Composite heat-absorbing material and application thereof in battery

Abstract

The invention provides a composite heat-absorbing material and application thereof in a battery. The composite heat-absorbing material comprises a heat-absorbing active material, chopped fibers and a heat-conducting reinforcing material, wherein the heat absorption active material is hydrate, and the thermal decomposition temperature and the phase change temperature of the hydrate are within the range of 70-200 DEG C. The composite heat-absorbing material can be well formed, is high in mechanical strength and good in heat conductivity and heat absorptivity, and is particularly suitable for continuous and effective thermal diffusion suppression of a thermal runaway battery.

Description

Technical Field

[0001] This application relates to the field of battery safety protection technology, specifically to a composite heat-absorbing material and its application in batteries. Background Technology

[0002] Battery modules (e.g., battery packs) typically use multiple individual cells for power supply. Therefore, when these modules are subjected to impacts, electrical abuse, or other adverse conditions, they are at high risk of thermal runaway, potentially leading to safety accidents. To mitigate thermal runaway under abusive conditions, the industry usually installs external cooling systems to manage the thermal performance of the modules. However, relying solely on these cooling systems is insufficient to quickly dissipate the heat from the modules within a short period.

[0003] Currently, the thermal safety of batteries has attracted significant attention. The industry primarily utilizes thermal insulation materials (such as aerogels) or phase change endothermic materials (such as paraffin wax and inorganic crystalline hydrated salts) to suppress thermal runaway in batteries. However, thermal insulation materials are not very effective at suppressing thermal runaway, while endothermic materials like paraffin wax suffer from low thermal conductivity, low density, and the risk of spontaneous combustion. Inorganic crystalline hydrated salts, compared to paraffin wax, have high thermal conductivity and no risk of spontaneous combustion, but their poor formability makes it difficult to achieve both high structural strength and high endothermic enthalpy. Therefore, there is an urgent need to develop a composite endothermic material with excellent endothermic performance and high structural strength. Summary of the Invention

[0004] In view of this, this application provides a composite heat-absorbing material and its application in batteries, which can effectively suppress thermal runaway battery thermal diffusion while also having high mechanical strength.

[0005] Specifically, the first aspect of this application provides a composite heat-absorbing material, which includes a heat-absorbing active material, chopped fibers, and a thermally conductive reinforcing material; wherein the heat-absorbing active material is a hydrate, the thermal decomposition temperature of the hydrate is in the range of 70-200℃, and the phase transition temperature of the hydrate is in the range of 70-200℃.

[0006] This composite heat-absorbing material uses hydrates with thermal decomposition and phase change temperatures that match the temperature at which the battery experiences thermal runaway as the heat-absorbing active material. With the synergistic effect of chopped fibers and thermally conductive reinforcing materials, the hydrates can be well molded, resulting in a stable overall structure, high mechanical strength, and good thermal conductivity and heat absorption properties. This allows the material to continuously and effectively suppress the thermal diffusion of the thermal runaway battery.

[0007] A second aspect of this application provides a heat-absorbing element, which includes the composite heat-absorbing material described in the first aspect of this application. The heat-absorbing element can be plate-shaped. This heat-absorbing element has good molding properties, strong heat absorption capacity, and good mechanical properties.

[0008] A third aspect of this application provides a heat-absorbing component, which includes an encapsulation film and a composite heat-absorbing material as described in the first aspect of this application or a heat-absorbing element as described in the second aspect of this application. This heat-absorbing component has strong heat absorption capacity and good mechanical properties.

[0009] The fourth aspect of this application provides a battery pack including a plurality of individual cells and a heat-absorbing element as described in the second aspect of this application or a heat-absorbing assembly as described in the third aspect of this application, wherein the heat-absorbing element or the heat-absorbing assembly is disposed between at least two adjacent individual cells.

[0010] A fifth aspect of this application provides a battery pack that satisfies at least one of the following (a), (b), and (c):

[0011] (a) The battery pack includes at least one battery pack, which is the battery pack described in the fourth aspect of this application;

[0012] (b) The battery pack includes a plurality of battery groups, and at least two of the battery groups are provided with a heat-absorbing element as described in the second aspect of this application or a heat-absorbing component as described in the third aspect of this application;

[0013] (c) The battery pack includes a tray, a top cover and a plurality of individual batteries, the tray and the top cover forming a receiving space for accommodating the individual batteries, and at least one individual battery is provided with a heat-absorbing element as described in the second aspect of this application or a heat-absorbing component as described in the third aspect of this application between it and the top cover.

[0014] The aforementioned battery packs or battery bags utilize the heat-absorbing elements or components described in the embodiments of this application for thermal protection, resulting in high safety performance. Attached Figure Description

[0015] Figure 1 This is a schematic diagram of the battery pack structure provided for some embodiments of this application.

[0016] Figure 2 This is a schematic diagram of a heat-absorbing component provided in an embodiment of this application.

[0017] Figure 3 This is a schematic diagram of the battery pack structure provided for some other embodiments of this application.

[0018] Figure 4A This is a schematic diagram of a battery pack provided in an embodiment of this application.

[0019] Figure 4B This is a schematic diagram of another structure of the battery pack provided in an embodiment of this application.

[0020] Figure 4CThis is another schematic diagram of the structure of the battery pack provided in the embodiments of this application.

[0021] Figure 5 The DSC curve of the plate-shaped heat absorber provided in Embodiment 1 of this application.

[0022] Figure 6 The DSC curve of the plate-shaped heat absorber provided in Embodiment 2 of this application.

[0023] Figure 7 The DSC curve of paraffin in Comparative Example 1 of this application is shown. Detailed Implementation

[0024] The technical solutions of the embodiments of this application will be described in detail below with reference to the accompanying drawings.

