A biomass hard carbon material, a sodium-ion battery negative electrode, a sodium-ion battery, and a preparation method and application thereof

Abstract

The present application relates to a kind of biomass hard carbon material, sodium ion battery negative pole, sodium ion battery and its preparation method and application.The preparation method of the biomass hard carbon material includes the following steps: first, specific biomass is carbonized, then high-temperature crystallization treatment is carried out, i.e., biomass hard carbon material is obtained.The morphology of the biomass hard carbon material is micron sheet and has nanopore, and the pore volume of nanopore is 0.1-0.3 mL / g.The biomass hard carbon material is used to prepare sodium ion battery negative pole, which can make sodium ion battery have high capacity, good cycle stability, high rate performance and low impedance.

Description

Technical Field

[0001] This invention relates to the field of sodium-ion batteries, and more specifically, to a biomass hard carbon material, a sodium-ion battery anode, a sodium-ion battery, its preparation method, and its application. Background Technology

[0002] Lithium-ion batteries possess advantages such as high open-circuit voltage, long cycle life, high energy density, and no memory effect, making them widely used in portable digital products, electric vehicles, and energy storage. However, the low availability and high cost of lithium metal in nature limit the further development of lithium-ion batteries in electric vehicles and large-scale energy storage. Sodium metal, on the other hand, is abundant and inexpensive in nature, making it an ideal alternative to lithium metal. Furthermore, sodium-ion batteries can utilize inexpensive aluminum current collectors, reducing battery production costs.

[0003] The negative electrode of a sodium-ion battery is one of the key components determining its performance. Lithium-ion batteries using graphite as the active material for their negative electrodes have been commercially available for over 40 years. When researching sodium-ion batteries, researchers initially tested graphite. However, because the radius of a sodium atom is larger than that of a lithium atom, embedding graphite in sodium-ion batteries resulted in very low reversible capacity and difficulties in atomic transport and insertion / extraction, leading to unsatisfactory rate performance.

[0004] Biomass hard carbon, as a material with diverse morphologies, abundant sources, and controllable structures, occupies an unparalleled position in the research of hard carbon materials, thus attracting widespread attention from researchers. Compared with graphite, using biomass hard carbon to prepare sodium-ion batteries can give sodium-ion batteries advantages such as large capacity and good conductivity. Currently, there are many reports on the preparation of sodium-ion battery anodes using biomass hard carbon, such as the Chinese patent for cotton straw-based biomass hard carbon anode material and its preparation method and application.

[0005] However, biomass hard carbon still has the following drawbacks: 1) During charging and discharging, the insertion and extraction of sodium ions in biomass hard carbon leads to volume expansion and contraction of the material. This volume change may cause structural damage and particle aggregation, thereby reducing the cycle stability of the battery. 2) Due to its disordered structure, biomass hard carbon usually has high impedance, resulting in low electronic conductivity, which limits the migration of sodium ions and affects the charge and discharge performance of the battery. 3) The insertion and extraction of sodium ions in biomass hard carbon materials may involve high activation energy, resulting in a slower charge and discharge rate of the battery. This may limit the high-speed charge and discharge performance of sodium-ion batteries, i.e., poor rate performance, affecting their practicality in some applications. 4) Existing reports suggest improving the poor rate performance of biomass hard carbon by creating pores and defects on it. However, this may lead to low conversion rate and fragile structure of biomass after hard carbonization, resulting in reduced capacity and even more fragile structure after pore creation, making it impossible to achieve a long service life. In other words, high rate performance, high capacity, and good cycle stability cannot be achieved simultaneously.

[0006] Therefore, developing biomass hard carbon materials that can be used as anodes in sodium-ion batteries, enabling sodium-ion batteries to simultaneously possess high capacity, good cycle stability, high rate performance, and low impedance, is of great significance. Summary of the Invention

[0007] The primary objective of this invention is to overcome the problem that existing biomass hard carbon materials used for sodium-ion battery anodes cannot simultaneously achieve high capacity, good cycle stability, high rate performance, and low impedance in sodium-ion batteries. This invention provides a method for preparing biomass hard carbon materials. The method involves first carbonizing specific biomass, followed by high-temperature crystallization to obtain a biomass hard carbon material with a specific morphology. This biomass hard carbon material, when used to prepare a sodium-ion battery anode, enables the sodium-ion battery to exhibit high capacity, good cycle stability, high rate performance, and low impedance.

