe specific embodiments and are not intended to limit the invention. Singular expressions include plural expressions unless the context clearly indicates otherwise. In this invention, terms such as "comprising" or "having" are intended to indicate the existence of the features, numbers, steps, actions, components, parts, or combinations thereof described in the specification, and should be understood as not precluding the existence or addition of one or more other features, numbers, steps, actions, components, parts, or combinations thereof.

[0053] In this specification, "length direction" refers to the ±x direction of FIG. 2, and unless otherwise defined, "side" refers to the side in the length direction. "Width direction" refers to the ±y direction of FIG. 2. "Height direction" refers to the ±z direction of FIG. 2, and unless otherwise defined, "top" or "top surface" refers to the top or top surface in the height direction, and "bottom" or "bottom surface" refers to the bottom or bottom surface in the height direction.

[0054] Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. Note that in the accompanying drawings, identical components are indicated by the same reference numerals whenever possible. Furthermore, detailed descriptions of known functions and configurations that may obscure the essence of the present invention will be omitted. For the same reason, some components in the accompanying drawings may be exaggerated, omitted, or schematically depicted.

[0055] Hereinafter, a secondary battery according to the first embodiment of the present invention will be described.

[0056] FIG. 1 is a perspective view illustrating a secondary battery according to a first embodiment of the present invention, FIG. 2 is a perspective view illustrating a disassembled state of a part of the secondary battery of FIG. 1, and FIG. 3a and FIG. 3b are top views of an example of a stacked electrode assembly of FIG. 2.

[0057] Referring to FIGS. 1, FIGS. 2, FIGS. 3a and FIGS. 3b, a secondary battery (10) according to a first embodiment of the present invention comprises an electrode assembly (300) having a separator (350) interposed between a first electrode (310) and a second electrode (330), a current collector (500) electrically connected to the electrode assembly (300), a case (100) in which the electrode assembly (300) is housed, and a cap assembly (700) that seals the case (100).

[0058] The electrode assembly (300) is formed by stacking a plurality of separators (350) along one direction and alternately arranging a first electrode (310) and a second electrode (330) between the plurality of separators (350). The electrode assembly (300) can be insulated from the case (100) by wrapping it with an insulating film or insulating tape. The insulating film or insulating tape may be made of a material that has excellent insulating performance even at high temperatures, such as polypropylene or polyimide.

[0059] In this embodiment, the electrode assembly (300) may be of a stack type (lamination and stack type, Z-folding type). However, the structure of the electrode assembly (300) is not necessarily limited to this and may be modified within the range that can be adopted by those skilled in the art, such as a wound type.

[0060] A plurality of separator membranes (350) can be stacked along the width direction (y direction). For example, as shown in FIG. 3a, the plurality of separator membranes (350) may be separated and stacked along the width direction (y direction) (lamination and stack type), or as shown in FIG. 3b, the separator membranes (350) may be connected to each other through the sides and folded into a 'Z' shape so as to be stacked along the width direction (y direction) (Z-folding type).

[0061] The first electrode (310) is positioned between an adjacent pair of separators (350a, 350b), and the second electrode (330) is positioned between another adjacent pair of separators (350b, 350c).

[0062] More specifically, the first electrode (310) and the second electrode (330) can be alternately arranged such that a separator (350) is interposed between them. That is, the separator (350) is positioned between the first electrode (310) and the second electrode (330), and the electrode assembly (300) can be formed by alternately stacking the first electrode (310), the separator (350), the second electrode (330), and the separator (350). In this embodiment, the electrode assembly (300) can be formed by the first electrode (310) and the second electrode (330) overlapping parallel to each other.

[0063] Here, the first electrode (310) and the second electrode (330) may be a positive electrode and a negative electrode, respectively, and conversely, the first electrode (310) and the second electrode (330) may be electrodes of different polarities, such as a negative electrode and a positive electrode, respectively.

[0064] The first electrode (310) and the second electrode (330) may each include a first electrode active portion (311) and a second electrode active portion (331), which are regions where an active material is applied to a thin plate formed of a metal foil, and a first electrode tab (313) and a second electrode tab (333), which are regions where an active material is not applied.

[0065] The first electrode active part (311) may have an active material such as a transition metal oxide coated on a metal foil such as aluminum, and the second electrode active part (331) may have an active material such as graphite or carbon coated on a metal foil such as copper or nickel.

[0066] The first electrode tab (313) may protrude to one side of the first electrode active part (311), and the second electrode tab (333) may protrude to one side of the second electrode active part (331). At this time, the first electrode tab (313) and the second electrode tab (333) may protrude in the same direction.

[0067] Specifically, the first electrode tab (313) and the second electrode tab (333) may each protrude upward from the first electrode (310) and the second electrode (330), respectively. For example, the first electrode tab (313) and the second electrode tab (333) may protrude upward from the electrode assembly (300) and protrude parallel to each other toward the cap assembly (700).

