Low-temperature-resistant lithium battery pole piece material and preparation method thereof

Abstract

The application discloses a low-temperature-resistant lithium battery pole piece material and a preparation method thereof, and belongs to the technical field of lithium batteries. The tetrabutyl titanate solution is fully penetrated into the internal pores of the microspheres through impregnation and capillary action, so that the subsequently generated titanium dioxide not only covers the surface of the microspheres, but also is embedded in the porous structure of the microspheres, and a porous metal skeleton is loaded on the surface of the activated microspheres, forming a core-shell structure, which can play a buffering role, better disperse stress, significantly relieve volume expansion in the charging and discharging process of the lithium battery, avoid the stress caused by the dispersion of volume expansion through interface slip of the sheet structure, cause the gradual peeling of the carbon coating layer and the sheet material, and thus can accommodate more lithium ions for intercalation and deintercalation, reduce the shuttle effect of polysulfides, and increase the cycle capacity, the initial discharge capacity and the initial coulombic efficiency of the lithium battery.

Description

TECHNICAL FIELD

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

[0002] Compared with lead-acid batteries, nickel-hydrogen batteries and nickel-cadmium batteries, lithium batteries have the advantages of higher energy density, wider working temperature range and longer cycle life, and thus have long occupied a mainstream position in the market. With the wide use of lithium ion batteries, higher requirements for their environmental adaptability are also put forward. Sometimes, electronic products and new energy vehicles must be used in very low temperature environments, and compared with conventional environments, the performance of lithium ion batteries will be significantly deteriorated under extreme conditions, such as extremely cold conditions in the north. The performance of the above-mentioned lithium ion battery negative electrode material will be affected under super-low temperature environment. The diffusion rate of lithium ions in the negative electrode material will be slowed down under super-low temperature, leading to the decrease of the lithium ion insertion and extraction speed in the charging and discharging process. Under the super-low temperature environment, the electronic conductivity of the negative electrode material is reduced, the internal resistance of the battery is increased, and significant volume change will occur in the charging and discharging process. The low temperature will exacerbate this swelling.

[0003] A low-temperature-resistant lithium ion battery negative electrode material and a preparation method thereof are disclosed in Chinese Patent No. CN118270835B. Titanium isobutylate and hydrofluoric acid are used to prepare sheet-shaped nanometer titanium dioxide, then the sheet-shaped nanometer titanium dioxide is wrapped with porous carbon, and finally the negative electrode material of the lithium ion battery is obtained through disproportionation reaction of sodium thiosulfate. However, in the scheme, the sheet-shaped nanometer titanium dioxide is wrapped with porous carbon, and the crack-type pores formed by the stacking of the sheets can avoid structural collapse by absorbing transverse expansion stress. The volume expansion of sulfur in the charging and discharging process will cause the sheet-shaped nanometer titanium dioxide to disperse stress through interface sliding. This sliding phenomenon will cause the carbon coating layer and the sheet-shaped material to gradually peel off, thereby reducing the overall efficiency and service life of the battery. SUMMARY

[0004] The purpose of the present application is to provide a low-temperature-resistant lithium battery pole piece material and a preparation method thereof. By means of immersion and capillary action, the tetrabutyl titanate solution is fully penetrated into the pores of the microspheres, so that the subsequently generated titanium dioxide not only covers the surface of the microspheres, but also is embedded in the porous structure thereof, and a porous metal skeleton is loaded on the surface to form a core-shell structure. The stress can be buffered through the same-direction and porous uniform compression, and interface peeling is avoided. The volume expansion in the charging and discharging process of the lithium battery is significantly alleviated, and the stress caused by the volume expansion is dispersed through interface sliding, which causes the carbon coating layer and the sheet-shaped material to gradually peel off. Therefore, more lithium ions can be accommodated for insertion and extraction, the shuttle effect of polysulfides is reduced, and the cycle capacity, the initial discharge capacity and the initial coulombic efficiency of the lithium battery are increased.

[0005] The object of the application can be achieved by the following technical solutions:

[0006] A preparation method of a low-temperature-resistant lithium battery pole piece material, comprising the following steps:

[0007] Step one: pyridine modified thiosalicylic acid, anhydrous methanol and dimethylformamide are added to a reaction kettle, stirred at 50-60 DEG C and 500-600 r / min for 30-40 min, then 10-20% ammonia water solution, ferric chloride hexahydrate and nitrogen-doped carbon microspheres are added, heated to 100-110 DEG C, and continue to stir for 1-2 h, filter, wash the filter cake with deionized water and anhydrous ethanol for 2-3 times, vacuum dry at 60-80 DEG C for 1-2 h, and obtain core-shell type nitrogen-doped carbon microspheres.

