Method for preparing sodium-ion battery negative electrode material by regulating and controlling hard carbon structure through chemical treatment of biomass precursor

Abstract

The invention belongs to the field of sodium ion secondary batteries, and particularly relates to a method for preparing a sodium ion battery negative electrode material by regulating and controlling a hard carbon structure through a chemical treatment biomass precursor. The preparation method comprises the following steps: firstly, carrying out pretreatment such as washing and drying on biomass to remove surface impurities, then obtaining a pretreated material by adopting a chemical treatment method, and finally, carrying out high-temperature carbonization in a nitrogen atmosphere to obtain the hard carbon material with good stability. Under the current density of 20 mA g <-1 >, the prepared hard carbon material has high specific capacity, the maximum specific capacity can reach 365 mAh g <-1 > or above, and after 2000 cycles under the current density of 1A g <-1 >, the capacity retention rate is still kept 89% or above. In addition, biomass is used as a precursor, raw materials are easy to obtain, cost is low, the preparation process is simple and easy to implement, efficiency is high, and comprehensive utilization of biomass waste is achieved.

Description

Technical Field

[0001] The present invention belongs to the field of sodium ion secondary batteries, and specifically relates to a preparation method for a sodium ion battery negative electrode material by regulating the hard carbon structure of a chemically treated biomass precursor. The structure of the biomass precursor is regulated by chemical treatment to construct a highly disordered hard carbon for use as a sodium ion battery negative electrode material. Technical Background

[0002] Due to the widespread distribution of sodium resources and the ease of extraction, as well as their similar physical and chemical properties to lithium, sodium-ion batteries (SIBs) have become the most promising next-generation energy storage batteries. Compared to lithium-ion batteries, SIBs offer improved safety, low-temperature performance, and rate capability, enabling them to maintain normal operating capabilities even under harsher operating conditions. However, due to their large ionic radius, sodium ions cannot embed between graphite layers to form a stable thermodynamic structure, leading to the need to develop carbon materials with larger interlayer spacing and greater disorder to provide reversible active sites for sodium ions.

[0003] As a difficult-to-graphitize carbon material, hard carbon has a suitable interlayer spacing and rich surface functional groups, which can provide more storage sites for sodium ions. At present, the commonly used hard carbon precursors are coal-based, asphalt-based and biomass. Biomass materials have become the most ideal and economical choice for hard carbon precursors due to their wide distribution and abundant resources. Studies have found that some metal salts (ZnCl2, AlCl3, LiCl, CaCl2, etc.) can simply and efficiently adjust the components in the precursor and then accurately construct hard carbon materials with large interlayer spacing and high disorder. In addition, the advantages of biomass such as wide distribution and easy collection also make it have huge industrialization potential. Therefore, the use of chemical treatment methods to pretreat biomass to prepare hard carbon negative electrode materials for sodium ion batteries has important research significance to solve the problems of high price and environmental pollution in traditional carbon material preparation methods.

[0004] Patent publication number CN118545702A proposes a method for preparing hard carbon, a negative electrode active material, and a sodium-ion battery. Lignin, a soft template, and a hard template are mixed and ball-milled to obtain a mixture. The mixture is then subjected to a first carbonization treatment in a first protective atmosphere to obtain a composite material. The composite material is then subjected to a second carbonization treatment in a second protective atmosphere to obtain a hard carbon material. This method utilizes a mixture of lignin and a template, ball-milled, and then carbonized twice to obtain the hard carbon material. However, the process requires the use of a template and two carbonizations at high temperatures, resulting in a lengthy and relatively high cost.

