A phenol-formaldehyde resin-based porous carbon and a method for preparing the same

Abstract

This invention relates to a phenolic resin-based porous carbon and its preparation method, comprising reacting a pore-forming agent with formaldehyde to generate an active intermediate, then polymerizing it with phenol to obtain a porous carbon precursor; subsequently, carbonization, activation treatment, acid solution treatment, washing, and drying are performed; the pore-forming agent is a first pore-forming agent and / or a second pore-forming agent, wherein the first pore-forming agent is selected from one or more of acrylamide polymers, water-soluble acrylate polymers, vinylpyrrolidone polymers, polyacrylates, and alginates; and the second pore-forming agent is selected from one or more of vinyl alcohol polymers, polyethers, and water-soluble aliphatic polyamide polymers. By directly introducing 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, molecular-level dispersion and covalent fixation of the pore-forming component in the resin matrix are achieved, which helps to form a more developed, interconnected, and uniform pore structure, thereby improving the overall performance of the carbon material.

Description

Technical Field

[0001] This invention relates to the field of porous carbon materials technology, specifically to a phenolic resin-based porous carbon and its preparation method. 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 novel phenolic resin-based porous carbon and its preparation method.

[0008] To achieve the above objectives, the technical solution adopted by the present invention is as follows: This invention provides a method for preparing phenolic resin-based porous carbon, which includes the following steps: A pore-forming agent is reacted with formaldehyde to generate an active intermediate, and then the active intermediate is polymerized with phenol to obtain a porous carbon precursor. The porous carbon precursor is subjected to carbonization and activation treatment to obtain an activated product; The activated product was treated with an acidic solution, followed by washing and drying to obtain the porous carbon. Wherein, the pore-forming agent is a first pore-forming agent and / or a second pore-forming agent, and the weight-average molecular weight of the first pore-forming agent and the second pore-forming agent is 5000~100000; 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.

[0009] 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.

[0010] In some embodiments, the acrylamide polymers include polyacrylamide and polymethacrylamide.

[0011] Furthermore, the weight-average molecular weights of the polyacrylamide and polymethacrylamide are independently 5,000 to 100,000, preferably 25,000 to 50,000.

[0012] In some embodiments, the water-soluble acrylate polymer includes hydroxyethyl polyacrylate and hydroxypropyl polyacrylate. Further, the weight-average molecular weight of the hydroxyethyl polyacrylate and hydroxypropyl polyacrylate is independently 5000-50000, preferably 15000-35000.

[0013] In some embodiments, the polyacrylate polymer includes ammonium polyacrylate, sodium polyacrylate, and potassium polyacrylate.

[0014] In some embodiments, the alginate compound includes ammonium alginate and sodium alginate.

[0015] 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.

[0016] In some embodiments, the vinylpyrrolidone polymer includes polyvinylpyrrolidone.

[0017] Furthermore, the weight-average molecular weight of the polyvinylpyrrolidone is 5,000 to 100,000, preferably 10,000 to 55,000.

[0018] In some embodiments, the ethylene alcohol polymer includes polyvinyl alcohol and partially etherified polyvinyl alcohol.

[0019] 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%.

[0020] 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.

[0021] 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.

[0022] 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.

[0023] 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.

[0024] In some embodiments, 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, wherein the number of moles of the pore-forming agent is calculated based on the equivalent of its repeating units.

[0025] In some embodiments, the reaction of the pore-forming agent with formaldehyde specifically includes: dissolving the pore-forming agent in water, adding the formaldehyde, adjusting the pH of the reaction system to 8-11, and reacting at 35℃-55℃.

[0026] Further, the pore-forming agent is dissolved in water, the formaldehyde is added, the pH of the reaction system is adjusted to 8-10, and the reaction is carried out at 40℃-50℃.

[0027] Furthermore, the pH value of the reaction system is adjusted by using one or more of sodium hydroxide, calcium hydroxide, potassium hydroxide, ammonia, ethylenediamine, triethylamine, triethanolamine, triethylenetetramine, and tetramethylammonium hydroxide.

[0028] In some embodiments, the polymerization reaction temperature is 50°C to 70°C, preferably 55°C to 65°C, and the polymerization reaction time is 2h to 5h.

