Modified resin polymer, derivative porous carbon of modified resin polymer, composite material, and preparation methods and applications of modified resin polymer and derivative porous carbon and composite material

Abstract

The invention discloses a modified resin polymer and derivative porous carbon thereof, a composite material and preparation and application of the modified resin polymer and the derivative porous carbon. The modified resin polymer is formed by copolymerizing and cross-linking high-coking chain segment monomers and low-coking chain segment monomers in an alternating, block or random arrangement manner. The modified resin polymer is carbonized at high temperature to obtain the resin derived carbon material, and the resin derived carbon material is a porous carbon material with uniform closed pores, adjustable porosity, low specific surface area and high conductivity. The invention also discloses an application of the modified resin polymer or the porous carbon in preparation of a lithium ion secondary battery negative electrode material, and the modified resin polymer or the porous carbon is compounded with an alloy type negative electrode material in polymerization and carbon forming processes of the modified resin polymer to form an alloy type-carbon composite porous material in situ. According to the invention, the types and proportions of the high-coking chain segment monomers and the low-coking chain segment monomers are modulated to regulate and control the pore size of the derived carbon, so that the pore size is matched with the expansion of the alloy type negative electrode, and the low-expansion alloy type-carbon composite negative electrode is obtained.

Description

Technical Field

[0001] This invention belongs to the field of polymer materials, specifically relating to a polymer material for preparing porous carbon and its application in the negative electrode of lithium-ion batteries. Background Technology

[0002] Alloy-type anode materials (including silicon, germanium, tin, antimony, aluminum, etc.) are based on lithium alloying (A + Li = Li). X Method A) of storing lithium ions in anode materials can significantly improve the energy density of lithium batteries, but it results in significant lithium intercalation expansion and a shorter battery cycle life. Using porous carbon as a carrier for the anode active material to create alloy-carbon composite anode materials can effectively mitigate the expansion caused by the cyclic alloying reaction and achieve excellent battery life. Using polymers as precursors, followed by pyrolysis, carbonization, and etching to create pores, is one of the mainstream methods for preparing porous carbon.

[0003] Existing polymer-based porous carbon still has several significant problems: (1) The specific surface area of ​​porous carbon is too large. In order to obtain high porosity, porous carbon often has a lot of open pores during the process of pyrolysis carbonization and etching pore formation, which will result in a high specific surface area (>500 m). 2 / g), when applied to the negative electrode, it can easily lead to a decrease in the first coulombic efficiency of the battery [Carbon Energy, 2019, 1(2): 219-245.]; (2) The pore size and porosity of porous carbon are difficult to control. Existing polymer-based porous carbon has a small pore size, often concentrated in micropores and mesopores (pore size in a few nanometers or tens of nanometers), and a low porosity (<30%). It is not possible to produce macroporous carbon with large porosity (porosity >40%) and pore size distribution concentrated in 50 nm or even hundreds of nanometers. Macropores are often more effective in alleviating electrode volume expansion [Advanced Functional Materials 33.26 (2023): 2301109.][Nano-Micro Letters, 2024, 16(1): 179.]; (3) Porous carbon generally has a low electronic conductivity. The presence of micropores and mesopores will significantly hinder electron transport and reduce particle conductivity. [A method for preparing composite high-entropy hard carbon anode material and sodium-ion battery CN120864481A] [Carbon-carbon composite material and its preparation method, anode sheet and sodium-ion battery CN120674437A] [New Carbon Materials, 2023, 38(1):96-108.]; (4) Porous carbon often uses alkaline etching or water vapor etching to generate pores, resulting in low carbon yield (i.e., porous carbon weight / carbon source weight <15%), complex equipment, and high cost.

[0004] Therefore, developing modified resin polymer materials that can be used to prepare closed-cell, low-specific-surface-area, and high-conductivity porous carbon (with pores uniformly distributed in the range of 50 to 500 nm) at low cost is expected to solve the production problems of the aforementioned polymer-based porous carbon and has significant potential application value. Summary of the Invention

[0005] This invention addresses the existing technical problems of porous carbon by providing modified resin polymers and their derived porous carbons, composite materials, and their preparation and application, in order to obtain porous carbon materials with uniform closed pores, adjustable porosity, low specific surface area, and high electrical conductivity, and to use them in lithium-ion battery anodes.

[0006] The modified resin polymer provided by this invention is copolymerized and crosslinked from high-coke-chain monomers and low-coke-chain monomers in an alternating, block, or random arrangement with the addition of a crosslinking agent and an initiator. The high-coke-chain monomers are one or more combinations of melamine, urea, resorcinol, furfuryl alcohol, and aniline, and the low-coke-chain monomers are at least one of sugars and sugar alcohols, preferably at least one of fructose, glucose, xylose, mannose, sucrose, xylitol, erythritol, sorbitol, and mannitol.

[0007] This invention also provides a method for preparing the above-mentioned modified resin polymer: (1) The high coking segment monomer, crosslinking agent, low coking segment monomer and solvent L1 are fully dispersed and mixed in a ratio of 1 g:(0.3~3) g:(0.3~3) g:(10~60) ml to obtain a mixture S1, so as to achieve uniform distribution.

[0008] (2) Add an initiator to the mixture S1 and adjust the pH to 4~10 to induce cross-linking and copolymerization of high coking segment monomers and low coking segment monomers; remove the solvent in the resulting mixture after polymerization, and then heat it in vacuum at 30~150℃ for 3~12h to obtain modified resin polymer S2.

[0009] The modified resin polymer described above further includes, in step (1), the high-coking segment monomer, which is one or more of melamine, urea, resorcinol, furfuryl alcohol, and aniline. The high-coking segment monomer is characterized by its high carbon yield and low porosity after carbonization. It is the main carbon-yielding phase (carbon-yielding phase) of the modified resin polymer, and the coking value of the high-coking segment polymerized from it is 40-70%, with a porosity of <50% after coking.

