Moldy strong-flavor liquor lees-based hard carbon negative electrode material and preparation method and application thereof

Abstract

The present application belongs to the technical field of electrochemical energy storage, and discloses a moldy strong-flavor liquor vinasse-based hard carbon negative electrode material and a preparation method and application thereof. The preparation method comprises five steps of moldy pretreatment, drying and crushing pretreatment, pre-carbonization, high-temperature carbonization and post-treatment. First, moldy for 7-21 days at 20-45 DEG C and 70%-90% humidity, using microorganisms to degrade lignin to construct primary through pores, and then carbonized into shape in two-stage gradient inert atmosphere. The present application uses moldy vinasse with high disposal cost and aflatoxin pollution as carbon source, does not use acid and alkali activation reagents in the whole process, and has green and low-cost process. The obtained hard carbon has a honeycomb-like multi-level interconnected porous structure, and when used as a sodium ion battery negative electrode, the 0.1 C reversible capacity reaches 216.4 mAh / g, and the capacity retention rate after 200 cycles is 93%. The hard carbon has the advantages of solid waste resource utilization, excellent sodium storage performance and industrialization value, and is suitable for large-scale energy storage and low-speed electric vehicle sodium ion batteries.

Description

Technical Field

[0001] This invention belongs to the field of electrochemical energy storage technology, specifically relating to hard carbon anode materials for sodium-ion batteries, and particularly to hard carbon anode materials based on moldy strong-aroma liquor lees, their preparation methods, and applications. Background Technology

[0002] Sodium-ion batteries benefit from abundant sodium resources and low manufacturing costs. Their working mechanism is similar to that of lithium-ion batteries, making them a preferred technology for large-scale energy storage and low-speed electric vehicle energy storage systems. The anode material determines the core electrochemical performance of sodium-ion batteries. Because the ionic radius of sodium ions is larger than that of lithium ions, the narrow interlayer spacing of commercially available graphite carbon cannot accommodate sodium ion insertion and extraction. Therefore, hard carbon materials with large interlayer spacing and abundant sodium storage sites have become the mainstream research direction for sodium-ion battery anodes.

[0003] Resource utilization of biomass solid waste is a key path to implementing the "dual carbon" strategy. Baijiu (Chinese liquor) lees are a major byproduct of the brewing industry. Moldy lees from strong-aroma baijiu, due to the presence of mold and aflatoxin, cannot be used as livestock feed or organic fertilizer, requiring companies to bear high costs for harmless disposal. Direct dumping or incineration would also cause toxin diffusion and atmospheric dust pollution, posing significant environmental pressure. Existing technologies only use fresh, mold-free lees to prepare hard carbon anodes, involving processes such as washing, acid washing, and single carbonization. Moldy lees, after microbial degradation, have a broken cellulose and lignin skeleton and a loose raw material structure, making it difficult to form a continuous conductive network through direct single carbonization, resulting in extremely poor electrochemical sodium storage performance. Currently, there is no complete solution for the resource utilization of moldy lees to prepare high-performance sodium anodes. Summary of the Invention

[0004] The purpose of this invention is to provide a hard carbon anode material based on moldy strong-aroma baijiu lees, its preparation method and application. Using waste moldy strong-aroma baijiu lees as carbon precursor, porous network hard carbon is prepared by natural mold pretreatment combined with a two-step inert atmosphere carbonization process, so as to realize the high-value utilization of toxic lees solid waste and obtain sodium-ion battery anode material with high reversible capacity and excellent cycle stability.

[0005] To achieve the above objectives, this invention provides a method for preparing a hard carbon anode material based on moldy strong-aroma baijiu lees, comprising the following steps:

[0006] S1. Pretreatment for mold growth: Take strong-aroma baijiu lees and place them in an environment with a temperature of 20-45℃ and a relative humidity of 70%-90% for natural mold growth for 7-21 days to obtain moldy lees.

[0007] S2. Drying and crushing pretreatment: After washing the moldy distiller's grains to remove impurities, dry them, crush them and sieve them to obtain moldy distiller's grains powder.

