Cooling patch for suppressing heat generation of secondary battery

Abstract

The present invention is designed to cool a secondary battery (B) (e.g., a lithium-ion battery) while suppressing heat generation when heat generated from the secondary battery causes the temperature thereof to become equal to or higher than a reference temperature. That is, the present invention relates to a cooling patch for suppressing heat generation of a secondary battery (B), wherein the cooling patch spontaneously exhibits a cooling function in a high-temperature environment when the secondary battery generates heat, thereby realizing rapid cooling, enabling long-term thermal management, and further improving the safety of the secondary battery even without a complicated cooling device or external power source.

Description

Secondary battery heat suppression cooling patch

[0001] The present invention relates to a cooling patch for suppressing heat generation in a secondary battery, and more specifically, to a cooling patch for suppressing heat generation in a secondary battery that enables rapid cooling by spontaneously performing a cooling function in a high-temperature environment when the secondary battery generates heat, enables long-term thermal management, and further improves the safety of the secondary battery without complex cooling devices or external power.

[0002] Recently, the use of high-energy-density secondary batteries has been expanding in various application fields such as electric vehicles, energy storage systems (ESS), and portable electronic devices. Due to their high output and large capacity characteristics, these secondary batteries exhibit localized high temperatures and heat generation during operation due to overcharging, short circuits, internal defects, or impacts. If left unchecked, these overheated conditions can cause thermal runaway, leading to serious accidents such as fires or explosions.

[0003] Typically, methods such as liquid coolant circulation, the attachment of metal heat sinks, or air circulation cooling are proposed for the thermal management of secondary batteries. However, these methods have disadvantages, including complex structures, the need for additional power devices such as pumps or fans, and electronic control units, as well as increased costs and weight. Furthermore, they present problems such as the difficulty of immediate cooling in emergency situations and the unavoidable need for separate energy consumption.

[0004] Accordingly, there is an increasing demand for simple and efficient cooling means capable of self-cooling when the surface temperature of a secondary battery rises, without external power or complex devices. As a specific example, technologies such as the following prior art documents are known in the United States and Japan.

[0005] U.S. Patent Publication No. 9312580 (April 12, 2016) of Prior Art Document 1 discloses a system battery module comprising a battery cell assembly that is a component of a battery module, wherein the system battery module includes a first flat plate surface that generates heat during operation, and a phase change material (PCM) layer stacked on the first flat plate surface, wherein the PCM layer is a phase change material disposed around a plurality of graphite layers that undergo phase change according to a predetermined heat absorption, and the PCM layer includes a plurality of graphite layers to facilitate heat conduction through a PCM layer of a certain thickness.

[0006] Prior Art Document 2, U.S. Patent Publication No. 8109324 (February 7, 2012), discloses a slurry comprising a liquid and / or solid microencapsulated particulate phase change material capable of melting in a heat range required for cooling a heat-generating component; a heat exchanger located or capable of being located in a heat-generating component, comprising a plurality of microchannels that are passages for the liquid slurry with a width of about 50 to 500 μm in a non-linear path, wherein the height-to-width ratio is at least 5:1; a microencapsulated particulate phase change material having a diameter of about 5 to about 20% of the microchannel width, wherein the slurry is located within the microchannels of the heat exchanger; a pump for moving a constant flow rate of the liquid slurry through the heat exchanger; and a microchannel heat exchanger for a heat-generating component having a heat capacity of at least 100 W / cm.

[0007] In Japanese Patent Publication No. 2011-527740 (November 4, 2011) of Prior Art Document 3, an array of capsules within a housing is described, wherein the array of capsules comprises a first capsule structure comprising at least two opposing TESMs and a plurality of capsules having a predetermined volume, and a ply that is joined in contact with each other on a portion of each of their respective opposing surfaces to define a first capsule structure comprising at least two opposing TESMs and a plurality of capsules having a predetermined volume, and a ply that is joined in contact with each other on a portion of each of their respective opposing surfaces to define a second capsule structure comprising at least one first array part and at least two opposing TESMs and a plurality of capsules having a predetermined volume, and further comprises a flow path defined by the volume between the first array component and the second array component.

[0008] The applicant intends to propose the present invention by developing a cooling patch that suppresses heat generation in secondary batteries by further advancing and developing these prior art documents.

