Preparation method and application of element-doped double-layer porous carbon based on in-situ polymerization
By modifying porous carbon with thiophene-based silanes and in-situ polymerization, a bilayer porous carbon is formed, which solves the structural stability problem of silicon-based anode materials during charge and discharge processes, and realizes the preparation of high-efficiency silicon-carbon anode materials suitable for lithium batteries.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- ZHEJIANG GEYUAN NEW MATERIAL TECH CO LTD
- Filing Date
- 2024-06-17
- Publication Date
- 2026-06-26
AI Technical Summary
In existing technologies, silicon-based anode materials suffer from structural collapse and electrode pulverization due to volume expansion during charging and discharging. Furthermore, the preparation methods are complex and costly, making them unsuitable for industrial production.
By modifying porous carbon with thiophene-based silane and in-situ polymerization, a bilayer porous carbon with a stable structure and complete pore structure is formed. Subsequently, silicon and carbon are coated by vapor deposition to prepare a silicon-carbon anode.
The structure stability and electrochemical performance of silicon-carbon anodes have been improved, with the first reversible capacity reaching over 1750 mAh/g, the first efficiency reaching over 89.5%, and the capacity retention rate reaching over 94% after 100 discharge cycles.
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Figure CN118579758B_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of battery technology, specifically relating to a method for preparing and applying element-doped bilayer porous carbon based on in-situ polymerization. Background Technology
[0002] Currently, graphite is the primary anode material in the lithium battery industry. However, the theoretical specific capacity of graphite anodes is only 372 mAh / g, while silicon's theoretical specific capacity can reach 4200 mAh / g. Silicon's coulombic efficiency is close to that of graphite anodes, its voltage plateau is slightly higher, and it does not deposit lithium during charging and discharging, exhibiting good safety performance, making it the most promising candidate to replace graphite anodes. However, silicon itself has poor conductivity, and its volume expansion during charging and discharging can reach up to 300%, leading to material structure collapse and electrode flaking and pulverization. Each charge and discharge cycle forms a new interface, continuously consuming silicon, lithium, and electrolyte, resulting in loss of active materials, a sharp reduction in battery capacity, and deterioration of cycle performance. To reduce the impact of silicon volume expansion during charging and discharging on the battery and extend cycle life, the main methods employed are reducing the silicon grain size or preparing porous silicon-carbon with core-shell or capsule structures. Existing technologies generally employ complex preparation methods, and the porous structure of porous carbon can be damaged to some extent. Often, further activation and pore expansion are required to obtain a suitable porosity for subsequent silicon deposition.
[0003] CN116040607A discloses a double-layered hollow core-shell porous carbon hybrid material, its preparation method, and its application. The method includes the following steps: dissolving 2-methylimidazole powder in methanol, adding double-layered hollow Co-MOF-74 powder to form a uniform suspension A; dissolving zinc nitrate hexahydrate in methanol to form a solution B; adding solution B to suspension A, centrifuging, washing, and drying to obtain double-layered hollow Co-MOF-74@ZIF-8 core-shell structure powder; annealing the double-layered hollow Co-MOF-74@ZIF-8 core-shell structure powder under argon protection to obtain the double-layered hollow core-shell porous carbon hybrid material. This patent fully utilizes the advantages of porous carbon derived from two MOF materials, combining the conductivity of graphitized carbon with the high specific surface area of porous carbon. However, the reaction process is complex and the preparation cost is high, making it unsuitable for large-scale industrial production. Summary of the Invention
[0004] To address the problems in the prior art, the present invention modifies oxidized porous carbon with thiophene-based silane, polymerizes it in situ, and then carbonizes it to form a bilayer porous carbon with stable structure, elemental doping, and intact pore structure. This bilayer porous carbon can be used to prepare silicon-carbon anodes by direct vapor deposition of silicon and carbon coating without activation.
[0005] The present invention achieves the above objectives through the following technical solutions:
[0006] A method for preparing element-doped bilayer porous carbon based on in-situ polymerization includes the following steps:
[0007] (S1) Oxidation: Porous carbon is soaked in a liquid oxidant for 2-6 hours. After soaking, it is rinsed and dried to obtain oxidized porous carbon.
[0008] (S2) Porous carbon modification: Oxidized porous carbon is dispersed in a mixture of solvent I and thiophene silane, and heated under reflux to obtain thiophene silane modified porous carbon.