[0029] In some embodiments, the carbonization process specifically includes: heating the porous carbon precursor to 600°C to 800°C, preferably 650°C to 750°C, at a rate of 1 to 10°C / min under an inert (such as nitrogen) atmosphere, and holding the temperature for carbonization for 1 to 4 hours.

[0030] 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 (such as nitrogen) atmosphere, and holding it at that temperature for 0.5 h to 3 h, more preferably 0.5 h to 2 h.

[0031] Further, the activator is selected from one or more of potassium hydroxide, sodium hydroxide, potassium carbonate, and sodium carbonate, preferably potassium carbonate. The mass ratio of the activator to the carbonization product is (1~2):1, preferably (1.2~1.8):1, such as 1.2:1 or 1.8:1.

[0032] In some embodiments, the acidic solution is hydrochloric acid, and the acidic solution is treated at a temperature of 50°C to 70°C.

[0033] Furthermore, the hydrochloric acid is a dilute hydrochloric acid of 0.1~1.0 mol / L.

[0034] The present invention also provides a phenolic resin-based porous carbon prepared by the preparation method described above.

[0035] Due to the application of the above technical solution, the present invention has the following advantages compared with the prior art: This invention introduces pore-forming agents as reactive components directly into the synthesis process of phenolic resins, enabling them to participate in the construction of molecular chain segments. Specifically, a first pore-forming agent is grafted onto the phenolic resin network via active side-chain groups; while the molecular chain of a second pore-forming agent serves as a main chain segment, covalently anchored or embedded in the phenolic resin main chain network through active end groups. This unique connection method achieves molecular-level dispersion and covalent fixation of the pore-forming components in the resin matrix, facilitating the formation of a more developed, interconnected, and uniform pore structure during processes such as carbonization, thereby improving the overall performance of carbon materials. Attached Figure Description

[0036] Figure 1 The graph shows the pore volume-pore size distribution curve of the porous carbon prepared in Example 10. Detailed Implementation

[0037] 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.

[0038] 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 applications, 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.

[0039] Unless otherwise specified, the reagents and instruments used in the following examples and comparative examples are all commercially available products, or can be prepared with reference to existing technologies.

[0040] Example 1: A phenolic 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 98g of 37% formaldehyde aqueous solution, adjust the pH of the system to 9.0 with ammonia, and then stir the reaction at 45℃ for 60min. After the reaction is completed, add 60g of phenol to the reaction system and react at 60℃ for 3h. The obtained product is dried under vacuum at room temperature to obtain a porous carbon precursor. (2) The obtained porous carbon precursor was placed in a tube furnace and heated to 700°C at a rate of 5°C / min under nitrogen atmosphere protection. It was then carbonized at 700°C for 2 hours and then naturally cooled to room temperature (25°C±5°C) to obtain the porous carbon primary product.

[0041] (3) Mix the obtained porous carbon primary product with the activator potassium carbonate at a mass ratio of 1:1.5, and then place it in a heating furnace (such as a tube furnace, rotary kiln or fluidized bed, etc.). Under the protection of nitrogen atmosphere, heat it to 850°C at a heating rate of 5°C / min, and activate it at 850°C for 1 hour. Then, let it cool naturally to room temperature.

[0042] (4) The activated product was added to 0.3 mol / L dilute hydrochloric acid and stirred and washed at 60°C for 6 hours. Then it was washed with deionized water until neutral. Finally, the washed product was vacuum dried at 80°C to obtain the final porous carbon.

[0043] Example 2: This embodiment provides a phenolic resin-based porous carbon, the preparation method of which is basically the same as that of Example 1, except that: an equal mass of double-hydroxyl-terminated polyethylene glycol (HO-PEG-OH, Mw=20,000, purchased from Shanghai Aladdin Biochemical Technology Co., Ltd., P103730) is used instead of nonionic polyacrylamide, and the amount of formaldehyde aqueous solution with a mass fraction of 37% is 93.2g.

[0044] Example 3: This embodiment provides a phenolic resin-based porous carbon, the preparation method of which is basically the same as that of Example 2, except that: an equal mass of low molecular weight linear polyvinyl alcohol (PVA, Mw=40,000, degree of alcoholysis 98~99%, purchased from Shanghai Aladdin Biochemical Technology Co., Ltd., P139535) is used to replace the hydroxyl-terminated polyethylene glycol.

