CN117623270A - Sodium ion battery hard carbon negative electrode material prepared by biomass-based crosslinking and application thereof - Google Patents

Abstract

The invention provides a sodium ion battery hard carbon negative electrode material prepared by biomass-based crosslinking and application thereof, and the preparation method comprises the following steps: (1) Dissolving chitosan with a certain mass in acetic acid solution, stirring to fully dissolve the chitosan, and preparing chitosan solution. (2) Adding cellulose with a certain mass into chitosan solution, and stirring to uniformly mix the cellulose and the chitosan solution. (3) Transferring the mixed solution into a hydrothermal reaction kettle for hydrothermal treatment for a certain time, and centrifuging, washing and drying the hydrothermal product after the reaction kettle is cooled to room temperature. (4) Transferring the treated hydrothermal product into a high-temperature tube furnace, and performing high-temperature pyrolysis carbonization treatment under inert atmosphere to obtain the hard carbon material. The hard carbon material prepared by carrying out chemical crosslinking treatment on the biomass base after pyrolysis carbonization has excellent multiplying power performance, and the first week coulomb efficiency is as high as 83.0%.

Description

A biomass-based cross-linked hard carbon negative electrode material for sodium ion batteries and its application

Technical field

The invention belongs to the technical field of secondary batteries, specifically relates to the technical field of sodium-ion battery negative electrodes, and particularly relates to a sodium-ion battery hard carbon negative electrode material prepared by biomass-based cross-linking and its application.

Background technique

With the rapid development of electric vehicles, electronic products, and energy storage devices, lithium-ion batteries have always dominated the field of energy storage technology due to their high energy density and good cycle stability. However, the high cost and uneven distribution of lithium resources have greatly limited its application in large-scale energy storage grids and low-cost energy storage devices. In contrast, sodium, which has similar chemical properties to lithium, has gradually entered people's field of vision. Due to its low cost, wide distribution of sodium and abundant reserves in my country, sodium-ion batteries can alleviate the shortage of lithium resources to a certain extent. At the same time, it can also gradually replace lead-acid batteries with safety hazards.

At this stage, realizing high-performance, low-cost sodium-ion batteries is still a huge challenge. In particular, hard carbon anode materials for sodium-ion batteries are considered to be the best choice for electrochemical performance, cost control, and sustainable resource development. As one of the non-graphitic carbons, hard carbon has large interlayer spacing and abundant defects and porosity, which can provide abundant active sites for Na ⁺ . More importantly, hard carbon has relatively high performance as an anode material for sodium ion batteries. Low operating voltage and high capacity meet the safety and functionality of battery applications.

China University of Petroleum (East China) provides a hard carbon material, its preparation method and application in sodium-ion batteries in CN115124025A. First, the particle size of the carbon source is controlled to ensure uniform particle size, and then "salt crystal hydrothermal-flash burning" is used. "In a synergistic approach, the transition metal salt is penetrated into the carbon source precursor through the salt crystal hydrothermal process, and the salt crystal is used as a template to precisely control the microscopic pore structure, surface chemical composition and graphite of the hard carbon material during the flash carbonization process. degree of chemicalization, forming a more stable structure that is beneficial to improving electrochemical performance; through the flash carbonization process, the local temperature around the salt crystal can be higher than that of the hard carbon matrix material, and the metal cations can catalyze the atomic rearrangement of carbon atoms at high temperatures. This increases the degree of local graphitization around the salt crystals, thereby instantly increasing the degree of graphitization of the hard carbon material, while limiting the defects of the hard carbon material and increasing the specific capacity of the sodium-ion battery.

Huizhou Yiwei Lithium Energy Co., Ltd. provides a hard carbon material and its preparation method and application in CN115321514A. The hard carbon material is doped with heteroatoms, and the heteroatoms include N atoms and M atoms. The M atoms Atoms include a combination of at least two of As, Se, Sb or Te. The hard carbon material can be prepared through a simple synthesis process and doped with at least three types of heteroatoms. Through the synergistic effect between heteroatoms, it can not only increase the interlayer spacing of the hard carbon material, but also introduce defect sites to make the hard carbon material more durable. The structure of the carbon material is greatly distorted, thereby increasing the insertion capacity and adsorption capacity of sodium ions, making the hard carbon material have high gram capacity and high rate performance.

