Battery heat dissipation device based on metal foam composite hydrogel and preparation method thereof

Abstract

This invention discloses a battery heat dissipation device based on metal foam composite hydrogel and its preparation method, relating to the field of battery thermal management technology. The device includes: a frame and a battery pack housed within the frame; the battery pack consists of multiple single-cell arrays arranged with a gap of 24mm-40mm between adjacent single-cell cells; the gaps are filled with metal foam composite hydrogel layers, and a single metal foam composite hydrogel layer is attached to the sidewall of each of two adjacent single-cell cells; the thickness of the metal foam composite hydrogel layer is 2mm-4mm; the metal foam composite hydrogel layer includes a metal foam skeleton, a highly hygroscopic hydrogel matrix loaded within the pores of the metal foam skeleton, and hygroscopic salts filled in the matrix network. This invention utilizes the high thermal conductivity of the metal foam skeleton and the hygroscopic evaporation heat dissipation of the hydrogel to significantly improve the heat dissipation efficiency of the battery pack, while also possessing structural stability and thermal runaway protection functions.

Description

Technical Field

[0001] This invention relates to the field of battery thermal management technology, specifically to a metal foam composite hydrogel based on metal foam and its preparation method. Background Technology

[0002] With the development of new energy vehicles and large-scale energy storage technologies, the energy density and power density of lithium-ion batteries are constantly increasing, and the problem of heat accumulation during charging and discharging is becoming increasingly serious. High-temperature environments not only lead to battery capacity decay and increased internal resistance, but may also trigger thermal runaway, posing safety hazards.

[0003] Existing battery cooling technologies mainly include air cooling, liquid cooling, and phase change material (PCM) cooling. Air cooling has a simple structure but low heat dissipation efficiency; liquid cooling has good heat dissipation effect but has leakage risk, complex structure, and high energy consumption; traditional paraffin-based phase change materials have low thermal conductivity and are prone to liquid phase leakage.

[0004] In recent years, pure polymer hydrogels have been considered potential battery heat dissipation materials due to their high water content and excellent heat absorption properties. However, pure polymer hydrogels have the following problems: First, the intrinsic thermal conductivity of pure polymer hydrogels is extremely low (typically below 0.5 W / m·K), resulting in a severely insufficient effective heat transfer coefficient. When the device generates high heat, the heat cannot be quickly transferred from the heat-generating interface to the interior of the hydrogel and the evaporation front, causing a huge temperature gradient inside the material. Heat accumulates at the contact interface, leading to an exponential decrease in heat dissipation efficiency. Second, pure polymer hydrogels undergo severe volume shrinkage and network structure collapse during dehydration, manifested as curling towards the center or peeling off from the heat source surface. This non-uniform deformation can cause air gaps (a sharp increase in thermal resistance) between the heat dissipation material and the device surface, leading to localized hot spots, and even damage to electronic devices due to uneven heat dissipation. Third, although the introduction of hygroscopic salts (such as LiBr) can endow the material with the ability to absorb water, it is limited by the small vapor pressure difference between the surface of the pure polymer hydrogel and the environment, and the exothermic effect accompanying the moisture absorption process will further inhibit the diffusion of water molecules, resulting in a water absorption and regeneration rate that is much lower than the evaporation rate, which cannot meet the rapid water replenishment requirements of intermittent or pulsed working modes. Summary of the Invention

[0005] In view of the shortcomings of the prior art, the purpose of this invention is to provide a battery heat dissipation device based on metal foam composite hydrogel and its preparation method, aiming to solve at least one of the problems in the above-mentioned background art.

[0006] One aspect of this invention is to provide a battery heat dissipation device based on a metal foam composite hydrogel, comprising: A frame, and a battery pack housed within the frame; The battery pack is composed of multiple single-cell arrays arranged together, with a gap of 24mm-40mm between adjacent single-cells; The gap is filled with a metal foam composite hydrogel layer, and a single metal foam composite hydrogel layer is attached to the sidewall of two adjacent single batteries. The thickness of the metal foam composite hydrogel layer is 2mm-4mm. The metal foam composite hydrogel layer includes a metal foam skeleton, a highly hygroscopic hydrogel matrix loaded within the pores of the metal foam skeleton, and hygroscopic salts filled in the network of the highly hygroscopic hydrogel matrix.

[0007] According to one aspect of the above technical solution, the metal foam skeleton is an aluminum metal foam skeleton with a pore density of 10ppi-30ppi.

[0008] According to one aspect of the above technical solution, the highly hygroscopic hydrogel matrix includes a hydrogel and a molding aid, wherein the hydrogel is selected from any one or more of polyacrylamide hydrogel, polyethylene glycol hydrogel, poly(hydroxyethyl methacrylate) hydrogel, poly(N-isopropylacrylamide) hydrogel, and sodium alginate hydrogel, the molding aid is agarose, and the hygroscopic salt is lithium bromide.

