Secondary battery

Abstract

Disclosed herein are secondary batteries having a venting member. The secondary battery can include an electrode assembly having an electrode lead attached thereto, a case including a receiving portion and a sealing portion. The receiving portion can be defined by a bent surface. The receiving portion can be configured to receive the electrode assembly and seal the electrode assembly therein. The sealing portion can contain a sealing resin to form a seal around the electrode assembly. The sealing portion can include an extension portion adjacent to and extending from the bent surface. The venting member can be at least partially disposed in the extension portion. The venting member can include a venting resin having a lower melting point than the sealing resin.

Description

TECHNICAL FIELD

[0001] This application claims priority to Korean Patent Application No. 10-2021-0049400, filed on April 15, 2021, and Korean Patent Application No. 10-2022-0001216, filed on January 4, 2022, the disclosures of which are incorporated herein in their entirety by reference.

[0002] The present application relates to a secondary battery, and more particularly, to a secondary battery having an exhaust member. BACKGROUND

[0003] Secondary batteries are very suitable for various products and exhibit excellent electrical properties such as high energy density, etc. The secondary batteries are generally used not only for portable devices but also for electric vehicles (EVs) or hybrid electric vehicles (HEVs) driven by power sources. The secondary batteries are attracting attention as a new energy source for improving environmental friendliness and energy efficiency since the use of fossil fuels can be greatly reduced and no by-products are generated in the energy consumption process.

[0004] The secondary batteries widely used at present include lithium ion batteries, lithium polymer batteries, nickel-cadmium batteries, nickel-hydrogen batteries, nickel-zinc batteries, etc.

[0005] The secondary battery generally has a structure in which an electrode assembly including at least one unit cell having a positive electrode / separator / negative electrode structure is accommodated in a case of a laminate sheet in which an outer layer, a metal barrier layer, and a sealant layer are sequentially laminated, and a sealant resin of the sealant layer is melted to seal the electrode assembly.

[0006] In the conventional secondary battery, the battery can catch fire for various reasons such as a short circuit inside the secondary battery, overcharging or overdischarging, temperature control, etc. At this time, heat propagation in which the temperature inside the secondary battery rapidly increases and at the same time heat is transferred to an adjacent battery can occur, which can further increase the fire.

[0007] In order to minimize damage to the electrode caused by gas when heat propagation occurs, i.e., when the internal temperature of the secondary battery increases, a directional venting characteristic is required so as to exhaust gas in one direction. However, the conventional secondary battery has a problem in that it is difficult to induce gas discharge in a specific direction.

[0008] Accordingly, the present application relates to providing a secondary battery in which safety is improved by inducing gas discharge in a specific direction. SUMMARY

[0009] TECHNICAL PROBLEM

[0010] Accordingly, the present application relates to providing a secondary battery in which safety is improved by inducing gas discharge in a specific direction.

[0011] Technical Solution

[0012] To solve the above technical problem, disclosed herein is a secondary battery according to the following embodiments.

[0013] A secondary battery according to this aspect includes:

[0014] an electrode assembly;

[0015] an electrode lead attached to the electrode assembly;

[0016] a case including a sealing portion, a bent surface, and a receiving portion configured to be defined by the bent surface and internally receive the electrode assembly, the sealing portion containing a sealing resin to form a seal around the electrode assembly;

[0017] wherein the sealing portion includes an extension portion adjacent to and extending away from the bent surface; and

[0018] an exhaust member disposed at least partially in the extension portion, the exhaust member including an exhaust resin having a lower melting point than the sealing resin.

[0019] Continuing according to this aspect, the exhaust member can be disposed at least partially in a bat ear region.

[0020] Continuing according to this aspect, the secondary battery can include a lead film surrounding an outer surface of the electrode lead. The lead film can be disposed between the electrode lead and the sealing portion. The exhaust member can extend through the receiving portion. A first end portion of the exhaust member can be spaced apart from the lead film in the sealing portion. A second end portion of the exhaust member can at least partially overlap or contact the lead film in the receiving portion.

[0021] Continuing according to this aspect, the secondary battery can further include a lead film surrounding an outer surface of the electrode lead. The lead film can be disposed between the electrode lead and the sealing portion. The electrode lead can extend away from the case along a Y-axis. The exhaust member can include a first portion and a second portion. The first portion can extend along an X-axis orthogonal to the Y-axis between the lead film and the second portion. The second portion can extend along the Y-axis.

[0022] Continuing from this aspect, the secondary battery may further include a lead film surrounding the outer surface of the electrode lead. The lead film may be disposed between the electrode lead and the sealing portion. The electrode lead may extend away from the housing along the Y-axis. The venting member may include a first portion and a second portion. The first portion may extend between the lead film and the second portion along a first direction not parallel to the Y-axis. The second portion may extend along a second direction orthogonal to the first direction. The venting member may have an L-shape. The venting member may include a tapered section at the intersection of the first and second portions. The tapered section may extend into the receiving portion. The first portion may be a bridging portion that at least partially overlaps with the lead film. The outer end of the first portion may be spaced apart from the inner end of the extension. The first portion may be located within the receiving portion. The second portion may not overlap with or contact the lead film.

[0023] Continuing from this point, the exhaust component can be defined as having a variable width. This variable width can decrease along the exhaust direction.

[0024] Continuing from this point, the exhaust component can be defined as any one of the following shapes: circular, elliptical, stepped, triangular, and trapezoidal.

[0025] Continuing from this aspect, the venting member can be defined as having a variable thickness. This variable thickness can decrease along the venting direction. The area where the venting member overlaps or contacts the lead film can be 1% to 30% of the area where the lead film does not overlap or contact the electrode lead.

[0026] Continuing from this aspect, the exhaust resin may comprise linear low-density polyethylene having comonomers having a carbon number of 6 or more. Based on 100% by weight of linear low-density polyethylene, the comonomers having a carbon number of 6 or more may be 15% by weight or less.

[0027] Continuing from this aspect, the venting member can be melted at 100°C to 120°C to discharge gas from the housing to the outside of the secondary battery. When the housing is under a pressure of 1.5 atm or higher, the venting member can discharge gas from the housing.