[0008] S3. Pre-carbonization: In an inert atmosphere, the moldy lees powder is heated to 300-500℃ at a heating rate of 1-5℃ / min and kept at that temperature for 1-5 hours for pre-carbonization. After natural cooling, it is ground and pulverized to obtain the pre-carbonized intermediate.

[0009] S4. High-temperature carbonization: In an inert atmosphere, the pre-carbonized intermediate is heated to 1200-1600℃ at a heating rate of 1-5℃ / min and held for 1-6 hours for high-temperature carbonization. After cooling, a coarse and hard carbon blank is obtained.

[0010] S5. Post-processing: The coarse hard carbon blank is crushed and sieved to obtain moldy strong-aroma baijiu lees-based hard carbon anode material.

[0011] This invention first pre-treats the naturally moldy lees of strong-aroma baijiu (Chinese liquor) in a controlled temperature and humidity environment. Mold microorganisms then directionally degrade lignin and cellulose components within the lees, pre-constructing a loose, interconnected native pore framework within the biomass precursor. This addresses the inherent defects of direct carbonization of moldy lees, such as framework collapse and conductive network breakage. The invention is coupled with a two-stage carbonization logic: low-temperature pre-carbonization for pore shaping and high-temperature deep carbonization for layer expansion and pore creation. The pre-carbonization stage removes volatile organic matter from the lees, preventing the massive gas production during high-temperature carbonization from destroying the pore structure. The high-temperature carbonization stage fully graphitizes and reconstructs the amorphous hard carbon with large interlayer spacing. Post-processing, including pulverization and sieving, controls the material particle size to optimize electrolyte wetting and sodium ion transport kinetics. The entire process does not introduce acids, alkalis, or activating salts; it relies solely on biological pre-degradation coupled with gradient carbonization to achieve controllable preparation of porous hard carbon. This not only renders toxic moldy lees waste harmless and valuable, but also endows the product with a continuous honeycomb porous network structure, significantly shortening the Na+ transport time. + Diffusion distance and sufficient sodium storage active sites are provided, simultaneously improving the reversible specific capacity, first coulombic efficiency and long-cycle capacity retention of hard carbon anode.

[0012] Furthermore, the drying temperature in step S2 is 100-120℃, and the drying time is 12-16 hours. This can gently remove the free and adsorbed water inside the moldy lees. The low drying temperature will not cause premature thermal decomposition and carbonization of the organic matter in the lees, thus avoiding premature caking and blockage of the original biological pores. Sufficient drying time can achieve uniform removal of moisture inside and outside the material, preventing residual moisture from rapidly vaporizing in the subsequent pre-carbonization stage, causing powder splashing and pore collapse. This ensures that after crushing and sieving, the moldy lees powder with uniform particle size and complete pore structure is obtained, providing a structural basis for the construction of a continuous porous hard carbon skeleton in the subsequent two carbonization steps.

[0013] Furthermore, the inert atmosphere described in steps S3 and S4 is nitrogen, argon, or a mixture of both, which can isolate oxygen in the tubular furnace, effectively preventing the oxidation and ablation of organic matter and carbon intermediates in the distiller's grains during the heating process, and ensuring the complete preservation of the carbon skeleton during the pre-carbonization and high-temperature carbonization stages. Nitrogen raw materials are readily available and inexpensive, while argon provides stronger inert protection. The mixed atmosphere can balance economy and anti-oxidation effect, adapting to different production scale requirements, suppressing the oxidation loss of carbon materials throughout the process, and ensuring that the final product has a complete interconnected porous network and excellent conductive sodium storage performance.

[0014] To achieve the above objectives, this invention also provides a hard carbon anode material based on moldy strong-aroma baijiu lees, prepared by the aforementioned method. It utilizes the synergistic effect of biodegradation of moldy lees and two-stage gradient carbonization to form an amorphous hard carbon matrix. Internally, it constructs an interconnected honeycomb-like multi-level porous network with larger carbon layer spacing. This provides abundant intercalation / deintercalation active sites for sodium ions and significantly shortens the solid-phase diffusion path of sodium ions, enhancing the electrolyte penetration and wetting effect. The raw material originates from waste moldy lees, achieving high-value conversion of solid waste. No strongly corrosive chemical reagents are introduced during the entire preparation process, resulting in no additional impurities remaining in the material. When used as an anode in sodium-ion batteries, it can achieve high reversible specific capacity, high initial coulombic efficiency, and excellent long-cycle capacity retention.