Generally speaking, there are not many methods for using hard carbon materials derived from biomass in the existing technology. At the same time, the structure control of hard carbon is low and its performance is poor. The present invention aims to overcome the above problems, select appropriate methods to cross-link biomass materials, reasonably control defects on the surface of hard carbon, and improve the reversible capacity and first-cycle Coulombic efficiency of hard carbon negative electrode materials.

Contents of the invention

The purpose of the present invention is to provide a hard carbon material with simple preparation process, economical applicability, application prospects for large-scale industrial production, excellent rate performance, and first-week Coulombic efficiency as high as 83.0%. Specifically, two biomass-based materials are cross-linked through a hydrothermal reaction method, so that the cross-linked biomass macromolecular structure can prevent the release of small molecule gases during the pyrolysis process and reduce hard carbon surface defects. The formation helps the transfer of electrons and improves the reversible capacity and first-cycle Coulombic efficiency of hard carbon anode materials.

The technical solutions adopted by the present invention are as follows:

A biomass-based cross-linking method for preparing hard carbon negative electrode materials for sodium ion batteries, including the following steps:

(1) Dissolve a certain mass of chitosan in the acetic acid solution, stir to fully dissolve, and prepare the chitosan solution.

(2) Add a certain mass of cellulose to the chitosan solution and stir to mix the two evenly.

(3) Transfer the above mixed solution to a hydrothermal reaction kettle for hydrothermal treatment for a certain period of time. After the reaction kettle is cooled to room temperature, the hydrothermal product is centrifuged, washed and dried.

(4) Transfer the hydrothermal product after the above treatment to a high-temperature tube furnace, and perform high-temperature pyrolysis and carbonization treatment under an inert atmosphere to obtain hard carbon materials.

Further, the acetic acid solution is 1-2g/L, and the chitosan solution concentration is 5-12g/L.

Further, the mass ratio of added cellulose to chitosan is 3:1-6:1.

Further, the mass ratio of cellulose to chitosan was 5:1.

Further, the hydrothermal reaction temperature of the mixed solution of cellulose and chitosan is 180-250°C, and the hydrothermal reaction time is 12-48 hours.

Further, the hydrothermal reaction temperature of the mixed solution of cellulose and chitosan is 200-240°C, and the hydrothermal reaction time is 24-36 hours.

Further, the high-temperature pyrolysis carbonization temperature is 1000-1800°C, the heating rate is 2-10°C/min, and the holding time is 2-10h.

Further, the high-temperature pyrolysis carbonization temperature is 1300-1500°C, the heating rate is 5°C/min, and the holding time is 3-5h.

The hard carbon negative electrode material for sodium ion batteries prepared according to the above method.

A method for preparing hard carbon electrode materials for sodium ion batteries, including the following steps:

The above biomass-based cross-linked hard carbon negative electrode material for sodium ion batteries is ground into a uniform slurry with the conductive agent acetylene black and the binder carboxymethyl cellulose sodium according to a mass ratio of 8:1:1, and scraped with a coater Coat it on the copper foil to ensure the mass of the active material is 1-1.5 mg/cm ² to obtain a hard carbon negative electrode sheet for a sodium ion battery.

Compared with existing technology, the beneficial effects are:

(1) The raw materials used in the present invention are all biomass-based materials, which have the advantages of wide sources, low prices, green environmental protection, etc. The method used has simple preparation process, applicability and economic feasibility, and has application prospects for large-scale industrial production.

(2) The present invention chemically cross-links the biomass base and prepares hard carbon materials after high-temperature pyrolysis and carbonization. It has excellent rate performance, and the Coulombic efficiency in the first week is as high as 83.0%.

Description of drawings

In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings needed to be used in the description of the embodiments will be briefly introduced below. Obviously, the drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, other drawings can also be obtained based on these drawings without exerting creative efforts.

Figure 1 is an SEM image of the biomass-based cross-linked hard carbon negative electrode material for sodium ion batteries prepared in Example 2.

