Secondary battery composite sheet for thermal runaway prevention, formed by combining silica aerogel and pouch film

Abstract

The present invention relates to a secondary battery composite sheet for thermal runaway prevention and a manufacturing method therefor, the composite sheet comprising: a silica aerogel layer; a first pouch film layer formed on the first surface of the silica aerogel layer; and a second pouch film layer formed on the second surface of the silica aerogel layer, wherein the first pouch film layer includes an outer resin layer, a metal layer and an inner resin layer, and the second pouch film layer includes an outer resin layer, a metal layer and an inner resin layer.

Description

Composite sheet for preventing thermal runaway for secondary batteries combining silica aerogel and pouch film

[0001] The present invention relates to a composite sheet using silica aerogel and a pouch film for preventing thermal runaway of a secondary battery.

[0002] Lithium-ion secondary batteries, due to their superior energy density and output characteristics, are widely used in devices and components such as mobile phones, laptops, tablets, power tools, and electric vehicles. They are particularly prevalent in mobile phones and other mobile devices, which require miniaturization and lightweight design. Traditionally, aluminum alloys have been used as packaging materials for these batteries due to their lightweight, formability, and economical advantages.

[0003] Recently, secondary batteries have seen explosive growth in use and application, from IT devices to key power supplies for electric vehicles, thanks to their diverse advantages, including high energy density and superior output. Pouch films, as outer packaging materials for these batteries, encapsulate the electrodes and electrolyte of these batteries. They must meet demanding specifications, including interlayer adhesion between metal thin films and polymers, thermal fusion strength, electrolyte resistance, airtightness, moisture permeability, and formability.

[0004] Pouch films are largely composed of an outer layer, a metal barrier layer, and an inner sealant layer. The metal barrier layer requires barrier properties against water vapor and other gases, electrolyte resistance, and formability. The barrier layer typically uses a metal, such as aluminum (Al) or an aluminum alloy. While aluminum is currently the most commonly used, the development of new materials continues to be required.

[0005] This pouch film for secondary batteries protects a battery composed of the electrode assembly and an electrolyte introduced into the interior through a subsequent process, and in order to protect it from external impact, an outer resin layer using a polymer resin or the like is formed on the aluminum thin film, and an inner resin layer using polyolefin or the like is formed on the other side of the aluminum thin film.

[0006] However, secondary batteries using the aluminum pouch film described above are experiencing difficulties in use in environments such as electric vehicles where large-capacity batteries are adopted for various reasons. Typically, electric vehicles require a range of around 500 km or more, up from an initial range of around 100-200 km. Consequently, the capacity of the individual batteries installed in electric vehicles also increases simultaneously. Furthermore, vehicles are exposed to a variety of environments, generating heat from the heat flowing in from the outside and during the charging and discharging of large-capacity batteries. This abnormal state of thermal runaway is called thermal runaway in secondary batteries. Large-capacity lithium-ion batteries used in electric vehicles have high energy densities, putting them at risk of thermal runaway in overheated conditions. Thermal runaway refers to a dangerous situation in which high temperatures and high pressures within the battery can occur, potentially leading to explosion or fire.

[0007] Thermal runaway in secondary batteries occurs under abnormal circumstances. This occurs when heat generated within the battery increases rapidly, rapidly raising its internal temperature. This causes rapid chemical reactions within the battery, releasing heat and gases, which can ultimately lead to explosion and fire. Thermal runaway can occur for a variety of reasons. The most common causes include overcharging, overdischarging, overcurrent, internal short circuits, and high temperatures. These abnormal conditions accelerate reactions within the battery, causing heat accumulation and a rapid increase in reaction rate, resulting in thermal runaway. Thermal runaway severely compromises battery safety and can lead to fire and explosion, resulting in personal injury and property damage. Therefore, it is crucial to consider safety during battery design and manufacturing to prevent such situations. Furthermore, it is crucial to proactively design the battery to prevent abnormalities, such as abnormal and uncontrollable temperature surges and propagation, both internally and externally. Fires that occur in high-temperature electric vehicle batteries are extremely dangerous, and such fires can cause significant damage, directly affecting the surrounding environment and passenger safety.

[0008] Therefore, in order to solve the above problems, a composite sheet technology for preventing thermal runaway between unit cells using a metal with excellent rigidity is being studied to effectively block heat leakage from an uncontrollable battery due to thermal runaway to an adjacent normal battery, delay the abnormal state in which the entire battery explodes by slowing down the speed of thermal runaway to the adjacent battery, and secure time for people to quickly evacuate, and to withstand the pressure inside the battery due to abnormally high temperatures.

[0009] [Prior Art Literature]

[0010] [Patent Document]

[0011] (Patent Document 1) Republic of Korea Patent Publication No. 10-2020-0140002

[0012] The present invention aims to provide a composite sheet for preventing thermal runaway for a secondary battery by combining silica aerogel having very low heat conduction and a pouch film having excellent mechanical properties to prevent thermal runaway from spreading to adjacent batteries when gas is generated inside a battery during charging and discharging due to an abnormal condition inside or outside the battery and the gas ignites and explodes due to a continuous rise in the internal temperature of the battery.

[0013] According to the first aspect of the present invention,

[0014] The present invention provides a composite sheet for preventing thermal runaway for a secondary battery.

[0015] In one specific example of the present invention, the composite sheet for preventing thermal runaway for a secondary battery comprises: a silica aerogel layer; a first pouch film layer formed on a first surface of the silica aerogel layer; a second pouch film layer formed on a second surface of the silica aerogel layer; the first pouch film layer includes an outer resin layer, a metal layer, and an inner resin layer, and the second pouch film layer includes an outer resin layer, a metal layer, and an inner resin layer.

[0016] In one specific example of the present invention, the composite sheet for preventing thermal runaway for a secondary battery includes a bonding layer in which the inner resin layer of the first pouch film layer and the inner resin layer of the second pouch film layer are bonded to a silica aerogel layer, respectively.

[0017] In one specific example of the present invention, the silica aerogel layer is formed by coating silica aerogel on a support or by including silica aerogel inside the support.

[0018] In one specific example of the present invention, the metal layer is an aluminum layer or a SUS layer.

[0019] In one specific example of the present invention, the silica aerogel layer comprises 10 wt% to 70 wt% of silica aerogel relative to the total weight of the silica aerogel layer.

[0020] According to the second aspect of the present invention,

[0021] The present invention provides a method for manufacturing the composite sheet for preventing thermal runaway for a secondary battery as described above.

[0022] In one specific example of the present invention, the manufacturing method comprises: (1) a step of preparing a silica aerogel layer; (2) a step of applying an adhesive layer to a first surface of the silica aerogel layer and then adhering a first pouch film layer; and (3) a step of applying an adhesive layer to a second surface of the silica aerogel layer and then adhering a second pouch film layer.

[0023] The pouch film of the composite sheet of the present invention not only has excellent corrosion resistance and chemical resistance even when the battery is exposed to external physical or chemical shocks or stresses, but also has the advantage of effectively transmitting heat generated during charging and discharging to the outside, thereby preventing thermal runaway. In addition, the composite sheet for preventing thermal runaway effectively disperses and discharges heat from the battery, thereby preventing fire and ensuring safety. Furthermore, high temperatures and heat leakage are the main causes of shortened battery lifespan, and the use of the composite sheet for preventing thermal runaway can extend the battery lifespan by maintaining the battery within a stable temperature range.