[0010] Furthermore, in the above-mentioned modified resin polymer, the crosslinking agent is one of formaldehyde and acetone. The crosslinking agent can crosslink and copolymerize with high-coke segments under the above-mentioned pH conditions.

[0011] Further, in the above-mentioned modified resin polymer, the low-coke segment monomer is at least one of sugars and sugar alcohols. The low-coke segment monomer and the high-coke segment monomer are uniformly dispersed and participate in macromolecular bonding, copolymerizing and crosslinking in an alternating, block, or random arrangement to form a modified resin polymer in the form of a long molecular chain. The low-coke segment monomer is characterized by a molecular weight of 60-300, low carbon yield, and high porosity after carbonization. It is the main pore-forming phase (porous phase) of the modified resin polymer, and the coke value of the low-coke segment monomer polymerized therefrom is 0-40%, and the porosity after coking is >50%. Preferably, the low-coke segment monomer is at least one of fructose, glucose, xylose, mannose, sucrose, xylitol, erythritol, sorbitol, and mannitol.

[0012] Further, in the above-mentioned modified resin polymer, the solvent L1 is one or a mixture of methanol, ethanol, isopropanol, toluene, and deionized water.

[0013] The modified resin polymer described above, further, the dispersion method in step (1) is one or more combinations of stirring and ultrasonication, and the dispersion time is 0.1~2h.

[0014] The modified resin polymer described above, further, the initiator mentioned in step (2) is at least one of ammonia, phytic acid, acetic acid, formic acid, hydrochloric acid, and phosphoric acid, and its function is to adjust the pH value of the solution to initiate the polymerization of each chain segment.

[0015] Further, in step (2), the stirring is performed at 100-800 rpm for 0.3-4 h; the solvent removal method is rotary evaporation, and the rotary evaporation conditions are a vacuum of -0.05--0.3 MPa, a temperature of 30-150°C, and stirring at 100-800 rpm for 3-12 h; the heat treatment method is secondary rotary evaporation, or treatment in a vacuum oven at 100-150°C for 3-12 h, and the specific parameters of the secondary rotary evaporation may be the same as or different from those of the rotary evaporation treatment.

[0016] This invention also provides a porous carbon with low specific surface area and high electrical conductivity, which is obtained by sintering and carbonizing a modified resin polymer S2 at an inert atmosphere and at 500-1200°C for 2-8 hours. During the carbonization process, the long molecular chains formed by the copolymerization of high-coke-chain monomers and low-coke-chain monomers are transformed into a uniformly distributed carbon matrix and closed pores, forming a porous carbon material.

[0017] The aforementioned porous carbon with low specific surface area and high electrical conductivity further includes an inert atmosphere of nitrogen, argon, or a mixture of hydrogen and argon (in which hydrogen accounts for 5-10% vol%), and a sintering carbonization heating rate of 1-10 °C / min.

[0018] Furthermore, for the aforementioned porous carbon with low specific surface area and high electrical conductivity, the carbonization temperature is preferably 800~1200℃.

[0019] The aforementioned porous carbon with low specific surface area and high electrical conductivity is a resin-derived carbon material obtained by high-temperature carbonization of the modified resin polymer. This carbon material has high density, uniformly distributed large-sized pores, a coking value >40%, a porosity of 50%~80%, a pore size of 50~1000 nm, and adjustable porosity and pore size, with a specific surface area of ​​5~20 m². 2 / g, compared to conventional hard carbon, the conductivity can be improved by 30% (from 37.5 S / cm to 49.0 S / cm). When used to prepare alloy-carbon composite particles, it can significantly reduce lithium intercalation expansion and improve the first coulombic efficiency and fast charging performance.

[0020] The present invention also provides a method for preparing the above-mentioned porous carbon, wherein the modified resin polymer S2 is sintered and carbonized at 500~1200℃ for 2~8h under an inert atmosphere.

[0021] The present invention also provides the application of the above-mentioned modified resin polymer or the above-mentioned porous carbon in the preparation of lithium-ion secondary battery anode materials.

[0022] The above application, further specifically, involves combining the modified resin polymer with an alloy-type negative electrode material during the polymerization and carbonization process to form an alloy-carbon composite porous material in situ.

[0023] The above application further involves, in the first step of polymerizing the modified resin polymer into carbon, mixing it with alloy-type anode material nanoparticles, high-coke-segment monomers, low-coke-segment monomers, crosslinking agents, and initiators. The specific method is as follows: (1) Alloy-type anode material nanoparticles, high coking segment monomers, crosslinking agents, low coking segment monomers and solvent L1 are thoroughly mixed in a ratio of 1 g: (0.3~3) g: (0.3~3) g: (0.3~3) g: (10~60) ml to obtain a mixture S1, thereby achieving a uniform distribution of alloy-type anode material, high coking segment monomers and low coking segment monomers.

[0024] (2) Add an initiator to the mixture S1 and adjust the pH to induce copolymerization of high coking segment monomers and low coking segment monomers; remove the solvent from the resulting mixture after polymerization, and then heat it under vacuum at 30~150℃ for 3~12 h to obtain alloy nanoparticle-modified resin composite precursor S2. (3) At least one of machine solid phase asphalt coating, liquid phase asphalt coating, and acetylene vapor phase deposition coating is used to coat the surface of S2 with a coating layer with a thickness of 50~700 nm (preferably 100~300 nm) to obtain the coated alloy nanoparticle-modified resin composite precursor S3.

[0025] (4) S3 is transferred to an inert atmosphere and kept at 500~1200℃ for 2~8h for sintering. During the sintering process, the long molecular chains after copolymerization of high-coke chain segment monomers and low-coke chain segment monomers decompose and are transformed into an alloy-carbon composite porous material in which carbon matrix and closed pores are uniformly distributed between alloy nanoparticles.

