Preparation method and application of cellulose-based hard carbon negative electrode material

Abstract

The invention provides a preparation method and application of a cellulose-based hard carbon negative electrode material, and belongs to the technical field of sodium ion battery negative electrode material preparation. Comprising the following steps: preparing a strong oxidizing acid solution, adding a cellulose raw material into the prepared solution, carrying out ultrasonic vibration, and uniformly stirring; then adding a long-chain molecular compound into the mixture, and stirring until the mixture is uniformly mixed to obtain a mixed solution; then transferring into a hydrothermal reaction kettle for hydrothermal treatment, and after the hydrothermal reaction kettle is cooled to room temperature, centrifuging, washing and drying a hydrothermal product; and finally, transferring the hydrothermal product into a high-temperature tubular furnace, and performing high-temperature pyrolysis carbonization treatment in an inert atmosphere to obtain the cellulose-based hard carbon negative electrode material. A hard carbon precursor containing a large amount of carbonyl and nitrogen doping is constructed through a hydrolysis competition mechanism, then the hard carbon negative electrode material is prepared through high-temperature pyrolysis carbonization, and the problems of low reversible capacity of biomass derived hard carbon, poor first-week coulombic efficiency, battery performance optimization under extremely high and low temperature conditions and the like are solved.

Description

Technical Field

[0001] The present invention relates to the technical field of sodium ion battery negative electrode material preparation, and in particular to a preparation method and application of a cellulose-based hard carbon negative electrode material. Background Art

[0002] With global lithium shortages and rising battery raw material costs, sodium-ion batteries (SIBs), due to their abundant and widespread sodium resources, have become a research focus for novel energy storage systems. Hard carbon materials, as anodes for SIBs, are widely recognized as the most promising SIB anode materials for industrialization due to their unique disordered microcrystalline structure, tunable interlayer spacing, and abundant nanopores.

[0003] However, hard carbon materials still face challenges in practical applications, such as low first-cycle coulombic efficiency, insufficient long-cycle stability, and significant attenuation of electrochemical performance under extreme high and low temperature conditions. Traditional hard carbon materials lack precise control of pore distribution and functional group modification, making it difficult to achieve high sodium storage sites and low interfacial impedance at the same time. Although existing biomass-derived hard carbons (such as cellulose-based) have cost and environmental advantages, they are limited in reversible capacity and first-efficiency improvement due to insufficient structural disorder and uneven distribution of functional groups. Although existing technologies have improved performance through precursor screening, micro-nanostructure regulation, and surface functional group modification, they have not yet broken through the kinetic limitations under a wide temperature range.

[0004] Therefore, providing a preparation method and application of cellulose-based hard carbon negative electrode materials that can maintain excellent electrochemical performance under extreme high and low temperature conditions, have both high first-cycle coulombic efficiency and long-cycle stability, and have a wide source of raw materials and low cost, is of great practical significance for promoting the large-scale application of sodium-ion batteries in wide-temperature energy storage scenarios. Summary of the Invention

[0005] In order to overcome the shortcomings of the existing technology, the purpose of the present invention is to provide a preparation method and application of cellulose-based hard carbon negative electrode materials. A hard carbon precursor containing a large amount of carbonyl and nitrogen doping is constructed through a hydrolysis competition mechanism, and then the hard carbon negative electrode material is prepared by high-temperature pyrolysis carbonization, which solves the problems of low reversible capacity of biomass-derived hard carbon, poor first-week coulombic efficiency and optimization of battery performance under extreme high and low temperature conditions.

[0006] To achieve the above object, the present invention provides the following solutions:

[0007] A method for preparing a cellulose-based hard carbon negative electrode material comprises the following steps:

[0008] S1. Prepare a strong oxidizing acid solution, add a cellulose raw material into the strong oxidizing acid solution, vibrate ultrasonically, and stir to obtain an initial solution;

[0009] S2, adding the long-chain molecular compound to the initial solution, stirring until the mixture is uniform, to obtain a mixed solution;

[0010] S3, transferring the mixed solution to a hydrothermal reactor for hydrothermal treatment, and after the hydrothermal reactor is cooled to room temperature, centrifuging, washing and drying the hydrothermal product in sequence;

[0011] S4. The treated hydrothermal product is transferred to a high-temperature tube furnace and subjected to high-temperature pyrolysis and carbonization treatment under an inert atmosphere to obtain a cellulose-based hard carbon negative electrode material.

[0012] Preferably, in S1, the strong oxidizing acid solution is a sulfuric acid solution or a nitric acid solution with a concentration of 0.2-1.0 M; the cellulose raw material is a biological raw material containing cellulose such as cellulose powder or wood powder, bamboo powder, or straw powder, and the added mass of the cellulose raw material is 2-10 g.

[0013] Preferably, in S1, the ultrasonic vibration time is 10 minutes and the stirring temperature is 60°C; in S2, the stirring temperature is 60°C and the stirring time is 3 hours.

[0014] Preferably, in S2, the long-chain molecular compound is one or more of polyvinyl pyrrolidone, polyethyleneimine or polydimethyldiallylammonium chloride, and the mass of the long-chain molecular compound is 2-10 g.

