A preparation method of a phenolic resin-based porous carbon precursor, a phenolic resin-based porous carbon and an electrode material

Abstract

This invention relates to a method for preparing a phenolic resin-based porous carbon precursor, phenolic resin-based porous carbon, and electrode materials. The preparation method includes mixing a pore-forming agent, a metal salt, and raw materials used to prepare phenolic resin, and carrying out a polycondensation reaction at 50°C to 100°C to form a phenolic resin-based porous carbon precursor containing the pore-forming agent and metal ions. This invention directly introduces the pore-forming agent as a reactive component into the synthesis process of phenolic resin, allowing it to participate in the construction of molecular chain segments, thus achieving molecular-level dispersion and covalent fixation of the pore-forming component in the resin matrix. This arrangement helps to form a more developed, interconnected, and uniform pore structure during subsequent heat treatment processes such as carbonization, thereby significantly improving the overall performance of the carbon material. Simultaneously, the introduction of specific metal ions during the synthesis process forms a chelate structure, which enhances the structural stability of the carbon matrix and improves the electrical conductivity and electrochemical cycling stability of the material.

Description

Technical Field

[0001] This invention relates to the field of porous carbon materials technology, specifically to a method for preparing a phenolic resin-based porous carbon precursor, phenolic resin-based porous carbon, and electrode materials. Background Technology

[0002] With the rapid development of the new energy industry, especially the deepening application of silicon-carbon anode materials in high-energy-density lithium-ion batteries, more stringent performance requirements have been placed on porous carbon, a key framework material. An ideal porous carbon carrier, in addition to structural toughness and high conductivity, needs a high specific surface area to load active materials, and a continuous, interconnected hierarchical pore structure with micropores and mesopores to achieve rapid ion transport and provide physical confinement. Phenolic resins are considered ideal precursors for porous carbon preparation due to their high carbon yield, good thermal stability, and tunable structure. However, existing porous carbons based on phenolic resins struggle to achieve synergistic optimization of the aforementioned key indicators, especially the optimization of high specific surface area and hierarchical pore structure.

[0003] On the one hand, existing technologies mostly focus on optimizing the local functions of carbon materials, such as improving performance through heteroatom doping (e.g., nitrogen, phosphorus, sulfur) or surface chemical modification. However, these technologies cannot fundamentally resolve the inherent contradiction between pore structure and volume expansion buffering in porous carbon. Specifically, while heteroatom doping can introduce active sites such as pyridine nitrogen and pyrrole nitrogen into the carbon framework, theoretically improving the pseudocapacitive contribution and electronic conductivity, the random distribution of doping sites easily leads to pore blockage or increased closed-pore ratio, making it difficult to construct continuous, interconnected hierarchical channels. Surface modification techniques can only improve the hydrophilicity / hydrophobicity or reactivity of the carbon material surface, failing to substantially affect the pore connectivity and spatial structure of the bulk material. They cannot provide sufficient and effective "buffer cavities" for silicon volume expansion, nor can they significantly increase the specific surface area of ​​the material. More importantly, none of the above technical approaches effectively solves the problem of the bonding stability between the carbon matrix and functional components. Doped elements or surface modification layers are prone to detachment due to structural strain during long-term electrochemical cycling, leading to decreased conductivity and deteriorated cycling performance.

[0004] On the other hand, the industry has also attempted to modify phenolic resins by blending or constructing semi-interpenetrating polymer networks (IPNs) followed by carbonization to create pores. However, this type of technology has inherent defects at the molecular structure design level. Because the introduced second-component polymer (such as a pore-forming agent or template polymer) and the phenolic resin matrix rely only on physical entanglement or weak hydrogen bond interactions, lacking stable covalent bond anchoring, severe microphase separation occurs during the curing and carbonization process, with phase separation sizes typically reaching tens or even hundreds of nanometers. This macroscopic phase separation directly leads to the non-uniform removal of pore-forming components during carbonization, resulting in a large number of isolated, non-penetrating collapsed or closed pores in the carbon matrix. The pore connectivity is extremely poor, the pore-forming efficiency is low, and it is difficult to meet the requirements for rapid ion transport and effective buffering of volume expansion.

[0005] In summary, regardless of element doping, surface modification, or physical blending modification techniques, the preparation of high-performance phenolic porous carbon generally faces the core challenge of poor controllability of pore structure.

[0006] The above background information is provided only to aid in understanding the concept and technical solution of this application. It does not necessarily belong to the prior art of this application, nor does it necessarily provide technical guidance. In the absence of clear evidence that the above information was disclosed before the filing date of this application, the above background information should not be used to evaluate the novelty and inventiveness of this application. Summary of the Invention

[0007] The purpose of this invention is to provide a method for preparing a phenolic resin-based porous carbon precursor, phenolic resin-based porous carbon, and electrode materials.

[0008] To achieve the above objectives, the technical solution adopted by the present invention is as follows: This invention provides a method for preparing a phenolic resin-based porous carbon precursor, comprising mixing a pore-forming agent, a metal salt, and raw materials for preparing phenolic resin, and carrying out a polycondensation reaction at 50°C to 100°C to form a phenolic resin-based porous carbon precursor containing a pore-forming agent and metal ions. The pore-forming agent is a first pore-forming agent and / or a second pore-forming agent, the weight-average molecular weight of the first and second pore-forming agents being 5000 to 100000. The first pore-forming agent is selected from one or more of acrylamide polymers, water-soluble acrylate polymers, vinylpyrrolidone polymers, polyacrylate polymers, and alginate compounds. The second pore-forming agent is selected from one or more of vinyl alcohol polymers, polyethers, and water-soluble aliphatic polyamide polymers. The two end groups of the polyether are independently selected from hydroxyl, amino, carboxyl, phenolic hydroxyl, amide, or hydroxymethyl groups. The metal salt is selected from one or more of titanium salts, zirconium salts, aluminum salts, nickel salts, and cobalt salts.

