Endothermic pad

Abstract

The present application relates to an endothermic pad. The endothermic pad of the present application can exhibit excellent endothermic performance and excellent thermal transfer delay characteristics. In the case of thermal runaway of a battery cell, the endothermic pad can be effectively used to delay thermal transfer to an adjacent battery cell.

Description

heat absorbing pad

[0001] This application relates to a heat absorbing pad. This application claims the benefit of priority to Korean Patent Application No. 10-2023-0107276, filed August 16, 2023, and Korean Patent Application No. 10-2023-0107279, filed August 16, 2023, the entire disclosures of which are incorporated herein by reference.

[0002] Thermal runaway in a battery occurs when the thermal stability of the chemicals within the cell exceeds its limit, causing the cell to rapidly release its internal energy to the outside. Thermal runaway is defined as a drop in the measured voltage of the cell, a measured temperature of dT / dt ≥ [4℃ / s], and exceeding the maximum operating temperature (approximately 120℃). Causes of thermal runaway include overcharging, collision / dropping, heat exposure, high voltage / current exposure, and external / internal short circuits. When thermal runaway begins, the internal pressure of the battery increases, causing combustible materials to erupt and ignite. This then heats adjacent cells and rapidly spreads into a fire. Battery fires are classified as electrical fires and are currently being extinguished using gas-based fire extinguishing systems. However, the battery module has a metal protective cover that makes it difficult for extinguishing agents to penetrate. In addition, when thermal runaway occurs, the temperature can quickly rise to 1000℃, so agent release must occur at the initial stage of the fire. Therefore, to stop thermal runaway, only sufficient cooling or total combustion in the early stages of a fire is the ultimate extinguishment (Prior Art Document 1: Republic of Korea Patent Publication No. 10-2020-0107214).

[0003] Phase change materials (PCMs) are materials that release and absorb energy through a phase transition, providing heat and cooling. The latent heat of the phase transition is higher than the typical sensible heat, and they store and release large amounts of energy when they transition from a solid or liquid state to another at their phase change temperature (PCT). PCMs are used in applications requiring energy storage and stable temperatures, such as heating pads, cooling devices, and clothing.

[0004] The present application relates to a heat-absorbing pad. The heat-absorbing pad of the present application can exhibit excellent heat absorption performance and excellent heat transfer delay characteristics. 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 heat absorbing pad may have a property of absorbing heat generated in 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 including the heat absorbing material and the 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 another layer other than the cured product of the resin composition is further included, it may be referred to as a multilayer heat absorbing pad.

[0006] Among the properties mentioned in this specification, the properties whose results are affected by the measurement temperature and / or measurement pressure are the results measured at room temperature and / or atmospheric pressure, unless otherwise specified. The term room temperature in this specification refers to the natural temperature that has not been heated or cooled, and is typically a temperature in the range of about 10°C to 30°C, a temperature in the range of 20°C to 30°C, or about 23°C or about 25°C. The unit of temperature in this specification is ℃, unless otherwise specified. The term atmospheric pressure in this specification refers to the natural pressure that has not been pressurized or decompressed, and typically means about 1 atm of the atmospheric pressure level. The properties whose results are affected by the measurement humidity in this specification are, unless otherwise specified, the properties are the properties measured at the natural humidity that has not been separately controlled in the above-mentioned room temperature and atmospheric pressure conditions.

[0007] As used herein, an endothermic material may refer to a material that absorbs or consumes heat generated from its surroundings. An endothermic material may spontaneously decompose or produce new substances using the absorbed heat energy.

[0008] The above-described heat-absorbing pad and / or resin composition may include an endothermic material that undergoes an irreversible heat-absorbing 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 heat absorption when the ambient temperature increases, and does not return to the state of the endothermic material before thermal decomposition even when the ambient temperature decreases. The thermal decomposition may mean that the material chemically decomposes into a simpler substance when heat is applied. This irreversibility may be advantageous in exhibiting excellent heat transfer delay characteristics. On the other hand, paraffin, a representative phase change material (PCM), absorbs heat when the ambient temperature increases, melts, and becomes a liquid, and releases heat and returns to a solid state when the ambient temperature decreases. The phase change material is a material that reacts reversibly through heat absorption and exotherm. The resin composition may not include such a reversibly reacting phase change material.

[0009] Endothermic substances exist in a solid state at room temperature, and can undergo a phase change from solid to liquid at temperatures below 200°C. In this specification, the phase change from solid to liquid may refer to a phenomenon in which water molecules separate (dissociate) from the endothermic substance when the endothermic substance is heated. The temperature at which the phase change from solid to liquid of the endothermic substance occurs may be specifically 190°C or less, 180°C or less, 170°C or less, 160°C or less, 150°C or less, 140°C or less, 130°C or less, 120°C or less, 110°C or less, or 100°C or less, and may be 50°C or more, 60°C or more, 70°C or more, 80°C or more, 90°C or more, 100°C or more, 110°C or more, 120°C or more, 130°C or more, 140°C or more, 150°C or more, 160°C or more, 170°C or more, 180°C or more, or 190°C or more.

