Rhizopus for synthesizing hard carbon negative electrode material by maillard reaction, preparation method and application thereof

Abstract

This invention belongs to the field of sodium-ion battery technology, and relates to the synthesis of hard carbon anode materials using Rhizopus molds via the Maillard reaction, its preparation method, and its application. The material uses the hydrothermal product of Rhizopus mold hyphae and glucose as a carbon source. After the Rhizopus mold hyphae and glucose undergo a Maillard reaction via hydrothermal treatment, the product is carbonized at high temperature to obtain the hard carbon anode material. The hard carbon anode material prepared by this invention exhibits high specific capacity, good cycle stability, and excellent rate performance and coulombic efficiency. Furthermore, the preparation method provided by this invention is simple, rapid, efficient, convenient, and under mild and easily controllable conditions. It can effectively introduce sodium-storage-enhancing heterogeneous elements into the hard carbon material, contributing to the development of hard carbon anode materials for sodium-ion batteries.

Description

Technical Field

[0001] This invention relates to the field of hard carbon anode materials for sodium-ion batteries, specifically to a method and materials for synthesizing hard carbon anode materials using Rhizopus mold via Maillard reaction, and their application in sodium-ion batteries. Background Technology

[0002] With the rapid development of modern technology, the demand for electrochemical energy storage devices, represented by lithium-ion batteries, is increasing daily. However, the scarcity of lithium resources on Earth leads to significant price fluctuations. Sodium, on the other hand, is the fourth most abundant element in the Earth's crust, widely distributed and unrestricted by resources or location. Furthermore, sodium-ion batteries offer better safety performance and a service life comparable to lithium-ion batteries, making their application prospects very broad. The positive and negative electrode materials are the core of sodium-ion battery operation; they are not only key to improving performance but also the main way to solve the cost bottleneck. Common negative electrode materials for sodium-ion batteries include alloy-type, conversion-type, and intercalation-type materials. Compared to alloy-type and conversion-type materials, intercalation-type materials exhibit better performance during charging and discharging. + Carbon-based materials exhibit low lattice volume expansion during insertion and extraction, demonstrating good structural integrity and cycle stability, as well as higher initial coulombic efficiency and higher rate performance. As a representative of intercalation materials, carbon-based materials are considered the most promising anode materials for sodium-ion batteries due to their abundant resources and environmental friendliness.

[0003] Carbon-based materials are classified into four categories based on the arrangement of carbon atoms: graphite, graphene, soft carbon, and hard carbon. Hard carbon anode materials have low sodium storage potential, high specific capacity, high theoretical reversible capacity, and are abundant, widely available, and low-cost, making them a key focus of research in sodium-ion battery anode materials. Researchers have developed a series of hard carbon anode materials based on carbon-containing raw materials such as pitch-based, biomass-based, and resin-based materials. Biomass materials have attracted much attention due to their unique advantages, such as abundant and readily available raw material sources, high carbon yield, environmental friendliness, and the presence of multiple elements, making them a promising precursor for sodium-ion battery anode materials.

[0004] However, hard carbon anodes still face many unresolved issues, such as low initial coulombic efficiency, poor rate performance, and low specific capacity. Therefore, it is necessary to find modification schemes to optimize the initial coulombic efficiency, cycle life, and rate performance of hard carbon anodes. Scientists have proposed many strategies to address these problems. Among them, heteroatom doping with N, P, and S is an important and effective method. As is well known, hard carbon is obtained by pyrolyzing a pretreated precursor in an inert atmosphere. In this process, inappropriate heating rates and carbonization temperatures may lead to poor carbon layer development or excessively small interlayer spacing. Simultaneously, the release of small precursor molecules during pyrolysis, coupled with a series of cross-linking reactions, results in hard carbon possessing abundant porosity and defects. However, the excessively small interlayer spacing in hard carbon is detrimental to sodium ion insertion / extraction, leading to poor rate performance and low specific capacity. Heteroatom doping is an effective method for controlling defects and interlayer spacing. Through heteroatom doping, the interlayer spacing of hard carbon is expanded, and the heteroatoms act as defects in the carbon layers, improving the conductivity of hard carbon and thus enhancing its rate performance and specific capacity. Surface engineering provides an advantageous method for protecting the anode by creating artificial interfaces, thereby effectively reducing the occurrence of side reactions. Furthermore, studies have shown that coatings can effectively improve the sodium ion diffusion coefficient because they provide three-dimensional diffusion rather than two-dimensional diffusion in the anode. Based on this, this invention proposes a surface engineering method to synthesize a carbon coating with a thickness of approximately 37 nm on a spherical hard carbon surface by forming a composite precursor from Rhizopus and glucose through hydrothermal synthesis. Summary of the Invention

[0005] The purpose of this invention is to address a series of problems in the initial coulombic efficiency, specific capacity, and rate performance of hard carbon anode materials in sodium-ion battery systems. It provides a method for synthesizing hard carbon anode material precursors via the Maillard reaction of Rhizopus. By controlling parameters such as hydrothermal reaction time, reaction temperature, carbonization process, Rhizopus mycelium mass ratio, and glucose mass ratio, high-performance hard carbon anode materials can be effectively prepared. First, self-doping is achieved using the natural nitrogen source in Rhizopus mycelium, reducing costs. Second, the mycelium, glucose, and water are co-treated with hydrothermal agents in a specific ratio. The Maillard reaction between the Rhizopus mycelium and glucose is utilized, and the co-thermal carbonization regulates the pore structure and interlayer spacing of the hard carbon, improving sodium-ion diffusion kinetics. Simultaneously, a uniform carbon coating is obtained on the hard carbon surface. The prepared sodium-ion battery hard carbon anode material exhibits high specific capacity, good cycle stability, excellent rate performance, and high coulombic efficiency, effectively promoting the commercialization of hard carbon anode materials.