[0068] The first electrode tab (313) and the second electrode tab (333) may be spaced apart from each other with different polarities. For example, the first electrode tab (313) and the second electrode tab (333) may be spaced apart from each other along the length direction (x direction).

[0069] The first electrode tab (313) and the second electrode tab (333) are formed by cutting so as to protrude from the metal foil, so they can be formed integrally with the metal foil of the first electrode active part (311) and the second electrode active part (331), respectively.

[0070] Each of the first electrode tab (313) and the second electrode tab (333) is formed by overlapping a plurality of thin films, and can be connected so that the thin films come into contact with each other using ultrasonic welding, laser welding, etc., to facilitate the movement of current.

[0071] The separator (350) is positioned between the first electrode (310) and the second electrode (330), more specifically between the first electrode active portion (311) and the second electrode active portion (331), to prevent short circuits between them and to enable the movement of ions. For example, the separator (350) may be made of various materials such as polyethylene, polypropylene, or a composite film thereof.

[0072] The separator (350) may be sized to cover both the first electrode (310) and the second electrode (330). For example, the length of the separator (350) in the x direction may be longer than the length of the first electrode (310) and the second electrode (330) in the x direction. Accordingly, both ends of the separator (350) in the length direction (x direction) may protrude beyond the first electrode (310) and the second electrode (330). For example, the length of the separator (350) in the z direction may also be longer than the length of the first electrode (310) and the second electrode (330) in the z direction (see FIG. 11). Accordingly, the lower end of the separator (350) in the height direction (z direction) may protrude beyond the first electrode (310) and the second electrode (330). However, the first electrode tab (313) and the second electrode tab (333) may protrude beyond the upper portion in the height direction (z direction) of the separator (350) (see FIG. 4).

[0073] The detailed structure of the other electrode assembly (300) will be described later.

[0074] The first current collector plate (510) electrically connects the first electrode terminal (710) exposed to the outside of the cap assembly (700) and the first electrode tab (313) to each other, and the second current collector plate (530) electrically connects the second electrode terminal (730) exposed to the outside of the cap assembly (700) and the second electrode tab (333) to each other.

[0075] One side of the first current collector plate (510) is coupled to the first electrode tab (313). The first electrode tab (313) may be coupled to the upper or lower surface of the first current collector plate (510) on one side of the first current collector plate (510). The first electrode tab (313) may be provided in multiple numbers, so that multiple first electrode tabs (313) may be coupled to a single first current collector plate (510). The first current collector plate (510) and multiple first electrode tabs (313) may be coupled to each other by welding. Laser welding, ultrasonic welding, etc. may be applied for welding.

[0076] When the first electrode tab (313) is coupled to the first current collector plate (510), the first electrode (310) and the first current collector plate (510) can be electrically connected.

[0077] The other side of the first current collector plate (510) is connected to the first electrode terminal (710). At this time, the first current collector plate (510) may be indirectly connected to the first electrode terminal (710) through the first connection terminal (511), etc.

[0078] The first connection terminal (511) may be formed on the upper surface of the first collector plate (510). The first connection terminal (511) may be located approximately in the center of the first collector plate (510), but is not limited thereto and may be located off-center on one side in the width direction (y-direction) of the first collector plate (510). The first connection terminal (511) may be formed integrally with the first collector plate (510) in a column shape or may be coupled to the first collector plate (510). The first connection terminal (511) may be inserted into the first terminal hole (711) to electrically connect the first collector plate (510) and the first electrode terminal (710). When the first collector plate (510) and the first electrode terminal (710) are electrically connected, the first electrode (310) and the first electrode terminal (710) may be electrically connected.

[0079] One side of the second current collector plate (530) is coupled to the second electrode tab (333). The second electrode tab (333) may be coupled to the upper or lower surface of the second current collector plate (530) on one side of the second current collector plate (530). The second electrode tab (333) may be provided in multiple numbers, so that multiple second electrode tabs (333) may be coupled to a single second current collector plate (530). The second current collector plate (530) and multiple second electrode tabs (333) may be coupled to each other by welding. Laser welding, ultrasonic welding, etc. may be applied for welding.

[0080] When the second electrode tab (333) is coupled to the second current collector plate (530), the second electrode (330) and the second current collector plate (530) can be electrically connected.

[0081] The other side of the second current collector plate (530) is connected to the second electrode terminal (730). At this time, the second current collector plate (530) may be indirectly connected to the second electrode terminal (730) through the second connection terminal (531), etc.

[0082] The second connection terminal (531) may be formed on the upper surface of the second current collector plate (530). The second connection terminal (531) may be located approximately in the center of the second current collector plate (530), but is not limited thereto and may be located off-center on one side in the width direction (y-direction) of the second current collector plate (530). The second connection terminal (531) may be formed integrally with the second current collector plate (530) in a column shape or may be coupled to the second current collector plate (530). The second connection terminal (531) may be inserted into the second terminal hole (731) to electrically connect the second current collector plate (530) and the second electrode terminal (730). When the second current collector plate (530) and the second electrode terminal (730) are electrically connected, the second electrode (330) and the second electrode terminal (730) may be electrically connected.