[0028] Continuing from this point, at temperatures above 100°C, the exhaust component can have a maximum sealing strength of less than 6 kgf / 15 mm.

[0029] Continuing from this point, at temperatures above 100°C, the exhaust component can have an average sealing strength of less than 4.5 kgf / 15 mm.

[0030] Continuing from this point, the exhaust component can have a maximum sealing strength of over 6 kgf / 15 mm at temperatures ranging from room temperature to 60°C.

[0031] According to a further aspect, the vent member can have an average sealing strength of 4.5 kgf / 15 mm or more at room temperature to 60°C.

[0032] According to a further aspect, the vent resin can be polymerized in the presence of a metallocene catalyst.

[0033] According to a further aspect, the vent resin can have a polydispersity index (PDI) of 4 or less.

[0034] According to a further aspect, a difference between a crystallization temperature of the sealant resin and a crystallization temperature of the vent resin can be 10°C or less. The vent resin can have a melting point of 100°C to 130°C.

[0035] According to a further aspect, the vent resin can have a weight average molecular weight of 100,000 g / mol to 400,000 g / mol.

[0036] According to a further aspect, the secondary battery can be a pouch-type secondary battery.

[0037] According to a further aspect, the vent member can have a maximum sealing strength of less than 3 kgf / 15 mm at 120°C or more.

[0038] According to a further aspect, the vent member can have an average sealing strength of less than 2 kgf / 15 mm at 120°C or more.

[0039] Advantageous effects

[0040] In a secondary battery according to one embodiment of the present application, since a vent member including a vent resin having a lower melting point than a sealant resin of a case is provided in an extension of a sealing portion, gas can be induced to be discharged to the extension, thereby improving safety. BRIEF DESCRIPTION OF DRAWINGS

[0041] The accompanying drawings, which are included to provide a further understanding of the application and are incorporated in and constitute a part of this application, illustrate embodiment(s) of the application and together with the description serve to explain the principle of the application. In the drawings:

[0042] Figure 1 A plan view of a secondary battery according to one embodiment of the present application is shown.

[0043] Figure 2 is a schematic view showing vent formation in a secondary battery according to one embodiment of the present application.

[0044] Figure 3A partial plan view of an electrode lead and an exhaust member in a secondary battery according to another embodiment of the present application is shown.

[0045] Figure 4 A partial plan view of an electrode lead and an exhaust member in a secondary battery according to another embodiment of the present application is shown.

[0046] Figure 5 A partial plan view of an electrode lead and an exhaust member in a secondary battery according to another embodiment of the present application is shown.

[0047] Figure 6 A partial plan view of an electrode lead and an exhaust member in a secondary battery according to another embodiment of the present application is shown.

[0048] Figure 7a A partial plan view of an electrode lead and an exhaust member in a secondary battery according to another embodiment of the present application is shown. Figure 1 A cross-sectional view of an exhaust member according to one embodiment of the present application is shown.

[0049] Figure 7b A cross-sectional view of an exhaust member according to another embodiment of the present application is shown. Figure 1 A cross-sectional view of an exhaust member according to another embodiment of the present application is shown.

[0050] Figure 8 A partial plan view of an electrode lead and an exhaust member in a secondary battery according to another embodiment of the present application is shown.

[0051] Figure 9 A partial plan view of an electrode lead and an exhaust member in a secondary battery according to another embodiment of the present application is shown.

[0052] Figure 10 A partial plan view of an electrode lead and an exhaust member in a secondary battery according to another embodiment of the present application is shown.

[0053] Figure 11 A partial plan view of an electrode lead and an exhaust member in a secondary battery according to another embodiment of the present application is shown.

[0054] Figure 12 A partial plan view of an electrode lead and an exhaust member in a secondary battery according to another embodiment of the present application is shown.

[0055] Figure 13 A partial plan view of an electrode lead and an exhaust member in a secondary battery according to another embodiment of the present application is shown. DETAILED DESCRIPTION

[0056] Hereinafter, preferred embodiments of the present application will be described in detail with reference to the accompanying drawings. Before the description, it is to be understood that the terminology used in the specification and the appended claims should not be interpreted as limiting, but should be interpreted based on the principles of the inventor's allowing the terms to be properly defined for the best explanation, based on the meanings and concepts corresponding to the technical aspects of the present application.

[0057] Therefore, the description set forth herein is merely illustrative of preferred embodiments of the application and is not intended to limit the scope of the application as defined by the appended claims. The application can be practiced with other equivalent and modifications such that the scope of the application is not limited to the preferred embodiments.

[0058] A secondary battery according to one embodiment of the present application includes an electrode assembly to which an electrode lead is attached, a case including an accommodation portion for accommodating the electrode assembly and a sealing portion containing a sealing resin and formed to seal the electrode assembly, and a lead film configured to surround a portion of an outer surface of the electrode lead and interposed between the electrode lead and the sealing portion of the case, wherein the sealing portion includes an extension portion in which an exhaust member containing an exhaust resin having a lower melting point than the sealing resin is included.

[0059] Figure 1 A secondary battery according to one embodiment of the present application is illustrated. Referring to Figure 1 , a secondary battery 10 according to one embodiment of the present application includes an electrode assembly 12 to which an electrode lead 11 is attached, and a case 13.

[0060] The electrode assembly 12 includes a positive electrode plate, a negative electrode plate, and a separator. In the electrode assembly 12, the positive electrode plate and the negative electrode plate can be sequentially stacked in a state in which the separator is interposed therebetween.

[0061] The positive electrode plate can include a positive electrode current collector made of a metal thin film (e.g., an aluminum (Al) foil) having excellent electrical conductivity, and a positive electrode active material layer coated on at least one surface thereof. In addition, the positive electrode plate can include a positive electrode tab made of a metal material (e.g., an aluminum (Al) material) at one side end portion thereof. The positive electrode tab can protrude from the one side end portion of the positive electrode plate. The positive electrode tab can be welded to the one side end portion of the positive electrode plate, or adhered thereto using a conductive adhesive.