[0015] To achieve the above objectives, the present invention also provides a sodium-ion battery anode comprising the aforementioned moldy, strong-aroma baijiu lees-based hard carbon anode material. This sodium-ion battery anode uses moldy, porous hard carbon as its core active material. The interconnected multi-level channels within the material accelerate the transport of sodium ions to the electrolyte, mitigating the volume expansion effect during sodium ion insertion / extraction and significantly reducing electrode polarization. The hard carbon, derived from waste materials, has low impurity content and a continuous, complete conductive network. Combined with conventional conductive agents and binders, it can produce uniform and stable electrode sheets. When assembled into a sodium-ion battery, it exhibits higher reversible specific capacity, superior initial coulombic efficiency, and long-cycle stability, while significantly reducing the cost of electrode preparation materials, thus meeting the development needs of low-cost, green manufacturing for large-scale energy storage batteries.

[0016] To achieve the above objectives, the present invention also provides a sodium-ion battery, comprising the aforementioned sodium-ion battery negative electrode. The internal interconnected honeycomb porous structure of the negative electrode can effectively shorten the sodium ion diffusion distance, buffer the intercalation and deintercalation volume deformation, reduce the polarization of the battery during charging and discharging, and endow the battery with higher reversible sodium storage capacity and excellent long-cycle capacity retention. The core negative electrode raw material of the battery is harmlessly treated brewing moldy solid waste. The entire preparation process is free of acid and alkali activating agents, resulting in green and low-carbon production that significantly reduces the cost of battery raw materials. It is suitable for large-scale energy storage, low-speed electric vehicles and other application scenarios, and has the triple advantages of excellent electrochemical performance, low production cost, and solid waste resource utilization and environmental protection.

[0017] Compared with the prior art, the present invention has the following beneficial effects:

[0018] 1. Breakthrough innovation in raw material sourcing: Existing biomass hard carbon anodes can only use fresh, unmolded distiller's grains as carbon precursors. This invention, for the first time, transforms moldy strong-aroma baijiu distiller's grains, which pose a risk of aflatoxin contamination, have high costs for harmless disposal in wineries, and are difficult to utilize through conventional methods, into high-performance sodium-ion battery hard carbon anode materials. This opens up a new technical route for the high-value utilization of moldy biomass solid waste, expands the types of carbon sources for energy storage, and simultaneously reduces enterprises' solid waste disposal expenditures and anode material raw material procurement costs.

[0019] 2. The preparation process is simple and green, and the industrial production cost is lower: This invention uses the pre-degradation of natural microbial mold to couple two-stage gradient carbonization to achieve pore-forming and shaping of carbon materials. The entire process does not introduce corrosive chemical reagents such as acid washing, alkali activation, and chemical pore-forming agents. The process is simplified and the reaction conditions are easy to control. On the one hand, it saves the extra costs of purchasing chemical reagents and treating waste. On the other hand, it eliminates the damage of chemical residues to the sodium storage active sites of carbon materials. The process is safe and environmentally friendly and suitable for large-scale continuous production.

[0020] 3. Possessing both significant environmental benefits and industrial circular economy value: This invention completely solves the industry's environmental problems of toxin diffusion from open-air stockpiling of moldy brewing lees and the emission of toxic waste gases from direct incineration, achieving the harmless disposal of toxic brewing solid waste; at the same time, it realizes the value upgrade of low-value brewing by-products into energy storage functional materials, opening up a resource recycling channel between the liquor brewing industry and the sodium-ion battery energy storage industry, highly aligning with the "dual carbon" goal and the policy of industrial solid waste resource utilization, and can simultaneously create considerable economic and social benefits after industrialization. Attached Figure Description

[0021] To more clearly illustrate the embodiments of the present invention, the accompanying drawings related to the embodiments are briefly described below.

