Unmanned aerial vehicle resistant expansion lithium battery pole piece material and preparation method thereof

Abstract

The application discloses a kind of unmanned aerial vehicle with expansion-resistant lithium battery pole piece material and preparation method thereof, belong to lithium battery technical field, with silica / carbon fiber composite powder as matrix, in surface cladding long-chain alkyl's cardanol graft glucose layer, and pyrolysis carbonization, carboxyl group in glucose and the isocyanate of modified silica / carbon fiber composite powder surface occurs amine esterification reaction and generates carbon dioxide, further increase the porosity of material, obtain cardanol cladding composite powder, again through coprecipitation method in cardanol cladding composite powder deposition nano-alumina, again through formation with silica / carbon fiber composite powder as core layer, long-chain alkyl cardanol graft glucose carbonization as intermediate layer, nano-alumina as the outermost layer of ternary composite structure, under the premise of not influencing porosity, can better synergistically relieve volume expansion.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of lithium batteries, and particularly relates to a lithium battery pole piece material resistant to expansion for a drone and a preparation method thereof. BACKGROUND

[0002] With the vigorous development of the drone industry, the battery power of a drone battery is required to be high. When the throttle is rapidly increased from the hovering state to the highest speed, the battery power will be rapidly increased, and the power will be increased by several times in a short time. In recent years, lithium ion batteries as green and clean new energy have been widely used in the drone industry. At present, the negative electrode material of the lithium ion battery commonly used in practical application is a carbon material, such as natural graphite and graphitized mesocarbon microbeads. Among non-carbon negative electrode materials, silicon has a very high theoretical specific capacity and a low lithium storage reaction voltage platform. However, the electronic conductivity and ionic conductivity of silicon are low, which leads to poor kinetic performance of the electrochemical reaction of silicon. The cycle stability of ordinary pure silicon is poor, and the phase change and volume expansion of silicon during lithiation will generate a large stress, which causes the electrode to break and pulverize, the resistance to increase, and the cycle performance to decrease sharply.

[0003] A Chinese patent with the publication number CN117776183B discloses a porous carbon and a preparation method thereof, a silicon-carbon negative electrode material, and a preparation method of the silicon-carbon negative electrode material. The method includes the steps of preparing a crude product of porous carbon, performing pore filling and sealing treatment on the crude product, sealing the pores with a medium size that is too small in the porous carbon, reducing the specific surface area of the porous carbon, improving the deposition efficiency in the process of preparing the silicon-carbon negative electrode material by chemical vapor deposition, saving organic carbon sources, and improving the mechanical properties and mechanical parameters of the silicon-carbon negative electrode material. However, the decrease in the porosity in the method cannot disperse the stress when lithium ions are repeatedly inserted and extracted, which leads to the easy breakage of the electrode material and cannot effectively inhibit the volume expansion of the electrode. SUMMARY

[0004] The application aims to provide a lithium battery pole piece material resistant to expansion for a drone and a preparation method thereof. The method includes the following steps: taking a silicon dioxide / carbon fiber composite powder as a base, coating a long-chain alkyl cardanol grafted glucose layer on the surface, pyrolyzing and carbonizing the glucose, and performing amine esterification reaction between the carboxyl groups in the glucose and isocyanate on the surface of the modified silicon dioxide / carbon fiber composite powder to generate carbon dioxide, so as to further increase the porosity of the material, obtain a cardanol-coated composite powder, and then deposit nano-aluminum oxide on the cardanol-coated composite powder by a co-precipitation method. A ternary composite structure is formed, in which the silicon dioxide / carbon fiber composite powder is used as a core layer, the long-chain alkyl cardanol grafted glucose after carbonization is used as an intermediate layer, and nano-aluminum oxide is used as an outermost layer. The volume expansion can be better relieved in the premise of not affecting the porosity.

[0005] A preparation method of a lithium battery pole piece material resistant to expansion for a drone includes the following steps:

[0006] Step one: through the hydrolysis and condensation of tetraethyl orthosilicate, the surface of the pretreated carbon fiber powder after acidification is combined with silicon dioxide to obtain a silicon dioxide / carbon fiber composite powder, and the silicon dioxide / carbon fiber composite powder is treated by gamma-isocyanate propyl triethoxysilane to obtain a modified silicon dioxide / carbon fiber composite powder with isocyanate groups.

[0007] Step two: through the grafting of carboxylated cardanol onto glucose, an amine esterification reaction occurs with the modified silicon dioxide / carbon fiber composite powder to achieve coating of the modified silicon dioxide / carbon fiber composite powder, and pyrolysis carbonization at high temperature to obtain a cardanol-coated composite powder.

[0008] Step three: through the coprecipitation method, nano-aluminum oxide is deposited on the surface of the cardanol-coated composite powder to obtain a lithium battery pole piece material for unmanned aerial vehicles.