[0083] The cap assembly (700) seals the opening of the case (100) in which the electrode assembly (300) is accommodated inside, and may include a cap plate (750), a first electrode terminal (710), and a second electrode terminal (730).

[0084] The cap plate (750) may be in the shape of a plate covering the opening of the case (100). The cap plate (750) may have a shape corresponding to the shape of the opening of the case (100). The cap plate (750) may be formed of the same material as the case (100), and the cap plate (750) may be fixed to the case (100) by laser welding.

[0085] The cap plate (750) may be formed with an electrolyte injection port (770) for injecting an electrolyte, a first terminal hole (711) into which a first connection terminal (511) is inserted, a second terminal hole (731) into which a second connection terminal (531) is inserted, and a vent hole (740) that opens when the pressure inside the case (100) exceeds a predetermined pressure value. However, the location of the vent hole (740) is not necessarily limited thereto and may be formed on one side of the case (100), for example, on the side or bottom surface of the case (100).

[0086] The first electrode terminal (710) and the second electrode terminal (730) may be formed protruding from the cap plate (750). The first electrode terminal (710) may be electrically connected to the first electrode (310) through the first current collector plate (510), and the second electrode terminal (730) may be electrically connected to the second electrode (330) through the second current collector plate (530). At this time, the first electrode terminal (710) may be electrically connected to the first current collector plate (510) through the first connection terminal (511), and the second electrode terminal (730) may also be electrically connected to the second current collector plate (530) through the second connection terminal (531).

[0087] The first electrode terminal (710) and the second electrode terminal (730) may be formed in the shape of a circular or square plate. These first electrode terminal (710) and the second electrode terminal (730) may be connected to a busbar, etc.

[0088] A first insulating member (not shown) is disposed between the first electrode terminal (710) and the cap plate (750) so that the first electrode terminal (710) and the cap plate (750) can be insulated from each other. Additionally, a second insulating member (not shown) is disposed between the second electrode terminal (730) and the cap plate (750) so that the second electrode terminal (730) and the cap plate (750) can be insulated from each other.

[0089] The case (100) forms the exterior of the secondary battery (10), and a space is formed inside to accommodate an electrode assembly (300), and an opening may be formed on one side. The case (100) may have a rectangular shape and may be made of a rigid material capable of protecting the electrode assembly (300) accommodated inside. For example, the case (100) may be made of a metal such as aluminum or stainless steel.

[0090] An electrolyte may be accommodated together with an electrode assembly (300) inside the case (100). The electrolyte may consist of a lithium salt such as LiPF6, LiBF4 in an organic solvent such as EC, PC, DEC, EMC, or DMC. The electrolyte may be in a liquid, solid, or gel form.

[0091] Meanwhile, a battery module (M) can be configured by including a plurality of secondary batteries (10) according to the present embodiment (see FIG. 18). A plurality of secondary batteries (10) can be connected to each other by a busbar (B), etc. to form a battery module (M). Additionally, a battery pack (P) can be configured by including a plurality of battery modules (M) (see FIG. 19). A battery pack (P) can be configured by arranging a plurality of battery modules (M) within an upper pack housing (VC) and a lower pack housing (LC) that constitute a pack housing (C). Furthermore, the battery pack (P) can be provided to a means of transport that moves cargo, people, etc., or performs work while moving. Such means of transport may include bicycles, heavy equipment, agricultural and fishing equipment, automobiles, buses, airplanes, etc. Here, the automobile may be an electric vehicle, a hybrid vehicle, or a plug-in hybrid vehicle. The automobile may include a four-wheeled or two-wheeled vehicle. The means of transport may operate by receiving power from the battery pack (P).

[0092] FIG. 4 is a side view of the electrode assembly of FIG. 2 housed in a case, viewed from the longitudinal side.

[0093] As illustrated in FIG. 4, the ends of the plurality of separators (350) are bent. For example, the ends of the plurality of separators (350) can be bent along one direction.

[0094] In this embodiment, the lower portion of the separator (350) may be folded along one direction. The lower portion of the separator (350) may refer to an end located at the bottom of the separator (350) in the height direction (z direction).

[0095] The lower portion of the plurality of separator membranes (350) can be folded, for example, along the width direction (y direction).

[0096] Accordingly, the first electrode (310) and the second electrode (330) can each overlap vertically with the folded end of the separator (350). That is, the folded end of the separator (350) can be located at the lower end of the height direction (z direction) of each of the first electrode (310) and the second electrode (330).