[0022] Figure 1 This is a scanning electron microscope (SEM) image of sample YP-1 from Example 1.

[0023] Figure 2 The first charge-discharge curve of sample YP-1 in Example 1 at a current density of 0.1 C is shown.

[0024] Figure 3 The performance curve of sample YP-1 in Example 1 after 200 cycles at a current density of 1.0 C is shown.

[0025] Figure 4 The first charge-discharge curve of Comparative Example 1 sample YP-2 at a current density of 0.1 C is shown.

[0026] Figure 5 The curves of the performance of Comparative Example 1 sample YP-2 after 200 constant current charge-discharge cycles at a current density of 1.0 C are shown.

[0027] Figure 6 The first charge-discharge curve of sample YP-3 in Comparative Example 2 at a current density of 0.1 C is shown. Detailed Implementation

[0028] 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.

[0029] Example 1

[0030] This embodiment provides a method for preparing a hard carbon anode material based on moldy, strong-aroma baijiu lees, including the following steps:

[0031] S1. Pretreatment for mold growth: Fresh strong-aroma baijiu (Chinese liquor) lees waste was placed in a constant temperature and humidity sealed environment (25℃, 80% relative humidity) for 14 days to allow natural mold growth, resulting in moldy lees. The cellulose, hemicellulose, and lignin components of both the fresh and moldy lees were quantitatively analyzed using the Fantai fiber assay. The results are shown in Table 1. Table 1 shows that after 14 days of controlled temperature and humidity natural mold growth, the lignin content decreased significantly from 22.19 wt% to 9.27 wt%, the cellulose content decreased slightly, and the hemicellulose content remained relatively stable. This indicates that microorganisms in the environment can preferentially degrade the lignin skeleton within the lees, disrupting the dense protobiota structure and forming numerous natural interconnected pores within the raw material, providing a natural precursor structure for subsequent carbonization to prepare porous hard carbon.

[0032] Table 1. Component analysis results of fresh strong-aroma baijiu lees and moldy lees Element Fresh strong-aroma baijiu lees Moldy lees Cellulose (wt%) 38.67 34.37 Hemicellulose (wt%) 14.91 15.17 Lignin (wt%) 22.19 9.27

[0033] S2. Drying and Crushing Pretreatment: The moldy distiller's grains are thoroughly washed three times with deionized water to remove soluble organic acids and microbial metabolic impurities. Then, they are transferred to a forced-air drying oven and dried at a constant temperature of 100°C for 12 hours to completely remove free water and adsorbed water from the inside and outside of the material. The completely dried material is crushed using a planetary pulverizer and all of it is passed through a 100-mesh standard sieve to obtain moldy distiller's grains powder with uniform particle size and no pore collapse.

[0034] S3. Pre-carbonization: The moldy lees powder is placed in a tube furnace, and high-purity nitrogen is continuously introduced as an inert protective atmosphere. The heating rate is set to 2℃ / min. After heating to 400℃, the temperature is kept constant for 2 hours to complete the pre-carbonization. The pre-carbonization process removes volatile organic matter from the lees and fixes the original pores formed by microbial degradation to avoid the collapse of the pore structure during the high-temperature carbonization stage. After the reaction is completed, the material is naturally cooled to room temperature with the tube furnace. The material is then taken out and ground again to obtain a pre-carbonized intermediate with uniform texture.

[0035] S4. High-temperature carbonization: The pre-carbonized intermediate obtained in step S3 is transferred to a tube furnace, and a nitrogen inert atmosphere is maintained. The heating rate is set to 4℃ / min. After heating to 1400℃, the carbonization is carried out at a constant temperature for 4 hours. The amorphous hard carbon layer structure is reconstructed under high temperature conditions, the carbon layer spacing is expanded and a large number of micropores and mesopores are generated. After carbonization, the carbon is cooled to room temperature with the furnace to obtain a blocky coarse hard carbon blank.

[0036] S5. Post-processing: The coarse hard carbon blank is crushed at high speed and sieved through a 200-mesh standard sieve to remove large particle agglomerates. Finally, a moldy strong-aroma baijiu lees-based hard carbon anode material with uniform particle size and complete porous structure is obtained, which is denoted as sample YP-1.

