A method for preparing a multifunctional aerogel thermal insulation sheet, the multifunctional aerogel thermal insulation sheet and its applications

Abstract

This invention discloses a method for preparing a multifunctional aerogel thermal insulation sheet, the multifunctional aerogel thermal insulation sheet itself, and its applications, belonging to the field of battery thermal management material preparation technology. The method for preparing the multifunctional aerogel thermal insulation sheet involves microencapsulating an inorganic phase change core material, dispersing it in a graphene-based coating system to obtain a composite coating, and finally loading the graphene-inorganic phase change microcapsule composite coating onto the surface of a hydrophobic aerogel thermal insulation sheet substrate to obtain the multifunctional aerogel thermal insulation sheet. The multifunctional aerogel thermal insulation sheet combines phase change heat storage buffering and thermal management regulation capabilities, significantly improving its interface stability and service reliability, and is suitable for thermal management and thermal runaway propagation suppression in lithium-ion battery modules or battery packs.

Description

Technical Field

[0001] This invention relates to the field of battery thermal management material preparation technology, and in particular to a method for preparing a multifunctional aerogel thermal insulation sheet, the multifunctional aerogel thermal insulation sheet and its applications. Background Technology

[0002] With the rapid development of the new energy vehicle industry, lithium-ion power battery packs, as the core energy system of the vehicle, have seen their thermal safety become a key factor restricting vehicle safety and reliability. Under complex operating conditions such as high-rate charging and discharging, frequent start-stop and rapid acceleration, long downhill energy recovery, extreme ambient temperatures, external short circuits, overcharging and over-discharging, and mechanical compression / collision, the heat generation and accumulation inside the battery cell are significantly enhanced. This can easily induce unstable processes such as separator shrinkage, aggravated electrode side reactions, and electrolyte decomposition, which can further develop into thermal runaway and potentially lead to serious accidents such as flames, combustion, or even explosions. This not only threatens the safety of occupants but may also cause significant damage to the vehicle and surrounding facilities. Therefore, developing materials and technologies with efficient thermal management and thermal runaway propagation suppression capabilities is an important research direction for the safety design of new energy vehicle power battery packs.

[0003] Currently, thermal safety protection materials for power battery packs mainly include polymer foam insulation materials, phase change energy storage materials, ceramic insulation pads, and aerogel insulation materials. Among them, aerogel materials have been widely used in scenarios such as cell insulation, module lateral insulation, and PACK inner lining thermal protection due to their advantages such as ultra-high porosity, extremely low thermal conductivity, high temperature resistance, and lightweight. However, single-function aerogel insulation sheets are mostly focused on "heat blocking" and cannot meet the temperature uniformity and heat dissipation requirements of batteries under daily operating conditions. At the same time, the aerogel body may also face problems such as insufficient interface adhesion, powdering and detachment, and insufficient structural and coating durability in engineering applications, which limits the thermal protection stability and reliability during long-term service.

[0004] On the other hand, phase change materials (PCMs) can absorb a large amount of latent heat in the phase change temperature range, possessing the potential to suppress temperature rise and buffer peak loads. However, traditional PCMs suffer from defects such as leakage, phase separation, and poor compatibility with the matrix. Furthermore, in the complex environment of battery packs, they often require microencapsulation and composite processing to improve encapsulation stability and cycle durability. Meanwhile, high thermal conductivity carbon-based materials such as graphene can be used to construct thermally conductive networks and improve interfacial heat transfer and temperature homogenization capabilities. However, their introduction methods in thermal insulation systems, their synergistic mechanisms with phase change units, and their coupling stability with aerogel matrices still need optimization.

[0005] In summary, existing technologies struggle to simultaneously achieve multi-objective synergy in a single thermal insulation sheet, encompassing "normal temperature uniform heat dissipation, abnormal thermal shock buffering, and thermal runaway prevention and isolation." Furthermore, the interface compatibility and engineering stability between the material and the battery pack structure remain insufficient. Therefore, there is an urgent need to develop a structurally stable, multifunctional composite thermal insulation sheet that combines thermal conductivity regulation and thermal storage buffering functions, and is reliably coupled with an aerogel insulation matrix, to improve the thermal management capabilities and thermal runaway propagation suppression level of new energy vehicle power battery packs under all operating conditions. Summary of the Invention

[0006] In view of this, the technical problem to be solved by the present invention is to provide a method for preparing a multifunctional aerogel thermal insulation sheet, and the multifunctional aerogel thermal insulation sheet and its applications. The multifunctional aerogel thermal insulation sheet prepared by the method can achieve synergistic effects of thermal insulation, thermal conductivity regulation and heat storage buffering, and has excellent normal thermal management and abnormal thermal protection functions.

[0007] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0008] This invention provides a method for preparing a multifunctional aerogel heat insulation sheet, comprising the following steps:

[0009] (1) Mix the emulsion solution, silicon source precursor and amino-containing silane coupling agent to react and obtain inorganic phase change microcapsules;

[0010] (2) The inorganic phase change microcapsules and graphene-based coatings are mixed to obtain a composite coating;

[0011] (3) The composite coating is applied to the surface of the hydrophobic aerogel insulation sheet substrate and cured to prepare a multifunctional aerogel insulation sheet with a graphene-inorganic phase change microcapsule composite coating.

[0012] The graphene-based coating comprises a graphene thermally conductive filler and a film-forming binder phase;

[0013] The emulsion solution is obtained by mixing and emulsifying an aqueous phase solution and an oil phase solution;

[0014] The aqueous solution is obtained by mixing molten hydrated inorganic salt, aqueous solvent and hydrophilic nonionic surfactant;

[0015] The oil phase solution is obtained by mixing a hydrophobic organic oil phase with a lipophilic nonionic surfactant.

[0016] In the above preparation method, the graphene-inorganic phase change microcapsule composite coating in step (3) is formed by curing the composite coating in step (2) on the surface of the hydrophobic aerogel heat insulation sheet substrate.

[0017] The inorganic phase change microcapsules prepared in step (1) have a core-shell structure, with the core material being molten hydrated inorganic salt phase change material and the shell material being inorganic silicon-based shell material. The core-shell structure can significantly improve the encapsulation stability of the phase change material and reduce its leakage risk.

[0018] The reaction in step (1) includes an in-situ hydrolysis-condensation reaction at the emulsion interface. Specifically, the phase change material is molten into a hydrated inorganic salt and introduced into an aqueous solvent to form a stable emulsion in an oil-phase continuous medium (hydrophobic organic oil phase). The silicon source precursor undergoes hydrolysis-condensation at the emulsion droplet interface under the action of an amino-containing silane coupling agent to generate an inorganic silicon-based shell and form core-shell structured microcapsules. This process effectively isolates the phase change core material from the inorganic shell, significantly improving the microcapsules' resistance to leakage and environmental interference. At the same time, the introduction of amino functional groups (from amino-containing silane coupling agents) can enhance the cross-linking and interfacial bonding of the shell, which is beneficial to the dispersion stability of the microcapsules in the graphene-based coating and the interfacial adhesion between the microcapsules and the film-forming binder phase and aerogel matrix. This significantly improves the durability and anti-detachment ability of the graphene-inorganic phase change microcapsule composite coating, ensuring the long-term stability of the heat insulation sheet under service conditions such as vehicle vibration and thermal cycling.

[0019] Preferably, the inorganic phase change microcapsules in the composite coating are powders.

