A hard carbon negative electrode material for a bamboo-based sodium ion battery and a preparation method and application thereof

Abstract

The application discloses a preparation method and application of a hard carbon negative electrode material for a bamboo-based sodium ion battery. The preparation method comprises the following steps: sterilizing, fungus erosion, calcining and washing bamboo powder in sequence to obtain the hard carbon negative electrode material. The hard carbon negative electrode material comprises a micron-sized bamboo carbon matrix and nanoscale fungus-derived carbon. The bamboo carbon matrix and the fungus-derived carbon are connected to each other. The fungus-derived carbon is formed by calcining and sintering of fungi grown in situ on the surface of the bamboo powder. The bamboo carbon matrix is formed by calcining and sintering of the bamboo powder after fungus erosion. The prepared hard carbon negative electrode material for the bamboo-based sodium ion battery has excellent electrochemical performance and cycle stability when applied as a negative electrode of a sodium ion battery. The preparation method has the advantages of rich raw material sources, environmental protection, renewability, simple process, low cost and large-scale industrial production.

Description

Technical Field

[0001] This invention relates to the field of anode materials, particularly to the field of sodium-ion battery anode materials, and specifically to a bamboo-based hard carbon anode material for sodium-ion batteries, its preparation method, and its application. Background Technology

[0002] With the rapid development of electric vehicles and electronic devices, the demand for battery performance is increasing. Lithium-ion batteries, limited by the theoretical lithium storage capacity of graphite (372 mAh / g) and the Earth's lithium reserves, cannot meet future needs. Sodium ions, belonging to the same group of elements, have attracted widespread attention. Sodium is abundant and distributed globally, making the price of sodium-ion batteries, the main material, much lower than that of lithium-ion batteries. However, due to the large radius of sodium ions and the small interlayer spacing of graphite, repeated insertion and extraction of sodium ions in the graphite electrode can lead to structural collapse and a sharp decline in cycle performance. Therefore, graphite is not suitable as a negative electrode material for sodium-ion batteries. Hard carbon materials have a disordered internal crystal arrangement and more pores. Furthermore, sodium can be stored in the interlayer spaces, closed micropores, surfaces, and defect sites of graphite sheets, resulting in a high capacity and making it an ideal negative electrode material for sodium-ion batteries.

[0003] The preparation of hard carbon materials from biomass offers advantages such as abundant precursor varieties, sustainable use, and low cost. In particular, my country possesses abundant bamboo resources, is easily renewable, and has a relatively complete bamboo industry chain, making it an ideal raw material for hard carbon anode materials in sodium-ion batteries. However, existing methods for preparing bamboo-based hard carbon anode materials are quite complex. Besides the carbonization process, additional chemical modification and other pretreatment processes are often required to improve their electrochemical performance. For example, fresh bamboo may be pretreated with acid or alkali solutions and then calcined, followed by further treatment with acid or alkali solutions. Alternatively, bamboo may be mixed with metal salts or metal compounds and then calcined. These material processing methods are cumbersome and may introduce new impurities, increasing the cost of large-scale production and causing environmental pollution.

[0004] Furthermore, the high performance of hard carbon anode materials in lithium-ion batteries does not guarantee the same results in sodium-ion batteries. Existing methods for preparing bamboo-based hard carbon anode materials still suffer from low initial coulombic efficiency and low capacity when applied to sodium-ion batteries. Therefore, a simple, economical, and environmentally friendly pretreatment modification method is urgently needed to improve the electrochemical performance of bamboo-based biomass hard carbon anode materials and obtain high-performance sodium-ion battery anode materials. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to overcome the shortcomings of the prior art and provide a hard carbon anode material for sodium-ion batteries with excellent electrochemical performance and cycle stability. It also provides a method for preparing and applying a hard carbon anode material for sodium-ion batteries that has abundant raw material sources, is environmentally friendly and renewable, has a simple process, low cost, and can be mass-produced industrially.

[0006] To solve the above-mentioned technical problems, the present invention adopts the following technical solution:

[0007] A method for preparing a hard carbon anode material for bamboo-based sodium-ion batteries includes the following steps:

[0008] S1. Sterilize the bamboo powder to obtain sterilized powder;

[0009] S2. The cultured fungal spore suspension is inoculated into sterilized powder for fungal erosion treatment. The fungal growth is used to regulate the pore structure of bamboo to obtain bamboo powder after fungal erosion.