[0005] Patent publication number CN118343754A proposes a hard carbon material and its preparation method. By controlling key parameters during the carbonization process, the self-activation of the hard carbon precursor can be achieved without the addition of an activator. This method achieves excellent self-activation and improves the electrochemical performance of the hard carbon material. However, relying on CO2 / H2O activation generated by the precursor itself prevents precise control of the hard carbon interlayer spacing and lacks chemical pretreatment, resulting in limited sodium ion embedding sites. While self-activation is achieved, it requires strict control of multiple parameters during the carbonization process, primarily addressing the activation issue. Summary of the Invention

[0006] In response to the current problems of low capacity and unsatisfactory rate performance of hard carbon negative electrodes for sodium ion batteries, the purpose of the present invention is to provide a preparation method for chemically treating biomass precursors to regulate the hard carbon structure for use as a negative electrode material for sodium ion batteries. The biomass precursor is modified by a rapid chemical method to obtain a hard carbon negative electrode material for sodium ion batteries with good electrochemical properties (such as high capacity, high rate, low cost, and environmental friendliness). The prepared hard carbon material sodium ion battery negative electrode has a high specific capacity and excellent rate performance.

[0007] In order to achieve the above object, the present invention adopts the following technical solutions:

[0008] A preparation method for regulating the hard carbon structure of a chemically treated biomass precursor for use as a negative electrode material for sodium ion batteries comprises the following steps: first, pretreating the biomass to remove surface impurities; then, chemical treatment and a carbonization step are performed to obtain a biomass-derived hard carbon negative electrode material with good electrochemical properties.

[0009] The method for preparing a chemically treated biomass precursor to regulate a hard carbon structure for use as a negative electrode material for sodium ion batteries comprises the following steps:

[0010] (1) The pretreatment includes washing, drying, and crushing. The biomass precursor is ultrasonically washed with deionized water and anhydrous ethanol for 0.5 to 2 hours respectively to remove impurities on the surface of the material. After the ultrasonication is completed, the material is placed in a blast drying oven and dried at 60°C to 80°C for 6 to 12 hours. The dried material is placed in a crusher and crushed to obtain powder;

[0011] (2) placing the powder crushed in step (1) in a beaker, adding a metal salt aqueous solution to soak, stirring at room temperature, filtering, washing, and drying; heating to 1200-1400° C. in a tubular furnace for high-temperature calcination, the calcination time is constant at a temperature of 2-4 hours, and the tubular furnace is cooled to room temperature to obtain biomass-derived hard carbon.

[0012] The method for preparing a sodium ion battery negative electrode material by regulating a hard carbon structure using a chemically treated biomass precursor, wherein in step (2), the solid-liquid ratio of the crushed powder to the metal salt aqueous solution is 1:20-30, the powder after grinding is 30-50 mesh, and the concentration of the metal salt aqueous solution is 0.5-6 mol / L.

[0013] The method for preparing a sodium ion battery negative electrode material by regulating a hard carbon structure using a chemically treated biomass precursor comprises the following steps: in step (2), the stirring temperature is room temperature, and the reaction time is 6 to 24 hours.

[0014] In the preparation method of the chemically treated biomass precursor to regulate the hard carbon structure for use as a negative electrode material for sodium ion batteries, in step (2), the protective gas in the tubular furnace is nitrogen.

[0015] The method for preparing a sodium ion battery negative electrode material by regulating a hard carbon structure using a chemically treated biomass precursor, wherein in step (2), the heating rate is 10°C / min below 1000°C and 5°C / min above 1000°C.

[0016] The method for preparing a chemically treated biomass precursor to regulate a hard carbon structure for use as a negative electrode material for a sodium ion battery, wherein in step (2), the aqueous metal salt solution is an aqueous solution of ZnCl2, AlCl3, LiCl or CaCl2, and the 002 interlayer spacing of the obtained precursor-derived hard carbon material is 0.375 to 0.410 nm, and the pore size range of the closed pores formed by using the metal salt as a pore-forming agent is 0.5 to 4.0 nm.

[0017] The invention discloses a preparation method for sodium ion battery negative electrode material by regulating hard carbon structure through chemical treatment of biomass precursor, wherein the biomass precursor is lotus stem, bamboo powder or gourd shell.