[0008] A further objective of this invention is to provide a biomass hard carbon material.

[0009] A further objective of this invention is to provide the application of the above-mentioned biomass hard carbon material in the preparation of sodium-ion battery anodes.

[0010] A further objective of this invention is to provide a sodium-ion battery negative electrode.

[0011] A further object of the present invention is to provide a sodium-ion battery.

[0012] A further objective of this invention is to provide a method for activating a sodium-ion battery.

[0013] The above-mentioned objective of the present invention is achieved through the following technical solution:

[0014] A method for preparing biomass hard carbon material includes the following steps:

[0015] First, the biomass is carbonized, and then subjected to high-temperature crystallization to obtain biomass hard carbon material.

[0016] The biomass hard carbon material has a morphology of micron-sized sheets and nanopores, and the pore volume of the nanopores in the biomass hard carbon material is 0.1 to 0.3 mL / g.

[0017] The biomass is at least one of the following: wood butterfly seeds, birch bark, or paper eucalyptus bark.

[0018] This invention first carbonizes specific biomass and then crystallizes it at high temperature to obtain a biomass hard carbon material with a specific morphology. This biomass hard carbon material is used to prepare the negative electrode for sodium-ion batteries, enabling the sodium-ion battery to have high capacity, good cycle stability, high rate performance, and low impedance. The reasons are as follows: the micron-sheet structure (compared to other morphologies, such as granules) can increase the contact area between the biomass hard carbon and the current collector of the sodium-ion battery negative electrode, thereby improving conductivity and reducing impedance; at the same time, the micron-sheet structure can also shorten the sodium ion insertion and extraction path, resulting in a low activation energy and thus improving the rate performance of the sodium-ion battery; and the specific morphology of the biomass hard carbon material formed through carbonization-high temperature crystallization makes the microstructure less susceptible to damage, thus enabling the sodium-ion battery to have both high rate performance and good cycle stability, while the nanopores can also enhance the capacity of the sodium-ion battery.

[0019] Without high-temperature crystallization, the resulting biomass hard carbon material, when used to prepare the anode for sodium-ion batteries, does not significantly improve the capacity and cycle stability of the sodium-ion battery, and its impedance is also relatively high. If high-temperature crystallization is not performed, and other methods (such as pore-forming agents) are used to improve the rate performance of the sheet-like biomass hard carbon material, the capacity and cycle stability of the sodium-ion battery will deteriorate, resulting in a lower performance compared to sodium-ion batteries made from the biomass hard carbon material of this invention.

[0020] In this invention, the pore volume of the nanopores in the biomass hard carbon material is measured by BET.

[0021] Preferably, the carbonization process for biomass further includes crushing and drying steps.

[0022] More preferably, the specific process of pulverization is as follows: pulverizing biomass using a pulverizer for 5 to 30 minutes.

[0023] Preferably, the carbonization process is carried out in an inert atmosphere.

[0024] More preferably, the inert atmosphere is at least one of nitrogen atmosphere or argon atmosphere.

[0025] Preferably, the carbonization treatment is carried out at a temperature of 500–600°C for a time of 0.5–10 hours.

[0026] Preferably, after the carbonization treatment and before the high-temperature crystallization treatment, the process further includes acid washing, drying, and ball milling.

[0027] More preferably, the specific process of acid washing is as follows: the carbonized biomass is immersed in an acidic solution, stirred at 30-120°C for 20-28 hours, washed with deionized water until neutral, and a black precipitate is obtained by separation.

[0028] More preferably, the acidic solution is at least one of hydrochloric acid solution or sulfuric acid solution; the concentration of the acidic solution is 1 to 5 mol / L.

[0029] More preferably, the drying conditions are: drying at 50–120°C for 12–24 hours.

[0030] More preferably, the specific process of ball milling is as follows: ball milling in a ball mill at a speed of 50-450 r / min for 3-12 hours.

[0031] Preferably, the high-temperature crystallization process is carried out in an inert atmosphere.

[0032] More preferably, the inert atmosphere is at least one of nitrogen atmosphere or argon atmosphere.

[0033] Preferably, the high-temperature crystallization treatment is carried out at a temperature of 1200–1700°C for a time of 0.5–3 hours.

[0034] More preferably, the high-temperature crystallization treatment is carried out at a temperature of 1300–1500°C for a time of 0.5–3 hours.

