Rechargeable battery

Abstract

The present invention provides a secondary battery capable of efficiently and reliably relieving an increase in internal pressure. A secondary battery according to one aspect of the present invention comprises a case having an internal space, an electrode assembly inserted into the case and including a positive electrode and a negative electrode, a cap plate coupled to the case, and a vent portion formed in the case or the cap plate and having a notch, wherein L11 is the length of the cap plate, L12 is the width of the cap plate, L21 is the maximum length of a line segment extending from the vent portion in the width direction of the cap plate, and L22 is the maximum length of a line segment extending from the vent portion in the length direction of the cap plate, L22 / L11 = AL * L21 / L12, and 0.08≤AL≤0.36 can be satisfied.

Description

Technology Field

[0001] The present invention relates to a secondary battery capable of charging and discharging. 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, research on high-performance secondary batteries capable of repeated charging and discharging is actively underway.

[0003] 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.

[0004] 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.

[0005] Meanwhile, lithium secondary batteries can be classified according to the shape of the battery case into can-type secondary batteries, in which the electrode assembly is embedded in a metal can, and pouch-type secondary batteries, in which the electrode assembly is embedded in a pouch of aluminum laminate sheets. Furthermore, can-type secondary batteries can be further classified into cylindrical batteries and prismatic batteries depending on the shape of the metal can.

[0006] In the case of a prismatic battery, a vent portion is provided that opens as internal pressure increases, and the safety of the secondary battery can be increased if the vent portion opens accurately at a preset pressure. The problem to be solved

[0007] The present invention provides a secondary battery capable of efficiently and reliably relieving an increase in internal pressure. In addition, the present invention provides a secondary battery capable of easily dissipating heat generated at the electrode tabs by expanding the gap between the electrode tabs. means of solving the problem

[0008] A secondary battery according to one aspect of the present invention comprises a case, an electrode assembly inserted into the case, a cap plate coupled to the case, and a vent portion formed in the case or the cap plate and having a notch, wherein the length of the cap plate is L11, the width of the cap plate is L12, the maximum length of a line segment passing through the center of the vent portion and connecting the outer end is L21, and the maximum length of a line segment extending from the vent portion in the longitudinal direction of the cap plate is L22, wherein the line segment passing through the center of the vent portion and connecting the outer end and having the maximum length extends in a direction intersecting the longitudinal direction of the cap plate, and can satisfy L22 / L11 = AL * L21 / L12, 0.08≤AL≤0.36.

[0009] In one aspect of the present invention, when a line segment extending in the width direction of the cap plate in the vent portion and having the maximum length is called the major axis, and a line segment extending in the length direction of the cap plate in the vent portion and having the maximum length is called the minor axis, the angle of inclination that the major axis makes with the length direction of the cap plate may be 60 to 120 degrees.

[0010] According to one aspect of the present invention, a plate-shaped anode comprises two spaced-apart anode tabs, and the gap between the anode tabs may be formed to be larger than the length of the short axis.

[0011] According to one aspect of the present invention, when the gap between the anode tabs is denoted as L31, L31 = BL * L22, 1.2≤BL≤6.5 can be satisfied.

[0012] According to one aspect of the present invention, the maximum length of the line segment extending in the longitudinal direction of the cap plate in the vent portion may be 0.03 to 0.08 times the length of the cap plate.

[0013] According to one aspect of the present invention, the vent portion includes a connecting notch that is connected in a curve, and the length of the connecting notch may be 0.9 to 1.3 times the length of the major axis.

[0014] According to one aspect of the present invention, the length of the connecting notch may be formed to be longer than the major axis length.

[0015] According to one aspect of the present invention, the vent portion includes a connecting notch connected by a curve and two side notches connected to the connecting notch, and the side notches include a curved portion connected by a curve, and the side notches may be formed convexly toward the outside of the vent portion.

[0016] According to one aspect of the present invention, when the length of the connecting notch is denoted as L41 and the length of the side notch is denoted as L42, L41 + 2 * L42 = DL * L21, and 2.5≤DL≤6.5 can be formed.

[0017] According to one aspect of the present invention, the length of the side notch may be formed to be longer than the length of the connecting notch.

[0018] According to one aspect of the present invention, the length of the side notch may be 1.02 to 1.27 times the length of the connecting notch.

[0019] According to one aspect of the present invention, the connecting notch includes a first curve line and a second curve line, and the first curve line and the second curve line may protrude convexly in opposite directions.

[0020] According to one aspect of the present invention, a first curve line or a second curve line has a first radius of curvature, and the curved portion has a second radius of curvature, and the first radius of curvature may be formed to be larger than the second radius of curvature.

[0021] According to one aspect of the present invention, the first radius of curvature may be 1.1 to 5.5 times the second radius of curvature.

[0022] According to one aspect of the present invention, the first radius of curvature is denoted as R11 and the second radius of curvature as R12, and the first gap, which is the maximum gap between the major axis and the connecting notch, is denoted as G11, so that R11 = AR * R12 + G11, and 1.3≤AR≤4.5.

[0023] According to one aspect of the present invention, an inflection point is formed in the connecting notch where the first curve line and the second curve line meet, and the tangent at the inflection point is located in the central part of the width direction of the vent portion, and the acute angle of inclination meeting the major axis can be 5 to 60 degrees.

[0024] According to one aspect of the present invention, the acute angle of inclination may be 10 to 30 degrees.

[0025] According to one aspect of the present invention, the side notch may include a first straight section connected to one end of the curved section and connected in a straight line, and a second straight section connected to the other end of the curved section and connected in a straight line.

[0026] According to one aspect of the present invention, the first curve line may be formed of a curve having a plurality of radii of curvature.

[0027] According to one aspect of the present invention, the first curve line comprises a first part, a second part connected to one end in the longitudinal direction of the first part, and a third part connected to the other end in the longitudinal direction of the first part, and the radius of curvature of the first part may be formed to be larger than the radii of curvature of the second part and the third part.

[0028] According to one aspect of the present invention, the first gap, which is the maximum gap with the connecting notch on the long axis, may be 0.05 to 0.4 times the second gap, which is the maximum gap with the first side notch on the long axis.

[0029] According to one aspect of the present invention, the vent portion includes a first linear protrusion that extends along the longitudinal direction of the connecting notch and protrudes convexly, and the connecting notch may be located at the first linear protrusion.

[0030] According to one aspect of the present invention, the vent portion includes a second linear protrusion that extends along the longitudinal direction of the side notch and protrudes convexly, and the side notch may be located at the second linear protrusion.

[0031] According to one aspect of the present invention, the vent portion includes a first linear groove portion that is concavely recessed and extends along the longitudinal direction of the connecting notch, and second linear groove portions that are concavely recessed and extend along the longitudinal direction of the side notch, wherein the connecting notch is located in the first linear groove portion and the side notches may be located in the second linear groove portions.