[0097] When the electrode assembly (300) is received in the case (100), the end bent in the width direction (y direction) at the bottom of the separator (350) may be located between either the first electrode (310) or the second electrode (330) and the bottom surface of the case (100).

[0098] Specifically, when the electrode assembly (300) is housed in the case (100), the first electrode (310) and the second electrode (330) sag in the -z direction due to their own weight. At this time, the folded lower portion of the separator (350) wraps around the lower portion of the first electrode (310) or the second electrode (330), thereby preventing the first electrode (310) and the second electrode (330) from being exposed to the lower portion of the separator (350).

[0099] Accordingly, even if the first electrode (310) or the second electrode (330) sags in the -z direction due to its own weight, it is not exposed to the lower part of the separator (350), so it does not come into direct contact with the bottom surface of the case (100), thereby improving the electrical stability of the secondary battery (10).

[0100] In addition, as the lower part of the separator (350) is bent, the height (z direction) of the electrode assembly (300) can be lowered, so the energy density of the secondary battery (10) can be improved.

[0101] Meanwhile, the folded end of one of the separators (350) can come into contact with another separator (350).

[0102] For example, the lower end of the separator (350a) that is folded in the width direction (y direction) in an adjacent pair of separators (350a, 350b) can come into contact with the lower end of another adjacent separator (350b), specifically the separator (350b).

[0103] In this case, since there is no gap between adjacent pairs of separators (350a, 350b) where the first electrode (310) is exposed, the folded lower portion of the separator (350a) can securely wrap the first electrode (310), thereby further improving the electrical stability of the secondary battery (10).

[0104] Figure 5 is a modified example of the electrode assembly of Figure 4.

[0105] As shown in FIG. 5, a plurality of separator membranes (350) may have at least some of their ends bent in one direction, while the remaining ends may be bent in a direction opposite to the one direction.

[0106] For example, among the plurality of separators (350), the lower portion from the separator (350a) located at one end in the width direction (y direction) to the separator (not shown) located at the center in the width direction (y direction) can be bent toward the +y direction.

[0107] Conversely, the lower portion from the separator (350z) located at the other end in the width direction (y direction) to the separator (not shown) located at the center in the width direction (y direction) can be bent toward the -y direction.

[0108] In particular, in the case of the present variation, two separators (350a, 350z) located at both ends in the width direction (y direction) among the plurality of separators (350) can be bent so that their respective ends face each other.

[0109] That is, in this modified example, the lower portions of the plurality of separators (350) can be bent from both outer sides in the width direction (y direction) toward the center. Accordingly, the lower portions of the plurality of separators (350) can be bent in a shape that is symmetrical to the left and right overall.

[0110] According to the structure of the present modified example, since the ends of the plurality of separators (350) are bent inward in the width direction (y direction) toward the center in the width direction (y direction), the electrode assembly (300) can be accommodated without any remaining space inside the case (100), so the energy density of the secondary battery (10) can be improved.

[0111] Figure 6 is another modified example of the electrode assembly of Figure 4.

[0112] As shown in FIG. 6, the folded ends of a plurality of separators (350) can be joined together to seal at least one side of the electrode assembly (300).

[0113] Specifically, the folded lower end of one of the multiple separators (350) (350a) can be joined to the lower end of an adjacent separator (350b). Additionally, the lower end of the separator (350b) can be joined to the lower end of an adjacent separator (350c). In this manner, the lower ends of the multiple separators (350) are joined to each other to seal the lower surface of the electrode assembly (300).

[0114] To this end, heat of 40°C or higher and 65°C or lower, preferably 50°C to 60°C, may be applied to the ends of the plurality of separators (350). Before bonding, the plurality of separators (350) are in a state where their respective lower ends are in contact with each other, and when heat is applied, the binder at the lower end of the separator (350) melts so that their respective ends can be bonded together.

[0115] Meanwhile, although not illustrated, a plurality of perforations (not illustrated) may be formed on the lower surface of the sealed electrode assembly (300), that is, on the lower portion of the plurality of separators (350) joined together. The plurality of perforations (not illustrated) can allow the electrolyte injected into the case (100) to flow into the interior of the electrode assembly (300).

[0116] According to the structure of the present modified example, the lower surface of the electrode assembly (300) is sealed so that the first electrode (310) or the second electrode (330) is not exposed to the lower surface of the electrode assembly (300) due to its own weight and does not come into direct contact with the bottom surface of the case (100), thereby improving the electrical stability of the secondary battery (10). In addition, even if the insulating film or insulating tape surrounding the electrode assembly (300) is damaged, the electrode assembly (300) and the case (100) can be insulated through the lower part of the bonded separator (350), so the electrical stability of the secondary battery (10) can be further improved.

[0117]

[0118] Hereinafter, a secondary battery according to the second embodiment of the present invention will be described.

[0119] FIG. 7 is a perspective view illustrating an electrode assembly of a secondary battery according to a second embodiment of the present invention, and FIG. 8 is a top view of the electrode assembly of FIG. 7 viewed from above.

