Preparation method of polymer modified spherical silicon oxide aerogel material

Abstract

The invention discloses a preparation method of a polymer modified spherical silicon oxide aerogel material. The preparation method comprises the following steps: firstly synthesizing 3-(acryloyloxy) propyl-2-thiophene acrylate through esterification and grafting reaction, then carrying out free radical polymerization on 3-(acryloyloxy) propyl-2-thiophene acrylate and vinylpyridine under the action of an initiator and a chain transfer agent, and carrying out protonic acid doping and spray drying to obtain the conductive polymer. Hydrolyzing tetraethoxysilane, mixing the hydrolyzed tetraethoxysilane with a conductive polymer, phosphorylated chitosan microspheres and a bridging agent, and adjusting pH and viscosity to obtain composite sol; and after ball-dropping emulsification, gelation, ultrasonic template removal, gradient replacement and subcritical drying, pulse electrochemical doping and plasma annealing treatment are performed. The prepared aerogel polymer is low in charge transfer resistance and excellent in conductivity, and has application potential in electrochemical energy storage devices such as supercapacitors.

Description

Technical Field

[0001] The invention relates to the technical field of spherical silicon oxide, and in particular to a method for preparing a polymer-modified spherical silicon oxide aerogel material. Background Art

[0002] Silica aerogel is a highly porous mesoporous material with ultra-low density, high porosity, high specific surface area, and low thermal conductivity. These exceptional properties hold great potential for application in various fields, including thermal insulation, catalysis, and adsorption. Currently, industrial production of silica aerogel typically utilizes organic silicon such as tetraethyl orthosilicate and tetramethyl orthosilicate through supercritical drying. However, high raw material costs, significant equipment investment, and a complex and hazardous manufacturing process limit its widespread industrial application. Summary of the Invention

[0003] In order to solve the above problems, the present invention aims to provide a method for preparing a polymer-modified spherical silica aerogel material.

[0004] In order to achieve the aforementioned object of the invention, the technical solutions adopted by the present invention include:

[0005] A method for preparing a polymer-modified spherical silica aerogel material comprises the following steps:

[0006] S1. Synthesis of a Conductive Polymer: 3-(Acryloyloxy)propyl-2-thiophene acrylate and vinyl pyridine in a molar ratio of 1:1.1-1.3 are reacted in the presence of an initiator and a chain transfer agent for 6-10 hours, and dried to obtain a conductive polymer.

[0007] S2. Composite sol preparation: Tetraethyl orthosilicate was hydrolyzed and mixed with a conductive polymer and phosphorylated chitosan microspheres, and a bridging agent was added. The pH was then adjusted to 8-9 with aqueous ammonia, and the viscosity was adjusted to 80-200 mPa·s with hydroxypropyl methylcellulose to obtain a composite sol.

[0008] The amount of the conductive polymer, bridging agent and phosphorylated chitosan microspheres is 5-15wt%, 0.5-2.0wt% and 0.05-0.2wt% respectively, calculated based on the mass of ethyl orthosilicate;

[0009] S3. Formation and Drying: The composite sol is sheared and emulsified using a spherical dropper and allowed to stand in a gel bath for 5–30 min to gel. The template is then removed by ultrasonic dissolution for 30–45 min. The sol is then subjected to gradient exchange using ethanol, acetone, and n-hexane, followed by subcritical drying to obtain a spherical xerogel.

[0010] S4. Dual doping strengthening: The dry gel is placed in a LiClO4-propylene glycol solution for pulse electrochemical doping treatment for 10 to 15 minutes, and then plasma annealed to obtain the spherical silica aerogel.

[0011] Preferably, the 3-(acryloyloxy)propyl-2-thiophene acrylate in step S1 is prepared by sequentially reacting 2-thiophene acrylic acid with 1,3-propylene glycol and grafting with acryloyl chloride.

[0012] The esterification reaction conditions are as follows: the raw materials are reacted in a carboxyl group:hydroxyl group ratio of 1:3-4 under 2-4 wt% concentrated sulfuric acid as a catalyst in an 80°C water bath until the acid value is less than 5 mgKOH / g;

[0013] The grafting reaction conditions are: using anhydrous dichloromethane as a medium, using triethylamine as an acid-binding agent, stirring and reacting in a salt ice bath at 0-5° C. for 3-4 hours.