[0010] The endothermic material may be a water-soluble material. The water-soluble material may refer to a material having a solubility in water of greater than 0 g / 100 ml at 20° C. In one example, the solubility of the endothermic material in water of greater than 4.5 g / 100 ml at 20° C. The solubility of the endothermic material in water may be specifically 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 material in water may be, for example, 50 g / 100 ml or less. The above solubility can be derived by adding 1g of the endothermic substance to 100ml of water at 20℃ and measuring the weight of the endothermic substance before a precipitate is formed.

[0011] 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. When the thermal conductivity of the endothermic material is within the above range, it may be advantageous for exhibiting excellent heat transfer delay characteristics. The thermal conductivity of the endothermic material may be specifically 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 by 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 a known thermal conductivity measuring device. Alternatively, the thermal conductivity of an endothermic material is generally known, and an endothermic material satisfying the above thermal conductivity can be used.

[0012] In one example, the endothermic material may have an endothermic peak temperature of less than 200°C when subjected to thermal analysis while heating from 0°C to 350°C at a rate of 10°C / min using a differential scanning calorimeter. In the present specification, the endothermic peak temperature may refer to a temperature at which the absolute value of Heat Flow (W / g) is the highest in a graph of Heat Flow (W / g) (y-axis) against temperature (°C) (x-axis) obtained through thermal analysis using a differential scanning calorimeter. The endothermic peak temperature may be, for example, 50°C or higher. When the endothermic peak temperature is within the above range, it may be advantageous for exhibiting excellent heat transfer characteristics. The above endothermic peak temperature may be specifically 190°C or less, 180°C or less, 170°C or less, 160°C or less, 150°C or less, 140°C or less, 130°C or less, 120°C or less, 110°C or less, or 100°C or less, and may be 60°C or more, 70°C or more, 80°C or more, 90°C or more, 100°C or more, 110°C or more, 120°C or more, 130°C or more, 140°C or more, 150°C or more, 160°C or more, 170°C or more, 180°C or more, or 190°C or more.

[0013] In one example, an endothermic material may have a single endothermic peak (one endothermic peak) at a temperature below 200°C. In another example, an endothermic material may have distributed endothermic peaks (two or more endothermic peaks) at a temperature below 200°C. Having two or more endothermic peaks may mean that there is one endothermic peak with the highest absolute value of Heat Flow (W / g) and one or more additional endothermic peaks with the next highest absolute value of Heat Flow (W / g). Assuming the same amount of heat absorption, an endothermic material with a single peak may have better 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, and CaSO4·2H2O.

[0014] In one example, an endothermic material may have an endothermic quantity of 500 J / g or more. In the present specification, the endothermic quantity may refer to the total amount of heat (integrated value on a DSC graph) from the point at which endothermic initiation occurs to the point at which endothermic initiation occurs. Specifically, the endothermic quantity may be obtained by calculating the area of ​​the graph of the endothermic section (by integrating the graph of the endothermic section) in a graph of Heat Flow (W / g) (y-axis) against Temperature (℃) (x-axis) obtained through thermal analysis using a differential scanning calorimeter. The endothermic section may refer to a section from the endothermic initiation temperature to the endothermic end temperature in the graph. The area may refer to the area of ​​a closed graph formed by a straight line (A) connecting a graph point at the endothermic initiation temperature and a graph point at the endothermic end temperature, and a continuous graph (B) of the section from the endothermic initiation temperature to the endothermic end temperature. When the endothermic quantity at the endothermic peak is within the above range, it may be advantageous for exhibiting excellent heat transfer characteristics. The above heat absorption may be specifically 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 may be a value measured while increasing the temperature at a rate of 10°C / min using a differential scanning calorimeter (DSC Q2000, TA Corporation).

[0015] The endothermic material may include a material containing water and / or a solid acid. The material containing water 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, at about 25°C.

[0016] In one example, the endothermic material may be a hydrate particle. The hydrate particle may refer to a particle containing water molecules (H2O). When the hydrate particle is applied as the endothermic material, water molecules may be dissociated from the endothermic material by the thermal decomposition. This may be advantageous in exhibiting excellent heat transfer delay characteristics. The hydrate particle may be an inorganic salt containing water molecules specifically bound to crystals of a metal compound. The water contained in the hydrate particle may be referred to as crystal water. The hydrate particle is different from a hydroxide particle, and the hydroxide particle may refer to a material containing -OH (-hydroxyl group) but not containing H2O.