[0009] Further, the specific preparation steps of the silicon dioxide / carbon fiber composite powder are as follows:

[0010] Tetraethyl orthosilicate, ethanol and deionized water are added to the reaction kettle, stirred at 20-25℃ and 500-600r / min for 5-10min, 1mol / L hydrochloric acid solution is added to adjust the pH value to 2-3, continue to stir for 3-4h, add pretreated carbon fiber powder, ultrasonic dispersion for 40-60min, add 20-30wt% ammonia solution to adjust the pH value to 7-8, pour the product into the mold, seal and stand for 40-50h, soak in n-hexane for 36-38h, filter, wash, freeze-dry in liquid nitrogen for 12-14h, transfer the product to a muffle furnace, heat to 700-800℃ under argon atmosphere, keep warm for 2-3h, naturally cool to room temperature, to obtain a silicon dioxide / carbon fiber composite powder.

[0011] Further, the amount ratio of tetraethyl orthosilicate, ethanol, deionized water, hydrochloric acid solution, pretreated carbon fiber powder, ammonia solution and n-hexane is 50-60mL:150-200mL:200-300mL:12-13mL:70-80g:15-20mL:200-300mL.

[0012] Further, the specific preparation steps of the modified silicon dioxide / carbon fiber composite powder are as follows:

[0013] The silicon dioxide / carbon fiber composite powder, methanol, deionized water and gamma-isocyanate propyl triethoxysilane are added to the reaction kettle, stirred at 70-80℃ and 500-600r / min for 1-2h, filtered, washed, vacuum dried to obtain a modified silicon dioxide / carbon fiber composite powder.

[0014] Furthermore, the ratio of silica / carbon fiber composite powder, methanol, deionized water and γ-isocyanate-propyltriethoxysilane is 60-70g: 100-120mL: 400-500mL: 40-50g.

[0015] Furthermore, the pretreated carbon fiber powder is prepared through the following steps:

[0016] Carbon fiber powder, 5-8 wt% hydrochloric acid solution and 7-8 wt% hydrogen peroxide solution are added to a reaction vessel and stirred at 70-80℃ and 500-600 r / min for 1-2 h. The mixture is then filtered, washed and vacuum dried to obtain pretreated carbon fiber powder.

[0017] Furthermore, the ratio of carbon fiber, hydrochloric acid solution, and hydrogen peroxide solution is 80-90g: 450-480mL: 250-260mL.

[0018] Furthermore, the specific preparation steps for carboxylated cashew nut shell alcohol are as follows:

[0019] Cashew nut phenol, methanol, sodium hydroxide, and deionized water were added to a reaction vessel and stirred at 20-25°C and 500-600 rpm for 1-2 hours. Then chloroacetic acid was added, and the mixture was heated to 70-80°C and stirred for another 4-5 hours. The mixture was then allowed to cool naturally. Next, 20-30 wt% hydrochloric acid solution was added to adjust the pH to 1-2. Then methanol, diethyl ether, and deionized water were added. The mixture was separated, the aqueous phase was removed, and the organic phase was retained. The mixture was concentrated, and the product was recrystallized in n-hexane and dried under vacuum to obtain carboxylated cashew nut phenol.

[0020] Furthermore, the ratio of cashew phenol, methanol, sodium hydroxide, deionized water, chloroacetic acid, hydrochloric acid solution, methanol, diethyl ether, and deionized water is 50-60g: 100-120mL: 3-4g: 200-300mL: 30-40g: 10-12mL: 250-300mL: 500-600mL: 400-500mL.

[0021] Furthermore, the specific preparation steps of the cashew phenol-coated composite powder are as follows:

[0022] Glucose, carboxylated cashew nut shell powder, and deionized water were added to a reaction vessel and ultrasonically dispersed for 30-40 min. The mixture was then stirred at 70-80℃ and 400-500 r / min for 10-20 min. Next, 10-20 wt% hydrochloric acid solution was added, and stirring was continued for 1-2 h. Then, modified silica / carbon fiber composite powder, dimethylformamide, and triethylamine were added. The mixture was heated to 170-180℃ and stirred for 5-6 h. The mixture was then filtered, washed, and vacuum dried to obtain cashew nut shell powder coated with composite powder.

[0023] Furthermore, the ratio of glucose, carboxylated cashew nut shell powder, deionized water, hydrochloric acid solution, modified silica / carbon fiber composite powder, dimethylformamide, and triethylamine is 30-40g: 20-30g: 1-2L: 10-12mL: 50-60g: 400-500mL: 1-2g.

[0024] Furthermore, the specific preparation steps for the expansion-resistant lithium battery electrode material for drones are as follows:

[0025] Cashew phenol-coated composite powder, aluminum nitrate, and deionized water were added to a reaction vessel and stirred for 20-30 minutes at 40-50℃ and 500-600 r / min. Then, 20-30% (w / w) ammonia solution and ethylene glycol were added, and the mixture was heated to 120-130℃ and reacted for 12-14 hours. The mixture was then filtered, and the filter cake was washed 2-3 times with deionized water and dried under vacuum to obtain an expansion-resistant lithium battery electrode material for UAVs.

