A method for preparing polymer-modified spherical silica aerogel material

Abstract

The application discloses a preparation method of a polymer modified spherical silica aerogel material. First, 3-(acryloyloxy)propyl-2-thiophene acrylate is synthesized through esterification and grafting reaction, and then is subjected to free radical polymerization with vinylpyridine under the action of an initiator and a chain transfer agent, and is subjected to proton acid doping and spray drying to obtain a conductive polymer. After hydrolysis of tetraethyl orthosilicate, the conductive polymer, phosphonated chitosan microspheres and a bridging agent are mixed, and pH and viscosity are adjusted to obtain a composite sol; after drop ball emulsification, gelation, ultrasonic template removal, gradient replacement and subcritical drying, the composite sol is subjected to pulse electrochemical doping and plasma annealing treatment. The prepared aerogel polymer has low charge transfer resistance and excellent conductivity, and has application potential in electrochemical energy storage devices such as supercapacitors.

Description

Technical Field

[0001] This invention relates to the field of spherical silica technology, and more particularly to a method for preparing polymer-modified spherical silica aerogel materials. Background Technology

[0002] Silica aerogel is a highly porous mesoporous material with ultra-low density, high porosity, high specific surface area, and low thermal conductivity. Due to these excellent properties, silica aerogel has great application potential in various fields such as thermal insulation, catalysis, and adsorption. Currently, the industrial production of silica aerogel typically uses organosilicon materials such as tetraethyl orthosilicate and tetramethyl orthosilicate as raw materials and is prepared through supercritical drying. The high cost of raw materials, huge equipment investment, and dangerous and complex manufacturing process limit its widespread industrial application. Summary of the Invention

[0003] To address the aforementioned problems, the present invention aims to provide a method for preparing polymer-modified spherical silica aerogel materials.

[0004] To achieve the aforementioned objectives, the technical solution adopted by this invention includes:

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

[0006] S1. Synthesis of conductive polymer: 3-(acryloyloxy)propyl-2-thiophene acrylate and vinylpyridine were reacted in a molar ratio of 1:1.1-1.3 in the presence of an initiator and a chain transfer agent for 6-10 h, and the conductive polymer was obtained after drying.

[0007] S2. Construction of composite sol: After hydrolyzing tetraethyl orthosilicate, it was mixed with conductive polymer and phosphorylated chitosan microspheres, and a bridging agent was added; then the pH was adjusted to 8-9 with ammonia water and the viscosity was adjusted to 80-200 mPa·s with hydroxypropyl methylcellulose to obtain composite sol;

[0008] The amounts of the conductive polymer, bridging agent, and phosphorylated chitosan microspheres are 5-15 wt%, 0.5-2.0 wt%, and 0.05-0.2 wt%, respectively, based on the mass of tetraethyl orthosilicate.

[0009] S3. Shaping and drying: The composite sol is sheared and emulsified by a dropper, and then placed in a gel bath for 5-30 minutes to gel and shape; the template is removed by ultrasonic dissolution for 30-45 minutes, and then subjected to ethanol-acetone-n-hexane gradient displacement and subcritical drying to obtain spherical dry gel.

[0010] S4. Double doping reinforcement: The dry gel is placed in a LiClO4-propylene glycol solution for pulsed electrochemical doping treatment for 10-15 min, followed by plasma annealing to obtain the spherical silica aerogel.

[0011] Preferably, the 3-(acryloyloxy)propyl-2-thiophene acrylate in step S1 is obtained by using 2-thiophene acrylic acid as a raw material, which is then subjected to an esterification reaction with 1,3-propanediol and a grafting reaction with acryloyl chloride.

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

[0013] The grafting reaction conditions are as follows: in anhydrous dichloromethane as the medium, triethylamine as the acid-binding agent, the reaction is carried out under stirring in a salt ice bath at 0-5°C for 3-4 hours.

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

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

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

[0017] The number-average molecular weight Mn of the conductive polymer is ≥1.5×10⁻⁶. 4 Da has a molecular weight distribution index (PDI) of 1.28–1.35 and an electrical conductivity of 2.28–2.41 S / cm.

