Modified carbon nanotube composite carbon material and preparation method thereof

Abstract

The application belongs to the technical field of battery negative electrode materials, and discloses a modified carbon nanotube composite carbon material and a preparation method thereof, the preparation method comprising the following steps: adding pretreated wood carbon powder into an aqueous solution of oxidized sodium hyaluronate, reacting at room temperature to obtain a precursor; pretreating carbon nanotubes, adding the pretreated carbon nanotubes into a mixed solution of ethanol and water, adding a silane coupling agent, and heating to react to obtain silane coupling agent modified carbon nanotubes; adding the silane coupling agent modified carbon nanotubes into an aqueous solution of zinc sulfate and cobalt sulfate, adding a catalyst and a reducing agent, and heating to react to obtain modified carbon nanotubes; uniformly mixing the precursor and the modified carbon nanotubes, and pyrolyzing under the protection of inert gas to obtain the modified carbon nanotube composite carbon material. When the material is applied to a sodium ion battery negative electrode, the material exhibits high specific capacity, high coulomb efficiency, excellent rate performance and good cycle stability, and has important application prospects.

Description

Technical Field

[0001] This invention belongs to the field of battery anode material technology, and particularly relates to a modified carbon nanotube composite carbon material and its preparation method. Background Technology

[0002] Sodium-ion batteries, as an emerging electrochemical energy storage technology, have received widespread attention from academia and industry in recent years. Compared with lithium-ion batteries, sodium resources are abundant, widely distributed, and inexpensive in the Earth's crust. Furthermore, sodium-ion batteries possess advantages such as good safety performance and stability, demonstrating enormous development potential in applications such as low-speed electric vehicles, large-scale energy storage power stations, and smart grids. Therefore, developing high-performance, low-cost sodium-ion battery electrode materials has become a current research hotspot in the energy storage field.

[0003] The anode material is one of the key factors determining the electrochemical performance of sodium-ion batteries. The main precursors of hard carbon include coal, resin, and biomass. Biomass resources are abundant in nature, and utilizing these inexpensive and readily available biomass wastes to prepare composite carbon materials not only achieves high-value utilization of resources but also helps reduce the manufacturing cost of sodium-ion batteries, aligning with the strategic requirements of green and sustainable development. However, biomass itself has a complex composition, containing a large number of heteroatoms such as nitrogen and oxygen. During high-temperature carbonization, these heteroatoms cause the microstructure of the derived hard carbon to tend towards disorder, forming numerous defects and pores. This leads to poor rate performance and reduced coulombic efficiency of the electrode material, limiting the improvement of battery energy density and failing to meet the application requirements of high-power scenarios.

[0004] To address the performance defects of biomass-derived hard carbon, existing technologies often employ modification methods such as doping and composites. Among these, carbon nanotubes, due to their excellent conductivity and flexible framework structure, have become a commonly used composite modification material. However, traditional carbon nanotubes are prone to aggregation, resulting in weak interfacial bonding with biomass-derived hard carbon. This leads to insufficient structural stability of the composite material and limited improvement in electrode rate performance and cycle stability. Summary of the Invention

[0005] To overcome the shortcomings of the prior art, the primary objective of this invention is to provide a method for preparing modified carbon nanotube composite carbon materials.

[0006] Another objective of this invention is to provide a modified carbon nanotube composite carbon material.

[0007] The objective of this invention is achieved through the following technical solution: A method for preparing a modified carbon nanotube composite carbon material includes the following steps: (1) Add wood charcoal powder to Tris-dopamine hydrochloride solution and heat to react to obtain pretreated wood charcoal powder; (2) The pretreated wood charcoal powder is added to an aqueous solution of sodium hyaluronate and reacted at room temperature to obtain the precursor; (3) After pretreatment, carbon nanotubes are added to a mixed solution of ethanol and water, then silane coupling agent is added, and the reaction is heated to obtain carbon nanotubes modified with silane coupling agent. (4) The carbon nanotubes modified by the silane coupling agent are added to an aqueous solution of zinc sulfate and cobalt sulfate, and then a catalyst and a reducing agent are added. After heating and reacting, modified carbon nanotubes are obtained. (5) The pretreatment and modified carbon nanotubes are mixed evenly and pyrolyzed under inert gas protection to obtain modified carbon nanotube composite carbon material.

