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 of priority based on Korean Patent Application No. 10-2023-0107276 and Korean Patent Application No. 10-2023-0107279, both 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 contain heat-absorbing materials. Heat-absorbing pads can also contain adhesive resins. In one example, a heat-absorbing pad can contain a resin composition in a cured state containing a heat-absorbing material and an adhesive resin. That is, the heat-absorbing pad can contain 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 referred to as 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 heat-absorbing pad and / or resin composition may contain an endothermic material that irreversibly undergoes an endothermic reaction. The endothermic material can be a substance that reacts irreversibly upon heating and cooling. In one example, when the ambient temperature rises, the endothermic material undergoes pyrolysis through endothermic absorption and does not revert to its pre-pyrolysis state even when the ambient temperature decreases. Pyrolysis can mean that when heat is applied to the material, it is chemically broken down into simpler materials. This irreversibility can be advantageous in exhibiting excellent heat transfer delay characteristics. On the other hand, paraffin, as a representative phase change material (PCM), absorbs heat and melts if the ambient temperature rises, thus becoming liquid, while releasing heat if the ambient temperature decreases, 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 endothermic substance exists as a solid at room temperature, and a phase transition from solid to liquid can occur at temperatures below 200°C. In this specification, the occurrence of a phase transition from solid to liquid can refer to the phenomenon where water molecules separate (dissociate) from the endothermic substance when it is heated. The temperature at which the endothermic substance undergoes a phase change from solid to liquid 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 50°C or higher, 60°C or higher, 70°C or higher, 80°C or higher, 90°C or higher, 100°C or higher, 110°C or higher, 120°C or higher, 130°C or higher, 140°C or higher, 150°C or higher, 160°C or higher, 170°C or higher, 180°C or higher, or 190°C or higher.

[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 endothermic substance may comprise water-containing materials and / or solid acids. Water-containing materials may include hydrate particles and / or water microcapsules. Solid acids may comprise solid acid particles that are solid at room temperature, for example, at about 25°C.

[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 instance, the endothermic material can be solid acid particles. Solid acids can include, for example, H3BO3 particles.

[0020] In one instance, the hydrate particles may comprise particles selected from one or more of the following types: 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, Na2B4O7·10H 2O, 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.

[0021] In one example, the endothermic material may 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 polydimethylsiloxane with vinyl groups at both ends. The silicone resin can be a compound represented by Formula 1 below. In Formula 1, n can be an integer of 1 or greater, and can be appropriately selected considering 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 or a silanol compound may be used as the curing agent. A silane compound may refer to a compound having a -SiH (silicon-hydride) group. A silanol compound may refer to a compound having a -Si-OH (silicon-hydride) group. The -SiH or -Si-OH group may react with the vinyl group 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 heat-absorbing pad and / or resin composition may not contain amine compounds and isocyanate compounds. Amine compounds and isocyanate compounds may not be suitable for formulation with water-containing heat-absorbing materials. When epoxy resin is used as the main resin, the amine compound can be a curing agent, and when polyol resin is used 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 another example, the catalyst can also promote the reaction between the carbon-carbon double bond of the silicone resin and the -Si-OH group of the curing agent. In one example, the catalyst may be a platinum group catalyst. 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 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 relative to 100 parts by weight of the binder resin.

[0033] In addition to the main resin, curing agent, and catalyst, the heat-absorbing pad and / or 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 may 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 may 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] Measurement Example 1. Measurement of Endothermic Peak Temperature and Heat Absorption

[0057] The endothermic peak temperature and endothermic heat were measured using a differential scanning calorimeter (DSC Q2000, TA). Specifically, 3 mg to 5 mg of sample were placed in a dish and covered with a lid. The dish and lid were Tzero-sealed. A hole was drilled in the lid due to the pressure caused by the gas generated during temperature increase. The sample was then stabilized isothermally at 0 °C for 3 minutes, and then DSC thermal analysis was performed while the temperature was increased to 350 °C at a rate of 10 °C / min. The endothermic peak temperature and endothermic heat were obtained from the DSC thermal analysis, where the x-axis represents temperature (°C) and the y-axis represents heat flux (W / g).

[0058] Example 1

[0059] In a paste mixer (Daehwa Tech, PDM-1K equipment), add 100 parts by weight of a silicone resin (Andisil VS1000, AB Specialty Silicones) with a molecular weight of 18,000 g / mol as the main resin, 13 parts by weight of a random side-attached hydride (Andisil XL12, AB Specialty Silicones) as the curing agent, 400 parts by weight of Al2(SO4)3·18H2O particles (Daejung Chemicals & Metals), and 3 parts by weight of a dispersant (LP X 21879, BYK), and mix for 2 minutes at 600 rpm revolution and 500 rpm rotation. After confirming uniform mixing, subject the particles to defoaming once and mix 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 at 600 rpm revolution and 200 rpm rotation for 2 minutes to prepare a resin composition. The endothermic peak temperature of Al2(SO4)3·18H2O was 103 °C, and the endothermic heat was 740 J / g.

[0060] 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).