[0008] Step two: the core-shell type nitrogen-doped carbon microspheres, sodium thiosulfate and deionized water are added to a reaction kettle, stirred at 40-50 DEG C and 400-500 r / min for 1-2 h, then 1-1.5 mol / L hydrochloric acid solution is added, continue to stir for 2-3 h, filter, wash the filter cake with deionized water and anhydrous ethanol until the last washing liquid is neutral, vacuum dry at 60-80 DEG C for 1-2 h, and obtain a low-temperature-resistant lithium battery pole piece material.

[0009] Further, the amount ratio of pyridine modified thiosalicylic acid, anhydrous methanol, dimethylformamide, ammonia water solution, ferric chloride hexahydrate and nitrogen-doped carbon microspheres in step one is 20-25 g: 400-500 mL: 500-600 L: 500-600 mL: 40-50 g: 30-40 g.

[0010] Further, the amount ratio of core-shell type nitrogen-doped carbon microspheres, sodium thiosulfate, deionized water and hydrochloric acid solution in step two is 70-80 g: 40-50 g: 800-900 mL: 80-100 mL.

[0011] Further, the nitrogen-doped carbon microspheres in step one are prepared by the following steps:

[0012] The modified microspheres and tris(hydroxymethyl)aminomethane are added to a reaction kettle, stirred at 20-25 DEG C and 400-500 r / min for 20-30 min, then dopamine hydrochloride is added, continue to stir for 24-26 h, the product is transferred to a muffle furnace, heated to 500-600 DEG C under nitrogen atmosphere, the holding time is 2-3 h, heated to 1200-1300 DEG C and hold for 1-2 h, and obtain nitrogen-doped carbon microspheres.

[0013] Further, the amount ratio of modified microspheres, tris(hydroxymethyl)aminomethane and dopamine hydrochloride is 50-60 g: 100-200 mL: 50-60 mL.

[0014] Further, the modified microspheres are prepared by the following steps:

[0015] The titanium dioxide composite microspheres, γ-aminopropyl triethoxysilane, anhydrous ethanol and deionized water are added to the reaction kettle, stirred at 60-75℃ and 400-500r / min for 40-60min, filtered, and the filter cake is washed with deionized water and anhydrous ethanol for 2-3 times, vacuum dried at 60-80℃ for 1-2h to obtain the modified microspheres.

[0016] Further, the amount ratio of titanium dioxide composite microspheres, γ-aminopropyl triethoxysilane, anhydrous ethanol and deionized water is 40-50g:30-40mL:120-140mL:200-300mL.

[0017] Further, the pyridine modified thiosalicylic acid in step one is prepared by the following steps:

[0018] 4-pyridine carboxyl chloride hydrochloride, triethylamine and dichloromethane are added to the reaction kettle, stirred at 20-25℃ and 400-500r / min for 30-40min, then thiosalicylic acid is added, and the stirring reaction is continued for 18-24h, concentrated, washed with deionized water for 2-3 times, then transferred to ethyl acetate for recrystallization, ground and crushed to obtain pyridine modified thiosalicylic acid.

[0019] Further, the amount ratio of 4-pyridine carboxyl chloride hydrochloride, triethylamine, dichloromethane and thiosalicylic acid is 25-28g:4-5mL:300-400mL:20-30g.

[0020] Further, the titanium dioxide composite microspheres are prepared by the following steps:

[0021] The activated microspheres and deionized water are added to the reaction kettle, stirred at 20-25℃ and 400-500r / min for 10-12min, then tetrabutyl titanate is added, vacuum impregnated for 1-2h, then a 40-50% mass fraction of glacial acetic acid solution is added, stirred at 140-155℃ and 400-500r / min for 1-2h, filtered, and the filter cake is washed with deionized water and anhydrous ethanol for 2-3 times, vacuum dried at 60-80℃ for 1-2h to obtain the titanium dioxide composite microspheres.

[0022] Further, the amount ratio of activated microspheres, deionized water, tetrabutyl titanate and glacial acetic acid solution is 50-60g:500-600mL:40-60mL:500-600mL.

[0023] Further, the activated microspheres are prepared by the following steps:

[0024] The polystyrene microspheres and concentrated sulfuric acid solution with a mass fraction of 97-98% are added into a reaction kettle according to a dosage ratio of 80-90g: 200-250mL, ultrasonic dispersion is carried out for 40-60min, stirring is carried out at 40-50 DEG C and 400-500r / min for 12-14h, filtration is carried out, the filter cake is washed with deionized water and anhydrous ethanol for 2-3 times respectively, and vacuum drying is carried out at 60-80 DEG C for 1-2h, so that the activated microspheres are obtained.