[0015] Preferably, in S3, the temperature of the hydrothermal treatment is 150-300°C, and the holding time is 12-24 hours.

[0016] Preferably, in S3, the hydrothermal product is centrifugally washed for no less than 3 times, and the drying temperature is 60-100°C.

[0017] Preferably, in S4, the inert atmosphere is nitrogen or argon.

[0018] Preferably, in S4, the heating rate of the high-temperature pyrolysis carbonization treatment is 2-10°C / min, the temperature is 1000-1800°C, and the holding time is 2-10h.

[0019] The present invention also provides an application of the cellulose-based hard carbon negative electrode material prepared by the above-mentioned preparation method of the cellulose-based hard carbon negative electrode material in a sodium ion battery.

[0020] Preferably, when preparing a hard carbon anode sodium ion battery according to the present invention, the cellulose-based 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, coated on a copper foil by a coater, and cut into 12mm battery pole pieces, and the mass of the active material of the battery pole piece is 1-1.5g / cm 2.

[0021] According to the specific embodiments provided by the present invention, the present invention discloses the following technical effects:

[0022] (1) The present invention introduces a large number of carbonyl groups (C=O) into the hard carbon precursor through a competitive mechanism of strong oxidizing acid pretreatment and hydrolysis of long-chain molecular compounds, and constructs a disordered carbon skeleton rich in closed pores and defect structures. The presence of carbonyl groups provides additional chemical adsorption sites for sodium ions, while defect structures and nanopores can shorten the ion transmission path and increase the active sites for sodium storage. At the same time, the conjugated structure formed by nitrogen doping stabilizes the electron cloud distribution near the carbonyl group, reduces the interfacial impedance, and optimizes the electron transmission path, so that the material exhibits a reversible specific capacity of 369mAh / g at room temperature of 25°C and 0.1A / g, and the first-week coulombic efficiency reaches 87.9%, which is significantly improved compared to the first efficiency of traditional hard carbon materials, and the capacity retention rate during the cycle is excellent.

[0023] (2) The present invention reduces the sodium ion diffusion barrier by optimizing the micro-nanopore structure of the material and expanding the interlayer spacing, while the carbonyl functional group still maintains ion adsorption activity at low temperatures, and nitrogen doping further improves the charge transfer dynamics under a wide temperature range. According to experimental data, the material has a capacity retention rate of 76% after 1000 cycles at -25°C and 1.0A / g, and no attenuation after 200 cycles at a high temperature of 70°C; the full battery assembled with the Na3V2(PO4)3 positive electrode has no capacity attenuation after 100 cycles at an extremely low temperature of -45°C, breaking the performance attenuation bottleneck of traditional hard carbon in wide temperature applications and meeting the energy storage needs in extreme environments.

[0024] (3) The present invention uses cellulose biomass (such as wood powder, bamboo powder, straw powder, etc.) as a precursor. The raw material source is wide and the cost is low. Compared with traditional phenolic resin or asphalt precursors, the cost is reduced and it has green and environmentally friendly characteristics. The preparation method adopts a hydrothermal method combined with high-temperature pyrolysis. The process is simple and controllable. The drying temperature only needs 60-100°C, and the pyrolysis temperature is 1000-1800°C to achieve efficient carbonization. The equipment requirements are low and the energy consumption is controllable. It is suitable for large-scale industrial production and provides a low-cost and high-reliability technical path for the industrialization of sodium ion battery negative electrode materials. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in 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 paying any creative work.

[0026] Figure 1This is a flow chart of a method for preparing a cellulose-based hard carbon negative electrode material according to the present invention;

[0027] Figure 2 This is an SEM image of the cellulose-based hard carbon negative electrode material prepared in Example 1 of the present invention;

[0028] Figure 3 This is a charge and discharge curve of the cellulose-based hard carbon negative electrode material prepared in Example 1 of the present invention at room temperature of 25° C. and a current density of 0.1 A / g;

[0029] Figure 4 The capacity retention rate of the cellulose-based hard carbon negative electrode material prepared in Example 1 of the present invention after 1000 cycles at a low temperature of -25°C and a current density of 1.0 A / g;

[0030] Figure 5 The capacity retention rate of the cellulose-based hard carbon negative electrode material prepared in Example 1 of the present invention after 200 cycles at a high temperature of 70°C and a current density of 1.0 A / g;

[0031] Figure 6 The cellulose-based hard carbon negative electrode material prepared in Example 1 of the present invention is assembled with the Na3V2(PO4)3 positive electrode at a low temperature of -45°C. The capacity retention rate of the full battery is maintained after 100 cycles even under extremely harsh low temperature conditions of -45°C. DETAILED DESCRIPTION

[0032] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0033] like Figure 1 As shown, the present invention provides a method for preparing a cellulose-based hard carbon negative electrode material, comprising the following steps:

[0034] S1. Prepare a strong oxidizing acid solution, add a cellulose raw material into the strong oxidizing acid solution, vibrate ultrasonically, and stir to obtain an initial solution;

[0035] S2, adding the long-chain molecular compound to the initial solution, stirring until the mixture is uniform, to obtain a mixed solution;

[0036] S3, transferring the mixed solution to a hydrothermal reactor for hydrothermal treatment, and after the hydrothermal reactor is cooled to room temperature, centrifuging, washing and drying the hydrothermal product in sequence;

[0037] S4. The treated hydrothermal product is transferred to a high-temperature tube furnace and subjected to high-temperature pyrolysis and carbonization treatment under an inert atmosphere to obtain a cellulose-based hard carbon negative electrode material.