[0020] Inorganic phase change microcapsules in powder form are easier to mix with graphene-based coatings to form composite coatings.

[0021] After obtaining the composite coating in step (2), the composite coating is applied to the surface of the hydrophobic aerogel heat insulation sheet substrate in step (3), thereby realizing the integrated construction of "heat insulation substrate-thermal conduction / heat storage composite coating". This enables the multifunctional aerogel heat insulation sheet with graphene-inorganic phase change microcapsule composite coating to take into account both the temperature balance control under normal working conditions and the thermal shock buffering and thermal diffusion suppression under abnormal working conditions, thereby significantly improving the use stability of the multifunctional aerogel heat insulation sheet and the thermal safety of the battery pack or module.

[0022] The inorganic silicon-based shell material is formed in situ by a hydrolysis-condensation reaction between a silicon source precursor and an amino-containing silane coupling agent at the droplet interface.

[0023] Specifically, in the W / O emulsion system, the aqueous phase containing the hydrated inorganic salt phase change material exists as dispersed droplets in the continuous oil phase medium. The silicon source precursor first undergoes a hydrolysis reaction near the emulsion droplet interface to generate silanol intermediates. Subsequently, condensation reactions further occur between silanol intermediates and between the silanol intermediates and the hydrolysis products of the amino-containing silane coupling agent, gradually constructing an inorganic silicon-based shell material with a Si-O-Si network structure. The amino-containing silane coupling agent participates in the interfacial condensation and cross-linking densification of the inorganic silicon-based shell material, and improves the interfacial compatibility between the shell material and the subsequent graphene-based coating system through its amino functional groups.

[0024] Thus, the inorganic silicon-based shell material is generated in situ at the droplet interface during the hydrolysis and condensation process of the silicon source precursor and the amino-containing silane coupling agent, and simultaneously encapsulates the hydrated inorganic salt phase change core material, thereby forming an inorganic phase change microcapsule with a core-shell structure.

[0025] In the above preparation method, the silicon source precursor in step (1) is hydrolyzed at the droplet interface to form a silanol intermediate, and then an inorganic silicon-based shell is constructed through a polycondensation reaction; the amino-containing silane coupling agent participates in the interfacial polycondensation to promote the uniform growth and densification of the shell, and enhances the interfacial compatibility between the microcapsule shell and the subsequent coating system, thereby improving the stability and loading capacity of the microcapsule.

[0026] Preferably, in step (1), the silicon source precursor is selected from one or more of silicate precursors, water-soluble silicon sources, and colloidal silicon dioxide.

[0027] The silicate ester precursors include, but are not limited to, tetraethyl orthosilicate, methyl orthosilicate, propyl orthosilicate, or butyl orthosilicate.

[0028] The water-soluble silicon source includes, but is not limited to, sodium silicate, potassium silicate, water glass, or sodium metasilicate.

[0029] The colloidal silica includes, but is not limited to, acidic silica sol, alkaline silica sol, neutral silica sol, or nano-silica aqueous dispersions; in some specific embodiments of the present invention, preferably, the silicon source precursor in step (1) is selected from tetraethyl orthosilicate. Preferably, the amino-containing silane coupling agent in step (1) is selected from one or more of aminoalkyltrialkoxysilane, aminoalkylmethyldialkoxysilane, and polyamine silane coupling agents.

[0030] The aminoalkyltrialkoxysilanes include, but are not limited to, 3-aminopropyltriethoxysilane, 3-aminopropyltrimethoxysilane, 4-aminobutyltriethoxysilane, or aminoethyltrimethoxysilane, etc.

[0031] The aminoalkylmethyldialkoxysilanes include, but are not limited to, 3-aminopropylmethyldimethoxysilane, 3-aminopropylmethyldiethoxysilane, aminoethylmethyldimethoxysilane, or aminoethylmethyldiethoxysilane.

[0032] The polyamine silane coupling agents include, but are not limited to, N-β-aminoethyl-γ-aminopropyltrimethoxysilane, N-β-aminoethyl-γ-aminopropyltriethoxysilane, N-β-aminoethyl-γ-aminopropylmethyldimethoxysilane, or N-β-aminoethyl-γ-aminopropylmethyldiethoxysilane.

[0033] In some specific embodiments of the present invention, preferably, the amino-containing silane coupling agent in step (1) is selected from 3-aminopropyltriethoxysilane.

[0034] More preferably, the volume ratio of the silicon source precursor to the amino-containing silane coupling agent is (10~1):(1~10).

[0035] The reaction condition in step (1) is constant temperature stirring; the preferred time for constant temperature stirring is 8 to 12 hours.

[0036] After constant temperature stirring, the mixture is allowed to stand for aging.

[0037] The preferred aging time is 6 to 72 hours.

[0038] After the reaction in step (1) is completed, the process also includes separation, washing and drying.

[0039] The above washing is used to remove residual oil phase, unreacted silicon source and free surfactant;

[0040] The above drying process is used to stabilize inorganic phase change microcapsules with a core-shell structure and obtain a powder product that is easy to disperse subsequently.

[0041] The present invention does not impose any particular limitation on the separation method, washing solvent, and drying method described above, and any method, solvent, or method known to those skilled in the art is acceptable.

[0042] In some specific embodiments of the present invention, the washing solvent is selected from a mixed solution of alcohol and water;

[0043] The alcohol content in the mixed solution of alcohol and water is preferably 20 wt% to 80 wt%.

[0044] The alcohol is preferably one or more selected from methanol, ethanol, and isopropanol;

[0045] The washing frequency is preferably 1 to 5 times.

[0046] After washing, a drying process is performed.

[0047] The drying temperature is preferably 20℃~50℃;

[0048] The drying time is preferably 6 to 72 hours.

[0049] Preferably, the graphene thermally conductive filler is selected from one or more of graphene, few-layer graphene, reduced graphene oxide, and graphene oxide.

[0050] The graphene includes, but is not limited to, single-layer graphene, double-layer graphene, graphene nanosheets, graphene powder, or graphene slurry.

[0051] The few-layer graphene includes, but is not limited to, few-layer graphene with 3 to 10 carbon atoms, few-layer graphene sheets with 3 to 10 carbon atoms, few-layer graphene nanosheets with 3 to 10 carbon atoms, few-layer graphene powder with 3 to 10 carbon atoms, or few-layer graphene slurry with 3 to 10 carbon atoms.

[0052] The reduced graphene oxide includes, but is not limited to, thermally reduced graphene oxide, chemically reduced graphene oxide, electrochemically reduced graphene oxide, ascorbic acid reduced graphene oxide, or hydrazine hydrate reduced graphene oxide.

[0053] The graphene oxide includes, but is not limited to, graphene oxide sheets, graphene oxide nanosheets, graphene oxide powder, graphene oxide aqueous dispersion, or graphene oxide organic dispersion.

[0054] In some specific embodiments of the present invention, preferably, the graphene thermally conductive filler is selected from few-layer graphene.

[0055] Preferably, the film-forming binder phase is selected from one or more of epoxy resin, polyurethane, acrylic resin, silicone resin, polyvinyl alcohol, styrene-butadiene emulsion, and fluorosilicone resin.

[0056] Preferably, in this invention, the mass ratio of the molten hydrated inorganic salt to the aqueous solution is (2~10):1;

[0057] Preferably, the amount of the hydrophilic nonionic surfactant used is 0.05 wt% to 2 wt% of the aqueous solution;

[0058] Preferably, the mass ratio of the hydrophobic organic oil phase to the lipophilic nonionic surfactant is (20~600):1.