[0035] More preferably, the heating program for the high-temperature crystallization treatment is as follows: first, the temperature is raised to 500-600℃ at a heating rate of 2-3℃ / min and held for 0.5-2h, then raised to 800-1000℃ and held for 0.5-2h, and finally raised to 1200-1700℃.

[0036] Preferably, the thickness of the micron sheet is 2 to 50 μm, and the ratio of the sheet diameter to the thickness is (5 to 500):1.

[0037] More preferably, the thickness of the micron sheet is 2 to 20 μm, and the ratio of the sheet diameter to the thickness is (10 to 20): 1.

[0038] Preferably, the pore size of the nanopore is 2–35 nm.

[0039] More preferably, the pore size of the nanopore is 2 to 10 nm.

[0040] A biomass hard carbon material is prepared by any of the preparation methods described above.

[0041] The application of the aforementioned biomass hard carbon materials in the preparation of sodium-ion battery anodes is also within the scope of protection of this invention.

[0042] A sodium-ion battery anode is prepared by the following process: a conductive agent, a binder, a solvent and the above-mentioned biomass hard carbon material are mixed to obtain a slurry, and then the slurry is coated onto a current collector and dried to obtain the sodium-ion battery anode.

[0043] Preferably, the conductive agent is at least one of acetylene black, polyaniline (PANI), or copper particles.

[0044] Preferably, the binder is at least one of carboxymethyl cellulose (CMC), polytetrafluoroethylene (PTFE), or polyvinylidene fluoride (PVDF).

[0045] Preferably, the solvent is water.

[0046] Preferably, the mass ratio of the biomass hard carbon material, conductive agent, and binder is 1:(0.042~0.125):(0.021~0.125).

[0047] Preferably, the current collector is at least one of aluminum foil or copper foil.

[0048] Preferably, the thickness of the current collector is 20–150 μm.

[0049] Preferably, the drying time is 12 to 24 hours.

[0050] A sodium-ion battery includes a positive electrode, a negative electrode, a separator, and an electrolyte; the negative electrode is the negative electrode of the aforementioned sodium-ion battery.

[0051] Preferably, the positive electrode is at least one of pure sodium sheet, sodium manganate, or sodium cobaltate.

[0052] Preferably, the diaphragm is made of at least one of glass fiber, polyethylene (PE), or polypropylene (PP).

[0053] Preferably, the solvent of the electrolyte is at least one of ether solvents or ester solvents, and the electrolyte is at least one of sodium hexafluorophosphate (NaPF6) or sodium trifluoromethyl carbonate (NaCFSO3).

[0054] More preferably, the solvent of the electrolyte is an ether solvent and the electrolyte is sodium hexafluorophosphate.

[0055] When the electrolyte solvent is an ether solvent and the electrolyte is sodium hexafluorophosphate, the two, when combined with the biomass hard carbon material of the present invention, can form a thinner and more stable SEI film, thereby making the sodium-ion battery have lower impedance and better rate performance.

[0056] More preferably, the ether solvent is at least one of ethylene glycol dimethyl ether (DME), tetrahydrofuran (THF), 2-methyltetrahydrofuran (2ME-THF), or 1,3-dioxocyclopentane (DOL).

[0057] More preferably, the concentration of sodium hexafluorophosphate in the electrolyte is 0.5–2 mol / L.

[0058] An activation method for a sodium-ion battery involves charging and discharging the sodium-ion battery for 3 to 30 cycles using a constant current.

[0059] Preferably, the current density of the constant current is 20-300 mA / g.

[0060] More preferably, the current density of the constant current is 250-300 mA / g.

[0061] Compared with the prior art, the beneficial effects of the present invention are:

[0062] This invention first carbonizes specific biomass and then crystallizes it at high temperature to obtain a biomass hard carbon material with a specific morphology. This biomass hard carbon material is used to prepare the negative electrode of a sodium-ion battery, which can enable the sodium-ion battery to have high capacity, good cycle stability, high rate performance and low impedance. Attached Figure Description

[0063] Figure 1 This is a scanning electron microscope image of the biomass hard carbon material of Example 1.

[0064] Figure 2 This is a pore size distribution diagram of the biomass hard carbon material in Example 1.

[0065] Figure 3 The graphs show the rate performance test and cycle performance test results of the sodium-ion battery in Example 6.

[0066] Figure 4 The Nyquist plot is for the sodium-ion battery of Example 6.

[0067] Figure 5 The graph shows the cycle performance test results of the sodium-ion battery in Example 7.

[0068] Figure 6 The graph shows the cycle performance test results of the sodium-ion battery in Comparative Example 8.