[0038] In the above steps, the strong oxidizing acid solution is a sulfuric acid solution or a nitric acid solution with a concentration of 0.2-1.0M; the cellulose raw material is cellulose powder or a cellulose-containing biological raw material such as wood powder, bamboo powder, or straw powder, and the added mass of the cellulose raw material is 2-10g. The ultrasonic vibration time is 10 minutes, and the stirring temperature is 60°C.

[0039] In S2, the stirring temperature is 60° C., the stirring time is 3 hours, the long-chain molecular compound is one or more of polyvinyl pyrrolidone, polyethyleneimine, or polydimethyldiallylammonium chloride, and the mass of the long-chain molecular compound is 2-10 g.

[0040] In S3, the temperature of the hydrothermal treatment is 150-300°C, and the holding time is 12-24 hours; the hydrothermal product is centrifugally washed for no less than 3 times, and the drying temperature is 60-100°C.

[0041] In S4, the inert atmosphere is nitrogen or argon. The high-temperature pyrolysis carbonization treatment has a heating rate of 2-10°C / min, a temperature of 1000-1800°C, and a holding time of 2-10 hours.

[0042] The present invention also provides an application of the cellulose-based hard carbon negative electrode material prepared by the above-mentioned preparation method of the cellulose-based hard carbon negative electrode material in a sodium ion battery.

[0043] Specifically, when preparing a hard carbon anode sodium ion battery in the present invention, the cellulose-based 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, coated on a copper foil by a coater, and cut into 12mm battery pole pieces, and the mass of the active material of the battery pole piece is 1-1.5g / cm 2 .

[0044] In order to make the above features and advantages of the present invention more obvious and easy to understand, the present invention is further described in detail below with reference to the accompanying drawings and specific embodiments.

[0045] Example 1

[0046] In this embodiment, the method for preparing the cellulose-based hard carbon material comprises the following steps:

[0047] Prepare 60 mL of 0.5 M sulfuric acid solution, add 5 g of cellulose powder into the 0.5 M sulfuric acid solution, and ultrasonically vibrate for 10 min to form a homogeneous solution, and continue stirring at 60°C.

[0048] 2.5 g of polyvinyl pyrrolidone was added to the uniform solution formed above, and the mixture was stirred at 60° C. for 3 h to uniformly mix the two to obtain a mixed solution.

[0049] The obtained mixed solution was transferred to a hydrothermal reactor for hydrothermal treatment. The hydrothermal reaction temperature was 200°C and the hydrothermal reaction time was 15 hours. After the reaction was completed and cooled to room temperature, the hydrothermal reaction product was centrifuged and washed for no less than three times and dried at 80°C.

[0050] Finally, the treated hydrothermal reaction product 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 1400°C at a heating rate of 5°C / min and kept warm for 3 hours to obtain a cellulose-based hard carbon material.

[0051] Example 2

[0052] In this embodiment, the method for preparing the cellulose-based hard carbon material comprises the following steps:

[0053] Prepare 60 mL of 1.0 M sulfuric acid solution, add 5 g of cellulose powder into the 1.0 M sulfuric acid solution, and ultrasonically vibrate for 10 min to form a homogeneous solution, and continue stirring at 60°C.

[0054] 2.5 g of polyvinyl pyrrolidone was added to the uniform solution formed above, and the mixture was stirred at 60° C. for 3 h to uniformly mix the two to obtain a mixed solution.

[0055] The obtained mixed solution was transferred to a hydrothermal reactor for hydrothermal treatment. The hydrothermal reaction temperature was 200°C and the hydrothermal reaction time was 15 hours. After the reaction was completed and cooled to room temperature, the hydrothermal reaction product was centrifuged and washed for no less than three times and dried at 80°C.

[0056] Finally, the treated hydrothermal reaction product 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 1400°C at a heating rate of 5°C / min and kept warm for 3 hours to obtain a cellulose-based hard carbon material.

[0057] Example 3

[0058] In this embodiment, the method for preparing the cellulose-based hard carbon material comprises the following steps:

[0059] Prepare 60 mL of 0.5 M sulfuric acid solution, add 2 g of cellulose powder into the 0.5 M sulfuric acid solution, and ultrasonically vibrate for 10 min to form a homogeneous solution, and continue stirring at 60°C.

[0060] 1 g of polyvinyl pyrrolidone was added to the uniform solution formed above, and the mixture was stirred at 60° C. for 3 h to mix the two uniformly, thereby obtaining a mixed solution.

