Preparation method of dual-oxygen-doped cellulose precursor derived hard carbon negative electrode material

Abstract

The invention discloses a preparation method of a dual-oxygen-doped cellulose precursor derived hard carbon negative electrode material, and relates to the technical field of battery negative electrode materials. The preparation method comprises the following steps: (1) dispersing microcrystalline cellulose in an alkaline system, adding an oxygen doping agent, stirring to react, adding an acidic system, heating, stirring and regenerating, and sequentially filtering, washing and freeze-drying to obtain an oxygen-doped cellulose precursor; (2) performing high-temperature annealing on the oxygen-doped cellulose precursor to obtain a precursor; and (3) performing high-temperature carbonization on the precursor, and performing ball milling and vibration screening to obtain the hard carbon negative electrode material. According to the invention, microcrystalline cellulose is used as a carbonization precursor, a dual oxygen doping strategy is adopted to prepare a dual oxygen doped cellulose precursor, a novel oxygen-containing bond is formed between cellulose chains, natural I-type cellulose is converted into amorphous II-type cellulose, and a limited graphitization-like interlayer spacing of the derived hard carbon negative electrode material is effectively expanded; and abundant closed pore structures are generated.

Description

Technical Field

[0001] The invention relates to the technical field of battery negative electrode materials, and in particular to a method for preparing a double oxygen-doped cellulose precursor-derived hard carbon negative electrode material. Background Art

[0002] Sodium-ion batteries have shown the potential to replace lithium-ion batteries due to their abundant sodium resources, low cost, high safety, and wide operating temperature range. However, the performance of sodium-ion batteries is limited by the lack of high-performance negative electrode materials. Currently, the main research on negative electrode materials is focused on carbon-based materials (such as hard carbon) and other material systems, but they face challenges such as specific capacity, rate performance, and cycle stability. Structural regulation, ion diffusion rate, and optimization of energy storage capacity are still research barriers, and the preparation process of existing materials is complex and costly, which restricts the widespread application of sodium-ion batteries.

[0003] The sodium storage mechanism of hard carbon materials mainly includes a three-step process of "adsorption-intercalation-pore filling": first, sodium ions enter the hard carbon structure through surface adsorption; second, sodium ions are embedded in the gaps between carbon layers through an intercalation mechanism; finally, sodium ions are further filled in the closed-pore structure. However, the graphitized interlayer spacing of hard carbon materials is limited, which hinders the mass transfer of sodium ions in the structure, limiting its high specific capacity and excellent cycle performance, thereby restricting the research progress and commercial application of sodium-ion batteries. Summary of the invention

[0004] In order to solve the above technical problems, the purpose of the present invention is to provide a method for preparing a hard carbon negative electrode material derived from a double oxygen-doped cellulose precursor. Microcrystalline cellulose is used as a carbonization precursor, and a double oxygen-doping strategy is adopted to prepare a double oxygen-doped cellulose precursor, forming a new oxygen-containing bond between cellulose chains, thereby converting natural type I cellulose into amorphous type II cellulose. The restricted graphite-like interlayer spacing of the derived hard carbon negative electrode material is effectively expanded, and a rich closed-pore structure is produced. This change helps to improve the mass transfer and storage performance of sodium ions.

[0005] The technical solution of the present invention to solve the above technical problem is as follows: a method for preparing a double oxygen-doped cellulose precursor-derived hard carbon negative electrode material is provided, comprising the following steps: (1) Dispersing microcrystalline cellulose in an alkaline system, adding an oxygen doping agent under mechanical stirring conditions, and then continuing to stir and react in an ice-water bath, then adding an acidic system, heating and stirring to regenerate, and filtering, washing and freeze-drying in sequence to obtain an oxygen-doped cellulose precursor; (2) placing the oxygen-doped cellulose precursor obtained in step (1) in a corundum crucible and annealing at high temperature in an air atmosphere to obtain a double oxygen-doped cellulose precursor; (3) The double oxygen-doped cellulose precursor obtained in step (2) is placed in a vacuum tube furnace, carbonized at high temperature in an argon atmosphere, and then ball-milled and vibrated to obtain a double oxygen-doped cellulose precursor-derived hard carbon negative electrode material.

