Expansion-resistant lithium battery pole piece material for unmanned aerial vehicle and preparation method of expansion-resistant lithium battery pole piece material

Abstract

The invention discloses an expansion-resistant lithium battery pole piece material for an unmanned aerial vehicle and a preparation method of the expansion-resistant lithium battery pole piece material, and belongs to the technical field of lithium batteries. Silicon dioxide / carbon fiber composite powder serves as a matrix, the surface of the matrix is coated with a long-chain alkyl cardanol grafted glucose layer, and pyrolysis carbonization is performed to obtain the expansion-resistant lithium battery pole piece material. Carboxyl groups in glucose and isocyanate on the surface of the modified silicon dioxide / carbon fiber composite powder are subjected to an amine esterification reaction, carbon dioxide is generated, the porosity of the material is further improved, cardanol-coated lithium-containing composite powder is obtained, nanometer aluminum oxide is deposited on the cardanol-coated lithium-containing composite powder through a coprecipitation method, and the composite material is obtained. By forming a ternary composite structure with the silicon dioxide / carbon fiber composite powder as a core layer, the carbonized long-chain alkyl cardanol grafted glucose as a middle layer and the nanometer aluminum oxide as an outermost layer, the volume expansion can be better and synergistically relieved on the premise that the porosity is not affected.

Description

Technical Field

[0001] The present invention belongs to the technical field of lithium batteries, and specifically relates to an expansion-resistant lithium battery pole piece material for unmanned aerial vehicles and a preparation method thereof. Background Art

[0002] With the booming drone industry, drone batteries have higher power requirements. When the throttle is quickly increased from a hovering state to maximum speed, the battery power will increase rapidly, increasing several times in a short period of time. In recent years, lithium-ion batteries have been widely used in the drone industry as a green and clean new energy source. Currently, the most commonly used lithium-ion battery anode materials are carbon materials, such as natural graphite and graphitized mesophase carbon microbeads. Among non-carbon anode materials, silicon has an extremely high theoretical specific capacity and a low lithium storage reaction voltage platform. However, silicon has low electronic and ionic conductivity, resulting in poor kinetic performance of its electrochemical reactions. Ordinary pure silicon has poor cycling stability, and the phase change and volume expansion of silicon during the lithiation process will generate significant stress, causing the electrode to break and pulverize, increase resistance, and suddenly reduce cycling performance.

[0003] The Chinese patent with announcement number CN117776183B announces porous carbon and its preparation method, silicon-carbon negative electrode material, and the preparation method of silicon-carbon negative electrode material. By preparing a crude porous carbon product and performing pore filling and sealing treatment, the pores of the porous carbon that are too small in size are sealed, thereby reducing the specific surface area of ​​the porous carbon, improving the deposition efficiency in the process of preparing silicon-carbon negative electrode material by chemical vapor deposition, saving organic carbon source, and improving the mechanical properties and mechanical parameters of the silicon-carbon negative electrode material. However, the decrease in porosity in this scheme cannot disperse stress when lithium ions are repeatedly inserted / released, resulting in the electrode material being easily broken and unable to effectively suppress the volume expansion of the electrode. Summary of the Invention

[0004] The purpose of the present invention is to provide an expansion-resistant lithium battery pole piece material for drones and a preparation method thereof, by using silica / carbon fiber composite powder as a matrix, coating the surface with a long-chain alkyl cardanol grafted glucose layer, and pyrolysis carbonization, the carboxyl group in the glucose reacts with the isocyanate on the surface of the modified silica / carbon fiber composite powder to produce carbon dioxide, further increasing the porosity of the material to obtain a cardanol-coated lithium-containing composite powder, and then depositing nano-alumina on the cardanol-coated lithium-containing composite powder by coprecipitation. By forming a ternary composite structure with silica / carbon fiber composite powder as the core layer, long-chain alkyl cardanol grafted glucose after carbonization as the middle layer, and nano-alumina as the outermost layer, the volume expansion can be better coordinated and alleviated without affecting the porosity. The purpose of the present invention can be achieved by the following technical solutions:

[0005] A method for preparing an expansion-resistant lithium battery electrode material for a drone comprises the following steps:

[0006] Step 1: Through the hydrolysis and condensation of ethyl orthosilicate, silica is bonded to the surface of the acidified pretreated carbon fiber powder to obtain a silica / carbon fiber composite powder, which is then treated with γ-isocyanatepropyltriethoxysilane to obtain a modified silica / carbon fiber composite powder with an isocyanate group.