[0026] In the above method, the alloy-type anode material mentioned in step (1) is at least one of silicon, germanium, tin, antimony, and aluminum; the nanoparticle size of the alloy-type anode material is 30~200 nm.

[0027] In the above application, further, the specific method of machine solid phase asphalt coating in step (3) is to put S2 and asphalt into the solid phase coating machine at a ratio of 1: (0.2~1.4) and stir continuously at a speed of 1000~6000 rpm and 30~200℃ for 5~120 minutes; The specific method for liquid phase coating is to thoroughly mix S2 with asphalt, toluene, quinoline, and alcohol in a ratio of 1g:(0.2~1.4)g:(0.3~8)ml:(0.3~8)ml:(0.3~8)ml, and then rotary evaporate the mixture under a vacuum of -0.05~-0.3 MPa and a temperature of 30~150℃, while simultaneously applying stirring at 100~800 rpm for 3~12 h. The acetylene vapor deposition coating process involves placing S2 in a high-purity nitrogen atmosphere, heating it to 600-900℃ at a rate of 3-10℃ / min, introducing methane gas at a rate of 0.2-8L / min for 0.5-7 h, and then naturally cooling it to room temperature.

[0028] In the above application, steps (3) and (4) are repeated once or multiple times. The purpose of repeated coating and carbonization is to improve the material surface through multiple coatings, thereby improving the initial coulombic efficiency of the material in lithium-ion batteries.

[0029] In the above application, before starting step (4), the material can be pre-oxidized. Specifically, the material is heated to 150-300℃ at a rate of 1-10℃ / min and held for 0.3-2 hours in an air or oxygen atmosphere. The purpose of pre-oxidation is to stabilize and cure the surface of the asphalt-coated composite material.

[0030] In the above applications, the inert atmosphere described in step (4) is any one of nitrogen, argon, and a mixture of hydrogen and argon (where hydrogen accounts for 5-10% vol%), and the sintering heating rate is 1-10℃ / min, preferably the sintering temperature is 800-1200℃.

[0031] The present invention also provides an alloy-carbon composite porous material, which is prepared by the specific method described above in the application of the modified resin polymer in the preparation of lithium-ion secondary battery anode materials.

[0032] This invention also provides a method for preparing an alloy-carbon composite porous material, which is the same as the method described above for the application of modified resin polymers in the preparation of lithium-ion secondary battery anode materials.

[0033] This invention also provides the application of porous carbon materials or alloy-carbon composite porous materials as negative electrode materials for lithium-ion secondary batteries.

[0034] Furthermore, the application involves using the porous carbon material or alloy-carbon composite material of the present invention as an active material, mixed with a binder and a conductive agent, and coated onto copper foil as a negative electrode for a lithium-ion battery; or using the porous carbon material or alloy-carbon composite material of the present invention mixed with graphite in a certain proportion as a mixed active material, and then mixed with a binder and a conductive agent and coated onto copper foil as a negative electrode for a lithium-ion battery, which can be cut into the required shape during use.

[0035] Compared with the prior art, the present invention has the following beneficial effects: 1. Compared to traditional resins that are polymerized and pyrolyzed from a single high-coke-segment monomer to form carbon materials, this invention proposes to modify resin materials by copolymerizing low-coke-segment monomers with high-coke-segment monomers. This constructs a three-dimensional molecular network structure, achieving modification of the resin material. Carbon and porous phases are uniformly dispersed at the molecular scale, allowing the modified resin polymer structure to spontaneously decompose during carbonization, forming a predominantly closed-pore internal pore structure and promoting carbon atom rearrangement to improve carbon defects. This enables the preparation of closed-pore, low-specific-surface-area, and high-conductivity porous carbon with high carbon yield. The resulting derived porous carbon material has a large pore size and good pore wall continuity, possessing both high porosity (50%~80%) and low specific surface area (<20m²). 2 The characteristics of / g) not only contribute to achieving high initial coulombic efficiency in lithium-ion batteries, but the rich porous structure can also fully accommodate the lithium intercalation expansion of the alloy-type anode, and can be used to prepare high-performance alloy-carbon composite anode materials.

[0036] 2. By adjusting the type and ratio of high-coke-chain segment monomers and low-coke-chain segment monomers, different assembly structures can be achieved, thereby changing the cracking behavior of copolymer macromolecules during carbonization. This allows for the regulation of the pore size (50~1000nm) of the derived carbon to match the expansion of the alloy-type anode, ultimately resulting in a low-expansion alloy-carbon composite anode.

[0037] 3. The modified resin polymer of this invention, after copolymerization, has a long molecular chain structure that facilitates the orderly rearrangement of carbon atoms during carbonization, reducing defects in the resulting carbon material and thus giving it high electrical conductivity (>40 S / cm). After composite formation, it can improve the performance of alloy-type anodes with poor conductivity, such as silicon and germanium, and significantly enhance the conductivity of alloy-carbon composite materials.

