Preparation method of lignin-doped sphere-like resin-based porous carbon

Abstract

The invention relates to the technical field of lithium ion battery negative electrode material preparation, in particular to a lignin-doped sphere-like resin-based porous carbon preparation method which comprises the following steps: adding deionized water, absolute ethyl alcohol and an ammonia water solution into a container, mixing for 10-30 minutes, adding a cationic surface active agent, stirring and mixing; stirring and mixing for 10-30 minutes, and then adding a phenolic compound and an aldehyde compound; adding lignin, stirring for 1-5 hours, pouring the stirred mixed solution into a pressure container, sealing, putting into a blast oven, carrying out primary drying reaction for 24 hours, washing, cooling to room temperature, centrifugally cleaning, and putting into the blast oven, and carrying out secondary drying, so as to obtain lignin-doped phenolic resin microsphere powder; performing carbonization treatment on the lignin-doped sphere-like resin in an inert gas atmosphere, and performing activation treatment on the lignin-doped sphere-like resin by using a physical activation method to obtain the lignin-doped sphere-like resin-based porous carbon. By optimizing the particle morphology uniformity, the safety and rate capability of the negative electrode material prepared from the porous carbon are improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of lithium ion battery negative electrode material preparation, and particularly relates to a preparation method of lignin-doped spherical resin-based porous carbon. BACKGROUND

[0002] Porous carbon has rich pore structure, good electrical conductivity and strong adsorption capacity, and is widely used in various industries. In recent years, it has been used as an energy storage material and applied in supercapacitors, lithium-sulfur batteries, lithium ion battery negative electrodes and other fields. Porous carbon is one of the core raw materials of silicon-carbon negative electrode material for lithium ion batteries. The skeleton strength, electrical conductivity, micro-morphology, composition and micropore structure of the porous carbon have a significant influence on the subsequent silane deposition, and further affect the initial efficiency and cycle performance of the battery.

[0003] Chinese Patent Publication No. CN119240693A discloses a kind of spherical porous carbon and its preparation method and preparation device, silicon-carbon negative electrode material. The preparation method of the spherical porous carbon includes the following specific steps: crushing the porous carbon precursor, adding thickening agent and surfactant to obtain a suspension; stirring and heating the suspension to form a surface-solidified spherical resin; washing and filtering the surface-solidified spherical resin; transferring the washed spherical resin to a hot roller press device, gradually heating and extruding to solidify the spherical resin, obtaining a solidified spherical resin; collecting the spherical resin by preliminary dispersion and sieving, carbonizing and activating the pores in a nitrogen atmosphere, drying and high-temperature passivating in a nitrogen atmosphere, and obtaining the required spherical porous carbon after dispersion. It can be seen that the spherical porous carbon and its preparation method and preparation device, silicon-carbon negative electrode material have the following problems: Resin-based porous carbon has the characteristics of high uniformity, low impurity content, few nanoscale defect holes on the surface, and high compaction density. The existing preparation process of resin-based porous carbon material is to perform curing, crushing, carbonization, activation, pore modification, crushing classification, passivation and other steps on resin powder. The structure of the cured resin is compact, has few nanoscale pore defects, and has few active sites. In the activation process, when the physical steam activation is used, water molecules continuously expand the pores, resulting in a slight decrease in micropore rate and a large pore size of the sample. This requires increasing the activity of the resin and improving the activation efficiency. In addition to the commonly used polyvinyl alcohol pore-forming agent, lignin can also be used as a pore-forming agent to add to the resin polymer to improve the reaction rate. In addition, the classified porous carbon particles have irregular sharp corners, which leads to low first coulomb efficiency of the material. The sharp corners may pierce the separator and the electrode sheet during the preparation of the negative electrode sheet, causing micro-short circuit. The airflow grinding shaping of the classified porous carbon particles can remove the corners and relieve this phenomenon, but this step consumes a huge production cost. The perfect spherical porous carbon particles have a small contact area and a low ion conduction rate, resulting in poor rate performance of the material. Therefore, compared with the perfect spherical particles, the first efficiency, rate performance and cycle performance of the spherical particles are outstanding, and the spherical particles are the better resin-based porous carbon particle morphology at present. SUMMARY

[0004] Therefore, the present application provides a lignin-doped spherical resin-based porous carbon preparation method to overcome the problems of low micropore rate and large pore size of the sample caused by physical steam activation in the prior art, and poor rate performance of perfect spherical porous carbon particles.