[0045] Example 4: This embodiment provides a phenolic resin-based porous carbon, the preparation method of which is basically the same as that of Example 2, except that an equal mass of N-alkylated modified oligomeric aromatic polyamide (oligomeric PA, alkylation degree 95%, laboratory-made) is used to replace the hydroxyl-terminated polyethylene glycol.

[0046] 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.

[0047] Example 5: This embodiment provides a phenolic resin-based porous carbon, the preparation method of which is basically the same as that of Example 2, except that: an equal mass of partially etherified low molecular weight polyvinyl alcohol (Mw=40,000, degree of etherification 25%, degree of alcoholysis 98%, purchased from Shanghai Maclean Biochemical Technology Co., Ltd., P816865-customized version) is used to replace the hydroxyl-terminated polyethylene glycol.

[0048] Example 6: This embodiment provides a phenolic resin-based porous carbon, the preparation method of which is basically the same as that of Example 1, except that: an equal mass of polymethylacrylamide (PMAM, Mw=30,000, purchased from Shanghai Aladdin Biochemical Technology Co., Ltd., custom-made (original manufacturer's registered custom-made)) is used instead of nonionic polyacrylamide.

[0049] Example 7: This embodiment provides a phenolic resin-based porous carbon, the preparation method of which is basically the same as that of Example 1, except that: an equal mass of poly(2-hydroxyethyl acrylate) (PHEA, Mw=20,000, purchased from Anaiji Chemical, W330017-customized version) is used instead of nonionic polyacrylamide.

[0050] Example 8: This embodiment provides a phenolic resin-based porous carbon, the preparation method of which is basically the same as that of Example 1, except that: an equal mass of polyvinylpyrrolidone (PVP, Mw=50,000, purchased from Shanghai Aladdin Biochemical Technology Co., Ltd., P434442) is used instead of nonionic polyacrylamide.

[0051] Example 9: This embodiment provides a phenolic resin-based porous carbon, the preparation method of which is basically the same as that of Example 2, except that: an equal mass of α,ω-diamino polyethylene oxide (Mw=20,000, purchased from Beijing Jiankai Technology Co., Ltd., 20201) is used to replace the hydroxyl-terminated polyethylene glycol.

[0052] Example 10: This embodiment provides a phenolic resin-based porous carbon, the preparation method of which is basically the same as that of Example 1, except that 1.5g of polyvinylpyrrolidone (same as Example 8) and 1.5g of oligomeric PA (same as Example 4) are used instead of 3g of nonionic polyacrylamide. The grafting rate of PVP is measured by potassium bromide-potassium bromate ultraviolet spectrophotometry and the grafting rate of oligomeric PA is measured by hydrochloric acid back titration, respectively. The total valence bond grafting rate is calculated to be 92% by weighted average according to mass ratio.

[0053] Example 11: This embodiment provides a phenolic resin-based porous carbon, the preparation method of which is basically the same as that of Example 2, except that: an equal mass of low molecular weight water-soluble aliphatic polyamide (same as Example 4) is used to replace the hydroxyl-terminated polyethylene glycol.

[0054] Example 12: This embodiment provides a phenolic resin-based porous carbon, the preparation method of which is basically the same as that in Example 1, except that an equal mass of sodium polyacrylate (PAAS, Mw=40,000, purchased from Shanghai Maclean Biochemical Technology Co., Ltd., S434409-customized version) is used instead of nonionic polyacrylamide. Example 13 This embodiment provides a phenolic resin-based porous carbon, the preparation method of which is basically the same as that of Example 2, except that: an equal mass of double-amino-terminated polyamide-amine (PAMAM, Mw=30,000, Sigma-Aldrich (Shanghai) Trading Co., Ltd., 648159) is used to replace double-hydroxyl-terminated polyethylene glycol.

[0055] Comparative Example 1: This comparative example provides a phenolic resin-based porous carbon, the preparation method of which is basically the same as that of Example 1, except that: nonionic PAM is not added in step (1).

