A porous carbon negative electrode material for lithium ion batteries and a preparation method thereof

Abstract

The application belongs to the technical field of lithium battery materials, and specifically discloses a kind of porous carbon negative electrode material for lithium ion battery and its preparation method. First, a copolymer is prepared by stage polymerization of functional monomers and chain transfer agent; second, a core-shell template is formed by ball milling and calcination using nano-molybdenum trioxide and zinc acetate dihydrate as raw materials; then, the copolymer, core-shell template, sodium chloride and polymethyl methacrylate microspheres are mixed and sieved to obtain a precursor; finally, the precursor is subjected to multi-stage temperature carbonization and post-processing to obtain a porous carbon negative electrode material. The obtained negative electrode material has a hierarchical porous structure and a high specific surface area, and realizes the synergistic doping of multiple elements such as nitrogen, phosphorus and molybdenum, effectively promoting the rapid transmission and efficient storage of lithium ions, significantly improving the rate performance and cycle stability of the battery, reducing the polarization impedance, and further optimizing the electronic conductivity and interface stability of the material, which exhibits excellent comprehensive electrochemical performance in high-energy-density lithium ion battery applications.

Description

Technical Field

[0001] This invention belongs to the field of lithium battery material technology, and more specifically, it relates to a porous carbon anode material for lithium-ion batteries and its preparation method. Background Technology

[0002] With the rapid development of the new energy industry, lithium-ion batteries have become the mainstream technology in the energy storage field due to their advantages such as high energy density, long cycle life, and environmental friendliness. As a core component of lithium-ion batteries, the performance of the anode material directly affects the battery's energy density, rate performance, and cycle stability. Although traditional graphite anode materials have achieved commercial application, their theoretical specific capacity is low, only 372 mAh / g, and they are prone to problems such as lithium dendrite growth and structural collapse under high-rate charge and discharge conditions, making it difficult to meet the development requirements of high-energy-density batteries.

[0003] Porous carbon materials exhibit significant advantages in lithium storage due to their tunable pore structure, rich surface chemistry, and good conductivity. Constructing hierarchical porous structures can effectively shorten lithium-ion diffusion distances, increase active sites, and buffer volume expansion, while heteroatom doping can modulate the electronic structure of carbon materials, improving surface wettability and lithium storage activity. However, existing porous carbon materials still suffer from key drawbacks. For example, traditional template methods struggle to achieve precise control of hierarchical pores; single-pore structures limit electrolyte wettability and ion transport efficiency; single-element doping has limited synergistic optimization effects on electronic conductivity and lithium storage sites, lacking synergistic effects among multiple elements; furthermore, insufficient interfacial stability between carbon materials and electrolytes easily leads to repeated SEI film formation, resulting in increased polarization impedance and capacity decay. Therefore, this invention provides a porous carbon anode material for lithium-ion batteries and its preparation method to address the aforementioned technical problems. Summary of the Invention

[0004] The purpose of this invention is to provide a porous carbon anode material for lithium-ion batteries and its preparation method. The material obtained by this preparation method has a hierarchical porous structure and a high specific surface area, and achieves synergistic doping of multiple elements such as nitrogen, phosphorus, and molybdenum, which effectively promotes rapid lithium-ion transport and efficient storage, significantly improves battery rate performance and cycle stability, reduces polarization impedance, and further optimizes the electronic conductivity and interface stability of the material, exhibiting excellent comprehensive electrochemical performance in high-energy-density lithium-ion battery applications.

[0005] In a first aspect, the present invention provides a method for preparing a porous carbon anode material for lithium-ion batteries, employing the following technical solution:

[0006] A method for preparing a porous carbon anode material for lithium-ion batteries includes the following preparation steps:

[0007] S1. Dissolve the functional monomer and chain transfer agent in N,N-dimethylformamide, add acrylonitrile and ammonium persulfate, and react at 68-72℃ under nitrogen protection for 3-5 hours. Then add acrylonitrile and azobisisobutyronitrile, raise the temperature to 83-87℃ and react for 5-7 hours. Add 5-7 times the volume of deionized water to precipitate, pulverize the gel, extract with Soxhlet, and dry to obtain the copolymer.

[0008] S2. Nano molybdenum trioxide and zinc acetate dihydrate are ball-milled and mixed, then calcined in air at 280-320℃ for 1-3 hours, followed by washing and filtration to obtain a core-shell template.

[0009] S3. Take the copolymer, core-shell template, sodium chloride and polymethyl methacrylate microspheres, ball mill and mix them and pass them through a 150-200 mesh sieve to obtain the precursor;

[0010] S4. Under argon protection, the precursor is heated to 580-620℃ at 4-6℃ / min and held for 1.5-2h. Then, the temperature is switched to mixed gas and heated to 730-770℃ at 9-11℃ / min and held for 0.8-1.2h. Then, the temperature is increased to 930-970℃ at 4-6℃ / min and held for 1.5-2.5h. The precursor is then treated with oxalic acid solution at 75-85℃ for 3.5-4.5h, washed with boiling water at 90-100℃ for 6-8h, and ball-milled through a 170-200 mesh sieve to obtain porous carbon anode material for lithium-ion batteries.