[0025] The beneficial effects of the present application are as follows:

[0026] 1. The low-temperature-resistant lithium battery pole piece material prepared by the present application is fully penetrated into the internal pores of the microspheres through the impregnation and capillary action of the tetrabutyl titanate solution, so that the subsequently generated titanium dioxide not only covers the surface of the microspheres, but also is embedded in the porous structure, and a porous metal skeleton is loaded on the surface of the activated microspheres, forming a core-shell structure, which can play a buffering role, better disperse stress, significantly relieve the volume expansion in the charging and discharging process of the lithium battery, accommodate more lithium ions for intercalation and deintercalation, reduce the shuttle effect of sulfur, and increase the cycle capacity, the first discharge capacity and the first coulombic efficiency of the lithium battery.

[0027] 2. The pyridine-modified thiosalicylic acid in the present application, the reaction of sulfur and lithium to generate soluble polysulfide is the main reason for the capacity attenuation of lithium-sulfur batteries, the nitrogen atom in the pyridine group has a lone pair of electrons, which can act as a Lewis base site and form a strong chemical adsorption with the sulfur atom (Lewis acid) in the polysulfide; the pyridine-modified thiosalicylic acid generates a metal skeleton structure with the pyridine-modified thiosalicylic acid as a ligand under the action of ferric chloride hexahydrate, the metal skeleton structure modified by the pyridine group is porous on the surface, and cooperates with the porous structure of the nitrogen-doped carbon microspheres to inhibit the diffusion of polysulfide and inhibit the shuttle effect through the dual action of micropore confinement and steric hindrance.

[0028] 3. The nitrogen-doped carbon microspheres in the present application, through the hydrolysis of gamma-aminopropyltriethoxysilane to generate silanol groups, condensation reaction occurs with the hydroxyl groups on the surface of the titanium dioxide composite carbon microspheres, the remaining amino groups impart positive charges and reactive sites to the surface of the microspheres, improve hydrophilicity and provide anchor points for subsequent dopamine adsorption, and the tris-hydroxymethyl aminomethane forms a buffer system at room temperature, providing an alkaline environment for the self-oxidation polymerization of dopamine, and the structure formula of the polydopamine after carbonization contains nitrogen elements to form nitrogen-doped carbon microspheres, the nitrogen atom has an extra lone pair of electrons, which can increase the conductivity of the nitrogen-doped electrode material, be conducive to the transmission of electrons in the lithium battery, and significantly improve the wettability of the nitrogen-doped carbon microspheres, and the nitrogen-containing functional groups have hydrophilicity, which is conducive to the direct contact of electrolyte ions with the electrode. DETAILED DESCRIPTION

[0029] The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments of the present application. Based on the embodiments of the present application, all other embodiments obtained by those of ordinary skill in the art without creative effort belong to the protection scope of the present application.

[0030] Embodiment 1: A preparation method of a low-temperature-resistant lithium battery pole piece material, comprising the following steps:

[0031] S1: 80 g of polystyrene microspheres and 200 mL of a concentrated sulfuric acid solution with a mass fraction of 97% are added into a reaction kettle, ultrasonic dispersion is performed for 40 min, stirring is performed at 40 DEG C and 400 r / min for 12 h, filtration is performed, the filter cake is washed with deionized water and anhydrous ethanol until the last washing liquid is neutral, and vacuum drying is performed at 60 DEG C for 1 h, to obtain activated microspheres.

[0032] The concentrated sulfuric acid acts as a strong acid and a sulfonating agent, attacks the benzene ring in the polystyrene molecule through an electrophilic substitution reaction, loads a large number of negatively charged sulfonic acid groups on the surface of the microspheres, and significantly improves the surface activity and adsorption capacity of the microspheres.

[0033] S2: 50 g of the activated microspheres and 500 mL of deionized water are added into a reaction kettle, stirring is performed at 20 DEG C and 400 r / min for 10 min, then 40 mL of tetrabutyl titanate is added, vacuum impregnation is performed for 1 h, 500 mL of a glacial acetic acid solution with a mass fraction of 40% is added, stirring is performed at 140 DEG C and 400 r / min for 1 h, and titanium dioxide composite microspheres are obtained.

[0034] The tetrabutyl titanate solution fully penetrates into the inside of the pores of the microspheres through impregnation and capillary action, realizes deep loading, and this process ensures that the subsequently generated titanium dioxide not only covers the surface of the microspheres but also embeds into the porous structure of the microspheres, forming a core-shell or uniform composite structure.