[0006] The technical solution adopted by this invention to solve its technical problem is:

[0007] The first objective of this invention is to provide a biomass hard carbon anode material, wherein the biomass precursor of the biomass hard carbon anode material is Rhizopus mycelium. By adopting the above technical solution, Rhizopus mycelium can fix the surrounding free nitrogen through nitrogen fixation, thereby achieving uniform and stable doping of elements such as nitrogen, phosphorus, and sulfur, resulting in a biomass hard carbon anode material with uniform nitrogen, phosphorus, and sulfur doping, good morphological uniformity, and high initial efficiency.

[0008] The second objective of this invention is to provide a method for preparing the aforementioned biomass hard carbon anode material. This method involves reacting Rhizopus mycelia with glucose via a hydrothermal Maillard reaction. This method regulates the pore structure and interlayer spacing of the hard carbon, thereby enhancing sodium ion diffusion kinetics. By controlling parameters such as hydrothermal reaction time, reaction temperature, carbonization process, Rhizopus mycelia mass ratio, and glucose mass ratio, high-performance hard carbon anode materials can be effectively prepared. This ensures that, when used as an anode material, it enables sodium-ion batteries to exhibit excellent electrochemical performance.

[0009] Specifically, a method for preparing hard carbon anode materials using Rhizopus molds via the Maillard reaction is described. The method involves using Rhizopus mold mycelia and glucose as raw materials, mixing them with pure water, performing a hydrothermal reaction, and then carbonizing them at high temperature to form hard carbon. The method includes the following steps:

[0010] (1) Rhizopus mycelium is cleaned, dried and pulverized to obtain Rhizopus mycelium powder;

[0011] (2) Mix Rhizopus mycelium, glucose and water in a mass ratio and stir evenly. Add the mixture to a polytetrafluoroethylene hydrothermal liner and carry out a hydrothermal reaction for a certain time under certain temperature conditions. Wash and dry the product after the hydrothermal reaction to obtain a hard carbon precursor.

[0012] (3) The dried hard carbon precursor is subjected to high-temperature carbonization treatment to obtain biomass hard carbon anode material.

[0013] By adopting the above technical solution

[0014] In this invention, various elements in the culture medium of Rhizopus mycelium can be fixed, thereby increasing the content and uniform distribution of nitrogen, phosphorus, sulfur and other elements in the Rhizopus mycelium.

[0015] In this invention, the co-hydrothermal process can introduce more oxygen-containing functional groups while fixing the carbon skeleton. That is, while maintaining a good surface morphology, it can also provide more Na due to the increased number of oxygen-containing functional groups. + Adsorption sites can significantly improve the specific capacity of hard carbon materials;

[0016] This invention utilizes biomass precursors to prepare biomass hard carbon materials, achieving uniform doping of nitrogen, phosphorus, and sulfur elements. Furthermore, by controlling the preparation process conditions, the electrochemical performance of the materials can be further improved, demonstrating broad prospects for market application. At the same time, the preparation method of this invention is simple and suitable for large-scale industrial production.

[0017] The following are preferred technical solutions of the present invention:

[0018] Preferably, in step (1), the Rhizopus mycelium is obtained through Rhizopus inoculum culture. More preferably, the culture specifically includes: first, mixing 10g peptone, 10g glucose, and 1000ml water, sterilizing at high temperature to obtain a culture medium, then adding the Rhizopus inoculum to the culture medium, and culturing in a shaker at room temperature (25℃). This invention uses the hydrothermal product of Rhizopus and glucose as a matrix, which has the advantages of low cost and wide availability of raw materials.

[0019] Preferably, in step (1), the washing and drying steps involve washing with deionized water more than three times followed by freeze-drying to remove moisture, more preferably with a freeze-drying time of 24 hours, and then pulverizing into powder. More preferably, the freeze-drying temperature is -50°C.

[0020] More preferably, in step (1), the pulverized material is further subjected to sieving, preferably with a sieve mesh size of 300-800 mesh; more preferably 300 mesh.

[0021] Preferably, in step (2), the raw materials, based on the total mass of Rhizopus mycelium, glucose and water as 100%, have a mass ratio of 10-25% for Rhizopus mycelium, 10-25% for glucose and 50-80% for water; more preferably, the mass ratio of Rhizopus mycelium to glucose is 1:1.

[0022] Preferably, in step (2), the temperature condition for co-thermal heating is preferably 180~220 ℃, more preferably 200 ℃; and / or, in step (2), the time condition for co-thermal heating is preferably 8~15 h, more preferably 10~12 h.

[0023] Preferably, in step (2), the product is filtered and washed with deionized water 3-5 times, the drying temperature is 50-100℃, and the drying time is 1-12 h.

[0024] Preferably, in step (3), the dried product is ground once to pulverize it, placed in a ceramic boat, and placed in a tube furnace for high-temperature carbonization reaction.

[0025] Preferably, in step (3), the high-temperature carbonization is carried out in an inert atmosphere, wherein the inert atmosphere is at least one of nitrogen, helium, and argon.

[0026] Preferably, in step (3), the high-temperature carbonization includes two carbonization processes. In the first carbonization process, the heating rate of the calcination temperature is 2-5 ℃ / min, the calcination temperature is 700-900 ℃, and the holding time of the calcination temperature is 1-3 h; more preferably, the heating rate is 5 ℃ / min, the calcination temperature is 800 ℃, and the holding time of the calcination temperature is 2 h. This carbonization process can promote the full decomposition and cross-linking of the precursor. In the second carbonization process, the heating rate of the calcination temperature is 2-5 ℃ / min, the calcination temperature is 1000-1300 ℃, and the holding time of the calcination temperature is 1-3 h; more preferably, the heating rate is 5 ℃ / min, the calcination temperature is 1200 ℃, and the holding time of the calcination temperature is 2 h. This carbonization process can optimize the formation and ordering of the carbon structure.

[0027] Preferably, in step (3), after high-temperature carbonization, the temperature is annealed to 300°C at a cooling rate of 2-10°C / min, and then naturally cooled to room temperature.

[0028] Preferably, in step (3), the high-temperature carbonization product is further ground and sieved, preferably with a sieve mesh size of 300-800 mesh; more preferably 300 mesh.

