Lead film for secondary battery and secondary battery including the same

Abstract

The present invention relates to a lead film for a secondary battery containing a fire extinguishing agent, which can improve safety while maintaining the battery's sealing properties, and a secondary battery including the same. The lead film for a secondary battery according to the present invention contains a fire extinguishing agent. According to the present invention, the fire extinguishing agent is contained in the lead film adjacent to the electrode lead, which generates a large amount of heat, so that the fire extinguishing agent can act quickly in response to an increase in the battery temperature.

Description

[Technical Field]

[0001] The present invention relates to a lead film for a secondary battery and a secondary battery including the same. This application claims priority to Korean Patent Application No. 10-2021-0131223, filed on October 1, 2021, the entire contents of which are incorporated herein by reference in their entirety. [Background technology]

[0002] Mobile IT devices such as mobile phones, laptops, and tablet PCs are closely related to modern life, and as the IT industry market grows, demand for secondary batteries, a key component, is also rapidly increasing. Secondary batteries can be used repeatedly by charging and discharging, and are an environmentally friendly battery technology that does not contain hazardous materials such as lead, nickel, or cadmium. They are lightweight, small in volume, and have high energy density, allowing them to store large amounts of energy. These advantages make them the core of a new, growing power industry. In particular, lithium secondary batteries are the most widely used power source for mobile IT devices, which are closely related to human life. In recent years, their applications have been expanding continuously as a power source for electric vehicles and as a power storage device for renewable energy.

[0003] In general, a secondary battery includes a positive electrode, a negative electrode, a separator separating them, an electrolyte for transferring lithium ions through the separator, a case containing these, and electrode leads that function as a current path to the outside of the case. Typically, a lead film is attached to the electrode leads to prevent short circuits from occurring in the electrode leads and also to seal the electrode leads and the case.

[0004] In such secondary batteries, fire can occur due to various causes such as short circuits inside the secondary battery, overcharging, over-discharging, temperature control, etc. When this happens, the internal temperature of the secondary battery rises rapidly, and thermal propagation (thermal runaway) occurs, in which heat is transferred to adjacent cells, which can further spread the fire. Summary of the Invention [Problem to be solved by the invention]

[0005] Therefore, an object of the present invention is to provide a lead film for a secondary battery that can minimize fire damage when the battery overheats, and a secondary battery including the lead film. [Means for solving the problem]

[0006] In order to solve the above technical problems, the lead film for a secondary battery according to the present invention may contain a fire extinguishing agent.

[0007] According to one aspect of the present invention, the lead film for a secondary battery may include an internal space, and the internal space may contain a fire extinguishing agent.

[0008] The internal space may be closed within the lead film for a secondary battery.

[0009] According to another aspect of the present invention, the lead film for a secondary battery may have a recess (depression) formed so as to be recessed inward, and the recess may be provided with a fire extinguishing agent.

[0010] The recess may be open toward the surface of the lead film for a secondary battery.

[0011] The recess may have a rectangular shape.

[0012] In the present invention, the lead film for a secondary battery may maintain continuity in the longitudinal direction, width direction and thickness direction except for the portion containing the fire extinguishing agent.

[0013] The extinguishing agent may be in solid, liquid or gas form.

[0014] The fire extinguishing agent may include carbonates, bicarbonates, protein foams, fluorinated protein foams, alcohol foams, aqueous film foams, synthetic surfactant foams, urea, halogen compounds, phosphate compounds, phosphazene compounds, silicates, ammonium salts, ethylmethylimidazole, fluoroethers, fluoroketones, fluorocarbons, or two or more thereof.

[0015] The secondary battery according to the present invention comprises an electrode assembly with electrode leads, a case for accommodating the electrode assembly, a seal portion formed to seal the electrode assembly in the case, and a lead film surrounding a portion of the outer surface of the electrode leads and interposed between the electrode leads and the seal portion of the case, and the lead film may contain a fire extinguishing agent.

[0016] In one configuration of the secondary battery according to the present invention, the lead film may include an internal space, and the internal space may contain a fire extinguishing agent.

[0017] The internal space may be enclosed within the lead film.

[0018] The internal space is preferably spaced apart from the edge of the lead film and the edge of the electrode lead.

[0019] In another configuration of the secondary battery according to the present invention, the lead film may have a recess formed on it so as to be recessed inward of the lead film, and the recess may contain a fire extinguishing agent.

[0020] The recess may be formed to be recessed in the direction of the electrode lead, and the recess may be open in the direction of the seal portion.

[0021] The recess may be formed to be recessed toward the seal portion, and the recess may be open toward the electrode lead.

[0022] The recess is preferably disposed at a distance from the edge of the lead film and the edge of the electrode lead.

[0023] The recess may have a rectangular shape.

[0024] In yet another configuration of the secondary battery of the present invention, the lead film may have a first portion corresponding to the seal portion and a second portion not corresponding to the seal portion, and the fire extinguishing agent may be contained in the first portion.

[0025] The first portion may include a third portion corresponding to the electrode lead and a fourth portion not corresponding to the electrode lead, and the extinguishing agent may be contained in the third portion.

[0026] The secondary battery may be a pouch-type secondary battery. [Effects of the Invention]

[0027] The lead film for a secondary battery according to the present invention contains a fire extinguishing agent, and therefore can improve the safety of the battery.

[0028] In one embodiment of the lead film for a secondary battery according to the present invention, a fire extinguishing agent is impregnated in the lead film adjacent to the electrode lead that generates a large amount of heat, allowing the fire extinguishing agent to act quickly in response to an increase in the temperature of the battery.

[0029] In another embodiment of the lead film for secondary batteries of the present invention, venting (venting / gassing) occurs at the interface between the surface of the portion of the lead film having the opening recess and the sealing portion of the case, and the fire extinguishing agent sealed in the sealing portion is ejected by the venting (venting), allowing the fire extinguishing agent to act quickly.

[0030] In a lead film for a secondary battery according to yet another aspect of the present invention, a fire extinguishing agent can act on the part of the electrode lead that generates the greatest amount of heat, which can help minimize fire damage when the battery overheats.