[0061] Example 2

[0062] The 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) were used instead of Al2(SO4)3·18H2O particles (Daejung Chemicals & Metals). The pad was then manufactured in the same manner as in Example 1. The endothermic peak temperature of MgSO4·7H2O was 94°C, and the endothermic heat was 1150 J / g.

[0063] Example 3

[0064] The 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) were used instead of Al2(SO4)3·18H2O particles (Daejung Chemicals & Metals). The pad was then manufactured in the same manner as in Example 1. The endothermic peak temperature of AlCl3·6H2O was 186°C, and the endothermic heat was 1750 J / g.

[0065] Example 4

[0066] The resin composition was prepared in the same manner as in Example 1, except that 250 parts by weight of H3BO3 particles (Daejung Chemicals & Metals) were used instead of Al2(SO4)3·18H2O particles (Daejung Chemicals & Metals). The pad was then manufactured in the same manner as in Example 1. The endothermic peak temperature of H3BO3 was 136°C, and the endothermic heat was 1133 J / g.

[0067] Comparative Example 1

[0068] The resin composition was prepared in the same manner as in Example 1, except that 200 parts by weight of xylitol granules (Daejung Chemicals & Metals) were used instead of Al2(SO4)3·18H2O granules (Daejung Chemicals & Metals). The pad was then manufactured in the same manner as in Example 1. The endothermic peak temperature of xylitol was 94°C, and the endothermic heat was 250 J / g.

[0069] Comparative Example 2

[0070] The resin composition was prepared in the same manner as in Example 1, except that 200 parts by weight of zinc hydroxystannate particles (Shinseung Hichem) were added instead of Al2(SO4)3·18H2O particles (Daejung Chemicals & Metals). The pad was then manufactured in the same manner as in Example 1. The endothermic peak temperature of zinc hydroxystannate was 250°C, and the heat of heat absorption was 350 J / g.

[0071] Comparative Example 3

[0072] The 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). The pad was then manufactured in the same manner as in Example 1. The endothermic peak temperature of Al(OH)3 was 298°C, and the heat of heat absorption was 1100 J / g.

[0073] Evaluation Example 1. Evaluation of Heat Transfer Delay Characteristics

[0074] The pads 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 frame was a frame with an overall dimension of width × length = 6 cm × 6 cm and a hole of width × length = 5 cm × 5 cm, such that the area of ​​the pad in actual contact with the flame was width × length = 5 cm × 5 cm. The SUS frame was used to prevent the sample from being bent by the flame. The pad with the attached SUS frame was vertically fixed to the fixture using clamps (the main surface of the pad was perpendicular to the ground, and the thickness direction of the pad was horizontal to the ground). A butane gas torch (butane gas: Sun Lighter Gas 295ML, TAEYANG; torch: 500JET, Honest) was placed on the first main surface side of the pad, and a thermal imaging camera (A655SC, FLIR) was placed on the second surface side of the pad 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. A gas torch was positioned such that the portion of its flame radiated was located at the center of the first main surface of the pad, and a thermal imaging camera was positioned such that its lens was located at the center of the second main surface of the pad. Furthermore, the distance between the first main surface of the pad and the portion of the gas torch flame radiated therein was approximately 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 radiated from the gas torch was approximately 25°C. While the pad was being heated by radiating the flame from the torch, the temperature of the second main surface of the pad was measured over time using the thermal imaging camera. The thermal imaging camera measured the infrared radiant heat emitted by the pad and calculated the temperature based on the measured infrared radiant heat value. The time for radiating the flame from the gas torch was set to 3 minutes. The temperature measured by the thermal imaging camera was the temperature at the highest temperature point in the heated portion of the pad.

[0075] 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.

[0076] [Table 1]

[0077]

Claims

1. A heat-absorbing pad comprising a cured product of a resin composition containing a heat-absorbing material and a binder resin, wherein the heat-absorbing material has a heat absorption of 500 J / g or greater and a heat-absorbing peak temperature below 200°C when the heat absorption is measured using a differential scanning calorimeter at a rate of 10°C / min from 0°C to 350°C.

2. The heat-absorbing pad according to claim 1, wherein the heat-absorbing material comprises a substance 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. The heat-absorbing pad according to claim 1, wherein the heat-absorbing material comprises one or more of the following: 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 O, CuSO4·5H2O, ZnSO4·7H2O, CoCl2·6H2O, CrCl3·6H2O, NiCl2·6H2O, MgSO4·7H2O, Al2(SO4)3·18H2O, Na2B4O7·10 H2O, 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 material has a peak heat absorption temperature of 50°C or higher.

5. The heat-absorbing pad according to claim 1, wherein the heat absorption capacity of the heat-absorbing material is 2,000 J / g or less.

6. The heat-absorbing pad according to claim 1, wherein the adhesive resin comprises silicone resin as the main resin.

7. The heat-absorbing pad according to claim 6, wherein the adhesive resin further comprises a curing agent.

8. The heat-absorbing pad according to claim 1, wherein the heat-absorbing material is included in the range of 50 parts by weight to 500 parts by weight relative to 100 parts by weight of the adhesive resin.

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

10. The heat-absorbing pad according to claim 1, wherein the heat-absorbing pad has a heat transfer delay temperature in the range of 50°C to 200°C and a heat transfer time of 30 seconds or longer.

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