[0026] The beneficial effects of this invention are:

[0027] 1. The expansion-resistant lithium battery electrode material prepared by this invention can significantly alleviate the volume expansion during the charging and discharging of lithium batteries, accommodate more lithium ions for insertion and extraction, reduce the generation of by-products, and increase the cycle stability and safety of lithium batteries. By using silica / carbon fiber composite powder as a matrix and depositing silica on the surface, the strength of silicon as an electrode material can be significantly enhanced, avoiding the brittleness of silica. Then, a long-chain alkyl cashew phenol-grafted glucose layer is coated on the surface and pyrolyzed and carbonized. The carboxyl groups in glucose react with the isocyanate on the surface of the modified silica / carbon fiber composite powder to undergo an amino esterification reaction and generate carbon dioxide, further increasing the porosity of the material. Finally, nano-alumina is deposited on the cashew phenol-coated composite powder by co-precipitation to generate a stable SEI film and reduce the occurrence of side reactions.

[0028] 2. The cashew nut shell coated composite powder of the present invention utilizes the carboxyl groups on the surface of carboxylated cashew nut shell to graft with the hydroxyl groups in glucose under the catalysis of hydrochloric acid, and carbonize at high temperature to generate an amorphous carbon layer, which coats the surface of modified silica / carbon fiber composite powder. At the same time, the carboxyl groups in glucose undergo an amino esterification reaction with the isocyanate on the surface of modified silica / carbon fiber composite powder to generate carbon dioxide. This allows the carboxylated cashew nut shell to be coated on the surface of modified silica / carbon fiber composite powder, further increasing the porosity of the material. Carboxylated cashew nut shell is a long-chain alkyl group, which improves the density of the carbon layer through cross-linking and physical winding, thereby improving the toughness of the carbon layer and avoiding volume expansion stress concentration that could lead to cracks in the electrode material.

[0029] 3. The present invention deposits nano-alumina on cashew phenol-coated composite powder via co-precipitation. Nano-alumina can significantly increase the overall strength of the material and alleviate local heat accumulation during battery charging and discharging. The abundant hydroxyl groups on the surface of alumina react with LiPF6 in the electrolyte to form a stable SEI film, reducing side reactions and inhibiting electrolyte decomposition. The nano-alumina coating layer can block direct contact between the silicon skeleton and the electrolyte, reducing the rate of interfacial side reactions. By forming a ternary composite structure with silica / carbon fiber composite powder as the core layer, long-chain alkyl cashew phenol grafted with glucose carbonized as the intermediate layer, and nano-alumina as the outermost layer, the volume expansion can be better mitigated synergistically. Detailed Implementation

[0030] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0031] Example 1: A method for preparing an expansion-resistant lithium battery electrode material for unmanned aerial vehicles, comprising the following steps:

[0032] S1: Add 80g of carbon fiber powder, 450mL of 5% hydrochloric acid solution and 250mL of 7% hydrogen peroxide solution to a reaction vessel, stir for 1h at 70℃ and 500r / min, filter, wash the filter cake with deionized water until the last washing liquid is neutral, and vacuum dry at 60℃ for 1h to obtain pretreated carbon fiber powder.

[0033] After carbon fibers are treated with hydrochloric acid solution and hydrogen peroxide solution, the surface will carry a large number of oxygen-containing groups, the surface roughness will increase, and the number of active sites will increase.

[0034] S2: Add 50 mL of tetraethyl orthosilicate, 150 mL of ethanol and 200 mL of deionized water to a reaction vessel, stir for 5 min at 20 °C and 500 r / min, add 12 mL of 1 mol / L hydrochloric acid solution to adjust the pH to 2, continue stirring for 3 h, add 70 g of pretreated carbon fiber powder, ultrasonically disperse for 40 min, then add 15 mL of 20% ammonia solution to adjust the pH to 7, pour the product into a mold, seal and let stand for 40 h, add 200 mL of n-hexane to soak for 36 h, filter, wash the filter cake twice with n-hexane and deionized water respectively, freeze dry with liquid nitrogen for 12 h, transfer the product to a muffle furnace, heat to 700 °C under an argon atmosphere, hold for 2 h, cool naturally to room temperature, grind and pulverize to obtain silica / carbon fiber composite powder.

[0035] The carboxyl groups on the surface of pretreated carbon fiber powder combine with the hydroxyl groups on the surface of silica under acidic conditions to obtain silica / carbon fiber composite powder. The carbon fiber disperses stress through physical support and chemical bonding, thus inhibiting crack propagation.