[0009] The objective of the present invention is to provide a cooling patch for suppressing heat generation in a secondary battery that can cool the secondary battery by melting the phase change material (PCM) through the destruction of the phase change microcapsule when the secondary battery reaches a high temperature (50 to 80°C) due to heat generation, and at the same time can stabilize the temperature over a long period of time through the absorption of latent heat of evaporation of the cooling liquid in the cooling liquid-containing medium layer, namely the water-glycol mixture contained in the hydrogel sheet or hydrogel nanofiber matrix.

[0010] A technical solution according to the present invention for achieving the above objective may comprise a secondary battery heat suppression cooling patch that cools while suppressing heat generation when the secondary battery exceeds a reference temperature due to heat generation, the patch comprising: a cooling liquid containing medium layer containing a cooling liquid; a phase change microcapsule that absorbs thermal energy and cools by releasing a phase change material (PCM) to the cooling liquid containing medium layer when the secondary battery exceeds a reference temperature due to heat generation; a protective film that protects the cooling liquid containing medium layer having the phase change microcapsule; and an adhesive layer that adheres the cooling liquid containing medium layer to the secondary battery.

[0011] The present invention enables rapid cooling by spontaneously performing a cooling function in a high-temperature environment when a secondary battery generates heat, allows for long-term thermal management, and further has the effect of improving the safety of the secondary battery without complex cooling devices or external power.

[0012] The present invention has the effect of continuously cooling thermal energy by absorbing the latent heat of evaporation of the cooling liquid in the cooling liquid-containing medium layer when the secondary battery generates heat above a reference temperature by releasing a phase-change material from the phase-change microcapsule.

[0013] The present invention has the effect of cooling the secondary battery by melting the phase change material (PCM) through the destruction of the phase change microcapsule when the secondary battery reaches a high temperature (50 to 80°C) due to heat generation, and simultaneously stabilizing the temperature over a long period of time through the absorption of latent heat of evaporation of the cooling liquid in the cooling liquid-containing medium layer, namely the water-glycol mixture contained in the hydrogel sheet or hydrogel nanofiber matrix.

[0014] FIG. 1 is a conceptual diagram showing a secondary battery heat suppression cooling patch according to the present invention.

[0015] The best embodiment for carrying out the present invention is a secondary battery heat suppression cooling patch that suppresses heat generation and cools when the secondary battery exceeds a reference temperature due to heat generation, comprising: a cooling liquid containing medium layer containing a cooling liquid; a phase change microcapsule that absorbs thermal energy and cools by releasing a phase change material (PCM) to the cooling liquid containing medium layer when the secondary battery exceeds a reference temperature due to heat generation; a protective film that protects the cooling liquid containing medium layer having the phase change microcapsule; and an adhesive layer that adheres the cooling liquid containing medium layer to the secondary battery.

[0016] Preferred embodiments of a secondary battery heat suppression cooling patch according to the present invention will be described with reference to the drawings. There may be multiple embodiments, and through these embodiments, the objectives, features, and advantages of the present invention can be better understood.

[0017] FIG. 1 is a conceptual diagram showing a cooling patch for suppressing heat generation in a secondary battery according to the present invention.

[0018] As shown in FIG. 1, the secondary battery heat suppression cooling patch according to the present invention is designed to suppress heat generation and cool the secondary battery (B: e.g., a lithium-ion battery) when the temperature exceeds a reference temperature due to heat generation. That is, when the secondary battery (B) generates heat, it spontaneously exerts a cooling function in a high-temperature environment to realize rapid cooling, enables long-term thermal management, and furthermore, improves the safety of the secondary battery (B) without complex cooling devices or external power.

[0019] Specifically, the secondary battery heat suppression cooling patch according to the present invention comprises a cooling liquid containing medium layer (10) containing a cooling liquid, a phase change microcapsule (11) that absorbs and cools thermal energy by releasing a phase change material (PCM) to the cooling liquid containing medium layer (10) when the temperature exceeds a reference temperature due to heat generation of the secondary battery (B), a protective film (20) that protects the cooling liquid containing medium layer (10) having the phase change microcapsule (11), and an adhesive layer (30) that adheres the cooling liquid containing medium layer (10) to the secondary battery (B).