[0017] In one example, the endothermic material may be a solid acid particle. The solid acid may comprise, for example, H3BO3 particles. ·

[0018] In one example, endotherms are H3BO3, (NH4)2O·5B2O3·8H2O, (Mg(H2PO4)2)·8H2O, 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 at least one 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.

[0019] In one example, the heat-absorbing material may be a water microcapsule. The microcapsule may include a capsule portion and water contained within the capsule portion. The capsule portion may include at least one 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.

[0020] 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 the 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 the 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. The content of the endothermic particles within the above range is suitable for manufacturing an endothermic pad and may be advantageous in exhibiting excellent heat transfer delay characteristics.

[0021] 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 in exhibiting excellent heat transfer delay characteristics. In particular, even when an endothermic material containing water is used as the heat-absorbing material, excellent heat transfer delay characteristics can be exhibited because the main resin and the endothermic material do not change over time or generate water after being mixed. Meanwhile, while organic materials such as urethane resin or epoxy resin burn in flames, silicone resins may exhibit better flame resistance as the Si-O-Si siloxane chains are converted to SiO2 by heat.

[0022] The silicone resin may be polydimethylsiloxane having vinyl groups at both ends. The 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 in consideration of the molecular weight of the silicone resin.

[0023] [Chemical Formula 1]

[0024]

[0025] 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 may be improved, which may be more advantageous in 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 viewpoint of handling the manufactured pad.

[0026] 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 in exhibiting excellent heat transfer delay characteristics. Specifically, the viscosity of the silicone resin may be 100,000 cSt or less, 50,000 cSt or less, 10,000 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. The lower limit of the viscosity of the above silicone resin may be 5 cSt or more, 10 cSt or more, 20 cSt or more, 40 cSt or more, 60 cSt or more, 80 cSt or more, or 100 cSt or more from the perspective of the pad manufacturing process. With regard to the viscosity of the silicone resin, for commercially available products, the seller provides information on the viscosity. Therefore, a silicone resin product that satisfies the above viscosity can be selected and used, and the viscosity measurement conditions can also follow those provided by the seller of the silicone resin. In one example, the viscosity of the silicone resin can be a value measured using a BROOKFIELD DV-II+ viscometer under the conditions of a temperature of 25°C, a rotation speed of 10 rpm, and a spindle of 6.

[0027] The binder resin may further include a curing agent. The curing agent may be one suitable for curing the main resin. 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 -SiH (Silicon-hydride). The silanol compound may refer to a compound having a -Si-OH (Silicon-hydride) group. The -SiH group or -Si-OH group may react with a vinyl group of the silicone resin. The silane compound may have at least one -CH3 of a terminal and / or a side chain. - It can be a polydimethylsiloxane substituted with H. In one example, the curing agent can be a pendent type curing agent. The pendent type curing agent can be a polydimethylsiloxane in which at least one -CH3 of the pendent type is substituted with -H, and both terminals are -CH3. In another example, the curing agent can be a hybrid type curing agent. The hybrid type curing agent can be a polydimethylsiloxane in which both terminals are substituted with -H, and at least one -CH3 of the pendent type is also substituted with -H.

[0028] In one example, the curing agent may be included in the resin composition so that the H / V ratio is in the range of 1 to 20. Wherein H is a value defined as H mmol / g Х H wt%, and V is a value defined as V mmol / g Х V wt%. In the above, H mmol / g means mmol of Si-H (silicon-hydrogen) per g of the curing agent included in the resin composition, and V mmol / g means mmol of Si-Vi (silicon-vinyl) per g of the silicone resin included in the resin composition. In the above, H wt% means a weight fraction of the curing agent with respect to the weight of the entire resin composition, and V wt% means a weight fraction of the silicone resin with respect to the weight of the entire resin composition. In the above, the weight fraction of the entire resin composition is 100 wt%.

[0029] The above-described heat-absorbing pad and / or resin composition may not contain an amine compound and an isocyanate compound. The amine compound and the isocyanate compound may not be suitable for mixing with a heat-absorbing material containing water. The amine compound may be a curing agent when an epoxy resin is used as the main resin, and the isocyanate compound may be a curing agent when a polyol resin is used as the main resin. According to the present application, the epoxy resin and the polyol resin may not be included as the main resin.

[0030] The above-described heat-absorbing pad and / or resin composition may further include a catalyst. The catalyst may promote a reaction between the main resin and the curing agent. In one example, the catalyst may promote a hydrosilylation addition reaction between a carbon-carbon double bond of the silicone resin and a -SiH group of the curing agent. In another example, the catalyst may also promote a reaction between a carbon-carbon double bond of the silicone resin and a -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 catalyst may be included in an amount 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, based on 100 parts by weight of the binder resin.

