Method for preparing hard carbon material by regulating and controlling structure and performance of biomass-based precursor

Abstract

The invention belongs to the technical field of hard carbon materials, and particularly relates to a method for preparing a hard carbon material through biomass-based precursor structure and performance regulation and control. According to the method, biomass is taken as a main material, and specific functional groups (such as aromatic or hydrocarbon substituent groups) are introduced through nucleophilic reaction, so that the charge distribution, rigid strength and high-temperature pyrolysis path of the biomass are regulated and controlled, and the performance of the hard carbon material is optimized; and finally, biomass-based hard carbon materials with different charge densities and different rigidity strengths, which are adjustable in structure and simple in method, are prepared. Compared with the prior art, the invention develops a simple and efficient method capable of directionally regulating and controlling a biomass precursor structure, the reaction condition is mild, the raw materials are rich and environment-friendly, and the prepared hard carbon material not only has low graphitization degree and more surface defects, but also has different charge densities and rigid structures.

Description

Technical Field

[0001] This invention belongs to the field of hard carbon materials technology, specifically relating to a method for preparing hard carbon materials by regulating the structure and properties of biomass-based precursors. Background Technology

[0002] With the rapid development of energy storage technology, hard carbon materials have shown broad application prospects in fields such as lithium / sodium-ion battery anode materials due to their excellent electrochemical performance, high stability, and abundant carbon source selection. Biomass, as a renewable, low-cost, and environmentally friendly carbon precursor, has become an important source for the preparation of hard carbon materials. However, the chemical composition and structure of natural biomass (such as lignocellulosic and fibrous biomass) result in significant deficiencies in the performance (such as charge density, pore structure, and mechanical strength) of hard carbon materials obtained through their direct carbonization, making it difficult to meet the requirements of high-performance energy storage devices.

[0003] Currently, the preparation of biomass-based hard carbon materials largely relies on traditional methods such as high-temperature carbonization or physical activation. However, these methods offer limited means of structural control over the precursors themselves, making it difficult to precisely control the microstructure and electrochemical properties of the carbonization products. Furthermore, the presence of numerous polar functional groups such as hydroxyl groups in biomass easily leads to the formation of disordered structures during carbonization, affecting the material's conductivity and stability. Although existing studies have optimized biomass carbon materials through acid treatment, doping, or template methods, these methods are often complex, costly, or introduce environmental pollution problems.

[0004] Therefore, developing a simple, efficient, and directionally tunable method for the structure of biomass precursors to modify their functional group composition and carbonization behavior through chemical structure modification, thereby preparing hard carbon materials with tunable properties, has become a key problem urgently needing to be solved in this field. Nucleophilic substitution reactions, as an efficient chemical modification method, can regulate the charge distribution and pyrolysis pathway of biomass precursors by introducing specific functional groups (such as aromatic or hydrocarbon substituents), thereby optimizing the performance of the final carbon material. This technical approach can not only enhance the added value of biomass resources but also provide a new approach for the large-scale preparation of green and sustainable carbon materials. Summary of the Invention

[0005] The purpose of this invention is to overcome the shortcomings of the existing technology and provide a method for preparing hard carbon materials by regulating the structure and properties of biomass-based precursors. This method achieves targeted regulation of the properties of hard carbon materials by chemically modifying the structure of biomass precursors. Using biomass as the main material, specific functional groups (such as aromatic or hydrocarbon substituents) are introduced through nucleophilic reactions to regulate the charge distribution, rigidity, and high-temperature pyrolysis pathway of the biomass, thereby optimizing the performance of the final carbon material. Based on the above methods, a class of biomass-based hard carbon materials with tunable structures, simple methods, and varying charge densities and rigidities can be prepared.

[0006] To achieve the above objectives, the technical solution of the present invention is as follows:

[0007] This invention provides a method for preparing hard carbon materials by regulating the structure and properties of biomass-based precursors, comprising the following steps:

[0008] Step 1, Pretreatment of biomass-based materials: The biomass-based materials are deashed and dried to obtain biomass-based precursors;

[0009] Step 2, chemical structure modification of biomass-based precursor: react the biomass-based precursor with a reaction precursor containing substituent R, and filter, Soxhlet extract and dry the reaction product to obtain the biomass-based carbon precursor;

[0010] Step 3, thermal decomposition of biomass-based carbon precursor: The biomass-based carbon precursor is pre-carbonized and carbonized to obtain hard carbon material.

[0011] Furthermore, in step 1, the biomass base is selected from at least one of lignocellulosic biomass and fibrous biomass; the lignocellulosic biomass is selected from at least one of pine, oak, birch, branches, bark, and sawdust; and the fibrous biomass is selected from at least one of straw, bagasse, cotton stalks, and furfural residue.

[0012] Furthermore, in step 1, the ash removal process uses water washing, acid washing, or alkali washing to dissolve the ash; the acid used in acid washing is selected from at least one of hydrofluoric acid, hydrochloric acid, sulfuric acid, or citric acid; the alkali used in alkali washing is selected from at least one of NaOH, KOH, Na2CO3, or K2CO3 solution; the drying process is carried out at a temperature of 20-120℃ for 2-48 hours.

[0013] Furthermore, in step 2, the reaction precursor containing the substituent R is selected from compounds capable of nucleophilic substitution reactions, including R-OH, R-COOH, R-COOR', R-COX, R-CO-O-CO-R', R-CONH2, R-NH2, R-SH, R-SR', R-CN, R-SO3H, and RX. R is selected from aryl, alkenyl, or alkyl, X is selected from F, Cl, Br, or I, and R' is selected from C1-C6 alkyl, C2-C6 alkenyl, or optionally aryl groups substituted with halogens or nitro groups. R' can act as a leaving group in the nucleophilic substitution reaction.

[0014] Furthermore, the aryl group is selected from phenyl, tolyl, xylyl, benzyl, naphthyl, anthracene, pyridyl, furanyl, or thiophene; the alkyl group is selected from n-hexyl, n-pentyl, n-propyl, n-butyl, isopropyl, isobutyl, isopentyl, cyclohexyl, or cyclopentyl; and the alkenyl group is selected from vinyl, propenyl, butenyl, cyclohexenyl, or cyclopentadienyl.