[0056] Comparative Example 2: This comparative example provides a phenolic resin-based porous carbon, the preparation method of which is basically the same as that of Example 1, except that: step (1).

[0057] The specific steps (1) of this comparative example are as follows: 180g of deionized water, 98g of formaldehyde aqueous solution with a mass fraction of 37% and 60g of phenol are mixed, the pH of the system is adjusted to 9.0 with ammonia water, and the reaction is carried out at 60℃ for 3h to obtain the first mixed system; Mix 20g of water with 3g of nonionic PAM (same as in Example 1), stir well, and obtain a second mixed system; After mixing the first and second mixtures, the mixture is kept at a constant temperature of 45°C for 60 minutes to complete the curing process.

[0058] The first and second mixed systems are homogeneous phases after mixing, and exhibit a macroscopically uniform dispersion and microscopically separated state during the curing process of phenolic resin.

[0059] Comparative Example 3: This comparative example provides a phenolic resin-based porous carbon, the preparation method of which is basically the same as that of comparative example 2, the only difference being that: the non-ionic PAM powder is dispersed in the first mixing system by mechanical stirring and mixing, and exhibits a macroscopic phase separation state during the curing process of the phenolic resin.

[0060] 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.

[0061] 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.

[0062] 3. Characterization of through-pore volume: A combined nitrogen adsorption method and mercury porosimetry were used for characterization. Specifically, nitrogen adsorption data were combined to analyze the distribution of mesopores and micropores, while mercury porosimetry was used to analyze the distribution of macropores and through-pores. The open pore volumes detected by the two methods were summed to obtain the through-pore volume of the sample.

[0063] 4. Covalent Bond Grafting Rate Determination: Based on the type of active groups contained in the pore-forming agent, the corresponding quantitative analysis method (including titration or spectrophotometry) was used for determination. All titrations were performed at room temperature (25℃) with magnetic stirring (300 r / min). The grafting rate was calculated by comparing the content of the corresponding active group in the ungrafted pore-forming agent (or physically mixed control sample) with the change in the content of the active group per unit mass of sample before and after grafting. As an example: 1) If the active group is amino: Titrate with 0.1 mol / L hydrochloric acid standard solution, react the amino group with excess hydrochloric acid, and then back titrate with 0.1 mol / L sodium hydroxide standard solution to calculate the amino content per unit mass of sample, thereby obtaining the grafting rate.

[0064] 2) If the active group is a hydroxyl group: use the acetic anhydride-pyridine acetylation titration method. Acetic anhydride reacts with the hydroxyl group to produce acetic acid, which is then titrated with a 0.1 mol / L sodium hydroxide-ethanol standard solution. The hydroxyl content per unit mass of the sample is calculated, thus determining the grafting rate.

[0065] The grafting rate of the remaining active groups in the pore-forming agent of this invention is determined by the industry-standard quantitative method for their respective functional groups. The determination principle is the same as the above method, and the covalent bond grafting efficiency is reflected by the amount of functional group binding.

[0066] 5. Microporosity: It is calculated by the ratio of the pore volume of micropores with a pore size of less than 2 nm to the total pore volume, i.e., microporosity = (micropore volume / total pore volume) × 100%.

[0067] The performance tests of the porous carbon obtained from each embodiment and comparative example are shown in Table 1.

[0068] Table 1 The porous carbon material prepared by this invention shows significant improvements in several key performance indicators, specifically in larger specific surface area, higher total pore volume and through pore volume, and higher covalent bond grafting rate.

[0069] Compared to traditional phenolic resin-based porous carbon materials (as shown in Comparative Example 1), this invention does not simply physically mix the pore-forming agent into the resin, but instead introduces it directly into the synthesis process of phenolic resin as a reactive component, allowing it to participate in the construction of molecular chain segments, thereby achieving molecular-level dispersion and covalent fixation of the pore-forming component in the resin matrix.

[0070] Taking Example 1 as an example, the specific implementation path is as follows: The amino groups on the nonionic polyacrylamide (PAM) molecular chain undergo a hydroxymethylation reaction with formaldehyde, 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, thereby covalently embedding the PAM chain segments into the crosslinked network of the phenolic resin in the form of side-linked branches. In this way, 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 composite / post-addition pore-forming methods (such as those described in Comparative Examples 2 and 3) between the phenolic resin and the pore-forming agent.