[0031] The above-described heat-absorbing pad and / or resin composition may further include additives in addition to the main resin, curing agent, and catalyst. In one example, the resin composition may further include a dispersant. As the dispersant, for example, an amino-silicone dispersant may be used. The dispersant may be included in an amount of 0.1 to 10 parts by weight, 0.1 to 5 parts by weight, or 0.5 to 5 parts by weight, relative to 100 parts by weight of the binder resin.

[0032] In one example, the resin composition may further include a chain extender. For example, a compound having -SiH (Silicon-hydride) at both ends may be used as the chain extender. The -SiH can react with a vinyl group of the silicone resin. In one example, the chain extender may be a polydimethylsiloxane in which -CH3 at both ends is replaced with -H and the side chain is -CH3. When the resin composition includes both a curing agent and a chain extender, the curing agent and the chain extender may be included in the resin composition so that the H / V ratio is within the range of 1 to 20. The H is a value defined as (H1 mmol / g Х H1 wt% + H2 mmol / g Х H2 wt%), and V is a value defined as V mmol / g Х V wt%. In the above, H1mmol / g means mmol of Si-H (silicone-resin) per g of the curing agent included in the resin composition, H2mmol / g means mmol of Si-H (silicone-resin) per g of the chain extender included in the resin composition, and V mmol / g means mmol of Si-Vi (silicone-vinyl) per g of the silicone resin included in the resin composition. In the above, H1wt% means the weight fraction of the curing agent with respect to the weight of the entire resin composition, H2wt% means the weight fraction of the chain extender with respect to the weight of the entire resin composition, and V wt% means the weight fraction of the silicone resin with respect to the weight of the entire resin composition. In the above, the weight fraction of the entire resin composition is 100 wt%.

[0033] In one example, the resin composition may further include 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 curing retardant is 1-ethynyl-1-cyclohexanol, 3-methyl-1-penten-3-ol, 2-methyl-3-butyn-2-ol, 3-phenyl-3-butyn-2-ol, 2-phenyl-3-butyn-2-ol, 3,5-dimethyl-1-hexyn-3-ol, 1,5-hexadiine, 1,6-heptadiine, 3,5-dimethyl-1-hexyne, 2-ethyl-3-butyne, 2-phenyl-3-butyne, 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 The curing retardant 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 an amount of 0.1 to 10 parts by weight, 0.1 to 5 parts by weight, or 0.5 to 5 parts by weight, based on 100 parts by weight of the binder resin.

[0034] In one example, the resin composition may further include a flame retardant. The flame retardant may be a solid filler flame retardant or a liquid flame retardant. The liquid flame retardant can be suitably used when the amount of filler filled in the resin composition is large, and examples of representative liquid flame retardants include TEP and TCPP described below. The flame retardant may include an organic flame retardant, an inorganic flame retardant, and / or an organic-inorganic composite flame retardant. The organic flame retardant may include a phosphorus-based flame retardant and / or a melamine-based flame retardant. The inorganic flame retardant may include a metal hydroxide-based flame retardant. The organic-inorganic composite flame retardant may include a phosphorus-metal-based flame retardant.

[0035] In one example, the flame retardant may include at least one 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 flame retardant and a metal hydroxide flame retardant.

[0036] In one example, the surface of the flame retardant may have a coating layer. The coating layer may be appropriately selected considering the desired functionality 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, when the APP flame retardant has the coating layer, it may exhibit superior water resistance.

[0037] In one example, the flame retardant may be included in an amount 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 the binder resin.

[0038] In one example, the resin composition may further include a flame retardant additive. The flame retardant additive is an additive that can be added to the resin composition along with the flame retardant to further enhance the flame retardancy of the resin composition. For example, the flame retardant additive may include polytetrafluoroethylene (PTFE). The inclusion of a flame retardant in the resin composition may be advantageous in terms of improving the heat transfer delay time, suppressing cracking due to flame, and reducing the final insulation temperature.

[0039] 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 in manufacturing a heat-absorbing pad through curing, and the heat-absorbing 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. The lower limit of the viscosity of the above 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 from the viewpoint of the pad manufacturing process. The viscosity is measured using a Brookfield DV2T HB viscometer at a temperature of 25°C, a rotation speed of 1.2 rpm, and a shear rate (sec). -1 ) 2.4, may be a value measured under the conditions of spindle CPA 52Z.