[0031] The lead film for a secondary battery according to the present invention can maintain the sealing property of the battery even when it contains a fire extinguishing agent.

[0032] The lead film for a secondary battery according to one embodiment of the present invention contains a fire extinguishing agent within the lead film, but has sufficient pressure resistance equivalent to that of conventional lead films, thereby enabling the battery to maintain its hermeticity even when the lead film contains a fire extinguishing agent. [Brief explanation of the drawings]

[0033] The following drawings attached to this specification illustrate preferred embodiments of the present invention and, together with the detailed description of the invention described below, serve to further understand the technical concept of the present invention, and the present invention should not be interpreted as being limited to only the matters depicted in such drawings.

[0034] [Figure 1] 1 is a plan view of a lead film for a secondary battery according to one embodiment of the present invention. [Figure 2] FIG. 2 is a cross-sectional view taken along line II-II′ in FIG. [Figure 3] FIG. 4 is a plan view of a lead film for a secondary battery according to another embodiment of the present invention. [Figure 4] FIG. 4 is a cross-sectional view taken along line IV-IV′ in FIG. 3. [Figure 5] 1 is a diagram showing a secondary battery according to an embodiment of the present invention; [Figure 6] FIG. 6 is a cross-sectional view taken along the AA' axis in FIG. [Figure 7] FIG. 6 is another cross-sectional view taken along the AA' axis of FIG. [Figure 8] FIG. 10 is a diagram showing a secondary battery according to another embodiment of the present invention. [Figure 9] FIG. 9 is a cross-sectional view taken along the BB' axis of FIG. [Figure 10] FIG. 10 is a diagram showing a secondary battery according to still another embodiment of the present invention. [Figure 11] FIG. 11 is a cross-sectional view taken along the CC' axis of FIG. [Figure 12] 2 is an enlarged view showing an electrode lead and a lead film portion of a secondary battery according to an embodiment of the present invention. FIG. DETAILED DESCRIPTION OF THE INVENTION

[0035] Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. Prior to this, the terms and words used in the specification and claims should not be interpreted in a limited manner based on their ordinary or dictionary meanings, but should be interpreted in a manner that corresponds to the technical concept of the present invention, in accordance with the principle that the inventor himself can appropriately define the concept of the term in order to best describe the invention.

[0036] Therefore, it should be understood that the embodiments described in this specification and the configurations shown in the drawings are merely the most preferred embodiments of the present invention and do not represent the entire technical idea of ​​the present invention, and that there may be various equivalents and modifications that can be substituted therefor at the time of this application.

[0037] A lead film for a secondary battery according to one aspect of the present invention is characterized by including a fire extinguishing agent.

[0038] The extinguishing agent extinguishes or cools the battery if it overheats, etc. If the battery goes from high temperature to high pressure due to abnormal operation, the extinguishing agent is sprayed from the lead film to extinguish or cool the battery.

[0039] The extinguishing agent may be any type of extinguishing agent used for fire suppression without any particular limitation. The extinguishing principle may be smothering, cooling, or a combination of these two principles.

[0040] In one embodiment of the present invention, the extinguishing agent may be any substance in solid, liquid or gas form.

[0041] In one embodiment of the present invention, the fire extinguishing agent may include carbonates, bicarbonates, protein foams, fluorinated protein foams, alcohol foams, aqueous film foams, synthetic surfactant foams, urea, halogen compounds, phosphate compounds, phosphazene compounds, silicates, ammonium salts, ethylmethylimidazole, fluoroethers, fluoroketones, fluorocarbons, or two or more of these.

[0042] The carbonates or bicarbonates react with acids to generate carbon dioxide gas, enabling fire extinguishing by suffocation. The protein foam, fluorinated protein foam, alcohol foam, aqueous film foam, synthetic surfactant foam, etc. can extinguish fires by vaporization heat and oxygen absorption function. The urea generates carbon dioxide gas and ammonia in the presence of water and heat, enabling fire extinguishing by suffocation and cooling. The ammonium salts generate ammonia in the presence of heat, enabling fire extinguishing by cooling. The halogen compounds may be evaporative liquefied fire extinguishing materials.

[0043] In other embodiments of the present invention, the fire extinguishing agent may include calcium carbonate (CaCO), potassium carbonate aqueous solution, fluorosurfactant, sodium silicate, anhydrous sodium carbonate, sodium bicarbonate, potassium bicarbonate, sodium phosphate, aluminum sulfate, ammonium chloride, ammonium nitrate, ammonium bicarbonate, ammonium sulfate, ammonium dihydrogen phosphate, calcined alum, Halon 1211, and the like.

[0044] In still other embodiments of the present invention, the extinguishing agent may comprise a first-class extinguishing powder having sodium bicarbonate (NaHCO3) as its main component, treated with zinc stearate or magnesium stearate as a moisture-proofing agent, and colored white; a second-class extinguishing powder having potassium bicarbonate (KHCO3) as its main component, treated with zinc stearate or magnesium stearate as a moisture-proofing agent, and colored purple; a third-class extinguishing powder having ammonium phosphate monobasic (NH4H2PO4) as its main component, treated with silicone oil as a moisture-proofing agent, and colored pink; or a fourth-class extinguishing powder comprising a combination of urea and potassium carbonate; or two or more of these.

[0045] In yet another embodiment of the present invention, the fire extinguishing agent may contain a high-boiling point liquid fire extinguishing agent having a boiling point of 120 to 400°C at normal pressure, or a low-boiling point liquid fire extinguishing agent having a boiling point of 70 to 120°C at normal pressure.

[0046] The high boiling point liquid fire extinguishing agent may include a phosphoric acid compound, a phosphazene compound having a P=N bond, ethylmethylimidazole, or the like.

[0047] The phosphate compound may be trimethyl phosphate, triethyl phosphate, tris(chloroethyl) phosphate, tri(dichloropropyl) phosphate, or the like.

[0048] The low-boiling point liquid fire extinguishing agent may contain fluoroethers, fluoroketones, fluorocarbons, or the like.