[0062] The negative electrode plate can include a negative electrode current collector made of a conductive metal thin film (e.g., a copper (Cu) foil), and a negative electrode active material layer coated on at least one surface thereof. In addition, the negative electrode plate can include a negative electrode tab formed of a metal material (e.g., a copper (Cu) or nickel (Ni) material) at one side end portion thereof. The negative electrode tab can protrude from the one side end of the negative electrode plate. The negative electrode tab can be welded to the one side end portion of the negative electrode plate, or adhered thereto using a conductive adhesive.

[0063] A separator is interposed between the positive electrode plate and the negative electrode plate to electrically insulate the positive electrode plate and the negative electrode plate from each other, and can be formed in a porous film form so that lithium ions can pass between the positive electrode plate and the negative electrode plate. The separator can include, for example, a porous film using polyethylene (PE), or polypropylene (PP), or a composite film thereof.

[0064] An inorganic coating layer can be provided on the surface of the separator. The inorganic coating layer can have a structure in which inorganic particles are bonded to each other by a binder so as to form interstitial volumes between the particles.

[0065] The electrode assembly 12 can be a jelly-roll (wound type) electrode assembly having a structure in which long sheet type positive and negative electrodes are wound in a state in which a separator is interposed therebetween, a stacked (stacked type) electrode assembly having a structure in which a plurality of positive and negative electrodes cut into a predetermined size are stacked in order in a state in which a separator is interposed therebetween, a stacked / folded type electrode assembly having a structure in which a dual cell or a full cell in which positive and negative electrodes of a predetermined unit are stacked in a state in which a separator is interposed therebetween is wound, or the like.

[0066] The case 13 can include an accommodation portion 13a for accommodating the electrode assembly 12, a bent face 17, and a sealing portion 13b containing a sealant resin and formed to seal the electrode assembly 12. The bent face 17 is formed by bending adjacent portions (an upper case portion and a lower case portion) of the case 13 to face each other, as best shown in Figure 1

[0067] The sealing portion 13b can be three-side sealed at the edge of the case 13. In the three-side sealing structure, the case 13 is bent so that the accommodation portion 13a is formed on the upper case, and the lower case is overlapped to form the accommodation portion. After the case is bent in this way, the edges of the remaining three sides except for the bent portion forming the bent face 17 are sealed.

[0068] The sealing portion 13b refers to a portion, for example, welded along the outer peripheral surface of the accommodation portion 13a to seal the electrode assembly 12. The sealing portion 13b can be welded by heat welding, ultrasonic welding, or the like, but is not particularly limited as long as the sealing portion can be welded. The electrode assembly 12 is surrounded by the three sides of the sealing portion 13b and the bent face 17 of the case 13, as best shown in Figure 1

[0069] The electrode lead 11 can be accommodated in the case 13 so that a portion thereof is exposed to the outside of the case 13. The secondary battery 10 according to one embodiment of the present application includes, as best shown in Figure 1 ​​The lead film 14 is shown in FIG. 1. The lead film 14 surrounds a portion of the outer surface of the electrode lead 11 and is interposed between the electrode lead 11 and the sealing portion 13b of the case 13 in the region in which the electrode lead 11 protrudes to assist in the adhesion of the electrode lead 11 to the sealing portion 13b of the case 13.

[0070] In one embodiment of the present application, the case 13 can be in the form of a pouch.

[0071] In this embodiment, the case 13 can include an upper pouch and a lower pouch. If the case 13 includes an upper pouch and a lower pouch, after the upper pouch and the lower pouch are arranged such that their sealant resins face each other, the sealant resins facing each other are fused to each other by heat and pressure to have a structure that seals the battery.

[0072] In one embodiment of the present application, the case 13 can be provided in the form of a film having a multi-layer structure including an outer layer for protection against external impact, a metal barrier layer for blocking moisture, and a sealant layer for sealing the case.

[0073] The outer layer can include a polyester film using polyethylene terephthalate (PET), polybutylene terephthalate, polyethylene naphthalate, polybutylene naphthalate, copolyester, polycarbonate, nylon, etc., and can be composed of a single layer or multiple layers. The metal barrier layer can include aluminum, copper, etc.

[0074] The sealant layer contains a sealant resin and can be composed of a single layer or multiple layers. The sealant resin can include polypropylene (PP), acid-modified polypropylene (PPa), random polypropylene, ethylene propylene copolymer, or two or more thereof. The ethylene propylene copolymer can include, but is not limited to, ethylene-propylene rubber, ethylene-propylene block copolymer, etc.

[0075] The sealing portion 13b includes an extension 15. When the case 13 of the secondary battery is bent to seal the edges of three sides other than the bending surface, the edge of one sealing edge adjacent to the bending surface of the secondary battery can protrude outward. The extension 15 can be a bat ear region. Throughout this specification, the "bat ear region" refers to an extension of the sealing portion that protrudes outward, not in a direction in which the edge of the bending surface 17 extends. The bat ear region is one example of an extension of the sealing portion that protrudes outward. Other embodiments can have extensions of the sealing portion of different shapes and sizes.

[0076] In this case, since the sealing strength of the bending surface 17 is greater than the sealing strength of the sealing portion, it is highly likely that the gas is discharged in the sealing portion other than the sealing portion adjacent to the bending surface, and thus there is a high risk of damaging the lead tab, the bus bar, etc.

[0077] After the electrolyte is injected in the seal portion other than the seal portion adjacent to the bent surface (i.e., the extension portion), the case can be sealed again. Therefore, if the exhaust member is included in the seal portion other than the extension portion, the electrolyte can be attached to the exhaust member. Further, since the sealing is performed again after the electrolyte is injected, the sealing strength of the seal portion other than the extension portion is greater than the sealing strength of the extension portion. Thereby, it will be more likely to induce the exhaust in the extension portion rather than in the remaining portion of the seal portion.

[0078] In the secondary battery according to one embodiment of the present application, the extension portion 15 includes the exhaust member 16. The secondary battery 10 according to one embodiment of the present application can induce the gas exhaust to the extension portion 15 spaced apart from the electrode lead 11, and thus can minimize the amount of gas directly contacting the electrode lead 11 by the exhaust, thereby further improving the safety of the battery. That is, it can minimize the amount of gas exhausted toward the side portion of the electrode lead 11, thereby further improving the safety of the battery. As Figure 1 As indicated by the direction arrow representing the exhaust direction, the exhaust is guided away from the electrode lead 11. The electrode lead 11 is a component whose temperature rapidly increases in an abnormal situation such as overcharge or internal short circuit. Therefore, if the direct contact between the exhausted gas and the electrode lead is minimized, the safety of the secondary battery can be improved. Throughout the present specification, the inclusion of the exhaust member 16 in the extension portion 15 means that the extension portion 15 and the exhaust member 16 can at least partially overlap.

