A biomass-based cross-linked prepared sodium-ion battery hard carbon negative electrode material and application thereof

Abstract

The application provides a biomass-based cross-linked prepared sodium ion battery hard carbon negative electrode material and application thereof, and a preparation method thereof, which comprises the following steps: (1) dissolving a certain mass of chitosan in an acetic acid solution, stirring to fully dissolve the chitosan, and preparing a chitosan solution; (2) adding a certain mass of cellulose into the chitosan solution, and stirring to uniformly mix the two; (3) transferring the mixed solution into a hydrothermal reaction kettle to perform hydrothermal treatment for a certain time, and after the reaction kettle is cooled to room temperature, performing centrifugation, washing and drying treatment on the hydrothermal product; and (4) transferring the treated hydrothermal product into a high-temperature tube furnace to perform high-temperature pyrolysis carbonization treatment under an inert atmosphere, and obtaining a hard carbon material. Through chemical cross-linking treatment on the biomass base, the hard carbon material prepared after high-temperature pyrolysis carbonization has excellent rate performance, and the first week coulombic efficiency is as high as 83.0%.

Description

Technical Field

[0001] The present invention belongs to the technical field of secondary batteries, specifically to the technical field of sodium ion battery negative electrodes, and in particular to a sodium ion battery hard carbon negative electrode material prepared by biomass-based cross-linking and its application. Background Art

[0002] With the rapid development of electric vehicles, electronic products, and energy storage devices, lithium-ion batteries have dominated the energy storage technology field due to their high energy density and excellent cycle stability. However, the high cost and uneven distribution of lithium resources have greatly limited their application in large-scale energy storage grids and low-cost energy storage devices. In contrast, sodium, with chemical properties similar to lithium, has gradually come into people's attention. 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 and can also gradually replace lead-acid batteries, which have safety risks.

[0003] At present, achieving high-performance and 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-graphite carbons, hard carbon has a large interlayer spacing, rich defects, and porosity, which can provide Na + It provides abundant active sites. More importantly, hard carbon as a negative electrode material for sodium ion batteries has a lower operating voltage and higher capacity, meeting the safety and functionality of battery applications.

[0004] China University of Petroleum (East China) provides a hard carbon material, its preparation method and application in sodium ion batteries in CN115124025A. First, the carbon source particle size is controlled to ensure uniform particle size. Then, a "salt crystal hydrothermal-flash burning" synergistic method is adopted to infiltrate the transition metal salt into the carbon source precursor through the salt crystal hydrothermal process. During the flash burning carbonization process, the salt crystals are used as templates to accurately control the microscopic pore structure, surface chemical composition and degree of graphitization of the hard carbon material, forming a more stable structure that is beneficial to improving electrochemical performance. The flash burning carbonization process can make the local temperature around the salt crystals higher than that of the hard carbon matrix material, and the metal cations can catalyze the atomic rearrangement of carbon atoms at high temperature, so that the local graphitization degree around the salt crystals is increased, thereby instantaneously increasing the degree of graphitization of the hard carbon material, while limiting the defects of the hard carbon material and improving the specific capacity of the sodium ion battery.

[0005] Huizhou Yiwei Lithium Energy Co., Ltd., in CN115321514A, provides a hard carbon material, its preparation method, and application. The hard carbon material is doped with heteroatoms, including nitrogen and nitrogen atoms, and the nitrogen atoms are 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 heteroatoms. The synergistic effect between the heteroatoms increases the interlayer spacing of the hard carbon material and introduces defect sites, significantly distorting the structure of the hard carbon material. This increases the sodium ion insertion and adsorption capacity, resulting in high gram capacity and high rate performance.