[0009] This invention constructs a single-phase integrated network by covalently bonding a water-soluble polymeric pore-forming agent with a phenolic resin precursor. This allows for the production of porous carbon with high specific surface area and hierarchical interconnected micropore-mesopore channels without deep activation, effectively solving problems such as easy channel collapse, low pore-forming efficiency, and reliance on deep activation in traditional technologies. Furthermore, specific metal ions are introduced during the polycondensation process to form a chelate structure, which enhances the structural stability of the carbon matrix and improves the material's conductivity. In the preparation of silicon-carbon anode materials with silicon, the strong interaction between the metal element and silicon achieves molecular-level anchoring at the silicon-carbon interface. Combined with the physical buffering effect of the hierarchical pore structure, a dual volume regulation mechanism is formed, effectively suppressing silicon particle pulverization and shedding, thereby significantly improving the electrochemical cycling stability of the silicon-carbon anode.

[0010] In some embodiments, the polycondensation reaction is carried out at 50°C to 70°C.

[0011] Furthermore, the polycondensation reaction is carried out at 55°C to 65°C.

[0012] In some embodiments, the acrylamide polymers include polyacrylamide and polymethacrylamide.

[0013] Furthermore, the weight-average molecular weights of the polyacrylamide and polymethacrylamide are independently 5,000 to 100,000, preferably 25,000 to 50,000.

[0014] In some embodiments, the water-soluble acrylate polymers include polyacrylate polymers with hydrophilic side chains, such as polyethyl acrylate and polyhydroxypropyl acrylate. Further, the weight-average molecular weights of the polyethyl acrylate and polyhydroxypropyl acrylate are independently 5000-50000, preferably 15000-35000.

[0015] In some embodiments, the polyacrylate polymer includes ammonium polyacrylate, sodium polyacrylate, and potassium polyacrylate.

[0016] In some embodiments, the alginate compound includes ammonium alginate and sodium alginate.

[0017] Furthermore, the weight-average molecular weight of the ammonium polyacrylate, sodium polyacrylate, potassium polyacrylate, ammonium alginate, and sodium alginate is independently 10,000 to 60,000, preferably 15,000 to 55,000.

[0018] In some embodiments, the vinylpyrrolidone polymer includes polyvinylpyrrolidone.

[0019] Furthermore, the weight-average molecular weight of the polyvinylpyrrolidone is 5,000 to 100,000, preferably 10,000 to 55,000.

[0020] In some embodiments, the ethylene alcohol polymer includes polyvinyl alcohol and partially etherified polyvinyl alcohol.

[0021] Furthermore, the weight-average molecular weight of the polyvinyl alcohol and the partially etherified polyvinyl alcohol is independently 30,000 to 60,000, preferably 35,000 to 45,000. The degree of etherification of the partially etherified polyvinyl alcohol is 20% to 30%.

[0022] In some embodiments, the polyether includes α,ω-dihydroxy polyethylene oxide, α,ω-dihydroxy polyethylene glycol, α,ω-diamino polyethylene oxide, polyethylene oxide-polypropylene oxide block copolymer, bihydroxymethylated polyethylene oxide, and bicarboxylated polyethylene glycol.

[0023] Furthermore, the weight-average molecular weights of the α,ω-dihydroxy polyethylene oxide, α,ω-dihydroxy polyethylene glycol, α,ω-diamino polyethylene oxide, polyethylene oxide-polypropylene oxide block copolymer, bihydroxymethylated polyethylene oxide, and bicarboxylated polyethylene glycol are each independently 10,000 to 50,000, preferably 15,000 to 25,000.

[0024] In some embodiments, the water-soluble aliphatic polyamide polymer includes water-soluble aliphatic polyamide, N-alkylated water-soluble aliphatic polyamide, and diamino-terminated polyamide-amine.

[0025] Furthermore, the weight average molecular weight of the water-soluble aliphatic polyamide, the N-alkylated water-soluble aliphatic polyamide, and the bi-amino-terminated polyamide-amine is independently 20,000 to 50,000, preferably 25,000 to 35,000.

[0026] In some embodiments, the raw materials used to prepare the phenolic resin include formaldehyde and phenol, and the molar ratio of the pore-forming agent, formaldehyde, and phenol is (0.01~0.25):(1.5~2.5):1, preferably (0.02~0.2):(1.5~2.5):1, and more preferably (0.02~0.15):(1.5~2.5):1. The number of moles of the pore-forming agent is calculated based on the equivalent of its repeating units.

[0027] In some embodiments, the titanium salt is selected from one or more of titanium nitrate, tetrabutyl titanate, titanium sulfate, titanium tetrachloride, titanium isopropoxide, and tetraisopropyl titanate.

[0028] In some embodiments, the zirconium salt is selected from one or more of zirconium nitrate, zirconium chloride, zirconium sulfate, zirconium dichloride, and zirconium acetate.