Figure 2 is the charge and discharge curve of the biomass-based cross-linked hard carbon negative electrode material for sodium ion batteries prepared in Example 2 at a current density of 50 mA/g.

Figure 3 is a rate performance diagram of the biomass-based cross-linked hard carbon negative electrode material for sodium ion batteries prepared in Example 2 at a current density of 0.05A/g-1A/g.

Figure 4 is the charge and discharge curve of the biomass-based cross-linked hard carbon negative electrode material for sodium ion batteries prepared in Example 2 at a current density of 0.05A/g-1A/g.

Figure 5 is a long cycle diagram of the biomass-based cross-linked hard carbon negative electrode material for sodium ion batteries prepared in Example 2 at a current density of 1 A/g.

Detailed ways

In order to enable those skilled in the art to better understand the technical solutions in the embodiments of the present invention and to make the above objects, features and advantages of the present invention more obvious and understandable, specific implementation modes of the present invention are further described below.

The endpoints of ranges and any values disclosed herein are not limited to the precise range or value, but these ranges or values are to be understood to include values approaching such ranges or values. For numerical ranges, the endpoint values of each range, the endpoint values of each range and individual point values, and the individual point values can be combined with each other to obtain one or more new numerical ranges. These values The scope should be deemed to be specifically disclosed herein.

Example 1

(1) Dissolve 0.5g chitosan in 2g/L 50mL acetic acid solution, stir at 80°C for 1 hour to fully dissolve, and prepare a 10g/L chitosan solution.

(2) Add 2.5g of cellulose to the above chitosan solution and stir at 80°C for 3 hours to mix evenly.

(3) Transfer the above mixed solution to a hydrothermal reaction kettle for hydrothermal treatment. The hydrothermal reaction temperature is 220°C and the hydrothermal reaction time is 24 hours. After the reaction is completed and cooled to room temperature, the hydrothermal reaction product is centrifuged and washed. and drying treatment.

(4) Transfer the hydrothermal reaction product after the above treatment to a high-temperature tube furnace, perform high-temperature pyrolysis carbonization treatment under an argon atmosphere, raise the temperature to 1100°C at a heating rate of 5°C/min, and keep it for 3 hours to obtain the product. Material-based cross-linked hard carbon materials.

Example 2

(1) Dissolve 0.5g chitosan in 2g/L 50mL acetic acid solution, stir at 80°C for 1 hour to fully dissolve, and prepare a 10g/L chitosan solution.

(2) Add 2.5g of cellulose to the above chitosan solution and stir at 80°C for 3 hours to mix evenly.

(3) Transfer the above mixed solution to a hydrothermal reaction kettle for hydrothermal treatment. The hydrothermal reaction temperature is 220°C and the hydrothermal reaction time is 24 hours. After the reaction is completed and cooled to room temperature, the hydrothermal reaction product is centrifuged and washed. and drying treatment.

(4) Transfer the hydrothermal reaction product after the above treatment to a high-temperature tube furnace, perform high-temperature pyrolysis carbonization treatment under an argon atmosphere, raise the temperature to 1300°C at a heating rate of 5°C/min, and keep it for 3 hours to obtain the product. Material-based cross-linked hard carbon materials.

Example 3

(1) Dissolve 0.5g chitosan in 2g/L 50mL acetic acid solution, stir at 80°C for 1 hour to fully dissolve, and prepare a 10g/L chitosan solution.

(2) Add 2.5g of cellulose to the above chitosan solution and stir at 80°C for 3 hours to mix evenly.

(3) Transfer the above mixed solution to a hydrothermal reaction kettle for hydrothermal treatment. The hydrothermal reaction temperature is 220°C and the hydrothermal reaction time is 24 hours. After the reaction is completed and cooled to room temperature, the hydrothermal reaction product is centrifuged and washed. and drying treatment.

(4) Transfer the hydrothermal reaction product after the above treatment to a high-temperature tube furnace, perform high-temperature pyrolysis carbonization treatment under an argon atmosphere, raise the temperature to 1500°C at a heating rate of 5°C/min, and keep it for 3 hours to obtain the product. Material-based cross-linked hard carbon materials.