[0024] Figure 1 is a schematic diagram showing a composite sheet for preventing thermal runaway for a secondary battery according to one specific example of the present invention.

[0025] The specific embodiments provided in accordance with the present invention can all be achieved by the following description. It should be understood that the following description describes preferred embodiments of the present invention and that the present invention is not necessarily limited thereto.

[0026] For the properties described in this specification, if the measurement conditions and methods are not specifically described, the properties are measured according to the measurement conditions and methods generally used by those skilled in the art.

[0027]

[0028] Hereinafter, with reference to Fig. 1, a composite sheet for preventing thermal runaway for a secondary battery according to one specific example of the present invention will be described. Fig. 1 is a schematic diagram showing a composite sheet for preventing thermal runaway for a secondary battery according to one specific example of the present invention.

[0029]

[0030] According to one specific example of the present invention, the present invention provides a composite sheet for preventing thermal runaway for a secondary battery, comprising: a silica aerogel layer; a first pouch film layer formed on a first surface of the silica aerogel layer; a second pouch film layer formed on a second surface of the silica aerogel layer, the first pouch film layer including an outer resin layer, a metal layer, and an inner resin layer, and the second pouch film layer including an outer resin layer, a metal layer, and an inner resin layer. Hereinafter, each component of the composite sheet for preventing thermal runaway for a secondary battery of the present invention will be described in detail.

[0031]

[0032] <Composite sheet for preventing thermal runaway for secondary batteries>

[0033]

[0034] (1) Silica aerogel layer

[0035] A composite sheet for preventing thermal runaway for a secondary battery according to one specific embodiment of the present invention comprises a silica aerogel layer. The aerogel contained in the silica aerogel layer may include an aerogel having a structure derived from polysiloxane or an aerogel containing silica as a main component, but is not limited thereto. Specifically, the aerogel may be an organic-inorganic hybridized silica aerogel by introducing an organic group or an organic chain, such as a methyl group.

[0036] The above silica aerogel layer can function as a heat barrier layer that blocks heat transfer to adjacent cells. As the silica aerogel layer, a dry gel obtained by using a supercritical drying method for a wet gel, a xerogel obtained by drying under atmospheric pressure, a cryogel obtained by freeze drying, etc. can be used, but are not limited thereto. Specifically, as the silica aerogel layer, a low-density dry gel obtained without using the above drying method for a wet gel, a 'gel comprised of a microporous solid in which the dispersed phase is a gas' can be used. The interior of the silica aerogel layer has a mesh-like microstructure and can have a cluster structure in which aerogel particles of about 2 nm to 20 nm are combined. Between the skeletons formed by the above clusters, there are pores with a particle size of 100 nm or less, so that a three-dimensional microporous structure can be formed.

[0037] The silica aerogel layer may include a reinforcing agent and a sealing coupling agent additive. Through this, the durability of the silica aerogel layer may be increased, thereby improving the puncture strength and heat insulation effect. Specifically, the silica aerogel layer may include 1 to 20 parts by weight of the reinforcing agent and 1 to 10 parts by weight of the silane coupling agent additive based on 100 parts by weight of the silica aerogel.

[0038] The thickness of the silica aerogel layer is 2 mm to 50 mm, and the total thickness of the pouch film layer including the silica aerogel layer may be 110 mm to 300 mm, but is not limited thereto. The thickness of the silica aerogel layer may be appropriately adjusted depending on the weight, strength, processing depth, etc. required as the outer material. When the thickness of the silica aerogel layer is less than 2 mm, the strength and processability are reduced, and the manufacturing cost increases rapidly due to the difficulty of the continuous film processing process, making it difficult to apply to mass production. When the thickness of the silica aerogel layer exceeds 50 mm, the heat blocking performance can be sufficiently expressed, but the formability as a heat blocking sheet is significantly reduced.

[0039] The density of the above silica aerogel layer is 0.05 g / cm 3 0.2g / cm 3 The heat transfer coefficient of the silica aerogel layer may be, but is not limited to, 0.015 to 0.02 W / mK, and the melting temperature may be, but is not limited to, 1,000°C to 1,500°C.

[0040] According to one specific example of the present invention, the silica aerogel layer is formed by coating silica aerogel on a support or by including silica aerogel inside the support.

[0041] As the support, short fibers made of organic or inorganic materials and nonwoven fabrics or fabrics woven therefrom, short fibers mixed with organic and inorganic materials and nonwoven fabrics or fabrics woven therefrom, organic or inorganic particle fillers or organic or inorganic porous fillers, porous inorganic layers, etc. can be used, but are not limited thereto. As long as the support can contain and maintain aerogel inside the support, it can be used without special restrictions. When a nonwoven fabric or a porous inorganic layer is used as the support, the nonwoven fabric or the porous inorganic layer can be impregnated with aerogel or coated with aerogel to produce the support. Through this, additional insulation can be provided due to the air layer included in the nonwoven fabric or the porous inorganic layer. The silica aerogel layer may additionally include a reinforcing sheet layer on or under the support layer including the aerogel.

[0042] According to one specific example of the present invention, the silica aerogel layer comprises 10 wt% to 70 wt% of silica aerogel relative to the total weight of the silica aerogel layer. When the content of the silica aerogel is less than 10 wt%, the insulation effect is reduced, and when the content of the silica aerogel exceeds 70 wt%, the mechanical properties and processability are reduced.

[0043]

[0044] (2) Pouch film layer

[0045] A composite sheet for preventing thermal runaway for a secondary battery according to one specific embodiment of the present invention includes a pouch film layer. The pouch film layer includes a first pouch film layer formed on a first surface of a silica aerogel layer and a second pouch film layer formed on a second surface of the silica aerogel layer. Hereinafter, each component of the pouch film layer will be described in detail.

[0046]

[0047] metal layer

[0048] A pouch film layer according to one specific example of the present invention includes an outer resin layer, a metal layer, and an inner resin layer. The pouch film layer can function as a barrier layer that prevents the penetration of oxygen and moisture from the outside.

[0049] According to one specific example of the present invention, the metal layer is an aluminum layer or a SUS layer. The aluminum layer may include a soft aluminum foil or an aluminum foil containing iron. The aluminum foil may have its surface etched or degreased to improve adhesion to the internal resin layer, but this may be omitted to reduce the process speed. When an aluminum foil containing iron is used as the aluminum foil, formability is imparted, thereby facilitating the processing of the metal layer. The aluminum foil may be an aluminum alloy foil of the 1000 or 8000 series, which has high purity and excellent processability. The aluminum alloy may be an alloy obtained by adding various metals and non-metals to pure aluminum, or a stainless steel alloy. Specifically, the alloy of the aluminum may include an element selected from the group consisting of silicon, boron, germanium, arsenic, antimony, copper, magnesium, manganese, zinc, lithium, iron, chromium, vanadium, titanium, bismuth, potassium, tin, lead, zirconium, nickel, cobalt, and combinations thereof.

[0050] The aluminum foil containing iron may contain iron in an amount of 0.1 wt% to 9.0 wt%, or 0.5 wt% to 2.0 wt%, based on the total weight of the aluminum foil. When the iron content of the aluminum foil is less than 0.1 wt%, the ductility of the aluminum layer decreases, and when it exceeds 9.0 wt%, the problem of reduced formability occurs.