[0029] This invention provides a biomass hard carbon anode material, wherein the biomass precursor of the biomass hard carbon anode material is a hydrothermal composite of Rhizopus mycelium and glucose. By employing this technical solution, a carbon coating with uniform thickness (e.g., 37 nm) and consistent morphology is synthesized on the surface of spherical hard carbon through the hydrothermal co-thermal formation of the composite precursor by Rhizopus and glucose. Furthermore, the Rhizopus mycelium can fix surrounding free nitrogen through nitrogen fixation, thereby achieving uniform and stable nitrogen and phosphorus doping, resulting in a biomass hard carbon anode material with uniform nitrogen and phosphorus doping, good morphological uniformity, and high initial efficiency. To date, there have been no reports in the field regarding the application of Rhizopus mycelium in the preparation of hard carbon anode materials for sodium-ion batteries. In this invention, by optimizing the process of hydrothermal co-thermal treatment with glucose, a structurally stable and high-performance hard carbon anode material was successfully prepared and synthesized at low temperatures (below 220 °C) using Rhizopus mycelium as the biomass raw material. By co-treating Rhizopus mycelia, glucose, and water in a specific ratio using hydrothermal methods, the Maillard reaction between the Rhizopus mycelia and glucose is utilized. This co-hydrothermal carbonization regulates the pore structure and interlayer spacing of hard carbon, enhancing sodium-ion diffusion kinetics. The resulting hard carbon anode material for sodium-ion batteries exhibits high specific capacity, good cycle stability, excellent rate performance, and coulombic efficiency. Therefore, the hard carbon anode material prepared by the co-hydrothermal method of Rhizopus mycelia and glucose demonstrates higher capacity, superior rate performance, and higher coulombic efficiency, providing new commercial application possibilities for sodium-ion batteries.

[0030] Compared with the prior art, the present invention has the following beneficial effects:

[0031] (1) The present invention forms a porous network structure by the Maillard reaction between Rhizopus hyphae and glucose, while traditional methods rely on the structure of the material itself. Therefore, the present invention can achieve the control and optimization of structural properties such as interlayer spacing and pore structure.

[0032] (2) The present invention uses the Maillard reaction between Rhizopus hyphae and glucose to carry out the reaction at a lower temperature and obtain a hard carbon precursor, and synthesizes a carbon coating on the surface of the hard carbon.

[0033] (3) By using Rhizopus mycelium and glucose as biomass carbon source, this invention can effectively achieve uniform and effective doping of heteroatoms such as nitrogen, phosphorus and sulfur.

[0034] The hard carbon anode material of this invention is prepared by a hydrothermal reaction of Rhizopus mycelium and glucose. After hydrothermal treatment with glucose, a hydrothermal composite precursor is formed, successfully regulating the pore structure and interlayer spacing of the hard carbon and improving sodium ion diffusion kinetics. This is beneficial for increasing the graphitization degree of the hard carbon and increasing the sodium storage sites in the material, while reducing side reactions occurring on the surface of the hard carbon material in contact with the electrolyte. Therefore, this hard carbon anode material exhibits good cycle stability, rate performance, and coulombic efficiency. The preparation method of the hard carbon anode material of this invention is simple, rapid, efficient, convenient, and under mild and easily controllable conditions. It can effectively introduce sodium-storage-enhancing heterogeneous elements into the hard carbon material, which is conducive to promoting the commercial development of hard carbon anodes for sodium-ion batteries. Attached Figure Description

[0035] Figure 1 Here is a scanning electron microscope (SEM) image of the hard carbon anode material from Example 1;

[0036] Figure 2 This is a scanning electron microscope (SEM) image of the hard carbon anode material in Comparative Example 1.

[0037] Figure 3 The elemental distribution diagram of EDS, a hard carbon anode material prepared by hydrothermal Maillard reaction of Rhizopus mycelium and glucose in Example 1;

[0038] Figure 4 Comparison of the cycling performance of the materials in Example 1 and Comparative Example 1 at a current density of 50 mA / g;

[0039] Figure 5 The images are transmission electron microscopy (TEM) images of the hard carbon anode materials of Example 1 and Comparative Example 1. Detailed Implementation

[0040] To facilitate understanding, the technical solutions and implementation methods of the present invention will be further described clearly, completely, and in detail below through specific embodiments and in conjunction with the accompanying drawings. It should be understood that the embodiments described herein are implemented based on the technical solutions of the present invention, providing detailed implementation methods and specific operating procedures, but are only some embodiments of the present invention, not all embodiments. The specific implementation methods described are limited to illustrating and explaining the present invention and do not limit the present invention. Based on the embodiments of the present invention, all other implementation methods obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0041] Unless otherwise specified, the experimental methods and conditions used in the following embodiments are conventional methods and conditions. The materials, reagents, instruments, and equipment used in the embodiments, unless otherwise specified, are all conventional substances or equipment known to those skilled in the art and are commercially available. The reaction conditions described in the invention can all achieve the reactions and obtain the desired products. Due to space limitations, only some embodiments are listed below to further illustrate the advantages of the technical solution of the present invention.

[0042] In this invention, Rhizopus mycelium is obtained through the culture of Rhizopus inoculum. Specifically, 10g of peptone, 10g of glucose, and 1000ml of water are mixed and sterilized at high temperature to form a culture medium. Then, the Rhizopus inoculum is added to the culture medium and cultured in a shaker at room temperature (25℃). After about seven days, the Rhizopus mycelium grows into spherical shapes, and the culture is complete.

[0043] Example 1

[0044] A biomass hard carbon anode material and its specific preparation steps are as follows:

[0045] (1) The cultured Rhizopus mycelium (and applicable to the following examples) was washed three times with deionized water, freeze-dried for 24 hours, pulverized into powder, and sieved through a 300-800 mesh sieve to obtain powdered mycelium precursor for use. It is preferred to sieve through a 300 mesh sieve.

