Graphite-based negative electrode material for lithium ion batteries and method for preparing the same
By using copper nanowires as a substrate for cobalt-nickel co-doping and polyaniline coating in lithium-ion battery anode materials, a graphite carbon nanotube framework was prepared, solving the problems of low specific capacity, short cycle life and significant volume expansion in the existing technology, and realizing a graphite anode material with high specific capacity and good cycle stability.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- 湖南镕锂新材料科技有限公司
- Filing Date
- 2026-03-20
- Publication Date
- 2026-06-16
AI Technical Summary
Existing lithium-ion battery anode materials suffer from problems such as low specific capacity, short cycle life, significant volume expansion, and numerous interfacial side reactions. Furthermore, their fabrication processes are unreasonable, making it difficult to meet the demands of high-performance lithium-ion batteries.
Cobalt-nickel co-doped copper nanowires were prepared using copper nanowires as a substrate. Graphite carbon nanogels were prepared by hydrothermal method, and copper nanowires were etched with FeCl3-HCl etching solution to form a graphite carbon nanotube framework. Then, aniline and phytic acid were used as nitrogen and phosphorus sources, respectively, and the graphite anode material was obtained by uniformly coating with polyaniline.
It significantly improves the reversible specific capacity, cycle stability, and rate performance of the anode material, solves the problems of low specific capacity, short cycle life, and slow reaction kinetics, forms a stable three-dimensional conductive network, and avoids metal agglomeration and interfacial side reactions.
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Abstract
Description
Technical Field
[0001] This invention relates to the field of battery anode material technology, specifically to an anode material based on graphite lithium-ion batteries and its preparation method. Background Technology
[0002] Lithium-ion batteries, due to their high energy density, long cycle life, and environmental friendliness, have been widely used in portable electronic devices, new energy vehicles, and energy storage. The anode material, as the core carrier for lithium-ion insertion / deintercalation, directly determines the battery's specific capacity, cycle stability, and coulombic efficiency. Currently, commercially available lithium-ion battery anodes mainly use graphite-based materials, but these have limitations such as relatively low theoretical specific capacity and significant volume expansion during charging and discharging, restricting further improvements in battery energy density. To address the aforementioned issues, existing technologies often employ metal doping (such as cobalt and nickel) combined with carbon nanostructures to optimize anode performance. However, these methods generally suffer from problems such as easy agglomeration and uneven dispersion of metal particles, easy passivation of externally generated cobalt and nickel particles, incomplete carbon nanoframework structure, poor continuity of conductive network, and increased interfacial side reactions due to uneven coating layers. Furthermore, unreasonable parameter matching in each step of the preparation process further degrades the electrochemical performance of the anode, making it difficult to meet the practical application requirements of high-performance lithium-ion batteries. Therefore, developing a graphite-based anode material with high specific capacity, excellent cycle stability, and good interfacial compatibility, along with its efficient preparation method, has become a current research hotspot and urgent need in this field. Summary of the Invention
[0003] The purpose of this invention is to provide a negative electrode material based on graphite lithium-ion batteries and its preparation method, so as to solve the problems existing in the prior art.
[0004] To solve the above-mentioned technical problems, the present invention provides the following technical solution:
[0005] A negative electrode material based on graphite lithium-ion batteries is disclosed. The negative electrode material is prepared by preparing cobalt-nickel co-doped copper nanowires using a hydrothermal method on copper nanowires as a substrate, and then preparing graphite carbon nanotube aerogel using cobalt-nickel co-doped copper nanowires as a template. The copper nanowires are then etched with FeCl3-HCl etching solution to obtain a graphite carbon nanotube framework. Finally, the graphite carbon nanotube framework is used as the base framework, and aniline and phytic acid are used as nitrogen and phosphorus sources, respectively. The graphite negative electrode material is obtained by uniformly coating with polyaniline.
[0006] As an optimization, the cobalt-nickel co-doped copper nanowires are prepared by a hydrothermal method using a nickel nitrate hexahydrate solution, a cobalt nitrate hexahydrate solution, and copper nanowires.
[0007] As an optimization, in the process of uniformly coating polyaniline, aniline is used as the polymerization monomer, ammonium persulfate is used as the initiator, and phytic acid is used to regulate the morphology of polyaniline so that polyaniline can uniformly coat the graphite carbon nanotube framework.