[0120] Since the secondary battery according to the second embodiment of the present invention has the same structure as the secondary battery according to the first embodiment and variations described above, except for the position of the bent end, a redundant description of the same configuration is omitted.

[0121] In this embodiment, the electrode assembly (300) may be of the lamination and stack type. However, the structure of the electrode assembly (300) is not necessarily limited thereto and may be modified within the range that can be adopted by those skilled in the art, such as a Z-folding type or a wound type.

[0122] Referring to FIGS. 7 and 8, in this embodiment, both ends of the separator (350) in the longitudinal direction (x direction) may be bent. That is, the bent ends of the separator (350) may be located on the sides of the separator (350).

[0123] Both ends of the longitudinal direction (x-direction) of the plurality of separators (350) can be folded in one direction. For example, both ends of the longitudinal direction (x-direction) of the plurality of separators (350) can be folded toward the width direction (y-direction).

[0124] In this case, among the plurality of separators (350), an adjacent pair of separators (350a, 350b) may have both ends of one (350a) in contact with both ends of the other (350b).

[0125] Accordingly, the first electrode (310) interposed between an adjacent pair of separators (350a, 350b) can be wrapped on both sides in the longitudinal direction (x direction) by the folded ends of the separator (350a).

[0126] As shown in FIGS. 7 and 8, the folded longitudinal (x-direction) ends of the plurality of separators (350) are located between either the first electrode (310) or the second electrode (330) and the longitudinal (x-direction) side of the case (100).

[0127] Accordingly, the first electrode (310) or the second electrode (330), which is wrapped around the folded ends in the longitudinal direction (x direction) of the plurality of separators (350), is not exposed to the ends in the longitudinal direction (x direction) of the separators (350), so even if left-right vibration occurs within the case (100), it does not come into direct contact with the parts in the longitudinal direction (x direction) of the case (100), thus improving the electrical stability of the secondary battery (10).

[0128] Figure 9 is a modified example of the electrode assembly of Figure 8.

[0129] As shown in FIG. 9, a plurality of separator membranes (350) may have at least some of their ends bent in one direction and the remaining ends bent in a direction facing the one direction.

[0130] Specifically, at least some of the multiple separators (350) may have their ends in the longitudinal direction (x direction) bent in the +y direction, and the remaining portion may have their ends in the longitudinal direction (x direction) bent in the -y direction.

[0131] For example, among the plurality of separators (350), from the separator (350a) located at one end in the width direction (y direction) to the separator (not shown) located at the center in the width direction (y direction), both ends in the length direction (x direction) can be bent toward the +y direction.

[0132] Conversely, from the separator (350z) located at the other end in the width direction (y direction) to the separator (not shown) located at the center in the width direction (y direction), both ends in the length direction (x direction) can be bent toward the -y direction.

[0133] In particular, in the case of the present variation, two separators (350a, 350z) located at both ends in the width direction (y direction) among the plurality of separators (350) may be folded so that both ends in the length direction (x direction) face each other.

[0134] That is, in this modified example, both ends of the plurality of separator membranes (350) in the length direction (x direction) can be bent toward the center in the width direction (y direction).

[0135] According to the structure of the present modified example, since the ends of both sides of the plurality of separators (350) are bent inward in the width direction (y direction) toward the center in the width direction (y direction) in the length direction (x direction), the electrode assembly (300) can be accommodated without any remaining space inside the case (100), thereby improving the energy density of the secondary battery (10).

[0136] Meanwhile, FIGS. 7 to 9 illustrate a second embodiment of the present invention and variations thereof, each having a structure in which a plurality of separated membranes (350) are stacked in the width direction (y direction), but is not limited thereto and may also be applied in a structure in which each membrane (350) is connected to each other on both sides in the length direction (x direction) and folded into a 'Z' shape to be stacked in the width direction (y direction), as shown in FIG. 3b.

[0137]

[0138] A secondary battery according to the third embodiment of the present invention will be described below.

[0139] FIG. 10 is a perspective view illustrating an electrode assembly of a secondary battery according to a third embodiment of the present invention, and FIG. 11 is a side view of the electrode assembly of FIG. 10 in a state housed in a case, viewed from a longitudinal side.

[0140] Since the secondary battery according to the third embodiment of the present invention has the same structure as the secondary batteries according to the first embodiment and variations described above, except for the position of the bent end, a redundant description of the same configuration is omitted.

[0141] Referring to FIGS. 10 and 11, in this embodiment, the lower and upper portions of the separator (350) may be folded. At this time, the upper portion of the separator (350) may be cut and partially folded, and the folding structure of the lower portion of the separator (350) may be the same as that of the first embodiment and variations described above.