[0049] Examples of the fluorocarbons include perfluorobutyltetrahydrofuran, perfluorotributylamine, perfluorotripropylamine, perfluoromethyldecalin, and perfluorodecalin.

[0050] In the lead film for a secondary battery according to one embodiment of the present invention, a fire-extinguishing agent is contained in the lead film adjacent to an electrode lead that generates a large amount of heat, allowing the fire-extinguishing agent to act quickly in response to a rise in battery temperature. In a secondary battery including the lead film for a secondary battery according to the present invention, even if a fire occurs, the fire is quickly extinguished by quickly discharging the fire-extinguishing agent, thereby preventing a thermal runaway phenomenon in which a sudden rise in the temperature inside the secondary battery is simultaneously transmitted to adjacent cells, and preventing the fire from becoming a larger fire.

[0051] The lead film for a secondary battery must have sufficient mechanical rigidity because it serves to seal the electrode lead and the case.

[0052] The lead film for a secondary battery according to one embodiment of the present invention contains a fire extinguishing agent within the lead film, but has sufficient pressure resistance equivalent to that of conventional lead films, thereby enabling the battery to maintain its hermeticity even when the lead film contains a fire extinguishing agent.

[0053] Fig. 1 is a plan view of a lead film for a secondary battery according to one embodiment of the present invention, and Fig. 2 is a cross-sectional view taken along line II-II' in Fig. 1.

[0054] 1 and 2, a lead film 1a for a secondary battery according to one embodiment of the present invention may have an internal space 2, and the internal space 2 may contain a fire-extinguishing agent 3a.

[0055] The lead film 1a may be a rectangular sheet member having a length L1 that is longer than the width W1 and thickness H1, and Figure 2 corresponds to a cross section along the longitudinal direction of the lead film 1a in Figure 1. Here, the thickness of the lead film means the maximum distance between both surfaces of the lead film.

[0056] In one embodiment of the present invention, the internal space 2 may be closed within the lead film 1a, as shown in FIG. 2. When the internal space 2 is closed within the lead film 1a, the extinguishing agent 3a is embedded within the lead film 1a. That is, the continuity of the lead film 1a is maintained except for the portion containing the extinguishing agent 3a. The extinguishing agents are arranged in the order of lead film 1a-extinguishing agent 3a-lead film 1a along the longitudinal direction of the lead film 1a. The extinguishing agents are arranged in the order of lead film 1a-extinguishing agent 3a-lead film 1a along the thickness direction of the lead film 1a. The extinguishing agents are arranged in the order of lead film 1a-extinguishing agent 3a-lead film 1a along the width direction of the lead film 1a. The continuity of the lead film 1a in the longitudinal, width, and thickness directions is maintained except for the portion containing the extinguishing agent 3a.

[0057] Therefore, the fire-extinguishing agent 3a is not exposed to the electrolyte, and an area is secured on the front and back surfaces of the lead film 1a that allows sufficient contact with the electrode leads, making it easy to ensure the airtightness and durability of the battery. If the internal space 2 is enclosed within the lead film 1a, the fire-extinguishing agent 3a may be ejected from the lead film 1a if the lead film 1a melts due to abnormal battery operation or the like.

[0058] In one embodiment of the present invention, as shown in Figures 1 and 2, the internal space 2 has a length L2 shorter than the length L1 of the lead film 1a, a thickness H2 smaller than the thickness H1 of the lead film 1a, and a width W2 smaller than the width W1 of the lead film 1a, so that its planar shape and cross-sectional shape may be rectangular, but are not particularly limited as long as they are shapes that contain the fire-extinguishing agent 3a.

[0059] For example, the thickness H1 of the lead film 1a for a secondary battery may be 0.2 mm, and the thickness H2 of the internal space 2 may be 0.15 mm. The internal space 2 may be disposed at a distance P of 2 mm from the longitudinal edge of the lead film 1a for a secondary battery. Therefore, even if the internal space 2 contains a fire extinguishing agent 3a, the hermeticity of the lead film 1a can be maintained. Furthermore, even if the lead film 1a contains a fire extinguishing agent 3a, the thickness H1 of the lead film 1a is constant along its longitudinal direction. By providing the internal space 2 inside the lead film 1a and embedding the fire extinguishing agent 3a, the thickness H1 can be maintained constant. Because the thickness of the lead film 1a remains constant, the existing sealing process can be used as is, eliminating the need for process changes to improve the lead film 1a in the secondary battery manufacturing process, which is effective for process management.

[0060] Fig. 3 is a plan view of a lead film for a secondary battery according to another embodiment of the present invention, and Fig. 4 is a cross-sectional view taken along line IV-IV' in Fig. 3.

[0061] Referring to Figures 3 and 4, a lead film 1b for a secondary battery according to another embodiment of the present invention may have a recess 4 formed so as to recess inward of the lead film 1b, and the recess 4 may be provided with a fire extinguishing agent 3b.

[0062] The lead film 1b may be a rectangular sheet member having a length L1 greater than the width W1 and thickness H1, similar to the lead film 1a described with reference to Figures 1 and 2, and Figure 4 corresponds to a cross section along the longitudinal direction of the lead film 1b in Figure 3.

[0063] In one embodiment of the present invention, the recess 4 may be open toward the surface of the lead film 1b, as shown in Figures 3 and 4. The continuity of the lead film 1b is maintained except for the portion containing the extinguishing agent 3a. The lead film 1b, the extinguishing agent 3b, and the lead film 1b are arranged in this order along the longitudinal direction of the lead film 1b. The lead film 1b, the extinguishing agent 3b, and the lead film 1b are arranged in this order along the thickness direction of the lead film 1b. The lead film 1b, the extinguishing agent 3b, and the lead film 1b are arranged in this order along the width direction of the lead film 1b.

[0064] In one embodiment of the present invention, as shown in Figures 3 and 4, the recess 4 has a length L2 shorter than the length L1 of the lead film 1b, a thickness H2 smaller than the thickness H1 of the lead film 1b, and a width W2 smaller than the width W1 of the lead film 1b, so that its planar shape and cross-sectional shape may be rectangular, but is not particularly limited as long as it is a shape that can contain the fire-extinguishing agent 3b.

