Pouch-type secondary battery with improved safety

Abstract

The present invention relates to a pouch-type secondary battery with improved safety. Specifically, the pouch-type secondary battery includes a pouch-type battery case that houses an electrode assembly and an electrolyte, and an explosion-preventing member formed to surround a portion of the pouch-type battery case. The explosion-preventing member may include a ring-shaped elastic band that surrounds a portion of the pouch-type battery case, and a scratch-inducing tip that is disposed between the pouch-type battery case and the elastic band.

Description

[Technical Field]

[0001] This application claims the benefit of priority based on Korean Patent Application Nos. 10-2023-0103196, filed August 7, 2023, and 10-2024-0079945, filed June 19, 2024, the entire contents of which are incorporated herein by reference.

[0002] The present invention relates to a pouch-type secondary battery with improved safety, and more particularly, to a pouch-type secondary battery including an explosion-preventing member that can damage the surface of a swelling pouch case to prevent electrolyte leakage, thereby preventing explosion when the secondary battery behaves abnormally. [Background technology]

[0003] In recent years, as the development and widespread use of electric vehicles, energy storage batteries, robots, satellites, etc. has progressed, active research has been conducted on high-performance secondary batteries that can be repeatedly charged and discharged. Representative examples include lithium secondary batteries, which can be freely charged and discharged due to almost no memory effect, have a very low self-discharge rate, and have a high energy density.

[0004] However, because lithium secondary batteries store a large amount of energy, they are susceptible to fire or explosion due to internal resistance and external impact. In particular, secondary batteries with low physical durability, such as pouch-type secondary batteries, are more susceptible to fire or explosion than can-type secondary batteries because they are vulnerable to internal resistance and external impact. In addition, in recent years, secondary batteries have been used in electric vehicles, and are often used in battery packs including multiple battery cells rather than as single battery cells. However, such battery packs have higher capacity or output than single battery cells, making them more susceptible to fire or explosion, and the risk of fire or explosion increases accordingly.

[0005] Secondary battery fires and explosions can occur for a variety of reasons, one of which is when an excessive current flows through a secondary battery beyond its limit due to prolonged use or use at high temperatures. When an excessive current flows, the secondary battery generates heat, causing the internal temperature to rise rapidly. This rise in the battery's internal temperature causes the liquid electrolyte to turn into a gas, which increases the battery's internal pressure and causes the pouch-type battery case to expand, a phenomenon known as swelling. This swelling causes the battery to deform, resulting in a short circuit or explosion.

[0006] To solve the problem of gas generation inside secondary batteries, a technology has been proposed in which a separate safety valve is attached to the battery pack to remove the internal gas. However, such an invention has a structure that is different from the original battery or pack, and requires a process to manufacture separate parts, and has problems such as having to manufacture a separate case instead of the conventional case.

[0007] Therefore, research is being conducted to ensure the safety of secondary batteries by preventing fires or explosions of secondary batteries when the lithium secondary batteries behave abnormally. Summary of the Invention [Problem to be solved by the invention]

[0008] The present invention provides a pouch-type secondary battery that can ensure safety by including an explosion-preventing member that can damage the surface of the pouch-type battery case and cause electrolyte leakage when the secondary battery behaves abnormally. [Means for solving the problem]

[0009] [1] The present invention provides a pouch-type battery case that houses an electrode assembly and an electrolyte; an explosion-proof member surrounding a portion of the pouch-type battery case; The explosion-preventing member provides a pouch-type secondary battery including a ring-shaped elastic band surrounding a part of the pouch-type battery case, and a scratch-inducing tip disposed between the pouch-type battery case and the elastic band.

[0010] [2] The present invention provides a pouch-type secondary battery according to the above [1], which includes one or more elastic bands.

[0011] [3] The present invention provides a pouch-type secondary battery according to the above [1] or [2], wherein the elastic band is located at the center of the pouch-type battery case.

[0012] [4] The present invention provides a pouch-type secondary battery according to at least one of the above [1] to [3], which includes two or more elastic bands, the two or more elastic bands being spaced apart from each other or intersecting each other.

[0013] [5] The present invention provides a pouch-type secondary battery according to at least one of the above items [1] to [4], wherein the elastic bands are positioned symmetrically on both sides of the center of the pouch-type battery case.