[0011] Preferably, the preparation step of the functional monomer in step S1 is as follows:

[0012] A1. Dissolve 2-pyridinecarboxaldehyde and 4-aminopyridine in anhydrous ethanol, add lanthanum trifluoromethanesulfonate, and reflux at 68-72℃ for 3-5 hours. After cooling the reaction solution, wash and filter to obtain the intermediate.

[0013] A2. Dissolve the intermediate in tetrahydrofuran, maintain the temperature in an ice bath at -12 to -8°C, add tetrahydrofuran solution of phenylphosphonodichloro dropwise, maintain the temperature at -7 to -3°C, and after the addition is complete, raise the temperature to 23-27°C and react for 11-13 hours. Adjust the pH of the reaction solution to 7-8 with saturated sodium bicarbonate solution, then extract, dry, filter, distill under reduced pressure and wash, and finally dry under vacuum to obtain the functional monomer.

[0014] Preferably, the preparation step of the chain transfer agent in step S1 is as follows: sodium lignosulfonate and 4-cyano-4-[(dodecylthioalkylthiocarbonyl)thioalkyl]valerate are dissolved in N,N-dimethylformamide and reacted at 78-82°C under nitrogen protection for 5-7 hours. The reaction solution is then added to 4-6 times its volume of acetone for precipitation. After filtration, washing and vacuum drying, the chain transfer agent is obtained.

[0015] Preferably, in step S1, the components by weight are 24-28 parts of functional monomer, 5-8 parts of chain transfer agent, 80-100 parts of N,N-dimethylformamide, 64-70 parts of acrylonitrile, 0.4-0.6 parts of ammonium persulfate, and 0.08-0.12 parts of azobisisobutyronitrile.

[0016] Preferably, in step S2, the components are 9-11 parts by weight of nano molybdenum trioxide and 14-16 parts by weight of zinc acetate dihydrate.

[0017] Preferably, in step S3, the components are 28-32 parts by weight of copolymer, 14-16 parts by weight of core-shell template, 19-23 parts by weight of sodium chloride and 18-22 parts by weight of polymethyl methacrylate microspheres, and in step S4, the mixed gas consists of ammonia and argon in a volume ratio of 1:(6-8).

[0018] Preferably, step A1 comprises 45-55 parts by weight of 2-pyridinecarboxaldehyde, 22-28 parts by weight of 4-aminopyridine, 90-100 parts by weight of anhydrous ethanol and 1-3 parts by weight of lanthanum trifluoromethanesulfonate.

[0019] Preferably, in step A2, the components are 5-7 parts by weight of the intermediate, 35-40 parts by weight of tetrahydrofuran, and 18-22 parts by weight of a 30-35 wt% tetrahydrofuran solution of phenylphosphonic dichloride.

[0020] Preferably, the chain transfer agent preparation step comprises, by weight, 18-22 parts sodium lignosulfonate, 4-6 parts 4-cyano-4-[(dodecylthioalkylthiocarbonyl)thioalkyl]valeric acid and 90-100 parts N,N-dimethylformamide.

[0021] Secondly, the present invention also provides a porous carbon anode material for lithium-ion batteries, which adopts the following technical solution:

[0022] A porous carbon anode material for lithium-ion batteries is prepared by the above-described method.

[0023] In summary, the present invention has the following beneficial effects:

[0024] 1. This invention produces a porous carbon anode material by staged polymerization of functional monomers and chain transfer agents to obtain copolymers, combined with a core-shell template formed by nano-molybdenum trioxide and zinc acetate dihydrate, sodium chloride, and polymethyl methacrylate microspheres to create pores, followed by gradient carbonization and post-treatment. In this material, the core-shell template undergoes pyrolysis to form mesopores and macropores, and its residual molybdenum species migrate to the carbon layer to achieve atomic-level doping; sodium chloride melt etching generates a microporous network, which, together with the macropores formed by the thermal decomposition of polymethyl methacrylate, synergistically constructs hierarchical mass transfer channels, significantly improving specific surface area and electrolyte wettability; the nitrogen and phosphorus heterocyclic structures introduced by the functional monomers are transformed into pyridine nitrogen, graphitic nitrogen, and CP bond active sites during carbonization, synergistically optimizing electron cloud distribution with molybdenum doping, reducing the lithium-ion adsorption energy barrier, and promoting rapid lithium storage behavior dominated by surface capacitance; the hierarchical channels and rigid carbon framework jointly buffer volumetric strain, inhibit structural pulverization, and ensure long-term cycling stability.

[0025] 2. The functional monomer of this invention is prepared by lanthanide catalytic condensation of 2-pyridine carboxaldehyde and 4-aminopyridine, followed by reaction with phenylphosphonic dichloride. Its rigid pyridine and imine skeletons maintain structural integrity during carbonization, serving as heteroatom doping precursors to provide site-specific doping sites for nitrogen and phosphorus elements in the copolymer. Furthermore, the conjugated structure enhances the intermolecular forces of the copolymer, giving the carbon skeleton formed after carbonization a more ordered graphitization tendency and improving electronic conductivity. The nitrogen atoms in the pyridine ring exist in the carbon matrix in three forms: pyrrole, pyridine, and graphitic. They respectively provide lone pairs of electrons, form defect sites, and enhance structural stability, thus synergistically improving the electron transport efficiency and lithium storage capacity of the material. The phosphorus atoms in the phosphonic group are embedded in the carbon network in a C3-P=O configuration, serving as Lewis acid sites to enhance the chemical adsorption of lithium ions, thereby achieving a dual function of physical and chemical lithium storage during charging and discharging.