[0036] S3: Add 60g of silica / carbon fiber composite powder, 100mL of methanol, 400mL of deionized water and 40g of γ-isocyanate-propyltriethoxysilane to a reaction vessel, stir for 1h at 70℃ and 500r / min, filter, wash the filter cake twice with deionized water, and dry under vacuum at 60℃ for 1h to obtain modified silica / carbon fiber composite powder.

[0037] γ-isocyanate-propyltriethoxysilane is hydrolyzed to generate silane bonds that combine with hydroxyl groups on the surface of silica / carbon fiber composite powder. After hydrolysis, the isocyanate groups are not consumed and retain high reactivity, thus obtaining modified silica / carbon fiber composite powder.

[0038] S4: Add 50g cashew nut alcohol, 100mL methanol, 3g sodium hydroxide and 200mL deionized water to a reaction vessel and stir for 1h at 20℃ and 500r / min. Then add 30g chloroacetic acid, heat to 70℃, continue stirring for 4h, and allow to cool naturally. Then add 10mL of 20% hydrochloric acid solution to adjust the pH to 1. Then add 250mL methanol, 500mL diethyl ether and 400mL deionized water. Separate the liquid and remove the aqueous phase, retain the organic phase, concentrate, and recrystallize the product in n-hexane. Dry under vacuum at 60℃ for 1h to obtain carboxylated cashew nut alcohol.

[0039] The phenolic hydroxyl group (-OH) of cashew nut shellac is deprotonated in a strongly alkaline environment and then replaces the chlorine atom of chloroacetic acid through a nucleophilic substitution reaction to obtain carboxylated cashew nut shellac.

[0040] S5: Add 30g glucose, 20g carboxylated cashew nut powder and 1L deionized water to a reaction vessel, sonicate for 30min, stir for 10min at 70℃ and 400r / min, then add 10mL of 10% hydrochloric acid solution, continue stirring for 1h, then add 50g modified silica / carbon fiber composite powder, 400mL dimethylformamide and 1g triethylamine, heat to 170℃, continue stirring for 5h, filter, wash the filter cake twice with deionized water and anhydrous ethanol respectively, and vacuum dry at 60℃ for 1h to obtain cashew nut powder coated composite powder.

[0041] The carboxyl groups on the surface of carboxylated cashew nut shells can graft with the hydroxyl groups in glucose under the catalysis of hydrochloric acid, and carbonize at high temperature to form an amorphous carbon layer that coats the surface of modified silica / carbon fiber composite powder. At the same time, the carboxyl groups in glucose undergo an amino esterification reaction with the isocyanate on the surface of modified silica / carbon fiber composite powder to generate carbon dioxide. This allows the carboxylated cashew nut shells to coat the surface of modified silica / carbon fiber composite powder while further increasing the porosity of the material. Carboxylated cashew nut shells are long-chain alkyl groups that improve the density of the carbon layer through cross-linking and physical winding, thereby improving the toughness of the carbon layer and avoiding stress concentration caused by volume expansion, which can lead to cracks in the electrode material.

[0042] S6: Add 30g of cashew phenol-coated composite powder, 50g of aluminum nitrate and 400mL of deionized water to a reaction vessel, stir for 20min at 40℃ and 500r / min, then add 10mL of 20% ammonia solution and 5mL of ethylene glycol, heat to 120℃ and react for 12h, filter, wash the filter cake twice with deionized water, and vacuum dry at 60℃ for 1h to obtain an expansion-resistant lithium battery electrode material for UAVs.

[0043] Nano-alumina was deposited on the surface of cashew phenol-coated composite powder via co-precipitation. Nano-alumina significantly increases the overall strength of the material and can alleviate local heat accumulation during battery charging and discharging. The alumina surface contains Lewis acid sites, which can react with PF5 or HF produced by the decomposition of LiPF6 to generate inorganic compounds containing Al-F, Al-OP, etc., which stabilize the SEI film. The reaction consumes HF, reducing its damage to the electrodes and electrolyte. The nano-alumina coating can block the direct contact between the silicon framework and the electrolyte, reducing the rate of interfacial side reactions.

[0044] Example 2: A method for preparing an expansion-resistant lithium battery electrode material for unmanned aerial vehicles, comprising the following steps:

[0045] S1: Add 85g of carbon fiber powder, 465mL of 6.5% hydrochloric acid solution and 255mL of 7.5% hydrogen peroxide solution to a reaction vessel, stir for 1.5h at 75℃ and 550r / min, filter, wash the filter cake with deionized water until the last washing liquid is neutral, and vacuum dry at 70℃ for 1.5h to obtain pretreated carbon fiber powder.