[0046] (2) Mix Rhizopus mycelium, glucose and water in a mass ratio of 1:1:4 and stir well;

[0047] (3) Add the well-stirred product into a polytetrafluoroethylene liner and perform hydrothermal treatment at 200 °C for 12 h. Filter, wash, and dry the hydrothermally treated product. Preferably, wash with deionized water 3-5 times, dry at 50-100 °C for 1-12 h.

[0048] (4) Grind the dried product once, place it in a porcelain boat, put it in a tube furnace, and under the protection of argon atmosphere, raise the temperature to 800 ℃ at a rate of 5 ℃ / min, calcine at a constant temperature for 2 h, then raise the temperature to 1200 ℃ at a rate of 5 ℃ / min, calcine at a constant temperature for 2 h, then cool it to 300 ℃ at a rate of 10 ℃ / min, and then let it cool naturally to room temperature. After grinding, sieve it through a 300 mesh sieve to obtain hard carbon material.

[0049] Example 2

[0050] A biomass hard carbon anode material and its specific preparation steps are as follows:

[0051] (1) Rhizopus mycelium was washed with deionized water three times, freeze-dried for 24 h, pulverized into powder, and sieved to obtain powdered mycelium precursor for later use.

[0052] (2) Mix Rhizopus mycelium, glucose and water in a mass ratio of 1.5:1:4 and stir well;

[0053] (3) Add the well-stirred product into the polytetrafluoroethylene liner and perform hydrothermal treatment at 200 °C for 12 h. Filter, wash and dry the hydrothermally treated product.

[0054] (4) Grind the dried product once, place it in a porcelain boat, put it in a tube furnace, and under the protection of argon atmosphere, raise the temperature to 800 ℃ at a rate of 5 ℃ / min, calcine at a constant temperature for 2 h, then raise the temperature to 1200 ℃ at a rate of 5 ℃ / min, calcine at a constant temperature for 2 h, then cool it to 300 ℃ at a rate of 10 ℃ / min, and then let it cool naturally to room temperature. After grinding, sieve it through a 300 mesh sieve to obtain hard carbon material.

[0055] Example 3

[0056] A biomass hard carbon anode material and its specific preparation steps are as follows:

[0057] (1) Rhizopus mycelium was washed with deionized water three times, freeze-dried for 24 h, pulverized into powder, and sieved to obtain powdered mycelium precursor for later use.

[0058] (2) Mix Rhizopus mycelium, glucose and water in a mass ratio of 1:1.5:4 and stir well;

[0059] (3) Add the well-stirred product into the polytetrafluoroethylene liner and perform hydrothermal treatment at 180 °C for 12 h. Filter, wash and dry the hydrothermally treated product.

[0060] (4) Grind the dried product once, place it in a porcelain boat, put it in a tube furnace, and under the protection of argon atmosphere, raise the temperature to 800 ℃ at a rate of 5 ℃ / min, calcine at a constant temperature for 2 h, then raise the temperature to 1200 ℃ at a rate of 5 ℃ / min, calcine at a constant temperature for 2 h, then cool it to 300 ℃ at a rate of 10 ℃ / min, and then let it cool naturally to room temperature. After grinding, sieve it through a 300 mesh sieve to obtain hard carbon material.

[0061] Example 4

[0062] A biomass hard carbon anode material and its specific preparation steps are as follows:

[0063] (1) Rhizopus mycelium was washed with deionized water three times, freeze-dried for 24 h, pulverized into powder, and sieved to obtain powdered mycelium precursor for later use.

[0064] (2) Mix Rhizopus mycelium, glucose and water in a mass ratio of 1:2:4 and stir well;

[0065] (3) Add the well-stirred product into the polytetrafluoroethylene liner and perform hydrothermal treatment at 180 °C for 12 h. Filter, wash and dry the hydrothermally treated product.

[0066] (4) Grind the dried product once, place it in a porcelain boat, put it in a tube furnace, and under the protection of argon atmosphere, raise the temperature to 800 ℃ at a rate of 5 ℃ / min, calcine at a constant temperature for 2 h, then raise the temperature to 1200 ℃ at a rate of 5 ℃ / min, calcine at a constant temperature for 2 h, then cool it to 300 ℃ at a rate of 10 ℃ / min, and then let it cool naturally to room temperature. After grinding, sieve it through a 300 mesh sieve to obtain hard carbon material.

[0067] Example 5

[0068] A biomass hard carbon anode material and its specific preparation steps are as follows:

[0069] (1) Rhizopus mycelium was washed with deionized water three times, freeze-dried for 24 h, pulverized into powder, and sieved to obtain powdered mycelium precursor for later use.

[0070] (2) Mix Rhizopus mycelium, glucose and water in a mass ratio of 1:2:4 and stir well;

[0071] (3) Add the well-stirred product into the polytetrafluoroethylene liner and perform hydrothermal treatment at 200 °C for 12 h. Filter, wash and dry the hydrothermally treated product.

[0072] (4) Grind the dried product once, place it in a porcelain boat, put it in a tube furnace, and under the protection of argon atmosphere, raise the temperature to 800 ℃ at a rate of 5 ℃ / min, calcine at a constant temperature for 2 h, then raise the temperature to 1000 ℃ at a rate of 5 ℃ / min, calcine at a constant temperature for 2 h, then cool it to 300 ℃ at a rate of 10 ℃ / min, and then let it cool naturally to room temperature. After grinding, sieve it through a 300 mesh sieve to obtain hard carbon material.

[0073] Example 6

[0074] A biomass hard carbon anode material and its specific preparation steps are as follows:

[0075] (1) Rhizopus mycelium was washed with deionized water three times, freeze-dried for 24 h, pulverized into powder, and sieved to obtain powdered mycelium precursor for later use.

[0076] (2) Mix Rhizopus mycelium, glucose and water in a mass ratio of 1:1:4 and stir well;

[0077] (3) Add the well-stirred product into the polytetrafluoroethylene liner and perform hydrothermal treatment at 200 °C for 12 h. Filter, wash and dry the hydrothermally treated product.