[0009] (S3) In-situ polymerization: Thiophene-based silane-modified porous carbon, thiophene, and initiator are added to solvent II and stirred at 50-80°C for 4-10 h under an inert atmosphere to obtain porous carbon / polythiophene composite material.
[0010] (S4) Carbonization: The porous carbon-polythiophene composite material is carbonized to obtain a double-layer porous carbon.
[0011] After oxidation, porous carbon develops abundant oxygen-containing functional groups such as -OH and -COOH on its surface, lowering its isoelectric point and facilitating subsequent silane modification. During thiophene-based silane modification, the -OH and -COOH functional groups on the oxidized porous carbon surface react with silanoxy groups, introducing the thiophene-based silane onto the porous carbon surface via chemical bonds. Simultaneously, the dispersibility of the modified porous carbon is significantly improved, promoting uniform polymerization on its surface. The active thiophene groups on the thiophene-based silane-modified porous carbon surface can then copolymerize with thiophene monomers, allowing polythiophene to be in situ grafted onto the porous carbon surface, forming a porous carbon / polythiophene composite material. Due to in-situ polymerization, the polythiophene is uniformly and stably distributed on the porous carbon surface through covalent bonds, and the porous structure of the porous carbon is fully preserved. Finally, after carbonization, polythiophene forms an amorphous carbon layer that uniformly and stably coats the surface of the porous carbon, forming a double-layer porous carbon. Furthermore, since the thiophene-based silane contains silicon, an organosilicon network film is formed in the structure. The Si-O bond energy is high and the stability is good, ultimately resulting in a double-layer porous carbon with a stable structure, good chemical corrosion resistance, and intact pore structure.
[0012] Further, in step (S1), the porous carbon has a particle size D50 of 3–10 μm and a specific surface area of 1500–2000 m². 2 / g; the liquid phase oxidant is at least one of 3-5 mol / L nitric acid or sulfuric acid.
[0013] Further, in step (S1), the solid-liquid ratio of the porous carbon powder to the liquid oxidant is 100g:(200~400)mL; the soaking temperature is 40~60℃; the rinsing is washing with water until neutral to remove residual oxidant; and the drying is drying until the moisture content is <5wt%.
[0014] Further, in step (S2), the thiophene silane is at least one of triethoxy-2-thiophene silane and trimethoxy-2-thiophene silane.
[0015] Further, in step (S2), the solvent I is at least one of toluene and xylene; the ratio of solvent I to thiophenesilane is 100 mL: (8-12) mL.
[0016] Further, in step (S2), the ratio of the oxidized porous carbon to thiophene silane is 100g:(60-90)mL; the heating and reflux reaction is carried out by heating to 100-120℃ and refluxing for 20-30h.
[0017] Further, in step (S3), the initiator is at least one of FeCl3, MoCl5, and RuCl3; and the solvent II is at least one of chloroform, carbon tetrachloride, dichloromethane, nitrobenzene, and acetone.
[0018] Further, in step (S3), the mass ratio of the thiophene-based silane-modified porous carbon, thiophene, and initiator is 100:(15-30):(2-4).
[0019] Further, in step (S3), the inert atmosphere is nitrogen and / or argon.
[0020] Further, in step (S4), the carbonization conditions are: holding at 300–800°C for 3–8 hours under an inert atmosphere; the inert atmosphere is nitrogen and / or argon.
[0021] Secondly, the present invention also provides a silicon-carbon anode, which is prepared by vapor-phase deposition of silicon and carbon coating of the bilayer porous carbon obtained by the aforementioned preparation method. The processes of vapor-phase deposition of silicon and carbon coating are well known to those skilled in the art. For example, when using an organosilicon source gas for vapor-phase deposition of silicon, the organosilicon source gas is selected from at least one of silane, dichlorosilane, trichlorosilane, silicon tetrachloride, silicon tetrafluoride, and dichlorosilane; when using a carbon source gas for carbon coating, the carbon source gas is selected from at least one of C1-4 alkanes, C2-4 alkenes, and C2-4 alkynes.
