An organic-inorganic hybrid nanocomposite, a preparation method thereof, and a nanofluid

Abstract

The application provides an organic-inorganic hybrid nanocomposite, a preparation method thereof and a power battery thermal management nanofluid, and belongs to the technical field of power battery thermal management. The application takes TiO2-h-BN binary compound as an inorganic heat-conducting core, covalently bonds a fixed-activated beta-cyclodextrin organic shell layer through APTES bridging, constructs a stable ternary hybrid structure, and effectively solves the industry bottleneck that the stability and heat conductivity of traditional nanofluids cannot be considered together and the viscosity is increased and the efficiency is reduced. The application adopts a step-by-step controllable process to prepare an ultrathin sheet layer hybrid material, uniformly disperses the hybrid material in an ethylene glycol water-based liquid with a low content to obtain the nanofluid. The nanofluid has ultrahigh dispersion stability and wide-temperature-range high-efficiency heat conduction capacity, the maximum heat conduction enhancement rate reaches 219.82%, the specific heat capacity is increased by 4.9%, and the viscosity increase is controllable and the comprehensive service efficiency is excellent. The application has simple and controllable process and can be produced on a large scale, can meet the long-term, low-energy-consumption and high-safety thermal management requirements of high-power power batteries, and has remarkable engineering application value.

Description

Technical Field

[0001] This invention belongs to the field of nanocomposite material modification and preparation technology, and more specifically, it relates to an organic-inorganic hybrid nanocomposite material, its preparation method and nanofluid. Background Technology

[0002] High-rate charge and discharge conditions of new energy power batteries generate a large amount of Joule heat. Excessive temperature of individual battery cells and large temperature differences can lead to safety issues such as capacity decay and thermal runaway. Liquid cooling thermal management is currently the mainstream temperature control technology for power batteries. Existing commercial cooling media mostly use ethylene glycol aqueous solution, but its inherent low thermal conductivity and limited heat storage capacity make it difficult to meet the rapid temperature equalization and heat dissipation requirements of high-power power batteries.

[0003] Nanofluids can significantly improve the thermophysical properties of a medium by doping it with highly thermally conductive nanofillers. Titanium dioxide has excellent chemical stability, low cost, and good dispersibility, while hexagonal boron nitride has a typical two-dimensional layered structure and ultra-high in-plane thermal conductivity. The TiO2-h-BN binary inorganic composite material constructed by combining the two can effectively balance structural stability and thermal conductivity, and has significant heat transfer advantages compared with TiO2 nanomaterials alone.

[0004] However, existing TiO2-h-BN binary composite materials still have significant technical defects: inorganic nanoparticles have a large specific surface area and high surface energy, and are prone to agglomeration and sedimentation when left to stand in ethylene glycol aqueous solution for a long time. The nanofluid has poor long-term dispersion stability, which can easily cause pipeline blockage and heat dissipation performance degradation during service, and cannot meet the engineering requirements for long-term stable service of power batteries. Summary of the Invention

[0005] This invention aims to overcome the shortcomings of existing TiO2-h-BN binary nanocomposites, such as poor fluid stability, easy agglomeration, and low overall service efficiency. It provides an organic-inorganic hybrid nanocomposite material with stable structure, excellent dispersibility, and outstanding thermophysical properties. At the same time, it provides a precise and controllable preparation method and develops a special nanofluid adapted to the thermal management of power batteries to achieve the technical effects of high thermal conductivity, high stability, low viscosity increase, and high overall efficiency.

[0006] An organic-inorganic hybrid nanocomposite material includes an inorganic core and an organic shell chemically grafted onto the surface of the inorganic core; the inorganic core includes hexagonal boron nitride nanosheets loaded with titanium dioxide; the organic shell includes β-cyclodextrin and a silane coupling agent derivative for connecting the inorganic core and the β-cyclodextrin; one end of the silane coupling agent derivative is bonded to the inorganic core via a silicon-oxygen bond, and the other end is bonded to the β-cyclodextrin via a carbon-nitrogen bond.

[0007] Furthermore, the silane coupling agent derivative is a hydrolysis-condensation derivative of 3-(aminopropyl)triethoxysilane (APTES); the β-cyclodextrin is activated by p-toluenesulfonyl chloride, and its 6-hydroxyl active site undergoes a nucleophilic substitution reaction to bond with the amino group of the silane coupling agent derivative, achieving site-directed covalent grafting with extremely strong structural stability.

[0008] Furthermore, when the organic-inorganic hybrid nanocomposite material is dispersed in an ethylene glycol aqueous solution with a volume ratio of 40:60 to prepare a nanofluid with a volume fraction of 0.025% to 0.1%, after standing at room temperature for 30 days, the absolute value of the zeta potential of the nanofluid is always greater than 40 mV, exhibiting excellent long-term anti-agglomeration and anti-settling properties.