[0078] (4) Grind the dried product once, place it in a porcelain boat, put it in a tube furnace, and under the protection of argon atmosphere, raise the temperature to 800 ℃ at a rate of 2 ℃ / min, calcine at a constant temperature for 2 h, then raise the temperature to 1200 ℃ at a rate of 2 ℃ / min, calcine at a constant temperature for 2 h, then cool it to 300 ℃ at a rate of 10 ℃ / min, and then let it cool naturally to room temperature. After grinding, sieve it through a 300-mesh sieve to obtain hard carbon material.

[0079] Example 7

[0080] A biomass hard carbon anode material and its specific preparation steps are as follows:

[0081] (1) Rhizopus mycelium was washed with deionized water three times, freeze-dried for 24 h, pulverized into powder, and sieved to obtain powdered mycelium precursor for later use.

[0082] (2) Mix Rhizopus mycelium, glucose and water in a mass ratio of 1:1:4 and stir well;

[0083] (3) Add the well-stirred product into the polytetrafluoroethylene liner and perform hydrothermal treatment at 200 °C for 12 h. Filter, wash and dry the hydrothermally treated product.

[0084] (4) Grind the dried product once, place it in a porcelain boat, put it in a tube furnace, and under the protection of argon atmosphere, raise the temperature to 800 ℃ at a rate of 10 ℃ / min and calcine at a constant temperature for 2 h. Then raise the temperature to 1200 ℃ at a rate of 10 ℃ / min and calcine at a constant temperature for 2 h. After that, cool the temperature to 300 ℃ at a rate of 10 ℃ / min and then let it cool naturally to room temperature. After grinding, sieve it through a 300-mesh sieve to obtain hard carbon material.

[0085] Example 8

[0086] A biomass hard carbon anode material and its specific preparation steps are as follows:

[0087] (1) Rhizopus mycelium was washed with deionized water three times, freeze-dried for 24 h, pulverized into powder, and sieved to obtain powdered mycelium precursor for later use.

[0088] (2) Mix Rhizopus mycelium, glucose and water in a mass ratio of 1:1:4 and stir well;

[0089] (3) Add the well-stirred product into the polytetrafluoroethylene liner and perform hydrothermal treatment at 200 °C for 16 h. Filter, wash and dry the hydrothermally treated product.

[0090] (4) Grind the dried product once, place it in a porcelain boat, put it in a tube furnace, and under the protection of argon atmosphere, raise the temperature to 800 ℃ at a rate of 5 ℃ / min, calcine at a constant temperature for 2 h, then raise the temperature to 1200 ℃ at a rate of 5 ℃ / min, calcine at a constant temperature for 2 h, then cool it to 300 ℃ at a rate of 10 ℃ / min, and then let it cool naturally to room temperature. After grinding, sieve it through a 300 mesh sieve to obtain hard carbon material.

[0091] Example 9

[0092] A biomass hard carbon anode material and its specific preparation steps are as follows:

[0093] (1) Rhizopus mycelium was washed with deionized water three times, freeze-dried for 24 h, pulverized into powder, and sieved to obtain powdered mycelium precursor for later use.

[0094] (2) Mix Rhizopus mycelium, glucose and water in a mass ratio of 1:1:4 and stir well;

[0095] (3) Add the well-stirred product into the polytetrafluoroethylene liner and perform hydrothermal treatment at 200 °C for 4 hours. Filter, wash and dry the hydrothermally treated product.

[0096] (4) Grind the dried product once, place it in a porcelain boat, put it in a tube furnace, and under the protection of argon atmosphere, raise the temperature to 800 ℃ at a rate of 5 ℃ / min, calcine at a constant temperature for 2 h, then raise the temperature to 1200 ℃ at a rate of 5 ℃ / min, calcine at a constant temperature for 2 h, then cool it to 300 ℃ at a rate of 10 ℃ / min, and then let it cool naturally to room temperature. After grinding, sieve it through a 300 mesh sieve to obtain hard carbon material.

[0097] Example 10

[0098] A biomass hard carbon anode material and its specific preparation steps are as follows:

[0099] (1) Rhizopus mycelium was washed with deionized water three times, freeze-dried for 24 h, pulverized into powder, and sieved to obtain powdered mycelium precursor for later use.

[0100] (2) Mix Rhizopus mycelium, glucose and water in a mass ratio of 1:1:4 and stir well;

[0101] (3) Add the well-stirred product into the polytetrafluoroethylene liner and perform hydrothermal treatment at 200 °C for 12 h. Filter, wash and dry the hydrothermally treated product.

[0102] (4) Grind the dried product once, place it in a porcelain boat, put it in a tube furnace, and under the protection of argon atmosphere, raise the temperature to 800 ℃ at a rate of 5 ℃ / min and calcine at a constant temperature for 4 h. Then raise the temperature to 1200 ℃ at a rate of 5 ℃ / min and calcine at a constant temperature for 4 h. After that, cool it to 300 ℃ at a rate of 10 ℃ / min and then let it cool naturally to room temperature. After grinding, sieve it through a 300-mesh sieve to obtain hard carbon material.

[0103] Comparative Example 1

[0104] A biomass hard carbon anode material and its specific preparation steps are as follows:

[0105] (1) Rhizopus mycelium was washed with deionized water three times, freeze-dried for 24 h, pulverized into powder, and sieved to obtain powdered mycelium precursor for later use.

[0106] (2) The dried product was ground once, placed in a porcelain boat, and placed in a tube furnace. Under the protection of argon atmosphere, the temperature was increased to 800 ℃ at a rate of 5 ℃ / min and calcined at a constant temperature for 2 h. Then, the temperature was increased to 1200 ℃ at a rate of 5 ℃ / min and calcined at a constant temperature for 2 h. After that, the temperature was cooled to 300 ℃ at a rate of 10 ℃ / min and then allowed to cool naturally to room temperature. The hard carbon material was obtained by sieving through a 300-mesh sieve after grinding.