[0009] Another aspect of the present invention provides a method for preparing a battery heat dissipation device based on a metal foam composite hydrogel, the method being used to prepare the aforementioned battery heat dissipation device based on a metal foam composite hydrogel, the method comprising: The metal foam skeleton is pretreated and dried; The monomer, crosslinking agent and UV initiator are mixed to prepare a hydrogel precursor solution. Then, the molding aid is added, and the mixture is heated and stirred until the molding aid is completely dissolved. After refrigeration, a highly hygroscopic hydrogel precursor solution with a three-dimensional network crosslinking structure is obtained. The pretreated metal foam skeleton is immersed in a highly hygroscopic hydrogel precursor solution, so that the highly hygroscopic hydrogel precursor solution completely fills the pores of the metal foam skeleton and adheres evenly to the surface until there is no exposed metal area. The soaked metal foam skeleton was removed and photo-initiated polymerization and curing was performed by ultraviolet irradiation to form a metal foam skeleton-hydrogel composite precursor. The metal foam skeleton-hydrogel composite precursor was immersed in a hygroscopic salt solution to fully load the hygroscopic salt into the three-dimensional network cross-linked structure. After removal, the surface was cleaned to remove the free salt, and the metal foam composite hydrogel was obtained. The metal foam composite hydrogel is cut to a thickness of 2mm-4mm and filled into the gap between adjacent single cells. A single metal foam composite hydrogel is then attached to the sidewall of each of the two adjacent single cells to assemble the battery heat dissipation device.

[0010] Furthermore, the pretreatment includes: ultrasonic cleaning sequentially with deionized water and anhydrous ethanol.

[0011] Further, the monomer is selected from any one or more of acrylamide, polyethylene glycol, hydroxyethyl methacrylate, N-isopropylacrylamide, and sodium alginate; the crosslinking agent is N,N'-methylenebisacrylamide; the ultraviolet initiator is 2-hydroxy-4'-(2-hydroxyethoxy)-2-methylphenylacetone; the mass ratio of the monomer to the crosslinking agent is (850-1000):1; the mass ratio of the crosslinking agent to the ultraviolet initiator is 1:(2-4); and the mass ratio of the monomer to water is 1:(6-8). The forming aid is agarose, and the amount added is 0.5wt%-2wt% of the hydrogel precursor solution; The refrigeration treatment is carried out at a temperature of -2℃ to 4℃ for a time of 20 min to 40 min.

[0012] Furthermore, the metal foam skeleton is immersed in the highly hygroscopic hydrogel precursor solution for no less than 3 minutes, and the solid-liquid ratio of the metal foam skeleton to the highly hygroscopic hydrogel precursor solution is 1g:(4-10)mL.

[0013] Furthermore, the wavelength of the ultraviolet irradiation is any one of 254nm, 365nm, and 405nm; The duration of ultraviolet irradiation is adjusted according to the type and amount of the highly hygroscopic hydrogel precursor solution, and the duration ranges from 1h to 10h.

[0014] Furthermore, following the step of forming the metal foam framework-hydrogel composite precursor, the process also includes: The metal foam skeleton-hydrogel composite precursor was washed with deionized water and dried at 45℃-95℃ until the weight reduction was 0.05%-2%.

[0015] Furthermore, the hygroscopic salt solution is a lithium bromide solution with a molar concentration of 0.5 mol / L to 19.6 mol / L.

[0016] Compared with the prior art, the beneficial effects of the present invention are as follows: 1. This invention introduces a three-dimensional interconnected metal foam framework, which utilizes its intrinsic thermal conductivity, which is much higher than that of hydrogels, to construct a rapid heat transfer channel inside the material. This breaks through the thermal bottleneck of traditional hydrogels, which rely solely on their own heat conduction. It can instantly distribute and conduct the heat on the surface of the heating device to the evaporation interface of the entire material, eliminating excessive temperature gradients inside the material and ensuring the synchronicity of heat supply and evaporative heat dissipation, thereby achieving a qualitative leap in passive heat dissipation efficiency.

[0017] 2. Through the strong interfacial bonding between the hydrogel and the porous framework (metal foam framework), the metal foam framework provides a rigid mechanical support structure for the hydrogel. During the weight loss process due to water evaporation, the metal foam framework effectively resists the shrinkage stress caused by capillary force changes in the hydrogel network, fundamentally eliminating the curling, collapse, and peeling from the heat source surface that are common in traditional hydrogels. This ensures that the material and the device surface always maintain close surface contact, avoiding local hot spots caused by sudden changes in contact thermal resistance, and greatly improving the safety and stability of operation.

[0018] 3. Through the synergistic effect of hygroscopic salt and highly hygroscopic hydrogel network, the surface vapor pressure of the material is regulated. In the working state, the material can maintain a high vapor pressure to accelerate evaporation; in the dormant state, by utilizing the heat exchange characteristics of the material itself and the hygroscopic characteristics of the salt solution, the maximum vapor pressure difference between the material and the environment is quickly established, thereby driving the rapid return of moisture. This dynamic balance mechanism of evaporation-regeneration rate solves the pain points of slow regeneration of hygroscopic materials and inability to adapt to intermittent working mode.