[0009] Furthermore, the composite material has an average particle size of 9.38 nm, retains the two-dimensional lamellar structure of h-BN, has 1 to 5 lamellar layers, a maximum lamellar thickness of 1.63 nm, an h-BN interlayer spacing of 0.335 nm, a TiO2 interlayer spacing of 0.355 nm, and a complete crystal structure without distortion.

[0010] A method for preparing an organic-inorganic hybrid nanocomposite material includes the following steps:

[0011] S1: Preparation of activated cyclodextrin: Under alkaline conditions, β-cyclodextrin undergoes a 6-position monosubstitution reaction with p-toluenesulfonyl chloride to precisely activate the 6-position hydroxyl site of β-cyclodextrin, thus preparing a 6-O-(p-toluenesulfonyl)-β-CD activated derivative. This avoids ineffective side reactions at the 3- and 2-position hydroxyl groups, ensuring subsequent directional grafting.

[0012] S2: Preparation of TiO2-h-BN binary composite: Hexagonal boron nitride with a mass fraction of 1% to 4% was uniformly dispersed in ethylene glycol solvent, and titanium trichloride titanium source precursor was introduced. After solvothermal reaction, centrifugation washing, drying and annealing, a uniformly loaded hexagonal boron nitride binary inorganic composite material was prepared.

[0013] S3: Preparation of amino-functionalized intermediate: The TiO2-h-BN binary complex was reacted with APTES silane coupling agent under reflux in an anhydrous DMF system and under nitrogen protection. The silanol groups after hydrolysis of the silane coupling agent were dehydrated and condensed with the inorganic core surface hydroxyl groups to prepare AP-TiO2-h-BN intermediate with uniformly modified amino groups on the surface.

[0014] S4: Grafting reaction: The amino-functionalized intermediate and the activated cyclodextrin derivative were subjected to a nucleophilic substitution reaction in a polar DMF solvent to achieve covalent bridging of carbon and nitrogen bonds. After washing and drying, β-CD-TiO2-h-BN organic-inorganic hybrid nanocomposite material was obtained.

[0015] Furthermore, the substitution reaction temperature in step S1 is 85℃~95℃; the nucleophilic substitution reaction temperature in step S4 is 75℃~85℃, preferably 80℃, and the reaction time is 20h~28h, preferably 24h, to ensure maximum grafting rate and no by-products are generated.

[0016] A power battery thermal management nanofluid includes a base liquid and the aforementioned organic-inorganic hybrid nanocomposite material dispersed in the base liquid; the base liquid is an ethylene glycol aqueous solution with a volume ratio of 40:60, which is suitable for the operating conditions of power batteries for low-temperature antifreeze and room-temperature heat dissipation.

[0017] Furthermore, the volume fraction of the organic-inorganic hybrid nanocomposite material in the nanofluid is 0.025% to 0.1%; at an operating temperature of 60°C, the thermal conductivity of the nanofluid is increased by more than 200% compared to the pure base liquid.

[0018] Compared with the prior art, the present invention has the following beneficial effects:

[0019] (1) This invention abandons the traditional physical doping modification method and uses silane coupling agent to bridge and achieve stable covalent bonding modification of inorganic core and β-cyclodextrin. Utilizing the unique external hydrophilic and internal hydrophobic ring topology of β-cyclodextrin, a stable organic modified shell is constructed on the surface of nanoparticles. Through the synergistic effect of steric hindrance and surface hydrophilic modification, the anti-agglomeration and anti-settling ability of nanoparticles in the base fluid is significantly improved. This effectively solves the inherent defects of high surface energy and easy agglomeration and sedimentation of inorganic nanoparticles, greatly improves the long-term static stability and service reliability of nanofluids, and meets the working conditions requirements of long-term cycle operation of power batteries.

[0020] (2) This invention retains the composite heat transfer structure of hexagonal boron nitride two-dimensional high thermal conductivity framework and titanium dioxide nanoparticles, and relies on the complementary heat transfer mechanisms of the two inorganic materials to construct a highly efficient composite heat conduction network. At the same time, the excellent dispersibility brought about by organic modification effectively avoids the problems of increased interfacial thermal resistance and broken heat transfer pathways caused by nanoparticle agglomeration. It can continuously and stably improve the thermal conductivity of the cooling medium under wide temperature conditions, enhance the system's rapid heat dissipation and temperature uniformity capabilities, and adapt to the concentrated heat dissipation requirements during the charging and discharging process of high-power power batteries.