[0020] The cooling liquid-containing medium layer (10) contains a cooling liquid and, when a phase change material is released from a phase change microcapsule (11), allows for the continuous cooling of thermal energy caused by heat generation of the secondary battery (B) by absorbing the latent heat of evaporation of the cooling liquid. At this time, the phase change material (PCM) is a material that undergoes a phase change between solid and liquid or between solid and gas within a specific temperature range and causes a change of state while absorbing or releasing heat. By utilizing this, heat can be preserved, cooled, or further heated by storing or releasing energy. For example, energy storage or temperature control can be achieved by utilizing the characteristic that the material absorbs heat when changing from solid to liquid and releases heat when changing from liquid to solid.

[0021] At this time, the reference temperature can be called the transition temperature, and the phase change material absorbs or releases a certain amount of heat during the phase change, which is called latent heat. This latent heat has the characteristic that when the phase change occurs, the temperature of the material does not change and only heat is stored or released. In the present invention, as a reference temperature, thermal stability can be expected when the heat generation temperature of the secondary battery (B) is less than 50°C, but above that, there is a concern of thermal runaway due to overheating, so the phase change microcapsule (11) is made to release the phase change material to the cooling liquid-containing medium layer (10) up to 80°C, that is, at 50°C to 80°C.

[0022] These phase change materials can be broadly classified into organic and inorganic phase change materials. Organic phase change materials include paraffin and fatty acids, which are relatively safe and allow for control of the phase change temperature. Inorganic phase change materials include sodium chloride (NaCl), calcium chloride (CaCl₂), and sodium hydroxide (NaOH), which have high thermal conductivity, excellent durability, and can possess high latent heat. Therefore, in this invention, these organic or inorganic phase change materials are effectively and appropriately applied.

[0023] Specifically, the phase change material absorbs high heat generated from the secondary battery (B) to prevent excessive heat rise, and automatically provides a cooling effect when high temperature is reached without an external power source or complex cooling circuit, thereby reducing the risk of heat generation in the secondary battery (B), and enables long-term temperature stabilization through initial rapid cooling [release of cooling liquid by destruction of the phase change microcapsule (11) or melting of the phase change material (PCM)] followed by stepwise evaporative cooling [gradual evaporation of residual cooling liquid within the hydrogel / nanofiber matrix described later].

[0024] That is, the cooling liquid-containing medium layer (10) is configured to continuously cool the thermal energy generated by the heat of the secondary battery (B) by absorbing the latent heat of evaporation of the cooling liquid when the phase change material is released from the phase change microcapsule (11).

[0025] At this time, the cooling liquid of the cooling liquid-containing medium layer (10) may be composed of a water-glycol mixture of purified water and ethylene glycol.

[0026] Ethylene glycol is an organic compound containing two hydroxyl groups (-OH) and is a viscous liquid that dissolves well in water. It has a low freezing point and a high boiling point of about 197.3°C, making it suitable as a coolant and antifreeze. Therefore, in this invention, a water-glycol mixture is applied as a coolant mixed with purified water.

[0027] According to the present invention, the cooling liquid-containing medium layer (10) may use a hydrogel sheet (10a) formed by mixing polyvinyl alcohol and a crosslinking agent, dissolving the hydrogel precursor in distilled water, and then stirring it in a water-glycol mixture.

[0028] Hydrogel is a polymer material that absorbs water and expands significantly in volume, and has a polymer network structure containing water, so it can contain a large amount of water, and such a hydrogel sheet (10a) is applied as a cooling liquid containing medium layer (10) so that when a phase change material is released from the phase change microcapsule (11), the thermal energy caused by the heat generation of the secondary battery (B) can be continuously cooled by absorbing the latent heat of evaporation of the cooling liquid.

[0029] According to the present invention, the cooling liquid-containing medium layer (10) may be formed by mixing polyvinyl alcohol and a crosslinking agent, dissolving the hydrogel precursor in distilled water, stirring it in a water-glycol mixture, and administering it to a nanofiber matrix prepared by electrospinning of PVDF (Polyvinylidene fluoride), thereby applying a hydrogel nanofiber matrix (10b).

