Heat-absorbing pad

Abstract

The present application relates to a heat-absorbing pad. The present application can provide a heat-absorbing pad having excellent flame resistance and compressive performance. The heat-absorbing pad can be effectively used to delay the transfer of heat to adjacent battery cells in the event of thermal runaway in a battery cell.

Description

heat absorption pad

[0001] The present application relates to a heat-absorbing pad. The present application claims the benefit of priority based on Korean Patent Application No. 10-2024-0130016 dated September 25, 2024, and all contents disclosed in the document of said Korean patent application are incorporated herein as part of the specification.

[0002] Thermal runaway in batteries occurs when the thermal stability of internal chemical substances exceeds its limits, causing the cell to rapidly release internal energy to the outside. It is defined as a drop in the cell's measured voltage, a measured temperature of dT / dt ≥ [4℃ / s], and a maximum operating temperature (approximately 120℃). Causes of thermal runaway include overcharging, collisions / drops, heat exposure, exposure to high voltage / current, and external / internal short circuits. Once thermal runaway begins, the battery's internal pressure increases, and flammable materials are ejected, leading to ignition. Subsequently, the fire heats adjacent cells and spreads rapidly. Although battery fires are classified as electrical fires and gas-based fire suppression systems are currently applied, battery modules are protected by metal covers, making it difficult for extinguishing agents to penetrate. Furthermore, since temperatures can rise to 1000℃ in a short period during thermal runaway, the release of extinguishing agents must occur at the very beginning of the fire. Therefore, to stop thermal runaway, sufficient cooling or complete combustion in the early stages of the fire is the ultimate means of extinguishment.

[0003] Phase Change Materials (PCMs) are materials that provide heat and cooling by releasing and absorbing energy through phase transitions. The latent heat generated by a phase transition is higher than general sensible heat, and the material converts from a solid or liquid state to another state, storing and releasing a large amount of energy at the Phase Change Temperature (PCT). Phase Change Materials are used in fields requiring energy storage and stable temperatures, such as heating pads, cooling devices, and clothing (Patent Document 1: Korean Patent Publication No. 10-2020-0107214).

[0004] The present application relates to a heat-absorbing pad having excellent flame resistance and compression performance. The heat-absorbing pad can be usefully used to delay heat transfer to adjacent battery cells during thermal runaway of a battery cell.

[0005] The present application relates to a heat-absorbing pad. The present application also relates to a resin composition. The resin composition may be for manufacturing the heat-absorbing pad. The heat-absorbing pad may have the property of absorbing heat generated from the surroundings. The heat-absorbing pad may include a heat-absorbing material. The heat-absorbing pad may further include a binder resin. In one example, the heat-absorbing pad may include a resin composition comprising a heat-absorbing material and a binder resin in a cured state. That is, the heat-absorbing pad may include a cured product of the resin composition. The heat-absorbing pad may be the cured product of the resin composition itself. If additional layers other than the cured product of the resin composition are included, it may be referred to as a multilayer heat-absorbing pad.

[0006] Among the physical properties mentioned in this specification, those whose results are affected by the measured temperature and / or measured pressure are, unless specifically stated otherwise, results measured at room temperature and / or atmospheric pressure. In this specification, the term "room temperature" refers to a natural temperature that has not been heated or cooled, and is typically a temperature within the range of about 10°C to 30°C, a temperature within the range of 20°C to 30°C, or about 23°C or about 25°C. In this specification, the unit of temperature is °C unless specifically defined otherwise. In this specification, the term "atmospheric pressure" refers to a natural pressure that has not been pressurized or depressurized, and typically means about 1 atmosphere, which is the level of atmospheric pressure. In this specification, physical properties whose results are affected by the measured humidity are, unless specifically defined otherwise, properties measured at natural humidity that has not been separately controlled under the above room temperature and atmospheric pressure conditions.

[0007] When the compression distance (d) and force (F) are measured by a compression test of a texture analyzer for the above heat-absorbing pad, the compression coefficient (n) in Equation 1 below may be less than 1.5. Such a heat-absorbing pad may have excellent flame resistance and compression performance.

[0008] [Equation 1]

[0009]

[0010] In Equation 1, F is force (unit: g), d is compression distance (unit: mm), α is a fixed constant 10, K is a variation constant, and n is the compression coefficient.

[0011] The above compression coefficient n may be 1.45 or less, 1.4 or less, 1.35 or less, 1.3 or less, 1.25 or less, 1.2 or less, 1.15 or less, or 1.1 or less. The above compression coefficient n may be 0.9 or more, 0.95 or more, 1.0 or more, 1.05 or more, 1.1 or more, 1.15 or more, 1.2 or more, 1.25 or more, or 1.3 or more.

[0012] The coefficient of determination R in Equation 1 2 It can be 95% or higher. Coefficient of determination R 2 R is a measure indicating the degree to which the data fits the fitting equation. 2 The closer this is to 100%, the higher the fitting rate may be. In Equation 1, α is a fixed constant, and as previously mentioned, its value may be 10. In this specification, the fixed constant may refer to a fixed constant that does not change depending on the heat-absorbing pad being measured. In Equation 1, K may be a variable constant. In this specification, the variable constant may refer to a constant that can vary depending on the heat-absorbing pad being measured. The above K may be, for example, a constant within the range of 1 to 500 or a constant within the range of 5 to 450.

[0013] In Equation 1, the force (F) is a value measured for a compression distance (d) by a compression test of a texture analyzer. When performing a compression test of 25% strain with a texture analyzer, the force (F) measured may be 3000g or less. The force (F) may be, for example, 2500g or less, 2000g or less, 1500g or less, or 1000g or less. The force (F) may be, for example, 0g or more or greater than 0g.

[0014] The method for obtaining an endothermic pad satisfying the above compression coefficient (n) is not particularly limited, but, for example, the compression coefficient (n) can be lowered as the compression performance of the endothermic pad is improved. Methods for improving compression performance include, for example, reducing the content of particles included in the endothermic pad or adjusting the degree of hardening.

[0015] In this specification, an endothermic material may refer to a material that absorbs or consumes heat generated from the surroundings. An endothermic material may spontaneously undergo thermal decomposition or generate new materials by utilizing the absorbed thermal energy.

[0016] The above-mentioned heat-absorbing pad and / or resin composition may include an endothermic material that undergoes an irreversible endothermic reaction. The endothermic material may be a material that reacts irreversibly when heated and cooled. In one example, the endothermic material undergoes thermal decomposition through endothermy when the ambient temperature rises, and does not return to the state of the endothermic material prior to thermal decomposition when the ambient temperature drops. Thermal decomposition may mean that the material chemically decomposes into a simpler substance when heat is applied to it. This irreversibility can be advantageous for exhibiting excellent heat transition delay characteristics. On the other hand, paraffin, a representative phase change material (PCM), absorbs heat and melts into a liquid state when the ambient temperature rises, and releases heat to return to a solid state when the ambient temperature drops. The above-mentioned phase change material is a material that reacts reversibly through endothermy and exothermy. The above-mentioned resin composition may not include such a reversibly reacting phase change material.

[0017] Endothermic substances exist in a solid state at room temperature, and a phase change from solid to liquid may occur at temperatures below 200°C. In this specification, a phase change from solid to liquid may refer to the phenomenon in which water molecules are separated (dissociated) from the endothermic substance when the endothermic substance is heated. Specifically, the temperature at which the phase change from solid to liquid of the endothermic material occurs may be 190°C or lower, 180°C or lower, 170°C or lower, 160°C or lower, 150°C or lower, 140°C or lower, 130°C or lower, 120°C or lower, 110°C or lower, or 100°C or lower, and may be 50°C or higher, 60°C or higher, 70°C or higher, 80°C or higher, 90°C or higher, 100°C or higher, 110°C or higher, 120°C or higher, 130°C or higher, 140°C or higher, 150°C or higher, 160°C or higher, 170°C or higher, 180°C or higher, or 190°C or higher.