[0007] Step 2: Carboxylated cardanol is grafted onto glucose, and an amine esterification reaction occurs with the modified silica / carbon fiber composite powder to achieve coating of the modified silica / carbon fiber composite powder, which is then pyrolyzed and carbonized at high temperature to obtain cardanol-coated lithium-containing composite powder.

[0008] Step 3: Deposit nano-alumina on the surface of the cardanol-coated composite powder by co-precipitation to obtain an expansion-resistant lithium battery electrode material for drones.

[0009] Furthermore, 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 a reactor, stirred at 20-25°C and 500-600r / min for 5-10min, 1mol / L hydrochloric acid solution is added to adjust the pH value to 2-3, and stirring is continued for 3-4h. Pretreated carbon fiber powder is added, ultrasonically dispersed for 40-60min, and then 20-30wt% ammonia solution is added to adjust the pH value to 7-8. The product is poured into a mold, sealed and allowed to stand for 40-50h, and n-hexane is added to soak for 36-38h. The product is filtered, washed, and freeze-dried with liquid nitrogen for 12-14h. The product is transferred to a muffle furnace, heated to 700-800°C under an argon atmosphere, kept warm for 2-3h, and naturally cooled to room temperature to obtain a silica / carbon fiber composite powder.

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

[0012] Furthermore, the specific preparation steps of the modified silica / carbon fiber composite powder are as follows:

[0013] Add silica / carbon fiber composite powder, methanol, deionized water and γ-isocyanate propyltriethoxysilane into a reaction kettle, stir at 70-80° C. and 500-600 r / min for 1-2 hours, filter, wash and vacuum dry to obtain modified silica / carbon fiber composite powder.

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

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

[0016] Add carbon fiber powder, 5-8wt% hydrochloric acid solution and 7-8wt% hydrogen peroxide solution into a reactor, stir at 70-80°C and 500-600r / min for 1-2h, filter, wash and vacuum dry to obtain pretreated carbon fiber powder.

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

[0018] Furthermore, the specific preparation steps of carboxylated cardanol are as follows:

[0019] Cardanol, methanol, sodium hydroxide and deionized water are added to a reactor, stirred at 20-25°C and 500-600 r / min for 1-2 hours, then chloroacetic acid is added, heated to 70-80°C, stirred for 4-5 hours, cooled naturally, then 20-30wt% hydrochloric acid solution is added, the pH value is adjusted to 1-2, methanol, diethyl ether and deionized water are added, the liquids are separated, the aqueous phase is removed, the organic phase is retained, concentrated, the product is recrystallized in n-hexane, and vacuum dried to obtain carboxylated cardanol.

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

[0021] Furthermore, the specific preparation steps of the cardanol-coated lithium-containing composite powder are as follows:

[0022] Glucose, carboxylated cardanol and deionized water are added to a reactor, ultrasonically dispersed for 30-40 minutes, stirred at 70-80°C and 400-500 r / min for 10-20 minutes, then a 10-20wt% hydrochloric acid solution is added, and stirring is continued for 1-2 hours. Modified silica / carbon fiber composite powder, dimethylformamide and triethylamine are then added, heated to 170-180°C, and stirring is continued for 5-6 hours. The mixture is filtered, washed, and vacuum dried to obtain a cardanol-coated composite powder.

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

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

[0025] The cardanol-coated lithium-containing composite powder, aluminum nitrate and deionized water are added to a reactor, stirred at 40-50°C and 500-600r / min for 20-30min, and then a 20-30% by mass ammonia solution and ethylene glycol are added. The mixture is heated to 120-130°C, reacted for 12-14h, filtered, and the filter cake is washed 2-3 times with deionized water and vacuum dried to obtain an expansion-resistant lithium battery electrode material for drones.