[0061] The obtained mixed solution was transferred to a hydrothermal reactor for hydrothermal treatment. The hydrothermal reaction temperature was 200°C and the hydrothermal reaction time was 15 hours. After the reaction was completed and cooled to room temperature, the hydrothermal reaction product was centrifuged and washed for no less than three times and dried at 80°C.

[0062] Finally, the treated hydrothermal reaction product 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 1400°C at a heating rate of 5°C / min and kept warm for 3 hours to obtain a cellulose-based hard carbon material.

[0063] Example 4

[0064] In this embodiment, the method for preparing the cellulose-based hard carbon material includes the following steps:

[0065] Prepare 60 mL of 0.5 M sulfuric acid solution, add 10 g of cellulose powder into the 0.5 M sulfuric acid solution, and ultrasonically vibrate for 10 min to form a homogeneous solution, and continue stirring at 60°C.

[0066] 5 g of polyvinyl pyrrolidone was added to the uniform solution formed above, and the mixture was stirred at 60° C. for 3 h to uniformly mix the two to obtain a mixed solution.

[0067] The obtained mixed solution was transferred to a hydrothermal reactor for hydrothermal treatment. The hydrothermal reaction temperature was 200°C and the hydrothermal reaction time was 15 hours. After the reaction was completed and cooled to room temperature, the hydrothermal reaction product was centrifuged and washed for no less than three times and dried at 80°C.

[0068] Finally, the treated hydrothermal reaction product 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 1400°C at a heating rate of 5°C / min and kept warm for 3 hours to obtain a cellulose-based hard carbon material.

[0069] Example 5

[0070] In this embodiment, the method for preparing the cellulose-based hard carbon material comprises the following steps:

[0071] Prepare 60 mL of 0.5 M nitric acid solution, add 5 g of cellulose powder into the 0.5 M nitric acid solution, and ultrasonically vibrate for 10 min to form a homogeneous solution, and continue stirring at 60°C.

[0072] 2.5 g of polyvinyl pyrrolidone was added to the uniform solution formed above, and the mixture was stirred at 60° C. for 3 h to uniformly mix the two to obtain a mixed solution.

[0073] The obtained mixed solution was transferred to a hydrothermal reactor for hydrothermal treatment. The hydrothermal reaction temperature was 200°C and the hydrothermal reaction time was 15 hours. After the reaction was completed and cooled to room temperature, the hydrothermal reaction product was centrifuged and washed for no less than three times and dried at 80°C.

[0074] Finally, the treated hydrothermal reaction product 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 1400°C at a heating rate of 5°C / min and kept warm for 3 hours to obtain a cellulose-based hard carbon material.

[0075] Example 6

[0076] In this embodiment, the method for preparing the cellulose-based hard carbon material comprises the following steps:

[0077] Prepare 60 mL of 0.5 M sulfuric acid solution, add 5 g of cellulose powder into the 0.5 M sulfuric acid solution, and ultrasonically vibrate for 10 min to form a homogeneous solution, and continue stirring at 60°C.

[0078] 2.5 g of polyethyleneimine was added to the uniform solution formed above, and the mixture was stirred at 60° C. for 3 h to mix the two uniformly, thereby obtaining a mixed solution.

[0079] The obtained mixed solution was transferred to a hydrothermal reactor for hydrothermal treatment. The hydrothermal reaction temperature was 200°C and the hydrothermal reaction time was 15 hours. After the reaction was completed and cooled to room temperature, the hydrothermal reaction product was centrifuged and washed for no less than three times and dried at 80°C.

[0080] Finally, the treated hydrothermal reaction product 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 1400°C at a heating rate of 5°C / min and kept warm for 3 hours to obtain a cellulose-based hard carbon material.

[0081] Example 7

[0082] In this embodiment, the method for preparing the cellulose-based hard carbon material comprises the following steps:

[0083] Prepare 60 mL of 0.5 M sulfuric acid solution, add 5 g of cellulose powder into the 0.5 M sulfuric acid solution, and ultrasonically vibrate for 10 min to form a homogeneous solution, and continue stirring at 60°C.

[0084] 2.5 g of polydimethyldiallylammonium chloride was added to the uniform solution formed above, and the mixture was stirred at 60° C. for 3 h to uniformly mix the two to obtain a mixed solution.

[0085] The obtained mixed solution was transferred to a hydrothermal reactor for hydrothermal treatment. The hydrothermal reaction temperature was 200°C and the hydrothermal reaction time was 15 hours. After the reaction was completed and cooled to room temperature, the hydrothermal reaction product was centrifuged and washed for no less than three times and dried at 80°C.

[0086] Finally, the treated hydrothermal reaction product 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 1400°C at a heating rate of 5°C / min and kept warm for 3 hours to obtain a cellulose-based hard carbon material.

[0087] Example 8

[0088] In this embodiment, the method for preparing the cellulose-based hard carbon material comprises the following steps:

[0089] Prepare 60 mL of 0.5 M sulfuric acid solution, add 5 g of cellulose powder into the 0.5 M sulfuric acid solution, and ultrasonically vibrate for 10 min to form a homogeneous solution, and continue stirring at 60°C.