[0018] Proton acid doping can be achieved through H + Protonation of the carbazole amino group and thiophene ring (s atom lone pair electrons) generates delocalized cations, improving the intrinsic conductivity of the polymer; ultrasound assistance ensures the uniformity of proton penetration and protonation, reducing conductive defects caused by local peroxidation.

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

[0020] Preferably, the inner diameter of the dropper in step S3 is 0.5–1.0 mm, the shearing speed 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 stage is 3 to 10 times the gel volume, the replacement temperature is constant at 30 to 50°C, and the time is 4 to 12 hours per stage; 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 agent, with a surface phosphorylation degree of 0.8-1.2 mmol / g and a Zeta potential ≤-25mV; the acetic acid concentration is 1-3 wt%, the phosphorylation agent is sodium tripolyphosphate, and the amount used is 0.8-1 times the molar amount of chitosan glucose unit.

[0023] Preferably, in step S4, the electrochemical doping pulse voltage is 2.8–3.2 V, with a 5-second interval after the 10-second pulse. + The doping concentration is 0.1–0.5 mol / L;

[0024] Electrochemical doping of LiClO4 causes Li + By embedding conjugated systems at the Si-OC interface and forming Si-O-Li coordination bonds, charge transfer at the polymer-silica interface is promoted, which helps to reduce charge transfer resistance.

[0025] The plasma is a He / NH3 mixture with a volume ratio of 1:3 to 5, and the plasma treatment time is 1 to 1.5 hours; the power density is 50 W / cm³. 3 The pressure was maintained at 10 Pa during the process.

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

[0027] Beneficial effects

[0028] This invention provides a conductive polymer-modified spherical silica aerogel material through a synergistic effect of dual doping: the polymer is co-doped with a protonic acid and electrochemically, forming a dual conductive mechanism of "delocalized cations + ion transport channels"; the protonic acid provides intrinsic charge carriers, protonating the polymer imine bonds to generate delocalized cations, thus improving conductivity; the Li+ introduced by electrochemical doping is embedded into the polymer conjugated system through Si-O-Li coordination bonds, forming ion transport channels and reducing charge transfer resistance. Furthermore, through pore structure control, the modulating effects of template phosphorylation and bridging agents, as well as the electrostatic stabilization and selective etching of phosphorylated chitosan templates, enable controllable pore construction, inducing mesoporous formation; the bridging agent, through the synergistic effect of Ti-OC and Si-OC bonds, enhances the rigidity of the framework, ensuring considerable compressive strength. The aerogel polymer prepared by this invention exhibits low charge transfer resistance and excellent conductivity, showing potential application in electrochemical energy storage devices such as supercapacitors. Attached Figure Description

[0029] Figure 1 The 1H NMR spectrum of the conductive polymer obtained in Example 1.

[0030] Figure 2 The Nyquist plots are for Examples 1 and 4, and Comparative Examples 1 and 3. Detailed Implementation

[0031] To make the above-mentioned objects, features, and advantages of the present invention more apparent and understandable, the specific embodiments of the present invention will be described in detail below with reference to specific examples. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of them. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0032] Unless otherwise specified, the experimental methods described below are generally performed under conventional conditions or as recommended by the manufacturer; all experimental raw materials mentioned can be purchased from conventional biochemical reagent companies.

[0033] As used herein, Mn is the exponentially average molecular weight, as in gel permeation chromatography using a Waters 2695 separation module with a Waters 410 differential refractometer (RI detector), using polystyrene standards, and a flow rate of 1 mL / min. -1 Tetrahydrofuran was used as the eluent, and two PL gels were mixed and a C1 column was used for separation to determine the separation.

[0034] Chitosan, degree of deacetylation 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] Synthesis of 3-(acryloyloxy)propyl-2-thiophene acrylate:

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

[0039] 2) Grafting reaction: 0.096 mol of 3-(2-thiopheneacryloxy)propanol was dissolved in 60 mL of anhydrous dichloromethane in a 0℃ reaction vessel. 0.12 mol of acryloyl chloride was added dropwise at a rate of 1.5 mL / min, with 0.12 mol of triethylamine added dropwise simultaneously. After the addition was complete, the reaction was continued with stirring in a 0℃ salt ice bath for 3.5 h. The mixture was filtered, and the organic phase was washed successively with 5 wt% HCl, saturated NaHCO3, and deionized water. After drying with anhydrous MgSO4, the mixture was concentrated under reduced pressure to obtain 3-(acryloyloxy)propyl-2-thiophene acrylate, with a yield of 93.5%.