[0069] Figure 7 The graph shows the cycle performance test results of the sodium-ion battery in Example 6 under different current densities.

[0070] Figure 8 The graph shows the rate performance test results of sodium-ion batteries in Comparative Example 1 and Example 6. Detailed Implementation

[0071] To more clearly and completely describe the technical solution of the present invention, the present invention will be further described in detail below through specific embodiments. It should be understood that the specific embodiments described herein are only for explaining the present invention and are not intended to limit the present invention. Various changes can be made within the scope of the claims of the present invention.

[0072] Example 1

[0073] This embodiment provides a method for preparing biomass hard carbon material, including the following steps:

[0074] 1) Weigh out the seeds of the wood butterfly and put them into a grinder to grind for 30 minutes; after the powder is fully dried, heat it in a nitrogen atmosphere from 25°C to 600°C at a rate of 2°C / min and keep it at that temperature for 5 hours to achieve carbonization of the wood butterfly seeds and obtain carbonized powder.

[0075] 2) The carbonized powder was immersed in 1 mol / L hydrochloric acid and stirred at 60°C for 24 h. After washing with deionized water until neutral, a black precipitate was obtained. After drying at 80°C for 24 h, the precipitate was placed in a ball mill and ball-milled at 380 r / min for 6 h. After thorough drying, a black powder was obtained.

[0076] 3) The black powder is placed in a nitrogen atmosphere, and then heated to 600℃ at a heating rate of 2℃ / min and held for 0.5h, then heated to 1000℃ and held for 0.5h, and finally heated to 1500℃ (denoted as temperature T) and held for 3h. It is then naturally cooled to room temperature to obtain the biomass hard carbon material.

[0077] Example 2

[0078] This embodiment provides a method for preparing biomass hard carbon material, which is basically the same as that in Example 1, except that the wood butterfly seeds in step 1) are replaced with birch bark.

[0079] Example 3

[0080] This embodiment provides a method for preparing biomass hard carbon material, which is basically the same as that in Example 1, except that the seeds of the wood butterfly in step 1) are replaced with paper eucalyptus bark.

[0081] Example 4

[0082] This embodiment provides a method for preparing biomass hard carbon material, which is basically the same as that in Example 1, except that the temperature T in step 3) is 1300℃.

[0083] Example 5

[0084] This embodiment provides a method for preparing biomass hard carbon material, which is basically the same as that in Example 1, except that the temperature T in step 3) is 1700℃.

[0085] Example 6

[0086] This embodiment provides a sodium-ion battery negative electrode and a sodium-ion battery made therefrom, the preparation process of which is as follows:

[0087] 1) Acetylene black, binder CMC and biomass hard carbon material from Example 1 were dispersed in deionized water and stirred and mixed according to a mass ratio of 1:1:8. The resulting slurry was coated on the current collector and vacuum dried for 12 hours to obtain the sodium-ion battery negative electrode.

[0088] 2) In a glove box filled with argon gas, assemble the sodium-ion battery according to the following method: outer shell, negative electrode of sodium-ion battery obtained in step 1), separator, positive electrode, and outer shell. At the same time, add electrolyte to obtain sodium-ion battery. The separator is glass fiber, the positive electrode is pure sodium sheet, and the electrolyte is 1 mol / L NaPF6 ethylene glycol dimethyl ether solution.

[0089] Example 7

[0090] This embodiment provides a sodium-ion battery negative electrode and a sodium-ion battery made therefrom, which is basically the same as that in embodiment 6, except that the biomass hard carbon material in step 1) is replaced with the biomass hard carbon material in embodiment 4.

[0091] Example 8

[0092] This embodiment provides a sodium-ion battery negative electrode and a sodium-ion battery made therefrom, which is basically the same as that in embodiment 6, except that the biomass hard carbon material in step 1) is replaced with the biomass hard carbon material in embodiment 5.

[0093] Example 9

[0094] This embodiment provides a sodium-ion battery negative electrode and a sodium-ion battery made therefrom, which is basically the same as that in embodiment 6, except that the biomass hard carbon material in step 1) is replaced with the biomass hard carbon material in embodiment 2.

[0095] Example 10

[0096] This embodiment provides a sodium-ion battery negative electrode and a sodium-ion battery made therefrom, which is basically the same as that in embodiment 6, except that the biomass hard carbon material in step 1) is replaced with the biomass hard carbon material in embodiment 3.

