Heat absorption pad

Abstract

The invention relates to a heat absorbing pad. The heat absorption pad of the present application can exhibit excellent heat absorption performance and excellent heat transfer delay characteristics. The heat absorbing pad may be usefully used to delay heat transfer to an adjacent battery cell when the battery cell is thermally runaway.

Description

Technical Field

[0001] This application relates to heat-absorbing pads. This application claims the benefit based on priority of Korean Patent Application No. 10-2023-0107271, dated August 16, 2023, and Korean Patent Application No. 10-2023-0107279, dated August 16, 2023, the disclosures of which are incorporated herein by reference in their entirety. Background Technology

[0002] Thermal runaway occurs when the thermal stability of the chemical substances inside a battery cell exceeds its limits, causing the cell to rapidly release internal energy to the outside. Thermal runaway is defined as a drop in the measured voltage of a battery cell and a measurement of temperature (dT / dt ≥ [4°C / sec]) exceeding the maximum operating temperature (approximately 120°C). Causes of thermal runaway include overcharging, impact / drop, thermal exposure, high voltage / current exposure, external / internal short circuits, etc. If thermal runaway begins, the internal pressure of the battery increases, flammable materials are ejected, and ignition occurs. This then heats adjacent battery cells and rapidly spreads into a fire. Battery fires are classified as electrical fires, and gas-based extinguishing equipment has been used. However, battery modules have metal protective caps, making it difficult for extinguishing agents to penetrate, and temperatures can rise to 1000°C in a short time during thermal runaway; therefore, extinguishing agents must be released at the onset of the fire. Therefore, in order to prevent thermal runaway, adequate cooling or complete elimination of fire at the onset of a fire is the ultimate way to extinguish it (Prior Art Document 1: Korean Patent Publication No. 10-2020-0107214).

[0003] Phase change materials (PCMs) are materials that provide heat and cooling by releasing and absorbing energy through phase changes. The latent heat caused by a phase change is higher than the sensible heat of the general. When they change from a solid or liquid to another state, they store and release a large amount of energy at the phase change temperature (PCT). PCMs are used in applications requiring energy storage and stable temperatures, such as heating pads, cooling devices, and clothing. Summary of the Invention

[0004] Technical issues

[0005] This application relates to a heat-absorbing pad. The heat-absorbing pad of this application can exhibit excellent heat absorption performance and excellent heat transfer delay characteristics. This heat-absorbing pad can be usefully used to delay heat transfer to adjacent battery cells in the event of thermal runaway of a battery cell.

[0006] Technical solution

[0007] This application relates to heat-absorbing pads. Heat-absorbing pads can have the property of absorbing heat generated in the surrounding environment. Heat-absorbing pads can comprise a heat-absorbing material and a binder resin. Heat-absorbing pads can comprise a resin composition containing a heat-absorbing material and a binder resin in a cured state. That is, heat-absorbing pads can comprise a cured product of the resin composition. The heat-absorbing pad can be the cured product of the resin composition itself. If it also includes other layers besides the cured product of the resin composition, it can be called a multilayer heat-absorbing pad.

[0008] Unless otherwise specified, the physical properties mentioned in this specification refer to those measured at room temperature and / or atmospheric pressure, where the effect of temperature and / or pressure on the results is the result of measurement at room temperature and / or normal pressure. In this specification, room temperature means natural temperature without heating or cooling, typically ranging from about 10°C to 30°C, from 20°C to 30°C, or around 23°C or 25°C. In this specification, unless otherwise explicitly defined, the unit of temperature is °C. In this specification, atmospheric pressure means natural pressure without pressurization or depressurization, typically meaning approximately one atmosphere at atmospheric pressure. In this specification, unless otherwise specified, the physical properties referred to as the effect of humidity on the results are those measured at room temperature and normal pressure under natural humidity conditions without separate control.

[0009] In this specification, endothermic material can refer to a substance that absorbs or consumes heat generated in the surrounding environment. Endothermic material can spontaneously undergo pyrolysis or generate new substances using the absorbed heat energy.

[0010] The resin composition may contain an endothermic substance that irreversibly undergoes an endothermic reaction. The endothermic substance can be a substance that reacts irreversibly upon heating and cooling. In one example, when the ambient temperature rises, the endothermic substance undergoes pyrolysis through endothermic absorption, and even when the ambient temperature decreases, it does not revert to its pre-pyrolysis state. This irreversibility can be advantageous in exhibiting excellent heat transfer delay characteristics. On the other hand, if the ambient temperature rises, paraffin, as a representative phase change material (PCM), absorbs heat and melts, thus becoming a liquid, while if the ambient temperature decreases, it releases heat, thus returning to a solid state. A phase change material is a material that reacts reversibly through endothermic and exothermic reactions. The resin composition may not contain any phase change material that reacts reversibly as described above.