[0014] [6] The present invention provides a pouch-type secondary battery according to at least one of the above items [1] to [5], wherein the elastic band contains a shape-memory polymeric material.

[0015] [7] The present invention provides a pouch-type secondary battery according to at least one of the above items [1] to [6], wherein the shape-memory polymer material includes at least one of fluorinated ethylene propylene (FEP), polytetrafluoroethylene (PTFE), polyolefin, polyvinyl chloride (PVC), polyvinylidene fluoride (PVDF), silicone rubber, and fluoropolymer elastomer.

[0016] [8] The present invention provides a pouch-type secondary battery according to at least one of the above items [1] to [7], wherein the separation distance between the pouch-type battery case and the elastic band is 0 μm to 40 μm.

[0017] [9] The present invention provides a pouch-type secondary battery according to at least one of the above items [1] to [8], wherein the width (W) of the minor axis of the elastic band is 10 mm to 40 mm.

[0018]

[10] The present invention provides a pouch-type secondary battery according to at least one of the above items [1] to [9], wherein the scratch-inducing tip comprises a metal or a thermoplastic resin.

[0019]

[11] The present invention provides a pouch-type secondary battery according to at least one of the above items [1] to

[10] , wherein the metal is at least one of aluminum, steel, stainless steel, and stainless steel.

[0020]

[12] The present invention provides a pouch-type secondary battery according to at least one of the above items [1] to

[11] , wherein the thermoplastic resin is at least one selected from the group consisting of fluorinated ethylene propylene (FEP), polytetrafluoroethylene (PTFE), polyvinyl chloride (PVC), polyvinylidene fluoride (PVDF), fiber reinforced plastic (FRP), polypropylene (PP), polyethylene (PE), polycarbonate (PC), and polyamide-imide (PAI).

[0021]

[13] The present invention provides a pouch-type secondary battery according to at least one of the above items [1] to

[12] , wherein the scratch inducing tip has a cylindrical, rectangular, spherical or bullet shape.

[0022]

[14] The present invention provides a pouch-type secondary battery according to at least one of the above [1] to

[13] , wherein when the scratch induction tip has a spherical shape, the diameter of the scratch induction tip is 1 mm to 10 mm.

[0023]

[15] The present invention provides a pouch-type secondary battery according to at least one of the above [1] to

[14] , wherein when the scratch induction tip has a cylindrical, rectangular or bullet shape, the height of the scratch induction tip is 5 μm to 40 μm.

[0024]

[16] The present invention provides a pouch-type secondary battery according to at least one of the above [1] to

[15] , wherein the width or lateral width of the scratch-inducing tip is the same as the width of the minor axis of the elastic band, or is 10% to 70% smaller than the width of the minor axis of the elastic band.

[0025]

[17] The present invention provides a pouch-type secondary battery according to at least one of the above items [1] to

[16] , wherein the scratch-inducing chip is adhered and fixed to the inner surface of an elastic band that is in contact with the pouch-type battery case. [Effects of the Invention]

[0026] According to the present invention, by forming an explosion-preventive member on the surface of the pouch-type battery case so as to surround a portion of the pouch-type battery case as described above, when the internal pressure of the secondary battery increases due to abnormal behavior caused by prolonged use or high temperature, causing swelling, the surface of the pouch-type battery case can be damaged, leading to electrolyte leakage. As a result, the movement of lithium ions is suppressed, reducing the energy of the secondary battery, thereby significantly reducing the probability of secondary battery ignition or explosion and ensuring battery safety. [Brief explanation of the drawings]

[0027] [Figure 1] 1 is a plan view of a pouch-type secondary battery to which an elastic band formed according to an embodiment of the present invention is applied; [Figure 2] 1 is a front view of a pouch-type secondary battery to which an elastic band formed according to an embodiment of the present invention is applied; [Figure 3]1 is a front view of a pouch-type secondary battery provided with an explosion-proof member according to an embodiment of the present invention; [Figure 4] 1 is a conceptual diagram illustrating the principle by which a pouch-type battery case is damaged by an explosion-preventing member when a secondary battery behaves abnormally. DETAILED DESCRIPTION OF THE INVENTION

[0028] The terms and words used in this specification and claims should not be interpreted in a limited way to their general or dictionary meanings, but should be interpreted in a way that is consistent with the technical idea of ​​the present invention, in accordance with the principle that an inventor can appropriately define the concept of terms in order to best describe his or her invention.