[0035] S3: 40 g of the titanium dioxide composite microspheres, 30 mL of γ-aminopropyl triethoxysilane, 120 mL of anhydrous ethanol and 200 mL of deionized water are added into a reaction kettle, stirring is performed at 60 DEG C and 400 r / min for 40 min, filtration is performed, the filter cake is washed with deionized water and anhydrous ethanol respectively for 2 times, and vacuum drying is performed at 60 DEG C for 1 h, to obtain modified microspheres; 50 g of the modified microspheres and 100 mL of tris(hydroxymethyl)aminomethane are added into a reaction kettle, stirring is performed at 20 DEG C and 400 r / min for 20 min, then 50 mL of dopamine hydrochloride is added, and stirring is continuously performed for 24 h, the product is transferred into a muffle furnace, heated to 500 DEG C under a nitrogen atmosphere, the holding time is 2 h, heated to 1200 DEG C and held for 1 h, and nitrogen-doped carbon microspheres are obtained.

[0036] The γ-aminopropyltriethoxysilane is hydrolyzed to generate silanol groups, which are condensed with the hydroxyl groups on the surface of the titanium dioxide composite carbon microspheres, and the amino groups are oriented outward, giving the microsphere surface a positive charge and a reactive site, improving hydrophilicity and providing an anchor point for subsequent dopamine adsorption. The tris(hydroxymethyl)aminomethane forms a buffer system at room temperature, providing an alkaline environment for the self-oxidation polymerization of dopamine.

[0037] The additional lone pair of electrons in the nitrogen atom can increase the conductivity of the nitrogen-doped electrode material, facilitate electron transport, and significantly improve the wettability of the carbon material. This is because the nitrogen-containing functional group has hydrophilic properties, which facilitates direct contact between electrolyte ions and the electrode.

[0038] S4: 25g of 4-pyridinecarbonyl chloride hydrochloride, 4mL of triethylamine and 300mL of dichloromethane were added to the reaction kettle, stirred at 20℃ and 400r / min for 30min, then 20g of thiosalicylic acid was added, and the reaction was continued for 18h. Concentrate, wash the concentrated solution with deionized water twice, then transfer to ethyl acetate for recrystallization, grind and crush to obtain pyridine-modified thiosalicylic acid.

[0039] The mercapto group of thiosalicylic acid reacts with acyl chloride. In alkaline conditions, the mercapto group of thiosalicylic acid is deprotonated, and has stronger nucleophilicity.

[0040] S5: 20g of pyridine-modified thiosalicylic acid, 400mL of anhydrous methanol and 500L of dimethylformamide were added to the reaction kettle, stirred at 50℃ and 500r / min for 30min, then 500mL of 10% ammonia solution, 40g of ferric chloride hexahydrate and 30g of nitrogen-doped carbon microspheres were added, heated to 100℃, and the reaction was continued for 1h. Filter, wash the filter cake with deionized water and anhydrous ethanol twice, vacuum dry at 60℃ for 1h to obtain core-shell type nitrogen-doped carbon microspheres. The nitrogen atom in the pyridine group has a lone pair of electrons, which can act as a Lewis base site and form a strong chemical adsorption with the sulfur atoms (Lewis acid) in polysulfide; pyridine-modified thiosalicylic acid generates a metal skeleton structure with pyridine-modified thiosalicylic acid as the ligand under the action of ferric chloride hexahydrate. The pyridine group modified metal skeleton structure is porous, and cooperates with the porous structure of the nitrogen-doped carbon microspheres to inhibit the diffusion of polysulfide through micropore confinement and steric hindrance. Pyridine-modified thiosalicylic acid acts as a ligand to form a stable coordination bond with iron ions, preventing the dissolution and diffusion of polysulfide. This interaction can significantly reduce the solubility of polysulfide and inhibit the shuttle effect.

[0041] The reaction of sulfur and lithium to form soluble polysulfides is the main cause of capacity fading of lithium-sulfur batteries. During the charge-discharge process of lithium-sulfur batteries, polysulfide ions will undergo a process of conversion from long-chain polysulfide ions to short-chain polysulfide ions and finally to lithium sulfide. The porous structure of the low-temperature-resistant lithium battery electrode material can provide more active sites due to its high specific surface area and abundant pore structure, thereby effectively promoting the conversion of polysulfide ions. During the conversion process of polysulfide ions, the surface active sites can adsorb polysulfide ions, reduce their activation energy, and accelerate their conversion rate. The metal nodes in the metal framework can promote the breaking and recombination of polysulfide ions through charge transfer between them. The confinement effect of the porous structure can increase the collision frequency between polysulfide ions and improve their conversion efficiency.