[0006] In general, existing methods for preparing hard carbon materials derived from biomass are limited, and they often suffer from poor structural control and performance. The present invention aims to overcome these issues by selecting a suitable method for cross-linking biomass materials, rationally controlling surface defects on the hard carbon, and improving the reversible capacity and initial coulombic efficiency of hard carbon anode materials. Summary of the Invention

[0007] The present invention aims to provide a hard carbon material with a simple preparation process, economical applicability, promising application prospects for large-scale industrial production, and excellent rate performance, with a first-cycle coulombic efficiency of up to 83.0%. Specifically, two biomass-based materials are cross-linked via a hydrothermal reaction. This cross-linked biomass macromolecular structure prevents the release of small molecule gases during pyrolysis, reduces the formation of surface defects on the hard carbon, facilitates electron transfer, and improves the reversible capacity and first-cycle coulombic efficiency of the hard carbon negative electrode material.

[0008] The technical solutions adopted in the present invention are as follows:

[0009] A method for preparing a hard carbon negative electrode material for a sodium ion battery by biomass-based cross-linking comprises the following steps:

[0010] (1) Dissolve a certain amount of chitosan in acetic acid solution and stir to fully dissolve it to prepare a chitosan solution.

[0011] (2) Add a certain amount of cellulose to the chitosan solution and stir to mix the two evenly.

[0012] (3) The mixed solution is transferred to a hydrothermal reactor for hydrothermal treatment for a certain period of time. After the reactor is cooled to room temperature, the hydrothermal product is centrifuged, washed and dried.

[0013] (4) The hydrothermal product after the above treatment is transferred to a high-temperature tube furnace and subjected to high-temperature pyrolysis and carbonization treatment under an inert atmosphere to obtain a hard carbon material.

[0014] Furthermore, the concentration of the acetic acid solution is 1-2 g / L, and the concentration of the chitosan solution is 5-12 g / L.

[0015] Furthermore, the mass ratio of cellulose to chitosan is 3:1-6:1.

[0016] Furthermore, the mass ratio of cellulose to chitosan is 5:1.

[0017] Furthermore, the hydrothermal reaction temperature of the cellulose and chitosan mixed solution is 180-250° C., and the hydrothermal reaction time is 12-48 hours.

[0018] Furthermore, the hydrothermal reaction temperature of the cellulose and chitosan mixed solution is 200-240° C., and the hydrothermal reaction time is 24-36 hours.

[0019] Furthermore, 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.

[0020] Furthermore, the high-temperature pyrolysis carbonization temperature is 1300-1500° C., the heating rate is 5° C. / min, and the holding time is 3-5 h.

[0021] A hard carbon negative electrode material for sodium ion batteries prepared according to the above method.

[0022] A method for preparing a hard carbon electrode material for a sodium ion battery comprises the following steps:

[0023] The biomass-based cross-linked hard carbon anode material for sodium ion batteries was ground into a uniform slurry with the conductive agent acetylene black and the binder sodium carboxymethyl cellulose in a mass ratio of 8:1:1. The slurry was then applied on copper foil using a coating device to ensure that the active material mass was 1-1.5 mg / cm 2 , and obtain a hard carbon negative electrode sheet for sodium ion batteries.

[0024] Compared with the prior art, the beneficial effects are:

[0025] (1) The raw materials used in the present invention are all biomass-based materials, which have the advantages of wide sources, low prices and green environmental protection. The preparation process adopted is simple, economical and feasible, and has application prospects for large-scale industrial production.

[0026] (2) The present invention chemically cross-links the biomass base and then pyrolyzes and carbonizes it at high temperature to prepare a hard carbon material with excellent rate performance, and the first-cycle coulombic efficiency is as high as 83.0%. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following briefly introduces the drawings required for use in the description of the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0028] Figure 1 This is the SEM image of the biomass-based cross-linked sodium ion battery hard carbon negative electrode material prepared in Example 2.

[0029] Figure 2 The charge and discharge curves of the biomass-based cross-linked sodium ion battery hard carbon negative electrode material prepared in Example 2 at a current density of 50 mA / g.

[0030] Figure 3 This is a rate performance diagram of the biomass-based cross-linked sodium ion battery hard carbon negative electrode material prepared in Example 2 at a current density of 0.05A / g-1A / g.

