Method for preparing anthracite-based amorphous carbon negative electrode material through self-template pre-carbonization, product and application

Abstract

The invention belongs to the technical field of sodium ion battery negative electrode materials, and discloses a method for preparing an anthracite-based amorphous carbon negative electrode material through self-template pre-carbonization, a product and application, anthracite powder with an average particle size of less than 1 [mu] m and zinc gluconate are ground and uniformly mixed to obtain mixed powder; the mixed powder is subjected to pre-carbonization treatment in protective gas at the temperature of 200-500 DEG C, and intermediate powder is obtained; purifying the intermediate powder by acid pickling, washing with water, and drying to obtain purified intermediate powder; and carbonizing the purified intermediate powder under protective gas at 1000-1500 DEG C to obtain the amorphous carbon negative electrode material. The amorphous carbon negative electrode material with high capacity and excellent rate capability and cycle performance is obtained by using the anthracite with the average particle size of less than 1 [mu] m as a carbon source and zinc gluconate as a self-sacrifice template and optimizing the microstructure of the anthracite-based precursor, and the preparation method is simple in process and suitable for large-scale production.

Description

Technical Field

[0001] This invention belongs to the technical field of sodium-ion battery anode materials, specifically relating to a method, product, and application of preparing anthracite-based amorphous carbon anode materials by self-templating pre-carbonization. Background Technology

[0002] With the increasing depletion of fossil fuels and the rapid growth of global energy demand, the development of efficient and sustainable new energy systems is of paramount importance. Lithium-ion batteries, with their advantages of low self-discharge rate, no memory effect, stable output voltage, high energy density, and environmental friendliness, have already achieved large-scale application in portable electronic devices. However, due to the scarcity and uneven distribution of lithium resources, lithium-ion batteries cannot meet people's energy needs, prompting researchers to turn their attention to new battery technologies with greater potential for sustainable development. Sodium-ion batteries, with their advantages of low cost, abundant resources, and high safety, are expected to be applied in large-scale energy storage devices and low-speed electric vehicles, becoming an important supplement to the lithium battery system.

[0003] In sodium-ion battery research, the performance of electrode materials directly affects the battery's electrochemical performance, such as energy density, cycle stability, and rate performance. In recent years, significant progress has been made in improving the energy density and optimizing the structural stability of cathode materials. However, the development of high-performance anode materials has become a bottleneck restricting the development of sodium-ion battery technology. Based on different sodium storage mechanisms, anode materials can be classified into four categories: alloy materials, organic compounds, conversion electrode materials, and intercalation electrode materials. Alloy electrode materials rely on alloying reactions to generate intermetallic compounds, achieving reversible sodium ion storage. They have the advantage of high theoretical specific capacity; however, during charge and discharge, the material volume expands severely, and the electrode is prone to pulverization, resulting in poor rate performance and cycle stability. Organic compounds have advantages such as sustainable resources and flexible structures, but their intrinsic conductivity is poor. In practical applications, they rely on the use of a high proportion of conductive agents, leading to severe electrolyte side reactions and low initial coulombic efficiency. The sodium storage mechanism of conversion electrode materials is based on multi-electron transfer reactions, involving the formation of new compounds in the main lattice, usually accompanied by sodium ion intercalation and alloying synergistic effects. Because a single atom can transfer multiple electrons, such anode materials exhibit a significant theoretical specific capacity advantage. However, their practical application is limited by drawbacks such as poor conductivity and significant volume changes. Typical intercalated electrode materials, such as carbon materials, have attracted widespread attention from researchers due to their advantages of low redox potential, high conductivity, and low cost. Graphite, as a commercial anode material for lithium-ion batteries, can balance electrochemical performance such as energy density, power density, and cycle life, while also possessing advantages such as wide availability of raw materials and simple preparation methods. However, the thermodynamic instability and narrow interlayer spacing of Na-C intercalated compounds result in poor sodium storage performance of graphite, with a specific capacity of approximately 35 mAh·g. -1However, amorphous carbon materials cannot be directly applied to sodium-ion batteries. In contrast, amorphous carbon materials with larger interlayer spacing, more defect content, and higher microstructural disorder have better sodium storage performance. Therefore, the preparation of high-performance, low-cost amorphous carbon anode materials is a key breakthrough for reducing costs and increasing efficiency in sodium-ion batteries.

[0004] Anthracite, as a natural mineral, is abundant and exhibits excellent carbon precursor characteristics due to its high carbonization yield and low ash content. However, during high-temperature carbonization, the aromatic structure of anthracite undergoes directional and orderly rearrangement, resulting in narrower interlayer spacing and a significant tendency towards soft carbonization. This leads to a low intrinsic sodium storage capacity in anthracite-based carbon materials, which cannot meet the needs of practical applications. Common modification methods include heteroatom doping and pre-oxidation, but these methods not only involve complex preparation processes, but the finished products often fail to simultaneously improve the charge-discharge ramp capacity and maintain a high initial coulombic efficiency. Therefore, developing anthracite-based carbon materials with high sodium storage capacity to meet practical application requirements is of great significance. Summary of the Invention

[0005] To address the problems of numerous and complex preparation steps in existing technologies, and the inability to simultaneously achieve high charge-discharge ramp capacity and high initial coulombic efficiency in the finished product, this invention provides a method and product for preparing anthracite-based amorphous carbon anode materials through self-template pre-carbonization. By optimizing the microstructure, an amorphous carbon anode material with high capacity, excellent rate performance, and superior cycle performance is obtained.