[0029] The present invention will be described in more detail below.

[0030] The pouch-type secondary battery according to the present invention includes at least one of the configurations disclosed below, and may include any technically possible combination of the following configurations.

[0031] Specifically, the pouch-type secondary battery according to the present invention comprises: a pouch-type battery case that accommodates the electrode assembly and the electrolyte; an explosion-preventing member formed to surround a portion of the pouch-type battery case, The explosion-preventing member includes a ring-shaped elastic band that surrounds a portion of the pouch-shaped battery case, and a scratch-inducing tip that is positioned between the pouch-shaped battery case and the elastic band.

[0032] Specifically, in the pouch-type secondary battery according to the present invention, if abnormal behavior (operation) within the battery, such as high-temperature storage, causes the electrolyte to decompose, generating flammable / volatile gases and increasing the internal pressure of the battery, i.e., if swelling occurs at the center of the pouch-type battery case, the explosion-preventing member surrounding the pouch-type battery case, e.g., the annular elastic band and scratch-inducing tip, moves from the center of the pouch-type battery case to the relatively thinner side edges, etching and / or damaging the surface of the pouch-type battery case and causing electrolyte leakage. If the electrolyte leaks out of the battery case, lithium ion mobility decreases, preventing the battery from operating. This significantly reduces the likelihood of secondary battery fire or explosion, thereby ensuring safety. Furthermore, if at least one pouch-type secondary battery according to the present invention is included in a battery pack, regardless of its location, the explosion-preventing member delays heat and / or temperature transfer to adjacent pouch-type secondary batteries, thereby improving the safety of the secondary batteries.

[0033] Hereinafter, the configuration of the pouch-type secondary battery of the present invention will be specifically described with reference to the drawings, but these are for easier understanding of the present invention and the scope of the present invention is not limited thereto.

[0034] Fig. 1 is a schematic plan view of a pouch-type secondary battery using an elastic band formed according to one embodiment of the present invention, Fig. 2 is a schematic front view of a pouch-type secondary battery using an elastic band formed according to one embodiment of the present invention, and Fig. 3 is a schematic front view of a pouch-type secondary battery equipped with an explosion-preventing member formed according to one embodiment of the present invention. Also, Fig. 4 is a conceptual diagram showing the principle by which a pouch-type battery case is damaged by an explosion-preventing member when the secondary battery behaves abnormally.

[0035] 1 to 3, the pouch-type secondary battery of the present invention includes a pouch-type battery case 10 that houses an electrode assembly (not shown) and an electrolyte (not shown), and an explosion-preventive member 30 formed to surround a portion of the pouch-type battery case. The explosion-preventive member 30 may include an elastic band 20 and scratch-inducing tips 22a, 22b, and 22c.

[0036] Specifically, referring to Figures 1 and 2, the elastic band 20 used in the pouch-type battery of the present invention may include one as shown in Figure 1(b), or may include two or more as shown in Figure 1(a).

[0037] When there is more than one elastic band, the elastic bands may be spaced apart or cross each other.

[0038] When one elastic band is used, it is preferably located at the center of the pouch-type battery case. When two or more elastic bands are used, the elastic bands may be located symmetrically on both sides of the center, and the elastic bands may be located within a range of about 5 mm to 100 mm, preferably 10 mm to 50 mm, from the center of the pouch-type battery case toward both ends. The spacing between the elastic bands may be the same or different.

[0039] Alternatively, the elastic band may be made of a shape memory polymer (SMP).

[0040] The shape memory polymer material is a polymer material that has the property of shrinking at a high temperature equal to or higher than its glass transition temperature, and representative examples thereof may include at least one of fluorinated ethylene propylene (FEP), polytetrafluoroethylene (PTFE), polyolefin, polyvinyl chloride (PVC), polyvinylidene fluoride (PVDF), silicone rubber, and fluoropolymer elastomer.

[0041] The separation distance between the pouch-type battery case and the elastic band may be 40 μm or less, specifically 0 μm to 40 μm.

[0042] If the separation distance between the pouch-type battery case and the elastic band exceeds 40 μm, the diameter or height of the scratch-inducing tip (described below) will be significantly exceeded, resulting in a larger space between the pouch-type battery case and the elastic band, which may cause the elastic band to detach from the pouch-type battery case or detach from its original position before the pouch-type battery swells. As a result, the surface damage to the pouch-type battery case during battery swelling will be minimal. In this case, electrolyte leakage from the pouch-type secondary battery will not occur during abnormal battery behavior, and the effect of suppressing battery fire and / or explosion will be minimal.