[0021] (3) In this invention, the β-cyclodextrin organic shell can effectively enhance the interfacial bonding between inorganic nanoparticles and ethylene glycol-based liquid, thicken the solid-liquid interface adsorption layer, optimize the solid-liquid interface heat transfer and heat storage mechanism, and improve the overall heat storage capacity of the nanofluid. It can effectively buffer the sudden temperature rise and temperature fluctuation under high-rate operation of the power battery, suppress the problem of local overheating and excessive temperature difference of the battery, and significantly improve the thermal balance and thermal safety redundancy of the power battery. Attached Figure Description

[0022] Figure 1Flowchart of the β-CD-TiO2-h-BN reaction;

[0023] Figure 2 X-ray diffraction pattern of β-CD-TiO2-h-BN;

[0024] Figure 3 Infrared spectrum of β-CD-TiO2-h-BN;

[0025] Figure 4 Scanning electron microscope (SEM) images of TiO2 (a) and β-CD-TiO2-h-BN (b), and transmission electron microscope (TEM) images of β-CD-TiO2-h-BN (c)(d);

[0026] Figure 5 AFM spectrum (a) and height map (b) of β-CD-TiO2-h-BN nanocomposite material;

[0027] Figure 6 XPS spectra of TiO2-h-BN and β-CD-TiO2-h-BN;

[0028] Figure 7 Zeta potential measurements of β-CD-TiO2-h-BN (a) and TiO2-h-BN (b) ethylene glycol-based nanofluids;

[0029] Figure 8 : Distribution of ΔBS as a function of time and height for ethylene glycol-based nanofluids in TiO2-h-BN (a) and β-CD-TiO2-h-BN (b);

[0030] Figure 9 Comparison of TSI of TiO2-h-BN and β-CD-TiO2-h-BN glycol-based nanofluids;

[0031] Figure 10 : Thermal conductivity of β-CD-TiO2-h-BN glycol-based nanofluid as a function of volume fraction (a) and temperature (b);

[0032] Figure 11 Schematic diagram of the thermal conductivity enhancement rate of β-CD-TiO2-h-BN glycol-based nanofluid as a function of volume fraction (a) and temperature (b);

[0033] Figure 12 A bar chart comparing the thermal conductivity of TiO2, TiO2-h-BN, and β-CD-TiO2-h-BN nanofluids;

[0034] Figure 13Comparison of measured and theoretically calculated specific heat capacities of β-CD-TiO2-h-BN glycol-based nanofluids;

[0035] Figure 14 Schematic diagram of the specific heat capacity of β-CD-TiO2-h-BN glycol-based nanofluid as a function of volume fraction (a) and temperature (b);

[0036] Figure 15 : Fitting curve of specific heat capacity mathematical model for β-CD-TiO2-h-BN ethylene glycol-based nanofluid;

[0037] Figure 16 : β-CD-TiO2-h-BN ethylene glycol-based nanofluid dynamic viscosity curve;

[0038] Figure 17 : Viscosity vs. volume fraction curve of β-CD-TiO2-h-BN glycol-based nanofluid;

[0039] Figure 18 Comparison of viscosity mathematical model fitting curves and literature models for β-CD-TiO2-h-BN ethylene glycol-based nanofluids;

[0040] Figure 19 Viscosity-temperature curves of β-CD-TiO2-h-BN glycol-based nanofluids. Detailed Implementation

[0041] The embodiments of the present invention will be described in further detail below with reference to the accompanying drawings and examples. The following examples are for illustrative purposes only and should not be construed as limiting the scope of the invention.

[0042] To facilitate concise expression and maintain consistency in technical terminology throughout the text, the following abbreviations are used to define the core raw materials, materials, and reagents in the specific embodiments of this invention:

[0043] 1. Hexagonal boron nitride, hereinafter referred to as h-BN;

[0044] 2. Titanium dioxide, hereinafter referred to as TiO2;

[0045] 3. Titanium dioxide-supported hexagonal boron nitride binary composite, hereinafter referred to as TiO2-h-BN;

[0046] 4. β-Cyclodextrin, hereinafter referred to as β-CD;

[0047] 5. β-cyclodextrin derivatives activated and modified with p-toluenesulfonyl chloride, hereinafter referred to as 6-TsO-β-CD;

[0048] 6,3-(aminopropyl)triethoxysilane, hereinafter referred to as APTES;

[0049] 7. Amino-functionalized TiO2-h-BN intermediate, hereinafter referred to as AP-TiO2-h-BN;

[0050] 8. N,N-Dimethylformamide, hereinafter referred to as DMF.

[0051] At the same time, the core technical structural terminology of this invention is clearly defined:

[0052] 1. Inorganic core: The inorganic core of the present invention is a TiO2-h-BN binary nanocomposite, which is a composite matrix formed by uniformly loading anatase TiO2 nanoparticles on the surface of two-dimensional sheet-like h-BN as the substrate. It combines the high thermal conductivity of h-BN sheet-like pathways with the high stability and high dispersion of TiO2 substrate.