[0008] A method for preparing a negative electrode material based on a graphite lithium-ion battery, applicable to any of the above-described graphite lithium-ion battery-based negative electrode materials, wherein the negative electrode material includes the following preparation steps:
[0009] S1. Add copper nanowires to 650-700 times their weight in deionized water, stir and disperse to prepare a copper nanowire dispersion for later use; weigh out 0.1 mol / L cobalt nitrate hexahydrate solution, 0.1 mol / L nickel nitrate hexahydrate solution, copper nanowire dispersion and 2 wt% polyvinylpyrrolidone glycol solution according to a volume ratio of 1:1:25-35:50-60. Mix the copper nanowires with a 2wt% polyvinylpyrrolidone glycol solution until homogeneous. Then, adjust the pH to 5-6 with a 0.5mol / L sodium hydroxide solution. Add the copper nanowire dispersion and stir thoroughly until homogeneous. Then, heat to 80-90℃ and grow at a constant temperature for 1-1.5h. Remove the nanowires and wash them with deionized water and ethanol alternately 3-5 times. Then, vacuum dry them at 60-70℃ for 12-14h. After drying, perform reduction treatment to prepare cobalt-nickel co-doped copper nanowires.
[0010] S2. Cobalt-nickel co-doped copper nanowires were added to 650-700 times their volume of deionized water and stirred until homogeneous to prepare a cobalt-nickel co-doped copper nanowire dispersion for later use. Polyvinylpyrrolidone solution was added to the cobalt-nickel co-doped copper nanowire dispersion at a volume ratio of 1:2-3. After stirring until homogeneous, the dispersion was frozen and then freeze-dried under vacuum for 48-54 hours. After drying, the dispersion was annealed at high temperature to obtain graphite carbon nanotube aerogel. The graphite carbon nanotube aerogel was washed alternately with ethanol and deionized water 3-5 times. After removing the surface deionized water, the aerogel was immersed in a 1 mol / L FeCl3-HCl etching solution for 24-30 hours. After etching, the aerogel was washed with deionized water 3-5 times and then freeze-dried to obtain a graphite carbon nanotube framework.
[0011] S3. Immerse the graphite carbon nanotube framework in aniline solution, let it stand for 30-40 minutes, then remove it and add it to the initiator solution. Shake and react for 30-40 minutes, then let it stand for 12-16 hours. After standing, remove it and wash it alternately with 85wt% methanol solution and deionized water 3-5 times. After washing, freeze dry for 24-30 hours. After drying, place it in a tube furnace for high-temperature annealing to obtain the anode material.
[0012] As an optimization, in the reduction process of S1, the temperature is 300℃, the atmosphere is 5% H2 / Ar, and the sample is reduced at a gas flow rate of 100 sccm for 2~3 hours.
[0013] As an optimization, the high-temperature annealing in S2 is carried out at a temperature of 600℃, with an atmosphere of 15% H2 / Ar and a holding time of 1~2h.
[0014] As an optimization, the polyvinylpyrrolidone solution includes the following preparation steps: adding polyvinylpyrrolidone to deionized water at a mass of 35 to 45 times that of polyvinylpyrrolidone, stirring evenly, and preparing a polyvinylpyrrolidone solution for later use.
[0015] As an optimization, the aniline solution includes the following preparation steps: adding aniline to isopropanol at a volume ratio of 1:35~45, stirring evenly, and preparing an aniline solution for later use.
[0016] As an optimization, the initiator solution is prepared by mixing 50wt% phytic acid solution and 9wt% ammonium persulfate aqueous solution at a volume ratio of 1:2.2~2.5.
[0017] As an optimization, the high-temperature annealing in S3 is carried out at a temperature of 600°C, with an atmosphere of Ar and a holding time of 1.5 to 2 hours.