[0046] S2: Add 55 mL of tetraethyl orthosilicate, 175 mL of ethanol, and 250 mL of deionized water to a reaction vessel. Stir for 7.5 min at 22.5 °C and 550 r / min. Add 12.5 mL of 1 mol / L hydrochloric acid solution to adjust the pH to 2.5. Continue stirring for 3.5 h. Add 75 g of pretreated carbon fiber powder and ultrasonically disperse for 50 min. Add 17.5 mL of 25% ammonia solution to adjust the pH to 7.5. Pour the product into a mold, seal and let stand for 45 h. Add 250 mL of n-hexane and soak for 37 h. Filter and wash the filter cake twice with n-hexane and deionized water, respectively. Freeze dry in liquid nitrogen for 13 h. Transfer the product to a muffle furnace and heat to 750 °C under an argon atmosphere. Hold for 2.5 h and cool naturally to room temperature to obtain silica / carbon fiber composite powder.

[0047] S3: Add 65g of silica / carbon fiber composite powder, 110mL of methanol, 450mL of deionized water and 45g of γ-isocyanate-propyltriethoxysilane to a reaction vessel, stir for 1.5h at 75℃ and 550r / min, filter, wash the filter cake twice with deionized water, and dry under vacuum at 70℃ for 1.5h to obtain modified silica / carbon fiber composite powder.

[0048] S4: Add 55g cashew nut powder, 110mL methanol, 3.5g sodium hydroxide and 250mL deionized water to a reaction vessel and stir for 1.5h at 22.5℃ and 550r / min. Then add 35g chloroacetic acid, heat to 75℃, and continue stirring for 4.5h. Allow to cool naturally, then add 11mL of 25% saline solution to adjust the pH to 1.5. Add 275mL methanol, 550mL diethyl ether and 450mL deionized water, separate the liquid and remove the aqueous phase, retain the organic phase, concentrate, and recrystallize the product in n-hexane. Dry under vacuum at 70℃ for 1.5h to obtain carboxylated cashew nut powder.

[0049] S5: Add 35g glucose, 25g carboxylated cashew nut shell powder and 1.2L deionized water to a reaction vessel, sonicate for 35min, stir for 15min at 75℃ and 450r / min, then add 11mL of 15% hydrochloric acid solution, continue stirring for 1.2h, then add 55g modified silica / carbon fiber composite powder, 450mL dimethylformamide and 1.2g triethylamine, heat to 175℃, continue stirring for 5.6h, filter, wash the filter cake twice with deionized water and anhydrous ethanol respectively, and vacuum dry at 70℃ for 1.2h to obtain cashew nut shell powder coated composite powder.

[0050] S6: Add 32g of cashew phenol-coated composite powder, 55g of aluminum nitrate and 450mL of deionized water to a reaction vessel, stir for 25min at 45℃ and 550r / min, then add 11mL of 25% ammonia solution and 5.5mL of ethylene glycol, heat to 125℃ and react for 13h, filter, wash the filter cake twice with deionized water, and vacuum dry at 70℃ for 1.5h to obtain an expansion-resistant lithium battery electrode material for UAVs.

[0051] Example 3: A method for preparing an expansion-resistant lithium battery electrode material for unmanned aerial vehicles, comprising the following steps:

[0052] S1: Add 90g of carbon fiber powder, 480mL of 8% hydrochloric acid solution and 260mL of 8% hydrogen peroxide solution to a reaction vessel, stir for 2h at 80℃ and 600r / min, filter, wash the filter cake with deionized water until the last washing liquid is neutral, and vacuum dry at 80℃ for 2h to obtain pretreated carbon fiber powder.

[0053] S2: Add 60 mL of tetraethyl orthosilicate, 200 mL of ethanol and 300 mL of deionized water to a reaction vessel, stir for 10 min at 25 °C and 600 r / min, add 13 mL of 1 mol / L hydrochloric acid solution to adjust the pH to 3, continue stirring for 4 h, add 80 g of pretreated carbon fiber powder, ultrasonically disperse for 60 min, then add 20 mL of 30% ammonia solution to adjust the pH to 8, pour the product into a mold, seal and let stand for 50 h, add 300 mL of n-hexane to soak for 38 h, filter, wash the filter cake three times with n-hexane and deionized water respectively, freeze dry with liquid nitrogen for 14 h, transfer the product to a muffle furnace, heat to 800 °C under an argon atmosphere, hold for 3 h, and naturally cool to room temperature to obtain silica / carbon fiber composite powder.

[0054] S3: Add 70g of silica / carbon fiber composite powder, 120mL of methanol, 500mL of deionized water and 50g of γ-isocyanate-propyltriethoxysilane to a reaction vessel, stir for 2h at 80℃ and 600r / min, filter, wash the filter cake three times with deionized water, and vacuum dry at 80℃ for 2h to obtain modified silica / carbon fiber composite powder.