[0008] Further, in step (1), the ratio of wood charcoal powder to Tris-dopamine hydrochloride solution is 1-3g:10mL; the concentration of dopamine hydrochloride in the Tris-dopamine hydrochloride solution is 1-2g / L; the reaction temperature is 40-50℃ and the time is 8-10h.

[0009] Further, in step (2), the mass ratio of pretreated wood charcoal powder to sodium oxidized hyaluronic acid is 1:(0.2-0.5), the concentration of sodium oxidized hyaluronic acid in the aqueous solution of sodium oxidized hyaluronic acid is 2wt%, and the reaction time at room temperature is 8-10h.

[0010] Further, in step (3), the concentration of carbon nanotubes in the mixed solution after pretreatment is 1 g / L; the concentration of the silane coupling agent in the mixed solution is 0.5-2 wt%; the volume ratio of ethanol to water is 95:5; the pH of the mixed solution is 3-4; the silane coupling agent is KH550; the temperature of the heating reaction is 75-85℃, and the time is 2-4 h.

[0011] Further, in step (4), the mass ratio of the silane coupling agent-modified carbon nanotubes, zinc sulfate, cobalt sulfate, catalyst, and reducing agent is 50:5:(2-3):(0.5-1):(2.5-4), the concentration of zinc sulfate in the aqueous solution of zinc sulfate and cobalt sulfate is 5wt%, the catalyst is triethylamine, the reducing agent is sodium thiosulfate, and the heating reaction temperature is 80-90℃ for 1-3h.

[0012] Further, in step (5), the mass ratio of the precursor to the modified carbon nanotube is 1:(0.03-0.05); the pyrolysis temperature is 1000-1500℃ and the time is 5-10h.

[0013] Further, the preparation process of the wood charcoal powder in step (1) is as follows: the wood biomass precursor is cleaned, dried, crushed and then carbonized in an inert atmosphere. The carbonized product is ground, sieved and purified to obtain wood charcoal powder.

[0014] Further, the preparation process of sodium oxidized hyaluronic acid in step (2) is as follows: sodium periodate is added to the sodium hyaluronic acid solution, and the reaction is carried out for 2-3 hours in the dark. Ethanol is added to terminate the reaction, and deionized water is used for dialysis purification to obtain sodium oxidized hyaluronic acid. The carbon nanotube pretreatment process in step (3) is as follows: carbon nanotubes are added to concentrated nitric acid and heated at 80-90℃ for 3-5 hours. After the reaction is completed, the carbon nanotubes are filtered, washed, and dried to obtain pretreated carbon nanotubes.

[0015] Further, in step (2), the molar ratio of repeating disaccharide units and sodium periodate in sodium hyaluronate is 1:(0.5-1), and the concentration of sodium hyaluronate solution is 1-2.5 g / L; in step (3), the mass ratio of carbon nanotubes and concentrated nitric acid is 1:(60-70).

[0016] A modified carbon nanotube composite carbon material is prepared using the method described above.

[0017] The present invention has the following advantages over the prior art: 1. This invention provides a modified carbon nanotube composite carbon material. The invention first pre-treats the carbon nanotubes with acidification to introduce active groups onto the surface of the tube wall. Then, it modifies the material with an amino-containing silane coupling agent. Through coordination between the amino groups and zinc and cobalt ions, the bimetallic ions are uniformly anchored and dispersed on the surface of the carbon nanotube framework, effectively inhibiting metal ion aggregation and local enrichment. Using sodium thiosulfate as a sulfur source and reducing agent, a Zn-Co bimetallic sulfide heterojunction nano-active layer is constructed in situ on the surface of the carbon nanotubes, tightly loaded onto the carbon nanotube conductive network. When this modified carbon nanotube and carbon material are combined for use as the anode of a sodium-ion battery, the Zn-Co bimetallic sulfide, through the synergistic effect of multiple metals and the regulation of the heterojunction interface, optimizes the band structure, reduces the energy barrier of sodium ion intercalation / deintercalation reactions, and significantly improves the electrode energy density and rate performance. The carbon nanotubes construct a continuous conductive network, improving electrode conductivity. Simultaneously, the flexible tubular framework effectively buffers the volume expansion of the bimetallic sulfide during charging and discharging, inhibiting the pulverization and shedding of the active material. KH550 covalent grafting and amino coordination anchoring enhance the interfacial bonding between sulfides and carbon nanotubes, alleviate the polysulfide dissolution and shuttle problem during charge and discharge, and improve the electrode cycle stability.