[0029] In some embodiments, the aluminum salt is selected from one or more of aluminum nitrate, aluminum chloride, aluminum sulfate, aluminum isopropoxide, and polyaluminum chloride.

[0030] In some embodiments, the nickel salt is selected from one or more of nickel nitrate, nickel chloride, nickel sulfate, nickel acetate, and nickel aminosulfonate.

[0031] In some embodiments, the cobalt salt is selected from one or more of cobalt nitrate, cobalt chloride, cobalt sulfate, and cobalt acetate.

[0032] In some embodiments, the mass ratio of the metal salt to the pore-forming agent is (0.1~1):1, preferably (0.2~0.6):1, and more preferably (0.3~0.5):1.

[0033] In some embodiments, the preparation method specifically includes the following steps: (1) The pore-forming agent, the metal salt solution, and water are mixed to form a first mixed solution, wherein the mass ratio of the pore-forming agent to the water is (0.005~0.05):1, and the mass fraction of the metal salt solution is 3%~10%; (2) Mix formaldehyde aqueous solution with a mass concentration of 30%~45% with phenol, adjust the pH of the system to 8~11 with ammonia water, and form a transparent prepolymer after condensation to prepare a second mixed solution; (3) The first mixed solution is mixed with the second mixed solution to carry out a further polycondensation reaction.

[0034] Furthermore, the mixing temperature in step (2) is 40℃~80℃ and the time is 30min~120min.

[0035] Furthermore, the mixing temperature in step (2) is 40℃~50℃ and the time is 30min~60min. In some embodiments, the preparation method further includes the steps of filtering, washing, and drying the reaction product after the polycondensation reaction is completed.

[0036] A second aspect of the present invention provides a porous carbon precursor prepared by the preparation method described above.

[0037] A third aspect of the present invention provides a phenolic resin-based porous carbon, which is obtained by carbonization, activation and acidic solution post-treatment of a porous carbon precursor prepared by the preparation method described above.

[0038] In some embodiments, the carbonization process specifically includes: heating the porous carbon precursor to 600°C to 800°C at a rate of 1 to 10°C / min under an inert atmosphere, and carbonizing it for 1 to 4 hours.

[0039] In some embodiments, the activation treatment specifically includes: mixing the carbonized product with an activator, and then heating it to 750°C to 950°C, preferably 800°C to 900°C, at a heating rate of 1 to 10°C / min under an inert atmosphere, and holding it at that temperature for 0.5 h to 3 h, more preferably 0.5 h to 2 h.

[0040] Furthermore, the activator is water vapor, the intake rate of the water vapor is 0.1~10 mL / min based on the feed rate of liquid water, and the ratio of the total feed rate of the water vapor to the mass of the carbonized product is (1~10):1.

[0041] Furthermore, the steam intake rate is 0.5~5 mL / min based on the liquid water feed rate, and the ratio of the total steam intake rate to the mass of the carbonized product is (1~5):1.

[0042] In some embodiments, the acidic solution is one or more of hydrochloric acid, phosphoric acid, sulfuric acid, and nitric acid, and the temperature for treating the acidic solution is 50°C to 70°C.

[0043] Furthermore, the hydrochloric acid is a dilute hydrochloric acid with a concentration of 0.1~1.0 mol / L.

[0044] A fourth aspect of the present invention is to provide an electrode material comprising phenolic resin-based porous carbon as described above.

[0045] In some embodiments, the electrode material further includes silicon material loaded within the pores of the phenolic resin-based porous carbon.

[0046] Furthermore, the electrode material also includes a carbon coating layer formed on the surface (including the outer surface and the inner surface of the pores) of the phenolic resin-based porous carbon after being loaded onto the silicon material.

[0047] This invention does not impose any particular limitation on the loading method used. Those skilled in the art can select conventional loading processes, such as chemical vapor deposition, according to actual needs. It should be noted that this example is merely illustrative and does not constitute a limitation on the scope of protection of this invention.

[0048] Due to the application of the above technical solution, the present invention has the following advantages compared with the prior art: This invention introduces a pore-forming agent directly as a reactive component into the synthesis process of phenolic resin, allowing it to participate in the construction of molecular chain segments. This achieves molecular-level dispersion and covalent fixation of the pore-forming component within the resin matrix. This configuration facilitates the formation of a more developed, interconnected, and uniform pore structure during subsequent heat treatments such as carbonization, thereby significantly improving the overall performance of the carbon material. Simultaneously, the introduction of specific metal ions during synthesis forms a chelate structure, which enhances the structural stability of the carbon matrix and improves the material's electrical conductivity and electrochemical cycling stability. Attached Figure Description

[0049] Figure 1 The isotherm curve of N2 adsorption-desorption of porous carbon prepared in Example 5; Figure 2 The integral distribution curve of the pore volume-pore size adsorption of the porous carbon BJH prepared in Example 5 is shown. Detailed Implementation

[0050] In this invention, unless the context explicitly requires otherwise, the numerical range referred to as "numerical value A to numerical value B" refers to the range including the endpoints A and B. The numerical range referred to as "above" or "below" refers to the numerical range including the stated number. "Optional" or "optional" indicates that certain substances, components, execution steps, application conditions, etc., may or may not be used, and there is no limitation on the manner of use.