[0053] 2. Silane coupling agent derivatives: Specifically refers to the functionalized derivatives formed by hydrolysis and dehydration condensation of APTES. One end is a siloxy group that can bond with inorganic hydroxyl groups, and the other end is an amino active group that can react with activated cyclodextrin, playing a covalent bridging role between the inorganic and organic phases.

[0054] 3. Activation of β-CD: 6-TsO-β-CD obtained by basic site-directed substitution modification with p-toluenesulfonyl chloride is a product of directional activation of the primary hydroxyl group at the 6-position of β-CD. It avoids the side reactions of the hydroxyl groups at the 2 and 3 positions and can undergo directional nucleophilic substitution reaction with amino groups to achieve precise covalent grafting.

[0055] 4. Organic-inorganic hybrid nanocomposite materials: Ternary hybrid materials with TiO2-h-BN as the inorganic rigid thermally conductive core and covalently bonded β-CD as the organic stable shell, which combine the high thermal conductivity of inorganic materials with the high stability and high hydrophilicity of organic supramolecular materials.

[0056] 5. Power Battery Thermal Management Nanofluid: Using an ethylene glycol aqueous solution with a volume ratio of 40:60 as the antifreeze and heat dissipation base liquid, a two-phase stable heat exchange medium formed by uniformly dispersing the above-mentioned ternary hybrid nanocomposite material is used to adapt to the wide temperature range thermal management conditions of power batteries.

[0057] Example 1:

[0058] like Figure 1 As shown, the preparation of β-CD-TiO2-h-BN organic-inorganic hybrid nanocomposite materials

[0059] S1: Preparation of activated cyclodextrin. 2 g NaOH was completely dissolved in 100 mL deionized water, and 10 g β-CD was added and stirred until a clear, homogeneous solution was obtained. The solution was then transferred to a three-necked flask. 1.98 g p-toluenesulfonyl chloride was dissolved in 10 mL acetonitrile and slowly added dropwise to the reaction system. The reaction was carried out at an ice-water bath for 3 h. The pH of the system was adjusted to 6-7 using dilute hydrochloric acid, and the mixture was allowed to stand and cool for 24 h to precipitate the crude product. The crude product was dissolved in 90℃ hot water, purified while hot, and recrystallized in an ice-water bath. This recrystallization process was repeated three times to obtain a high-purity 6-TsO-β-CD activated product, achieving single activation of the 6-hydroxyl group of β-CD and eliminating multi-substituted byproducts.

[0060] S2: Preparation of TiO2-h-BN binary inorganic composite. 4% (w / w) of h-BN nanosheets were dispersed in ethylene glycol solvent and mechanically stirred coupled with ultrasonic dispersion for 10 h to achieve uniform exfoliation of the h-BN sheets. A TiCl3 precursor solution was added, and after thorough mixing, the mixture was transferred to a high-pressure reactor and subjected to a solvothermal reaction at 150℃ for 12 h. The product was centrifuged, washed multiple times with ethanol, vacuum dried at 60℃ for 24 h, and annealed at 350℃ for 2 h to obtain a TiO2-h-BN binary composite with intact crystal structure and uniform particle distribution.

[0061] S3: Preparation of amino-functionalized intermediate. 5 g of TiO2-h-BN was uniformly dispersed in anhydrous DMF solvent, stirred, and sonicated for 1 h to ensure monodispersity of inorganic particles; APTES silane coupling agent was added, and the reaction was carried out under nitrogen protection and vacuum reflux at 96℃ for 6 h. The intermediate AP-TiO2-h-BN was prepared by utilizing the hydrolysis of silanol groups by APTES to dehydrate and condense with the hydroxyl groups on the surface of the inorganic core, and uniformly grafting amino active sites on the surface of the inorganic core.

[0062] S4: Covalent grafting preparation of ternary hybrid materials. 0.12 g AP-TiO2-h-BN and 0.2 g 6-TsO-β-CD were uniformly dispersed in DMF solvent and agglomerated for 15 min to break up the aggregation. The reaction was stirred at 80℃ for 24 h to construct C–N covalent bonds through nucleophilic substitution reaction of amino groups and activated cyclodextrins, achieving stable bridging of the organic and inorganic phases. The product was washed multiple times with ethanol and vacuum dried at 50℃ for 8 h to finally obtain β-CD-TiO2-h-BN organic-inorganic hybrid nanocomposite material.