[0025] Figure 1 This is a schematic diagram of the structure of a battery pack provided in some embodiments of this application. The battery pack 100 includes a plurality of individual cells 10, and a heat-absorbing element 20 is disposed between adjacent individual cells 10. The heat-absorbing element 20 may include the composite heat-absorbing material described in the embodiments of this application.

[0026] The composite heat-absorbing material provided in this application includes: a heat-absorbing active material, chopped fibers, and a thermally conductive reinforcing material; wherein the heat-absorbing active material is a hydrate, the thermal decomposition temperature of the hydrate is in the range of 70-200℃, and the phase transition temperature of the hydrate is in the range of 70-200℃.

[0027] The aforementioned composite heat-absorbing material incorporates at least one hydrate as a heat-absorbing active material, and is reinforced with chopped fibers and thermally conductive reinforcing materials to ensure good molding ability of the composite material system. It can be molded mainly by intermolecular forces and van der Waals forces without the need for binders to aid molding. This ensures that the overall composite heat-absorbing material has high mechanical strength and is not easily broken, while significantly increasing the total content of heat-absorbing active materials in the composite heat-absorbing material, ensuring a high enthalpy value of the composite heat-absorbing material, and thus improving its heat absorption capacity. Furthermore, the hydrate's thermal decomposition and phase transition temperatures are within the range of 70-200℃, which is suitable for the temperature at which a battery experiences thermal runaway. It also has a high total enthalpy, enabling it to effectively absorb heat during its thermal decomposition and / or phase transition. However, while its thermal conductivity is higher than paraffin, it is still not high enough. The presence of a thermally conductive enhancement material can significantly improve the thermal conductivity of the composite heat-absorbing material, rapidly dispersing the heat generated by the thermal runaway battery throughout the entire composite heat-absorbing material and preventing heat from concentrating in a specific area. This ensures that the entire composite heat-absorbing material can absorb heat quickly and uniformly, effectively suppressing heat transfer in the thermal runaway battery and reducing its temperature. The aforementioned heat-absorbing active material can be understood as the material that plays the main role in heat absorption within the composite heat-absorbing material.

[0028] Therefore, the aforementioned composite heat-absorbing material can balance high structural stability, good thermal conductivity, and good heat absorption performance, thus enabling it to sustainably and stably absorb energy rapidly and effectively. This composite heat-absorbing material is particularly suitable for thermal safety protection of thermal runaway batteries.

[0029] In this application, the thermal decomposition temperature and phase transition temperature of the hydrate are in the range of 70℃-200℃. The temperature at which a battery experiences thermal runaway is typically within this range. Choosing hydrates with thermal decomposition and phase transition temperatures within this range allows them to absorb heat and suppress heat diffusion in the initial stages of thermal runaway. Here, "thermal decomposition temperature" refers to the temperature at which the hydrate undergoes a chemical decomposition reaction to release its water of crystallization. It is understood that some hydrates may contain multiple water molecules, resulting in multiple different thermal decomposition temperatures and phase transition temperatures. "Phase transition temperature" refers to the temperature at which the released water of crystallization changes from a liquid to a gaseous state. Specifically, when the thermal decomposition temperature of the hydrate is <100℃, the released water of crystallization is liquid in the composite heat-absorbing material. At this point, no phase transition occurs, and it forms a solid-liquid mixture with other materials in the composite heat-absorbing material. As the temperature rises to 100℃, the aforementioned liquid water can transform into a gaseous state. When the thermal decomposition temperature is >100℃, the released water of crystallization immediately undergoes a phase transition from liquid to gaseous state in the composite heat-absorbing material. In some cases, certain thermal decomposition temperatures of hydrates can be the same as their phase transition temperatures. In such cases, the hydrate is more compatible with the temperature range of a thermal runaway battery.

[0030] In composite endothermic materials, the thermal decomposition temperature and phase transition temperature of the hydrate can be obtained from the DSC curve measured by Differential Scanning Calorimetry (DSC). In the DSC curve, the horizontal axis represents temperature, and the vertical axis represents heat flux. The initial thermal decomposition temperature can be represented by the horizontal axis corresponding to the point where the vertical axis of the main endothermic peak begins to change significantly after baseline subtraction (i.e., the endothermic starting point recognized by those skilled in the art). The phase transition temperature of the material as a whole can be represented by the peak temperature of the main endothermic peak, at which point the endothermic enthalpy is at its maximum. The thermal decomposition temperature can be represented by the temperature range between the initial thermal decomposition temperature and the peak temperature of the main endothermic peak. The "main endothermic peak" can be understood as an endothermic peak in the DSC curve with an integral area greater than 100 J / g. For example, for the hydrate corresponding to the composite endothermic material in Example 1 below, the peak temperatures of the main endothermic peak are 142℃ and 191℃; for the hydrate corresponding to the composite endothermic material in Example 2, the peak temperatures of the main endothermic peak are 150℃ and 167℃.

[0031] In this application, the hydrate has at least one thermal decomposition temperature in the range of 70°C to 200°C. In some embodiments of this application, the hydrate has a thermal decomposition temperature in the range of 80-150°C or 155°C to 200°C. Specifically, the phase transition temperature of the hydrate can be 100°C, 105°C, 110°C, 120°C, 130°C, 140°C, 150°C, 160°C, 170°C, 180°C, or 190°C, etc. In some embodiments of this application, the phase transition temperature of the hydrate is in the range of 80-160°C.