[0040] b. Synthesis of conductive polymer: 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 deoxygenation by nitrogen blowing for 30 min, 0.60 g of AIBN was added. The system was gradually heated to 65 °C, and 0.18 mL of 0.1 g / mL dodecyl mercaptan-ethanol solution was added simultaneously through 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 dodecyl mercaptan-ethanol solution were added, and the reaction was continued until the viscosity reached 900 mPa·s. The system was then rapidly cooled to 10 °C in an ice-water bath, and 10 mL of 0.1 wt% hydroquinone-ethanol solution was added. The mixture was stirred for 15 min to quench the reaction. After the reaction was completed, the solution was recrystallized with ice-cold ether and washed three times with acetone. Then, it was dialyzed for 48 hours with a dialysis bag of 8 kDa and a neutral solution of 0.01 mol / L ammonium chloride as the dialysate. The dialysate was replaced every 6 hours to obtain the 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 with an ultrasonic frequency of 40 kHz for 24 h, with the solution temperature controlled at ≤30℃ using an ice bath; after treatment, the polymer powder was obtained by spray drying at 0.3 MPa atomization pressure and 180℃, and the D50 was measured to be 12.5 μm.

[0042] The conductive polymer obtained in Preparation Example 1 was subjected to 1H NMR spectroscopy (Mercury VX-300 NMR spectrometer, Varian, USA), using TMS as an internal standard and CDCl3 as the solvent. The test results are shown below. 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 h.

[0047] Preparation Example 4

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

[0049] Preparation Example 5

[0050] Step c is omitted; the rest is the same as in Preparation Example 1.

[0051] The properties of the conductive polymers obtained in Examples 1-5 were tested, and the results are shown in Table 1.

[0052] Table 1

[0053] conductive polymer <![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 using the following steps:

[0056] Take 100g of chitosan raw material, sonicate it in a 5wt% sodium hydroxide + 3wt% H2O2 treatment solution for 2h, wash it with water until neutral, dry it and sieve it; the surface zeta potential was measured to be +15mV.

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

[0058] Furthermore, while maintaining the above procedures, the concentration of 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. Synthesize and prepare the conductive polymers of Examples 1-5;

[0062] S2. Construction of composite sol:

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

[0064] S3. Molding and Drying:

[0065] Using a dropper with an inner diameter of 0.8 mm, the emulsified sol was sheared at 12000 rpm; then dropped into a 60℃ dimethyl silicone oil coagulation bath and allowed to stand for 15 min to gel, forming a spherical wet gel. The wet gel was then transferred to deionized water and sonicated at 40 kHz for 40 min to dissolve the phosphorylated chitosan template. This process was repeated three times until no sulfonate residue remained (AgNO3 detection).

[0066] The solvents were successively replaced with ethanol (3 × gel volume, 40℃, 8 h / stage), acetone (2 × gel volume, 45℃, 6 h / stage), and n-hexane (1 × gel volume, 50℃, 4 h / stage). After the replacements were completed, the gel was placed in a subcritical drying apparatus and dried at 0.4 MPa and 40℃ for 24 h to obtain a dry gel.

[0067] S4. Post-processing enhancement

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

[0069] Then, using a He / NH3 mixture with a volume ratio of 1:4 as the working gas, at a pressure of 50 W / cm³... 3 Microwave plasma annealing at a power density of 10 Pa for 1 hour yielded the final spherical silica aerogel.

[0070] Examples 2-3

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

[0072] Example 4

[0073] In step S4, during electrochemical doping, the concentration of LiClO4 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 epoxysilane to tetrabutyl titanate was 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 were used in step S1.

[0080] Comparative Example 3

[0081] Unphosphorylated chitosan nanospheres were selected instead of phosphorylated chitosan microspheres.