[0065] For example, the thickness H1 of the lead film 1b for a secondary battery may be 0.2 mm, and the thickness H2 of the recess 4 may be 0.15 mm. The recess 4 may be disposed at a distance P of 2 mm from the longitudinal edge of the lead film 1b for a secondary battery. The contact area of ​​the lead film 1b with the electrode lead is reduced by the area of ​​the recess 4 compared to when the recess 4 is not included, but by adjusting the size and position of the recess 4 as described above, it is possible to maintain the same level of sealing performance as the existing type.

[0066] In one embodiment of the present invention, the lead films 1a and 1b for secondary batteries may contain polyethylene, polypropylene, polyimide, or two or more of these, or may contain other materials commonly used in lead films for secondary batteries. Lead films 1a and 1b made of such materials have excellent sealing properties, maintaining the airtightness of the battery and preventing leakage of the internal electrolyte.

[0067] A secondary battery can be manufactured by interposing the lead film for a secondary battery according to an embodiment of the present invention between an electrode lead and a case.

[0068] A secondary battery according to one embodiment of the present invention comprises an electrode assembly with electrode leads, a case that houses the electrode assembly, a seal that seals the electrode assembly in the case, and a lead film that surrounds a portion of the outer surface of the electrode leads and is interposed between the electrode leads and the seal of the case, and the lead film contains a fire extinguishing agent.

[0069] Fig. 5 is a diagram showing a secondary battery according to one embodiment of the present invention, and Fig. 6 is a cross-sectional view taken along the AA' axis in Fig. 5.

[0070] 5 and 6, a secondary battery 10 according to one embodiment of the present invention includes an electrode assembly 12 with electrode leads 11, and a case 13.

[0071] The electrode lead 11 is a type of terminal that is exposed to the outside and connected to an external device, and may be made of a conductive material. The electrode lead 11 may include a positive electrode lead and a negative electrode lead. The positive electrode lead and the negative electrode lead may be arranged in opposite directions relative to the longitudinal direction (X direction) of the battery, or the positive electrode lead and the negative electrode lead may be arranged in the same direction relative to the longitudinal direction of the battery.

[0072] The electrode assembly 12 includes a positive electrode plate, a negative electrode plate, and a separator. The electrode assembly 12 may be formed by sequentially stacking a positive electrode plate and a negative electrode plate with a separator interposed therebetween.

[0073] The positive electrode plate may include a positive electrode current collector made of a thin metal plate with excellent conductivity, for example, aluminum (Al) foil, and a positive electrode active material layer coated on at least one surface of the positive electrode current collector. The positive electrode plate may also include a positive electrode lead made of a metal material, for example, aluminum (Al), at one end. The positive electrode lead may extend and protrude from one end of the positive electrode plate, or may be welded to one end of the positive electrode plate or bonded to it using a conductive adhesive.

[0074] The negative electrode plate may include a negative electrode current collector made of a conductive metal thin plate, for example, copper (Cu) foil, and a negative electrode active material layer coated on at least one surface of the negative electrode current collector. The negative electrode plate may also include a negative electrode lead made of a metal material, for example, nickel (Ni), at one end. The negative electrode lead may extend and protrude from one end of the negative electrode plate, or may be welded to one end of the negative electrode plate or bonded to it using a conductive adhesive.

[0075] The separator may be disposed between the positive electrode plate and the negative electrode plate to electrically insulate them from each other, or may be formed as a porous membrane to allow lithium ions and the like to pass between the positive electrode plate and the negative electrode plate. Such a separator may include, for example, a porous membrane using polyethylene (PE), polypropylene (PP), or a composite film thereof.

[0076] An inorganic coating layer may be provided on the surface of the separator. The inorganic coating layer may have a pore structure formed by interstitial volumes between inorganic particles bound together by a binder.

[0077] Examples of the electrode assembly 12 include a jelly roll (winding) electrode assembly having a structure in which long sheet-like positive and negative electrodes are wound with a separator interposed therebetween, a stack (layered) electrode assembly in which a large number of positive and negative electrodes cut into units of a predetermined size are stacked in sequence with a separator interposed therebetween, and a stack / folding (layered / folding) electrode assembly having a structure in which a bi-cell or full cell in which a predetermined unit of positive and negative electrodes is stacked with a separator interposed therebetween is wound up.

[0078] The case 13 serves to house the electrode assembly 12 .

[0079] The case 13 may include a housing portion 13a that houses the electrode assembly 12 and a seal portion 13b that seals the electrode assembly 12. The seal portion 13b may be fused along the outer circumferential surface of the housing portion 13a to seal the electrode assembly 12. The fusion may be thermal fusion, ultrasonic fusion, or the like, but is not particularly limited as long as the seal portion 13b can be fused.

[0080] In one embodiment of the present invention, the case 13 may be formed as a multi-layer film including an outer layer for protection from external impact, a metal barrier layer for blocking moisture, and a sealant layer for sealing the case.

[0081] The outer layer may include poly(ethylene terephthalate) (PET), polybutylene terephthalate, polyethylene naphthalate, polybutylene naphthalate, copolymer polyester, polycarbonate, nylon, or other polyester-based film, and may be configured as a single layer or multiple layers.

[0082] The metal barrier layer may include aluminum, copper, or the like.

[0083] The sealant layer may contain a sealant resin and may be configured as a single layer or multiple layers.

[0084] The sealant resin may include polypropylene (PP), acid-modified polypropylene (PPa), random polypropylene, ethylene-propylene copolymer, or two or more thereof. The ethylene-propylene copolymer may include, but is not limited to, ethylene-propylene rubber, ethylene-propylene block copolymer, etc.

[0085] In one embodiment of the present invention, the case 13 may be a pouch type.

[0086] In one embodiment of the present invention, when the case 13 is a pouch type, it may include an upper pouch and a lower pouch. When the case 13 includes an upper pouch and a lower pouch, the upper pouch and the lower pouch may be fused together at the outer periphery to form a structure that seals the battery.