[0051] In this invention, "filtration" refers to the operation of separating the solid product (such as porous carbon precursor) generated in the reaction system from the reaction mother liquor using conventional solid-liquid separation methods in the art. This invention does not strictly limit the specific filtration method; those skilled in the art can choose a suitable method based on material characteristics, production scale, and equipment conditions. As an example, the filtration can be performed using one or more of the following methods: atmospheric pressure filtration, vacuum filtration, pressure filtration, and centrifugal separation. The temperature of the filtration operation can be adjusted according to the material viscosity and process requirements; for example, it can be performed at room temperature or under conditions close to the reaction temperature to ensure good separation results.

[0052] In this invention, "washing" refers to purifying solid products using conventional washing processes in the art. For example, the washing may use one or more of deionized water, anhydrous ethanol, or acetone as the washing solvent, and the washing may be performed 1 to 5 times. Heating or ultrasonic treatment may be used during the washing process to improve the washing effect. The washing operation is usually repeated until no obvious impurities are detected in the washing solution.

[0053] In this invention, "drying" refers to removing moisture or organic solvents from a solid product using conventional drying processes. As an example, the drying can be performed using atmospheric pressure hot air drying (drying temperature 50℃~150℃, drying time 2~24 hours) or vacuum drying (drying temperature 40℃~120℃, vacuum degree -0.08 MPa~-0.1 MPa). The drying operation is typically carried out until the solid product reaches a constant weight or the moisture content is below 5wt%.

[0054] In this invention, "carbonization" refers to the process of heat-treating a porous carbon precursor at high temperature under an inert atmosphere to transform it into a carbon-rich solid material. The obtained porous carbon precursor is placed in a heating furnace (such as a tubular furnace, rotary kiln, or fluidized bed), and heated to 700°C at a rate of 5°C / min under a nitrogen atmosphere. It is then carbonized at 700°C for 2 hours, followed by natural cooling to room temperature (25°C ± 5°C) to obtain the porous carbon primary product. Those skilled in the art can reasonably adjust parameters such as carbonization temperature, heating rate, holding time, and atmosphere according to actual needs.

[0055] In this invention, "activation" refers to the process of using physical or chemical methods to create pores in carbonized products to increase their specific surface area and pore volume. As an example, steam activation is used. The carbonized products are placed in a heating furnace (such as a tubular furnace, rotary kiln, or fluidized bed), and steam is introduced. The steam inlet rate is 1 mL / min, calculated as the feed rate of liquid water, and the total steam feed rate to the mass ratio of the carbonized product is 1.5:1. Under a nitrogen atmosphere, the temperature is increased to 850°C at a rate of 5°C / min, and activated at 850°C for 1 hour, followed by natural cooling to room temperature. This invention does not impose strict limitations on the type of activator, activation temperature, activation time, or amount of activator; those skilled in the art can make reasonable adjustments as needed.

[0056] In this invention, "post-treatment" refers to the purification process of the activated product, including acid washing, water washing, and drying, to remove residual activating agents and byproducts. As an example, the activated product is added to 0.3 mol / L dilute hydrochloric acid and washed at a constant temperature of 60°C with stirring for 6 hours. It is then washed with deionized water until neutral, and finally, the washed product is vacuum dried at 80°C to obtain the final porous carbon. Those skilled in the art can reasonably adjust the acid washing conditions, number of washing cycles, and drying parameters according to the type of activating agent and the required product purity.

[0057] The present invention will be further described below with reference to embodiments. However, the present invention is not limited to the following embodiments. The implementation conditions used in the embodiments can be further adjusted according to different requirements of specific use, and the implementation conditions not specified are conventional conditions in the industry. The technical features involved in the various embodiments of the present invention can be combined with each other as long as they do not conflict with each other. Unless otherwise specified, the reagents and instruments used in the following embodiments and comparative examples are commercially available products or can be prepared with reference to existing technology.

[0058] Example 1: A resin-based porous carbon, the preparation method of which includes the following steps: (1) Dissolve 3g of nonionic polyacrylamide (PAM, Mw=40,000, degree of hydrolysis 3%, purchased from Shanghai Aladdin Biochemical Technology Co., Ltd., P434411) in 200g of deionized water, add 24g of 5% titanium nitrate aqueous solution to prepare solution A.

[0059] (2) Add 60g of phenol to 98g of formaldehyde aqueous solution with a mass fraction of 37%, then adjust the pH of the system to 9.0 with ammonia, and then stir for 60min at a constant temperature of 45℃ to prepare solution B.

[0060] (3) Mix solution A from step (1) and solution B from step (2), stir at 60°C for 3 hours, and then filter, wash and dry in sequence to obtain a porous carbon precursor. The porous carbon precursor is then carbonized, activated and post-treated to obtain the target porous carbon.

[0061] Example 2: This embodiment provides a resin-based porous carbon, the preparation method of which is basically the same as that in Example 1, except that: In solution A, an equal mass of hydroxyl-terminated polyethylene glycol (PEG, Mw=20,000, purchased from Shanghai Aladdin Biotechnology Co., Ltd., P103730) was used to replace nonionic polyacrylamide, and an equal mass of 5% zirconium nitrate aqueous solution was used to replace titanium nitrate aqueous solution. In solution B, the amount of formaldehyde aqueous solution with a mass fraction of 37% is 93.2g.

[0062] Example 3: This embodiment provides a resin-based porous carbon, the preparation method of which is basically the same as that in Example 1, except that: Nonionic polyacrylamide was replaced with an equal mass of polyvinylpyrrolidone (PVP, Mw=50,000, purchased from Shanghai Aladdin Biochemical Technology Co., Ltd., P434442), and titanium nitrate aqueous solution with a mass fraction of 5% was replaced with an equal mass of aluminum nitrate aqueous solution.