[0005] The present application aims to provide a spherical resin-based porous carbon preparation method with good particle morphology uniformity and the ability to improve the safety and rate performance of the porous carbon prepared as a negative electrode material.

[0006] To achieve the above-mentioned purpose, the present application provides a lignin-doped spherical resin-based porous carbon preparation method, comprising: Deionized water, anhydrous ethanol, and ammonia solution are added to a container and mixed for 10-30 min, then a cationic surfactant CTAB is added and stirred and mixed for 10-30 min, then a phenolic compound and an aldehyde compound are added; The lignin is added and stirred for 1-5 h, the stirred mixture is poured into a pressure container and sealed, and then placed in a forced air oven for a first drying reaction for 24 h, and then washed and cooled to room temperature; After cooling, the mixture is centrifuged and washed, and then placed in a forced air oven for a second drying, and then dried to obtain a lignin-doped phenolic resin microsphere powder; The lignin-doped spherical resin powder is heat-treated in an air environment, starting from ambient temperature and heating to 110-150 DEG C for 1-5 h, and then kept at a semi-melted state for 1-5 h to obtain a molten material; stirring, dispersing and solidifying the molten material until the resin does not melt again after being heated to the same temperature again, the same temperature being 110-150℃, to obtain a lignin-doped spherical resin; carbonizing the lignin-doped spherical resin by heating to 400-800℃ under an inert gas atmosphere for 1-5h; etching the carbonized lignin-doped spherical resin by an active medium using a physical activation method, and activating the lignin-doped spherical resin for 1-10h to obtain a lignin-doped spherical resin-based porous carbon; When the physical activation method is used for activation, the temperature range is 700-1200℃.

[0007] Further, the deionized water, anhydrous ethanol and ammonia solution are mixed at 30-60℃, and the volume ratio of deionized water, anhydrous ethanol and ammonia solution is 300-500: 50-150: 1.

[0008] Further, the lignin is added in an amount of 0.1%-5%, the temperature range of the first drying is 100-130℃, and the temperature range of the second drying is 40-80℃.

[0009] Further, the cationic surfactant CTAB, the phenolic compound and the aldehyde compound are added in a molar mass ratio of 1-3: 1: 1-2.

[0010] Further, the phenolic compound is selected from one or more of phenol, cardanol, m-dihydroxybenzene and p-dihydroxybenzene, and the aldehyde compound is selected from one or more of formaldehyde, acetaldehyde, furfural and salicylaldehyde.

[0011] Further, the active medium is one or more of water vapor, carbon dioxide and other oxidizing gases.

[0012] Further, the carbonization parameter range of the carbonization treatment is 400-800℃ for 1-5h, and the activation parameter range of the activation treatment is 700-1200℃ for 1-10h.

[0013] Further, the shape of the lignin-doped spherical resin is one or more of ellipsoidal, potato-shaped, dice-shaped and pomegranate seed-shaped.

[0014] Further, the sphericity of the resin microspheres is reduced by applying shear force by stirring the molten material combined with the adhesion of the semi-melted material.

[0015] Further, the lignin-doped spherical resin-based porous carbon is used to prepare a battery negative electrode.

