A pine-based hard carbon material, a sodium-ion battery anode, a sodium-ion battery, its preparation method and application

Abstract

This invention relates to a pine-based hard carbon material, its preparation method, and its applications. The preparation method of the pine-based hard carbon material includes the following steps: carbonizing pine wood, acid washing, and finally performing segmented high-temperature treatment to obtain the pine-based hard carbon material. This pine-based hard carbon material is used to prepare the negative electrode for sodium-ion batteries, enabling the sodium-ion batteries to have high specific capacity and good rate performance.

Description

Technical Field

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

[0002] Sodium-ion batteries are an emerging battery technology. Compared to traditional lithium-ion batteries, sodium is a relatively inexpensive and abundant element, easier to obtain and produce than lithium, thus potentially reducing battery costs. Sodium is also more abundant on Earth, implying a sustainable energy supply chain. Furthermore, sodium-ion batteries have a higher energy density, meaning they can store more energy. However, several technical challenges remain unresolved: sodium-ion batteries have a slow charge / discharge rate, limiting their ability to perform rapid charging and discharging; and their poor charge / discharge cycle performance results in a short lifespan.

[0003] To overcome these challenges, researchers developed hard carbon materials. Hard carbon materials possess high conductivity, which facilitates rapid charge transfer during the charging and discharging process of sodium-ion batteries, improving their fast charge / discharge performance. Compared to soft carbon materials, hard carbon materials can improve battery cycle performance and extend battery life. Biomass hard carbon materials are environmentally friendly, containing no harmful substances, thus reducing environmental impact; they are also inexpensive and readily available, effectively lowering the manufacturing cost of sodium-ion batteries and making them more competitive in commercial applications. Numerous research reports exist on biomass hard carbon, such as a Chinese patent entitled "A Two-Stage Carbonization Preparation Method for Biomass Hard Carbon Materials."

[0004] However, biomass hard carbon materials still have shortcomings. Due to their structural instability, sodium-ion batteries exhibit poor rate performance. Furthermore, the specific capacity of sodium-ion batteries is unsatisfactory, limiting their application in fields requiring high capacity. Therefore, it is necessary to develop a biomass hard carbon material that enables sodium-ion batteries to possess good specific capacity and rate performance. Summary of the Invention

[0005] The primary objective of this invention is to overcome the problems of poor specific capacity and rate performance of existing biomass hard carbon materials used in sodium-ion batteries, and to provide a method for preparing pine-based hard carbon materials. This method involves carbonizing pine wood, acid washing, and segmented high-temperature treatment. The resulting pine-based hard carbon material is used to prepare the negative electrode for sodium-ion batteries, enabling the batteries to exhibit high specific capacity and good rate performance; furthermore, it also provides the sodium-ion batteries with good cycle stability.

[0006] A further object of the present invention is to provide a pine-based hard carbon material.

[0007] A further objective of this invention is to provide the application of the above-mentioned pine-based hard carbon material in the preparation of sodium-ion battery anodes.

[0008] A further objective of this invention is to provide a sodium-ion battery negative electrode.

[0009] A further object of the present invention is to provide a sodium-ion battery.

[0010] The above-mentioned objective of the present invention is achieved through the following technical solution:

[0011] A method for preparing a pine-based hard carbon material includes the following steps:

[0012] The pine wood is carbonized, then acid-washed, and finally subjected to segmented high-temperature treatment to obtain the pine wood-based hard carbon material.

[0013] The segmented high-temperature treatment process is as follows: first, maintain at 500-600℃ for 1-2 hours, then maintain at 1300-1600℃ for 1-4 hours, and finally maintain at 500-600℃ for 1-2 hours.

[0014] Pine wood is a widely distributed plant with abundant and renewable resources. Hard carbon prepared from pine wood exhibits good cycle performance, thus helping to reduce the overall production cost of sodium-ion batteries. However, hard carbon prepared from pine wood has weak sodium storage capacity and slow charge transport rate, resulting in poor specific capacity and rate performance of sodium-ion batteries.

[0015] The inventors of this invention have discovered that by first carbonizing pine wood, then acid washing, and finally performing segmented high-temperature treatment, the resulting pine-based hard carbon material can be used to prepare the negative electrode for sodium-ion batteries, enabling the sodium-ion batteries to have high specific capacity and good rate performance.