[0032] In some embodiments of this application, the composite heat-absorbing material comprises the following components in the following mass percentages: 80%-90% of the heat-absorbing active material, 2%-10% of the chopped fibers, and 2%-10% of the thermally conductive reinforcing material. By combining appropriate amounts of chopped fibers and thermally conductive reinforcing material with the hydrate, which serves as the heat-absorbing active material, good hydrate formation and uniform dispersion can be ensured, resulting in good mechanical strength of the composite heat-absorbing material. Furthermore, its high mass percentage ensures that the composite heat-absorbing material can absorb a large amount of heat.

[0033] In this application, the heat-absorbing active material in the composite heat-absorbing material has a mass percentage content of 80%-90%, for example, 80%, 81%, 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, or 90%. In some embodiments, the heat-absorbing active material has a mass percentage content of 85%-90% in the composite heat-absorbing material. In this case, the heat absorption performance of the composite heat-absorbing material is better, while its structural stability remains high. In this application, the chopped fiber in the composite heat-absorbing material has a mass percentage content of 2%-10%, for example, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, or 10%. In some embodiments, the chopped fiber has a mass percentage content of 3%-5% in the composite heat-absorbing material. An appropriate amount of chopped fiber can ensure that the composite heat-absorbing material has good structural stability and high mechanical strength, while its heat absorption performance is not reduced. In this application, the thermally conductive reinforcing material comprises 2%-10% by mass in the composite heat-absorbing material, specifically 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, or 10%. In some embodiments, the thermally conductive reinforcing material comprises 5%-8% by mass in the composite heat-absorbing material. The presence of an appropriate amount of thermally conductive reinforcing material helps to improve the thermal conductivity rate of the composite heat-absorbing material, thereby increasing its heat absorption rate. Furthermore, it also helps to improve the mechanical strength of the composite heat-absorbing material.

[0034] In some embodiments of this application, the hydrate includes at least one of crystalline hydrate and oxalate dihydrate; the crystalline hydrate may include one or more of calcium chloride hexahydrate, barium hydroxide octahydrate, sodium acetate trihydrate, magnesium sulfate heptahydrate, calcium sulfate dihydrate, magnesium sulfate octahydrate, sodium metasilicate pentahydrate, magnesium sulfate heptahydrate, disodium hydrogen phosphate dodecahydrate, sodium silicate nonahydrate, aluminum sulfate dodecahydrate, sodium sulfate decahydrate, sodium carbonate decahydrate, sodium pyrophosphate decahydrate, potassium aluminum sulfate dodecahydrate, ammonium aluminum sulfate dodecahydrate, and sodium bicarbonate decahydrate, but is not limited thereto.

[0035] In some embodiments of this application, the particle size of the hydrate is 1-100 μm. Here, particle size refers to the most probable particle size, that is, the particle size value corresponding to the highest point of the frequency particle size distribution curve. A suitable particle size of the hydrate ensures that it has an appropriately high compaction density after pressing, thereby resulting in a higher enthalpy per unit volume of the composite heat-absorbing material and a higher heat absorption capacity. Simultaneously, it avoids defects during molding, prevents cracks in the heat-absorbing parts made of the composite heat-absorbing material, and avoids affecting fiber dispersion. Specifically, the particle size of the hydrate can be 2 μm, 5 μm, 10 μm, 15 μm, 20 μm, 25 μm, 30 μm, 35 μm, 40 μm, 45 μm, 50 μm, 60 μm, 70 μm, 80 μm, 90 μm, or 95 μm, etc. In some embodiments, the particle size of the hydrate is 20-50 μm. In this case, the components in the above-mentioned composite heat-absorbing material containing the hydrate are well dispersed, and its enthalpy per unit volume is high.

[0036] In some embodiments of this application, the chopped fibers include one or more of glass fibers, aluminosilicate fibers, magnesium silicate fibers, basalt fibers, mullite fibers, silicon carbide fibers, alumina fibers, and zirconium oxide fibers, but are not limited thereto. Any chopped fiber that is heat-resistant, provides reinforcement, and is non-conductive is acceptable. In some embodiments, the chopped fibers are one or more of glass fibers, aluminosilicate fibers, and silicon carbide fibers.

[0037] In some embodiments of this application, the average length of the chopped fibers is 1-20 mm, and the average diameter of the chopped fibers is 8-20 μm. The average length and average diameter of the chopped fibers can be measured using a scanning electron microscope (SEM). A suitable length of chopped fibers ensures that the hydrates are fully dispersed and well-pressed, and that the composite heat-absorbing material possesses good mechanical properties. Chopped fibers of a suitable diameter have good toughness and are not excessively rigid, allowing for better dispersion of the hydrates. The hydrates can be uniformly distributed within the fiber-reinforced three-dimensional porous structure and pressed together with it. Specifically, the average length of the chopped fibers can be 2 mm, 3 mm, 4 mm, 5 mm, 6 mm, 7 mm, 8 mm, 9 mm, 10 mm, 11 mm, 12 mm, 13 mm, 14 mm, 15 mm, 16 mm, 17 mm, 18 mm, or 19 mm, etc. The diameter of the chopped fibers can be specifically 9μm, 10μm, 11μm, 12μm, 13μm, 14μm, 15μm, 16μm, 17μm, 18μm, or 19μm, etc. In some embodiments, the average length of the chopped fibers is 5-10mm, and the diameter of the chopped fibers is 9-13μm.