[0015] Furthermore, in step 2, a reaction solvent is added during the reaction process. The reaction solvent is selected from at least one of DMSO, DMF, NMP, water, ethanol, tetrahydrofuran, dioxane, toluene, and diphenyl ether. When the reactants are low-viscosity liquids (such as small molecule alcohols) or the reaction is carried out at high temperatures (such as microwave-assisted reactions), no additional reaction solvent is required, and the biomass-based precursor can be directly mixed with it.

[0016] Furthermore, in step 2, a catalyst is added during the reaction process. The catalyst is selected from at least one of organic or inorganic acid catalysts, organic or inorganic base catalysts, and acidic or basic molecular sieves. When the reactants themselves have high reactivity, such as the substrate containing highly active hydroxyl groups (benzyl alcohol or allyl alcohol), the nucleophile has strong nucleophilicity (thiols or thiophenols); the reaction conditions can provide activation energy, such as high temperature (>150°C), microwave or ultrasonic assistance (energy input replaces the catalyst); the medium effect promotes the reaction, such as acidic or basic solvents (the solvent itself participates in proton transfer), ionic liquid environment (ionic liquid provides a proton / hydrogen bond network), or the biomass itself has inherent characteristics (natural acidic / basic groups), such as the carboxyl groups (-COOH) or phenolic hydroxyl groups (Ph-OH) in lignin, which can provide a localized acidic environment, then a catalyst is not required.

[0017] Furthermore, the organic acid catalyst is selected from at least one of phosphoric acid, superphosphoric acid, hydrochloric acid, sulfuric acid, benzenesulfonic acid, sulfonic acid, p-toluenesulfonic acid, and Lewis acid; the inorganic acid catalyst is selected from at least one of FeCl3, AlCl3, and ZnCl2; the inorganic base catalyst is selected from at least one of sodium hydroxide, potassium hydroxide, sodium hydride, and sodium carbonate; the organic base catalyst is selected from at least one of tetramethylammonium hydroxide, triethylamine, and pyridine; the acidic molecule is screened from at least one of H-ZSM-5, HY, H-Beta, and H-MOR; and the basic molecule is screened from at least one of Na-X, KL, Cs-MCM-41, and MgO / molecular sieve complex.

[0018] Further, the molar ratio of repeating unit to substituent R in the biomass-based precursor is 1:(0.01-5); the molar ratio of repeating unit to reaction precursor in the biomass-based precursor is 1:(0.01-10); and the molar ratio of repeating unit to catalyst in the biomass-based precursor is 1:(0.01-5).

[0019] Furthermore, the reaction in step 2 is a reflux reaction, with a temperature of 30-200℃ and a time of 2-24 hours. When the reactants themselves have high reactivity, such as the substrate containing a highly reactive hydroxyl group (benzyl alcohol or allyl alcohol), or the nucleophile has strong nucleophilicity (thiol or thiophenol), or when the reaction is driven by a medium effect, such as in a strong acid or basic solvent, ionic liquid, or superacid environment, the reaction does not require heating and therefore does not require reflux.

[0020] Furthermore, in step 2, the Soxhlet extraction temperature is 20-200℃ and the time is 2-24 h; the drying temperature is 20-120℃ and the time is 2-48 h.

[0021] Further, the pre-carbonization treatment conditions in step 3 are as follows: pre-purify with inert gas for 10-120 min, and under the protection of an inert atmosphere, heat up to 100℃-700℃ at a rate of 1-10℃ / min, hold at that temperature for 0.5h-12h, and then cool down; the carbonization treatment conditions are as follows: pre-purify with inert gas for 10-120 min, and under the protection of an inert atmosphere, heat up to 700℃-1500℃ at a rate of 1-5℃ / min, hold at that temperature for 1-3h, and then cool down to 50℃ at a rate of 1-5℃ / min.

[0022] Another aspect of the present invention provides a hard carbon material prepared by the method described above.

[0023] In another aspect, the present invention also provides the application of the hard carbon material as described above for the preparation of electrode materials, conductive materials, adsorbent materials, coating materials or catalyst supports.

[0024] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0025] In this invention, different proportions and types of functional groups are introduced into biomass-based precursors through chemical reactions to regulate the chemical structure of biomass-based precursor molecules, thereby forming biomass-based carbon precursors with different charge densities and rigid structures.

[0026] During high-temperature sintering, biomass-based carbon precursor molecules can undergo further chemical reactions to form larger molecular clusters. The hard carbon obtained after sintering not only has a low degree of graphitization and more surface defects, but also possesses different charge densities and rigid structures. This enables the preparation of hard carbon materials with tunable properties by modifying the chemical structure of the precursor to change its functional group composition and carbonization behavior. These hard carbon materials with different properties can contribute to fields that require different hard carbon materials.

[0027] Compared to other processes, this process develops a simple, efficient, and directionally controllable method for biomass precursor structure. The reaction conditions are mild, the raw materials are abundant and environmentally friendly, and the prepared hard carbon materials not only have a low degree of graphitization and more surface defects, but also possess different charge densities and rigid structures. Attached Figure Description

[0028] Figure 1 The figures show the constant current charge-discharge (GCD) curves of the hard carbon materials prepared in Comparative Example 1 and Examples 1-5.

[0029] Figure 2 These are the galvanostatic charge-discharge (GCD) curves of the hard carbon materials prepared in Examples 6-11.

[0030] Figure 3 These are the galvanostatic charge-discharge (GCD) curves of the hard carbon materials prepared in Examples 12-17.

[0031] Figure 4-7 These are Raman diagrams of the hard carbon materials prepared in Comparative Example 1 and Examples 1-3.

[0032] Figure 8-11 These are transmission electron microscope (TEM) images of the hard carbon materials prepared in Comparative Example 1 and Examples 1-3.

[0033] Figures 12-15 This is an atomic force microscope (AFM) surface potential distribution diagram of the hard carbon materials prepared in Comparative Example 1 and Examples 1-3. Detailed Implementation

[0034] To facilitate understanding of the present invention, a more comprehensive description will be given below. However, the present invention can be implemented in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided to provide a thorough and complete understanding of the disclosure of the present invention.