[0038] 4. This process boasts high production efficiency and environmental friendliness, completely avoiding etching and pore-forming steps, achieving a carbon yield of >40%, and significantly reducing the cost of porous carbon preparation. The porous carbon material prepared using this method can be combined with alloy-type anode materials to prepare alloy-carbon composite porous materials, avoiding complex alkaline etching or water vapor etching processes, resulting in low overall cost and excellent electrochemical performance. Attached Figure Description

[0039] Figure 1 The image shows a cross-sectional view of the porous carbon material 1 prepared in Example 1 after argon ion milling by SEM. Figure 2 The image shows a cross-sectional view of the porous carbon material 2 prepared in Example 2 after argon ion milling using a scanning electron microscope (SEM). Figure 3 The charge-discharge curves of the silicon-carbon composite porous material 2 electrode prepared in Example 2 are shown. Figure 4 The image shows a cross-sectional view of the porous carbon material 3 prepared in Example 3 after argon ion milling using a scanning electron microscope. Figure 5 The charge-discharge curves of the porous carbon material electrode 3 prepared in Example 3 are shown. Figure 6 The charge-discharge curves of the silicon-carbon composite porous material electrode 3 prepared in Example 3 are shown. Figure 7 The cycling curve of the silicon-carbon composite porous material electrode 3 prepared in Example 3 at 0.5C; Figure 8 The image shows a cross-sectional view of the porous carbon material 5 prepared in Example 5 after argon ion milling using a scanning electron microscope. Figure 9 A cross-sectional SEM image of the comparative carbon material 1 prepared in Comparative Example 1 after argon ion milling. Figure 10The charge-discharge curves are for the comparative carbon material 1 electrode prepared in Comparative Example 1. Figure 11 The conductivity curves of porous carbon material 1 prepared in Example 1, porous carbon material 2 prepared in Example 2, and comparative carbon material 1 prepared in Comparative Example 1 are shown in the range of 0 to 100 MPa. Detailed Implementation

[0040] The present invention will be further illustrated below with specific examples. It should be noted that the following embodiments are only used to further illustrate the present invention and should not be construed as limiting the scope of protection of the present invention. Those skilled in the art can make some non-essential improvements and adjustments to the present invention based on the above-described invention.

[0041] In the following examples, all percentage concentrations of the solvents used are volume concentrations.

[0042] Experimental Example 1 (1) Resorcinol as a high coking segment monomer, formaldehyde as a crosslinking agent, and fructose as a low coking segment monomer are added to an ethanol / water solvent in a ratio of 1 g:1.56 g:1 g:50 ml and mixed thoroughly to obtain S1 mixture S1, wherein the isopropanol ratio of ethanol / water solvent is 40%.

[0043] (2) Ammonia water was added dropwise to the mixture S1 to adjust the pH to 8.7, and the monomers of each chain segment were induced to polymerize. The mixture was stirred at 500 rpm for 0.8 h. Then it was transferred to a rotary evaporator and subjected to rotary evaporation at 55℃, -0.1 MPa and 200 rpm for 6 h to remove the solvent. The mixture was then treated in a vacuum oven at 150℃ for 12 h to obtain the modified resin polymer 1.

[0044] (3) The modified resin polymer 1 was transferred to an argon atmosphere and heated to 1000℃ at a heating rate of 5℃ / min and held for 3 h to obtain porous carbon material 1.

[0045] Example 2 (1) Resorcinol as a high coking segment monomer, formaldehyde as a crosslinking agent, and xylitol as a low coking segment monomer are added to an ethanol / water solvent in a ratio of 1 g: 1.43 g: 1 g: 30 ml and mixed thoroughly to obtain S1 mixture, wherein the alcohol ratio of the ethanol / water solvent is 80%.

[0046] (2) Ammonia water was added dropwise to the mixture S1 to adjust the pH to 9 and induce the polymerization of each monomer segment. The mixture was stirred at 100 rpm for 3 h. Then it was transferred to a rotary evaporator and subjected to rotary evaporation at 70℃, -0.05 MPa and 300 rpm for 3 h to remove the solvent. The mixture was then treated in a vacuum oven at 150℃ for 10 h to obtain the modified resin polymer 2.

[0047] (3) The modified resin polymer 2 was transferred to an argon atmosphere and heated to 1050℃ at a heating rate of 8℃ / min and held for 3 h to obtain porous carbon material 2.

[0048] Furthermore, porous carbon material 2 is used as a silicon-carbon composite porous material: (1) Silicon nanoparticles (size 30 nm), resorcinol, formaldehyde, xylitol and ethanol / water solvent (alcohol ratio of 80%) are thoroughly mixed in a ratio of 1 g: 1 g: 1.43 g: 1 g: 30 ml to obtain a mixture S1. While uniformly dispersing with silicon nanoparticles, the silicon phase, carbon-forming phase and pore-forming phase are uniformly distributed.

[0049] (2) Ammonia was added dropwise to the mixture S1 to adjust the pH to 9, inducing the polymerization of monomers in each chain segment between silicon nanoparticles. The mixture was stirred at 100 rpm for 3 h. Then it was transferred to a rotary evaporator and subjected to rotary evaporation at 70℃, -0.05 MPa and 300 rpm for 3 h to remove the solvent. The mixture was then treated in a vacuum oven at 150℃ for 10 h to obtain the silicon-modified resin composite precursor S2.

[0050] (3) Mix S2:asphalt = 1:0.3 by mass, and perform solid phase coating at 1800 rpm and 30℃ for 40 min to obtain the coated silicon-modified resin composite precursor S3.

[0051] (4) S3 was transferred to argon gas and heated to 500°C at a heating rate of 8°C / min and held for 3 h. Then, it was coated again with the same asphalt ratio, rotation speed and treatment time as in step (3) to further improve the surface of the material. Then it was transferred to argon gas atmosphere and heated to 1050°C at a heating rate of 8°C / min and held for 3 h to obtain silicon-carbon composite porous material 2.

[0052] Example 3 (1) Resorcinol as a high coking segment monomer, formaldehyde as a crosslinking agent, and glucose as a low coking segment monomer are added to an ethanol / water solvent in a ratio of 1 g: 1.2 g: 1 g: 50 ml and mixed thoroughly to obtain S1 mixture, wherein the alcohol ratio of the ethanol / water solvent is 50%.