[0079] The secondary battery 10 according to one embodiment of the present application includes the exhaust member 16 containing the exhaust resin having a lower melting point than the sealant resin. Since the exhaust member 16 contains the exhaust resin having a lower melting point than the sealant resin, the exhaust member 16 melts before the sealant resin as the temperature increases. The sealing strength of the portion into which the exhaust member 16 is inserted is further reduced at high temperatures compared to the sealing strength of the case portion containing the sealant resin, and thus the exhaust property can be easily achieved. Therefore, since the sealing strength is reduced when heat propagation occurs, the extension portion 15 can be induced to exhaust, i.e., to function as a pipe to release the gas from the accommodation portion to the outside of the secondary battery, thereby effectively preventing the electrode lead 11 and the like from being damaged by the gas, flame, or the like.

[0080] Figure 2 is a schematic view illustrating the exhaust formation in the secondary battery according to one embodiment of the present application. Specifically, Figure 2 is a cross-sectional view illustrating the exhaust member in the secondary battery according to one embodiment of the present application.

[0081] Referring to Figure 2The exhaust member 16 is used to seal the outside of the case 13 at a normal temperature at which the battery is operated. If the temperature of the battery is excessively increased due to abnormal operation of the battery, the sealing strength of the portion of the exhaust member 16 inserted is reduced as the exhaust member 16 melts. Accordingly, as the sealing strength of the portion of the exhaust member 16 inserted is reduced, an exhaust portion can be formed at the location to exhaust gas from the case. For example, as the pressure inside the battery is applied at the interface between the exhaust member 16 and the extension 15, a gap or an exhaust portion is formed between the exhaust member 16 and the extension 15 to exhaust gas.

[0082] The exhaust member 16 can be attached to the case 13 by heat fusion. In another example, the exhaust member 16 and the case 13 can be overlapped by an adhesive such as glue. In another example, the exhaust member 16 and the case 13 can be physically coupled to each other by a clip or the like. In another example, at least a portion of the exhaust member 16 can be embedded in a film (e.g., a sealant resin) constituting the case 13.

[0083] In one embodiment of the present application, the exhaust member 16 can be located within the extension 15. In another embodiment of the present application, the exhaust member 16 can be located in the extension 15 through the accommodation portion 13a. In another embodiment of the present application, the exhaust member 16 can extend to the outside of the case 13 through the extension 15. In another embodiment of the present application, the exhaust member 16 can be positioned to pass through the accommodation portion 13a via the extension 15 to be exposed to the outside of the case 13.

[0084] Figure 3 A secondary battery 10 according to another embodiment of the present application is illustrated. Referring to FIG. 2, the secondary battery 10 includes a case 13, an electrode lead 11, and an exhaust member 16. Figure 3 The exhaust member 16 can be inclined in the extension 15, for example, the exhaust member 16 can have an inclination angle of 10° to 80°, or 20° to 60°, or 40° to 50°. The inclination angle can be defined as an angle between the exhaust member and a protruding direction of the electrode lead 11.

[0085] In one embodiment of the present application, the exhaust member 16 can not overlap or contact the lead film 14.

[0086] The exhaust member 16 can be positioned to have a region at least partially overlapping or contacting the lead film 14. When the exhaust member 16 has at least a partial region overlapping or contacting the lead film 14, it is easy to align and easy to fix the position of the exhaust member 16. For example, when the exhaust member 16 is inserted and then fused, since a portion of the exhaust member 16 overlaps or contacts the lead film 14, the exhaust member 16 can be inserted and then fused at a predetermined position.

[0087] The exhaust member 15 can have various shapes to easily induce or promote exhaust. In one embodiment of the invention, the exhaust member 16 can have a shape along... Figure 1 The structure with a narrowing exhaust direction indicated by the directional arrow in the diagram. The width of the exhaust member 16 can be continuously or discontinuously narrowed along the exhaust direction. When the exhaust member 16 has a structure that narrows along the exhaust direction, the exhaust angle of the emitted gas can be reduced to minimize the amount of gas emitted toward the side of the electrode lead 11, thereby further improving the safety of the battery.

[0088] Figures 4 to 6 This is a partially enlarged view showing the leads and venting components in a secondary battery according to other embodiments of the present invention.

[0089] Reference Figure 4 and Figure 5 The exhaust component 16 may have, for example, an elliptical shape ( Figure 4 ) or step shape ( Figure 5 However, in other embodiments, the exhaust component 16 can be circular, triangular, trapezoidal, etc.

[0090] like Figure 6 As shown, the exhaust member 16 can be an asymmetrical stepped structure. In an asymmetrical stepped structure, the differences in the steps can be formed corresponding to the sides of the electrode lead 11. For example, the size (exhaust angle of the exhaust gas) and position (distance from the electrode lead 11) of the exhaust end of the exhaust member 16 can be configured to minimize the contact between the exhaust gas and the electrode lead, preferably as follows: Figure 6 As shown in the diagram. Therefore, reducing the size of the exhaust end of the exhaust component to guide the gas away from the electrode lead 11 and positioning the exhaust end away from the electrode lead will minimize any contact between the exhaust gas and the electrode lead.

[0091] In one embodiment of the present invention, the thickness of the exhaust component 16 may decrease continuously or discontinuously along the protruding direction of the electrode lead 11. Figure 7a and Figure 7b It shows a variable thickness Figure 1 Two embodiments of the cross-section of the exhaust component. See reference. Figure 7a The thickness of the exhaust component 16 can be reduced discontinuously in a stepped shape. Figure 7b An exhaust component with a gradually or continuously varying thickness is shown.