[0018] The endothermic substance may be a water-soluble substance. The water-soluble substance may refer to a substance having a solubility in water at 20°C greater than 0 g / 100 ml. In one example, the solubility of the endothermic substance in water at 20°C may be 4.5 g / 100 ml or more. Specifically, the solubility of the endothermic substance in water may be 5 g / 100 ml or more, 10 g / 100 ml or more, 15 g / 100 ml or more, 20 g / 100 ml or more, 25 g / 100 ml or more, 30 g / 100 ml or more, 35 g / 100 ml or more, or 40 g / 100 ml or more. The upper limit of the solubility of the endothermic substance in water may be, for example, 50 g / 100 ml or less. The above solubility can be determined by adding 1g of the endothermic substance to 100ml of water at a temperature of 20℃ and measuring the weight of the endothermic substance until a precipitate is formed.

[0019] The endothermic material may have thermal conductivity. In one example, the thermal conductivity (λ) of the endothermic material may be 20 W / mK or less. If the thermal conductivity of the endothermic material is within the above range, it may be advantageous for exhibiting excellent heat transfer delay characteristics. Specifically, the thermal conductivity of the endothermic material may be 15 W / mK or less, 10 W / mK or less, 5 W / mK or less, 4 W / mK or less, 3 W / mK or less, 2 W / mK or less, 1 W / mK or less, or 0.5 W / mK or less. The lower limit of the thermal conductivity of the endothermic material may be, for example, 0.001 W / mK or more. The thermal conductivity (λ) is a value defined as thermal diffusivity (α) × specific heat (Cp) × density (ρ). The thermal conductivity (λ) may be a value measured at a temperature of 25°C. The thermal conductivity of an endothermic material can be measured using known thermal conductivity measuring equipment. Alternatively, the thermal conductivity of an endothermic material is largely known, and an endothermic material satisfying the above thermal conductivity can be used.

[0020] In one example, when the endothermic material is thermally analyzed by increasing the temperature from 0°C to 350°C at a rate of 10°C / min using a differential scanning calorimeter, the endothermic peak temperature may be less than 200°C. This may be advantageous for providing an endothermic pad with excellent compression performance and flame resistance. In this specification, the endothermic peak temperature may refer to the temperature at the point where the absolute value of Heat Flow (W / g) is greatest in a graph of Heat Flow (W / g) (y-axis) versus Temperature (°C) (x-axis) obtained through thermal analysis using a differential scanning calorimeter. If the endothermic peak temperature is within the above range, it may be advantageous for exhibiting excellent heat transfer characteristics. The endothermic peak temperature may be, for example, 50°C or higher. Specifically, the above endothermic peak temperature may be 190°C or lower, 180°C or lower, 170°C or lower, 160°C or lower, 150°C or lower, 140°C or lower, 130°C or lower, 120°C or lower, 110°C or lower, or 100°C or lower, and may be 60°C or higher, 70°C or higher, 80°C or higher, 90°C or higher, 100°C or higher, 110°C or higher, 120°C or higher, 130°C or higher, 140°C or higher, 150°C or higher, 160°C or higher, 170°C or higher, 180°C or higher, or 190°C or higher.

[0021] In one example, the endothermic material may have a single endothermic peak (one endothermic peak) at a temperature below 200°C. In another example, the endothermic material may have dispersed endothermic peaks (two or three or more endothermic peaks) at a temperature below 200°C. Having two or three or more endothermic peaks may mean having one endothermic peak with the highest absolute value of Heat Flow (W / g) and one or two or more additional endothermic peaks with the next highest absolute value of Heat Flow (W / g). Assuming the amount of heat absorbed is the same, the endothermic material having a single peak may have superior heat transfer delay characteristics. Examples of endothermic substances having a single peak include AlCl3·6H2O, MgSO4·7H2O, NiSO4·6H2O, Na4P2O7·10H2O, Sr(OH)2·8H2O, CaSO4·2H2O, etc.

[0022] In one example, the endothermic material may have an endothermic amount of 500 J / g or more. In this specification, the endothermic amount may refer to the total sum of heat (integral value on the DSC graph) from the point at which endothermic Specifically, the above heat absorption amount may be 600 J / g or more, 700 J / g or more, 800 J / g or more, 900 J / g or more, 1,000 J / g or more, 1,100 J / g or more, 1,200 J / g or more, 1,300 J / g or more, 1,400 J / g or more, 1,500 J / g or more, 1,600 J / g or more, or 1,700 J / g or more, and may be 2,000 J / g or less. The above heat absorption amount may be a value measured while increasing the temperature at a rate of 10 ℃ / min using a differential scanning calorimeter (DSC Q2000, TA).

[0023] The endothermic material may include a water-containing material and / or a solid acid. The water-containing material may include hydrate particles and / or water microcapsules. The solid acid may include solid acid particles that exist in a solid state at room temperature, for example, about 25°C.

[0024] In one example, the endothermic substance may be hydrate particles. The hydrate particles may refer to particles containing water molecules (H2O). When hydrate particles are applied as the endothermic substance, water molecules may be dissociated from the endothermic substance by thermal decomposition. This may be advantageous for exhibiting excellent thermal transfer delay characteristics. Specifically, the hydrate particles may be inorganic salts containing water molecules bonded to the crystals of a metal compound. The water contained in the hydrate particles may be referred to as crystal water. The hydrate particles are different from hydroxide particles, which may refer to a substance containing -OH (-hydroxyl group) without containing H2O.

[0025] In one example, the endothermic material may be solid acid particles. The solid acid particles may include, for example, H3BO3 particles.

[0026] In one example, the endothermic substances are H3BO3, (NH4)2O·5B2O3·8H2O, (Mg(H2PO4)2)·H2O, MgCl2·6H2O, AlCl3·6H2O, Na4P2O7·10H2O, KAl(SO4)2·12H2O, NiSO4·6H2O, Mg(NO3)2·6H2O, CoSO4·7H2O, (NH4)2Fe(SO4)2·6H2O, CuSO4·5H2O, ZnSO4·7H2O, CoCl2·6H2O, CrCl3·6H2O, NiCl2·6H2O, MgSO4·7H2O, Al2(SO4)3·18H2O, Na2B4O7·10H2O, Sr(OH)2·8H2O, It may include one or more selected from the group consisting of CaC2O4·H2O, Ba(OH)2·8H2O, Ba(OH)2·H2O, Mg3(PO4)2·5H2O, Mg3(PO4)2·8H2O and FeSO4·7H2O.

[0027] In one example, the endothermic material may be a water microcapsule. The microcapsule may comprise a capsule portion and water contained within the capsule portion. The capsule portion may comprise one or more selected from the group consisting of poly(vinyl alcohol), poly(ethylene oxide), polyethylene glycol, poly(methyl methacrylate), butyl acrylate, and silicate. The size of the microcapsule may be, for example, in the range of 50 µm to 500 µm.

[0028] The content of the endothermic material may be appropriately selected within a range that does not impair the purpose of the present application. In one example, the endothermic material may be included in a range of 50 to 500 parts by weight relative to 100 parts by weight of binder resin. Specifically, the endothermic material may be included in an amount of 50 parts by weight or more, 100 parts by weight or more, 150 parts by weight or more, 200 parts by weight or more, 250 parts by weight or more, 300 parts by weight or more, 350 parts by weight or more, or 400 parts by weight or more, relative to 100 parts by weight of binder resin, and may be included in an amount of 500 parts by weight or less, 450 parts by weight or less, 400 parts by weight or less, 350 parts by weight or less, 300 parts by weight or less, 250 parts by weight or less, or 250 parts by weight or less. An endothermic pad in which the content of the endothermic particles is within the above range is suitable for production and may be advantageous for exhibiting excellent heat transfer delay characteristics.

[0029] The binder resin may include a main resin. The main resin may be a silicone resin. When a silicone resin is used as the main resin, it may be advantageous for exhibiting excellent heat transfer delay characteristics. In particular, even when an endothermic material containing water is used as the endothermic material, excellent heat transfer delay characteristics can be exhibited because no changes over time or water generation occur after mixing the main resin and the endothermic material. Meanwhile, organic materials such as urethane resin or epoxy resin burn up in a flame, whereas in the case of silicone resin, the Si-O-Si siloxane chains change into SiO2 by heat, so the durability against flame may be superior.