[0011] The pyrolysis temperature of an endothermic substance can be 50°C or higher. The pyrolysis temperature of an endothermic substance can also be 300°C or lower. The pyrolysis temperature can also be referred to as the temperature at which an endothermic substance undergoes an endothermic reaction (endothermic reaction temperature). Pyrolysis can mean that when heat is applied to a material, it is chemically decomposed into simpler materials. The pyrolysis temperature can refer to the temperature at which pyrolysis occurs. The pyrolysis temperature of an endothermic substance can be 300°C or lower, 280°C or lower, 260°C or lower, 240°C or lower, 220°C or lower, 200°C or lower, 180°C or lower, 160°C or lower, 140°C or lower, 120°C or lower, or 100°C or lower. The pyrolysis temperature of an endothermic material can specifically 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, 120°C or higher, 140°C or higher, 160°C or higher, or 180°C or higher. When an endothermic material is heated to its pyrolysis temperature, it decomposes endothermically into its constituent components. When the pyrolysis temperature of the endothermic material is within this range, there is no or almost no endothermic reaction at the normal operating temperature of the battery, and if thermal runaway of the battery occurs, the endothermic reaction of the endothermic material (e.g., pyrolysis) can provide cooling to the ignited battery cell, and this can be advantageous in terms of delaying heat transfer to adjacent battery cells. The pyrolysis temperature can be a value measured simultaneously using a differential scanning calorimeter (DSC Q2000, TA Corporation) at a rate of 10°C / min. A graph can be obtained from a differential scanning calorimeter, in which the x-axis represents temperature (°C) and the y-axis represents heat flux (W / g). In this graph, the temperature at the point where the heat flux (W / g) value (e.g., the absolute value of heat flux (W / g)) is the largest can be set as the pyrolysis temperature.

[0012] The endothermic substance can be a water-soluble substance. A water-soluble substance can be defined as a substance whose solubility in water at 20°C is greater than 0 g / 100 ml. In one example, the solubility of the endothermic substance in water at 20°C can be 4.5 g / 100 ml or greater. Specifically, the solubility of the endothermic substance in water can be 5 g / 100 ml or greater, 10 g / 100 ml or greater, 15 g / 100 ml or greater, 20 g / 100 ml or greater, 25 g / 100 ml or greater, 30 g / 100 ml or greater, 35 g / 100 ml or greater, or 40 g / 100 ml or greater. The upper limit of the solubility of the endothermic substance in water can be, for example, 50 g / 100 ml or less. Solubility can be obtained by measuring the weight of the endothermic substance before precipitation occurs while adding 1 g of the endothermic substance to 100 ml of water at 20°C each time.

[0013] Endothermic materials can be thermally conductive. In one example, the thermal conductivity (λ) of an endothermic material can be 20 W / mK or less. When the thermal conductivity of an endothermic material is in this range, it can be advantageous in exhibiting excellent heat transfer delay characteristics. Specifically, the thermal conductivity of an endothermic material can 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 an endothermic material can be, for example, 0.001 W / mK or greater. Thermal conductivity (λ) is a value defined by thermal diffusivity (α) × specific heat (Cp) × density (ρ). Thermal conductivity (λ) can 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 most endothermic materials is known, and an endothermic material that meets that thermal conductivity can be used.

[0014] In one example, when performing thermal analysis using a differential scanning calorimeter at a rate of 10°C / min while heating from 0°C to 350°C, the endothermic peak temperature of the endothermic substance can be below 200°C. In this specification, the endothermic peak temperature can refer to the temperature at the point in a graph of heat flux (W / g) (y-axis) versus temperature (°C) (x-axis) obtained by thermal analysis using a differential scanning calorimeter, where the absolute value of the heat flux (W / g) is highest. The endothermic peak temperature can be, for example, 50°C or higher. When the endothermic peak temperature is within this range, it can be advantageous for exhibiting excellent heat transfer characteristics. The endothermic peak temperature can be specifically 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 can 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.

[0015] In one example, an endothermic substance may have a single endothermic peak (one endothermic peak) at temperatures below 200°C. In another example, an endothermic substance may have distributed endothermic peaks (two or three or more endothermic peaks) at temperatures below 200°C. Having two or three or more endothermic peaks can mean having one endothermic peak with the highest absolute heat flux (W / g) and one or two or more endothermic peaks with the second highest absolute heat flux (W / g). Given the same amount of heat absorption, an endothermic substance with a single peak may have better heat transfer delay characteristics. Examples of endothermic substances with a single peak include, for example, AlCl3·6H2O, MgSO4·7H2O, NiSO4·6H2O, Na4P2O7·10H2O, Sr(OH)2·8H2O, CaSO4·2H2O, etc.

[0016] In one example, the heat absorption of the endothermic substance can be 500 J / g or greater. In this specification, heat absorption can refer to the total heat (integral value on a DSC plot) from the point at which heat absorption begins to the point at which it ends. Specifically, heat absorption can be obtained by calculating the area of ​​the endothermic segment in a graph of heat flow (W / g) (y-axis) versus temperature (°C) (x-axis) obtained through thermal analysis using a differential scanning calorimeter (DSC). The endothermic segment can refer to the section in the graph from the onset temperature to the end temperature. This area can refer to the area of ​​the closed graph formed by the straight line (A) connecting the point at the onset temperature and the point at the end temperature, and the continuous graph (B) of the segment from the onset temperature to the end temperature. When the heat absorption at the endothermic peak is within this range, it can be beneficial to exhibit excellent heat transfer characteristics. The heat absorption can specifically be 600 J / g or greater, 700 J / g or greater, 800 J / g or greater, 900 J / g or greater, 1,000 J / g or greater, 1,100 J / g or greater, 1,200 J / g or greater, 1,300 J / g or greater, 1,400 J / g or greater, 1,500 J / g or greater, 1,600 J / g or greater, or 1,700 J / g or greater, and can be 2,000 J / g or less. The heat absorption can be a value measured while the temperature is increased at a rate of 10°C / min using a differential scanning calorimeter (DSC Q2000, TA Corporation).