[0014] Preferably, the vinyl pyridine in step S1 is selected from 2-vinyl pyridine, 3-vinyl pyridine, 4-vinyl pyridine, 3-(2-nitrovinyl) pyridine, and 4-phenylvinyl pyridine; the initiator is azobisisobutyronitrile, and the amount used is 0.5-2 wt% of the total weight of the monomer; the chain transfer agent is dodecanethiol, and the amount used is 0.05-0.1 wt% of the total weight of the monomer;

[0015] The reaction conditions of step S1 are: free radical polymerization in a 75 vol% ethanol-water solvent at 60-70°C in an oil bath under a nitrogen atmosphere for 7-10 hours, followed by cooling with ice water and quenching with 0.1 wt% hydroquinone; dialysis with 0.01 mol / L ammonium chloride using an 8 kDa dialysis bag to remove ionic impurities, and spray drying.

[0016] Preferably, the conductive polymer in step S1 is further subjected to a protonic acid solution doping and strengthening treatment for 24 to 48 hours before drying; the doping process is performed under the assistance of 40 to 60 kHz ultrasound, and the protonic acid is p-toluenesulfonic acid or camphorsulfonic acid with a concentration of 0.1 to 0.3 mol / L;

[0017] The number average molecular weight Mn of the conductive polymer is ≥1.5×10 4 Da, molecular weight distribution index PDI is 1.28~1.35, and electrical conductivity is 2.28~2.41S / cm.

[0018] Protonic acid doping can be achieved by H + Protonation of the carbazole amino group and thiophene ring (lone pair electrons of the S atom) generates delocalized cations, which improves the intrinsic conductivity of the polymer; ultrasonic assistance can ensure the uniformity of proton penetration and protonation, reducing conductive defects caused by local overoxidation.

[0019] Preferably, the water-to-silicon molar ratio of the ethyl orthosilicate hydrolysis in step S2 is 3 to 8, and the hydrolysis conditions are: hydrolysis in 0.1 to 0.3 M hydrochloric acid and a water bath at 50 to 65° C. for 1 to 2 hours; the bridging agent is epoxysilane 2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane and tetrabutyl titanate in a mass ratio of 1:1.2 to 1.5.

[0020] Preferably, the inner diameter of the dropper in step S3 is 0.5-1.0 mm, the shear rate is 5000-10000 rpm, the gelation temperature is 60-65° C., and the ultrasonic dissolution power is 40-60 kHz;

[0021] The gradient replacement conditions are as follows: the solvent volume of each level is 3 to 10 times the gel volume, the replacement temperature is constant at 30 to 50° C., the time is 4 to 12 hours per level, and the subcritical drying pressure is 0.3 to 0.5 MPa.

[0022] Preferably, the phosphorylated chitosan microspheres in step S3 are obtained by emulsifying chitosan with acetic acid and cross-linking with a phosphorylation reagent, with a surface phosphorylation degree of 0.8 to 1.2 mmol / g and a Zeta potential ≤-25 mV; the acetic acid concentration is 1 to 3 wt%, and the phosphorylation reagent is sodium tripolyphosphate, and the amount used is 0.8 to 1 times the molar amount of the chitosan glucose unit.

[0023] As a preference, in step S4, the electrochemical doping pulse voltage is 2.8 to 3.2 V, with a 10s pulse followed by a 5s interval, and Li + Doping concentration is 0.1~0.5mol / L;

[0024] LiClO4 electrochemical doping + By embedding the conjugated system at the Si-OC interface and forming Si-O-Li coordination bonds, the charge transfer at the polymer-silicon oxide interface is promoted, which helps to reduce the charge transfer resistance.

[0025] The plasma is a He / NH3 mixed gas with a volume ratio of 1:3-5, and the plasma treatment time is 1-1.5 hours; the power density is 50W / cm 3 , the pressure is maintained at 10Pa during the treatment process.

[0026] Another aspect of the present invention provides a polymer-modified spherical silica aerogel material prepared by the above method, which has an electrical conductivity of ≥3.6 S / cm and a charge transfer resistance of ≤3.0Ω.

[0027] Beneficial effects

[0028] The present invention provides a spherical silica aerogel material modified by a conductive polymer, which achieves a dual doping synergistic effect: the polymer is doped with proton acid and electrochemically to form a dual conductive mechanism of "delocalized cations + ion transport channels"; the proton acid provides intrinsic carriers, protonating the polymer imine bonds to generate delocalized cations, thereby improving the electrical conductivity; the Li+ introduced by electrochemical doping is embedded in the polymer conjugated system through Si-O-Li coordination bonds, forming ion transport channels, thereby reducing the charge transfer resistance. In addition, through the regulation of the pore structure, the controllable pore construction is achieved by utilizing the regulatory effects of template phosphorylation and bridging agents, as well as the electrostatic stabilization and selective etching of the phosphorylated chitosan template, thereby inducing the formation of mesopores; the bridging agent synergistically acts through the Ti-OC bond and the Si-OC bond to enhance the skeleton rigidity and ensure considerable compressive strength. The aerogel polymer prepared by the present invention has low charge transfer resistance and excellent electrical conductivity, and has the potential for application in electrochemical energy storage devices such as supercapacitors. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 This is the H-NMR spectrum of the conductive polymer obtained in Preparation Example 1.