[0030] The above silicone resin may be a polydimethylsiloxane having vinyl groups at both ends. The above silicone resin may be a compound represented by the following chemical formula 1. In the following chemical formula 1, n may be an integer greater than or equal to 1 and may be appropriately selected considering the molecular weight of the silicone resin.

[0031] [Chemical Formula 1]

[0032]

[0033] The molecular weight of the silicone resin may be selected within a range that does not impair the purpose of the present application. The molecular weight of the silicone resin refers to the molecular weight of the silicone polymer constituting the silicone resin. In one example, the molecular weight of the silicone resin may be 100,000 g / mol or less. When the molecular weight of the silicone resin is within the above range, the heat resistance performance is improved, which may be more advantageous for exhibiting excellent heat transfer delay characteristics. Specifically, the molecular weight of the silicone resin may be 90,000 g / mol or less, 80,000 g / mol or less, 70,000 g / mol or less, 60,000 g / mol or less, 50,000 g / mol or less, 40,000 g / mol or less, 30,000 g / mol or less, 25,000 g / mol or less, 20,000 g / mol or less, 15,000 g / mol or less, or 10,000 g / mol or less. The lower limit of the molecular weight of the above silicone resin may be 100 g / mol or more, 500 g / mol or more, or 1,000 g / mol from the perspective of handling the fabricated pad.

[0034] The viscosity of the silicone resin may be selected within a range that does not impair the purpose of the present application. In one example, the viscosity of the silicone resin may be 150,000 cSt or less. When the viscosity of the silicone resin is within the above range, it may be more advantageous to exhibit excellent heat transfer delay characteristics. The viscosity of the silicone resin may be 100,000 cSt or less, 50,000 cSt or less, or 10,000 cSt or less. Specifically, the viscosity of the above silicone resin may be less than 10,000 cSt, 9,000 cSt or less, 8,000 cSt or less, 7,000 cSt or less, 6,000 cSt or less, 5,000 cSt or less, 4,500 cSt or less, 4,000 cSt or less, 3,500 cSt or less, 3,000 cSt or less, 2,500 cSt or less, 2,000 cSt or less, 1,500 cSt or less, or 1,000 cSt or less. Regarding the viscosity of the silicone resin, for commercially available products, information on viscosity is provided by the seller. Therefore, a silicone resin product satisfying the above viscosity can be selected and used, and the viscosity measurement conditions can also follow those provided by the silicone resin seller. In one example, viscosity in cSt units can be measured using a Canon-Fenske Viscomete. The method for measuring viscosity using a Canon-Fenske viscometer is known. For example, cSt viscosity can be calculated from Efflux time x Viscometer Factor. Efflux time refers to the time it takes for a sample (relative to the top surface of the fluid) to descend from a specific upper mark to a specific lower mark due to gravity after filling the viscometer with the sample. At this time, the viscometer filled with the sample can be placed in a constant temperature water bath to allow the sample to reach the temperature to be measured, and then the time can be measured.The above temperature may be, for example, a temperature within the range of about 10°C to 30°C, about 20°C, or about 25°C. The Viscometer Factor is a coefficient unique to the viscometer at the temperature at which viscosity is to be measured, provided by the manufacturer of the viscometer. If the coefficient is not provided by the manufacturer, the coefficient may be corrected directly using water or other standard liquids.

[0035] The binder resin may further include a curing agent. As the curing agent, one suitable for curing the main resin may be used. In one example, when the main resin is a silicone resin, a silane compound or a silanol compound may be used as the curing agent. The silane compound may refer to a compound having an -SiH (silicon-hydride) group. The silanol compound may refer to a compound having an -Si-OH (silicon-hydroxide) group. The -SiH group or the -Si-OH group may react with the vinyl groups of the silicone resin. The silane compound has at least one -CH3 group at the terminal and / or side chain. - It may be a polydimethylsiloxane substituted with H. In one example, the curing agent may be a pendent type curing agent. The pendent type curing agent may be a polydimethylsiloxane in which at least one -CH3 group of the pendent chain is substituted with -H and both ends are -CH3. In another example, the curing agent may be a hybrid type curing agent. The hybrid type curing agent may be a polydimethylsiloxane in which -CH3 groups at both ends are substituted with -H and at least one -CH3 group of the pendent chain is also substituted with -H.

[0036] In one example, a curing agent may be included in the resin composition such that the H / V ratio is within the range of 1 to 20. H is a value defined as H mmol / g × H wt%, and V is a value defined as V mmol / g × V wt%. In the above, H mmol / g refers to the mmol of Si-H (silicon-hydrogen) per gram of curing agent included in the resin composition, and V mmol / g refers to the mmol of Si-Vi (silicon-vinyl) per gram of silicone resin included in the resin composition. In the above, H wt% refers to the weight fraction of the curing agent relative to the weight of the total resin composition, and V wt% refers to the weight fraction of the silicone resin relative to the weight of the total resin composition. In the above, the weight fraction of the total resin composition is 100 wt%.

[0037] The above heat-absorbing pad and / or resin composition may not include amine compounds and / or isocyanate compounds. The above amine compounds and / or isocyanate compounds may not be suitable for compounding with the heat-absorbing material. The amine compound may be a curing agent when using an epoxy resin as the main resin, and the isocyanate compound may be a curing agent when using a polyol resin or a urethane resin as the main resin. According to the present application, epoxy resin, polyol resin, and / or urethane resin may not be included as the main resin.

[0038] The above-described heat-absorbing pad and / or resin composition may further include a catalyst. The catalyst may promote the reaction between the main resin and the curing agent. In one example, the catalyst may promote the hydrosilylation addition reaction between the carbon-carbon double bond of the silicone resin and the -SiH group of the curing agent. In another example, the catalyst may promote the reaction between the carbon-carbon double bond of the silicone resin and the -Si-OH group of the curing agent. In one example, the catalyst may be a platinum group catalyst. The platinum group catalyst may include a platinum-based metal catalyst, a palladium-based metal catalyst, a rhodium-based metal catalyst, or a mixture thereof. In another example, the catalyst may be a metal salt catalyst. The metal salt catalyst may include a tin-based metal salt such as bis(2-ethylhexanoate)tin or dibutyldilauryltin, a zinc-based metal salt such as zinc octoate, an iron-based metal salt such as iron octoate, or a mixture thereof. The above catalyst may be included in a range of 0.01 to 10 parts by weight, 0.01 to 5 parts by weight, 0.01 to 3 parts by weight, 0.01 to 1 part by weight, or 0.01 to 0.5 parts by weight per 100 parts by weight of binder resin.

[0039] The above resin composition and / or heat-absorbing pad may further include additives in addition to the main resin, curing agent, and catalyst.

[0040] In one example, the resin composition and / or heat-absorbing pad may further include a dispersant. For example, an amino-silicone dispersant may be used as the dispersant. The dispersant may be included in a range of 0.1 to 10 parts by weight, 0.1 to 5 parts by weight, or 0.5 to 5 parts by weight per 100 parts by weight of binder resin.

[0041] In one example, the resin composition and / or heat-absorbing pad may further comprise a chain extender. As the chain extender, for example, a compound having -SiH (silicon-hydride) at both ends may be used. The -SiH may react with the vinyl groups of the silicone resin. In one example, the chain extender may be a polydimethylsiloxane in which -CH3 at both ends are substituted with -H and the side chain is -CH3. When the heat-absorbing pad and / or resin composition comprises both a curing agent and a chain extender, the curing agent and the chain extender may be included in the resin composition such that the H / V ratio is within the range of 1 to 20. H is a value defined as (H1 mmol / g ≠ H1 wt% + H2 mmol / g ≠ H2 wt%), and V is a value defined as V mmol / g ≠ V wt%. In the above, H1 mmol / g refers to the mmol of Si-H (silicon-resin) per gram of the curing agent included in the resin composition, H2 mmol / g refers to the mmol of Si-H (silicon-resin) per gram of the chain extender included in the resin composition, and V mmol / g refers to the mmol of Si-Vi (silicon-vinyl) per gram of the silicone resin included in the resin composition. In the above, H1 wt% refers to the weight fraction of the curing agent relative to the weight of the total resin composition, H2 wt% refers to the weight fraction of the chain extender relative to the weight of the total resin composition, and V wt% refers to the weight fraction of the silicone resin relative to the weight of the total resin composition. In the above, the weight fraction of the total resin composition is 100 wt%.