Example 4

(1) Dissolve 0.5g chitosan in 2g/L 50mL acetic acid solution, stir at 80°C for 1 hour to fully dissolve, and prepare a 10g/L chitosan solution.

(2) Add 2.5g of cellulose to the above chitosan solution and stir at 80°C for 3 hours to mix evenly.

(3) Transfer the above mixed solution to a hydrothermal reaction kettle for hydrothermal treatment. The hydrothermal reaction temperature is 180°C and the hydrothermal reaction time is 24 hours. After the reaction is completed and cooled to room temperature, the hydrothermal reaction product is centrifuged and washed. and drying treatment.

(4) Transfer the hydrothermal reaction product after the above treatment to a high-temperature tube furnace, perform high-temperature pyrolysis carbonization treatment under an argon atmosphere, raise the temperature to 1300°C at a heating rate of 5°C/min, and keep it for 3 hours to obtain the product. Material-based cross-linked hard carbon materials.

Example 5

(1) Dissolve 0.5g chitosan in 2g/L 50mL acetic acid solution, stir at 80°C for 1 hour to fully dissolve, and prepare a 10g/L chitosan solution.

(2) Add 1.5g of cellulose to the above chitosan solution and stir at 80°C for 3 hours to mix the two evenly.

(3) Transfer the above mixed solution to a hydrothermal reaction kettle for hydrothermal treatment. The hydrothermal reaction temperature is 220°C and the hydrothermal reaction time is 24 hours. After the reaction is completed and cooled to room temperature, the hydrothermal reaction product is centrifuged and washed. and drying treatment.

(4) Transfer the hydrothermal reaction product after the above treatment to a high-temperature tube furnace, perform high-temperature pyrolysis carbonization treatment under an argon atmosphere, raise the temperature to 1300°C at a heating rate of 5°C/min, and keep it for 3 hours to obtain the product. Material-based cross-linked hard carbon materials.

Example 6

(1) Dissolve 0.5g chitosan in 2g/L 50mL acetic acid solution, stir at 80°C for 1 hour to fully dissolve, and prepare a 10g/L chitosan solution.

(2) Add 2.5g of cellulose to the above chitosan solution and stir at 80°C for 3 hours to mix evenly.

(3) Transfer the above mixed solution to a hydrothermal reaction kettle for hydrothermal treatment. The hydrothermal reaction temperature is 250°C and the hydrothermal reaction time is 24 hours. After the reaction is completed and cooled to room temperature, the hydrothermal reaction product is centrifuged and washed. and drying treatment.

(4) Transfer the hydrothermal reaction product after the above treatment to a high-temperature tube furnace, perform high-temperature pyrolysis carbonization treatment under an argon atmosphere, raise the temperature to 1300°C at a heating rate of 5°C/min, and keep it for 3 hours to obtain the product. Material-based cross-linked hard carbon materials.

Example 7

(1) Dissolve 0.5g chitosan in 2g/L 50mL acetic acid solution, stir at 80°C for 1 hour to fully dissolve, and prepare a 10g/L chitosan solution.

(2) Add 2.5g of cellulose to the above chitosan solution and stir at 80°C for 3 hours to mix evenly.

(3) Transfer the above mixed solution to a hydrothermal reaction kettle for hydrothermal treatment. The hydrothermal reaction temperature is 200°C and the hydrothermal reaction time is 24 hours. After the reaction is completed and cooled to room temperature, the hydrothermal reaction product is centrifuged and washed. and drying treatment.

(4) Transfer the hydrothermal reaction product after the above treatment to a high-temperature tube furnace, perform high-temperature pyrolysis carbonization treatment under an argon atmosphere, raise the temperature to 1300°C at a heating rate of 5°C/min, and keep it for 3 hours to obtain the product. Material-based cross-linked hard carbon materials.

Example 8

(1) Dissolve 0.5g chitosan in 2g/L 50mL acetic acid solution, stir at 80°C for 1 hour to fully dissolve, and prepare a 10g/L chitosan solution.

(2) Add 2.5g of cellulose to the above chitosan solution and stir at 80°C for 3 hours to mix evenly.