[0051] The thickness of the aluminum layer may be, but is not limited to, 10 ㎛ to 100 ㎛, 30 ㎛ to 50 ㎛. The aluminum layer is intended to prevent gas and water vapor from penetrating into the battery from the outside, and may be appropriately adjusted to prevent pinholes in the aluminum thin film and poor processability (pouching, embossing). If the thickness of the aluminum layer is less than 10 ㎛, it may be easily torn, resulting in poor electrolytic resistance and insulation, and if it exceeds 100 ㎛, its formability may be poor.

[0052] An additional corrosion-prevention layer may be formed on the aluminum layer. The corrosion-prevention layer may be formed to prevent corrosion of the aluminum foil layer by an electrolyte or hydrofluoric acid. For this purpose, corrosion-prevention treatments may include degreasing, hydrothermal modification, anodizing, chemical conversion, coating-type corrosion-prevention treatments in which a coating agent with corrosion-prevention properties is applied, or a combination of two or more of these treatments. Among the corrosion-prevention treatments, degreasing, hydrothermal modification, and anodizing, particularly hydrothermal modification or anodizing, are treatments that dissolve the surface of the aluminum foil with a treatment agent to form an aluminum compound (boehmite, alumite) with excellent corrosion resistance. Such treatments may be included in the definition of chemical conversion in order to obtain a structure that forms a co-continuous structure from the metal foil to the corrosion-prevention layer. However, the present invention is not limited thereto, and it is also possible to form a corrosion-prevention layer only by a pure coating treatment that is not included in the definition of chemical conversion, such as a method of using a coating agent containing a rare earth element oxide sol.

[0053] The aluminum layer may be chemically treated on at least one side, preferably both sides, in order to stabilize adhesion, prevent dissolution or corrosion, etc. The chemically treated layer may refer to a treatment to form an acid-resistant film on the surface of the metal layer. The chemically treated layer may include a chromic acid chromate treatment using a chromic acid compound such as chromium nitrate, chromium fluoride, chromium sulfate, chromium acetate, chromium oxalate, chromium phosphoric acid, acetylacetate chromate, chromium chloride, or potassium chromium sulfate; a phosphoric acid chromate treatment using a phosphoric acid compound such as sodium phosphate, potassium phosphate, ammonium phosphate, or polyphosphoric acid; a chromate treatment using an aminated phenol polymer, etc. As a chemically treated layer method for imparting corrosion resistance to the aluminum layer, there may be mentioned a method of forming a corrosion-resistant layer on the surface of the metal layer by coating a substance in which fine particles of a metal oxide such as aluminum oxide, titanium oxide, cerium oxide, or tin oxide or barium sulfate are dispersed in phosphoric acid, and baking the resultant in a temperature of 150°C or higher. In addition, on the corrosion-resistant treatment layer, a resin layer crosslinked with a cationic polymer using a crosslinking agent can be formed. At this time, as the cationic polymer, polyethyleneimine, an ionic polymer complex including a polymer having polyethyleneimine and carboxylic acid, a primary amine-grafted acrylic resin in which a primary amine is grafted onto an acrylic backbone, polyarylamine or a derivative thereof, aminophenol, etc. can be used. The cationic polymer can be used singly or in combination of two or more. The crosslinking agent can be used a compound having at least one functional group selected from the group consisting of an isocyanate group, a glycidyl group, a carboxyl group, and an oxazoline group, a silane coupling agent, etc. The crosslinking agent can be used singly or in combination of two or more.

[0054] The above chemical conversion treatment can be performed by applying a solution containing a compound used for forming an acid-resistant film to the surface of the metal layer by a bar coating method, a roll coating method, a gravure coating method, an immersion method, etc., and then heating the metal layer so that the temperature of the metal layer becomes about 70°C to 200°C. Before the chemical conversion treatment, the metal layer can be degreased in advance by an alkaline immersion method, an electrolytic cleaning method, an acid cleaning method, an electrolytic acid cleaning method, etc. Through this, the chemical conversion treatment of the surface of the metal layer can be performed more efficiently. Specifically, the boehmite treatment obtained by immersing the metal foil in boiling water to which triethanolamine has been added can be performed by the hydrothermal modification treatment. In addition, the anodic oxidation treatment can be specifically performed by the alumite treatment, and the chemical conversion treatment can be performed by various chemical conversion treatments including a chromate treatment, a zirconium treatment, a titanium treatment, a vanadium treatment, a molybdenum treatment, a calcium phosphate treatment, a strontium hydroxide treatment, a cerium treatment, a ruthenium treatment, or a mixed phase containing materials used in these treatments.

[0055] The metal layer may be a stainless steel layer including stainless steel. The stainless steel may be a steel grade including one selected from the group consisting of austenitic, ferritic, and martensitic steels. The ferritic and martensitic steels have significantly lower corrosion resistance than the austenitic steels and are magnetic. Therefore, when using ferritic and martensitic steels as the stainless steel, the usage environment of a finished device including a secondary battery using a pouch film manufactured using the same may be affected. Therefore, it may be preferable to use an austenitic steel grade as the stainless steel. Specifically, the steel grade may include SUS304, SUS430, and SUS316.

[0056] For the surface finishing of the above stainless steel layer, BA, 2B, 2D, No. 4, and HL can be used, but are not limited thereto. Specifically, for the surface finishing of the above stainless steel layer, 304, 304L, 304J1, 316, and 316L, which have excellent corrosion resistance and workability, can be used.

[0057] The thickness of the above stainless steel foil is 20㎛ to 60㎛, and the total thickness of the pouch film layer including the stainless steel foil may be 110㎛ to 160㎛, but is not limited thereto. The thickness of the stainless steel foil may be appropriately adjusted in consideration of the required weight or strength, ease of process, etc. When the thickness of the stainless steel foil is less than 20㎛, rolling processing is very difficult, and it is difficult to apply to mass production due to a sharp increase in manufacturing cost. When the thickness of the stainless steel foil exceeds 60㎛, the rolling process is easy, but the formability as a battery outer material is significantly reduced.

[0058] The thickness of the above stainless steel layer may be, but is not limited to, 20 µm to 150 µm or 40 µm to 60 µm. The thickness of the above stainless steel layer may be appropriately adjusted depending on the weight, strength, processing depth, etc. required as a battery outer shell material.

[0059] The above stainless steel layer may include 0.02 wt% to 0.1 wt% of carbon, 0.1 wt% to 1.0 wt% of silicon, 10 wt% to 30 wt% of chromium, and 0.05 wt% to 0.3 wt% of nickel based on the total weight of the stainless steel layer.

[0060] The yield strength of the above stainless steel layer is 100 N / mm 2 Up to 300N / mm 2 , tensile strength is 200N / mm 2 Up to 700 N / mm 2 The elongation may be, but is not limited to, 20% to 60%.

[0061]

[0062] outer resin layer (outermost layer)

[0063] A pouch film layer according to one embodiment of the present invention comprises an outer resin layer, a metal layer, and an inner resin layer. The outer resin layer may refer to the outermost layer. Since the outer resin layer is in direct contact with hardware, it may function as an insulating layer.

[0064] To this end, the outer resin layer may include a resin having insulating properties. Specifically, the outer resin layer may include a polyester resin such as polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, polybutylene naphthalate, copolyester, polycarbonate, or a polyamide resin, a polyimide resin, or a copolymer of polyamide and polyimide, and preferably, a copolymer of polyamide and polyimide, but is not limited thereto. The polyester resin may include polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polyethylene naphthalate (PEN), polybutylene naphthalate (PBN), copolyester, polycarbonate (PC), or the like. The above polyester may include polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, polybutylene naphthalate, polyethylene isophthalate, polycarbonate, a copolymer polyester having ethylene terephthalate as a main repeating unit, a copolymer polyester having butylene terephthalate as a main repeating unit, etc.