[0042] S6: 70 g of core-shell type nitrogen-doped carbon microspheres, 40 g of sodium thiosulfate, and 800 mL of deionized water were added to a reaction kettle, stirred at 40°C and 400 r / min for 1 h, then 80 mL of 1 mol / L hydrochloric acid solution was added, and stirring was continued for 2 h. The filter cake was washed with deionized water and anhydrous ethanol until the last washing liquid was neutral, and vacuum dried at 60°C for 1 h to obtain a low-temperature-resistant lithium battery electrode material.

[0043] Sodium thiosulfate undergoes a disproportionation reaction under acidic conditions to generate elemental sulfur which is deposited on the surface of the core-shell type nitrogen-doped carbon microspheres by electrostatic adsorption to obtain a low-temperature-resistant lithium battery electrode material.

[0044] Example 2: A method for preparing a low-temperature-resistant lithium battery electrode material, comprising the following steps:

[0045] S1: 85 g of polystyrene microspheres and 225 mL of 97.5% concentrated sulfuric acid solution were added to a reaction kettle, ultrasonically dispersed for 50 min, stirred at 45°C and 450 r / min for 13 h, filtered, and the filter cake was washed with deionized water and anhydrous ethanol for 2 times respectively, and vacuum dried at 70°C for 1.5 h to obtain activated microspheres.

[0046] S2: 55 g of activated microspheres and 550 mL of deionized water were added to a reaction kettle, stirred at 22.5°C and 450 r / min for 11 min, then 50 mL of tetrabutyl titanate was added, vacuum impregnated for 1.5 h, then 550 mL of 45% glacial acetic acid solution was added, stirred at 147.5°C and 450 r / min for 1.5 h, filtered, and the filter cake was washed with deionized water and anhydrous ethanol for 2 times respectively, and vacuum dried at 70°C for 1.5 h to obtain titanium dioxide composite microspheres.

[0047] S3: 45 g of titanium dioxide composite microspheres, 35 mL of γ-aminopropyl triethoxysilane, 130 mL of anhydrous ethanol and 250 mL of deionized water were added to the reaction kettle, stirred at 67.5℃ and 450 r / min for 50 min, filtered, and the filter cake was washed with deionized water and anhydrous ethanol for 2 times respectively, and vacuum dried at 70℃ for 1.2 h to obtain modified microspheres; 55 g of modified microspheres, 150 mL of tris-hydroxymethyl aminomethane were added to the reaction kettle, stirred at 22.5℃ and 450 r / min for 25 min, then 55 mL of dopamine hydrochloride was added, and the stirring was continued for 25 h, then the product was transferred to a muffle furnace, heated to 550℃ under nitrogen atmosphere, and kept for 2.5 h, and heated to 1250℃ and kept for 1.5 h to obtain nitrogen-doped carbon microspheres.

[0048] S4: 26.5 g of 4-pyridine formyl chloride hydrochloride, 4.5 mL of triethylamine and 350 mL of dichloromethane were added to the reaction kettle, stirred at 22.5℃ and 450 r / min for 35 min, then 25 g of thiosalicylic acid was added, and the stirring was continued for 21 h, then the concentrated solution was washed with deionized water for 2 times, then transferred to ethyl acetate for recrystallization, and ground to obtain pyridine-modified thiosalicylic acid.

[0049] S5: 22.5 g of pyridine-modified thiosalicylic acid, 450 mL of anhydrous methanol and 550 mL of dimethylformamide were added to the reaction kettle, stirred at 55℃ and 550 r / min for 35 min, then 550 mL of 15% ammonia water solution, 45 g of iron chloride hexahydrate and 35 g of nitrogen-doped carbon microspheres were added, heated to 105℃, and the stirring was continued for 1.5 h, then filtered, and the filter cake was washed with deionized water and anhydrous ethanol for 2 times respectively, and vacuum dried at 70℃ for 1.5 h to obtain core-shell type nitrogen-doped carbon microspheres.

[0050] S6: 75 g of core-shell type nitrogen-doped carbon microspheres, 45 g of sodium thiosulfate and 85 mL of deionized water were added to the reaction kettle, stirred at 45℃ and 450 r / min for 1.2 h, then 85 mL of 1.3 mol / L hydrochloric acid solution was added, and the stirring was continued for 2.3 h, then filtered, and the filter cake was washed with deionized water and anhydrous ethanol until the last washing liquid was neutral, and vacuum dried at 70℃ for 1.2 h to obtain a low-temperature-resistant lithium battery pole piece material.