[0019] 4. By introducing trace amounts of agarose as a physical crosslinking point and nucleating agent, the microstructure uniformity of the composite material is significantly improved without sacrificing the water content of the hydrogel. This not only endows the precursor liquid with excellent thixotropic properties to facilitate load molding, but more importantly, it effectively inhibits the local oversaturation and abnormal crystallization of hygroscopic salts during the circulation process, prevents the blockage of water transport channels, and ensures the long-term dynamic transport capability of water inside the material.

[0020] 5. In this invention, a metal foam composite hydrogel layer is filled into the 24mm-40mm gap between adjacent single-cell batteries. The thickness of the metal foam composite hydrogel layer is controlled at 2mm-4mm, which ensures sufficient heat dissipation medium volume while avoiding increased thermal resistance and wasted space due to excessive thickness. The metal foam composite hydrogel layer is tightly adhered to the sidewall of the battery, ensuring good thermal contact and heat transfer efficiency. Attached Figure Description

[0021] The above and / or additional aspects and advantages of the present invention will become apparent and readily understood from the description of the embodiments taken in conjunction with the following drawings, in which: Figure 1 This is a schematic diagram illustrating the evaporation-regeneration principle of the metal foam composite hydrogel of the present invention. Figure 2 This is a structural diagram of the metal foam composite hydrogel of Embodiment 1 of the present invention; Figure 3 This is a scanning electron microscope image of the metal foam composite hydrogel of Example 1 of the present invention after freeze-drying; Figure 4 This is a comparison chart of the thermal conductivity of the present invention; Figure 5 This is a comparison diagram of the surface temperature changes of the device according to the present invention; Figure 6 A graph showing the evaporation and water absorption rate of metal foam composite hydrogels prepared for metal foam skeletons with different pore densities according to the present invention. Figure 7 This is a test diagram of the evaporation and moisture absorption cycle of the metal foam composite hydrogel in Example 1 of the present invention; Figure 8 This is a graph showing the mass change during the evaporation and regeneration process of the present invention; Figure 9 This is a comparison chart of the mass change curves of the present invention; Figure 10 Comparison of metal foam framework-hydrogel composite precursors with different agarose mass fractions. Detailed Implementation

[0022] To make the objectives, features, and advantages of the present invention more apparent and understandable, specific embodiments of the present invention are described in detail below with reference to the accompanying drawings. Several embodiments of the present invention are shown in the drawings. However, the present invention can be implemented in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0023] This invention provides a battery heat dissipation device based on metal foam composite hydrogel, comprising: A frame, and a battery pack housed within the frame; The battery pack is composed of multiple single-cell arrays arranged together, with a gap of 24mm-40mm between adjacent single-cells; The gap is filled with a metal foam composite hydrogel layer, and a single metal foam composite hydrogel layer is attached to the sidewall of two adjacent single batteries. The thickness of the metal foam composite hydrogel layer is 2mm-4mm. The metal foam composite hydrogel layer includes a metal foam skeleton, a highly hygroscopic hydrogel matrix loaded within the pores of the metal foam skeleton, and hygroscopic salts filled in the network of the highly hygroscopic hydrogel matrix.

[0024] The metal foam skeleton is an aluminum metal foam skeleton with a pore density of 10ppi-30ppi.

[0025] Furthermore, the highly hygroscopic hydrogel matrix includes a hydrogel and a molding aid, wherein the hydrogel is selected from any one or more of polyacrylamide hydrogel, polyethylene glycol hydrogel, poly(hydroxyethyl methacrylate) hydrogel, poly(N-isopropylacrylamide) hydrogel, and sodium alginate hydrogel, the molding aid is agarose, and the hygroscopic salt is lithium bromide.

[0026] like Figure 1 As shown, when a single battery cell is in operation and its surface temperature rises, heat first enters the highly thermally conductive aluminum foam skeleton closely attached to the surface of the single battery cell. The three-dimensional interconnected structure rapidly distributes the localized high heat flux evenly throughout the network, eliminating heat accumulation at the contact interface. Simultaneously, a highly hygroscopic hydrogel matrix is ​​infused and anchored to the inner walls of the pores in the aluminum foam skeleton, forming numerous gel-pore wall-air three-phase evaporation interfaces. Utilizing the extremely low equilibrium vapor pressure of the lithium bromide (LiBr) solution, a significant vapor pressure difference driving force is formed between the surface of the metal foam composite hydrogel layer and the environment, greatly increasing the water evaporation flux. Through the latent heat of phase change, heat is efficiently carried away, achieving passive heat dissipation.

[0027] In dormant mode, individual cells cease heat generation, and the surface temperature of the metal foam composite hydrogel layer drops. At this time, the LiBr solution within the gel network, due to water loss and concentration, exhibits a stronger hygroscopic driving force (ambient water vapor partial pressure > material surface vapor pressure), prompting ambient moisture to spontaneously migrate into the material's interior, completing regeneration. Crucially, the high heat capacity and thermal conductivity of the metal foam skeleton, combined with the residual effect of evaporative cooling, often create a slight temperature difference below the ambient temperature on the surface of the metal foam composite hydrogel layer. This further increases the relative humidity of the surface air boundary layer, generating a tendency for micro-condensation. This, coupled with the temperature difference-driven hygroscopic gain on top of the vapor pressure difference-driven effect, significantly shortens the regeneration cycle. By adjusting the hygroscopic salt concentration, a dynamic balance between evaporation and regeneration rates is achieved, solving the problem of rapid heat dissipation efficiency decay and slow regeneration inherent in traditional hydrogels.