[0032] According to one aspect of the present invention, the vent portion includes a first groove portion surrounding the side notches and the connecting notch, and a second groove portion located at the bottom of the first groove portion and extending in the longitudinal direction of the connecting notch, wherein the side notches are located in the first groove portion and the connecting notch may be located in the second groove portion. Effects of the invention

[0033] According to a secondary battery in one aspect of the present invention, not only can the rupture pressure be precisely set, but airborne substances such as gas can also be rapidly discharged when the vent portion is opened. The spacing between the electrode tabs is increased so that heat generated in the electrode tabs can be easily released.

[0034] Furthermore, if the connecting notch includes convex curve lines in different directions, the pressure-receiving area increases compared to a straight line, allowing for accurate and easy fracture at a preset fracture pressure. Additionally, since the pressure-receiving area increases, the overall rigidity of the vent section can be designed to be high, and consequently, when the connecting notch fractures, the vent section can open wide under a large force. Brief explanation of the drawing

[0035] FIG. 1 is a perspective view illustrating a secondary battery according to a first embodiment of the present invention. Figure 2 is a cross-sectional view taken along the line A1-A1 in Figure 1. FIG. 3 is a plan view illustrating a cap assembly according to a first embodiment of the present invention. FIG. 4 is a plan view illustrating a vent portion according to a first embodiment of the present invention. FIG. 5 is a drawing partially illustrating a connecting notch according to a first embodiment of the present invention. Figure 6 is a cross-sectional view taken along the line A2-A2 in Figure 3. FIG. 7 is a perspective view illustrating a vent portion according to a second embodiment of the present invention. Figure 8 is a cross-sectional view taken along A3-A3 in Figure 7. FIG. 9 is a cross-sectional view illustrating a vent portion according to a third embodiment of the present invention. FIG. 10 is a perspective view illustrating a vent portion according to a fourth embodiment of the present invention. Figure 11 is a cross-sectional view taken along the line A4-A4 in Figure 10. FIG. 12 is a plan view illustrating a vent portion according to the fifth embodiment of the present invention. FIG. 13 is a perspective view illustrating a secondary battery according to the sixth embodiment of the present invention. FIG. 14 is a drawing illustrating a vent protection film according to the 6th embodiment of the present invention. Figure 15 is a cross-sectional view taken along the line A5-A5 in Figure 13. FIG. 16 is a plan view of a secondary battery according to the seventh embodiment of the present invention. Specific details for implementing the invention

[0036] 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.

[0037] 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.

[0038] 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.

[0039] A secondary battery according to one embodiment of the present invention will be described below.

[0040] FIG. 1 is a perspective view illustrating a secondary battery according to a first embodiment of the present invention, FIG. 2 is a cross-sectional view taken along the line A1-A1 in FIG. 1, and FIG. 3 is a plan view illustrating a secondary battery according to a first embodiment of the present invention.

[0041] Referring to FIGS. 1 to 3, the secondary battery (100) according to the present embodiment may include an electrode assembly (10) including a positive electrode (11) and a negative electrode (12), a case (30) that accommodates the electrode assembly (10), a cap plate (21) coupled to the case (30), terminals (23, 24) installed on the cap plate (21), an upper insulating member (29) disposed between the cap plate (21) and the electrode assembly (10), and a vent portion (50) disposed on the cap plate (21).

[0042] The electrode assembly (10) performs charging and discharging and can be made in various forms such as an all-solid electrode assembly, a lithium-ion electrode assembly, a sodium-ion electrode assembly, etc.

[0043] The electrode assembly (10) includes an anode (11), a cathode (12), and a separator (13) interposed between the anode (11) and the cathode (12), and the anode (11), separator (13), and cathode (12) may be formed in a stacked structure or in a structure wound in the form of a jelly roll.

[0044] Additionally, the electrode assembly (10) may be structured such that an anode (11) and a cathode (12) are alternately inserted between separators (13) that are folded in a zigzag shape. Furthermore, the electrode assembly (10) may be formed in various forms, such as an all-solid type without a separator. The separator may be a material such as an electrically non-conductive polymer or ceramic material that separates the anode and cathode while allowing the permeation of the electrolyte and / or the movement of charge carriers. The electrode assembly (10) may also be implemented in various forms, such as an all-solid type in which there is no separate separator and the solid electrolyte performs both the roles of the electrolyte and the separator.

[0045] In this embodiment, the z-axis direction (or vertical direction) may mean a direction perpendicular to, for example, the cap or cap plate (21) (or the corresponding opening in the case (30)). That is, a direction perpendicular to the surface of the cap or cap plate (21), particularly the main surface. The x-axis and y-axis directions (or horizontal direction or horizontal plane) may mean a direction parallel to, for example, the cap or cap plate (21) (for example, a direction parallel to the surface of the cap or cap plate (21), particularly the main surface) or the opening in the case (30). The x-axis direction and the y-axis direction may be located along, for example, the smallest horizontal expansion direction and the largest horizontal expansion direction of the case (30), respectively.

[0046] With respect to the case (30), the direction perpendicular to the opening of the cap or cap plate (21) and the case (30) (z-axis direction) may be referred to as the longitudinal direction of the case (30). In a plane perpendicular to the longitudinal direction, the smallest expansion direction of the case (30) may also be referred to as the thickness direction of the case (30), which may coincide with the x-axis direction. In a plane perpendicular to the longitudinal direction, the largest expansion direction of the case (30) may also be referred to as the width direction of the case (30), which may or may not be perpendicular to the thickness direction and may coincide with the y-axis direction. The largest expansion direction of the case (30) may be, for example, the longitudinal direction or the width direction.

[0047] With respect to other configurations (e.g., parts, structures, elements, etc.), particularly configurations that may have a planar or substantially planar shape (e.g., cap plate (21) and vent portion (50)), the largest extension direction of the configuration may be referred to as the longitudinal direction (or length direction) of the configuration. The smallest extension direction of the configuration (e.g., a direction perpendicular to the main plane of the object) may be referred to as the thickness direction of the configuration. In a plane perpendicular to the thickness direction (lateral extension), the smallest extension direction of the configuration may be referred to as the width direction (or lateral direction) of the configuration.

[0048] The positive electrode (11) and the negative electrode (12) may include a coated portion, which is an area where an active material is applied to a metal foil, and a non-coated portion, where no active material is applied. The positive electrode tab (15) may protrude from the side end of the positive electrode (11), and the negative electrode tab (16) may protrude from the side end of the negative electrode (12). The positive electrode tab (15) and the negative electrode tab (16) may protrude in the same direction, but may protrude in a direction (z-axis direction) toward the cap plate (21).

[0049] The positive tab (15) and the negative tab (16) may be spaced apart in the width direction (y-axis direction) of the case (30). The positive tabs (15) and the negative tabs (16) may be stacked in the thickness direction (x-axis direction) of the case (30). The tabs may be formed integrally with the electrodes and formed by notching. Additionally, the tabs may be members that are separately coupled to the electrodes.

[0050] Additionally, the positive tab (15) can be connected to the first terminal (23) via a current collector (41), and the negative tab (16) can be connected to the second terminal (24) via a current collector (42).