[0042] In one example, the resin composition and / or heat-absorbing pad may further comprise a curing retardant. The curing retardant may be, for example, a compound having a carbon-carbon double bond or a carbon-carbon triple bond. The above-mentioned curing retardant is 1-ethynyl-1-cyclohexanol, 3-methyl-1-pentene-3-ol, 2-methyl-3-butyn-2-ol, 3-phenyl-3-butyn-2-ol, 2-phenyl-3-butyn-2-ol, 3,5-dimethyl-1-hexine-3-ol, 1,5-hexadiine, 1,6-heptadiine, 3,5-dimethyl-1-hexine, 2-ethyl-3-butine, 2-phenyl-3-butine, 1,3-divinyltetramethyldisiloxane, 1,3,5,7-tetravinyl-1,3,5,7-tetramethylcyclotetrasiloxane, 1,3-divinyl-1,3-diphenyldimethyldisiloxane, 2,4,6,8-tetramethyl-2,4,6,8-tetravinylcyclotetrasiloxane and It may be one or more selected from the group consisting of divinyl-1,1,3,3-detramethyldisilazane, but is not limited thereto. The curing retardant may be included in the range of 0.1 to 10 parts by weight, 0.1 to 5 parts by weight, or 0.5 to 5 parts by weight per 100 parts by weight of binder resin.

[0043] In one example, the resin composition and / or heat-absorbing pad may further include a flame retardant. The flame retardant may be a solid flame retardant in the form of a filler or a liquid flame retardant. Liquid flame retardants may be suitably used when the amount of filler filled in the resin composition and / or heat-absorbing pad is large; for example, TEP, TCPP, etc. described below are representative liquid flame retardants. The flame retardant may include organic flame retardants, inorganic flame retardants, and / or organic-inorganic composite flame retardants. Organic flame retardants may include phosphorus-based flame retardants and / or melamine-based flame retardants. Inorganic flame retardants may include metal hydroxide-based flame retardants. Organic-inorganic composite flame retardants may include phosphorus-metal-based flame retardants.

[0044] In one example, the flame retardant may include one or more selected from the group consisting of: phosphorus-based flame retardants including ammonium polyphosphate (APP), red phosphorus, tris(2-chloroethyl) phosphate (TCEP), isopropylphenyl diphenyl phosphate (IPDP), tris(1-chloro-2-propyl) phosphate (TCPP), triphenyl phosphate (TPP), and triethyl phosphate (TEP); melamine-based flame retardants including melamine cyanurate; metal hydroxide-based flame retardants including aluminum hydroxide and magnesium hydroxide; and organic-inorganic composite flame retardants including aluminum diethyl phosphinate. According to one embodiment of the present application, the flame retardant may include a phosphorus-based flame retardant and a metal hydroxide flame retardant.

[0045] In one example, a coating layer may be present on the surface of the flame retardant. The coating layer may be appropriately selected considering the function to be added to the flame retardant. The coating layer may include, for example, one or more selected from the group consisting of a silicone-based coating layer, an epoxy-based coating layer, and a melamine-based coating layer. As a specific example, if the APP flame retardant has the coating layer, it may exhibit superior water resistance.

[0046] In one example, the flame retardant may be included in a range of 10 to 300 parts by weight, 10 to 200 parts by weight, or 30 to 150 parts by weight per 100 parts by weight of binder resin.

[0047] In one example, the resin composition and / or heat-absorbing pad may further include a flame retardant adjuvant. The flame retardant adjuvant is an additive that can be added to the resin composition and / or heat-absorbing pad together with a flame retardant to further improve the flame retardancy of the resin composition, and may include, for example, PTFE (Polytetrafluoroethylene). If the resin composition further includes a flame retardant, it may be advantageous in terms of improving the heat transfer delay time, suppressing crack formation due to flame, and reducing the final insulation temperature.

[0048] In one example, the resin composition may further include a foaming agent described below. By including a foaming agent in the resin composition, a foam pad with a porous structure can be manufactured. The content of the foaming agent can be appropriately selected considering the desired porous structure. In one example, the resin composition may further include a retardant to control the curing speed. For example, a silicone-based retardant may be used as the retardant.

[0049] In one example, the viscosity of the resin composition may be 500,000 cps or less. When the viscosity of the resin composition is within the above range, it may be advantageous to manufacture an endothermic pad through curing, and the endothermic pad manufactured therefrom may exhibit excellent heat transfer delay characteristics. Specifically, the viscosity of the resin composition may be 450,000 cps or less, 400,000 cps or less, 350,000 cps or less, 300,000 cps or less, 250,000 cps or less, 200,000 cps or less, 150,000 cps or less, or 100,000 cps or less. From the perspective of the pad manufacturing process, the lower limit of the viscosity of the resin composition may be 1,000 cps or more, 5,000 cps or more, 10,000 cps or more, 30,000 cps or more, or 50,000 cps or more. The above viscosity was determined using a Brookfield DV2T HB viscometer at a temperature of 25℃, a rotation speed of 1.2 rpm, and a shear rate (sec -1 ) 2.4, it may be a value measured under the condition of spindle CPA 52Z.

[0050] In one example, the resin composition may be a room-temperature curing resin composition. Accordingly, the resin composition can be cured by maintaining it at room temperature (e.g., about 20°C to 30°C), and separate processes for curing, such as the application of moisture, the application of heat, or irradiation with active energy rays (e.g., ultraviolet rays), may not be required. Furthermore, considering that the resin composition may be used as a heat-absorbing pad containing an endothermic material, it may be more advantageous to be a room-temperature curing type because it may be sensitive to heat that may entail a phase change of the endothermic material. Additionally, a room-temperature curing resin composition may be advantageous when curing must be performed inside a battery. This is because applying heat to the battery for curing inside the battery can be dangerous. Moreover, a room-temperature curing resin composition may be advantageous in that the curing speed can be easily controlled, as it can be cured by applying heat if necessary. In other words, in this specification, a room-temperature curable resin composition means that it can be cured by maintaining it at room temperature, and is not limited to a resin composition that is cured only by maintaining it at room temperature.

[0051] In one example, the resin composition may be a thermosetting resin composition. That is, the resin composition may be cured by the application of heat. The heating temperature and heating time for curing may be selected within a range suitable for manufacturing the heat-absorbing pad. The heating temperature may be performed within a range that properly cures the resin composition without causing damage to the heat-absorbing material. In one example, the heating temperature for curing may be in the range of 50°C to 200°C. The heating time may be, for example, in the range of 1 minute to 20 minutes.

[0052] The above-mentioned heat-absorbing pad may have an endothermic amount of 200 J / g or more when subjected to thermal analysis while increasing the temperature from 0°C to 350°C at a rate of 10°C / min using a differential scanning calorimeter. Additionally, the above-mentioned heat-absorbing pad may have an endothermic peak temperature of less than 200°C when subjected to thermal analysis while increasing the temperature from 0°C to 350°C at a rate of 10°C / min using a differential scanning calorimeter. The definitions of the endothermic amount and endothermic peak temperature of the above-mentioned heat-absorbing pad may be applied identically to the definitions of the endothermic amount and endothermic peak temperature of the aforementioned endothermic material, provided that the measurement target is changed from the endothermic material to the heat-absorbing pad. An endothermic pad having the above characteristics may have excellent compression performance and flame-resistant performance. The above-mentioned endothermic peak temperature may be, for example, less than 200°C, 190°C or less, 180°C or less, or 170°C or less. The lower limit of the above-mentioned endothermic peak temperature may be, for example, 100°C or higher, 120°C or higher, 140°C or higher, or 160°C or higher. The amount of heat absorbed by the above-mentioned heat absorbing pad may be, for example, 250 J / g or higher, 300 J / g or higher, 350 J / g or higher, 400 J / g or higher, 450 J / g or higher, 500 J / g or higher, 550 J / g or higher, or 600 J / g or higher. The upper limit of the amount of heat absorbed by the above-mentioned heat absorbing pad may be, for example, 2,000 J / g or lower, 1,500 J / g or lower, 1,000 J / g or lower, or 800 J / g or lower.