[0018] The design idea of ​​the present invention is:

[0019] This method uses biomass precursors, pre-treating them with solutions such as ZnCl2, AlCl3, LiCl, and CaCl2, followed by a carbonization step. Chemical etching allows for direct structural control, eliminating the need for templates and post-processing, simplifying the process and reducing costs. This chemical pre-treatment method eliminates the need for complex extraction processes, reduces the use of chemical reagents, and is more environmentally friendly. Furthermore, by controlling key factors such as solution concentration, immersion time, and carbonization temperature, the hard carbon material structure can be effectively manipulated, improving its performance.

[0020] The present invention can effectively regulate the structure of biomass precursors through the synergistic effect of solution pretreatment pore formation and graphite crucible high-temperature carbonization, promote the formation of a larger interlayer spacing (>0.375nm), pore structure and higher disorder in hard carbon materials, and provide more storage sites and faster transmission channels for sodium ions, thereby significantly improving the specific capacity and rate performance of the material, with a capacity retention rate of more than 89% after 2000 cycles.

[0021] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0022] The present invention provides a chemical pretreatment-plus-one-step carbonization method with a short reaction time to produce biomass-derived hard carbon materials with excellent electrochemical properties. This method uses readily available, low-cost, simple, and efficient precursors such as lotus stems, bamboo powder, and gourd shells. Furthermore, the method requires no templates or surfactants, enabling the comprehensive utilization of biomass waste.

[0023] 2. The biomass-based hard carbon negative electrode material prepared by the method of the present invention effectively reduces the specific surface area, increases the interlayer spacing of the carbon layer, increases the disorder of the material, and forms more closed pore structures, which is conducive to the insertion and extraction of sodium ions.

[0024] 3. The sodium ion battery assembled with biomass-derived hard carbon prepared by the present invention has excellent electrochemical performance. -1 At a current density of 1.5 GHz, the prepared hard carbon material has a high specific capacity, with a maximum specific capacity of 365 mAh g -1 Above 1A g -1 After 2000 cycles at a current density of 1.5 GHz, the capacity retention rate still remains above 89%. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 The embodiment is to regulate the hard carbon structure as the negative electrode material of sodium ion battery at 0-2.5V and 20mA g with different zinc chloride solution concentrations. -1 Charge and discharge curves at current density.

[0026] Figure 2 The embodiment is to regulate the hard carbon structure as the negative electrode material of sodium ion battery at 0-2.5V and 1A g with different zinc chloride concentrations. -1 Long cycle diagram at current density of .

[0027] Figure 3 The following are transmission electron micrographs of the hard carbon structure used as a negative electrode material for sodium ion batteries using different zinc chloride concentrations in the embodiment. (a) Before immersion, (b) After immersion.

[0028] Figure 4This is an embodiment of the Raman map of different zinc chloride concentrations to regulate the hard carbon structure and chemical treatment to regulate the hard carbon structure as a negative electrode material for sodium ion batteries.

[0029] Figure 5 This is an X-ray diffraction pattern of the hard carbon structure as the negative electrode material of the sodium ion battery under different zinc chloride concentrations in the embodiment.

[0030] Figure 6 This is a graph showing the rate performance of a hard carbon structure as a negative electrode material for sodium ion batteries at different current densities in the range of 0 to 2.5 V using different zinc chloride concentrations. DETAILED DESCRIPTION

[0031] In a specific implementation process, the present invention first pre-treats the biomass by washing and drying to remove surface impurities, then chemically treats the biomass to obtain a pre-treated material, and finally carbonizes the material at high temperature in a nitrogen atmosphere to obtain a hard carbon material with good stability. The pre-treatment comprises washing, drying, and crushing. The biomass is ultrasonically washed with deionized water and anhydrous ethanol for 0.5 to 2 hours, respectively, to remove impurities on the surface of the material. After the ultrasonication is completed, the biomass is placed in a forced air drying oven and dried at 60°C to 80°C for 6 to 12 hours. The dried material is then placed in a crusher and crushed to obtain a powder with a particle size of 30 to 50 mesh.

[0032] The present invention will be described in further detail below with reference to examples and drawings, but the embodiments of the present invention are not limited thereto.