[0028] Furthermore, a gap of 24mm-40mm is left between adjacent single cells to form an open air circulation channel. This provides sufficient space and convection conditions for the water evaporation phase change of the metal foam composite hydrogel layer in the working state, ensuring heat dissipation efficiency under high heat flux density. It also reserves sufficient environmental contact area for the metal foam composite hydrogel layer in the dormant state to spontaneously absorb moisture from the air for regeneration, achieving synergistic optimization of efficient heat dissipation and rapid regeneration.

[0029] Accordingly, the present invention also provides a method for preparing a battery heat dissipation device based on a metal foam composite hydrogel, the method comprising: steps S1-S6, Step S1: Pre-treat and dry the metal foam skeleton; Pretreatment included ultrasonic cleaning with deionized water and anhydrous ethanol sequentially. The solid-liquid ratio of the metal foam skeleton to deionized water or anhydrous ethanol was 1 g: (4-10) mL.

[0030] Specifically, the surface is ultrasonically cleaned in deionized water for 10-20 minutes to remove dust and soluble impurities; after pouring out the cleaning solution, it is then immersed in anhydrous ethanol with a mass fraction >95% and ultrasonically cleaned for 20-40 minutes to remove grease and impurities; after removal, it is placed in an oven at 60℃-80℃ for 10-30 minutes to dry.

[0031] It should be noted that the metal foam skeleton is an aluminum metal foam skeleton, which has high thermal conductivity (about 200 W / m·K) and three-dimensional interconnected channels. Pretreatment can effectively activate the surface, enhance the adhesion of the subsequent hydrogel, and prevent interface debonding.

[0032] Step S2: Mix the monomer, crosslinking agent and UV initiator to prepare hydrogel precursor solution, then add molding aid, heat and stir until the molding aid is completely dissolved, and after refrigeration, obtain a highly hygroscopic hydrogel precursor solution with a three-dimensional network crosslinking structure. The monomer is selected from any one or more of acrylamide, polyethylene glycol, hydroxyethyl methacrylate, N-isopropylacrylamide, and sodium alginate; the crosslinking agent is N,N'-methylenebisacrylamide; and the UV initiator is 2-hydroxy-4'-(2-hydroxyethoxy)-2-methylphenylacetone. The heating and stirring temperature is 90℃-100℃, the stirring time is 10min-30min, and the stirring speed is 400r / min-600r / min.

[0033] Furthermore, the mass ratio of monomer to crosslinking agent is (850-1000):1, the mass ratio of crosslinking agent to UV initiator is 1:(2-4), and the mass ratio of monomer to water is 1:(6-8).

[0034] The forming aid is agarose, and the amount added is 0.5wt%-2wt% of the hydrogel precursor solution. The refrigeration treatment temperature is -2℃-4℃, and the time is 20min-40min. At low temperature, agarose forms a physical entanglement network, which gives the precursor solution a certain thixotropic property and prevents it from being lost due to gravity during subsequent loading. The microscopic heterostructure formed after warming helps to suppress the macroscopic crystallization of hygroscopic salts in the later stage.

[0035] Step S3: Immerse the pretreated metal foam skeleton in a highly hygroscopic hydrogel precursor solution, so that the highly hygroscopic hydrogel precursor solution completely fills the pores of the metal foam skeleton and adheres evenly to the surface until there is no exposed metal area. Specifically, the metal foam skeleton is immersed in the highly hygroscopic hydrogel precursor solution for no less than 3 minutes to ensure that the highly hygroscopic hydrogel precursor solution fully fills the capillary force of the pores of the metal foam skeleton.

[0036] Step S4: Remove the soaked metal foam skeleton and use ultraviolet irradiation for photo-initiated polymerization and curing to form a metal foam skeleton-hydrogel composite precursor. Specifically, the wavelength of the ultraviolet irradiation is any one of 254nm, 365nm, and 405nm; The duration of ultraviolet irradiation is adjusted according to the type and amount of the hyperhygroscopic hydrogel precursor solution, ranging from 1 hour to 10 hours. This causes the monomers in the hyperhygroscopic hydrogel precursor solution to undergo free radical polymerization, forming a chemical cross-linked network that interlocks with the agarose physical network, and solidifies to form a metal foam framework / hydrogel composite precursor.

[0037] Furthermore, following the step of forming the metal foam framework-hydrogel composite precursor, the process also includes: The metal foam skeleton-hydrogel composite precursor was washed with deionized water and dried at 45℃-95℃ until the weight reduction was 0.05%-2%.

[0038] Step S5: Immerse the metal foam skeleton-hydrogel composite precursor in a hygroscopic salt solution to fully load the hygroscopic salt into the three-dimensional network cross-linked structure. After removal, clean the surface to remove free salt and obtain the metal foam composite hydrogel. The hygroscopic salt solution is a lithium bromide solution with a molar concentration of 0.5 mol / L to 19.6 mol / L.