[0087] The sealed portion 13b may be four-sided sealed or three-sided sealed around the periphery of the case 13. A three-sided sealed structure refers to a structure in which the upper and lower pouches are formed from a single pouch sheet, the boundary between the upper and lower pouches is folded so that the electrode assembly receiving portions 13a formed in the upper and lower pouches are stacked, and the remaining three peripheries excluding the folded portion are sealed. Figure 5 is a diagram showing the receiving portion 13a of the lower pouch before the upper pouch is covered.

[0088] The electrode lead 11 may be housed in the case 13 such that a portion thereof is exposed to the outside of the case 13. The electrode lead 11 is electrically connected to an electrode tab (not shown) included in the electrode assembly 12 and protrudes outside the case 13 via a sealing portion 13b. The lead film 14a serves as insulation by preventing electrical contact between the case 13 and the electrode lead 11. Referring to FIG. 5, a secondary battery 10 according to one embodiment of the present invention includes a lead film 14a. The lead film 14a contains a fire extinguishing agent therein.

[0089] 5, the lead film 14a surrounds a portion of the outer surface of the electrode lead 11 and is interposed between the electrode lead 11 and the case 13. For example, the lead film 14a may be interposed between the electrode lead 11 and the seal portion 13b of the case 13 in the portion where the electrode lead 11 protrudes. This allows the lead film 14a to prevent a short circuit from occurring in the electrode lead 11 during sealing, and also improves the sealing performance between the seal portion 13b and the electrode lead 11.

[0090] FIG. 7 is another cross-sectional view taken along the A-A' axis in FIG. 5. Although FIG. 7 shows that the lead film 14a is provided on both sides of the electrode lead 11, the lead film 14a may be located on at least one side of the electrode lead 11. For example, as shown in FIG. 6, the lead film 14a according to the present invention may be provided on one side of the electrode lead 11, and another lead film 14a' may be provided on the other side of the electrode lead 11. The lead film 14a may be located above the electrode lead 11, and the other lead film 14a' or the lead film 14a may be located below the electrode lead 11. In this case, the electrode lead 11 may be sealed with the seal portion 13b with the electrode lead 11 positioned between the lead film 14a and the other lead film 14a' or between two lead films 14a, thereby connecting the lead films around the electrode lead 11 to each other. As a result, the lead films 14a, 14a' can prevent the side surfaces of the electrode leads 11 from being exposed to the outside, and can improve the sealing performance between the seal portions 13b and the electrode leads 11.

[0091] In one embodiment of the present invention, the length L1 of the lead film 14a may be longer than the width LW of the electrode lead 11. Here, the length of the lead film refers to the maximum distance between one end and the other end of the lead film in a direction (Y-axis direction) perpendicular to the protruding direction (X-axis direction) of the electrode lead 11. In other words, it refers to the length of the lead film in the width direction (Y-axis direction) of the electrode lead 11. By making the length L1 of the lead film 14a longer than the width LW of the electrode lead 11 in this way, it is possible to prevent the lead film 14a from further extending from the side surface of the electrode lead 11 and exposing the side surface of the electrode lead 11 to the outside, and improve the sealing performance between the seal portion 13b and the electrode lead 11.

[0092] In one embodiment of the present invention, the width W1 of the lead film 14a may be greater than the width SW of the seal portion 13b and less than the length LL of the electrode lead 11. Here, the width of the lead film 14a refers to the maximum distance between one end and the other end of the lead film 14a in the protruding direction of the electrode lead 11. In other words, it refers to the length of the lead film in a direction perpendicular to the width direction of the electrode lead 11. The width of the seal portion 13b refers to the maximum distance between one end and the other end of the seal portion 13b in the protruding direction of the electrode lead 11. The length of the electrode lead 11 refers to the maximum distance between one end and the other end of the electrode lead 11 in the protruding direction of the electrode lead 11.

[0093] By making the width W1 of the lead film 14a larger than the width SW of the seal portion 13b, the lead film 14a may protrude outside the case 13, and the sealing performance can be improved by further protecting the portion of the electrode lead 11 protruding outside the case 13. If the width W1 of the lead film 14a is smaller than the length LL of the electrode lead 11, the portion of the electrode lead 11 that is not covered by the lead film 14a can be used for electrical connection.

[0094] In another embodiment of the present invention, the overall width of the lead film 14 may be smaller than the width of the seal portion 13b and smaller than the length of the electrode lead 11. In this case, the lead film 14a may not protrude outside the case 13.

[0095] In one embodiment of the present invention, the entire area of ​​the lead film 14a may correspond to the seal portion 13b.

[0096] In another embodiment of the present invention, only a partial area of ​​the lead film 14a may correspond to the seal portion 13b.

[0097] Referring to FIG. 6, the lead film 14a may have an internal space 15, and the internal space 15 may contain a fire extinguishing agent 16.

[0098] Although FIG. 6 shows that the lead film 14a having the internal space 15 is located on one side of the electrode lead 11, as shown in FIG. 7, the lead film 14a having the internal space 15 may be located on both sides of the electrode lead 11. In one embodiment of the present invention, the internal space 15 may be structured to be enclosed within the lead film 14a. This structure is described with reference to FIGS. 1 and 2. When the internal space 15 is enclosed within the lead film 14a, the fire-extinguishing agent 16 may not be exposed to the electrolyte, making it easy to ensure the airtightness and durability of the battery. In addition, the position of the internal space 15 can be freely selected.

[0099] If the internal space 15 is enclosed within the lead film 14a, the extinguishing agent 16 may be ejected from the lead film 14a when the lead film 14a melts due to abnormal operation of the battery or the like.

[0100] In one embodiment of the present invention, the internal space 15 may have a rectangular shape as shown in FIGS. 6 and 7, but is not particularly limited to any shape as long as it can contain the fire extinguishing agent 16.

[0101] For example, the thickness H1 of the lead film 14a may be 0.2 mm, and the thickness H2 of the internal space 15 may be 0.15 mm. The internal space 15 may be disposed at a distance P from the edge of the lead film 14a along the longitudinal direction. For example, the distance P may be 2 mm. When the internal space 15 is located above the electrode lead 11, the internal space 15 may be disposed at a distance P' from the edge of the electrode lead 11 along the longitudinal direction. For example, the distance P' may be 2 mm.