[0033] Example 1: Lotus stem as precursor

[0034] In this embodiment, a chemical pretreatment method for regulating hard carbon structure to achieve the preparation and application of high-performance sodium ion battery energy storage materials includes the following steps:

[0035] S1: Soak 4 g of carbon source precursor lotus stems with a particle size of 30-50 mesh in 100 ml of 2 mol / L ZnCl2 aqueous solution and place in a beaker and stir at room temperature for 12 h.

[0036] S2: The obtained material is carried in a graphite crucible and carbonized at 1300°C in a nitrogen (N2) atmosphere (the heating rate is 10°C / min below 1000°C and 5°C / min above 1000°C) for 3 hours to obtain a hard carbon material regulated by chemical pretreatment.

[0037] S3: Thoroughly grind the carbonized powder and mix the hard carbon, conductive carbon black, and sodium carboxymethyl cellulose in a mass ratio of 80:10:10. Grind the resulting mixture thoroughly in a mortar and pestle. Add an appropriate amount of deionized water using a pipette and grind again to obtain a uniform slurry. Apply the slurry to aluminum foil. Place the slurry in a vacuum drying oven at 90°C for 12 hours to allow the solvent to completely evaporate. Then, use a cutting machine (MSK-T10) to cut the slurry into 10 mm diameter circular pieces. These pieces are weighed and the calculated active material mass is 0.8-0.9 mg.

[0038] In this embodiment, the lotus stem is the stem of the lotus, and its main components are cellulose, hemicellulose and lignin. These components can be converted into hard carbon materials during high-temperature carbonization, providing good electrochemical properties for the negative electrode material of sodium ion batteries.

[0039] Electrochemical performance test of the chemically pretreated hard carbon material prepared in this example:

[0040] Sodium metal was used as the counter electrode, the electrolyte was a 1 mol / L NaPF6 solution in diethylene glycol dimethyl ether (DEGDME), and the separator was a glass fiber (GF / C). CR2032 button cells were assembled in a glove box filled with argon (Ar). The charge and discharge performance tests were carried out using the battery testing system of Shenzhen Newwell Electronics Co., Ltd.

[0041] like Figure 1 As shown in the figure, immersion in 2 mol / L ZnCl2 aqueous solution for 12 h has an obvious effect on the capacity change of hard carbon.

[0042] like Figure 2 As shown, among the hard carbon materials regulated by different aqueous solutions, the 2 mol / L ZnCl2 aqueous solution has the best capacity retention rate after immersion for 12 h.

[0043] like Figure 3-Figure 5 As shown in the figure, immersion in 2 mol / L ZnCl2 aqueous solution for 12 h significantly changed the interlayer spacing and disorder of hard carbon.

[0044] like Figure 6 As shown in the figure, the hard carbon material controlled by immersing in 2 mol / L ZnCl2 aqueous solution for 12 h has good rate performance.

[0045] In this example, a stem-derived hard carbon material was obtained by controlling the carbon source component of the precursor with a ZnCl2 aqueous solution to obtain a 002 interlayer spacing of 0.386 to 0.410 nm. Transmission images show that the stem-derived hard carbon prepared using this method has a high degree of disorder and a large number of closed pores, which effectively allows sodium ions to be inserted and removed, ultimately obtaining a hard carbon negative electrode material for sodium ion batteries with high capacity, high rate, and excellent cycle performance.-1 At a current density of 1.5 GHz, the prepared hard carbon material has a high specific capacity, with a maximum specific capacity of 379.8 mAh g -1 , at 1A g -1 After 2000 cycles at a current density of , the capacity retention rate can reach 93.2%.

[0046] Example 2: Bamboo powder as precursor

[0047] In this embodiment, a chemical pretreatment method for regulating hard carbon structure to achieve the preparation and application of high-performance sodium ion battery energy storage materials includes the following steps:

[0048] S1: Soak 4 g of carbon source precursor bamboo powder with a particle size of 30-50 mesh in 100 ml of 1.5 mol / L AlCl3 aqueous solution and place it in a beaker and stir at room temperature for 24 h.