[0035] Comparative Example 1:

[0036] A method for preparing a hard carbon material without structural modification includes the following steps:

[0037] (1) Weigh 60g of furfural residue (DFR) and place it in a 1000ml beaker. Add 300ml of HCl and stir at room temperature for 12h. Then, centrifuge at 900-1200r / min for 5min to remove HCl. Place the remaining furfural residue in a polytetrafluoroethylene bottle, add 300ml of HF, and stir at room temperature for 12h. Then, centrifuge at 900-1200r / min for 5-10min to remove HF. Wash with deionized water until it is close to neutral and then place it in a forced-air drying oven at 50℃ for 12h.

[0038] (2) According to the molar ratio of repeating unit to catalyst in the biomass-based precursor being 1:5, 4g of DFR treated in step (1) and 4.84g of phosphoric acid were weighed and placed in a 250ml round-bottom flask, and 80ml of toluene solution was added. The mixture was refluxed at 130℃ for 9h. The product was filtered to obtain the product, and the unreacted phosphoric acid was washed away by Soxhlet extraction at 120℃ for 12h. The product was then dried in a vacuum drying oven at 80℃ for 12h to obtain the unmodified biomass-based carbon precursor.

[0039] (3) The biomass-based carbon precursor was placed in a ceramic boat and placed in a tube furnace for pre-carbonization treatment. Argon gas was pre-purged for 30 min. Under argon protection, the temperature was increased to 700℃ at 2℃ / min, held for 2 h, and then cooled to obtain the pre-carbonized product. The pre-carbonized product was placed in a high-temperature furnace and argon gas was pre-purged for 30 min. Under argon protection, the temperature was increased to 1400℃ at 2℃ / min, held for 2 h, and then cooled to 50℃ at 2℃ / min to obtain the high-temperature carbonized product, i.e., hard carbon material.

[0040] Example 1:

[0041] A method for preparing hard carbon materials by regulating the structure and properties of biomass-based precursors includes the following steps:

[0042] (1) Weigh 60g of furfural residue and place it in a 1000ml beaker. Add 300ml of HCl and stir at room temperature for 12h. Then, centrifuge at 900-1200r / min for 5min to remove HCl. Place the remaining furfural residue in a polytetrafluoroethylene bottle, add 300ml of HF, and stir at room temperature for 12h. Then, centrifuge at 900-1200r / min for 5-10min to remove HF. Wash with deionized water until it is close to neutral and then place it in a forced-air drying oven and dry at 50℃ for 12h.

[0043] (2) Based on the molar ratio of repeating unit to reaction precursor and catalyst in the biomass-based precursor being 1:5:0.85, and the molar ratio of repeating unit to substituent R in the biomass-based precursor being 1:1.5, taking the furfural residue used in this embodiment with a cellulose content of approximately 40% of the dry weight as an example, 4g of furfural residue treated in step (1) (containing approximately 1.6g of cellulose, corresponding to approximately 0.00988 mol of glucose units), 7.113g of naphthol, and 0.82g of phosphoric acid were weighed and placed in a 250ml round-bottom flask, and 80ml of toluene solution was added. The mixture was refluxed at 130℃ for 9h. The product was filtered, and the unreacted naphthol and phosphoric acid were washed away by Soxhlet extraction at 120℃ for 12h. The product was then dried in a vacuum drying oven at 80℃ for 12h to obtain a biomass-based carbon precursor with a naphthalene content of 1:1.5.

[0044] (3) The biomass-based carbon precursor was placed in a ceramic boat and placed in a tube furnace for pre-carbonization treatment. Argon gas was pre-purged for 30 min. Under argon protection, the temperature was increased to 700℃ at 2℃ / min, held for 2 h, and then cooled to obtain the pre-carbonized product. The pre-carbonized product was placed in a high-temperature furnace and argon gas was pre-purged for 30 min. Under argon protection, the temperature was increased to 1400℃ at 2℃ / min, held for 2 h, and then cooled to 50℃ at 2℃ / min to obtain the high-temperature carbonized product, i.e., hard carbon material.

[0045] Example 2:

[0046] A method for preparing hard carbon materials by regulating the structure and properties of biomass-based precursors includes the following steps:

[0047] (1) Same as step (1) in Example 1.

[0048] (2) Taking the following as an example, with a molar ratio of repeating unit to reaction precursor and catalyst of 1:6:0.6 in the biomass-based precursor and a molar ratio of repeating unit to substituent R of 1:1.0 in the biomass-based precursor, and with furfural residue containing approximately 40% cellulose by dry weight, 4g of furfural residue treated in step (1), 5.93g of cyclohexanol and 1.03g of TsOH were weighed and placed in a 250ml round-bottom flask. 20ml of toluene solution was added, and the mixture was refluxed at 80℃ for 12h. The product was filtered, and the unreacted cyclohexanol and TsOH were washed away by Soxhlet extraction at 120℃ for 12h. The product was then dried in a vacuum drying oven at 80℃ for 12h to obtain a biomass-based carbon precursor with a cyclohexyl content of 1:1.0.

[0049] (3) Same as step (3) in Example 1.

[0050] Example 3:

[0051] A method for preparing hard carbon materials by regulating the structure and properties of biomass-based precursors includes the following steps:

[0052] (1) Same as step (1) in Example 1.

[0053] (2) Taking the following as an example, the molar ratio of repeating unit to reaction precursor and catalyst in the biomass-based precursor is 1:6:0.6, the molar ratio of repeating unit to substituent R in the biomass-based precursor is 1:1.35, and the cellulose content of furfural residue is about 40% of the dry weight, 4g of furfural residue treated in step (1), 6.04g of n-hexanol and 1.03g of TsOH are weighed and placed in a 250ml round-bottom flask, and 20ml of toluene solution is added. The mixture is refluxed at 80℃ for 12h. The product is filtered and extracted by Soxhlet extraction at 120℃ for 12h to wash away the unreacted n-hexanol and TsOH. The product is dried in a vacuum drying oven at 80℃ for 12h to obtain a biomass-based carbon precursor with a n-hexyl content of 1:1.35.