[0016] Compared with the prior art, the hydrothermal method for synthesizing the resin powder is more environmentally friendly, but the prepared resin powder is prone to adhesion and affects separation, the key point of the method is the influence of lignin on various aspects, first, lignin is added to ensure the uniformity of its distribution, lignin is used as a pore forming agent in resin-based polymers to improve the reaction rate through lignin acid group catalysis, in terms of pore generation, lignin is partially degraded under high-temperature hydrothermal conditions to produce gases such as CO2 / H2O, forming a microporous structure, reducing inter-particle contact, and being suitable for subsequent activated porous materials, on the other hand, the prior art does not add lignin to the hydrothermal method for synthesizing the resin powder, but relies only on the polycondensation reaction of the resin itself (such as the crosslinking of the hydroxymethyl of phenolic aldehyde), after adding lignin in the method, the phenolic hydroxyl group of lignin co-crosslinks with the phenolic aldehyde resin to form a more complex three-dimensional network to increase the mechanical strength, and the specific surface area is higher under the combined influence of the lignin-derived pores and the inherent pores of the resin; the problem of adhesion and separation of the resin powder synthesized by the hydrothermal method is solved by replacing part of the petrochemical-based resin with lignin, which reduces the cost and is renewable.

[0017] Further, the method is stirred and dispersed to solidify the lignin-doped phenolic resin microsphere powder, so that the material continuously flows without sticking together, and the sphericity of the material is changed by the shear force applied by the stirring and the adhesion force of the semi-melted material during the stirring and dispersing process, the key of the lignin-doped spherical resin powder solidification treatment is to moderately reduce the sphericity of the lignin-doped resin microspheres under controllable conditions, to form a uniform and stable spherical structure to meet the subsequent process requirements.

[0018] Further, the lignin-doped spherical resin is carbonized to purify and remove light components to avoid impurities interfering with the reaction, and the resin-lignin composite is converted into a carbon skeleton to preliminarily form a pore structure, the method enlarges the pores by physical activation through gas etching to improve the controllability of the specific surface area and the pore size distribution; the lignin-doped spherical resin-based porous carbon prepared by the method has high content of biobased material, good environmental friendliness, and strong interfacial bonding force (polarity matching), and the doping of heteroatoms (O, N) in the lignin-doped spherical resin-based porous carbon improves the electrical conductivity and electrochemical activity after carbonization.

[0019] Further, lignin pyrolysis produces gases such as H2O and CO2, lignin promotes pore formation to form initial micropores, and the O and N elements in lignin are doped to enhance the surface polarity of the carbon material, through precise control of the carbonization-activation synergy, lignin-based porous carbon with high specific surface area, controllable pore size and rich surface chemistry can be prepared, which is suitable for high-end needs in the fields of energy and environment. BRIEF DESCRIPTION OF DRAWINGS

[0020] Fig. 1 The micro-morphology diagram of the lignin-doped spherical resin in the embodiments of the present application; Fig. 2 The flow chart of the method for preparing the lignin-doped spherical resin-based porous carbon in the embodiment of the present application is shown in Figure 1. DETAILED DESCRIPTION

[0021] In order to make the objects and advantages of the present application clearer, the present application will be further described in conjunction with the embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application and should not be used to limit the present application.

[0022] The preferred embodiments of the present application will be described below with reference to the accompanying drawings. It should be understood by those skilled in the art that the embodiments are only used to explain the technical principles of the present application and are not used to limit the protection scope of the present application.

[0023] It should be noted that, in the description of the present application, the terms indicating the direction or positional relationship such as "upper", "lower", "left", "right", "inner", "outer" and the like are based on the direction or positional relationship shown in the drawings, which is only for the convenience of description and does not indicate or imply that the device or element must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the present application.

[0024] In addition, it should also be noted that, in the description of the present application, unless otherwise explicitly specified and limited, the terms "mounting", "connecting", "connection" should be understood in a broad sense, for example, it can be fixed connection, or detachable connection, or integrally connected; it can be mechanical connection, or electrical connection; it can be directly connected, or indirectly connected through an intermediate medium, or the internal communication of two elements. For those skilled in the art, the specific meaning of the above terms in the present application can be understood according to the specific circumstances.

[0025] Please refer to Figs. 1-2 shown in Figure 1, Fig. 1 The micro-morphology diagram of the lignin-doped spherical resin in the embodiment of the present application is shown in Figure 2; Fig. 2 The flow chart of the method for preparing the lignin-doped spherical resin-based porous carbon in the embodiment of the present application is shown in Figure 1.