[0092] The exhaust member 16 can be positioned at a predetermined distance apart from the electrode lead 11. Thus, it is easier to minimize the amount of gas discharged toward a direction that can directly contact the electrode lead 11, i.e., toward the side of the electrode lead 11, thereby further improving the safety of the battery. The temperature of the electrode lead 11 rapidly increases in abnormal situations such as overcharge or internal short circuit. Thus, if direct contact between the discharged gas and the electrode lead is minimized, the safety can be improved.

[0093] In one embodiment of the present application, the exhaust member 16 can be spaced apart from the lead film 14 in the sealing portion, and the exhaust member 16 can at least partially overlap or contact the lead film 14 in the accommodation portion 13a. As the exhaust member 16 does not overlap or contact the lead film 14 in the sealing portion, i.e., the exhaust member 16 is positioned away from the electrode lead 11, it is easier to minimize the amount of gas discharged toward the side of the electrode lead 11, thereby further improving the safety of the battery.

[0094] In one embodiment of the present application, the area where the exhaust member overlaps or contacts the lead film can be 1% to 30%, or 1.3% to 23%, or 1.5% to 12%, or 2% to 9% of the area where the lead film does not overlap the electrode lead. Here, the area where the lead film does not overlap the electrode lead refers to the sum of the two areas of the electrode lead and the lead film that do not overlap.

[0095] A portion of the exhaust member 16 and a portion of the lead film 14 can overlap or contact each other by heat fusion. In another example, a portion of the exhaust member 16 and a portion of the lead film 14 can overlap or contact each other by an adhesive such as glue. In another example, a portion of the exhaust member 16 and a portion of the lead film 14 can be physically coupled to each other by a clip or the like. In another example, a portion of the exhaust member 16 can be embedded in the film constituting the lead film 14.

[0096] Figure 8 FIG. 2 is a partial enlarged view showing the electrode lead 11 and the exhaust member 16 in the secondary battery according to another embodiment of the present application. Referring to FIG. 2, the exhaust member 16 can include a first portion 16b extending in the X-axis direction and a second portion 16a extending in the Y-axis direction. Figure 8 When the protruding direction of the electrode lead 11 is set as the Y-axis and the direction orthogonal to the Y-axis is set as the X-axis, the exhaust member 16 can include a first portion 16b extending in the X-axis direction and a second portion 16a extending in the Y-axis direction. As shown in FIG. 2, the first portion 16b extends from or bridges the second portion 15b to the lead film 14. Figure 8

[0097] In one embodiment of the present application, the exhaust member 16 can have an L shape as shown in FIG. 3. Figure 8

[0098] ​​In another embodiment of the invention, the exhaust component 16 can be as follows: Figure 9 The configuration shown is such that the inner end of the second portion 16a is cut to form a tapered section. For example, the inner end of the second portion 16a can be cut in a direction not orthogonal to the Y-axis. If the exhaust member 16 is shaped as described above, it is easier to prevent the electrode assembly 12 inside the receiving portion 13a from contacting the inner end of the second portion 16a. Here, the inner end of the second portion 16a refers to the end of the second portion closer to the receiving portion.

[0099] Figure 10 This is a partially enlarged view showing the electrode lead 11 and the venting member 16 in a secondary battery according to another embodiment of the present invention. (Refer to...) Figure 10 The first portion may extend between the lead film and the second portion in a first direction not parallel to the Y-axis. The second portion may extend in a second direction orthogonal to the first direction. For example, when the first direction is set at an angle of 45° relative to the protruding direction of the electrode lead 11, the exhaust member 16 may have an L-shape.

[0100] In another embodiment of the invention, the exhaust member 16 can be configured such that the inner end of the second portion 16a is cut to form a tapered cross-section. For example, the inner end of the second portion 16a can be cut in a direction not orthogonal to the second direction. If the exhaust member 16 is shaped as described above, it is easier to prevent the electrode assembly 12 inside the receiving portion 13a from contacting the inner end of the second portion 16a. Here, the inner end of the second portion 16a refers to the end of the second portion closer to the receiving portion.

[0101] In one embodiment of the invention, the second portion 16a (such as the main body portion) may be substantially vented, and the first portion 16b (such as the bridging portion) may be substantially non-vented.

[0102] Reference Figures 8 to 10 In one embodiment of the invention, the first portion 16b may have at least a portion of its area overlapping or contacting the lead film 14. Because the first portion 16b has at least a portion of its area overlapping or contacting the lead film 14, the position of the venting member 16 can be easily and consistently fixed. For example, when the venting member 16 is inserted and then welded, because a portion of the first portion 16b overlaps or contacts the lead film 14, the venting member 16 can be inserted and welded at a predetermined position.

[0103] A portion of the first portion 16b can be overlapped or contacted with a portion of the lead film 14 by heat fusion. In another example, a portion of the first portion 16b can be overlapped or contacted with a portion of the lead film 14 by an adhesive such as glue. In another example, a portion of the first portion 16b can be physically combined with a portion of the lead film 14 by a clip or the like. In another example, a portion of the first portion 16b can be embedded in the film constituting the lead film 14.

[0104] Referring to Figures 8 to 10 In one embodiment of the present application, the second portion 16a of the exhaust member 16 can not be overlapped or contacted with the lead film 14. For example, the second portion 16a can not be overlapped or contacted with the lead film 14 in the sealing portion. When the second portion 16a of the exhaust member 16 is not overlapped or contacted with the lead film 14, the amount of gas discharged toward the side of the electrode lead 11 can be minimized, thereby further improving the safety of the battery.

[0105] Referring to Figures 8 to 10 The outer side end of the first portion 16b can be spaced apart from the inner side end of the extension portion 15. Here, the "outer side end of the first portion of the exhaust member" refers to the end of the first portion 16b that is closer to the extension portion. The term "inner side end of the extension portion" refers to the end of the sealing portion adjacent to the accommodation portion of the extension portion. In this case, the entire first portion 16b can be located within the accommodation portion 13a. Accordingly, the gap or space between the first portion 16b and the extension portion 15 can be exposed to the accommodation portion 13a, as a result of which the pressure of the gas is concentrated at the gap or space, facilitating rapid exhaust in the event of an abnormal situation.