[0017] The heat-absorbing material may comprise hydrate particles and / or solid acid particles. The resin composition and / or pad may comprise hydrate particles as the heat-absorbing material, or may comprise solid acid particles as the heat-absorbing material, or may comprise both hydrate particles and solid acid particles as the heat-absorbing material.

[0018] In one example, the endothermic material can be hydrate particles. Hydrate particles can refer to particles containing water molecules (H₂O). When hydrate particles are used as endothermic materials, water molecules can dissociate from the endothermic material through pyrolysis. This can be advantageous in exhibiting excellent heat transfer delay characteristics. Specifically, hydrate particles can be inorganic salts containing water molecules bound to the crystals of a metal compound. The water contained in hydrate particles can be referred to as water of crystallization. Hydrate particles differ from hydroxide particles, and hydroxide particles can refer to substances containing -OH (-hydroxyl groups) but not H₂O.

[0019] In one example, the hydrate particles may include particles selected from one or more of the following types: 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, CaC2O4·H2O, Ba(OH)2·8H2O, Ba(OH)2·H2O, Mg3(PO4)2·5H2O, Mg3(PO4)2·8H2O and FeSO4·7H2O.

[0020] In one example, the endothermic material can be solid acid particles. Solid acid particles can refer to solid acid particles that exist in a solid state at room temperature (approximately 25°C). When solid acids are used as endothermic materials, they can exhibit excellent heat transfer delay characteristics. As solid acids, solid acids that irreversibly undergo an endothermic reaction can be used. In one example, solid acid particles may include one or more types of particles selected from stearic acid, palmitic acid, boric acid, oxalic acid, tartaric acid, citric acid, and maleic acid.

[0021] In another example, the endothermic material can be a water microcapsule. The microcapsule may include a capsule portion and water contained within the capsule portion. The capsule portion may contain one or more of poly(vinyl alcohol), poly(ethylene oxide), polyethylene glycol, poly(methyl methacrylate), butyl acrylate, and silicates. The size of the microcapsule may, for example, range from 50 μm to 500 μm.

[0022] The content of the heat-absorbing material can be suitably selected without prejudice to the purpose of this application. In one example, the heat-absorbing material may be included in the range of 50 to 500 parts by weight relative to 100 parts by weight of the adhesive resin. The heat-absorbing material may be included in amounts 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 adhesive resin, and may also be included in amounts 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. This is suitable for manufacturing heat-absorbing pads with heat-absorbing particle content within this range and can be advantageous in exhibiting excellent heat transfer delay characteristics.

[0023] The binder resin may contain a main resin. The main resin may be a silicone resin. When a silicone resin is used as the main resin, it can advantageously exhibit excellent heat transfer delay characteristics. In particular, even when using an endothermic material containing water as the endothermic material, after mixing the main resin and the endothermic material, it will not change or produce water over time, thus exhibiting excellent heat transfer delay characteristics. Furthermore, while organic materials such as polyurethane resins or epoxy resins burn in a flame, silicone resins exhibit better flame resistance as the Si-O-Si siloxane chains are thermally converted to SiO2.

[0024] The silicone resin can be a silicone resin having vinyl groups at both ends. In one example, the silicone resin can be a polydimethylsiloxane having vinyl groups at both ends. The silicone resin can be a compound represented by Formula 1 below. In Formula 1 below, n can be an integer of 1 or greater, and can be appropriately selected taking into account the molecular weight of the silicone resin.

[0025] [Formula 1]

[0026]

[0027] The molecular weight of the silicone resin can be selected within a range that does not impair the purpose of this 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 can be 100,000 g / mol or less. When the molecular weight of the silicone resin is within this range, the heat resistance is improved, which can be more advantageous in exhibiting excellent heat transfer delay characteristics. Specifically, the molecular weight of the silicone resin can 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. For the treatment of the manufactured pads, the lower limit of the molecular weight of the silicone resin can be 100 g / mol or greater, 500 g / mol or greater, or 1,000 g / mol.

[0028] The viscosity of the silicone resin can be selected within a range that does not impair the purpose of this application. In one example, the viscosity of the silicone resin can be 150,000 cSt or less. When the viscosity of the silicone resin is in this range, it can be more advantageous in exhibiting excellent heat transfer delay characteristics. Specifically, the viscosity of the silicone resin can 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. From a pad manufacturing perspective, the lower limit of the viscosity of silicone resin can be 5 cSt or greater, 10 cSt or greater, 20 cSt or greater, 40 cSt or greater, 60 cSt or greater, 80 cSt or greater, or 100 cSt or greater. Regarding the viscosity of silicone resin, in the case of commercially available products, the seller provides information on viscosity. Therefore, silicone resin products that meet this viscosity can be selected and used, and the viscosity measurement conditions can also follow those provided by the silicone resin seller. In one example, the viscosity of the silicone resin can be the value measured using a BROOKFIELD DV-II+ viscometer at a temperature of 25°C, a rotation speed of 10 rpm, and a No. 6 rotor.