[0026] The present application provides a method for preparing lignin-doped spherical resin-based porous carbon, comprising: S1, adding deionized water, anhydrous ethanol, ammonia solution into a container and mixing at 30-60℃ for 10-30min until uniform, then adding cationic surfactant CTAB and stirring for 10-30min, and then adding phenolic compound and aldehyde compound; Step S2: Add 0.1%-5% lignin and stir for 1-5 hours. Pour the stirred mixture into a pressure vessel and seal it. Place it in a forced-air oven at 100-130℃ and react for 24 hours. After the reaction, rinse with cooling water and cool to room temperature. After centrifugation with deionized water, dry it in a forced-air oven at 40-80℃ to obtain lignin-doped phenolic resin microsphere powder. Step S3: Heat-treat the lignin-doped spherical resin powder in an air environment, starting from the ambient temperature and raising the temperature to 110-150℃ over 1-5 hours, and maintaining the heat treatment for 1-5 hours until it becomes a semi-molten material. Step S4: Stir, disperse and solidify the molten material until the resin will not melt again after being reheated to the same temperature to obtain lignin-doped spherical resin, wherein the same temperature is 150-160℃. Step S5: Carbonize the lignin-doped spherical resin by heating it to 400-800℃ and holding it for 1-5 hours in an inert gas atmosphere. Step S6: The lignin-doped spherical resin is activated by physical activation at a temperature range of 700-1200℃ for 1-10 hours by etching with an active medium to obtain lignin-doped spherical resin-based porous carbon. The active medium is one or more of water vapor, carbon dioxide, and other oxidizing gases; the phenolic compound is selected from one or more of phenol, cashew nut shell powder, resorcinol, and hydroquinone; and the aldehyde compound is selected from one or more of formaldehyde, acetaldehyde, furfural, and salicylaldehyde.

[0027] The method for preparing lignin-doped spherical porous carbon provided by the present invention adopts a three-step method. The first step is the synthesis of lignin-doped spherical resin; the second step is to slowly solidify and shape the lignin-doped spherical resin at high temperature to become lignin-doped spherical resin; the third step is carbonization and activation to obtain lignin-doped spherical resin-based porous carbon.

[0028] First, resin powder is synthesized using a hydrothermal method, and then a special curing treatment is performed to obtain a spherical resin. The spherical resin is then subjected to carbonization and activation treatment to obtain lignin-doped spherical resin-based porous carbon. The specific steps for hydrothermal synthesis of resin powder are as follows: Add deionized water, anhydrous ethanol, and ammonia solution to a container and mix at 30-60℃ for 10-30 minutes until homogeneous. The volume ratio of the deionized water, anhydrous ethanol, and ammonia solution is 300-500:50-150:1. Then, the cationic surfactant CTAB is added and stirred for 10-30 minutes. Finally, phenolic compounds and aldehyde compounds are added to synthesize phenolic resin. The cationic surfactant CTAB, phenolic compounds and aldehyde compounds are added in a molar ratio of 1-3:1:1-2. Then add 0.1%-5% lignin and stir for 1-5 hours. Pour the stirred mixture into a pressure vessel, seal it, and place it in a forced-air oven at 100-130℃ for 24 hours. After the reaction, rinse with cold water and cool rapidly to room temperature.

[0029] The product was removed, washed by centrifugation with deionized water, and then dried in a forced-air drying oven at 40-80℃ to obtain lignin-doped phenolic resin microsphere powder.

[0030] The rigid aromatic ring structure of lignin can physically isolate resin molecular chains, reduce the close packing during polymerization, and decrease the contact area between microspheres. It is especially suitable for linear resins (such as phenolic resins) and can prevent molten adhesion.

[0031] The polar groups such as phenolic hydroxyl and carboxyl groups in lignin can alter the surface energy of resins, reducing agglomeration caused by van der Waals forces. Therefore, the lignin content needs to be controlled; excessive lignin can introduce too many active sites, which in turn promotes cross-linking.

[0032] In terms of pore formation, lignin partially degrades under high-temperature hydrothermal conditions, producing gases such as CO2 / H2O, forming a microporous structure, reducing interparticle contact, and is suitable for porous materials that require subsequent activation.