[0055] S4: Add 60g cashew nut alcohol, 120mL methanol, 4g sodium hydroxide and 300mL deionized water to a reaction vessel and stir for 2h at 25℃ and 600r / min. Then add 40g chloroacetic acid, heat to 80℃, continue stirring for 5h, and allow to cool naturally. Then add 12mL of 30% hydrochloric acid solution to adjust the pH to 2. Then add 300mL methanol, 600mL diethyl ether and 500mL deionized water. Separate the liquid and remove the aqueous phase, retain the organic phase, concentrate, and recrystallize the product in n-hexane. Dry under vacuum at 80℃ for 2h to obtain carboxylated cashew nut alcohol.

[0056] S5: Add 40g glucose, 30g carboxylated cashew nut powder and 2L deionized water to a reaction vessel, sonicate for 40min, stir for 20min at 80℃ and 500r / min, then add 12mL of 20% hydrochloric acid solution, continue stirring for 2h, then add 60g modified silica / carbon fiber composite powder, 500mL dimethylformamide and 2g triethylamine, heat to 180℃, continue stirring for 6h, filter, wash the filter cake three times with deionized water and anhydrous ethanol respectively, and vacuum dry at 80℃ for 2h to obtain cashew nut powder coated composite powder.

[0057] S6: Add 34g of cashew phenol-coated composite powder, 60g of aluminum nitrate and 500mL of deionized water to a reaction vessel, stir for 30min at 50℃ and 600r / min, then add 12mL of 30% ammonia solution and 6mL of ethylene glycol, heat to 130℃ and react for 14h, filter, wash the filter cake three times with deionized water, and vacuum dry at 80℃ for 2h to obtain an expansion-resistant lithium battery electrode material for UAVs.

[0058] Comparative Example 1: Based on Example 3, the pretreated carbon fiber powder in step S2 was replaced with the same mass of carbon fiber powder in step S1, while the other steps remained unchanged, to prepare an expansion-resistant lithium battery electrode material for drones.

[0059] Comparative Example 2: Based on Example 3, without step S4, the carboxylated cashew phenol in step S5 was removed, and the remaining steps remained unchanged, to prepare an expansion-resistant lithium battery electrode material for drones.

[0060] Comparative Example 3: Based on Example 3, without the processing in step S6, the cashew phenol-coated composite powder in step S5 was directly used as the electrode material for the lithium battery with resistance to expansion.

[0061] The carbon fiber powder was purchased from Shanghai Lishuo Composite Materials Technology Co., Ltd., with a diameter of 1-5μm and a length of 40-60μm.

[0062] The lithium battery materials with resistance to expansion obtained in Examples 1-3 and Comparative Examples 1-3 were used to prepare lithium batteries, and the performance of the batteries was tested. The results are shown in Table 1.

[0063] The prepared expansion-resistant lithium battery electrode material, styrene-butadiene rubber binder, and N-methylpyrrolidone were mixed in a mass ratio of 8:1:9 to form a slurry. The slurry was then uniformly coated onto a copper foil current collector with a density of 55 mg / cm³. 2 The negative electrode sheet was prepared by vacuum drying for 12 hours; graphite, carbon nanotubes, styrene-butadiene rubber (SBR) and N-methylpyrrolidone (N-methylpyrrolidone) were mixed in a mass ratio of 8:2:1:9 to form a slurry, which was then coated onto aluminum foil with a density of 20 mg / cm³. 2 After vacuum drying for 12 hours, a positive electrode sheet was prepared. The lithium-phosphorus-sulfur-chlorine solid electrolyte solution was then prepared according to a surface density of 12 mg / cm³. 2 The coating is applied to the surface of the positive electrode sheet and dried at 80℃ for 12 hours, then at 30℃ for 24 hours. The temperature is then adjusted back to 80℃ and the pressure is 1000 kg / cm². 2 Hot-press for 2 minutes; set the temperature to 30℃ and the pressure to 500 kg / cm². 2 Cold-press for 2 minutes to obtain a composite positive electrode sheet; stack the composite positive electrode sheet, glass fiber membrane, and negative electrode sheet to obtain a battery cell; place the battery cell into a casing, set the temperature to 75℃, and the pressure to 1000 kg / cm². 2 Hot-press for 5 minutes, set the temperature to 30℃ and the pressure to 1000 kg / cm². 2 The lithium battery was obtained by cold pressing for 3 minutes. The first charge-discharge performance test was conducted at room temperature, with constant current charge and discharge at 0.1C for 10 cycles, followed by constant current charge and discharge at 0.5C for 100 cycles. The capacity retention rate was then calculated.

