A hard carbon negative material based on sauce-flavor liquor lees and a preparation method and application thereof
Patent Information
- Application Number
- CN202611332182.1
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2026-08-31
- Publication Date
- 2026-11-03
AI Technical Summary
Existing hard carbon materials based on the lees of Maotai-flavor liquor have achieved a coulombic efficiency of less than 60% for the first time in sodium-ion batteries, and traditional processes are difficult to achieve synergistic optimization of capacity and initial efficiency, resulting in poor process reproducibility.
A dual-stage low-temperature carbonization coupling function is adopted to decouple the dual-stage high-temperature carbonization process. By matching the characteristics of pyrolysis of distiller's grains, the carbon structure is precisely controlled, including the first low-temperature carbonization and the second low-temperature carbonization. The first high-temperature carbonization and the second high-temperature carbonization are combined to construct graphite-like microcrystals adapted for sodium ion storage and repair surface activity defects.
This study achieves a simultaneous increase in high reversible sodium storage capacity and high initial coulombic efficiency of hard carbon materials. The materials exhibit good structural stability, reduce manufacturing costs, and are suitable for large-scale application in sodium-ion batteries.
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Abstract
Description
Technical Field
[0001] This invention belongs to the field of electrochemical energy storage materials technology, specifically relating to hard carbon materials for sodium-ion battery anodes, and particularly to a hard carbon anode material based on the lees of Maotai-flavor liquor, its preparation method, and its application. Background Technology
[0002] Sodium-ion batteries, due to their abundant resources, low cost, and good safety performance, have shown promising application prospects in large-scale energy storage and low-speed electric vehicles. The anode material is a key component determining the performance of sodium-ion batteries. Hard carbon materials, with their disordered carbon layer structure suitable for sodium ion insertion / extraction, abundant sodium storage sites, and good cycle stability, are considered the most commercially promising anode material for sodium-ion batteries.
[0003] Utilizing biomass waste to prepare hard carbon materials is an effective way to achieve high-value utilization of resources. As a major byproduct of the brewing industry, the lees of Maotai-flavor liquor are produced in huge quantities annually. They contain abundant organic components such as cellulose, hemicellulose, lignin, and crude protein, and have a high carbon content, making them an ideal precursor for hard carbon materials. However, hard carbon materials obtained by directly carbonizing Maotai-flavor liquor lees generally suffer from high microstructural disorder, large specific surface area, and excessive surface active sites, resulting in low initial coulombic efficiency (typically below 60%), severely restricting their practical application in sodium-ion batteries.
[0004] To improve the initial efficiency of hard carbon materials, existing technologies mainly employ two strategies: one is to reduce the specific surface area and promote graphite microcrystal growth through high-temperature carbonization (>1300℃), but this often leads to a significant decrease in sodium storage capacity; the other is to use chemical activation or doping modification, but this process is complex, costly, and environmentally challenging. Furthermore, traditional pyrolysis processes are mostly one-stage or simple two-stage carbonization, with relatively crude control over the carbon structure evolution process, making it difficult to achieve synergistic optimization of capacity and initial efficiency. Especially for complex biomass raw materials such as the lees of Maotai-flavor liquor, whose pyrolysis behavior exhibits multi-stage characteristics, if the low-temperature carbonization process is not matched with the intrinsic pyrolysis reaction of the raw material, it will lead to heterogeneous intermediate product structures, thus affecting the stability and reproducibility of the final product performance.
[0005] Therefore, developing a hard carbon preparation method that can accurately design the process based on the pyrolysis characteristics of raw materials from Maotai-flavor liquor, achieve stepwise control of carbon structure, and thus synergistically improve capacity and first-efficiency has significant industrial value and practical significance. Summary of the Invention
[0006] The purpose of this invention is to solve the problems of existing hard carbon based on distiller's grains failing to achieve both initial coulombic efficiency and reversible capacity, as well as poor process reproducibility. This invention provides a hard carbon anode material based on distiller's grains for Maotai-flavor liquor, its preparation method, and its application. By using a dual-stage low-temperature carbonization coupling function that matches the pyrolysis characteristics of distiller's grains to decouple the dual-stage high-temperature carbonization process, the carbon structure can be precisely controlled, thereby simultaneously improving the reversible sodium storage capacity and initial coulombic efficiency of hard carbon.