[0033] Specifically, hydrothermal synthesis of resin powder is relatively environmentally friendly, but its drawback is that the prepared resin powder is prone to adhesion, affecting separation. The key point of this method lies in the impact of adding lignin on various aspects. First, lignin is added during the raw material synthesis to ensure its uniform distribution. On the one hand, lignin is used as a pore-forming agent added to resin polymers, and the reaction rate is increased by the catalysis of the acidic groups of lignin. On the other hand, in the existing technology, hydrothermal synthesis of resin powder does not add lignin and relies solely on the condensation reaction of the resin itself (such as the hydroxymethyl crosslinking of phenolic resin). After adding lignin in this method, the phenolic hydroxyl groups of lignin co-crosslink with phenolic resin to form a more complex three-dimensional network, increasing mechanical strength. Moreover, the specific surface area is higher due to the combined influence of lignin-derived pores and the inherent pores of the resin. By replacing part of the petrochemical-based resin with lignin, the problem of adhesion and separation of hydrothermal synthesized resin powder is solved, reducing costs and making it renewable.

[0034] The specific steps of the curing process during implementation are as follows: The lignin-doped spherical resin powder was heat-treated in an air environment, starting from the ambient temperature and gradually increasing to 110-150℃ over 1-5 hours, and then held for 1-5 hours. The lignin-doped phenolic resin microsphere powder is stirred and dispersed to solidify it, so that the material continues to flow and does not stick together into lumps, until the material can no longer be melted by high temperature, thus obtaining lignin-doped spherical resin. The spherical resin is any one or more of ellipsoidal resin, potato-shaped resin, dice-shaped resin and pomegranate seed-shaped resin.

[0035] Specifically, the high-temperature stirring during heat treatment causes the resin to solidify, and the material will not melt due to high temperature. This means that the resin will not melt again after being reheated to the same temperature, which is 110-150℃. During implementation, a rotating device drives a stirring rod to stir the material, which is then dispersed to ensure uniform mixing. During the stirring and dispersing process, the shear force applied by the machine and the adhesive force of the material in its semi-molten state change the sphericity of the material, and the spherical resin gradually becomes a near-spherical structure.

[0036] The stirring speed range is 200~250 rpm.

[0037] Specifically, the key to the curing treatment of lignin-doped spherical resin powder lies in achieving a moderate reduction in the sphericity of lignin-doped resin microspheres under controllable conditions, forming a uniform and stable spherical structure to meet the requirements of subsequent processes.

[0038] During the curing process, key parameters can be monitored and process conditions adjusted in real time to optimize the curing effect, morphology control, and prevent adhesion of spherical resins.

[0039] This method can adjust the stirring speed of the lignin-doped phenolic resin microsphere powder in a semi-molten state according to the material flowability during the stirring process, so as to prevent adhesion and control the degree of sphericity deformation. The heating rate of the heat treatment is adjusted according to the actual ratio of lignin to phenolic resin and the temperature uniformity of the lignin-doped phenolic resin microsphere powder during the curing process. Specifically, the lignin-doped phenolic resin microsphere powder is heat-treated in air at the heating rate to a semi-molten state, and the material flowability of the molten material in the current semi-molten state is detected to predict the degree of reduction in the sphericity of the resin microspheres in the lignin at the current stirring speed. Determine whether the degree of reduction in sphericity meets the requirements for a near-spherical structure after the material is stirred, dispersed, and solidified at the current stirring speed in its current semi-molten state. Adjust the stirring speed according to the degree of sphericity reduction, and cure according to the adjusted stirring speed to obtain lignin-doped spherical resin.

[0040] Specifically, uneven temperature or insufficient shear force during the curing process can easily lead to particle adhesion, while excessive stirring time or high speed can cause excessive destruction of sphericity. This method can adjust the stirring speed according to the real-time flowability, predict the degree of sphericity reduction of spherical resin particles, and adjust the shear force application mode (continuous / intermittent stirring) to intelligently regulate and control the curing process of lignin-doped spherical resin powder.