[0018] 2. This invention utilizes the autonomous oxidative polymerization of dopamine in a weakly alkaline environment to form a uniform and dense polydopamine coating layer in situ on the surface of wood charcoal powder, thereby introducing active functional groups such as amino and hydroxyl groups onto the surface of the carbon material. Then, the active groups such as aldehyde groups on the molecular chain of oxidized sodium hyaluronate react with the amino groups in the polydopamine layer to form a Schiff base reaction, grafting a polymer interface layer rich in oxygen functional groups onto the surface of the wood charcoal. This alleviates the volume deformation during charging and discharging, while enhancing the interfacial bonding strength with the modified carbon nanotubes and improving the overall structural stability of the composite material.

[0019] Furthermore, the polydopamine formed in situ on the surface of the wood charcoal powder of this invention is pyrolyzed with sodium oxyhyaluronate to transform into a nitrogen-oxygen co-doped porous carbon structure. Zinc-cobalt sulfide is stably anchored at the interface between the carbon matrix and carbon nanotubes, ultimately forming a modified carbon nanotube composite carbon material with a three-dimensional continuous conductive network. This material has high specific capacity and coulombic efficiency. When applied to sodium-ion batteries, it can improve the rate performance of sodium-ion batteries, exhibit good cycle stability, and extend their service life. Attached Figure Description

[0020] Figure 1 This is an electron microscope image of the modified carbon nanotubes obtained in Example 1 of the present invention. Detailed Implementation

[0021] The present invention will be further described in detail below with reference to embodiments, but the implementation of the present invention is not limited thereto. Unless otherwise specified, the reagents, methods, and equipment used in the present invention are conventional reagents, methods, and equipment in this technical field. Test methods in the following embodiments that do not specify specific experimental conditions are generally performed according to conventional experimental conditions or experimental conditions recommended by the manufacturer. Unless otherwise specified, the reagents and raw materials used in the present invention are commercially available.