[0022] Compared with the prior art, the beneficial effects of the present invention are as follows:
[0023] I. This invention involves in-situ copolymerization of thiophene monomers on the surface of thiophene-based silane-modified porous carbon to form a covalently bonded porous carbon / polythiophene composite material. Due to the in-situ polymerization, polythiophene is uniformly and stably distributed on the surface of the porous carbon through covalent bonds, and the porous structure of the porous carbon is completely preserved. After carbonization, the polythiophene forms an amorphous carbon layer that uniformly and stably coats the surface of the porous carbon. Therefore, the preparation method of this invention produces a bilayer porous carbon with a completely preserved pore structure. It can be directly used to prepare a silicon-carbon anode without activation, and can be directly carried out in the next step of silicon vapor deposition and carbon coating. At the same time, since polythiophene contains silicon, an organosilicon network film is formed in the structure. The silicon content of the obtained bilayer porous carbon is 2.5% to 3.9%, and the Si-O bond energy is high and the stability is good, which can further improve its electrochemical stability. The final product is a double-layer porous carbon with stable structure, good chemical corrosion resistance and intact pore structure. This double-layer porous carbon can be used to prepare silicon-carbon anodes by direct vapor deposition of silicon and carbon coating without activation.
[0024] II. When the bilayer porous carbon prepared by the preparation method of the present invention is used as a silicon-carbon anode in lithium batteries, it has good cycle stability and charge-discharge capacity. Its initial reversible capacity is above 1750 mAh / g, the initial efficiency is above 89.5%, and the capacity retention rate after 100 discharge cycles can still reach above 94%. Attached Figure Description
[0025] Figure 1 This is a pore size distribution diagram of the porous carbon used in the examples.
[0026] Figure 2 The image shows the pore size distribution of the bilayer porous carbon prepared in Example 1. Detailed Implementation
[0027] To better explain the present invention, detailed descriptions are provided with reference to the embodiments of the present invention, and the main contents of the present invention are further clarified in conjunction with specific embodiments. However, the contents of the present invention are not limited to the following embodiments.
[0028] Unless otherwise specified, all "parts" mentioned in the embodiments of this invention refer to parts by weight. All reagents used are commercially available in the art.
[0029] The porous carbon was purchased from Shandong Shengquan New Energy Technology Co., Ltd., with a particle size D50 of 6.2 μm and a specific surface area of 1826 m². 2 / g, average pore size 2.29nm, total pore volume 0.941cm³ 3 / g.
[0030] Polythiophene was purchased from Hubei Biaoyue Biotechnology Development Co., Ltd., with a number average molecular weight of 18,000 to 22,000.
[0031] Example 1
[0032] An element-doped bilayer porous carbon based on in-situ polymerization is prepared by the following steps:
[0033] (S1) Oxidation: 1000g of porous carbon was added to 2500mL of 4mol / L nitric acid and soaked at 50℃ for 4h; the solid was filtered out and rinsed with pure water until neutral, and dried in an oven at 90℃ for 24h to obtain oxidized porous carbon;
[0034] (S2) Porous carbon modification: 200g of oxidized porous carbon was dispersed in a mixture of 1500mL toluene and 120mL triethoxy-2-thiophenesilane, and heated under reflux for 24h with stirring; then cooled, filtered, washed with pure water until the filtrate was colorless, and dried in an oven at 50℃ for 24h to obtain thiophenesilane modified porous carbon.
[0035] (S3) In-situ polymerization: 100g of thiophene-based silane-modified porous carbon, 15g of thiophene, and 2g of FeCl3 were added to chloroform and stirred and refluxed at 50°C for 8h under nitrogen atmosphere to obtain a reddish-brown mixed turbid liquid; the mixed turbid liquid was centrifuged, washed, and then dried at 80°C for 24h to obtain a porous carbon / polythiophene composite material.
[0036] (S4) Carbonization: The porous carbon / polythiophene composite material was carbonized at 500℃ for 4 hours under an argon atmosphere and then cooled naturally to obtain a double-layer porous carbon.
[0037] Example 2
[0038] The rest is the same as in Example 1, except that in step (S2), trimethoxy-2-thiophenesilane is used instead of triethoxy-2-thiophenesilane.
[0039] Example 3
[0040] The rest is the same as in Example 1, except that in step (S3), the amount of materials used is: 100g thiophene-based silane-modified porous carbon, 22g thiophene, and 3g FeCl3; the reaction conditions are: stirring and reflux reaction at 65°C for 6h.