(3) Transfer the above mixed solution to a hydrothermal reaction kettle for hydrothermal treatment. The hydrothermal reaction temperature is 240°C and the hydrothermal reaction time is 24 hours. After the reaction is completed and cooled to room temperature, the hydrothermal reaction product is centrifuged and washed. and drying treatment.

(4) Transfer the hydrothermal reaction product after the above treatment to a high-temperature tube furnace, perform high-temperature pyrolysis carbonization treatment under an argon atmosphere, raise the temperature to 1300°C at a heating rate of 5°C/min, and keep it for 3 hours to obtain the product. Material-based cross-linked hard carbon materials.

Example 9

(1) Dissolve 0.5g chitosan in 2g/L 50mL acetic acid solution, stir at 80°C for 1 hour to fully dissolve, and prepare a 10g/L chitosan solution.

(2) Add 2.5g of cellulose to the above chitosan solution and stir at 80°C for 3 hours to mix evenly.

(3) Transfer the above mixed solution to a hydrothermal reaction kettle for hydrothermal treatment. The hydrothermal reaction temperature is 220°C and the hydrothermal reaction time is 24 hours. After the reaction is completed and cooled to room temperature, the hydrothermal reaction product is centrifuged and washed. and drying treatment.

(4) Transfer the hydrothermal reaction product after the above treatment to a high-temperature tube furnace, perform high-temperature pyrolysis carbonization treatment under an argon atmosphere, raise the temperature to 1000°C at a heating rate of 5°C/min, and keep it for 3 hours to obtain the product. Material-based cross-linked hard carbon materials.

Example 10

(1) Dissolve 0.5g chitosan in 2g/L 50mL acetic acid solution, stir at 80°C for 1 hour to fully dissolve, and prepare a 10g/L chitosan solution.

(2) Add 2.5g of cellulose to the above chitosan solution and stir at 80°C for 3 hours to mix evenly.

(3) Transfer the above mixed solution to a hydrothermal reaction kettle for hydrothermal treatment. The hydrothermal reaction temperature is 220°C and the hydrothermal reaction time is 24 hours. After the reaction is completed and cooled to room temperature, the hydrothermal reaction product is centrifuged and washed. and drying treatment.

(4) Transfer the hydrothermal reaction product after the above treatment to a high-temperature tube furnace, perform high-temperature pyrolysis carbonization treatment under an argon atmosphere, raise the temperature to 1800°C at a heating rate of 5°C/min, and keep it for 3 hours to obtain the product. Material-based cross-linked hard carbon materials.

Example 11

(1) Dissolve 0.5g chitosan in 2g/L 50mL acetic acid solution, stir at 80°C for 1 hour to fully dissolve, and prepare a 10g/L chitosan solution.

(2) Add 2.0g of cellulose to the above chitosan solution and stir at 80°C for 3 hours to mix the two evenly.

(3) Transfer the above mixed solution to a hydrothermal reaction kettle for hydrothermal treatment. The hydrothermal reaction temperature is 220°C and the hydrothermal reaction time is 24 hours. After the reaction is completed and cooled to room temperature, the hydrothermal reaction product is centrifuged and washed. and drying treatment.

(4) Transfer the hydrothermal reaction product after the above treatment to a high-temperature tube furnace, perform high-temperature pyrolysis carbonization treatment under an argon atmosphere, raise the temperature to 1300°C at a heating rate of 5°C/min, and keep it for 3 hours to obtain the product. Material-based cross-linked hard carbon materials.

Example 12

(1) Dissolve 0.5g chitosan in 2g/L 50mL acetic acid solution, stir at 80°C for 1 hour to fully dissolve, and prepare a 10g/L chitosan solution.

(2) Add 3.0g of cellulose to the above chitosan solution and stir at 80°C for 3 hours to mix the two evenly.

(3) Transfer the above mixed solution to a hydrothermal reaction kettle for hydrothermal treatment. The hydrothermal reaction temperature is 220°C and the hydrothermal reaction time is 24 hours. After the reaction is completed and cooled to room temperature, the hydrothermal reaction product is centrifuged and washed. and drying treatment.