[0142] Specifically, in this embodiment, the upper portion of the separator (350) may be divided into first to third segments (SEG1, SEG2, SEG3) by cutting twice along the longitudinal direction (x-direction). However, it is not necessarily limited to this, and the upper portion of the separator (350) may be divided into various numbers so that it can be partially folded between the first electrode tab (313) and the second electrode tab (333).

[0143] The second segment (SEG2) is located in the middle of the first to third segments (SEG1, SEG2, SEG3), and more specifically, refers to the portion located between the first electrode tab (313) and the second electrode tab (333) that are spaced apart in the longitudinal direction (x direction) of the upper part of the separator (350).

[0144] In this embodiment, in addition to the lower portion of the separator (350), the second segment (SEG2) of the upper portion of the separator (350) may be partially folded, and the folded upper portion referred to in this embodiment means the second segment (SEG2) located at the upper portion of the separator (350).

[0145] In a plurality of separators (350), the second segments (SEG2) can all be folded in one direction. For example, the second segments (SEG2) can all be folded toward the width direction (y direction).

[0146] In this case, among the plurality of separators (350), an adjacent pair of separators (350a, 350b) can have the second segment (SEG2) of one of (350a) come into contact with the second segment (SEG2) of the other of (350b).

[0147] Accordingly, the first electrode (310) interposed between an adjacent pair of separators (350a, 350b) can be covered at the top by the second segment (SEG2) of the separator (350a).

[0148] The folded upper portion of the plurality of separators (350), i.e., the second segment (SEG2), is located between either the first electrode (310) or the second electrode (330) and the cap assembly (700, see FIG. 2). Accordingly, the upper portion of the first electrode (310) or the second electrode (330) can be wrapped by the second segment (SEG2) of the plurality of separators (350).

[0149] As a result, the first electrode (310) or the second electrode (330) can be prevented from being exposed to the upper part of the electrode assembly (300) and the second segment (SEG2) can block foreign substances from entering the interior of the electrode assembly (300), so the electrical stability of the secondary battery (10) can be improved.

[0150] Meanwhile, since the lower portion of the multiple separator (350) is also folded, the first electrode (310) or the second electrode (330) may not be exposed even if vibration occurs in the vertical direction, as the upper and lower portions are covered by the folded lower portion of the separator (350) and the folded second segment (SEG2). Accordingly, the electrical stability of the secondary battery (10) can be further improved.

[0151] Figure 12 is a modified example of the electrode assembly of Figure 11.

[0152] As illustrated in FIG. 12, a plurality of separators (350) may have at least some of the second segments (SEG2) folded in one direction and the remaining portion of the second segments (SEG2) folded in a direction facing the one direction.

[0153] Specifically, at least some of the plurality of separators (350) may have the second segment (SEG2) folded in the +y direction, and the remaining portion may have the second segment (SEG2) folded in the -y direction.

[0154] For example, among the plurality of separators (350), the second segment (SEG2) can be bent in the +y direction from the separator (350a) located at one end in the width direction (y direction) to the separator (not shown) located at the center in the width direction (y direction).

[0155] Conversely, from the separator (350z) located at the other end in the width direction (y direction) to the separator (not shown) located at the center in the width direction (y direction), the second segment (SEG2) can be bent toward the -y direction.

[0156] In particular, in the case of the present variation, two separators (350a, 350z) located at both ends in the width direction (y direction) among the plurality of separators (350) can be folded so that each second segment (SEG2) faces each other.

[0157] That is, in this modified example, the second segment (SEG2) of the plurality of separators (350) can be folded in a direction toward the center in the width direction (y direction).

[0158] According to the structure of the present modified example, the second segment (SEG2) of the plurality of separators (350) is folded inward in the width direction (y direction) toward the center in the width direction (y direction), so that the energy density of the secondary battery (10) can be improved by reducing the height of the electrode assembly (300).

[0159] Meanwhile, FIGS. 10 to 12 illustrate a third embodiment of the present invention and variations thereof, each having a structure in which a plurality of separated membranes (350) are stacked in the width direction (y direction), but is not limited thereto and may be applied in a structure in which each membrane (350) is connected to each other on both sides in the length direction (x direction) and folded into a 'Z' shape so as to be stacked in the width direction (y direction), as shown in FIG. 3b.

[0160]

[0161] Hereinafter, a method for manufacturing an electrode assembly according to the first embodiment of the present invention will be described.

[0162] FIG. 13 is a block diagram illustrating a method for manufacturing an electrode assembly according to a first embodiment of the present invention, FIG. 14 is a diagram illustrating a stacking step, FIG. 15a, FIG. 15b, and FIG. 15c are diagrams illustrating a first bending step in sequence. FIG. 16a, FIG. 16b, and FIG. 16c are diagrams illustrating a first bending step and a second bending step in sequence, FIG. 17a, FIG. 17b, and FIG. 17c are diagrams illustrating a sealing step.