[0026] Beneficial effects of the present invention:

[0027] 1. The expansion-resistant lithium battery pole piece material prepared by the present invention can significantly alleviate the volume expansion during the charge and discharge process of the lithium battery, can accommodate more lithium ions for insertion and deinsertion, reduce the generation of by-products, and increase the cycle stability and safety of the lithium battery; by using silica / carbon fiber composite powder as the matrix and depositing silica on the surface, the strength of silicon as an electrode material can be significantly enhanced, avoiding the brittleness of silica, and then coating the surface with a long-chain alkyl cardanol grafted glucose layer, and pyrolysis and carbonization, the carboxyl groups in the glucose react with the isocyanate on the surface of the modified silica / carbon fiber composite powder to produce carbon dioxide, further increasing the porosity of the material, and finally depositing nano-alumina on the cardanol-coated composite powder by a coprecipitation method to form a stable SEI film, thereby reducing the occurrence of side reactions.

[0028] 2. The cardanol-coated composite powder of the present invention can react with the hydroxyl groups in glucose in a graft reaction under the catalysis of hydrochloric acid through the carboxyl groups contained in the carboxylated cardanol, and carbonize at high temperature to generate an amorphous carbon layer, which is coated on the surface of the modified silica / carbon fiber composite powder. At the same time, the carboxyl groups in the glucose react with the isocyanate on the surface of the modified silica / carbon fiber composite powder to produce carbon dioxide, so that the carboxylated cardanol is coated on the surface of the modified silica / carbon fiber composite powder and the porosity of the material can be further increased. The carboxylated cardanol is a long-chain alkyl group, which improves the density of the carbon layer and thus the toughness of the carbon layer through cross-linking and physical entanglement, thereby avoiding cracks in the electrode material caused by volume expansion stress concentration.

[0029] 3. The present invention deposits nano-alumina on the cardanol-coated lithium-containing composite powder by a co-precipitation method. Nano-alumina can significantly increase the overall strength of the material and alleviate local heat accumulation during battery charging and discharging. The rich hydroxyl groups on the surface of alumina react with LiPF6 in the electrolyte to form a stable SEI film, reduce side reactions, and inhibit electrolyte decomposition. The nano-alumina coating layer can block the direct contact between the silicon skeleton and the electrolyte, reduce the rate of interfacial side reactions, and form a ternary composite structure with silica / carbon fiber composite powder as the core layer, long-chain alkyl cardanol grafted with glucose after carbonization as the middle layer, and nano-alumina as the outermost layer, which can better synergistically alleviate volume expansion. DETAILED DESCRIPTION

[0030] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts 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 a drone, comprising the following steps:

[0032] S1: 80 g of carbon fiber powder, 450 mL of 5% hydrochloric acid solution and 250 mL of 7% hydrogen peroxide solution were added to a reactor, stirred at 70 ° C and 500 r / min for 1 hour, filtered, and the filter cake was washed with deionized water until the last washing liquid was neutral, and vacuum dried at 60 ° C for 1 hour to obtain pretreated carbon fiber powder.

[0033] After carbon fiber is treated with hydrochloric acid solution and hydrogen peroxide solution, its 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 50mL of tetraethyl orthosilicate, 150mL of ethanol and 200mL of deionized water into the reactor, stir at 20℃ and 500r / min for 5min, add 12mL of 1mol / L hydrochloric acid solution to adjust the pH value to 2, continue stirring for 3h, add 70g of pretreated carbon fiber powder, ultrasonically disperse for 40min, and then add 15mL of 20% ammonia solution to adjust the pH value to 7. Pour the product into a mold, seal and let it stand for 40h, add 200mL of n-hexane and soak for 36h, filter, wash the filter cake with n-hexane and deionized water twice respectively, freeze-dry with liquid nitrogen for 12h, transfer the product to a muffle furnace, heat to 700℃ under argon atmosphere, keep warm for 2h, cool naturally to room temperature, grind and crush to obtain silica / carbon fiber composite powder.