[0063] To fully verify the novelty, structural stability, and process controllability of the microstructure of the material prepared by this invention, the prepared composite material was subjected to XRD crystal form testing, FT-IR infrared spectroscopy testing, micromorphology testing, and XPS bonding characteristic testing. The quantitative data in conjunction with the corresponding figures can fully demonstrate the structural innovation and technological progress of this invention. The specific test results and inventiveness analysis are as follows.

[0064] The XRD crystal structure test results of the composite material of this invention are as follows: Figure 2 As shown, the test data indicates that the sample completely retains the characteristic diffraction peaks of TiO2 and h-BN, with no impurity peaks generated, proving that the prepared product is pure and free of byproducts. The characteristic diffraction peaks of TiO2 correspond to the standard anatase crystal structure, and the characteristic peaks of h-BN lamellar structure are completely retained. There is no obvious shift in the characteristic peaks, only a slight decrease in peak intensity and a slight increase in peak width, indicating that the organic modification process did not destroy the core crystal structure of the inorganic matrix.

[0065] Grain size statistics show that the grain size of the material is 7.7 nm for the 101 crystal facet, 7.1 nm for the 004 crystal facet, 8.4 nm for the 200 crystal facet, 12.1 nm for the 106 crystal facet, 12.0 nm for the 211 crystal facet, and 9.0 nm for the 204 crystal facet. The overall average grain size is only 9.38 nm. The grain size distribution of each crystal facet has a small range, the size uniformity is high, and the particle size is uniform and controllable.

[0066] Quantitative analysis shows that after β-CD modification by covalent bridging with APTES, the crystallinity of the material only slightly decreases. The core crystal structure of TiO2 and h-BN is completely preserved, and the diffraction peaks are not shifted. Compared with the crystal structure destruction, structural collapse, and significant reduction in thermal conductivity that are very easy to occur in traditional organic modification technology, this invention achieves a structural breakthrough. At the same time, the uniform grain size proves that the covalent grafting modification process does not cause abnormal particle growth and local agglomeration. While successfully introducing an organic hydrophilic stabilizing layer, the high thermal conductivity intrinsic properties of the inorganic matrix are completely preserved. From the microstructure level, the invention achieves a two-way synergistic improvement in thermal conductivity and dispersion stability, overcoming the technical contradiction that the existing technology cannot achieve both simultaneously.

[0067] The FT-IR infrared spectroscopy test results of the composite material of the present invention are as follows: Figure 3 As shown, the spectral data confirms that the material of this invention achieves precise covalent composite of multiple components, rather than simple physical mixing. The sample simultaneously exhibits characteristic peaks of β-CD glycosidic bonds, 6-TsO-β-CD benzene rings and sulfur-oxygen bonds, and APTES amino groups, while retaining complete TiO2 and h-BN inorganic framework characteristic peaks. The characteristic peaks of each functional group are precisely matched, with no redundant impurity functional group signals or missing functional groups, demonstrating sufficient reaction and high degree of compositeness among the components. Compared to traditional physical doping modification, which relies solely on weak intermolecular forces, resulting in low bonding strength and easy peeling failure, this method achieves molecular-level composite through chemical bonding, significantly improving bonding stability. Spectroscopic quantitative data precisely confirms the novelty and structural stability advantages of the hybrid structure of this invention, completely distinguishing it from the inefficient composite methods of existing physical modifications.

[0068] The microstructure test results of the composite material of this invention are as follows: Figures 4-5As shown, the SEM, HRTEM, and AFM characterization results clearly demonstrate that the prepared β-CD-TiO2-h-BN hybrid material is a 1-5 layer ultrathin two-dimensional sheet structure with a maximum sheet thickness of only 1.63 nm. The standard interlayer spacing of h-BN is 0.335 nm, corresponding to the h-BN (002) crystal plane, and the interlayer spacing of TiO2 particles is 0.355 nm, corresponding to the TiO2 (101) crystal plane. The overall structure is regular and orderly, without structural distortion or interlayer stacking. TiO2 nanoparticles are preferentially and uniformly loaded on the edges and surface defect sites of h-BN sheets, without agglomeration, stacking, or exposed blank areas. The sheet structure is intact and undamaged. The introduction of β-CD did not change the growth morphology of TiO2 or the sheet structure and layer number characteristics of h-BN. Precise numerical analysis of the microstructure reveals that the ultrathin sheet structure significantly reduces interfacial thermal resistance compared to thick stacked materials. The regular and uniform interlayer spacing ensures the continuity of the heat conduction pathway. At the same time, the uniform loading of TiO2 nanoparticles without agglomeration completely solves the problems of particle agglomeration, broken heat conduction pathways, and insufficient effective heat exchange area in traditional binary composites. This regular microstructure provides precise structural support for constructing a continuous, low-resistance, and efficient heat conduction network, which is the core microscopic mechanism by which the thermal conductivity of this invention is significantly superior to that of existing technologies.