[0106] In one embodiment of the present application, the first portion 16b can have a rectangular shape. For example, the long side of the first portion can be located in the X-axis direction, and the short side of the first portion can be located in the Y-axis direction. In one embodiment of the present application, the second portion 16a can have a rectangular shape. For example, the short side of the rectangular-shaped second portion can be located in the X-axis direction, and the long side of the rectangular-shaped second portion can be located in the Y-axis direction.

[0107] Figures 11 to 13 FIGS. 7 and 8 are partial enlarged views illustrating the lead film and the exhaust member in the secondary battery according to other embodiments of the present application.

[0108] Referring to Figures 11 to 13 As described above, the exhaust member 16 can include the first portion 16b and the second portion 16a, and the second portion 16a can have, for example, an elliptical or stepped shape. However, in other embodiments, the shape of the second portion 16a can be circular, triangular, or trapezoidal, or the like.

[0109] Further, referring toFigure 13 The second portion 16a can be an asymmetric stepped structure. In the asymmetric stepped structure, the difference in the steps can be formed to correspond to the side of the electrode lead 11. For example, the size (exhaust gas discharge angle) and position (distance from the electrode lead 11) of the discharge end portion of the second portion 16a can be configured to minimize the contact of the exhaust gas with the electrode lead, optimally as shown in FIG. 10. Figure 13 By thus reducing the size of the discharge end portion of the second portion to direct the gas away from the electrode lead 11 and positioning the discharge end portion away from the electrode lead, any contact between the exhaust gas and the electrode lead will be minimized.

[0110] In one embodiment of the present application, the exhaust member 16 can exhaust at 100°C to 120°C. Further, the exhaust member 16 can exhaust at a pressure of 1.5 atm or more.

[0111] Since the exhaust member 16 exhausts at the aforementioned temperature range and / or the aforementioned pressure conditions, it is easier to seal the battery during normal operation of the battery and induce gas discharge only during abnormal operation of the battery.

[0112] In one embodiment of the present application, the exhaust resin having a lower melting point than the sealant resin can contain a linear low-density polyethylene having a comonomer with a carbon number of 6 or more. Since the exhaust resin having a lower melting point than the sealant resin contains a linear low-density polyethylene having a comonomer with a carbon number of 6 or more, excellent fusion with the sealant resin can be ensured in the normal temperature range, and the sealing strength of the sealing portion including the exhaust member 16 can be reduced at high temperatures to achieve the exhaust characteristics.

[0113] In one embodiment of the present application, the exhaust resin having a lower melting point than the sealant resin can contain a linear low-density polyethylene having a comonomer with a carbon number of 6 to 8.

[0114] In one embodiment of the present application, the exhaust resin having a lower melting point than the sealant resin can have a melting point of 100°C to 130°C, or 105°C to 125°C, or 110°C to 120°C. If the melting point of the exhaust resin satisfies the above range, the sealing strength of the sealing portion including the exhaust member 16 can be reduced at high temperatures (e.g., 100°C or more), so that the exhaust characteristics can be more easily achieved.

[0115] The melting point of the vent resin having a lower melting point than the sealing resin can be measured using differential scanning calorimetry (DSC). For example, the temperature of a sample is raised from 30°C to 280°C at 10°C / minute, held at 280°C for 10 minutes, cooled to 30°C at 10°C / minute, and then held at 30°C for 10 minutes. Subsequently, the melting point is measured by holding the temperature at 280°C for 10 minutes after raising the temperature of the sample from 30°C to 280°C at 10°C / minute.

[0116] In one embodiment of the present application, the vent member can have a maximum sealing strength of less than 6 kgf / 15 mm or less than 5 kgf / 15 mm or less than 4.5 kgf / 15 mm at 100°C or higher. In one embodiment of the present application, the vent member 15 can have a maximum sealing strength of less than 6 kgf / 15 mm or less than 5 kgf / 15 mm or less than 4.5 kgf / 15 mm at 100°C to 120°C. In one embodiment of the present application, the vent member 16 can have a maximum sealing strength of less than 3 kgf / 15 mm or less than 2 kgf / 15 mm or less than 1 kgf / 15 mm or less than 0.5 kgf / 15 mm at 120°C or higher. If the vent member satisfies the above sealing strength in the above temperature range, the sealing strength of the sealing portion including the vent member 16 can be reduced at high temperature (for example, 100°C or higher), so that the venting property can be easily achieved.

[0117] Further, in one embodiment of the present application, the vent member can have a maximum sealing strength of 6 kgf / 15 mm or more or 8 kgf / 15 mm or more or 10 kgf / 15 mm or more at room temperature to 60°C. If the vent member satisfies the above sealing strength in the above temperature range, excellent sealing strength can be ensured during normal operation of the battery, so that the sealing property of the battery can be easily ensured.

[0118] In one embodiment of the present application, the vent member can have a maximum sealing strength of less than 6 kgf / 15 mm at 100°C or higher, and the vent member can have a maximum sealing strength of 6 kgf / 15 mm or more at room temperature to 60°C. If the vent member satisfies the above sealing strength, the sealing strength of the sealing portion including the vent member 16 can be reduced at high temperature, so that the venting property can be easily achieved. Further, since excellent sealing strength is ensured during normal operation of the battery, the sealing property of the battery can be easily ensured.

[0119] In one embodiment of the present application, the exhaust member can have an average sealing strength of less than 4.5 kgf / 15 mm or less than 3 kgf / 15 mm at 100°C or higher. In one embodiment of the present application, the exhaust member 16 can have an average sealing strength of less than 4.5 kgf / 15 mm or less than 3 kgf / 15 mm at 100°C to 120°C. In one embodiment of the present application, the exhaust member 16 can have an average sealing strength of less than 2 kgf / 15 mm or less than 1 kgf / 15 mm or less than 0.5 kgf / 15 mm at 120°C or higher. If the exhaust member satisfies the above sealing strength in the above temperature range, the sealing strength of the sealing portion including the exhaust member 16 can be reduced at high temperature, so that the exhaust characteristic can be easily achieved.

[0120] In one embodiment of the present application, the exhaust member can have an average sealing strength of 4.5 kgf / 15 mm or more or 5 kgf / 15 mm or more or 6 kgf / 15 mm or more or 7 kgf / 15 mm or more at room temperature to 60°C. If the exhaust member satisfies the above sealing strength in the above temperature range, excellent sealing strength can be ensured during normal operation of the battery, thereby easily ensuring the sealing characteristic.