[0065] Among the copolymer polyesters having ethylene terephthalate as the main repeating unit, copolymer polyesters having ethylene terephthalate as the main repeating unit and polymerizing ethylene isophthalate, polyethylene (terephthalate / isophthalate), polyethylene (terephthalate / adipate), polyethylene (terephthalate / sodium sulfoisophthalate), polyethylene (terephthalate / sodium isophthalate), polyethylene (terephthalate / phenyl-dicarboxylate), polyethylene (terephthalate / decanedicarboxylate), etc. can be used. As the copolymer polyester having butylene terephthalate as the main repeating unit, copolymer polyester having butylene terephthalate as the main repeating unit and polymerizing butylene isophthalate, polybutylene (terephthalate / adipate), polybutylene (terephthalate / sebacate), polybutylene (terephthalate / decanedicarboxylate), polybutylene naphthalate, etc. can be used. At this time, the polyester can be used alone or in combination of two or more types. As the polyamide resin, aliphatic polyamides such as nylon 6, nylon 66, nylon 610, nylon 12, nylon 46, and copolymers of nylon 6 and nylon 66; Hexamethylenediamine-isophthalic acid-terephthalic acid copolymer polyamides such as nylon 6I, nylon 6T, nylon 6IT, nylon 6I6T (I represents isophthalic acid, T represents terephthalic acid) containing structural units derived from terephthalic acid and / or isophthalic acid, polyamides containing aromatics such as polymethaxylene adipamide (MXD6); alicyclic polyamides such as polyaminomethylcyclohexyl adipamide (PACM6); polyamides copolymerized with a lactam component or an isocyanate component such as 4,4'-diphenylmethane-diisocyanate, polyesteramide copolymers or polyetheresteramide copolymers which are copolymers of copolymerized polyamides with polyester or polyalkylene ether glycol; these copolymers, etc. can be used.At this time, the above polyamide can be used alone or in combination of two or more types.

[0066] When polyethylene terephthalate, polyamide, or a copolymer thereof is used as the outer resin layer, the thickness of the outer resin layer may be 10 μm to 30 μm, or 12 μm to 25 μm. When the outer resin layer satisfies the thickness range described above, processing flexibility increases, the weight of the entire film decreases, and the overall production cost is lowered, thereby enhancing the price competitiveness of the product.

[0067]

[0068] Inner resin layer (innermost layer)

[0069] A pouch film layer according to one specific embodiment of the present invention includes an outer resin layer, a metal layer, and an inner resin layer. The inner resin layer may refer to the innermost layer.

[0070] The internal resin layer may include a polyolefin such as polyethylene (PE), polypropylene (PP), or a copolymer thereof. When a polyolefin such as polyethylene, polypropylene, or a copolymer thereof is used as the internal resin layer, not only does it have the properties required as a secondary battery packaging material such as good heat sealability, moisture resistance, and heat resistance, but also it may be easy to process such as lamination. The internal resin layer may include a resin layer selected from the group consisting of ethylene copolymer, propylene copolymer, polyester, polyamide, polycarbonate, fluorine, silicone, acrylic, ethylene-propylene-diene-monomer rubber (EPDM), and mixtures thereof, and preferably, may include a polyolefin resin layer or a mixed resin layer of polybutadiene and polyolefin, but is not limited thereto. The polyolefin may be polyethylene such as low-density polyethylene, medium-density polyethylene, high-density polyethylene, and linear low-density polyethylene; Polypropylene such as homopolypropylene, block copolymers of polypropylene (e.g., block copolymers of propylene and ethylene), random copolymers of polypropylene (e.g., random copolymers of propylene and ethylene); terpolymers of ethylene-butene-propylene; etc., and preferably includes polyethylene and polypropylene, but is not limited thereto.

[0071] The thickness of the internal resin layer may be, but is not limited to, 20 µm to 100 µm or 30 µm to 80 µm. When the internal resin layer satisfies the thickness range described above, formability, insulation, and electrolyte resistance may be increased.

[0072]

[0073] (3) Bonding layer

[0074] According to one specific example of the present invention, the composite sheet for preventing thermal runaway for a secondary battery includes a bonding layer that bonds the inner resin layer of the first pouch film layer and the inner resin layer of the second pouch film layer to a silica aerogel layer, respectively. The bonding layer may allow the inner resin layer of the first pouch film layer and the inner resin layer of the second pouch film layer to bond to a silica aerogel layer, respectively. Specifically, the adhesive layer may include a first adhesive layer that bonds an outer resin layer including NY, PET, etc. and a metal layer, a second adhesive layer that bonds the metal layer and the inner resin layer including cPP, PE, etc., and a third adhesive layer that bonds the inner resin layer and the silica aerogel layer.

[0075]

[0076] The above first adhesive layer is formed by an adhesive resin capable of bonding the outer resin layer and the metal layer. Specifically, the adhesive resin may be a one-component curing adhesive resin or a two-component curing adhesive resin. The adhesive mechanism of the adhesive resin used to form the above first adhesive layer may use a chemical reaction type, solvent evaporation type, heat melting type, or heat extrusion type adhesive mechanism.

[0077] The above adhesive resin may include polyester resins such as polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, polybutylene naphthalate, polyethylene isophthalate, polycarbonate, and copolymerized polyester; polyether adhesives; polyurethane adhesives; epoxy resins; phenolic resins; polyamide resins such as nylon 6, nylon 66, nylon 12, and copolymerized polyamide; polyolefin resins such as polyolefin, acid-modified polyolefin, and metal-modified polyolefin; polyvinyl acetate resins; all-cellulose adhesives; (meth)acrylic resins; polyimide resins; amino resins such as urea resin and melamine resin; rubbers such as chloroprene rubber, nitrile rubber, and styrene-butadiene rubber; silicone resins; fluorinated ethylene propylene copolymers, and the like. The above adhesive resins may be used alone or in combination of two or more.

[0078] The combination of the above two or more types of adhesive resin components may be, but is not limited to, a mixed resin of polyamide and acid-modified polyolefin, a mixed resin of polyamide and metal-modified polyolefin, a mixed resin of polyamide and polyester, a mixed resin of polyester and acid-modified polyolefin, and a mixed resin of polyester and metal-modified polyolefin. When a polyurethane-based two-component curing adhesive resin; a blend resin of polyamide, polyester, or these with modified polyolefin is used as the above-mentioned adhesive resin, the adhesive has excellent ductility, durability under high-humidity conditions, suppression of response, suppression of deterioration during heat sealing, etc., and can effectively suppress the occurrence of delamination by suppressing the decrease in lamination strength between the base layer and the metal layer.

[0079] The above adhesive resin may include a polyurethane adhesive containing a subject matter including a polyol such as polyester polyol, polyether polyol, acrylic polyol, or carbonate polyol, which is a known material, and a curing agent including a bifunctional or higher isocyanate compound. In this case, a polyurethane resin can be formed by causing the curing agent to act on the subject matter.