[0007] To achieve the above objectives, this invention provides a method for preparing a hard carbon anode material based on the lees of Maotai-flavor liquor, comprising the following steps:
[0008] S1. Raw material pretreatment: Wash, dry, crush and sieve the lees of sauce-flavored baijiu to obtain lees powder;
[0009] S2. Pyrolysis characteristic analysis: Thermogravimetric-differential thermogravimetric analysis was performed on the distiller's grains powder to obtain the thermogravimetric-differential thermogravimetric curve. Based on the pyrolysis characteristics, the first low-temperature carbonization temperature and the second low-temperature carbonization temperature were determined.
[0010] The first low-temperature carbonization temperature is higher than the peak temperature of the main weight loss peak in the thermogravimetric-differential thermogravimetric curve;
[0011] The second low-temperature carbonization temperature is higher than the starting temperature at which the weight loss rate of the thermogravimetric-differential thermogravimetric curve tends to stabilize.
[0012] S3, Two-stage low-temperature carbonization: Under an inert atmosphere, the lees powder is heated to the first low-temperature carbonization temperature at a heating rate of 0.5 to 2℃ / min and held for 1 to 3 hours, and then heated to the second low-temperature carbonization temperature at the same rate and held for 1 to 3 hours to obtain a low-temperature carbonization intermediate with a homogeneous structure.
[0013] S4. Two-stage high-temperature carbonization: The low-temperature carbonization intermediate obtained in step S3 is placed in an inert atmosphere and heated to the first high-temperature carbonization temperature at a heating rate of 2-5℃ / min and held for 2-6 hours. Then, it is heated to the second high-temperature carbonization temperature at the same rate and held for 2-6 hours. The carbon is then cooled in the furnace to obtain a coarse and hard carbon billet. The first high-temperature carbonization temperature is 1000-1300℃ and the second high-temperature carbonization temperature is 1350-1600℃.
[0014] S5. Post-processing: The coarse hard carbon blank is crushed and sieved to obtain distillers' grains-based hard carbon material.
[0015] This invention utilizes the TG-DTG pyrolysis characteristics of distiller's grains powder to precisely set two levels of low-temperature carbonization temperatures. The first low-temperature carbonization temperature is higher than the peak temperature of the main weight loss peak, allowing for controlled release at a constant temperature within the core reaction zone of the vigorous pyrolysis of organic matter in the distiller's grains. This enables the gradual and gentle release of volatile components from the raw material, avoiding the problems of instantaneous large-scale release of volatiles causing the collapse of the carbon precursor framework and disordered proliferation of pores. The second low-temperature carbonization temperature is selected above the starting temperature where the weight loss rate tends to stabilize. This allows for sufficient dehydrogenation and aromatization solidification of the intermediate after the main thermal decomposition of the raw material, obtaining a low-temperature carbonization intermediate with highly uniform structure and composition, thus reducing a large number of open defect sites from the source of the precursor. The process involves two-stage high-temperature carbonization to decouple the carbon skeleton construction from defect porosity control. First, short-range graphite-like microcrystals are constructed at 1000–1300℃ to provide sufficient sodium ion storage sites. Then, the temperature is raised to 1350–1600℃ to drive carbon atom rearrangement with sufficient thermodynamic force, repairing surface activity defects and closing some open micropores. This solves the technical contradiction that it is difficult to simultaneously improve reversible capacity and initial coulombic efficiency in the traditional biomass hard carbon preparation process. The entire process does not require strong corrosion chemical activation methods and has strong process controllability. It can realize the high-value resource utilization of brewing solid waste and stably prepare high-performance hard carbon anode materials suitable for sodium-ion batteries.