[0006] Furthermore, in step (1), the alkaline system is prepared by dissolving an alkaline substance and thiourea in water, and the alkaline substance is sodium hydroxide; the acidic system is prepared by dissolving an acidic substance in water, and the acidic substance is sulfuric acid or hydrochloric acid; and the oxygen dopant is epichlorohydrin or ethylene glycol diglycidyl ether.

[0007] Furthermore, in the alkaline system, the mass volume ratio of the alkaline substance, thiourea and water is 5 g:4 g:50 mL; in the acidic system, the mass volume ratio of the acidic substance and water is 60 g:100 mL.

[0008] Furthermore, in step (1), the mass volume ratio of microcrystalline cellulose to the alkaline system is 3 g:50 mL; the volume ratio of the oxygen dopant to the alkaline system is 1-3 mL:100 mL; and the volume ratio of the acidic system to the alkaline system is 1:1.

[0009] Furthermore, in step (1), the reaction is continued to be stirred in an ice-water bath for 2 h, and then an acidic system is added to stir and regenerate at 65 °C, filtered, washed with deionized water for 2-3 times, and freeze-dried at -50 °C for 24 h.

[0010] Furthermore, in step (2), during high temperature annealing, the temperature is raised at 50°C-170°C for 120 min, then at 170°C-190°C for 240 min, then kept at 190°C for 60 min, then raised at 190°C-230°C for 480 min, then kept at 230°C for 60 min, and then naturally cooled to room temperature for annealing.

[0011] Furthermore, in step (3), the temperature is increased at 50-190°C for 60 min, maintained at 190°C for 120 min, then increased at 190-450°C for 60 min, maintained at 450°C for 120 min, then increased at 450-1350°C for 300 min, maintained at 1350°C for 120 min, and finally cooled at 1350-250°C for 400 min and naturally cooled to room temperature.

[0012] Furthermore, in step (3), the mixture is ball milled at 3500 rpm for 1-2 h and vibrated and sieved with a 300-mesh sieve 2-3 times.

[0013] Furthermore, in step (3), the purity of argon is 99.99%.

[0014] The present invention also provides a double oxygen-doped cellulose precursor-derived hard carbon negative electrode material prepared by the preparation method of the double oxygen-doped cellulose precursor-derived hard carbon negative electrode material.

[0015] The present invention has the following beneficial effects: 1. The present invention uses microcrystalline cellulose as the main body and adopts a double oxygen doping strategy to pretreat cellulose. Through chemical pretreatment, the chemical structure of the oxygen-doped cellulose precursor is changed, the hydrogen bond effect is destroyed, and a new ether oxygen bond effect is formed. By adding a dilute acid system, a neutralization reaction occurs with the alkaline substance in the cellulose system. On the one hand, a regeneration reaction of cellulose from a solution state to a gel state is achieved. On the other hand, the alkaline system is neutralized to prevent the residual sodium hydroxide and thiourea in the precursor from forming open pores during the carbonization process, resulting in a larger mass transfer resistance and an unfavorable Coulomb first effect. At the same time, the double doping converts natural type I cellulose into amorphous type II cellulose.

[0016] 2. In addition to chemical oxygen doping, the present invention increases the oxygen-containing bonds of the precursor by pre-oxidation in an air atmosphere, thereby achieving secondary oxygen doping of the cellulose precursor, forming more closed-cell generating sites during the carbonization process, and at the same time, the doped oxygen element can play a role in expanding the graphitized interlayer spacing.

[0017] 3. The present invention uses double oxygen-doped cellulose as a carbonization precursor to prepare a double oxygen-doped cellulose precursor-derived hard carbon negative electrode material, which improves the restricted graphitized interlayer spacing, inhibits the degree of graphitization, and the curved graphite layers are wrapped to form a rich closed pore structure, which is conducive to the reversible capacity contributed by the "intercalation-pore filling" behavior of sodium ions during the charge and discharge process, thereby improving the cycle performance.