[0031] Figure 4 The charge and discharge curves of the biomass-based cross-linked sodium ion battery hard carbon negative electrode material prepared in Example 2 at a current density of 0.05A / g-1A / g.

[0032] Figure 5 This is the long cycle diagram of the biomass-based cross-linked sodium ion battery hard carbon negative electrode material prepared in Example 2 at a current density of 1 A / g. DETAILED DESCRIPTION

[0033] 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-mentioned objects, features and advantages of the present invention more obvious and understandable, the specific implementation methods of the present invention are further described below.

[0034] The endpoints of the ranges and any values ​​disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoints of each range, the endpoints 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, which should be considered as specifically disclosed herein.

[0035] Example 1

[0036] (1) Dissolve 0.5 g of chitosan in 50 mL of 2 g / L acetic acid solution and stir at 80 °C for 1 h to fully dissolve it to prepare a 10 g / L chitosan solution.

[0037] (2) Add 2.5 g of cellulose to the chitosan solution and stir at 80 °C for 3 h to mix the two evenly.

[0038] (3) The mixed solution was transferred to a hydrothermal reactor for hydrothermal treatment at a temperature of 220°C for 24 hours. After the reaction was completed and cooled to room temperature, the hydrothermal reaction product was centrifuged, washed, and dried.

[0039] (4) The hydrothermal reaction product after the above treatment was transferred to a high-temperature tubular furnace and subjected to high-temperature pyrolysis carbonization treatment under an argon atmosphere. The temperature was raised to 1100°C at a heating rate of 5°C / min and kept at this temperature for 3 hours to obtain a biomass-based cross-linked hard carbon material.

[0040] Example 2

[0041] (1) Dissolve 0.5 g of chitosan in 50 mL of 2 g / L acetic acid solution and stir at 80 °C for 1 h to fully dissolve it to prepare a 10 g / L chitosan solution.

[0042] (2) Add 2.5 g of cellulose to the chitosan solution and stir at 80 °C for 3 h to mix the two evenly.

[0043] (3) The mixed solution was transferred to a hydrothermal reactor for hydrothermal treatment at a temperature of 220°C for 24 hours. After the reaction was completed and cooled to room temperature, the hydrothermal reaction product was centrifuged, washed, and dried.

[0044] (4) The hydrothermal reaction product after the above treatment was transferred to a high-temperature tubular furnace and subjected to high-temperature pyrolysis carbonization treatment under an argon atmosphere. The temperature was raised to 1300°C at a heating rate of 5°C / min and kept at this temperature for 3 hours to obtain a biomass-based cross-linked hard carbon material.

[0045] Example 3

[0046] (1) Dissolve 0.5 g of chitosan in 50 mL of 2 g / L acetic acid solution and stir at 80 °C for 1 h to fully dissolve it to prepare a 10 g / L chitosan solution.

[0047] (2) Add 2.5 g of cellulose to the chitosan solution and stir at 80 °C for 3 h to mix the two evenly.

[0048] (3) The mixed solution was transferred to a hydrothermal reactor for hydrothermal treatment at a temperature of 220°C for 24 hours. After the reaction was completed and cooled to room temperature, the hydrothermal reaction product was centrifuged, washed, and dried.

[0049] (4) The hydrothermal reaction product after the above treatment was transferred to a high-temperature tubular furnace and subjected to high-temperature pyrolysis carbonization treatment under an argon atmosphere. The temperature was raised to 1500°C at a heating rate of 5°C / min and kept at this temperature for 3 hours to obtain a biomass-based cross-linked hard carbon material.

[0050] Example 4

[0051] (1) Dissolve 0.5 g of chitosan in 50 mL of 2 g / L acetic acid solution and stir at 80 °C for 1 h to fully dissolve it to prepare a 10 g / L chitosan solution.

[0052] (2) Add 2.5 g of cellulose to the chitosan solution and stir at 80 °C for 3 h to mix the two evenly.