[0037] Micromorphological characterization

[0038] The microstructure of sample YP-1 was characterized using scanning electron microscopy (SEM), and the results are as follows: Figure 1 As shown in the scanning electron microscope morphology image, it can be clearly observed that the hard carbon material prepared by the controlled mold pretreatment coupled with the two-stage gradient carbonization process forms a complete, continuous, and interconnected honeycomb-shaped three-dimensional carbon skeleton. A large number of micron-sized open pores are evenly distributed on the surface of the matrix, constructing a multi-level interconnected pore structure in which macropores, mesopores, and micropores coexist. There is no obvious blockage of the pores, which is completely consistent with the process mechanism of microbial preferential degradation of lignin in distiller's grains to create pores and segmented gradient carbonization to lock and shape the pores.

[0039] This multi-level disordered porous carbon network has multiple advantages: First, it significantly improves the penetration and wetting efficiency of the electrolyte inside the electrode, constructs a continuous and unobstructed sodium ion transport channel, significantly shortens the solid-phase diffusion distance of sodium ions, and reduces the charge transfer impedance during the charging and discharging process; Second, the loose and interconnected pore structure can effectively buffer the material volume stress deformation caused by repeated sodium ion insertion and extraction, avoid the pulverization and collapse of the carbon skeleton, and simultaneously improve the reversible specific capacity, rate discharge performance and long-term cycle stability of the hard carbon anode from the microstructure level.

[0040] Comparative Example 1

[0041] This comparative example provides a method for preparing a hard carbon material based on strong-aroma baijiu lees. The only difference from Example 1 is that no mold pretreatment is performed. Instead, fresh strong-aroma baijiu lees raw material is directly placed in a forced-air drying oven and dried at 100°C for 12 hours. Then, it is pulverized and passed through a 100-mesh sieve to obtain lees powder. The same pre-carbonization, high-temperature carbonization and post-treatment process as in Example 1 is used to obtain the hard carbon material based on strong-aroma baijiu lees, which is denoted as sample YP-2.

[0042] Comparative Example 2

[0043] This comparative example provides a method for preparing a moldy strong-aroma baijiu lees-based hard carbon material. The only difference between this method and Example 1 is the temperature and humidity of the mold pretreatment and the mold growth time. In this comparative example, fresh strong-aroma baijiu lees waste is placed in a constant temperature and humidity sealed environment at 35°C and 50% relative humidity for 7 days to naturally mold, thus obtaining moldy lees. Then, the same drying and crushing pretreatment, pre-carbonization, high-temperature carbonization and post-treatment process as in Example 1 is used to obtain the moldy strong-aroma baijiu lees-based hard carbon material, which is designated as sample YP-3.

[0044] Battery assembly and electrochemical testing

[0045] Samples YP-1, YP-2, and YP-3 prepared in Example 1, Comparative Example 1, and Comparative Example 2 were used as active materials and mixed with conductive carbon black (Super P), sodium carboxymethyl cellulose (CMC), and styrene-butadiene rubber (SBR) at a mass ratio of 9.4:0.15:0.2:0.25. Deionized water was used as a solvent to prepare a uniform electrode slurry. The slurry was uniformly coated on the surface of a copper foil current collector, dried under vacuum at 80°C for 12 hours, rolled and compacted, and then punched into a circular negative electrode sheet with a diameter of 12 mm. The prepared electrode sheet was used as the working electrode, a sodium metal sheet 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).

[0046] Electrochemical performance tests were conducted using the Blue Battery testing system. The current density for the initial charge-discharge test was set to 20 mA / g (0.1 C); the current density for the cycle performance test was set to 200 mA / g (1.0 C). The test results are as follows: Figures 2-6 As shown in Table 2.