[0041] The specific steps for carbonization and activation treatments are as follows: The lignin-doped spherical resin was carbonized by heating to 400-800℃ and holding for 1-5 hours in an inert gas atmosphere to remove its light components. During the carbonization process, some sites of lignin were exposed, and the carbonized samples also showed a certain porosity structure.

[0042] By carbonizing lignin-doped spherical resins to purify and remove their light components and avoid impurities interfering with the reaction, the resin-lignin complex is transformed into a carbon skeleton, initially forming a porous structure.

[0043] The lignin-doped spherical resin was activated by physical activation at a temperature range of 700-1200℃ for 1-10 hours by etching with an active medium, wherein the active medium is one or more of water vapor, carbon dioxide, and other oxidizing gases, to obtain lignin-doped spherical resin-based porous carbon.

[0044] Physical activation expands pores through gas etching, which can improve the controllability of specific surface area and pore size distribution. In this embodiment, water vapor activation is used to initially form a porous carbon skeleton, generating micropores and mesopores (2~5nm) in porous carbon. Specifically, the key to carbonization and activation treatments lies in the microporosity and pore volume of lignin-doped spherical resin-based porous carbon. This method can adjust the holding time of carbonization treatment according to the changing trend of gas release rate of lignin-doped spherical resin during carbonization. Extending the holding time can increase the carbon yield, but may reduce the micropores of porous carbon in spherical resin. Simultaneously, the activation time (1-10h) can be adjusted according to the real-time weight loss rate of the lignin-doped spherical resin after carbonization during the activation process, thus optimizing the balance between pore formation and carbon yield in the process of preparing lignin-doped spherical resin-based porous carbon.

[0045] The lignin-doped spherical resin-based porous carbon prepared by this method has improved conductivity and electrochemical activity after carbonization due to heteroatom (O, N) doping. It has high bio-based content, good environmental protection, and strong interfacial bonding (polarity matching). Specifically, lignin pyrolysis produces gases such as H2O and CO2. Lignin promotes pore formation and the initial micropores. The doping of O and N elements in lignin enhances the surface polarity of carbon materials. By precisely controlling the synergistic effect of carbonization and activation, lignin-based porous carbon with high specific surface area, controllable pore size and rich surface chemistry can be prepared, which is suitable for high-end needs in the energy and environment fields.

[0046] This embodiment provides test results based on specific surface area analysis for lignin-doped spherical resin-based porous carbon under different activation conditions, with different calculation models selected for different pore types. Table 1. Pore diameter data of activated samples

[0047] In practice, the activation condition is the activation temperature. The activation temperature in Example 1 is 850℃, the activation temperature in Example 2 is 950℃, and the activation temperature in Example 3 is 1050℃. Add deionized water, anhydrous ethanol, and ammonia solution to a container and mix at 40°C for 30 minutes. Add the cationic surfactant CTAB and stir to mix. After stirring and mixing for 30 minutes, add phenolic compounds and aldehyde compounds. During implementation, the volume ratio of deionized water, anhydrous ethanol, and ammonia solution is 300:100:1. The mixing time may be shortened or extended depending on the actual weight and proportion of the materials, as long as the materials are mixed evenly. The cationic surfactant CTAB, phenolic compounds, and aldehyde compounds are added in a molar mass ratio of 3:1:2, wherein the phenolic compound is phenol and the aldehyde compound is formaldehyde.

[0048] Add lignin and stir at a constant temperature of 40℃ for 1 hour in a magnetic stirrer to obtain a brownish-red mixed solution. Perform a first drying and a second drying to obtain lignin-doped spherical resin powder. In practice, the amount of lignin added is 2%, and the amount of lignin added is positively correlated with the stirring time. The temperature of the first drying is 120°C, and the temperature of the second drying is 80°C.