[0053] (3) The mixed solution was transferred to a hydrothermal reactor for hydrothermal treatment at a temperature of 180°C for 24 hours. After the reaction was completed and cooled to room temperature, the hydrothermal reaction product was centrifuged, washed, and dried.

[0054] (4) The hydrothermal reaction product after the above treatment was transferred to a high-temperature tubular furnace and subjected to high-temperature pyrolysis carbonization treatment under an argon atmosphere. The temperature was raised to 1300°C at a heating rate of 5°C / min and kept at this temperature for 3 hours to obtain a biomass-based cross-linked hard carbon material.

[0055] Example 5

[0056] (1) Dissolve 0.5 g of chitosan in 50 mL of 2 g / L acetic acid solution and stir at 80 °C for 1 h to fully dissolve it to prepare a 10 g / L chitosan solution.

[0057] (2) Add 1.5 g of cellulose to the chitosan solution and stir at 80 °C for 3 h to mix the two evenly.

[0058] (3) The mixed solution was transferred to a hydrothermal reactor for hydrothermal treatment at a temperature of 220°C for 24 hours. After the reaction was completed and cooled to room temperature, the hydrothermal reaction product was centrifuged, washed, and dried.

[0059] (4) The hydrothermal reaction product after the above treatment was transferred to a high-temperature tubular furnace and subjected to high-temperature pyrolysis carbonization treatment under an argon atmosphere. The temperature was raised to 1300°C at a heating rate of 5°C / min and kept at this temperature for 3 hours to obtain a biomass-based cross-linked hard carbon material.

[0060] Example 6

[0061] (1) Dissolve 0.5 g of chitosan in 50 mL of 2 g / L acetic acid solution and stir at 80 °C for 1 h to fully dissolve it to prepare a 10 g / L chitosan solution.

[0062] (2) Add 2.5 g of cellulose to the chitosan solution and stir at 80 °C for 3 h to mix the two evenly.

[0063] (3) The mixed solution was transferred to a hydrothermal reactor for hydrothermal treatment at a temperature of 250°C for 24 hours. After the reaction was completed and cooled to room temperature, the hydrothermal reaction product was centrifuged, washed, and dried.

[0064] (4) The hydrothermal reaction product after the above treatment was transferred to a high-temperature tubular furnace and subjected to high-temperature pyrolysis carbonization treatment under an argon atmosphere. The temperature was raised to 1300°C at a heating rate of 5°C / min and kept at this temperature for 3 hours to obtain a biomass-based cross-linked hard carbon material.

[0065] Example 7

[0066] (1) Dissolve 0.5 g of chitosan in 50 mL of 2 g / L acetic acid solution and stir at 80 °C for 1 h to fully dissolve it to prepare a 10 g / L chitosan solution.

[0067] (2) Add 2.5 g of cellulose to the chitosan solution and stir at 80 °C for 3 h to mix the two evenly.

[0068] (3) The mixed solution was transferred to a hydrothermal reactor for hydrothermal treatment at a temperature of 200°C for 24 hours. After the reaction was completed and cooled to room temperature, the hydrothermal reaction product was centrifuged, washed, and dried.

[0069] (4) The hydrothermal reaction product after the above treatment was transferred to a high-temperature tubular furnace and subjected to high-temperature pyrolysis carbonization treatment under an argon atmosphere. The temperature was raised to 1300°C at a heating rate of 5°C / min and kept at this temperature for 3 hours to obtain a biomass-based cross-linked hard carbon material.

[0070] Example 8

[0071] (1) Dissolve 0.5 g of chitosan in 50 mL of 2 g / L acetic acid solution and stir at 80 °C for 1 h to fully dissolve it to prepare a 10 g / L chitosan solution.

[0072] (2) Add 2.5 g of cellulose to the chitosan solution and stir at 80 °C for 3 h to mix the two evenly.