[0018] Compared with the prior art, the beneficial effects achieved by the present invention are:
[0019] This technical solution uses transition metal-doped copper nanowires as the substrate for carbon nanotube fabrication. After etching to remove the copper core, the transition metal is uniformly anchored in the hollow cavities and inter-cell lattice gaps inside the carbon nanotubes in the form of single atoms and sub-nano clusters, forming a stable confined structure. This method has significant advantages over existing methods that involve direct physical mixing of transition metals and carbon nanotubes or the simultaneous generation of carbon nanotubes through transition metal precursors and carbon sources. In existing strategies, transition metal particles, lacking any physical constraint, are highly susceptible to agglomeration, grain growth, and even detachment from the carbon nanotube surface during high-temperature annealing, battery charge-discharge cycles, or electrolyte immersion. Furthermore, directly exposed metal particles are easily oxidized and dissolved, forming a passivation film, leading to rapid attenuation of active sites, extremely low utilization, and potential blockage of carbon nanotube pores, hindering ion transport. In contrast, this solution tightly encapsulates the transition metal within a carbon nanotube graphite layer. This physical confinement effectively prevents metal agglomeration and loss, isolates direct contact between the electrolyte and the metal, and inhibits metal dissolution and passivation. Simultaneously, the strong electronic interaction between the metal and the carbon nanotube graphite lattice modulates the electronic structure of the carbon nanotube, significantly enhancing its conductivity and energy storage activity. Moreover, the transition metal acts as a graphitization catalyst, promoting the conversion of amorphous carbon to highly crystalline graphitic carbon, filling lattice defects in the carbon nanotube, enhancing its mechanical strength, and contributing to the formation of a continuous and stable three-dimensional conductive network. This fundamentally solves the core problems of unstable active sites, low utilization, and easily damaged carbon nanotube structures inherent in direct mixing methods.
[0020] After uniformly coating the inner and outer surfaces of carbon nanotubes with polyaniline, a synergistic effect is formed with the transition metal confined inside the carbon nanotubes, further improving the overall performance of the anode material and achieving an energy storage effect of 1+1>2. Polyaniline, as a conductive polymer with high conductivity and good environmental stability, can not only provide a flexible coating layer for carbon nanotube frameworks, effectively buffering the volume expansion of carbon nanotubes and themselves during battery charging and discharging, preventing carbon nanotube structure collapse and coating layer detachment, but also serve as a nitrogen source to provide highly active doping sites for carbon materials. This forms a synergistic modification effect with the confined doping of transition metals inside the carbon nanotubes, further enriching the types and density of active sites. At the same time, the uniform coating of polyaniline can improve the surface wettability of carbon nanotubes, promoting the full wetting of the inside and outside of the carbon nanotubes by the electrolyte. Combined with the fast ion transport channels in the hollow cavity of the carbon nanotubes, it can significantly shorten the ion diffusion path and improve the mass transfer efficiency. Meanwhile, the confined transition metals inside the carbon nanotubes can further optimize the interfacial bonding force between polyaniline and carbon nanotubes through strong electronic coupling, improving the electron transport rate and avoiding the waste of active sites caused by polyaniline agglomeration. Compared to single polyaniline coating or single transition metal confined doping, the synergistic effect of the two not only makes up for the deficiency of polyaniline's own insufficient cycle stability, but also gives full play to the activity advantage of transition metal confined doping, significantly improving the reversible specific capacity, cycle stability and rate performance of the anode material, and solving the technical pain points of low specific capacity, short cycle life and slow reaction kinetics of existing carbon-based anodes. Detailed Implementation
[0021] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.
[0022] Example 1
[0023] S1. Add copper nanowires to deionized water at a concentration 650 times their weight, stir and disperse to prepare a copper nanowire dispersion for later use. Weigh out 0.1 mol / L cobalt nitrate hexahydrate solution, 0.1 mol / L nickel nitrate hexahydrate solution, copper nanowire dispersion, and 2 wt% polyvinylpyrrolidone glycol solution according to a volume ratio of 1:1:25:50. Mix the 0.1 mol / L cobalt nitrate hexahydrate solution, 0.1 mol / L nickel nitrate hexahydrate solution, and 2 wt% polyvinylpyrrolidone glycol solution thoroughly. The pH was then adjusted to 5 with 0.5 mol / L sodium hydroxide solution, and copper nanowire dispersion was added. The mixture was stirred thoroughly until evenly dispersed, then heated to 80℃ and grown at this temperature for 1 hour. The nanowires were then removed and washed three times alternately with deionized water and ethanol. After drying under vacuum at 60℃ for 12 hours, a reduction treatment was performed to prepare cobalt-nickel co-doped copper nanowires. The reduction treatment was carried out at 300℃ in an atmosphere of 5% H2 / Ar with a gas flow rate of 100 sccm for 2 hours.