[0090] 2.5 g of polyvinyl pyrrolidone was added to the uniform solution formed above, and the mixture was stirred at 60° C. for 3 h to uniformly mix the two to obtain a mixed solution.

[0091] The obtained mixed solution was transferred to a hydrothermal reactor for hydrothermal treatment. The hydrothermal reaction temperature was 150°C and the hydrothermal reaction time was 15 hours. After the reaction was completed and cooled to room temperature, the hydrothermal reaction product was centrifuged and washed for no less than three times and dried at 80°C.

[0092] Finally, the treated hydrothermal reaction product 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 1400°C at a heating rate of 5°C / min and kept warm for 3 hours to obtain a cellulose-based hard carbon material.

[0093] Example 9

[0094] In this embodiment, the method for preparing the cellulose-based hard carbon material comprises the following steps:

[0095] Prepare 60 mL of 0.5 M sulfuric acid solution, add 5 g of cellulose powder into the 0.5 M sulfuric acid solution, and ultrasonically vibrate for 10 min to form a homogeneous solution, and continue stirring at 60°C.

[0096] 2.5 g of polyvinyl pyrrolidone was added to the uniform solution formed above, and the mixture was stirred at 60° C. for 3 h to uniformly mix the two to obtain a mixed solution.

[0097] The obtained mixed solution was transferred to a hydrothermal reactor for hydrothermal treatment. The hydrothermal reaction temperature was 250°C and the hydrothermal reaction time was 15 hours. After the reaction was completed and cooled to room temperature, the hydrothermal reaction product was centrifuged and washed for no less than three times and dried at 80°C.

[0098] Finally, the treated hydrothermal reaction product 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 1400°C at a heating rate of 5°C / min and kept warm for 3 hours to obtain a cellulose-based hard carbon material.

[0099] Example 10

[0100] In this embodiment, the method for preparing the cellulose-based hard carbon material comprises the following steps:

[0101] Prepare 60 mL of 0.5 M sulfuric acid solution, add 5 g of cellulose powder into the 0.5 M sulfuric acid solution, and ultrasonically vibrate for 10 min to form a homogeneous solution, and continue stirring at 60°C.

[0102] 2.5 g of polyvinyl pyrrolidone was added to the uniform solution formed above, and the mixture was stirred at 60° C. for 3 h to uniformly mix the two to obtain a mixed solution.

[0103] The obtained mixed solution was transferred to a hydrothermal reactor for hydrothermal treatment. The hydrothermal reaction temperature was 300°C and the hydrothermal reaction time was 15 hours. After the reaction was completed and cooled to room temperature, the hydrothermal reaction product was centrifuged and washed for no less than three times and dried at 80°C.

[0104] Finally, the treated hydrothermal reaction product 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 1400°C at a heating rate of 5°C / min and kept warm for 3 hours to obtain a cellulose-based hard carbon material.

[0105] Example 11

[0106] In this embodiment, the method for preparing the cellulose-based hard carbon material comprises the following steps:

[0107] Prepare 60 mL of 0.5 M sulfuric acid solution, add 5 g of cellulose powder into the 0.5 M sulfuric acid solution, and ultrasonically vibrate for 10 min to form a homogeneous solution, and continue stirring at 60°C.

[0108] 2.5 g of polyvinyl pyrrolidone was added to the uniform solution formed above, and the mixture was stirred at 60° C. for 3 h to uniformly mix the two to obtain a mixed solution.

[0109] The obtained mixed solution was transferred to a hydrothermal reactor for hydrothermal treatment. The hydrothermal reaction temperature was 200°C and the hydrothermal reaction time was 10 hours. After the reaction was completed and cooled to room temperature, the hydrothermal reaction product was centrifuged and washed for no less than three times and dried at 80°C.

[0110] Finally, the treated hydrothermal reaction product 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 1400°C at a heating rate of 5°C / min and kept warm for 3 hours to obtain a cellulose-based hard carbon material.

[0111] Example 12

[0112] In this embodiment, the method for preparing the cellulose-based hard carbon material comprises the following steps:

[0113] Prepare 60 mL of 0.5 M sulfuric acid solution, add 5 g of cellulose powder into the 0.5 M sulfuric acid solution, and ultrasonically vibrate for 10 min to form a homogeneous solution, and continue stirring at 60°C.

[0114] 2.5 g of polyvinyl pyrrolidone was added to the uniform solution formed above, and the mixture was stirred at 60° C. for 3 h to uniformly mix the two to obtain a mixed solution.

[0115] The obtained mixed solution was transferred to a hydrothermal reactor for hydrothermal treatment. The hydrothermal reaction temperature was 250°C and the hydrothermal reaction time was 20 hours. After the reaction was completed and cooled to room temperature, the hydrothermal reaction product was centrifuged and washed for no less than three times and dried at 80°C.

[0116] Finally, the treated hydrothermal reaction product 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 1400°C at a heating rate of 5°C / min and kept warm for 3 hours to obtain a cellulose-based hard carbon material.