[0053] (2) Ammonia water was added dropwise to the mixture S1 to adjust the pH to 9, and the monomers of each chain segment were induced to polymerize. The mixture was stirred at 200 rpm for 2 h. Then it was transferred to a rotary evaporator and rotary evaporated at 50℃, -0.08 MPa and 200 rpm for 5 h to remove the solvent. A second rotary evaporation treatment was carried out at 120℃, -0.2 MPa and 50 rpm for 3 h to obtain the modified resin polymer 3.

[0054] (3) The modified resin polymer 3 was transferred to an argon atmosphere and heated to 1050℃ at a heating rate of 5℃ / min and held for 3 h to obtain porous carbon material 3.

[0055] Furthermore, porous carbon material 3 is used as a silicon-carbon composite porous material: (1) Silicon nanoparticles (size 50 nm), resorcinol, formaldehyde, glucose and ethanol / water solvent (alcohol ratio of 80%) are thoroughly mixed in a ratio of 1 g: 1 g: 1.2 g: 1 g: 50 ml to obtain a mixture S1. While uniformly dispersing with silicon nanoparticles, the silicon phase, carbon-forming phase and pore-forming phase are uniformly distributed.

[0056] (2) Ammonia was added dropwise to the mixture S1 to adjust the pH to 9, inducing the polymerization of monomers of each chain segment between silicon nanoparticles. The mixture was stirred at 200 rpm for 2 h. Then it was transferred to a rotary evaporator and subjected to rotary evaporation at 50℃, -0.08 MPa and 200 rpm for 5 h to remove the solvent. A second rotary evaporation was then performed at 120℃, -0.2 MPa and 50 rpm for 3 h to obtain the silicon-modified resin composite precursor S2.

[0057] (3) Mix S2:asphalt = 1:0.8 by mass, and perform solid phase coating at 2000 rpm and 25°C for 30 min to obtain the coated silicon-modified resin composite precursor S3.

[0058] (4) S3 was transferred to air and pre-oxidized at 270°C for 0.5 h at a rate of 5°C / min. Then it was heated to 1050°C in argon at a rate of 5°C / min and held for 3 h to obtain silicon-carbon composite porous material 3.

[0059] Example 4 (1) Melamine as a high coking segment monomer, formaldehyde as a crosslinking agent, and fructose as a low coking segment monomer are added to ethanol / water solvent in a ratio of 1 g : 1.33 g : 0.5 g : 40 ml and mixed thoroughly to obtain S1 mixture, wherein the isopropanol ratio of isopropanol in the isopropanol / water solvent is 40%.

[0060] (2) Formic acid was added dropwise to the mixture S1 to adjust the pH to 4.8, inducing the polymerization of each monomer segment. The mixture was stirred at 300 rpm for 1 h. Then it was transferred to a rotary evaporator and subjected to rotary evaporation at 70℃, -0.05 MPa and 300 rpm for 7 h to remove the solvent. The mixture was then treated in a vacuum oven at 150℃ for 10 h to obtain the modified resin polymer 4.

[0061] (3) The modified resin polymer 4 was transferred to an argon atmosphere and heated to 900℃ at a heating rate of 3℃ / min and held for 3h to obtain porous carbon material 4.

[0062] Furthermore, porous carbon material 4 is used as a tin-carbon composite porous material: (1) Tin nanoparticles (size 100 nm), resorcinol, formaldehyde, xylitol and ethanol / water solvent (alcohol ratio of 80%) are thoroughly mixed in a ratio of 1 g: 0.5 g: 1.2 g: 1 g: 60 ml to obtain a mixture S1. While uniformly dispersing with tin nanoparticles, the tin phase, carbon-forming phase and pore-forming phase are uniformly distributed.

[0063] (2) Ammonia was added dropwise to the mixture S1 to adjust the pH to 9, inducing the polymerization of monomers of each chain segment between tin nanoparticles. The mixture was stirred at 100 rpm for 3 h. Then it was transferred to a rotary evaporator and subjected to rotary evaporation at 70℃, -0.05 MPa and 300 rpm for 3 h to remove the solvent. The mixture was then treated in a vacuum oven at 150℃ for 10 h to obtain the silicon-modified resin composite precursor S2.

[0064] (3) Mix S2:asphalt = 1:0.8 by mass and coat it with solid phase at 2000 rpm and 25°C for 30 min to obtain the coated tin-modified resin composite precursor S3.

[0065] (4) S3 was transferred to argon gas and heated to 1050℃ at a heating rate of 5℃ / min and held for 3 h to obtain tin-carbon composite porous material 4.

[0066] Example 5 (Carbon materials with a modified low coking chain segment monomer ratio) (1) Resorcinol as a high coking segment monomer, formaldehyde as a crosslinking agent, and xylitol as a low coking segment monomer are added to an ethanol / water solvent in a ratio of 1 g: 1.43 g: 0.33 g: 30 ml and mixed thoroughly to obtain S1 mixture, wherein the alcohol ratio of the ethanol / water solvent is 80%.

[0067] (2) Ammonia water was added dropwise to the mixture S1 to adjust the pH to 9, and the monomers of each chain segment were induced to polymerize. The mixture was stirred at 100 rpm for 3 h. Then it was transferred to a rotary evaporator and subjected to rotary evaporation at 70℃, -0.05 MPa and 300 rpm for 3 h to remove the solvent. The mixture was then treated in a vacuum oven at 150℃ for 10 h to obtain the modified resin polymer 5.

[0068] (3) The modified resin polymer 5 was transferred to an argon atmosphere and heated to 1050℃ at a heating rate of 8℃ / min and held for 3 h to obtain porous carbon material 5.

[0069] Comparative Example 1 (Carbon material without the introduction of low coking chain segment monomers) (1) Resorcinol is used as a high coking chain monomer and formaldehyde is used as a crosslinking agent. They are added to an ethanol / water solvent in a ratio of 1 g: 1.2 g: 50 ml and mixed thoroughly to obtain S1 mixture, wherein the alcohol ratio of the ethanol / water solvent is 50%.