[0107] Comparative Example 2

[0108] A biomass hard carbon anode material and its specific preparation steps are as follows:

[0109] (1) Rhizopus mycelium was washed with deionized water three times, freeze-dried for 24 h, pulverized into powder, and sieved to obtain powdered mycelium precursor for later use.

[0110] (2) The dried product was ground once, placed in a porcelain boat, and placed in a tube furnace. Under the protection of argon atmosphere, the temperature was raised to 1200 ℃ at a rate of 5 ℃ / min, and calcined at a constant temperature for 2 h. Then, it was cooled to 300 ℃ at a rate of 10 ℃ / min and then naturally cooled to room temperature. The hard carbon material was obtained by sieving through a 300-mesh sieve after grinding.

[0111] Comparative Example 3

[0112] A biomass hard carbon anode material and its specific preparation steps are as follows:

[0113] (1) Rhizopus mycelium was washed with deionized water three times, freeze-dried for 24 h, pulverized into powder, and sieved to obtain powdered mycelium precursor for later use.

[0114] (2) Mix Rhizopus mycelium, xylose and water in a mass ratio of 1:1:4 and stir well;

[0115] (3) Add the well-stirred product into the polytetrafluoroethylene liner and perform hydrothermal treatment at 200 °C for 12 h. Filter, wash and dry the hydrothermally treated product.

[0116] (4) Grind the dried product once, place it in a porcelain boat, put it in a tube furnace, and under the protection of argon atmosphere, raise the temperature to 800 ℃ at a rate of 5 ℃ / min, calcine at a constant temperature for 2 h, then raise the temperature to 1200 ℃ at a rate of 5 ℃ / min, calcine at a constant temperature for 2 h, then cool it to 300 ℃ at a rate of 10 ℃ / min, and then let it cool naturally to room temperature. After grinding, sieve it through a 300 mesh sieve to obtain hard carbon material.

[0117] Comparative Example 4

[0118] A biomass hard carbon anode material and its specific preparation steps are as follows:

[0119] (1) Rhizopus mycelium was washed with deionized water three times, freeze-dried for 24 h, pulverized into powder, and sieved to obtain powdered mycelium precursor for later use.

[0120] (2) Mix Rhizopus mycelium, chitosan and water in a mass ratio of 1:1:4 and stir until homogeneous;

[0121] (3) Add the well-stirred product into the polytetrafluoroethylene liner and perform hydrothermal treatment at 200 °C for 12 h. Filter, wash and dry the hydrothermally treated product.

[0122] (4) Grind the dried product once, place it in a porcelain boat, put it in a tube furnace, and under the protection of argon atmosphere, raise the temperature to 800 ℃ at a rate of 5 ℃ / min, calcine at a constant temperature for 2 h, then raise the temperature to 1200 ℃ at a rate of 5 ℃ / min, calcine at a constant temperature for 2 h, then cool it to 300 ℃ at a rate of 10 ℃ / min, and then let it cool naturally to room temperature. After grinding, sieve it through a 300 mesh sieve to obtain hard carbon material.

[0123] Comparative Example 5

[0124] A biomass hard carbon anode material and its specific preparation steps are as follows:

[0125] (1) Rhizopus mycelium was washed with deionized water three times, freeze-dried for 24 h, pulverized into powder, and sieved to obtain powdered mycelium precursor for later use.

[0126] (2) Mix Rhizopus mycelium, sucrose and water in a mass ratio of 1:1:4 and stir well;

[0127] (3) Add the well-stirred product into the polytetrafluoroethylene liner and perform hydrothermal treatment at 180 °C for 12 h. Filter, wash and dry the hydrothermally treated product.

[0128] (4) Grind the dried product once, place it in a porcelain boat, put it in a tube furnace, and under the protection of argon atmosphere, raise the temperature to 500 ℃ at a rate of 5 ℃ / min, calcine at a constant temperature for 2 h, then raise the temperature to 1200 ℃ at a rate of 5 ℃ / min, calcine at a constant temperature for 2 h, then cool it to 300 ℃ at a rate of 10 ℃ / min, and then let it cool naturally to room temperature. After grinding, sieve it through a 300 mesh sieve to obtain hard carbon material.

[0129] Comparative Example 6

[0130] A biomass hard carbon anode material and its specific preparation steps are as follows:

[0131] (1) Rhizopus mycelium was washed with deionized water three times, freeze-dried for 24 h, pulverized into powder, and sieved to obtain powdered mycelium precursor for later use.

[0132] (2) Mix Rhizopus mycelium, fructose and water in a mass ratio of 1:1:4 and stir well;

[0133] (3) Add the well-stirred product into the polytetrafluoroethylene liner and perform hydrothermal treatment at 200 °C for 10 h. Filter, wash and dry the hydrothermally treated product.

[0134] (4) Grind the dried product once, place it in a porcelain boat, put it in a tube furnace, and under the protection of argon atmosphere, raise the temperature to 800 ℃ at a rate of 5 ℃ / min, calcine at a constant temperature for 2 h, then raise the temperature to 1200 ℃ at a rate of 5 ℃ / min, calcine at a constant temperature for 2 h, then cool it to 300 ℃ at a rate of 10 ℃ / min, and then let it cool naturally to room temperature. After grinding, sieve it through a 300 mesh sieve to obtain hard carbon material.

[0135] Comparative Example 7

[0136] A biomass hard carbon anode material and its specific preparation steps are as follows:

[0137] (1) Rhizopus mycelium was washed with deionized water three times, freeze-dried for 24 h, pulverized into powder, and sieved to obtain powdered mycelium precursor for later use.

[0138] (2) Mix Rhizopus mycelium, glucose and water in a mass ratio of 1:1:4 and stir well;

[0139] (3) Add the well-stirred product into the polytetrafluoroethylene liner and perform hydrothermal treatment at 200 °C for 10 h. Filter, wash and dry the hydrothermally treated product.