[0018] 4. The double oxygen-doped cellulose precursor-derived hard carbon negative electrode material prepared by the present invention effectively improves the mass transfer process of sodium ions, improves the mass transfer kinetics of sodium ions, and reduces the mass transfer resistance of sodium ions. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 Schematic diagram of oxygen doping mechanism; Figure 2 FT-IR spectra of the double oxygen-doped cellulose precursors obtained in Examples 1 to 3; Figure 3 The XRD spectra of the double oxygen-doped cellulose precursors obtained in Examples 1 to 3 are as follows; Figure 4 The XRD peak fitting spectra of the double oxygen-doped cellulose precursors obtained in Examples 1 to 3; Figure 5 The crystallinity bar graphs of the double oxygen-doped cellulose precursors obtained in Examples 1 to 3; Figure 6The scanning electron microscope images of the hard carbon negative electrode materials obtained in Examples 1 to 3; Figure A is a scanning electron microscope image of the hard carbon negative electrode material obtained in Example 1, Figure B is a scanning electron microscope image of the hard carbon negative electrode material obtained in Example 2, and Figure C is a scanning electron microscope image of the hard carbon negative electrode material obtained in Example 3; Figure 7 The nitrogen adsorption / desorption images of the hard carbon negative electrode materials obtained in Examples 1 to 3; Figure 8 The pore size distribution spectra of the hard carbon negative electrode materials obtained in Examples 1 to 3; Fig. 9 The SAXS spectra of the hard carbon negative electrode materials obtained in Examples 1 to 3, and the inset is a line graph of the closed pore radius obtained by fitting; Fig.10 The true density and closed pore volume spectra of the hard carbon negative electrode materials obtained in Examples 1 to 3; Fig.11 The hard carbon negative electrode materials obtained in Examples 1 to 3 are TEM images; Figure A is a TEM image of the hard carbon negative electrode material obtained in Example 1, Figure B is a TEM image of the hard carbon negative electrode material obtained in Example 2, and Figure C is a TEM image of the hard carbon negative electrode material obtained in Example 3; Fig.12 The XRD patterns of the hard carbon negative electrode materials obtained in Examples 1 to 3; Fig.13 The Raman spectra of the hard carbon negative electrode materials obtained in Examples 1 to 3; Fig.14 This is the XPS overall spectrum of the hard carbon negative electrode materials obtained in Examples 1 to 3; Fig.15 XPS fine C spectrum images of the hard carbon negative electrode materials obtained in Examples 1 to 3; Fig.16 The C peak fitting spectra of pure cellulose-derived hard carbon and the hard carbon negative electrode materials obtained in Examples 1 to 3; Fig.17 This is a schematic diagram of half-battery charging and discharging; Fig.18 The half-cell constant current charge-discharge curves of the hard carbon negative electrode materials obtained in Examples 1 to 3; Fig.19 This is a rate performance diagram of the slope capacity / platform capacity of the second cycle of the hard carbon negative electrode materials obtained in Examples 1 to 3; Fig. 20 It is a line graph of platform capacity-graphitization interlayer spacing of the hard carbon negative electrode materials obtained in Examples 1 to 3; Fig.21Schematic diagram of the mechanism of the enlarged graphitized interlayer spacing of the hard carbon negative electrode materials obtained in Examples 1 to 3; Fig. 22 The rate performance diagram of the hard carbon negative electrode material obtained in Example 1 to Example 3; Fig.23 The cycle performance diagram of the hard carbon negative electrode material obtained in Example 1 to Example 3; Fig.24 This is a half-cell constant current intermittent titration curve diagram of the hard carbon negative electrode material obtained in Example 1 to Example 3; Fig.25 This is a graph showing the relationship between the sodium ion diffusion coefficient of the hard carbon negative electrode material obtained in Example 1 to Example 3 and the change in voltage. DETAILED DESCRIPTION