[0059] More preferably, the hydrated inorganic salt in the molten hydrated inorganic salt is selected from one or more of hydrated phosphate, acetate hydrate, sulfate hydrate, nitrate hydrate, chloride hydrate and carbonate hydrate;

[0060] More preferably, the aqueous solvent is selected from one or more of deionized water, distilled water, and a mixed solvent of deionized water and low-carbon alcohols;

[0061] More preferably, the lower alcohol is selected from one or more of methanol, ethanol and isopropanol;

[0062] More preferably, the hydrophobic organic oil phase is selected from one or more of alkane oil phases, ester oil phases, silicone oils, mineral oils, and aromatic solvents;

[0063] The alkane oil phase includes, but is not limited to, n-hexane, n-heptane, n-octane, isooctane, dodecane, tetradecane, or hexadecane.

[0064] The ester oil phase includes, but is not limited to, ethyl acetate, butyl acetate, methyl oleate, ethyl oleate, isopropyl myristate, or dimethyl carbonate.

[0065] The silicone oils include, but are not limited to, dimethyl silicone oil, methylphenyl silicone oil, hydroxyl silicone oil, or vinyl silicone oil.

[0066] The mineral oils and aromatic solvents include, but are not limited to, liquid paraffin, white oil, mineral insulating oil, or industrial-grade mineral oil.

[0067] In some specific embodiments of the present invention, preferably, the hydrophobic organic oil phase is selected from liquid paraffin.

[0068] More preferably, the lipophilic nonionic surfactant is selected from one or more of sorbitol fatty acid esters, polyglycerol fatty acid esters, and fatty acid glycerides.

[0069] Preferably, in step (3) of this invention, the hydrophobic aerogel insulation sheet substrate is obtained by hydrophobic treatment of one or more of the following: silica aerogel felt, aluminosilicate aerogel felt, glass fiber reinforced aerogel felt, mullite fiber reinforced aerogel felt, and ceramic fiber reinforced aerogel insulation sheet.

[0070] Preferably, the hydrophobic treatment method is selected from one or more of silanization modification, siloxane impregnation modification, and fluorinated silane modification.

[0071] The silanization modification specifically involves placing the aerogel insulation sheet substrate in a solution or vapor environment containing a silane modifier, causing the silane modifier to undergo a condensation reaction with the hydroxyl groups on the surface of the aerogel insulation sheet substrate, thereby introducing hydrophobic organosilicon groups on the surface of the aerogel insulation sheet substrate.

[0072] The silanes mentioned include, but are not limited to, methyltrimethoxysilane, methyltriethoxysilane, trimethylchlorosilane, hexamethyldisilazane, or dimethyldimethoxysilane.

[0073] The siloxane impregnation modification specifically involves pretreating the aerogel insulation sheet substrate in an acid-alcohol solution, and then impregnating the pretreated aerogel insulation sheet substrate in a solution containing a siloxane modifier, so that the siloxane modifier undergoes a condensation reaction on the surface and in the pores of the aerogel insulation sheet substrate, thereby forming a hydrophobic modified layer.

[0074] The volume ratio of acid to alcohol in the acid-alcohol solution is preferably 1:(5~30); more preferably 1:(8~15).

[0075] The pretreatment time is preferably 6 to 48 hours; more preferably 12 to 24 hours.

[0076] The impregnation time of the siloxane modifier is preferably 6 to 36 hours.

[0077] The siloxanes include, but are not limited to, hexamethyldisiloxane, octamethylcyclotetrasiloxane, decamethylcyclopentasiloxane, polydimethylsiloxane, or methyl silicone oil.

[0078] Specifically, the fluorinated silane modification involves placing the aerogel insulation sheet substrate in a solution or vapor environment containing a fluorinated silane modifier, causing the fluorinated silane modifier to undergo a condensation reaction with the active hydroxyl groups on the surface of the aerogel insulation sheet substrate, and forming a low surface energy fluorinated hydrophobic layer on its surface.

[0079] The fluorinated silanes include, but are not limited to, trifluoropropyltrimethoxysilane, trifluoropropylmethyldimethoxysilane, heptadecafluorodecyltrimethoxysilane, heptadecafluorodecyltriethoxysilane, or tridecafluorooctyltriethoxysilane.

[0080] In the preparation method of the present invention, the stirring time for emulsification in step (1) is 30~60 min;

[0081] The stirring speed for emulsification is 500~800 r / min.

[0082] In the preparation method described in this invention, the molten hydrated inorganic salt serves as a phase change material to form a homogeneous liquid phase under heating conditions, and acts as a dispersed phase core material in the subsequent emulsification process;

[0083] The hydrophilic nonionic surfactant can reduce the interfacial tension between the aqueous and oil phase solutions, improve the stability of the emulsion, and provide a basis for the subsequent formation of inorganic phase change microcapsules with controllable particle size and core-shell structure.

[0084] In the preparation method of the present invention, the hydrophobic organic oil phase serves as a medium for the continuous phase, providing a dispersion environment for the aqueous droplets;

[0085] The lipophilic nonionic surfactant works synergistically with the hydrophilic nonionic surfactant to adjust the HLB value (hydrophilic-lipophilic balance value) of the composite emulsion system, making the resulting emulsion more conducive to forming a stable W / O system ("water-in-oil" system).

[0086] In the above preparation method, in step (2), the graphene thermally conductive filler constructs an in-plane thermally conductive pathway in the coating formed by the composite coating, which can enhance the rapid diffusion of heat in the plane direction of the coating; the inorganic phase change microcapsules achieve thermal buffering through phase change heat absorption during the temperature rise process; in step (3), the hydrophobic aerogel insulation sheet substrate relies on its porous structure to inhibit further heat penetration; the effects of (2) and (3) above are combined and mutually reinforcing, constructing a synergistic integrated thermal protection system of "thermal diffusion-phase change heat storage-aerogel insulation". The preparation method of the present invention is simple and easy to implement, safe and reliable, has low production cost, and is suitable for continuous and large-scale production.

[0087] The present invention also provides a multifunctional aerogel heat insulation sheet with a graphene-inorganic phase change microcapsule composite coating prepared by the above preparation method.

[0088] The multifunctional aerogel thermal insulation sheet with a graphene-inorganic phase change microcapsule composite coating consists of a hydrophobic aerogel thermal insulation sheet substrate and a graphene-inorganic phase change microcapsule composite coating loaded on its surface.

[0089] The multifunctional aerogel heat insulation sheet with graphene-inorganic phase change microcapsule composite coating described in this invention can improve the operational safety and service reliability of battery systems through phase change peak clipping buffering, interface thermal conductivity regulation and thermal insulation synergy.