[0026] 3. The chain transfer agent of this invention is prepared by grafting sodium lignosulfonate with a sulfur-containing carbonyl compound. The molecular self-assembly effect induced by its sulfonic acid group enables the copolymer to form a cross-linked network. After carbonization, a three-dimensional continuous conductive framework is derived. The controllable chain scission characteristics of the sulfur carbonyl group regulate the molecular weight distribution of the polymer and avoid pore closure caused by excessive graphitization of the carbon skeleton. The lignin-derived biomass carbon source provides intrinsic oxygen and sulfur doping sites. The sulfur atoms enhance the edge reaction activity of the carbon layer in the thiophene-S configuration and optimize the SEI film composition in conjunction with nitrogen and phosphorus doping to form a Li3N-Li2S composite interface layer with high ionic conductivity. Detailed Implementation

[0027] 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.

[0028] Unless otherwise specified, the experimental methods used in the following examples are conventional methods, and the experimental materials used, unless otherwise specified, were all purchased from conventional biochemical reagent stores. All quantitative experiments in the following examples were performed in triplicate, and the data are the average of the three replicates or the average ± standard deviation.

[0029] Nano molybdenum trioxide, purchased from Zhejiang Yamei Nanotechnology Co., Ltd., CAS No. 1313-27-5;

[0030] Zinc acetate dihydrate, purchased from Guangdong Wengjiang Chemical Reagent Co., Ltd., product number PA01180;

[0031] Polymethyl methacrylate microspheres were purchased from Wenzhou Pinzhuo Biotechnology Co., Ltd., CAS No. 25188-98-1.

[0032] Lanthanum trifluoromethanesulfonate, purchased from Shanghai Yuanye Biotechnology Co., Ltd., product number S47858;

[0033] Benzyl dichloride, purchased from Hubei Kewode Chemical Co., Ltd., CAS No. 824-72-6;

[0034] 4-Cyano-4-[(dodecylthioalkylthiocarbonyl)thioalkyl]valeric acid, purchased from Beijing Bailingwei Technology Co., Ltd., item number 16-0415.

[0035] Example 1

[0036] A method for preparing a porous carbon anode material for lithium-ion batteries includes the following preparation steps:

[0037] S1. Dissolve 24 parts of functional monomer and 5 parts of chain transfer agent in 80 parts of N,N-dimethylformamide, add 32 parts of acrylonitrile and 0.4 parts of ammonium persulfate, and react at 400 rpm for 5 h under nitrogen protection at 68 °C. Then add 32 parts of acrylonitrile and 0.08 parts of azobisisobutyronitrile, and heat to 83 °C for 7 h. After the reaction is completed, add the reaction solution to 5 times the volume of deionized water for precipitation. After the gel is crushed, it is extracted by Soxhlet extraction and dried to obtain the copolymer.

[0038] S2. Place 9 parts of nano molybdenum trioxide and 14 parts of zinc acetate dihydrate in a ball mill and mix them at 300 r / min for 4 h. Transfer the mixture to a muffle furnace and calcine it in an air atmosphere at 280 ℃ for 3 h. After natural cooling, wash it with deionized water and filter it to obtain the core-shell template.

[0039] S3. Take 28 parts of copolymer, 14 parts of core-shell template, 20 parts of sodium chloride and 18 parts of polymethyl methacrylate microspheres and add them to a ball mill. Mix them at 400 r / min for 4 h and pass them through a 150 mesh sieve to obtain the precursor.

[0040] S4. The precursor was placed in a tube furnace and heated to 580℃ for 2 hours under argon protection at a heating rate of 4℃ / min. Then, a mixture of ammonia and argon with a volume ratio of 1:6 was used, and the temperature was increased to 730℃ at a heating rate of 9℃ / min and held for 1.2 hours. The temperature was increased again to 930℃ at a heating rate of 4℃ / min and held for 2.5 hours. After carbonization, the product was cooled to room temperature and added to a 0.1 mol / L oxalic acid solution. The solution was treated at 75℃ and 200 rpm for 4.5 hours. After treatment, the product was filtered and washed with boiling water at 90℃ for 8 hours, with the water changed every 2 hours during the washing process. Finally, the product was ball-milled at 200 rpm for 40 minutes and passed through a 150-mesh sieve to obtain porous carbon anode material for lithium-ion batteries.

[0041] The preparation steps of the functional monomer in step S1 are as follows:

[0042] A1. Add 45 parts of 2-pyridinecarboxaldehyde, 22 parts of 4-aminopyridine, 90 parts of anhydrous ethanol and 1 part of lanthanum trifluoromethanesulfonate to a three-necked flask and reflux at 68°C for 5 hours. During the reaction, use a reflux condenser to maintain a nitrogen atmosphere. After the reaction is completed, cool the reaction solution to room temperature, then wash with deionized water and filter to obtain the intermediate.