[0117] Example 13

[0118] In this embodiment, the method for preparing the cellulose-based hard carbon material comprises the following steps:

[0119] Prepare 60 mL of 0.5 M sulfuric acid solution, add 5 g of cellulose powder into the 0.5 M sulfuric acid solution, and ultrasonically vibrate for 10 min to form a homogeneous solution, and continue stirring at 60°C.

[0120] 2.5 g of polyvinyl pyrrolidone was added to the uniform solution formed above, and the mixture was stirred at 60° C. for 3 h to uniformly mix the two to obtain a mixed solution.

[0121] The obtained mixed solution was transferred to a hydrothermal reactor for hydrothermal treatment. The hydrothermal reaction temperature was 200°C and the hydrothermal reaction time was 15 hours. After the reaction was completed and cooled to room temperature, the hydrothermal reaction product was centrifuged and washed for no less than three times and dried at 80°C.

[0122] Finally, the treated hydrothermal reaction product 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 1400°C at a heating rate of 2°C / min and kept warm for 3 hours to obtain a cellulose-based hard carbon material.

[0123] Example 14

[0124] In this embodiment, the method for preparing the cellulose-based hard carbon material comprises the following steps:

[0125] Prepare 60 mL of 0.5 M sulfuric acid solution, add 5 g of cellulose powder into the 0.5 M sulfuric acid solution, and ultrasonically vibrate for 10 min to form a homogeneous solution, and continue stirring at 60°C.

[0126] 2.5 g of polyvinyl pyrrolidone was added to the uniform solution formed above, and the mixture was stirred at 60° C. for 3 h to uniformly mix the two to obtain a mixed solution.

[0127] The obtained mixed solution was transferred to a hydrothermal reactor for hydrothermal treatment. The hydrothermal reaction temperature was 200°C and the hydrothermal reaction time was 15 hours. After the reaction was completed and cooled to room temperature, the hydrothermal reaction product was centrifuged and washed for no less than three times and dried at 80°C.

[0128] Finally, the treated hydrothermal reaction product 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 1400°C at a heating rate of 10°C / min and kept warm for 3 hours to obtain a cellulose-based hard carbon material.

[0129] Example 15

[0130] In this embodiment, the method for preparing the cellulose-based hard carbon material comprises the following steps:

[0131] Prepare 60 mL of 0.5 M sulfuric acid solution, add 5 g of cellulose powder into the 0.5 M sulfuric acid solution, and ultrasonically vibrate for 10 min to form a homogeneous solution, and continue stirring at 60°C.

[0132] 2.5 g of polyvinyl pyrrolidone was added to the uniform solution formed above, and the mixture was stirred at 60° C. for 3 h to uniformly mix the two to obtain a mixed solution.

[0133] The obtained mixed solution was transferred to a hydrothermal reactor for hydrothermal treatment. The hydrothermal reaction temperature was 200°C and the hydrothermal reaction time was 15 hours. After the reaction was completed and cooled to room temperature, the hydrothermal reaction product was centrifuged and washed for no less than three times and dried at 80°C.

[0134] Finally, the treated hydrothermal reaction product 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 warm for 3 hours to obtain a cellulose-based hard carbon material.

[0135] Example 16

[0136] In this embodiment, the method for preparing the cellulose-based hard carbon material comprises the following steps:

[0137] Prepare 60 mL of 0.5 M sulfuric acid solution, add 5 g of cellulose powder into the 0.5 M sulfuric acid solution, and ultrasonically vibrate for 10 min to form a homogeneous solution, and continue stirring at 60°C.

[0138] 2.5 g of polyvinyl pyrrolidone was added to the uniform solution formed above, and the mixture was stirred at 60° C. for 3 h to uniformly mix the two to obtain a mixed solution.

[0139] The obtained mixed solution was transferred to a hydrothermal reactor for hydrothermal treatment. The hydrothermal reaction temperature was 200°C and the hydrothermal reaction time was 15 hours. After the reaction was completed and cooled to room temperature, the hydrothermal reaction product was centrifuged and washed for no less than three times and dried at 80°C.

[0140] Finally, the treated hydrothermal reaction product 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 warm for 3 hours to obtain a cellulose-based hard carbon material.

[0141] Example 17

[0142] In this embodiment, the method for preparing the cellulose-based hard carbon material comprises the following steps:

[0143] Prepare 60 mL of 0.5 M sulfuric acid solution, add 5 g of cellulose powder into the 0.5 M sulfuric acid solution, and ultrasonically vibrate for 10 min to form a homogeneous solution, and continue stirring at 60°C.

[0144] 2.5 g of polyvinyl pyrrolidone was added to the uniform solution formed above, and the mixture was stirred at 60° C. for 3 h to uniformly mix the two to obtain a mixed solution.

[0145] The obtained mixed solution was transferred to a hydrothermal reactor for hydrothermal treatment. The hydrothermal reaction temperature was 200°C and the hydrothermal reaction time was 15 hours. After the reaction was completed and cooled to room temperature, the hydrothermal reaction product was centrifuged and washed for no less than three times and dried at 80°C.