[0090] The multifunctional aerogel thermal insulation sheet described in this invention possesses excellent thermal buffering and thermal diffusion suppression capabilities, and can be used to improve the thermal isolation effect of power battery packs under thermal runaway conditions. When thermal runaway occurs, heat first acts on the composite coating (graphene-inorganic phase change microcapsule composite coating) on ​​the surface of the insulation sheet. The thermally conductive network of the graphene-based coating can rapidly disperse local hot spots in the planar direction, reducing interfacial heat concentration and delaying heat penetration to single points. Simultaneously, the inorganic phase change microcapsules dispersed in the composite coating absorb latent heat in the phase change temperature range, playing a peak-shaving and buffering role against thermal shock, reducing the temperature rise rate of the insulation sheet near the heat source. Subsequently, when heat is transferred inward to the hydrophobic aerogel insulation sheet matrix, its nanoporous structure significantly inhibits gas-phase heat conduction. Heat is mainly transferred through the solid-phase framework via a higher thermal resistance path, thereby effectively reducing the penetration heat flux and suppressing heat diffusion to adjacent cells. The above mechanisms work together and promote each other, thus constructing a multi-level synergistic thermal protection system of "thermal conduction and temperature equalization - phase change heat absorption - aerogel heat resistance", which can significantly improve the thermal isolation and thermal runaway propagation suppression capabilities of power battery packs under extreme thermal events, and has good application value.

[0091] The present invention also provides a lithium-ion battery comprising the above-mentioned multifunctional aerogel heat insulation sheet with a graphene-inorganic phase change microcapsule composite coating.

[0092] Preferably, the multifunctional aerogel heat insulation sheet with graphene-inorganic phase change microcapsule composite coating is disposed between the cells of the lithium-ion battery module or battery pack, on the side of the module, or in the inner lining of the battery pack housing.

[0093] The aforementioned lithium-ion battery, containing the multifunctional aerogel thermal insulation sheet with a graphene-inorganic phase change microcapsule composite coating as described in this invention, can effectively suppress the propagation of thermal runaway.

[0094] Compared with the prior art, the preparation method of the multifunctional aerogel heat insulation sheet provided by the present invention includes the following steps: (1) mixing an emulsion solution, a silicon source precursor and an amino-containing silane coupling agent to react and obtain inorganic phase change microcapsules; (2) mixing the inorganic phase change microcapsules and a graphene-based coating to obtain a composite coating; (3) coating the composite coating on the surface of a hydrophobic aerogel heat insulation sheet substrate and curing it to prepare a multifunctional aerogel heat insulation sheet with a graphene-inorganic phase change microcapsule composite coating; wherein, the graphene-based coating includes a graphene thermally conductive filler and a film-forming binder phase; the emulsion solution is obtained by mixing and emulsifying an aqueous phase solution and an oil phase solution; the aqueous phase solution is obtained by mixing molten hydrated inorganic salt, an aqueous solvent and a hydrophilic nonionic surfactant; the oil phase solution is obtained by mixing a hydrophobic organic oil phase and a lipophilic nonionic surfactant. The preparation method of this invention involves microencapsulating inorganic phase change core materials, dispersing them in a graphene-based coating system to obtain a composite coating, and finally loading the graphene-inorganic phase change microcapsule composite coating onto the surface of a hydrophobic aerogel thermal insulation sheet substrate to construct a composite structure with a synergistic effect of multiple mechanisms: thermal conductivity diffusion, phase change buffering, and thermal insulation. This structure not only enhances the rapid spread of heat on the surface of the thermal insulation sheet and reduces local hot spots, but also slows down the temperature rise through the phase change endothermic effect of the microcapsules and reduces the further transfer of heat to adjacent areas through the low thermal conductivity of the aerogel substrate. This provides more stable and efficient thermal safety protection for the power battery pack, enabling the multifunctional aerogel thermal insulation sheet to combine phase change heat storage buffering and thermal management regulation capabilities, and significantly improve its interface stability and service reliability. It is suitable for thermal management and thermal runaway propagation suppression of lithium-ion battery modules or battery packs. Attached Figure Description

[0095] Figure 1 A schematic diagram of the process flow for preparing the multifunctional aerogel heat insulation sheet loaded with graphene-inorganic phase change microcapsules provided by the present invention.

[0096] Figure 2 Scanning electron microscope (SEM) image of the inorganic phase change microcapsules prepared in Example 1.

[0097] Figure 3 The X-ray photoelectron spectroscopy (XPS) peak fitting diagram of the inorganic phase change microcapsules prepared in Example 1 includes Si 2p (a), C 1s (b), O 1s (c) and P 2p (d) spectra;

[0098] Figure 4 Fourier transform infrared (FTIR) spectrum of the inorganic phase change microcapsules prepared in Example 1;

[0099] Figure 5 Differential scanning calorimetry (DSC) curve of the inorganic phase change microcapsules prepared in Example 1;

[0100] Figure 6 The temperature-time curve of the multifunctional aerogel thermal insulation sheet loaded with graphene-inorganic phase change microcapsules in Example 1 during charge-discharge cycle testing.

[0101] Figure 7 The temperature-time / voltage curve of the multifunctional aerogel insulation sheet loaded with graphene-inorganic phase change microcapsules in Example 1 during the thermal runaway barrier test.

[0102] Figure 8 This is a temperature-time curve of the pure aerogel insulation sheet in Comparative Example 1 during charge-discharge cycle testing;

[0103] Figure 9 The temperature-time / voltage curves of the pure aerogel insulation sheet in Comparative Example 1 during the thermal runaway barrier test are shown. Detailed Implementation

[0104] To further illustrate the present invention, the preparation method of the multifunctional aerogel insulation sheet provided by the present invention, as well as the multifunctional aerogel insulation sheet and its applications, are described in detail below with reference to embodiments.

[0105] The following raw materials and reaction solvents are all commercially available products.

[0106] This invention provides a method for preparing a multifunctional aerogel thermal insulation sheet with a graphene-inorganic phase change microcapsule composite coating, comprising the following steps:

[0107] (1) Mix the emulsion solution, silicon source precursor and amino-containing silane coupling agent to react and obtain inorganic phase change microcapsules;

[0108] (2) The inorganic phase change microcapsules and graphene-based coatings are mixed to obtain a composite coating;

[0109] (3) The composite coating is applied to the surface of the hydrophobic aerogel insulation sheet substrate and cured to prepare a multifunctional aerogel insulation sheet with a graphene-inorganic phase change microcapsule composite coating.

[0110] The graphene-based coating comprises a graphene thermally conductive filler and a film-forming binder phase;

[0111] The emulsion solution is obtained by mixing and emulsifying an aqueous phase solution and an oil phase solution;

[0112] The aqueous solution is obtained by mixing molten hydrated inorganic salt, aqueous solvent and hydrophilic nonionic surfactant;

[0113] The oil phase solution is obtained by mixing a hydrophobic organic oil phase with a lipophilic nonionic surfactant.

[0114] In the above preparation method, the graphene-inorganic phase change microcapsule composite coating in step (3) is formed by curing the composite coating in step (2) on the surface of the hydrophobic aerogel heat insulation sheet substrate.

[0115] The inorganic phase change microcapsules prepared in step (1) have a core-shell structure, with the core material being molten hydrated inorganic salt phase change material and the shell material being inorganic silicon-based shell material. The core-shell structure can significantly improve the encapsulation stability of the phase change material and reduce its leakage risk.

[0116] The reaction in step (1) includes an in-situ hydrolysis-condensation reaction at the emulsion interface.