[0082] Performance testing:

[0083] 1. Conventional physicochemical 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℃, 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 10mm diameter planar probe was used as the test probe. The test was conducted for 300s using a Hot Disk TPS2500S thermal constant analyzer with a heating power of 10mW at a temperature of 25℃ and a relative humidity of 50%.

[0086] (3) Compressive strength: Compression test (GB / T 1041-2008). Equipment: Instron 5967 universal testing machine. Sample size: cylinder (diameter 10mm, height 10mm); loading rate: 1mm / min; data acquisition: record compressive strength (peak stress) and strain curve.

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

[0088] Table 2

[0089]

[0090] In terms of specific surface area optimization, mesopores (2-50 nm) are the main contributor to the specific surface area. The dual-bridged polymer and phosphorylated template synergistically induce a high specific surface area mesoporous structure; in all examples (Examples 1-4), the mesopore content is 62%–68%, and the specific surface area is ≥860 nm. 2 / g; Comparative Examples 1-3, due to the lack of processing, showed a significant decrease in the proportion of mesopores and a sharp reduction in specific surface area. Specifically, Comparative Example 3 used an unphosphorylated chitosan template, which had no negative surface charge, making it impossible to induce uniform mesopore formation through electrostatic repulsion. This resulted in a porosity reduction to 60%, a pore size distribution broadened to 30 nm, and a specific surface area decreased to 554 m². 2 / g. Verify the regulatory effect of phosphorylated chitosan template on pore structure.

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

[0092] 2. Nyquist plot:

[0093] Nyquist plots visually reflect the dynamic processes at the electrode interface through the relationship between the real and imaginary parts of impedance.

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

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

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

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

[0098] Test steps:

[0099] 1) Tableting: Take 100mg of aerogel powder and press it into a Φ10mm×1mm disc under a pressure of 10MPa. The surface is then polished (Ra≤0.1μm).

[0100] 2) Electrode assembly: In a glove box (H2O, O2 < 1ppm), install the sample welding nickel current collector onto the electrode holder, ensuring contact resistance < 0.5Ω; calibrate the equipment with a standard resistor (1kΩ ± 0.1%), the open-circuit pile potential drift ≤ 2mV / h.

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

[0102] 4) Data acquisition: Start frequency scanning and automatically record the real impedance Z' (Ω) and the negative imaginary impedance -Z (Ω). The test time is about 15-20 minutes. Use Kramers-Kronig transform to verify data consistency. Repeat the test 3 times (RSD≤5%).

[0103] Plot a Nyquist diagram with Z' as the x-axis and -Z” as the y-axis, see [link to diagram]. Figure 2 In the Nyquist plot, the semicircle of the main plot corresponds to the high-frequency charge transfer region (>10). 3 The frequency (Hz) is dominated by rapid kinetics of interfacial charge transfer. The diameter corresponds to the charge transfer resistance (Rct, unit: Ω) at the aerogel / electrolyte interface. The inset diagram in the upper right corner sequentially represents the low-frequency ion diffusion region (1–10 Hz). 3 Magnified views of the Hz and ultra-high frequency ohmic regions (>10kHz). The ultra-high frequency ohmic region is depicted as a near-vertical curve in the embedding diagram. The smaller the resistance, the closer the vertical line is to the origin; the vertical line in Comparative Example 3 is the longest, due to poor contact caused by the unsulfonated template. The low-frequency diffusion region is a sloping line, dominated by the slow process of ion diffusion. The slope of the sloping line is related to the Li... + Warburg impedance coefficient of diffusion (σ, unit: Ω·s) -1 / 2 Positive correlation.

[0104] Depend on Figure 2 In the high-frequency region, Comparative Example 1 exhibits the largest Rct value (6.6 Ω), while Example 1 has an Rct of 4.5 Ω, indicating that the Si-O-Li coordination bonds enhance interfacial charge transport. In Example 4, the LiClO4 concentration was further increased to 0.3 mol / L, leading to a decrease in Li... + Increased activity and enhanced intercalation driving force result in Rct = 3.2Ω.