[0043] A2. Dissolve 7 parts of the intermediate in 35 parts of tetrahydrofuran. In an ice bath at -8°C, add 18 parts of a 30wt% tetrahydrofuran solution of phenylphosphonic dichloride at a rate of 2 mL / min, maintaining the temperature at -3°C during the addition process. After the addition is complete, raise the temperature to 23°C and continue the reaction for 13 h. After the reaction is complete, adjust the pH to 7 with saturated sodium bicarbonate solution, then extract. The organic phase is dried with anhydrous sodium sulfate, filtered, distilled under reduced pressure and washed, and finally dried under vacuum to obtain the functional monomer.

[0044] The chain transfer agent step in step S1 is as follows:

[0045] 22 parts of sodium lignosulfonate, 6 parts of 4-cyano-4-[(dodecylthioalkylthiocarbonyl)thioalkyl]valeric acid and 90N,N-dimethylformamide were added to a three-necked flask and reacted at 78°C under nitrogen protection for 7 hours. After the reaction was completed, the reaction solution was added to acetone with a volume of 5 times that of the reaction solution for precipitation. After filtration, washing and vacuum drying, the chain transfer agent was obtained.

[0046] Example 2

[0047] A method for preparing a porous carbon anode material for lithium-ion batteries includes the following preparation steps:

[0048] S1. Dissolve 25 parts of functional monomer and 6 parts of chain transfer agent in 85 parts of N,N-dimethylformamide, add 33 parts of acrylonitrile and 0.5 parts of ammonium persulfate, and react at 410 rpm for 4.5 h under nitrogen protection at 69 °C. Then add 33 parts of acrylonitrile and 0.09 parts of azobisisobutyronitrile, raise the temperature to 84 °C, and continue to react for 6.8 h while keeping the nitrogen flow rate and stirring speed constant. After the reaction is completed, add the reaction solution to deionized water with a volume of 6 times that of the reaction solution for precipitation. After the gel is crushed, it is extracted by Soxhlet extraction and dried to obtain the copolymer.

[0049] S2. Place 10 parts of nano molybdenum trioxide and 15 parts of zinc acetate dihydrate in a ball mill and mix them at 310 r / min for 3.8 h. Transfer the mixture to a muffle furnace and calcine it in an air atmosphere at 290 °C for 2.8 h. After natural cooling, wash it with deionized water and filter it to obtain the core-shell template.

[0050] S3. Take 29 parts of copolymer, 15 parts of core-shell template, 21 parts of sodium chloride and 19 parts of polymethyl methacrylate microspheres and add them to a ball mill. Mix them at 410 r / min for 3.8 h and pass them through a 150 mesh sieve to obtain the precursor.

[0051] S4. The precursor was placed in a tube furnace and heated to 590℃ at a rate of 5℃ / min under argon protection, and held for 1.9h. Then, a mixture of ammonia and argon with a volume ratio of 1:7 was used, and the temperature was increased to 740℃ at a rate of 10℃ / min, and held for 1.1h. The temperature was increased again to 940℃ at a rate of 5℃ / min, and held for 2.4h. After carbonization, the product was cooled to room temperature, removed, and added to a 0.2mol / L oxalic acid solution. The solution was treated at 220rpm and 78℃ for 4.2h. After treatment, the product was filtered and washed with boiling water at 93℃ for 7.6h, with the water changed every 2h during the washing process. Finally, the product was ball-milled at 220rpm for 36min and passed through a 170-mesh sieve to obtain porous carbon anode material for lithium-ion batteries.

[0052] The preparation steps of the functional monomer in step S1 are as follows:

[0053] A1. 47 parts of 2-pyridinecarboxaldehyde, 24 parts of 4-aminopyridine, 95 parts of anhydrous ethanol and 2 parts of lanthanum trifluoromethanesulfonate were added to a three-necked flask and refluxed at 69°C for 4.8 h. During the reaction, a reflux condenser was used to maintain a nitrogen atmosphere. After the reaction was completed, the reaction solution was cooled to room temperature and then washed with deionized water and filtered to obtain the intermediate.

[0054] A2. Dissolve 6 parts of the intermediate in 36 parts of tetrahydrofuran. In an ice bath at -10℃, add 19 parts of a 31wt% tetrahydrofuran solution of phenylphosphonic dichlorophenate at a rate of 3 mL / min, maintaining the temperature at -4℃ during the addition process. After the addition is complete, raise the temperature to 24℃ and continue the reaction for 12 h. After the reaction is complete, adjust the pH to 7.5 with saturated sodium bicarbonate solution, then extract. After drying the organic phase with anhydrous sodium sulfate, filter, distill under reduced pressure and wash, and finally dry under vacuum to obtain the functional monomer.

[0055] The chain transfer agent step in step S1 is as follows:

[0056] 19 parts of sodium lignosulfonate, 5 parts of 4-cyano-4-[(dodecylthioalkylthiocarbonyl)thioalkyl]valeric acid and 95 parts of N,N-dimethylformamide were added to a three-necked flask and reacted at 79°C under nitrogen protection for 6.8 h. After the reaction was completed, the reaction solution was added to acetone with a volume of 6 times that of the reaction solution for precipitation. After filtration, washing and vacuum drying, the chain transfer agent was obtained.