[0024] S2. Polyvinylpyrrolidone (PVP) was added to 35 times its weight of deionized water and stirred until homogeneous to prepare a PPVP solution for later use. Cobalt-nickel co-doped copper nanowires were added to 650 times their weight of deionized water and stirred until homogeneous to prepare a cobalt-nickel co-doped copper nanowire dispersion for later use. The PPVP solution was added to the cobalt-nickel co-doped copper nanowire dispersion at a volume ratio of 1:2, stirred until homogeneous, frozen into shape, and then freeze-dried under vacuum for 48 hours. After drying, it was annealed at high temperature to obtain graphite carbon nanotube aerogel. The graphite carbon nanotube aerogel was washed three times alternately with ethanol and deionized water. After removing the surface deionized water, it was immersed in a 1 mol / L FeCl3-HCl etching solution for 24 hours. After etching, it was washed three times with deionized water and then freeze-dried to obtain a graphite carbon nanotube framework. The high-temperature annealing was carried out at 600℃ in an atmosphere of 15% H2 / Ar for 1 hour.
[0025] S3. Aniline was added to isopropanol at a volume ratio of 1:35 and stirred until homogeneous to prepare an aniline solution for later use. 50 wt% phytic acid solution and 9 wt% ammonium persulfate aqueous solution were mixed at a volume ratio of 1:2.2 to prepare an initiator solution for later use. The graphite carbon nanotube framework was immersed in the aniline solution, allowed to stand for 30 min, and then removed. It was then added to the initiator solution and reacted with shaking for 30 min, followed by standing for 12 h. After standing, it was removed and washed three times alternately with 85 wt% methanol solution and deionized water. After washing, it was freeze-dried for 24 h. After drying, it was placed in a tube furnace for high-temperature annealing to obtain the negative electrode material. The high-temperature annealing temperature was 600℃, the atmosphere was Ar, and the holding time was 1.5 h.
[0026] Example 2
[0027] S1. Add copper nanowires to deionized water at a concentration 675 times their weight, stir and disperse to prepare a copper nanowire dispersion for later use. Weigh out 0.1 mol / L cobalt nitrate hexahydrate solution, 0.1 mol / L nickel nitrate hexahydrate solution, the copper nanowire dispersion, and 2 wt% polyvinylpyrrolidone glycol solution according to a volume ratio of 1:1:30:55. Mix the 0.1 mol / L cobalt nitrate hexahydrate solution, 0.1 mol / L nickel nitrate hexahydrate solution, and 2 wt% polyvinylpyrrolidone glycol solution thoroughly. The pH was adjusted to 5.5 with 0.5 mol / L sodium hydroxide solution, and then copper nanowire dispersion was added. The mixture was stirred thoroughly until it was evenly dispersed. The temperature was then raised to 85℃ and grown at this temperature for 1.25 h. The nanowires were then removed and washed four times with deionized water and ethanol alternately. After drying under vacuum at 65℃ for 13 h, a reduction treatment was performed to prepare cobalt-nickel co-doped copper nanowires. The reduction treatment was carried out at 300℃ in an atmosphere of 5% H2 / Ar with a gas flow rate of 100 sccm for 2.5 h.
[0028] S2. Polyvinylpyrrolidone (PVP) was added to deionized water at a volume ratio of 40:1 and stirred until homogeneous to prepare a PPVP solution for later use. Cobalt-nickel co-doped copper nanowires were added to deionized water at a volume ratio of 675:1 and stirred until homogeneous to prepare a cobalt-nickel co-doped copper nanowire dispersion for later use. The PPVP solution was added to the cobalt-nickel co-doped copper nanowire dispersion at a volume ratio of 1:2.5 and stirred until homogeneous. The mixture was then freeze-dried under vacuum for 51 hours. After drying, it was annealed at high temperature to obtain graphite carbon nanotube aerogel. The graphite carbon nanotube aerogel was washed four times alternately with ethanol and deionized water. After removing the surface deionized water, it was immersed in a 1 mol / L FeCl3-HCl etching solution for 27 hours. After etching, it was washed four times with deionized water and then freeze-dried to obtain a graphite carbon nanotube framework. The high-temperature annealing was carried out at 600℃ under an atmosphere of 15% H2 / Ar for 1.5 hours.