[0006] To achieve the above-mentioned objectives, the technical solution adopted by the present invention is as follows:

[0007] A method for preparing anthracite-based amorphous carbon anode materials by self-templating pre-carbonization includes the following process steps:

[0008] (1) Grind and mix anthracite powder with an average particle size of less than 1 μm with zinc gluconate to obtain a mixed powder;

[0009] (2) The mixed powder is pre-carbonized in a protective gas at 200~500℃ to obtain intermediate powder;

[0010] (3) The intermediate powder is purified by acid washing, and then washed with water and dried to obtain the purified intermediate powder;

[0011] (4) The purified intermediate powder is carbonized at 1000~1500℃ under a protective gas to obtain amorphous carbon anode material.

[0012] In the above-mentioned carbon anode material preparation method, anthracite powder is used as raw material and zinc gluconate is used as a self-sacrificing template. The template effect of zinc gluconate, as well as its multiple functions such as catalysis, activation, and carbon source, are used to effectively regulate the microstructure of the anthracite precursor.

[0013] In step (1), the anthracite is subjected to impurity removal and grinding to obtain pure anthracite powder with an average particle size Z-Average of less than 1 μm. Preferably, the average particle size of the anthracite powder in step (1) is 200~500 nm, so as to facilitate uniform mixing with zinc gluconate and increase the contact area between the two materials. At the same time, the smaller particle size can also improve the reactivity of the anthracite powder during pre-carbonization treatment. Furthermore, subsequent steps do not require grinding operations to maintain the average particle size of the material basically below 1 μm. In addition, even if the average particle size of the material increases after high-temperature carbonization, it can still be kept below 1 μm. The mass ratio of the anthracite powder to zinc gluconate is 1:(0.1~2). By changing the mass ratio of the anthracite powder to zinc gluconate, the microstructure of the amorphous carbon material can be adjusted.

[0014] In step (2), the pre-carbonization step is beneficial for forming a structurally stable intermediate powder before high-temperature carbonization. The zinc gluconate has multiple effects in the pre-carbonization process: First, the solid products generated by decomposition play a space-occupying role, leaving abundant pores (similar to a hard template) after acid washing; Second, the gaseous products generated by decomposition have an activating effect on the carbon matrix, and the gas escape can also form slit-type pores, further increasing the active surface of the carbon material; Third, the zinc oxide generated by decomposition has a catalytic graphitization effect on the adjacent carbon matrix, that is, it promotes the rearrangement of the surrounding carbon matrix and the formation of graphite microcrystals; Fourth, the carbon contained in zinc gluconate itself can act as a carbon source, and together with anthracite carbon, it forms an amorphous carbon material with a complex microstructure.

[0015] In the specific implementation, the pre-carbonization time is 1~3 hours. The average particle size Z-Average of the intermediate powder obtained by pre-carbonization is in the range of 700~1000 nm.

[0016] In step (3), the washing step after pre-carbonization can avoid the continuous catalytic graphitization of the carbon matrix by zinc gluconate during the subsequent carbonization process, and prevent excessive growth of graphite microdomains.

[0017] In the specific implementation, the acid used for pickling is hydrochloric acid or sulfuric acid, with a pH value below 1. The pickling time is 1-24 hours. In the specific implementation process, the intermediate powder is first placed in an acid solution for ultrasonic cleaning, and then transferred to a 60-80℃ water bath for magnetic stirring. Water washing is required until the pH of the washing solution is neutral (pH≈7). Drying removes moisture from the surface of the intermediate powder, and conventional drying methods can be used. After washing to remove zinc gluconate, the average particle size (Z-Average) of the intermediate powder is 450-550 nm.

[0018] In step (4), amorphous carbon is obtained by high-temperature carbonization. The carbonization time is 1~5h. The average particle size Z-Average of the finally obtained amorphous carbon anode material is 600~800 nm.

[0019] In steps (2) and (4) above, the heating rate during the carbonization process in steps (2) and (4) is the same or different, both being 0.5~10℃ / min. The protective gas used in the carbonization process in steps (2) and (4) is the same, both being argon.

[0020] This invention also provides a product, which is an anthracite-based amorphous carbon anode material prepared by the above method. The anthracite-based amorphous carbon anode material prepared by the method of this invention has an average particle size of 600~800 nm and a specific surface area of ​​20~50 m². 2 ·g -1 Under 0.1C electrochemical testing conditions, the initial discharge capacity reaches 377.3 mAh·g. -1 The initial charge capacity can reach 313.2 mAh·g. -1 The coulombic efficiency is 83%; therefore, the anthracite-based amorphous carbon anode material prepared by this method has a suitable microstructure; electrochemical tests show that the material has advantages such as high capacity, excellent rate performance and cycle performance, and is expected to have further application prospects in the field of sodium-ion batteries.

[0021] The reason why no other excipients are needed in this invention is that, as described above, the solid product zinc oxide catalyzes graphitization of adjacent carbon, promoting the growth of local graphite microcrystals in the pre-carbonized material. This change does not change with acid washing and water washing, but the shear force generated by grinding will seriously affect the microstructure of the material. This invention selects to control the average particle size of anthracite powder to below 1 μm before pre-carbonization, ensuring that the average particle size of the intermediates and the final product during the carbonization process is below 1 μm. This guarantees that the material after pre-carbonization with zinc salt-promoted catalytic graphitization can be directly carbonized at high temperature without grinding, avoiding changes in the material's microstructure caused by grinding during the two carbonization processes. Therefore, under the synergistic regulation of the multiple effects of zinc gluconate in this invention, the final anthracite-based amorphous carbon anode material has high microcrystalline disorder, high defect content, and large specific surface area, providing more sodium storage active sites. Therefore, its electrochemical performance, such as specific capacity, rate performance, and cycle stability, is excellent.