[0022] Example Example 1 A method for preparing a modified carbon nanotube composite carbon material includes the following steps: (1) Wash and dry the wood biomass precursors such as tree trunks and leaves, crush them, place them in a nitrogen atmosphere, carbonize them at 600℃ for 2 hours, cool them naturally to room temperature, grind them into powder, pass them through a 325-mesh sieve, and collect the sieve residue; put the sieve residue and ammonium bifluoride powder into a reaction vessel at a mass ratio of 10:1, add water to cover the mixed solids until the liquid level is 1 cm higher than the mixed solids, mix and stir to form a slurry, then add a 6wt% hydrochloric acid solution (the mass of the hydrochloric acid solution is 18% of the mixed solids), stir evenly, soak and stir at 80℃ for 16 hours; filter, rinse with pure water, vacuum filter until the TDS tester can measure the washings. The TDS of the washing water was less than 10 mg / L, and then dried at 120℃ for 6 h to obtain wood charcoal powder. Dopamine hydrochloride was added to Tris buffer and stirred to dissolve to obtain Tris-dopamine hydrochloride solution with a concentration of 1.5 g / L. Wood charcoal powder was added to the Tris-dopamine hydrochloride solution at a ratio of 2 g:10 mL. The pH was adjusted to 8.5, and then the reaction was carried out at 45℃ for 9 h. After the reaction was completed, the mixture was filtered, washed, and dried to obtain pretreated wood charcoal powder. (2) Sodium hyaluronate (molecular weight 1200kDa) was added to water to prepare a sodium hyaluronate solution with a concentration of 2g / L. Sodium periodate was added to the sodium hyaluronate solution, wherein the molar ratio of the repeating disaccharide unit in sodium hyaluronate to sodium periodate was 1:0.8. The reaction was carried out under light-protected conditions for 2.5h. Ethanol was added to terminate the reaction. The product was purified by dialysis with deionized water to obtain oxidized sodium hyaluronate. The pretreated wood charcoal powder described in step (1) was added to an aqueous solution of oxidized sodium hyaluronate with a concentration of 2wt%. The mass ratio of the pretreated wood charcoal powder to oxidized sodium hyaluronate was 1:0.3. The product was reacted at room temperature for 9h. After the reaction was completed, the product was purified to obtain the precursor. (3) Carbon nanotubes were added to concentrated nitric acid with a concentration of 68 wt%, wherein the mass ratio of carbon nanotubes to concentrated nitric acid was 1:65, and then heated at 85°C for 4 h. After the reaction was completed, the carbon nanotubes were filtered, washed and dried to obtain pretreated carbon nanotubes. The pretreated carbon nanotubes were added to a mixed solution of ethanol and water (volume ratio of ethanol to water was 95:5), and the pH was adjusted to 3.5. The concentration of pretreated carbon nanotubes in the mixed solution was 1 g / L. KH550 was then added, wherein the concentration of KH550 in the mixed solution was 1 wt%. The mixture was then heated at 80°C for 3 h and dried to obtain carbon nanotubes modified with silane coupling agent. (4) The silane coupling agent-modified carbon nanotubes from step (3) were added to an aqueous solution of zinc sulfate and cobalt sulfate, followed by the addition of a catalyst (triethylamine) and a reducing agent (sodium thiosulfate). The mass ratio of the silane coupling agent-modified carbon nanotubes, zinc sulfate, cobalt sulfate, triethylamine, and sodium thiosulfate was 50:5:2.5:0.8:3, and the concentration of zinc sulfate in the aqueous solution of zinc sulfate and cobalt sulfate was 5 wt%. After heating the reaction at 85°C for 2 hours, the reactants were filtered, washed, and dried to obtain modified carbon nanotubes. The electron micrograph of the modified carbon nanotubes is shown below. Figure 1 As shown.

[0023] (5) The pretreatment and modified carbon nanotubes are mixed evenly at a mass ratio of 1:0.04, and pyrolyzed at 1350℃ for 8 hours under a nitrogen atmosphere at a rate of 10℃ / min. The mixture is then cooled, ground and dispersed to obtain the modified carbon nanotube composite carbon material.