[0030] The nanofiber matrix is ​​formed by arranging nanometer-sized fibers prepared by electrospinning of PVDF in an intertwined or tangled manner, and is desirable because it can be preserved at a high density when a hydrogel precursor, which is dissolved in distilled water by mixing polyvinyl alcohol and a crosslinking agent, is stirred and administered into a water-glycol mixture. In particular, fine PVDF nanofibers have a large surface area and excellent mechanical, electrical, and thermal properties, so they can be suitably applied as the cooling liquid-containing medium layer (10) of the present invention.

[0031] Meanwhile, the phase-change microcapsule (11) can be prepared by drying a suspension of palmitic acid and melamine formaldehyde resin to form a microcapsule.

[0032] Palmitic acid is a type of saturated fatty acid and is an organic compound containing 16 carbon atoms, 32 hydrogen atoms, and 2 oxygen atoms. Since all carbon-carbon bonds are single bonds, it maintains a solid state at room temperature and has a wax-like texture when in this solid state. By reacting melamine and formaldehyde, it is possible to achieve excellent durability, heat resistance, chemical resistance, and insulation properties. In particular, the suspension mixed with melamine formaldehyde, a synthetic resin that is resistant to moisture and resistant to water and moisture, can be dried quickly and easily, that is, microencapsulated. This allows the suspension mixed with palmitic acid and melamine formaldehyde resin to be immediately released when the reference temperature of the secondary battery (B) is 50 to 80°C, thereby enabling the suppression of heat generation and cooling of the secondary battery (B).

[0033] Meanwhile, the protective film (20) is applied to the surface of the cooling liquid-containing medium layer (10) having phase change microcapsules (11) to ensure safe protection, and the adhesive layer (30) is applied to the back surface of the cooling liquid-containing medium layer (10) having phase change microcapsules (11) to prevent separation from the secondary battery (B) due to overheating.

[0034] The polymer film is a polymer material that is thin, flexible, and has excellent resistance to chemicals and stability, and furthermore, has durability, so it is desirable to stably protect the cooling liquid-containing medium layer (10) containing phase change microcapsules (11), and the heat-resistant silicone resin is a silicone-based synthetic resin that provides excellent heat resistance in a high-temperature environment, and has excellent high-temperature heat resistance, water resistance, chemical resistance, and electrical insulation, so when it is bonded to the secondary battery (B) together with an adhesive, it is desirable to thoroughly prevent release due to high heat.

[0035] As such, the secondary battery heat suppression cooling patch according to the present invention is advantageous in that it can cool the secondary battery (B) by melting the phase change material (PCM) through the destruction of the phase change microcapsule (11) when the secondary battery (B) reaches a high temperature condition (50 to 80°C) due to heat generation, and at the same time, stabilize the temperature over a long period of time through the absorption of latent heat of evaporation of the cooling liquid contained in the cooling liquid-containing medium layer (10), that is, the hydrogel sheet (10a) or the hydrogel nanofiber matrix (10b).

[0036] [Example]

[0037] As an example, a secondary battery heat suppression cooling patch of the present invention was attached to a secondary battery (B) for an electric vehicle, and a thermal runaway simulation experiment was performed. As a result, it was confirmed that when the surface temperature of the secondary battery (B) reached 100°C, it was rapidly cooled to 60°C or lower within 10 seconds, and then maintained a stable temperature of around 45°C for about 5 minutes. Through this, it was found that heat suppression and stability improvement are possible without a separate cooling device.

[0038] In another embodiment, it was confirmed that stable temperature control is possible without fire or explosion even in overheating situations as a result of applying the secondary battery heat suppression cooling patch of the present invention to the surface of a small ESS module.

[0039] We will now examine in detail an embodiment of the secondary battery heat suppression cooling patch according to the present invention that realizes these functions and effects.

[0040] (1) Water-glycol mixture

[0041] Mix 300 ml of ethylene glycol (approx. 99.5% purity) with 700 ml of purified water (purity 99.9% or higher).

[0042] After homogeneously mixing this mixture with a stirrer (stirring speed about 300 rpm) at room temperature (25℃) for 10 minutes, the pH is maintained in the neutral range (6.5~7.5).

[0043] (2) Hydrogel precursor

[0044] 10g of polyvinyl alcohol (PVA, molecular weight 85,000–124,000) and a crosslinking agent (glutaraldehyde) are dissolved in 190g of distilled water.