[0029] The adhesive resin may also contain a curing agent. As a curing agent, a curing agent suitable for curing the main resin may be used. In one example, when the main resin is a silicone resin, a silane compound may be used as the curing agent. A silane compound may refer to a compound having -SiH (silane-hydride). -SiH can react with the vinyl groups of the silicone resin. The silane compound may be a polydimethylsiloxane in which at least one -CH3 terminal and / or side chain is replaced by -H. In one example, the curing agent may be a side-chain type (side-hanging) curing agent. A side-chain type curing agent may be a polydimethylsiloxane in which at least one -CH3 terminal of the side chain is replaced by -H and both terminals are -CH3. In another example, the curing agent may be a hybrid curing agent. A hybrid curing agent may be a polydimethylsiloxane in which two terminal -CH3 terminals are replaced by -H and at least one -CH3 terminal of the side chain is also replaced by -H.

[0030] In one example, the curing agent can be included in the resin composition with an H / V ratio ranging from 1 to 20. H is defined as H mmol / g × H wt% and V is defined as V mmol / g × V wt%. Here, H mmol / g means mmol of Si-H (silicon-hydrogen) per g of curing agent contained in the resin composition, and V mmol / g means mmol of Si-Vi (silicon-vinyl) per g of silicone resin contained in the resin composition. Here, H wt% means the weight fraction of the curing agent relative to the total weight of the resin composition, and V wt% means the weight fraction of the silicone resin relative to the total weight of the resin composition. Here, the total weight fraction of the resin composition is 100 wt%.

[0031] The resin composition may be free of amine compounds and isocyanate compounds. Amine compounds and isocyanate compounds may not be suitable for formulation with endothermic substances containing water. When using epoxy resin as the main resin, the amine compound can be a curing agent, and when using polyol resin as the main resin, the isocyanate compound can be a curing agent. According to this application, epoxy resin and polyol resin may not be included as the main resin.

[0032] The heat-absorbing pad and / or resin composition may also contain a catalyst. The catalyst can promote the reaction between the main resin and the curing agent. In one example, the catalyst can promote a hydrosilylation addition reaction between the carbon-carbon double bond of the silicone resin and the -SiH group of the curing agent. In one example, the catalyst may be a platinum group catalyst. Platinum group catalysts may include platinum-based metal catalysts, palladium-based metal catalysts, rhodium-based metal catalysts, or mixtures thereof. In another example, the catalyst may be a metal salt catalyst. Metal salt catalysts may include tin-based metal salts such as bis(2-ethylhexanoate)tin and dibutyldilauryltin, zinc-based metal salts such as zinc octoate, iron-based metal salts such as iron octoate, or mixtures thereof. The catalyst may be included in amounts from 0.01 parts by weight to 10 parts by weight, 0.01 parts by weight to 5 parts by weight, 0.01 parts by weight to 3 parts by weight, 0.01 parts by weight to 1 part by weight, or 0.01 parts by weight to 0.5 parts by weight relative to 100 parts by weight of the adhesive resin.

[0033] In addition to the main resin, curing agent, and catalyst, the resin composition may also contain additives. In one example, the resin composition may also contain a dispersant. As a dispersant, for example, an amino silicone dispersant may be used. The dispersant may be included in the range of 0.1 parts by weight to 10 parts by weight, 0.1 parts by weight to 5 parts by weight, or 0.5 parts by weight to 5 parts by weight relative to 100 parts by weight of the adhesive resin.

[0034] In one example, the resin composition may also contain a chain extender. As a chain extender, for example, a compound having -SiH (silicon-hydride) at both ends can be used. -SiH can react with the vinyl groups of the silicone resin. In one example, the chain extender can be a polydimethylsiloxane in which the -CH3 at both ends is replaced by -H and the side chain is -CH3. When the resin composition contains both a curing agent and a chain extender, the curing agent and the chain extender can be included in the resin composition such that the H / V ratio is in the range of 1 to 20. H is defined as a value of (H1 mmol / g × H1 wt% + H2 mmol / g × H2 wt%), and V is defined as a value of V mmol / g × V wt%. Here, H1 mmol / g refers to the mmol of Si-H (silicone-resin) per gram of curing agent contained in the resin composition, H2 mmol / g refers to the mmol of Si-H (silicone-resin) per gram of chain extender contained in the resin composition, and V mmol / g refers to the mmol of Si-Vi (silicone-vinyl) per gram of silicone resin contained in the resin composition. Here, H1 wt% refers to the weight fraction of the curing agent relative to the total weight of the resin composition, H2 wt% refers to the weight fraction of the chain extender relative to the total weight of the resin composition, and V wt% refers to the weight fraction of the silicone resin relative to the total weight of the resin composition. Here, the total weight fraction of the resin composition is 100 wt%.

[0035] In one example, the resin composition may also contain a curing retarder. The curing retarder may be, for example, a compound having carbon-carbon double or triple bonds. The curing retarder may be selected from 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-hexadiyne, 1,6-heptadiyne, 3,5-dimethyl-1-hexyne, 2-ethyl-3-butyne, 2-phenyl-3- The adhesive may contain, but is not limited to, one or more of 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 divinyl-1,1,3,3-tetramethyldisilazane. The curing delay agent 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 relative to 100 parts by weight of the adhesive resin.