[0054] (3) Same as step (3) in Example 1.

[0055] Example 4:

[0056] A method for preparing hard carbon materials by regulating the structure and properties of biomass-based precursors includes the following steps:

[0057] (1) Same as step (1) in Example 1.

[0058] (2) Taking the following as an example, the molar ratio of repeating unit to reaction precursor and catalyst in the biomass-based precursor is 1:3:0.6, and the molar ratio of repeating unit to substituent R in the biomass-based precursor is 1:1.645. The cellulose content of the furfural residue used is about 40% of the dry weight. Weigh 4g of furfural residue treated in step (1) (containing about 1.6g of cellulose, corresponding to about 0.00988 mol of glucose unit), 2.78g of phenol and 1.03g of p-toluenesulfonic acid (TsOH), place them in a 100ml round-bottom flask, add 10ml of toluene solution, and reflux at 80℃ for 12h. Filter to obtain the product, extract with Soxhlet at 120℃ for 12h to wash away the unreacted phenol and TsOH, and dry the product in a vacuum drying oven at 80℃ for 12h to obtain a biomass-based carbon precursor with a benzene content of 1:1.645.

[0059] (3) Same as step (3) in Example 1.

[0060] Example 5:

[0061] A method for preparing hard carbon materials by regulating the structure and properties of biomass-based precursors includes the following steps:

[0062] (1) The only difference from step (1) of Example 1 is that furfural residue is replaced with sugarcane bagasse (DSB).

[0063] (2) Taking the following example, with a molar ratio of repeating unit to reaction precursor of 1:5 and a molar ratio of repeating unit to substituent R of 1:1 in the biomass-based precursor, and sugarcane bagasse with a cellulose content of approximately 40% by dry weight, 4g of sugarcane bagasse treated in step (1) and 6.12g of benzyl mercaptan were weighed and placed in a 250ml round-bottom flask, and 100ml of diphenyl ether was added as a high-temperature solvent. Under nitrogen protection, the mixture was refluxed at 180-200℃ for 24h. After the reaction was completed, the mixture was cooled to room temperature and filtered to obtain the product. The product was extracted with n-hexane at 70℃ for 24h to thoroughly wash away the unreacted benzyl mercaptan and diphenyl ether. Finally, the product was dried in a vacuum drying oven at 120℃ for 2h to obtain the benzyl-modified biomass-based carbon precursor.

[0064] (3) Same as step (3) in Example 1.

[0065] Example 6:

[0066] A method for preparing hard carbon materials by regulating the structure and properties of biomass-based precursors includes the following steps:

[0067] (1) The only difference from step (1) of Example 1 is that furfural residue is replaced with straw.

[0068] (2) The following operations were performed according to the following: the molar ratio of repeating unit to reaction precursor and catalyst in the biomass-based precursor was 1:5:0.85, and the molar ratio of repeating unit to substituent R in the biomass-based precursor was 1:2. Taking the straw used in this example, whose cellulose content accounted for about 40% of the dry weight, 4g of straw treated in step (1) (containing about 1.6g of cellulose, corresponding to about 0.00988 mol of glucose units), 8.05g of cyclohexyl bromide and 0.336g of sodium hydroxide (NaOH) were weighed and placed in a 250ml dry round-bottom flask, and 100ml of anhydrous DMF solution was added. Under nitrogen protection, the reaction was refluxed at 80℃ for 12h. After the reaction was completed, the product was cooled to room temperature and filtered to obtain a solid product. The product was washed three times each with deionized water and anhydrous ethanol, and finally dried in a vacuum drying oven at 80℃ for 12h to obtain a cyclohexyl-modified biomass-based carbon precursor.

[0069] (3) Same as step (3) in Example 1.

[0070] Example 7:

[0071] A method for preparing hard carbon materials by regulating the structure and properties of biomass-based precursors includes the following steps:

[0072] (1) Weigh 60g of pine wood powder and place it in a 1000ml beaker. Add 500ml of 1-5% HNO3 solution and heat and stir at 50-80℃ for 5h. Then, centrifuge at 900-1200r / min for 5min to remove HNO3. Add NaOH solution to neutralize excess acid and wash with deionized water until it is close to neutral. Place it in a forced-air drying oven and dry at 120℃ for 48h.

[0073] (2) The following operations were performed according to the following: the molar ratio of repeating unit to reaction precursor and catalyst in the biomass-based precursor was 1:1:1.2, and the molar ratio of repeating unit to substituent R in the biomass-based precursor was 1:1.2. Taking the pine wood used in this example, whose cellulose content accounted for about 40% of the dry weight, 4g of pine wood treated in step (1) (containing about 1.6g of cellulose, corresponding to about 0.00988 mol of glucose units) and 1.24g of benzyl chloride were weighed and placed in a 250ml dry round-bottom flask, and 100ml of anhydrous DMF was added as a solvent. 0.28g of sodium hydride was added in batches under ice-water bath cooling and stirring. The ice bath was removed, the reaction mixture was heated to 85°C, and refluxed under nitrogen protection for 12h. After the reaction was completed, it was cooled to room temperature, and a small amount of methanol was carefully added to quench the excess NaH. The solid product was obtained by filtration, and was thoroughly washed by Soxhlet extraction with ethanol at 80°C for 12 h. Finally, the product was dried in a vacuum drying oven at 20°C for 48 h to obtain a benzyl-modified biomass-based carbon precursor.

[0074] (3) The biomass carbon material precursor is placed in a ceramic boat and placed in a tube furnace for pre-carbonization treatment. Argon gas is pre-purified for 120 min. Under argon protection, the temperature is increased to 500 ℃ at 10 ℃ / min, held for 12 h, and then cooled to obtain the pre-carbonized product. The pre-carbonized product is placed in a high-temperature furnace and argon gas is pre-purified for 120 min. Under argon protection, the temperature is increased to 1500 ℃ at 5 ℃ / min, held for 4 h, and then cooled to 50 ℃ at 5 ℃ / min to obtain the high-temperature carbonized product, i.e., the hard carbon material.