[0053] The above heat-absorbing pad may have a compressive strength of 2,000 kPa or less at 50% strain when subjected to a compression test using a Universal Testing Machine (UTM). This may be advantageous for providing a heat-absorbing pad with excellent compressive performance and flame resistance. The above compressive strength may be, for example, 1,900 kPa or less, 1,800 kPa or less, 1,700 kPa or less, 1,600 kPa or less, 1,500 kPa or less, 1,400 kPa or less, or 1,300 kPa or less. The lower limit of the above compressive strength may be, for example, 50 kPa or more, 100 kPa or more, 500 kPa or more, or 1,000 kPa or more. The above compressive strength can be measured by installing circular, flat jigs with a diameter of 90 mm at the top and bottom of a Universal Testing Machine (UTM) (UTM Z010, Zwick Roell), placing a sample (prepared by cutting a heat-absorbing pad to a size of 5 cm × 5 cm) onto the bottom jig, positioning the upper jig installed above close to the sample, and then performing a compression test. Specifically, it can be measured by taking the compressive strength (kPa) at 50% strain when the sample is deformed to 80% of its thickness at a speed of 10 mm / min in compression test mode (i.e., the target distance is calculated as 80% of the sample thickness). The compressive strength at 50% strain refers to the compressive strength when the sample thickness is compressed to 50%, with the point where the sample measurement started set as the 0% reference. In addition, the above compression test can be performed at 25°C and 50% RH (relative humidity). The method of controlling the compression strength of the heat-absorbing pad within the above range is not particularly limited, but in one example, if the density of the heat-absorbing pad is high, the compression strength tends to increase, and if the density of the heat-absorbing pad is low, the compression strength tends to decrease.

[0054] The above-mentioned heat-absorbing pad may have a porous structure. A heat-absorbing pad having a porous structure may be referred to as a heat-absorbing foam pad. In one example, the density of the heat-absorbing pad is 1 g / cm³. 3 It may be less than or equal to. The density of the heat-absorbing pad is, for example, 0.9 g / cm³ 3 Below, 0.8 g / cm³ 3 Below, 0.7 g / cm³ 3 Less than or equal to 0.6 g / cm³ 3 It may be less than or equal to. The lower limit of the density of the heat-absorbing pad is, for example, 0.1 g / cm³. 3 Above, 0.2 g / cm³ 3 Above or 0.3 g / cm³ 3 It could be more than that.

[0055] The method of forming a porous structure in the above heat-absorbing foam pad is preferably performed within a range that satisfies the compression coefficient (n) of Equation 1.

[0056] In one example, the heat-absorbing foam pad can be obtained by including a solvent in a resin composition for manufacturing the heat-absorbing pad and evaporating the solvent to form a porous structure.

[0057] In a method for forming a porous structure by evaporating the above solvent, the solvent may be an organic solvent. The conditions for evaporating the solvent may be performed within a range suitable for curing while forming a porous structure on the heat-absorbing pad. The temperature for evaporating the solvent may be higher than the boiling point of the solvent used. In one example, the organic solvent component may have a boiling point of 65°C or higher. The boiling point of the organic solvent component may be, for example, within the range of 65°C to 150°C. The above boiling point may be 65°C or higher, 70°C or higher, 75°C or higher, 80°C or higher, 85°C or higher, 90°C or higher, 95°C or higher, 100°C or higher, or 105°C or higher, and may be 145°C or lower, 140°C or lower, 135°C or lower, 130°C or lower, 125°C or lower, 120°C or lower, 115°C or lower, 110°C or lower, 105°C or lower, 100°C or lower, 95°C or lower, 90°C or lower, 85°C or lower, or 80°C or lower.

[0058] In another example, the heat-absorbing foam pad can be obtained by forming a porous structure by including foam particles in a resin composition for manufacturing the heat-absorbing pad. The foam particles include CO2 or at high temperatures (when heated). Foam particles capable of forming pores by generating an outgas such as H2O may be used. The foam particles may include one or more particles selected from the group consisting of NaHCO3, Na2CO3, KHCO3, and CaCO3. In one example, the foam particles may generate an outgas upon heating. Examples of such foam particles include NaHCO3, KHCO3, and CaCO3. In another example, the foam particles may generate an outgas by reacting with a solid acid, in particular, as an endothermic material upon heating. Examples of such foam particles include Na2CO3.

[0059] In another example, the heat-absorbing foam pad may form a porous structure by the reaction of -Si-OH groups and -Si-H groups in a resin composition for manufacturing the heat-absorbing pad by incorporating a silicone hydroxy resin and a silicone hydride resin. The silicone hydroxy resin may refer to a silicone polymer having -Si-OH groups at both ends, for example, it may be a polydimethylsiloxane in which -CH3 groups at both ends are substituted with -OH groups. The silicone hydride resin may refer to a silicone polymer having -Si-H groups at the side chains and / or at both ends, for example, it may be a polydimethylsiloxane in which -CH3 groups at both ends and / or some of the side chains are substituted with -H groups. The -Si-OH groups of the silicone hydroxy resin and the -Si-H groups of the silicone hydride resin may undergo a condensation reaction at high temperatures (when heated) to leave -Si-O-Si- cross-links and generate outgas H2. The above H2 gas can be generated to form pores and cause foaming.

[0060] The high temperature (heating) for generating the above outgas may be in the range of about 40°C to 200°C, specifically, it may be 40°C or higher, 50°C or higher, 60°C or higher, 70°C or higher, or 80°C or higher, and 200°C or lower, 190°C or lower, 180°C or lower, 170°C or lower, 160°C or lower, or 150°C or lower.

[0061] The heat-absorbing pad described above may have a heat transfer delay effect. In this specification, the heat transfer delay effect may mean that when a flame is radiated onto a single heat-absorbing pad (in a state where no other layer affecting the thermal properties of the heat-absorbing pad is laminated), the heat-absorbing pad absorbs heat and maintains the temperature of the heat-absorbing pad for a certain period without rising. When a heat-absorbing pad having a heat transfer delay effect is applied to a battery cell, the transfer of heat to adjacent battery cells can be effectively delayed even if the battery cell to which the heat-absorbing pad is applied ignites. In this specification, when describing the characteristics of the heat-absorbing pad regarding a flame, the flame may refer to a flame resulting from the combustion of LPG (Liquid Petroleum Gas) or butane gas. The temperature of the flame may be, for example, about 1000°C or higher. The upper limit of the flame temperature may be, for example, 2000°C or lower or 1500°C or lower.

[0062] The fact that the heat-absorbing pad has a heat transfer delay effect may mean that the heat-absorbing pad has a heat transfer delay section. The heat transfer delay section can be defined as a continuous section in which the temperature change is less than 10°C or 5°C or less in a graph of temperature (°C) versus time (seconds) measured while applying a flame to the heat-absorbing pad. The above temperature change being less than 10°C or 5°C or less means that the temperature rise per second is less than 10°C or 5°C or less.