[0045] This solution is heated at about 90°C for 1 hour and stirred. Once the solution becomes a transparent hydrogel precursor, it is cooled to room temperature.

[0046] (3) Hydrogel nanofiber matrix (10b)

[0047] A hydrogel nanofiber matrix (10b) with a thickness of about 50 μm is prepared by electrospinning a PVDF (Polyvinylidene fluoride) 10 wt% solution (dimethylformamide / acetone mixed solvent) using an electrospinning device (voltage 15 kV, flow rate 0.5 ml / h, collection distance 15 cm).

[0048] This hydrogel nanofiber matrix (10b) is subsequently laminated with a hydrogel precursor to improve the ability to retain coolant.

[0049] (4) Hydrogel sheet (10a)

[0050] A water-glycol mixture is added to the prepared hydrogel precursor at a level of 40 wt% relative to the solution, and mixed at room temperature for 20 minutes using a stirrer.

[0051] This solution is poured into a silicone mold (thickness about 1 mm) and applied in a flat manner, then cured in a 60°C oven for 2 hours to obtain an elastic hydrogel sheet (10a).

[0052] (5) Phase change microcapsule (11)

[0053] Prepare 5g of a palmitic acid derivative with a melting point of about 55°C as a phase change material (PCM).

[0054] A palmitic acid derivative is emulsified in an aqueous phase (95 g of water) using an emulsification stirrer (stirring at 1,000 rpm, maintained at 60°C) to proceed with microencapsulation (e.g., melamine-formaldehyde resin wall formation reaction). After about 3 hours of reaction, a suspension with an average capsule diameter of 10 to 20 μm is obtained.

[0055] After filtering and drying the suspension, about 0.5g of the dried capsule powder (moisture content <5%) is homogeneously sprayed onto the surface of the hydrogel sheet (10a) and laminated onto the surface with a low pressure (flat plate roll, 0.2MPa). As a result, the phase change microcapsules (11) are attached to the hydrogel sheet (10a) or the hydrogel nanofiber matrix (10b), and when a specific temperature, i.e., a reference temperature (50–80℃), is reached, the cooling component can be released through the melting of the phase change material (PCM).

[0056] (6) Protective film (20) and adhesive layer (30)

[0057] A high moisture-permeability polymer film (polyurethane-based, thickness 20 μm) is laminated (roll pressing, 50°C, 0.1 MPa) onto the surface of the cooling liquid-containing medium layer (10).

[0058] An adhesive layer (30) is formed by attaching a heat-resistant silicone resin (PSA; Pressure Sensitive Adhesive - thickness 50㎛) capable of withstanding up to 180℃ to the back surface of the cooling liquid-containing medium layer (10).

[0059] (7) Foundation and Packaging

[0060] The completed secondary battery heat suppression cooling patch of the present invention is cut into a 50×50 mm square patch shape.

[0061] The secondary battery heat suppression cooling patch cut in this way is vacuum-sealed in an aluminum foil pouch (residual oxygen concentration of 1% or less) under an inert atmosphere (N₂ gas atmosphere) so as to minimize changes in performance during long-term storage.

[0062] (8) Application to secondary battery (B) and performance verification

[0063] After washing and drying the surface of the secondary battery (B: for example, a lithium-ion battery module for an electric vehicle) with ethanol, the unpackaged secondary battery heat suppression cooling patch is attached through the adhesive layer (30).

[0064] The attachment area is concentrated at local points where heat generation of the secondary battery (B) is expected (areas where high heat generation is expected based on the temperature sensor).

[0065] It is maintained in a standby state without any cooling action under normal operating conditions (25℃).

[0066] In a simulation test, the secondary battery (B) is heated to 100°C using a heater (heater block). As a result, the phase change material (PCM) melts at 55°C or higher, and the latent heat absorption phenomenon begins due to the evaporation of the water-glycol mixture along with the release of some of the cooling liquid.

[0067] It is confirmed that the temperature of the secondary battery (B) drops from 100°C to about 60°C within 10 seconds, and then stabilizes between 45°C and 50°C for 5 minutes. This demonstrates rapid initial cooling performance without a separate pump or piping compared to conventional liquid injection cooling.