[0010] S3. The bamboo powder eroded by fungi is placed in a protective atmosphere and calcined to obtain a hard carbon precursor.

[0011] S4. Wash the hard carbon precursor powder with an acid solution, then wash it with water until neutral, and dry it to obtain the hard carbon anode material.

[0012] As a further improvement to the above technical solution:

[0013] Before sterilization, the bamboo powder is further subjected to a crushing and sieving process, wherein the mesh size during sieving is 40 to 1000 mesh.

[0014] In step S2, the fungi in the fungal spore suspension are one or more of molds or yeasts.

[0015] Preferably, the mold is one or more of the following: white rot fungi, Aspergillus flavus, Chaetomium, Aspergillus niger, Penicillium, Trichoderma viride, Rhizopus spp., and Fusarium flexures.

[0016] Preferably, in step S2, the volume-to-mass ratio of the fungal spore suspension to the sterilized powder is 3 μL:1g to 700 μL:1g. Preferably, the volume-to-mass ratio of the fungal spore suspension to the sterilized powder is 50 μL:1g to 500 μL:1g.

[0017] In step S2, the environment in which the fungus invades is a constant temperature and humidity environment.

[0018] Preferably, the constant temperature and humidity environment refers to a temperature between 20-30℃ and a humidity between 70%-90%.

[0019] In step S2, the fungal erosion time is 0.5 to 30 days.

[0020] Preferably, the fungal invasion time is 10 to 20 days.

[0021] In step S3, the protective atmosphere is an inert gas and / or nitrogen, and the calcination includes the following steps: first, calcining at a temperature of 300-500°C for 1-4 hours, and then calcining at a temperature of 800-1700°C for 1-4 hours.

[0022] Preferably, the heating rate for each calcination is 2-10 °C / min.

[0023] In step S4, the acid solution is one or more of hydrochloric acid, nitric acid, and sulfuric acid, the concentration of the acid solution is 0.1-2 M / L, and the washing time of the acid solution is 1-48 h.

[0024] Preferably, the washing time with the acid solution is 3 to 9 hours.

[0025] As a general inventive concept, the present invention also provides a hard carbon negative electrode material for bamboo-based sodium-ion batteries, which is prepared by the aforementioned preparation method and includes a micron-sized bamboo charcoal matrix and a nano-sized fungal-derived carbon. The bamboo charcoal matrix and the fungal-derived carbon are interconnected. The fungal-derived carbon is formed by calcining and sintering fungi that grow in situ on the surface of bamboo powder. The bamboo charcoal matrix is ​​formed by calcining and sintering bamboo powder that has been eroded by fungi.

[0026] As a general technical concept, the present invention also provides the application of the bamboo-based hard carbon anode material for sodium-ion batteries prepared by the above-mentioned preparation method in the anode of sodium-ion batteries.

[0027] In the above application, preferably, the application includes the following steps: mixing bamboo-based sodium-ion battery hard carbon anode material, CMC and conductive carbon black in a mass ratio of 8:1:1, dispersing the resulting mixture in an aqueous solution to form a uniform slurry, then coating the slurry onto aluminum foil and drying it to obtain a sodium-ion battery anode.

[0028] The aforementioned hard carbon anode materials or sodium-ion battery anodes are used in sodium-ion batteries in fields including electric vehicles, mobile phones, laptops, smart grids, electronic products, and the manufacturing of mobile energy storage devices.

[0029] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0030] (1) The present invention provides a bamboo-based hard carbon negative electrode material for sodium-ion batteries, using bamboo as the treatment target for microorganisms. On the one hand, bamboo is inexpensive and readily available, abundant in my country, easily renewable, and possesses a relatively complete bamboo industry chain, which can significantly reduce the cost of sodium-ion batteries. On the other hand, compared to wood and other biomass, bamboo is rich in nutrients such as starch, protein, sugars, fats, pectin, and tannins, making it more susceptible to fungal erosion, resulting in fungal decay and mold. This method can regulate the pore structure of bamboo itself. The fungal pretreatment technology for bamboo in this invention has the following effects:

[0031] A. In the traditional field of bamboo resource processing and utilization, due to the characteristics of bamboo being prone to fungal decay and mold, it is necessary to carry out anti-mold and antibacterial treatment on bamboo to inhibit the growth of fungi. However, this application cleverly utilizes the easy growth characteristics of fungi to erode bamboo, using microorganisms to consume some nutrients in bamboo powder and destroy the cell wall component structure of bamboo, to create pores in the bamboo substrate, improve the original disadvantage of bamboo's lack of pores, further enrich the pore structure of bamboo itself, and increase the sodium ion storage sites of bamboo-based hard carbon.