[0097] Comparative Example 1

[0098] This comparative example provides a non-sheet-like porous biomass hard carbon material and a sodium-ion battery, the preparation method of which includes the following steps:

[0099] 1) Replace the wood butterfly seeds in step 1) of Example 1 with walnut shells, and follow the same steps as in Example 1 to obtain non-sheet porous biomass hard carbon material.

[0100] 2) Replace the biomass hard carbon material in step 1) of Example 6 with the non-sheet porous biomass hard carbon material in step 1) of this comparative example, and the other steps are the same as in Example 6 to obtain the sodium-ion battery of this comparative example.

[0101] Performance testing

[0102] 1. Morphological characteristics

[0103] Scanning electron microscopy (SEM) analysis of the biomass hard carbon material prepared in Example 1 clearly revealed that the biomass hard carbon material exhibits a micron-scale sheet-like structure, i.e., micron-sheets. Magnification analysis of a single micron-sheet yielded the following results: Figure 1 As shown, Figure 1 a and Figure 1 In the figures, b represents scanning electron microscope (SEM) images of two different micrometer-sized sheets prepared in Example 1. From... Figure 1 It is known that the thickness of the micron-sheet is approximately 2–8 μm, and the diameter is approximately 10–20 times the thickness. Furthermore, numerous nanopores can be observed on the surface of the micron-sheet.

[0104] The biomass hard carbon material prepared in Example 1 was further subjected to BET testing (by detecting the volume change of nitrogen adsorption and desorption under a specific pressure), and the results are as follows. Figure 2 As shown. Figure 2 The diagram shows the pore size distribution of the biomass hard carbon material. It can be seen that the pore volume of the nanopores in the biomass hard carbon material is 0.2 mL / g, and the pore size is concentrated in the range of 3 to 8 nm.

[0105] The morphology of the biomass hard carbon materials in Examples 2-5 was characterized, and the results were similar to those in Example 1. That is, the biomass hard carbon materials in Examples 2-5 were all micron-sized sheets with a thickness of 2-20 μm and a sheet diameter to thickness ratio of approximately (10-20):1. The pore volume of the nanopores in the biomass hard carbon materials was 0.1-0.3 mL / g, and the pore size of the nanopores was concentrated in the range of 3-8 nm.

[0106] 2. Electrochemical performance testing

[0107] The sodium-ion batteries from Examples 6-8 were activated by 10 cycles of constant current charge-discharge at 300 mA / g, respectively. Then, rate performance, cycle performance, and impedance tests were performed. The test results are as follows: Figures 3-6 As shown.

[0108] Figure 3 a and Figure 3 In the figures, b represents the rate performance test chart and cycle performance test chart of the sodium-ion battery in Example 6, respectively. From... Figure 3 As shown in section a, the reversible capacities of the sodium-ion battery in Example 6 at current densities of 20, 30, 60, 120, 240, 300, 600, 900, and 1500 mA / g (with 10 cycles at each current density) are 398.5, 409.9, 432.7, 435.8, 423.4, 410.9, 390.2, 372.5, and 357.0 mAh / g, respectively, exhibiting high capacity (the maximum capacity of existing sodium-ion batteries made from hard carbon is typically around 300 mAh / g); furthermore, its capacity at 1.5 A / g to its maximum capacity (i.e., the capacity measured at a current density of 120 mA / g) is 81.9%, higher than the average level of existing sodium-ion batteries. From Figure 3 As shown in b, the sodium-ion battery of Example 6 has an initial charging capacity of 422.3 mAh / g at a current density of 300 mA / g, and retains 438.8 mAh / g after 200 cycles, with a capacity retention rate of 103.9%. This indicates that the biomass hard carbon material of the present invention, when used to prepare the anode of a sodium-ion battery, can enable the sodium-ion battery to exhibit good rate performance and cycle performance. Furthermore, the coulombic efficiency of Example 6 reaches over 92.21%, indicating that the biomass hard carbon material of the present invention, when used to prepare the anode of a sodium-ion battery, can enable the sodium-ion battery to exhibit high coulombic efficiency.

[0109] Figure 4 This is the Nyquist plot of the sodium-ion battery in Example 6, from... Figure 4 It can be seen that after equivalent circuit fitting, the electrochemical impedance of the sodium-ion battery in Example 6 is only 7Ω, indicating that the biomass hard carbon material of the present invention can be used to prepare the negative electrode of sodium-ion battery, so that the sodium-ion battery can exhibit low impedance.