[0140] (4) Grind the dried product once, place it in a porcelain boat, put it in a tube furnace, and under the protection of argon atmosphere, raise the temperature to 500 ℃ at a rate of 5 ℃ / min, calcine at a constant temperature for 2 h, then raise the temperature to 1200 ℃ at a rate of 5 ℃ / min, calcine at a constant temperature for 2 h, then cool it to 300 ℃ at a rate of 10 ℃ / min, and then let it cool naturally to room temperature. After grinding, sieve it through a 300 mesh sieve to obtain hard carbon material.

[0141] Comparative Example 8

[0142] A biomass hard carbon anode material and its specific preparation steps are as follows:

[0143] (1) Rhizopus mycelium was washed with deionized water three times, freeze-dried for 24 h, pulverized into powder, and sieved to obtain powdered mycelium precursor for later use.

[0144] (2) Mix Rhizopus mycelium, glucose and water in a mass ratio of 4:4:3 and stir well;

[0145] (3) Add the well-stirred product into the polytetrafluoroethylene liner and perform hydrothermal treatment at 200 °C for 10 h. Filter, wash and dry the hydrothermally treated product.

[0146] (4) Grind the dried product once, place it in a porcelain boat, put it in a tube furnace, and under the protection of argon atmosphere, raise the temperature to 800 ℃ at a rate of 5 ℃ / min, calcine at a constant temperature for 2 h, then raise the temperature to 1200 ℃ at a rate of 5 ℃ / min, calcine at a constant temperature for 2 h, then cool it to 300 ℃ at a rate of 10 ℃ / min, and then let it cool naturally to room temperature. After grinding, sieve it through a 300 mesh sieve to obtain hard carbon material.

[0147] Comparative Example 9

[0148] A biomass hard carbon anode material and its specific preparation steps are as follows:

[0149] (1) Rhizopus mycelium was washed with deionized water three times, freeze-dried for 24 h, pulverized into powder, and sieved to obtain powdered mycelium precursor for later use.

[0150] (2) Mix Rhizopus mycelium, glucose and water in a mass ratio of 1:1:4 and stir well;

[0151] (3) Add the well-stirred product into the polytetrafluoroethylene liner and perform hydrothermal treatment at 200 °C for 12 h. Filter, wash and dry the hydrothermally treated product.

[0152] (4) Grind the dried product once, place it in a porcelain boat, put it in a tube furnace, and under the protection of argon atmosphere, raise the temperature to 800 ℃ at a rate of 5 ℃ / min and calcine at a constant temperature for 2 h. Then raise the temperature to 1400 ℃ at a rate of 5 ℃ / min and calcine at a constant temperature for 2 h. After that, cool it to 300 ℃ at a rate of 10 ℃ / min and then let it cool naturally to room temperature. After grinding, sieve it through a 300-mesh sieve to obtain hard carbon material.

[0153] Comparative Example 10

[0154] A biomass hard carbon anode material and its specific preparation steps are as follows:

[0155] (1) Rhizopus mycelium was washed with deionized water three times, freeze-dried for 24 h, pulverized into powder, and sieved to obtain powdered mycelium precursor for later use.

[0156] (2) Mix Rhizopus mycelium, glucose and water in a mass ratio of 1:1:4 and stir well;

[0157] (3) Add the well-stirred product into the polytetrafluoroethylene liner and perform hydrothermal treatment at 200 °C for 12 h. Filter, wash and dry the hydrothermally treated product.

[0158] (4) Grind the dried product once, place it in a porcelain boat, put it in a tube furnace, and under the protection of argon atmosphere, raise the temperature to 500 ℃ at a rate of 5 ℃ / min and calcine at a constant temperature for 2 h. Then raise the temperature to 1400 ℃ at a rate of 5 ℃ / min and calcine at a constant temperature for 2 h. After that, cool it to 300 ℃ at a rate of 10 ℃ / min and then let it cool naturally to room temperature. After grinding, sieve it through a 300-mesh sieve to obtain hard carbon material.

[0159] Performance testing

[0160] The materials prepared in the above embodiments and comparative examples were assembled into coin half-cells for electrochemical testing. The electrolyte was 1 mol / L NaPF6 in DME = 100 vol % (DME: ethylene glycol dimethyl ether), and the separator was glass fiber Whatman GF / F. The batteries were assembled in the order of positive electrode shell, hard carbon negative electrode sheet, electrolyte, separator, sodium sheet, and negative electrode shell, and then sealed with a sealing machine. The hard carbon negative electrode sheet was prepared by adding an appropriate amount of deionized water to the Rhizopus hard carbon negative electrode material prepared in each example, conductive carbon black, and sodium carboxymethyl cellulose in a mass ratio of 8:1:1, and stirring in a homogenizer for 30 min to form a slurry. The slurry was then uniformly coated onto bright aluminum foil and vacuum dried at 80 °C for 12 h. Finally, the electrode sheet was cut into circular electrodes with a diameter of 12 mm. The active material loading of each electrode was 0.9-1.5 mg. After the batteries were allowed to stand for 24 hours, electrochemical tests were performed using the Xinwei testing system and Chenhua electrochemical workstation. Electrochemical tests were all within 30 o The test was conducted under constant temperature conditions (C), primarily involving constant current charge-discharge testing. The constant current charge-discharge test mainly included indicators such as reversible capacity, cycle life, and coulombic efficiency. The long-cycle performance of the battery was tested at a current density of 50 mA / g. The constant current charge-discharge test process was as follows: rest for 5 min - constant current discharge - rest for 5 min - constant current charge, for 50 cycles.

[0161] The specific surface area and average pore size of the materials obtained in Examples 1-10 and Comparative Examples 1-10 were tested, and the specific parameters are shown in Table 1:

[0162]

[0163] The batteries obtained in Examples 1-10 and Comparative Examples 1-10 were tested for their initial coulombic efficiency and discharge capacity after 50 cycles. This further demonstrates that the sodium-ion batteries using the hard carbon negative electrode of this application maintain a high charge-discharge capacity after cycling. See Table 2 for details.