[0051] One anode (11) includes two anode tabs (15), and the two anode tabs (15) protruding from one anode (11) can be spaced apart in the width direction (y-axis direction) of the case (30).

[0052] One cathode (12) includes two cathode tabs (16), and the two cathode tabs (16) protruding from one cathode (12) can be spaced apart in the width direction (y-axis direction) of the case (30).

[0053] A separator (13) is placed between the positive electrode (11) and the negative electrode (12), and the separator (13) prevents short circuits and enables the movement of ions. If the secondary battery (100) is made of an all-solid-state battery, a solid electrolyte may be placed between the positive electrode (11) and the negative electrode (12) instead of the separator (13).

[0054] The case (30) may be formed in the shape of a box having an internal space for accommodating the electrode assembly (10). The case (30) may be formed in various shapes, such as prismatic or cylindrical. A single electrode assembly (10) or multiple electrode assemblies (10) may be inserted into the case (30).

[0055] The case (30) may have a prism shape (i.e., at least substantially a prism shape), and in particular may have a square (quadrilateral) prism shape, such as a rectangular prism shape (i.e., at least substantially a rectangular prism shape). Alternatively, the case and / or housing may have a cylindrical shape, for example. An opening may be formed in the case (30) for inserting, for example, an electrode assembly into the case (30). The opening may be formed on at least one side of the case (e.g., a surface, a top side, or a top surface). In some examples, the opening may extend across the entire side of the case (e.g., the entire top or top surface).

[0056] An electrolyte may be contained together with an electrode assembly (10) inside the case (100). The electrolyte may be in the form of a liquid, solid, or gel.

[0057] The cap plate (21) is made of a plate material that covers the opening of the case (30) and may have a shape corresponding to the shape of the opening of the case (30). The cap plate (21) may be fixed to the case (30) by welding.

[0058] In the cap plate (21), an electrolyte injection port (H1) for injecting the electrolyte and a vent hole (H2) in which a vent portion (50) is installed may be formed. A sealing plug (28) that blocks the electrolyte injection port (H1) is installed in the electrolyte injection port (H1), and a vent portion (50) that opens at a preset pressure may be formed in the vent hole (H2).

[0059] An upper insulating member (29) may be disposed on the lower part of the cap plate (21), and the upper insulating member (29) may be formed as a plate parallel to the cap plate (21) and may extend along the longitudinal direction (y-axis direction) of the cap plate (21).

[0060] Terminals (23, 24) are coupled to the cap plate (21), and one or two terminals (23, 24) may be installed on the cap plate (21). When two terminals (23, 24) are installed on the cap plate (21), the first terminal (23) may be a positive terminal and the second terminal (24) may be a negative terminal. When one terminal is installed on the cap plate (21), the case (30) may be charged as a negative terminal.

[0061] The first terminal (23) and the second terminal (24) may be plate-shaped. As long as the shape enables an effective electrical connection to an external load, the first terminal (23) and the second terminal (24) may be used in any form including, but not limited to, rods, tubes, studs, posts, buttons, or pins, and the first terminal (23) and the second terminal (24) may be bent or straight. An insulating gasket (25) may be installed between the first terminal (23) and the cap plate (21), and an insulating gasket (26) may also be installed between the second terminal (24) and the cap plate (21). Additionally, the gaskets (25, 26) may extend downward and be located between the current collector (41, 42) and the cap plate (21). The gaskets (25, 26) may be made of a single component or divided into multiple components.

[0062] The first terminal (23) is electrically connected to the positive tab (15) via the first current collector (41), and the second terminal (24) can be electrically connected to the negative tab (16) via the second current collector (42).

[0063] The first terminal (23) and the second terminal (24) are formed in a plate shape, and a hole may be formed in the center of the first terminal (23) and the second terminal (24) into which a connecting column of the first current collecting member (41) or the second current collecting member (42) is inserted.

[0064] The electrode assembly (10) may include two positive tab arrays having the same polarity, and the positive tab arrays may be arranged so as not to overlap in the width direction (y-axis direction) and thickness direction (x-axis direction) of the electrode assembly (10). The positive tab arrays may be welded to the first current collector (41).

[0065] Additionally, the electrode assembly (10) may include two negative tab arrays having the same polarity, and the negative tab arrays may be arranged so as not to overlap in the width direction (y-axis direction) and thickness direction (x-axis direction) of the electrode assembly (10). The negative tab array (16) may be welded to the first current collector (41).

[0066] FIG. 4 is a plan view illustrating a vent portion according to a first embodiment of the present invention, FIG. 5 is a drawing partially illustrating a connecting notch according to a first embodiment of the present invention, and FIG. 6 is a cross-sectional view taken along the line A2-A2 in FIG. 3.

[0067] Referring to FIGS. 3 to 6, the vent portion (50) is formed of an elliptical, track-shaped plate in which two arcs are connected by a straight line, and opens at a preset pressure. However, the present invention is not limited thereto. Other shapes including rounded sides and / or straight sides, such as squares, rectangles, polygons, or circles, may also be applied.

[0068] Additionally, the vent portion (50) may be formed in a plate shape and fixed to the cap plate (21) by welding. Alternatively, the vent portion (50) may be fixed to the cap plate (21) by another method of firmly fixing it to the cap plate (21). The vent portion (50) may be fixed to the lower surface of the cap plate (21), but may also be fixed to the upper surface of the cap plate (21). The vent portion (50) may be fixed to the cap plate (21) by being sandwiched between the upper and lower portions of the cap plate (21). However, the present invention is not limited thereto, and the vent portion (50) may be formed integrally with the case or the cap plate. Accordingly, in this description, the vent portion (50) is defined as a portion exposed to the outside of the cap plate (21).

[0069] The vent portion (50) has a long axis (X11) and a short axis (X12), wherein the long axis (X11) represents a line segment having the maximum length that passes through the center of the vent portion (50) and connects the outer ends of the vent portion (50). The long axis (X11) may extend in a direction that intersects the longitudinal direction of the cap plate (21). Additionally, the long axis (X11) may extend in a direction perpendicular to the longitudinal direction of the cap plate (21), that is, in the width direction of the cap plate (21). However, the present invention is not limited thereto, and the long axis (X11) may be positioned at an angle with respect to the longitudinal direction of the cap plate (21).

[0070] The short axis (X12) connects the outer ends of the vent portion (50) and extends along the longitudinal direction of the cap plate (21), representing the longest line segment. The short axis (X12) may connect the outer ends while passing through the center of the vent portion (50) and may be perpendicular to the long axis (X11).

[0071] The long axis (X11) is formed to be longer than the short axis (X12), and the long axis (X11) can be 1.2 to 3.5 times the length of the short axis (X12).

[0072] The long axis (X11) extends in the longitudinal direction of the vent portion (50) and the width direction of the cap plate (21), and the short axis (X12) extends in the width direction of the vent portion (50) and the longitudinal direction of the cap plate (21).

[0073] In the description, the length of the major axis (X11) may refer to the length of the vent portion (50) exposed to the outside through the vent hole (H2). The major axis (X11) may intersect the longitudinal direction of the cap plate (21). Additionally, the major axis (X11) may be formed perpendicular to the longitudinal direction of the cap plate (21).