[0036] In one example, the resin composition may also contain a flame retardant. The flame retardant may be a solid filler-type flame retardant or a liquid flame retardant. When the amount of filler in the resin composition is large, a liquid flame retardant may be suitably used, and, for example, TEP, TCPP, etc., described below are representative liquid flame retardants. Flame retardants 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.

[0037] In one example, the flame retardant may include one or more of the following: 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 diethylphosphinate. According to one example of this application, the flame retardant may include phosphorus-based flame retardants and metal hydroxide flame retardants.

[0038] In one instance, a coating may also be present on the surface of the flame retardant. The coating can be appropriately selected considering the function to be added to the flame retardant. The coating may include, for example, one or more selected from silicone-based coatings, epoxy resin-based coatings, and melamine-based coatings. As a specific example, when the APP flame retardant has a coating, it can exhibit better water resistance.

[0039] In one instance, the flame retardant may be included in the range of 10 to 300 parts by weight, 10 to 200 parts by weight, or 30 to 150 parts by weight relative to 100 parts by weight of the adhesive resin.

[0040] In one example, the resin composition may also contain a flame retardant additive. The flame retardant additive is an additive that can be added to the resin composition together with a flame retardant to further improve the flame retardancy of the resin composition; it may include, for example, PTFE (polytetrafluoroethylene). When the resin composition also contains a flame retardant, it can be advantageous in terms of improving heat transfer delay time, inhibiting the initiation of cracks due to flame, and reducing the final insulation temperature.

[0041] In one example, the viscosity of the resin composition can be 500,000 cps or less. When the viscosity of the resin composition is in this range, it can be advantageous in manufacturing heat-absorbing pads by curing, and the heat-absorbing pads manufactured therefrom can exhibit excellent heat transfer delay characteristics. Specifically, the viscosity of the resin composition can 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 pad manufacturing process, the lower limit of the viscosity of the above resin composition can be 1,000 cps or greater, 5,000 cps or greater, 10,000 cps or greater, 30,000 cps or greater, or 50,000 cps or greater. Viscosity can be measured using a Brookfield DV2THB viscometer at a temperature of 25°C, a rotation speed of 1.2 rpm, and a shear rate of 2.4 (seconds). -1 The values ​​were measured under the conditions of rotor CPA 52Z.

[0042] In one example, the resin composition can be a room-temperature curing resin composition. Therefore, the resin composition can be cured by keeping it at room temperature (e.g., about 20°C to 30°C), and separate curing processes such as applying moisture, applying heat, or irradiation with active energy rays (e.g., ultraviolet light) are not required. Furthermore, considering that the resin composition can be used as a heat-absorbing pad by containing an endothermic material, it may be thermally sensitive to the potential phase change associated with the endothermic material, making it more advantageous to be room-temperature curing. Additionally, in the case of a room-temperature curing resin composition, it is also advantageous when curing must take place inside the battery. This is because applying heat to the battery to cure it inside could be dangerous. Furthermore, in the case of a room-temperature curing resin composition, the curing rate can be easily adjusted because it can be cured by applying heat if necessary. That is, in this specification, a room-temperature curing resin composition means a resin composition that can be cured even by keeping it at room temperature, and is not limited to resin compositions that are cured solely by keeping them at room temperature.

[0043] The heat-absorbing pad can have a heat transfer delay effect. In this specification, a heat transfer delay effect can mean that when a flame has radiated onto a single heat-absorbing pad (where there are no other layers laminated thereto that affect the thermal properties of the heat-absorbing pad), the heat-absorbing pad has a section in which its temperature does not rise due to heat absorption and is maintained for a certain period of time. When a heat-absorbing pad with a heat transfer delay effect is applied to a battery cell, even if the battery cell with the heat-absorbing pad ignites, heat can be effectively delayed in transferring to adjacent battery cells. In this specification, when explaining the characteristics of the heat-absorbing pad to a flame, a flame can mean a flame produced by the combustion of LPG (liquefied petroleum gas) or butane gas. The flame temperature can be, for example, about 1000°C or higher. The upper limit of the flame temperature can be, for example, 2000°C or lower, or 1500°C or lower.

[0044] The presence of a heat transfer delay effect in an absorbent pad can be understood as the pad exhibiting a heat transfer delay segment. This delay segment can be defined as a continuous segment in a graph of temperature (°C) versus time (seconds) measured simultaneously with the application of a flame to the absorbent pad, where the temperature change is less than 10°C, or 5°C or less. The delay segment may be caused by the endothermic reaction of the absorbent material. In one example, in a graph of temperature (°C) versus time (seconds) measured simultaneously with the application of a flame to the absorbent pad, the delay segment may appear after a temperature rise segment. In the temperature rise segment, the initial temperature (temperature at 0 seconds) is approximately 25°C, and the temperature can increase almost linearly until the start of the delay segment. Afterward, the temperature can remain almost constant within the delay segment. Another temperature rise segment may appear after the delay segment. If a distinction is necessary, the temperature rise segment before the delay segment can be referred to as the first temperature rise segment, and the temperature rise segment after the delay segment can be referred to as the second temperature rise segment. After the second temperature rise phase, it can converge again to a constant temperature, which can also be referred to as the final adiabatic temperature. The final adiabatic temperature can occur, for example, at a time point of about 3 minutes, about 5 minutes, or about 10 minutes after the flame radiates onto the heat-absorbing pad.