[0040] In one example, the resin composition may be a room temperature curable resin composition. Accordingly, the resin composition may be cured by maintaining it at room temperature (e.g., about 20°C to 30°C), and may not require a separate process for curing, such as application of moisture, application of heat, or irradiation with active energy rays (e.g., ultraviolet rays). In addition, considering that the resin composition may be used as a heat-absorbing pad, including a heat-absorbing material, it may be more advantageous to be a room temperature curable type because it may be sensitive to heat that may accompany a phase change of the heat-absorbing material. In addition, the room temperature curable resin composition may also be advantageous when curing must be performed inside a battery. This is because applying heat to the battery for curing inside the battery may be dangerous. In addition, the room temperature curable resin composition may be advantageous in that the curing speed can be easily controlled because it can be cured by applying heat when necessary. That is, in this specification, the room temperature curable resin composition means a resin composition that can be cured even by maintaining it at room temperature, and is not limited to a resin composition that is cured only by maintaining it at room temperature.

[0041] The above-described heat-absorbing pad may have a heat transfer delay effect. In the present specification, the heat transfer delay effect may mean that when a flame is radiated to a single heat-absorbing pad (in a state where no other layers that affect the thermal characteristics of the heat-absorbing pad are laminated), the heat-absorbing pad absorbs heat and has a section in which the temperature of the heat-absorbing pad does not rise and is maintained for a certain period of time. When an heat-absorbing pad having a heat transfer delay effect is applied to a battery cell, even if the battery cell to which the heat-absorbing pad is applied ignites, the heat transfer to an adjacent battery cell can be effectively delayed. When describing the characteristics of the heat-absorbing pad with respect to a flame in the present specification, the flame may mean a flame caused by the combustion of LPG gas (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.

[0042] The fact that the absorbent pad has a heat transfer delay effect may mean that the absorbent pad has a heat transfer delay period. The heat transfer delay period may be defined as a continuous period in which the temperature change is less than 10°C or less than 5°C in a graph of temperature (°C) versus time (seconds) measured while applying a flame to the absorbent pad. The heat transfer delay period may be due to an endothermic reaction of the endothermic material. In one example, in a graph of temperature (°C) versus time (seconds) measured while applying a flame to the absorbent pad, a heat transfer delay period may appear after a temperature rise period. In the temperature rise period, 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 period. Thereafter, the temperature may be almost constant during the heat transfer delay period. After the heat transfer delay period, a temperature rise period may appear again. If a distinction is necessary, the temperature rise period before the heat transfer delay period can be referred to as the first temperature rise period, and the temperature rise period after the heat transfer delay period can be referred to as the second temperature rise period. After the second temperature rise period, the temperature can converge to a constant temperature again, and the temperature at this time can be referred to as the final adiabatic temperature. The final adiabatic temperature can appear, for example, at a time point of about 3 minutes, about 5 minutes, or about 10 minutes after irradiating the flame to the heat-absorbing pad.

[0043] In one example, the temperature of the heat transfer delay of the heat absorbing pad may be 50°C or higher. The temperature of the heat transfer delay 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 lower limit of the above thermal transfer delay temperature may be, for example, 300°C or less, 260°C or less, 240°C or less, 220°C or less, 200°C or less, 190°C or less, 180°C or less, 170°C or less, 160°C or less, 150°C or less, 140°C or less, 130°C or less, 120°C or less, 110°C or less, or 100°C or less. The above thermal transfer delay temperature may mean a part of the temperature in the thermal transfer delay section (for example, the temperature at the start time and / or the temperature at the end time of the thermal transfer delay section), or may mean the temperature in the entire time of the thermal transfer delay section. When the thermal transfer delay temperature is within the above range, it may be appropriate to delay rapid ignition by flame at the beginning by absorbing the initial heat generation amount when the battery cell explodes.

[0044] In one example, the heat transfer delay time of the heat absorption pad may be, for example, 5 seconds or longer. The heat transfer delay time may be 10 seconds or longer, 20 seconds or longer, 30 seconds or longer, 40 seconds or longer, 60 seconds or longer, 80 seconds or longer, 100 seconds or longer, 120 seconds or longer, 140 seconds or longer, 160 seconds or longer, 180 seconds or longer, or 200 seconds or longer. The longer the heat transfer delay time is advantageous, and the upper limit thereof is not particularly limited, but may be, for example, 60 minutes or shorter.

[0045] The absorbent pad may have irreversibility in which its shape does not return to its original state after heating and cooling. In one example, the XRD (X-ray diffraction) pattern of the absorbent pad measured after heating the absorbent pad to 200°C and cooling it to room temperature may be different from the XRD (X-ray diffraction) pattern of the absorbent pad before heating. The heating of the absorbent pad to 200°C may be maintained for about 60 minutes. The absorbent pad before heating refers to the absorbent 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 absorbent pad does not have the irreversibility, the XRD patterns before and after heating may be the same. Specifically, when an XRD analysis is performed on a heat-absorbing pad, a graph can be obtained in which the x-axis is 2θ (2Theta) and the y-axis is intensity (au) (θ is the incident angle of the diffracted X-ray, and intensity is the intensity of the diffracted X-ray). Multiple diffraction peaks appear in the graph, and a pattern can be obtained from these. 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.