[0024] Example 2 A method for preparing a modified carbon nanotube composite carbon material includes the following steps: (1) Add dopamine hydrochloride to Tris buffer and stir to dissolve to obtain Tris-dopamine hydrochloride solution. The concentration of dopamine hydrochloride in Tris-dopamine hydrochloride solution is 1 g / L. Take wood charcoal powder (preparation method is the same as in Example 1) and add it to Tris-dopamine hydrochloride solution. The ratio of wood charcoal powder to Tris-dopamine hydrochloride solution is 1 g: 10 mL. Adjust the pH to 8.5 and then react at 40℃ for 10 h. After the reaction is completed, filter, wash and dry to obtain pretreated wood charcoal powder. (2) Sodium hyaluronate (molecular weight 1200kDa) was added to water to prepare a sodium hyaluronate solution with a concentration of 1g / L. Sodium periodate was added to the sodium hyaluronate solution, wherein the molar ratio of the repeating disaccharide unit in sodium hyaluronate to sodium periodate was 1:0.5. The reaction was carried out for 3 hours under light-protected conditions. Ethanol was added to terminate the reaction. The product was purified by dialysis with deionized water to obtain sodium oxidized hyaluronate. The pretreated wood charcoal powder described in step (1) was added to an aqueous solution of sodium oxidized hyaluronate with a concentration of 2wt%. The mass ratio of the pretreated wood charcoal powder to sodium oxidized hyaluronate was 1:0.2. The product was reacted at room temperature for 10 hours. After the reaction was completed, the product was purified to obtain the precursor. (3) Carbon nanotubes were added to concentrated nitric acid with a concentration of 68 wt%, wherein the mass ratio of carbon nanotubes to concentrated nitric acid was 1:60, and then heated at 80°C for 5 h. After the reaction was completed, the carbon nanotubes were filtered, washed and dried to obtain pretreated carbon nanotubes. The pretreated carbon nanotubes were added to a mixed solution of ethanol and water (volume ratio of ethanol to water was 95:5), and the pH was adjusted to 3. The concentration of pretreated carbon nanotubes in the mixed solution was 1 g / L. KH550 was then added, wherein the concentration of KH550 in the mixed solution was 0.5 wt%. The mixture was then heated at 75°C for 4 h and dried to obtain carbon nanotubes modified with silane coupling agent. (4) The carbon nanotubes modified with silane coupling agent in step (3) are added to an aqueous solution of zinc sulfate and cobalt sulfate, and then a catalyst (triethylamine) and a reducing agent (sodium thiosulfate) are added. The mass ratio of the carbon nanotubes modified with silane coupling agent, zinc sulfate, cobalt sulfate, triethylamine and sodium thiosulfate is 50:5:2:0.5:2.5, and the concentration of zinc sulfate in the aqueous solution of zinc sulfate and cobalt sulfate is 5wt%. After heating the reaction at 80°C for 3 hours, the reactants are filtered, washed and dried to obtain modified carbon nanotubes. (5) The pretreatment and modified carbon nanotubes are mixed evenly at a mass ratio of 1:0.03, and pyrolyzed at 1000℃ for 10h under a nitrogen atmosphere by heating at 10℃ / min. After cooling and grinding, the modified carbon nanotube composite carbon material is obtained.

[0025] Example 3 A method for preparing a modified carbon nanotube composite carbon material includes the following steps: (1) Add dopamine hydrochloride to Tris buffer and stir to dissolve to obtain Tris-dopamine hydrochloride solution. The concentration of dopamine hydrochloride in Tris-dopamine hydrochloride solution is 2 g / L. Take wood charcoal powder (preparation method is the same as in Example 1) and add it to Tris-dopamine hydrochloride solution. The ratio of wood charcoal powder to Tris-dopamine hydrochloride solution is 3 g: 10 mL. Adjust the pH to 8.5 and then react at 50 °C for 8 h. After the reaction is completed, filter, wash and dry to obtain pretreated wood charcoal powder. (2) Sodium hyaluronate (molecular weight 1200kDa) was added to water to prepare a sodium hyaluronate solution with a concentration of 2.5g / L. Sodium periodate was added to the sodium hyaluronate solution, wherein the molar ratio of the repeating disaccharide unit in sodium hyaluronate to sodium periodate was 1:1. The reaction was carried out for 2 hours under light-protected conditions. Ethanol was added to terminate the reaction. The product was purified by dialysis with deionized water to obtain sodium oxidized hyaluronate. The pretreated wood charcoal powder described in step (1) was added to an aqueous solution of sodium oxidized hyaluronate with a concentration of 2wt%. The mass ratio of the pretreated wood charcoal powder to sodium oxidized hyaluronate was 1:0.5. The product was reacted at room temperature for 10 hours. After the reaction was completed, the product was purified to obtain the precursor. (3) Carbon nanotubes were added to concentrated nitric acid with a concentration of 68 wt%, wherein the mass ratio of carbon nanotubes to concentrated nitric acid was 1:70, and then heated at 90°C for 3 h. After the reaction was completed, the carbon nanotubes were filtered, washed and dried to obtain pretreated carbon nanotubes. The pretreated carbon nanotubes were added to a mixed solution of ethanol and water (volume ratio of ethanol to water was 95:5), and the pH was adjusted to 4. The concentration of pretreated carbon nanotubes in the mixed solution was 1 g / L. KH550 was then added, wherein the concentration of KH550 in the mixed solution was 2 wt%. The mixture was then heated at 85°C for 2 h and dried to obtain carbon nanotubes modified with silane coupling agent. (4) The carbon nanotubes modified with silane coupling agent in step (3) are added to an aqueous solution of zinc sulfate and cobalt sulfate, and then a catalyst (triethylamine) and a reducing agent (sodium thiosulfate) are added. The mass ratio of the carbon nanotubes modified with silane coupling agent, zinc sulfate, cobalt sulfate, triethylamine and sodium thiosulfate is 50:5:3:1:4, and the concentration of zinc sulfate in the aqueous solution of zinc sulfate and cobalt sulfate is 5wt%. After heating the reaction at 90°C for 1 hour, the reactants are filtered, washed and dried to obtain modified carbon nanotubes. (5) The pretreatment and modified carbon nanotubes are mixed evenly at a mass ratio of 1:0.05, and pyrolyzed at 1500℃ for 5 hours under a nitrogen atmosphere at a temperature of 10℃ / min. The mixture is then cooled, ground and dispersed to obtain the modified carbon nanotube composite carbon material.