[0030] Figure 2 1 and 2 are Nyquist plots of Example 1, Example 4 and Comparative Example 1, Comparative Example 3. DETAILED DESCRIPTION

[0031] To make the above-mentioned objects, features, and advantages of the present invention more clearly understood, the specific embodiments of the present invention are described in detail below with reference to specific embodiments. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making any creative efforts are within the scope of protection of the present invention.

[0032] The experimental methods in the following embodiments where specific conditions are not specified are generally performed under conventional conditions or conditions recommended by the manufacturer; the experimental raw materials mentioned can be purchased from conventional biochemical reagent companies.

[0033] As used herein, Mn refers to the number average molecular weight as determined by gel permeation chromatography using a Waters 2695 Separations Module with a Waters 410 Differential Refractometer (RI detector) using polystyrene standards at a flow rate of 1 mL min -1 Tetrahydrofuran was used as the eluent and two PL gel mixed C columns were used for separation.

[0034] Chitosan, deacetylation degree 95%, Xi'an Lvteng Biotechnology Co., Ltd.

[0035] CBE-10L subcritical fluid extraction laboratory complete equipment, Henan Subcritical Biotechnology Co., Ltd.

[0036] Preparation Example 1

[0037] a. Synthesis of 3-(acryloyloxy)propyl-2-thiophene acrylate:

[0038] 1) Esterification: To a three-necked flask, 0.1 mol of 2-thiopheneacrylic acid, 0.15 mol of 1,3-propylene glycol, and 2 wt% concentrated sulfuric acid were added and nitrogen was introduced. The system was reacted in an 80°C water bath until the acid value was <5 mgKOH / g. The catalyst was recovered by hot filtration, and the excess propylene glycol was removed by reduced pressure distillation at 80°C and 10 kPa to obtain 3-(2-thiopheneacryloyloxy)propanol in a yield of 96.3%.

[0039] 2) Grafting Reaction: 0.096 mol of 3-(2-thiopheneacryloyloxy)propanol was dissolved in 60 mL of anhydrous dichloromethane in a 0°C reactor. 0.12 mol of acryloyl chloride was added dropwise at a rate of 1.5 mL / min. Simultaneously, 0.12 mol of triethylamine was added dropwise. After the addition was complete, the reaction was stirred in a 0°C ice bath for 3.5 hours. The mixture was filtered, and the organic phase was washed sequentially with 5 wt% HCl, saturated NaHCO₃, and deionized water, dried over anhydrous MgSO₄, and concentrated under reduced pressure to obtain 3-(acryloyloxy)propyl-2-thiopheneacrylate in a yield of 93.5%.

[0040] b. Conductive polymer synthesis: 0.1 mol of 3-(acryloyloxy)propyl-2-thiophene acrylate and 0.11 mol of 4-vinylpyridine were dissolved in 150 mL of ethanol-water solvent (75 vol%). After nitrogen purging for 30 min to deoxygenate, 0.60 g of AIBN was added. The system was gradually heated to 65°C, and 0.18 mL of a 0.1 g / mL dodecanethiol-ethanol solution was simultaneously added using a constant pressure funnel. The reaction was stirred in an oil bath at 65°C for 3 h. Subsequently, 0.60 g of AIBN and 0.18 mL of a dodecanethiol-ethanol solution were added, and the reaction was continued until the viscosity reached 900 mPa·s. The reaction was quenched to 10°C in an ice-water bath, and 10 mL of a 0.1 wt% hydroquinone-ethanol solution was added and stirred for 15 min to quench the reaction. After the reaction, the mixture was recrystallized with glacial ether and washed with acetone three times. Then, an 8 kDa dialysis bag was used to perform cyclic dialysis for 48 hours using a 0.01 mol / L neutral ammonium chloride solution as the dialysate. The dialysate was replaced with new one every 6 hours to obtain a conductive polymer.

[0041] c. Protonic Acid Doping: The conductive polymer was dissolved in a 0.2 mol / L p-toluenesulfonic acid-acetonitrile solution and treated at a 40 kHz ultrasonic frequency for 24 h. The solution temperature was controlled at ≤30°C in an ice bath. After treatment, the polymer powder was spray-dried at 0.3 MPa atomization pressure and 180°C to obtain a polymer powder with a measured D50 of 12.5 μm.

