Preparation method of low-ash bamboo-based hard charcoal based on mechanochemical modification
By integrating grinding and acid-base deashing processes through mechanochemical modification, the problems of cumbersome steps and incomplete deashing in traditional processes are solved, achieving efficient preparation of low-ash bamboo-based hard carbon and improving its application performance in sodium-ion batteries.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- NINGBO DAHONGYING UNIV
- Filing Date
- 2026-03-12
- Publication Date
- 2026-05-15
AI Technical Summary
The existing production process of bamboo-based hard carbon for sodium-ion batteries is cumbersome, time-consuming, and has low ash removal efficiency. It is difficult to achieve microstructure control, resulting in incomplete ash removal, which fails to meet high performance requirements and poses safety hazards.
The mechanical chemical modification method integrates grinding and acid-base deashing processes, and achieves "grinding and deashing at the same time" through two-stage ball milling. It uses mechanical force and chemical reaction to completely remove ash, and optimizes the structure through medium-temperature carbonization.
The production process is simplified, costs are significantly reduced, ash is completely removed, the microstructure properties of bamboo-based hard charcoal are improved, and its energy storage performance in sodium-ion batteries is enhanced.
Smart Images
Figure CN122035831A_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the technical field of bamboo-based hard carbon preparation for sodium-ion batteries, specifically a method for preparing low-ash bamboo-based hard carbon based on mechanochemical modification. Background Technology
[0002] Bamboo-based hard carbon is a core material for the anode of sodium-ion batteries. Its ash content and microstructure directly determine the energy storage performance of sodium-ion batteries. The mainstream production process of bamboo-based hard carbon for sodium-ion batteries follows the requirements of the group standard "Process Specification for Bamboo-based Biomass Hard Carbon Anode Material for Sodium-ion Batteries". It requires the sequential completion of seven major steps: removing external ash, removing volatile matter, grinding, acid washing and purification, adjusting pore size, carbonization, inspection and packaging. Among them, grinding and acid washing and purification are independent processes, and the "grind first and then wash" method is adopted. The bamboo charcoal precursor is first mechanically crushed, and then purified and deashed by acid immersion. This process only requires that the ash content after pre-carbonization is <5%, and the deashing requirements are relatively low.
[0003] This traditional process has significant shortcomings: First, it involves cumbersome steps and a long production cycle, with grinding and deashing being performed separately, increasing the operating costs of industrial production. Second, the deashing efficiency is limited; the acid solution can only react with the ash on the surface of the bamboo charcoal particles and cannot fully penetrate into the particles, failing to achieve sufficient contact and reaction with the minerals encapsulated inside, resulting in incomplete ash removal. This makes it difficult to meet the high-performance requirements of sodium-ion batteries for low-ash bamboo-based hard carbon. Adding hydrofluoric acid (HF) increases the risk factor and aggravates equipment corrosion. Third, it cannot achieve effective structural control. The crushing and deashing processes in the traditional process are independent of each other, only achieving a reduction in material particle size and basic ash removal. It is difficult to perform targeted modification of the microstructure of bamboo charcoal, such as the carbon interlayer spacing and surface functional groups, thus restricting the performance improvement of bamboo-based hard carbon in the field of sodium-ion batteries. Summary of the Invention
[0004] The purpose of this invention is to provide a method for preparing low-ash bamboo-based hard charcoal based on mechanochemical modification, so as to solve the problems mentioned in the background art.
[0005] To achieve the above objectives, the present invention provides the following technical solution: a method for preparing low-ash bamboo-based hard charcoal based on mechanochemical modification, comprising the following steps:
[0006] (1) Bamboo raw material pretreatment: After washing the bamboo, it is pre-carbonized at 600℃ to remove volatiles and obtain bamboo charcoal precursor. The bamboo charcoal precursor is then coarsely crushed to a particle size of less than 5mm.