[0016] Preferably, the first low-temperature carbonization temperature is 350–400°C, and the second low-temperature carbonization temperature is 450–550°C. The first low-temperature carbonization temperature range is higher than the peak temperature of the main weight loss of the distillers' grains, and is in the later stage of vigorous pyrolysis of organic matter. Holding at this temperature can continue to slowly release the residual volatile components inside the distillers' grains, avoiding the explosive escape of volatiles that damages the carbon precursor skeleton, while promoting the cross-linking reaction of macromolecules. The second low-temperature carbonization temperature is higher than the starting temperature at which the weight loss rate of DTG tends to stabilize, and the main thermal decomposition reaction of the distillers' grains has been basically completed. Holding at this temperature range can fully realize the dehydrogenation and aromatization reaction of the intermediate, further solidify the carbon skeleton, effectively inhibit the formation of disordered macropores inside the intermediate, and obtain a low-temperature carbonized intermediate with uniform composition and dense and stable structure. This lays a solid foundation for the subsequent two-stage high-temperature carbonization to construct an ideal hard carbon microstructure, which is conducive to the final hard carbon material obtaining both high sodium storage specific capacity and excellent first coulombic efficiency.
[0017] Preferably, the temperature difference between the second high-temperature carbonization temperature and the first high-temperature carbonization temperature is ≥150℃, ensuring that the two high-temperature carbonization stages achieve differentiated structural control effects and avoiding the failure of carbon structure control due to the overlap of the two carbonization temperature ranges. The first high-temperature carbonization temperature mainly completes the construction of short-range microcrystals in the carbon matrix. Sufficient temperature difference can provide enough thermodynamic driving force for the second high-temperature carbonization stage, promote further rearrangement of carbon atoms, realize the closed reconstruction of open micropores on the material surface and inside, effectively reduce the defect sites of irreversible sodium storage, and reduce the ineffective consumption of sodium ions during the first charge and discharge process. At the same time, sufficient temperature gradient can also prevent the excessive development of graphitization in the carbon matrix, maintain the long-range disordered framework characteristics required for hard carbon, ensure the sodium ion storage capacity, and take into account both high initial coulombic efficiency and sodium storage specific capacity, so that the microstructure control effect of different batches of samples is stable, which is conducive to improving the consistency of the performance of the anode material.
[0018] Preferably, the inert atmosphere is nitrogen, argon, or a mixture of both, which can isolate oxygen throughout the high and low temperature segmented carbonization process, avoid high-temperature oxidation and ablation of the distillers' grains-based carbon precursor, prevent carbon matrix oxidation and loss, avoid the resulting reduction in material yield and carbon skeleton damage, ensure that the precursor completes cracking, cross-linking and microcrystalline rearrangement in sequence, precisely control the disordered carbon skeleton and pore structure of hard carbon, and ensure that the obtained hard carbon anode material has stable and excellent sodium storage electrochemical performance.
[0019] To achieve the above objectives, this invention also provides a hard carbon anode material based on the lees of Maotai-flavor liquor, prepared by the aforementioned method. Utilizing a dual-stage low-temperature-high-temperature carbonization process that matches the pyrolysis characteristics of the lees, it achieves synergistic control over the microcrystalline structure, pore distribution, and surface functional groups of the carbon matrix. This retains abundant sodium-ion storage sites in the hard carbon material to ensure a high sodium storage capacity, while effectively reducing excessively open defect sites within the material, mitigating electrolyte side-reaction consumption during charging and discharging, and improving the material's initial coulombic efficiency. Furthermore, this material uses lees, a solid waste from the brewing industry, as its carbon source, making the raw materials widely available and inexpensive, achieving high-value utilization of solid waste resources. The material exhibits good overall microstructural stability, and the carbon skeleton is not easily collapsed during repeated sodium ion insertion and extraction, demonstrating excellent cycle durability. It is suitable for large-scale application as a negative electrode active material in sodium-ion batteries.
[0020] To achieve the above objectives, the present invention also provides a sodium-ion battery anode comprising the aforementioned hard carbon anode material based on the lees of Maotai-flavor liquor. Benefiting from a segmented carbonization preparation process that matches the pyrolysis characteristics of the lees, the sodium-ion battery anode constructs a stable long-range disordered carbon framework and a controllable pore structure, providing ample sodium-ion storage sites and imparting a high sodium storage capacity. Simultaneously, harmful oxygen-containing defective functional groups on the material surface are effectively suppressed, reducing side reactions such as electrolyte decomposition, decreasing irreversible sodium-ion loss, improving the initial coulombic efficiency of the electrode, and maintaining the integrity of the electrode structure during repeated sodium-ion insertion and extraction, exhibiting excellent cycle stability.