[0020] The principles and features of the present invention are described below, and the examples are only used to explain the present invention and are not used to limit the scope of the present invention. If no specific conditions are specified in the embodiments, they are carried out according to normal conditions or conditions recommended by the manufacturer. If the manufacturer of the reagents or instruments is not specified, they are all conventional products that can be purchased commercially. Example

[0021] A double oxygen-doped cellulose precursor-derived hard carbon negative electrode material, the preparation method of which comprises the following steps: (1) Disperse 6 g of microcrystalline cellulose in 100 mL of alkaline system (10 g of sodium hydroxide / 8 g of thiourea / 100 mL of water), add 1 mL of oxygen doping agent (epichlorohydrin) under mechanical stirring, and then continue to stir and react in an ice-water bath for 2 h, then add an acidic system (60 g of sulfuric acid / 100 mL of water), stir and regenerate at 65 °C, filter, wash with deionized water 3 times, and freeze-dry at -50 °C for 24 h to obtain an oxygen-doped cellulose precursor; (2) placing the oxygen-doped cellulose precursor obtained in step (1) in a corundum crucible, annealing at high temperature in an air atmosphere, heating at 50°C-170°C for 120 min, heating at 170°C-190°C for 240 min, keeping at 190°C for 60 min, heating at 190°C-230°C for 480 min, keeping at 230°C for 60 min, and naturally cooling and annealing to room temperature to obtain a double oxygen-doped cellulose precursor, recorded as PCP-1; (3) The double oxygen-doped cellulose precursor obtained in step (2) was placed in a vacuum tube furnace and carbonized at high temperature under an argon atmosphere, heating at 50-190 °C for 60 min, keeping at 190 °C for 120 min, then heating at 190-450 °C for 60 min, keeping at 450 °C for 120 min, then heating at 450-1350 °C for 300 min, keeping at 1350 °C for 120 min, and finally cooling at 1350-250 °C for 400 min, naturally cooling to room temperature, ball milling at 3500 rpm for 2 h, and vibrating and sieving with a 300-mesh sieve twice to obtain a double oxygen-doped cellulose precursor-derived hard carbon negative electrode material, recorded as PCHC-1. Example