[0007] (2) Primary acid mechanical chemical treatment: The bamboo charcoal precursor obtained in step (1) is mixed with hydrochloric acid solution and then put into a ball mill for ball milling. The ball-to-material ratio is 15:1, the mass concentration of hydrochloric acid solution is 15%, the ball mill filling rate is 40%, the rotation speed is 75% of the critical speed, and the ball milling time is 1 to 2 hours. After ball milling, the product is filtered and washed with water until pH < 3.
[0008] (3) Secondary alkaline mechanical chemical treatment: The product washed in step (2) is mixed with sodium hydroxide alkaline solution and then put into a ball mill for secondary ball milling. The ball-to-material ratio is 15:1, the ball mill filling rate is 40%, the speed is 75% of the critical speed, and the ball milling time is 1 to 2 hours. The amount of sodium hydroxide added is 5% of the mass of the bamboo charcoal precursor added. After ball milling, the product is washed with water to remove ash. The pH of the filtrate at the end of the water washing is controlled to be <11. Then, vacuum drying is used to prevent sodium hydroxide from deteriorating. The residual sodium hydroxide is used for subsequent reactions.
[0009] (4) Surface treatment: The product after vacuum drying in step (3) is carbonized at 800℃ in a medium temperature. The residual sodium hydroxide is used to achieve in-situ pore formation, and the residual sodium hydroxide reacts further with the SiO2 that has not been removed from the bamboo charcoal precursor to generate soluble salt.
[0010] (5) High-temperature carbonization: The product after medium-temperature carbonization is subjected to high-temperature carbonization at 1300℃ to obtain low-ash bamboo-based hard carbon.
[0011] As a further preferred embodiment of this technical solution, the hydrochloric acid solution in step (2) can be replaced with a nitric acid solution.
[0012] As a further preferred embodiment of this technical solution: the sodium hydroxide solution in step (3) can be replaced with potassium hydroxide solution.
[0013] As a further preferred embodiment of this technical solution: the two-stage mechanochemical treatment consisting of the primary acidic mechanochemical treatment and the secondary alkaline mechanochemical treatment is a wet ball milling process, which simultaneously achieves the fine granulation, deashing and structural pre-modification of the bamboo charcoal precursor.
[0014] As a further preferred embodiment of this technical solution: in the first-stage acidic mechanochemical treatment, hydrochloric acid reacts with the CaO and K2O alkaline mineral ash in the bamboo charcoal precursor to generate soluble salts; in the second-stage alkaline mechanochemical treatment, sodium hydroxide reacts with the SiO2 acidic mineral ash in the bamboo charcoal precursor to generate soluble salts; the soluble salts are removed by filtration and water washing; in the surface treatment stage of step (4), the remaining sodium hydroxide is used to further react with the unremoved SiO2 in the bamboo charcoal precursor to remove ash, and in-situ pore formation is achieved simultaneously.
[0015] As a further preferred embodiment of this technical solution: the average ash content of the obtained low-ash bamboo-based hard charcoal is ≤0.98%, and the carbon interlayer spacing is increased, the surface oxygen-containing functional groups are increased, and the carbon defects are increased.
[0016] Compared with the prior art, the beneficial effects of the present invention are:
[0017] 1. In this invention, the traditionally independent grinding and acid-base deashing processes are integrated into one, and "grinding and deashing at the same time" is achieved through two-stage mechanochemical treatment. This eliminates the need for separate acid washing and alkali washing soaking steps, simplifies the production process, significantly shortens the production cycle, and reduces the operating costs and equipment investment for industrial production.
[0018] 2. In this invention, the mechanical pressure generated during ball milling forces the acid and alkali solutions to fully penetrate into the internal gaps of the bamboo charcoal precursor particles, allowing the acid and alkali to achieve full contact and reaction with the mineral ash such as CaO, K2O, and SiO2 encapsulated inside at the microscopic scale. This results in more thorough deashing, and the average ash content of the obtained bamboo-based hard charcoal is ≤0.98%. This value is far lower than the requirement of <5% ash content for pre-carbonization intermediate products in the group standard, and it has significant advantages even compared with the final product of traditional processes. It is more in line with the performance requirements of sodium-ion batteries for low-ash bamboo-based hard charcoal. At the same time, the combined use of water washing and filtration achieves efficient removal of soluble salts, further reducing ash residue.