[0046] 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. When the thickness of the heat-absorbing pad is within the above range, it may be advantageous in improving heat absorption performance and exhibiting excellent heat transfer delay characteristics. The upper limit of the thickness of the heat-absorbing pad may be appropriately adjusted in consideration of the battery module to which the pad is to be applied, and may be, 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. When the thickness of the pad is within the above range, it may be more advantageous in that it may exhibit a secondary temperature delay section.

[0047] The present application relates to the use of the resin composition and / or pad. In one example, the present application relates to a battery module comprising the resin composition and / or the pad. The present application also relates to a battery pack cover comprising the resin composition and / or the pad. The battery module or battery pack cover may comprise the resin composition in a cured state (i.e., a cured product of the resin composition).

[0048] The battery module may include a module case and battery cells. The battery cells may be housed within the module case. One or more battery cells may be present 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 particularly limited and may be adjusted depending on the purpose, etc. The battery cells housed within the module case may be electrically connected to each other. The type of battery cells housed within the module case is also not particularly limited, and various known battery cells may be applied. In one example, the battery cell may be pouch-type. A pouch-type battery cell may typically include an electrode assembly, an electrolyte, and a pouch outer material.

[0049] The module case may include at least a side wall and a bottom plate forming an internal space in which battery cells can be accommodated. In addition, the module case may further include an upper plate sealing the internal space. The side wall, the bottom plate, and the upper plate may be formed integrally with each other, or the module case may be formed by assembling separate side walls, bottom plates, and / or upper plates. The shape and size of the module case are not particularly limited and may be appropriately selected depending on the intended use or the shape and number of battery cells accommodated in the internal space. The terms upper plate and lower plate as used above are relative terms used to distinguish between at least two plates constituting the module case. In other words, it does not mean that the upper plate must be located at the upper side and the lower plate must be located at the lower side in an actual use state.

[0050] The resin composition and / or pad may be present on one side of the battery cell. When the battery module includes a plurality of battery cells, the resin composition and / or pad may be positioned between the battery cells. The resin composition and / or pad maintains its original shape without any change in state at the operating temperature of the battery, but when thermal runaway occurs, the resin composition and / or pad may provide a cooling effect to the ignition cell through a change in state and delay the transfer of heat to adjacent cells.

[0051] The heat-absorbing pad of the present invention can exhibit excellent heat absorption performance and excellent heat transfer delay characteristics. The heat-absorbing pad can be usefully used to delay heat transfer to adjacent battery cells during thermal runaway of a battery cell.

[0052] Hereinafter, the present application will be described in detail through examples according to the present application, but the scope of the present application is not limited by the examples presented below.

[0053] Measurement Example 1. Measurement of endothermic peak temperature and heat absorption amount

[0054] The endothermic peak temperature and heat absorption were measured using a differential scanning calorimeter (DSC Q2000, TA). Specifically, 3 mg to 5 mg of sample was placed in a pan and covered with a lid. The pan and lid were of the Tzero Hermetic type. A hole was drilled in the lid to prevent the pressure generated by the gas during heating. After stabilizing in an isothermal state at 0 °C for 3 minutes, DSC thermal analysis was performed while heating at a rate of 10 °C / min to 350 °C. Through DSC thermal analysis, a graph was obtained in which the x-axis is temperature (°C) and the y-axis is Heat Flow (W / g), and the endothermic peak temperature and heat absorption were derived from the graph.

[0055] Example 1

[0056] In a paste mixer container (Daehwa Tech, PDM-1K equipment), 100 parts by weight of silicone resin with a molecular weight of 18,000 g / mol (Andisil VS1000, AB Specialty Silicones) as the main resin, 13 parts by weight of random pendant type silicon-hydride (Andisil XL12, AB Specialty Silicones) as a curing agent, 400 parts by weight of Al2(SO4)3·18H2O particles (Daejung Chemicals), and 3 parts by weight of a dispersant (LP X 21879, BYK) were added and mixed at 600 rpm for 2 minutes. After confirming that the mixture was uniform, the particles were degassed for the first time and mixed at 600 rpm for 2 minutes at 200 rpm for 2 minutes. Afterwards, 0.3 parts by weight of a platinum catalyst (SRX-212, Dow Chemical Company) was added, and secondary defoaming was performed. The mixture was mixed for 2 minutes at a revolution of 600 rpm and a rotation of 200 rpm to prepare a resin composition. The endothermic peak temperature of Al2(SO4)3·18H2O is 103°C, and the endothermic amount is 740 J / g.