[0041] Example 4
[0042] The rest is the same as in Example 1, except that in step (S3), the amount of materials used is: 100g thiophene-based silane-modified porous carbon, 30g thiophene, and 4g FeCl3; the reaction conditions are: stirring and reflux reaction at 80°C for 4h.
[0043] Example 5
[0044] The rest is the same as in Example 1, except that in step (S3), 2g of MoCl5 is used instead of 2g of FeCl3.
[0045] Example 6
[0046] The rest is the same as in Example 1, except that in step (S2), the amount of material and reaction conditions are as follows: 200g of oxidized porous carbon is dispersed in a mixture of 2000mL toluene and 180mL triethoxy-2-thiophene silane, and heated under reflux for 30h with stirring.
[0047] Comparative Example 1
[0048] The rest is the same as in Example 1, except that in step (S3) the in-situ polymerization method is not used. The thiophene-based silane modified porous carbon is dispersed in a polythiophene solution and then spray granulation is performed to obtain a porous carbon / polythiophene composite material, that is, the surface of the porous carbon is physically coated with a carbon source containing impurities.
[0049] Comparative Example 2
[0050] The rest is the same as in Example 1, except that in step (S2), triethoxy-2-thiophenesilane is replaced with thiopheneformylhydrazine.
[0051] Application Example 1
[0052] The bilayer porous carbon obtained in Example 1 was subjected to chemical vapor deposition and carbon coating to form a silicon-carbon anode material. This silicon-carbon anode material was then applied to the anode of a lithium-ion battery, assembled into a lithium battery, and its electrochemical performance was tested. Specifically, the silicon-carbon anode material, conductive carbon black, and LA133 adhesive were mixed in a mass ratio of 91:3:6 to form a slurry (where the solid content of LA133 adhesive was 5%). This slurry was uniformly coated onto a copper foil current collector and vacuum dried for 12 hours to form the anode sheet. The counter electrode was a lithium metal sheet, the separator was Celgard 2400, and the electrolyte was 1 mol / L LiPF6 / EC+DMC+EMC (EC to DMC to EMD volume ratio of 1:1:1). The batteries were assembled into coin cells in an argon-atmosphere glove box. The assembled batteries were then subjected to charge-discharge tests on a LAND battery tester, with a voltage range of 5mV to 1.5V and a current density of 80mA / g.
[0053] Application Example 2-6
[0054] The other conditions are the same as in Application Example 1, except that the double-layer porous carbon was prepared in Examples 2-6.
[0055] Comparative Application Examples 1-2
[0056] The other conditions are the same as in Application Example 1, except that the multi-layered porous carbon was prepared in Comparative Examples 1-2.
[0057] Testing and Analysis
[0058] The bilayer porous carbon of the above-mentioned embodiments and comparative examples were tested using the following test methods, and the data are shown in Table 1.
[0059] Specific surface area and pore size distribution determination: According to GB / T 19587-2017 Gas Adsorption BET Method, a Tristar II 3020 fully automated specific surface area and pore size analyzer (Micromeritics Instrument Corporation, USA) was used to conduct low-temperature nitrogen adsorption experiments on the bilayer porous carbon prepared in the examples and comparative examples to determine their specific surface area, pore size distribution, and pore volume. The pore size distribution diagram of the raw material porous carbon used in the examples is shown below. Figure 1 As shown; the pore size distribution diagram of the bilayer porous carbon obtained in Example 1 is shown below. Figure 2 As shown.
[0060] Element content: The silicon content of double-layer porous carbon was tested using a high-temperature box-type resistance furnace from Shanghai Jingqi Instrument Co., Ltd., in accordance with GB / T 38823-2020.
[0061] Table 1. Specific surface area, pore size distribution, pore volume, and silicon content of bilayer porous carbon.
[0062]
[0063] Figure 1 The image shows the pore size distribution of the raw material porous carbon. Figure 2 The figure shows the pore size distribution of the bilayer porous carbon obtained in Example 1. A comparison of the two shows that the pore size distributions are similar. Table 1 also shows that the bilayer porous carbon prepared by the method of this invention does not experience a decrease in specific surface area or pore size due to the formation of a bilayer structure. In contrast, the bilayer porous carbon prepared in Comparative Example 1 has a significantly lower specific surface area and pore size than the original porous carbon; while the bilayer porous carbon prepared in Comparative Example 2 does not show a significant change in specific surface area and pore size, it does not contain silicon. This indicates that in this invention, the porous carbon / polythiophene composite material is formed by in-situ copolymerization of thiophene monomers on the surface of thiophene-modified porous carbon, followed by the carbonization of polythiophene to form amorphous carbon coating the surface of the porous carbon, without damaging the pore structure of the original porous carbon. Furthermore, the silicon content of the prepared bilayer porous carbon is between 2.5% and 3.9%, achieving the formation of an organosilicon network film in the structure, which is beneficial for improving electrochemical performance.