[0075] Example 8:

[0076] A method for preparing hard carbon materials by regulating the structure and properties of biomass-based precursors includes the following steps:

[0077] (1) The only difference from step (1) of Example 7 is that pine wood is replaced with sawdust.

[0078] (2) According to the molar ratio of repeating unit to reaction precursor and catalyst in the biomass-based precursor being 1:8:2, and the molar ratio of repeating unit to substituent R in the biomass-based precursor being 1:2, taking the sawdust used in this example with a cellulose content of about 40% of the dry weight as an example, 4g of sawdust treated in step (1), 12.4g of bromobenzene and 0.79g of NaOH were weighed and placed in a 250ml round-bottom flask, and 100ml of anhydrous dimethylformamide (DMF) solution was added. Under nitrogen protection, the mixture was refluxed at 100℃ for 12h. After the reaction was completed, the product was filtered and extracted with ethanol at 80℃ for 24h using a Soxhlet extractor to wash away unreacted bromobenzene, byproducts and solvent. Finally, the product was dried in a vacuum drying oven at 80℃ for 12h to obtain a phenyl-modified biomass-based carbon precursor.

[0079] (3) Same as step (3) in Example 7.

[0080] Example 9:

[0081] A method for preparing hard carbon materials by regulating the structure and properties of biomass-based precursors includes the following steps:

[0082] (1) The only difference from step (1) of Example 7 is that pine wood is replaced with birch wood.

[0083] (2) The following operations were performed according to the following: the molar ratio of repeating unit to reaction precursor and catalyst in the biomass-based precursor is 1:4:3, and the molar ratio of repeating unit to substituent R in the biomass-based precursor is 1:2. Taking the birch wood used in this example, whose cellulose content accounts for about 40% of the dry weight, 4g of birch wood treated in step (1), 5.41g of n-bromobutane and 1.19g of sodium hydroxide (NaOH) were weighed and placed in a 250ml dry round-bottom flask, and 100ml of anhydrous DMF solution was added. Under nitrogen protection, the mixture was refluxed at 90℃ for 12h. After the reaction was completed, the mixture was cooled to room temperature and filtered to obtain a solid product. The solid product was extracted with ethanol at 80℃ using a Soxhlet extractor for 12h to wash away the unreacted n-bromobutane, byproducts and solvent. Finally, the product was dried in a vacuum drying oven at 80℃ for 12h to obtain a n-butyl-modified biomass-based carbon precursor.

[0084] (3) Same as step (3) in Example 7.

[0085] Example 10:

[0086] A method for preparing hard carbon materials by regulating the structure and properties of biomass-based precursors includes the following steps:

[0087] (1) The only difference from step (1) of Example 7 is that the pine wood is replaced with sugarcane bagasse.

[0088] (2) The following operations were performed according to the following: the molar ratio of repeating unit to reaction precursor and catalyst in the biomass-based precursor was 1:10:5, and the molar ratio of repeating unit to substituent R in the biomass-based precursor was 1:3. Taking the sugarcane bagasse used in this example, whose cellulose content accounted for about 40% of the dry weight, 4g of sugarcane bagasse treated in step (1), 16.2g of 4-chloromethylpyridine hydrochloride and 1.976g of sodium hydroxide were weighed and placed in a 250ml dry round-bottom flask, and 100ml of anhydrous DMSO solution was added. Under nitrogen protection, the reaction was refluxed at 90℃ for 12h. After the reaction was completed, the mixture was cooled to room temperature and filtered to obtain a solid product. The product was extracted with ethanol at 85℃ using a Soxhlet extractor for 12h to wash away unreacted reagents and byproducts. Finally, the product was dried in a vacuum drying oven at 80℃ for 12h to obtain a pyridinemethyl-modified biomass-based carbon precursor.

[0089] (3) Same as step (3) in Example 7.

[0090] Example 11:

[0091] A method for preparing hard carbon materials by regulating the structure and properties of biomass-based precursors includes the following steps:

[0092] (1) Weigh 60g of sugarcane bagasse and place it in a 1000ml beaker. Add 300ml of sulfuric acid and stir at room temperature for 12 hours. Then, centrifuge at 900-1200 r / min for 5 minutes to remove the sulfuric acid. Wash with deionized water until it is close to neutral and then place it in a forced-air drying oven at 20℃ for 48 hours.

[0093] (2) a. Acyl chloride reaction: According to the molar ratio of repeating unit to bridging agent in the biomass-based precursor of 1:10, 4g of sugarcane bagasse treated in step (1) and 17.29g of p-chlorobenzoyl chloride were weighed and placed in a 100ml dry round-bottom flask, and 30ml of anhydrous pyridine was added as solvent and acid-binding agent. Under nitrogen protection, the reaction was refluxed at 80℃ for 6h. After the reaction was completed, the mixture was cooled, filtered, washed thoroughly with anhydrous ethanol, and dried under vacuum at 60℃ for 12h to obtain the acyl chloride-treated sugarcane bagasse intermediate.

[0094] b. Amination reaction: All the above-mentioned acyl chloride intermediates, 6.51 g of aniline, and 1 g of potassium carbonate were placed in a 100 ml round-bottom flask, and 30 ml of N-methylpyrrolidone (NMP) was added as a solvent. Under nitrogen protection, the reaction was refluxed at 180 °C for 24 h. After the reaction was completed, the mixture was cooled to room temperature, filtered to obtain the product, and extracted with ethanol at 85 °C using a Soxhlet extractor for 12 h to wash away unreacted aniline and byproducts. Finally, the product was dried in a vacuum drying oven at 80 °C for 12 h to obtain the aniline-modified biomass-based carbon precursor.

[0095] (3) The biomass-based carbon precursor was placed in a ceramic boat and placed in a tube furnace for pre-carbonization treatment. Argon gas was pre-purged for 10 min. Under argon protection, the temperature was increased to 100℃ at 1℃ / min, held for 12 h, and then cooled to obtain the pre-carbonized product. The pre-carbonized product was placed in a high-temperature furnace and argon gas was pre-purged for 30 min. Under argon protection, the temperature was increased to 700℃ at 1℃ / min, held for 5 h, and then cooled to 50℃ at 1℃ / min to obtain the high-temperature carbonized product, i.e., hard carbon material.