[0042] The conductive polymer obtained in Preparation Example 1 was tested by H NMR (Mercury VX-300 NMR spectrometer, Varian, USA) with TMS as internal standard and CDCl3 as solvent. Figure 1 .

[0043] Preparation Example 2

[0044] The difference from Preparation Example 1 is that the vinyl pyridine used in step b is 3-(2-nitrovinyl)pyridine.

[0045] Preparation Example 3

[0046] The difference from Preparation Example 1 is that the doping treatment time in step c is 40 hours.

[0047] Preparation Example 4

[0048] The difference from Preparation Example 1 is that step a is omitted, that is, 2-thiopheneacrylic acid and 4-vinylpyridine are directly subjected to free radical polymerization.

[0049] Preparation Example 5

[0050] Omit step c, and the rest is the same as in Preparation Example 1.

[0051] The conductive polymers obtained in Preparation Examples 1 to 5 were tested for relevant properties. The results are shown in Table 1.

[0052] Table 1

[0053] Conductive polymers <![CDATA[Mn / ×10 4 Yes]]> PDI Conductivity / S / cm Preparation Example 1 1.85 1.32 2.35 Preparation Example 2 1.90 1.33 2.42 Preparation Example 3 1.88 1.31 2.48 Preparation Example 4 0.85 2.05 0.82 Preparation Example 5 1.80 1.95 1.25

[0054] Preparation Example 6

[0055] The phosphorylated chitosan microspheres used in the following examples were prepared as follows:

[0056] 100 g of chitosan raw material was taken, ultrasonicated in a 5 wt % sodium hydroxide + 3 wt % H2O2 treatment solution for 2 h, washed with water until neutral, dried and sieved; the surface Zeta potential was measured to be +15 mV.

[0057] 50g of treated chitosan powder was premixed with 2.5wt% acetic acid solution and 8g of Span80 emulsifier in 500mL of liquid paraffin and stirred at 75°C and 800rpm for 1 hour to form a milky white emulsion. 20mL of a 42.5wt% aqueous sodium tripolyphosphate solution and 50mL of a 6wt% aqueous sodium dihydrogen phosphate solution were added, and the mixture was heated to 80°C and stirred for 1 hour. After the phosphorylation process was completed, the mixture was extracted with petroleum ether. The aqueous layer was centrifuged, washed three times with alcohol, filtered, dried at 60°C, and passed through a 200-mesh sieve to obtain the product. The measured zeta potential was -28mV, the degree of phosphorylation was 1.2mmol / g, and the D50 value was 8.5μm.

[0058] In addition, the above operation was maintained, but the concentration of the sodium tripolyphosphate was reduced to 30 wt %. The zeta potential of the phosphorylated chitosan microspheres was measured to be -21 mW, and the degree of phosphorylation was 0.8 mmol / g.

[0059] Example 1

[0060] A polymer-modified spherical silica aerogel is prepared as follows:

[0061] S1. Synthesis of the conductive polymers of Preparation Examples 1 to 5;

[0062] S2. Composite sol construction:

[0063] 10 mL of tetraethyl orthosilicate (TEOS) was mixed with 30 mL of deionized water at a water-silicon molar ratio of 5:1, 0.1 mol / L hydrochloric acid aqueous solution (50 mL) was added, and hydrolysis was carried out in a water bath at 50°C for 1 h to obtain a tetraethyl orthosilicate hydrolyzate; the conductive polymer (10 wt%) of Preparation Example 1, epoxysilane 2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane (0.5 wt%), a mixed bridging agent of tetrabutyl titanate (0.75 wt%), and phosphorylated chitosan microspheres (0.1 wt%, phosphorylation degree of 1.2 mmol / g) were added thereto in sequence; the viscosity was adjusted to 150 mPa·s with hydroxypropyl methylcellulose, and the pH was adjusted to 8.5 with aqueous ammonia; the conductive polymer (10 wt%) obtained in Preparation Example 1 was then added, and ultrasonic dispersion was carried out for 30 min to obtain a uniform sol.

[0064] S3. Molding and drying:

[0065] The emulsified sol was sheared at 12,000 rpm using a 0.8 mm inner diameter ball dropper. The sol was then dropped into a 60°C dimethyl silicone oil coagulation bath and allowed to gel for 15 minutes, forming a spherical wet gel. The wet gel was then transferred to deionized water and sonicated at 40 kHz for 40 minutes to dissolve the phosphorylated chitosan template. The replacement was repeated three times until no sulfonate residue remained (as determined by AgNO3).