[0021] To achieve the above objectives, the present invention also provides a sodium-ion secondary battery, comprising the aforementioned sodium-ion battery anode. Thanks to the precise microstructure control achieved through graded carbonization of the anode material, the battery can balance high discharge specific capacity with excellent initial coulombic efficiency, reducing irreversible sodium loss within the battery. Simultaneously, the stable carbon skeleton of the anode can mitigate structural degradation during cycling, resulting in a good cycle life. Furthermore, the anode uses brewing waste as raw material, which helps reduce the overall manufacturing cost of the battery. This battery system is suitable for the development needs of low-cost, large-scale application of sodium-ion batteries, possessing excellent comprehensive electrochemical performance and promising prospects for industrial application.
[0022] Compared with the prior art, the present invention has the following beneficial effects:
[0023] 1. This invention targets and limits the low-temperature carbonization process temperature based on the TG-DTG pyrolysis characteristics of the distillers' grains raw material. The first low-temperature carbonization temperature is set in a temperature range higher than the main weight loss peak of the raw material, so that the process heat input is precisely matched with the reaction kinetics of the violent pyrolysis of the organic matter in the distillers' grains. This achieves a smooth and controllable release of volatiles and avoids the problem of the collapse of the carbon precursor skeleton caused by the instantaneous large-scale escape of volatiles. The second low-temperature carbonization temperature is selected above the starting temperature where the weight loss rate tends to be stable. This completes the dehydrogenation and aromatization solidification of the intermediate, achieves the initial shaping of the carbon skeleton, and obtains a low-temperature carbonization intermediate with highly uniform composition and structure. This provides a stable and controllable precursor substrate for subsequent high-temperature carbonization control, overcoming the defects of the traditional biomass carbon preparation process, such as the mismatch between the pyrolysis behavior of the raw material and the process parameters and the large fluctuation of the precursor structure.
[0024] 2. This invention employs a differentiated temperature control strategy of two-stage high-temperature carbonization to decouple the "sodium storage structure construction" and "defect-pore regulation" of hard carbon materials. In the first high-temperature carbonization stage, graphite-like short-range disordered microcrystals adapted for sodium ion storage are directionally constructed at 1000–1300℃, fully generating effective sodium storage sites and ensuring high reversible specific capacity of the material. In the second high-temperature carbonization stage, the temperature is increased to 1350–1600℃, using a sufficient temperature difference to provide the thermodynamic driving force required for carbon atom rearrangement, promoting further regularization and rearrangement of the carbon layer. This effectively eliminates a large number of active defect sites on the material surface, induces the shrinkage and closure of some open micropores, significantly reduces irreversible sodium storage sites, and overcomes the technical pain point of the trade-off between reversible capacity and initial coulombic efficiency in traditional single-stage carbonization processes. This synergistically achieves a simultaneous increase in high sodium storage capacity and high initial coulombic efficiency in hard carbon materials.
[0025] 3. The overall process route of this invention is simple, and the process parameters can be adapted and adjusted according to the pyrolysis characteristics of the raw materials. The process is highly controllable and the batch reproducibility of the samples is excellent. No strong corrosive activating reagents are introduced throughout the process, making the process green and environmentally friendly. The raw material is the lees of Maotai-flavor liquor, which is widely available and can significantly reduce the preparation cost of hard carbon materials. It completes the high-value transformation of solid waste from the brewing industry, which is in line with the development direction of circular economy and green chemical industry. The prepared lees-based hard carbon anode material has extremely high practical application value and broad industrialization prospects in the field of sodium-ion batteries. Attached Figure Description
[0026] To more clearly illustrate the embodiments of the present invention, the accompanying drawings related to the embodiments are briefly described below.