[0080] Polyol compounds used in the above urethane-type adhesive may include polyester polyol, polyester polyurethane polyol, polyether polyol, polyether polyurethane polyol, etc. The hydroxyl equivalent (number / mol) of the polyol compound may be 0.5 to 2.5, preferably 0.7 to 1.9, but is not limited thereto. The weight average molecular weight of the polyol compound may be 500 g / mol to 120,000 g / mol, 1,000 g / mol to 80,000 g / mol, but is not limited thereto. The hydroxyl equivalent and weight average molecular weight of the polyol compound may be adjusted to a range that ultimately satisfies the physical properties in relation to the isocyanate-based compound to be combined. Polyester polyol, polyester polyurethane polyol, polyether polyurethane polyol may be used as the polyol compound. The above polyol compounds can be used alone or in combination of two or more types.

[0081] The above polyester polyol can be used as a material obtained by reacting at least one polybasic acid and at least one diol. As the polybasic acid, aliphatic dibasic acids such as succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, and brassylic acid can be used; aromatic dibasic acids such as isophthalic acid, terephthalic acid, and naphthalene dicarboxylic acid can be used; and as the diol, aliphatic diols such as ethylene glycol, propylene glycol, butanediol, neopentyl glycol, methyl pentanediol, hexanediol, heptanediol, octanediol, nonanediol, decanediol, and dodecanediol can be used; alicyclic diols such as cyclohexanediol and hydrogenated xylylene glycol can be used; and aromatic diols such as xylylene glycol can be used.

[0082] As the polyester polyol, a polyester urethane polyol, etc., in which the hydroxyl groups at both ends are extended using a single isocyanate compound or an adduct, biuret, or isocyanurate compound containing at least one isocyanate compound, can be used. As the above isocyanate compound, 2,4- or 2,6-tolylene diisocyanate, xylylene isocyanate, 4,4'-diphenylmethane diisocyanate, methylene diisocyanate, isopropylene diisocyanate, lysine diisocyanate, 2,2,4- or 2,4,4-trimethylhexamethylene diisocyanate, 1,6-hexamethylene diisocyanate, methylcyclohexane diisocyanate, isophorone diisocyanate, 4,4'-dicyclohexylmethane diisocyanate, isopropylidene dicyclohexyl-4,4'-diisocyanate, etc. can be used.

[0083] A copolymer containing poly(meth)acrylic acid as a main component can be used as the above acrylic polyol. The above copolymer includes hydroxyl group-containing monomers such as 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, etc., and alkyl (meth)acrylate monomers having methyl, ethyl, n-propyl, i-propyl, n-butyl, i-butyl, t-butyl, 2-ethylhexyl, and cyclohexyl groups as alkyl groups, or (meth)acrylamide, N-alkyl (meth)acrylamide, N,N-dialkyl (meth)acrylamide (alkyl groups include methyl, ethyl, n-propyl, i-propyl, n-butyl, i-butyl, t-butyl, 2-ethylhexyl, and cyclohexyl groups, etc.), N-alkoxy (meth)acrylamide, N,N-dialkoxy (meth)acrylamide (alkoxy groups include, A material copolymerized with an amide group-containing monomer such as N-methylol (meth)acrylamide, N-phenyl (meth)acrylamide, etc. (methoxy group, ethoxy group, butoxy group, isobutoxy group, etc.), a glycidyl group-containing monomer such as glycidyl (meth)acrylate, allyl glycidyl ether, a silane-containing monomer such as (meth)acryloxypropyl trimethoxysilane, (meth)acryloxypropyl triethoxysilane, and an isocyanate group-containing monomer such as (meth)acryloxypropyl isocyanate can be used. As the carbonate polyol, a material obtained by reacting a carbonate compound with a diol can be used. As the carbonate compound, dimethyl carbonate, diphenyl carbonate, ethylene carbonate, etc. can be used. The above diols may be aliphatic diols such as ethylene glycol, propylene glycol, butanediol, neopentyl glycol, methylpentanediol, hexanediol, heptanediol, octanediol, nonanediol, decanediol, and dodecanediol; alicyclic diols such as cyclohexanediol and hydrogenated xylylene glycol; and aromatic diols such as xylylene glycol.

[0084] In addition, a polycarbonate urethane polyol chained with the above-described isocyanate compound at the terminal hydroxyl group of the above-described carbonate polyol can be used.

[0085] As the isocyanate-based compounds used in the above urethane-type adhesive, polyisocyanate, its adduct, its isocyanurate modified form, its carbodiimide modified form, its allophanate modified form, its biuret modified form, etc. can be used. As the above polyisocyanate, aromatic diisocyanates such as diphenylmethane diisocyanate (MDI), polyphenylmethane diisocyanate (polymeric MDI), toluene diisocyanate (TDI), hexamethylene diisocyanate (HDI), bis(4-isocyanatecyclohexyl)methane (H12MDI), isophorone diisocyanate (IPDI), 1,5-naphthalene diisocyanate (1,5-NDI), 3,3'-dimethyl-4,4'-diphenylene diisocyanate (TODI), and xylene diisocyanate (XDI) can be used; Aliphatic diisocyanates such as tramethylene diisocyanate, hexamethylene diisocyanate, trimethylhexamethylene diisocyanate, and isophorone diisocyanate; alicyclic diisocyanates such as 4,4'-methylenebis(cyclohexylisocyanate) and isophorone diisocyanate; and the like can be used. As the adduct, a polyisocyanate with trimethylolpropane, glycol, or the like can be used. Among these isocyanate compounds, polyisocyanates and their adducts are preferable; aromatic diisocyanates, their adducts, and their isocyanurate modified forms are more preferable; MDI, polymeric MDI, TDI, their adducts, and their isocyanurate modified forms are more preferable; and particularly preferably, adducts of MDI, adducts of TDI, polymeric MDI, and their isocyanurate modified forms of TDI can be used, but are not limited thereto. The above isocyanate compounds can be used alone or in combination of two or more types.

[0086] A difunctional or higher isocyanate compound used as the curing agent, a type of isocyanate compound used as a chain extender, 2,4- or 2,6-tolylene diisocyanate, xylylene isocyanate, 4,4'-diphenylmethane diisocyanate, methylene diisocyanate, isopropylene diisocyanate, lysine diisocyanate, 2,2,4- or 2,4,4-trimethylhexamethylene diisocyanate, 1,6-hexamethylene diisocyanate, methylcyclohexane diisocyanate, isophorone diisocyanate, 4,4'-dicyclohexylmethane diisocyanate, isopropylidene dicyclohexyl-4,4'-diisocyanate, etc., a single isocyanate compound selected from the above isocyanate compounds, or at least one isocyanate compound selected from the above isocyanate compounds. Adduct, burette, and isocyanurate bodies can be used.

[0087] The blending amount of the above-mentioned hardener may include 1 to 100 parts by weight, or 5 to 50 parts by weight, based on 100 parts by weight of the main agent, but is not limited thereto. If the blending amount of the above-mentioned hardener is less than 1 part by weight, the performance may not be realized. If the blending amount of the above-mentioned hardener exceeds 100 parts by weight, an excessive amount of isocyanate groups may exist, which may affect the film quality or hardness of the adhesive due to the residual unreacted substances.

[0088] The above polyurethane adhesive may additionally contain a carbodiimide compound, an oxazoline compound, an epoxy compound, a phosphorus compound, a silane coupling agent, etc. to promote adhesion.