[0032] B. The growth process of fungi in bamboo not only utilizes the organic nutrients inside, but also absorbs and utilizes the inorganic mineral elements in bamboo, which greatly reduces the negative impact of inorganic impurities such as Fe, Ca, and Si in bamboo on the sodium storage capacity and cycle life of bamboo charcoal negative electrode.

[0033] C. At the same time, the fungi growing in situ on the bamboo will form nanoscale fungal-derived char after calcination. The new nanostructure formed on the micron-sized bamboo char surface will obtain a rich micro-interface, which will improve the sodium ion migration rate. Meanwhile, the additional pores generated by the fungal-derived char and the doping of N, S and other atoms rich in fungi can significantly increase the active sites for sodium storage in the negative electrode of bamboo char.

[0034] D. In addition, the present invention utilizes fungal erosion followed by acid washing, which has advantages such as being green and environmentally friendly, simple to operate, low in cost, and easy to scale up compared to other bamboo modification methods. It has good practical application prospects and can be widely used in the preparation of hard carbon for sodium-ion battery anodes. In particular, compared with directly using cultured fungi as raw materials for biomass hard carbon anodes, the present invention can eliminate problems such as the separation of fungi and culture medium materials and low yield, resulting in lower cost, simpler operation, and greater industrialization.

[0035] (2) This invention provides a bamboo-based hard carbon anode material for sodium-ion batteries. Micron-sized bamboo charcoal matrix is ​​directly connected to nano-sized fungal-derived carbon. The epitaxially grown fungal-derived carbon significantly increases the contact area between the micron-sized bamboo charcoal matrix during the preparation of the hard carbon anode, thereby further enhancing its conductivity. In particular, the derived carbon obtained from rod-shaped fungi (such as white-rot fungi) can significantly improve the bonding effect between the micron-sized bamboo charcoal matrix. Therefore, the electrochemical performance of the hard carbon anode material for sodium-ion batteries is effectively improved, resulting in a bamboo-based hard carbon anode with high initial coulombic efficiency and capacity, thus improving the energy density of sodium-ion batteries. When used as a sodium-ion battery anode material, it exhibits a larger discharge specific capacity and charge specific capacity than batteries assembled from untreated bamboo powder, and possesses excellent initial coulombic efficiency, excellent electrochemical performance, and cycle stability. Attached Figure Description

[0036] Figure 1 These are the discharge / charge ratio capacity and voltage curves of the negative electrode in Examples 1 to 4 and Comparative Example 1 of the present invention at a current density of 30 mA / g during the first cycle.

[0037] Figure 2 The bar chart shows the initial charge-discharge capacity of the negative electrode in Examples 1 to 4 and Comparative Example 1 of the present invention at a current density of 30 mA / g.

[0038] Figure 3 The first coulombic efficiency histograms of the negative electrode in Examples 1 to 4 and Comparative Example 1 of the present invention at a current density of 30 mA / g are shown.

[0039] Figure 4 These are digital photographs and optical micrographs of the bamboo powder samples in Examples 1, 2 and Comparative Example 1 of the present invention.

[0040] Figure 5 This is a process flow diagram of Embodiment 1 of the present invention.

[0041] Figure 6 This is a schematic diagram of the cycle stability of the negative electrode in Embodiment 1 of the present invention at a rate of 0.33C.

[0042] Figure 7 This is a schematic diagram of the cycle stability of the negative electrode in Embodiment 3 of the present invention at a rate of 0.33C.

[0043] Figure 8 This is a schematic diagram of the cycle stability of the negative electrode in Comparative Example 1 of the present invention at a rate of 0.33C. Detailed Implementation

[0044] The present invention will be further described below with reference to the accompanying drawings and specific preferred embodiments, but this does not limit the scope of protection of the present invention.

[0045] The materials and instruments used in the following examples are all commercially available.