[0164]

[0165] Figure 1 and Figure 2The images show transmission electron microscopy (SEM) images of the hard carbon anode materials prepared in Example 1 and Comparative Example 1. The SEM images demonstrate that the hard carbon materials prepared by the hydrothermal Maillard reaction of Rhizopus hyphae and glucose exhibit reduced agglomerates and more complete tubular structures. The SEM images also show that the hard carbon materials prepared by the hydrothermal Maillard reaction of Rhizopus hyphae and glucose have a more stable structure and more complete and abundant tubular structures, which is beneficial for sodium ion migration.

[0166] Figure 3 The EDS elemental distribution diagram of the hard carbon anode material shows that phosphorus can be detected in the hard carbon anode material after Rhizopus and glucose hydrothermal treatment, and the phosphorus element is relatively uniformly distributed.

[0167] Figure 4 As shown in the cycling performance diagrams of Example 1 and Comparative Example 1, the hard carbon anode material prepared by co-thermally heating Rhizopus mycelium with glucose exhibits excellent cycling performance. At a current density of 50 mA / g, the initial charging capacity is 270.19 mAh / g, the first-cycle coulombic efficiency reaches 86.97%, and after 50 cycles, the capacity retention is 96.7%. In contrast, the unmodified hard carbon anode material has a low and rapidly decaying discharge capacity, with an initial charging capacity of only 220.99 mAh / g, a first-cycle coulombic efficiency below 70%, and only 87.5% of the capacity remaining after 50 cycles. This indicates that the hard carbon material prepared by co-thermally heating Rhizopus mycelium with glucose can effectively improve the reversible sodium storage capacity and cycling stability of the material.

[0168] Figure 5 These are transmission electron microscopy (TEM) images of the hard carbon anode materials of Example 1 and Comparative Example 1. Figure 5 The TEM image shows that a carbon layer of about 37 nm is generated on the surface of the hard carbon material prepared by hydrothermal Maillard reaction of Rhizopus hyphae and glucose, which makes the hard carbon structure more stable and facilitates the migration of sodium ions.

[0169] This application presents a sodium-ion battery hard carbon anode material prepared using a hydrothermal technique involving Rhizopus mycelium and glucose. This material possesses more sodium storage sites, and the hard carbon anode prepared from it exhibits low impedance and excellent cycle and rate performance. It shows broad application prospects in small mobile electronic devices, electric vehicles, solar power generation, and aerospace.

[0170] The embodiments described above are merely preferred embodiments of the present invention and are not intended to limit the present invention in any way. Other variations and modifications may be made without departing from the technical solutions described in the claims.

Claims

1. A method for preparing hard carbon anode materials using Rhizopus molds via Maillard reaction, characterized in that, The preparation method involves a co-hydrothermal reaction of Rhizopus mycelium and glucose as raw materials. The reaction product is then subjected to a high-temperature carbonization reaction to obtain a hard carbon anode material. In the co-hydrothermal reaction, based on the total mass of Rhizopus mycelium, glucose, and water as 100%, the mass percentages of Rhizopus mycelium, glucose, and water are 10-25%, 10-25%, and 50-80%, respectively. The temperature in the co-hydrothermal reaction is 180-220℃, and the time is 8-15 h. The high-temperature carbonization reaction includes two carbonization processes: the first carbonization process has a heating rate of 2-5℃ / min, a calcination temperature of 700-900℃, and a holding time of 1-3 h; the second carbonization process has a heating rate of 2-5℃ / min, a calcination temperature of 1000-1300℃, and a holding time of 1-3 h.

2. The method for preparing hard carbon anode materials by synthesizing Rhizopus using the Maillard reaction according to claim 1, characterized in that, The Rhizopus mycelium was cleaned, dried, and pulverized.

3. The method for preparing hard carbon anode materials by synthesizing Rhizopus using the Maillard reaction according to claim 1, characterized in that, The mass ratio of Rhizopus mycelium to glucose is 1:

1.

4. The method for preparing hard carbon anode material by synthesizing Rhizopus using Maillard reaction according to claim 1, characterized in that, In the aforementioned hydrothermal reaction, the temperature is 200℃ and the time is 10~12 h; the heating rate of the first carbonization process is 5 ℃ / min, the calcination temperature is 800 ℃, and the holding time is 2 h; the heating rate of the second carbonization process is 5 ℃ / min, the calcination temperature is 1200 ℃, and the holding time is 2 h.

5. The method for preparing hard carbon anode material by synthesizing Rhizopus using Maillard reaction according to claim 1, characterized in that, After the hydrothermal reaction, the product is washed, dried and pulverized, and then subjected to a high-temperature carbonization reaction under an inert atmosphere.

6. The method for preparing hard carbon anode material by synthesizing Rhizopus using Maillard reaction according to claim 1, characterized in that, After high-temperature carbonization, the temperature is annealed to 300℃ at a cooling rate of 2-10℃ / min, and then naturally cooled to room temperature.

7. The method for preparing hard carbon anode material by synthesizing Rhizopus using Maillard reaction according to claim 1, characterized in that, Specifically, the following steps are included: (1) Rhizopus mycelium is cleaned, dried and pulverized to obtain Rhizopus mycelium powder; (2) Rhizopus mycelial powder, glucose and water were subjected to a co-hydrothermal reaction at 180~220 ℃ for 8~15 h. The reaction product after hydrothermal reaction was washed, dried and pulverized. The drying temperature was 50-100 ℃ and the time was 1-12 h. (3) The product is subjected to high-temperature carbonization treatment. First, the first stage of carbonization treatment is carried out with a heating rate of 2-5 ℃ / min, a calcination temperature of 700-900 ℃, and a holding time of 1-3 h. Then, the second stage of carbonization treatment is carried out with a heating rate of 2-5 ℃ / min, a calcination temperature of 1000-1300 ℃, and a holding time of 1-3 h to obtain hard carbon anode material.

8. A hard carbon anode material synthesized by Maillard reaction from Rhizopus prepared by the preparation method according to any one of claims 1-7.

9. The application of a hard carbon anode material synthesized by the Rhizopus fungus according to claim 8 using the Maillard reaction in the field of sodium-ion batteries.

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