[0146] Finally, the treated hydrothermal reaction product 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 1400°C at a heating rate of 5°C / min and kept warm for 1 hour to obtain a cellulose-based hard carbon material.

[0147] Example 18

[0148] In this embodiment, the method for preparing the cellulose-based hard carbon material comprises the following steps:

[0149] Prepare 60 mL of 0.5 M sulfuric acid solution, add 5 g of cellulose powder into the 0.5 M sulfuric acid solution, and ultrasonically vibrate for 10 min to form a homogeneous solution, and continue stirring at 60°C.

[0150] 2.5 g of polyvinyl pyrrolidone was added to the uniform solution formed above, and the mixture was stirred at 60° C. for 3 h to uniformly mix the two to obtain a mixed solution.

[0151] The obtained mixed solution was transferred to a hydrothermal reactor for hydrothermal treatment. The hydrothermal reaction temperature was 200°C and the hydrothermal reaction time was 15 hours. After the reaction was completed and cooled to room temperature, the hydrothermal reaction product was centrifuged and washed for no less than three times and dried at 80°C.

[0152] Finally, the treated hydrothermal reaction product 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 1400°C at a heating rate of 5°C / min and kept warm for 5 hours to obtain a cellulose-based hard carbon material.

[0153] Comparative Example 1

[0154] In this comparative example, 5 g of cellulose powder was transferred to a high-temperature tubular furnace without any treatment, and subjected to high-temperature pyrolysis and carbonization treatment under an argon atmosphere. The temperature was raised to 1400°C at a heating rate of 5°C / min and kept warm for 3 hours to obtain the hard carbon material of comparative example 1.

[0155] Comparative Example 2

[0156] In this comparative example, the following steps are included:

[0157] Prepare 60 mL of 0.2 M sulfuric acid solution, add 5 g of cellulose powder into the 0.2 M sulfuric acid solution, and ultrasonically vibrate for 10 min to form a homogeneous solution, and continue stirring at 60°C.

[0158] The above uniform solution was transferred to a hydrothermal reactor for hydrothermal treatment. The hydrothermal reaction temperature was 200°C and the hydrothermal reaction time was 15 hours. After the reaction was completed and cooled to room temperature, the hydrothermal reaction product was centrifuged and washed for no less than three times and dried at 80°C.

[0159] Finally, the treated hydrothermal reaction product was transferred to a high-temperature tubular furnace and subjected to high-temperature pyrolysis and carbonization treatment under an argon atmosphere. The temperature was raised to 1400°C at a heating rate of 5°C / min and kept warm for 5 hours to obtain the hard carbon material of Comparative Example 2.

[0160] According to Examples 1 to 18 and Comparative Example 1 provided above, the hard carbon material prepared was applied to a sodium ion battery, and the prepared hard carbon material was used as the negative electrode active material of the sodium ion battery to prepare an electrode sheet. Sodium ion button batteries were prepared under an inert atmosphere in a glove box, and the electrochemical performance of the button batteries was tested. The results are shown in Table 1.

[0161] Table 1 Electrochemical performance test results

[0162]

[0163]

[0164] As shown in Table 1, compared with Comparative Examples 1 to 2, Example 1 has higher reversible capacity and first-cycle coulombic efficiency. This is because the acid-catalyzed hydrolysis of cellulose can form a uniform carbon sphere structure with a particle size of 50-500 nm. Figure 2 This micro-nanostructure is beneficial for optimizing pore distribution and increasing the number of closed pores during the subsequent high-temperature carbonization process, thereby improving the efficiency of sodium ion transmission. Furthermore, during the acid hydrolysis process, cellulose and long-chain macromolecules form a hydrolysis competition mechanism, which may introduce functional groups such as hydroxyl (-OH) and carbonyl (C=O) onto the surface of the hard carbon precursor. These functional groups can enhance the material's reactivity and the adsorption / diffusion capacity of sodium ions, positively affecting the electrochemical properties of the hard carbon material.

[0165] In addition, refer to Figure 3 The results shown in the figure show that the cellulose-based hard carbon prepared in Example 1 achieved a high reversible capacity of 369 mAh / g and an ultra-high first-cycle coulombic efficiency of 87.9% under the current condition of 0.1 A / g. In addition, in order to further improve the application prospects of batteries under extreme temperature conditions (-45℃~70℃), high and low temperature tests were carried out on the sodium ion battery assembled with cellulose-based hard carbon materials. The results obtained are as follows Figure 4 and Figure 5As shown, under low temperature test conditions of -45°C, the capacity retention rate of cellulose-based hard carbon sodium ion battery was as high as 76% after 1000 cycles. Under low temperature test conditions of 70°C, the cellulose-based hard carbon sodium ion battery had no capacity decay after 200 cycles. This result fully demonstrates the adaptability of cellulose-based hard carbon under high and low temperature conditions. The optimized micro-nanopore structure and large interlayer spacing of cellulose-based hard carbon reduce the diffusion barrier of sodium ions. At the same time, a large number of carbonyl functional groups introduced by the hydrolysis competition mechanism can still remain active at low temperatures, promoting ion embedding dynamics. These advantages make cellulose-based hard carbon materials an ideal negative electrode candidate material for sodium ion batteries in extreme temperature environments, especially in low temperature capacity retention and high temperature cycle stability. It shows significant potential. In order to further verify its commercial application prospects, the cellulose-based hard carbon negative electrode and sodium vanadium phosphate (Na3V2(PO4)3) positive electrode were assembled into a full battery and tested under extreme low temperature test conditions of -45°C. The results are as follows Figure 6 As shown, the capacity retention rate after 95 cycles is as high as 100%, which proves the excellent electrochemical performance of cellulose-based hard carbon negative electrode materials and has significant advantages in application scenarios with strict requirements on environmental adaptability.