[0046] Example 1:

[0047] like Figure 5 As shown, a method for preparing a hard carbon anode material for a bamboo-based sodium-ion battery according to this embodiment includes the following steps:

[0048] S1. Crushing process: The dried fresh bamboo is crushed and sieved to 80 mesh using a crusher to obtain bamboo powder.

[0049] S2. Sterilization treatment: Place the pulverized bamboo powder in a high-pressure steam cooker and sterilize it with high-pressure steam at 121℃ for 15 minutes to obtain sterilized powder.

[0050] S3. Fungal inoculation: White-rot fungi (purchased from China General Microbiological Culture Collection Center) were selected for cultivation, and a white-rot fungi spore suspension was prepared. The sterilized powder was then inoculated with the white-rot fungi spore suspension to obtain pretreated material. The volume-to-mass ratio of the white-rot fungi spore suspension to the sterilized powder was 200 μL: 3 g.

[0051] In other embodiments, the volume-to-mass ratio of fungal spore suspension to sterilized powder is between 3 μL:1g and 700 μL:1g to achieve the same or similar technical effects. If the volume-to-mass ratio is lower than the volume-to-mass ratio of 3 μL:1g in this application, the number of fungal spores is too small, the bamboo powder is too large, and the erosion efficiency is low. If it is higher than 700 μL:1g, the number of fungal spores is too large, the bamboo powder is too small, the fungal spore density is too large, and the fungal spores are easy to die, and it also causes waste of raw materials.

[0052] S4. Fungal culture: The pretreated material was placed in a constant temperature and humidity incubator and cultured at 28℃ and 80% humidity for 14 days. The pretreated material was then removed to obtain bamboo powder after fungal erosion.

[0053] S5. Calcination: The bamboo powder that has been eroded by fungi is placed directly into a tube furnace filled with argon and calcined at 500°C for 2 hours without any cleaning process. Then it is calcined at 1300°C for 2 hours in the tube furnace. The heating rate is 10°C / min for both times to obtain the hard carbon precursor.

[0054] S6. Acid washing and purification: After cooling, the hard carbon precursor is acid washed with 2 mol / L HCl for 3 hours, then washed with deionized water until neutral, and dried to obtain the hard carbon anode material.

[0055] The acid washing and purification step of this invention is performed after calcination. Compared with acid washing before calcination, acid washing after calcination can remove impurities generated during calcination, resulting in better performance.

[0056] The hard carbon anode material of the present invention includes a micron-sized bamboo charcoal matrix and a nano-sized fungal-derived carbon. The bamboo charcoal matrix and the fungal-derived carbon are interconnected. The fungal-derived carbon is formed by calcining and sintering fungi that grow in situ on the surface of bamboo powder. The bamboo charcoal matrix is ​​formed by calcining and sintering bamboo powder that has been eroded by fungi.

[0057] An application of the bamboo-based hard carbon anode material for sodium-ion batteries prepared in this embodiment includes the following steps:

[0058] A1. The bamboo-based sodium-ion battery hard carbon negative electrode material prepared in this embodiment, CMC and conductive carbon black are mixed evenly in a mass ratio of 8:1:1 and dispersed in an aqueous solution to form a uniform slurry. The slurry is then coated on aluminum foil and vacuum dried at 80°C to obtain a hard carbon electrode sheet.

[0059] A2. Hard carbon electrode sheets were paired with metallic sodium negative electrodes, and CR2016 coin cells were assembled in an inert atmosphere in a glove box. The electrochemical performance of the hard carbon electrode was then tested. The coin cell structure includes a positive electrode shell (stainless steel), a negative electrode shell (stainless steel), a gasket (stainless steel), a hard carbon electrode, a sodium sheet, an electrolyte, and a separator (PP).

[0060] Example 2:

[0061] A method for preparing a hard carbon negative electrode material for a bamboo-based sodium-ion battery according to this embodiment (the number of days of fungal erosion of bamboo powder is different from that in Example 1) includes the following steps:

[0062] S1. Bamboo Pulverization Processing: The dried fresh bamboo is pulverized and sieved to 80 mesh using a pulverizer to obtain bamboo powder.

[0063] S2. Sterilization treatment: Place the pulverized bamboo powder in a high-pressure steam cooker and sterilize it with high-pressure steam at 121℃ for 15 minutes to obtain sterilized powder.