[0022] A double oxygen-doped cellulose precursor-derived hard carbon negative electrode material, the preparation method of which comprises the following steps: (1) Disperse 6 g of microcrystalline cellulose in 100 mL of alkaline system (10 g of sodium hydroxide / 8 g of thiourea / 100 mL of water), add 2 mL of oxygen doping agent (epichlorohydrin) under mechanical stirring, and then continue to stir and react in an ice-water bath for 2 h, then add an acidic system (60 g of sulfuric acid / 100 mL of water), stir and regenerate at 65 °C, filter, wash with deionized water 3 times, and freeze-dry at -50 °C for 24 h to obtain an oxygen-doped cellulose precursor; (2) placing the oxygen-doped cellulose precursor obtained in step (1) in a corundum crucible, annealing at high temperature in an air atmosphere, heating at 50°C-170°C for 120 min, heating at 170°C-190°C for 240 min, keeping at 190°C for 60 min, heating at 190°C-230°C for 480 min, keeping at 230°C for 60 min, and naturally cooling and annealing to room temperature to obtain a double oxygen-doped cellulose precursor, denoted as PCP-2; (3) The double oxygen-doped cellulose precursor obtained in step (2) was placed in a vacuum tube furnace and carbonized at high temperature under an argon atmosphere, heated at 50-190 °C for 60 min, kept at 190 °C for 120 min, then heated at 190-450 °C for 60 min, kept at 450 °C for 120 min, then heated at 450-1350 °C for 300 min, kept at 1350 °C for 120 min, and finally cooled at 1350-250 °C for 400 min, naturally cooled to room temperature, ball milled at 3500 rpm for 2 h, and vibrated and sieved twice with a 300-mesh sieve to obtain a double oxygen-doped cellulose precursor-derived hard carbon negative electrode material, recorded as PCHC-2. Example 3: A double oxygen-doped cellulose precursor-derived hard carbon negative electrode material, the preparation method of which comprises the following steps: (1) Disperse 6 g of microcrystalline cellulose in 100 mL of alkaline system (10 g of sodium hydroxide / 8 g of thiourea / 100 mL of water), add 3 mL of oxygen doping agent (epichlorohydrin) under mechanical stirring, and then continue stirring and reacting in an ice-water bath for 2 h. Then add an acidic system (60 g of sulfuric acid / 100 mL of water), stir and regenerate at 65 °C, filter, wash with deionized water 3 times, and freeze-dry at -50 °C for 24 h to obtain an oxygen-doped cellulose precursor. (2) placing the oxygen-doped cellulose precursor obtained in step (1) in a corundum crucible, annealing at high temperature in an air atmosphere, heating at 50°C-170°C for 120 min, heating at 170°C-190°C for 240 min, keeping at 190°C for 60 min, heating at 190°C-230°C for 480 min, keeping at 230°C for 60 min, and naturally cooling and annealing to room temperature to obtain a double oxygen-doped cellulose precursor, recorded as PCP-3; (3) The double oxygen-doped cellulose precursor obtained in step (2) is placed in a vacuum tube furnace and carbonized at high temperature under an argon atmosphere, heating at 50-190 °C for 60 min, keeping at 190 °C for 120 min, then heating at 190-450 °C for 60 min, keeping at 450 °C for 120 min, then heating at 450-1350 °C for 300 min, keeping at 1350 °C for 120 min, and finally cooling at 1350-250 °C for 400 min, naturally cooling to room temperature, ball milling at 3500 rpm for 1-2 h, and vibrating and sieving with a 300-mesh sieve twice to obtain a double oxygen-doped cellulose precursor-derived hard carbon negative electrode material, recorded as PCHC-3.

[0023] Test Example 1: The infrared spectra and XRD patterns of the double oxygen-doped cellulose precursors obtained in Examples 1 to 3, as well as the peak fitting and crystallinity calculation values, are obtained respectively. Figure 1-Figure 5 As shown; the scanning electron microscope image of the hard carbon negative electrode material derived from the double oxygen-doped cellulose precursor is shown Figure 6 As shown; nitrogen adsorption and desorption curves, pore size distribution, SAXS spectra and true density and closed pore volume spectra are shown respectively Figure 7-10 As shown; high-resolution transmission electron microscopy images are shown Fig.11 As shown; Oxygen-doped cellulose precursor derived hard carbon surface chemical structure: Example 1-Example 3 obtained hard carbon negative electrode material XRD spectrum, Raman spectrum, XPS total spectrum, XPS fine C spectrum image and C peak fitting spectrum are shown respectively Figure 12-16 As shown. Among them, Fig.12 In, CHC represents pure cellulose-derived hard carbon; Fig.16In the figure, from top to bottom and from left to right are pure cellulose-derived hard carbon and Example 1 to Example 3.

[0024] Depend on Figure 1-Figure 5 It can be seen that after chemical oxygen doping, the oxygen-doped cellulose precursor showed an obvious ether bond absorption peak, and the XRD data showed that natural type I cellulose was successfully transformed into amorphous type II cellulose, and the crystallinity decreased from 92.7% to 43.9%.

[0025] Depend on Figure 6 It can be seen that the hard carbon material derived from oxygen-doped cellulose precursor has a smooth surface and a relatively uniform particle size.

[0026] Depend on Figure 7-10 It can be seen that the specific surface area of ​​the hard carbon material derived from the oxygen-doped cellulose precursor is reduced, and the curved stacked graphite layers form a rich closed-pore structure. Among them, the PCHC-3 hard carbon shows a significantly larger number of closed-pore structures, which is conducive to the formation of closed-pore sodium storage and the improvement of the platform sodium storage capacity.

[0027] Depend on Fig.11 It can be seen that the degree of graphitization of the hard carbon material derived from the oxygen-doped cellulose precursor is reduced, the long-range ordered graphitized structure is broken, and the graphitized interlayer spacing is effectively expanded.