[0038] In this application, the thermal conductivity of the thermally conductive enhancing material is higher than that of the aforementioned hydrate, and the introduction of the thermally conductive enhancing material can improve the thermal conductivity of the composite heat-absorbing material. In some embodiments of this application, the thermally conductive enhancing material includes one or more of non-conductive particles, conductive carbon particles, and metal particles. The non-conductive particles may include one or more of aluminum trihydrate, silicon carbide, boron nitride, silicon nitride, metal oxides, and metal nitrides. In some embodiments, the non-conductive particles may be ceramic particles composed of multiple of aluminum trihydrate, silicon carbide, boron nitride, silicon nitride, metal oxides, and metal nitrides. Exemplary metal oxides may be alumina, zinc oxide, magnesium oxide, etc., and exemplary metal nitrides may be aluminum nitride, etc. The conductive carbon particles may include one or more of silica, graphite powder, expanded graphite, and graphene. The metal particles may be one or more of aluminum, copper, nickel, silver, platinum, and gold. In some embodiments, the metal particles may be one of aluminum powder, copper powder, nickel powder, silver powder, platinum powder, and gold powder, or a metal alloy powder composed of at least two of aluminum, copper, nickel, silver, platinum, and gold.

[0039] In some embodiments of this application, the particle size of the thermally conductive reinforcing material is 1-20 μm. Here, particle size refers to the most probable particle size, i.e., the particle size value corresponding to the highest point of the frequency particle size distribution curve. The particle size of the thermally conductive reinforcing material is smaller than the particle size of the hydrate, ensuring that the thermally conductive reinforcing material particles can fill the gaps between the hydrate particles, and that there are enough thermally conductive reinforcing material particles to achieve heat conduction, thereby improving the thermal conductivity of the composite heat-absorbing material. At the same time, it avoids agglomeration due to excessively small particle size, which would prevent effective improvement of the overall thermal conductivity uniformity of the composite heat-absorbing material. Specifically, the particle size of the thermally conductive reinforcing material can be 2 μm, 3 μm, 4 μm, 5 μm, 6 μm, 7 μm, 8 μm, 9 μm, 10 μm, 11 μm, 12 μm, 13 μm, 14 μm, 15 μm, 16 μm, 17 μm, 18 μm, or 19 μm, etc. In some embodiments, the particle size of the thermally conductive reinforcing material is 2-8 μm. In this case, thermally conductive reinforcing materials are more effective at improving the thermal conductivity of the aforementioned composite heat-absorbing materials.

[0040] In some embodiments of this application, the heat-absorbing active material, the chopped fibers, and the thermally conductive reinforcing material are uniformly distributed in the composite heat-absorbing material. This uniform distribution ensures high mechanical strength, good structural stability, and uniform thermal conductivity and heat absorption capacity in all regions of the composite heat-absorbing material.

[0041] In some embodiments of this application, the composite heat-absorbing material does not contain a binder. Without a binder, the composite heat-absorbing material can be well molded, has high mechanical strength, and can contain a high content of heat-absorbing active materials, thereby ensuring that the composite heat-absorbing material has high compressive strength and excellent heat absorption performance.

[0042] In some embodiments of this application, the aforementioned composite heat-absorbing material is a plate-shaped molded body obtained by a compression molding process. In other cases, the mixture of the aforementioned heat-absorbing active material, chopped fibers, and thermally conductive reinforcing material can be molded into a plate-shaped composite heat-absorbing material by a compression molding process.

[0043] This application also provides a method for preparing the above-mentioned composite heat-absorbing material, including the following steps:

[0044] A mixture is prepared by mixing a heat-absorbing active material, chopped fibers, and a thermally conductive reinforcing material; wherein the heat-absorbing active material is a hydrate, and the thermal decomposition temperature and phase transition temperature of the hydrate are in the range of 70-200℃.

[0045] The mixture is loaded into a mold of a certain shape and the mold is closed. The composite heat-absorbing material is obtained by pressing.

[0046] By mixing and pressing the raw materials that constitute the composite heat-absorbing material, a composite heat-absorbing material with good formability and high mechanical strength can be obtained. No binder is needed, which increases the mass ratio of heat-absorbing active materials in the composite heat-absorbing material and improves its heat absorption performance. The preparation method of this composite heat-absorbing material is simple and suitable for industrial production.

[0047] In some embodiments of this application, the mixing may specifically be carried out in a mixing vessel with stirring. Heating may be performed simultaneously with stirring to increase the intermolecular forces of the raw materials, thereby achieving a more uniform mixture. However, the heating temperature does not cause the raw materials to melt or decompose. For example, the heating temperature may be 45-65°C, specifically 50°C, 55°C, 60°C, etc.

[0048] In this embodiment, the pressing pressure can be in the range of 5-15 MPa. The pressed composite heat-absorbing material is typically in block form and can be cut to the required size using machining or a slitting machine. In some embodiments, the resulting composite heat-absorbing material can be encapsulated and protected with an encapsulation film for better application in battery packs / packs.

[0049] This application also provides a heat-absorbing element, which may include the composite heat-absorbing material described in the embodiments of this application. In some embodiments, Figure 1 The heat-absorbing element 20 may include only the composite heat-absorbing material described in the embodiments of this application.

[0050] In some embodiments of this application, the heat-absorbing element is plate-shaped. For example, the heat-absorbing element may be a plate-shaped molded body obtained by pressing the composite heat-absorbing material.

[0051] In some embodiments of this application, the thickness of the heat-absorbing element can be 1mm-10mm, specifically 2mm, 3mm, 4mm, 5mm, 6mm, 7mm, 8mm, or 9mm. The thickness of the heat-absorbing element can be adjusted according to actual needs.

[0052] In some embodiments of this application, the density of the heat-absorbing element is 1000-1800 kg / m³. 3 Within the specified range. The heat-absorbing component formed by pressing the mixture of the aforementioned heat-absorbing active material, chopped fibers, and thermally conductive reinforcing material has a high density. This ensures that the mass of heat-absorbing active material in a given volume of heat-absorbing component is relatively large, which in turn contributes to a high enthalpy per unit volume and a high heat absorption capacity. Specifically, the density of this heat-absorbing component can be 1000 kg / m³. 3 1100kg / m 3 1200kg / m 3 1300kg / m 3 1400kg / m3 1500kg / m 3 1600kg / m 3 1700kg / m 3 1800kg / m 3 In some embodiments, the density of the heat-absorbing element is 1200-1400 kg / m³. 3 Within the range.