[0043] On the other hand, the width (W) of the minor axis of the elastic band may be about 10 mm to 40 mm, specifically 10 mm to 20 mm.

[0044] When the width of the short axis of the elastic band is within the above range, it is possible to ensure the safety of battery use by preventing energy drain caused by damage to the pouch case during abnormal battery behavior. If the width of the short axis of the elastic band is less than 10 mm, the band cannot withstand the pressure when the pouch-type secondary battery swells, causing the band to break or the scratch-inducing chip to easily come off, resulting in little improvement in the safety of the secondary battery. Also, if the width of the short axis of the elastic band is more than 40 mm, sufficient force is not transmitted to the pouch-type case, causing only slight damage to the pouch-type case during swelling, thereby reducing the safety improvement effect of the secondary battery.

[0045] Also, referring to FIG. 3, the pouch-type secondary battery of the present invention may have scratch-inducing tips 22a, 22b, and 22c disposed between the surface of the pouch-type battery case and the inner surface of the elastic band so as to damage the surface (outer surface) of the pouch-type battery case when the pouch-type secondary battery swells due to an increase in the internal pressure of the pouch-type secondary battery.

[0046] The scratch-inducing tip may be made of a metal or a thermoplastic resin that is stronger than the pouch film that constitutes the pouch-type battery case.

[0047] The metal may include at least one of aluminum, steel, stainless steel, and stainless steel, and the thermoplastic resin may include at least one selected from the group consisting of fluorinated ethylene propylene (FEP), polytetrafluoroethylene (PTFE), polyvinyl chloride (PVC), polyvinylidene fluoride (PVDF), fiber reinforced plastic (FRP), polypropylene (PP), polyethylene (PE), polycarbonate (PC), and polyamide-imide (PAI).

[0048] The shape of the scratch-inducing tip is not particularly limited, but may be cylindrical, rectangular (22a), spherical (22b), or bullet (22c) so that it can easily move together with the elastic band and easily scratch, etch, or damage the surface (outer surface) of the pouch-type battery case. Specifically, the scratch-inducing tip may be rectangular, spherical, or bullet-shaped, or may be rectangular or spherical.

[0049] When the scratch-inducing tip has a spherical shape (22b), the diameter of the scratch-inducing tip may be about 1 mm to 10 mm, specifically 1 mm to 5 mm.

[0050] Furthermore, when the scratch-inducing tip has a cylindrical, rectangular (22a) or bullet (22c) shape, the height of the scratch-inducing tip may be 5 μm to 40 μm, specifically 15 μm to 40 μm.

[0051] That is, when the diameter or height of the scratch-inducing chip satisfies the above range, it is possible to achieve an improved safety effect by preventing energy drain by damaging the pouch-type case during abnormal battery behavior. Here, even if the diameter of the metal layer is as small as less than 1 mm or less than 5 μm, cracks can initiate and propagate from the outermost layer of the pouch-type case, causing damage to the pouch. However, for a more effective effect, it is preferable that the diameter or height of the scratch-inducing chip be the same as or relatively higher than the height of the substrate layer, which is the outermost layer of the pouch-type case, as described below.

[0052] Furthermore, when the scratch-inducing tip has a cylindrical, rectangular (22a) or bullet (22c) shape, the diameter or width of the scratch-inducing tip is preferably the same as the width of the minor axis of the elastic band or about 10% to 70% smaller than the width of the minor axis of the elastic band so that it does not easily detach and / or separate from the elastic band and can move at the same speed and in the same direction.

[0053] If the diameter or width of the scratch-inducing tip is slightly larger than that of the elastic band, the total weight of the battery increases due to the increased volume and weight of the scratch-inducing tip, thereby reducing the energy density of the battery and making it difficult to move at the same speed and direction as the elastic band.Also, if the diameter or width of the scratch-inducing tip is slightly smaller than that of the elastic band, it is difficult to move at the same speed and direction as the elastic band, and sufficient force is not transmitted to the pouch-type case, reducing the degree of damage to the pouch-type case during swelling, resulting in little improvement in the safety of the secondary battery.