[0045] In one example, the heat transfer delay temperature of the heat-absorbing pad can be 50°C or higher. The heat transfer delay temperature can 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 heat transfer delay temperature can 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 heat transfer delay temperature mentioned above can refer to a portion of the temperature within the heat transfer delay segment (e.g., the start and / or end time temperature of the heat transfer delay segment), or it can refer to the temperature over the entire duration of the heat transfer delay segment. When the heat transfer delay temperature is within this range, it may be appropriate to delay the initial rapid ignition caused by the flame by absorbing the initial heat generated by the explosion of the battery cells within it.

[0046] In one example, the heat transfer delay time of the heat-absorbing pad can be, for example, 5 seconds or longer. The heat transfer delay time can 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. A longer heat transfer delay time is more advantageous, and there is no particular upper limit, but it can be, for example, 60 minutes or less.

[0047] An absorber pad can possess irreversibility, meaning its shape does not recover after heating and cooling. In one example, the XRD (X-ray diffraction) pattern of an absorber pad measured after heating it to 200°C and then cooling it to room temperature may differ from the XRD pattern of the absorber pad before heating. The absorber pad can be heated to 200°C and held for approximately 60 minutes. "Absorber pad before heating" refers to an absorber pad at room temperature without heating. Room temperature can be, for example, in the range of 20°C to 30°C, or approximately 25°C. If the absorber pad is not irreversible, the XRD patterns before and after heating can be identical. Specifically, when performing XRD analysis on an absorber pad, a plot can be obtained where the x-axis is 2θ (2 thera) and the y-axis is intensity (au) (θ is the incident angle of the diffracted X-rays, and intensity is the intensity of the diffracted X-rays). Multiple diffraction peaks can appear in the plot, from which patterns can be obtained. Different XRD patterns can mean that at least one of the multiple diffraction peaks is absent. Identical XRD patterns can mean that multiple diffraction peaks appear in the same manner.

[0048] In one example, the thickness of the heat-absorbing pad can be, for example, 0.5 mm or greater. Specifically, the thickness of the heat-absorbing pad can be 1 mm or greater, 1.5 mm or greater, 2 mm or greater, 2.5 mm or greater, or 3 mm or greater. When the thickness of the heat-absorbing pad is within this range, it can be advantageous in terms of improving heat absorption performance and exhibiting excellent heat transfer delay characteristics. The upper limit of the thickness of the heat-absorbing pad can be appropriately adjusted considering the battery module to which the pad is to be applied, and can 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 can 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 this range, it can be more advantageous because it can exhibit a secondary temperature delay segment.

[0049] This application relates to the use of resin compositions and / or pads. In one example, this application relates to a battery module comprising a resin composition and / or pad. Furthermore, this application relates to a battery pack cover comprising a resin composition and / or pad. The battery module or battery pack cover may contain a resin composition in a cured state (i.e., a cured product of the resin composition).

[0050] A battery module may include a module housing and battery cells. The battery cells may be housed within the module housing. One or more battery cells may be present in the module housing, and a plurality of battery cells may be housed within the module housing. The number of battery cells housed in the module housing is adjusted according to the application, etc., and is not particularly limited. The battery cells housed in the module housing may be electrically connected to each other. There is also no particular limitation on the type of battery cells housed in the module housing, and all known battery cells can be used. In one example, the battery cell may be pouch-shaped. Pouch-shaped battery cells typically include electrode assemblies, electrolyte, and external pouch material.

[0051] The module housing may include at least sidewalls and a bottom plate forming an internal space therein for accommodating battery cells. Furthermore, the module housing may also include a top plate that seals the internal space. The sidewalls, bottom plate, and top plate may be integrally formed with each other, or the module housing may be formed by assembling separate sidewalls, bottom plates, and / or top plates. There are no particular limitations on the shape and size of such a module housing, which may be appropriately selected depending on the application or the shape and number of battery cells housed in the internal space. Here, since there are at least two plates constituting the module housing, the terms top plate and bottom plate are used to distinguish them as relative concepts. That is, in practical use, this does not mean that the top plate must be at the top and the bottom plate must be at the bottom.

[0052] The resin composition and / or pad may be present on one side surface of the battery cell. When the battery module comprises a plurality of battery cells, the resin composition and / or pad may be disposed between the battery cells. The resin composition and / or pad retain their original form without change of state at the battery operating temperature, and then, in the event of thermal runaway, can provide cooling to the ignited cell and delay the transfer of heat to adjacent cells through change of state.

[0053] Beneficial effects

[0054] The heat-absorbing pad of this application exhibits excellent heat absorption performance and excellent heat transfer delay characteristics. This heat-absorbing pad can be usefully used to delay heat transfer to adjacent battery cells during thermal runaway of a battery cell. Detailed Implementation

[0055] In the following description, the present application will be specifically described by way of embodiments thereof, but the scope of the present application is not limited to the embodiments presented below.