[0089] The above carbodiimide compounds include N,N'-di-o-toluyl carbodiimide, N,N'-diphenyl carbodiimide, N,N'-di-2,6-dimethylphenyl carbodiimide, N,N'-bis(2,6-diisopropylphenyl)carbodiimide, N,N'-dioctyldecyl carbodiimide, N-triyl-N'-cyclohexyl carbodiimide, N,N'-di-2,2-di-t-butylphenyl carbodiimide, N-triyl-N'-phenyl carbodiimide, N,N'-di-p-nitrophenyl carbodiimide, N,N'-di-p-aminophenyl carbodiimide, N,N'-di-p-hydroxyphenyl carbodiimide, N,N'-di-cyclohexyl carbodiimide and N,N'-di-p-toluyl carbodiimide, etc. can be used. As the oxazoline compound, monooxazoline compounds such as 2-oxazoline, 2-methyl-2-oxazoline, 2-phenyl-2-oxazoline, 2,5-dimethyl-2-oxazoline, and 2,4-diphenyl-2-oxazoline, and dioxazoline compounds such as 2,2'-(1,3-phenylene)-bis(2-oxazoline), 2,2'-(1,2-ethylene)-bis(2-oxazoline), 2,2'-(1,4-butylene)-bis(2-oxazoline), and 2,2'-(1,4-phenylene)-bis(2-oxazoline) can be used.The above epoxy compounds include diglycidyl ethers of aliphatic diols such as 1,6-hexanediol, neopentyl glycol, and polyalkylene glycol, polyglycidyl ethers of aliphatic polyols such as sorbitol, sorbitan, polyglycerol, pentaerythritol, diglycerol, glycerol, and trimethylolpropane, polyglycidyl ethers of alicyclic polyols such as cyclohexane dimethanol, diglycidyl esters or polyglycidyl esters of aliphatic and aromatic polycarboxylic acids such as terephthalic acid, isophthalic acid, naphthalene dicarboxylic acid, trimellitic acid, adipic acid, and sebacic acid, resorcinol, bis-(p-hydroxyphenyl)methane, 2,2-bis-(p-hydroxyphenyl)propane, tris-(p-hydroxyphenyl)methane, Diglycidyl ethers or polyglycidyl ethers of polyhydric phenols such as 1,1,2,2-tetrakis(p-hydroxyphenyl)ethane, N-glycidyl derivatives of amines such as N,N'-diglycidylaniline, N,N,N-diglycidyltoluidine, N,N,N',N'-tetraglycidyl-bis-(p-aminophenyl)methane, triglycidyl derivatives of aminophenols, triglycidyltris(2-hydroxyethyl)isocyanurate, triglycidyl isocyanurate, orthocresol-type epoxy, phenol novolac-type epoxy resin, etc. can be used. The above phosphorus compounds include tris(2,4-di-t-butylphenyl)phosphite, tetrakis(2,4-di-t-butylphenyl)-4,4'-biphenylenephosphonite, bis(2,4-di-t-butylphenyl)pentaerythritol-di-phosphite, bis(2,6-di-t-butyl-4-methylphenyl)pentaerythritol-di-phosphite, 2,2-methylene bis(4,6-di-t-butylphenyl)octyl phosphite, 4,4'-butylidene-bis(3-methyl-6-t-butylphenyl-di-tridecyl)phosphite, 1,1,3-tris(2-methyl-4-ditridecyl phosphite-5-t-butyl-phenyl)butane, tris(mixed mono- and di-nonylphenyl)phosphite, Tris(nonylphenyl)phosphite, 4,4'-isopropylidene bis(phenyl-dialkylphosphite), etc. can be used.As the above silane coupling agent, various silane coupling agents can be used, such as vinyltriethoxysilane, vinyltris(β-methoxyethoxy)silane, γ-methacryloxypropyltrimethoxysilane, vinyltriacetoxysilane, γ-glycidoxypropyltrimethoxysilane, γ-glycidoxypropyltriethoxysilane, β-(3,4-epoxycyclohexyl)ethyltrimethoxysilane, γ-chloropropylmethoxysilane, vinyltrichlorosilane, γ-mercaptopropyl trimethoxysilane, γ-aminopropyltriethoxysilane, and N-β-(aminoethyl)-γ-aminopropyltrimethoxysilane.

[0090] The first adhesive layer may include a urethane adhesive comprising at least one polyol compound selected from the group consisting of polyester polyol, polyester polyurethane polyol, polyether polyol, and polyether polyurethane polyol, and at least one isocyanate-based compound selected from the group consisting of aromatic diisocyanates, adducts thereof, and isocyanurate-modified forms thereof; more preferably, a urethane adhesive comprising at least one polyol compound selected from the group consisting of polyester polyol, polyester polyurethane polyol, polyether polyol, and polyether polyurethane polyol, and at least one isocyanate-based compound selected from the group consisting of MDI, polymeric MDI, TDI, adducts thereof, and isocyanurate-modified forms thereof.

[0091] In addition, in the adhesive comprising the polyol compound (subject) and the isocyanate-based compound (curing agent), the ratio of the isocyanate group of the isocyanate-based compound per 1 mol of the hydroxyl group of the polyol compound may be 1 mol to 30 mol, preferably 3 mol to 20 mol, but is not limited thereto. The ratio may be appropriately adjusted depending on the physical properties to be provided in the adhesive layer.

[0092] The thickness of the first adhesive layer may be, but is not limited to, 2 μm to 10 μm, or 3 μm to 5 μm. The thickness of the first adhesive layer may be appropriately adjusted in consideration of the adhesiveness with the external resin layer and the thickness after molding. If the thickness is less than 2 μm, the adhesiveness is reduced, and if it exceeds 10 μm, cracks may occur.

[0093]

[0094] The second adhesive layer is a layer that bonds the metal layer and the internal resin layer. The second adhesive layer may include polyurethane, acid-modified polyolefin resin, epoxy, or the like. Specifically, the second adhesive layer may include maleic anhydride polypropylene (MAHPP), or the like.

[0095] The above heat-adhesive olefin resin may include polyethylene, ethylene-α-olefin copolymer, ethylene-acrylic acid copolymer, ethylene-methacrylic acid copolymer, ethylene-acrylic acid ester copolymer, ethylene-methacrylic acid ester copolymer, ethylene-vinyl acetate copolymer, ionomers, polypropylene, maleic anhydride-modified polypropylene, ethylene-propylene copolymer, and propylene-1-butene-ethylene copolymer, and preferably may include at least one olefin resin selected from the group consisting of polypropylene, ethylene-propylene copolymer, and propylene-1-butene-ethylene copolymer.

[0096] The acid-modified polyolefin used in forming the second adhesive layer is a polymer modified by graft polymerization of polyolefin with an unsaturated carboxylic acid, etc. As the acid-modified polyolefin, there may be used polyethylene such as low-density polyethylene, medium-density polyethylene, high-density polyethylene, and linear low-density polyethylene; crystalline or amorphous polypropylene such as homopolypropylene, block copolymers of polypropylene (e.g., block copolymers of propylene and ethylene), and random copolymers of polypropylene (e.g., random copolymers of propylene and ethylene); terpolymers of ethylene-butene-propylene, etc. At this time, in consideration of the aspect of heat resistance, among the polyolefins, a polyolefin having at least propylene as a constituent monomer, preferably, a terpolymer of ethylene-butene-propylene and a random copolymer of propylene-ethylene, may be used. Unsaturated carboxylic acids used in the above modification include maleic acid, acrylic acid, itaconic acid, crotonic acid, maleic anhydride, and itaconic anhydride. Specifically, among the unsaturated carboxylic acids, maleic acid and maleic anhydride can be used. The acid-modified polyolefin can be used alone or in combination of two or more types.