[0057] Example 3

[0058] A method for preparing a porous carbon anode material for lithium-ion batteries includes the following preparation steps:

[0059] S1. Dissolve 28 parts of functional monomer and 8 parts of chain transfer agent in 100 parts of N,N-dimethylformamide, add 35 parts of acrylonitrile and 0.6 parts of ammonium persulfate, and react at 72°C and nitrogen protection with stirring at 450 rpm for 3 h. Then add 35 parts of acrylonitrile and 0.12 parts of azobisisobutyronitrile, raise the temperature to 87°C, and continue to react for 5 h while keeping the nitrogen flow rate and stirring speed constant. After the reaction is completed, add the reaction solution to deionized water with a volume of 7 times that of the reaction solution for precipitation. After the gel is crushed, it is extracted by Soxhlet extraction and dried to obtain the copolymer.

[0060] S2. Place 11 parts of nano molybdenum trioxide and 16 parts of zinc acetate dihydrate in a ball mill and mix them at 340 r / min for 2 h. Transfer the mixture to a muffle furnace and calcine it at 320 ℃ in air atmosphere for 1 h. After natural cooling, wash it with deionized water and filter it to obtain the core-shell template.

[0061] S3. Take 32 parts of copolymer, 16 parts of core-shell template, 23 parts of sodium chloride and 22 parts of polymethyl methacrylate microspheres and add them to a ball mill. Mix them at 440 r / min for 4 h and pass them through a 200 mesh sieve to obtain the precursor.

[0062] S4. The precursor is placed in a tube furnace and heated to 620℃ at a rate of 6℃ / min under argon protection, and held for 1.5h. Then, a mixture of ammonia and argon with a volume ratio of 1:8 is used, and the temperature is increased to 770℃ at a rate of 11℃ / min and held for 0.8h. The temperature is increased again to 970℃ at a rate of 6℃ / min and held for 1.5h. After carbonization, the product is cooled to room temperature, removed, and added to a 0.3mol / L oxalic acid solution. The solution is treated at 300rpm and 85℃ for 3.5h. After treatment, the product is filtered and washed with boiling water at 100℃ for 6h, with the water changed every 2h during the washing process. Finally, the product is ball-milled at 260rpm for 30min and passed through a 200-mesh sieve to obtain porous carbon anode material for lithium-ion batteries.

[0063] The preparation steps of the functional monomer in step S1 are as follows:

[0064] A1. 55 parts of 2-pyridinecarboxaldehyde, 28 parts of 4-aminopyridine, 100 parts of anhydrous ethanol and 3 parts of lanthanum trifluoromethanesulfonate were added to a three-necked flask and refluxed at 72°C for 3 hours. During the reaction, a reflux condenser was used to maintain a nitrogen atmosphere. After the reaction was completed, the reaction solution was cooled to room temperature and then washed with deionized water and filtered to obtain the intermediate.

[0065] A2. Dissolve 7 parts of the intermediate in 40 parts of tetrahydrofuran. In an ice bath at -12°C, add 22 parts of 35wt% tetrahydrofuran solution of phenylphosphonic dichlorophenate dropwise at a rate of 2 mL / min, maintaining the temperature at -7°C during the dropwise addition. After the dropwise addition is complete, raise the temperature to 27°C and continue the reaction for 11 h. After the reaction is complete, adjust the pH to 8 with saturated sodium bicarbonate solution, then extract. The organic phase is dried with anhydrous sodium sulfate, filtered, distilled under reduced pressure and washed, and finally dried under vacuum to obtain the functional monomer.

[0066] The chain transfer agent step in step S1 is as follows:

[0067] 22 parts of sodium lignosulfonate, 6 parts of 4-cyano-4-[(dodecylthioalkylthiocarbonyl)thioalkyl]valeric acid and 100 parts of N,N-dimethylformamide were added to a three-necked flask and reacted at 82°C under nitrogen protection for 5 hours. After the reaction was completed, the reaction solution was added to acetone with a volume of 7 times that of the reaction solution for precipitation. After filtration, washing and vacuum drying, the chain transfer agent was obtained.

[0068] Example 4

[0069] A method for preparing a porous carbon anode material for lithium-ion batteries includes the following preparation steps:

[0070] S1. Dissolve 28 parts of functional monomer and 8 parts of chain transfer agent in 100 parts of N,N-dimethylformamide, add 34 parts of acrylonitrile and 0.5 parts of ammonium persulfate, and react at 72℃ and nitrogen protection with stirring speed of 450 rpm for 3.5 h. Then add 34 parts of acrylonitrile and 0.1 parts of azobisisobutyronitrile, raise the temperature to 85℃, keep the nitrogen flow rate and stirring speed constant, and continue to react for 5 h. After the reaction is completed, add the reaction solution to deionized water with a volume of 7 times that of the reaction solution for precipitation. After the gel is crushed, it is extracted by Soxhlet extraction and dried to obtain the copolymer.

[0071] S2. Place 10 parts of nano molybdenum trioxide and 15 parts of zinc acetate dihydrate in a ball mill and mix them at 340 r / min for 2.5 h. Transfer the mixture to a muffle furnace and calcine it in an air atmosphere at 320 °C for 1 h. After natural cooling, wash it with deionized water and filter it to obtain the core-shell template.

[0072] S3. Take 32 parts of copolymer, 15 parts of core-shell template, 22 parts of sodium chloride and 20 parts of polymethyl methacrylate microspheres and add them to a ball mill. Mix them at 440 r / min for 3 h and pass them through a 170 mesh sieve to obtain the precursor.