[0063] Example 4: This embodiment provides a resin-based porous carbon, the preparation method of which is basically the same as that in Example 2, except that: An equal mass of N-alkylated modified oligomeric aromatic polyamide (oligomeric PA, 95% alkylation degree, prepared in the laboratory) was used to replace the hydroxyl-terminated polyethylene oxide, and an equal mass of 5% nickel nitrate aqueous solution was used to replace the zirconium nitrate aqueous solution.

[0064] The preparation method of oligomeric PA includes: dissolving 3g of low molecular weight water-soluble aliphatic polyamide (Mw=30,000, double-terminated amino, Shanghai Yuanye Biotechnology Co., Ltd., S18076-customized version) in 80mL of N,N-dimethylformamide (DMF, Sinopharm Chemical Reagent Co., Ltd., analytical grade), adding bromoethane (molar ratio of polyamide to bromoethane 1:1.2), stirring at 60℃ for 8h, precipitating three times with anhydrous ethanol after the reaction, and drying under vacuum at 60℃ to constant weight to obtain oligomeric PA.

[0065] Example 5: This embodiment provides a resin-based porous carbon, the preparation method of which is basically the same as that in Example 1, except that: 1.5g of polyvinylpyrrolidone (same as in Example 3) and 1.5g of oligomeric PA (same as in Example 4) were used to replace 3g of nonionic polyacrylamide; 12g of 5% zirconium nitrate aqueous solution was used to replace 12g of titanium nitrate aqueous solution, that is, solution A contains 12g of 5% zirconium nitrate aqueous solution and 12g of 5% titanium nitrate aqueous solution.

[0066] Comparative Example 1: This comparative example provides a resin-based porous carbon, the preparation method of which is basically the same as that of Example 5, except that: Solution A does not contain zirconium nitrate aqueous solution or titanium nitrate aqueous solution; that is, solution A consists only of 1.5g polyvinylpyrrolidone, 1.5g oligomeric PA and 200g deionized water.

[0067] Comparative Example 2: This comparative example provides a resin-based porous carbon, the preparation method of which is basically the same as that of Example 5, except that: Solution A does not contain polyvinylpyrrolidone or oligomeric PA; that is, solution A consists only of 12g of 5% zirconium nitrate aqueous solution, 12g of 5% titanium nitrate aqueous solution, and 200g of deionized water.

[0068] Comparative Example 3: This comparative example provides a resin-based porous carbon, the preparation method of which is basically the same as that of Example 5, except that: The preparation conditions for solution B in step (2) are different. Specifically, 60g of phenol is added to 98g of formaldehyde aqueous solution with a mass fraction of 37%, and the pH of the system is adjusted to 9.0 with ammonia. Then, the reaction is carried out at a constant temperature of 100℃ for 3h to prepare solution B.

[0069] This comparative example, by deepening the degree of crosslinking of phenolic resin, simulates the scenario of asynchronous reaction between pore-forming agent / metal ions and phenolic resin, and verifies the key impact of synchronous polycondensation / crosslinking of pore-forming agent, metal ions and phenolic resin on performance.

[0070] Performance testing: 1. Specific surface area determination: The specific surface area of ​​the sample was calculated using the nitrogen adsorption method based on the Brown-Noor-Emmett-Taylor (BET) theory.

[0071] 2. Total pore volume determination: Using the nitrogen adsorption isotherm, under the condition of relative pressure P / P0 ≈ 0.99 (P is the actual pressure of nitrogen in the system during the test; P0 is the pressure when nitrogen is liquefied at the test temperature), the total pore volume in the sample is calculated based on the adsorption amount. The t-plot method combined with the BJH model is used to calculate the pore volume of micropores with a pore size of less than 2 nm and the pore volume of mesopores with a pore size of 2~50 nm.

[0072] 3. Conductivity Measurement: Take an appropriate amount of dry porous carbon powder sample, place it in an insulating mold, and press it into a cylindrical block under a constant pressure of 10-20 MPa. Use a four-probe powder conductivity meter to measure the resistance of the block, and calculate the conductivity of the porous carbon based on the thickness and cross-sectional area of ​​the sample.

[0073] 4. Determination of metal ion chelation rate: Porous carbon samples were completely digested using microwave digestion (e.g., nitric acid + hydrofluoric acid). The total concentration of metal ions in the digestion solution was determined using ICP-OES (or ICP-MS) and denoted as C. 总 Take an equal amount of porous carbon sample. To avoid disrupting the formed coordination chelate bonds, add deionized water (or a 0.01 mol / L neutral salt solution, such as potassium chloride solution or sodium nitrate solution). Extract by shaking at room temperature for 1–2 hours, then filter. Determine the concentration of free metal ions in the filtrate using ICP-OES (or ICP-MS), denoted as C. 游离 Calculate the chelation rate using the following formula: Chelation rate = (C 总 -C 游离 ) / C 总 ×100%.

[0074] The performance tests of the porous carbon obtained from each embodiment and comparative example are shown in Table 1.

[0075] Table 1 The porous carbon material prepared by this invention exhibits significant improvements in several key performance indicators, specifically in terms of larger specific surface area, higher total pore volume, and higher electrical conductivity. It should be noted that all data in the table are averages from three parallel experiments, with test errors within ±2%.