[0064] S3. Fungal inoculation: White-rot fungi (purchased from China General Microbiological Culture Collection Center) were selected for cultivation, and a white-rot fungi spore suspension was prepared. The sterilized powder was then inoculated with the white-rot fungi spore suspension to obtain pretreated material. The volume-to-mass ratio of the white-rot fungi spore suspension to the sterilized powder was 200 μL: 3 g.

[0065] S4. Fungal culture: The pretreated material is placed in a constant temperature and humidity incubator and cultured at 28℃ and 80% humidity for 5 days. The pretreated material is then removed to obtain bamboo powder after fungal erosion.

[0066] S5. Calcination: The bamboo powder that has been eroded by fungi is placed directly into a tube furnace filled with argon and calcined at 500°C for 2 hours without any cleaning process. Then it is calcined at 1300°C for 2 hours in the tube furnace. The heating rate is 10°C / min for both times to obtain the hard carbon precursor.

[0067] S6. Acid washing and purification: After cooling, the hard carbon precursor is acid washed with 2 mol / L HCl for 3 hours, then washed with deionized water until neutral, and dried to obtain the hard carbon anode material.

[0068] Example 3:

[0069] A method for preparing a hard carbon negative electrode material for a bamboo-based sodium-ion battery according to this embodiment (the fungal species is different from that in Example 1) includes the following steps:

[0070] S1. Bamboo Pulverization Processing: The dried fresh bamboo is pulverized and sieved to 80 mesh using a pulverizer to obtain bamboo powder.

[0071] S2. Sterilization treatment: Place the pulverized bamboo powder in a high-pressure steam cooker and sterilize it with high-pressure steam at 121℃ for 15 minutes to obtain sterilized powder.

[0072] S3. Fungal inoculation: Aspergillus flavus (purchased from China General Microbiological Culture Collection Center) was cultured to prepare an Aspergillus flavus spore suspension. The sterilized powder was then inoculated with the Aspergillus flavus spore suspension to obtain pretreated material. The volume-to-mass ratio of the Aspergillus flavus spore suspension to the sterilized powder was 200 μL: 3 g.

[0073] S4. Fungal culture: The pretreated material is placed in a constant temperature and humidity incubator and cultured at 28℃ and 80% humidity for 14 days. The pretreated material is then removed to obtain bamboo powder after fungal erosion.

[0074] S5. Calcination: The bamboo powder that has been eroded by fungi is placed directly into a tube furnace filled with argon and calcined at 500°C for 2 hours without any cleaning process. Then it is calcined at 1300°C for 2 hours in the tube furnace. The heating rate is 10°C / min for both times to obtain the hard carbon precursor.

[0075] S6. Acid washing and purification: After cooling, the hard carbon precursor is acid washed with 2 mol / L HCl for 3 hours, then washed with deionized water until neutral, and dried to obtain the hard carbon anode material.

[0076] Example 4

[0077] A method for preparing a hard carbon negative electrode material for a bamboo-based sodium-ion battery according to this embodiment (the fungal species is different from that in Example 1) includes the following steps:

[0078] S1. Bamboo Pulverization Processing: The dried fresh bamboo is pulverized and sieved to 80 mesh using a pulverizer to obtain bamboo powder.

[0079] S2. Sterilization treatment: Place the pulverized bamboo powder in a high-pressure steam cooker and sterilize it with high-pressure steam at 121℃ for 15 minutes to obtain sterilized powder.

[0080] S3. Fungal inoculation: Yeast (purchased from China General Microbiological Culture Collection Center) was selected and rehydrated and activated to prepare a yeast spore suspension. The sterilized powder was then inoculated with the yeast spore suspension to obtain pretreated material. The volume-to-mass ratio of the yeast spore suspension to the sterilized powder was 500 μL: 1 g.

[0081] S4. Fungal culture: The pretreated material is placed in a constant temperature and humidity incubator and sealed for anaerobic fermentation at 28℃ and 80% humidity for 14 days. After the pretreated material is removed, bamboo powder after fungal erosion is obtained.

[0082] S5. Calcination: The bamboo powder that has been eroded by fungi is placed directly into a tube furnace filled with argon and calcined at 500°C for 2 hours without any cleaning process. Then it is calcined at 1300°C for 2 hours in the tube furnace. The heating rate is 10°C / min for both times to obtain the hard carbon precursor.