[0073] (3) The mixed solution was transferred to a hydrothermal reactor for hydrothermal treatment at a temperature of 240°C for 24 hours. After the reaction was completed and cooled to room temperature, the hydrothermal reaction product was centrifuged, washed, and dried.

[0074] (4) The hydrothermal reaction product after the above treatment was transferred to a high-temperature tubular furnace and subjected to high-temperature pyrolysis carbonization treatment under an argon atmosphere. The temperature was raised to 1300°C at a heating rate of 5°C / min and kept at this temperature for 3 hours to obtain a biomass-based cross-linked hard carbon material.

[0075] Example 9

[0076] (1) Dissolve 0.5 g of chitosan in 50 mL of 2 g / L acetic acid solution and stir at 80 °C for 1 h to fully dissolve it to prepare a 10 g / L chitosan solution.

[0077] (2) Add 2.5 g of cellulose to the chitosan solution and stir at 80 °C for 3 h to mix the two evenly.

[0078] (3) The mixed solution was transferred to a hydrothermal reactor for hydrothermal treatment at a temperature of 220°C for 24 hours. After the reaction was completed and cooled to room temperature, the hydrothermal reaction product was centrifuged, washed, and dried.

[0079] (4) The hydrothermal reaction product after the above treatment was transferred to a high-temperature tubular furnace and subjected to high-temperature pyrolysis carbonization treatment under an argon atmosphere. The temperature was raised to 1000°C at a heating rate of 5°C / min and kept at this temperature for 3 hours to obtain a biomass-based cross-linked hard carbon material.

[0080] Example 10

[0081] (1) Dissolve 0.5 g of chitosan in 50 mL of 2 g / L acetic acid solution and stir at 80 °C for 1 h to fully dissolve it to prepare a 10 g / L chitosan solution.

[0082] (2) Add 2.5 g of cellulose to the chitosan solution and stir at 80 °C for 3 h to mix the two evenly.

[0083] (3) The mixed solution was transferred to a hydrothermal reactor for hydrothermal treatment at a temperature of 220°C for 24 hours. After the reaction was completed and cooled to room temperature, the hydrothermal reaction product was centrifuged, washed, and dried.

[0084] (4) The hydrothermal reaction product after the above treatment was transferred to a high-temperature tubular furnace and subjected to high-temperature pyrolysis carbonization treatment under an argon atmosphere. The temperature was raised to 1800°C at a heating rate of 5°C / min and kept at this temperature for 3 hours to obtain a biomass-based cross-linked hard carbon material.

[0085] Example 11

[0086] (1) Dissolve 0.5 g of chitosan in 50 mL of 2 g / L acetic acid solution and stir at 80 °C for 1 h to fully dissolve it to prepare a 10 g / L chitosan solution.

[0087] (2) Add 2.0 g of cellulose to the chitosan solution and stir at 80°C for 3 h to mix the two evenly.

[0088] (3) The mixed solution was transferred to a hydrothermal reactor for hydrothermal treatment at a temperature of 220°C for 24 hours. After the reaction was completed and cooled to room temperature, the hydrothermal reaction product was centrifuged, washed, and dried.

[0089] (4) The hydrothermal reaction product after the above treatment was transferred to a high-temperature tubular furnace and subjected to high-temperature pyrolysis carbonization treatment under an argon atmosphere. The temperature was raised to 1300°C at a heating rate of 5°C / min and kept at this temperature for 3 hours to obtain a biomass-based cross-linked hard carbon material.

[0090] Example 12

[0091] (1) Dissolve 0.5 g of chitosan in 50 mL of 2 g / L acetic acid solution and stir at 80 °C for 1 h to fully dissolve it to prepare a 10 g / L chitosan solution.

[0092] (2) Add 3.0 g of cellulose to the chitosan solution and stir at 80°C for 3 h to mix the two evenly.

[0093] (3) The mixed solution was transferred to a hydrothermal reactor for hydrothermal treatment at a temperature of 220°C for 24 hours. After the reaction was completed and cooled to room temperature, the hydrothermal reaction product was centrifuged, washed, and dried.