[0117] Specifically, the process involves introducing hydrated inorganic salts of the phase change material into an aqueous solvent and forming a stable emulsion in an oil-phase continuous medium (hydrophobic organic oil phase). The silicon precursor undergoes hydrolysis and condensation at the droplet interface under the action of an amino-containing silane coupling agent, generating an inorganic silicon-based shell and forming core-shell microcapsules. This process effectively isolates the phase change core material from the inorganic shell, significantly improving the microcapsules' resistance to leakage and environmental disturbance. Simultaneously, the introduction of amino functional groups (from the amino-containing silane coupling agent) enhances shell crosslinking and interfacial bonding, which is beneficial for the subsequent dispersion stability of the microcapsules in graphene-based coatings and their interfacial adhesion with the film-forming binder phase and aerogel matrix. This significantly improves the durability and anti-detachment ability of the graphene-inorganic phase change microcapsule composite coating, ensuring the long-term stability of the heat insulation sheet under service conditions such as vehicle vibration and thermal cycling.

[0118] Preferably, the inorganic phase change microcapsules in the composite coating are powders.

[0119] After obtaining the composite coating in step (2), the composite coating is applied to the surface of the hydrophobic aerogel heat insulation sheet substrate in step (3), thereby realizing the integrated construction of "heat insulation substrate-thermal conduction / heat storage composite coating". This enables the multifunctional aerogel heat insulation sheet with graphene-inorganic phase change microcapsule composite coating to take into account both the temperature balance control under normal working conditions and the thermal shock buffering and thermal diffusion suppression under abnormal working conditions, thereby significantly improving the use stability of the multifunctional aerogel heat insulation sheet and the thermal safety of the battery pack or module.

[0120] The inorganic silicon-based shell material is formed in situ by a hydrolysis-condensation reaction between a silicon source precursor and an amino-containing silane coupling agent at the droplet interface.

[0121] In the above preparation method, the silicon source precursor in step (1) is hydrolyzed at the droplet interface to form a silanol intermediate, and then an inorganic silicon-based shell is constructed through a polycondensation reaction; the amino-containing silane coupling agent participates in the interfacial polycondensation to promote the uniform growth and densification of the shell, and enhances the interfacial compatibility between the microcapsule shell and the subsequent coating system, thereby improving the stability and loading capacity of the microcapsule.

[0122] In the above preparation method, in step (2), the graphene thermally conductive filler constructs an in-plane thermally conductive pathway in the coating formed by the composite coating, which can enhance the rapid diffusion of heat in the plane direction of the coating; the inorganic phase change microcapsules achieve thermal buffering through phase change heat absorption during the temperature rise process; in step (3), the hydrophobic aerogel insulation sheet substrate relies on its porous structure to inhibit further heat penetration; the effects of (2) and (3) above are combined and mutually reinforcing, constructing a synergistic integrated thermal protection system of "thermal diffusion-phase change heat storage-aerogel insulation". The preparation method of the present invention is simple and easy to implement, safe and reliable, has low production cost, and is suitable for continuous and large-scale production.

[0123] Preferably, in step (3) of this invention, the hydrophobic aerogel insulation sheet substrate is obtained by hydrophobic treatment of one or more of the following: silica aerogel felt, aluminosilicate aerogel felt, glass fiber reinforced aerogel felt, mullite fiber reinforced aerogel felt, and ceramic fiber reinforced aerogel insulation sheet.

[0124] Preferably, the hydrophobic treatment method is selected from one or more of silanization modification, siloxane impregnation modification, and fluorinated silane modification.

[0125] The silanization modification specifically involves placing the aerogel insulation sheet substrate in a solution or vapor environment containing a silane modifier, causing the silane modifier to undergo a condensation reaction with the hydroxyl groups on the surface of the aerogel insulation sheet substrate, thereby introducing hydrophobic organosilicon groups on the surface of the aerogel insulation sheet substrate.

[0126] The silanes mentioned include, but are not limited to, methyltrimethoxysilane, methyltriethoxysilane, trimethylchlorosilane, hexamethyldisilazane, or dimethyldimethoxysilane.

[0127] The siloxane impregnation modification specifically involves pretreating the aerogel insulation sheet substrate in an acid-alcohol solution, and then impregnating the pretreated aerogel insulation sheet substrate in a solution containing a siloxane modifier, so that the siloxane modifier undergoes a condensation reaction on the surface and in the pores of the aerogel insulation sheet substrate, thereby forming a hydrophobic modified layer.

[0128] The volume ratio of acid to alcohol in the acid-alcohol solution is preferably 1:(5~30); more preferably 1:(8~15).

[0129] The pretreatment time is preferably 6 to 48 hours; more preferably 12 to 24 hours.

[0130] The impregnation time of the siloxane modifier is preferably 6 to 36 hours.

[0131] The siloxanes include, but are not limited to, hexamethyldisiloxane, octamethylcyclotetrasiloxane, decamethylcyclopentasiloxane, polydimethylsiloxane, or methyl silicone oil.

[0132] Specifically, the fluorinated silane modification involves placing the aerogel insulation sheet substrate in a solution or vapor environment containing a fluorinated silane modifier, causing the fluorinated silane modifier to undergo a condensation reaction with the active hydroxyl groups on the surface of the aerogel insulation sheet substrate, and forming a low surface energy fluorinated hydrophobic layer on its surface.

[0133] The fluorinated silanes include, but are not limited to, trifluoropropyltrimethoxysilane, trifluoropropylmethyldimethoxysilane, heptadecafluorodecyltrimethoxysilane, heptadecafluorodecyltriethoxysilane, or tridecafluorooctyltriethoxysilane. This invention also provides a multifunctional aerogel thermal insulation sheet with a graphene-inorganic phase change microcapsule composite coating prepared by the above-described method.

[0134] The multifunctional aerogel thermal insulation sheet with a graphene-inorganic phase change microcapsule composite coating consists of a hydrophobic aerogel thermal insulation sheet substrate and a graphene-inorganic phase change microcapsule composite coating loaded on its surface.

[0135] The multifunctional aerogel heat insulation sheet with graphene-inorganic phase change microcapsule composite coating described in this invention can improve the operational safety and service reliability of battery systems through phase change peak clipping buffering, interface thermal conductivity regulation and thermal insulation synergy.

[0136] The multifunctional aerogel thermal insulation sheet described in this invention possesses excellent thermal buffering and thermal diffusion suppression capabilities, and can be used to improve the thermal isolation effect of power battery packs under thermal runaway conditions. When thermal runaway occurs, heat first acts on the composite coating (graphene-inorganic phase change microcapsule composite coating) on ​​the surface of the insulation sheet. The thermally conductive network of the graphene-based coating can rapidly disperse local hot spots in the planar direction, reducing interfacial heat concentration and delaying heat penetration to single points. Simultaneously, the inorganic phase change microcapsules dispersed in the composite coating absorb latent heat in the phase change temperature range, playing a peak-shaving and buffering role against thermal shock, reducing the temperature rise rate of the insulation sheet near the heat source. Subsequently, when heat is transferred inward to the hydrophobic aerogel insulation sheet matrix, its nanoporous structure significantly inhibits gas-phase heat conduction. Heat is mainly transferred through the solid-phase framework via a higher thermal resistance path, thereby effectively reducing the penetration heat flux and suppressing heat diffusion to adjacent cells. The above mechanisms work together and promote each other, thus constructing a multi-level synergistic thermal protection system of "thermal conduction and temperature equalization - phase change heat absorption - aerogel heat resistance", which can significantly improve the thermal isolation and thermal runaway propagation suppression capabilities of power battery packs under extreme thermal events, and has good application value.

[0137] The present invention also provides a lithium-ion battery comprising the above-mentioned multifunctional aerogel heat insulation sheet with a graphene-inorganic phase change microcapsule composite coating.