[0066] Solvent exchange was performed sequentially with ethanol (3× the gel volume, 40°C, 8 h / step), acetone (2× the gel volume, 45°C, 6 h / step), and n-hexane (1× the gel volume, 50°C, 4 h / step). After exchange, the mixture was placed in a subcritical drying apparatus and dried at 0.4 MPa and 40°C for 24 h to obtain a xerogel.

[0067] S4. Post-processing enhancement

[0068] The dry gel was immersed in 0.1 mol / L LiClO4-propylene glycol solution and treated with 3.0 V pulse pressure for 10 s every 5 s for a total of 12 min.+ The embedding amount is 0.20~0.26mmol / g.

[0069] Then, a He / NH3 mixture with a volume ratio of 1:4 was used as the working gas and the 3 The final spherical silica aerogel was obtained by microwave plasma annealing treatment at a power density of 10 Pa and a pressure of 10 Pa for 1 h.

[0070] Examples 2-3

[0071] The difference from Example 1 is that the conductive polymers used in step S1 are replaced with those obtained in Preparation Examples 2 to 3 respectively.

[0072] Example 4

[0073] During electrochemical doping in step S4, the LiClO4 concentration was increased to 0.3 mol / L and the doping time was extended to 20 min.

[0074] Example 5

[0075] The difference from Example 1 is that the phosphorylation degree of the phosphorylated chitosan microspheres used is 0.8 mmol / g.

[0076] Example 6

[0077] The difference from Example 1 is that the ratio of epoxy silane to tetrabutyl titanate is reduced from 1:1.5 to 1:1.2).

[0078] Comparative Examples 1-2

[0079] The difference from Example 1 is that the conductive polymers obtained in Preparation Examples 4 to 5 are used in step S1.

[0080] Comparative Example 3

[0081] Unphosphorylated nano-chitosan was used instead of phosphorylated chitosan microspheres.

[0082] Performance testing:

[0083] 1. Conventional physical and chemical properties of aerogels

[0084] (1) Specific surface area and pore size distribution: Nitrogen adsorption-desorption method (BET, GB / T19587-2017). Measured using a Micromeritics ASAP 2010 analyzer. Conditions: Degassing temperature 200°C, 3h, vacuum degree <10 -3 Pa; adsorption temperature: 77K (liquid nitrogen bath).

[0085] (2) Thermal conductivity: Hot wire method (GB / T 10297-2015). Test conditions: A 10 mm diameter flat probe was used as the test probe. The test was performed using a Hot Disk TPS2500S thermal constant analyzer at a heating power of 10 mW for 300 s at a temperature of 25°C and a relative humidity of 50%.

[0086] (3) Compressive strength: Compression test (GB / T 1041-2008). Equipment: Instron 5967 universal testing machine. Sample size: Cylindrical (10 mm diameter, 10 mm height); Loading rate: 1 mm / min; Data acquisition: Compressive strength (peak stress) versus strain curves were recorded.

[0087] The above test results are shown in Table 2.

[0088] Table 2

[0089]

[0090] In terms of surface area optimization, mesopores (2-50 nm) are the main contributor to the surface area. The double-bridged polymer and the phosphorylated template synergistically induce a high surface area mesoporous structure. In all examples 1-4, the mesopores account for 62% to 68%, and the surface area is ≥860 m 2 / g; Due to the lack of process, the proportion of mesopores in Comparative Examples 1 to 3 decreased significantly and the specific surface area decreased sharply. Among them, Comparative Example 3 used unphosphorylated chitosan template, which had no negative charge on the surface and could not induce uniform mesopore formation by electrostatic repulsion. The porosity dropped to 60%, the pore size distribution widened to 30nm, and the specific surface area dropped to 554m 2 / g. Verify the regulatory effect of phosphorylated chitosan template on pore structure.

[0091] In terms of compressive strength, the preparation method of the present invention forms a covalent Si-OC bond interface, which helps reduce stress concentration and improve mechanical properties. Regarding thermal conductivity optimization, porosity is directly negatively correlated with thermal conductivity. Comparative Example 1, which lacks the grafting process, has a porosity drop of 63%, a wider pore size distribution, and a sharp decrease in specific surface area, while thermal conductivity increases to 0.036 W / (m·K).

[0092] 2. Nyquist plot:

[0093] The Nyquist diagram intuitively reflects the electrode interface dynamics process through the relationship between the real and imaginary parts of the impedance.

[0094] Equipment: CHI660E electrochemical workstation (Shanghai Chenhua), frequency range 10 -2 ~10 5 Hz.