[0049] S2: The obtained material is carried in a graphite crucible and carbonized at 1200°C in a nitrogen (N2) atmosphere (the heating rate is 10°C / min below 1000°C and 5°C / min above 1000°C) for 4 hours to obtain a hard carbon material regulated by chemical pretreatment.

[0050] S3: Thoroughly grind the carbonized powder and mix the hard carbon, conductive carbon black, and sodium carboxymethyl cellulose in a mass ratio of 75:15:10. Grind the resulting mixture thoroughly in a mortar and pestle. Add an appropriate amount of deionized water using a pipette and grind again to obtain a uniform slurry. Apply the slurry to aluminum foil. Place the slurry in a vacuum drying oven at 90°C for 12 hours to allow the solvent to completely evaporate. Then, use a cutting machine (MSK-T10) to cut the slurry into 10 mm diameter circular pieces. These pieces are weighed and the calculated active material mass is 0.8-0.9 mg.

[0051] In this embodiment, bamboo powder is a powdery substance obtained after processing bamboo. Its main components include cellulose, hemicellulose and lignin. These components can be converted into hard carbon materials during high-temperature carbonization, providing good electrochemical properties for sodium ion battery negative electrode materials.

[0052] The electrochemical performance test of the chemically pretreated hard carbon material prepared in this example was conducted by using sodium metal as the counter electrode, a 1 mol / L NaPF6 solution of diethylene glycol dimethyl ether (DEGDME) as the electrolyte, and a glass fiber (GF / C) separator. CR2032 button cells were assembled in a glove box filled with argon (Ar) and the charge and discharge performance was tested using the battery test system of Shenzhen Newwell Electronics Co., Ltd. -1 At a current density of 1.5 GHz, the prepared hard carbon material has a high specific capacity, with a maximum specific capacity of 391.6 mAh g-1 , at 1A g -1 After 2000 cycles at a current density of 1.5 GHz, the capacity retention rate can reach 90.1%. In addition, the hard carbon layer spacing of the prepared hard carbon material is 0.378 to 0.405 nm.

[0053] Example 3: Gourd shell as precursor

[0054] In this embodiment, a chemical pretreatment method for regulating hard carbon structure to achieve the preparation and application of high-performance sodium ion battery energy storage materials includes the following steps:

[0055] S1: 4 g of gourd shell (carbon source precursor) with a particle size of 30-50 mesh was soaked in 100 ml of 3 mol / L LiCl aqueous solution and placed in a beaker and stirred at room temperature for 6 h.

[0056] S2: The obtained material is carried in a graphite crucible and carbonized at 1400°C in a nitrogen (N2) atmosphere (the heating rate is 10°C / min below 1000°C and 5°C / min above 1000°C) for 2 hours to obtain a hard carbon material regulated by chemical pretreatment.

[0057] S3: Thoroughly grind the carbonized powder and mix the hard carbon, conductive carbon black, and sodium carboxymethyl cellulose in a mass ratio of 85:10:5. Grind the resulting mixture thoroughly in a mortar and pestle. Add an appropriate amount of deionized water using a pipette and grind again to obtain a uniform slurry. Apply the slurry to aluminum foil. Place the slurry in a vacuum drying oven at 90°C for 12 hours to allow the solvent to completely evaporate. Then, use a cutting machine (MSK-T10) to cut the slurry into 10 mm diameter circular pieces. These pieces are weighed and the calculated active material mass is 0.8-0.9 mg.

[0058] In this embodiment, the main components of gourd shell are cellulose, hemicellulose and lignin, which can be converted into hard carbon materials during high-temperature carbonization, providing good electrochemical properties for sodium ion battery negative electrode materials.

[0059] The electrochemical performance test of the chemically pretreated hard carbon material prepared in this example was conducted by using sodium metal as the counter electrode, a 1 mol / L NaPF6 solution of diethylene glycol dimethyl ether (DEGDME) as the electrolyte, and a glass fiber (GF / C) separator. CR2032 button cells were assembled in a glove box filled with argon (Ar) and the charge and discharge performance was tested using the battery test system of Shenzhen Newwell Electronics Co., Ltd. -1 At a current density of 1.5 GHz, the prepared hard carbon material has a high specific capacity, with a maximum specific capacity of 365.2 mAh g -1 , at 1A g -1After 2000 cycles at a current density of 1.5 GHz, the capacity retention rate can reach 89.9%. In addition, the hard carbon layer spacing of the prepared hard carbon material is 0.376 to 0.402 nm.