[0063] The above-mentioned heat transfer delay section may be due to the endothermic reaction of the endothermic material. In one example, in a graph of temperature (°C) versus time (seconds) measured while applying a flame to an endothermic pad, a heat transfer delay section may appear after a temperature rise section. In the temperature rise section, the starting temperature (temperature at 0 seconds) is approximately 25°C, and the temperature may increase almost linearly until the start time of the heat transfer delay section. Afterward, the temperature may remain almost constant in the heat transfer delay section. After the above-mentioned heat transfer delay section, another temperature rise section may appear. If distinction is necessary, the temperature rise section before the heat transfer delay section may be referred to as the first temperature rise section, and the temperature rise section after the heat transfer delay section may be referred to as the second temperature rise section. After the second temperature rise section, the temperature may converge to a constant temperature again, and this temperature may be referred to as the final adiabatic temperature. The above final adiabatic temperature may appear, for example, after about 3 minutes, about 5 minutes, or about 10 minutes have passed since the flame was radiated onto the heat absorption pad.

[0064] The heat-absorbing pad described above may exhibit excellent thermal insulation performance against flames. In one example, after radiating a flame onto one side of the heat-absorbing pad for 5 minutes, the temperature on the side opposite to the side radiating the flame may be 400°C or lower. Since a lower final insulation temperature is preferable, the lower limit is not specifically restricted, but it may be, for example, 90°C or higher, 100°C or higher, 110°C or higher, or 120°C or higher.

[0065] The above heat-absorbing pad can exhibit excellent structural stability against flames. In one example, after radiating a flame onto the heat-absorbing pad for 5 minutes, it can be said that there is no case where the structure of the pad collapses so that the flame is visible in the opposite direction, or where a part with a temperature exceeding 600°C occurs due to structural deformation of the pad.

[0066] In one example, the heat transfer delay temperature of the heat-absorbing pad may be 50°C or higher. The heat transfer delay temperature may be, for example, 60°C or higher, 70°C or higher, 80°C or higher, 90°C or higher, 100°C or higher, 110°C or higher, 120°C or higher, 130°C or higher, 140°C or higher, 150°C or higher, 160°C or higher, 170°C or higher, 180°C or higher, or 190°C or higher. The above heat transfer delay temperature may be, for example, 300°C or lower, 260°C or lower, 240°C or lower, 220°C or lower, 200°C or lower, 190°C or lower, 180°C or lower, 170°C or lower, 160°C or lower, 150°C or lower, 140°C or lower, 130°C or lower, 120°C or lower, 110°C or lower, or 100°C or lower. The above heat transfer delay temperature may refer to a part of the temperature in the heat transfer delay section (for example, the temperature at the start time and / or the end time of the heat transfer delay section), or it may refer to the temperature over the entire time of the heat transfer delay section. When the heat transfer delay temperature is within the above range, it may be suitable for delaying rapid ignition caused by flames in the early stages by absorbing the initial heat generated when the battery cell explodes.

[0067] In one example, the heat transfer delay time of the heat-absorbing pad may be, for example, 5 seconds or more. The heat transfer delay time may be 10 seconds or more, 20 seconds or more, 30 seconds or more, 40 seconds or more, 60 seconds or more, 80 seconds or more, 100 seconds or more, 120 seconds or more, 140 seconds or more, 160 seconds or more, 180 seconds or more, or 200 seconds or more. The longer the heat transfer delay time, the more advantageous it is, and although there is no specific upper limit, it may be, for example, 60 minutes or less.

[0068] The heat-absorbing pad may have irreversibility, meaning its shape does not return to its original state after heating and cooling. In one example, the X-ray diffraction (XRD) pattern of the heat-absorbing pad measured after heating it to 200°C and cooling it to room temperature may differ from the X-ray diffraction (XRD) pattern of the heat-absorbing pad before heating. Heating the heat-absorbing pad to 200°C may be maintained for about 60 minutes. The heat-absorbing pad before heating refers to the heat-absorbing pad at room temperature without heating. The room temperature may be, for example, in the range of 20°C to 30°C or about 25°C. If the heat-absorbing pad does not have the irreversibility, the XRD patterns before and after heating may be identical. Specifically, when XRD analysis is performed on an endothermic pad, a graph can be obtained where the x-axis is 2θ (2Theta) and the y-axis is intensity (au) (θ is the angle of incidence of the diffracted X-ray, and intensity is the intensity of the diffracted X-ray). Multiple diffraction peaks appear on the graph, and a pattern can be obtained from them. Different XRD patterns may mean that at least one of the multiple diffraction peaks does not appear. Identical XRD patterns may mean that the multiple diffraction peaks appear identically.

[0069] In one example, the thickness of the heat-absorbing pad may be, for example, 0.5 mm or more. Specifically, the thickness of the heat-absorbing pad may be 1 mm or more, 1.5 mm or more, 2 mm or more, 2.5 mm or more, or 3 mm or more. If the thickness of the heat-absorbing pad is within the above range, it may be advantageous to improve heat absorption performance and exhibit excellent heat transfer delay characteristics. The upper limit of the thickness of the heat-absorbing pad may be appropriately adjusted considering the battery module to which the pad is to be applied, for example, 10 mm or less, 9 mm or less, 8 mm or less, 7 mm or less, 6 mm or less, 5 mm or less, 4 mm or less, or 3 mm or less. In one example, the thickness of the pad may be less than 4 mm, 3.5 mm or less, 3.0 mm or less, 2.5 mm or less, or 2.0 mm or less. If the thickness of the pad is within the above range, it may be more advantageous in that it can exhibit a secondary temperature delay section.

[0070] The present application also relates to a multilayer heat-absorbing pad. As previously mentioned, if an additional layer or film is included in addition to the heat-absorbing pad, it may be referred to as a multilayer heat-absorbing pad.

[0071] The multilayer heat-absorbing pad may further include a flame-resistant protective layer. The flame-resistant protective layer may be present on at least one or both sides of the heat-absorbing pad. In one example, the flame-resistant protective layer may be a layer of inorganic material. In another example, the flame-resistant protective layer may be a polymer film. As a specific example, the flame-resistant protective layer may include one or more selected from the group consisting of an aluminum (Al) layer, a copper (Cu) layer, a stainless steel layer, a graphite layer, a mica sheet, ceramic paper, a silica fiber sheet, a PI (Polyimide) film, a PEEK (Polyether ether ketone) film, and a FLAME BARRIER (FRB film). The FRB film is a flame-retardant material product available from 3M and is composed of inorganic material.

[0072] In the case of a graphite layer, a functional layer having insulating and / or scratch-resistant properties may be formed on one or both sides of the graphite layer. The functional layer may be, for example, a polymer coating layer. For example, a Teflon layer may be exemplified as the polymer coating layer. The thickness of the polymer coating layer may be, for example, in the range of 1 μm to 50 μm.

[0073] In one example, the heat-absorbing pad and the flame-resistant protective layer may be attached by an adhesive layer. That is, one side of the adhesive layer may be in contact with the heat-absorbing pad, and the other side of the adhesive layer may be in contact with the flame-resistant protective layer. An acrylic adhesive layer or a silicone adhesive layer may be used as the adhesive layer. The thickness of the adhesive layer may be, for example, in the range of 10 µm to 500 µm. More specifically, the thickness of the adhesive layer may be 10 µm or more, 50 µm or more, or 100 µm or more, and 500 µm or less, 400 µm or less, or 300 µm or less. In another example, the heat-absorbing pad and the flame-resistant protective layer may be attached by a hot-melt adhesive. In another example, the heat-absorbing pad may be treated with a primer and the flame-resistant protective layer may be attached directly, or the flame-resistant protective layer may be attached after additional lamination with an adhesive. In another example, the heat-absorbing pad can be attached by directly coating the flame-resistant protective layer onto the heat-absorbing pad or by directly coating the heat-absorbing pad onto the flame-resistant protective layer.

[0074] In one example, the multilayer heat-absorbing pad may have a first structure comprising at least two heat-absorbing pads and one flame-resistant protective layer existing between the two heat-absorbing pads. The first structure may be advantageous in terms of increasing the heat transfer delay time and securing excellent insulation performance. In another example, the multilayer heat-absorbing pad may have a second structure comprising at least two flame-resistant protective layers and one heat-absorbing pad existing between the two flame-resistant protective layers. The second structure may be more advantageous in terms of securing structural stability against flames. In yet another example, the multilayer heat-absorbing pad may have a third structure comprising one flame-resistant protective layer and one heat-absorbing pad. The above first structure, second structure, and third structure describe the basic laminated structure of a multilayer heat-absorbing pad, but the structure of the multilayer heat-absorbing pad is not limited thereto, and one or more of the first structure, second structure, and third structure may be repeated, two or more of the first structure, second structure, and third structure may be combined, and a heat-absorbing pad and a protective layer may be further added to one or both sides of the first structure, second structure, and third structure.