[0094] (4) The hydrothermal reaction product after the above treatment was transferred to a high-temperature tubular furnace and subjected to high-temperature pyrolysis carbonization treatment under an argon atmosphere. The temperature was raised to 1300°C at a heating rate of 5°C / min and kept at this temperature for 3 hours to obtain a biomass-based cross-linked hard carbon material.

[0095] Example 13

[0096] (1) Dissolve 0.5 g of chitosan in 50 mL of 2 g / L acetic acid solution and stir at 80 °C for 1 h to fully dissolve it to prepare a 10 g / L chitosan solution.

[0097] (2) Add 1.0 g of cellulose to the chitosan solution and stir at 80°C for 3 h to mix the two evenly.

[0098] (3) The mixed solution was transferred to a hydrothermal reactor for hydrothermal treatment at a temperature of 220°C for 24 hours. After the reaction was completed and cooled to room temperature, the hydrothermal reaction product was centrifuged, washed, and dried.

[0099] (4) The hydrothermal reaction product after the above treatment was transferred to a high-temperature tubular furnace and subjected to high-temperature pyrolysis carbonization treatment under an argon atmosphere. The temperature was raised to 1300°C at a heating rate of 5°C / min and kept at this temperature for 3 hours to obtain a biomass-based cross-linked hard carbon material.

[0100] Example 2

[0101] (1) Dissolve 0.5 g of chitosan in 50 mL of 2 g / L acetic acid solution and stir at 80 °C for 1 h to fully dissolve it to prepare a 10 g / L chitosan solution.

[0102] (2) Add 2.5 g of bamboo powder to the chitosan solution and stir at 80 °C for 3 h to mix the two evenly.

[0103] (3) The mixed solution was transferred to a hydrothermal reactor for hydrothermal treatment at a temperature of 220°C for 24 hours. After the reaction was completed and cooled to room temperature, the hydrothermal reaction product was centrifuged, washed, and dried.

[0104] (4) The hydrothermal reaction product after the above treatment was transferred to a high-temperature tubular furnace and subjected to high-temperature pyrolysis carbonization treatment under an argon atmosphere. The temperature was raised to 1300°C at a heating rate of 5°C / min and kept at this temperature for 3 hours to obtain a biomass-based cross-linked hard carbon material.

[0105] Example 15

[0106] (1) Dissolve 0.5 g of chitosan in 50 mL of 2 g / L acetic acid solution and stir at 80 °C for 1 h to fully dissolve it to prepare a 10 g / L chitosan solution.

[0107] (2) Add 2.5 g of wood powder to the chitosan solution and stir at 80 °C for 3 h to mix the two evenly.

[0108] (3) The mixed solution was transferred to a hydrothermal reactor for hydrothermal treatment at a temperature of 220°C for 24 hours. After the reaction was completed and cooled to room temperature, the hydrothermal reaction product was centrifuged, washed, and dried.

[0109] (4) The hydrothermal reaction product after the above treatment was transferred to a high-temperature tubular furnace and subjected to high-temperature pyrolysis carbonization treatment under an argon atmosphere. The temperature was raised to 1300°C at a heating rate of 5°C / min and kept at this temperature for 3 hours to obtain a biomass-based cross-linked hard carbon material.

[0110] Example 16

[0111] (1) Dissolve 0.5 g of chitosan in 50 mL of 2 g / L acetic acid solution and stir at 80 °C for 1 h to fully dissolve it to prepare a 10 g / L chitosan solution.

[0112] (2) Add 2.5 g peanut shell powder to the chitosan solution and stir at 80 °C for 3 h to mix the two evenly.

[0113] (3) The mixed solution was transferred to a hydrothermal reactor for hydrothermal treatment at a temperature of 220°C for 24 hours. After the reaction was completed and cooled to room temperature, the hydrothermal reaction product was centrifuged, washed, and dried.