[0138] Preferably, the multifunctional aerogel heat insulation sheet with graphene-inorganic phase change microcapsule composite coating is disposed between the cells of the lithium-ion battery module or battery pack, on the side of the module, or in the inner lining of the battery pack housing.

[0139] The aforementioned lithium-ion battery, containing the multifunctional aerogel thermal insulation sheet with a graphene-inorganic phase change microcapsule composite coating as described in this invention, can effectively suppress the propagation of thermal runaway.

[0140] The preparation method of the multifunctional aerogel heat insulation sheet of the present invention is shown in the schematic diagram below. Figure 1 As shown. Figure 1 The preparation method of [the substance] specifically includes the following steps:

[0141] (1) At a preset temperature, molten hydrated inorganic salt phase change material, aqueous solvent and hydrophilic nonionic surfactant are mixed to prepare an aqueous phase;

[0142] In this step, the hydrated inorganic salt phase change material forms a homogeneous liquid phase under heating conditions and serves as the core material of the dispersed phase in the subsequent emulsification process; the hydrophilic nonionic surfactant can reduce the interfacial tension between the aqueous phase and the oil phase, improve the stability of the emulsion, and provide a basis for the subsequent formation of core-shell structured microcapsules with controllable particle size.

[0143] (2) At a preset temperature, a hydrophobic organic oil phase medium is mixed with a lipophilic nonionic surfactant to prepare an oil phase;

[0144] In this step, the hydrophobic organic oil phase medium serves as the continuous phase, providing a dispersion environment for the aqueous droplets; the lipophilic nonionic surfactant works synergistically with the hydrophilic nonionic surfactant in step (1) to adjust the HLB value of the composite emulsion system, making the resulting emulsion more conducive to forming a stable W / O system.

[0145] (3) Add the aqueous phase to the oil phase and emulsify and stir for a preset time to form a stable emulsion; then add the silicon source precursor and the silane coupling agent containing amino functional groups dropwise, stir the reaction at a constant temperature for a preset time and let it stand for a preset time to age, so that the inorganic shell material is hydrolyzed and condensed in situ at the emulsion droplet interface to form inorganic phase change microcapsules.

[0146] In this step, the silicon source precursor is hydrolyzed at the droplet interface to form a silanol intermediate, which is then used to construct an inorganic silicon-based shell through a condensation reaction. The silane coupling agent containing amino functional groups participates in the interfacial condensation to promote uniform growth and densification of the shell, and enhances the interfacial compatibility between the microcapsule shell and the subsequent coating system, thereby improving the stability and loading capacity of the microcapsules.

[0147] (4) The precipitate obtained in step (3) is separated and removed, washed with alcohol-water mixed washing solution and dried for a preset time to obtain inorganic phase change microcapsules;

[0148] In this step, the washing process is used to remove residual oil phase, unreacted silicon source and free surfactant; the drying process is used to stabilize the core-shell structured microcapsules and obtain a powder product that is easy to disperse in the future.

[0149] (5) The inorganic phase change microcapsules are dispersed into a graphene-based coating system to obtain a composite coating. The composite coating is uniformly coated on the surface of a hydrophobic aerogel insulation sheet substrate and cured to obtain a multifunctional aerogel insulation sheet loaded with graphene-inorganic phase change microcapsules.

[0150] In this step, graphene thermally conductive filler constructs in-plane thermal conduction pathways in the coating, which can enhance the rapid diffusion of heat in the plane direction of the coating; inorganic phase change microcapsules achieve thermal buffering through phase change heat absorption during the temperature rise process; and the hydrophobic aerogel insulation film substrate relies on its porous structure to inhibit further heat penetration, thereby constructing a synergistic integrated thermal protection system of "thermal conduction diffusion - phase change heat storage - aerogel insulation".

[0151] Example 1

[0152] The multifunctional aerogel insulation sheet prepared by this method has both good heat diffusion capacity and excellent heat insulation and buffering performance. The specific preparation process includes the following steps:

[0153] (1) Prepare the aqueous phase

[0154] Under a water bath at 45 ℃, 20 g of disodium hydrogen phosphate dodecahydrate was heated to a molten state, followed by the addition of 5 g of deionized water and 0.30 g of Tween80 (polysorbate 80), and the mixture was stirred continuously until the system was uniform and transparent to obtain an aqueous phase.

[0155] (2) Prepare the oil phase

[0156] 30 g of liquid paraffin was mixed with 1.50 g of Span80 (sorbitan monooleate) and stirred evenly at 45 °C to obtain the oil phase.

[0157] (3) Emulsion construction and preparation of inorganic phase change microcapsules

[0158] The aqueous phase was slowly poured into the oil phase and vigorously stirred at 600 r / min for 45 min to form a stable W / O emulsion. Then, 4 mL of tetraethyl orthosilicate and 1 mL of 3-aminopropyltriethoxysilane were added dropwise to the emulsion, and the mixture was stirred at 45 °C for 8 h and allowed to stand for 24 h to age, resulting in inorganic phase change microcapsule precipitates.

[0159] (4) Microcapsule washing and drying

[0160] The above precipitate was separated and washed three times with 50% ethanol aqueous solution, and then dried at room temperature for 24 h to obtain inorganic phase change microcapsule powder.

[0161] (5) Graphene loaded and coated with aerogel insulation sheet

[0162] The obtained inorganic phase change microcapsule powder was added to a graphene-based coating system (specifically composed of few-layer graphene and epoxy resin) at a ratio of 30 wt% of the total mass of the composite coating. The mixture was stirred and dispersed evenly to obtain a graphene-inorganic phase change microcapsule composite coating. The composite coating was uniformly coated onto the surface of a hydrophobic silica aerogel insulation sheet (obtained by impregnation and modification of silica aerogel felt with siloxane, wherein the volume ratio of acid to alcohol is 1:10, the pretreatment time is 24 h, and the siloxane modifier is hexamethyldisiloxane, which was soaked for 12 hours). The aerogel insulation sheet had a size of 150×150×2 mm and was cured at room temperature for 12 h to obtain a multifunctional aerogel insulation sheet loaded with graphene-inorganic phase change microcapsules.

[0163] Figure 1This is a schematic diagram of the process flow for preparing the multifunctional aerogel thermal insulation sheet loaded with graphene-inorganic phase change microcapsules provided by the present invention. As shown in the figure, the method mainly includes aqueous phase preparation, oil phase preparation, emulsification to construct a W / O emulsion, dropwise addition of a silicon source precursor and a silane coupling agent to form microcapsules, washing and drying to obtain microcapsules, and the process of co-loading the microcapsules and graphene-based coating onto the surface of the aerogel thermal insulation sheet.

[0164] Figure 2 The image shows the scanning electron microscope (SEM) image of the inorganic phase change microcapsules prepared in Example 1. As can be seen from the image, the obtained microcapsules have a relatively regular spherical structure, high particle integrity, and a relatively continuous surface, indicating that the in-situ hydrolysis-condensation method at the emulsion interface can effectively encapsulate the phase change core material.

[0165] Figure 3 The X-ray photoelectron spectroscopy (XPS) peak fitting diagram of the inorganic phase change microcapsules prepared in Example 1 includes Si 2p, C 1s, O 1s, and P 2p spectra. The results show that characteristic chemical bond information such as Si–O–Si, P–O, and oxygen-containing functional groups are present in the sample, indicating that the inorganic silicon-based shell has been successfully constructed and effective encapsulation of phosphorus-containing hydrated inorganic salt phase change materials has been achieved.