[0035] The carboxyl groups on the surface of the 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, thereby inhibiting crack propagation.

[0036] S3: Add 60 g of silica / carbon fiber composite powder, 100 mL of methanol, 400 mL of deionized water and 40 g of γ-isocyanatepropyltriethoxysilane into a reactor, stir at 70 ° C and 500 r / min for 1 hour, filter, wash the filter cake with deionized water twice, and vacuum dry at 60 ° C for 1 hour to obtain modified silica / carbon fiber composite powder.

[0037] γ-isocyanatepropyltriethoxysilane generates silane bonds through hydrolysis and combines with hydroxyl groups on the surface of silica / carbon fiber composite powder. After hydrolysis, the isocyanate groups are not consumed and still retain high reactivity to obtain modified silica / carbon fiber composite powder.

[0038] S4: Add 50g of cardanol, 100mL of methanol, 3g of sodium hydroxide and 200mL of deionized water into the reactor, stir at 20°C and 500r / min for 1h, then add 30g of chloroacetic acid, heat to 70°C, continue stirring for 4h, cool naturally, then add 10mL of 20% hydrochloric acid solution, adjust the pH value to 1, then add 250mL of methanol, 500mL of diethyl ether and 400mL of deionized water, separate the liquids, remove the aqueous phase, retain the organic phase, concentrate, place the product in n-hexane for recrystallization, and vacuum dry at 60°C for 1h to obtain carboxylated cardanol.

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

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

[0041] The carboxyl groups on the surface of carboxylated cardanol can react with the hydroxyl groups in glucose under the catalysis of hydrochloric acid, and carbonize at high temperature to form an amorphous carbon layer, which is coated on the surface of the modified silica / carbon fiber composite powder. At the same time, the carboxyl groups in glucose react with the isocyanate on the surface of the modified silica / carbon fiber composite powder to produce carbon dioxide, so that the carboxylated cardanol is coated on the surface of the modified silica / carbon fiber composite powder and can further increase the porosity of the material. Carboxylated cardanol is a long-chain alkyl group, which improves the density of the carbon layer and thus the toughness of the carbon layer through cross-linking and physical entanglement, avoiding the volume expansion stress concentration that causes cracks in the electrode material.

[0042] S6: 30g of cardanol-coated composite powder, 50g of aluminum nitrate and 400mL of deionized water were added to the reactor, stirred at 40°C and 500r / min for 20min, then 10mL of 20% ammonia solution and 5mL of ethylene glycol were added, heated to 120°C, reacted for 12h, filtered, and the filter cake was washed twice with deionized water, and vacuum dried at 60°C for 1h to obtain an expansion-resistant lithium battery electrode material for drones.

[0043] Nano-alumina is deposited on the surface of the cardanol-coated composite powder by co-precipitation. Nano-alumina can significantly increase the overall strength of the material and alleviate local heat accumulation during battery charging and discharging. Lewis acid sites exist on the surface of alumina, which can react with PF5 or HF produced by the decomposition of LiPF6 to generate inorganic compounds containing Al-F, Al-OP and other components, stabilize the SEI film, consume HF through reaction, and reduce its damage to the electrode and electrolyte. The nano-alumina coating can block the direct contact between the silicon skeleton 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 a drone, comprising the following steps:

[0045] S1: 85 g of carbon fiber powder, 465 mL of 6.5% hydrochloric acid solution and 255 mL of 7.5% hydrogen peroxide solution were added to a reactor, stirred at 75 ° C and 550 r / min for 1.5 h, filtered, and the filter cake was washed with deionized water until the last washing liquid was neutral, and vacuum dried at 70 ° C for 1.5 h to obtain pretreated carbon fiber powder.

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

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

[0048] S4: Add 55g of cardanol, 110mL of methanol, 3.5g of sodium hydroxide and 250mL of deionized water into the reactor, stir at 22.5℃ and 550r / min for 1.5h, then add 35g of chloroacetic acid, heat to 75℃, continue stirring for 4.5h, cool naturally, then add 11mL of 25% saline solution, adjust the pH value to 1.5, then add 275mL of methanol, 550mL of diethyl ether and 450mL of deionized water, separate the liquids, remove the aqueous phase, retain the organic phase, concentrate, place the product in n-hexane for recrystallization, and vacuum dry at 70℃ for 1.5h to obtain carboxylated cardanol.