[0051] Example 3: A preparation method of a low-temperature-resistant lithium battery pole piece material, comprising the following steps:

[0052] S1: 90 g of polystyrene microspheres and 250 mL of a concentrated sulfuric acid solution with a mass fraction of 98% were added to a reaction kettle, ultrasonic dispersion was performed for 60 min, stirring was performed at 50°C and 500 r / min for 14 h, filtration was performed, the filter cake was washed with deionized water and anhydrous ethanol for 3 times respectively, and vacuum drying was performed at 80°C for 2 h to obtain activated microspheres.

[0053] S2: 60 g of activated microspheres and 600 mL of deionized water were added to a reaction kettle, stirring was performed at 25°C and 500 r / min for 12 min, then 60 mL of tetrabutyl titanate was added, vacuum impregnation was performed for 2 h, 600 mL of a glacial acetic acid solution with a mass fraction of 50% was added, stirring was performed at 155°C and 500 r / min for 2 h, filtration was performed, the filter cake was washed with deionized water and anhydrous ethanol for 3 times respectively, and vacuum drying was performed at 80°C for 2 h to obtain titanium dioxide composite microspheres.

[0054] S3: 50 g of titanium dioxide composite microspheres, 40 mL of γ-aminopropyl triethoxysilane, 140 mL of anhydrous ethanol and 300 mL of deionized water were added to a reaction kettle, stirring was performed at 75°C and 500 r / min for 60 min, filtration was performed, the filter cake was washed with deionized water and anhydrous ethanol for 3 times respectively, and vacuum drying was performed at 80°C for 2 h to obtain modified microspheres; 60 g of modified microspheres and 200 mL of tris-hydroxymethyl aminomethane were added to a reaction kettle, stirring was performed at 25°C and 500 r / min for 30 min, then 60 mL of dopamine hydrochloride was added, and stirring was continued for 26 h, the product was transferred to a muffle furnace, heated to 600°C under a nitrogen atmosphere, and kept for 3 h, and heated to 1300°C and kept for 2 h to obtain nitrogen-doped carbon microspheres.

[0055] S4: 28 g of 4-pyridine formyl chloride hydrochloride, 5 mL of triethylamine and 400 mL of dichloromethane were added to a reaction kettle, stirring was performed at 25°C and 500 r / min for 40 min, then 30 g of thiosalicylic acid was added, and stirring was continued for 24 h, the concentrated solution was washed with deionized water for 3 times, and then transferred to ethyl acetate for recrystallization, and grinded to obtain pyridine-modified thiosalicylic acid.

[0056] S5: 25 g of pyridine-modified thiosalicylic acid, 500 mL of anhydrous methanol and 600 mL of dimethylformamide were added to a reaction kettle, stirring was performed at 60°C and 600 r / min for 40 min, then 600 mL of a 20% ammonia water solution, 50 g of iron chloride hexahydrate and 40 g of nitrogen-doped carbon microspheres were added, heated to 110°C, and stirring was continued for 2 h, the filter cake was washed with deionized water and anhydrous ethanol for 3 times respectively, and vacuum drying was performed at 80°C for 2 h to obtain core-shell type nitrogen-doped carbon microspheres.

[0057] S6: 80 g of core-shell type nitrogen-doped carbon microspheres, 50 g of sodium thiosulfate, and 900 mL of deionized water were added to a reaction kettle, stirred at 50 °C and 500 r / min for 2 h, then 100 mL of hydrochloric acid solution with a concentration of 1.5 mol / L was added, and stirring was continued for 3 h. The filter cake was washed with deionized water and anhydrous ethanol until the last washing liquid was neutral. The filter cake was vacuum dried at 80 °C for 2 h to obtain a low-temperature-resistant lithium battery pole piece material.

[0058] Comparative Example 1: On the basis of Example 3, according to a low-temperature-resistant lithium ion battery negative electrode material and a preparation method thereof disclosed in a Chinese patent publication No. CN118270835B, the activated microspheres were added to a titanium isobutyl ester solution with a concentration of 0.2 mol / L and stirred and mixed. Hydrofluoric acid solution was slowly added dropwise, and the reaction was carried out at 160 °C for 24 h. The mixture was naturally cooled to room temperature to form sheet-shaped nanometer titanium dioxide. The remaining steps were unchanged, and a low-temperature-resistant lithium battery pole piece material was prepared.

[0059] Comparative Example 2: On the basis of Example 3, the nitrogen-doped carbon microspheres in step S5 were replaced by the titanium dioxide composite carbon microspheres in step S2, and the remaining steps were unchanged. A low-temperature-resistant lithium battery pole piece material was prepared.