[0102] By adjusting the position of the internal space 15 in this way, the durability and airtightness of the lead film 14a can be controlled. Since lead films for secondary batteries serve to seal the electrode lead and the case, they must have sufficient mechanical rigidity. The lead film 14a contains a fire-extinguishing agent 16 within it, but by adjusting the position of the internal space 15 as described above, the lead film 14a can have sufficient pressure resistance, similar to conventional lead films. This allows the battery to maintain its airtightness even when it contains a fire-extinguishing agent.

[0103] FIG. 8 is a diagram showing a secondary battery according to still another embodiment of the present invention.

[0104] A secondary battery 10 according to still another embodiment of the present invention includes an electrode assembly 12 with an electrode lead 11, a case 13, and a lead film 14b. For the electrode lead 11, the electrode assembly 12, and the case 13, refer to the above description.

[0105] 8, the lead film 14b surrounds a part of the outer surface of the electrode lead 11 and is interposed between the electrode lead 11 and the case 13. For example, the lead film 14b may be interposed between the electrode lead 11 and the seal portion 13b of the case 13 in the part where the electrode lead 11 protrudes.

[0106] FIG. 9 is a cross-sectional view taken along the BB' axis of FIG.

[0107] Referring to FIG. 9, the lead film 14b may have a recess 17a formed to be recessed inward of the lead film 14b, and the recess 17a may be provided with a fire extinguishing agent 16.

[0108] Referring to FIG. 9, the recess 17a may be formed so as to be recessed in a direction (-Z axis direction) toward the electrode lead 11 located below the position of the lead film 14b located above the electrode lead 11.

[0109] In one embodiment of the present invention, the recess 17a may be open in the direction from the lead film 14b toward the sealing portion 13b (Z-axis direction), that is, toward the surface of the lead film 14b.

[0110] Generally, the adhesive strength at the interface between the lead film surrounding the electrode lead and the case is weak, which can lead to venting at the interface between the lead film and the case when the battery malfunctions.

[0111] When the recess 17a is formed so as to open toward the sealing portion 13b, a vent is generated at the interface between the surface of the lead film 14b where the recess 17a is opened and the sealing portion 13b of the case 13, and this vent ejects the fire extinguishing agent 16 that was sealed by the sealing portion 13b, allowing the fire extinguishing agent to act quickly.

[0112] Figure 9 shows that the lead film 14b having the recess 17a formed therein is located on one side of the electrode lead 11, and that another lead film 14b' is provided on the other side of the electrode lead 11, but the lead film 14b having the recess 17a formed therein may also be located on both sides of the electrode lead 11.

[0113] 10 is a diagram showing a secondary battery according to another embodiment of the present invention. A secondary battery 10 according to another embodiment of the present invention includes an electrode assembly 12 with an electrode lead 11, a case 13, and a lead film 14c. For details of the electrode lead 11, the electrode assembly 12, and the case 13, please refer to the above contents.

[0114] 10, the lead film 14c surrounds a part of the outer surface of the electrode lead 11 and is interposed between the electrode lead 11 and the case 13. For example, the lead film 14c may be interposed between the electrode lead 11 and the seal portion 13b of the case 13 in the portion where the electrode lead 11 protrudes.

[0115] FIG. 11 is a cross-sectional view taken along the BB' axis of FIG.

[0116] Referring to FIG. 11, the lead film 14c may have a recess 17b formed so as to recess inward (in the Z-axis direction) of the lead film 14c, and the recess 17b may be provided with a fire extinguishing agent 16.

[0117] Referring to FIG. 11, the recess 17b may be formed so as to be recessed in a direction from the lead film 14c toward the seal portion 13b.

[0118] In one embodiment of the present invention, the recess 17b may be open in the direction from the lead film 14c toward the electrode lead 11 (-Z axis direction).

[0119] Generally, when thermal runaway occurs, the amount of heat generated at the electrode lead becomes extremely large. Furthermore, the adhesive strength at the interface between the electrode lead and the lead film is weak. As a result, when abnormal battery operation or other issues occur, venting occurs at the interface between the electrode lead and the lead film. In other words, the electrode lead and the lead film peel off from each other. As a result, when abnormal battery operation or other issues occur, venting occurs at the interface between the electrode lead and the lead film.

[0120] If the recess 17b is formed so as to open toward the electrode lead 11, a vent is generated at the interface between the electrode lead 11 and the lead film 14c, and this vent ejects the fire extinguishing agent 16 sealed by the electrode lead 11, allowing the fire extinguishing agent to act quickly. Furthermore, because the recess 17b faces the electrode lead 11, the fire extinguishing agent can act on a portion of the electrode lead that generates a large amount of heat, which helps to minimize fire damage when the battery overheats.

[0121] Figure 11 shows that the lead film 14c having the recess 17b formed therein is located on one side of the electrode lead 11, and that another lead film 14c' is provided on the other side of the electrode lead 11, but the lead film 14c having the recess 17b formed therein may also be located on both sides of the electrode lead 11.

[0122] In one embodiment of the present invention, the recesses 17a and 17b may have a rectangular shape as shown in FIGS. 8 to 11, but are not particularly limited to any shape as long as they can contain the fire extinguishing agent 16.

[0123] For example, the thickness H1 of the lead films 14b and 14c may be 0.2 mm, and the thickness H2 of the recesses 17a and 17b may be 0.15 mm. The recesses 17a and 17b may be disposed at a distance P of 2 mm from the longitudinal edge of the lead films 14b and 14c. When the recesses 17a and 17b are located on the electrode lead 11, the recesses 17a and 17b may be disposed at a distance P' of 2 mm from the longitudinal edge of the electrode lead 11.

[0124] By adjusting the positions of the recesses 17a and 17b, the durability and airtightness of the lead films 14b and 14c can be controlled. Lead films for secondary batteries serve to seal the electrode leads and the case, so they must have sufficient mechanical rigidity. The lead films 14b and 14c contain the fire extinguishing agent 16, but by adjusting the positions of the recesses 17a and 17b, they can have sufficient pressure resistance similar to that of conventional lead films. This allows the battery to maintain its airtightness even when the fire extinguishing agent is contained.