[0095] Test conditions: disturbance voltage 5mV, DC bias set to open circuit potential.

[0096] Electrolytic cell: three-electrode system, with aerogel sheet as working electrode, Ag / AgCl as reference electrode, and platinum sheet / lithium foil as counter electrode.

[0097] Electrolyte: 1.0 mol / L LiPF6 dissolved in ethylene carbonate (EC)-diethyl carbonate (DEC) in a volume ratio of 1:1, dehydrated to H2O < 20 ppm before use.

[0098] Test steps:

[0099] 1) Tablet molding: 100 mg of aerogel powder was pressed into a Φ10 mm × 1 mm disc at a pressure of 10 MPa, and the surface was polished (Ra ≤ 0.1 μm).

[0100] 2) Electrode Assembly: In a glove box (H2O, O2 <1 ppm), weld the sample to the nickel current collector and install it into the electrode holder, ensuring that the contact resistance is <0.5Ω. Use a standard resistor (1 kΩ ± 0.1%) to calibrate the equipment, and the open-circuit foundation potential drift is ≤2 mV / h.

[0101] 3) Electrolytic cell assembly and static equilibrium: Inject 5 mL of electrolyte to completely immerse the working electrode, with the reference electrode 2 ± 0.5 mm away from the working electrode; incubate at a constant temperature of 25°C for 30 min, and monitor the open circuit potential until the fluctuation is <1 mV / min.

[0102] 4) Data Acquisition: Start frequency sweep and automatically record the real impedance Z' (Ω) and the negative imaginary impedance -Z" (Ω). A single test lasts approximately 15-20 minutes. Use Kramers-Kronig transformation to verify data consistency. Repeat the test three times (RSD ≤ 5%).

[0103] Draw the Nyquist diagram with Z' as the horizontal coordinate and -Z" as the vertical coordinate, see Figure 2 In the Nyquist diagram, the main semicircle corresponds to the high-frequency charge transfer region (>10 3 Hz), which is dominated by the fast kinetics of interfacial charge transfer. The diameter corresponds to the charge transfer resistance (Rct, unit: Ω) of the aerogel / electrolyte interface. The inset in the upper right corner shows the low-frequency ion diffusion region (1 to 10 3 Hz) and an enlarged view of the ultra-high frequency ohmic region (>10kHz). The ultra-high frequency ohmic region is embedded in the figure as a curve close to the vertical line. The smaller the resistance, the closer the vertical line is to the origin; the vertical line of comparative example 3 is the longest, due to poor contact caused by the unsulfonated template. The low frequency diffusion region is a slant line, which is dominated by the slow process of ion diffusion. The slope of the slant line is related to Li + Warburg impedance coefficient of diffusion (σ, unit: Ω·s -1 / 2 ) is positively correlated.

[0104] Depend on Figure 2 In the high frequency region, the comparative example 1 has the largest Rct value (6.6Ω), and the Rct of Example 1 is 4.5Ω, indicating that the Si-O-Li coordination bond strengthens the interfacial charge transfer; in Example 4, the concentration of LiClO4 is further increased to 0.3 mol / L, resulting in Li + The activity increases and the embedding driving force increases, so Rct = 3.2Ω.

[0105] In the low frequency region, the slope of the low frequency region of Comparative Example 1 is the steepest, while that of Example 4 is the flattest: σ corresponds to 12.5Ω·s -1 / 2 Down to 8.0Ω·s -1 / 2 , demonstrating that increasing electrochemical doping concentration optimizes Li + Diffusion path, electrochemical performance is improved. In contrast, the template of Example 3 is not phosphorylated, and the pore size distribution is broadened, making Li + The diffusion path is extended and the ion diffusion path is tortuous, corresponding to only 0.14 mmol / g of Li in Table 3. + Embed amount.

[0106] 3. Aerogel conductivity

[0107] (1) Conductivity: Four-probe method. Use RTS-9 four-probe tester; test conditions: room temperature 25°C, tablet thickness 1 mm, pressure 10 MPa, test current 1 mA.

[0108] (2)Li + Embedding amount: According to GB / T 31360-2015. The aerogel sample was dissolved in 40% hydrofluoric acid and acidified with 65% nitric acid; then diluted to 100 mL and filtered through a 0.22 μm filter; Li was measured using an Agilent 7900 inductively coupled plasma mass spectrometer. + concentration and calculate the embedding amount.

[0109] In addition, the charge transfer resistance is calculated based on the difference in real impedance values ​​at both ends of the semicircle diameter of the Nyquist plot drawn in Part 2.