[0097] The thickness of the second adhesive layer may be, but is not limited to, 2 μm to 10 μm, or 3 μm to 5 μm. The thickness of the second adhesive layer may be appropriately adjusted in consideration of the adhesiveness with the internal resin layer and the thickness after molding. If the thickness is less than 2 μm, the adhesiveness is reduced, and if it exceeds 10 μm, cracks may occur.

[0098] When laminating the inner resin layer and the metal layer on the second adhesive layer, lamination can be performed using a dry lamination method, a heat lamination method, or an extrusion lamination method, but is not limited thereto.

[0099]

[0100] The third bonding layer is a layer that bonds the inner resin layer and the silica aerogel layer. The third bonding layer may include polyurethane, acid-modified polyolefin resin, or epoxy. Specifically, the third bonding layer may include maleic anhydride polypropylene (MAHPP).

[0101] The above heat-adhesive olefin resin may include polyethylene, ethylene-α-olefin copolymer, ethylene-acrylic acid copolymer, ethylene-methacrylic acid copolymer, ethylene-acrylic acid ester copolymer, ethylene-methacrylic acid ester copolymer, ethylene-vinyl acetate copolymer, ionomers, polypropylene, maleic anhydride-modified polypropylene, ethylene-propylene copolymer, and propylene-1-butene-ethylene copolymer, and preferably may include at least one olefin resin selected from the group consisting of polypropylene, ethylene-propylene copolymer, and propylene-1-butene-ethylene copolymer.

[0102] The acid-modified polyolefin used in forming the third adhesive layer is a polymer modified by graft polymerization of polyolefin with an unsaturated carboxylic acid, etc. As the acid-modified polyolefin, there may be used polyethylene such as low-density polyethylene, medium-density polyethylene, high-density polyethylene, and linear low-density polyethylene; crystalline or amorphous polypropylene such as homopolypropylene, block copolymers of polypropylene (e.g., block copolymers of propylene and ethylene), and random copolymers of polypropylene (e.g., random copolymers of propylene and ethylene); terpolymers of ethylene-butene-propylene, etc. In this case, in consideration of the aspect of heat resistance, among the polyolefins, a polyolefin having at least propylene as a constituent monomer, preferably, a terpolymer of ethylene-butene-propylene and a random copolymer of propylene-ethylene, may be used. Unsaturated carboxylic acids used in the above modification include maleic acid, acrylic acid, itaconic acid, crotonic acid, maleic anhydride, and itaconic anhydride. Specifically, among the unsaturated carboxylic acids, maleic acid and maleic anhydride can be used. The acid-modified polyolefin can be used alone or in combination of two or more types.

[0103] The thickness of the third adhesive layer may be, but is not limited to, 2 μm to 30 μm, or 3 μm to 15 μm. The thickness of the third adhesive layer may be appropriately adjusted in consideration of the adhesiveness with the internal resin layer and the thickness after molding. If the thickness is less than 2 μm, the adhesiveness is reduced, and if it exceeds 10 μm, cracks may occur.

[0104] When laminating the inner resin layer and the metal layer on the third adhesive layer, lamination can be performed using a dry lamination method, a heat lamination method, or an extrusion lamination method, but is not limited thereto.

[0105]

[0106] According to one embodiment of the present invention, the pouch film layer may include a surface treatment layer on at least one side of the first pouch film layer and the second pouch film layer. The surface treatment layer may refer to a layer on which at least one process among a corona treatment process and a chromate treatment process has been performed. The corona treatment process is performed at 500 W / cm 2 Up to 15,000 W / cm 2 It can be processed at a speed of 20M / min to 60M / min with an energy density of . After the corona treatment process, a chromate treatment process can be performed. Specifically, the chromate treatment process uses a gravure roll to apply 1g / m of trivalent chromate to the corona-treated surface. 2 5g / m 2 It can be performed by applying at a concentration of 60°C to 150°C and drying at that temperature. The corona treatment process and the chromate treatment process can be repeated two or more times.

[0107]

[0108] <Method for manufacturing a composite sheet for preventing thermal runaway for secondary batteries>

[0109]

[0110] According to one specific example of the present invention, the present invention provides a method for manufacturing a composite sheet for preventing thermal runaway for a secondary battery, comprising the steps of: (1) preparing a silica aerogel layer; (2) applying an adhesive layer to a first surface of the silica aerogel layer and then adhering a first pouch film layer; and (3) applying an adhesive layer to a second surface of the silica aerogel layer and then adhering a second pouch film layer. Hereinafter, each step of the method for manufacturing a composite sheet for preventing thermal runaway for a secondary battery of the present invention will be described in detail.

[0111]

[0112] (1) Step of preparing a silica aerogel layer

[0113] The above step (1) may include a first stirring process, a second stirring process, and a molding process. The first stirring process may include a process of mixing and stirring silica aerogel and a solvent to prepare a dough form. The second stirring process may include a process of adding a reinforcing agent to the dough form after the first stirring process and mixing them together. At this time, 5 to 10 parts by weight of the reinforcing agent may be added based on 100 parts by weight of the dough form. In the second stirring process, fibers, fabrics, etc. including inorganic materials, natural fibers, and chemical fibers may be added. Through this, the reinforcing agent may be mixed between silica aerogel particles to improve mechanical strength. In the second stirring process, 10 parts by weight of mica may be added based on 100 parts by weight of the dough form. The molding process includes a process of extruding and cooling the dough form stirred in the second stirring process through an extruder and simultaneously completing a silica aerogel sheet in the form of a continuous sheet having a predetermined thickness, width, and length.

[0114]

[0115] A pouch film layer according to one specific embodiment of the present invention may be manufactured by the following method. The method for manufacturing the pouch film layer may include a step of forming an outer resin layer on the metal outer surface of the pouch film layer. The outer resin layer may be formed by laminating nylon or polyethylene terephthalate using a dry lamination method or an extrusion lamination method. At this time, the thickness of the outer resin layer may be 10 µm to 30 µm, or 12 µm to 25 µm. When the outer resin layer satisfies the above-described thickness range, the flexibility of processing is increased, and the weight of the entire film is reduced, thereby lowering the overall production cost and enhancing the price competitiveness of the product. The outer resin layer may include, but is not limited to, a nylon resin or a PET resin. The method for manufacturing the pouch film layer may include a step of forming an inner resin layer on another metal outer surface of the pouch film layer. In the step of bonding the inner resin layer to the metal inner surface of the above pouch film layer, polyurethane, acid-modified polyolefin resin, epoxy, etc. can be used as the bonding layer, and maleic anhydride polypropylene (MAHPP) can be preferably used, but is not limited thereto.

[0116] The thickness of the adhesive layer may be 2 μm to 30 μm, or 3 μm to 15 μm. When the adhesive layer satisfies the above-described thickness range, cracks do not occur and excellent adhesiveness can be achieved. The internal resin layer may include a polypropylene resin such as cPP, but is not limited thereto. Dry lamination or extrusion lamination may be used to laminate the internal resin layer, but is not limited thereto.

[0117]

[0118] (2) A step of applying an adhesive layer to the first surface of the silica aerogel layer and then adhering the first pouch film layer.

[0119] The above step (2) may include a process of forming a third bonding layer using an adhesive to bond the inner resin layer of the first pouch film layer and the silica aerogel layer. To this end, the third bonding layer may use polyurethane, acid-modified polyolefin resin, or epoxy as the adhesive, and specifically, maleic anhydride polypropylene (MAHPP) may be used, but is not limited thereto.