[0027] Figure 1 This is a process flow diagram of the preparation method of the present invention.
[0028] Figure 2 This is the TG-DTG diagram of the raw material of soy sauce-flavored liquor lees used in this invention.
[0029] Figure 3 Scanning electron microscope (SEM) images of the low-temperature carbonization intermediates P1 and P5 and the distillers grains-based hard carbon materials SPL1 and SPL3 of this invention.
[0030] Figure 4 The first charge-discharge curve of the hard carbon material SPL1 obtained in Example 1 at a current density of 0.1 C is shown.
[0031] Figure 5 The first charge-discharge curve of the hard carbon material SPL2 obtained in Example 2 at a current density of 0.1 C is shown.
[0032] Figure 6 The first charge-discharge curve of the hard carbon material SPL3 obtained in Example 3 at a current density of 0.1 C is shown.
[0033] Figure 7 The first charge-discharge curve of the hard carbon material SPL4 obtained in Example 4 at a current density of 0.1 C is shown.
[0034] Figure 8 The first charge-discharge curve of the hard carbon material SPL5 obtained in Example 5 at a current density of 0.1 C is shown. Detailed Implementation
[0035] The technical solution of the present invention will be described in detail below with reference to the accompanying drawings and specific embodiments. It should be understood that these embodiments are only for explaining the present invention and do not constitute any limitation on the scope of protection of the present invention. 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.
[0036] Example 1
[0037] This embodiment provides a method for preparing a hard carbon anode material based on the lees of a type of soy sauce-flavored liquor, the process of which is as follows: Figure 1 As shown, using the lees of Maotai-flavor liquor as a carbon precursor, the process includes the following steps:
[0038] S1. Raw material pretreatment: Take the lees of sauce-flavored liquor, wash them repeatedly with deionized water to remove impurities, dry them in a 105℃ forced-air drying oven for 24 hours, pulverize them through a 100-mesh sieve, and obtain lees powder for later use.
[0039] S2. Pyrolysis Characteristic Analysis: The obtained distiller's grains powder was analyzed by TG-DTG under the following conditions: nitrogen atmosphere, heating rate 10℃ / min, from room temperature to 800℃. Results are as follows: Figure 2 As shown, the pyrolysis of raw materials from the lees of Maotai-flavor liquor includes two typical weight loss stages: the first is the stage of severe peak weight loss, where the peak temperature of the sharp weight loss peak in the DTG curve is 301.3℃, and the main weight loss range is 200-400℃. During this stage, organic matter undergoes concentrated pyrolysis, resulting in a mass loss of 49.63%. The second is the stage of high-temperature stable weight loss, where the starting temperature at which the DTG weight loss rate tends to stabilize is around 400℃. During this stage, residual groups are removed, resulting in a mass loss of 18.73%. Below 200℃, there is slight weight loss, corresponding to the volatilization of adsorbed water and small molecules, resulting in a mass loss of -5.14%.
[0040] S3, Two-stage low-temperature carbonization: Take the lees powder and heat it to 380°C in a tube furnace under an argon atmosphere at a heating rate of 1°C / min, and hold it for 2 hours; then heat it to 500°C at a heating rate of 1°C / min, and hold it for 2 hours to obtain a low-temperature carbonization intermediate, denoted as P1.
[0041] S4. Two-stage high-temperature carbonization: The low-temperature carbonization intermediate is heated to 1200℃ at a heating rate of 3℃ / min and held for 4 hours; then heated to 1400℃ at a heating rate of 3℃ / min and held for 4 hours; and cooled in a tube furnace under argon atmosphere protection at a cooling rate of 5℃ / min to obtain a coarse and hard carbon billet.
[0042] S5. Post-processing: The coarse hard carbon blank is crushed and passed through a 200-mesh sieve to obtain distillers' grains-based hard carbon material, denoted as SPL1.
[0043] Example 2
[0044] This embodiment provides a method for preparing a hard carbon anode material based on the lees of a type of soy sauce-flavored liquor. The difference between this method and that of Embodiment 1 is that the two-stage high-temperature carbonization in step S4 is changed to a single-stage high-temperature carbonization. The temperature is directly raised to 1400℃ at a heating rate of 3℃ / min, held for 8 hours, and cooled in the furnace to obtain a coarse hard carbon blank. After post-treatment, the hard carbon material based on the lees is obtained, denoted as SPL2.