[0070] (2) Ammonia water was added dropwise to the mixture S1 to adjust the pH to 9 and induce the polymerization of resorcinol monomer. The mixture was stirred at 100 rpm for 3 h. Then it was transferred to a rotary evaporator and subjected to rotary evaporation at 70 °C, -0.05 MPa and 300 rpm for 3 h to remove the solvent. The mixture was then treated in a vacuum oven at 150 °C for 10 h to obtain unmodified resin polymer 1.

[0071] (3) The unmodified resin polymer 1 was transferred to an argon atmosphere and heated to 1050℃ at a heating rate of 8℃ / min and held for 3 h to obtain the comparative carbon material 1.

[0072] Comparative Example 2 (Carbon material formed by polymerization of low-coke chain segment monomers outside the scope of this invention) (1) Aniline as a high coking segment monomer, ammonium persulfate as a crosslinking agent, and N-vinylpyrrolidone as a low coking segment monomer are added to an ethanol / water solvent in a ratio of 1 g: 1.23 g: 0.5 g: 30 ml and mixed thoroughly to obtain S1 mixture, wherein the alcohol ratio of the ethanol / water solvent is 80%.

[0073] (2) Phytic acid was added dropwise to the mixture S1 to adjust the pH to 6 and induce the polymerization of monomers of each chain segment. The mixture was stirred at 130 rpm for 1 h. Then it was transferred to a rotary evaporator and subjected to rotary evaporation at 70 °C, -0.05 MPa and 300 rpm for 3 h to remove the solvent. The mixture was then treated in a vacuum oven at 150 °C for 10 h to obtain unmodified resin polymer 2.

[0074] (3) The unmodified resin polymer 2 was transferred to an argon atmosphere and heated to 1050℃ at a heating rate of 8℃ / min and held for 3 h to obtain the comparative carbon material 2.

[0075] Results Analysis (1) The coking value of modified resin polymer 1 after carbonization was 56%, indicating that modified resin polymer 1 has a high carbon yield. After argon ion cross-section grinding of porous carbon material 1, the cross-section of the particles was observed using SEM scanning electron microscopy, such as... Figure 1 As shown, the carbon material particles contain a high density of closed pores with a diameter of approximately 1000 nm. Conductivity compaction tests were performed on the porous carbon material 1. Figure 11 As shown, its electrical conductivity reaches 41.9 S / cm at 100 MPa, indicating that porous carbon material 1 has high electrical conductivity. This result shows that the modified phenolic resin polymer formed by copolymerizing resorcinol as a high-coke-segment monomer and fructose as a low-coke-segment monomer can spontaneously form high-density, closed, and large-size (~1000 nm) porous carbon after carbonization.

[0076] (2) The coking value of modified resin polymer 2 after carbonization was 47%, indicating that modified resin polymer 2 has a high carbon yield. After argon ion cross-section grinding of porous carbon material 2, the cross-section of the particles was observed using SEM scanning electron microscopy, such as... Figure 2 As shown, the carbon material particles exhibit a high density of closed pores with a pore size of approximately 400 nm, indicating that uniform, high-porosity closed porous carbon can be obtained by controlling the bonding and fragmentation behavior of high-coke-chain segment monomers and low-coke-chain segment monomers. Conductivity compaction tests were performed on porous carbon material 2, as shown... Figure 11 As shown, its conductivity reaches 49.0 S / cm at 100 MPa, indicating that the porous carbon material 2 has high conductivity. Furthermore, the prepared porous carbon material 2 was used as the negative electrode to fabricate a coin cell with a lithium sheet as the counter electrode. Charge-discharge tests were conducted using multi-stage discharge (cutoff 0.005 V) at 0.2C, 0.1C, 0.05C, and 0.02C, and a 0.1C charge (cutoff 2 V). Figure 3As shown, the material exhibits a discharge specific capacity of 1404.3 mAh / g and an initial coulombic efficiency of 88.4%, indicating that the silicon-carbon material obtained by using porous carbon material 2 can achieve high initial coulombic efficiency and capacity utilization. Before and after lithiation, the thickness of the silicon-carbon composite porous material 2 electrode expanded from 40 μm to 48 μm, an expansion rate of 20%, indicating that the pores of the porous carbon can provide space for the silicon-carbon material to accommodate volume expansion, thereby significantly reducing electrode expansion. These results demonstrate that the modified phenolic resin polymer formed by copolymerizing resorcinol as a high-coke-chain monomer and xylitol as a low-coke-chain monomer can spontaneously form highly conductive porous carbon with high density, closed pores of moderate size (~400 nm) after carbonization. This porous carbon can be composited with silicon alloy-type anodes, effectively reducing electrode expansion and extending battery life.