[0166] Therefore, the above-mentioned preparation method and application of a cellulose-based hard carbon negative electrode material are adopted, a hard carbon precursor containing a large amount of carbonyl and nitrogen doping is constructed through a hydrolysis competition mechanism, and then the hard carbon negative electrode material is prepared by high-temperature pyrolysis carbonization, which solves the problems of low reversible capacity of biomass-derived hard carbon, poor first-week coulombic efficiency and optimization of battery performance under extreme high and low temperature conditions.

[0167] The various embodiments in this specification are described in a progressive manner, and each embodiment focuses on the differences from other embodiments. The same or similar parts between the various embodiments can be referenced to each other.

[0168] This document uses specific examples to illustrate the principles and implementation methods of the present invention. The above examples are only intended to help understand the method and core concept of the present invention. At the same time, those skilled in the art will find that the specific implementation methods and application scopes may vary based on the concept of the present invention. In summary, the contents of this specification should not be construed as limiting the present invention.

Claims

1. A method for preparing a cellulose-based hard carbon negative electrode material, characterized in that: The following steps are involved: S1. Prepare a strong oxidizing acid solution, add a cellulose raw material into the strong oxidizing acid solution, vibrate ultrasonically, and stir to obtain an initial solution; S2, adding the long-chain molecular compound to the initial solution, stirring until the mixture is uniform, to obtain a mixed solution; S3, transferring the mixed solution to a hydrothermal reactor for hydrothermal treatment, and after the hydrothermal reactor is cooled to room temperature, centrifuging, washing and drying the hydrothermal product in sequence; S4. The treated hydrothermal product is transferred to a high-temperature tube furnace and subjected to high-temperature pyrolysis and carbonization treatment under an inert atmosphere to obtain a cellulose-based hard carbon negative electrode material.

2. The method for preparing a cellulose-based hard carbon negative electrode material according to claim 1, characterized in that: In S1, the strong oxidizing acid solution is a sulfuric acid solution or a nitric acid solution with a concentration of 0.2-1.0 M; the cellulose raw material is a cellulose powder or a biological raw material containing cellulose such as wood powder, bamboo powder, or straw powder, and the added mass of the cellulose raw material is 2-10 g.

3. The method for preparing a cellulose-based hard carbon negative electrode material according to claim 1, characterized in that: In S1, the ultrasonic vibration time is 10 minutes and the stirring temperature is 60°C; in S2, the stirring temperature is 60°C and the stirring time is 3 hours.

4. The method for preparing a cellulose-based hard carbon negative electrode material according to claim 1, characterized in that: In S2, the long-chain molecular compound is one or more of polyvinyl pyrrolidone, polyethylene imine or polydimethyldiallylammonium chloride, and the mass of the long-chain molecular compound is 2-10 g.

5. The method for preparing a cellulose-based hard carbon negative electrode material according to claim 1, characterized in that: In S3, the temperature of the hydrothermal treatment is 150-300°C, and the holding time is 12-24 hours.

6. The method for preparing a cellulose-based hard carbon negative electrode material according to claim 1, characterized in that: In S3, the hydrothermal product is centrifugally washed for no less than 3 times, and the drying temperature is 60-100°C.

7. The method for preparing a cellulose-based hard carbon negative electrode material according to claim 1, characterized in that: In S4, the inert atmosphere is nitrogen or argon.

8. The method for preparing a cellulose-based hard carbon negative electrode material according to claim 1, characterized in that: In S4, the high-temperature pyrolysis carbonization treatment is performed at a heating rate of 2-10°C / min, a temperature of 1000-1800°C, and a holding time of 2-10h.

9. Use of a cellulose-based hard carbon negative electrode material prepared according to the method for preparing a cellulose-based hard carbon negative electrode material according to any one of claims 1 to 8 in a sodium ion battery.

10. Application of the cellulose-based hard carbon negative electrode material prepared by the method for preparing a cellulose-based hard carbon negative electrode material according to claim 9 in a sodium ion battery, characterized in that: When preparing a hard carbon anode sodium ion battery, the cellulose-based 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, coated on a copper foil by a coater, and cut into 12mm battery pole pieces, and the mass of the active material of the battery pole piece is 1-1.5g / cm 2 .

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