[0045] Example 3
[0046] This embodiment provides a method for preparing a hard carbon anode material based on the lees of a type of soy sauce-flavored liquor. The difference between this method and that of Embodiment 1 is that the two-stage low-temperature carbonization in step S3 is changed to a single-stage low-temperature carbonization, with the temperature directly increased to 380°C at a heating rate of 1°C / min and held for 4 hours to obtain a low-temperature carbonization intermediate, denoted as P3. At the same time, the two-stage high-temperature carbonization in step S4 is also changed to a single-stage high-temperature carbonization, with the temperature directly increased to 1400°C at a heating rate of 3°C / min and held for 8 hours. The material is then cooled in the furnace to obtain a coarse hard carbon preform, which is then post-treated to obtain the lees-based hard carbon material, denoted as SPL3.
[0047] Example 4
[0048] This embodiment provides a method for preparing a hard carbon anode material based on the lees of a type of soy sauce-flavored liquor. The difference between this method and that of Embodiment 1 is that the two-stage low-temperature carbonization in step S3 is changed to a single-stage low-temperature carbonization, with the temperature directly increased to 380°C at a heating rate of 1°C / min and held for 4 hours to obtain a low-temperature carbonization intermediate (P3). At the same time, the two-stage high-temperature carbonization in step S4 is also changed to a single-stage high-temperature carbonization, with the temperature directly increased to 1200°C at a heating rate of 3°C / min and held for 8 hours. The material is then cooled in the furnace to obtain a coarse hard carbon preform, which is then post-treated to obtain the lees-based hard carbon material, denoted as SPL4.
[0049] Example 5
[0050] This embodiment provides a method for preparing a hard carbon anode material based on the lees of a type of soy sauce-flavored liquor. The difference between this method and that of Example 1 is that the two-stage low-temperature carbonization in step S3 is changed to a single-stage low-temperature carbonization. The temperature is directly raised to 500°C at a heating rate of 1°C / min and held for 3 hours to obtain a low-temperature carbonization intermediate, denoted as P5. The two-stage high-temperature carbonization method of Example 1 is used to obtain the lees-based hard carbon material, denoted as SPL5.
[0051] Micromorphological characterization
[0052] The microstructure of hard carbon products SPL1 and SPL3, as well as their corresponding low-temperature carbonization intermediates P1 and P3, was characterized using scanning electron microscopy (SEM). The results are as follows: Figure 3 As shown: SPL1, a distillers' grains-based hard carbon material prepared by two-stage low-temperature-high-temperature carbonization in Example 1, has regular particle morphology and a relatively flat and dense surface; SPL3, a distillers' grains-based hard carbon material prepared by single-stage carbonization in Example 3, has a rough particle surface and a large number of honeycomb pores; P1, an intermediate prepared by two-stage low-temperature carbonization in Example 1, has uniform particle distribution, a relatively smooth surface, and an intact carbon skeleton; P3, an intermediate prepared by single-stage 380℃ low-temperature carbonization in Example 3, has a rough surface and a significant porous structure. The comparison shows that two-stage low-temperature carbonization can achieve a gradual release of volatiles, protecting the carbon precursor skeleton and reducing pore defects; in the single-stage low-temperature carbonization process, volatiles are concentrated and explosively released, resulting in a large number of pores in the intermediate. This defect is difficult to eliminate by high-temperature carbonization, and the final product retains a large number of open pores, introducing irreversible sodium storage sites and reducing the material's initial coulombic efficiency.
