Hard carbon-carbon nanotube composite modified battery negative electrode and preparation method thereof
By modifying the negative electrode with hard carbon-carbon nanotube composites, a continuous three-dimensional conductive network is constructed, sulfation is suppressed, the problem of short lifespan of lead-acid batteries is solved, and a significant performance improvement is achieved.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- ANHUI LEOCH POWER SUPPLY
- Filing Date
- 2026-04-09
- Publication Date
- 2026-07-21
AI Technical Summary
Traditional lead-acid batteries are prone to sulfation of the negative electrode during cycling, which leads to the failure of active materials and a shortened cycle life.
A hard carbon-carbon nanotube composite modified anode is adopted. Through the synergistic effect of hard carbon and carbon nanotubes, a continuous three-dimensional conductive network is constructed, which inhibits sulfation, improves electrolyte permeability and electron transport efficiency, forms a uniform microporous structure, and optimizes battery performance.
It significantly extends the deep cycle life and low-discharge tolerance of lead-acid batteries, improves the utilization rate of active materials and high-current discharge performance, enhances conductivity and utilization, and improves the overall performance of the battery.
Smart Images
Figure CN122436446A_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of battery technology, and particularly relates to a hard carbon-carbon nanotube composite modified battery negative electrode, and a method for preparing the hard carbon-carbon nanotube composite modified battery negative electrode. Background Technology
[0002] Lead-acid batteries are a type of storage battery whose electrodes are mainly made of lead and its oxides, and whose electrolyte is a sulfuric acid solution. Due to their low cost, high safety, and good recyclability, lead-acid batteries are widely used in electrical systems, construction machinery, automotive starting and backup power, and energy storage.
[0003] However, the negative electrode of traditional lead-acid batteries is prone to sulfation during cycling, which leads to the failure of active materials and shortens cycle life. Summary of the Invention
[0004] To address the problems in the prior art, the present invention proposes the following technical solution: A hard carbon-carbon nanotube composite modified battery negative electrode includes: a negative electrode grid and a negative electrode lead paste. The negative electrode lead paste comprises, by mass percentage: 88.8%–89.5% lead powder, 8.8%–9.0% dilute sulfuric acid reaction components, 0.4%–0.6% modified carbon composite material, 0.8%–0.9% barium sulfate, 0.4%–0.5% humic acid, 0.2%–0.3% sodium lignosulfonate, and 0.15%–0.20% short fibers, with the sum of the mass percentages of all components being 100%. The modified carbon composite material is composed of hard carbon and carbon nanotubes, with the mass ratio of hard carbon to carbon nanotubes being 5:1-20:1.
[0005] As a preferred embodiment of the above technical solution, the hard carbon D 50 The particle size is 50nm to 500nm, and the specific surface area of the hard carbon BET is 800 to 1500m² / g.
[0006] As a preferred embodiment of the above technical solution, the carbon nanotube is a multi-walled carbon nanotube with a diameter of 10 nm to 50 nm and a length of 1 μm to 20 μm.
[0007] As a preferred embodiment of the above technical solution, the short fiber is a polyester short fiber or a polypropylene short fiber, and the short fiber has a length of 1-3 mm.