[0026] Comparative Example Comparative Example 1 The difference between Comparative Example 1 and Example 1 is that the pre-substrate in step (5) is replaced with pretreated wood charcoal powder; otherwise, it remains the same as Example 1.

[0027] Comparative Example 2 The difference between Comparative Example 2 and Example 1 is that the modified carbon nanotubes in step (5) are replaced with carbon nanotubes; otherwise, they are the same as in Example 1.

[0028] Comparative Example 3 The difference between Comparative Example 3 and Example 1 is as follows: Step (5) of this comparative example is: steps (3) and (4) are omitted. The pretreatment is added to an aqueous solution of zinc sulfate and cobalt sulfate. The amount of zinc sulfate and cobalt sulfate is the same as in Example 1. Then, the mixture is stirred at 100°C for 15 hours. The pretreatment is filtered under reduced pressure, washed, and dried to obtain the treated pretreatment. Carbon nanotubes are then added and mixed evenly. The mass ratio of the treated pretreatment to carbon nanotubes is 1:0.04. The mixture is pyrolyzed at 1500°C for 5 hours under a nitrogen atmosphere at a rate of 10°C / min. After cooling and grinding, the modified carbon nanotube composite carbon material is obtained. Everything else is the same as in Example 1.

[0029] Experimental Example 1 The modified carbon nanotube composite carbon materials obtained in Examples 1-3 and Comparative Examples 1-3 of this invention were used as the negative electrode materials for sodium-ion batteries. Specifically, the modified carbon nanotube composite carbon material, SuperP, SBR, and CMC were weighed in a weight ratio of 90:5:3:2, and a small amount of pure water was added. The mixture was then ground until the slurry had no obvious particle texture. The slurry was then coated onto copper foil, pre-dried at 75°C for 40 minutes, and then dried in a vacuum drying oven at 120°C for 6 hours. The slurry was then compacted and stamped into a disc with a diameter of 10 mm, which served as the negative electrode of the sodium-ion button battery. A sodium sheet was used as the counter electrode, and Waterman glass fiber was used as the separator. The electrolyte consisted of 1M NaClO4 as the electrolyte, ethylene carbonate and dimethyl carbonate in a volume ratio of 1:1 as the electrolyte, and 1% fluoroethylene carbonate was added. The assembly was carried out in an inert atmosphere glove box to obtain the sodium-ion button battery. After the assembled sodium-ion button batteries were left to stand for 4 hours, performance tests were conducted using a battery tester. The initial charge-discharge test voltage was 0-1.5V, and the rate was 0.1C. The initial discharge specific capacity, initial charge specific capacity, and initial coulombic efficiency of each group of button batteries at 0.1C rate were recorded. Simultaneously, the capacity retention rate of the sodium-ion button batteries after 500 charge-discharge cycles was calculated: Capacity retention rate = (Specific capacity after 500 cycles / Initial charge specific capacity) × 100%.