[0022] This invention also provides the application of the anthracite-based amorphous carbon anode material prepared by the above method in the preparation of sodium-ion batteries.

[0023] Compared with the prior art, the technical solution of the present invention has the following beneficial technical effects:

[0024] (1) This invention uses anthracite with an average particle size of less than 1 μm as a carbon source and zinc gluconate as a template. The solid pyrolysis products of zinc gluconate and zinc gluconate have a space occupation effect that can form closed pores. In addition, the gas products during pyrolysis can activate and create pores in the carbon material. The solid product zinc oxide also has a catalytic graphitization effect on the adjacent carbon, which can promote the growth of local graphite microcrystals. Under the synergistic regulation of the above-mentioned multiple effects, the microcrystal disorder of the anthracite-based carbon material is high, the defect content is high, and the specific surface area is large, which can provide more sodium storage active sites. Therefore, its electrochemical performance such as specific capacity, rate performance and cycle stability is excellent.

[0025] (2) The preparation method of the present invention is simple and does not require the addition of other auxiliary materials. Only the substrate ground to an average particle size of less than 1 μm and zinc gluconate are pre-carbonized and carbonized to control the microstructure of the amorphous carbon anode material, thereby improving the specific capacity, rate performance and cycle stability of the material. This greatly simplifies the preparation process and production efficiency, and has the potential for large-scale production.

[0026] (3) The microstructure characterization of the anthracite-based amorphous carbon anode material provided by the present invention confirms that the carbon material prepared by this method has a high degree of structural disorder, a large amount of defect content and a large specific surface area. Thanks to the suitable microstructure, electrochemical tests show that the specific capacity, rate performance and cycle stability of the electrode material have also been greatly improved. Attached Figure Description

[0027] Figure 1 These are the XRD diffraction patterns of the intermediate powders prepared after pre-carbonization in Example 3 and Comparative Example 1.

[0028] Figure 2 This is the SEM image of the intermediate powder prepared after pre-carbonization in Example 3 at a magnification of 5000x.

[0029] Figure 3 This is the SEM image of the intermediate powder prepared after pre-carbonization in Comparative Example 1 at a magnification of 5000x.

[0030] Figure 4 These are the XRD diffraction patterns of the anthracite-based amorphous carbon anode materials prepared in Example 3, Comparative Example 1, and Comparative Example 2.

[0031] Figure 5 These are the nitrogen adsorption-desorption curves and pore size distribution curves of the anthracite-based amorphous carbon anode material prepared in Example 3.

[0032] Figure 6 The images show the RAMAN spectra of the anthracite-based amorphous carbon anode materials prepared in Examples 3, 1, and 2.

[0033] Figure 7 The first three cycles of constant current charge-discharge curves of the anthracite-based amorphous carbon anode material prepared in Example 1 at a rate of 0.1C are shown.

[0034] Figure 8 The rate performance of the anthracite-based amorphous carbon anode material prepared in Example 1 was tested at current densities of 0.1C, 0.2C, 0.5C, 1C, 2C, 5C, 10C, and 0.2C.

[0035] Figure 9 This is a graph showing the long-cycle performance of the anthracite-based amorphous carbon anode material prepared in Example 1 at a high rate of 10C. Detailed Implementation

[0036] The following examples further illustrate the preparation of anthracite-based amorphous carbon anode material by self-templating pre-carbonization, as provided by the present invention. It should be noted that the following examples are only for further illustration and should not be construed as limiting the scope of protection of the present invention. Any non-essential improvements and adjustments made by those skilled in the art based on the above description of the invention are still within the scope of protection of the present invention.

[0037] The anthracite raw material used was produced in Hunyuan County, Datong City, Shanxi Province; zinc gluconate was purchased from Shandong Keyuan Biochemical Co., Ltd.; and nano zinc oxide was purchased from Shanghai Aladdin Biochemical Technology Co., Ltd.

[0038] The electrode materials prepared in the following examples were all assembled into CR2032 coin cells and then subjected to electrochemical testing. The separator was made of glass fiber (Whatman, GF / D), the electrolyte was 1 mole of sodium hexafluorophosphate (NaPF6) dissolved in 1 liter of ethylene glycol dimethyl ether (DME), and the counter electrode was metallic sodium. The active material loading in this invention was 1-2 mg.

[0039] Example 1

[0040] This embodiment provides a method for preparing anthracite-based amorphous carbon anode materials by self-templating pre-carbonization, including the following steps:

[0041] (1) The anthracite was cleaned and ball-milled to obtain pure anthracite powder with an average particle size of 200~500 nm; then the pure anthracite powder and zinc gluconate (particle size 50~200 μm) were ground in an agate mortar for 0.5 h at a mass ratio of 1:1 to obtain mixed powder.

[0042] (2) Transfer the mixed powder to an alumina crucible, and then place it in a tube furnace under argon protection at 5℃·min. -1The temperature was increased to 450℃ at a certain rate and held for 1 hour. After the temperature inside the furnace cooled naturally to room temperature, the argon gas was stopped, and the powder in the crucible was removed to obtain intermediate powder.

[0043] (3) The intermediate powder was ultrasonically cleaned with 5% HCl solution for 1 hour and then transferred to a 70°C water bath and magnetically stirred for 12 hours to remove residual zinc gluconate. It was then centrifuged and washed with deionized water until the solution pH was neutral, and then dried at 120°C for 12 hours before use.