[0057] A frame-shaped silicone dam (the overall size of the dam is width X height = 12 cm X 12 cm, the size of the inside of the dam is width X height = 10 cm X 10 cm, and the height of the dam is 2 mm) was prepared on a fluorine release coating paper. The resin composition was applied inside the silicone dam and then covered with a fluorine release coating paper. The fluorine release coating paper was pressed with a glass plate and left at room temperature (25°C) for 24 hours to harden, thereby producing a pad of uniform thickness (2 mm).

[0058] Example 2

[0059] A resin composition was prepared in the same manner as in Example 1, except that 300 parts by weight of MgSO4·7H2O particles (Daejung Chemicals & Metals Co., Ltd.) were used instead of Al2(SO4)3·18H2O particles (Daejung Chemicals & Metals Co., Ltd.). Thereafter, a pad was manufactured in the same manner as in Example 1. The endothermic peak temperature of MgSO4·7H2O is 94°C, and the endothermic amount is 1150 J / g.

[0060] Example 3

[0061] A resin composition was prepared in the same manner as in Example 1, except that 250 parts by weight of AlCl3·6H2O particles (Daejung Chemicals & Metals Co., Ltd.) were mixed instead of Al2(SO4)3·18H2O particles (Daejung Chemicals & Metals Co., Ltd.). Thereafter, a pad was manufactured in the same manner as in Example 1. The endothermic peak temperature of AlCl3·6H2O is 186°C, and the endothermic amount is 1750 J / g.

[0062] Example 4

[0063] A resin composition was prepared in the same manner as in Example 1, except that 250 parts by weight of H3BO3 particles (Daejung Chemicals & Metals Co., Ltd.) were mixed instead of Al2(SO4)3·18H2O particles (Daejung Chemicals & Metals Co., Ltd.). Thereafter, a pad was manufactured in the same manner as in Example 1. The endothermic peak temperature of H3BO3 is 136°C, and the endothermic amount is 1133 J / g.

[0064] Comparative Example 1

[0065] A resin composition was prepared in the same manner as in Example 1, except that 200 parts by weight of Xylitol particles (Daejung Chemicals & Metals Co., Ltd.) were added instead of Al2(SO4)3·18H2O particles (Daejung Chemicals & Metals Co., Ltd.). Thereafter, a pad was manufactured in the same manner as in Example 1. The endothermic peak temperature of Xylitol is 94°C, and the endothermic amount is 250 J / g.

[0066] Comparative Example 2

[0067] A resin composition was prepared in the same manner as in Example 1, except that 200 parts by weight of zinc hydroxystannate particles (Shinseung Hichem Co., Ltd.) were added instead of Al2(SO4)3·18H2O particles (Daejung Chemicals & Metals Co., Ltd.). Thereafter, a pad was manufactured in the same manner as in Example 1. The endothermic peak temperature of zinc hydroxystannate is 250°C, and the endothermic amount is 350 J / g.

[0068] Comparative Example 3

[0069] A resin composition was prepared in the same manner as in Example 1, except that 300 parts by weight of Al(OH)3 particles (Chalco Qingdao) were used instead of Al2(SO4)3·18H2O particles (Daejung Chemicals & Metals Co., Ltd.). Thereafter, a pad was manufactured in the same manner as in Example 1. The endothermic peak temperature of Al(OH)3 is 298°C, and the endothermic amount is 1100 J / g.

[0070] Evaluation Example 1. Evaluation of thermal transfer delay characteristics

[0071] In the examples and comparative examples, the finally manufactured pads were cut into width X length = 6 cm X 6 cm and prepared as samples. SUS frames were attached to the front and back of the samples. The SUS frame has an overall size of width X length = 6 cm X 6 cm and has a hole of width X length = 5 cm X 5 cm, so the area where the flame actually touches the pad is width X length = 5 cm X 5 cm. The SUS frame prevents the sample from being bent by the flame. The pad with the SUS frame attached was vertically clamped to the jig (the main surface of the pad is perpendicular to the ground, and the thickness direction of the pad is parallel to the ground). A butane gas torch (butane gas: Sunlighter Gas 295ML, Taeyang Industry Co., Ltd., gas torch: 500JET, Honest Co., Ltd.) was placed on the first main surface side of the pad, and a thermal imaging camera (A655SC, FLIR Co., Ltd.) was placed on the second surface side of the pad opposite the first main surface. The pixel resolution of the thermal imaging camera is 640X480, and the upper limit of the measured temperature is 660℃. The gas torch was placed so that the flame-emitting part was at the center of the first main surface of the pad, and the lens of the thermal imaging camera was placed so that the lens of the thermal imaging camera was at the center of the second main surface of the pad. In addition, the distance between the first main surface of the pad and the flame-emitting part of the gas torch was about 3 cm, and the distance between the second main surface of the pad and the lens of the thermal imaging camera was 40 cm. The ambient temperature before the flame was emitted from the gas torch was about 25℃. The temperature of the pad's second surface was measured over time using a thermal imaging camera while the pad was heated by emitting a flame from a gas torch. The thermal imaging camera measures the infrared radiation emitted by the pad and calculates the temperature based on the measured infrared radiation value. The flame was emitted by the gas torch for 3 minutes. The temperature measured by the thermal imaging camera is the temperature at the highest point in the heated area of ​​the pad.