[0029] S3. Aniline was added to isopropanol at a volume ratio of 1:40 and stirred until homogeneous to prepare an aniline solution for later use. 50 wt% phytic acid solution and 9 wt% ammonium persulfate aqueous solution were mixed at a volume ratio of 1:2.35 to prepare an initiator solution for later use. The graphite carbon nanotube framework was immersed in the aniline solution, allowed to stand for 35 min, and then removed. It was then added to the initiator solution and reacted with shaking for 35 min, followed by standing for 14 h. After standing, it was removed and washed four times alternately with 85 wt% methanol solution and deionized water. After washing, it was freeze-dried for 27 h. After drying, it was placed in a tube furnace for high-temperature annealing to obtain the anode material. The high-temperature annealing temperature was 600℃, the atmosphere was Ar, and the holding time was 1.75 h.
[0030] Example 3
[0031] S1. Add copper nanowires to deionized water at a concentration 700 times their weight, stir and disperse to prepare a copper nanowire dispersion for later use. Weigh out 0.1 mol / L cobalt nitrate hexahydrate solution, 0.1 mol / L nickel nitrate hexahydrate solution, copper nanowire dispersion, and 2 wt% polyvinylpyrrolidone glycol solution according to a volume ratio of 1:1:35:60. Mix the 0.1 mol / L cobalt nitrate hexahydrate solution, 0.1 mol / L nickel nitrate hexahydrate solution, and 2 wt% polyvinylpyrrolidone glycol solution thoroughly. The pH was then adjusted to 6 with 0.5 mol / L sodium hydroxide solution, and copper nanowire dispersion was added. The mixture was stirred thoroughly until homogeneous, then heated to 90℃ and grown at this temperature for 1.5 h. The nanowires were then removed and washed five times alternately with deionized water and ethanol. After drying under vacuum at 70℃ for 14 h, a reduction treatment was performed to prepare cobalt-nickel co-doped copper nanowires. The reduction treatment was carried out at 300℃ in an atmosphere of 5% H2 / Ar with a gas flow rate of 100 sccm for 3 h.
[0032] S2. Polyvinylpyrrolidone (PVP) was added to 45 times its weight of deionized water and stirred until homogeneous to prepare a PPVP solution for later use. Cobalt-nickel co-doped copper nanowires were added to 700 times their weight of deionized water and stirred until homogeneous to prepare a cobalt-nickel co-doped copper nanowire dispersion for later use. The PPVP solution was added to the cobalt-nickel co-doped copper nanowire dispersion at a volume ratio of 1:3. After stirring until homogeneous, the mixture was freeze-formed and vacuum freeze-dried for 54 hours. After drying, it was annealed at high temperature to obtain graphite carbon nanotube aerogel. The graphite carbon nanotube aerogel was washed 5 times alternately with ethanol and deionized water. After removing the surface deionized water, it was immersed in a 1 mol / L FeCl3-HCl etching solution for 30 hours. After etching, it was washed 5 times with deionized water and then freeze-dried to obtain a graphite carbon nanotube framework. The high-temperature annealing was carried out at 600℃ in an atmosphere of 15% H2 / Ar for 2 hours.
[0033] S3. Aniline was added to isopropanol at a volume ratio of 1:45 and stirred until homogeneous to prepare an aniline solution for later use. A 50wt% phytic acid solution and a 9wt% ammonium persulfate aqueous solution were mixed at a volume ratio of 1:2.5 to prepare an initiator solution for later use. The graphite carbon nanotube framework was immersed in the aniline solution, allowed to stand for 40 minutes, then removed and added to the initiator solution. The mixture was shaken and reacted for 40 minutes, then allowed to stand for 16 hours. After standing, the framework was removed and washed five times alternately with 85wt% methanol solution and deionized water. After washing, it was freeze-dried for 30 hours. After drying, it was placed in a tube furnace for high-temperature annealing to obtain the negative electrode material. The high-temperature annealing temperature was 600℃, the atmosphere was Ar, and the holding time was 2 hours.