[0008] A method for preparing a hard carbon-carbon nanotube composite modified negative electrode for a storage battery includes the following steps: S1. Raw material pretreatment; Hard carbon was vacuum dried at 110℃ for 4-6 hours to remove adsorbed water in the pores, and carbon nanotubes were dried by forced air at 80℃ for 2 hours. Both were then cooled and put into use. S2. Prepare the dispersant-positioning agent system; Using deionized water as the base liquid, add a dispersant at 0.3% to 0.8% of the mass of deionized water. The dispersant is mPEG-200 or trisodium citrate. Stir at 800 to 1200 r / min for 15 to 30 min until the dispersant is completely dissolved. Add 1.0% to 2.5% of a spacer (urea) by mass of the deionized water, and continue stirring at 800 r / min for 20 to 30 minutes to ensure complete dissolution of the spacer and obtain a homogeneous base solution. S3. Step-by-step feeding and mixing; First, carbon nanotubes are introduced and pre-dispersed at a speed of 600-800 r / min for 20-30 min. Urea molecules are uniformly filled in the gaps between the carbon nanotube bundles, and physical spacers prevent the unwound carbon nanotubes from re-intertwining and winding. Then, hard carbon powder was added at a mass ratio of hard carbon to carbon nanotubes of 5:1 to 20:1, and mixed at a speed of 600 to 800 r / min for 20 to 30 min. Urea molecules further filled the gaps between hard carbon particles and between hard carbon and carbon nanotubes, thus physically supporting and preventing the dense agglomeration of hard carbon particles. S4, Strengthen Dispersion; The premixed slurry is transferred to an enhanced dispersion device and first ultrasonically dispersed at 300-500W for 30-60 minutes to further break up residual micro-agglomerates. Then, it is immediately subjected to high-speed shear homogenization treatment. The interfacial forces are broken by mechanical shear force to achieve deep and uniform dispersion of carbon materials, and finally a composite slurry with no obvious agglomeration, uniform particle distribution, and pores fully occupied and supported by urea is obtained. S5. The spacer and dispersant are removed by washing with water; The composite slurry is transferred into a vacuum filtration device and repeatedly rinsed and filtered with deionized water 3 to 5 times, with the amount of water used each time being 1 to 2 times the volume of the slurry, until the conductivity of the filtrate is ≤10μS / cm, thus achieving the removal of the site-occupying agent and dispersant with virtually no residue. S6. Drying and post-treatment; The filtered cake was redispersed in a small amount of deionized water to form a fluid slurry, which was then dried using a vacuum drying method. After drying, the slurry was sieved through a 200-300 mesh screen to obtain modified carbon composite powder with a moisture content of ≤0.8%. S7. Material weighing and dry mixing; Weigh out lead powder, modified carbon composite material, barium sulfate, humic acid, sodium lignosulfonate, and short fiber by mass percentage, add them to the paste mixer and dry mix at low speed for 5-8 minutes until the materials are uniform. S8, Materials and Paste and Curing; Add 7.6%–12.2% of deionized water and 6.1%–9.8% of dilute sulfuric acid by weight of lead paste to the dry mixture in sequence. Cool and stir throughout the process, strictly control the paste temperature below 60°C, and after stirring and maturing, obtain a negative electrode lead paste with fine texture and good coating performance. S9, Negative electrode plate preparation process; After uniformly coating the negative electrode lead paste onto the surface of the lead-calcium-tin-aluminum alloy negative electrode grid, the plate is sent into a curing and drying chamber and a gradient curing method is used to obtain a negative electrode green plate with a dense structure, reasonable porosity, and strong bonding.
[0009] As a preferred embodiment of the above technical solution, in step S3, the mass ratio of the total mass of hard carbon and carbon nanotubes to the mass of deionized water is 1:5 to 1:10.
[0010] As a preferred embodiment of the above technical solution, in step S4, the shearing rate of the high-speed shearing homogenization process is 10000-15000 r / min, and the processing time is 15-20 min.
[0011] As a preferred embodiment of the above technical solution, the drying process in step S6 includes the following: The slurry is transferred to a tray in a vacuum drying oven. First, a vacuum is drawn to -0.08 to -0.1 MPa, and then the temperature is raised to 80℃ to 100℃. The slurry is dried at a constant temperature and pressure for 8 to 12 hours. During the drying process, free water and adsorbed water in the material are removed. Trace amounts of residual urea are decomposed into gas by heating and discharged with the vacuum system.