[0121] In one embodiment of the present application, the exhaust member can have an average sealing strength of less than 4.5 kgf / 15 mm at 100°C or higher, and the exhaust member can have an average sealing strength of 4.5 kgf / 15 mm or more at room temperature to 60°C. If the exhaust member has the above sealing strength in the above temperature range, the sealing strength of the sealing portion including the exhaust member 16 can be reduced at high temperature, so that the exhaust characteristic can be easily achieved. Further, since excellent sealing strength is ensured during normal operation of the battery, the sealing characteristic of the battery can be easily ensured.

[0122] The sealing strength of the exhaust member according to temperature can be measured as follows: after cutting a portion of a case to be inserted into the exhaust member into a width of 15 mm and a length of 5 cm and then spreading both ends thereof to 180°, and gripping both ends thereof using a UTM jig, a tensile test is performed at a speed of 5 mm / min.

[0123] At this time, the "maximum sealing strength" means a maximum value when the case is broken, and the "average sealing strength" means an average value when the case is stretched by 8 mm at 4.5 kgf / 15 mm if the maximum sealing strength is 4.5 kgf / 15 mm or more, and an average value when the case is stretched by 8 mm at the maximum sealing strength if the maximum sealing strength is less than 4.5 kgf / 15 mm.

[0124] In one embodiment of the present application, the vent resin can be polymerized in the presence of a metallocene catalyst. If the vent resin is polymerized in the presence of a metallocene catalyst, it can be more advantageous in terms of sealing strength and properties compared to the case where it is polymerized in the presence of a Ziegler-Natta catalyst.

[0125] In one embodiment of the present application, the content of the comonomer having 6 or more carbon atoms in the linear low density polyethylene having a comonomer having 6 or more carbon atoms can be 15% by weight or less, or 12% by weight or less, or 11.8% by weight or less, or 10% by weight or less, or 9% by weight or less, or 8% by weight or less, or 7.6% by weight or less, based on 100% by weight of the linear low density polyethylene having a comonomer having 6 or more carbon atoms. Meanwhile, it can be 5% by weight or more, or 7.6% by weight or more, or 8% by weight or more, or 9.0% by weight or more, or 10% by weight or more, or 11.8% by weight or more, or 12% by weight or more. If the content of the comonomer having 6 or more carbon atoms satisfies the above range, the sealing strength can be easily secured not to be reduced during the normal operation of the battery due to the reduction in the packing density between molecules.

[0126] The content of the comonomer having 6 or more carbon atoms can be measured using H-NMR. For example, after about 10 mg of a sample is completely dissolved in about 0.6 ml of trichloroethylene solvent using a hot air gun, it can be sampled in an NMR tube and analyzed using 1 H-NMR or 13 C-NMR analysis method.

[0127] In one embodiment of the present application, the vent resin having a lower melting point than the sealant resin can have a weight average molecular weight of 100,000 g / mol to 400,000 g / mol, or 200,000 g / mol to 350,000 g / mol, or 230,000 g / mol to 300,000 g / mol. If the vent resin satisfies the above range, the sealing strength of the sealant resin can be more excellent during the normal operation of the battery.

[0128] In one embodiment of the present application, the vent resin having a lower melting point than the sealant resin can have a polydispersity index (PDI) of 4 or less, or 3.8 or less, or 3.796 or less, or 3.5 or less, or 3.023 or less, or 3 or less, or 2.7 or less, or 2.674 or less. Further, the polydispersity index (PDI) can be 1.0 or more. If the vent resin satisfies the above range, the molecular weight distribution is narrow, and thus the sealing strength and properties of the sealant resin can be improved during the normal operation of the battery.

[0129] The weight average molecular weight and the polydispersity index of the exhaust resin having a lower melting point than the sealant resin can be measured by gel permeation chromatography (GPC) under the following conditions:

[0130] - Column: Tosoh, HLC-8321 GPC / HT

[0131] - Solvent: TCB (Trichlorobenzene) + 0.04% BHT (after drying with 0.1% CaCl2)

[0132] - Flow rate: 1.0 ml / min

[0133] - Sample concentration: 1.5 mg / ml

[0134] - Dose: 300 μl

[0135] - Column temperature: 160°C

[0136] - Detector: RI detector

[0137] - Standard: Polystyrene (calibrated with a third order function)

[0138] In one embodiment of the present application, the crystallization temperature of the sealant resin and the crystallization temperature of the exhaust resin having a lower melting point than the sealant resin can be similar. For example, the difference between the crystallization temperature of the sealant resin and the crystallization temperature of the exhaust resin can be 10°C or less, or 5°C or less. Further, the difference between the crystallization temperature of the sealant resin and the crystallization temperature of the exhaust resin can be 0.1°C or more. If the difference between the crystallization temperature of the sealant resin and the crystallization temperature of the exhaust resin satisfies the above range, the sealant resin and the exhaust resin can have improved fusion characteristics during normal operation of the battery.

[0139] In one embodiment of the present application, the exhaust resin having a lower melting point than the sealant resin can have a crystallization temperature of 90°C to 115°C, or 95°C to 110°C, or 100°C to 110°C, or 105°C to 110°C. If the exhaust resin satisfies the above range, the sealant resin and the exhaust resin can have improved fusion characteristics.

[0140] The crystallization temperature can be measured using differential scanning calorimetry (DSC). For example, the temperature of a sample is raised from 30°C to 280°C at 10°C / minute, held at 280°C for 10 minutes, cooled to 30°C at 10°C / minute, and then held at 30°C for 10 minutes. Subsequently, the crystallization temperature is measured by holding the temperature at 280°C for 10 minutes after raising the temperature of the sample from 30°C to 280°C at 10°C / minute.

[0141] In one embodiment of the present application, the exhaust member 16 can have a thickness of the film.

[0142] The exhaust member 16 can be formed to have a predetermined thickness of a predetermined size. In addition, the exhaust member 16 can be inserted into the extension portion 15 so that its insertion length can be changed, or its exhaust pressure and position can be controlled according to design needs.