[0030] Charge-discharge tests were conducted at 3C and 0.5C rates, and the discharge specific capacity was recorded. The rate performance was calculated using the following formula: Rate performance (%) = (3C discharge specific capacity / 0.5C discharge specific capacity) × 100%. The results are shown in Table 1.

[0031] Table 1 As shown in Table 1, the modified carbon nanotube composite carbon materials prepared in Examples 1-3 of this invention exhibit significantly better electrochemical performance than comparative examples 1-3 when used as anode materials for sodium-ion batteries. They can effectively improve the specific capacity, coulombic efficiency, rate performance, and electrode cycle stability of sodium-ion batteries.

[0032] Comparative Example 1 replaced the pretreatment material with pretreated wood-based charcoal powder; its initial discharge specific capacity, coulombic efficiency, capacity retention after 500 cycles, and rate performance were all lower than those of Example 1. This indicates that the polydopamine coating layer and sodium oxyhyaluronate graft layer on the surface of the wood-based charcoal powder are crucial for improving specific capacity, mitigating volume deformation during charge and discharge, and enhancing the interfacial bonding strength with modified carbon nanotubes. The absence of this interfacial layer leads to increased electrode side reactions and decreased overall structural stability.

[0033] Comparative Example 2, where the modified carbon nanotubes were replaced with unmodified original carbon nanotubes, showed lower initial discharge specific capacity, coulombic efficiency, capacity retention after 500 cycles, and rate performance compared to Example 1. This indicates that ordinary carbon nanotubes without KH550 covalent grafting and Zn-Co bimetallic sulfide heterojunction loading cannot provide metal synergy and heterojunction interface modulation, resulting in a high sodium ion intercalation / deintercalation barrier and a significant decrease in electrode energy density and rate performance. Furthermore, the modified carbon nanotubes also struggle to achieve strong interfacial bonding with the carbon matrix, preventing the construction of a continuous conductive network and leading to poorer electrode conductivity and cycling stability.

[0034] Comparative Example 3 used pristine carbon nanotubes and directly mixed aqueous solutions of zinc sulfate and cobalt sulfate with the pretreatment, rather than anchoring them to the carbon nanotube surface; its performance was lower than that of Example 1. This comparative example shows that without coordination of amino groups on the carbon nanotube surface, bimetallic ions easily aggregate and accumulate locally, and cannot effectively form a Zn-Co bimetallic sulfide heterostructure nano-active layer. The material experiences severe volume expansion and easy shedding of active material during charge and discharge, and the lack of a conductive network results in low capacity, poor coulombic efficiency, and rapid cycle decay.

[0035] In summary, the polydopamine formed in situ on the surface of the wood charcoal powder of this invention is pyrolyzed with sodium oxyhyaluronate to transform into a nitrogen-oxygen co-doped porous carbon structure. Zinc-cobalt sulfide is stably anchored at the interface between the carbon matrix and carbon nanotubes, ultimately forming a modified carbon nanotube composite carbon material with a three-dimensional continuous conductive network. This material has high specific capacity and coulombic efficiency. When applied to sodium-ion batteries, it can improve the rate performance of sodium-ion batteries, exhibit good cycle stability, and extend their service life.

[0036] The above embodiments are merely preferred embodiments of the present invention and should not be construed as limiting the scope of protection of the present invention. Any non-substantial changes and substitutions made by those skilled in the art based on the present invention shall fall within the scope of protection claimed by the present invention.

Claims

1. A method for preparing a modified carbon nanotube composite carbon material, characterized in that, Includes the following steps: (1) Add wood charcoal powder to Tris-dopamine hydrochloride solution and heat to react to obtain pretreated wood charcoal powder; (2) The pretreated wood charcoal powder is added to an aqueous solution of sodium hyaluronate and reacted at room temperature to obtain the precursor; (3) After pretreatment, carbon nanotubes are added to a mixed solution of ethanol and water, then silane coupling agent is added, and the reaction is heated to obtain carbon nanotubes modified with silane coupling agent. (4) The carbon nanotubes modified by the silane coupling agent are added to an aqueous solution of zinc sulfate and cobalt sulfate, and then a catalyst and a reducing agent are added. After heating and reacting, modified carbon nanotubes are obtained. (5) The pretreatment and modified carbon nanotubes are mixed evenly and pyrolyzed under inert gas protection to obtain modified carbon nanotube composite carbon material.