(4) Transfer the hydrothermal reaction product after the above treatment to a high-temperature tube furnace, perform high-temperature pyrolysis carbonization treatment under an argon atmosphere, raise the temperature to 1300°C at a heating rate of 5°C/min, and keep it for 3 hours to obtain the product. Material-based cross-linked hard carbon materials.

Example 13

(1) Dissolve 0.5g chitosan in 2g/L 50mL acetic acid solution, stir at 80°C for 1 hour to fully dissolve, and prepare a 10g/L chitosan solution.

(2) Add 1.0g of cellulose to the above chitosan solution and stir at 80°C for 3 hours to mix evenly.

(3) Transfer the above mixed solution to a hydrothermal reaction kettle for hydrothermal treatment. The hydrothermal reaction temperature is 220°C and the hydrothermal reaction time is 24 hours. After the reaction is completed and cooled to room temperature, the hydrothermal reaction product is centrifuged and washed. and drying treatment.

(4) Transfer the hydrothermal reaction product after the above treatment to a high-temperature tube furnace, perform high-temperature pyrolysis carbonization treatment under an argon atmosphere, raise the temperature to 1300°C at a heating rate of 5°C/min, and keep it for 3 hours to obtain the product. Material-based cross-linked hard carbon materials.

Example 2

(1) Dissolve 0.5g chitosan in 2g/L 50mL acetic acid solution, stir at 80°C for 1 hour to fully dissolve, and prepare a 10g/L chitosan solution.

(2) Add 2.5g of bamboo powder to the above chitosan solution and stir at 80°C for 3 hours to mix evenly.

(3) Transfer the above mixed solution to a hydrothermal reaction kettle for hydrothermal treatment. The hydrothermal reaction temperature is 220°C and the hydrothermal reaction time is 24 hours. After the reaction is completed and cooled to room temperature, the hydrothermal reaction product is centrifuged and washed. and drying treatment.

(4) Transfer the hydrothermal reaction product after the above treatment to a high-temperature tube furnace, perform high-temperature pyrolysis carbonization treatment under an argon atmosphere, raise the temperature to 1300°C at a heating rate of 5°C/min, and keep it for 3 hours to obtain the product. Material-based cross-linked hard carbon materials.

Example 15

(1) Dissolve 0.5g chitosan in 2g/L 50mL acetic acid solution, stir at 80°C for 1 hour to fully dissolve, and prepare a 10g/L chitosan solution.

(2) Add 2.5g of wood powder to the above chitosan solution and stir at 80°C for 3 hours to mix evenly.

(3) Transfer the above mixed solution to a hydrothermal reaction kettle for hydrothermal treatment. The hydrothermal reaction temperature is 220°C and the hydrothermal reaction time is 24 hours. After the reaction is completed and cooled to room temperature, the hydrothermal reaction product is centrifuged and washed. and drying treatment.

(4) Transfer the hydrothermal reaction product after the above treatment to a high-temperature tube furnace, perform high-temperature pyrolysis carbonization treatment under an argon atmosphere, raise the temperature to 1300°C at a heating rate of 5°C/min, and keep it for 3 hours to obtain the product. Material-based cross-linked hard carbon materials.

Example 16

(1) Dissolve 0.5g chitosan in 2g/L 50mL acetic acid solution, stir at 80°C for 1 hour to fully dissolve, and prepare a 10g/L chitosan solution.

(2) Add 2.5g of peanut shell powder to the above chitosan solution and stir at 80°C for 3 hours to mix evenly.

(3) Transfer the above mixed solution to a hydrothermal reaction kettle for hydrothermal treatment. The hydrothermal reaction temperature is 220°C and the hydrothermal reaction time is 24 hours. After the reaction is completed and cooled to room temperature, the hydrothermal reaction product is centrifuged and washed. and drying treatment.

(4) Transfer the hydrothermal reaction product after the above treatment to a high-temperature tube furnace, perform high-temperature pyrolysis carbonization treatment under an argon atmosphere, raise the temperature to 1300°C at a heating rate of 5°C/min, and keep it for 3 hours to obtain the product. Material-based cross-linked hard carbon materials.