[0069] The XPS photoelectron spectroscopy results of the composite material of this invention are as follows: Figure 6 As shown, compared to the unmodified TiO2-h-BN binary composite, the binding energy of the characteristic peak of Ti element in the hybrid material of this invention is slightly reduced by 0.53 eV, the content of hydroxyl functional groups on the material surface is significantly increased, and a typical CN covalent bond characteristic peak is added, with no invalid bonding signal generated. Specific bonding data show that the binding energies of Ti 2p3 / 2 and Ti 2p1 / 2 are 458.44 eV and 464.13 eV, respectively. The O 1s spectrum contains Ti-OB, Ti-O, and OH chemical bonds, with binding energies of 533.24 eV, 529.83 eV, and 532.21 eV, respectively. The N 1s spectrum adds a CN bond characteristic peak at 400.04 eV, and the C 1s spectrum corresponds to the characteristic binding energies of CC / CH, COC, and CO bonds, fully demonstrating the precise bonding of the multi-components.

[0070] The quantitative bonding data accurately demonstrates the innovation and stability of the modification mechanism of this invention. The newly added exclusive CN covalent bond characteristic peak directly proves that the APTES bridging reaction occurred completely, and the organic and inorganic phases achieved stable chemical bond connection. The binding energy of Ti element decreased slightly and the surface hydroxyl content increased significantly. Quantitatively, it is confirmed that the hydrophilic active sites on the material surface increased significantly, which effectively improved the interfacial compatibility between nanoparticles and water-based media. It fundamentally solves the inherent defects of inorganic nanomaterials, such as high surface energy and easy aggregation and sedimentation. Compared with traditional surface adsorption modification schemes without chemical bond bonding, the stability improvement of this invention has substantial and quantifiable structural basis.

[0071] In summary, this scheme employs a coupling agent method, using KH550 silane coupling agent to modify TiO2-h-BN to obtain AP-TiO2-h-BN; subsequently, β-CD is activated using p-toluenesulfonyl chloride to obtain 6-TsO-β-CD; and the β-CD-TiO2-h-BN ternary complex is successfully prepared by reacting AP-TiO2-h-BN and 6-TsO-β-CD under certain conditions. Experiments demonstrate that the introduction of cyclodextrin does not alter the crystal structure of the binary complex, preserving its original structural characteristics, and only introduces organic functional groups into the original inorganic material. Furthermore, the introduction of organic matter does not change the number of layers in the sheet-like material.

[0072] Example 2

[0073] A power battery thermal management nanofluid includes a base liquid and the aforementioned organic-inorganic hybrid nanocomposite material dispersed in the base liquid. This embodiment employs a two-step method to prepare the power battery-specific nanofluid. An ethylene glycol aqueous solution with a volume ratio of 40:60 is selected as the antifreeze and heat dissipation base liquid. β-CD-TiO2-h-BN nanofluids with gradient concentrations of 0.025 vol%, 0.05 vol%, 0.075 vol%, and 0.1 vol% are prepared sequentially and thoroughly treated using a combination of magnetic stirring and ultrasonic dispersion to ensure uniform dispersion of nanoparticles in the base liquid, without agglomeration or precipitation. After sealing and settling, various performance tests are conducted to fully verify the stability, thermal conductivity, heat storage capacity, and overall service efficiency of the nanofluid of this invention.

[0074] The test results of the dispersion stability of nanofluids are as follows: Figures 7-9 As shown, the stability breakthrough advantage of this invention can be quantitatively verified by long-term static Zeta potential test and 14-day multiple light scattering test. After being left to stand at room temperature for 30 days, the absolute value of the Zeta potential of each concentration of nanofluid is stable at more than 40 mV, which is far greater than the critical value of fluid stability of 30 mV. It belongs to a highly stable fluid system. The fluid remains uniform and transparent throughout the process, without layering, precipitation or turbidity.

[0075] Continuous monitoring data of multiple light scattering over 14 days showed that the backscattered light change rate ΔBS of the β-CD-TiO2-h-BN nanofluid was <0.5%, the overall stability index TSI was <0.3, the homogeneity of the fluid system was almost unaffected, and the probability of particle sedimentation, floating and agglomeration was extremely low; while the TSI of the unmodified TiO2-h-BN binary nanofluid increased rapidly and ΔBS fluctuated significantly, and obvious sedimentation and stability failure occurred within 7 days.

[0076] Clear numerical comparisons fully demonstrate that the invention, through the dual stabilization mechanism of steric hindrance combined with hydrophilic modification constructed by β-CD covalent modification, significantly improves the long-term service stability of nanofluids, completely solves the industry pain point of easy aggregation and failure of traditional inorganic nanofluids, and is fully adaptable to the harsh working conditions of long-term cycling, no performance degradation, and no pipeline blockage of power batteries.