[0060] Comparative Example 3: On the basis of Example 3, the pyridine-modified thio salicylic acid in step S5 was replaced by the same mass of thio salicylic acid used as a raw material in step S4, and the remaining steps were unchanged. A low-temperature-resistant lithium battery pole piece material was prepared.

[0061] The low-temperature-resistant lithium battery pole piece materials obtained in Examples 1-3 and Comparative Examples 1-3 were used to prepare lithium ion button cells, respectively, and performance tests were carried out.

[0062] The low-temperature-resistant lithium battery pole piece material, conductive agent carbon black, and binder polyvinylidene fluoride were added to N-methyl pyrrolidone in a mass ratio of 9.5:1:1, and uniformly dispersed to obtain a slurry with a solid content of 40%. The slurry was coated on a current collector copper foil, dried, and cut into a circular electrode piece to obtain a negative electrode. The loading amount of the negative electrode active material on the negative electrode was controlled to be 2 mg·cm -1 Then, lithium sheet was used as the positive electrode; the electrolyte was 1 mol / L lithium hexafluorophosphate solution, and the solvent was a mixture of dimethyl carbonate, diethyl carbonate, and methyl ethyl carbonate in a volume ratio of 1:1:1; the separator was Celgard 2400 polypropylene. The lithium ion button cell was assembled in an argon glove box, and the results are shown in Table 1:

[0063] Table 1: Performance test results of lithium ion button cells

[0064]

[0065] As can be seen from Table 1, the low-temperature-resistant lithium battery pole piece materials obtained in Examples 1-3 are prepared into lithium batteries, and the first discharge capacity, the first coulomb efficiency and the 100-cycle capacity are all significantly better than those of the comparative examples, and the percentage change in volume is significantly lower than that of the comparative examples, indicating that the low-temperature-resistant lithium battery pole piece material prepared by the present application can significantly alleviate the volume expansion of the lithium battery during the charging and discharging process, can accommodate more lithium ions for intercalation and deintercalation, reduce the shuttle effect of sulfides, and increase the cycle capacity, the first discharge capacity and the first coulomb efficiency of the lithium battery.

[0066] In Comparative Example 1, the sheet-shaped nano-titanium dioxide has crack-type pores formed by stacking of sheets, which can avoid structural collapse by absorbing transverse expansion stress, and the volume expansion of sulfur during the charging and discharging process will cause the sheet-shaped nano-titanium dioxide to disperse stress by interfacial sliding, which will cause the carbon coating layer and the sheet-shaped material to gradually peel off, thereby reducing the overall efficiency and service life of the battery.

[0067] In Comparative Example 2, the nitrogen-doped carbon microspheres are replaced by titanium dioxide composite carbon microspheres, and the additional lone pair electrons in nitrogen atoms can increase the electrical conductivity of the nitrogen-doped electrode material, which is beneficial to the transmission of electrons and can significantly improve the wettability of the carbon material. This is because the nitrogen-containing functional group has hydrophilicity, which is beneficial to the direct contact of electrolyte ions with the electrode.

[0068] In Comparative Example 3, the pyridine-modified thiosalicylic acid is replaced by thiosalicylic acid, and the nitrogen atom in the pyridine group has a lone pair of electrons, which can form a strong chemical adsorption with the sulfur atom in polysulfide as a Lewis base. The pyridine-modified thiosalicylic acid generates a metal skeleton structure with pyridine-modified thiosalicylic acid as a ligand under the action of ferric chloride hexahydrate. The metal skeleton structure modified by the pyridine group is porous on the surface, and cooperates with the porous structure of the nitrogen-doped carbon microspheres to inhibit the diffusion of polysulfide through micropore confinement and steric hindrance.

[0069] It should be noted that in this document, terms such as "comprise", "include" or any other variant thereof are intended to cover non-exclusive inclusion, so that processes, methods, articles or devices including a series of elements not only include those elements, but also include other elements not explicitly listed or inherent to such processes, methods, articles or devices.

[0070] Although the embodiments of the present application have been shown and described, it will be understood by those of ordinary skill in the art that various changes, modifications, substitutions and alterations can be made to the embodiments without departing from the principles and spirit of the present application.