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

[0050] S6: 32g of cardanol-coated composite powder, 55g of aluminum nitrate and 450mL of deionized water were added to the reactor, stirred at 45°C and 550r / min for 25min, then 11mL of 25% ammonia solution and 5.5mL of ethylene glycol were added, heated to 125°C, reacted for 13h, filtered, and the filter cake was washed twice with deionized water, and vacuum dried at 70°C for 1.5h to obtain an expansion-resistant lithium battery electrode material for drones.

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

[0052] S1: 90 g of carbon fiber powder, 480 mL of 8% hydrochloric acid solution and 260 mL of 8% hydrogen peroxide solution were added to a reactor, stirred at 80 ° C and 600 r / min for 2 h, filtered, and the filter cake was washed with deionized water until the last washing liquid was neutral, and vacuum dried at 80 ° C for 2 h to obtain pretreated carbon fiber powder.

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

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

[0055] S4: Add 60g of cardanol, 120mL of methanol, 4g of sodium hydroxide and 300mL of deionized water into the reactor, stir at 25°C and 600r / min for 2h, then add 40g of chloroacetic acid, heat to 80°C, continue stirring for 5h, cool naturally, then add 12mL of 30% hydrochloric acid solution, adjust the pH value to 2, then add 300mL of methanol, 600mL of diethyl ether and 500mL of deionized water, separate the liquids, remove the aqueous phase, retain the organic phase, concentrate, place the product in n-hexane for recrystallization, and vacuum dry at 80°C for 2h to obtain carboxylated cardanol.

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

[0057] S6: 34 g of cardanol-coated composite powder, 60 g of aluminum nitrate and 500 mL of deionized water were added to the reactor, stirred at 50 ° C and 600 r / min for 30 minutes, and then 12 mL of 30% ammonia solution and 6 mL of ethylene glycol were added. The mixture was heated to 130 ° C, reacted for 14 hours, filtered, and the filter cake was washed with deionized water for 3 times, and vacuum dried at 80 ° C for 2 hours to obtain an expansion-resistant lithium battery electrode material for drones.

[0058] Comparative Example 1: Based on Example 3, the pretreated carbon fiber powder in step S2 is replaced with carbon fiber powder of equal mass in step S1, and the remaining steps remain unchanged to prepare an expansion-resistant lithium battery electrode material for drones.

[0059] Comparative Example 2: Based on Example 3, step S4 was not performed, the carboxylated cardanol in step S5 was omitted, 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 treatment in step S6, the cardanol-coated composite powder in step S5 is directly used as the expansion-resistant lithium battery electrode material.

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

[0062] The performance of lithium batteries prepared from the expansion-resistant lithium battery pole piece materials obtained in Examples 1 to 3 and Comparative Examples 1 to 3 was tested. The results are shown in Table 1:

[0063] The prepared expansion-resistant lithium battery pole piece material, binder styrene-butadiene rubber and N-methylpyrrolidone were mixed in a mass ratio of 8:1:9 to form a slurry, and the slurry was evenly coated on the copper foil current collector with a density of 55 mg / cm 2 , and vacuum dried for 12 hours to make the negative electrode; Graphite, carbon nanotubes, binder styrene-butadiene rubber and N-methylpyrrolidone were mixed in a mass ratio of 8:2:1:9 to form a slurry and coated on aluminum foil with a density of 20 mg / cm 2 After vacuum drying for 12 hours, the positive electrode sheet was prepared. The lithium phosphorus sulfur chlorine solid electrolyte solution was added at a surface density of 12 mg / cm 2 Coated on the surface of the positive electrode, set the temperature to 80℃ and dry for 12 hours, set the temperature to 30℃ and dry for 24 hours, set the temperature to 80℃ and the pressure to 1000kg / cm 2 Hot pressing for 2 minutes; set the temperature to 30°C and the pressure to 500kg / cm 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 in the shell, set the temperature to 75 ° C and the pressure to 1000 kg / cm 2 Hot pressing for 5 minutes, setting the temperature to 30°C and the pressure to 1000kg / cm 2 The lithium battery was obtained by cold pressing for 3 minutes. The first charge and discharge performance test was carried out at room temperature, with a constant current of 0.1C charge and discharge. After 10 cycles, it was switched to a constant current of 0.5C charge and discharge, and cycled for 100 cycles to calculate its capacity retention rate.