[0166] Figure 4 The Fourier transform infrared (FTIR) spectrum of the inorganic phase change microcapsules prepared in Example 1 is shown in the figure. As can be seen from the figure, characteristic absorption peaks such as O–H, P–O–H, Si–OH, and O–P–O are present in the sample, further proving that the obtained microcapsules simultaneously possess the characteristics of an inorganic silicon-based shell structure and a phosphorus-containing hydrated inorganic salt phase change core material.

[0167] Figure 5 The differential scanning calorimetry (DSC) curve of the inorganic phase change microcapsules prepared in Example 1 is shown. It can be seen that the latent heat of phase change of the obtained microcapsules is 163.1 kJ / kg, and the phase change temperature is 51.4 ℃, indicating that they have high heat storage capacity and good thermal response characteristics.

[0168] The multifunctional aerogel thermal insulation sheet loaded with graphene-inorganic phase change microcapsules prepared in Example 1 and the pure aerogel thermal insulation sheet of Comparative Example 1 were respectively applied in the battery pack, which included three 59 Ah power ternary lithium batteries, and were subjected to charge-discharge cycle testing and thermal runaway barrier testing.

[0169] Figure 6 The figure shows the temperature-time curves of the multifunctional aerogel insulation sheet loaded with graphene-inorganic phase change microcapsules in Example 1 during charge-discharge cycle testing. As can be seen from the figure, the highest system temperature is 59.2 ℃, and the maximum temperature difference is 2.7 ℃, indicating that the material has good thermal diffusion ability and temperature uniformity control performance.

[0170] Figure 7 This is a temperature-time / voltage curve of the multifunctional aerogel thermal insulation sheet loaded with graphene-inorganic phase change microcapsules in Example 1 during a thermal runaway prevention test. In the figure, LIB.Ⅰ, LIB.Ⅱ, and LIB.Ⅲ represent the first, second, and third cells (close to the heating plate), respectively, and f and b represent the temperature measurement points on both sides of the large surface of the cell. As can be seen from the figure, after thermal runaway occurs in the triggered cell, the temperature rise of adjacent cells is effectively suppressed, indicating that this material can significantly delay and block the propagation of thermal runaway in the battery module.

[0171] Example 2

[0172] Example 2 shows a multifunctional aerogel insulation sheet prepared using this method, which has both good heat diffusion capacity and excellent heat insulation and buffering performance. The specific preparation process includes the following steps:

[0173] (1) Prepare the aqueous phase

[0174] Under 45 ℃ water bath conditions, 20 g of disodium hydrogen phosphate dodecahydrate was heated to a molten state, then 5 g of deionized water and 0.25 g of Tween80 were added, and the mixture was stirred continuously until the system was uniform and transparent to obtain an aqueous phase.

[0175] (2) Prepare the oil phase

[0176] 30 g of liquid paraffin was mixed with 1.20 g of Span80 and stirred evenly at 45 °C to obtain the oil phase.

[0177] (3) Emulsion construction and preparation of inorganic phase change microcapsules

[0178] The aqueous phase was slowly poured into the oil phase and vigorously stirred at 500 r / min for 30 min to form a stable W / O emulsion. Then, 4 mL of tetraethyl orthosilicate and 1 mL of 3-aminopropyltriethoxysilane were added dropwise to the emulsion, and the mixture was stirred at 45 °C for 10 h and allowed to stand for aging for 24 h to obtain inorganic phase change microcapsule precipitates.

[0179] (4) Microcapsule washing and drying

[0180] The above precipitate was separated and washed three times with 50% ethanol aqueous solution, and then dried at 40 ℃ for 24 h to obtain inorganic phase change microcapsule powder.

[0181] (5) Graphene loaded and coated with aerogel insulation sheet

[0182] The obtained inorganic phase change microcapsule powder was added to a graphene-based coating system (specifically composed of few-layer graphene and epoxy resin) at a ratio of 40 wt% of the total mass of the composite coating. The mixture was stirred and dispersed evenly to obtain a graphene-inorganic phase change microcapsule composite coating. The composite coating was uniformly coated onto the surface of a hydrophobic aluminosilicate oxygen gel thermal insulation sheet (obtained by impregnation and modification of aluminosilicate oxygen gel felt with a volume ratio of acid to alcohol of 1:10, a pretreatment time of 24 h, and hexamethyldisiloxane as the siloxane modifier, which was soaked for 12 hours). The aerogel thermal insulation sheet had a size of 150×150×2 mm and was cured at room temperature for 12 h to obtain a multifunctional aerogel thermal insulation sheet loaded with graphene-inorganic phase change microcapsules.

[0183] Example 3

[0184] Example 3 shows a multifunctional aerogel insulation sheet prepared using this method, which has both good heat diffusion capacity and excellent heat insulation and buffering performance. The specific preparation process includes the following steps:

[0185] (1) Prepare the aqueous phase

[0186] Under a water bath at 45 °C, 20 g of disodium hydrogen phosphate dodecahydrate was heated to a molten state, followed by the addition of 5 g of deionized water and 0.40 g of Tween80, and the mixture was stirred continuously until the system was uniform and transparent to obtain an aqueous phase.

[0187] (2) Prepare the oil phase

[0188] 30 g of liquid paraffin was mixed with 1.00 g of Span80 and stirred evenly at 45 °C to obtain the oil phase.

[0189] (3) Emulsion construction and preparation of inorganic phase change microcapsules

[0190] The aqueous phase was slowly poured into the oil phase and vigorously stirred at 800 r / min for 60 min to form a stable W / O emulsion. Then, 4 mL of tetraethyl orthosilicate and 1 mL of 3-aminopropyltriethoxysilane were added dropwise to the emulsion, and the mixture was stirred at a constant temperature of 45 °C for 12 h and allowed to stand for aging for 48 h to obtain inorganic phase change microcapsule precipitates.

[0191] (4) Microcapsule washing and drying

[0192] The above precipitate was separated and washed three times with 50% ethanol aqueous solution, and then dried at room temperature for 24 h to obtain inorganic phase change microcapsule powder.

[0193] (5) Graphene loaded and coated with aerogel insulation sheet

[0194] The obtained inorganic phase change microcapsules were added to a graphene-based coating system (specifically composed of few-layer graphene and epoxy resin) at a ratio of 50 wt% of the total mass of the composite coating. The mixture was stirred and dispersed evenly to obtain a graphene-inorganic phase change microcapsule composite coating. The composite coating was then uniformly coated onto the surface of a hydrophobic glass fiber reinforced aerogel insulation sheet (obtained by impregnation and modification of glass fiber reinforced aerogel felt with siloxane impregnation, wherein the volume ratio of acid to alcohol was 1:10, the pretreatment time was 24 h, and the siloxane modifier was hexamethyldisiloxane, which was soaked for 12 hours). The aerogel insulation sheet had a size of 150×150×2 mm and was cured at room temperature for 12 h to obtain a multifunctional aerogel insulation sheet loaded with graphene-inorganic phase change microcapsules.

[0195] Comparative Example 1

[0196] The difference between this comparative example and Example 1 is that the inorganic phase change microcapsules are not dispersed into the graphene-based coating system in step (5), nor is a composite coating performed on the surface of the hydrophobic aerogel insulation sheet substrate. The sample used is a pure aerogel (i.e., a silicon-aluminum binary aerogel) insulation sheet.