[0012] As a preferred embodiment of the above technical solution, in step S8, the dilute sulfuric acid is added by spraying, the concentration of the dilute sulfuric acid is 1.3-1.5 g / cm³, and the mass fraction of the dilute sulfuric acid is 45%~55%. The beneficial effects of this invention are as follows: 1. Hard carbon can disperse lead sulfate crystals and reduce negative electrode polarization by relying on its high specific surface area and excellent energy storage capacity, thereby inhibiting sulfation from the root, delaying capacity decay, and significantly improving deep cycle life and resistance to power loss. Meanwhile, carbon nanotubes can construct a continuous three-dimensional conductive network inside the lead paste, shortening the electron transport path, reducing internal resistance, improving electrolyte penetration, greatly improving the utilization rate of active materials, and enhancing charge acceptance and high current discharge performance. With the synergistic effect of the two, the battery can solve the pain points of easy sulfation and short life of traditional lead-acid batteries, while also improving the shortcomings of poor conductivity, low utilization rate, and poor rate capability, thereby greatly optimizing the performance of the battery. 2. First, carbon nanotubes are added to a urea-containing dispersion system. Urea molecules fill the gaps between carbon nanotube bundles, physically separating them to prevent re-entanglement, ensuring a single / small bundle dispersion and reserving embedding space. Then, hard carbon powder is added, and urea further fills the gaps between hard carbon particles and between hard carbon and carbon nanotubes, physically supporting and preventing dense aggregation of hard carbon and excessive encapsulation of carbon nanotubes. The entire process does not change the intrinsic properties of the two carbon materials, ultimately forming a loose hybrid structure with "carbon nanotubes as conductive bridges and hard carbon as support points." Subsequent water washing to remove urea forms uniform micropores / mesopores, significantly improving electrolyte wettability and ion transport efficiency. This lays the structural foundation for constructing a continuous conductive network and suppressing negative electrode sulfation, further optimizing the battery. Attached Figure Description
[0013] Figure 1 The diagram shown is a schematic representation of the overall structure of the embodiment; Figure 2 The figure shown is a comparison curve of the battery in the 70% DOD cycle life test in the embodiment; Figure 3 The figure shown is a comparison of the low-temperature discharge capacity of the batteries in the examples at -20°C.
[0014] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the present invention will be clearly and completely described below in conjunction with the embodiments and the accompanying drawings. Example
[0015] Figures 1-3 Among them, a hard carbon-carbon nanotube composite modified battery negative electrode includes: a negative electrode grid and a negative electrode lead paste. The negative electrode lead paste comprises, by mass percentage: 88.8%–89.5% lead powder, 8.8%–9.0% dilute sulfuric acid reaction components, 0.4%–0.6% modified carbon composite material, 0.8%–0.9% barium sulfate, 0.4%–0.5% humic acid, 0.2%–0.3% sodium lignosulfonate, and 0.15%–0.20% short fibers, with the sum of the mass percentages of each component being 100%. The modified carbon composite material is composed of hard carbon and carbon nanotubes, with the mass ratio of hard carbon to carbon nanotubes being 5:1-20:1.
[0016] The hard carbon D 50 The particle size is 50nm to 500nm, and the specific surface area of the hard carbon BET is 800 to 1500m² / g.
[0017] The carbon nanotubes are multi-walled carbon nanotubes with a diameter of 10 nm to 50 nm and a length of 1 μm to 20 μm.
[0018] The short fibers are polyester short fibers or polypropylene short fibers, and the length of the short fibers is 1-3 mm.
[0019] Hard carbon, with its high specific surface area and excellent energy storage capacity, can disperse lead sulfate crystals, reduce negative electrode polarization, inhibit sulfation at its source, delay capacity decay, and significantly improve deep cycle life and low-voltage tolerance. Meanwhile, carbon nanotubes can construct a continuous three-dimensional conductive network inside the lead paste, shortening the electron transport path, reducing internal resistance, and improving electrolyte penetration. This greatly improves the utilization rate of active materials, enhances charge acceptance, and improves high-current discharge performance. With the synergistic effect of both, the battery not only solves the problems of easy sulfation and short life of traditional lead-acid batteries, but also improves the shortcomings of poor conductivity, low utilization rate, and poor rate capability, thereby significantly optimizing the performance of the battery.
[0020] A method for preparing a hard carbon-carbon nanotube composite modified negative electrode for a storage battery includes the following steps: S1. Raw material pretreatment; Hard carbon was vacuum dried at 110℃ for 4-6 hours to remove adsorbed water in the pores, and carbon nanotubes were dried by forced air at 80℃ for 2 hours. Both were then cooled and put into use. S2. Prepare the dispersant-positioning agent system; Using deionized water as the base liquid, add a dispersant at 0.3% to 0.8% of the mass of deionized water. The dispersant is mPEG-200 or trisodium citrate. Stir at 800 to 1200 r / min for 15 to 30 min until the dispersant is completely dissolved. Add 1.0% to 2.5% of a spacer (urea) by mass of the deionized water, and continue stirring at 800 r / min for 20 to 30 minutes to ensure complete dissolution of the spacer and obtain a homogeneous base solution. S3. Step-by-step feeding and mixing; First, carbon nanotubes are introduced and pre-dispersed at a speed of 600-800 r / min for 20-30 min. Urea molecules are uniformly filled in the gaps between the carbon nanotube bundles. Physical spacers prevent the unwound carbon nanotubes from re-intertwining and entangled. This ensures the dispersion of single or small bundles of carbon nanotubes and reserves uniform space for the subsequent embedding of hard carbon, avoiding the formation of dense agglomerates of carbon nanotubes and laying the foundation for building a continuous conductive network. Subsequently, hard carbon powder was added at a mass ratio of hard carbon to carbon nanotubes of 5:1 to 20:1, and mixed at a speed of 600 to 800 r / min for 20 to 30 min. Urea molecules further filled the gaps between hard carbon particles and between hard carbon and carbon nanotubes, physically supporting and preventing the dense agglomeration of hard carbon particles, while avoiding excessive encapsulation of carbon nanotubes by hard carbon particles. Without changing the intrinsic properties of the two carbon materials, the two carbon materials formed a loose mixed structure with "carbon nanotubes as conductive bridges and hard carbon as support points". After the urea was removed by subsequent water washing, uniform micropores / mesopores were formed, improving electrolyte wettability and ion transport efficiency. In step S3, the total mass ratio of hard carbon and carbon nanotubes to deionized water is 1:5 to 1:10.