[0049] The lignin-doped spherical resin powder was heat-treated in an air environment. The temperature was increased from the ambient temperature for 2 hours to 120°C and held for 1 hour to produce a semi-molten material. The molten material is stirred, dispersed, and solidified until it no longer melts after being reheated to the same temperature to obtain lignin-doped spherical resin, wherein the same temperature is 120°C. The lignin-doped spherical resin was carbonized by heating to 600℃ and holding for 2 hours in an inert gas atmosphere. Under oxygen-free conditions, the carbonization process is mainly used to remove more light components, retain more fixed carbon, and maintain the morphology. The lignin-doped spherical resin was carbonized by etching with an active medium using a physical activation method, and then activated at the activation temperature corresponding to Examples 1-3 for 2 hours to obtain lignin-doped spherical resin-based porous carbon. The activation time depends on the amount of material and the type of furnace used for activation. Adding lignin has a certain effect on promoting activation. For example, 100 grams of material corresponds to an activation time of 1 hour, and 300 grams corresponds to an activation time of 2 hours.

[0050] In practice, as shown in Example 2, the specific activation temperature is programmed to be 950°C, while the actual temperature inside the furnace is 925°C. The activation temperature is matched to the furnace type used in production, and the furnace material is steel. The carbonization parameters for the carbonization process are 600℃ for 2 hours.

[0051] The pore volume adsorption in the table refers to the volume of gas or liquid that can be adsorbed by the pores in a unit mass of material, and the average pore size reflects the concentrated distribution trend of pore size.

[0052] The micropores of lignin-doped spherical resin-based porous carbon are pores with a width of less than 2 nm. Samples of lignin-doped spherical resin-based porous carbon prepared under different activation conditions were selected. The isotherms of the samples were tested by gas adsorption, followed by pore size analysis. The micropore analysis models selected in the implementation included the Horvath-Kawazoe (HK) and Saito-Foley (SF) methods, DR, DA (an extension of DR theory), and T-Plot method.

[0053] The density functional theory (DFT) method uses the NLDFT model, which solves the systematic error problem of traditional thermodynamic methods (such as BJH and SF) in the analysis of micropores and narrow mesopores through molecular-level simulation. For example, the SF method can have an error of up to 42.3% when uncorrected, while DFT, combined with experimental data (such as N2 or CO2 adsorption isotherms), can accurately calculate the pore size distribution in the range of 0.35-500 nm, and its reliability is verified by independent methods such as XRD and TEM.

[0054] The calculation model used in the HK method is the original HK model (the version for slit pores). The theoretical basis of the HK method is that it assumes that the adsorbate (such as liquid nitrogen) is confined within the slit-shaped micropores. Based on thermodynamic discussions, considering the adsorbent-adsorbate interaction, the relationship between filling pressure and pore size is derived.

[0055] The t-method, also known as the t-plot method, is used to calculate the total pore volume of micropores (cm³ / g) and is suitable for distinguishing between micropore filling and multilayer adsorption. By comparing the adsorption isotherm of the experiment with the adsorption layer thickness (t-curve) of the standard non-porous material, micropore filling and surface area adsorption are separated. In practice, the calculation model used for the t-method is the same as that for the T-method. The T(T-Plot) method uses the Carbon Black model for calculation. It can be understood that in specific surface area testing, the T method usually refers to the T-plot method, which is a commonly used technique for estimating micropore area, micropore volume, and external surface area.

[0056] The T-plot method compares the nitrogen adsorption capacity of a sample with that of a non-porous reference material, plotting the adsorption capacity as a function of the statistical adsorption layer thickness (T). The slope of the linear portion of the curve can be used to calculate the external surface area, while the deviation from the linear portion can be used to estimate the micropore volume and micropore area.

[0057] The technical solution of the present invention has been described above with reference to the preferred embodiments shown in the accompanying drawings. However, it will be readily understood by those skilled in the art that the scope of protection of the present invention is obviously not limited to these specific embodiments. Without departing from the principles of the present invention, those skilled in the art can make equivalent changes or substitutions to the relevant technical features, and the technical solutions after these changes or substitutions will all fall within the scope of protection of the present invention.