[0105] In the low-frequency region, the slope is steepest in Comparative Example 1, while it is gentlest in Example 4: σ corresponds to a slope from 12.5 Ω·s -1 / 2 Reduced to 8.0 Ω·s -1 / 2 This demonstrates that increasing the electrochemical doping concentration optimizes Li + The diffusion pathway is improved, resulting in enhanced electrochemical performance. In contrast, in Comparative Example 3, the template was not phosphorylated, leading to a wider pore size distribution and improved Li... + The diffusion path is elongated and the ion diffusion path is tortuous, corresponding to the Li in Table 3, which is only 0.14 mmol / g. + Embedded quantity.

[0106] 3. Electrical conductivity of aerogel

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

[0108] (2)Li + Intercalation 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 membrane; Li was determined using an Agilent 7900 inductively coupled plasma mass spectrometer. + Concentration, 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 diagram 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 Tables 1 and 3, compared with Example 1, the added nitro groups in the free radical polymerization raw materials of Example 2 enhanced the electron-withdrawing effect of the conjugated system, expanded the delocalization range of π electrons, and increased the conductivity. In Comparative Example 1, the 3-(acryloyloxy)propyl-2-thiophene acrylate grafting step was omitted, and the polymer molecular weight plummeted to 0.85 × 10⁻⁶. 4 In Da, insufficient conjugated chain length leads to weakened π-π stacking, resulting in an electrical conductivity of only 0.82 S / cm. Figure 2 In the mid-to-high frequency region, the charge transfer resistance Rct reaches 6.8Ω, increasing the resistance to carrier transport. Comparative Example 3 uses an unphosphorylated chitosan template with a surface Zeta potential of +15mV, which fails to induce uniform mesopores through electrostatic repulsion. The pore size distribution widens, clogging the channels and hindering Li... + diffusion.

[0114] Example 3: Extending the protonated acid doping time increased the degree of carbazole protonation and the concentration of delocalized cations, resulting in an increase in conductivity to 2.45 S / cm. Comparative Example 2: Omitting protonated acid doping and relying solely on electrochemical doping, this method could not compensate for the intrinsic conductivity defects of the polymer. The lack of protonation of the imine groups led to insufficient delocalized cations, and the hydrogen bonding of the protonated imine bonds was lost, resulting in the formation of Li at the polymer-silica interface. + The transmission dead end causes a surge in charge transfer resistance.

[0115] In Example 4, the concentration of LiClO4 was increased, and the Li in the electrolyte... + Increased activity and enhanced embedding drive: Li + The Si-O-Li bonds and coordination bonds at the polymer-silica interface are fully embedded in the conjugated system, forming ion transport channels. + The embedding amount increased to 0.23 mmol / g. The phosphorylation degree of the template used in Example 5 decreased to 0.8 mmol / g, leading to a weakening of the electrostatic repulsion on the template surface and the hydrogen bonding between the template and the sol. This resulted in template aggregation and pore blockage, making the pores prone to collapse during gelation. Therefore, the lower limit of phosphorylation degree could be determined. In Example 6, the proportion of tetrabutyl titanate in the bridging agent decreased slightly, leading to a reduction in the number of Ti-OC bonds and a weakening of the rigid support of the silica framework, resulting in a decrease in compressive strength to 0.80 MPa. However, slow gelation induced the formation of more mesopores, increasing the mesopore ratio to 75% and the pore volume to 1.35 cm³. 3 / g.

[0116] It should be understood that the above descriptions are only some embodiments of the present invention. It should be noted that those skilled in the art can make other modifications and improvements without departing from the inventive concept of the present invention, and these all fall within the protection scope of the present invention.