[0096] Example 12:

[0097] A method for preparing hard carbon materials by regulating the structure and properties of biomass-based precursors includes the following steps:

[0098] (1) Weigh 60g of straw and place it in a 1000ml beaker. Add 300ml of citric acid and stir at room temperature for 12h. Then, centrifuge at 900-1200 r / min for 5min to remove the citric acid. Add 300ml of nitric acid to the remaining straw and stir at room temperature for 12h. Then, centrifuge at 900-1200 r / min for 5-10min to remove the nitric acid. Wash with deionized water until it is close to neutral and then place it in a drying oven at 50℃ for 12h.

[0099] (2) According to the molar ratio of repeating unit to reaction precursor and catalyst in the biomass-based precursor of 1:5:0.1, 4g of straw treated in step (1), 4.018g of cyclohexene and 0.15g of benzenesulfonic acid were weighed and placed in a 250ml round-bottom flask, and 80ml of 1,4-dioxane solution was added. A Dean-Stark water separator was installed, and the mixture was refluxed at 110℃ for 12h. After the reaction was completed, the mixture was cooled to room temperature, filtered to obtain the product, and extracted with ethanol at 85℃ for 12h to wash away unreacted cyclohexene, catalyst and byproducts. Finally, the product was dried in a vacuum drying oven at 80℃ for 12h to obtain the cyclohexyl-modified biomass-based carbon precursor.

[0100] (3) The biomass-based carbon precursor was placed in a ceramic boat and placed in a tube furnace for pre-carbonization treatment. Inert gas was pre-purified for 60 min. Under inert gas protection, the temperature was increased to 700℃ at 5℃ / min, held for 0.5 h, and then cooled to obtain the pre-carbonized product. The pre-carbonized product was placed in a high-temperature furnace and argon gas was pre-purified for 120 min. Under argon gas protection, the temperature was increased to 700℃ at 1℃ / min, held for 1 h, and then cooled to 50℃ at 2℃ / min to obtain the high-temperature carbonized product, i.e., hard carbon material.

[0101] Example 13:

[0102] A method for preparing hard carbon materials by regulating the structure and properties of biomass-based precursors includes the following steps:

[0103] (1) Weigh 60g of cotton stalks and place them in a 1000ml beaker. Add 300ml of 2-5% NaOH and heat and stir at 90℃ for 2h. Then neutralize the remaining NaOH with 0.5% HCl. Centrifuge at 900-1200 r / min for 5min to remove the solution. Wash with deionized water until it is close to neutral and place it in a drying oven at 120℃ for 2h.

[0104] (2) According to the molar ratio of repeating unit to reaction precursor in the biomass-based precursor being 1:6:5, and the molar ratio of repeating unit to substituent R in the biomass-based precursor being 1:1.35, 4g of cotton stalks treated in step (1), 9.78g of 1-bromohexane, and 1.976g of sodium hydroxide were weighed and placed in a 250ml round-bottom flask. 100ml of N,N-dimethylformamide solution was added to the flask, and the mixture was refluxed at 130℃ for 15h. After the reaction was completed, the mixture was cooled to room temperature, filtered to obtain the product, and extracted with n-hexane at 70℃ using a Soxhlet extractor for 15h to thoroughly wash away unreacted 1-bromohexane and byproducts. Finally, the product was dried in a vacuum drying oven at 100℃ for 12h to obtain the n-hexyl-modified biomass-based carbon precursor.

[0105] (3) The biomass-based carbon precursor was placed in a ceramic boat and placed in a tube furnace for pre-carbonization treatment. Inert gas was passed through for 100 min. Under inert gas protection, the temperature was increased to 600℃ at 3℃ / min and held for 10 h before cooling to obtain the pre-carbonized product. The pre-carbonized product was placed in a high-temperature furnace and inert gas was passed through for 100 min. Under inert gas protection, the temperature was increased to 1300℃ at 2℃ / min and held for 3 h before cooling to 50℃ at 2℃ / min to obtain the high-temperature carbonized product, i.e., hard carbon material.

[0106] Example 14:

[0107] A method for preparing hard carbon materials by regulating the structure and properties of biomass-based precursors includes the following steps:

[0108] (1) The only difference from step (1) of Example 13 is that the cotton stalks are replaced with pine wood and NaOH is replaced with KOH.

[0109] (2) Perform the following steps according to the following: The molar ratio of repeating unit to reaction precursor in the biomass-based precursor is 1:5, and the molar ratio of repeating unit to substituent R in the biomass-based precursor is 1:1:

[0110] a. Preparation of acyl chloride: Weigh 6.6 g of benzoic acid into a 100 ml dry round-bottom flask, add 30 ml of thionyl chloride (SOCl2) and 2 drops of anhydrous DMF as catalyst, and reflux at 60 °C for 2 h (the tail gas is absorbed with alkaline solution). After the reaction is complete, remove excess thionyl chloride completely by rotary evaporation to obtain crude acyl chloride, which can be used in the next step without further purification.

[0111] b. Esterification reaction: Weigh 4g of pine wood treated in step (1) and place it in a 250ml round-bottom flask. Add 100ml of anhydrous pyridine (which acts as both a solvent and an acid-binding agent). Dissolve the acyl chloride prepared in the previous step in 20ml of anhydrous dichloromethane and slowly add it dropwise to the mixture of pine wood and pyridine under ice-water bath cooling and stirring. After the addition is complete, remove the ice bath and reflux the mixture at 80℃ for 12h under nitrogen protection. After the reaction is complete, cool to room temperature, filter to obtain the product, and extract with ethanol at 80℃ using a Soxhlet extractor for 12h to wash away unreacted reagents and byproducts. Finally, dry the product in a vacuum drying oven at 80℃ for 12h to obtain an alkyl / aryl ester modified biomass-based carbon precursor.

[0112] (3) Same as step (3) in Example 13.

[0113] Example 15:

[0114] A method for preparing hard carbon materials by regulating the structure and properties of biomass-based precursors includes the following steps:

[0115] (1) The only difference from step (1) of Example 13 is that the cotton stalks are replaced with oak wood and NaOH is replaced with Na2CO3.