[0120] The thickness of the third adhesive layer may be 2 μm to 30 μm, preferably 3 μm to 15 μm, but is not limited thereto. The thickness of the third adhesive layer may be appropriately adjusted in consideration of the adhesiveness with the inner resin layer and the thickness after molding. If the thickness is less than 2 μm, the adhesiveness is reduced, and if it exceeds 10 μm, cracks may occur.

[0121] Dry lamination or extrusion lamination may be used to laminate the above inner resin layer, but is not limited thereto.

[0122]

[0123] (3) A step of applying an adhesive layer to the second surface of the silica aerogel layer and then adhering the second pouch film layer.

[0124] The above step (3) can be performed in the same manner as step (2).

[0125]

[0126] Below, specific embodiments of the present invention are presented. However, the embodiments described below are intended solely to specifically illustrate or explain the present invention and are not intended to limit the scope of the invention. Furthermore, any details not described herein are technically feasible to those skilled in the art and thus are omitted.

[0127]

[0128] Example (Manufacturing of composite sheets for preventing thermal runaway for secondary batteries)

[0129]

[0130] Example 1

[0131] In the first stirring process, silica aerogel (Gelhaus, AP-1000) and solvent (Deoksan Comprehensive Science, MEK, EA, Toluene) are mixed and stirred at 200 to 300 rpm for 0.5 to 1 hour using a stirrer (Poonglim Tech, PLSS051) to prepare a first dough. In the second stirring process, a reinforcing agent (BASF, Ultradur B4300) and a silane coupling agent additive (Evonik, Dynasylan SIVO 160) are added to the first dough, and then mixed and stirred at 100 to 200 rpm for 1 to 2 hours using a stirrer (Poonglim Tech, PLSS051) to prepare a second dough. At this time, the second dough contains 10 parts by weight of the reinforcing agent and 5 parts by weight of the silane coupling agent additive based on 100 parts by weight of the first dough. The above secondary dough is extruded through an extruder, cooled at 25°C for 24 hours, and then cut into pieces of 40 mm thickness, 150 mm width, and 150 mm length to produce a silica aerogel sheet.

[0132] A composite sheet for preventing thermal runaway for secondary batteries was manufactured by dry laminating a pouch film so that both sides of the silica aerogel sheet (4 cm) were bonded to the cPP resin layer of a pouch film (PET 12 ㎛, SUS 304 40 ㎛, cPP 40 ㎛) and then double-sided laminating the pouch film using a dry lamination process.

[0133]

[0134] Example 2

[0135] A composite sheet for preventing thermal runaway for a secondary battery was manufactured in the same manner as in Example 1, except that the secondary dough contained 7 parts by weight of a reinforcing agent.

[0136]

[0137] Example 3

[0138] A composite sheet for preventing thermal runaway for a secondary battery was manufactured in the same manner as in Example 1, except that the secondary dough contained 5 parts by weight of a reinforcing agent.

[0139]

[0140] Example 4

[0141] A composite sheet for preventing thermal runaway for a secondary battery was manufactured in the same manner as in Example 1, except that the secondary dough contained 3 parts by weight of a reinforcing agent.

[0142]

[0143] Example 5

[0144] A composite sheet for preventing thermal runaway for a secondary battery was manufactured in the same manner as in Example 1, except that the pouch film was laminated on both sides by dry lamination so that both sides of the silica aerogel sheet (4 cm) were bonded to the cPP resin layer of the pouch film (PET 12 ㎛, aluminum 40 ㎛, cPP 40 ㎛) by dry lamination, and the pouch film was laminated on both sides by dry lamination.

[0145]

[0146] Comparative Example 1

[0147] A composite sheet for preventing thermal runaway for secondary batteries was manufactured by dry lamination of PET 12㎛, SUS 304 40㎛, and cPP 40㎛.

[0148]

[0149] Comparative Example 2

[0150] A composite sheet for preventing thermal runaway for secondary batteries was manufactured by dry lamination of PET 12㎛, aluminum 40㎛, and cPP 40㎛.

[0151]

[0152] Experimental example

[0153]

[0154] Experimental Example 1 (Puncture Strength Evaluation)

[0155] The puncture strength evaluation of the above examples and comparative examples was performed by measuring the puncture strength of the samples as the maximum load (N) according to the method specified in ASTM D4830 (Standard Test Methods for Characterizing Thermoplastic Fabrics Used in Roofing and Waterproofing).

[0156]

[0157] Experimental Example 2 (Thermal Runaway Blocking Evaluation)

[0158] After radiant heat (750℃) was transferred to one side of the sample by contact with a heat source, the temperature of the other side was measured after 7 minutes.

[0159]

[0160] Experimental Example 3 (Flame Penetration Evaluation)

[0161] An acetylene flame was placed 140 mm away from one side of the sample, and the time it took for the flame to pass through the other side was measured.

[0162]

[0163] Pouch film layer Silica aerogel layer Puncture strength (N) Thermal runaway blocking evaluation (℃) Flame puncture time (min) SUS 304 (㎛) Aluminum (㎛) Reinforcement (parts by weight) Thickness (cm) Example 1 40-10 490 <210 11 Example 2 40-74 70 <220 11 Example 3 40-54 60 <240 10 Example 4 40-34 40 <270 9 Example 5 40 10 420 <210 9 Comparative example 1 40--- 15 > 700 3 Comparative example 2 40--10 > 700 2

[0164] Referring to Table 1 above, it can be confirmed that the composite sheets for preventing thermal runaway for secondary batteries according to Examples 1 to 5 have improved puncture strength, increased thermal runaway blocking effect, and extended flame puncture time due to the inclusion of a silica aerogel layer. Accordingly, when using the composite sheets for preventing thermal runaway for secondary batteries according to one specific example of the present invention, the puncture time of the composite sheets due to flame contact can be extended, ultimately securing time necessary for the evacuation of precious lives in the event of an abnormal accident.

Claims

1. Silica aerogel layer; A first pouch film layer formed on a first surface of the silica aerogel layer; A second pouch film layer formed on the second surface of the silica aerogel layer; The first pouch film layer includes an outer resin layer, a metal layer, and an inner resin layer, The second pouch film layer is a composite sheet for preventing thermal runaway for a secondary battery, comprising an outer resin layer, a metal layer, and an inner resin layer.

2. In paragraph 1, The composite sheet for preventing thermal runaway for a secondary battery is characterized in that the composite sheet for preventing thermal runaway for a secondary battery includes a bonding layer in which the inner resin layer of the first pouch film layer and the inner resin layer of the second pouch film layer are bonded to a silica aerogel layer.

3. In paragraph 1, The above silica aerogel layer A composite sheet for preventing thermal runaway for a secondary battery, characterized in that silica aerogel is coated on a support or silica aerogel is included inside the support.

4. In paragraph 1, A composite sheet for preventing thermal runaway for a secondary battery, characterized in that the metal layer is an aluminum layer or a SUS layer.

5. In paragraph 1, A composite sheet for preventing thermal runaway for a secondary battery, characterized in that the silica aerogel layer comprises silica aerogel in an amount of 10 wt% to 70 wt% based on the total weight of the silica aerogel layer. 6.(1) Step of preparing a silica aerogel layer; (2) a step of applying an adhesive layer to the first surface of the silica aerogel layer and then adhering the first pouch film layer; and (3) A method for manufacturing a composite sheet for preventing thermal runaway for a secondary battery, comprising the step of applying an adhesive layer to the second surface of the silica aerogel layer and then adhering a second pouch film layer.

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