[0054] In addition, the scratch-inducing tip may be adhered and fixed to the inner surface of the elastic band abutting the surface of the pouch-type battery case so that it can move at the same speed and in the same direction together with the elastic band when the secondary battery swells.

[0055] Specifically, the scratch inducing tip may be adhered and fixed to the inner surface of the elastic band using an acrylic adhesive, an epoxy adhesive, a silicone adhesive, or a urethane adhesive.

[0056] As described above, in the pouch-type secondary battery of the present invention, if the internal pressure of the battery increases due to gas generation caused by abnormal behavior (operation) inside the battery during long-term use or at high temperatures, causing the center of the pouch-type battery case to swell, the explosion-preventive member surrounding the pouch-type battery case moves from the center of the pouch-type secondary battery to the relatively thinner edge (edge) of the pouch-type secondary battery, causing scratches and damage to the surface of the pouch-type battery case, leading to leakage of electrolyte inside the pouch-type battery case, as shown in Figure 4. As a result, the energy of the secondary battery decreases (drains), and the secondary battery stops operating, preventing and suppressing fire and explosion of the secondary battery.

[0057] Meanwhile, the pouch-type battery case used in the present invention is formed of a lower case having a pocket for accommodating an electrode assembly and an electrolyte, and an upper case for covering the lower part, which are symmetrically formed, and the edge where the lower case and the upper case overlap is sealed.

[0058] Specifically, the pouch-type battery case is formed from a pouch film laminate including a gas barrier layer (not shown), a base layer (not shown) disposed on one side of the gas barrier layer, and a sealant layer (not shown) disposed on the other side of the gas barrier layer.

[0059] The substrate layer is disposed on the outermost layer of the battery case, and serves to protect the electrode assembly from external impact and to provide electrical insulation, and may be formed from one or more polymer materials selected from the group consisting of polyethylene, polypropylene, polycarbonate, polyethylene terephthalate, polyvinyl chloride, acrylic polymers, polyacrylonitrile, polyimide, polyamide, cellulose, aramid, nylon, polyester, polyparaphenylene benzobisoxazole, polyarylate, and Teflon (registered trademark).

[0060] The gas barrier layer ensures the mechanical strength of the battery case, blocks the entry and exit of gases and moisture from the exterior of the secondary battery, and prevents electrolyte leakage. The gas barrier layer may be formed from a metal material, specifically, from an aluminum alloy thin film.

[0061] The sealant layer is bonded by thermocompression to seal the battery case, and is located as the innermost layer of the pouch film laminate.

[0062] The sealant layer, which is the surface that comes into contact with the electrolyte and the electrode assembly after being formed in the battery case, must have insulating and corrosion resistance, and must have high sealing properties because it must completely seal the interior to prevent the transfer of substances between the interior and the exterior. Specifically, the sealant layer may be formed from one or more polymers selected from the group consisting of polyethylene, polypropylene, polycarbonate, polyethylene terephthalate, polyvinyl chloride, acrylic polymers, polyacrylonitrile, polyimide, polyamide, cellulose, aramid, nylon, polyester, polyparaphenylene benzobisoxazole, polyarylate, and Teflon®. Among these, polypropylene (PP) is particularly preferred, as it has excellent mechanical properties such as tensile strength, rigidity, surface hardness, abrasion resistance, and heat resistance, as well as chemical properties such as corrosion resistance.

[0063] Here, the thickness of the base layer may be 10 μm to 50 μm, specifically 12 μm to 40 μm. When the thickness of the base layer satisfies the above numerical range, even when sufficient heat is applied to the sealant layer for sealing, the base layer is not damaged and has excellent insulating properties. Furthermore, the thickness of the gas barrier layer may be 20 μm to 80 μm, specifically 20 μm to 65 μm, more specifically 30 μm to 60 μm. When the thickness of the gas barrier layer satisfies the above numerical range, the gas barrier layer is not damaged during the sealing process and has excellent insulating properties. Furthermore, the thickness of the sealant layer may be 40 μm to 80 μm, specifically 50 μm to 80 μm, more specifically 60 μm to 80 μm. When the thickness of the sealant layer satisfies the above numerical range, the sealant layer does not easily melt during the sealing process, and sufficient heat energy is supplied, effectively reducing the modulus of the sealant layer. Furthermore, when the thicknesses of the substrate layer, gas barrier layer, and sealant layer satisfy the above ranges, the pouch is easily damaged by scratch-induced chips when the battery behaves abnormally, and the safety of the battery can be improved.