[0116] (2) According to the molar ratio of repeating unit to reaction precursor in the biomass-based precursor being 1:5 and the molar ratio of repeating unit to substituent R in the biomass-based precursor being 1:2, 4g of oak wood treated in step (1) and 4.446g of acryloyl chloride were weighed and placed in a 250ml dry round-bottom flask, and 50ml of anhydrous pyridine (as solvent and acid-binding agent) was added. Under ice-water bath cooling and nitrogen protection, the reaction was stirred at 0-5℃ for 2 hours, and then the ice bath was removed, and the reaction was continued at room temperature for 12 hours. After the reaction was completed, the product was filtered to obtain the product, and Soxhlet extracted with ethanol at 80℃ for 12h to thoroughly wash away unreacted monomers, byproduct pyridine hydrochloride and possible polymers. Finally, the product was dried in a vacuum drying oven at 80℃ for 12h to obtain the vinyl-modified biomass-based carbon precursor.

[0117] (3) Same as step (3) in Example 13.

[0118] Example 16

[0119] A method for preparing hard carbon materials by regulating the structure and properties of biomass-based precursors includes the following steps:

[0120] (1) Weigh 60g of bark and place it in a 1000ml beaker. Add 300ml of 2-5% NaOH solution. Heat and stir at 90℃ for 2h. Neutralize the remaining NaOH with 0.5% HCl. Centrifuge at 10000 r / min for 5min to remove the solution. Wash with deionized water until the washing liquid is neutral. Place in a forced-air drying oven and dry at 80℃ for 12h to obtain pretreated bark.

[0121] (2) According to the molar ratio of repeating unit to reaction precursor and catalyst in the biomass-based precursor being 1:10:1, and the molar ratio of repeating unit to substituent R in the biomass-based precursor being 1:2, weigh 4g of bark treated in step (1), 9.08g of toluene and 1.6g of anhydrous ferric chloride, place them in a 250ml dry round-bottom flask, and add 80ml of 1,2-dichloroethane as solvent. Install a Dean-Stark water separator, and reflux the reaction at 85℃ for 24h under nitrogen protection. After the reaction is completed, cool to room temperature, slowly pour the reaction mixture into 200ml of ice water to quench, and filter to obtain a solid product. Wash once with hydrochloric acid solution to remove iron salt, then wash with deionized water until neutral, and finally dry the product in a vacuum drying oven at 100℃ for 24h to obtain a benzyl-modified biomass-based carbon precursor.

[0122] (3) Same as step (3) in Example 13.

[0123] Example 17

[0124] A method for preparing hard carbon materials by regulating the structure and properties of biomass-based precursors includes the following steps:

[0125] (1) Same as step (1) in Example 16.

[0126] (2) According to the molar ratio of repeating unit to reaction precursor in the biomass-based precursor being 1:8 and the molar ratio of repeating unit to substituent R in the biomass-based precursor being 1:2.5, 4g of pine wood treated in step (1) and 9.95g of benzyl chloride were weighed and placed in a 250ml dry round-bottom flask. The system was placed in an oil bath and slowly heated to 140℃ under nitrogen protection, and the reaction was magnetically stirred at this temperature for 12h. After the reaction was completed, it was cooled to room temperature. Most of the unreacted benzyl chloride was poured off, and the obtained solid product was extracted with anhydrous ethanol at 80℃ using a Soxhlet extractor for 24h to thoroughly wash away the residual benzyl chloride and byproducts. Finally, the product was dried in a vacuum drying oven at 80℃ for 12h to obtain the benzyl-modified biomass-based carbon precursor.

[0127] (3) Same as step (3) in Example 13.

[0128] In summary, the method for preparing hard carbon materials in this invention utilizes the active sites in biomass molecules to induce nucleophilic substitution reactions with aromatic compounds or alkanes and alkenes. This type of reaction allows for the selection of catalysts, solvents, heating, and reflux depending on the substrate. By controlling the proportions and structure of the reactants, different types and numbers of functional groups are introduced into the biomass framework, achieving precise control over the precursor molecular structure. Furthermore, it enables effective control over the precursor charge density, molecular stacking mode (steric hindrance effect), and thermal stability. This structural control strategy not only increases the free volume and framework rigidity of the precursor through steric hindrance, suppressing excessive graphitization during carbonization, but also enhances the charge density of the carbon framework by introducing electron-rich groups. After high-temperature carbonization, the resulting hard carbon material exhibits lower graphitization, more surface defects, increased interlayer spacing, abundant closed-pore distribution, a highly disordered turbulent layer structure, and higher charge density.

[0129] To verify the advantages of structural modification in improving electrochemical performance, a half-cell testing system was used to evaluate the electrochemical performance of different hard carbon material structures in CR2025 coin cells (with a sodium sheet as the counter electrode). The galvanostatic charge-discharge (GCD) curves are shown in the figure. Figure 1-3 This demonstrates that the structurally modified hard carbon material exhibits excellent electrochemical performance as a sodium electrode anode material. The unmodified raw hard carbon material (Comparative Example 1) only had a reversible capacity of 185.0 mAh / g and an initial coulombic efficiency of 41.19%, while the structurally modified hard carbon samples (Examples 1-17) showed reversible capacity and initial coulombic efficiency increases to 313 mAh / g and 61.37%, 263 mAh / g and 48.37%, and 236 mAh / g and 44.01%, respectively. %, 297mAh / g and 78.67%, 259mAh / g and 55.27%, 222mAh / g and 42.04%, 230mAh / g and 42.17%, 269mAh / g and 55.78%, 275mAh / g and 57.3%, 273mAh / g and 52.33%, 282mAh / g and 54.82%, 294mAh / g and 50.65%, 307mAh / g and 54.39%, 255mAh / g and 58.82%, 260mAh / g and 49.31%, 270mAh / g and 55.87%, 266mAh / g and 56.52%.