[0071] Furthermore, a comparative analysis of Example 1 with Comparative Examples 2 and 3 reveals that Comparative Example 2 follows the traditional semi-interpenetrating polymer network approach, introducing pore-forming chain segments after the formation of the phenolic resin prepolymer. These molecules form a composite structure with the phenolic network primarily through physical entanglement and weak interactions such as hydrogen bonding / polarity. While this type of non-covalent connection can improve compatibility to some extent, the lack of covalent anchoring means that chain segment migration and microphase separation can still occur during curing and carbonization, leading to uneven spatial and temporal distribution of pore-forming activity. This easily results in isolated pores, collapsed pores, or closed pores, making it difficult to consistently improve pore connectivity and pore-forming efficiency, and hindering the synergistic optimization of "high specific surface area and hierarchical interconnected pore structure" described in the background art.

[0072] Comparative Example 3 represents a mechanical-physical blending route (prepolymer added later, mechanically stirred and dispersed). Due to the lack of relatively mild weak interaction constraints in the semi-interpenetrating polymer network system, it is more difficult to form a uniform and stable composite structure. Macroscopic phase separation and local enrichment are more likely to occur during curing. Non-uniform removal of pore-forming agents is more significant during carbonization, further reducing the uniformity, continuity, and controllability of the pore structure. Its overall performance is difficult to meet the requirements of silicon-carbon anodes for rapid ion transport and volume expansion buffering.

[0073] 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 is no longer an independent phase dispersed in the resin matrix, but rather 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-anchored 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, effectively improving the mechanical properties and pore structure stability of porous carbon materials, thereby enhancing their overall performance.

[0074] 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 phenolic resin-based porous carbon, characterized in that, Includes the following steps: A pore-forming agent is reacted with formaldehyde to generate an active intermediate, and then the active intermediate is polymerized with phenol to obtain a porous carbon precursor. The porous carbon precursor is subjected to carbonization and activation treatment to obtain an activated product; The activated product was treated with an acidic solution, followed by washing and drying to obtain the porous carbon. Wherein, the pore-forming agent is a first pore-forming agent and / or a second pore-forming agent, and the weight-average molecular weight of the first pore-forming agent and the second pore-forming agent is 5000~100000; 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, wherein the two end groups of the polyether are independently selected from hydroxyl, amino, carboxyl, phenolic hydroxyl, amide, or hydroxymethyl groups.

2. The method for preparing phenolic resin-based porous carbon 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 phenolic resin-based porous carbon 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 hydroxyethyl acrylate and hydroxypropyl acrylate 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 phenolic resin-based porous carbon according to any one of claims 1 to 3, characterized in that, The molar ratio of the pore-forming agent, formaldehyde, and phenol is (0.01~0.25):(1.5~2.5):1, and the number of moles of the pore-forming agent is calculated based on the equivalent of its repeating unit.

5. The method for preparing phenolic resin-based porous carbon according to claim 1, characterized in that, The reaction between the pore-forming agent and formaldehyde specifically includes: dissolving the pore-forming agent in water, adding the formaldehyde, adjusting the pH of the reaction system to 8-11, and reacting at 35℃-55℃.

6. The method for preparing phenolic resin-based porous carbon according to claim 5, characterized in that, The pH value of the reaction system is adjusted by one or more of the following: sodium hydroxide, calcium hydroxide, potassium hydroxide, ammonia, ethylenediamine, triethylamine, triethanolamine, triethylenetetramine, and tetramethylammonium hydroxide.

7. The method for preparing phenolic resin-based porous carbon according to claim 1, characterized in that, The polymerization reaction is carried out at a temperature of 50℃ to 70℃ for a time of 2h to 5h.

8. The method for preparing phenolic resin-based porous carbon according to claim 1, 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 is hydrochloric acid, and the acidic solution is treated at a temperature of 50°C to 70°C.

9. The method for preparing phenolic resin-based porous carbon according to claim 8, characterized in that, The activator is potassium carbonate; and / or, The mass ratio of the activator to the carbonized product is (1~2):

1.

10. Phenolic resin-based porous carbon prepared by any one of claims 1 to 9.

Images