[0044] (4) The dried intermediate powder is put back into the crucible and heated in a tube furnace filled with argon at 5°C·min. -1 The temperature is raised to 1300℃ and held for 2 hours. After the temperature inside the furnace cools naturally to room temperature, the amorphous carbon anode material is obtained.

[0045] Example 2

[0046] This embodiment provides a method for preparing anthracite-based amorphous carbon anode materials by self-templating pre-carbonization, including the following steps:

[0047] (1) The anthracite was cleaned and ball-milled to obtain pure anthracite powder with an average particle size of 200~500 nm; then the pure anthracite powder and zinc gluconate (particle size 50~200 μm) were ground in an agate mortar for 0.5 h at a mass ratio of 1:1 to obtain mixed powder.

[0048] (2) Transfer the mixed powder to an alumina crucible, and then place it in a tube furnace under argon protection at 5℃·min. -1 The temperature was increased to 450℃ at a certain rate and held for 1 hour. After the temperature inside the furnace cooled naturally to room temperature, the argon gas was stopped, and the powder in the crucible was removed to obtain intermediate powder.

[0049] (3) The intermediate powder was ultrasonically cleaned with 5% HCl solution for 1 hour and then transferred to a 70°C water bath and magnetically stirred for 12 hours to remove residual zinc gluconate. It was then centrifuged and washed with deionized water until the solution pH was neutral, and then dried at 120°C for 12 hours before use.

[0050] (4) The dried intermediate powder is put back into the crucible and heated in a tube furnace filled with argon at 5°C·min. -1 The temperature is raised to 1000℃ at a heating rate and held for 2 hours. After the temperature inside the furnace cools naturally to room temperature, the amorphous carbon anode material is obtained.

[0051] Example 3

[0052] This embodiment provides a method for preparing anthracite-based amorphous carbon anode materials by self-templating pre-carbonization, including the following steps:

[0053] (1) The anthracite was cleaned and ball-milled to obtain pure anthracite powder with an average particle size of 200~500 nm; then the pure anthracite powder and zinc gluconate (particle size 50~200 μm) were ground in an agate mortar for 0.5 h at a mass ratio of 1:1 to obtain mixed powder.

[0054] (2) Transfer the mixed powder to an alumina crucible, and then place it in a tube furnace under argon protection at 5℃·min. -1 The temperature was increased to 450℃ at a heating rate and held for 1 hour. After the temperature inside the furnace cooled naturally to room temperature, the argon gas was stopped, and the powder in the crucible was removed to obtain intermediate powder.

[0055] (3) The intermediate powder was ultrasonically cleaned with 5% HCl solution for 1 hour and then transferred to a 70°C water bath and magnetically stirred for 12 hours to remove residual zinc gluconate. It was then centrifuged and washed with deionized water until the solution pH was neutral, and then dried at 120°C for 12 hours before use.

[0056] (4) The dried intermediate powder is put back into the crucible and heated in a tube furnace filled with argon at 5°C·min. -1 The temperature was raised to 1100℃ and held for 2 hours. After the temperature inside the furnace cooled naturally to room temperature, the amorphous carbon anode material was obtained, denoted as ZGWYM.

[0057] Example 4

[0058] This embodiment provides a method for preparing anthracite-based amorphous carbon anode materials by self-templating pre-carbonization, including the following process steps:

[0059] (1) The anthracite was cleaned and ball-milled to obtain pure anthracite powder with an average particle size of 200~500 nm; then the pure anthracite powder and zinc gluconate (particle size 50~200 μm) were ground in an agate mortar for 0.5 h at a mass ratio of 1:1 to obtain mixed powder.

[0060] (2) Transfer the mixed powder to an alumina crucible, and then place it in a tube furnace under argon protection at 5℃·min. -1 The temperature was increased to 450℃ at a certain rate and held for 2 hours. After the temperature inside the furnace cooled naturally to room temperature, the argon gas was stopped, and the powder in the crucible was removed to obtain intermediate powder.

[0061] (3) The intermediate powder was ultrasonically cleaned with 5% HCl solution for 1 hour and then transferred to a 70°C water bath and magnetically stirred for 12 hours to remove residual zinc gluconate. It was then centrifuged and washed with deionized water until the solution pH was neutral, and then dried at 120°C for 12 hours before use.

[0062] (4) The dried intermediate powder is put back into the crucible and heated in a tube furnace filled with argon at 5°C·min. -1 The temperature is raised to 1200℃ and held for 2 hours. After the temperature inside the furnace cools naturally to room temperature, the amorphous carbon anode material is obtained.

[0063] Example 5

[0064] This embodiment provides a method for preparing anthracite-based amorphous carbon anode materials by self-templating pre-carbonization, including the following steps:

[0065] (1) The anthracite was cleaned and ball-milled to obtain pure anthracite powder with an average particle size of 200~500 nm; then the pure anthracite powder and zinc gluconate (particle size 50~200μm) were ground in an agate mortar at a mass ratio of 1:1 for 0.5 h to obtain mixed powder.

[0066] (2) Transfer the mixed powder to an alumina crucible, and then place it in a tube furnace under argon protection at 5℃·min. -1 The temperature was increased to 450℃ at a certain rate and held for 1 hour. After the temperature inside the furnace cooled naturally to room temperature, the argon gas was stopped, and the powder in the crucible was removed to obtain intermediate powder.

[0067] (3) The intermediate powder was ultrasonically cleaned with 5% HCl solution for 1 hour and then transferred to a 70°C water bath and magnetically stirred for 12 hours to remove residual zinc gluconate. It was then centrifuged and washed with deionized water until the solution pH was neutral, and then dried at 120°C for 12 hours before use.