[0064] Table 1. Lithium-ion battery performance test results

[0065] Item Example 1 Example 2 Example 3 Comparative Example 1 Comparative Example 2 Comparative Example 3 Conductivity (S / cm) 32.7 33.9 35.4 21.0 18.3 19.3 Capacity retention rate after 100 cycles (%) 94.2 94.4 94.5 85.5 80.2 82.2 Initial efficiency (%) 96.5 98.7 99.1 88.2 83.6 84.3 Volume change percentage (%) 78 73 68 90 120 115 Initial discharge capacity (mAh / g) 1500.8 1528.2 1539.4 1452.3 1306.7 1386.6

[0066] As shown in Table 1, the lithium batteries prepared from the expansion-resistant lithium battery electrode materials obtained in Examples 1-3 exhibit significantly better conductivity, 100-cycle capacity retention, initial efficiency, and initial discharge capacity than the comparative examples, and significantly lower volume change percentage. This indicates that the expansion-resistant lithium battery electrode material prepared in this invention can significantly alleviate volume expansion during the charging and discharging process of lithium batteries, accommodate more lithium ions for insertion and extraction, reduce the generation of by-products, and increase the cycle stability and safety of lithium batteries.

[0067] In Comparative Example 1, the pretreated carbon fiber powder replaced the carbon fiber powder. The carboxyl groups on the surface of the pretreated carbon fiber powder combined with the hydroxyl groups on the surface of silica under acidic conditions, so that silica was uniformly loaded on the carbon fiber, increasing the interfacial bonding force between silica and carbon fiber. This can effectively alleviate the volume expansion during the charging and discharging of lithium batteries, and the insulation is also insufficient to meet the requirements for lithium ion insertion and extraction. Carbon fiber can significantly increase the conductivity of the material.

[0068] In Comparative Example 2, carboxylated cashew phenol was omitted. The carboxyl groups on the surface of carboxylated cashew phenol can undergo a grafting reaction with the hydroxyl groups in glucose under the catalysis of hydrochloric acid, and carbonize at high temperature to generate an amorphous carbon layer, which coats the surface of the modified silica / carbon fiber composite powder. At the same time, the carboxyl groups in glucose undergo an amino esterification reaction with the isocyanate on the surface of the modified silica / carbon fiber composite powder to generate carbon dioxide, which can further increase the porosity of the material. Carboxylated cashew phenol is a long-chain alkyl group, which improves the density of the carbon layer through cross-linking and physical winding, thereby improving the toughness of the carbon layer and avoiding stress concentration caused by volume expansion, which can lead to cracks in the electrode material.

[0069] In Comparative Example 3, cashew nut shell powder was directly used as an electrode material for a lithium-ion battery with resistance to expansion. Nano-alumina was deposited on the cashew nut shell powder using a co-precipitation method. The nano-alumina significantly increased the overall strength of the material and alleviated local heat accumulation during battery charging and discharging. The abundant hydroxyl groups on the surface of the alumina reacted with LiPF6 in the electrolyte to form a stable SEI film, reducing side reactions and inhibiting electrolyte decomposition. The nano-alumina coating layer can block the direct contact between the silicon skeleton and the electrolyte, reducing the rate of interfacial side reactions.

[0070] It should be noted that, in this document, terms such as “comprising,” “including,” or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such process, method, article, or apparatus.

[0071] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and variations can be made to these embodiments without departing from the principles and spirit of the invention.

Claims

1. A method for preparing an expansion-resistant lithium battery electrode material for unmanned aerial vehicles, characterized in that, Includes the following steps: Step 1: By hydrolyzing and condensing tetraethyl orthosilicate, silica is bonded to the surface of the acidified pretreated carbon fiber powder to obtain silica / carbon fiber composite powder. Then, by treating it with γ-isocyanate-propyltriethoxysilane, modified silica / carbon fiber composite powder with isocyanate groups is obtained. Step 2: Glucose grafted onto carboxylated cashew nutmeg is subjected to an amino esterification reaction with modified silica / carbon fiber composite powder to achieve coating of modified silica / carbon fiber composite powder, and then pyrolyzed and carbonized at high temperature to obtain cashew nutmeg coated composite powder. Step 3: Nano-alumina is deposited on the surface of cashew phenol-coated composite powder by co-precipitation method to obtain expansion-resistant lithium battery electrode material for UAVs.

2. The method for preparing an expansion-resistant lithium battery electrode material for unmanned aerial vehicles according to claim 1, characterized in that, The specific preparation steps of the silica / carbon fiber composite powder are as follows: Tetraethyl orthosilicate, ethanol, and deionized water were added to a reaction vessel and stirred at 20-25℃ and 500-600 r / min for 5-10 min. 1 mol / L hydrochloric acid solution was added to adjust the pH to 2-3, and stirring was continued for 3-4 h. Pretreated carbon fiber powder was added and ultrasonically dispersed for 40-60 min. Then, 20-30 wt% ammonia solution was added to adjust the pH to 7-8. The product was poured into a mold, sealed, and allowed to stand for 40-50 h. Hexane was added and soaked for 36-38 h. The product was filtered, washed, and freeze-dried in liquid nitrogen for 12-14 h. The product was transferred to a muffle furnace and heated to 700-800℃ under an argon atmosphere for 2-3 h. It was then naturally cooled to room temperature to obtain silica / carbon fiber composite powder. The ratio of tetraethyl orthosilicate, ethanol, deionized water, hydrochloric acid solution, pretreated carbon fiber powder, ammonia solution and n-hexane is 50-60mL: 150-200mL: 200-300mL: 12-13mL: 70-80g: 15-20mL: 200-300mL.