Claims

1. A method for preparing a low-temperature resistant lithium battery electrode material, characterized in that, Includes the following steps: Step 1: Add pyridine-modified thiosalicylic acid, anhydrous methanol and dimethylformamide to a reaction vessel, stir at 50-60℃ and 500-600 r / min for 30-40 min, then add 10-20 wt% ammonia solution, ferric chloride hexahydrate and nitrogen-doped carbon microspheres, heat to 100-110℃, continue stirring for 1-2 h, filter, wash, and vacuum dry to obtain core-shell nitrogen-doped carbon microspheres; Step 2: Add core-shell nitrogen-doped carbon microspheres, sodium thiosulfate and deionized water to a reaction vessel, heat at 40-50℃ and 400-500 r / min for 1-2 h, then add hydrochloric acid solution with a concentration of 1-1.5 mol / L, continue stirring for 2-3 h, filter, wash, and vacuum dry to obtain a low-temperature resistant lithium battery electrode material. The nitrogen-doped carbon microspheres described in step one are prepared through the following steps: Modified microspheres and tris(hydroxymethyl)aminomethane were added to a reaction vessel and stirred for 20-30 min at 20-25℃ and 400-500 r / min. Then, dopamine hydrochloride was added and stirring was continued for 24-26 h. The product was transferred to a muffle furnace and heated to 500-600℃ under a nitrogen atmosphere for 2-3 h. Then, it was heated to 1200-1300℃ and held for 1-2 h to obtain nitrogen-doped carbon microspheres. The ratio of the modified microspheres, tris(hydroxymethyl)aminomethane, and dopamine hydrochloride is 50-60g: 100-200mL: 50-60mL. The modified microspheres are prepared through the following steps: Titanium dioxide composite microspheres, γ-aminopropyltriethoxysilane, anhydrous ethanol and deionized water were added to a reaction vessel and stirred at 60-75℃ and 400-500 r / min for 40-60 min. The mixture was then filtered, washed, and vacuum dried to obtain the modified microspheres. The ratio of titanium dioxide composite microspheres, γ-aminopropyltriethoxysilane, anhydrous ethanol and deionized water is 40-50g: 30-40mL: 120-140mL: 200-300mL. The pyridine-modified thiosalicylic acid described in step one is prepared through the following steps: 4-Pyridinecarboxyl chloride hydrochloride, triethylamine and dichloromethane were added to a reaction vessel and stirred at 20-25℃ and 400-500 r / min for 30-40 min. Thiosalic acid was then added and the reaction was continued to be stirred for 18-24 h. The mixture was concentrated and washed 2-3 times with deionized water. Then it was transferred to ethyl acetate for recrystallization and ground to obtain pyridine-modified thiosalic acid. The titanium dioxide composite microspheres were prepared through the following steps: Activated microspheres and deionized water were added to a reaction vessel and stirred at 20-25℃ and 400-500 r / min for 10-12 min. Then tetrabutyl titanate was added and the mixture was vacuum impregnated for 1-2 h. Next, 40-50 wt% glacial acetic acid solution was added and stirred at 140-155℃ and 400-500 r / min for 1-2 h. The mixture was then filtered, washed, and vacuum dried to obtain titanium dioxide composite carbon microspheres. The ratio of activated microspheres, deionized water, tetrabutyl titanate, and glacial acetic acid solution is 50-60g: 500-600mL: 40-60mL: 500-600mL.

2. The method for preparing a low-temperature resistant lithium battery electrode material according to claim 1, characterized in that, In step one, the ratio of pyridine-modified thiosalicylic acid, anhydrous methanol, dimethylformamide, ammonia solution, ferric chloride hexahydrate, and nitrogen-doped carbon microspheres is 20-25g: 400-500mL: 500-600mL: 500-600mL: 40-50g: 30-40g.

3. The method for preparing a low-temperature resistant lithium battery electrode material according to claim 1, characterized in that, In step two, the ratio of the amount of core-shell nitrogen-doped carbon microspheres, sodium thiosulfate, deionized water and hydrochloric acid solution used is 70-80g: 40-50g: 800-900mL: 80-100mL.

4. The method for preparing a low-temperature resistant lithium battery electrode material according to claim 1, characterized in that, The ratio of 4-pyridinecarboxyl chloride hydrochloride, triethylamine, dichloromethane, and thiosalicylic acid is 25-28g: 4-5mL: 300-400mL: 20-30g.

5. The method for preparing a low-temperature resistant lithium battery electrode material according to claim 1, characterized in that, The activated microspheres are prepared through the following steps: Polystyrene microspheres and 97-98 wt% concentrated sulfuric acid solution were added to a reaction vessel at a ratio of 80-90 g: 200-250 mL. The mixture was ultrasonically dispersed for 40-60 min, stirred at 40-50 °C and 400-500 r / min for 12-14 h, filtered, washed, and vacuum dried to obtain activated microspheres.

6. A low-temperature resistant lithium battery electrode material, characterized in that, It is prepared by the preparation method described in any one of claims 1-5.

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