[0114] (4) The hydrothermal reaction product after the above treatment was transferred to a high-temperature tubular furnace and subjected to high-temperature pyrolysis carbonization treatment under an argon atmosphere. The temperature was raised to 1300°C at a heating rate of 5°C / min and kept at this temperature for 3 hours to obtain a biomass-based cross-linked hard carbon material.

[0115] Comparative Example 1

[0116] (1) Add 2.5 g of cellulose to a deionized water solution and stir at 80 °C for 3 h to disperse it evenly.

[0117] (2) The above solution was transferred to a hydrothermal reactor for hydrothermal treatment. The hydrothermal reaction temperature was 220°C and the hydrothermal reaction time was 24 hours. After the reaction was completed and cooled to room temperature, the hydrothermal reaction product was centrifuged, washed and dried.

[0118] (3) The hydrothermal reaction product after the above treatment was transferred to a high-temperature tubular furnace and subjected to high-temperature pyrolysis carbonization treatment under an argon atmosphere. The temperature was raised to 1300°C at a heating rate of 5°C / min and kept at this temperature for 3 hours to obtain a cellulose-based hard carbon material.

[0119] Comparative Example 2

[0120] (1) Dissolve 2.5 g of chitosan in 50 mL of 2 g / L acetic acid solution and stir at 80 °C for 1 h to fully dissolve it to prepare a 10 g / L chitosan solution.

[0121] (2) The above solution was transferred to a hydrothermal reactor for hydrothermal treatment. The hydrothermal reaction temperature was 220°C and the hydrothermal reaction time was 24 hours. After the reaction was completed and cooled to room temperature, the hydrothermal reaction product was centrifuged, washed and dried.

[0122] (3) The hydrothermal reaction product after the above treatment was transferred to a high-temperature tubular furnace and subjected to high-temperature pyrolysis carbonization treatment under an argon atmosphere. The temperature was raised to 1300°C at a heating rate of 5°C / min and kept at this temperature for 3 hours to obtain a cellulose-based hard carbon material.

[0123] Comparative Example 3

[0124] (1) Dissolve 0.5 g of glucose in 50 mL of deionized water and stir at room temperature for 1 h to fully dissolve it.

[0125] (2) Add 2.5 g of cellulose to the glucose solution and stir at 80 °C for 3 h to mix the two evenly.

[0126] (3) The mixed solution was transferred to a hydrothermal reactor for hydrothermal treatment at a temperature of 220°C for 24 hours. After the reaction was completed and cooled to room temperature, the hydrothermal reaction product was centrifuged, washed, and dried.

[0127] (4) The hydrothermal reaction product after the above treatment was transferred to a high-temperature tubular furnace and subjected to high-temperature pyrolysis carbonization treatment under an argon atmosphere. The temperature was raised to 1300°C at a heating rate of 5°C / min and kept at this temperature for 3 hours to obtain a biomass-based cross-linked hard carbon material.

[0128] The above is only a preferred example of a biomass-based cross-linked method for preparing a hard carbon negative electrode material for sodium-ion batteries, and the scope of protection of the present invention is not limited to this example. The technical solution of the present invention is to improve and optimize the preparation conditions of the hard carbon material under the same conditions, and all of these conditions are within the scope of protection of the present invention.

[0129] Application and performance testing

[0130] The hard carbon material prepared in the above-mentioned embodiments and comparative examples is used as the negative electrode active material for sodium ion batteries to prepare the electrode sheet. The specific method is as follows: the sodium ion battery hard carbon negative electrode material, the conductive agent acetylene black, and the binder sodium carboxymethyl cellulose are ground into a uniform slurry in a mass ratio of 8:1:1, and then coated on the copper foil with a coater to ensure that the active material surface loading is 1-1.5 g / cm 2 , a hard carbon negative electrode sheet for sodium ion batteries was obtained, and sodium ion button batteries were prepared in a glove box, and the electrochemical performance of the button batteries was tested.