[0075] In one example, the multilayer heat-absorbing pad may further include an additional protective layer attached to one or both sides of the flame-resistant protective layer. The additional protective layer may be attached to the flame-resistant protective layer through an adhesive layer. If the multilayer heat-absorbing pad includes an additional protective layer attached to one side of the flame-resistant protective layer, the additional protective layer may be attached to the side opposite to the side of the flame-resistant protective layer facing the heat-absorbing pad. If the multilayer heat-absorbing pad includes additional protective layers attached to both sides of the flame-resistant protective layer, the laminate of the additional protective layer / flame-resistant protective layer / additional protective layer itself may be referred to as a metal pouch. The adhesive layer may be, for example, an acrylic adhesive layer. Additionally, since the flame-resistant protective layer is electrically conductive, the additional protective layer may serve as an insulating layer. A polymer film may be used as the additional protective layer. For example, the additional protective layer may be made of PET (Polyethylene terephthalate) film, PE (Polyethylene) film, PC (Polycarbonate) film, or PP (Polypropylene) film. Alternatively, the additional protective layer may be made of a polymer film that has been flame-retardant treated. The type of flame-retardant treatment is not particularly limited, and known flame-retardant treatments may be applied. The thickness of the additional protective layer may be appropriately selected within a range that allows the total thickness of the multilayer heat-absorbing pad to be controlled within the range described below.

[0076] The thickness of the flame-resistant protective layer (a standalone flame-resistant protective layer without an additional protective layer attached) or the laminate with an additional protective layer attached to the flame-resistant protective layer may be appropriately selected in consideration of the purpose of this application. If the thickness of the flame-resistant protective layer is thin, it may not be sufficient to obtain the effect of lowering the adiabatic temperature and / or improving the heat transfer delay characteristics resulting from the application of the flame-resistant protective layer. Meanwhile, considering the thickness of the final multilayer heat-absorbing pad, if the thickness of the flame-resistant protective layer is excessively thick, the thickness of the heat-absorbing pad must be designed to be thin, which may result in reduced heat transfer delay characteristics or cracks occurring in the heat-absorbing pad. The thickness of the flame-resistant protective layer may be appropriately selected in consideration of the above, and may be, for example, 5 μm or more. Specifically, the thickness of the flame-resistant protective layer may be 15㎛ or more, 20㎛ or more, 30㎛ or more, or 40㎛ or more, and may be 2 mm or less, 1.5 mm or less, 1 mm or less, 800㎛ or less, 600㎛ or less, 400㎛ or less, 200㎛ or less, 100㎛ or less, 80㎛ or less, 60㎛ or less, or 50㎛ or less.

[0077] The above-described multilayer heat-absorbing pad can further increase the heat transfer delay time by applying a flame-resistant protective layer to the heat-absorbing pad. In one example, the difference (S1-S2) between the heat transfer delay time (S1) of the multilayer heat-absorbing pad and the heat transfer delay time (S2) of the heat-absorbing pad alone may be 5 seconds or more, 10 seconds or more, 30 seconds or more, 60 seconds or more, 90 seconds or more, 120 seconds or more, 150 seconds or more, 180 seconds or more, or 210 seconds or more. Since a larger value of S1-S2 is more advantageous, the upper limit is not specifically restricted, but, for example, it may be 1000 seconds or less.

[0078] In one example, the dielectric breakdown voltage of the multilayer heat-absorbing pad may be 4.0 Kv / mm or higher, 5.0 Kv / mm or higher, or 6.0 Kv / mm or higher. The dielectric breakdown voltage may be measured under a step-up condition of 500 V / s according to ASTM D149 standards. The dielectric breakdown voltage refers to the voltage at which a short circuit occurs as the voltage rises, and can be measured as dielectric breakdown value / thickness. The upper limit of the dielectric breakdown voltage of the multilayer heat-absorbing pad may be, for example, 20.0 Kv / mm or lower, 15 Kv / mm or lower, or 10 Kv / mm or lower.

[0079] The present application relates to the use of a resin composition, an absorbent pad, and / or a multilayer absorbent pad. In one example, the present application relates to a battery module comprising said resin composition, an absorbent pad, and / or a multilayer absorbent pad. Additionally, the present application relates to a battery pack cover comprising said resin composition, an absorbent pad, and / or a multilayer absorbent pad. The battery module or battery pack cover may comprise said resin composition in a cured state (i.e., a cured product of said resin composition).

[0080] The battery module described above may include a module case and battery cells. The battery cells may be housed within the module case. One or more battery cells may exist within the module case, and multiple battery cells may be housed within the module case. The number of battery cells housed within the module case is not specifically limited and is adjusted according to the intended use, etc. The battery cells housed within the module case may be electrically connected to one another. The type of battery cell housed within the module case is also not specifically limited, and various known battery cells may all be applied. In one example, the battery cell may be of the pouch type. A pouch-type battery cell may typically include an electrode assembly, an electrolyte, and a pouch outer casing.

[0081] A module case may include at least a side wall and a bottom plate forming an internal space in which a battery cell can be housed. Additionally, the module case may further include a top plate that seals the internal space. The side wall, bottom plate, and top plate may be formed integrally with each other, or the module case may be formed by assembling separate side walls, bottom plates, and / or top plates. The shape and size of such a module case are not particularly limited and may be appropriately selected depending on the application or the shape and number of battery cells housed in the internal space. In the above, the terms "top plate" and "bottom plate" are relative terms used to distinguish between the plates constituting the module case, as there are at least two plates. That is, it does not mean that in actual use, the top plate must necessarily be located at the top and the bottom plate must necessarily be located at the bottom.

[0082] The resin composition, heat absorption pad, and / or multilayer heat absorption pad may be present on one side of the battery cell. If the battery module comprises a plurality of battery cells, the resin composition, heat absorption pad, and / or multilayer heat absorption pad may be disposed between the battery cells. The resin composition, heat absorption pad, and / or multilayer heat absorption pad maintain their original form without a change of state at the operating temperature of the battery, but when thermal runaway occurs, they can provide a cooling effect to the ignited cell through a change of state and delay the transfer of heat to adjacent cells.

[0083] The present application relates to a heat-absorbing pad. The present application can provide a heat-absorbing pad with excellent flame resistance and compression performance. The heat-absorbing pad can be usefully used to delay heat transfer to adjacent battery cells during thermal runaway of a battery cell.

[0084] The present application will be described in detail below through embodiments according to the present application, but the scope of the present application is not limited by the embodiments presented below.

[0085] Example 1

[0086] 68 parts by weight of silicone resin (VP10000, Dami Polychem Co.) and 32 parts by weight of curing agent (Andisil XL12, AB Specialty Silicones Co.) were added to a container of a paste mixer (Daehwa Tech Co., PDM-1K equipment) and 100 parts by weight of binder resin was added. A mixture (resin composition) was prepared by adding 125 parts by weight of boric acid particles (Daejeong Chemical Co., Ltd.), 40 parts by weight of APP (Ammonium Phosphate) (FR-624E, Chempia Co., Ltd.) as flame retardant particles, 20 parts by weight of aluminum hydroxide particles (HWF-20, Chalco Co., Ltd.), 0.9 parts by weight of dispersant (LP X 21879, BYK Co., Ltd.), 0.8 parts by weight of curing retardant (VMC, HRS Co., Ltd.), 26 parts by weight of hexane solvent (Daejeong Chemical Co., Ltd.), and 0.4 parts by weight of catalyst (SRX-212, Dow Co., Ltd.) to 100 parts by weight of binder resin, and then mixing for 1 minute at 600 rpm and 500 rpm. After placing a fluorine release film on an automatic coating device, the coating gap was adjusted, and the mixture was poured onto the fluorine release film and coated. Subsequently, the heat-absorbing pad was manufactured by drying in a Matisse oven at 130°C for 10 minutes. The thickness of the manufactured heat-absorbing pad was approximately 2.0 mm.