[0039] Step S6: Cut the metal foam composite hydrogel to a thickness of 2mm-4mm and fill it into the gap between adjacent single cells. Apply a single metal foam composite hydrogel to the sidewall of each of the two adjacent single cells to assemble the battery heat dissipation device.

[0040] The present invention is further illustrated below with specific embodiments: Example 1 Embodiment 1 of the present invention provides a battery heat dissipation device based on metal foam composite hydrogel, comprising: The frame, and the battery pack housed within the frame; The battery pack consists of an array of multiple individual cells arranged in a 26mm gap between adjacent cells. The gap is filled with a metal foam composite hydrogel layer, and the sidewalls of two adjacent single cells are respectively covered with metal foam composite hydrogel layers, the thickness of which is 3mm. The metal foam composite hydrogel layer includes a metal foam skeleton, a highly hygroscopic hydrogel matrix loaded within the pores of the metal foam skeleton, and hygroscopic salts filled in the network of the highly hygroscopic hydrogel matrix.

[0041] Accordingly, the preparation method of the metal foam composite hydrogel layer includes steps S1-S6.

[0042] Step S1: Select aluminum metal foam skeleton as metal foam skeleton, immerse it in deionized water and ultrasonically clean it for 15 min, then immerse it in anhydrous ethanol with a mass fraction >95% and ultrasonically clean it for 30 min, take it out and dry it in an oven at 70℃ for 15 min. The solid-liquid ratio of metal foam skeleton to deionized water or anhydrous ethanol is 1 g: 5 mL.

[0043] Step S2: Using acrylamide as a monomer, N,N'-methylenebisacrylamide as a crosslinking agent, and 2-hydroxy-4'-(2-hydroxyethoxy)-2-methylphenylacetone as a UV initiator, a hydrogel precursor solution is prepared. Then, 0.5 wt% agarose is added, and the mixture is heated to 97°C and stirred for 20 min at a stirring speed of 400 r / min-600 r / min. After the solution becomes completely transparent, it is refrigerated at -2°C for 30 min and then allowed to stand at room temperature to obtain a highly hygroscopic hydrogel precursor solution with a three-dimensional network crosslinked structure. Taking 1 L of water as an example, 142.16 g of acrylamide, 0.154 g of N,N'-methylenebisacrylamide, and 0.4485 g of 2-hydroxy-4'-(2-hydroxyethoxy)-2-methylphenylacetone need to be added.

[0044] Step S3: Immerse the pretreated aluminum metal foam skeleton completely in the super hygroscopic hydrogel precursor solution for 5 minutes to ensure that the pores and surface are completely wetted and there are no exposed areas. After taking it out, place it in a petri dish. The solid-liquid ratio of the metal foam skeleton to the super hygroscopic hydrogel precursor solution is 1g:5mL.

[0045] Step S4: Irradiate with ultraviolet light at a wavelength of 365nm for 6 hours to fully crosslink and solidify, forming a metal foam skeleton-hydrogel composite precursor. Wash with deionized water and dry at 60℃. Weigh twice at 10-minute intervals, and the weight change rate is less than 1% of the total weight to obtain the dried metal foam skeleton-hydrogel composite precursor.

[0046] Step S5: Immerse the dried metal foam framework-hydrogel composite precursor in a 4.93 mol / L lithium bromide solution for 4 hours to allow the hygroscopic salts to fully load. Wipe off excess salt solution from the surface, and wash with deionized water to remove free salts, obtaining the metal foam composite hydrogel. Figure 2 As shown.

[0047] from Figure 3The microstructure shows that the surface material of the metal foam composite hydrogel is complete and continuous, without large-area fractures, and the pores are interconnected to form continuous channels, allowing fluid to transport freely within the pores.

[0048] Step S6: Cut the metal foam composite hydrogel to a thickness of 3mm and fill it into the gap between adjacent single cells. Apply a single piece of the metal foam composite hydrogel to the sidewall of each of the two adjacent single cells to assemble a battery heat dissipation device. Leave a 26mm gap between adjacent single cells.

[0049] Example 2 The difference between Example 2 and Example 1 is that the amount of agarose added is 1%, while the other steps and conditions remain unchanged.

[0050] Example 3 The difference between Example 3 and Example 1 is that the amount of agarose added is 2%, while the other steps and conditions remain unchanged.

[0051] Example 4 The difference between Example 4 and Example 1 is that the amount of agarose added is 5%, while the other steps remain unchanged.

[0052] Example 5 The difference between Embodiment 5 and Embodiment 1 is that the pore density of the aluminum metal foam is 10 ppi, while the other steps and conditions remain unchanged.

[0053] Example 6 The difference between Embodiment 6 and Embodiment 1 is that the pore density of the aluminum metal foam is 20 ppi, while the other steps and conditions remain unchanged.

[0054] Comparative Example 1 The difference between Comparative Example 1 and Example 1 is that pure hydrogel (aluminum-free metal foam skeleton) is prepared using the exact same method.