[0019] 3. In this invention, during the mechanochemical treatment process, the structure of the bamboo charcoal precursor is pre-modified while achieving deep deashing. This results in bamboo-based hard charcoal exhibiting microstructural characteristics such as increased carbon interlayer spacing, increased surface oxygen-containing functional groups, and increased carbon structural defects. At the same time, the in-situ pore-forming during the medium-temperature carbonization stage further optimizes the pore structure and can also further react with SiO2 for deashing, significantly improving the energy storage performance of bamboo-based hard charcoal in the field of sodium-ion batteries.
[0020] 4. In this invention, the reaction process between acid and alkali and mineral ash will etch the minerals to form in-situ pores, making the bamboo charcoal particles easier to be ball-milled and improving the ball milling efficiency, allowing more internal ash to be exposed and etched away; at the same time, the mechanochemical action increases the oxygen-containing functional groups on the surface of bamboo charcoal, improves the wettability of the material, promotes further penetration of acid and alkali solutions, and forms a virtuous cycle of particle size reduction and ash removal, continuously improving the deashing and structural modification effects. Attached Figure Description
[0021] Figure 1 This is a process flow diagram of a method for preparing low-ash bamboo-based hard charcoal based on mechanochemical modification according to the present invention.
[0022] Figure 2 This is a flow chart of the mainstream production process for bamboo-based hard carbon used in existing sodium-ion batteries.
[0023] Figure 3 This table compares the ash content detection results of the process and the control group for the preparation method of low-ash bamboo-based hard charcoal based on mechanochemical modification according to the present invention. Detailed Implementation
[0024] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.
[0025] Example 1
[0026] Please see Figure 1 - Figure 2 As shown, the ash content detection results are as follows: Figure 3 This invention provides a technical solution: a method for preparing low-ash bamboo-based hard charcoal based on mechanochemical modification, comprising the following steps:
[0027] (1) Bamboo raw material pretreatment: After washing the bamboo to remove surface mud and impurities, it is pre-carbonized at 600℃ to remove volatiles and obtain bamboo charcoal precursor. Then, the bamboo charcoal precursor is coarsely crushed to a particle size of less than 5mm using coarse crushing equipment to provide a suitable raw material particle size for subsequent mechanochemical treatment.
[0028] (2) Primary acid mechanical chemical treatment: The bamboo charcoal precursor obtained in step (1) is mixed with a hydrochloric acid solution with a mass concentration of 15% and then placed in a ball mill for wet ball milling. The ball-to-material ratio of the ball mill is 15:1, the filling rate is 40%, the rotation speed is 75% of the critical speed, and the ball milling time is 1 to 2 hours. During the ball milling process, the mechanical impact destroys the dense structure of the bamboo charcoal precursor, allowing the hydrochloric acid solution to fully penetrate. The hydrochloric acid reacts chemically with the CaO and K2O mineral ash in the bamboo charcoal precursor to generate soluble salts, achieving preliminary deashing and preliminary control of the carbon structure. After the ball milling is completed, the product is filtered and repeatedly washed with deionized water until the pH of the filtrate is <3 to remove most of the soluble salts and residual acid in the system.
[0029] Hydrochloric acid solution can be replaced with nitric acid solution, as nitric acid and hydrochloric acid have the same reaction properties.