[0068] (4) The dried intermediate powder is put back into the crucible and heated in a tube furnace filled with argon at 5°C·min. -1 The temperature was raised to 1400℃ and held for 2 hours. After the temperature inside the furnace cooled naturally to room temperature, the amorphous carbon anode material was obtained.

[0069] Example 6

[0070] This embodiment provides a method for preparing anthracite-based amorphous carbon anode materials by self-templating pre-carbonization, including the following steps:

[0071] (1) The anthracite was cleaned and ball-milled to obtain pure anthracite powder with an average particle size of 200~500 nm; then the pure anthracite powder and zinc gluconate (particle size 50~200μm) were ground in an agate mortar at a mass ratio of 1:1 for 0.5 h to obtain mixed powder.

[0072] (2) Transfer the mixed powder to an alumina crucible, and then place it in a tube furnace under argon protection at 5℃·min. -1The temperature was increased to 450℃ at a certain rate and held for 1 hour. After the temperature inside the furnace cooled naturally to room temperature, the argon gas was stopped, and the powder in the crucible was removed to obtain intermediate powder.

[0073] (3) The intermediate powder was ultrasonically cleaned with 5% HCl solution for 1 hour and then transferred to a 70°C water bath and magnetically stirred for 12 hours to remove residual zinc gluconate. It was then centrifuged and washed with deionized water until the solution pH was neutral, and then dried at 120°C for 12 hours before use.

[0074] (4) The dried intermediate powder is put back into the crucible and heated in a tube furnace filled with argon at 5°C·min. -1 The temperature is raised to 1500℃ and held for 2 hours. After the temperature inside the furnace cools naturally to room temperature, the amorphous carbon anode material is obtained.

[0075] Example 7

[0076] This embodiment provides a method for preparing anthracite-based amorphous carbon anode materials by self-templating pre-carbonization, including the following steps:

[0077] (1) The anthracite was cleaned and ball-milled to obtain pure anthracite powder with an average particle size of 200~500 nm; then the pure anthracite powder and zinc gluconate (particle size 50~200μm) were ground in an agate mortar for 0.5 h at a mass ratio of 1:0.1 to obtain mixed powder.

[0078] (2) Transfer the mixed powder to an alumina crucible, and then place it in a tube furnace under argon protection at 0.5℃·min. -1 The temperature was increased to 200℃ at a certain rate and held for 3 hours. After the temperature inside the furnace cooled naturally to room temperature, the argon gas was stopped, and the powder in the crucible was removed to obtain intermediate powder.

[0079] (3) The intermediate powder was ultrasonically cleaned with 5% sulfuric acid solution for 2 hours and then transferred to an 80°C water bath and magnetically stirred for 6 hours to remove residual zinc gluconate. It was then centrifuged and washed with deionized water until the solution pH was neutral, and then dried at 120°C for 12 hours before use.

[0080] (4) The dried intermediate powder is put back into the crucible and heated in a tube furnace filled with argon at 5°C·min. -1 The temperature is raised to 1000℃ at a heating rate and held for 5 hours. After the temperature inside the furnace cools naturally to room temperature, the amorphous carbon anode material is obtained.

[0081] Example 8

[0082] This embodiment provides a method for preparing anthracite-based amorphous carbon anode materials by self-templating pre-carbonization, including the following steps:

[0083] (1) The anthracite was cleaned and ball-milled to obtain pure anthracite powder with an average particle size of 200~500 nm; then the pure anthracite powder and zinc gluconate (particle size 50~200μm) were ground in an agate mortar for 0.5 h at a mass ratio of 1:2 to obtain mixed powder.

[0084] (2) Transfer the mixed powder to an alumina crucible, and then place it in a tube furnace under argon protection at 5℃·min. -1 The temperature was increased to 500℃ at a certain rate and held for 1 hour. After the temperature inside the furnace cooled naturally to room temperature, the argon gas was stopped, and the powder in the crucible was removed to obtain intermediate powder.

[0085] (3) The intermediate powder was ultrasonically cleaned with 5% HCl solution for 1 hour and then transferred to a 60℃ water bath and magnetically stirred for 20 hours to remove residual zinc gluconate. It was then centrifuged and washed with deionized water until the solution pH was neutral, and then dried at 120℃ for 12 hours before use.

[0086] (4) The dried intermediate powder is put back into the crucible and heated in a tube furnace filled with argon at 10 °C·min. -1 The temperature is raised to 1500℃ and held for 1 hour. After the temperature inside the furnace cools naturally to room temperature, the amorphous carbon anode material is obtained.

[0087] Comparative Example 1

[0088] This comparative example provides a method for preparing anthracite-based amorphous carbon anode materials, including the following steps:

[0089] (1) The anthracite was cleaned and ball-milled to obtain pure anthracite powder with an average particle size of 200~500 nm; then the pure anthracite powder and nano zinc oxide powder (particle size 30±10 nm) were ground in an agate mortar for 0.5 h at a mass ratio of 1:1 to obtain mixed powder.

[0090] (2) Transfer the mixed powder to an alumina crucible, and then place it in a tube furnace under argon protection at 5℃·min. -1 The temperature was increased to 450℃ at a certain rate and held for 1 hour. After the temperature inside the furnace cooled naturally to room temperature, the argon gas was stopped, and the powder in the crucible was removed to obtain intermediate powder.

[0091] (3) The intermediate powder was ultrasonically cleaned with 5% HCl solution for 1 hour and then transferred to a 70°C water bath and magnetically stirred for 12 hours to remove residual nano zinc oxide. It was then centrifuged and washed with deionized water until the solution pH was neutral, and then dried at 120°C for 12 hours before use.