[0068] (9) Rechargeability test (optional)

[0069] After exerting a cooling effect, the secondary battery heat suppression cooling patch evaporates a significant portion of the moisture and becomes dry; however, if re-exposed to an environment chamber at a temperature of 25°C and 80% relative humidity for 24 hours, some of the hydrogel absorbs external moisture and is partially restored. However, since only about 60–70% of the initial cooling performance is restored, a separate process for re-injecting the coolant or recharging the phase change material (PCM) is required to utilize it as a fully rechargeable type.

[0070] (10) Reliability test

[0071] After testing a temperature cycle from -20℃ to 60℃ (twice a day, for a total of 30 days), the structural stability of the patch and changes in cooling performance are inspected. Even after 30 days, the patch maintains approximately 85% of its initial cooling performance without significant performance degradation, except for physical adhesion and a small loss of phase change material (PCM).

[0072] Even after a vibration test (3 GHz, 10 to 200 GHz, 4 hours), there is no significant separation of the layer structure of the secondary battery heat suppression cooling patch or damage to the phase change microcapsule (11).

[0073] (11) Safety considerations

[0074] With an ethylene glycol content of 30%, resistance to the risk of ignition can be improved by applying an additional flame-retardant coating.

[0075] Fire safety can be enhanced by using non-toxic, flame-retardant materials when selecting phase change materials (PCM).

[0076] Stability can be maximized at the system level by optimizing the patch attachment location, number, and area through consultation with the battery module manufacturer.

[0077] The present invention can be used in industrial fields related to fire suppression and cooling, such as secondary batteries.

[0078]

Claims

1. A secondary battery heat suppression cooling patch that cools while suppressing heat generation when the secondary battery exceeds a reference temperature due to heat generation, A cooling liquid-containing medium layer containing a cooling liquid, and A phase change microcapsule that absorbs thermal energy and cools by releasing a phase change material (PCM) into the cooling liquid-containing medium layer when the temperature exceeds a reference temperature due to heat generation of the secondary battery, and A protective film protecting the cooling liquid-containing medium layer having the above-mentioned phase-change microcapsules, and A secondary battery heat suppression cooling patch characterized by including an adhesive layer that adheres the above-mentioned coolant-containing medium layer to the secondary battery.

2. In Paragraph 1, A secondary battery heat suppression cooling patch characterized in that the above-described cooling liquid-containing medium layer continuously cools the thermal energy caused by heat generation of the secondary battery by absorbing the latent heat of evaporation of the cooling liquid when a phase change material is released from the above-described phase change microcapsule.

3. In Paragraph 2, A secondary battery heat suppression cooling patch characterized in that the cooling liquid in the above-mentioned cooling liquid-containing medium layer is composed of a water-glycol mixture obtained by mixing purified water and ethylene glycol.

4. In Paragraph 3, A secondary battery heat suppression cooling patch characterized in that the above-mentioned cooling liquid-containing medium layer is a hydrogel sheet formed by mixing polyvinyl alcohol and a crosslinking agent, dissolving the hydrogel precursor in distilled water, and then stirring and molding it in the above-mentioned water-glycol mixture.

5. In Paragraph 3, A secondary battery heat suppression cooling patch characterized in that the above-mentioned cooling liquid-containing medium layer is a hydrogel nanofiber matrix formed by mixing polyvinyl alcohol and a crosslinking agent, dissolving the hydrogel precursor in distilled water, stirring it into the above-mentioned water-glycol mixture, and administering it to a nanofiber matrix prepared by electrospinning of PVDF (Polyvinylidene fluoride).

6. In any one of paragraphs 3 through 5, A secondary battery heat suppression cooling patch characterized by the above-mentioned phase-change microcapsule being prepared by drying and microencapsulating a suspension of palmitic acid and melamine formaldehyde resin.

7. In any one of paragraphs 1 through 5, A secondary battery heat suppression cooling patch characterized by a reference temperature of 50 to 80°C due to heat generation of the secondary battery.

8. In any one of paragraphs 1 through 5, A secondary battery heat suppression cooling patch characterized in that the protective film is a polymer film laminated to the surface of the cooling liquid-containing medium layer having the phase change microcapsules.

9. In any one of paragraphs 1 through 5, A secondary battery heat suppression cooling patch characterized by the adhesive layer being formed by applying an adhesive containing a heat-resistant silicone resin to the back surface of the cooling liquid-containing medium layer having the phase-change microcapsules.

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