[0076] This invention achieves multiple technical effects—"pore construction, structural enhancement, and interface stabilization"—by simultaneously introducing a pore-forming agent and specific metal ions during the synthesis of phenolic resin. On one hand, the pore-forming agent, as a reactive component, directly participates in the construction of molecular chain segments, achieving molecular-level dispersion and covalent fixation within the resin matrix. On the other hand, the metal ions undergo coordination chelation reactions with the active functional groups (such as hydroxyl and amide groups) of the phenolic resin and the pore-forming agent, achieving chemical anchoring of the metal component. This design not only catalyzes in-situ pore formation during the carbonization stage, reducing the dependence on strong bases during activation, but also constructs a double-crosslinked carbon framework composed of both covalent and coordinate bonds, enhancing the structural stability of the carbon matrix. This, in turn, enables interface anchoring during subsequent strong bonding with silicon particles, significantly improving the electrochemical performance of the silicon-carbon anode. In addition, the appropriate degree of curing is the key to balancing the number of pores and structural stability: if the curing degree is too deep (as in Comparative Example 3), the three-dimensional network of phenolic resin will be too dense, which will lead to insufficient space for pore expansion when the pore-forming agent is thermally removed, and some micropores / mesopores will be blocked. At the same time, the number of free functional groups that can participate in chelation will be reduced, which will ultimately result in a significant decrease in specific surface area, pore volume and metal chelation rate.

[0077] Taking Example 1 as an example, the specific implementation path is as follows: Nonionic polyacrylamide (PAM) and titanium ions are introduced into the phenolic resin precursor solution (Solution B). The amino groups on the PAM molecular chain undergo a hydroxymethylation reaction with formaldehyde in the precursor solution, generating an active intermediate containing an N-hydroxymethylamide structure in situ. Subsequently, this intermediate undergoes a condensation reaction with the hydroxymethylphenol in the phenolic resin prepolymer generated in situ from phenol and formaldehyde in the system, thereby covalently embedding the PAM chain segments into the crosslinked network of the phenolic resin in the form of side-linked branches. Through the above method, the PAM pore-forming component is no longer a simple physical admixture, but becomes part of the resin molecular chain segment, achieving uniform distribution and fixation of the pore-forming agent at the molecular level. This not only helps to form a more developed, interconnected, and uniform pore structure during carbonization, but more importantly, this method fundamentally avoids the problems of phase separation, pore collapse, and low pore-forming efficiency commonly found in non-covalent bonding or post-addition pore-forming methods. Meanwhile, titanium ions can undergo coordination chelation reactions with the active functional groups (such as hydroxyl and amide groups) of prepolymers and pore-forming agents to achieve chemical anchoring of metal components. This can catalyze in-situ pore formation during the carbonization stage, reduce the dependence of the activation process on strong bases, and construct a double cross-linked carbon skeleton composed of covalent and coordinate bonds, thereby improving the conductivity and structural stability of the carbon matrix and further optimizing electron transport efficiency.

[0078] Furthermore, this invention provides another technical approach for introducing pore-forming agents into molecular chain segments. Taking Example 2 as an example, by introducing bi-hydroxyl-terminated polyethylene glycol (PEG), the active hydroxyl groups at both ends of PEG undergo a dehydration condensation reaction with the hydroxymethyl groups in the phenolic resin prepolymer generated in situ in the system, allowing PEG segments to be covalently embedded in the cross-linked network of the phenolic resin in a bridging manner. In this structure, PEG does not exist as an independent phase dispersed in the resin matrix, but rather as a component of the molecular chain segments, forming a covalent connection structure with flexible segments bridging between different phenolic cross-linking nodes. This bi-terminal block anchoring bridging method not only achieves the covalent fixation of the pore-forming agent in the molecular chain segments, but also constructs a covalent three-dimensional network structure with flexible segment connections, thereby effectively improving the mechanical properties and pore structure stability of porous carbon materials. Simultaneously, zirconium ions can undergo coordination chelation reactions with the active functional groups of the prepolymer and the pore-forming agent, achieving chemical anchoring of the metal components and further enhancing the stability of the carbon matrix.

[0079] Furthermore, a comparison of Example 5 with Comparative Examples 1 and 2 shows that the absence of a pore-forming agent or metal ion solution leads to a decrease in material performance indicators.

[0080] N2 adsorption-desorption isotherms in Example 5 ( Figure 1 The microporous-mesoporous hierarchical pore structure of porous carbon is clearly presented. In the low relative pressure region (P / P0 < 0.1), the adsorption capacity increases rapidly, corresponding to the presence of abundant micropores; in the medium-high relative pressure region (P / P0 = 0.4~1.0), the appearance of the adsorption-desorption hysteresis loop confirms the integrity of the mesoporous structure. These characteristics support the rationale for the high specific surface area and high total pore volume in the examples. Its BJH adsorption pore volume-pore size integral distribution curve (… Figure 2 The data clearly demonstrates the pore volume accumulation pattern across different pore size ranges, reflecting the pore structure distribution characteristics of porous carbon in the micropore (<2 nm) and mesopore (2–50 nm) ranges. This directly corresponds to the total pore volume data in Example 5, further proving the effectiveness of pore structure control. The inventors further utilized the aforementioned porous carbon to prepare a silicon-carbon anode and conducted electrochemical performance tests on it. The specific testing methods are as follows: Preparation of silicon-carbon composite materials: Using the phenolic resin-based porous carbon obtained in the examples and comparative examples as the carbon matrix, silicon loading was performed by chemical vapor deposition (CVD). Specifically, the porous carbon was placed in a reaction furnace (such as a tube furnace, rotary kiln, fluidized bed, or roller kiln), heated to 450–500°C under an argon atmosphere, and then a mixed gas containing silane (SiH4) was introduced to carry out a deposition reaction, depositing nano-silicon within the pores of the porous carbon. After silicon deposition, further carbon coating treatment was performed: the silicon-deposited material was heated to 600–900°C in a reaction furnace, and a carbon source gas (selected from one or more of methane, ethylene, acetylene, or propylene) was introduced to perform chemical vapor deposition carbon coating (or it was mixed with carbon sources such as pitch or resin and then subjected to high-temperature carbonization coating), forming an amorphous carbon coating layer on the material surface. Finally, a silicon-carbon anode active material was obtained.