[0053] Battery assembly and electrochemical testing
[0054] The distillers' grains-based hard carbon materials SPL1, SPL2, SPL3, SPL4, and SPL5 prepared in Examples 1-5 were used as active materials and mixed with conductive carbon black (Super P) and polyvinylidene fluoride (PVDF) at a mass ratio of 8:1:1. An electrode slurry was prepared using N-methylpyrrolidone (NMP) as a solvent and uniformly coated onto a copper foil current collector. After vacuum drying at 80°C for 12 hours, a negative electrode sheet with a diameter of 14 mm was obtained by die-cutting. A sodium metal sheet was used as the counter electrode, glass fiber as the separator, and sodium electrolyte (KLD-NF22) (1.0 M NaPF6 dissolved in TE-DME) as the electrolyte. CR2032 coin cell half-cells were assembled in an argon glove box (oxygen value <0.1 ppm). Constant current charge-discharge tests were performed on a Blue Battery testing system, with the voltage test window set to 0.01–2.0 V. The current density for the first three charge-discharge tests was set to 20 mA / g (0.1C), and the current density for the cycle performance test was set to 200 mA / g (1C). The test results are as follows: Figures 4-8 As shown in Table 1.
[0055] Table 1 Electrochemical performance test results
[0056] Comparing the electrochemical performance of SPL1, SPL2, and SPL5 coin cells, it can be seen that sample SPL1 from Example 1 of this invention exhibits the best overall electrochemical performance, with an initial coulombic efficiency of 66.1% and a reversible specific capacity of 289.7 mAh / g at 0.1 C, both of which are superior to the other comparative samples. This result fully demonstrates that the dual-stage low-temperature carbonization designed based on the pyrolysis characteristics of the raw materials in this invention has a significant synergistic gain effect with the functionally decoupled dual-stage high-temperature carbonization. The dual-stage low-temperature carbonization ensures the uniformity of the composition and structure of the low-temperature carbonization intermediates from the source; the dual-stage high-temperature carbonization achieves the construction of the sodium storage framework and the control of defects and pores stepwise. The two processes work together to effectively alleviate the technical challenge of the trade-off between reversible capacity and initial coulombic efficiency in traditional biomass hard carbon materials.
[0057] A comparison of the electrochemical test results of SPL3 (single-stage 380℃ low-temperature carbonization + single-stage 1400℃ high-temperature carbonization) and SPL4 (single-stage 380℃ low-temperature carbonization + single-stage 1200℃ high-temperature carbonization) shows that their initial coulombic efficiencies are similar, at 53.7% and 53.4%, respectively; the difference in reversible specific capacity is also small, at 163.7 mAh / g and 178.2 mAh / g, respectively. This indicates that under the premise of single-stage low-temperature carbonization, simply changing the high-temperature carbonization temperature is insufficient to effectively improve the initial coulombic efficiency of the material, nor can it simultaneously achieve high reversible capacity. Traditional single-stage carbonization processes struggle to achieve synergistic optimization of capacity and initial coulombic efficiency.
[0058] A comparison of the electrochemical performance of SPL2 and SPL3 shows that SPL2, employing a two-stage low-temperature carbonization process combined with a single-stage high-temperature carbonization, achieves a higher initial coulombic efficiency (ICE) compared to SPL3 (64.8%), and a higher reversible specific capacity (256.8 mAh / g). Furthermore, compared to SPL4, SPL2 also demonstrates significant improvements in both ICE and reversible specific capacity. This comparison proves that two-stage low-temperature carbonization can significantly optimize the microstructure of the precursor intermediates, providing a higher-quality carbon framework for subsequent high-temperature carbonization, thereby improving the overall electrochemical performance of hard carbon materials.
[0059] Comparing the electrochemical performance of SPL3, SPL4, and SPL5, it can be seen that SPL5, employing a single-stage 500℃ low-temperature carbonization combined with the dual-stage high-temperature carbonization of this invention, achieves an initial coulombic efficiency of 61.1% and a reversible specific capacity of 250.0 mAh / g, both significantly superior to the single-stage carbonization control samples SPL3 and SPL4. This result demonstrates that the dual-stage high-temperature carbonization process truly decouples the functions of "sodium storage structure construction" and "surface defect and pore opening control": the first stage, 1200℃ high-temperature carbonization, primarily develops the disordered carbon layer and microporous structure required for hard carbon, providing high reversible sodium storage capacity; the second stage, 1400℃ high-temperature carbonization, further optimizes the carbon framework, achieving surface defect repair and open pore control, reducing irreversible sodium storage sites, thereby simultaneously improving the initial coulombic efficiency and reversible specific capacity of the hard carbon anode.