[0053] In some embodiments of this application, the latent heat per unit volume of the aforementioned heat-absorbing element in the range of 70°C-200°C is in the range of 1200-2100 kJ / L, preferably in the range of 1600-2100 kJ / L. The latent heat per unit mass of the aforementioned heat-absorbing element in the range of 70°C-200°C is obtained from the DSC curve measured by Differential Scanning Calorimetry (DSC), and then its latent heat per unit volume is calculated based on density. Refer to GB / T 19466.5-2002 Plastics Differential Scanning Calorimetry (DSC) Part 5: Determination of Temperature, Time, Enthalpy and Conversion Rate of Characteristic Reaction Curves. Hydrates have good heat absorption capacity, and heat-absorbing elements made from them have a high latent heat per unit volume, which to some extent reflects the high density and high heat absorption capacity of the heat-absorbing element, thereby effectively suppressing the thermal runaway of the battery.

[0054] In some embodiments of this application, the latent heat per unit mass of the aforementioned heat-absorbing element in the range of 70°C-200°C is in the range of 1000-1500 kJ / kg, preferably in the range of 1300-1500 kJ / kg. The latent heat parameter per unit mass of the aforementioned heat-absorbing element in the range of 70°C-200°C can be obtained from the DSC curve of the heat-absorbing element, referring to GB / T 19466.5-2002 Differential Scanning Calorimetry (DSC) for Plastics, Part 5: Determination of Temperature, Time, Enthalpy and Conversion Rate of Characteristic Reaction Curves. A higher latent heat per unit mass of the heat-absorbing element can, to a certain extent, reflect a higher heat absorption capacity, which is beneficial for suppressing the thermal runaway of the battery.

[0055] In some embodiments of this application, the thermal conductivity of the heat absorber at 25°C is in the range of 1-8 W / (mK), preferably in the range of 5-8 W / (mK). With the synergistic effect of the thermally conductive reinforcing material and the hydrate, the thermal conductivity of the heat absorber can be further increased, facilitating its rapid absorption of large amounts of heat. Furthermore, the compression molding process involving the aforementioned chopped fibers, thermally conductive reinforcing material, and hydrate ensures that the thermal conductivity of different regions of the resulting heat absorber is not significantly different.

[0056] In some embodiments of this application, the strain of the heat absorber under a stress of 1 MPa is less than 18%, for example, in the range of 8-15%. Thus, the heat absorber can meet the mechanical property requirements of heat-absorbing materials under most common conditions.

[0057] This application also provides a heat-absorbing component, which may include an encapsulation film and the composite heat-absorbing material or the heat-absorbing element described in this application embodiment. The composite heat-absorbing material or the heat-absorbing element can be encapsulated within the encapsulation film. The encapsulation film can wrap and protect the composite heat-absorbing material or the heat-absorbing element, preventing leakage or detachment of the composite heat-absorbing material, and ensuring high reliability of the heat-absorbing component.

[0058] In some embodiments of this application, such as Figure 2 As shown, the heat-absorbing component 30 includes the heat-absorbing element 20 and the encapsulation film 22 described in this embodiment. The heat-absorbing element 20 can be encapsulated within the encapsulation film 22. The encapsulation film 22 can wrap and protect the heat-absorbing element 20, improving the reliability of the heat-absorbing element 20.

[0059] The encapsulation film 22 may have a cavity inside, and the heat-absorbing element 20 or composite heat-absorbing material is disposed in the cavity. Exemplarily, the encapsulation film 22 may be selected from one or more of polyethylene terephthalate (PET), polyimide (PI), polytetrafluoroethylene (PTFE), polypropylene (PP), PET-PP composite film or laminated film, aluminum-plastic film, etc., but is not limited thereto.

[0060] This application also provides the application of the above-mentioned composite heat-absorbing material or heat-absorbing component in battery thermal protection materials. Specifically, the composite heat-absorbing material can be used as a thermal protection material disposed between individual cells, between battery packs, or on the top cover of a battery pack.

[0061] Specifically, this application provides a battery pack 100, which includes a plurality of individual cells 10, wherein at least some adjacent individual cells 10 are provided with heat-absorbing elements 20 using the composite heat-absorbing material of this application embodiment (e.g., Figure 1 (as shown); or at least some adjacent individual cells 10 are provided with the heat-absorbing components 30 described in the embodiments of this application (such as...). Figure 3 (As shown). Among them, Figure 1 and Figure 3 In the diagram, heat-absorbing elements 20 or heat-absorbing components 30 are arranged between any two adjacent individual cells 10. In the battery pack 100, multiple individual cells 10 are arranged in parallel, specifically along the length of the battery pack 100 (in the direction indicated by the arrow in the figure).

[0062] When the heat-absorbing element 20 or heat-absorbing component 30 described in the present application embodiment is provided between adjacent individual cells 10 of the battery pack 100, when one or more individual cells experience thermal runaway under abnormal conditions (such as puncture, collision, continuous overcharging of the electrode, etc.), the heat-absorbing element 20 or heat-absorbing component 30 can fully and quickly absorb the heat generated by the thermal runaway battery, effectively suppressing the heat from spreading to adjacent cells, thereby ensuring the safety of the entire battery pack 100.