[0163] As illustrated in FIG. 13, the method for manufacturing an electrode assembly according to the first embodiment of the present invention includes a stacking step (S100) and a bending step (S300).

[0164] Referring to FIG. 14, in the stacking step (S100), a separator (350a), a first electrode (310), a separator (350b), and a second electrode (330) are stacked in sequence along one direction, for example, the width direction (y direction). That is, in the stacking step (S100), an electrode assembly (300) can be formed in such a way that a separator (350) is interposed between the first electrode (310) and the second electrode (330) which are alternately arranged.

[0165] For convenience, the first electrode (310) and the second electrode (330) are each shown with their lower ends aligned in a specific position in the height direction (z direction), but this is not necessarily limited thereto. The lower end of the first electrode (310) and the lower end of the second electrode (330) may be positioned at different locations. For example, the lower end of the first electrode (310) may be positioned at a location protruding in the height direction (z direction) more than the lower end of the second electrode (330), or conversely, the lower end of the second electrode (330) may be positioned at a location protruding in the height direction (z direction) more than the lower end of the first electrode (310).

[0166] The lower portion of the electrode corresponding to the negative electrode among the first electrode (310) and the second electrode (330) may be positioned so that it protrudes in the height direction (z direction) more than the lower portion of the positive electrode. For example, the negative electrode is designed to have a larger surface area than the positive electrode, thereby preventing lithium ions from being excessively deposited on the negative electrode during charging of the secondary battery (10), which can prevent short circuits or thermal runaway.

[0167] Meanwhile, the lower portions (E) in the height direction (z direction) of the plurality of separators (350) may be stacked so that they face each other, without facing the first electrode (310) and the second electrode (330).

[0168] Additionally, the first electrode tab (313) and the second electrode tab (333) can both protrude in the same direction, for example, both facing the upper part of the electrode assembly (300).

[0169] In the bending step (S300), the lower portion (E) of the separator (350) is bent. Specifically, the bending step (S300) includes a first bending step (S310) in which at least some of the lower portions (E) of the plurality of separators (350) are bent in one direction.

[0170] Referring to FIG. 15a, in the first bending step (S310), the first roller (R1) is positioned on one side in the width direction (y direction) of the electrode assembly (300).

[0171] Specifically, the first roller (R1) contacts the separator (350) located at the far end of one side in the width direction (y direction) and rotates and advances toward the lower part (E).

[0172] Subsequently, the first roller (R1) that reaches the lower portion (E) folds the lower portion (E) of the plurality of separators (350) in the width direction (+y direction). Accordingly, the lower portions (E) of the plurality of separators (350) can all be folded in the width direction (+y direction).

[0173] Meanwhile, the bending step (S300) may optionally include a second bending step (S320) after the first bending step (S310).

[0174] As shown in FIG. 15b, in the first bending step (S310), only the lower portion (E) of some of the multiple separators (350) is bent in one direction, in the second bending step (S320), the lower portion (E) of the remaining portion of the multiple separators (350) that is not bent in one direction may be bent in a direction facing the one direction.

[0175] Specifically, as shown in FIG. 16a, the first roller (R1) and the second roller (R2) can be placed at both ends of the electrode assembly (300) in the width direction (y direction).

[0176] The first roller (R1) may contact the separator (350) located at the far end of one side in the width direction (y direction), and the second roller (R2) may contact the separator (350) located at the far end of the other side in the width direction (y direction). At this time, the first roller (R1) may be positioned closer to the lower portions (E1, E2) of the separator (350) than the second roller (R2).

[0177] The first roller (R1) and the second roller (R2) can rotate in opposite directions but at the same speed. Accordingly, the first roller (R1) can reach the lower part (E1) before the second roller (R2).

[0178] The first roller (R1) can bend the lower portion (E1) of some of the plurality of separators (350) in the +y direction. Subsequently, the second roller (R2) can bend the lower portion (E2) of the remaining unbent portion of the plurality of separators (350) in the -y direction. Accordingly, the lower portions (E1, E2) of the plurality of separators (350) can be bent in a shape that converges toward the center in the width direction (y direction).

[0179] Meanwhile, the method for manufacturing an electrode assembly according to the present embodiment may additionally include a sealing step (S500) after the bending step (S300, see FIG. 13). In the sealing step (S500), the bent ends (E) of a plurality of separators (350) are joined to seal at least one side of the electrode assembly (300).

[0180] For example, referring to FIG. 17a, the lower portions (E) of a plurality of separator membranes (350) that are all folded in the +y direction in FIG. 15c can be joined together by a sealing machine (S).

[0181] Specifically, the sealing device (S) can come into contact with the lower portions (E) of a plurality of separator membranes (350). At this time, the folded lower portion (E) of each separator membrane (350) can come into contact with the folded lower portion (E) of another separator membrane (350).