[0034] Example 4
[0035] The difference from Example 2 lies only in step S2: Polyvinylpyrrolidone (PVP) is added to deionized water at a volume ratio of 40:1 and stirred until homogeneous to prepare a PPVP solution for later use; copper nanowires are added to deionized water at a volume ratio of 675:1 and stirred until homogeneous to prepare a copper nanowire dispersion for later use; the PPVP solution is added to the copper nanowire dispersion at a volume ratio of 1:2.5, stirred until homogeneous, frozen into shape, and then freeze-dried under vacuum for 51 hours. After drying, the mixture is annealed at high temperature to obtain graphite carbon nanotube aerogel; the graphite carbon nanotube aerogel is washed four times alternately with ethanol and deionized water, the surface deionized water is removed, and the aerogel is immersed in a 1 mol / L FeCl3-HCl etching solution for 27 hours. After etching, the aerogel is washed four times with deionized water and then freeze-dried to obtain a graphite carbon nanotube framework; the high-temperature annealing is carried out at a temperature of 600°C, an atmosphere of 15% H2 / Ar, and a holding time of 1.5 hours.
[0036] Example 5
[0037] The difference from Example 2 lies in step S2: Polyvinylpyrrolidone (PVP) is added to deionized water at a volume ratio of 40:1, stirred until homogeneous, and a PPVP solution is prepared for later use; copper nanowires are added to deionized water at a volume ratio of 675:1, stirred until homogeneous, and a copper nanowire dispersion is prepared for later use; the PPVP solution is added to the copper nanowire dispersion at a volume ratio of 1:2.5, stirred until homogeneous, frozen into shape, and then freeze-dried under vacuum for 51 hours. After drying, it is annealed at high temperature to obtain graphite carbon nanotube aerogel; the graphite carbon nanotube aerogel is then processed using ethanol and... After washing with deionized water four times alternately, the surface deionized water was removed and the sample was immersed in a 1 mol / L FeCl3-HCl etching solution for 27 h. After etching, the sample was washed with deionized water four times and then freeze-dried. After drying, the sample was immersed in a mixed solution of 0.1 mol / L cobalt nitrate hexahydrate and 0.1 mol / L nickel nitrate hexahydrate, and the vacuum was drawn to a vacuum degree of 0.05 Pa. After standing for 3 h, the sample was taken out to obtain a graphite carbon nanotube framework. The high-temperature annealing was carried out at a temperature of 600℃ and an atmosphere of 15% H2 / Ar for 1.5 h.
[0038] Electrochemical testing:
[0039] First, the negative electrode material, Ketjen Black, and PVDF were ground into a powder in an agate mortar at a mass ratio of 7:2:1. Then, an appropriate amount of deionized water was added and the mixture was stirred for 6-7 hours at a speed of 600 rpm / min. The resulting uniformly ground black viscous slurry was coated onto a 15cm wide, single-sided smooth copper foil, with a thickness of 150μm. After coating, the foil was vacuum dried at 60℃ for 24 hours. After drying, it was pressed into 14mm diameter discs using a tablet press and stored in a glove box for later use. A Φ15.6mm lithium metal sheet was selected as the electrode, and the electrolyte was 1mol / L LiPF6. The electrolyte was dissolved in a mixed solution of methyl ethyl carbonate, ethylene carbonate, and dimethyl carbonate, with a volume ratio of 1:1:1. The separator was a 19mm diameter polypropylene membrane. The button cell battery is assembled in the following order: negative electrode shell, electrode plate, separator, lithium metal plate, gasket, spring, and positive electrode shell. During this process, an appropriate amount of electrolyte is added. Finally, the battery is pressed firmly to seal it, and any electrolyte that overflows from the surface is wiped dry with a paper towel before being taken out of the glove box.
[0040] Charge-discharge performance testing: The prepared half-cell was tested using a blue electrode at a current density of 0.1 A / g. The test results are shown in Table 1 below.
[0041] Table 1 Performance Test Results
[0042]
[0043] Examples 1-3 all exhibited excellent electrochemical performance, with Example 2 showing the best overall performance. Its initial discharge specific capacity reached 596.4 mAh / g, the highest among all groups, and the specific capacity remained at 220.7 mAh / g after 200 discharges, demonstrating the best cycle capacity retention. Furthermore, its initial coulombic efficiency was 44.48%, and its coulombic efficiency after 200 discharges was 99.88%, the highest among all groups, and it also showed leading stability, exhibiting sufficient lithium storage activity, good cycle stability, and interfacial compatibility.