[0021] S4, Strengthen Dispersion; The premixed slurry is transferred to an enhanced dispersion device and first ultrasonically dispersed at 300-500W for 30-60 minutes to further break up residual micro-agglomerates. Then, it is immediately subjected to high-speed shear homogenization treatment. The interfacial forces are broken by mechanical shear force to achieve deep and uniform dispersion of carbon materials, and finally a composite slurry with no obvious agglomeration, uniform particle distribution, and pores fully occupied and supported by urea is obtained. In step S4, the shearing rate of the high-speed shearing homogenization process is 10,000 to 15,000 r / min, and the processing time is 15 to 20 min.
[0022] S5. The spacer and dispersant are removed by washing with water; The composite slurry is transferred into a vacuum filtration device and repeatedly rinsed and filtered with deionized water 3 to 5 times, with the amount of water used each time being 1 to 2 times the volume of the slurry, until the conductivity of the filtrate is ≤10μS / cm, thus achieving the removal of the site-occupying agent and dispersant with virtually no residue. S6. Drying and post-treatment; The filtered cake was redispersed in a small amount of deionized water to form a fluid slurry, which was then dried using a vacuum drying method. After drying, the slurry was sieved through a 200-300 mesh screen to obtain modified carbon composite powder with a moisture content of ≤0.8%. The drying process in step S6 includes the following: The slurry is transferred to a tray in a vacuum drying oven. First, a vacuum is drawn to -0.08 to -0.1 MPa, and then the temperature is raised to 80℃ to 100℃. The slurry is dried at a constant temperature and pressure for 8 to 12 hours. During the drying process, free water and adsorbed water in the material are removed. Trace amounts of residual urea are decomposed into gas by heating and discharged with the vacuum system.
[0023] S7. Material weighing and dry mixing; Weigh out lead powder, modified carbon composite material, barium sulfate, humic acid, sodium lignin sulfonate, and short fiber by weight percentage, add them to the paste mixer and dry mix at low speed for 5-8 minutes until the materials are uniform.
[0024] S8, Materials and Paste and Curing; Add 7.6%–12.2% of deionized water and 6.1%–9.8% of dilute sulfuric acid by weight of lead paste to the dry mixture in sequence. Cool and stir throughout the process, strictly control the paste temperature below 60°C, and after stirring and maturing, obtain a negative electrode lead paste with fine texture and good coating performance. In step S8, the dilute sulfuric acid is added by spraying, and the concentration of the dilute sulfuric acid is 1.3-1.5 g / cm3, with a mass fraction of 45%-55%.
[0025] S9, Negative electrode plate preparation process; After uniformly coating the negative electrode lead paste onto the surface of the lead-calcium-tin-aluminum alloy negative electrode grid, the plate is sent into a curing and drying chamber and a gradient curing method is used to obtain a negative electrode green plate with a dense structure, reasonable porosity, and strong bonding.