[0060] The results show that the chemical pretreatment method used in the present invention is simpler to operate and can significantly improve the specific capacity and cycle stability of hard carbon materials. -1 At a current density of 365 mAh g -1 The reversible capacity above 1A g -1 After 2000 cycles at a current density of 1.5 GHz, the capacity retention rate still reaches more than 89%.

[0061] The above embodiments are preferred implementation modes of the present invention, but the implementation modes of the present invention are not limited to the above embodiments. Any other changes, modifications, substitutions, combinations, and simplifications made without departing from the spirit and principles of the present invention should be considered as equivalent replacement methods and are included in the scope of protection of the present invention.

Claims

1. A method for preparing a chemically treated biomass precursor to control a hard carbon structure for use as a negative electrode material for sodium ion batteries, characterized in that: First, the biomass is pretreated to remove surface impurities; Then, through chemical treatment and a one-step carbonization method, a biomass-derived hard carbon anode material with good electrochemical performance is obtained.

2. The method for preparing a chemically treated biomass precursor to control a hard carbon structure for use as a negative electrode material for sodium ion batteries according to claim 1, characterized in that: The steps include: (1) The pretreatment includes washing, drying, and crushing. The biomass precursor is ultrasonically washed with deionized water and anhydrous ethanol for 0.5 to 2 hours respectively to remove impurities on the surface of the material. After the ultrasonication is completed, the material is placed in a blast drying oven and dried at 60°C to 80°C for 6 to 12 hours. The dried material is placed in a crusher and crushed to obtain powder; (2) placing the powder crushed in step (1) in a beaker, adding a metal salt aqueous solution to soak, stirring at room temperature, filtering, washing, and drying; heating to 1200-1400° C. in a tubular furnace for high-temperature calcination, the calcination time is constant at a temperature of 2-4 hours, and the tubular furnace is cooled to room temperature to obtain biomass-derived hard carbon.

3. The method for preparing a chemically treated biomass precursor to control a hard carbon structure for use as a negative electrode material for sodium ion batteries according to claim 2, characterized in that: In step (2), the solid-liquid ratio of the crushed powder to the metal salt aqueous solution is 1:20-30, the powder after grinding is 30-50 mesh, and the concentration of the metal salt aqueous solution is 0.5-6 mol / L.

4. The method for preparing a chemically treated biomass precursor to control a hard carbon structure for use as a negative electrode material for sodium ion batteries according to claim 2, characterized in that: In step (2), the stirring temperature is room temperature and the reaction time is 6 to 24 hours.

5. The method for preparing a chemically treated biomass precursor to control a hard carbon structure for use as a negative electrode material for sodium ion batteries according to claim 2, characterized in that: In step (2), the protective gas in the tubular furnace is nitrogen.

6. The method for preparing a chemically treated biomass precursor to control a hard carbon structure for use as a negative electrode material for sodium ion batteries according to claim 2, characterized in that: In step (2), the heating rate is 10°C / min below 1000°C and 5°C / min above 1000°C.

7. The method for preparing a chemically treated biomass precursor to control a hard carbon structure for use as a negative electrode material for sodium ion batteries according to claim 2, characterized in that: In step (2), the metal salt aqueous solution is an aqueous solution of ZnCl2, AlCl3, LiCl or CaCl2, and the 002 interlayer spacing of the precursor-derived hard carbon material is obtained to be 0.375 to 0.410 nm, and the pore size range of the closed pores formed by using the metal salt as a pore-forming agent is 0.5 to 4.0 nm.

8. The method for preparing a chemically treated biomass precursor to control a hard carbon structure for use as a negative electrode material for sodium ion batteries according to claim 2, characterized in that: The biomass precursors are lotus stems, bamboo powder or gourd shells.

Images