[0063] This application embodiment also provides a battery pack 300, wherein the battery pack 300 satisfies at least one of the following (a), (b), and (c):

[0064] (a) The battery pack 300 includes at least one battery group 200, which is the aforementioned battery group 100 in the embodiments of this application;

[0065] (b) The battery pack 300 includes a plurality of battery groups 200, and at least two adjacent battery groups 200 are provided with the heat-absorbing element 20 or the heat-absorbing assembly 30 described in the embodiments of this application (e.g., Figure 4A (as shown);

[0066] (c) The battery pack 300 includes a tray 301, a top cover 302, and a plurality of individual batteries 10. The tray 301 and the top cover 302 form a receiving space for accommodating the plurality of individual batteries 10. At least one individual battery 10 is provided with a heat-absorbing element 20 or a heat-absorbing assembly 30 (as described in the embodiments of this application) between it and the top cover 302. Figure 4B and Figure 4C (As shown).

[0067] The battery pack 300 may satisfy only one of (a), (b), and (c) above, or it may satisfy any two or three of (a), (b), and (c) above.

[0068] in, Figure 4A The battery pack 300 may also include a tray 301 and a top cover 302, with the top cover 302 covering the top of the tray 301, forming a receiving space in which multiple battery packs 200 are encapsulated. Further, Figure 4A In addition, at least some of the battery packs 200 may also be provided with heat-absorbing components 30 or heat-absorbing elements 20 between the top cover 302 and the top cover 302.

[0069] Figure 4B The illustration shows that a heat-absorbing component 30 is provided between any single cell 10 and the top cover 302. Figure 4C The illustration shows a heat-absorbing component 30 positioned between only a portion of the individual cells 10 and the top cover 302. Furthermore, Figure 4B and Figure 4C In addition, heat-absorbing components 30 can be provided between at least some adjacent individual cells.

[0070] The battery pack 300 employs the heat-absorbing element 20 or heat-absorbing assembly 30 described in the embodiments of this application, which has good heat absorption performance and high mechanical strength, for thermal protection. This can ensure that the heat generation of the thermal runaway individual cell / battery pack is effectively suppressed, thereby improving the safety performance of the battery pack 300.

[0071] This battery pack 300 is typically used as a battery for power vehicles. These power vehicles can be new energy vehicles, such as pure electric vehicles, hybrid electric vehicles, or range-extended electric vehicles.

[0072] The embodiments of this application will be further described below through multiple examples.

[0073] Example 1

[0074] A plate-shaped heat-absorbing component is formed by mixing a heat-absorbing active material, chopped fibers, and a thermally conductive reinforcing material in a mass ratio of 80:10:10 to form a composite heat-absorbing material, which is then pressed. The heat-absorbing active material is a mixture of potassium aluminum sulfate dodecahydrate and calcium chloride hexahydrate, both with a particle size of 30-50 μm; the chopped fibers are glass fibers with a length of 15-20 mm and a diameter of 11-13 μm; and the thermally conductive reinforcing material is graphene particles with a particle size of 4-6 μm.

[0075] The heat-absorbing element has a thickness of 1.8 mm and a density of 1400 kg / m³. 3 Its thermal conductivity at 25℃ is 5.6-6.0 W / (mK). Furthermore, a compression test was conducted on the plate-shaped heat absorber. The specific steps were as follows: the sample size was 50×50 mm, and the thickness was 1.8 mm. A universal testing machine was used to apply an external force to the sample at a loading rate of 10 mm / min and an initial force of 5 N until the sample failed. The compressive strength was then recorded. The results showed that under a stress of 1 MPa, the strain of the plate-shaped heat absorber was approximately 15-20%; after compression under a maximum stress of 4 MPa, the plate-shaped heat absorber showed no damage or cracking.

[0076] The plate-shaped heat absorber was tested using a differential scanning calorimeter, and the obtained DSC curve is shown below. Figure 5 As shown. From Figure 5It can be determined that the thermal decomposition initiation temperature of the plate-shaped heat absorber is 80℃, and the thermal decomposition temperatures are 80℃-142℃ and 176℃-191℃, with the peak temperatures of the endothermic peak (i.e., phase transition temperatures) being 142℃ and 191℃, respectively. The latent heat enthalpy per unit mass of this plate-shaped heat absorber within the 80℃-200℃ range is 1323 kJ / kg, of which the latent heat enthalpy per unit mass within the 80℃-170℃ range is 964.5 kJ / kg, and the latent heat enthalpy per unit mass within the 170℃-200℃ range is 358.6 kJ / kg. The latent heat enthalpy per unit volume of this plate-shaped heat absorber within the 80℃-200℃ range is 1852 kJ / L.

[0077] A battery pack was prepared for a 45°C high-temperature needle penetration thermal runaway test on the positive electrode. Specifically, 1) multiple lithium iron phosphate cells were provided, each with a capacity of 170 A·h and a state of charge of 100%; 2) the multiple cells were arranged in parallel and assembled into a battery pack, and the heat-absorbing assembly obtained by heat-sealing the plate-shaped heat-absorbing component described in Example 1 with an aluminum-plastic film was placed between any two adjacent cells (e.g., ...). Figure 3 (As shown). 3) Keep the battery pack at 45°C for 2 hours, and then trigger thermal runaway of a single cell by puncturing it from the positive electrode side (a temperature rise rate of a single cell greater than 1°C / second is considered thermal runaway).

[0078] The results showed that in the high-temperature needle penetration positive electrode thermal runaway test of the battery pack in Example 1, the highest temperature of the thermal runaway single cell was 324°C, the highest temperature on the positive electrode side of the battery adjacent to the thermal runaway cell was 265°C, and the highest temperature on the negative electrode side was 142°C. The thermal runaway cell took only 105 seconds to rise from room temperature to the highest temperature of 265°C, after which it began to cool down, and finally the battery pack did not experience thermal diffusion.