[0087] Example 2

[0088] The heat-absorbing pad of Example 2 was manufactured by additionally performing a rolling process on the heat-absorbing pad manufactured in Example 1. The rolling process was carried out as a roll rolling process, and the process conditions were set to a temperature of 24℃, a pressure condition gap of 1000㎛, and a speed of 20 mpm.

[0089] Comparative Example 1

[0090] A urethane foam pad (LGC) with a thickness of approximately 2.0 mm was prepared as Comparative Example 1. The urethane foam pad of Comparative Example 1 did not contain endothermic particles.

[0091] Comparative Example 2

[0092] A silicone foam pad (L2Y) with a thickness of approximately 2.0 mm was prepared as Comparative Example 2.

[0093] Comparative Example 3

[0094] An aerogel insulation material (Aspen Aerogel) with a thickness of about 2.7 mm was prepared as Comparative Example 3.

[0095] Evaluation Example 1. Compression Performance Evaluation

[0096] The pads or aerogels of the Examples and Comparative Examples were cut into samples measuring 30mm x 30mm (width x length) and their thicknesses were measured. Using a TA (Texture Analyzer, XT plus-EXPONENT) device, a circular jig with a diameter of 6.5mm was installed, and a flat fixing jig was prepared underneath. The sample was placed on the flat jig below, and the circular jig installed above was positioned close to the sample to conduct a compression test. The compression test was performed at 25°C and 50% RH (relative humidity). The detailed conditions for the compression test were: Test Mode = Compression, Test speed = 0.05mm / s, Target Distance = a value calculated as 90% of the measured sample thickness, and Trigger force = 3g. From the above compression test, a graph was obtained with the x-axis representing distance (mm) and the y-axis representing force (g). In the graph, Examples 1-2 and Comparative Examples 1-3 both showed a tendency for the y-value to increase as the x-value increased. In the graph above, the point where the sample measurement began was set as the 0% reference, and values ​​between 1 and 25% strain were taken. Using the distance (d) and force (F) measured above, each variable was calculated according to Equation 1 below (R 2(95% or more). When the compression factor n is less than 1.5, the compression performance was evaluated as excellent.

[0097] [Equation 1]

[0098]

[0099] α : Constant (10 fixed), K : Constant (variable value), d : Compression distance (mm)

[0100] Evaluation Example 2. Flame Performance Evaluation

[0101] The pads or aerogels of the examples and comparative examples were cut into widths × lengths = 6cm × 6cm to prepare samples. SUS frames were attached to the front and back of the samples. Since the SUS frame has an overall size of widths × lengths = 6cm × 6cm and has a hole of widths × lengths = 5cm × 5cm, the actual flame contact area of ​​the sample is widths × lengths = 5cm × 5cm. The SUS frame serves to prevent the sample from bending due to the flame. The sample with the attached SUS frame was fixed vertically to a jig using a clamp (the main surface of the sample is perpendicular to the ground, and the thickness direction of the sample is parallel to the ground). An LPG gas torch (LPG gas: Sun Lighter Gas, Taiyo Industry Co., Ltd., gas torch: 500JET, Honest Co., Ltd.) was placed on the first main surface side of the sample, and a thermal imaging camera (A655SC, FLIR Co., Ltd.) was placed on the second surface side of the sample, opposite to the first main surface. The pixel resolution of the thermal imaging camera is 640×480, and the upper limit of the measurement temperature is 660°C. The gas torch was positioned so that the flame-emitting part of the gas torch was positioned at the center of the first main surface of the sample, and the lens of the thermal imaging camera was positioned so that it was positioned at the center of the second main surface of the sample. In addition, the distance between the first main surface of the sample and the flame-emitting part of the gas torch was approximately 3 cm, and the distance between the second main surface of the sample and the lens of the thermal imaging camera was 40 cm. The ambient temperature before the flame was emitted from the gas torch was approximately 25°C. The temperature of the second main surface was measured using the thermal imaging camera while heating the sample by emitting a flame from the torch. The thermal imaging camera measures the infrared radiation emitted by the sample and calculates the temperature based on the measured infrared radiation value. After radiating a flame toward the first main surface of the sample by a gas torch for 5 minutes, the temperature of the second main surface of the sample was measured, and the temperature measured by the thermal imaging camera is the temperature of the highest temperature point in the heated part of the sample. The temperature of the second main surface was measured at the point when the heating time was 5 minutes.Flame performance was evaluated according to the criteria below, and the results are listed in Table 1 below.

[0102] - OK: The temperature of the side opposite the flame-applied side is 400℃ or lower

[0103] - NG: The temperature of the side opposite to the flame-applied side exceeds 400℃

[0104] Evaluation Example 3. Structural Stability Evaluation

[0105] After setting up as in Evaluation Example 2, a flame was radiated toward the first main surface of the sample for 5 minutes, and the degree of degradation of the sample was evaluated according to the criteria below, and the results were recorded in Table 1 below.

[0106] - OK: Maintains the structure of the sample

[0107] - NG: Flames are visible in the opposite direction due to the collapse of the sample structure, or parts exceeding 600℃ occur due to structural deformation of the sample.

[0108] Compressibility n Flame Evaluation Structure Stability Example 11.34 OK OK Example 21.05 OK OK Comparative Example 10.93 NG NG Comparative Example 21.14 NG NG Comparative Example 31.84 NG OK

Claims

1. An endothermic pad comprising an endothermic material and a binder resin, wherein the compression distance (d) and force (F) are measured by a compression test of a texture analyzer, and the compression modulus (n) in Equation 1 below is less than 1.5: [Equation 1] In Equation 1, F is force (unit: g), d is compression distance (unit: mm), α is a fixed constant 10, K is a variation constant, and n is the compression factor.

2. In claim 1, the heat-absorbing pad is a heat-absorbing pad having a porous structure.

3. In claim 1, the density of the heat-absorbing pad is 1 g / cm³ 3 Heat absorption pad for Lee Ha-in.

4. An absorbent pad according to claim 1, wherein the force (F) measured when performing a compression test with a strain of 25% using a texture analyzer is 3000g or less.

5. The heat-absorbing pad according to claim 1, wherein after radiating a flame to one side of the heat-absorbing pad for 5 minutes, the temperature on the side opposite to the radiated side is 400℃ or lower.

6. In claim 1, the binder resin is a heat-absorbing pad comprising a silicone resin.

7. The heat-absorbing pad according to claim 6, wherein the binder resin further comprises a silane compound or a silanol compound as a curing agent.

8. The heat-absorbing pad according to claim 1, wherein the heat-absorbing material exists in a solid state at room temperature and undergoes a phase change from solid to liquid at a temperature below 200°C.

9. In claim 1, the endothermic substance is H3BO3, (NH4)2O·5B2O3·8H2O, (Mg(H2PO4)2)·H2O, MgCl2·6H2O, AlCl3·6H2O, Na4P2O7·10H2O, KAl(SO4)2·12H2O, NiSO4·6H2O, Mg(NO3)2·6H2O, CoSO4·7H2O, (NH4)2Fe(SO4)2·6H2O, CuSO4·5H2O, ZnSO4·7H2O, CoCl2·6H2O, CrCl3·6H2O, NiCl2·6H2O, MgSO4·7H2O, Al2(SO4)3·18H2O, Na2B4O7·10H2O, Sr(OH)2·8H2O, An endothermic pad comprising one or more selected from the group consisting of CaC2O4·H2O, Ba(OH)2·8H2O, Ba(OH)2·H2O, Mg3(PO4)2·5H2O, Mg3(PO4)2·8H2O, and FeSO4·7H2O.

10. The heat-absorbing pad according to claim 1, wherein the thickness of the heat-absorbing pad is within the range of 0.5 mm to 10 mm.

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