[0077] The test results of the thermal conductivity of nanofluids are as follows: Figure 10-12 As shown, the thermal conductivity of the nanofluid was tested under a wide temperature range of 20–60 °C and multiple concentration gradients. The thermal conductivity of the pure 40:60 ethylene glycol-based liquid at 25 °C was 0.427 W·m. -1 ·K -1 The thermal conductivity at 60℃ is 0.454 W·m. -1 ·K -1 Nanofluids at all concentration gradients exhibited significant thermal conductivity enhancement effects, showing obvious positive correlations between concentration and temperature.

[0078] At 25℃, the thermal conductivity of the 0.025 vol%, 0.05 vol%, 0.075 vol%, and 0.1 vol% nanofluids is 0.512 W·m. -1 ·K -1 0.568 W·m -1 ·K -1 0.621 W·m -1 ·K -1 0.676 W·m -1 ·K -1 The thermal conductivity reaches 0.989 W·m under high temperature conditions of 60℃. -1 ·K -1 1.142 W·m -1 ·K -1 1.297 W·m -1 ·K -1 1.452 W·m -1 ·K -1The thermal conductivity enhancement rates were 117.84%, 151.54%, 185.68%, and 219.82%, respectively. Compared with TiO2 and TiO2-h-BN nanofluids, the ternary modified composite material showed significantly better thermal conductivity gain than the binary and unary nanofillers, with a more pronounced increase in high-temperature gain.

[0079] Quantitative data analysis shows that this invention achieves an ultra-high thermal conductivity gain of 219.82% at a very low doping concentration of 0.1 vol% and a high temperature of 60°C. The low-doping and high-efficiency characteristics significantly reduce filler usage and effectively control fluid viscosity increments. Simultaneously, it exhibits no agglomeration failure and stable thermal conductivity under high-temperature conditions, perfectly adapting to the high-rate, high-temperature heat dissipation scenarios of power batteries. Numerical analysis fully demonstrates the innovative advantages of this solution: low-doping, high-efficiency, and strong adaptability to various operating conditions. Furthermore, this invention derives a mathematical model of thermal conductivity suitable for this system based on experimental data fitting, with a prediction accuracy of R²=0.994, accurately predicting thermal conductivity performance at different temperatures and concentrations.

[0080] The test results of the thermal storage performance of nanofluids are as follows: Figures 13-15 As shown, under the conventional high-temperature operating condition of 60℃ for power batteries, the specific heat capacity of pure ethylene glycol-based liquid is 3.610 J·g. -1 ·K -1 The specific heat capacity of the nanofluid at the optimal concentration of 0.1 vol% in this invention can reach 3.787 J·g. -1 ·K -1 Compared to the pure base liquid, the specific heat capacity increased by 4.9%, resulting in a significant improvement in heat storage capacity. The β-CD organic functional shell effectively enhances the adsorption at the solid-liquid interface between inorganic particles and the base liquid, thickening the interfacial heat storage layer. Combined with the excellent dispersion uniformity of the modified nanoparticles, it fully releases the material's specific surface area, effectively optimizing the solid-liquid interfacial heat storage mechanism and improving the overall thermal capacity of the fluid. Under the instantaneous high-rate charge and discharge conditions of power batteries, the improved heat storage performance can effectively absorb the instantaneous surge of heat, suppress the sudden rise in battery temperature and local temperature differences, improve the defects of traditional cooling media such as lag in temperature control and poor temperature uniformity, significantly improve the thermal balance and thermal safety redundancy of power batteries, and further improve the comprehensive performance of nanofluid thermal management.

[0081] The test results of nanofluid rheological properties and overall service efficiency are as follows: Figures 16-19As shown, under standard vehicle-mounted shear rate conditions of 20℃ and 200 s⁻¹, the viscosity of the pure base fluid is 2.356 mPa·s, and the viscosity of the 0.1 vol% high-concentration nanofluid is 3.274 mPa·s. The viscosity increase is controllable, the pumping resistance is low, and the overall rheological characteristics are excellent, exhibiting a fluid change pattern suitable for vehicle-mounted liquid cooling systems and meeting the requirements for stable pipeline flow. Under all temperature and concentration conditions, the overall working efficiency coefficient of the nanofluid is always much less than 1, with a maximum efficiency coefficient of only 0.193. This indicates that the heat dissipation gain brought by the thermal conductivity is far greater than the energy loss from fluid pumping, and the overall heat dissipation benefit is significantly positive. This completely solves the industry technical bottleneck of "modification and stability enhancement inevitably lead to viscosity increase, and viscosity increase inevitably leads to efficiency reduction" that is common in traditional organic modified nanofluids. This invention achieves optimal synergy among multiple parameters, including thermal conductivity, stability, rheology, and energy consumption, by precisely covalently grafting modification, while simultaneously improving fluid stability and thermal conductivity. This makes it suitable for the low-energy, high-reliability, and long-cycle operation requirements of vehicle thermal management systems.