[0110] Figure 5 This is a cycle performance test graph of the sodium-ion battery in Example 7. From Figure 5 It can be seen that the sodium-ion battery of Example 7 has an initial charging capacity of 315 mAh / g at a current density of 300 mA / g, and a capacity of 328 mAh / g after 200 cycles, with a capacity retention rate of 104.1%.

[0111] Figure 6This is a cycle performance test graph of the sodium-ion battery in Example 8. From Figure 6 It can be seen that the sodium-ion battery of Example 8 has an initial discharge capacity of 194.9 mAh / g at a current density of 300 mA / g, and a capacity of 209.1 mAh / g after 200 cycles, with a capacity retention rate of 107.3%.

[0112] The cycle performance test results of sodium-ion batteries in Examples 6-8 show that the biomass hard carbon materials obtained by high-temperature crystallization treatment at different temperatures can all make sodium-ion batteries exhibit good cycle stability when used as negative electrodes. When the high-temperature crystallization temperature is controlled at 1300-1500℃, the initial charging capacity of the sodium-ion battery is higher, and the capacity after multiple cycles is also higher.

[0113] The electrochemical performance of the sodium-ion batteries in Examples 9 and 10 is similar to that in Example 6. The rate performance and impedance of the sodium-ion batteries in Examples 7 and 8 are similar to those in Example 6.

[0114] The sodium-ion battery from Example 6 was activated at constant currents of 300 mA / g and 20 mA / g, respectively, and the results are as follows. Figure 7 As shown. From Figure 7 It can be seen that during the activation process, the capacity first decreases and then increases. This is due to the repeated wetting of the electrolyte and the full insertion of sodium ions. At 300 mA / g, about 20 charge-discharge cycles are enough to bring the capacity to a stable level, while at 20 mA / g, about 50 charge-discharge cycles are required to bring the capacity to a stable level. It can be seen that the constant current activation method at high current density is more efficient.

[0115] The sodium-ion battery from Comparative Example 1 was activated by 10 cycles of constant current charge-discharge at 300 mA / g, followed by rate performance testing. The results are as follows. Figure 8 As shown. From Figure 8 It can be seen that, under different current densities, the reversible capacity of Example 6 is greater than that of Comparative Example 1. This indicates that the biomass hard carbon material of the present invention, when used to prepare the negative electrode of sodium-ion batteries, can not only enable sodium-ion batteries to exhibit high capacity, but also enable them to exhibit good rate performance.

[0116] Obviously, the above embodiments of the present invention are merely examples for clearly illustrating the present invention, and are not intended to limit the implementation of the present invention. Those skilled in the art can make other variations or modifications based on the above description. It is neither necessary nor possible to exhaustively describe all embodiments here. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the claims of the present invention.

Claims

1. A method for preparing biomass hard carbon material, characterized in that, Includes the following steps: The biomass is first carbonized, and then subjected to high-temperature crystallization to obtain the biomass hard carbon material. The biomass hard carbon material has a morphology of micron-sized sheets and nanopores, and the pore volume of the nanopores of the biomass hard carbon material is 0.1~0.3 mL / g; The biomass is the seed of the wood butterfly; The carbonization treatment is carried out at a temperature of 500~600℃ for a time of 0.5~10h. The high-temperature crystallization treatment is performed at a temperature of 1200~1700℃ for a time of 0.5~3h. The thickness of the micron sheet is 2~50µm, and the ratio of the sheet diameter to the thickness is (5~500):

1.

2. A biomass hard carbon material, characterized in that, It is prepared by the preparation method described in claim 1.

3. The application of the biomass hard carbon material according to claim 2 in the preparation of sodium-ion battery anodes.

4. A sodium-ion battery negative electrode, characterized in that, The sodium-ion battery negative electrode is prepared by mixing a conductive agent, a binder, a solvent, and the biomass hard carbon material described in claim 2 to obtain a slurry. The slurry is then coated onto a current collector and dried to obtain the negative electrode.

5. A sodium-ion battery, characterized in that, It includes a positive electrode, a negative electrode, a separator, and an electrolyte; the negative electrode is the negative electrode of the sodium-ion battery according to claim 4.

6. The sodium-ion battery according to claim 5, characterized in that, The solvent of the electrolyte is at least one of ether solvents or ester solvents; the electrolyte of the electrolyte is at least one of sodium hexafluorophosphate or sodium trifluoromethyl carbonate.

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