[0026] First, carbon nanotubes are introduced into a urea-containing dispersion system. Urea molecules fill the gaps between the carbon nanotube bundles, physically separating them to prevent re-entanglement, ensuring a single / small bundle dispersion and reserving embedding space. Then, hard carbon powder is added, and urea further fills the gaps between hard carbon particles and between hard carbon and carbon nanotubes, physically supporting and preventing dense aggregation of hard carbon and excessive encapsulation of carbon nanotubes. The entire process does not change the intrinsic properties of the two carbon materials, ultimately forming a loose hybrid structure with carbon nanotubes as conductive bridges and hard carbon as support points. Subsequent water washing to remove urea forms uniform micropores / mesopores, significantly improving electrolyte wettability and ion transport efficiency. This lays the structural foundation for constructing a continuous conductive network and suppressing negative electrode sulfation, further optimizing the battery. Example
[0027] Weigh 100 parts of hard carbon and 10 parts of single-walled carbon nanotubes, add them to deionized water containing 2 parts of sodium dodecylbenzenesulfonate, ultrasonically disperse for 30 min, and then mix in a ball mill for 2 h to obtain a uniformly dispersed slurry. Spray dry the slurry to obtain hard carbon-carbon nanotube modified carbon composite powder.
[0028] According to the formula: 1000 parts lead powder, 1 part of the above composite powder, 10 parts barium sulfate, 5 parts humic acid, 2 parts sodium lignosulfonate, and 1.5 parts short fiber are placed in a paste mixer and dry-mixed for 5 minutes; then 100 parts dilute sulfuric acid with a density of 1.4 g / cm³ and 120 parts deionized water are slowly added and stirred for 40 minutes, controlling the paste temperature not to exceed 50℃, to obtain negative electrode lead paste.
[0029] Lead paste is applied to the grid of the negative electrode plate, and then cured and dried to obtain the negative electrode plate.
[0030] The negative electrode plate, positive electrode plate, and AGM separator are assembled into a battery, which is then filled with sulfuric acid electrolyte and subjected to formation to obtain the finished battery.
[0031] Comparative Example 1: The same steps as in Example 1 were used, but only 1 part of ordinary carbon black was used as the negative electrode additive, without the addition of hard carbon and carbon nanotubes.
[0032] Performance testing: The batteries prepared in Example 1 and Comparative Example 1 (four 12V 20Ah batteries in series) were subjected to 70% DOD cycle life testing and low temperature testing. The test results are as follows. Figure 2 and Figure 3 As shown.
[0033] The above results indicate that the hard carbon-carbon nanotube composite modified negative electrode provided by this invention can significantly improve the cycle performance and low-temperature discharge capability of lead-acid batteries.
[0034] The above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it.
Claims
1. A hard carbon-carbon nanotube composite modified negative electrode for a storage battery, characterized in that, include: The negative electrode grid and negative electrode lead paste, wherein the negative electrode lead paste comprises, by mass percentage: 88.8%–89.5% lead powder, 8.8%–9.0% dilute sulfuric acid reaction components, 0.4%–0.6% modified carbon composite material, 0.8%–0.9% barium sulfate, 0.4%–0.5% humic acid, 0.2%–0.3% sodium lignosulfonate, and 0.15%–0.20% short fibers, the sum of the mass percentages of each component being 100%; The modified carbon composite material is composed of hard carbon and carbon nanotubes, with the mass ratio of hard carbon to carbon nanotubes being 5:1-20:
1.
2. The hard carbon-carbon nanotube composite modified battery negative electrode according to claim 1, characterized in that, The hard carbon D 50 The hard carbon BET has a particle size of 50 nm to 500 nm and a specific surface area of 800 to 1500 m². 2 g.
3. The hard carbon-carbon nanotube composite modified battery negative electrode according to claim 1, characterized in that, The carbon nanotubes are multi-walled carbon nanotubes with a diameter of 10 nm to 50 nm and a length of 1 μm to 20 μm.
4. The hard carbon-carbon nanotube composite modified battery negative electrode according to claim 1, characterized in that, The short fibers are polyester short fibers or polypropylene short fibers, and the length of the short fibers is 1-3 mm.