[0130] Meanwhile, Raman, Tem, and AFM tests were performed on the hard carbon materials of Examples 1-3, and compared with the original hard carbon material without structural modification in Comparative Example 1. The correlation between this series of tests and various properties of the hard carbon materials is briefly described below: Figure 4-7 Raman spectroscopy revealed that the ID / IG ratio of the structurally modified hard carbon materials was higher than that of the unmodified control sample, indicating that the structurally modified hard carbon materials had a lower degree of graphitization and more surface defects; while TEM spectroscopy showed that... Figure 8-11 It can be clearly seen that the modified hard carbon material is conducive to the formation of short-range carbon layers and abundant pores; the surface potential measured by AFM ( Figure 12-15 This indicates that the modified hard carbon material has a higher charge density. These tests demonstrate how the introduction of functional groups alters the various properties of hard carbon materials.

[0131] The above description is only for better explaining the embodiments of the present invention and is not intended to limit them. Any modifications or equivalent substitutions that do not depart from the spirit and scope of the present invention shall fall within the scope of the present invention.

Claims

1. A method for the production of hard carbon materials from biomass-based precursor structures and performance tuning, characterized by, The method comprises the following steps: Step 1, pretreatment of biomass base: the biomass base is subjected to deashing and drying treatment to obtain a biomass base precursor; Step 2, chemical structure modification of the biomass base precursor: the biomass base precursor and a reaction precursor containing a substituent group R are reacted, and the reaction product is filtered, Soxhlet extracted and dried to obtain a biomass base carbon precursor; Step 3, thermal decomposition of the biomass base carbon precursor: the biomass base carbon precursor is subjected to pre-carbonization and carbonization treatment to obtain a hard carbon material.

2. The method for preparing hard carbon material by controlling structure and performance of biomass-based precursor according to claim 1, characterized in that, In the step 1, the biomass base is at least one selected from wood biomass and fiber biomass; the wood biomass is at least one selected from pine, oak, birch, branches, bark and sawdust; the fiber biomass is at least one selected from straw, sugarcane residue, cotton stalk and furfural residue; the deashing treatment uses water washing, acid washing or alkali washing to dissolve ash; the acid used in the acid washing is at least one selected from hydrofluoric acid, hydrochloric acid, sulfuric acid, nitric acid and citric acid; the alkali used in the alkali washing is at least one selected from NaOH, KOH, Na2CO3 and K2CO3 solution; the drying treatment is performed at a temperature of 20-120°C for 2-48h.

3. The method for preparing hard carbon materials by regulating the structure and properties of biomass-based precursors according to claim 1, characterized in that, In the step 2, the reaction precursor containing the substituent group R is a compound capable of undergoing nucleophilic substitution reaction, including R-OH, R-COOH, R-COOR', R-COX, R-CO-O-CO-R', R-CONH2, R-NH2, R-SH, R-SR', R-CN, R-SO3H and R-X, R is selected from aryl, alkenyl or alkyl, X is selected from F, Cl, Br or I, and R' is selected from C1-C6 alkyl, C2-C6 alkenyl or aryl optionally substituted with halogen or nitro, and R' can act as a leaving group in the nucleophilic substitution reaction.

4. The method for preparing hard carbon materials by regulating the structure and properties of biomass-based precursors according to claim 1, characterized in that, In the step 2, a reaction solvent is further added during the reaction, and the reaction solvent is at least one selected from DMSO, DMF, NMP, water, ethanol, tetrahydrofuran, dioxane, toluene and diphenyl ether.

5. The method for preparing hard carbon materials by regulating the structure and properties of biomass-based precursors according to claim 1, characterized in that, In the step 2, a catalyst is further added during the reaction, and the catalyst is at least one selected from organic or inorganic acid catalysts, organic or inorganic base catalysts, acidic or basic molecular sieves; the organic acid catalyst is at least one selected from phosphoric acid, superphosphoric acid, hydrochloric acid, sulfuric acid, benzene sulfonic acid, sulfonic acid, p-toluenesulfonic acid and Lewis acid; the inorganic acid catalyst is at least one selected from FeCl3, AlCl3 and ZnCl2; the inorganic base catalyst is at least one selected from NaOH, KOH, NaH and Na2CO3; the organic base catalyst is at least one selected from tetramethylammonium hydroxide, triethylamine and pyridine; the acidic molecular sieve is at least one selected from H-ZSM-5, H-Y, H-Beta and H-MOR; and the basic molecular sieve is at least one selected from Na-X, K-L, Cs-MCM-41 and MgO / molecular sieve composite.

6. The method for preparing hard carbon materials by regulating the structure and properties of biomass-based precursors according to claim 5, characterized in that, The molar ratio of the repeating unit to the substituent R in the biomass-based precursor is 1:(0.01-5); the molar ratio of the repeating unit to the reaction precursor in the biomass-based precursor is 1:(0.01-10), and the molar ratio of the repeating unit to the catalyst in the biomass-based precursor is 1:(0.01-5).

7. The method for preparing hard carbon materials by regulating the structure and properties of biomass-based precursors according to claim 6, characterized in that, The reaction in step 2 is a condensation reflux reaction, the temperature of the condensation reflux reaction is 30-200℃, and the time is 2-24h; the temperature of the Soxhlet extraction is 20-200℃, and the time is 2-24h; the temperature of the drying is 20-120℃, and the time is 2-48h.

8. The method for preparing hard carbon materials by regulating the structure and properties of biomass-based precursors according to claim 1, characterized in that, The pre-carbonization treatment in step 3 is performed under the following conditions: pre-inert gas for 10-120min, heating to 100℃-700℃ at a rate of 1-10℃ / min under the protection of inert atmosphere, holding for 0.5h-12h, and then cooling; the carbonization treatment is performed under the following conditions: pre-inert gas for 30-120min, heating to 700℃-1500℃ at a rate of 1-5℃ / min under the protection of inert atmosphere, holding for 1-3h, and then cooling to 50℃ at a rate of 1-5℃ / min.

9. The hard carbon material prepared by the method of any one of claims 1-8.

10. Use of the hard carbon material according to claim 9, characterized in that The hard carbon material is used for preparing electrode materials, conductive materials, adsorption materials, coating materials, or catalyst carriers. The hard carbon material is used for preparing electrode materials, conductive materials, adsorption materials, coating materials, or catalyst carriers.

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