[0074] When the length of the cap plate (21) is L11, the width of the cap plate (21) is L12, the length of the major axis (X11), which is the longest line segment extending from the vent portion in the width direction of the cap plate, is L21, and the length of the minor axis (X12), which is the longest line segment extending from the vent portion in the length direction of the cap plate, is L22, the length of the minor axis (X12) (L22) / length of the cap plate (21) (L11) = AL * length of the major axis (X11) (L21) / width of the cap plate (21) (L12) can be satisfied. Here, AL can be a constant satisfying 0.08 ≤ AL ≤ 0.36.

[0075] If the length (L22) of the short axis (X12) / the length (L11) of the cap plate (21) is equal to the length (L21) of the long axis (X11) / the width (L12) of the cap plate (21), the breaking pressure of the vent portion (50) can be precisely set, and when the vent portion (50) is opened, flying materials such as gas can be quickly discharged. In addition, sufficient lower space is secured, allowing the gap between the electrode tabs to be increased.

[0076] Meanwhile, the electrode assembly (10) is structured such that a separator (13) is laminated between a plate-shaped anode (11) and a cathode (12), the plate-shaped anode (11) has two anode tabs (15), and the plate-shaped cathode (12) has two cathode tabs (16).

[0077] The positive tabs (15) may be spaced apart along the longitudinal direction of the cap plate (21), and the negative tabs (16) may also be spaced apart along the longitudinal direction of the cap plate (21). The gap (L31) between the positive tabs (15) may be formed to be larger than the maximum width (L22) of the vent portion (50).

[0078] More specifically, when the spacing between the anode tabs (15) located on a plate-shaped anode (11) is denoted as L31, the spacing between the anode tabs (15) (L31) = BL * the short length (L22) of the vent portion (50) can be satisfied. Here, BL can be a constant satisfying 1.2 ≤ BL ≤ 6.5.

[0079] If the gap (L31) between the positive tabs (15) is made of the BL * short length (L22), the heat generated between the tabs where the current is concentrated is quickly released, and problems such as increased heat generation can be prevented.

[0080] The vent portion (50) may include two side notches (52, 53) and a connecting notch (51) connecting the side notches (52, 53). The connecting notch (51) and the side notches (52, 53) may be formed as long, continuous grooves and may be formed as grooves having a trapezoidal cross-section. However, the present invention is not limited thereto, and the connecting notch (51) and the side notches (52, 53) may have cross-sections of various shapes, such as triangles or arcs.

[0081] The vent portion (50) may form a portion that is weakened compared to an adjacent or surrounding portion to create a connecting notch (51) and a side notch (52, 53). The connecting notch (51) and the side notch (52, 53) may be in the form of notches having a groove shape on the surface of the vent material, or the connecting notch (51) and the side notch (52, 53) may be formed by weakening the vent material, such as through chemical, thermal, compression, or radiation. The connecting notch (51) and the side notch (52, 53) may be configured to break easily when a specific predetermined breaking pressure is reached within the secondary battery. The pressure may be a pressure difference between the inside and outside of the secondary battery (100), and may be caused, for example, by gas formation within the secondary battery or by the expansion of the electrolyte and / or the electrode assembly (10).

[0082] The vent portion (50) may be configured, for example, to seal the electrolyte of the secondary battery. The vent portion (50) may be configured to open as the internal pressure of the secondary battery (e.g., case and / or housing) increases (e.g., at a preset pressure, for example, when the internal pressure is equal to or greater than the preset pressure). The vent portion (50) may be configured to allow gas (and optionally liquid) to be discharged from inside the secondary battery when opened.

[0083] In this embodiment, the vent portion (50) may include a base having a first side and a second side. Here, the base represents a plate forming the vent portion (50), the first side represents the upper side of the base, i.e., an outer side facing the outside of the secondary battery, and the second side represents the lower side of the base, i.e., an inner side facing the inside of the secondary battery.

[0084] At this time, the connecting notch (51) and the side notch (52, 53) may be formed on the first side of the base, that is, on the upper side of the base. Alternatively, the connecting notch (51) and the side notch (52, 53) may be formed on the second side of the base, that is, on the lower side of the base.

[0085] Additionally, the connecting notch (51) and the side notches (52, 53) can be broken at a preset pressure. The connecting notch (51) may include a first curve line (51a) and a second curve line (51b) formed by a curve. The first curve line (51a) and the second curve line (51b) may be formed in an arc shape and may protrude convexly in different directions.

[0086] The first curve line (51a) may protrude convexly toward one side end of the vent portion (50) (in the y-axis direction), and the second curve line (51b) may protrude convexly toward the other side end of the vent portion (50) (in the -y-axis direction). Accordingly, the first curve line (51a) and the second curve line (51b) may protrude convexly in opposite directions to form a wave shape or an S shape.

[0087] Here, the inflection point (CP1) where the first curve line (51a) and the second curve line (51b) meet can be formed at the center of the longitudinal direction (x-axis direction) of the connecting notch (51). Additionally, the first curve line (51a) and the second curve line (51b) have the same radius of curvature, and the first curve line (51a) and the second curve line (51b) can be formed to have a first radius of curvature (R11). Accordingly, the connecting notch (51) can be formed point-symmetrically with respect to the inflection point (CP1).

[0088] The connecting notch (51) may be connected at an angle to, for example, the two side notches (52 53) (e.g., may meet or intersect), where the angle (e.g., the smallest angle formed between each break line) may be, for example, between 20° and 90°, for example, 45° or 60° or greater and / or 90°, 80° or 70° or less. The two side notches (52 53) may be spatially separated from each other (e.g., may not be directly connected only by the connecting notch (51) (indirectly)) or alternatively connected to each other, for example, may form part of a single break line.

[0089] Here, the length of the connecting notch (51) can be 0.9 to 1.3 times the length of the major axis (X11) (L21). Additionally, the length of the connecting notch (51) can be formed to be longer than the length of the major axis (X11) (L21). For example, the length of the connecting notch (51) can be 1.01 to 1.3 times the length of the major axis (X11) (L21).

[0090] Meanwhile, the two side notches (52, 53) are formed convexly in opposite directions, but may protrude convexly toward the outer side in the longitudinal direction (x-axis direction) of the vent portion (50). The first side notch (52) and the second side notch (53) are connected to the connecting notch (51), and the first side notch (52) and the second side notch (53) have the same structure and may be arranged symmetrically.

[0091] The first side notch (52) may include a curved section (52a) that is curved in an arc shape, a first straight section (52b) that is connected to one end of the curved section (52a) and is connected in a straight line, and a second straight section (52c) that is connected to the other end of the curved section (52a) and is connected in a straight line.

[0092] The first straight section (52b) and the second straight section (52c) are connected in the width direction (x-axis direction) of the cap plate (21) and can be arranged parallel to each other. The curved section (52a) is formed as an arc having a second radius of curvature (R12) and is formed to partially wrap around the connecting notch (51).