[0055] Comparative Example 2 The difference between Comparative Example 2 and Example 1 is that: agarose is removed, but other step conditions remain unchanged, and the metal foam skeleton-hydrogel composite precursor cannot be formed.

[0056] Comparative Example 3 The difference between Comparative Example 3 and Example 1 is that step S5 is omitted, while the conditions for other steps remain unchanged.

[0057] Thermal conductivity test: The thermal conductivity of the material was determined using the transient plane heat source method (Hot Disk method). All tests were conducted under constant temperature conditions (e.g., 25℃±1℃) and repeated at least three times, with the average value taken.

[0058] Li-PAAm-Al / 30ppi: Metal foam composite hydrogel of Example 1.

[0059] Li-PAAm: Pure hydrogel (aluminum-free metal foam skeleton) of Comparative Example 1.

[0060] from Figure 4 It can be seen that the thermal conductivity of Example 1 is significantly higher than that of Comparative Example 1 (without aluminum metal foam skeleton), proving that the aluminum metal foam skeleton can significantly improve the thermal conductivity of the metal foam composite hydrogel by utilizing its intrinsic thermal conductivity which is much higher than that of the hydrogel.

[0061] Heat dissipation performance test: Test conditions: At a temperature of 25℃±1℃ and a relative humidity of 60%±5%, a heat dissipation test was conducted on a battery heat dissipation device made using lithium-ion batteries as single cells. An infrared thermal imager (Fluke TiS75) and a patch thermocouple (K-type, accuracy ±0.1℃) were used to simultaneously monitor the surface temperature. The lithium-ion battery had a capacity of 5000mAh, a rated voltage of 3.7V, a charging cut-off voltage of 4.25V, a discharging cut-off voltage of 2.75V, and a normal operating temperature of -20℃ to 60℃. The lithium-ion battery discharge rate was controlled at 2.0C during the heat dissipation test. The surface temperature was recorded every 5 minutes, along with changes in material mass.

[0062] Blank: No heat dissipation material is attached.

[0063] Li-PAAm-Al / 30ppi: Surface-adhesive metal foam composite hydrogel of Example 1.

[0064] Li-PAAm: Surface-adhesive pure hydrogel (aluminum-free metal foam skeleton) of Comparative Example 1.

[0065] like Figure 5 As shown, the surface temperature of the blank material can reach a maximum of approximately 70°C; Li-PAAm can control the surface temperature to approximately 56.2°C; while Li-PAAm-Al / 30ppi, utilizing an aluminum foam skeleton to construct a continuous heat conduction network, exhibits superior heat dissipation, stabilizing the surface temperature at approximately 42.8°C. Compared to Li-PAAm, it achieves an additional cooling rate of up to 14.3°C, significantly improving heat dissipation performance.

[0066] Evaporation and regeneration rate test: In a constant temperature and humidity chamber, the temperature is controlled at 25℃±1℃ and the relative humidity at 90%±5%. The metal foam composite hydrogel is adhered to the surface of the heating element, and an 18650 lithium-ion battery (nominal capacity 9800mWh, voltage 3.7V) is used to power the heating element. The entire assembly (metal foam composite hydrogel + heating element + battery) is placed on the weighing pan of an electronic balance (accuracy not less than 0.01g).

[0067] Start the heating element and continuously record the change in the electronic balance reading (i.e., total mass). When the total mass changes by less than 0.01g within 10 minutes, it is considered to have reached a constant mass state, at which point the heating element power is turned off. Continue recording the sample mass increase curve over time until it reaches a constant mass again. The rate of mass increase in this stage is the water absorption rate of the metal foam composite hydrogel under these temperature and humidity conditions.

[0068] Collect the mass-time data for each stage, calculate the evaporation rate (mass loss stage) and water absorption rate (mass increase stage), and take the average of at least 3 parallel experiments as the final result.

[0069] Li-PAAm-Al / 30ppi: Surface-adhesive metal foam composite hydrogel of Example 1.

[0070] Li-PAAm-Al / 20ppi: Surface-adhesive metal foam composite hydrogel of Example 6.

[0071] Li-PAAm-Al / 10ppi: Surface-adhesive metal foam composite hydrogel of Example 5.

[0072] Li-PAAm: Surface-adhesive pure hydrogel (aluminum-free metal foam skeleton) of Comparative Example 1.

[0073] like Figure 6 As shown, the evaporation rate of Li-PAAm-Al / 30ppi reached 1.13 g / h, and the regeneration rate reached 0.48 g / h, which were 44.87% and 65.52% higher than those of Li-PAAm, respectively. This indicates that aluminum foam not only promotes heat transfer but also optimizes the transport pathways of water and ions. Within the test range of 10ppi-30ppi, the evaporation rate and regeneration rate of the metal foam composite hydrogel both increased with the increase of the pore density of the aluminum foam skeleton (i.e., 30ppi>20ppi>10ppi>pure hydrogel), proving that increasing ppi (i.e., refining the pore size and increasing the pore density) is beneficial to further improve the heat and mass transfer efficiency.