[0092] (4) The dried intermediate powder is put back into the crucible and heated in a tube furnace filled with argon at 5°C·min. -1The temperature was raised to 1100℃ and held for 2 hours. After the temperature inside the furnace cooled naturally to room temperature, the amorphous carbon anode material, denoted as ZOWYM, was obtained.

[0093] Comparative Example 2

[0094] This comparative example provides a method for preparing anthracite-based amorphous carbon anode materials, including the following steps:

[0095] (1) The anthracite was cleaned and ball-milled to obtain pure anthracite powder with an average particle size of 200~500 nm; then the pure anthracite powder and zinc gluconate (particle size 50~200 μm) were ground in an agate mortar for 0.5 h at a mass ratio of 1:1 to obtain mixed powder.

[0096] (2) Transfer the mixed powder to an alumina crucible, and then place it in a tube furnace under argon protection at 5℃·min. -1 The temperature was increased to 1100℃ at a rising rate and held for 2 hours. After the temperature inside the furnace cooled naturally to room temperature, the argon gas was stopped and the powder in the crucible was removed.

[0097] (3) The powder in the crucible was ultrasonically cleaned with 5% HCl solution for 1 hour and then transferred to a 70°C water bath and magnetically stirred for 12 hours to remove residual zinc gluconate. Then it was centrifuged and washed with deionized water until the solution pH was neutral. Finally, it was dried at 120°C for 12 hours to obtain the amorphous carbon anode material, denoted as ZGWYM-DH.

[0098] Application Example 1

[0099] The battery was prepared using the amorphous carbon anode material obtained in Example 1, as follows:

[0100] The amorphous carbon anode material obtained in Example 1, conductive carbon (Super Pli), and binder (PVDF) were mixed in a mass ratio of 90:5:5 and dissolved in N-methylpyrrolidone (NMP) to obtain an active material slurry with a solid content of 35-45%. The obtained active material slurry was then uniformly coated on copper foil (the active material loading was 1-2 mg), dried, and cut into 14 mm round pieces. The pieces were then assembled into CR2032 coin cells in a glove box protected by high-purity argon gas and left to stand for 8 hours to obtain the battery.

[0101] Application Example 2

[0102] In this application example, the amorphous carbon anode material obtained in Example 2 is used to prepare the battery, and the method is as follows:

[0103] The amorphous carbon anode material obtained in Example 2, conductive carbon (Super Pli), and binder (PVDF) were mixed in a mass ratio of 90:5:5 and dissolved in N-methylpyrrolidone (NMP) to obtain an active material slurry with a solid content of 35-45%. The obtained active material slurry (with an active material loading of 1-2 mg) was then uniformly coated on copper foil, dried, and cut into 14 mm round pieces. The pieces were then assembled into CR2032 coin cells in a glove box protected by high-purity argon gas and left to stand for 8 hours to obtain the battery.

[0104] Application Example 3

[0105] In this application example, the amorphous carbon anode material obtained in Example 3 is used to prepare the battery, and the method is as follows:

[0106] The amorphous carbon anode material obtained in Example 3, conductive carbon (Super Pli), and binder (PVDF) were mixed in a mass ratio of 90:5:5 and dissolved in N-methylpyrrolidone (NMP) to obtain an active material slurry with a solid content of 35-45%. The obtained active material slurry was then uniformly coated on copper foil (the active material loading was 1-2 mg), dried, and cut into 14 mm round pieces. The pieces were then assembled into CR2032 coin cells in a glove box protected by high-purity argon gas and left to stand for 8 hours to obtain the battery.

[0107] Application Example 4

[0108] In this application example, the amorphous carbon anode material obtained in Example 4 is used to prepare the battery, and the method is as follows:

[0109] The amorphous carbon anode material obtained in Example 4, conductive carbon (Super Pli), and binder (PVDF) were mixed in a mass ratio of 90:5:5 and dissolved in N-methylpyrrolidone (NMP) to obtain an active material slurry with a solid content of 35-45%. The obtained active material slurry was then uniformly coated on copper foil (the active material loading was 1-2 mg), dried, and cut into 14 mm round pieces. The pieces were then assembled into CR2032 coin cells in a glove box protected by high-purity argon gas and left to stand for 8 hours to obtain the battery.

[0110] Application Example 5

[0111] In this application example, the amorphous carbon anode material obtained in Example 5 is used to prepare the battery, and the method is as follows:

[0112] The amorphous carbon anode material obtained in Example 5, conductive carbon (Super Pli), and binder (PVDF) were mixed in a mass ratio of 90:5:5 and dissolved in N-methylpyrrolidone (NMP) to obtain an active material slurry with a solid content of 35-45%. The obtained active material slurry was then uniformly coated on copper foil (the active material loading was 1-2 mg), dried, and cut into 14 mm round pieces. The pieces were then assembled into CR2032 coin cells in a glove box protected by high-purity argon gas and left to stand for 8 hours to obtain the battery.

[0113] Application Example 6

[0114] In this application example, the amorphous carbon anode material obtained in Example 6 is used to prepare the battery, and the method is as follows:

[0115] The amorphous carbon anode material obtained in Example 6, conductive carbon (Super Pli), and binder (PVDF) were mixed in a mass ratio of 90:5:5 and dissolved in N-methylpyrrolidone (NMP) to obtain an active material slurry with a solid content of 35-45%. The obtained active material slurry was then uniformly coated on copper foil (the active material loading was 1-2 mg), dried, and cut into 14 mm round pieces. The pieces were then assembled into CR2032 coin cells in a glove box protected by high-purity argon gas and left to stand for 8 hours to obtain the battery.