[0082] In terms of performance, this invention overcomes multiple technical shortcomings of traditional nanofluids, such as poor stability, low thermal conductivity gain, weak heat storage capacity, high energy consumption, and poor temperature control, through multiple test data on stability, thermal conductivity, heat storage, and rheological efficiency. It achieves optimal multi-dimensional performance synergy of high stability, high thermal conductivity, high heat storage, and low energy consumption, and can perfectly adapt to the demanding thermal management conditions of power batteries with high power, long life, low energy consumption, and high safety. Compared with existing technologies, it has significant, quantifiable, and reproducible technological progress and has extremely high industrial application value.

[0083] The embodiments of the present invention are given for illustrative and descriptive purposes only, and are not intended to be exhaustive or to limit the invention to the forms disclosed. Many modifications and variations will be apparent to those skilled in the art. The embodiments were chosen and described to better illustrate the principles and practical application of the invention, and to enable those skilled in the art to understand the invention and design various embodiments with various modifications suitable for a particular purpose.

Claims

1. An organic-inorganic hybrid nanocomposite material, characterized in that, It includes an inorganic core and an organic shell chemically grafted onto the surface of the inorganic core; The inorganic core comprises hexagonal boron nitride nanosheets loaded with titanium dioxide. The organic shell includes β-cyclodextrin and a silane coupling agent derivative for connecting the inorganic core to the β-cyclodextrin; One end of the silane coupling agent derivative is bonded to the inorganic core via a silicon-oxygen bond, and the other end is bonded to the β-cyclodextrin via a carbon-nitrogen bond.

2. The organic-inorganic hybrid nanocomposite material according to claim 1, characterized in that, The silane coupling agent derivative is a hydrolysis-condensation derivative of 3-(aminopropyl)triethoxysilane; the β-cyclodextrin binds to the silane coupling agent derivative through its 6-hydroxyl site.

3. An organic-inorganic hybrid nanocomposite material according to claim 1 or 2, characterized in that, When the organic-inorganic hybrid nanocomposite material is dispersed in an aqueous ethylene glycol solution to form a nanofluid with a volume fraction of 0.025% to 0.1%, the absolute value of the Zeta potential of the nanofluid in a static state is greater than 40 mV.

4. A method for preparing an organic-inorganic hybrid nanocomposite material as described in any one of claims 1 to 3, characterized in that, Includes the following steps: S1: Preparation of activated cyclodextrin: Under alkaline conditions, β-cyclodextrin is subjected to a substitution reaction with p-toluenesulfonyl chloride to obtain a β-cyclodextrin derivative with an activated hydroxyl group at the 6-position. S2: Preparation of TiO2-h-BN binary composite: Hexagonal boron nitride was dispersed in a solvent, a titanium source precursor was introduced, and after solvothermal reaction and annealing, hexagonal boron nitride loaded with titanium dioxide was obtained. S3: Preparation of amino-functionalized intermediate: The TiO2-h-BN binary complex obtained in step S2 is reacted with a silane coupling agent under anhydrous conditions to obtain an intermediate with amino-modified surface. S4: Grafting reaction: The amino-functionalized intermediate obtained in step S3 and the activated cyclodextrin derivative obtained in step S1 are subjected to a nucleophilic substitution reaction in a polar solvent to obtain the organic-inorganic hybrid nanocomposite material.

5. The method for preparing an organic-inorganic hybrid nanocomposite material according to claim 4, characterized in that, In step S1, the temperature of the substitution reaction is 85℃~95℃; in step S2, the mass fraction of the hexagonal boron nitride in the solvent is 1%~4%; in step S4, the temperature of the nucleophilic substitution reaction is 75℃~85℃, and the reaction time is 20h~28h.

6. A nanofluid, characterized in that, The invention relates to thermal management of power batteries and includes a base fluid and an organic-inorganic hybrid nanocomposite material as described in any one of claims 1 to 3 dispersed in the base fluid; the base fluid includes an aqueous solution of ethylene glycol.

7. A nanofluid according to claim 6, characterized in that, The organic-inorganic hybrid nanocomposite material has a volume fraction of 0.025% to 0.1% in the nanofluid; the thermal conductivity of the nanofluid at 60°C is increased by more than 200% compared to the pure base liquid.

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