[0110] The test results of the conductivity-related properties of the aerogel are shown in Table 3.

[0111] Table 3

[0112] index Conductivity / S / cm Charge transfer resistance / Ω <![CDATA[Li + Embedding amount / mmol / g]]> Example 1 2.20 4.6 0.18 Example 2 2.38 4.4 0.18 Example 3 2.45 4.3 0.18 Example 4 2.55 3.5 0.23 Example 5 2.38 5.6 0.18 Example 6 2.75 3.9 0.18 Comparative Example 1 1.42 6.8 0.09 Comparative Example 2 1.18 7.5 0.11 Comparative Example 3 1.75 6.0 0.14

[0113] From Table 1 and Table 3, compared with Example 1, the nitro group added to the free radical polymerization raw material in Example 2 enhanced the electron-withdrawing effect of the conjugated system, expanded the range of π electron delocalization, and increased the conductivity. In Comparative Example 1, the 3-(acryloyloxy)propyl-2-thiophene acrylate grafting step was omitted, and the polymer molecular weight dropped sharply to 0.85×10 4 Da, insufficient conjugated chain length leads to weakened π-π stacking, and the conductivity is only 0.82S / cm. Figure 2 The charge transfer resistance Rct in the medium and high frequency region reaches 6.8Ω, and the carrier transmission resistance increases. Comparative Example 3 uses an unphosphorylated chitosan template with a surface Zeta potential of +15mV. It is unable to induce uniform mesopores through electrostatic repulsion, and the pore size distribution is broadened, blocking the pores, which hinders the Li + diffusion.

[0114] In Example 3, the proton acid doping time was extended, the protonation degree of carbazole and the delocalized cation concentration increased, and the conductivity was improved to 2.45S / cm. In Comparative Example 2, the proton acid doping was omitted, and only electrochemical doping was used, which could not make up for the intrinsic conductive defects of the polymer. The imine group was not protonated, resulting in insufficient delocalized cations and the loss of hydrogen bonding of the protonated imine bond. Li+ was formed at the polymer-silicon oxide interface. + Transmission dead end causes the charge transfer resistance to surge.

[0115] In Example 4, the concentration of LiClO4 is increased, and the Li + Increased activity and enhanced embedding driving force: Li + The Si-O-Li bond and coordination bond at the polymer-silicon oxide interface are fully embedded in the conjugated system to form an ion transport channel. + The embedding amount increased to 0.23mmol / g. The phosphorylation degree of the template used in Example 5 was reduced to 0.8mmol / g, resulting in a weakening of the electrostatic repulsion force on the template surface and the hydrogen bonding between the template and the sol, causing template agglomeration and pore blockage. The pores are prone to collapse during the gelation process, so the lower limit of the phosphorylation degree can be determined. In Example 6, the proportion of tetrabutyl titanate as the bridging agent was slightly reduced, resulting in a decrease in the number of Ti-OC bonds, a weakening of the rigid support of the silica skeleton, and a decrease in the compressive strength to 0.80MPa; however, slow gelation induced the formation of more mesopores, with the proportion of mesopores increasing to 75% and the pore volume increasing to 1.35cm 3 / g.

[0116] It should be understood that the above are only some embodiments of the present invention. It should be pointed out that for ordinary technicians in this field, other variations and improvements can be made without departing from the creative concept of the present invention, and these all fall within the scope of protection of the present invention.

Claims

1. A method for preparing a polymer-modified spherical silica aerogel material, characterized in that: The following steps are involved: S1. Synthesis of a Conductive Polymer: 3-(Acryloyloxy)propyl-2-thiophene acrylate and vinyl pyridine in a molar ratio of 1:1.1-1.3 are reacted in the presence of an initiator and a chain transfer agent for 6-10 hours, and dried to obtain a conductive polymer. S2. Composite sol preparation: Tetraethyl orthosilicate was hydrolyzed and mixed with a conductive polymer and phosphorylated chitosan microspheres, and a bridging agent was added. The pH was then adjusted to 8-9 with aqueous ammonia, and the viscosity was adjusted to 80-200 mPa·s with hydroxypropyl methylcellulose to obtain a composite sol. The amount of the conductive polymer, bridging agent and phosphorylated chitosan microspheres is 5-15wt%, 0.5-2.0wt% and 0.05-0.2wt% respectively, calculated based on the mass of ethyl orthosilicate; S3. Formation and Drying: The composite sol is sheared and emulsified using a spherical dropper and allowed to stand in a gel bath for 5–30 min to gel. The template is then removed by ultrasonic dissolution for 30–45 min. The sol is then subjected to gradient exchange using ethanol, acetone, and n-hexane, followed by subcritical drying to obtain a spherical xerogel. S4. Dual doping strengthening: The dry gel is placed in a LiClO4-propylene glycol solution for pulse electrochemical doping treatment for 10 to 15 minutes, and then plasma annealed to obtain the spherical silica aerogel.