[0093] Additionally, the second side notch (53) may include a curved section (53a) that is curved in an arc shape, a first straight section (53b) that is connected to one end of the curved section (53a) and is connected in a straight line, and a second straight section (53c) that is connected to the other end of the curved section (53a) and is connected in a straight line. Additionally, the connecting notch (51) may be connected to the longitudinal central portion of the first side notch (52) and the second side notch (53).

[0094] The side notches (52, 53) may encircle 25% to 100% of the length of the connecting notch (51), preferably 50% to 90%, and in one example, 60% to 80% (i.e., encircle the connecting notch (51) according to the corresponding portion of the length). The length of the connecting notch (51) is, for example, the distance between the two points furthest apart from each other at the connecting notch (51) and / or the length of the (curved) path through which the connecting notch (51) extends. The connecting notch (51) may be considered "encircled" by two side notches (52, 53) if the side notches (52, 53) are placed on both sides of the connecting notch (510) (e.g., in a direction perpendicular to the connecting notch (51)).

[0095] The first side notch (52) and the second side notch (53) are spaced apart and can be formed to partially wrap around the connecting notch (51). Here, the first side notch (52) and the second side notch (53) can wrap around the connecting notch (51) by 50% to 90%.

[0096] One or both of the first straight section (52b) and the second straight section (52c) may be smoothly connected to the curved section (i.e., without twisting or abrupt bending), and may be connected, for example, tangentially to the corresponding end of the curved section. One or both of the first straight section (52b) and the second straight section (52c) may extend parallel or substantially parallel to the greatest extension direction (vertical direction) of the vent section (50) and / or the greatest extension direction (vertical direction) of the side of the cap or case where the vent structure is formed. The first straight section (52b) and the second straight section (52c) may be parallel or substantially parallel to each other. One or more (e.g., all) side notches (52, 53) may have a U-shape (where the curved section connects the two straight legs / linear sections). As described in this specification, two directions or elements being substantially parallel means that each direction and element are positioned (e.g., extended or projected) at an angle (acute) between -20° and 20° to each other, and in some examples between -10° and 10°, in one example between -5° and 5°, and in another example between -2° and 2°.

[0097] Meanwhile, the first side notch (52) and the second side notch (53) have the same length, and the lengths of the side notches (52, 53) can be formed to be longer than the length of the connecting notch (51). The lengths of the side notches (52, 53) can be 1.02 to 1.27 times the length of the connecting notch (51). For example, the length of the connecting notch (51) can be 18 mm to 55 mm, and the lengths of the side notches (52, 53) can be 19 mm to 60 mm.

[0098] If the lengths of the side notches (52, 53) are 1.02 to 1.27 times the length of the connecting notch (51), the connecting notch (51) may break first, and the side notches (52, 53) may break first. If the side notches (52, 53) break first, two openings may be formed, and if the connecting notch (51) breaks first, two pieces may rise to form one opening.

[0099] In addition, when the length of the connecting notch (51) is denoted as L41 and the length of the side notch (52, 53) is denoted as L42, the equation ‘connecting notch (L41)’ + 2 * ‘length of side notch (L42)’ = DL * ‘maximum width of the vent portion (L21)’ can be satisfied. Here, DL can be a constant such that 2.5 ≤ DL ≤ 6.5.

[0100] Meanwhile, the first gap (G11), which is the maximum gap between the long axis (X11) and the connecting notch (51), can be 0.05 to 0.4 times the second gap (G12), which is the maximum gap between the long axis (X11) and the first side notch (52).

[0101] Meanwhile, as shown in FIG. 5, the acute angle of inclination (K11) at which the tangent (SL2) at the inflection point (CP1) meets the major axis (X11) can be 5 to 60 degrees. Preferably, the acute angle of inclination (K11) can be 10 to 30 degrees.

[0102] The first radius of curvature (R11) and the second radius of curvature (R12) are formed differently, and the first radius of curvature (R11) may be formed larger than the second radius of curvature (R12). The first radius of curvature (R11) may be 1.2 to 5.5 times the second radius of curvature (R12), and the first radius of curvature (R11) may also be 1.8 to 2.2 times the second radius of curvature (R12).

[0103] The equation 1st radius of curvature (R11) = AR * 2nd radius of curvature (R12) + 1st interval (G11) can be satisfied. Here, AR is 1.3 ≤ <AR≤4.5을 만족하는 상수로 이루어질 수 있다.

[0104] If the first radius of curvature (R11) is formed to be larger than the second radius of curvature (R12), the line of the connecting notch (51) is formed as a gentle curve, so that when the connecting notch (51) is broken, the connecting notch can be easily broken along the curve.

[0105] In addition, if the first radius of curvature (R11) is formed to be smaller than the second radius of curvature (R12), there is a problem in that the height difference of the vent piece that breaks and folds becomes too large. If the height difference of the vent piece is large, the higher part touches the upper structure and cannot be opened properly, or there is a problem in that a large amount of space must be secured at the top.

[0106] If the connecting notch (51) is connected in a curve similar to an S, the pressure-receiving area increases compared to a straight line, so it can be broken accurately and easily at a preset breaking pressure. In addition, when the connecting notch (51) is broken, it can be broken easily and quickly along the curve. By allowing it to break easily and quickly along the curve, the connecting notch can start opening the vent portion.

[0107] If the connecting notch (51) and the side notch include a curve, the stress is distributed rather than concentrated, allowing it to open at a rapid speed at opening pressure.

[0108] Additionally, at the side notches (52, 53), the curved portion (52a) can be broken, while the first straight portion (52b) and the second straight portion (52c) can be folded without being broken. When the first straight portion (52b) and the second straight portion (52c) are formed, the vent piece can be easily bent to quickly secure a discharge space. Additionally, the first straight portion (52b) and the second straight portion (52c) may be partially or completely broken depending on the breaking environment. The side notches (52, 53) allow the vent portion to be opened as much as possible after opening is initiated by the connecting notch (51). Furthermore, the side notches (52, 53) can minimize obstruction or interference from the vent piece (50a, 50b) during gas discharge.

[0109] Meanwhile, in some cases, the connecting notch (51) may not break and the side notch (52, 53) may break first. In this case, the curved portion (52a), the first straight portion (52b), and the second straight portion (52c) may all break, forming two openings on both sides, thereby securing sufficient space for gas to be discharged.

[0110] Additionally, since the long axis (X11) of the vent section (50) intersects the longitudinal direction of the cap plate (21), the area occupied by the vent section (50) in the longitudinal direction of the cap plate (21) is reduced, and the spacing between the positive tabs (15) and the negative tabs (16) can be increased. When the vent section (50) is formed, space must be secured below the vent section (50) for gas discharge. If the vent section (50) is arranged lengthwise in the width direction of the cap plate (21), the space occupied by the vent section in the longitudinal direction of the cap plate is minimized, and the spacing between the positive tabs (15) and the negative tabs (16) can be increased.