[0028] Depend on Figure 12-16 It can be seen that the XRD spectrum shows that the d002 peak shifts significantly to the left, indicating that the degree of graphitization is reduced and the interlayer spacing is increased, which is conducive to the deintercalation of sodium ions. The proportion of graphitized carbon and amorphous carbon can be obtained by peak fitting of the Raman spectrum. D / I G The results show that the sp of the cross-linked lignin hard carbon increases from 0.893 to 0.935 with the increase of cross-linking regeneration degree, indicating that the disorder degree of the hard carbon material increases. XPS images further prove that through the cross-linking reaction, the sp 2 Hybridized carbon ratio decreases, sp 3 As the proportion of hybridized carbon increases, it can be seen that the internal structure tends to be short-range ordered.

[0029] Test Example 2: Half-cell assembly and testing, the specific steps are as follows: (1) Preparation of negative electrode sheets: 0.8 g of the cross-linked cellulose lignin-derived high closed-pore hard carbon negative electrode material obtained in Examples 1 to 3, 0.1 g of conductive carbon black (hereinafter referred to as Super P), and 3.33 g of 3.0 wt% polyvinylidene fluoride / N-methylpyrrolidone solution were weighed and ground evenly in a mortar, coated on a smooth aluminum foil surface using a 100 μm four-sided preparation device, placed in a vacuum drying oven at 80 ° C for 12 h, and cut into circular negative electrode sheets using a cutting machine with a diameter specification of 6 mm; (2) Preparation of positive electrode sheets: Using metallic sodium as the standard positive electrode, first use a roller press to press the sheets to a thickness of 0.8 mm, and then cut the circular sodium sheets into 12 mm diameter sheets; (3) Assemble button-type half-cell: positive electrode shell, spring, gasket, sodium sheet, glass fiber diaphragm, about 1mL sodium hexafluorophosphate electrolyte, negative electrode sheet, negative electrode shell, assembled from bottom to top. All assembly processes are carried out in a glove box continuously filled with argon (O2 concentration ≤ 0.5 ppm, H2O concentration ≤ 0.1 ppm).

[0030] The above half-cell was subjected to constant current charge and discharge, rate performance, cycle performance, and mass transfer kinetics tests. Figure 17-Figure 23 As shown, the constant current intermittent titration picture and the relationship between the Na+ diffusion coefficient and the voltage are shown in Figure 24-25 shown.

[0031] Depend on Figure 17-Figure 23 It can be seen that the constant current charge and discharge results show that the sodium storage capacity of the hard carbon after cross-linking regeneration has increased significantly. From the slope capacity / platform capacity reference graph, it can be seen that the slope capacity of the hard carbon negative electrode material with rich effective closed-pore structure derived from cross-linked regenerated cellulose shows a downward trend, and the platform capacity increases, which proves that the reduction of crystallization and the formation of effective closed pores are conducive to the improvement of sodium storage performance. In addition, the higher effective closed-pore content of PCHC-3 has created its excellent electrochemical performance. From its rate curve, it can be seen that the higher the specific capacity at high current, the better the capacity retention rate, indicating that the rate performance is better. From the cycle capacity curve, it can be seen that the hard carbon negative electrode material with rich effective closed-pore structure derived from cross-linked regenerated cellulose has good cycle stability. After 150 cycles, the capacity retention rate is about 84.1%.

[0032] Depend on Figure 24-25 It can be seen that the diffusion coefficient of the hard carbon negative electrode material with rich effective closed-pore structure derived from cross-linked regenerated cellulose is relatively stable during the charge and discharge process, and the mass transfer is uniform. When the discharge voltage is less than 0.2V, the diffusion coefficient decreases suddenly and the mass transfer slows down, indicating that the formation of closed pores is beneficial to filling pores and storing sodium on the low-potential platform, thereby improving the electrochemical stability.