Comparative example 1

(1) Add 2.5g of cellulose to the deionized water solution and stir at 80°C for 3 hours to disperse evenly.

(2) Transfer the above solution to a hydrothermal reaction kettle for hydrothermal treatment. The hydrothermal reaction temperature is 220°C and the hydrothermal reaction time is 24 hours. After the reaction is completed and cooled to room temperature, the hydrothermal reaction product is centrifuged, washed and Drying process.

(3) Transfer the hydrothermal reaction product after the above treatment to a high-temperature tube furnace, perform high-temperature pyrolysis carbonization treatment under an argon atmosphere, raise the temperature to 1300°C at a heating rate of 5°C/min, and keep it for 3 hours to obtain fibers. Plain hard carbon material.

Comparative example 2

(1) Dissolve 2.5g chitosan in 2g/L 50mL acetic acid solution, stir at 80°C for 1 hour to fully dissolve, and prepare a 10g/L chitosan solution.

(2) Transfer the above solution to a hydrothermal reaction kettle for hydrothermal treatment. The hydrothermal reaction temperature is 220°C and the hydrothermal reaction time is 24 hours. After the reaction is completed and cooled to room temperature, the hydrothermal reaction product is centrifuged, washed and Drying process.

(3) Transfer the hydrothermal reaction product after the above treatment to a high-temperature tube furnace, perform high-temperature pyrolysis carbonization treatment under an argon atmosphere, raise the temperature to 1300°C at a heating rate of 5°C/min, and keep it for 3 hours to obtain fibers. Plain hard carbon material.

Comparative example 3

(1) Dissolve 0.5g glucose in 50mL deionized water solution and stir for 1 hour at room temperature to fully dissolve.

(2) Add 2.5g of cellulose to the above glucose solution and stir at 80°C for 3 hours to mix evenly.

(3) Transfer the above mixed solution to a hydrothermal reaction kettle for hydrothermal treatment. The hydrothermal reaction temperature is 220°C and the hydrothermal reaction time is 24 hours. After the reaction is completed and cooled to room temperature, the hydrothermal reaction product is centrifuged and washed. and drying treatment.

(4) Transfer the hydrothermal reaction product after the above treatment to a high-temperature tube furnace, perform high-temperature pyrolysis carbonization treatment under an argon atmosphere, raise the temperature to 1300°C at a heating rate of 5°C/min, and keep it for 3 hours to obtain the product. Material-based cross-linked hard carbon materials.

The above is only a preferred example of a biomass-based cross-linking method for preparing hard carbon negative electrode materials for sodium ion batteries, and the scope of protection of the present invention is not limited to the examples. The technical solution of the present invention is to improve and optimize the preparation conditions of hard carbon materials under the same conditions, which again basically fall within the protection scope of the present invention.

Application and performance testing

The hard carbon material prepared by the above-mentioned examples and comparative examples is used as the negative active material of the sodium ion battery to prepare the pole piece. The specific method is as follows: combine the hard carbon negative electrode material of the sodium ion battery with the conductive agent acetylene black and the binder carboxymethyl Grind sodium cellulose into a uniform slurry according to the mass ratio of 8:1:1, and apply it on the copper foil with an applicator to ensure that the active material surface loading is 1-1.5g/cm ² to obtain a sodium ion battery hardener. Carbon negative electrode sheets were prepared, and sodium-ion button batteries were prepared in the glove box, and the electrochemical performance of the button batteries was tested.

Table 1 shows the battery performance of the sodium ion battery hard carbon negative electrode materials prepared in various examples and comparative examples. Compared with the comparative examples, the examples have higher reversible capacity and first-week Coulombic efficiency. This is because biomass as a macromolecule The base extends the molecular chain structure through chemical cross-linking, which can effectively prevent the release of small molecular gases during high-temperature pyrolysis, minimize the formation of hard carbon surface defects, and promote the transfer of electrons, giving it excellent rate performance . Table 2 shows the electrochemical properties of Example 2 at different current densities (50-1000mA/g). As shown in Table 2, Example 2 still has a reversible capacity of 227mAh/g at a current density of 500mA/g. It still has a reversible capacity of 209mAh/g at a current density of g, which shows the excellence of the present invention under high current density. Figure 1 shows that the scanning electron microscope image of Example 2 is amorphous. Figures 2 and 4 show that the battery prepared by the present invention has a longer plateau area. Figure 3 shows the rate performance of Example 2, indicating that the present invention operates at different current densities. Excellent cycling stability. Figure 5 shows the long cycle performance of Example 2 at a larger current density (1A/g). It still maintains 80% of the capacity even after 750 cycles, proving its excellent cycle stability.