[0083] S6. Acid washing and purification: After cooling, the hard carbon precursor is acid washed with 2 mol / L HCl for 3 hours, then washed with deionized water until neutral, and dried to obtain the hard carbon anode material.

[0084] Comparative Example 1:

[0085] A method for preparing a hard carbon negative electrode material for bamboo-based sodium-ion batteries (the bamboo powder has not been subjected to fungal erosion) includes the following steps:

[0086] S1. Crushing process: The dried fresh bamboo is crushed and sieved to 80 mesh using a crusher to obtain bamboo powder.

[0087] S2. Calcination: The fungal-infested pretreated material was placed directly in a tube furnace filled with argon and calcined at 500°C for 2 hours, and then calcined at 1300°C for 2 hours in the tube furnace. The heating rate was 10°C / min for both times to obtain the hard carbon precursor.

[0088] S3. Acid washing and purification: After cooling, the hard carbon precursor is acid washed with 2 mol / L HCl for 3 hours, then washed with deionized water until neutral, and dried to obtain the hard carbon anode material.

[0089] Performance testing

[0090] Taking the button cells assembled in the examples and comparative examples as examples, the performance of batteries assembled with bamboo-based hard carbon electrodes prepared by eroding bamboo powder with white-rot fungi and bamboo powder eroded by Aspergillus flavus were evaluated using a charge-discharge device (Blue Electric 3001). Examples 1 and 2 investigated the effect of white-rot fungi on bamboo powder erosion time at different times. Meanwhile, as a comparison, the above-mentioned performance of the battery assembled with hard carbon prepared from untreated bamboo powder (Comparative Example 1) was also tested.

[0091] like Figures 1 to 3 As shown, the results indicate that, at a current density of 30 mA / g, the initial discharge specific capacities of bamboo-based hard carbon electrodes prepared by white-rot fungus erosion of bamboo powder (Example 1, erosion time 14 days), Aspergillus flavus erosion of bamboo powder (Example 3, erosion time 14 days), and yeast erosion of bamboo powder (Example 4, erosion time 14 days) were 361.67 mAh / g, 351.96 mAh / g, and 342.77 mAh / g, respectively; the charge specific capacities were 334.16 mAh / g, 283.97 mAh / g, and 276.3 mAh / g, respectively; and the initial coulombic efficiencies were 92.39%, 80.68%, and 80.61%, respectively. The technical effect of yeast erosion in Example 4 of this invention is inferior to that of white rot fungi and Aspergillus flavus erosion. This is because white rot fungi and Aspergillus flavus have rod-shaped microstructures, while yeast has spherical structure. The surface area of ​​fungal-derived carbon after calcination and sintering of spherical yeast is smaller than that after calcination and sintering of rod-shaped fungi. Therefore, when making hard carbon materials, the electrochemical performance of white rot fungi and Aspergillus flavus erosion is better than that of yeast.

[0092] The bamboo-based hard carbon electrode prepared by eroding bamboo powder with white-rot fungi (Example 2, erosion time of 5 days) had an initial discharge specific capacity of 366.41 mAh / g, a charge specific capacity of 299.38 mAh / g, and an initial coulombic efficiency of 81.71%. The initial charge specific capacity and initial coulombic efficiency were lower than those of Example 1 (erosion time of 14 days). The erosion time of white-rot fungi has a significant impact on the electrochemical performance of the bamboo-based hard carbon electrode.

[0093] Compared to the bamboo-based hard carbon anode prepared from untreated bamboo powder in Comparative Example 1 (with initial discharge / charge specific capacities of 318.96 mAh / g and 227.45 mAh / g, and an initial coulombic efficiency of 71.31%), the discharge / charge specific capacities were significantly improved after microbial treatment, and the hard carbon anode prepared from bamboo powder eroded by white rot fungi exhibited excellent initial coulombic efficiency.

[0094] Depend on Figure 4As can be seen, compared with 5 days of erosion in Example 2, more mycelial structures grew on the surface of bamboo powder particles after 14 days of erosion in Example 1. The abundant mycelial micro-interface structure can regulate and enrich the pore structure of bamboo itself, increase the sodium ion storage sites of bamboo-based hard carbon, and further enhance its conductivity by increasing the contact area of ​​hard carbon powder through the epitaxial growth of mycelium. Thus, it can effectively improve the electrochemical performance of hard carbon anode material for sodium-ion batteries and improve the energy density of sodium-ion batteries.