[0056] Example 1

[0057] In a paste mixer (Daehwa Tech, PDM-1K equipment), 88.5 parts by weight of silicone resin with a molecular weight of 18,000 g / mol (Andisil VS1000, AB Specialty Silicones) and 11.5 parts by weight of random side-attached hydride curing agent (Andisil XL12, AB Specialty Silicones) were added to obtain 100 parts by weight of binder resin. 400 parts by weight of KAl(SO4)2·12H2O particles (Daejung Chemicals & Metals) and 3 parts by weight of dispersant (LP X 21879, BYK) were added to the 100 parts by weight of binder resin, and the mixture was stirred for 2 minutes at 600 rpm revolution and 500 rpm rotation. After confirming uniform mixing, the particles were defoamed once and stirred for 2 minutes at 600 rpm revolution and 200 rpm rotation. Subsequently, 0.3 parts by weight of a platinum-based catalyst (SRX-212, Dow Chemical) was added and subjected to secondary defoaming to mix the mixture for 2 minutes at 600 rpm revolution and 200 rpm rotation, thereby preparing the resin composition.

[0058] A frame-shaped silicone dam (total dimensions of the dam being width × length = 12 cm × 12 cm, internal dimensions of the dam being width × length = 10 cm × 10 cm, and a height of 2 mm) was prepared on fluorinated release-coated paper. A resin composition was applied to the interior of the silicone dam, which was then covered with fluorinated release-coated paper. After pressing the fluorinated release-coated paper with a glass plate, it was left to cure at room temperature (25°C) for 24 hours to produce a pad with a uniform thickness (2 mm).

[0059] Example 2

[0060] The resin composition and pad were prepared in the same manner as in Example 1, except that 250 parts by weight of MgCl2·6H2O particles (Daejung Chemicals & Metals) were prepared instead of KAl(SO4)2·12H2O particles (Daejung Chemicals & Metals).

[0061] Example 3

[0062] The resin composition and pad were prepared in the same manner as in Example 1, except that 300 parts by weight of MgSO4·7H2O particles (Daejung Chemicals & Metals) were prepared instead of KAl(SO4)2·12H2O particles (Daejung Chemicals & Metals).

[0063] Example 4

[0064] The resin composition and pad were prepared in the same manner as in Example 1, except that 250 parts by weight of AlCl3·6H2O particles (Daejung Chemicals & Metals) were prepared instead of KAl(SO4)2·12H2O particles (Daejung Chemicals & Metals).

[0065] Example 5

[0066] The resin composition and pad were prepared in the same manner as in Example 1, except that 400 parts by weight of Al2(SO4)3·18H2O particles (Daejung Chemicals & Metals) were prepared instead of KAl(SO4)2·12H2O particles (Daejung Chemicals & Metals).

[0067] Example 6

[0068] The resin composition and pad were prepared in the same manner as in Example 1, except that 300 parts by weight of Sr(OH)2·8H2O particles (Junsei) were prepared instead of KAl(SO4)2·12H2O particles (Daejung Chemicals & Metals).

[0069] Example 7

[0070] The resin composition was prepared in the same manner as in Example 1. Subsequently, the pad was manufactured in the same manner as in Example 1, except that the thickness of the pad was changed to 1 mm by using an organosilicon dam with a height of 3 mm.

[0071] Example 8

[0072] The resin composition was prepared in the same manner as in Example 1. Subsequently, the pad was manufactured in the same manner as in Example 1, except that the thickness of the pad was changed to 3 mm by using an organosilicon dam with a height of 4 mm.

[0073] Example 9

[0074] The resin composition and pad were prepared in the same manner as in Example 1, except that 230 parts by weight of H3BO3 particles (Daejung Chemicals & Metals) were used instead of KAl(SO4)2·12H2O particles (Daejung Chemicals & Metals).

[0075] Comparative Example 1

[0076] The resin composition was prepared in the same manner as in Example 1. Subsequently, the pad was manufactured in the same manner as in Example 1, except that the thickness of the pad was changed to 0.5 mm by using an organosilicon dam with a height of 0.5 mm.

[0077] Comparative Example 2

[0078] The resin composition and pad were prepared in the same manner as in Example 1, except that 300 parts by weight of Al(OH)3 particles (H-WF-75, Chalco) were prepared instead of KAl(SO4)2·12H2O particles (Daejung Chemicals & Metals).

[0079] Comparative Example 3

[0080] The resin composition and pad were prepared in the same manner as in Example 1, except that 200 parts by weight of Mg(OH)2 particles (Zerogen 100SP, Huber Materials) were prepared instead of KAl(SO4)2·12H2O particles (Daejung Chemicals & Metals).

[0081] Comparative Example 4

[0082] The resin composition and pad were prepared in the same manner as in Example 1, except that 500 parts by weight of Al2O3 particles (BAK-70, Shanghai Bestry Performance Materials) were prepared instead of KAl(SO4)2·12H2O particles (Daejung Chemicals & Metals).

[0083] Comparative Example 5

[0084] The resin composition and pad were prepared in the same manner as in Example 1, except that 200 parts by weight of MgO particles (magnesium oxide, Sigma Aldrich) were prepared instead of KAl(SO4)2·12H2O particles (Daejung Chemicals & Metals).