[0125] Even though the lead films 14a, 14b, and 14c contain the fire-extinguishing agent 16 inside, the thickness H1 of the lead films 14a, 14b, and 14c is constant along their longitudinal direction. Where the internal space 15 and recesses 17a and 17b are located, portions of the lead films 14a, 14b, and 14c in the thickness direction are removed. Even in such cases, it is necessary to confirm whether the lead films have sufficient mechanical rigidity. An internal pressure simulation experiment was conducted under the conditions of the thicknesses (H1, H2) and spacings (P, P') described above.

[0126] The deformation of the entire structure (electrode lead, lead film, and case) was analyzed assuming that gas was generated inside the pouch-shaped case and an internal pressure of 0.1 MPa acted on the electrode lead inside the case. The bottom edge of the case was fixed. In the comparative example without fire extinguishing agent, the maximum displacement from the inner end of the width direction of the seal toward the electrode lead was simulated to be 0.05063 mm, while in the present invention, the maximum displacement was simulated to be 0.05766 mm. The simulation results show that the inclusion of fire extinguishing agent inevitably increases the maximum displacement, but the difference in deformation even under 0.1 MPa pressure is negligible. Therefore, it was confirmed that the present invention has sufficient pressure resistance, similar to that of conventional lead films.

[0127] A simulation experiment was also conducted to determine the maximum stress experienced by the lead film when internal pressure was applied as described above. In the comparative example that did not contain a fire extinguishing agent, the maximum stress was simulated to be 0.01603 MPa, while in the present invention, the maximum stress was simulated to be 0.01611 MPa. This maximum stress was at a level that did not result in plastic deformation, and it was found that there was no significant difference.

[0128] In this way, it was confirmed that even when a fire extinguishing agent is contained in the lead film, the configuration proposed in this invention not only maintains the battery's airtightness, but also has the remarkable effect of realizing a safety device through the action of the fire extinguishing agent.

[0129] FIG. 12 is an enlarged view showing the electrode lead and lead film portions of a secondary battery according to one embodiment of the present invention.

[0130] Referring to FIG. 12, the lead film 14 may include a first portion 100 corresponding to the seal portion 13b and a second portion 200 not corresponding to the seal portion 13b.

[0131] 12, the first part 100 may contain a fire extinguishing agent. If the first part 100 contains a fire extinguishing agent, the fire extinguishing agent will not be exposed to the electrolyte during normal battery operation, but during abnormal battery operation, the fire extinguishing agent may be vented at the interface between the seal part 13b and the lead film 14 and may be ejected from the lead film 14. In particular, if the lead film 14 has a recess 17, the recess 17 may be formed in the first part 100 to prevent the fire extinguishing agent from being exposed to the electrolyte during normal battery operation.

[0132] In another embodiment of the present invention, the second part 200 may contain a fire extinguishing agent. If the second part 200 contains a fire extinguishing agent, the fire extinguishing agent will not be exposed to the electrolyte during normal operation of the battery, and the lead film 14 may melt and the fire extinguishing agent may be ejected from the lead film 14 during abnormal operation of the battery. In particular, if the lead film 14 has an internal space, the fire extinguishing agent will not be exposed to the electrolyte even if it is not sealed by the seal part 13b, so the fire extinguishing agent may be contained in the second part 200.

[0133] Referring to Figure 12, the lead film 14 may have a first part 100 corresponding to the sealing portion 13b and a second part 200 not corresponding to the sealing portion 13b, and the first part 100 may have a third part 300 corresponding to the electrode lead 11 and a fourth part 400 not corresponding to the electrode lead 11.

[0134] In another embodiment of the present invention, the lead film 14 may have a first portion 100 corresponding to the sealing portion 13b and a second portion 200 which is a portion that does not correspond to the sealing portion 13b, and the second portion 200 may have a fifth portion 500 which is a portion that corresponds to the electrode lead 11 and a sixth portion 600 which is a portion that does not correspond to the electrode lead 11.

[0135] In one embodiment of the present invention, the third part 300 may include a fire extinguishing agent. When the third part 300 includes a fire extinguishing agent, the fire extinguishing agent is located in a portion of the electrode lead 11 that generates a large amount of heat, which can help the fire extinguishing agent to function quickly in response to an increase in the temperature of the battery.

[0136] In another embodiment of the present invention, a fire extinguishing agent may be included in the fourth part 400. If a fire extinguishing agent is included in the fourth part 400, this can help the fire extinguishing agent to act quickly when peeling occurs between the lead film 14 and the seal part 13b.

[0137] In yet another embodiment of the present invention, the fifth part 500 or the sixth part 600 may include a fire extinguishing agent.

[0138] In one embodiment of the present invention, the secondary battery may be a cylindrical secondary battery, a prismatic secondary battery, or a pouch-type secondary battery. In particular, the secondary battery may be a pouch-type secondary battery. Pouch-type secondary batteries are easy to increase the volume ratio, but have the disadvantage that the pouch itself has difficulty holding the cells. Unlike cylindrical batteries equipped with a positive temperature coefficient (PTC) overcurrent protection device or a current interrupt device (CID), pouch-type secondary batteries lack thermal stability when the cell temperature rises out of control. According to the present invention, by improving the lead film, a safety device can also be provided in pouch-type secondary batteries.