[0060] In summary, this invention uses the lees of Maotai-flavor liquor as raw material to prepare hard carbon anode materials for sodium-ion batteries. A two-stage low-temperature carbonization process is designed to match the pyrolysis behavior of the lees, achieving a gradual release of volatile components from the precursor and avoiding the large number of open pores and structural damage to the carbon framework caused by violent gas generation, resulting in a structurally uniform low-temperature carbonization intermediate. Then, a functionally decoupled two-stage high-temperature carbonization process is employed to complete the construction of the hard carbon sodium storage framework and the regulation and repair of surface defects and open pores step by step. The prepared hard carbon anode material can simultaneously achieve high reversible specific capacity and excellent first-time coulombic efficiency, effectively overcoming the capacity-first-time efficiency constraint problem of traditional biomass-based hard carbon materials. It exhibits excellent comprehensive electrochemical performance and has promising application prospects in the field of sodium-ion batteries.
[0061] The above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit them; those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions will not cause the essence of the corresponding technical solutions to deviate from the protection scope of the present invention.
Claims
1. A method for preparing a hard carbon anode material based on the lees of a type of soy sauce-flavored liquor, characterized in that, Includes the following steps: S1. Raw material pretreatment: Wash, dry, crush and sieve the lees of sauce-flavored baijiu to obtain lees powder; S2. Pyrolysis characteristic analysis: Thermogravimetric-differential thermogravimetric analysis was performed on the distiller's grains powder to obtain the thermogravimetric-differential thermogravimetric curve. Based on the pyrolysis characteristics, the first low-temperature carbonization temperature and the second low-temperature carbonization temperature were determined. The first low-temperature carbonization temperature is higher than the peak temperature of the main weight loss peak in the thermogravimetric-differential thermogravimetric curve; The second low-temperature carbonization temperature is higher than the starting temperature at which the weight loss rate of the thermogravimetric-differential thermogravimetric curve tends to stabilize. S3, Two-stage low-temperature carbonization: Under an inert atmosphere, the lees powder is heated to the first low-temperature carbonization temperature at a heating rate of 0.5 to 2℃ / min and held for 1 to 3 hours, and then heated to the second low-temperature carbonization temperature at the same rate and held for 1 to 3 hours to obtain a low-temperature carbonization intermediate with a homogeneous structure. S4. Two-stage high-temperature carbonization: The low-temperature carbonization intermediate obtained in step S3 is placed in an inert atmosphere and heated to the first high-temperature carbonization temperature at a heating rate of 2-5℃ / min and held for 2-6 hours. Then, it is heated to the second high-temperature carbonization temperature at the same rate and held for 2-6 hours. The carbon is then cooled in the furnace to obtain a coarse and hard carbon billet. The first high-temperature carbonization temperature is 1000-1300℃ and the second high-temperature carbonization temperature is 1350-1600℃. S5. Post-processing: The coarse hard carbon preform is crushed and sieved to obtain distillers' grains-based hard carbon anode material.
2. The preparation method according to claim 1, characterized in that: The first low-temperature carbonization temperature is 350–400°C, and the second low-temperature carbonization temperature is 450–550°C.
3. The preparation method according to claim 1, characterized in that: The temperature difference between the second high-temperature carbonization temperature and the first high-temperature carbonization temperature is ≥150℃.
4. The preparation method according to claim 1, characterized in that: The inert atmosphere is nitrogen, argon, or a mixture of both.
5. A hard carbon anode material based on the lees of a type of soy sauce-flavored baijiu (Chinese liquor), characterized in that, It is prepared by the preparation method described in any one of claims 1-4.
6. A sodium-ion battery negative electrode, characterized in that: It includes the hard carbon anode material based on the lees of Maotai-flavor liquor as described in claim 5.
7. A sodium-ion secondary battery, characterized in that: It includes the sodium-ion battery negative electrode as described in claim 6.