[0143] In one embodiment of the present application, the exhaust member 16 can further include an adhesive layer for improved placement and sealing between a sealant resin and an exhaust resin having a lower melting point than the sealant resin.

[0144] Since the secondary battery according to one embodiment of the present application has an extension portion including an exhaust member having an exhaust resin with a lower melting point than a sealant resin, when heat propagation occurs, directional exhaust of gas toward the extension portion by reducing the sealing strength at high temperature can be easily and effectively achieved.

[0145] In one embodiment of the present application, the secondary battery can be a cylindrical, prismatic, or pouch-type secondary battery.

[0146] Although preferred embodiments of the present application have been shown and described above, the present application is not limited to the specific embodiments described above and those skilled in the art can modify the present application in various ways without departing from the spirit of the present application defined in the claims, and these modifications should not be individually understood from the technical idea or prospect of the present application.

Claims

1. A secondary battery comprising: an electrode assembly; an electrode lead attached to the electrode assembly; a case including a sealing portion, a bent face, and an accommodation portion configured to be defined by the bent face and internally accommodate the electrode assembly, the sealing portion containing a sealing resin to form a seal around the electrode assembly, wherein the sealing portion includes an extension portion adjacent to and extending away from the bent face; and an exhaust member disposed at least partially in the extension portion, the exhaust member including an exhaust resin having a lower melting point than the sealing resin, wherein the exhaust member is disposed at least partially in a bat ear region that protrudes to an outside of the secondary battery, rather than the extension portion of the sealing portion that protrudes in a direction in which an edge of the bent face extends. 2.The secondary battery of claim 1, further comprising a lead film surrounding an outer surface of the electrode lead, the lead film being disposed between the electrode lead and the sealing portion, wherein the exhaust member extending through the accommodation portion, a first end portion of the exhaust member being spaced apart from the lead film in the sealing portion, and a second end portion of the exhaust member at least partially overlapping or contacting the lead film in the accommodation portion. 3.The secondary battery of claim 1, further comprising a lead film surrounding an outer surface of the electrode lead, the lead film being disposed between the electrode lead and the sealing portion, the electrode lead extending away from the case along a Y-axis, the exhaust member including a first portion and a second portion, the first portion extending between the lead film and the second portion along an X-axis orthogonal to the Y-axis, the second portion extending along the Y-axis. 4.The secondary battery of claim 1, further comprising a lead film surrounding an outer surface of the electrode lead, the lead film being disposed between the electrode lead and the sealing portion, the electrode lead extending away from the case along a Y-axis, the exhaust member including a first portion and a second portion, the first portion extending between the lead film and the second portion along a first direction that is not parallel to the Y-axis, the second portion extending along a second direction orthogonal to the first direction.

5. The secondary battery according to claim 3, wherein the exhaust member has an L shape.

6. The secondary battery according to claim 3, wherein the exhaust member includes a tapered cross section at an intersection of the first portion and the second portion, the tapered cross section extending into the accommodation portion.

7. The secondary battery according to claim 3, wherein the first portion is a bridging portion that at least partially overlaps the lead film.

8. The secondary battery according to claim 3, wherein an outer end portion of the first portion is spaced apart from an inner end portion of the extension portion, the first portion being located in the accommodation portion.

9. The secondary battery according to claim 3, wherein the second portion does not overlap or contact the lead film.

10. The secondary battery according to claim 1, wherein the exhaust member defines a variable width that decreases along an exhaust direction.

11. The secondary battery according to claim 1, wherein the exhaust member is defined as any one of a circular shape, an elliptical shape, a stepped shape, a triangular shape, and a trapezoidal shape.

12. The secondary battery according to claim 1, wherein the exhaust member defines a variable thickness that decreases along an exhaust direction.

13. The secondary battery according to claim 2, wherein An area where the gas discharge member overlaps or contacts the lead film is 1 to 30% of an area where the lead film does not overlap or contact the electrode lead.

14. The secondary battery according to claim 1, wherein The gas discharge resin contains a linear low-density polyethylene having a comonomer with a carbon number of 6 or more.

15. The secondary battery according to claim 1, wherein The gas discharge member melts at 100°C to 120°C to discharge gas from the accommodation portion to the outside of the secondary battery.

16. The secondary battery according to claim 15, wherein The gas discharge member discharges gas from the accommodation portion when the accommodation portion is at a pressure of 1.5 atm or more.

17. The secondary battery according to claim 1, wherein The gas discharge member has a maximum seal strength of less than 6 kgf / 15 mm at 100°C or more.

18. The secondary battery according to claim 1, wherein The gas discharge member has an average seal strength of less than 4.5 kgf / 15 mm at 100°C or more.

19. The secondary battery according to claim 1, wherein The gas discharge member has a maximum seal strength of 6 kgf / 15 mm or more at room temperature to 60°C.

20. The secondary battery according to claim 1, wherein The gas discharge member has an average seal strength of 4.5 kgf / 15 mm or more at room temperature to 60°C.

21. The secondary battery according to claim 1, wherein The gas discharge resin is polymerized in the presence of a metallocene catalyst.

22. The secondary battery of claim 14, wherein, The content of the comonomer with a carbon number of 6 or more is 15% by weight or less based on 100% by weight of the linear low-density polyethylene.

23. The secondary battery of claim 1, wherein, The gas discharge resin has a polydispersity index, PDI, of 4 or less.

24. The secondary battery of claim 1, wherein, The difference between the crystallization temperature of the sealant resin and the crystallization temperature of the gas discharge resin is 10°C or less.

25. The secondary battery of claim 1, wherein, The gas discharge resin has a melting point of 100°C to 130°C.

26. The secondary battery of claim 1, wherein, The gas discharge resin has a weight average molecular weight of 100000 g / mol to 400000 g / mol.

27. The secondary battery of claim 1, wherein, The secondary battery is a soft-packaged secondary battery.

28. The secondary battery of claim 1, wherein, The gas discharge member has a maximum seal strength of less than 3 kgf / 15 mm at 120°C or more.

29. The secondary battery of claim 1, wherein, The gas discharge member has an average seal strength of less than 2 kgf / 15 mm at 120°C or more.

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