[0074] Cyclic stability test: The test method is consistent with the evaporation and regeneration rate test. During the evaporation phase (simulating heat dissipation / exothermic processes), the heating element is activated, and the moisture in the sample evaporates, causing the total mass to continuously decrease. The electronic balance reading is continuously monitored. When the change in total mass within 10 minutes is less than 0.01 g, it is considered that the mass has reached a constant state (i.e., the moisture has evaporated completely or reached dynamic equilibrium). After reaching a constant state, the power to the heating element is immediately turned off (at this point, the moisture absorption phase begins). After the power is turned off, the sample naturally absorbs moisture from the air in a constant temperature and humidity chamber, and the total mass begins to rise again. The mass increase curve continues to be recorded until the mass reaches a constant state again (again, following the standard of <0.01 g change within 10 minutes). Once a constant state is reached, one complete "evaporation-moisture absorption" cycle is completed. The mass change during multiple "evaporation-moisture absorption" cycles is tested.

[0075] like Figure 7 As shown, the metal foam composite hydrogel of the present invention exhibits stable periodic oscillations in mass change during multiple "evaporation-hygroscopic" cycles, and can eventually fully recover its initial mass, demonstrating its excellent cycle stability, reversible moisture absorption and regeneration capability, and long-term heat dissipation potential.

[0076] Optimization effect test of lithium bromide concentration: The testing method is consistent with the evaporation and cycle stability test method, testing the mass change and lithium bromide concentration change during multiple "evaporation-hygroscopic" cycles.

[0077] like Figure 8 As shown, by adjusting the lithium bromide concentration, Li-PAAm-Al / 30ppi can automatically enter the optimal concentration range of 40wt%-45wt% during actual operation, which significantly reduces the regeneration / evaporation time ratio from the initial 2.35 times to 1.25 times, achieving a synergistic match between rapid heat dissipation and efficient regeneration.

[0078] Testing the performance impact of lithium bromide: The testing method is the same as that used for evaporation and regeneration rate testing.

[0079] Li-PAAm-Al / 30ppi: Surface-adhesive metal foam composite hydrogel of Example 1.

[0080] PAAm-Al / 30ppi: Surface-adhesive metal foam composite hydrogel (LiBr-free) of Comparative Example 3.

[0081] like Figure 9 As shown, PAAm-Al / 30ppi (without LiBr): During operation, moisture evaporates rapidly and weight is lost. However, due to the lack of moisture absorption driving force, it cannot spontaneously absorb water from the environment after the device stops working and the temperature drops, resulting in a continuous decline in quality and failure to complete the cycle.

[0082] Li-PAAm-Al / 30ppi (containing LiBr): During operation, it loses weight; during dormancy, it spontaneously absorbs moisture from the air, gradually recovering its initial mass, achieving a complete "weight loss-weight gain" cycle. This comparative result directly proves that lithium bromide is the core functional component that endows the material with moisture absorption and regeneration capabilities, enabling cyclic operation. Materials without lithium bromide only possess one-time heat dissipation capabilities and cannot meet the requirements for long-term, cyclic thermal management.

[0083] Test on the effect of agarose content on performance: Metal foam framework-hydrogel composite precursors were prepared by varying the agarose mass fraction to 5 wt% (Example 4), 2 wt% (Example 3), 1 wt% (Example 2), and 0.5 wt% (Example 1). The color and transparency of the precursors were recorded by photographing under natural light. Each precursor was immersed in a lithium bromide solution (4.93 mol / L), and after 12 hours, it was removed and the turbidity of the leaching solution and the permeability of the material pores were observed.

[0084] like Figure 10 As shown, when the agarose content is 5 wt% (Example 4), the metal foam skeleton-hydrogel composite precursor is dark in color, and obvious agarose accumulation appears in the pores of the aluminum metal foam, resulting in an uneven structure. During subsequent impregnation, the accumulated agarose is difficult to completely dissolve (during subsequent impregnation, even after several hours of continuous soaking, the material still retains the inherent pale blue color of agarose, proving that agarose cannot be precipitated), easily clogging the water transport channels. When the agarose content is reduced to 2 wt% (Example 3) and 1 wt% (Example 2), the color of the metal foam skeleton-hydrogel composite precursor gradually becomes lighter, and the agarose accumulation phenomenon is alleviated to some extent, but there is still a risk of local enrichment, and the subsequent impregnation process still has the hidden danger of insufficient dissolution. When the content is reduced to 0.5 wt%, the metal foam skeleton-hydrogel composite precursor is almost transparent, uniformly fills the pores without accumulation, and the water transport channels are unobstructed during subsequent salt impregnation. Without the addition of agarose, the metal foam skeleton-hydrogel composite precursor cannot be formed. 0.5wt% (Example 1) is the optimal balance point to ensure uniform molding and unobstructed channels, but if the content is too low, the system will not be able to solidify and form.

[0085] In the description of this specification, references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0086] The embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the present invention. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these all fall within the protection scope of the present invention. Therefore, the protection scope of this patent should be determined by the appended claims.