[0064] The electrode assembly used in the pouch-type secondary battery of the present invention may be a conventional electrode assembly used in lithium secondary batteries, such as an electrode assembly having a stacked structure of anode / separator / cathode / separator / anode, and the electrode assembly may be any number of cathodes and anodes. The electrode assembly may be of a stack type, a stack-and-fold type, or a jelly roll type.

[0065] The electrolyte used in the present invention is not particularly limited and may be any of various electrolytes used in lithium secondary batteries. Specifically, the electrolyte may contain an organic solvent and a lithium salt.

[0066] The organic solvent may be any solvent that can act as a medium through which ions involved in the electrochemical reaction of the battery can migrate. Specifically, examples of the organic solvent include ester solvents such as methyl acetate, ethyl acetate, γ-butyrolactone, and ε-caprolactone; ether solvents such as dibutyl ether and tetrahydrofuran; ketone solvents such as cyclohexanone; aromatic hydrocarbon solvents such as benzene and fluorobenzene; dimethylcarbonate (DMC), diethylcarbonate (DEC), methylethylcarbonate (MEC), ethylmethylcarbonate (EMC), ethylene carbonate (EC), and propylene carbonate. Examples of solvents that can be used include carbonate-based solvents such as ethylene carbonate (PC), alcohol-based solvents such as ethanol and isopropyl alcohol, nitriles such as R-CN (R is a C2-C20 linear, branched, or cyclic hydrocarbon group that may contain a double-bonded aromatic ring or an ether bond), amides such as dimethylformamide, dioxolanes such as 1,3-dioxolane, and sulfolanes. Among these, carbonate-based solvents are preferred, and more preferred are mixtures of cyclic carbonates (e.g., ethylene carbonate, propylene carbonate, etc.) with high ionic conductivity and high dielectric constant, which can improve the charge / discharge performance of batteries, and low-viscosity linear carbonate compounds (e.g., ethyl methyl carbonate, dimethyl carbonate, diethyl carbonate, etc.).

[0067] The lithium salt may be any compound capable of providing lithium ions for use in lithium secondary batteries, without particular limitation. Specifically, examples of the lithium salt include LiPF6, LiClO4, LiAsF6, LiBF4, LiSbF6, LiAlO4, LiAlCl4, LiCF3SO3, LiC4F9SO3, LiN(C2F5SO3)2, LiN(C2F5SO2)2, LiN(CF3SO2)2, LiCl, LiI, and LiB(C2O4)2. The lithium salt may be used at a concentration of 0.1 to 5.0 M, preferably 0.1 to 3.0 M. When the lithium salt concentration is within the above range, the electrolyte has appropriate conductivity and viscosity, exhibiting excellent electrolyte performance and allowing lithium ions to migrate effectively.

[0068] In addition to the electrolyte components, the electrolyte may further contain additives for purposes such as improving the battery's lifespan, suppressing battery capacity loss, and improving the battery's discharge capacity. Examples of additives include, but are not limited to, haloalkylene carbonate compounds such as difluoroethylene carbonate, pyridine, triethyl phosphite, triethanolamine, cyclic ethers, ethylenediamine, n-glyme, hexamethylphosphoric triamide, nitrobenzene derivatives, sulfur, quinoneimine dyes, N-substituted oxazolidinones, N,N-substituted imidazolidines, ethylene glycol dialkyl ethers, ammonium salts, pyrrole, 2-methoxyethanol, and aluminum trichloride, which may be used alone or in combination. The additives may be present in an amount of 0.1 to 10 wt %, preferably 0.1 to 5 wt %, based on the total weight of the electrolyte.

[0069] The above description has been given with reference to the drawings of embodiments of the present invention, but a person having ordinary knowledge in the field to which the present invention belongs will be able to make various applications and modifications within the scope of the present invention based on the above content.

[0070] Example The present invention will be described in more detail below with reference to specific examples.

[0071] Example Manufacturing example (Manufacturing pouch-type battery cases) An aluminum pouch film was fabricated by dry-laminating 25 μm thick nylon 6 and 12 μm thick polyethylene terephthalate (PET) onto the surface of a 60 μm thick aluminum foil to laminate nylon onto the aluminum layer, and then laminating an 80 μm thick polypropylene onto the other side of the nylon-laminated aluminum layer. The aluminum pouch film was then placed in a molding device and formed into a pouch-type battery case.