3. The method for preparing an expansion-resistant lithium battery electrode material for unmanned aerial vehicles according to claim 1, characterized in that, The specific preparation steps of the modified silica / carbon fiber composite powder are as follows: Add silica / carbon fiber composite powder, methanol, deionized water and γ-isocyanate-propyltriethoxysilane to a reaction vessel, stir at 70-80℃ and 500-600 r / min for 1-2 h, filter, wash and vacuum dry to obtain modified silica / carbon fiber composite powder. The ratio of the silica / carbon fiber composite powder, methanol, deionized water and γ-isocyanate-propyltriethoxysilane is 60-70g: 100-120mL: 400-500mL: 40-50g.

4. The method for preparing an expansion-resistant lithium battery electrode material for unmanned aerial vehicles according to claim 1, characterized in that, The pretreated carbon fiber powder is prepared through the following steps: Carbon fiber powder, 5-8 wt% hydrochloric acid solution and 7-8 wt% hydrogen peroxide solution are added to a reaction vessel, stirred at 70-80℃ and 500-600 r / min for 1-2 h, filtered, washed and vacuum dried to obtain pretreated carbon fiber powder. The ratio of carbon fiber, hydrochloric acid solution, and hydrogen peroxide solution is 80-90g: 450-480mL: 250-260mL.

5. The method for preparing an expansion-resistant lithium battery electrode material for unmanned aerial vehicles according to claim 1, characterized in that, The specific preparation steps for the carboxylated cashew nut phenol are as follows: Cashew nut phenol, methanol, sodium hydroxide, and deionized water were added to a reaction vessel and stirred at 20-25°C and 500-600 rpm for 1-2 hours. Then chloroacetic acid was added, and the mixture was heated to 70-80°C and stirred for another 4-5 hours. The mixture was then allowed to cool naturally. Next, 20-30 wt% hydrochloric acid solution was added to adjust the pH to 1-2. Then methanol, diethyl ether, and deionized water were added. The mixture was separated, the aqueous phase was removed, and the organic phase was retained. The mixture was concentrated, and the product was recrystallized in n-hexane and dried under vacuum to obtain carboxylated cashew nut phenol.

6. A method for preparing an expansion-resistant lithium battery electrode material for unmanned aerial vehicles according to claim 5, characterized in that, The ratio of cashew phenol, methanol, sodium hydroxide, deionized water, chloroacetic acid, hydrochloric acid solution, methanol, diethyl ether, and deionized water is 50-60g: 100-120mL: 3-4g: 200-300mL: 30-40g: 10-12mL: 250-300mL: 500-600mL: 400-500mL.

7. The method for preparing an expansion-resistant lithium battery electrode material for unmanned aerial vehicles according to claim 1, characterized in that, The specific preparation steps of the cashew phenol-coated composite powder are as follows: Glucose, carboxylated cashew nut shell powder, and deionized water were added to a reaction vessel and ultrasonically dispersed for 30-40 min. The mixture was then stirred at 70-80℃ and 400-500 r / min for 10-20 min. Next, 10-20 wt% hydrochloric acid solution was added, and stirring was continued for 1-2 h. Then, modified silica / carbon fiber composite powder, dimethylformamide, and triethylamine were added. The mixture was heated to 170-180℃ and stirred for 5-6 h. The mixture was then filtered, washed, and vacuum dried to obtain cashew nut shell powder coated with composite powder.

8. A method for preparing an expansion-resistant lithium battery electrode material for unmanned aerial vehicles according to claim 7, characterized in that, The ratio of glucose, carboxylated cashew nut shell powder, deionized water, hydrochloric acid solution, modified silica / carbon fiber composite powder, dimethylformamide and triethylamine is 30-40g: 20-30g: 1-2L: 10-12mL: 50-60g: 400-500mL: 1-2g.

9. A method for preparing an expansion-resistant lithium battery electrode material for unmanned aerial vehicles according to claim 1, characterized in that, The specific preparation steps for the expansion-resistant lithium battery electrode material for UAVs are as follows: Cashew phenol-coated composite powder, aluminum nitrate, and deionized water were added to a reaction vessel and stirred for 20-30 minutes at 40-50℃ and 500-600 r / min. Then, 20-30% (w / w) ammonia solution and ethylene glycol were added, and the mixture was heated to 120-130℃ and reacted for 12-14 hours. The mixture was then filtered, washed, and vacuum dried to obtain an expansion-resistant lithium battery electrode material for drones.

10. An expansion-resistant lithium battery electrode material for unmanned aerial vehicles, characterized in that, It is prepared by the preparation method according to any one of claims 1-9.