[0111] FIG. 7 is a perspective view illustrating a vent portion according to a second embodiment of the present invention, and FIG. 8 is a cross-sectional view taken along A3-A3 in FIG. 7.

[0112] Referring to FIGS. 7 and 8, the secondary battery according to the second embodiment has the same structure as the secondary battery according to the first embodiment described above, except for the vent portion (210), so a redundant description of the same configuration is omitted.

[0113] The vent portion (210) may include two side notches (212, 213) and a connecting notch (211) connecting the side notches (212, 213). The connecting notch (211) may be arranged lengthwise in the width direction of the cap plate.

[0114] Additionally, the vent portion (210) may include a first linear protrusion (215) that extends convexly along the longitudinal direction of the connecting notch (211) and a second linear protrusion (216) that extends convexly along the longitudinal direction of the side notches (212, 213). The vent portion (210) includes two second linear protrusions (216), and the second linear protrusions (216) may be connected to the first linear protrusion (215). Additionally, a first linear groove portion (214) may be formed on the opposite side of the first linear protrusion (215), and a second linear groove portion (217) may be formed on the opposite side of the second linear protrusion (216).

[0115] The first linear protrusion (215) and the second linear protrusion (216) may protrude convexly from the surface of the vent portion (210). The first linear protrusion (215) and the second linear protrusion (216) may be formed, for example, as raised portions protruding from the surface of the vent portion (210). The first linear protrusion (215) and the second linear protrusion (216) may each have a constant top height along the longitudinal direction. The first linear protrusion (215) and the second linear protrusion (216) may have varying top heights along the longitudinal direction. The height, maximum height, or minimum height of the first linear protrusion (215) and the second linear protrusion (216) may be the same or different.

[0116] A connecting notch (211) is formed in the first linear protrusion (215) and may be located at the very top of the first linear protrusion (215). The connecting notch (211) may be located along the first linear protrusion (215) at a height other than the highest part of the first linear protrusion (215). A portion of the connecting notch (211) may be located at the top of the linear protrusion (215), and a portion of the connecting notch (211) may be located along the first linear protrusion (215) at a height other than the highest part of the first linear protrusion (215). Additionally, side notches (212, 213) are formed in the second linear protrusion (216) and may be located at the very top of the second linear protrusion (216). The longitudinal sections of the first linear protrusion (215) and the second linear protrusion (216) may be arc-shaped or triangular. The side notches (212, 213) may also be located along the second linear protrusion (216) at a height other than the highest part of the linear protrusion (216). Part of either or both of the side notches (212, 213) may be located at the top of the second linear protrusion (216), and part of either or both of the side notches (212, 213) may be located along the second linear protrusion (216) at a height other than the highest part of the second linear protrusion (216).

[0117] The width of the first linear protrusion (215) or the second linear protrusion (216) (e.g., perpendicular to the vertical direction in which the protrusion is mainly extended) may be equal to or greater than the width of the connecting notch (510) (e.g., 1.5 to 20 times the width of the connecting notch (51), and in some examples, 2.0 to 10 times). In particular, when the connecting notch (51) is implemented as a notch. In the example where the connecting notch (51) is implemented as a notch, the depth of the notch may be less than or equal to the height of the first linear protrusion (215) or the second linear protrusion (216) (e.g., in the direction perpendicular to the bottom surface of the vent and / or in the thickness direction of the vent), and may be, for example, 0.05 to 0.9 times, and in some examples, 0.1 to 0.5 times.

[0118] When the first linear protrusion (215) and the second linear protrusion (216) are formed as in the second embodiment, the connecting notch (211) and the side notches (212, 213) can be easily broken.

[0119] A secondary battery according to the third embodiment of the present invention will be described below.

[0120] FIG. 9 is a cross-sectional view illustrating a vent portion according to a third embodiment of the present invention.

[0121] Referring to FIG. 9, the secondary battery according to the third embodiment has the same structure as the secondary battery according to the first embodiment described above, except for the vent portion (220), so a redundant description of the same configuration is omitted.

[0122] The vent portion (220) may include two side notches (222) and a connecting notch (221) connecting the side notches (222). Additionally, the vent portion (220) may include a first linear protrusion (225) that extends convexly along the longitudinal direction of the connecting notch (221) and a second linear protrusion (226) that extends convexly along the longitudinal direction of the side notch (222).

[0123] The vent portion (220) includes two second linear protrusions (226), and the second linear protrusions (226) can be connected to the first linear protrusion (225). A first linear groove (224) may be formed on the opposite side of the first linear protrusion (225), and a second linear groove (227) may be formed on the opposite side of the second linear protrusion (226).

[0124] The first linear groove (224) and the second linear groove (227) may be formed on the surface facing the inside of the case from the vent portion (220). The first linear groove (224) may be formed as a concavely recessed structure extending along the longitudinal direction of the connecting notch (221). The second linear groove (227) may be formed as a concavely recessed structure extending along the longitudinal direction of the side notch (222).

[0125] The connecting notch (221) is located at the bottom of the first linear groove (224), and the side notch (222) may be located at the bottom of the second linear groove (227). Accordingly, the connecting notch (221) and the side notch (222) are also formed on the surface facing the inside of the case in the vent portion (220).

[0126] Hereinafter, a secondary battery according to the fourth embodiment of the present invention will be described.

[0127] FIG. 10 is a perspective view illustrating a vent portion according to a fourth embodiment of the present invention, and FIG. 11 is a cross-sectional view taken along line A4-A4 in FIG. 10.

[0128] Referring to FIGS. 10 and 11, the secondary battery according to the fourth embodiment has the same structure as the secondary battery according to the first embodiment described above, except for the vent portion, so a redundant description of the same configuration is omitted.

[0129] The vent portion (230) may include two side notches (232, 233) and a connecting notch (231) connecting the side notches (232, 233). Additionally, the vent portion (230) may include a first groove portion (234) surrounding the side notches (232, 233) and the connecting notch (231), and a second groove portion (237) extending along the longitudinal direction of the connecting notch (231).

[0130] The first groove (234) is located on the lower surface of the vent (230), and side notches (232, 233) may be located in the first groove (234). The first groove (234) may have a track-shaped cross-section in which two semicircles are connected by two straight lines.

[0131] Meanwhile, the second groove (237) is formed by being sunken into the bottom of the first groove (234), and the connecting notch (231) may be located in the second groove (237). The second groove (237) extends along the longitudinal direction of the connecting notch (231) and may be formed to surround the connecting notch (231).

[0132] Meanwhile, a first protrusion (235) may be formed on the opposite side of the first groove (234), and a second protrusion (236) may be formed on the opposite side of the second groove (237). The second protrusion (236) may be located on the first protrusion (235).

[0133] As in the fourth embodiment, a second groove (237) is formed at the bottom of the first groove (234), and when the connecting notch (231) is positioned in the second groove (237), pressure is concentrated on the connecting notch (231), so that the connecting notch (231) can be easily broken.

[0134] Hereinafter, a secondary battery according to the fifth embodiment of the present invention will be described.

[0135] FIG. 12 is a plan view illustrating a vent portion according to the fifth embodiment of the present invention.