[0073] S4. The precursor is placed in a tube furnace and heated to 600℃ for 1.6h at a heating rate of 5℃ / min under argon protection. Then, a mixture of ammonia and argon with a volume ratio of 1:8 is used and the temperature is increased to 760℃ at a heating rate of 10℃ / min and held for 1h. The temperature is increased again to 960℃ at a heating rate of 5℃ / min and held for 2h. After carbonization, the product is cooled to room temperature and added to a 0.3mol / L oxalic acid solution. The solution is treated at 300rpm and 85℃ for 4h. After treatment, the product is filtered and washed with boiling water at 100℃ for 6h, with the water changed every 2h during the washing process. Finally, the product is ball-milled at 260rpm for 32min and passed through a 200-mesh sieve to obtain porous carbon anode material for lithium-ion batteries.

[0074] The preparation steps of the functional monomer in step S1 are as follows:

[0075] A1. 55 parts of 2-pyridinecarboxaldehyde, 28 parts of 4-aminopyridine, 100 parts of anhydrous ethanol and 2 parts of lanthanum trifluoromethanesulfonate were added to a three-necked flask and refluxed at 72°C for 3.4 h. During the reaction, a reflux condenser was used to maintain a nitrogen atmosphere. After the reaction was completed, the reaction solution was cooled to room temperature and then washed with deionized water and filtered to obtain the intermediate.

[0076] A2. Dissolve 6 parts of the intermediate in 40 parts of tetrahydrofuran. In an ice bath at -10℃, add 21 parts of 32wt% tetrahydrofuran solution of phenylphosphonic dichlorophenate at a rate of 2mL / min, maintaining the temperature at -6℃ during the addition process. After the addition is complete, raise the temperature to 26℃ and continue the reaction. After the reaction is complete, adjust the pH to 7 with saturated sodium bicarbonate solution, then extract. After drying the organic phase with anhydrous sodium sulfate, filter, distill under reduced pressure and wash, and finally dry under vacuum to obtain the functional monomer.

[0077] The chain transfer agent step in step S1 is as follows:

[0078] 22 parts of sodium lignosulfonate, 5 parts of 4-cyano-4-[(dodecylthioalkylthiocarbonyl)thioalkyl]valeric acid and 100 parts of N,N-dimethylformamide were added to a three-necked flask and reacted at 80°C under nitrogen protection for 6 hours. After the reaction was completed, the reaction solution was added to acetone with a volume of 7 times that of the reaction solution for precipitation. After filtration, washing and vacuum drying, the chain transfer agent was obtained.

[0079] Comparative Example 1

[0080] A method for preparing a porous carbon anode material for lithium-ion batteries differs from Example 4 in that the functional monomer synthesis step is omitted, and pyridine monomers directly participate in the polymerization reaction. Specifically, in step S1, 28 parts of 4-vinylpyridine are used to directly replace the functional monomer, while the remaining chain transfer agent, reaction solvent, and polymerization conditions are the same as in Example 4.

[0081] Comparative Example 2

[0082] A method for preparing a porous carbon anode material for lithium-ion batteries differs from Example 4 in that the phenylphosphonic dichloride reaction is omitted in the preparation of the functional monomer. Specifically, in the synthesis of the functional monomer, only the reflux reaction of 2-pyridinecarboxaldehyde and 4-aminopyridine is carried out to obtain an intermediate, and the subsequent reaction step of the intermediate with phenylphosphonic dichloride is no longer performed, that is, the introduction path of phosphorus doping is omitted. Subsequently, this unmodified intermediate replaces the fully synthesized functional monomer and participates in the preparation of the copolymer. The remaining chain transfer agent, polymerization reaction and post-treatment conditions are the same as in Example 4.

[0083] Comparative Example 3

[0084] A method for preparing a porous carbon anode material for lithium-ion batteries differs from Example 4 in that, in the preparation of the core-shell template, the ball milling and calcination process of nano-molybdenum trioxide and zinc acetate dihydrate is abandoned, and an equal weight portion of zinc oxide powder is used as a single template agent. Specifically, in step S2, 15 parts of zinc oxide powder are directly used to replace the core-shell template, and the ball milling and high-temperature calcination treatment are no longer performed. Subsequently, this single template agent is mixed with other components to prepare a precursor and carbonization is completed. The remaining copolymer synthesis, pore-forming agent addition, and post-carbonization treatment conditions are the same as in Example 4.

[0085] Comparative Example 4

[0086] A method for preparing a porous carbon anode material for lithium-ion batteries differs from Example 4 in that, in the chain transfer agent preparation process, unmodified sodium lignosulfonate is used to directly participate in the polymerization reaction, eliminating the grafting reaction step with 4-cyano-4-[(dodecylthioalkylthiocarbonyl)thioalkyl]pentanoic acid. Specifically, in step S1, 8 parts of unmodified sodium lignosulfonate are directly used to replace the modified chain transfer agent and added to the polymerization system to participate in the reaction. The remaining functional monomers, polymerization reaction conditions, and post-treatment steps are the same as in Example 4.

[0087] Comparative Example 5

[0088] A method for preparing a porous carbon anode material for lithium-ion batteries differs from Example 4 in that polymethyl methacrylate microspheres are not added during the precursor preparation in step S3. Specifically, sodium chloride is used as a single pore-forming agent to mix and ball-mill with the copolymer and core-shell template, without adding polymethyl methacrylate microspheres. The remaining copolymer synthesis, core-shell template preparation, and carbonization post-treatment conditions are the same as in Example 4.