Claims

1. A battery heat dissipation device based on metal foam composite hydrogel, characterized in that, include: A frame, and a battery pack housed within the frame; The battery pack is composed of multiple single-cell arrays arranged together, with a gap of 24mm-40mm between adjacent single-cells; The gap is filled with a metal foam composite hydrogel layer, and a single metal foam composite hydrogel layer is attached to the sidewall of two adjacent single batteries. The thickness of the metal foam composite hydrogel layer is 2mm-4mm. The metal foam composite hydrogel layer includes a metal foam skeleton, a highly hygroscopic hydrogel matrix loaded within the pores of the metal foam skeleton, and hygroscopic salts filled in the network of the highly hygroscopic hydrogel matrix.

2. The battery heat dissipation device based on metal foam composite hydrogel according to claim 1, characterized in that, The metal foam skeleton is an aluminum metal foam skeleton with a pore density of 10ppi-30ppi.

3. The battery heat dissipation device based on metal foam composite hydrogel according to claim 1, characterized in that, The highly hygroscopic hydrogel matrix includes a hydrogel and a molding aid. The hydrogel is selected from any one or more of polyacrylamide hydrogel, polyethylene glycol hydrogel, poly(hydroxyethyl methacrylate) hydrogel, poly(N-isopropylacrylamide) hydrogel, and sodium alginate hydrogel. The molding aid is agarose, and the hygroscopic salt is lithium bromide.

4. A method for preparing a battery heat dissipation device based on a metal foam composite hydrogel, the method being used to prepare the battery heat dissipation device based on a metal foam composite hydrogel as described in any one of claims 1-3, characterized in that, The method includes: The metal foam skeleton is pretreated and dried; The monomer, crosslinking agent and UV initiator are mixed to prepare a hydrogel precursor solution. Then, the molding aid is added, and the mixture is heated and stirred until the molding aid is completely dissolved. After refrigeration, a highly hygroscopic hydrogel precursor solution with a three-dimensional network crosslinking structure is obtained. The pretreated metal foam skeleton is immersed in a highly hygroscopic hydrogel precursor solution, so that the highly hygroscopic hydrogel precursor solution completely fills the pores of the metal foam skeleton and adheres evenly to the surface until there is no exposed metal area. The soaked metal foam skeleton was removed and photo-initiated polymerization and curing was performed by ultraviolet irradiation to form a metal foam skeleton-hydrogel composite precursor. The metal foam skeleton-hydrogel composite precursor was immersed in a hygroscopic salt solution to fully load the hygroscopic salt into the three-dimensional network cross-linked structure. After removal, the surface was cleaned to remove the free salt, and the metal foam composite hydrogel was obtained. The metal foam composite hydrogel is cut to a thickness of 2mm-4mm and filled into the gap between adjacent single cells. A single metal foam composite hydrogel is then attached to the sidewall of each of the two adjacent single cells to assemble the battery heat dissipation device.

5. The method for preparing a battery heat dissipation device based on metal foam composite hydrogel according to claim 4, characterized in that, The pretreatment includes ultrasonic cleaning sequentially with deionized water and anhydrous ethanol.

6. The method for preparing a battery heat dissipation device based on metal foam composite hydrogel according to claim 4, characterized in that, The monomer is selected from any one or more of acrylamide, polyethylene glycol, hydroxyethyl methacrylate, N-isopropylacrylamide, and sodium alginate; the crosslinking agent is N,N'-methylenebisacrylamide; the ultraviolet initiator is 2-hydroxy-4'-(2-hydroxyethoxy)-2-methylphenylacetone; the mass ratio of the monomer to the crosslinking agent is (850-1000):1; the mass ratio of the crosslinking agent to the ultraviolet initiator is 1:(2-4); and the mass ratio of the monomer to water is 1:(6-8). The forming aid is agarose, and the amount added is 0.5wt%-5wt% of the hydrogel precursor solution; The refrigeration treatment is carried out at a temperature of -2℃ to 4℃ for a time of 20 min to 40 min.

7. The method for preparing a battery heat dissipation device based on metal foam composite hydrogel according to claim 4, characterized in that, The metal foam skeleton is immersed in the highly hygroscopic hydrogel precursor solution for no less than 3 minutes, and the solid-liquid ratio of the metal foam skeleton to the highly hygroscopic hydrogel precursor solution is 1 g: (4-10) mL.

8. The method for preparing a battery heat dissipation device based on metal foam composite hydrogel according to claim 6, characterized in that, The wavelength of the ultraviolet irradiation is any one of 254nm, 365nm, and 405nm; The duration of ultraviolet irradiation is adjusted according to the type and amount of the highly hygroscopic hydrogel precursor solution, and the duration ranges from 1h to 10h.

9. The method for preparing a battery heat dissipation device based on metal foam composite hydrogel according to claim 4, characterized in that, Following the step of forming the metal foam framework-hydrogel composite precursor, the process also includes: The metal foam skeleton-hydrogel composite precursor was washed with deionized water and dried at 45℃-95℃ until the weight reduction was 0.05%-2%.

10. The method for preparing a battery heat dissipation device based on metal foam composite hydrogel according to claim 4, characterized in that, The hygroscopic salt solution is a lithium bromide solution with a molar concentration of 0.5 mol / L to 19.6 mol / L.

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