[0030] (3) Secondary alkaline mechanochemical treatment: The product washed in step (2) is mixed with sodium hydroxide alkaline solution and then put into a ball mill for secondary wet ball milling. The ball-to-material ratio of the ball mill is 15:1, the filling rate is 40%, the rotation speed is 75% of the critical speed, and the ball milling time is 1 to 2 hours. The amount of sodium hydroxide added is 5% of the mass of the bamboo charcoal precursor added in this step. In this step, sodium hydroxide neutralizes the acid solution remaining in the system in step (2) to avoid the residual acid affecting the subsequent process. On the other hand, it reacts with the SiO2 acidic mineral ash that is difficult to remove in the bamboo charcoal precursor to generate soluble salt, thereby achieving deep deashing of the bamboo charcoal precursor. At the same time, the carbon structure of the bamboo charcoal precursor is further modified through the synergistic effect of mechanochemical treatment, thereby achieving the effect of expanding the carbon interlayer spacing and increasing the surface oxygen-containing functional groups. After ball milling, the product is washed with water to remove ash. The pH of the final filtrate is controlled to be <11. Then, vacuum drying is used to prevent the sodium hydroxide from deteriorating. The residual sodium hydroxide is used for subsequent reactions.
[0031] Sodium hydroxide solution can be replaced with potassium hydroxide solution;
[0032] (4) Surface treatment: The product after vacuum drying in step (3) is transferred to a carbonization furnace and carbonized at 800°C. The small amount of sodium hydroxide remaining in the system is used to etch the bamboo charcoal in situ to achieve the effect of in situ pore formation, optimize the pore structure of bamboo charcoal, and increase the specific surface area of the material. At the same time, the residual sodium hydroxide reacts with the incompletely removed SiO2 in the bamboo charcoal precursor to generate soluble salts, thereby achieving deep deashing.
[0033] (5) High-temperature carbonization: The product after medium-temperature carbonization is washed with deionized water to remove the soluble salts generated in the reaction. Then, it is subjected to high-temperature carbonization at 1300℃ to complete the carbon structure shaping of bamboo charcoal and finally obtain low-ash bamboo-based hard charcoal.
[0034] In this embodiment, specifically: characterization analysis shows that, compared with products from traditional processes, the bamboo powder precursor II after mechanochemical treatment exhibits a significantly increased carbon interlayer spacing, a greater number of oxygen-containing functional groups on the surface, and a significant increase in carbon defects; CaO, K2O, and SiO2 mineral ash are efficiently removed through filtration and washing, leaving no obvious residue. The ash content of the bamboo-based hard charcoal prepared in this embodiment was tested, and the result was 1.07%.
[0035] Example 2
[0036] Please see Figure 1 - Figure 2 As shown, the ash content detection results are as follows: Figure 3 This invention provides a technical solution: a method for preparing low-ash bamboo-based hard charcoal based on mechanochemical modification, comprising the following steps:
[0037] (1) Bamboo raw material pretreatment: The operation is exactly the same as step (1) in Example 1;
[0038] (2) Primary acid mechanical chemical treatment: Replace the hydrochloric acid solution with a nitric acid solution of the same mass concentration of 15%, and keep the other ball milling parameters and filtration and washing operations exactly the same as step (2) of Example 1;
[0039] (3) Secondary alkaline mechanochemical treatment: Replace sodium hydroxide alkaline solution with potassium hydroxide alkaline solution of equal amount, and the remaining ball milling parameters are exactly the same as step (3) of Example 1;
[0040] (4) Surface treatment: The medium-temperature carbonization, in-situ pore making and deep deashing operations are exactly the same as those in step (4) of Example 1;
[0041] (5) High-temperature carbonization: The operation is exactly the same as step (5) in Example 1.
[0042] In this embodiment, specifically: characterization analysis shows that the carbon interlayer spacing, the number of oxygen-containing functional groups on the surface, and the pore structure of the bamboo powder precursor II after mechanochemical treatment all achieve excellent modification effects. The removal rate of CaO, K2O, and SiO2 mineral ash is further improved. The ash content of the bamboo-based hard charcoal prepared in this embodiment is tested and the result is 0.88%. The comprehensive physicochemical properties are better than those of the product in Example 1.