[0139] Although the present invention has been described above using limited embodiments and drawings, the technical concept of the present invention is not limited to these, and it goes without saying that a person having ordinary knowledge in the technical field to which the present invention pertains can make various modifications and variations within the scope of the technical concept of the present invention and the equivalent scope of the claims. [Explanation of symbols]

[0140] 1a, 1b lead film 2. Interior space 3a.3b Fire extinguishing agents 4 recess 10 Secondary battery 11 Electrode Lead 12 Electrode assembly 13 cases 13a Storage section 13b Seal part 14, 14a, 14b, 14c Lead film 15 Interior Space 16 Fire extinguishing agents 17, 17a, 17b recesses 100 Part 1 200 Part 2 300 Part 3 400 Part 4 500 Part 5 600 Part 6

Claims

1. A lead film for a secondary battery containing a fire extinguishing agent, the lead film for a secondary battery includes an internal space, A fire extinguishing agent is provided in the internal space, the internal space is disposed at a distance from an edge of the lead film for a secondary battery, the internal space is enclosed within the lead film for a secondary battery, When the lead film for the secondary battery melts or when venting occurs at the interface between the surface of the lead film for the secondary battery and the seal part of the case, the extinguishing agent is ejected from the lead film for the secondary battery, and the extinguishing agent extinguishes the fire by suffocation and / or cooling, The internal space is defined so that, from one end to the other end of the lead film for a secondary battery, the lead film for a secondary battery - the internal space - the lead film for a secondary battery are arranged in this order along the longitudinal direction of the lead film for a secondary battery; from one end to the other end of the lead film for a secondary battery, the lead film for a secondary battery - the internal space - the lead film for a secondary battery are arranged in this order along the thickness direction of the lead film for a secondary battery, from one end to the other end of the lead film for a secondary battery; and from one end to the other end of the lead film for a secondary battery, the lead film for a secondary battery - the internal space - the lead film for a secondary battery are arranged in this order along the width direction of the lead film for a secondary battery.

2. A lead film for a secondary battery containing a fire extinguishing agent, The lead film for a secondary battery has a recess formed so as to be recessed inward, A fire extinguishing agent is provided in the recess, the recess is open toward the surface of the lead film for a secondary battery, When the lead film for the secondary battery melts or when venting occurs at the interface between the surface of the lead film for the secondary battery and the seal part of the case, the extinguishing agent is ejected from the lead film for the secondary battery, and the extinguishing agent extinguishes the fire by suffocation and / or cooling, The recesses are defined so that, from one end to the other end of the lead film for a secondary battery, the recesses are arranged in the following order along the longitudinal direction of the lead film for a secondary battery: the lead film for a secondary battery - the recesses - the lead film for a secondary battery; from one end to the other end of the lead film for a secondary battery along the thickness direction of the lead film for a secondary battery: the lead film for a secondary battery - the recesses; and from one end to the other end of the lead film for a secondary battery along the width direction of the lead film for a secondary battery: the lead film for a secondary battery - the recesses - the lead film for a secondary battery.

3. 3. The lead film for a secondary battery according to claim 1, wherein continuity of the lead film for a secondary battery is maintained in the longitudinal, width and thickness directions except for the portion containing the fire extinguishing agent.

4. The lead film for a secondary battery according to claim 1 or 2, wherein the fire extinguishing agent is in the form of a solid, liquid, or gas.

5. 3. The lead film for a secondary battery according to claim 1 or 2, wherein the fire extinguishing agent comprises carbonate, bicarbonate, protein foam, fluorinated protein foam, alcohol foam, aqueous film foam, synthetic surfactant foam, urea, a halogen compound, a phosphate compound, a phosphazene compound, silicate, ammonium salt, ethylmethylimidazole, fluoroethers, fluoroketones, fluorocarbons, or two or more of these.

6. an electrode assembly with an electrode lead; a case that accommodates the electrode assembly; a seal portion formed in the case to seal the electrode assembly; a lead film surrounding a part of an outer surface of the electrode lead and interposed between the electrode lead and a seal portion of the case; Equipped with the lead film includes an internal space; A fire extinguishing agent is provided in the internal space, the internal space is disposed at a distance from an edge of the lead film and an edge of the electrode lead; the internal space is enclosed within the lead film, When the lead film melts or venting occurs at the interface between the surface of the lead film and the seal portion of the case, the extinguishing agent is ejected from the lead film, and the extinguishing agent extinguishes the fire by smothering and / or cooling, The internal space is defined so that, from one end to the other end of the lead film, the lead film - the internal space - the lead film are arranged in this order along the longitudinal direction of the lead film, the lead film - the internal space - the lead film are arranged in this order along the thickness direction of the lead film, from one end to the other end of the lead film, and the lead film - the internal space - the lead film are arranged in this order along the width direction of the lead film, from one end to the other end of the lead film.

7. an electrode assembly with an electrode lead; a case that accommodates the electrode assembly; a seal portion formed in the case to seal the electrode assembly; a lead film surrounding a part of an outer surface of the electrode lead and interposed between the electrode lead and a seal portion of the case; Equipped with a recess formed on the lead film so as to be recessed inward of the lead film; A fire extinguishing agent is provided in the recess, the recess is open toward the surface of the lead film, When the lead film melts or venting occurs at the interface between the surface of the lead film and the seal portion of the case, the extinguishing agent is ejected from the lead film, and the extinguishing agent extinguishes the fire by smothering and / or cooling, The recesses are defined so that, from one end to the other end of the lead film along the longitudinal direction of the lead film, they are arranged in the order of: lead film - recess - lead film; from one end to the other end of the lead film along the thickness direction of the lead film, they are arranged in the order of: lead film - recess - lead film; and from one end to the other end of the lead film along the width direction of the lead film, they are arranged in the order: lead film - recess - lead film.

8. The secondary battery according to claim 7 , wherein the recess is formed to recess toward the electrode lead.

9. The secondary battery according to claim 8 , wherein the recess is open toward the sealing portion.

10. The secondary battery according to claim 7 , wherein the recess is formed to be recessed in a direction toward the sealing portion.

11. The secondary battery according to claim 10 , wherein the recess is open toward the electrode lead.

12. The secondary battery according to claim 7 , wherein the recess is disposed at a distance from an edge of the lead film and an edge of the electrode lead.

13. the lead film includes a first portion corresponding to the seal portion and a second portion not corresponding to the seal portion; The secondary battery according to claim 6 or 7, wherein the fire extinguishing agent is contained in the first part.

14. the first portion includes a third portion corresponding to the electrode lead and a fourth portion not corresponding to the electrode lead; The secondary battery according to claim 13 , wherein the fire extinguishing agent is contained in the third part.

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