[0116] Comparative Application Example 1

[0117] In this application example, the amorphous carbon anode material obtained in Comparative Example 1 is used to prepare the battery, and the method is as follows:

[0118] The amorphous carbon anode material obtained in Comparative Example 1, conductive carbon (Super P li), and binder (PVDF) were mixed in a mass ratio of 90:5:5 and dissolved in N-methylpyrrolidone (NMP) to obtain an active material slurry with a solid content of 35-45%. The obtained active material slurry was then uniformly coated on copper foil (the active material loading was 1-2 mg), dried, and cut into 14 mm round pieces. The pieces were then assembled into CR2032 coin cells in a glove box protected by high-purity argon gas and left to stand for 8 hours to obtain the battery.

[0119] Comparative Application Example 2

[0120] In this application example, the amorphous carbon anode material obtained in Comparative Example 2 is used to prepare the battery, and the method is as follows:

[0121] The amorphous carbon anode material obtained in Comparative Example 2, conductive carbon (Super P li), and binder (PVDF) were mixed in a mass ratio of 90:5:5 and dissolved in N-methylpyrrolidone (NMP) to obtain an active material slurry with a solid content of 35-45%. The obtained active material slurry was then uniformly coated on copper foil (the active material loading was 1-2 mg), dried, and cut into 14 mm round pieces. The pieces were then assembled into CR2032 coin cells in a glove box protected by high-purity argon gas and left to stand for 8 hours to obtain the battery.

[0122] (I) Structural Analysis

[0123] The XRD diffraction and SEM results of the intermediate powder obtained in Example 3 and Comparative Example 1 are as follows: Figure 1 , Figure 2 and Figure 3 As shown. The XRD diffraction and RAMAN test results of the amorphous carbon anode materials obtained in Example 3, Comparative Example 1, and Comparative Example 2 are respectively shown in the figures. Figure 4 and Figure 6 As shown. The nitrogen adsorption / desorption and pore size distribution test results of the carbon anode material obtained in Example 3 are as follows. Figure 5 .

[0124] Depend on Figure 1 It can be seen that the intermediate powder obtained in Example 3 can be observed to have the characteristic diffraction peak of graphene near 2θ=26°; the diffraction peaks of the intermediate powder obtained in Comparative Example 1 at 2θ=31.77°, 34.42°, 36.25°, 47.54°, 56.60°, 62.86°, 67.96° and 69.10° correspond to the (100), (002), (101), (102), (110), (103), (112) and (201) crystal planes of ZnO crystal (JCPDS no. 36-1451). It can be seen that in Example 3, the zinc gluconate template and the anthracite precursor have undergone a relatively violent reaction. The characteristic peak of zinc oxide produced by the decomposition of zinc gluconate is relatively broad, indicating its amorphous characteristics. In addition, the ZGWYM-ZJT sample (i.e. the intermediate powder of Example 3) shows a diffraction peak signal at 26° that corresponds well with the characteristic peak of graphene (002), and a typical amorphous carbon material broad diffraction peak appears near 23°, indicating that the unique microstructure of the ZGWYM sample has been initially formed.

[0125] Depend on Figure 2It is known that the gaseous products generated by the heating of zinc gluconate have an etching effect on the carbon matrix, resulting in a rough and uneven surface of the anthracite flakes, with protrusions and edges. Furthermore, the smooth zinc gluconate solid decomposition products are interspersed with the rough anthracite flakes, effectively regulating the microstructure and morphology of the carbon material. However, if nano-zinc oxide is used directly as a template, the SEM test of the intermediate after pre-carbonization... Figure 3 This indicates that a large number of fine zinc oxide particles are aggregated on the surface of the anthracite matrix, as shown by XRD analysis. Figure 1 The diffraction pattern of the intermediate (ZOWYM-ZJT sample curve) shows obvious ZnO diffraction peaks, with only weak carbon diffraction peaks around 26°. This indicates that the ZnO clusters almost completely encapsulate the anthracite flakes, resulting in a weak control effect of commercially available zinc oxide templates on carbon structure and morphology.

[0126] Figure 4 It can be observed that the three materials prepared in Example 1, Comparative Example 1, and Comparative Example 2 all exhibit broad diffraction peaks around 23°, consistent with the diffraction characteristics of amorphous carbon materials. Simultaneously, a sharp small peak appears at 26°, corresponding well to the (002) diffraction peak of graphene. This is attributed to the diffraction signal of graphite microcrystals in the structure, confirming that ZnO has a catalytic graphitization effect on the adjacent carbon matrix during high-temperature carbonization. Furthermore, the residual carbon from zinc gluconate in Example 3, after high-temperature carbonization, together with the anthracite carbon matrix, constitutes an amorphous carbon material with a complex microstructure; therefore, the ZGWYM material exhibits the highest microstructural disorder.

[0127] Figure 5 The specific surface area of ​​the ZGWYM electrode material was tested, and the results showed that the specific surface area of ​​the electrode material prepared in Example 3 was 44.85 m². 2 ·g -1 The specific capacity is greater than that of Comparative Examples 1 and 2. This is because zinc gluconate produces a variety of gaseous products during in-situ thermal decomposition, which have an activating effect on adjacent carbons. Furthermore, the gas escape can generate a large number of pores, thus providing more active sites for sodium storage. As a result, its specific capacity and rate performance are also superior.