[0079] Example 2

[0080] A plate-shaped heat-absorbing element is formed by mixing a heat-absorbing active material, chopped fibers, and a thermally conductive reinforcing material in a mass ratio of 90:5:5 to form a composite heat-absorbing material, which is then pressed. The heat-absorbing active material is a mixture of barium hydroxide octahydrate with a particle size of 20-30 μm; the chopped fibers are glass fibers with a length of 15-20 mm and a diameter of 6-9 μm; the thermally conductive reinforcing material is a mixture of ceramic particles and graphite particles, both with a particle size in the range of 2-5 μm.

[0081] In Example 2, the plate-shaped heat absorber has a thickness of 1.5 mm and a density of 1.4 kg / m³. 3Its thermal conductivity at 25°C is 2.0-3.0 W / (mK). Compression tests were conducted under the same conditions as in Example 1. The results showed that the strain of the heat absorber in Example 2 was approximately 10-12% under a stress of 1 MPa; after compression with a maximum stress of 4 MPa, the plate-shaped heat absorber showed no damage or cracking.

[0082] The plate-shaped heat absorber was tested using a differential scanning calorimeter, and the obtained DSC curve is shown below. Figure 6 As shown. From Figure 6 It can be determined that the thermal decomposition initiation temperature of the plate-shaped heat absorber is 80℃, and the thermal decomposition temperatures are 80℃-150℃ and 156℃-167℃, with the peak temperatures of the endothermic peak (i.e., phase transition temperatures) being 150℃ and 167℃, respectively. The latent heat enthalpy per unit mass of the plate-shaped heat absorber within the 80℃-180℃ range is 1338 kJ / kg, and the latent heat enthalpy per unit volume within the 80℃-180℃ range is 1872 kJ / L.

[0083] A battery pack was prepared for a 45°C high-temperature needle penetration thermal runaway experiment on the positive electrode. Specifically, 1) multiple lithium iron phosphate cells were provided, each with a capacity of 217 A·h and a state of charge of 100%; 2) the multiple cells were arranged in parallel and assembled into a battery pack, and the heat-absorbing assembly obtained by heat-sealing the plate-shaped heat-absorbing component described in Example 2 with an aluminum-plastic film was placed between any two adjacent cells (e.g., ...). Figure 3 (As shown). 3) Keep the battery pack at 45°C for 2 hours, and then trigger thermal runaway of a single cell by puncturing it from the positive electrode side (a temperature rise rate of a single cell greater than 1°C / second is considered thermal runaway).

[0084] The results showed that in the high-temperature needle penetration thermal runaway test of the battery pack in Example 2, the highest temperature of the thermal runaway single cell was 410°C, and the highest temperature of the surface of the adjacent battery near the thermal runaway single cell was 250°C, lasting for 136 seconds. Afterward, the temperature began to decrease, and finally, no thermal diffusion occurred in the battery pack. This indicates that introducing a heat-absorbing component into the battery pack of Example 2 can effectively suppress the thermal diffusion of a single thermal runaway cell within the battery pack, achieving a thermal runaway protection effect.

[0085] Comparative Example 1

[0086] Compared with Example 1, the difference in Comparative Example 1 is that the heat-absorbing active material in the heat-absorbing element is paraffin.

[0087] The selected high-temperature phase change paraffin has an initial phase change temperature of 98℃ and a peak temperature of 112℃. Within the temperature range of 473-500℃, the paraffin still possesses some endothermic capacity, with a total enthalpy of approximately 386 KJ / Kg. Its endothermic capacity is relatively poor. Figure 7 As shown.

[0088] A battery pack was prepared for a 45°C high-temperature needle penetration thermal runaway experiment on the positive electrode. Specifically, 1) multiple lithium iron phosphate cells were provided, each with a capacity of 81 A·h and a state of charge (SOC) of 100%; 2) the multiple cells were arranged in parallel and assembled into a battery pack, and the heat-absorbing component obtained by heat-sealing the plate-shaped composite heat-absorbing material described in Comparative Example 1 with an aluminum-plastic film was placed between any two adjacent cells; 3) the battery pack was kept at 45°C for 2 hours, and then thermal runaway was triggered in one of the cells by needle penetration from the positive electrode side (a temperature rise rate greater than 1°C / second for a single cell was considered thermal runaway).

[0089] The results showed that in the high-temperature needle penetration thermal runaway test of the battery pack in Comparative Example 1, the highest temperature of the thermal runaway single cell was 592°C, and the highest temperature of the adjacent single cell was 651°C. After the single cell went into runaway state by needle penetration, the adjacent single cell on one side of it immediately went into runaway state. After about 7 minutes, the temperature of the single cell on the other side also rose sharply and went into thermal runaway state. This shows that the scheme of Comparative Example 1 failed to suppress the occurrence of thermal diffusion. Moreover, compared with Example 1, the single cell of Comparative Example 1 has a smaller capacity and less heat generation, and the plate-shaped composite heat-absorbing material is thicker, but it still failed to prevent the occurrence of thermal spread.

[0090] The embodiments described above are merely examples of several implementation methods of this application, and while the descriptions are specific and detailed, they should not be construed as limiting the scope of this patent application. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of this application, and these modifications and improvements all fall within the protection scope of this application.

Claims

1. A composite heat-absorbing material, characterized in that, The composite heat-absorbing material includes a heat-absorbing active material, chopped fibers, and a thermally conductive reinforcing material; wherein the heat-absorbing active material is a hydrate, the thermal decomposition temperature of the hydrate is in the range of 70-200℃, and the phase transition temperature of the hydrate is in the range of 70-200℃.