[0064] Table 1 Lithium battery performance test results

[0065]

[0066] As can be seen from Table 1, the expansion-resistant lithium battery pole piece materials obtained in Examples 1 to 3 are prepared into lithium batteries, and the electrical conductivity, 100 cycle capacity retention rate, initial efficiency and initial discharge capacity are significantly better than those of the comparative example, and the volume change percentage is significantly lower than that of the comparative example, indicating that the expansion-resistant lithium battery pole piece material prepared by the present invention can significantly alleviate the volume expansion during the charge and discharge process of the lithium battery, can accommodate more lithium ions for insertion and deintercalation, reduce the generation of by-products, and increase the cycle stability and safety of the lithium battery.

[0067] In Comparative Example 1, the pretreated carbon fiber powder replaces the carbon fiber powder. The carboxyl groups on the surface of the pretreated carbon fiber powder combine with the hydroxyl groups on the surface of the silica under acidic conditions, so that the silica is evenly loaded on the carbon fiber, increasing the interfacial bonding force between the silica and the carbon fiber, which can effectively alleviate the volume expansion during the charging and discharging process of the lithium battery. The insulation cannot meet the requirements of lithium ion embedding and de-embedding, and the carbon fiber can significantly increase the conductivity of the material.

[0068] In Comparative Example 2, the carboxylated cardanol is discarded. The carboxyl groups on the surface of the carboxylated cardanol can react with the hydroxyl groups in glucose under the catalysis of hydrochloric acid, and carbonize at high temperature to form an amorphous carbon layer, which is coated on the surface of the modified silica / carbon fiber composite powder. At the same time, the carboxyl groups in the glucose react with the isocyanate on the surface of the modified silica / carbon fiber composite powder to produce carbon dioxide, which can further increase the porosity of the material. Carboxylated cardanol is a long-chain alkyl group, which improves the density of the carbon layer and thus the toughness of the carbon layer through cross-linking and physical entanglement, thereby avoiding cracks in the electrode material caused by volume expansion stress concentration.

[0069] In Comparative Example 3, the cardanol-coated composite powder is directly used as the expansion-resistant lithium battery electrode material. Nano-alumina is deposited on the cardanol-coated composite powder by co-precipitation. Nano-alumina can significantly increase the overall strength of the material and alleviate local heat accumulation during battery charging and discharging. The rich hydroxyl groups on the surface of alumina react with LiPF6 in the electrolyte to form a stable SEI film, reduce side reactions, and inhibit the decomposition of the electrolyte. The nano-alumina coating can block the direct contact between the silicon skeleton and the electrolyte, thereby reducing the rate of interfacial side reactions.

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

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

Claims

1. A method for preparing an expansion-resistant lithium battery pole piece material for a drone, characterized in that: The steps include: Step 1: Through the hydrolysis and condensation of ethyl orthosilicate, silica is bonded to the surface of the acidified pretreated carbon fiber powder to obtain a silica / carbon fiber composite powder, which is then treated with γ-isocyanate propyl triethoxysilane to obtain a modified silica / carbon fiber composite powder with an isocyanate group; Step 2: Carboxylated cardanol is grafted with glucose, and an amine esterification reaction is carried out with the modified silica / carbon fiber composite powder to achieve coating of the modified silica / carbon fiber composite powder, and then pyrolysis and carbonization are carried out at high temperature to obtain a cardanol-coated lithium-containing composite powder; Step 3: Deposit nano-alumina on the surface of the cardanol-coated composite powder by co-precipitation to obtain an expansion-resistant lithium battery electrode material for drones.