[0128] Figure 6 These are Raman spectra of different amorphous carbon anode materials. The results show that the amorphous carbon anode material prepared using zinc gluconate as a template (Example 3) has a higher strength than I. D / I GThe value was 1.73, higher than that of Comparative Examples 1 and 2. Meanwhile, the pseudographite microdomain size of the amorphous carbon anode material prepared in Example 3 was also smaller than that of Comparative Examples 1 and 2, indicating that it had the highest microstructural disorder and local defect content, which is beneficial for increasing sodium ion storage active sites and rapid sodium ion storage behavior. The reason for the larger pseudographite microdomain size in Comparative Example 2 is that the pre-carbonization treatment step and the corresponding hydrochloric acid cleaning step were omitted in Comparative Example 2. The zinc oxide generated from the decomposition of zinc gluconate from the template continuously catalyzed the graphitization of the carbon matrix throughout the carbonization process, resulting in well-developed graphite microdomains and a reduced degree of disorder in the microstructure of the carbon material.

[0129] (II) Electrochemical Testing

[0130] The electrochemical performance of the batteries obtained in each application example was tested separately.

[0131] The electrochemical testing method is as follows: the battery charge / discharge voltage range is set to 0.001-2.5V, 0.1C (i.e., 30mA·g). -1 The charge and discharge capacity measured at the current density is used to evaluate the charge and discharge performance of the material. The rate performance of the material is evaluated by changing the current density to conduct charge and discharge tests (the current density is continuously increased from 0.1C to 10C, and finally returned to 0.2C).

[0132] The battery obtained from Example 1 was tested for its constant current charge / discharge performance in the first three cycles, rate performance at different current densities, and long-cycle performance at high rates, as shown below. Figure 7 , Figure 8 and Figure 9 As shown.

[0133] The specific capacity and initial coulombic efficiency test results of the batteries obtained from each application example are shown in Table 1.

[0134] Table 1 Electrochemical Test Results

[0135]

[0136] Depend on Figure 7 It can be seen that its initial discharge capacity is 377.3 mAh·g. -1 The initial charge capacity is 313.2 mAh·g. -1 The coulombic efficiency was 83%, and the charge-discharge curves of the second and third cycles almost overlapped, indicating that the electrode material has high sodium storage reversibility. Figure 8 and Figure 9 It can be seen that when the current density increases to 10C, its reversible specific capacity can still maintain 241.3 mAh·g. -1 Even after 100 cycles at a high rate of 10C, it still retains 220mAh·g. -1The specific capacity and capacity retention rate reached 95.3%. These test results confirm that the carbon material prepared by the self-template pre-carbonization strategy in Example 1 has excellent electrochemical performance and great application prospects.

[0137] Furthermore, as shown in the electrochemical test results table, within the temperature range studied in this invention, the specific capacity and initial coulombic efficiency first increase and then decrease, reaching a peak at 1300℃, proving that 1300℃ is the optimal preparation temperature. Moreover, at a high rate of 10C, the specific capacity of the battery obtained in Example 3 is 189.1 mAh·g. -1 This is higher than that of Comparative Application Example 1 (139.0 mAh·g). -1 ) and Comparative Application Example 2 (132.0 mAh·g) -1 This confirms the effectiveness of the zinc gluconate self-templating stepwise carbonization strategy in improving material properties.

Claims

1. A method for preparing anthracite-based amorphous carbon anode materials by self-templating pre-carbonization, characterized in that, Includes the following steps: (1) Grind and mix anthracite powder with an average particle size of less than 1 μm with zinc gluconate to obtain a mixed powder; (2) The mixed powder is pre-carbonized in a protective gas at 200~500℃ to obtain intermediate powder; (3) The intermediate powder is purified by acid washing, and then washed with water and dried to obtain the purified intermediate powder; (4) The purified intermediate powder is carbonized at 1000~1500℃ under a protective gas to obtain amorphous carbon anode material.

2. The method for preparing anthracite-based amorphous carbon anode materials by self-templating pre-carbonization according to claim 1, characterized in that, In step (1), the average particle size of the anthracite powder is 200~500 nm.

3. The method for preparing anthracite-based amorphous carbon anode materials by self-templating pre-carbonization according to claim 1 or 2, characterized in that, In step (1), the mass ratio of the anthracite powder to zinc gluconate is 1:(0.1~2).

4. The method for preparing anthracite-based amorphous carbon anode materials by self-templating pre-carbonization according to claim 1, characterized in that, In step (2), the pre-carbonization time is 1~3h; the average particle size of the intermediate powder obtained by pre-carbonization is in the range of 700~1000 nm.

5. The method for preparing anthracite-based amorphous carbon anode materials by self-templating pre-carbonization according to claim 1, characterized in that, In step (3), the acid used for pickling is hydrochloric acid or sulfuric acid with a pH value below 1, and the pickling time is 1 to 24 hours; the water washing needs to be done until the pH of the washing solution is neutral; the average particle size of the purified intermediate powder is 450 to 550 nm.

6. The method for preparing anthracite-based amorphous carbon anode materials by self-templating pre-carbonization according to claim 1, characterized in that, In step (4), the carbonization time is 1~5h; the average particle size of the resulting amorphous carbon anode material is 600~800 nm.

7. The method for preparing anthracite-based amorphous carbon anode materials by self-templating pre-carbonization according to claim 1, characterized in that, In both steps (2) and (4), argon is used as the protective gas during the carbonization process.

8. A product characterized in that, The anthracite-based amorphous carbon anode material prepared using the method described in any one of claims 1 to 7.

9. The application of the anthracite-based amorphous carbon anode material prepared by the method according to any one of claims 1 to 7 in the preparation of sodium-ion batteries.

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