2. The composite heat-absorbing material as described in claim 1, characterized in that, In the composite heat-absorbing material, the mass percentage of the heat-absorbing active material is 80%-90%, preferably 85%-90%; The chopped fiber has a mass percentage content of 2%-10%, preferably 3%-5%; The thermally conductive reinforcing material has a mass percentage content of 2%-10%, preferably 5%-8%.

3. The composite heat-absorbing material as described in claim 1 or 2, characterized in that, The thermal decomposition temperature is in the range of 80-160℃; and / or the phase transition temperature is in the range of 80-160℃.

4. The composite heat-absorbing material according to any one of claims 1-3, characterized in that, The hydrate includes at least one of crystalline hydrate and oxalate dihydrate; the crystalline hydrate includes one or more of calcium chloride hexahydrate, barium hydroxide octahydrate, sodium acetate trihydrate, magnesium sulfate heptahydrate, calcium sulfate dihydrate, magnesium sulfate octahydrate, sodium metasilicate pentahydrate, magnesium sulfate heptahydrate, disodium hydrogen phosphate dodecahydrate, sodium silicate nonahydrate, aluminum sulfate dodecahydrate, sodium sulfate decahydrate, sodium carbonate decahydrate, sodium pyrophosphate decahydrate, potassium aluminum sulfate dodecahydrate, ammonium aluminum sulfate dodecahydrate, and sodium bicarbonate decahydrate.

5. The composite heat-absorbing material according to any one of claims 1-4, characterized in that, The particle size of the hydrate is 1-100 μm, preferably 20-50 μm.

6. The composite heat-absorbing material according to any one of claims 1-5, characterized in that, The chopped fibers include one or more of the following: glass fiber, aluminum silicate fiber, magnesium silicate fiber, basalt fiber, mullite fiber, silicon carbide fiber, alumina fiber, and zirconium oxide fiber.

7. The composite heat-absorbing material according to any one of claims 1-6, characterized in that, The average length of the chopped fibers is 1-20 mm, and the average diameter of the chopped fibers is 8-20 μm; preferably, the average length of the chopped fibers is 5-10 mm, and the average diameter of the chopped fibers is 9-13 μm.

8. The composite heat-absorbing material according to any one of claims 1-7, characterized in that, The thermally conductive enhancement material includes one or more of non-conductive particles, conductive carbon particles, and metal particles; wherein... The non-conductive particles are made of one or more of the following materials: aluminum trihydrate, silicon carbide, boron nitride, silicon nitride, metal oxides, and metal nitrides; and / or The conductive carbon particles are made of one or more of the following materials: silica, graphite powder, expanded graphite, and graphene; and / or The metal particles are made of one or more of the following materials: aluminum, copper, nickel, silver, platinum, and gold.

9. The composite heat-absorbing material according to any one of claims 1-8, characterized in that, The particle size of the thermally conductive reinforcing material is 1-20 μm, preferably 2-8 μm.

10. The composite heat-absorbing material according to any one of claims 1-9, characterized in that, The composite heat-absorbing material does not contain a binder.

11. A heat-absorbing element, characterized in that, The heat-absorbing element includes the composite heat-absorbing material as described in any one of claims 1-10.

12. The heat-absorbing element as claimed in claim 11, characterized in that, The heat-absorbing element is plate-shaped.

13. The heat-absorbing element as described in claim 12, characterized in that, The thickness of the heat-absorbing element is 1mm-10mm.

14. The heat-absorbing element according to any one of claims 11-13, characterized in that, The density of the heat-absorbing element is 1000-1800 kg / m³ 3 Within the range of 1200-1400 kg / m³, it is preferred. 3 Within the range.

15. The heat-absorbing element according to any one of claims 1-14, characterized in that, The latent heat per unit mass of the heat-absorbing element in the range of 70℃-200℃ is in the range of 1000kJ / kg-1500kJ / kg, preferably in the range of 1300kJ / kg-1500kJ / kg.

16. The heat-absorbing element according to any one of claims 1-15, characterized in that, The latent heat per unit volume of the heat-absorbing element in the range of 70°C-200°C is in the range of 1200kJ / L-2100kJ / L, preferably in the range of 1600kJ / L-2100kJ / L.

17. The heat-absorbing element according to any one of claims 1-12, characterized in that, The thermal conductivity of the heat absorber at 25°C is in the range of 1-8 W / (mK), preferably in the range of 5-8 W / (mK).

18. A heat-absorbing component, characterized in that, The heat-absorbing component includes an encapsulation film and a composite heat-absorbing material as described in any one of claims 1-10 or a heat-absorbing element as described in any one of claims 11-17, wherein the composite heat-absorbing material or the heat-absorbing element is encapsulated within the encapsulation film.

19. A battery pack, characterized in that, The battery pack includes a plurality of individual cells and a heat-absorbing element as described in any one of claims 11-17 or a heat-absorbing assembly as described in claim 18, wherein the heat-absorbing element or the heat-absorbing assembly is disposed between at least two adjacent individual cells.

20. A battery pack, characterized in that, in, The battery pack satisfies at least one of the following (a), (b), and (c): (a) The battery pack includes a battery pack, which is the battery pack as described in claim 19; (b) The battery pack includes a plurality of battery groups, and a heat-absorbing element as described in any one of claims 11-17 or a heat-absorbing component as described in claim 18 is disposed between at least two adjacent battery groups; (c) The battery pack includes a tray, a top cover and a plurality of individual cells, the tray and the top cover forming a receiving space for accommodating the plurality of individual cells, and at least one of the individual cells is provided with a heat-absorbing element as described in any one of claims 11-17 or a heat-absorbing assembly as described in claim 18 between it and the top cover.

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