[0072] As described above, when a flame is applied to the pad, if the pad absorbs the heat and the temperature does not rise and is maintained for a certain period of time, it is evaluated that there is a heat transfer delay effect. Specifically, in the graph of the temperature (℃) of the pad against the measured time (second) when a flame is applied to the pad, a continuous section in which the temperature change is 5℃ or less can be defined as a heat transfer delay section, and the temperature at the end point of the heat transfer delay section is defined as the heat transfer delay temperature, and the time for which the heat transfer delay section is maintained is defined as the heat transfer delay time, and these are listed in Table 1 below.

[0073] Endothermic substanceEndothermic peak temperature (℃)Amount of heat absorbed (J / g)Heat transfer delay temperatureHeat transfer delay timeExample 1Al2(SO4)3·18H2O103740100℃130 secExample 2MgSO4·7H2O941150100℃70 secExample 3AlCl3·6H2O1861750190℃200 secExample 4H3BO31361133140℃100 secComparative Example 1Xylitol9425095℃15 secComparative Example 2Zinc hydroxystannate250350195℃20 secComparative Example 3Al(OH)32981100310℃50 sec

Claims

1. An absorbing pad including a cured product of a resin composition including an absorbing material and a binder resin having an absorbing amount of 500 J / g or more and an absorbing peak temperature of less than 200°C when measuring the absorbing amount while increasing the temperature from 0°C to 350°C at a rate of 10°C / min using a differential scanning calorimeter.

2. In the first paragraph, the heat absorbing material is a heat absorbing pad including a material that exists in a solid state at room temperature and undergoes a phase change from solid to liquid at a temperature below 200°C.

3. as per section 1, the thermal substance is H. 3 BO 3 , (NH 4 , 2 O 5B 2 O 3 ·8H 2 O, (Mg(H 2 PO 4 , 2 )·8H 2 MgCl2O 2 ·6H 2 O, AlCl 3 ·6H 2 O,Na 4 P 2 O 7 ·10H 2 O, KAl(SO 4 , 2 ·12H 2 O, NiSO 4 ·6H 2 Mg(NO 3 , 2 ·6H 2 O,CoSO 4 ·7H 2 O, (NH 4 , 2 Fe(SO 4 , 2 ·6H 2 O, CuSO 4 ·5H 2 O, ZnSO 4 ·7H 2 O, CoCl 2 ·6H 2 CrClO 3 ·6H 2 O, NiCl 2 ·6H 2 O, MgSO 4 ·7H 2 O,Al 2 (SO 4 , 3 ·18H 2 O,Na 2 B 4 O 7 ·10H 2 2Sr(OH) 2 ·8H 2 O, CaC 2 O 4 ·H 2 O, Ba(OH) 2 ·8H 2 O, Ba(OH) 2 ·H 2 O, Mg 3 (PO 4 ) 2 ·5H 2 O, Mg 3 (PO 4 ) 2 ·8H 2 O and FeSO 4 ·7H 2 A heat absorbing pad comprising at least one member selected from the group consisting of O.

4. An absorbent pad in accordance with claim 1, wherein the absorbent material has an absorbent peak temperature of 50°C or higher.

5. An absorbent pad in accordance with claim 1, wherein the absorbent material has an absorbent amount of 2,000 J / g or less.

6. In the first paragraph, the binder resin is a heat absorbing pad containing a silicone resin as the main resin.

7. A heat absorbing pad according to claim 6, wherein the binder resin further contains a curing agent.

8. A heat absorbing pad in accordance with claim 1, wherein the heat absorbing material is contained in an amount of 50 to 500 parts by weight relative to 100 parts by weight of the binder resin.

9. In the first paragraph, the heat absorbing pad has a thickness in the range of 1 mm to 10 mm.

10. A heat absorbing pad in accordance with claim 1, wherein the heat transfer delay temperature of the heat absorbing pad is in the range of 50°C to 200°C, and the heat transfer time of the heat absorbing pad is 30 seconds or longer.

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