[0136] Referring to FIG. 12, the secondary battery according to the fifth embodiment has the same structure as the secondary battery according to the first embodiment described above, except for the vent portion (240), so a redundant description of the same configuration is omitted.

[0137] The vent portion (240) may include two side notches (242, 243) and a connecting notch (241) connecting the side notches (242, 243). The connecting notch (241) may be arranged lengthwise in the width direction of the cap plate.

[0138] The connecting notch (241) may include a first curve line (241a) and a second curve line (241b) formed by a curve. The first curve line (241a) and the second curve line (241b) may be formed in an arc shape and may protrude convexly in different directions. For example, a line protruding in one direction may be bent like a bow in the direction in which the line protrudes to form a bulge of the line.

[0139] The first curve line (241a) may protrude convexly toward one side of the vent portion (240), and the second curve line (241b) may protrude convexly toward the other side of the vent portion (240). The first curve line (241a) and the second curve line (241b) may have the same shape but may protrude convexly in opposite directions.

[0140] The first curve line (241a) may be formed as a curve having multiple radii of curvature. The first curve line (241a) may include a first part (241aa) having a first radius of curvature (R21), a second part (241ab) having a second radius of curvature (R22) connected to one end of the first part (241aa) in the longitudinal direction, and a third part (241ac) having a third radius of curvature (R23) connected to the other end of the first part (241aa) in the longitudinal direction. The first radius of curvature (R21) is formed to be larger than the second radius of curvature (R22), and the first radius of curvature (R21) may be formed to be 1.1 to 2.5 times the second radius of curvature (R22). The second radius of curvature (R22) and the third radius of curvature (R23) may be formed to be the same.

[0141] Or the first radius of curvature (R21) may be larger than one or both of the second radius of curvature (R22) and the third radius of curvature (R23), for example, at least 10% larger, at least 25% larger in some examples, at least 50% larger in one example, or at least 100% larger in one example.

[0142] Meanwhile, the second curve line (241b) may be formed of a curve having multiple radii of curvature. The second curve line (241b) may include a first part (241ba), a second part (241bb) connected to one end of the first part (241ba) in the longitudinal direction, and a third part (241bc) connected to the other end of the first part (241ba) in the longitudinal direction.

[0143] The radius of curvature of the first part (241ba) is formed to be larger than the radius of curvature of the second part (241bb) and the third part (241bc), and the radius of curvature of the second part (241bb) and the radius of curvature of the third part (241bc) can be formed to be the same.

[0144] The two side notches (242, 243) may include a curved portion that protrudes convexly in opposite directions and is connected in an arc shape. The two side notches (242, 243) may be spaced apart and formed to partially wrap around the connecting notch (241). The curved portion of the side notches (242, 243) may have a fourth radius of curvature (R24).

[0145] The fourth radius of curvature (R24) may be formed to be smaller than the first radius of curvature (R21) and the second radius of curvature (R22), and the fourth radius of curvature (R24) may be 0.3 to 0.7 times the second radius of curvature (R22).

[0146] As in the fifth embodiment, if the first curve line (241a) and the second curve line (241b) have multiple radii of curvature, the design freedom of the connecting notch (241) is further increased, and the connecting notch (241) can be easily broken at a more precise pressure. As the length of the connecting notch increases, the pressure-receiving area also increases due to the increased notch length compared to the case where a single radius of curvature is present, making it easier for venting to occur.

[0147] Hereinafter, a secondary battery according to the 6th embodiment of the present invention will be described.

[0148] FIG. 13 is a perspective view illustrating a secondary battery according to the 6th embodiment of the present invention, FIG. 14 is a drawing illustrating a vent protection film according to the 6th embodiment of the present invention, and FIG. 15 is a cross-sectional view taken along the line A5-A5 in FIG. 13.

[0149] Referring to FIGS. 13 to 15, the secondary battery (101) according to the sixth embodiment is formed with the same structure as the secondary battery according to the first embodiment described above, except for the vent portion (130), so a redundant description of the same configuration is omitted.

[0150] The secondary battery (101) may be composed of a rectangular battery having a case (30) in the shape of a rectangular prism, and the vent portion (130) may be fixed to the bottom (35) of the case (30). The bottom (35) of the case (30) may be formed integrally with the case (30) or fixed to the case (30) by welding or the like.

[0151] An exhaust hole (36) for discharging gas is formed in the bottom (35) of the case (30), and a first stepped portion (37) into which a vent portion (130) is inserted is formed on the lower outer side of the exhaust hole (36), and a second stepped portion (38) into which a vent protection film (60) is inserted can be formed on the lower outer side of the first stepped portion (37).

[0152] The vent portion (130) is formed in the shape of a plate and can be fixed to the case (30) by welding. The vent portion (50) can extend along the width direction (x-axis direction) of the bottom of the case.

[0153] The vent portion (130) may include two side notches (132, 133) and a connecting notch (131) connecting the side notches (132, 133). Since the connecting notch (131) and the side notches (132, 133) are formed with the same structure as the connecting notch and side notches according to the first embodiment described above, a redundant description thereof is omitted.

[0154] Meanwhile, a vent protection film (60) may be installed on the lower part of the vent section (50). The vent protection film (60) may be made of a flexible film, and a connection hole (61) for discharging pressure may be formed in the vent protection film (60). Additionally, a fixing area (62) for fixing may be formed on the outer side of the vent protection film (61). The fixing area (62) may be adhered or fused to the vent section (50) or the cap plate (21).

[0155] As described above, according to the sixth embodiment, a vent portion (130) is formed on the bottom (35) of the case (30), so that the electrolyte can also be discharged when the vent portion (130) is opened.

[0156] FIG. 16 is a plan view of a secondary battery according to the seventh embodiment of the present invention.

[0157] Referring to FIG. 16, the secondary battery (101) according to the seventh embodiment is made of the same structure as the secondary battery according to the first embodiment described above, except for the vent portion (130), so a redundant description of the same configuration is omitted.

[0158] The secondary battery (102) may be composed of a rectangular battery having a case (30) in the shape of a rectangular prism, and the vent portion (240) may be fixed to the cap plate (21). The bottom (35) of the case (30) may be formed integrally with the case (30) or fixed to the case (30) by welding or the like.

[0159] The vent portion (130) is formed in the shape of a plate and can be fixed to the cap plate (21) by welding. The vent portion (50) can be positioned so that its longitudinal direction is inclined with respect to the longitudinal direction of the cap plate (21). The vent portion (240) has a long axis (X11) and a short axis (X12), wherein the long axis (X11) is the longest line connecting the outer ends while passing through the center of the vent portion (240). The short axis (X12) is a line perpendicular to the long axis (X11) while passing through the center of the vent portion (240) and connecting the outer ends.

[0160] The long axis (X11) of the vent portion (240) may be positioned at an angle with respect to the longitudinal direction of the cap plate (21). The angle of inclination (K12) formed by the long axis (X11) of the vent portion (240) and the longitudinal direction of the cap plate (21) may be 60 to 120 degrees.