[0182] The sealing device (S) can apply heat of 40°C or higher and 65°C or lower, preferably 50°C to 60°C, to the lower portion (E) of the separator (350). When heat is applied, the binder of the lower portion (E) of the separator (350) melts, and the respective lower portions (E) can be bonded together. Accordingly, the lower portion in the height direction (z direction) of the electrode assembly (300), that is, the lower surface of the electrode assembly (300), can be sealed.

[0183] In the above state, the electrode assembly (300) can be erected and accommodated inside a case (100, see FIG. 2).

[0184] Meanwhile, in FIGS. 17a, 17b, and 17c, the sealing step (S500) is exemplified as being performed after the first folding step (S310, see FIG. 13), but is not limited thereto, and the sealing step (S500) may optionally be performed after the second folding step (S320, see FIG. 13) is performed. In this case, as shown in FIG. 16c, the lower portions (E1, E2) of the plurality of separators (350) are joined together while being folded along the width direction (y-direction), thereby sealing the lower surface of the electrode assembly (300).

[0185] Although an embodiment of the present invention has been described above, those skilled in the art may modify and change the present invention in various ways by adding, changing, deleting, or adding components, etc., without departing from the spirit of the present invention as described in the claims, and such modifications and changes are also to be included within the scope of the rights of the present invention.

Claims

1. Multiple separators stacked along one direction; Among the plurality of separators, a first electrode and a second electrode alternately arranged with one of the separators in between; A first electrode tab coupled to the first electrode; and It includes a second electrode tab coupled to the second electrode, The above plurality of separators are electrode assemblies with bent ends.

2. In Paragraph 1, At least some of the plurality of separators mentioned above are, An electrode assembly in which the above end is bent in the above one direction.

3. In Paragraph 2, The remaining portion of the above plurality of separators is, An electrode assembly in which the above end is bent in a direction facing the above one direction.

4. In Paragraph 3, An electrode assembly in which two separators located at both ends of the plurality of separators in the above-mentioned direction are each bent in a direction facing each other.

5. In Paragraph 1, An electrode assembly in which the folded end of the above separator contacts another above separator.

6. In Paragraph 1, The folded ends of the plurality of separators are joined together to seal at least one surface of the electrode assembly.

7. In Paragraph 1, The above-mentioned bent end is an electrode assembly located at the bottom of the separator.

8. In Paragraph 7, Each of the first electrode and the second electrode is, An electrode assembly that overlaps the above-mentioned bent end vertically.

9. In Paragraph 1, The above-mentioned bent end is an electrode assembly located at the side end of the separator.

10. In Paragraph 1, The above-mentioned bent end is an electrode assembly located at the top of the separator.

11. In Paragraph 1, The first electrode tab and the second electrode tab are protruded in the same direction, forming an electrode assembly.

12. In Paragraph 11, The first electrode tab and the second electrode tab are electrode assemblies that protrude upward from the first electrode and the second electrode, respectively.

13. Case; An electrode assembly according to any one of claims 1 to 12 accommodated in the above case; A first current collector plate coupled to the first electrode tab above; A second current collector plate coupled to the second electrode tab; and A secondary battery comprising a cap assembly that seals the above case and has a first electrode terminal and a second electrode terminal located thereon, which are respectively connected to the first current collector plate and the second current collector plate.

14. In Paragraph 13, The folded end of the above separator is, A secondary battery located between either the first electrode or the second electrode and the lower surface of the case.

15. In Paragraph 13, The folded end of the above separator is, A secondary battery located between either the first electrode or the second electrode and the side of the case.

16. In Paragraph 13, The folded end of the above separator is, A secondary battery located between either the first electrode or the second electrode and the cap assembly.

17. In Paragraph 13, A secondary battery in which the first electrode tab and the second electrode tab protrude toward the cap assembly.

18. In Paragraph 13, The above electrode assembly is a stacked type secondary battery.

19. A method for manufacturing an electrode assembly according to any one of claims 1 to 12, A stacking step of sequentially stacking the separator, the first electrode, the separator, and the second electrode along the above-mentioned unidirectional direction; and A method for manufacturing an electrode assembly comprising a bending step of bending the end of the separator above.

20. In Paragraph 19, The above bending step is, A method for manufacturing an electrode assembly comprising a first bending step in which a first roller rotates to bend at least some of the ends of the plurality of separators in the same direction.

21. In Paragraph 20, The above bending step is, After the first bending step mentioned above, A method for manufacturing an electrode assembly, further comprising a second bending step in which a second roller rotates to bend the end of the remaining portion of the plurality of separators in a direction facing the one direction.

22. In Paragraph 19, After the above bending step, A method for manufacturing an electrode assembly, further comprising a sealing step of joining the folded ends of the plurality of separators to seal at least one surface of the electrode assembly.

23. In Paragraph 22, The above sealing step is, A method for manufacturing an electrode assembly by applying heat of 40°C or higher and 65°C or lower to the above-mentioned separator.

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