Table 1 Electrochemical properties of Examples and Comparative Examples (current density 50mAg ^-1 )

Table 2 Electrochemical properties of different current densities (50-1000mA/g) in Example 2

Current density (mA/g) 50 100 200 300 500 800 1000 Discharge specific capacity (mAh/g) 330 265 252 241 233 221 212 Charging specific capacity (mAh/g) 274 258 246 237 227 217 209

The embodiments of the present invention are described in detail above, but the present invention is not limited to the described embodiments. For those skilled in the art, various changes, modifications, substitutions and modifications to these embodiments without departing from the principle and spirit of the invention will still fall within the protection scope of the invention.

Claims (10)

1. The method for preparing the hard carbon anode material of the sodium ion battery by biomass-based crosslinking is characterized by comprising the following steps of:

(1) Dissolving chitosan with a certain mass in acetic acid solution, stirring to fully dissolve the chitosan, and preparing chitosan solution;

(2) Adding cellulose with a certain mass into chitosan solution, and stirring to uniformly mix the cellulose and the chitosan solution;

(3) Transferring the mixed solution into a hydrothermal reaction kettle for hydrothermal treatment for a certain time, and centrifuging, washing and drying the hydrothermal product after the reaction kettle is cooled to room temperature;

(4) Transferring the treated hydrothermal product into a high-temperature tube furnace, and performing high-temperature pyrolysis carbonization treatment under inert atmosphere to obtain the hard carbon material.

2. The method for preparing the hard carbon anode material of the sodium ion battery by biomass-based crosslinking of claim 1, wherein the acetic acid solution is 1-2g/L and the chitosan solution concentration is 5-12g/L.

3. The method for preparing the hard carbon negative electrode material of the sodium ion battery by biomass-based crosslinking according to claim 1, wherein the mass ratio of added cellulose to chitosan is 3:1-6:1.

4. The method for preparing a hard carbon negative electrode material of a sodium ion battery by biomass-based crosslinking according to claim 1 or 3, wherein the mass ratio of cellulose to chitosan is 5:1.

5. The method for preparing the hard carbon negative electrode material of the sodium ion battery by biomass-based crosslinking of claim 1, wherein the hydrothermal reaction temperature of the mixed solution of cellulose and chitosan is 180-250 ℃ and the hydrothermal reaction time is 12-48h.

6. The method for preparing the hard carbon negative electrode material of the sodium ion battery by biomass-based crosslinking according to claim 1 or 5, wherein the hydrothermal reaction temperature of the mixed solution of cellulose and chitosan is 200-240 ℃ and the hydrothermal reaction time is 24-36h.

7. The method for preparing the hard carbon negative electrode material of the sodium ion battery by biomass-based crosslinking according to claim 1, wherein the pyrolysis carbonization temperature is 1000-1800 ℃, the heating rate is 2-10 ℃/min, and the heat preservation time is 2-10h.

8. The method for preparing the hard carbon anode material of the sodium ion battery by biomass-based crosslinking according to claim 1 or 7, wherein the high-temperature pyrolysis carbonization temperature is 1300-1500 ℃, the heating rate is 5 ℃/min, and the heat preservation time is 3-5h.

9. A sodium ion battery hard carbon anode material prepared according to the method of any one of claims 1-8.

10. A hard carbon negative electrode of a sodium ion battery, which is characterized in that the electrode slurry comprises the hard carbon negative electrode material of the sodium ion battery as claimed in claim 9, an electroconductive agent of acetylene black and a binder of sodium carboxymethyl cellulose.