[0089] Comparative Example 6

[0090] A method for preparing a porous carbon anode material for lithium-ion batteries differs from Example 4 in that nano-molybdenum trioxide is not used in step S2. Specifically, 15 parts of zinc acetate dihydrate are ball-milled and calcined at high temperature, omitting the addition of nano-molybdenum trioxide. The molybdenum-free template is then mixed with other components to prepare a precursor and carbonized. The remaining copolymer synthesis, pore-forming agent addition, and post-carbonization treatment conditions are the same as in Example 4.

[0091] The porous carbon anode materials for lithium-ion batteries prepared in Examples 1-4 and Comparative Examples 1-6 were tested for pore structure performance. The test results are shown in Table 1.

[0092] The lithium-ion batteries prepared in Examples 1-4 and Comparative Examples 1-6 were mixed with porous carbon anode material, acetylene black, and polyvinylidene fluoride at a mass ratio of 8:1:1, and a slurry was prepared using N-methylpyrrolidone as a solvent. This slurry was coated onto copper foil, dried, and then cut into electrode sheets. Using lithium metal sheets as the counter electrode, Celgard 2400 as the separator, and 1 mol / L, 1:1 volume ratio LiPF6-EC / DEC as the electrolyte, CR2032 coin cells were assembled in a glove box. The electrochemical performance of the assembled lithium-ion batteries was tested, and the results are shown in Table 2.

[0093] Table 1

[0094] Test Project <![CDATA[Specific surface area (m 2 / g)]]> <![CDATA[Micropore volume (cm 3 / g)]]> <![CDATA[Mesopore volume (cm 3 / g)]]> <![CDATA[Total pore volume (cm 3 / g)]]> Electrical conductivity (S / cm) Example 1 2585 0.77 1.22 2.02 8.83 Example 2 2693 0.78 1.25 2.05 9.54 Example 3 2829 0.81 1.28 2.25 9.96 Example 4 2952 0.83 1.30 2.28 11.05 Comparative Example 1 2311 0.75 1.18 2.01 6.82 Comparative Example 2 2451 0.77 1.21 2.07 7.53 Comparative Example 3 2127 0.73 1.12 1.95 6.35 Comparative Example 4 2414 0.76 1.16 1.99 5.97 Comparative Example 5 2517 0.79 1.14 1.81 8.14 Comparative Example 6 2363 0.74 1.19 2.04 7.12

[0095] Table 2

[0096] Test Project Initial discharge capacity (mAh / g) Capacity retention rate after 100 cycles (%) 5C rate capacity (mAh / g) Charge transfer impedance (Ω) Example 1 685 92.55 518 18.26 Example 2 705 93.86 538 16.55 Example 3 728 95.27 562 14.34 Example 4 782 97.68 605 11.73 Comparative Example 1 645 87.49 450 27.63 Comparative Example 2 655 88.77 465 26.88 Comparative Example 3 595 82.22 405 36.22 Comparative Example 4 632 86.55 438 29.49 Comparative Example 5 668 89.16 480 20.37 Comparative Example 6 610 85.31 420 32.50

[0097] The test data in Tables 1 and 2 show a significant synergistic optimization effect between material structure and performance. Examples 1-4 exhibit excellent pore structure characteristics and electrochemical performance, with Example 4 being the best. Its high specific surface area of ​​2952 m² / g, balanced micropore and mesopore volumes of 0.83 cm³ / g and 1.30 cm³ / g, and high total pore volume of 2.28 cm³ / g indicate successful hierarchical pore construction. This is attributed to the synergistic pore-forming effect of the core-shell template, sodium chloride, and polymethyl methacrylate microspheres. The pyrolysis of the core-shell template forms a mesoporous framework and retains molybdenum doping sites; the melting and etching of sodium chloride generates a microporous network; and the decomposition of polymethyl methacrylate contributes macroporous channels. These three factors collectively optimize ion transport pathways and electrolyte wettability. Meanwhile, the high electronic conductivity of 11.05 S / cm and low charge transfer impedance of 11.73 Ω in Example 4 verified the synergistic effect of multi-element doping of nitrogen, phosphorus and molybdenum. That is, the pyridine nitrogen / graphite nitrogen and CP bond active sites provided by the functional monomers optimized the electron cloud distribution, molybdenum doping improved the conductivity of the carbon layer, and sulfur doping derived from the chain transfer agent promoted the formation of a Li3N-Li2S composite interface layer with high ionic conductivity, which together reduced the lithium ion diffusion barrier.