5. A method for preparing a hard carbon-carbon nanotube composite modified negative electrode for a storage battery according to any one of claims 1-4, characterized in that, Includes the following steps: S1. Raw material pretreatment; Hard carbon was vacuum dried at 110℃ for 4-6 hours to remove adsorbed water in the pores, and carbon nanotubes were dried by forced air at 80℃ for 2 hours. Both were then cooled and put into use. S2. Prepare the dispersant-positioning agent system; Using deionized water as the base liquid, add a dispersant at 0.3% to 0.8% of the mass of deionized water. The dispersant is mPEG-200 or trisodium citrate. Stir at 800 to 1200 r / min for 15 to 30 min until the dispersant is completely dissolved. Add 1.0% to 2.5% of a spacer (urea) by mass of the deionized water, and continue stirring at 800 r / min for 20 to 30 minutes to ensure complete dissolution of the spacer and obtain a homogeneous base solution. S3. Step-by-step feeding and mixing; First, carbon nanotubes are introduced and pre-dispersed at a speed of 600-800 r / min for 20-30 min. Urea molecules are uniformly filled in the gaps between the carbon nanotube bundles, and physical spacers prevent the unwound carbon nanotubes from re-intertwining and winding. Then, hard carbon powder was added at a mass ratio of hard carbon to carbon nanotubes of 5:1 to 20:1, and mixed at a speed of 600 to 800 r / min for 20 to 30 min. Urea molecules further filled the gaps between hard carbon particles and between hard carbon and carbon nanotubes, thus physically supporting and preventing the dense agglomeration of hard carbon particles. S4, Strengthen Dispersion; The premixed slurry is transferred to an enhanced dispersion device and first ultrasonically dispersed at 300-500W for 30-60 minutes to further break up residual micro-agglomerates. Then, it is immediately subjected to high-speed shear homogenization treatment. The interfacial forces are broken by mechanical shear force to achieve deep and uniform dispersion of carbon materials, and finally a composite slurry with no obvious agglomeration, uniform particle distribution, and pores fully occupied and supported by urea is obtained. S5. The spacer and dispersant are removed by washing with water; The composite slurry is transferred into a vacuum filtration device and repeatedly rinsed and filtered with deionized water 3 to 5 times, with the amount of water used each time being 1 to 2 times the volume of the slurry, until the conductivity of the filtrate is ≤10μS / cm, thus achieving the removal of the site-occupying agent and dispersant with virtually no residue. S6. Drying and post-treatment; The filtered cake was redispersed in a small amount of deionized water to form a fluid slurry, which was then dried using a vacuum drying method. After drying, the slurry was sieved through a 200-300 mesh screen to obtain modified carbon composite powder with a moisture content of ≤0.8%. S7. Material weighing and dry mixing; Weigh out lead powder, modified carbon composite material, barium sulfate, humic acid, sodium lignosulfonate, and short fiber by weight percentage, add them to the paste mixer and dry mix at low speed for 5-8 minutes until the materials are uniform. S8, Materials and Paste and Curing; Add 7.6%–12.2% of deionized water and 6.1%–9.8% of dilute sulfuric acid by weight of lead paste to the dry mixture in sequence. Cool and stir throughout the process, strictly control the paste temperature below 60°C, and after stirring and maturing, obtain a negative electrode lead paste with fine texture and good coating performance. S9, Negative electrode plate preparation process; After uniformly coating the negative electrode lead paste onto the surface of the lead-calcium-tin-aluminum alloy negative electrode grid, the plate is sent into a curing and drying chamber and a gradient curing method is used to obtain a negative electrode green plate with a dense structure, reasonable porosity, and strong bonding.
6. The method for preparing a hard carbon-carbon nanotube composite modified negative electrode for a storage battery according to claim 5, characterized in that, In step S3, the total mass ratio of hard carbon and carbon nanotubes to deionized water is 1:5 to 1:
10.
7. The method for preparing a hard carbon-carbon nanotube composite modified negative electrode for a storage battery according to claim 5, characterized in that, In step S4, the shearing rate of the high-speed shearing homogenization process is 10,000 to 15,000 r / min, and the processing time is 15 to 20 min.
8. The method for preparing a hard carbon-carbon nanotube composite modified negative electrode for a storage battery according to claim 5, characterized in that, The drying process in step S6 includes the following: The slurry is transferred to a tray in a vacuum drying oven. First, a vacuum is drawn to -0.08 to -0.1 MPa, and then the temperature is raised to 80℃ to 100℃. The slurry is dried at a constant temperature and pressure for 8 to 12 hours. During the drying process, free water and adsorbed water in the material are removed. Trace amounts of residual urea are decomposed into gas by heating and discharged with the vacuum system.
9. The method for preparing a hard carbon-carbon nanotube composite modified negative electrode for a storage battery according to claim 5, characterized in that, In step S8, the dilute sulfuric acid is added by spraying, and the concentration of the dilute sulfuric acid is 1.3-1.5 g / cm3, with a mass fraction of 20%-30%.