[0077] (3) The coking value of modified resin polymer 3 after carbonization was 62%, indicating that modified resin polymer 3 has a high carbon yield. After argon ion cross-section grinding of porous carbon material 3, the cross-section of the particles was observed using SEM scanning electron microscopy, such as... Figure 4 As shown, the carbon material particles contain a high density of closed pores with a pore size of approximately 200 nm. Nitrogen adsorption / desorption tests were performed on the porous carbon material 3, and its specific surface area was determined to be 15.9 m² based on the BET adsorption model. 2 / g indicates that porous carbon material 3 has a low specific surface area and few exposed pores. Furthermore, porous carbon material 3 was used as the negative electrode to fabricate a coin cell with a lithium sheet as the counter electrode. Charge-discharge tests were conducted using 0.1C discharge (cutoff 0.005 V) and 0.1C charge (cutoff 1.5 V), as shown in the figure. Figure 5 As shown, the material's discharge specific capacity is 430.7 mAh / g, and its initial coulombic efficiency is 41.1%, indicating that porous carbon material 3 has a higher initial coulombic efficiency compared to other hard carbon materials. The silicon-carbon composite porous material 3 was further used as the negative electrode to fabricate a coin cell with a lithium sheet as the counter electrode. Charge-discharge tests were conducted using multi-stage discharge (cutoff 0.005 V) at 0.2C, 0.1C, 0.05C, and 0.02C (cutoff 0.005 V) and a 0.1C charge (cutoff 2 V) method. Figure 6 As shown, the material's discharge specific capacity is 1866.3 mAh / g, and its initial coulombic efficiency is 88.4%, indicating that the silicon-carbon material obtained by using porous carbon material 3 can achieve high initial coulombic efficiency and capacity. Before and after lithiation, the thickness of the silicon-carbon composite porous material 3 electrode expanded from 38 μm to 43 μm, an expansion rate of 13%, indicating that the pores of the porous carbon can provide space for the silicon-carbon material to accommodate volume expansion, thereby significantly reducing electrode expansion. Cyclic testing was performed on it at a current of 0.5C. Figure 7As shown, its cycling stability indicates that porous carbon can provide good structural strength and mechanical support for silicon-carbon materials, which is beneficial to extending cycle life. This result demonstrates that the modified phenolic resin polymer formed by copolymerizing resorcinol as a high-coke-chain monomer and glucose as a low-coke-chain monomer can spontaneously form highly conductive porous carbon with high density, closed pores, and small size (~200 nm) after carbonization. This carbon can be combined with silicon alloy-type anodes to effectively reduce electrode expansion and extend battery life.

[0078] As can be seen from Examples 1-4, by adjusting the composition of high-coking-chain segment monomers and low-coking-chain segment monomers, the cracking behavior during bonding and carbonization can be controlled, thereby obtaining closed porous carbon with different pore sizes and porosities.

[0079] (4) The coking value of modified resin polymer 4 after carbonization was 42%, indicating that modified resin polymer 4 has a high carbon yield. Nitrogen adsorption / desorption tests were performed on porous carbon material 4, and its specific surface area was measured to be 13.2 m² based on the BET adsorption model. 2 / g. The low specific surface area of ​​porous carbon material 4 indicates that by changing the type of low-coke-chain monomers, their copolymerization behavior with high-coke-chain monomers can be controlled, thereby controlling the specific surface area of ​​the porous carbon after carbonization. Furthermore, the prepared tin-carbon composite porous material 4 was used as the negative electrode to fabricate a coin cell with a lithium sheet as the counter electrode. Charge-discharge tests were conducted using multi-stage discharge (cutoff 0.005 V) at 0.2C, 0.1C, 0.05C, and 0.02C and a charge-discharge (cutoff 2 V) at 0.1C. The material's discharge specific capacity was 557.3 mAh / g, and its initial coulombic efficiency was 86.2%, indicating that the tin-carbon material obtained by using porous carbon material 4 can achieve high initial coulombic efficiency and capacity utilization. The results indicate that the modified amine-aldehyde resin polymer formed by copolymerizing melamine as a high-coking-chain monomer and xylitol as a low-coking-chain monomer can form porous carbon with low specific surface area and closed pores after carbonization, which can be composited with tin alloy type anode.

[0080] (5) The coking value of modified resin polymer 5 after carbonization was 53%, indicating that modified resin polymer 5 has a high carbon yield. After argon ion cross-section grinding of porous carbon material 5, the cross-section of the particles was observed using SEM scanning electron microscopy, such as... Figure 8 As shown, the carbon material particles have a high density of closed pores uniformly distributed within them, but the pore size is approximately 100 nm. Combined with Example 2, it can be seen that the pore size and porosity of the closed porous carbon can be controlled by changing the ratio of high-coke-chain segment monomers to low-coke-chain segment monomers.

[0081] (6) After argon ion cross-section grinding of the control carbon material 1, the cross-section of the particles was observed using a scanning electron microscope (SEM). Figure 9As shown, the carbon material particles have relatively few pores, indicating that without the introduction of low-coke-chain segment monomers for copolymerization, the carbon obtained after carbonization is dense and non-porous. Mercury porosimetry of the control carbon material 1 showed a porosity of 51.6%, indicating its low porosity. Nitrogen adsorption / desorption testing of the control carbon material 1, based on the BET adsorption model, yielded a specific surface area of ​​18.5 m². 2 / g indicates that comparative carbon material 1 has a high specific surface area. Conductivity compaction tests were performed on comparative carbon material 1, such as... Figure 11 As shown, its conductivity at 100 MPa is 37.5 S / cm, which is lower than that of porous carbon material 1 and porous carbon material 2. Furthermore, a coin cell with lithium foil as the counter electrode was fabricated using comparative carbon material 1 as the negative electrode. Charge-discharge tests were conducted using 0.1C discharge (cutoff 0.005 V) and 0.1C charge (cutoff 1.5 V), as shown... Figure 10 As shown, the material's discharge specific capacity is 430.7 mAh / g, and its initial coulombic efficiency is 39.9%, indicating that the initial coulombic efficiency of the carbon material without the introduction of low-coke segment copolymerization is relatively low. This comparative sample shows that if low-coke segment monomers are not introduced to form bonds with high-coke segments, the unmodified resin polymer obtained solely through the polymerization of high-coke segment monomers does not possess sufficient porous phases to form closed pores. Furthermore, carbon atoms are difficult to rearrange, resulting in numerous defects. Consequently, the carbon obtained through carbonization cannot achieve high porosity, low specific surface area, and high electrical conductivity.