Claims

1. A method for the preparation of a polymer-modified spherical silica aerogel material, characterized in that, The method comprises the following steps: S1. Synthesis of conductive polymer: 3-(acryloyloxy)propyl-2-thiophene acrylate and vinylpyridine are reacted in a molar ratio of 1:1.1-1.3 in the presence of an initiator and a chain transfer agent for 6-10 hours, and the conductive polymer is obtained after drying; S2. Composite sol construction: hydrolyzed tetraethyl orthosilicate is mixed with the conductive polymer, phosphonated chitosan microspheres, and a bridging agent, and then ammonia water is used to adjust the pH to 8-9 and hydroxypropyl methyl cellulose is used to adjust the viscosity to 80-200 mPa·s, to obtain a composite sol; the amounts of the conductive polymer, the bridging agent, and the phosphonated chitosan microspheres are 5-15 wt%, 0.5-2.0 wt%, and 0.05-0.2 wt% respectively, based on the mass of tetraethyl orthosilicate; S3. Molding and drying: the composite sol is sheared and emulsified by a drop ball device, and is placed in a gel bath for 5-30 minutes to form a gel; the template is removed by ultrasonic dissolution for 30-45 minutes, and then the gel is subjected to gradient displacement with ethanol-acetone-n-hexane and subcritical drying to obtain a spherical xerogel; S4. Double-doping reinforcement: the dry gel is placed in a LiClO4-propylene glycol solution for pulse electrochemical doping treatment for 10-15 min, and then plasma annealing is performed to obtain the polymer-modified spherical silica aerogel; the conductive polymer before drying is also subjected to doping reinforcement treatment in a protic acid solution for 24-48 h; the doping process is performed under the assistance of ultrasonic waves at 40-60 kHz, and the protic acid is p-toluenesulfonic acid or camphorsulfonic acid with a concentration of 0.1-0.3 mol / L; the number average molecular weight Mn of the conductive polymer is ≥1.5×10 4 Da, the molecular weight distribution index PDI is 1.28-1.35, and the conductivity is 2.28-2.41 S / cm.

2. The production method according to claim 1, wherein The 3-(acryloyloxy)propyl-2-thiophene acrylate in step S1 is obtained by esterification with 1,3-propanediol and grafting with acryloyl chloride in sequence from 2-thiophene acrylic acid; the esterification conditions are: the raw material is catalyzed by 2-4 wt% concentrated sulfuric acid with a carboxyl:hydroxyl molar ratio of 1:3-4, and reacted in a water bath at 80°C until the acid value is less than 5 mgKOH / g; the grafting conditions are: triethylamine is used as an acid binding agent in anhydrous dichloromethane as a medium, and the reaction is stirred at 0-5°C for 3-4 hours.

3. The production method according to claim 1, wherein The vinylpyridine in step S1 is selected from one of 2-vinylpyridine, 3-vinylpyridine, 4-vinylpyridine, 3-(2-nitrovinyl)pyridine, and 4-styrylpyridine; the initiator is azobisisobutyronitrile, and the amount is 0.5-2 wt% of the total mass of monomers; the chain transfer agent is dodecanethiol, and the amount is 0.05-0.1 wt% of the total mass of monomers; the reaction conditions in step S1 are: radical polymerization in a nitrogen atmosphere in a 75 vol% ethanol-water solvent in an oil bath at 60-70°C for 7-10 hours, cooling with ice water, and quenching with 0.1 wt% hydroquinone; ion impurities are removed by dialysis with ammonium chloride dialysis solution, and the product is spray dried.

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

5.

5. The preparation method according to claim 1, characterized in that, The inner diameter of the drop ball device in step S3 is 0.5-1.0 mm, and the shearing speed is 5000-10000 rpm; the gelation temperature is 60-65°C, and the ultrasonic dissolution power is 40-60 kHz; the gradient displacement conditions are: the volume of each solvent is 3-10 times the volume of the gel, the displacement temperature is constant at 30-50°C, and the time is 4-12 hours per stage; the subcritical drying pressure is 0.3-0.5 MPa.

6. The method of claim 1, wherein, The phosphated chitosan microspheres in step S3 are obtained by emulsifying chitosan with acetic acid, cross-linking with a phosphating agent, and have a surface phosphating degree of 0.8-1.2 mmol / g and a Zeta potential of ≤-25 mV; the acetic acid concentration is 1-3 wt%, and the phosphating agent is sodium tripolyphosphate, which is used in an amount of 0.8-1 times the molar amount of chitosan glucose units.

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

8. A spherical silica aerogel, characterized by, The polymer-modified spherical silica aerogel material prepared by the method of any one of claims 1-7 has an electrical conductivity of ≥3.6 S / cm and a charge transfer resistance of ≤3.0 Ω.

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