[0044] The electrochemical performance of Example 4 was significantly worse than that of Example 2. Its initial discharge specific capacity decreased by approximately 9.42% compared to Example 2, its initial coulombic efficiency decreased by approximately 1.22 percentage points, and its 200th discharge specific capacity decreased by approximately 12.32% compared to Example 2. The core reason is that Example 4 did not use cobalt-nickel co-doped copper nanowires, but only used pure copper nanowires to prepare the graphite carbon nanotube framework. The lithium storage active sites of cobalt-nickel nanoparticles were missing, and the support and conductivity continuity of the framework were greatly weakened after the pure copper nanowires were etched, making it impossible to construct an efficient lithium storage-conductivity synergistic network. At the same time, the lack of the binding effect between cobalt-nickel and the carbon matrix to buffer the volume expansion during charge and discharge exacerbated the charge and discharge polarization phenomenon, ultimately leading to a decrease in specific capacity and a deterioration in cycle stability.
[0045] Example 5 exhibited the worst electrochemical performance among all groups, with an initial discharge specific capacity of only 512.8 mAh / g, a decrease of approximately 13.99% compared to Example 2. Its initial coulombic efficiency was as low as 41.83%, and further decreased to 98.42% after 200 cycles. The cycle capacity retention rate was significantly reduced, and its overall performance was far inferior to Example 2. This is because Example 5 did not perform in-situ co-doping of cobalt and nickel before the formation of the graphite carbon nanotube framework. Instead, it used an etching-based impregnation doping method, resulting in easy agglomeration and uneven dispersion of cobalt and nickel particles. Cobalt and nickel particles were distributed both inside and outside the graphite carbon nanotube framework, and the externally generated cobalt and nickel particles were prone to passivation. This resulted in a significant reduction in lithium storage site utilization and a marked decrease in lithium storage activity due to the uneven agglomeration and dispersion of cobalt and nickel particles. Furthermore, the passivation of external cobalt and nickel particles increased electrode polarization, leading to more interfacial side reactions during charge and discharge. Simultaneously, the weak bonding between the agglomerated particles and the carbon framework prevented effective buffering of volume expansion, making the conductive network easily damaged. Ultimately, this led to a significant decrease in initial coulombic efficiency, accelerated cycle capacity decay, and overall deterioration of electrochemical performance.
[0046] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the invention can be implemented in other specific forms without departing from its spirit or essential characteristics. Therefore, the embodiments should be considered in all respects as exemplary and non-limiting, and the scope of the invention is defined by the appended claims rather than the foregoing description. Thus, all variations falling within the meaning and scope of equivalents of the claims are intended to be included within the present invention. No markings in the claims should be construed as limiting the scope of the claims.
Claims
1. A negative electrode material based on graphite lithium-ion batteries, characterized in that, The anode material is prepared by hydrothermal method using copper nanowires as substrate to prepare cobalt-nickel co-doped copper nanowires, and graphite carbon nanogel is prepared using cobalt-nickel co-doped copper nanowires as template. Then, the copper nanowires are etched with FeCl3-HCl etching solution to obtain graphite carbon nanotube framework. Finally, the graphite carbon nanotube framework is used as the basic framework, and aniline and phytic acid are used as nitrogen and phosphorus sources, respectively. The graphite anode material is obtained by uniformly coating with polyaniline. The transition metal is uniformly anchored in the hollow cavities and inter-lattice spaces of the carbon nanotubes in the form of single atoms and sub-nano clusters. The cobalt-nickel co-doped copper nanowires were prepared by a hydrothermal method using a nickel nitrate hexahydrate solution, a cobalt nitrate hexahydrate solution, and copper nanowires.
2. The negative electrode material based on graphite lithium-ion batteries according to claim 1, characterized in that, In the process of uniformly coating polyaniline, aniline is used as the polymerization monomer, ammonium persulfate is used as the initiator, and phytic acid is used to regulate the morphology of polyaniline so that polyaniline can uniformly coat the graphite carbon nanotube framework.