[0047] Comparing the electrochemical performance of coin half-cells of samples YP-1 and YP-2, it can be seen that compared to sample YP-2 without mold pretreatment, sample YP-1, prepared using the controlled mold bio-poration combined with segmented gradient carbonization process of this invention, showed a 1.8 percentage point improvement in initial coulombic efficiency and a significant increase in reversible specific capacity at 0.1 C from 163.0 mAh / g to 216.4 mAh / g. After 200 cycles at a current density of 1.0 C, the capacity retention rate increased significantly from 72% to 93%. This fully demonstrates that the controlled mold pretreatment of distiller's grains is the core process for optimizing the porous microstructure of hard carbon, which can significantly improve the sodium ion transport kinetics and enhance the structural stability of the carbon skeleton during repeated sodium intercalation and deintercalation processes.

[0048] Table 2 Electrochemical performance test results sample First-time Coulomb efficiency (%) Reversible specific capacity (mAh / g, 0.1C) Capacity retention rate (%) after 200 cycles YP-1 86.0 216.4 93 YP-2 84.2 163.0 72 YP-3 83.1 157.2 68.5

[0049] Comparing the electrochemical test results of samples YP-1 and YP-3, it can be seen that sample YP-3 has an initial coulombic efficiency of only 83.1%, a reversible specific capacity of 157.2 mAh / g at 0.1 C, and a capacity retention rate of only 68.5% after 200 cycles, showing a significant performance gap compared to sample YP-1. This confirms that mold pretreatment under suitable conditions is necessary to fully degrade lignin in distillers' grains and construct a multi-level porous framework, which significantly and synergistically improves the reversible sodium storage capacity, initial coulombic efficiency, and cycle stability of the carbonized hard carbon anode.

[0050] In summary, this invention, through the synergistic effect of controlled mold-induced precursor bio-pore-forming modification and multi-level gradient carbonization process, has simultaneously achieved high reversible sodium storage capacity (216.4 mAh / g@0.1C), high initial coulombic efficiency (86.0%), and long-term cycling stability (93% capacity retention after 200 cycles) in the prepared hard carbon anode material YP-1. This breakthrough solves the industry pain point of mutual constraint between reversible capacity and initial coulombic efficiency in traditional biomass-based hard carbon anodes. It has outstanding comprehensive electrochemical performance advantages, and the use of waste moldy strong-aroma liquor lees as raw material significantly reduces the manufacturing cost of the anode. It has extremely high practical value and industrialization prospects in the fields of low-cost sodium-ion battery large-scale energy storage and low-speed electric vehicles.

[0051] 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 moldy, strong-aroma baijiu lees, characterized in that, Includes the following steps: S1. Pretreatment for mold growth: Take strong-aroma baijiu lees and place them in an environment with a temperature of 20-45℃ and a relative humidity of 70%-90% for natural mold growth for 7-21 days to obtain moldy lees. S2. Drying and crushing pretreatment: After washing the moldy distiller's grains to remove impurities, dry them, crush them and sieve them to obtain moldy distiller's grains powder. S3. Pre-carbonization: In an inert atmosphere, the moldy lees powder is heated to 300-500℃ at a heating rate of 1-5℃ / min and kept at that temperature for 1-5 hours for pre-carbonization. After natural cooling, it is ground and pulverized to obtain the pre-carbonized intermediate. S4. High-temperature carbonization: In an inert atmosphere, the pre-carbonized intermediate is heated to 1200-1600℃ at a heating rate of 1-5℃ / min and held for 1-6 hours for high-temperature carbonization. After cooling, a coarse and hard carbon blank is obtained. S5. Post-processing: The coarse hard carbon blank is crushed and sieved to obtain moldy strong-aroma baijiu lees-based hard carbon anode material.

2. The preparation method according to claim 1, characterized in that: The drying temperature in step S2 is 100-120°C, and the drying time is 12-16 hours.

3. The preparation method according to claim 1, characterized in that: The inert atmosphere described in steps S3 and S4 is nitrogen, argon, or a mixture of both.

4. A hard carbon anode material based on moldy, strong-aroma baijiu lees, characterized in that, It is prepared by the preparation method according to any one of claims 1-3.

5. A sodium-ion battery negative electrode, characterized in that: It includes the moldy, strong-aroma baijiu lees-based hard carbon anode material as described in claim 4.

6. A sodium-ion battery, characterized in that: It includes the sodium-ion battery negative electrode as described in claim 5.

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