[0161] As in this embodiment, the long axis (X11) of the vent portion (240) has an inclination angle of 60 to 120 degrees with respect to the longitudinal direction of the cap plate (21). When positioned at an angle, the proportion of the vent portion (240) in the longitudinal direction of the cap plate (21) is reduced, and more free space can be secured at the bottom of the cap plate (21). In addition, the direction of gas discharge through the vent portion (240) can be easily controlled by adjusting the angle of inclination of the vent portion (240).

[0162] 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. Explanation of the symbols

[0163] 100, 101, 102: Secondary battery 10: Electrode assembly 11: Anode 12: Cathode 13: Separator 15: Anode non-existent part 16: Cathode non-cathode area 21: Cap plate 23: 1st terminal 24: 2nd terminal 25, 26: Gasket 28: Sealing plug 29: Upper insulating member 30: Case 32: Side 35: Bottom 37: 1st step section 38: 2nd step section 41: First Servant 42: Second Servant 50, 130, 140, 210, 220, 230, 240: Vent section 51, 131, 211, 221, 231, 241: Connection notch 51a, 241a: 1st curve line 51b, 241b: 2nd curve line 52: 1st side notch 53: 2nd side notch 52a, 53a: Curved section 52b, 53b: First straight section 52c, 53c: Second straight section 55: Base groove 60: Vent protective film 61: Connection hole 62: Fixed area 122, 123, 132, 133, 212, 213, 222, 232, 233, 242, 243: Side notch 214, 224: First linear groove 215, 225: First linear protrusion 216, 226: Second linear protrusion 217, 227: Second linear groove 234: First groove 235: First projection 236: Second protrusion 237: Second groove 241aa, 241ba: Part 1 241ab 241bb: Part 2 241ac, 241bc: Part 3

Claims

Claim 1 Case; electrode assembly inserted into the case; cap plate coupled to the case; A secondary battery comprising a vent portion having a notch formed in the case or the cap plate, wherein the length of the cap plate is L11, the width of the cap plate is L12, the length of a major axis is a line segment having the maximum length that passes through the center of the vent portion and connects the outer end of the vent portion, and the length of a minor axis is a line segment having the maximum length that extends from the vent portion in the longitudinal direction of the cap plate, and L22, wherein the major axis extends in a direction intersecting the longitudinal direction of the cap plate, satisfying L22 / L11 = AL * L21 / L12, 0.08≤AL≤0.36, and the vent portion includes a connecting notch connected by a curve and a plurality of side notches connected to the connecting notch, wherein the side notches include a curved portion connected by a curve, and the connecting notch is connected to an inner portion located between the two ends of the curved portion of the side notches along the longitudinal direction of the vent portion. Claim 2 A secondary battery according to claim 1, wherein the angle of inclination formed by the long axis with the longitudinal direction of the cap plate is 60 to 120 degrees. Claim 3 A secondary battery according to claim 2, wherein one positive electrode formed in a plate shape comprises two spaced positive electrode tabs, and the gap between the positive electrode tabs is greater than the length of the short axis. Claim 4 A secondary battery according to claim 3, wherein L31 = BL * L22, satisfying 1.2≤BL≤6.5, where L31 is the gap between the positive tabs. Claim 5 A secondary battery according to claim 2, wherein the length of the shortening member is 0.03 to 0.08 times the length of the cap plate. Claim 6 A secondary battery according to claim 2, wherein the length of the connecting notch is 0.9 to 1.3 times the length of the major axis. Claim 7 In claim 6, a secondary battery in which the length of the connecting notch is formed to be longer than the major axis length. Claim 8 A secondary battery according to claim 1, wherein the side notch is formed convexly toward the outer side of the vent portion. Claim 9 A secondary battery according to claim 8, wherein the length of the connecting notch is L41 and the length of the side notch is L42, L41 + 2 * L42 = DL * L21, 2.5 ≤ DL ≤ 6.

5. Claim 10 In claim 8, a secondary battery in which the length of the side notch is formed to be longer than the length of the connecting notch. Claim 11 A secondary battery according to claim 10, wherein the length of the side notch is 1.02 to 1.27 times the length of the connecting notch. Claim 12 In claim 8, the connecting notch includes a first curve line and a second curve line, and the first curve line and the second curve line protrude convexly in opposite directions, a secondary battery. Claim 13 A secondary battery according to claim 12, wherein the first curve line or the second curve line has a first radius of curvature, the curved portion has a second radius of curvature, and the first radius of curvature is larger than the second radius of curvature. Claim 14 A secondary battery according to claim 13, wherein the first radius of curvature is 1.1 to 5.5 times the second radius of curvature. Claim 15 In Clause 13, let the first radius of curvature be R11 and the second radius of curvature be R12, and let the first gap, which is the maximum gap between the major axis and the connecting notch, be G11, then R11 = AR * R12 + G11, 1.3≤ <AR≤4.5인, 이차 전지. Claim 16 A secondary battery according to claim 12, wherein an inflection point is formed in the connecting notch where the first curve line and the second curve line meet, the tangent at the inflection point is located in the central part in the width direction of the vent portion, and the acute angle of inclination meeting the major axis is 5 to 60 degrees. Claim 17 A secondary battery according to claim 8, wherein the side notch comprises a first straight section connected to one end of the curved portion and connected in a straight line, and a second straight section connected to the other end of the curved portion and connected in a straight line. Claim 18 In claim 12, the first curve line is composed of a curve having a plurality of radii of curvature, a secondary battery. Claim 19 A secondary battery according to claim 18, wherein the first curve line comprises a first part, a second part connected to one longitudinal end of the first part, and a third part connected to the other longitudinal end of the first part, and the radius of curvature of the first part is formed to be larger than the radii of curvature of the second part and the third part. Claim 20 A secondary battery according to claim 8, wherein the first gap, which is the maximum gap with the connecting notch on the long axis, is 0.05 to 0.4 times the second gap, which is the maximum gap with the first side notch on the long axis. Claim 21 A secondary battery according to claim 8, wherein the vent portion includes a first linear protrusion that extends along the longitudinal direction of the connecting notch and protrudes convexly, and the connecting notch is located at the first linear protrusion. Claim 22 A secondary battery according to claim 21, wherein the vent portion includes a second linear protrusion that extends along the longitudinal direction of the side notch and protrudes convexly, and the side notch is located at the second linear protrusion. Claim 23 In claim 8, the vent portion comprises a first linear groove portion that is concavely recessed and extends along the longitudinal direction of the connecting notch, and a second linear groove portion that is concavely recessed and extends along the longitudinal direction of the side notch, wherein the connecting notch is located in the first linear groove portion and the side notches are located in the second linear groove portions, a secondary battery. Claim 24 A secondary battery according to claim 8, wherein the vent portion comprises a first groove portion surrounding the side notches and the connecting notch, and a second groove portion located at the bottom of the first groove portion and extending in the longitudinal direction of the connecting notch, wherein the side notches are located in the first groove portion and the connecting notch is located in the second groove portion.

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