2. The method for preparing a modified carbon nanotube composite carbon material according to claim 1, characterized in that, In step (1), the ratio of wood charcoal powder to Tris-dopamine hydrochloride solution is 1-3g:10mL; the concentration of dopamine hydrochloride in the Tris-dopamine hydrochloride solution is 1-2g / L; the reaction temperature is 40-50℃ and the reaction time is 8-10h.

3. The method for preparing a modified carbon nanotube composite carbon material according to claim 1, characterized in that, In step (2), the mass ratio of pretreated wood charcoal powder to sodium oxidized hyaluronic acid is 1:(0.2-0.5), and the concentration of sodium oxidized hyaluronic acid in the aqueous solution of sodium oxidized hyaluronic acid is 2wt%; the reaction time at room temperature is 8-10h.

4. The method for preparing a modified carbon nanotube composite carbon material according to claim 1, characterized in that, In step (3), the concentration of carbon nanotubes in the mixed solution after pretreatment is 1 g / L; the concentration of the silane coupling agent in the mixed solution is 0.5-2 wt%; the volume ratio of ethanol to water is 95:5; the pH of the mixed solution is 3-4; the silane coupling agent is KH550; the temperature of the heating reaction is 75-85℃, and the time is 2-4 h.

5. The method for preparing a modified carbon nanotube composite carbon material according to claim 1, characterized in that, In step (4), the mass ratio of the silane coupling agent-modified carbon nanotubes, zinc sulfate, cobalt sulfate, catalyst, and reducing agent is 50:5:(2-3):(0.5-1):(2.5-4), the concentration of zinc sulfate in the aqueous solution of zinc sulfate and cobalt sulfate is 5wt%, the catalyst is triethylamine, the reducing agent is sodium thiosulfate, and the heating reaction temperature is 80-90℃ for 1-3h.

6. The method for preparing a modified carbon nanotube composite carbon material according to claim 1, characterized in that, In step (5), the mass ratio of the precursor to the modified carbon nanotubes is 1:(0.03-0.05); the pyrolysis temperature is 1000-1500℃ and the time is 5-10h.

7. The method for preparing a modified carbon nanotube composite carbon material according to claim 1, characterized in that, The preparation process of the wood charcoal powder in step (1) is as follows: the wood biomass precursor is cleaned, dried, crushed and then carbonized in an inert atmosphere. The carbonized product is ground, sieved and purified to obtain wood charcoal powder.

8. The method for preparing a modified carbon nanotube composite carbon material according to claim 1, characterized in that, The preparation process of sodium oxidized hyaluronic acid in step (2) is as follows: sodium periodate is added to the sodium hyaluronic acid solution, and the reaction is carried out for 2-3 hours under light-protected conditions. Ethanol is added to terminate the reaction, and deionized water is used for dialysis purification to obtain sodium oxidized hyaluronic acid. The carbon nanotube pretreatment process in step (3) is as follows: add carbon nanotubes to concentrated nitric acid, heat at 80-90℃ for 3-5 hours, and after the reaction is completed, filter, wash and dry to obtain pretreated carbon nanotubes.

9. The method for preparing a modified carbon nanotube composite carbon material according to claim 8, characterized in that, In step (2), the molar ratio of repeating disaccharide units and sodium periodate in sodium hyaluronate is 1:(0.5-1), and the concentration of sodium hyaluronate solution is 1-2.5 g / L; in step (3), the mass ratio of carbon nanotubes and concentrated nitric acid is 1:(60-70).

10. A modified carbon nanotube composite carbon material, characterized in that, It is prepared by the preparation method according to any one of claims 1-9.

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