[0082] (7) Nitrogen adsorption / desorption tests were performed on the control carbon material 2. Based on the BET adsorption model, its specific surface area was measured to be 34.2 m². 2 / g indicates that the comparative carbon material 2 has a high specific surface area. The low-coking segment monomer outside the scope of this invention, namely N-vinylpyrrolidone, polymerizes into polyvinylpyrrolidone segments. Although the coking value is still within the 0-40% range described in this patent, this monomer cannot copolymerize and crosslink with high-coking-value segment monomers. This results in the inability to uniformly disperse the carbon phase and porous phase at the molecular scale. The resulting unmodified resin polymer cannot be decomposed into low-specific-surface-area porous carbon with closed pores during carbonization.

Claims

1. A modified resin polymer, characterized in that, It is copolymerized and crosslinked from high-coke-chain monomers and low-coke-chain monomers in an alternating, block, or random arrangement with the addition of a crosslinking agent and an initiator; the high-coke-chain monomers are one or more combinations of melamine, urea, resorcinol, furfuryl alcohol, and aniline, and the low-coke-chain monomers are at least one of fructose, glucose, xylose, mannose, sucrose, xylitol, erythritol, sorbitol, and mannitol.

2. The method for preparing the modified resin polymer according to claim 1, characterized in that, Includes the following steps: (1) The high coking segment monomer, crosslinking agent, low coking segment monomer and solvent L1 are fully dispersed and mixed in a ratio of 1 g:(0.3~3) g:(0.3~3) g:(10~60) ml to obtain a mixture S1, so as to achieve uniform distribution; The high coking chain monomer is one or more combinations of melamine, urea, resorcinol, furfuryl alcohol, and aniline; the low coking chain monomer is at least one of fructose, glucose, xylose, mannose, sucrose, xylitol, erythritol, sorbitol, and mannitol; the crosslinking agent is one of formaldehyde and acetone; and the initiator is at least one of ammonia, phytic acid, acetic acid, formic acid, hydrochloric acid, and phosphoric acid. (2) Add an initiator to the mixture S1 and adjust the pH to 4-10 to induce cross-linking copolymerization of high coking segment monomers and low coking segment monomers; After polymerization, the solvent in the resulting mixed solution is removed, and then the solution is heated under vacuum at 30~150℃ for 3~12 h to obtain the modified resin polymer S2.

3. A porous carbon with low specific surface area and high electrical conductivity, characterized in that, The modified resin polymer S2 as described in claim 1 is obtained by sintering and carbonizing at an inert atmosphere and a temperature of 500-1200°C for 2-8 hours.

4. The method for preparing porous carbon according to claim 3, wherein after preparing the modified resin polymer S2 according to the method of claim 2, sintering and carbonization are carried out at 500~1200℃ for 2~8h under an inert atmosphere.

5. The application of the modified resin polymer of claim 1 or the porous carbon of claim 3 in the preparation of lithium-ion secondary battery anode materials.

6. The application according to claim 5, characterized in that, Includes the following steps: (1) Alloy-type anode material nanoparticles, high coking segment monomers, crosslinking agents, low coking segment monomers and solvent L1 are thoroughly mixed in a ratio of 1 g: (0.3~3) g: (0.3~3) g: (0.3~3) g: (10~60) ml to obtain a mixture S1, thereby achieving a uniform distribution of alloy-type anode material, high coking segment monomers and low coking segment monomers; (2) Add an initiator to the mixture S1 and adjust the pH to induce copolymerization of high coking segment monomers and low coking segment monomers; remove the solvent from the resulting mixture after polymerization, and then heat it under vacuum at 30~150℃ for 3~12 h to obtain alloy nanoparticle-modified resin composite precursor S2. (3) Using at least one of machine solid phase asphalt coating, liquid phase asphalt coating, and acetylene vapor phase deposition coating, a coating layer with a thickness of 50~700 nm (preferably 100~300 nm) is coated on the surface of S2 to obtain the coated alloy nanoparticle-modified resin composite precursor S3. (4) S3 is transferred to an inert atmosphere and kept at 500~1200℃ for 2~8h for sintering. During the sintering process, the long molecular chains after copolymerization of high-coke chain segment monomers and low-coke chain segment monomers decompose and are transformed into an alloy-carbon composite porous material in which carbon matrix and closed pores are uniformly distributed between alloy nanoparticles. The alloy-type anode material mentioned in step (1) is at least one of silicon, germanium, tin, antimony, and aluminum; the nanoparticle size of the alloy-type anode material is 30~200 nm.

7. The application according to claim 6, characterized in that, The specific method for solid phase asphalt coating in step (3) is to add S2 and asphalt in a solid phase coating machine at a ratio of 1:(0.2~1.4) and stir continuously at 1000~6000 rpm and 30~200℃ for 5~120 min; the specific method for liquid phase coating is to mix S2 with asphalt, toluene, quinoline, and alcohol in a ratio of 1g:(0.2~1.4)g:(0.3~8)ml:(0.3~8)ml:(0.3~8)ml, and rotary evaporate under a vacuum of -0.05~-0.3 MPa and 30~150℃, while stirring at 100~800 rpm for 3~12 h; the acetylene vapor phase deposition coating is to place S2 in a high-purity nitrogen atmosphere, heat it to 600~900℃ at a rate of 3~10℃ / min, and introduce methane gas at a rate of 0.2~8L / min for 0.5~7 h, allow to cool naturally to room temperature.

8. The application according to claim 6, characterized in that, Steps (3) and (4) are repeated once or multiple times; before starting step (4), the material is pre-oxidized: in an air or oxygen atmosphere, the temperature is increased to 150-300℃ at 1-10℃ / min and held for 0.3-2 h.

9. An alloy-carbon composite porous material, characterized in that, It is prepared by the specific method described in claim 6 in the application of the modified resin polymer in the preparation of lithium-ion secondary battery anode materials.

10. The application of the porous carbon of claim 3 or the alloy-carbon composite porous material of claim 9 as a negative electrode material for lithium-ion secondary batteries.

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