2. The preparation method according to claim 1, wherein The 3-(acryloyloxy)propyl-2-thiophene acrylate in step S1 is obtained by sequentially reacting 2-thiophene acrylic acid with 1,3-propylene glycol and grafting with acryloyl chloride. The esterification reaction conditions are as follows: the raw materials are reacted in a carboxyl group:hydroxyl group ratio of 1:3-4 under 2-4 wt% concentrated sulfuric acid as a catalyst in an 80°C water bath until the acid value is less than 5 mgKOH / g; The grafting reaction conditions are: using anhydrous dichloromethane as a medium, using triethylamine as an acid-binding agent, and stirring the reaction at 0-5° C. for 3-4 hours.

3. The preparation method according to claim 1, wherein The vinyl pyridine in step S1 is selected from 2-vinyl pyridine, 3-vinyl pyridine, 4-vinyl pyridine, 3-(2-nitrovinyl) pyridine, and 4-phenylvinyl pyridine; the initiator is azobisisobutyronitrile, and the amount used is 0.5-2 wt% of the total weight of the monomer; the chain transfer agent is dodecanethiol, and the amount used is 0.05-0.1 wt% of the total weight of the monomer; The reaction conditions of step S1 are: free radical polymerization in a 75 vol% ethanol-water solvent at 60-70°C oil bath under nitrogen atmosphere for 7-10 hours, cooling with ice water, quenching with 0.1 wt% hydroquinone; dialysis with ammonium chloride dialysate to remove ionic impurities, and spray drying.

4. The preparation method according to claim 1, characterized in that In step S1, the conductive polymer is further subjected to a protonic acid solution doping and strengthening treatment for 24 to 48 hours before drying; the doping process is performed under the assistance of 40 to 60 kHz ultrasound, and the protonic acid is p-toluenesulfonic acid or camphorsulfonic acid with a concentration of 0.1 to 0.3 mol / L; The number average molecular weight Mn of the conductive polymer is ≥1.5×10 4 Da, molecular weight distribution index PDI is 1.28~1.35, and electrical conductivity is 2.28~2.41S / cm.

5. The preparation method according to claim 1, characterized in that The water-silicon molar ratio of the ethyl orthosilicate hydrolyzed in step S2 is 3 to 8, and the hydrolysis conditions are: hydrolysis in 0.1 to 0.3 M hydrochloric acid and a water bath at 50 to 65° C. for 1 to 2 hours; the bridging agent is epoxysilane 2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane and tetrabutyl titanate in a mass ratio of 1:1.2 to 1.

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6. The preparation method according to claim 1, characterized in that In step S3, the inner diameter of the dropper is 0.5-1.0 mm, the shear rate is 5000-10000 rpm, the gelation temperature is 60-65° C., and the ultrasonic dissolution power is 40-60 kHz; The gradient replacement conditions are as follows: the solvent volume of each level is 3 to 10 times the gel volume, the replacement temperature is constant at 30 to 50° C., the time is 4 to 12 hours per level, and the subcritical drying pressure is 0.3 to 0.5 MPa.

7. The preparation method according to claim 1, characterized in that The phosphorylated chitosan microspheres described in step S3 are obtained by emulsifying chitosan with acetic acid and cross-linking with a phosphorylation reagent, with a surface phosphorylation degree of 0.8 to 1.2 mmol / g and a Zeta potential of ≤-25 mV; the acetic acid concentration is 1 to 3 wt%, and the phosphorylation reagent is sodium tripolyphosphate, and the amount used is 0.8 to 1 times the molar amount of the chitosan glucose unit.

8. The preparation method according to claim 1, characterized in that In step S4, the electrochemical doping pulse voltage is 2.8-3.2V, and the pulse is followed by a 5s interval after 10s. + Doping concentration is 0.1~0.5mol / L; The plasma is a He / NH3 mixed gas with a volume ratio of 1:3-5, and the plasma treatment time is 1-1.5 hours; the power density is 50W / cm 3 , the pressure is maintained at 10Pa during the treatment process.

9. A spherical silica aerogel, characterized in that: The spherical silica aerogel material is prepared by the preparation method of the polymer-modified spherical silica aerogel material according to any one of claims 1 to 8, and has an electrical conductivity of ≥3.6S / cm and a charge transfer resistance of ≤3.0Ω.

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