[0064] The batteries assembled in the application examples and comparative application examples were subjected to charge-discharge tests on the LAND battery tester. The voltage range was 5mV to 1.5V, and the current density was 80mA / g. The battery performance test results are shown in Table 2.
[0065] Table 2 Electrochemical Performance Tests
[0066]
[0067] As can be seen from the data in Table 2, when the bilayer porous carbon prepared by the method of the present invention is used as the silicon-carbon anode of lithium battery, its initial reversible capacity reaches more than 1750 mAh / g, the initial efficiency reaches more than 89.5%, and the capacity retention rate after 100 discharge cycles can still reach more than 94%, indicating that the assembled lithium battery has good cycle stability and charge-discharge capacity.
[0068] The above detailed description is a specific description of one of the feasible embodiments of the present invention. This embodiment is not intended to limit the patent scope of the present invention. All equivalent implementations or modifications that do not depart from the present invention should be included within the scope of the technical solution of the present invention.
Claims
1. A method for preparing element-doped bilayer porous carbon based on in-situ polymerization, characterized in that, Includes the following steps: (S1) Oxidation: Porous carbon is immersed in a liquid oxidant for 2-6 hours. After immersion, it is rinsed and dried to obtain oxidized porous carbon. (S2) Porous carbon modification: Oxidized porous carbon is dispersed in a mixture of solvent I and thiophene silane, and heated under reflux to obtain thiophene silane modified porous carbon; (S3) In-situ polymerization: Thiophene-modified porous carbon, thiophene, and initiator are added to solvent II and stirred at 50~80℃ for 4~10h under an inert atmosphere to obtain porous carbon / polythiophene composite material; (S4) Carbonization: The porous carbon-polythiophene composite material is carbonized to obtain a double-layer porous carbon.
2. The preparation method according to claim 1, characterized in that, In step (S1), the porous carbon has a particle size D50 of 3~10 μm and a specific surface area of 1500~2000 m². 2 / g; the liquid phase oxidant is at least one of 3~5 mol / L nitric acid or sulfuric acid.
3. The preparation method according to claim 1, characterized in that, In step (S1), the solid-liquid ratio of the porous carbon to the liquid oxidant is 100g:(200~400)mL; the soaking temperature is 40~60℃; the rinsing is washing with water until neutral; and the drying is drying until the moisture content is <5wt%.
4. The preparation method according to claim 1, characterized in that, In step (S2), the thiophene silane is at least one of triethoxy-2-thiophene silane and trimethoxy-2-thiophene silane.
5. The preparation method according to claim 1, characterized in that, In step (S2), solvent I is at least one of toluene and xylene; the ratio of solvent I to thiophenesilane is 100 mL: (8~12) mL.
6. The preparation method according to claim 1, characterized in that, In step (S2), the ratio of the amount of oxidized porous carbon to thiophene silane is 100g: (60~90)mL; the heating and reflux reaction is carried out by heating to 100~120℃ and refluxing for 20~30h.
7. The preparation method according to claim 1, characterized in that, In step (S3), the initiator is at least one of FeCl3, MoCl5, and RuCl3; the solvent II is at least one of chloroform, carbon tetrachloride, dichloromethane, nitrobenzene, and acetone.
8. The preparation method according to claim 1, characterized in that, In step (S3), the mass ratio of the thiophene-modified porous carbon, thiophene, and initiator is 100:(15~30):(2~4).
9. The preparation method according to claim 1, characterized in that, In step (S4), the carbonization conditions are: holding at 300~800℃ for 3~8h under an inert atmosphere; the inert atmosphere is nitrogen and / or argon.
10. A silicon-carbon anode, characterized in that, The double-layer porous carbon prepared by the preparation method according to any one of claims 1-9 is prepared by silicon vapor deposition and carbon coating.