[0072] (Manufacturing pouch-type secondary batteries) A cathode mixture slurry (solid content 65 wt%) was prepared by adding LiCoO2 as a cathode active material, carbon black as a conductive material, and PVDF as a binder to N-methyl-2-pyrrolidone (NMP) as a solvent in a weight ratio of 94:3:3. The cathode mixture slurry was applied to an aluminum (Al) thin film cathode current collector with a thickness of approximately 20 μm, dried, and then roll-pressed to prepare a cathode.

[0073] Next, carbon powder as the negative electrode active material, PVDF as the binder, and carbon black as the conductive material were added to NMP as the solvent in a weight ratio of 96:3:1 to prepare a negative electrode mixture slurry (solid content 75 wt%). The negative electrode mixture slurry was applied to a copper (Cu) thin film as a negative electrode current collector with a thickness of 10 μm, dried, and then roll-pressed to prepare a negative electrode.

[0074] Next, a 20 μm thick polyethylene (PE) separator was interposed between the prepared electrodes, and the resulting electrode assembly was wound and compressed. The electrode assembly was then inserted into the prepared pouch-type battery case, and an electrolyte (EC:DMC=30:70 volume ratio, 1 M LiPF, 0.5% vinylene carbonate, and 0.5% 1,3-propane sultone) was injected to prepare a pouch-type secondary battery.

[0075] Example 1 An elastic band with a width (w) of 10 mm was manufactured using polytetrafluoroethylene (PTFE).

[0076] Next, one elastic band prepared in the above Preparation Example was placed in the center of the pouch-type secondary battery, and then three rectangular scratch-inducing chips (width: 5 mm, height: 40 μm) were inserted between the surface of the pouch-type secondary battery and the elastic band to prepare an explosion-proof member (see Figures 1(b) and 3(a)).

[0077] Example 2 An elastic band with a width (w) of 50 mm was manufactured using polytetrafluoroethylene (PTFE).

[0078] Next, one elastic band manufactured in the above manufacturing example was placed in the center of the pouch-type secondary battery, and then three rectangular scratch-inducing chips (width: 5 mm, height: 40 μm) were inserted between the surface of the pouch-type secondary battery and the elastic band to fabricate an explosion-proof member (see Figure 1(b) and Figure 3(a)).

[0079] Example 3 An elastic band with a width (w) of 50 mm was manufactured using polytetrafluoroethylene (PTFE).

[0080] Next, one elastic band prepared in the above-mentioned manufacturing example was placed in the center of the pouch-type secondary battery, and then two spherical scratch-inducing chips (diameter: 2 mm) made of fluorinated ethylene propylene (FEP) material were inserted between the surface of the pouch-type secondary battery and the elastic band to prepare an explosion-proof member (see Figures 1(b) and 3(b)).

[0081] Experimental example 1: Time delay evaluation for thermal propagation Five pouch-type secondary batteries equipped with the explosion-preventive members manufactured in Examples 1 to 3 and five pouch-type secondary batteries without the explosion-preventive members of the Manufacturing Example were manufactured into one module, and then heat was applied to the outermost pouch-type secondary battery at a rate of 0.5°C / sec using a heating pad. Then, the heat of the adjacent pouch-type secondary battery was measured with a thermocouple to evaluate the presence or absence of a time delay in heat propagation.

[0082] Experimental example 2: Safety evaluation against physical impact The pouch-type secondary batteries equipped with the explosion-preventive members manufactured in Examples 1 to 3 and the pouch-type secondary battery without the explosion-preventive member of the Manufacturing Example were each fully charged to 4.4 V at a current of 0.2 C in a constant current-constant voltage mode, and then the presence or absence of ignition of the pouch-type secondary batteries was measured by a method in which a rod with a diameter of 15.8 mm was dropped from a height of 6.1 cm onto the center of the secondary battery. The above experiment was repeated 10 times for each, and the results are shown in Table 1 below.

[0083] Experimental example 3: Safety evaluation during nail penetration The pouch-type secondary batteries equipped with the explosion-preventive members manufactured in Examples 1 to 3 above and the pouch-type secondary batteries without the explosion-preventive members of the Manufacturing Example were each fully charged to 4.4 V in constant current-constant voltage mode at a current of 0.2 C to an SOC of 100%, and then a nail penetration test was conducted in which a nail with a diameter of 3 mm was used to pierce each pouch-type secondary battery at a speed of 0.1 mm / s to determine whether or not the pouch-type secondary batteries caught fire. The above test was repeated 10 times for each, and the results are shown in Table 1 below.