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

3. The method for preparing an expansion-resistant lithium battery pole piece material for a drone 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 into a reaction kettle, stir at 70-80°C and 500-600 r / min for 1-2 hours, filter, wash and vacuum dry to obtain modified silica / carbon fiber composite powder; The usage ratio of the silicon dioxide / carbon fiber composite powder, methanol, deionized water and gamma-isocyanate propyltriethoxysilane is 60-70 g: 100-120 mL: 400-500 mL: 40-50 g.

4. The method for preparing an expansion-resistant lithium battery pole piece material for a drone according to claim 1, characterized in that: The pretreated carbon fiber powder is prepared by the following steps: Add carbon fiber powder, 5-8 wt% hydrochloric acid solution and 7-8 wt% hydrogen peroxide solution into a reactor, stir at 70-80°C and 500-600 r / min for 1-2 hours, filter, wash and vacuum dry to obtain pretreated carbon fiber powder; The usage ratio of the carbon fiber, hydrochloric acid solution and hydrogen peroxide solution is 80-90 g: 450-480 mL: 250-260 mL.

5. The method for preparing an expansion-resistant lithium battery pole piece material for a drone according to claim 1, characterized in that: The specific preparation steps of the carboxylated cardanol are as follows: Cardanol, methanol, sodium hydroxide and deionized water are added to a reactor, stirred at 20-25°C and 500-600 r / min for 1-2 hours, then chloroacetic acid is added, heated to 70-80°C, stirred for 4-5 hours, cooled naturally, then 20-30wt% hydrochloric acid solution is added, the pH value is adjusted to 1-2, methanol, diethyl ether and deionized water are added, the liquids are separated, the aqueous phase is removed, the organic phase is retained, concentrated, the product is recrystallized in n-hexane, and vacuum dried to obtain carboxylated cardanol.

6. The method for preparing an expansion-resistant lithium battery pole piece material for a drone according to claim 5, characterized in that: The usage ratio of the cardanol, methanol, sodium hydroxide, deionized water, chloroacetic acid, hydrochloric acid solution, methanol, diethyl ether and deionized water is 50-60 g: 100-120 mL: 3-4 g: 200-300 mL: 30-40 g: 10-12 mL: 250-300 mL: 500-600 mL: 400-500 mL.

7. The method for preparing an expansion-resistant lithium battery pole piece material for a drone according to claim 1, characterized in that: The specific preparation steps of the cardanol-coated lithium-containing composite powder are as follows: Glucose, carboxylated cardanol and deionized water are added to a reactor, ultrasonically dispersed for 30-40 minutes, stirred at 70-80°C and 400-500 r / min for 10-20 minutes, then a 10-20wt% hydrochloric acid solution is added, and stirring is continued for 1-2 hours. Modified silica / carbon fiber composite powder, dimethylformamide and triethylamine are then added, heated to 170-180°C, and stirring is continued for 5-6 hours. The mixture is filtered, washed, and vacuum dried to obtain a cardanol-coated composite powder.

8. The method for preparing an expansion-resistant lithium battery pole piece material for a drone according to claim 7, characterized in that: The usage ratio of the glucose, carboxylated cardanol, deionized water, hydrochloric acid solution, modified silicon dioxide / carbon fiber composite powder, dimethylformamide and triethylamine is 30-40g:20-30g:1-2L:10-12mL:50-60g:400-500mL:1-2g.

9. The method for preparing an expansion-resistant lithium battery pole piece material for a drone according to claim 1, characterized in that: The specific preparation steps of the expansion-resistant lithium battery electrode material for drones are as follows: The cardanol-coated lithium-containing composite powder, aluminum nitrate and deionized water are added to a reactor, stirred at 40-50°C and 500-600r / min for 20-30min, and then a 20-30% by mass ammonia solution and ethylene glycol are added. The mixture is heated to 120-130°C, reacted for 12-14h, filtered, washed and vacuum dried to obtain an expansion-resistant lithium battery electrode material for drones.

10. A swelling-resistant lithium battery pole piece material for drones, characterized in that: Prepared by the preparation method according to any one of claims 1 to 9.

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