[0098] Comparative Example 1 directly replaced the functional monomer with 4-vinylpyridine, losing the advantages of phosphorus doping and a rigid framework, resulting in a 38% decrease in electronic conductivity and a 10% reduction in cycle retention, demonstrating that the molecular design of the functional monomer is indispensable for multi-element synergistic doping. Comparative Example 2 lacked the phenylphosphonic dichloride modification step, resulting in no phosphorus doping and a 129% increase in charge transfer impedance, highlighting the key role of phosphorus atoms as Lewis acid sites for lithium-ion chemisorption. Comparative Example 3 replaced the core-shell template with a single zinc oxide, resulting in a 28% decrease in specific surface area and a 33% capacity decay at 5C rate, reflecting the core-shell structure. The study investigated the dual failures of mesoporous structure and molybdenum doping. Comparative Example 4, using unmodified sodium lignosulfonate, showed a 46% decrease in electronic conductivity and a 151% increase in interfacial impedance due to the lack of molecular weight regulation by thiocarbonyl groups and the contribution of sulfur doping. Comparative Example 5, without the addition of polymethyl methacrylate microspheres, resulted in a 12% reduction in mesopore volume and a 21% decrease in total pore volume due to the absence of macropores, confirming that hierarchical pores require multi-template synergy. Comparative Example 6, omitting nano-molybdenum trioxide, showed a 12% decrease in cycle retention due to the lack of molybdenum species doping and template framework support, revealing the necessity of molybdenum for stabilizing the carbon framework and improving interfacial stability.

[0099] The above description is merely an example and illustration of the present invention. Those skilled in the art can make various modifications or additions to the specific embodiments described, or use similar methods to replace them, as long as they do not deviate from the invention or exceed the scope defined in the claims, all of which should fall within the protection scope of the present invention.

Claims

1. A method for preparing a porous carbon anode material for lithium-ion batteries, characterized in that, Includes the following steps: S1. Dissolve the functional monomer and chain transfer agent in N,N-dimethylformamide, add acrylonitrile and ammonium persulfate, carry out the first stage polymerization reaction under nitrogen protection, then add acrylonitrile and azobisisobutyronitrile to carry out the second stage heating polymerization reaction, precipitate the reaction solution in deionized water, and obtain the copolymer by Soxhlet extraction and drying after gel pulverization. S2. Nano molybdenum trioxide and zinc acetate dihydrate are ball-milled and mixed, then calcined, washed and filtered to obtain a core-shell template. S3. Take the copolymer, core-shell template, sodium chloride and polymethyl methacrylate microspheres, ball mill and mix them and sieve them to obtain the precursor; S4. The precursor is first heated to the first carbonization temperature and held in an inert atmosphere, then switched to a mixed gas atmosphere and heated to the second carbonization temperature and held, and then heated to the third carbonization temperature and held. The product is treated with oxalic acid solution, washed with boiling water, ball-milled and sieved to obtain porous carbon anode material for lithium-ion batteries. The functional monomer described in step S1 is prepared through the following steps: A1. Dissolve 2-pyridinecarboxaldehyde and 4-aminopyridine in anhydrous ethanol, add lanthanum trifluoromethanesulfonate and reflux the reaction. After cooling the reaction solution, wash and filter to obtain the intermediate. A2. The intermediate was dissolved in tetrahydrofuran, and a tetrahydrofuran solution of phenylphosphonic dichloride was added dropwise under ice bath conditions. The reaction was maintained at a low temperature and then heated to continue the reaction. After adjusting the pH of the reaction solution, the product was extracted, dried, filtered, distilled under reduced pressure and washed, and then dried under vacuum to obtain the functional monomer. The chain transfer agent described in step S1 is prepared by the following steps: sodium lignosulfonate and a sulfur-containing carbonyl compound are dissolved in N,N-dimethylformamide and reacted under nitrogen protection. The reaction solution is precipitated in acetone and then filtered, washed and vacuum dried to obtain the product.

2. The preparation method according to claim 1, characterized in that, In step S1, the components are 24-28 parts by weight of functional monomer, 5-8 parts by chain transfer agent, 80-100 parts by weight of N,N-dimethylformamide, 64-70 parts by weight of acrylonitrile, 0.4-0.6 parts by weight of ammonium persulfate, and 0.08-0.12 parts by weight of azobisisobutyronitrile.

3. The preparation method according to claim 1, characterized in that, In step S2, the components are 9-11 parts by weight of nano molybdenum trioxide and 14-16 parts by weight of zinc acetate dihydrate.

4. The preparation method according to claim 1, characterized in that, In step S3, the components are 28-32 parts by weight of copolymer, 14-16 parts by weight of core-shell template, 19-23 parts by weight of sodium chloride and 18-22 parts by weight of polymethyl methacrylate microspheres. In step S4, the mixed gas consists of ammonia and argon in a volume ratio of 1:(6-8).

5. The preparation method according to claim 1, characterized in that, In step A1, the ingredients are 45-55 parts by weight of 2-pyridinecarboxaldehyde, 22-28 parts of 4-aminopyridine, 90-100 parts of anhydrous ethanol, and 1-3 parts of lanthanum trifluoromethanesulfonate.

6. The preparation method according to claim 1, characterized in that, In step A2, the components are 5-7 parts by weight of the intermediate, 35-40 parts by weight of tetrahydrofuran, and 18-22 parts by weight of 30-35 wt% tetrahydrofuran solution of phenylphosphonic dichloride.

7. The preparation method according to claim 1, characterized in that, The chain transfer agent preparation steps consist of 18-22 parts by weight of sodium lignosulfonate, 4-6 parts by weight of 4-cyano-4-[(dodecylthioalkylthiocarbonyl)thioalkyl]valeric acid, and 90-100 parts by weight of N,N-dimethylformamide.

8. A porous carbon anode material for lithium-ion batteries, characterized in that, It is prepared by the method for preparing porous carbon anode material for lithium-ion batteries according to any one of claims 1-7.