[0084] [Table 1]

[0085] In Table 1, the mark "◯" means good, meaning that there is almost no heat propagation or that there is almost no ignition or explosion.

[0086] The "△" mark above means average, meaning that no fire or explosion occurred in 5 or less of the 10 test specimens.

[0087] The above-mentioned "x" indicates poor quality, meaning that most of the 10 test specimens ignited and exploded.

[0088] Referring to Table 1 above, it can be seen that the pouch-type secondary batteries of Examples 1 to 3 are superior in all respects of time delay effect against heat propagation, safety against physical impact, and safety against nail penetration, compared to the pouch-type secondary batteries of the manufacturing examples not equipped with explosive components. [Explanation of symbols]

[0089] 10 Pouch-type battery case 20 elastic bands 22a, 22b, 22c Scratch-inducing chip 30 Explosion prevention materials

Claims

1. a pouch-type battery case that accommodates the electrode assembly and the electrolyte; an explosion-proof member surrounding a portion of the pouch-type battery case; The explosion-proof member is an annular elastic band surrounding a portion of the pouch-type battery case; a scratch-inducing tip disposed between the pouch-type battery case and the elastic band.

2. The pouch-type secondary battery according to claim 1 , comprising one or more elastic bands.

3. The pouch-type secondary battery according to claim 2 , wherein the elastic band is located at the center of the pouch-type battery case.

4. The elastic band includes two or more of the elastic bands, The pouch-type secondary battery according to claim 1 , wherein two or more of the elastic bands are spaced apart from each other or cross each other.

5. The pouch-type secondary battery according to claim 4 , wherein the elastic bands are positioned symmetrically on both sides of the center of the pouch-type battery case.

6. The pouch-type secondary battery according to claim 1 , wherein the elastic band comprises a shape-memory polymer material.

7. 7. The pouch-type secondary battery according to claim 6, wherein the shape-memory polymer material includes at least one of fluorinated ethylene propylene (FEP), polytetrafluoroethylene (PTFE), polyolefin, polyvinyl chloride (PVC), polyvinylidene fluoride (PVDF), silicone rubber, and fluororubber.

8. 4. The pouch-type secondary battery according to claim 1, wherein a distance between the pouch-type battery case and the elastic band is 0 μm to 40 μm.

9. 4. The pouch-type secondary battery according to claim 1, wherein the width of the minor axis of the elastic band is 10 mm to 40 mm.

10. The pouch-type secondary battery according to claim 1 , wherein the scratch-inducing tip includes a metal or a thermoplastic resin.

11. 11. The pouch-type secondary battery according to claim 10, wherein the metal is at least one of aluminum, steel, stainless steel, and stainless steel.

12. 11. The pouch-type secondary battery according to claim 10, wherein the thermoplastic resin is at least one selected from the group consisting of fluorinated ethylene propylene (FEP), polytetrafluoroethylene (PTFE), polyvinyl chloride (PVC), polyvinylidene fluoride (PVDF), fiber reinforced plastic (FRP), polypropylene (PP), polyethylene (PE), polycarbonate (PC), and polyamide-imide (PAI).

13. The pouch-type secondary battery according to claim 1 , wherein the scratch-inducing tip has a cylindrical, rectangular, spherical or bullet shape.

14. The pouch-type secondary battery according to claim 13, wherein when the scratch-inducing tip has a spherical shape, the scratch-inducing tip has a diameter of 1 mm to 10 mm.

15. The pouch-type secondary battery according to claim 13, wherein when the scratch-inducing tip has a cylindrical, rectangular or bullet shape, the height of the scratch-inducing tip is 5 μm to 40 μm.

16. The pouch-type secondary battery according to claim 15, wherein the width or lateral width of the scratch-inducing tip is the same as the width of the minor axis of the elastic band, or is 10% to 70% smaller than the width of the minor axis of the elastic band.

17. 4. The pouch-type secondary battery according to claim 1, wherein the scratch-inducing tip is adhered and fixed to the inner surface of the elastic band that is in contact with the pouch-type battery case.

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