[0033] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for preparing a double oxygen-doped cellulose precursor-derived hard carbon negative electrode material, characterized in that: The following steps are involved: (1) Dispersing microcrystalline cellulose in an alkaline system, adding an oxygen doping agent under mechanical stirring conditions, and then continuing to stir and react in an ice-water bath, then adding an acidic system, heating and stirring to regenerate, and filtering, washing and freeze-drying in sequence to obtain an oxygen-doped cellulose precursor; (2) placing the oxygen-doped cellulose precursor obtained in step (1) in a corundum crucible and annealing at high temperature in an air atmosphere to obtain a double oxygen-doped cellulose precursor; (3) The double oxygen-doped cellulose precursor obtained in step (2) is placed in a vacuum tube furnace, carbonized at high temperature in an argon atmosphere, and then ball-milled and vibrated to obtain a double oxygen-doped cellulose precursor-derived hard carbon negative electrode material.

2. The method for preparing a double oxygen-doped cellulose precursor-derived hard carbon negative electrode material according to claim 1, characterized in that: In step (1), the alkaline system is prepared by dissolving an alkaline substance and thiourea in water, and the alkaline substance is sodium hydroxide; the acidic system is prepared by dissolving an acidic substance in water, and the acidic substance is sulfuric acid or hydrochloric acid; and the oxygen dopant is epichlorohydrin or ethylene glycol diglycidyl ether.

3. The method for preparing a double oxygen-doped cellulose precursor-derived hard carbon negative electrode material according to claim 2, characterized in that: In the alkaline system, the mass volume ratio of the alkaline substance, thiourea and water is 5 g:4 g:50 mL; in the acidic system, the mass volume ratio of the acidic substance and water is 60 g:100 mL.

4. The method for preparing a double oxygen-doped cellulose precursor-derived hard carbon negative electrode material according to claim 1, characterized in that: In step (1), the mass volume ratio of the microcrystalline cellulose to the alkaline system is 3 g:50 mL; the volume ratio of the oxygen dopant to the alkaline system is 1-3 mL:100 mL; and the volume ratio of the acidic system to the alkaline system is 1:

1.

5. The method for preparing a double oxygen-doped cellulose precursor-derived hard carbon negative electrode material according to claim 1, characterized in that: In step (1), the reaction is continued to stir in an ice-water bath for 2 h, then an acidic system is added and stirred at 65 °C for regeneration, filtered, washed with deionized water 2-3 times, and freeze-dried at -50 °C for 24 h.

6. The method for preparing a double oxygen-doped cellulose precursor-derived hard carbon negative electrode material according to claim 1, characterized in that: In step (2), during high temperature annealing, the temperature is raised at 50°C-170°C for 120 min, then at 170°C-190°C for 240 min, then kept at 190°C for 60 min, then raised at 190°C-230°C for 480 min, then kept at 230°C for 60 min, and then naturally cooled and annealed to room temperature.

7. The method for preparing a double oxygen-doped cellulose precursor-derived hard carbon negative electrode material according to claim 1, characterized in that: In step (3), the temperature is increased at 50-190°C for 60 min, kept at 190°C for 120 min, then increased at 190-450°C for 60 min, kept at 450°C for 120 min, then increased at 450-1350°C for 300 min, kept at 1350°C for 120 min, and finally cooled at 1350-250°C for 400 min and naturally cooled to room temperature.

8. The method for preparing a double oxygen-doped cellulose precursor-derived hard carbon negative electrode material according to claim 1, characterized in that: In step (3), the mixture is ball milled at 3500 rpm for 1-2 h and vibrated and sieved using a 300-mesh sieve for 2-3 times.

9. The method for preparing a double oxygen-doped cellulose precursor-derived hard carbon negative electrode material according to claim 1, characterized in that: In step (3), the purity of argon is 99.99%.

10. A double oxygen-doped cellulose precursor-derived hard carbon negative electrode material obtained by the method for preparing a double oxygen-doped cellulose precursor-derived hard carbon negative electrode material according to any one of claims 1 to 9.

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