[0131] Table 1 shows the battery performance of the sodium ion battery hard carbon negative electrode material prepared in each embodiment and comparative example. Compared with the comparative example, the embodiment has a higher reversible capacity and first-week coulombic efficiency. This is because the biomass base as a macromolecule extends the molecular chain structure through chemical cross-linking, which can effectively prevent the release of small molecule gases during high-temperature pyrolysis, minimize the formation of surface defects of hard carbon, promote electron transfer, and give it excellent rate performance. Table 2 shows the electrochemical performance 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 and a reversible capacity of 209mAh / g at a current density of 1000mA / g, showing the excellence of the present invention at high current density. Figure 1 The scanning electron microscope image of Example 2 shows that it is amorphous. Figure 2 and Figure 4This shows that the battery prepared by the present invention has a longer platform area. Figure 3 This is the rate performance of Example 2, indicating that the present invention has good cycle stability at different current densities. Figure 5 The long cycle performance of Example 2 at a larger current density (1 A / g) shows that 80% of the capacity is still maintained even after 750 cycles, demonstrating its excellent cycle stability.

[0132] Table 1 Electrochemical performance of the examples and comparative examples (current density 50 mAg -1 )

[0133]

[0134]

[0135] Table 2 Electrochemical performance of Example 2 at different current densities (50-1000 mA / g)

[0136] Current density (mA / g) 50 100 200 300 500 800 1000 Discharge capacity (mAh / g) 330 265 252 241 233 221 212 Charge specific capacity (mAh / g) 274 258 246 237 227 217 209

[0137] The embodiments of the present invention are described in detail above, but the present invention is not limited to the described embodiments. It is apparent to those skilled in the art that various changes, modifications, substitutions, and variations made to these embodiments without departing from the principles and spirit of the present invention are still within the scope of protection of the present invention.

Claims

1. A method for preparing a hard carbon negative electrode material for sodium ion batteries by biomass-based crosslinking, characterized in that: The steps include: (1) dissolving a certain amount of chitosan in an acetic acid solution and stirring to fully dissolve it to prepare a chitosan solution; the concentration of the acetic acid solution is 1-2 g / L, and the concentration of the chitosan solution is 5-12 g / L; (2) adding a certain amount of cellulose to the chitosan solution and stirring to mix the two evenly; the mass ratio of the added cellulose to chitosan is 3:1-6:1; (3) transferring the mixed solution to a hydrothermal reactor for hydrothermal treatment for a certain period of time; after the reactor is cooled to room temperature, the hydrothermal product is centrifuged, washed, and dried; The hydrothermal reaction temperature of the cellulose and chitosan mixed solution is 180-250°C, and the hydrothermal reaction time is 12-48h; (4) transferring the hydrothermal product after the above treatment to a high-temperature tube furnace and performing high-temperature pyrolysis and carbonization treatment under an inert atmosphere to obtain a hard carbon material; 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.

2. The method for preparing a hard carbon negative electrode material for sodium ion batteries by biomass-based crosslinking according to claim 1, characterized in that: The mass ratio of cellulose to chitosan is 5:

1.

3. The method for preparing a hard carbon negative electrode material for sodium ion batteries by biomass-based cross-linking according to claim 1 or 2, characterized in that: The hydrothermal reaction temperature of the cellulose and chitosan mixed solution is 200-240° C., and the hydrothermal reaction time is 24-36 hours.

4. The method for preparing a biomass-based cross-linked hard carbon negative electrode material for sodium ion batteries according to claim 1 or 2, characterized in that: The high-temperature pyrolysis carbonization temperature is 1300-1500°C, the heating rate is 5°C / min, and the holding time is 3-5h.

5. A hard carbon negative electrode material for sodium ion batteries prepared by the method according to any one of claims 1 to 4.

6. A hard carbon negative electrode for a sodium ion battery, characterized in that: The electrode slurry comprises the sodium ion battery hard carbon negative electrode material according to claim 5, a conductive agent acetylene black and a binder sodium carboxymethyl cellulose.

Images