[0095] Figures 6 to 8 The diagram illustrates the cycle stability of the negative electrode in Embodiments 1, 3, and Comparative Example 1 at a rate of 0.33C. The upper curve represents the coulombic efficiency, and the lower curve represents the specific capacity. The cycle stability of Embodiments 1 and 3 is higher than that of Comparative Example 1.

[0096] The above results indicate that fungal pretreatment significantly improves the electrochemical performance of bamboo-based sodium-ion battery hard carbon anode materials.

[0097] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make many possible variations and modifications to the technical solutions of the present invention using the methods and techniques disclosed above, or modify them into equivalent embodiments with equivalent changes, without departing from the spirit and technical essence of the present invention. Therefore, any simple modifications, equivalent substitutions, equivalent changes, and modifications made to the above embodiments based on the technical essence of the present invention without departing from the content of the technical solutions of the present invention shall still fall within the protection scope of the technical solutions of the present invention.

Claims

1. A method for preparing a hard carbon anode material for bamboo-based sodium-ion batteries, characterized in that: Includes the following steps: S1. Sterilize the bamboo powder to obtain sterilized powder; S2. The cultured fungal spore suspension is inoculated into sterilized powder for fungal erosion treatment to obtain fungically eroded bamboo powder. The fungus destroys the cell wall components of bamboo, creates pores in the bamboo, and absorbs and utilizes the inorganic mineral elements in the bamboo. The volume-to-mass ratio of the fungal spore suspension to the sterilized powder is 3μL:1g-700μL:1g. The fungal erosion time is 10-20 days. S3. The bamboo powder after fungal erosion is placed in a protective atmosphere and calcined to obtain a hard carbon precursor. The calcination includes the following steps: first, calcining at 300~500℃ for 1~4 hours, and then calcining at 800~1700℃ for 1~4 hours. S4. Wash the hard carbon precursor powder with an acid solution, then wash it with water until neutral, and dry it to obtain the hard carbon anode material.

2. The method for preparing the hard carbon anode material for bamboo-based sodium-ion batteries according to claim 1, characterized in that: Before sterilization, the bamboo powder is further subjected to a crushing and sieving process, wherein the mesh size during sieving is 40-1000 mesh.

3. The method for preparing the hard carbon anode material for bamboo-based sodium-ion batteries according to claim 1, characterized in that: In step S2, the fungi in the fungal spore suspension are one or more of molds or yeasts.

4. The method for preparing the hard carbon anode material for bamboo-based sodium-ion batteries according to claim 3, characterized in that: In step S2, the environment in which the fungus invades is a constant temperature and humidity environment.

5. The method for preparing the hard carbon negative electrode material for bamboo-based sodium-ion batteries according to any one of claims 1 to 4, characterized in that: In step S3, the protective atmosphere is an inert gas and / or nitrogen.

6. The method for preparing the hard carbon negative electrode material for bamboo-based sodium-ion batteries according to any one of claims 1 to 4, characterized in that: In step S4, the acid solution is one or more of hydrochloric acid, nitric acid, and sulfuric acid; the concentration of the acid solution is 0.1~2M / L, and the washing time of the acid solution is 1~48h.

7. A bamboo-based hard carbon anode material for sodium-ion batteries, characterized in that, The bamboo-based sodium-ion battery hard carbon anode material is prepared by the preparation method of bamboo-based sodium-ion battery hard carbon anode material according to any one of claims 1 to 6, comprising a micron-sized bamboo charcoal matrix and a nano-sized fungal-derived carbon, wherein the bamboo charcoal matrix and the fungal-derived carbon are interconnected, the fungal-derived carbon is formed by calcining and sintering fungi that grow in situ on the surface of bamboo powder, and the bamboo charcoal matrix is ​​formed by calcining and sintering bamboo powder after fungal erosion.

8. The application of the bamboo-based hard carbon anode material for sodium-ion batteries prepared by the method of any one of claims 1 to 6 in the anode of a sodium-ion battery.

9. The application according to claim 8, characterized in that, The application includes the following steps: mixing bamboo-based sodium-ion battery hard carbon negative electrode material, CMC and conductive carbon black evenly, dispersing the resulting mixture in an aqueous solution to form a uniform slurry, and then coating the slurry onto a conductive foil and drying it to obtain a sodium-ion battery negative electrode.

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