[0081] By controlling the deposition and coating process parameters, the mass fraction of silicon in the resulting silicon-carbon composite material is 15%–30%, and the mass fraction of carbon coating layer is 2%–10%.

[0082] Electrode Preparation: The silicon-carbon anode materials obtained in each embodiment and comparative example were used as active materials and mixed with a binder (such as polyacrylic acid, PAA) at a mass ratio of 95:5. A suitable amount of solvent (preferably deionized water, or a mixture of deionized water and a small amount of anhydrous ethanol, or N-methylpyrrolidone NMP) was added to prepare a uniform slurry. This slurry was coated onto a copper foil current collector, vacuum dried, rolled, and then cut into electrode sheets. Battery Assembly: A lithium metal sheet was used as the counter electrode. A polypropylene (PP) microporous membrane or glass fiber filter membrane was used as the separator. The electrolyte was a mixed solution of 1 mol / L LiPF6 dissolved in EC / DMC / EMC (volume ratio 1:1:1), with 5% FEC added as a film-forming additive. CR2032 coin cells were assembled in an argon-protected glove box (water and oxygen content <0.1ppm).

[0083] Electrochemical testing: A constant current charge-discharge testing system was used. Within a voltage window of 0.01 to 1.5 V, activation was performed at a rate of 0.1 C (usually for the first 2 to 5 cycles), followed by cycle performance testing at a rate of 1 C. All tests were conducted at 25±1℃.

[0084] The test results are shown in Table 2.

[0085] Table 2 As shown in Table 2, the silicon-carbon anode prepared by the porous carbon of the embodiments of the present invention significantly outperforms the comparative examples in all electrochemical performance indicators. This result fully demonstrates that when the porous carbon prepared by the present invention is used as a carbon matrix in the silicon-carbon anode of lithium-ion batteries, its unique pore structure, high specific surface area, and chemical anchoring effect of the metal components can effectively buffer the volume expansion of silicon particles during charge and discharge, providing a stable ion / electron transport channel, thereby significantly improving the rate performance and cycle stability of the silicon-carbon anode. Therefore, the porous carbon material proposed in this invention has important application prospects in the field of high-performance silicon-carbon anodes.

[0086] The present invention has been described in detail above, with the aim of enabling those skilled in the art to understand and implement the invention. However, this description should not be construed as limiting the scope of protection of the invention. All equivalent changes or modifications made in accordance with the spirit and essence of the invention should be included within the scope of protection of the invention.

Claims

1. A method for preparing a phenolic resin-based porous carbon precursor, characterized in that, The preparation method includes mixing a pore-forming agent, a metal salt, and raw materials for preparing phenolic resin, and carrying out a polycondensation reaction at 50°C to 100°C to form a phenolic resin-based porous carbon precursor containing the pore-forming agent and metal ions. The pore-forming agent is a first pore-forming agent and / or a second pore-forming agent, wherein the weight-average molecular weight of the first pore-forming agent and the second pore-forming agent is 5000~100000, and the first pore-forming agent is selected from one or more of acrylamide polymers, water-soluble acrylate polymers, vinylpyrrolidone polymers, polyacrylate polymers, and alginate compounds; the second pore-forming agent is selected from one or more of vinyl alcohol polymers, polyethers, and water-soluble aliphatic polyamide polymers, wherein the two end groups of the polyether are independently selected from hydroxyl, amino, carboxyl, phenolic hydroxyl, amide, or hydroxymethyl groups; The metal salt is selected from one or more of titanium salts, zirconium salts, aluminum salts, nickel salts, and cobalt salts.

2. The method for preparing the phenolic resin-based porous carbon precursor according to claim 1, characterized in that, The acrylamide polymers include polyacrylamide and polymethacrylamide; and / or, The water-soluble acrylate polymers include hydroxyethyl polyacrylate and hydroxypropyl polyacrylate; and / or, The polyacrylate polymers include ammonium polyacrylate, sodium polyacrylate, and potassium polyacrylate; and / or, The alginate compounds include ammonium alginate and sodium alginate; and / or, The vinylpyrrolidone polymers include polyvinylpyrrolidone; and / or, The vinyl alcohol polymers include polyvinyl alcohol and partially etherified polyvinyl alcohol; and / or, The polyether comprises α,ω-dihydroxy polyethylene oxide, α,ω-dihydroxy polyethylene glycol, α,ω-diamino polyethylene oxide, polyethylene oxide-polypropylene oxide block copolymer, bihydroxymethylated polyethylene oxide, and bicarboxylated polyethylene glycol; and / or The water-soluble aliphatic polyamide polymers include water-soluble aliphatic polyamides, N-alkylated water-soluble aliphatic polyamides, and bi-amino-terminated polyamide-amines.