[0085] Comparative Example 6

[0086] The resin composition and pad were prepared in the same manner as in Example 1, except that 200 parts by weight of Al particles (CNPC-Al5, CNPC POWDER) were prepared instead of KAl(SO4)2·12H2O particles (Daejung Chemicals & Metals).

[0087] Comparative Example 7

[0088] The resin composition and pad were prepared in the same manner as in Example 1, except that 200 parts by weight of Cu particles (CNPC-UCu100, CNPC POWDER) were used instead of KAl(SO4)2·12H2O particles (Daejung Chemicals & Metals).

[0089] Comparative Example 8

[0090] Manufacture a 2 mm thick polyurethane foam pad without the application of heat-absorbing particles. The polyurethane foam pad used is a product mass-produced by LG Chemical for battery modules.

[0091] Comparative Example 9

[0092] Manufacture a 2 mm thick silicone foam pad without the application of heat-absorbing particles. The silicone foam pad used is a product mass-produced by LG Chemical for battery modules.

[0093] Evaluation Example 1. Evaluation of Heat Transfer Delay Characteristics

[0094] The mats ultimately manufactured in the examples and comparative examples were cut into width × length = 6 cm × 6 cm and prepared as samples. SUS frames were attached to the front and back of the samples. The SUS frames prevented the samples from being bent by the flame. The mats with attached SUS frames were vertically secured to the fixture using clamps (the main surface of the mat was perpendicular to the ground, and the thickness direction of the mat was horizontal to the ground). A butane gas torch (butane gas: Sun Lighter Gas 295ML, TAEYANG; gas torch: 500JET, Honest) was positioned on the first main surface side of the mat, and a thermal imaging camera (A655SC, FLIR) was positioned on the second surface side of the mat opposite to the first main surface. The thermal imaging camera had a pixel resolution of 640 × 480 and an upper limit for measuring temperature of 660°C. The gas torch was positioned such that the portion of its flame radiation was located at the center of the first main surface of the mat, and the thermal imaging camera was positioned such that its lens was located at the center of the second main surface of the mat. Furthermore, the distance between the first main surface of the pad and the portion radiated by the flame from the gas torch is approximately 3 cm, and the distance between the second main surface of the pad and the lens of the thermal imaging camera is 40 cm. The ambient temperature before the flame is radiated from the gas torch is approximately 25°C. While the pad is heated by radiating the flame from the torch, the temperature of the second main surface of the pad changes over time using the thermal imaging camera. The thermal imaging camera measures the infrared radiant heat emitted by the pad and calculates the temperature based on the measured infrared radiant heat value. The time used for radiating the flame from the gas torch is set to 3 minutes. The temperature measured by the thermal imaging camera is the temperature at the highest temperature point in the heated portion of the pad.

[0095] When a flame is applied to the pad as described above, and the pad absorbs heat to maintain its temperature for a certain period of time without rising, it is evaluated as having a heat transfer delay effect. Specifically, in the temperature (°C) graph of the pad against measurement time (seconds) when a flame is applied to the pad, a continuous segment in which the temperature changes by 5°C or less can be defined as a heat transfer delay segment, the temperature at the end of the heat transfer delay segment can be defined as the heat transfer delay temperature, and the time during which the heat transfer delay segment is maintained can be defined as the heat transfer delay time, as described in Table 1 below.

[0096] [Table 1]

[0097]

Claims

1. A heat absorbing pad comprising a cured product of a resin composition containing a heat absorbing substance and a binder resin, wherein the heat absorbing substance is a hydrate particle or a solid acid particle, the binder resin contains a silicone resin as a main resin, and the thickness of the heat absorbing pad is 1 mm or more.

2. The heat absorbing pad according to claim 1, wherein the heat absorbing substance has a pyrolysis temperature in the range of 50°C to 300°C.

3. The heat absorbing pad according to claim 1, wherein the heat absorbing substance is a hydrate particle, and the hydrate particle includes one or more selected from the group consisting of 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, CaC2O4-H2O, Ba(OH)2-8H2O, Ba(OH)2-H2O, Mg3(PO4)2-5H2O, Mg3(PO4)2-8H2O, and FeSO4-7H2O.

4. The heat absorbing pad according to claim 1, wherein the heat absorbing substance is a solid acid particle, and the solid acid particle includes one or more particles selected from the group consisting of stearic acid, palmitic acid, boric acid, oxalic acid, tartaric acid, citric acid, and maleic acid.

5. The heat absorbing pad according to claim 1, wherein the heat absorbing substance is contained in the range of 50 parts by weight to 500 parts by weight with respect to 100 parts by weight of the binder resin.

6. The heat absorbing pad according to claim 1, wherein the silicone resin is a silicone resin having a vinyl group at both terminals.

7. The heat absorbing pad according to claim 1, wherein the silicone resin has a molecular weight in the range of 500 g / mol to 30,000 g / mol.

8. The heat absorbing pad according to claim 1, wherein the thickness of the heat absorbing pad is 10 mm or less.

9. The heat absorbing pad according to claim 1, wherein the heat transfer delay temperature of the heat absorbing pad is 300°C or less.

10. The heat absorbing pad according to claim 1, wherein the heat transfer delay time of the heat absorbing pad is 60 seconds or more.

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