[0058] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for preparing a lignin-doped spherical-like resin-based porous carbon, characterized by, The method comprises the following steps: Deionized water, anhydrous ethanol, and ammonia solution are mixed for 10-30 min, and then cationic surfactant CTAB is added and stirred for mixing, and after stirring and mixing for 10-30 min, phenolic compounds and aldehyde compounds are added; Lignin is added and stirred for 1-5 h, and then the stirred mixture is poured into a pressure container, sealed, and placed in a forced air oven for primary drying reaction for 24 h, and then washed and cooled to room temperature; After cooling, the mixture is centrifuged and washed, and then placed in a forced air oven for secondary drying, and then dried to obtain lignin-doped phenolic aldehyde resin microspheres powder; The lignin-doped spherical resin powder is subjected to heat treatment in an air environment, and the temperature is raised to 110-150 ℃ from ambient temperature over 1-5 h, and then maintained for 1-5 h to obtain a molten material in a semi-melted state; The molten material is stirred, dispersed, and solidified until the resin does not melt again after being heated to the same temperature, and then lignin-doped spherical resin is obtained, wherein the same temperature is 110-150 ℃; During the stirring, dispersing, and solidifying process, the molten material is stirred by a rotating device with a stirring rod, and the molten material is uniformly mixed by stirring and dispersing, and the sphericity of the resin microspheres is changed by the shear force applied by the stirring and the adhesive force of the semi-melted material, and the spherical resin gradually changes into a spherical structure. The lignin-doped spherical resin is subjected to carbonization treatment under an inert gas atmosphere at a temperature of 400-800 ℃ for 1-5 h; The lignin-doped spherical resin after carbonization treatment is etched by an active medium by a physical activation method, and then activated for 1-10 h to obtain lignin-doped spherical resin-based porous carbon. When the physical activation method is used for activation treatment, the temperature is maintained in the range of 700-1200 ℃, and the stirring speed is in the range of 200-250 rpm.

2. The method for preparing lignin-doped spherical resin-based porous carbon according to claim 1, characterized in that, The deionized water, anhydrous ethanol, and ammonia solution are mixed at 30-60 ℃, and the volume ratio of the deionized water, anhydrous ethanol, and ammonia solution is 300-500:50-150:

1.

3. The method for preparing lignin-doped spherical resin-based porous carbon according to claim 2, characterized in that, The lignin is added in an amount of 0.1%-5%, the temperature range of the primary drying is 100-130 ℃, and the temperature range of the secondary drying is 40-80 ℃.

4. The method for preparing lignin-doped spherical resin-based porous carbon according to claim 3, characterized in that, The cationic surfactant CTAB, phenolic compounds, and aldehyde compounds are added in a molar mass ratio of 1-3:1:1-2.

5. The method for preparing lignin-doped spherical resin-based porous carbon according to claim 4, characterized in that, The phenolic compounds are selected from one or more of phenol, cardanol, m-dihydroxybenzene, and p-dihydroxybenzene, and the aldehyde compounds are selected from one or more of formaldehyde, acetaldehyde, furfural, and salicylaldehyde.

6. The method for preparing lignin-doped spherical resin-based porous carbon according to claim 5, characterized in that, The active medium is one or more of water vapor, carbon dioxide, and other oxidizing gases.

7. The method for preparing lignin-doped spherical resin-based porous carbon according to claim 6, characterized in that, The carbonization parameter range of the carbonization treatment is 400-800 ℃ for 1-5 h, and the activation parameter range of the activation treatment is 700-1200 ℃ for 1-10 h.

8. The method for preparing lignin-doped spherical resin-based porous carbon according to claim 7, characterized in that, The shape of the lignin-doped spherical resin is one or more of ellipsoidal, potato-shaped, dice-shaped, and pomegranate seed-shaped.

9. The method for preparing lignin-doped spherical resin-based porous carbon according to claim 8, characterized in that, The sphericity of the resin microspheres is reduced by applying shear force to the molten material by stirring and the adhesive force of the semi-melted material.

10. The method for preparing lignin-doped spherical resin-based porous carbon according to claim 9, characterized in that, The lignin-doped spherical resin-based porous carbon is used for preparing a battery negative electrode.

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