3. A method for preparing a negative electrode material based on a graphite lithium-ion battery, applied to the negative electrode material based on a graphite lithium-ion battery as described in any one of claims 1-2, characterized in that, The negative electrode material includes the following preparation steps: S1. Add copper nanowires to 650-700 times their weight in deionized water, stir and disperse to prepare a copper nanowire dispersion for later use; weigh out 0.1 mol / L cobalt nitrate hexahydrate solution, 0.1 mol / L nickel nitrate hexahydrate solution, copper nanowire dispersion and 2 wt% polyvinylpyrrolidone glycol solution according to a volume ratio of 1:1:25-35:50-60. Mix the copper nanowires with a 2wt% polyvinylpyrrolidone glycol solution until homogeneous. Then, adjust the pH to 5-6 with a 0.5mol / L sodium hydroxide solution. Add the copper nanowire dispersion and stir thoroughly until homogeneous. Then, heat to 80-90℃ and grow at a constant temperature for 1-1.5h. Remove the nanowires and wash them with deionized water and ethanol alternately 3-5 times. Then, vacuum dry them at 60-70℃ for 12-14h. After drying, perform reduction treatment to prepare cobalt-nickel co-doped copper nanowires. S2. Cobalt-nickel co-doped copper nanowires were added to 650-700 times their volume of deionized water and stirred until homogeneous to prepare a cobalt-nickel co-doped copper nanowire dispersion for later use. Polyvinylpyrrolidone solution was added to the cobalt-nickel co-doped copper nanowire dispersion at a volume ratio of 1:2-3. After stirring until homogeneous, the dispersion was frozen and then freeze-dried under vacuum for 48-54 hours. After drying, the dispersion was annealed at high temperature to obtain graphite carbon nanotube aerogel. The graphite carbon nanotube aerogel was washed alternately with ethanol and deionized water 3-5 times. After removing the surface deionized water, the aerogel was immersed in a 1 mol / L FeCl3-HCl etching solution for 24-30 hours. After etching, the aerogel was washed with deionized water 3-5 times and then freeze-dried to obtain a graphite carbon nanotube framework. S3. Immerse the graphite carbon nanotube framework in aniline solution, let it stand for 30-40 minutes, then remove it and add it to the initiator solution. Shake and react for 30-40 minutes, then let it stand for 12-16 hours. After standing, remove it and wash it alternately with 85wt% methanol solution and deionized water 3-5 times. After washing, freeze dry for 24-30 hours. After drying, place it in a tube furnace for high-temperature annealing to obtain the anode material.
4. The method for preparing the negative electrode material based on graphite lithium-ion batteries according to claim 3, characterized in that, In the reduction process described in S1, the temperature is 300℃, the atmosphere is 5% H2 / Ar, and the sample is reduced at a gas flow rate of 100 sccm for 2-3 hours.
5. The method for preparing the negative electrode material based on graphite lithium-ion batteries according to claim 3, characterized in that, In the S2 high-temperature annealing process, the temperature is 600℃, the atmosphere is 15% H2 / Ar, and the holding time is 1~2h.
6. The method for preparing the negative electrode material based on graphite lithium-ion batteries according to claim 3, characterized in that, The polyvinylpyrrolidone solution comprises the following preparation steps: adding polyvinylpyrrolidone to deionized water at a mass of 35 to 45 times that of polyvinylpyrrolidone, stirring evenly, and preparing a polyvinylpyrrolidone solution for later use.
7. The method for preparing the negative electrode material based on graphite lithium-ion batteries according to claim 3, characterized in that, The aniline solution includes the following preparation steps: aniline is added to isopropanol at a volume ratio of 1:35~45, stirred evenly, and the aniline solution is prepared for later use.
8. The method for preparing the negative electrode material based on graphite lithium-ion batteries according to claim 3, characterized in that, The initiator solution is prepared by mixing 50wt% phytic acid solution and 9wt% ammonium persulfate aqueous solution at a volume ratio of 1:2.2~2.
5.
9. The method for preparing the negative electrode material based on graphite lithium-ion batteries according to claim 3, characterized in that, The high-temperature annealing in S3 is carried out at a temperature of 600℃, in an Ar atmosphere, for a holding time of 1.5~2h.