[0043] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.
Claims
1. A method for preparing low-ash bamboo-based hard charcoal based on mechanochemical modification, characterized in that, Includes the following steps: (1) Bamboo raw material pretreatment: After washing the bamboo, it is pre-carbonized at 600℃ to remove volatiles and obtain bamboo charcoal precursor. The bamboo charcoal precursor is then coarsely crushed to a particle size of less than 5mm. (2) Primary acid mechanical chemical treatment: The bamboo charcoal precursor obtained in step (1) is mixed with hydrochloric acid solution and then put into a ball mill for ball milling. The ball-to-material ratio is 15:1, the mass concentration of hydrochloric acid solution is 15%, the ball mill filling rate is 40%, the rotation speed is 75% of the critical speed, and the ball milling time is 1 to 2 hours. After ball milling, the product is filtered and washed with water until pH < 3. (3) Secondary alkaline mechanical chemical treatment: The product washed in step (2) is mixed with sodium hydroxide alkaline solution and then put into a ball mill for secondary ball milling. The ball-to-material ratio is 15:1, the ball mill filling rate is 40%, the speed is 75% of the critical speed, and the ball milling time is 1 to 2 hours. The amount of sodium hydroxide added is 5% of the mass of the bamboo charcoal precursor added. After ball milling, the product is washed with water to remove ash. The pH of the filtrate at the end of the water washing is controlled to be <11. Then, vacuum drying is used to prevent sodium hydroxide from deteriorating. The residual sodium hydroxide is used for subsequent reactions. (4) Surface treatment: The product after vacuum drying in step (3) is carbonized at 800℃ in a medium temperature. The residual sodium hydroxide is used to achieve in-situ pore formation, and the residual sodium hydroxide reacts further with the SiO2 that has not been removed from the bamboo charcoal precursor to generate soluble salt. (5) High-temperature carbonization: The product after medium-temperature carbonization is subjected to high-temperature carbonization at 1300℃ to obtain low-ash bamboo-based hard carbon.
2. The method for preparing low-ash bamboo-based hard charcoal based on mechanochemical modification according to claim 1, characterized in that, The hydrochloric acid solution mentioned in step (2) can be replaced with nitric acid solution.
3. The method for preparing low-ash bamboo-based hard charcoal based on mechanochemical modification according to claim 1, characterized in that, The sodium hydroxide solution mentioned in step (3) can be replaced with potassium hydroxide solution.
4. A method for preparing low-ash bamboo-based hard charcoal based on mechanochemical modification according to any one of claims 1-3, characterized in that, The two-stage mechanochemical treatment consisting of the primary acidic mechanochemical treatment and the secondary alkaline mechanochemical treatment is a wet ball milling process, which simultaneously achieves the fine granulation, deashing, and structural pre-modification of the bamboo charcoal precursor.
5. The method for preparing low-ash bamboo-based hard charcoal based on mechanochemical modification according to claim 1, characterized in that, In the first-stage acidic mechanochemical treatment, hydrochloric acid reacts with the CaO and K2O alkaline mineral ash in the bamboo charcoal precursor to generate soluble salts. In the second-stage alkaline mechanochemical treatment, sodium hydroxide reacts with the SiO2 acidic mineral ash in the bamboo charcoal precursor to generate soluble salts. The soluble salts are removed by filtration and washing with water. In the surface treatment stage of step (4), the remaining sodium hydroxide is used to further react with the remaining SiO2 in the bamboo charcoal precursor to remove ash, and in-situ pore formation is achieved simultaneously.
6. The method for preparing low-ash bamboo-based hard charcoal based on mechanochemical modification according to claim 1, characterized in that, The low-ash bamboo-based hard charcoal obtained has an average ash content of ≤0.98%, and the carbon interlayer spacing is increased, the surface oxygen-containing functional groups are increased, and the carbon defects are increased.