[0197] Example 1 and Comparative Example 1 were applied to battery packs respectively, and charge-discharge cycle tests and thermal runaway barrier tests were performed. Figure 8 The temperature-time curve of Comparative Example 1 during the charge-discharge cycle is shown. The highest temperature of the system is 69.99 ℃ and the maximum temperature difference is 8.01 ℃. The results show that although Comparative Example 1 has a certain heat insulation effect under normal charge-discharge conditions, its temperature uniformity and heat diffusion capacity are relatively limited. Figure 9 The temperature-time curve of the thermal runaway process after Comparative Example 1 was applied in the battery pack is shown. The second battery experienced thermal runaway 2413 s after the first battery experienced thermal runaway, and the safety valve of the third battery ruptured. The test results show that although Comparative Example 1 can delay the thermal runaway propagation time to a certain extent, it cannot effectively block the further propagation of thermal runaway in the battery pack.

[0198] Figure 8 The figure shows the temperature-time curve of the pure aerogel insulation sheet in Comparative Example 1 during charge-discharge cycle testing. The results show that the highest temperature is 69.99 ℃ and the maximum temperature difference is 8.01 ℃, indicating that although the pure aerogel insulation sheet has a certain insulation effect, its heat diffusion and temperature uniformity under normal operating conditions are significantly weaker than those of Example 1.

[0199] Figure 9The figure shows the temperature-time / voltage curve of the pure aerogel insulation sheet in Comparative Example 1 during the thermal runaway prevention test. The experimental results show that while Comparative Example 1 can delay the thermal runaway propagation time to some extent, it cannot effectively block further propagation of thermal runaway within the battery pack. In summary, the multifunctional aerogel insulation sheet provided by this invention mainly comprises two parts: a hydrophobic aerogel insulation sheet substrate and a graphene-inorganic phase change microcapsule composite coating loaded on its surface. In the composite coating, the graphene thermally conductive filler can construct in-plane thermal conductivity pathways, which is beneficial for improving the diffusion and temperature uniformity of heat on the material surface; the inorganic phase change microcapsules can absorb heat in the phase change temperature range, achieving thermal buffering and peak temperature rise reduction; the hydrophobic aerogel insulation sheet substrate, relying on its low thermal conductivity and porous structure, effectively blocks further heat penetration and lateral propagation. Based on the above synergistic effect, the multifunctional aerogel heat insulation sheet can improve the temperature distribution uniformity within the power battery pack and reduce local heat accumulation under normal charging and discharging conditions; under abnormal conditions such as thermal runaway, it can delay and suppress the spread of heat to adjacent cells, thereby significantly improving the overall thermal safety performance of the power battery pack, and has good application prospects and engineering promotion value.

[0200] The above description of the embodiments is only for the purpose of helping to understand the method and core ideas of the present invention. It should be noted that those skilled in the art can make several improvements and modifications to the present invention without departing from the principles of the present invention, and these improvements and modifications also fall within the protection scope of the claims of the present invention.

Claims

1. A method for preparing a multifunctional aerogel heat insulation sheet, characterized in that, Includes the following steps: (1) Mix the emulsion solution, silicon source precursor and amino-containing silane coupling agent to react and obtain inorganic phase change microcapsules; (2) The inorganic phase change microcapsules and graphene-based coatings are mixed to obtain a composite coating; (3) The composite coating is applied to the surface of the hydrophobic aerogel insulation sheet substrate and cured to prepare a multifunctional aerogel insulation sheet with a graphene-inorganic phase change microcapsule composite coating. The graphene-based coating comprises a graphene thermally conductive filler and a film-forming binder phase; The emulsion solution is obtained by mixing and emulsifying an aqueous phase solution and an oil phase solution; The aqueous solution is obtained by mixing molten hydrated inorganic salt, aqueous solvent and hydrophilic nonionic surfactant; The oil phase solution is obtained by mixing a hydrophobic organic oil phase with a lipophilic nonionic surfactant.

2. The preparation method according to claim 1, characterized in that, The silicon source precursor in step (1) is selected from one or more of silicate precursors, water-soluble silicon sources, and colloidal silicon dioxide; The amino-containing silane coupling agent in step (1) is selected from one or more of aminoalkyltrialkoxysilane, aminoalkylmethyldialkoxysilane and polyamine silane coupling agents.

3. The preparation method according to claim 1 or 2, characterized in that, The volume ratio of the silicon source precursor to the amino-containing silane coupling agent is (10~1):(1~10).

4. The preparation method according to claim 1, characterized in that, The graphene thermally conductive filler is selected from one or more of graphene, few-layer graphene, reduced graphene oxide, and graphene oxide. The film-forming binder phase is selected from one or more of epoxy resin, polyurethane, acrylic resin, silicone resin, polyvinyl alcohol, styrene-butadiene emulsion, and fluorosilicone resin.

5. The preparation method according to claim 1, characterized in that, The mass ratio of the molten hydrated inorganic salt to the aqueous solution is (2~10):1; The amount of the hydrophilic nonionic surfactant used is 0.05 wt% to 2 wt% of the aqueous solution; The mass ratio of the hydrophobic organic oil phase to the lipophilic nonionic surfactant is (20~600):

1.

6. The preparation method according to claim 1 or 5, characterized in that, The hydrated inorganic salt in the molten hydrated inorganic salt is selected from one or more of hydrated phosphate, acetate hydrate, sulfate hydrate, nitrate hydrate, chloride hydrate and carbonate hydrate; The aqueous solvent is selected from one or more of deionized water, distilled water, and a mixed solvent of deionized water and low-carbon alcohols; The lower alcohol is selected from one or more of methanol, ethanol, and isopropanol; The hydrophobic organic oil phase is selected from one or more of alkane oil phases, ester oil phases, silicone oils, mineral oils, and aromatic solvents; The lipophilic nonionic surfactant is selected from one or more of sorbitol fatty acid esters, polyglycerol fatty acid esters, and fatty acid glycerides.

7. The preparation method according to claim 1, characterized in that, In step (3), the hydrophobic aerogel insulation sheet substrate is obtained by hydrophobic treatment of one or more of the following: silica aerogel felt, aluminosilicate aerogel felt, glass fiber reinforced aerogel felt, mullite fiber reinforced aerogel felt and ceramic fiber reinforced aerogel insulation sheet. The hydrophobic treatment method is selected from one or more of silanization modification, siloxane impregnation modification, and fluorinated silane modification.

8. A multifunctional aerogel heat insulation sheet with a graphene-inorganic phase change microcapsule composite coating prepared by the preparation method according to any one of claims 1 to 7; The multifunctional aerogel insulation sheet with a graphene-inorganic phase change microcapsule composite coating consists of a hydrophobic aerogel insulation sheet substrate and a graphene-inorganic phase change microcapsule composite coating loaded on its surface.

9. A lithium-ion battery, characterized in that, The multifunctional aerogel heat insulation sheet includes the graphene-inorganic phase change microcapsule composite coating as described in claim 8.

10. The lithium-ion battery according to claim 9, characterized in that, The multifunctional aerogel heat insulation sheet with a graphene-inorganic phase change microcapsule composite coating is disposed between the cells of the lithium-ion battery module or battery pack, on the side of the module, or in the inner lining of the battery pack casing.

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