3. The method for preparing the phenolic resin-based porous carbon precursor according to claim 2, characterized in that, The weight-average molecular weights of the polyacrylamide and polymethacrylamide are each independently 5000~100000; and / or, The weight-average molecular weights of the poly(hydroxyethyl acrylate), polyacrylate, and polymethacrylate are each independently 5000~50000; and / or, The weight-average molecular weights of the ammonium polyacrylate, sodium polyacrylate, potassium polyacrylate, ammonium alginate, and sodium alginate are each independently between 10,000 and 60,000; and / or, The polyvinylpyrrolidone has a weight-average molecular weight of 5,000 to 100,000; and / or, The polyvinyl alcohol and the partially etherified polyvinyl alcohol each have a weight-average molecular weight of 30,000 to 60,000, and the degree of etherification of the partially etherified polyvinyl alcohol is 20% to 30%; and / or, The weight-average molecular weights of the polyethylene oxide-polypropylene oxide block copolymer, α,ω-dihydroxy polyethylene oxide, α,ω-dihydroxy polyethylene glycol, α,ω-diamino polyethylene oxide, diamino-terminated polyamide-amine, dihydroxymethylated polyethylene oxide, and dicarboxyl-terminated polyethylene glycol are each independently 10,000 to 50,000; and / or, The weight average molecular weights of the water-soluble aliphatic polyamide, the N-alkylated water-soluble aliphatic polyamide, and the bi-amino-terminated polyamide-amine are each independently 20,000 to 50,000.

4. The method for preparing the phenolic resin-based porous carbon precursor according to claim 1, characterized in that, The raw materials used to prepare phenolic resin include formaldehyde and phenol, and the molar ratio of the pore-forming agent, formaldehyde and phenol is (0.01~0.25):(1.5~2.5):

1. The number of moles of the pore-forming agent is calculated based on the equivalent of its repeating unit.

5. The method for preparing the phenolic resin-based porous carbon precursor according to claim 1, characterized in that, The titanium salt is selected from one or more of titanium nitrate, tetrabutyl titanate, titanium sulfate, titanium tetrachloride, titanium isopropoxide, and tetraisopropyl titanate; and / or, The zirconium salt is selected from one or more of zirconium nitrate, zirconium chloride, zirconium sulfate, zirconium dichloride, and zirconium acetate; and / or, The aluminum salt is selected from one or more of aluminum nitrate, aluminum chloride, aluminum sulfate, aluminum isopropoxide, and polyaluminum chloride; and / or, The nickel salt is selected from one or more of nickel nitrate, nickel chloride, nickel sulfate, nickel acetate, and nickel sulfamate; and / or, The cobalt salt is selected from one or more of cobalt nitrate, cobalt chloride, cobalt sulfate, and cobalt acetate; and / or, The mass ratio of the metal salt to the pore-forming agent is (0.1~1):

1.

6. The method for preparing the phenolic resin-based porous carbon precursor according to any one of claims 1 to 5, characterized in that, The preparation method specifically includes the following steps: (1) The pore-forming agent, the metal salt solution, and water are mixed to form a first mixed solution, wherein the mass ratio of the pore-forming agent to the water is (0.005~0.05):1, and the mass fraction of the metal salt solution is 3%~10%; (2) Mix formaldehyde aqueous solution with a mass concentration of 30%~45% with phenol, and adjust the pH of the system to 8~11 with ammonia water to prepare a second mixed solution; (3) The first mixed solution and the second mixed solution are mixed to carry out the polycondensation reaction.

7. The method for preparing the phenolic resin-based porous carbon precursor according to claim 1, characterized in that, The preparation method further includes the steps of filtering, washing and drying the reaction product after the polycondensation reaction is completed.

8. A phenolic resin-based porous carbon, characterized in that, The phenolic resin-based porous carbon is obtained by carbonization, activation, and acidic solution post-treatment of the porous carbon precursor prepared by any one of claims 1 to 7.

9. The phenolic resin-based porous carbon according to claim 8, characterized in that, The carbonization process specifically includes: heating the porous carbon precursor to 600℃~800℃ at a rate of 1~10℃ / min under an inert atmosphere, and holding the temperature for carbonization for 1 h~4 h; and / or, The activation treatment specifically includes: mixing the carbonized product with an activating agent, and then heating it to 750℃~950℃ at a heating rate of 1~10℃ / min under an inert atmosphere, and holding it at that temperature for 0.5h~3h; and / or, The acidic solution treatment temperature is 50℃~70℃.

10. The phenolic resin-based porous carbon according to claim 9, characterized in that, The activator is water vapor, the intake rate of the water vapor is 0.1~10 mL / min based on the feed rate of liquid water, and the ratio of the total feed rate of the water vapor to the mass of the carbonized product is (1~10):

1.

11. An electrode material, characterized in that, It includes phenolic resin-based porous carbon as described in any one of claims 8 to 10.

12. The electrode material according to claim 11, characterized in that, The electrode material also includes silicon material loaded within the pores of the phenolic resin-based porous carbon and a carbon coating layer formed on the surface of the phenolic resin-based porous carbon after the silicon material is loaded.

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