[0016] The segmented high-temperature treatment consists of three stages at different temperatures, and its mechanism is as follows:

[0017] Maintaining the material at 500-600℃ (first stage temperature) for a period of time helps to perform a structural stabilization treatment at a relatively low temperature, reducing the structural changes or defects that may occur during the subsequent higher temperature treatment (second stage temperature), thus facilitating the formation of pore structures during the higher temperature treatment (second stage temperature).

[0018] In the 1300–1600℃ range (the second temperature range), the material transforms into a highly crystalline state. The higher the crystallinity of the material, the better its conductivity and cycle stability. More importantly, under this high temperature condition, more porous structures are formed inside the material. These porous structures can provide more storage space for sodium ions, improve the energy density and charge transport rate of the battery, and thus improve the specific capacity and rate performance of the sodium-ion battery.

[0019] After high-temperature treatment, materials accumulate internal stress, and rapid cooling may lead to a decline in material performance (such as reduced hardness and increased brittleness). This invention maintains the material at 500–600°C (the third temperature stage) for 1–2 hours after the second temperature stage. This allows the stress accumulated after high-temperature treatment to gradually release, reducing the risk of cracking or deformation caused by rapid cooling, and thus improving the retention of capacity and rate performance in sodium-ion batteries.

[0020] If the segmented high-temperature treatment does not include the first stage temperature, it is not conducive to the formation of pore structure in pine-based hard carbon materials; if the segmented high-temperature treatment does not include the third stage temperature, the pore structure formed in pine-based hard carbon materials will change during the cooling process (cracking or closing), and both of these situations are not conducive to improving the capacity and rate performance of sodium-ion batteries.

[0021] In addition, the present invention requires acid washing during the segmented high-temperature treatment, which can remove the metal components in the carbon material, and this is also beneficial to the formation of pore structure.

[0022] This invention involves carbonizing, acid washing, and segmented high-temperature treatment of pine wood to obtain a pine-based hard carbon material, which is used to prepare the negative electrode for sodium-ion batteries. This material enables the sodium-ion batteries to have high specific capacity and good rate performance. In addition, it also enables the sodium-ion batteries to have good cycle stability.

[0023] Preferably, prior to the carbonization treatment, the process further includes a step of mixing pine wood and a pore-forming agent.

[0024] More preferably, the pine wood and the pore-forming agent are mixed by ball milling.

[0025] More preferably, the ball mill rotates at a speed of 400–600 rad / min for 8–12 hours.

[0026] More preferably, the pore-forming agent is at least one of phosphoric acid, citric acid, or potassium hydroxide.

[0027] More preferably, the mass ratio of the pine wood to the pore-forming agent is 1:(0.1-0.5).

[0028] More preferably, the mass ratio of the pine wood to the pore-forming agent is 1:(0.2-0.3).

[0029] More preferably, the pine wood is further dried before being mixed with the pore-forming agent.

[0030] More preferably, the drying temperature is 50–120°C and the time is 16–28 hours.

[0031] Preferably, the carbonization treatment is carried out at a temperature of 400–800°C for 1–5 hours.

[0032] More preferably, the carbonization treatment is carried out at a temperature of 500–600°C for 2–3 hours.

[0033] Preferably, the carbonization process is carried out in an inert gas atmosphere.

[0034] More preferably, the inert gas atmosphere is at least one of nitrogen atmosphere or argon atmosphere.

[0035] Preferably, after the carbonization treatment and before the pickling, a grinding step is also included.

[0036] More preferably, the grinding time is 15 to 30 minutes.

[0037] More preferably, the grinding time is 20 to 25 minutes.

[0038] Preferably, the pickling process is as follows: the carbon material obtained after carbonization is immersed in a strong acid solution, stirred at 50-80°C for 20-30 hours, filtered, and washed with deionized water until neutral.

[0039] More preferably, the strong acid solution is at least one of hydrochloric acid, sulfuric acid, or nitric acid; and the concentration of the strong acid solution is 0.1–3 mol / L.

[0040] Preferably, after pickling and before the segmented high-temperature treatment, a drying step is also included.

[0041] More preferably, the drying temperature is 80–150°C and the time is 30–60 hours.

[0042] Preferably, the segmented high-temperature treatment process is as follows: first, the temperature is raised to 500-600℃ at a rate of 1-5℃ / min and held for 1-2 hours; then, the temperature is raised to 1300-1600℃ at a rate of 1-5℃ / min and held for 1-4 hours; finally, the temperature is lowered to 500-600℃ at a rate of 1-5℃ / min and held for 1-2 hours.

[0043] Preferably, the segmented high-temperature treatment process is as follows: first, maintain at 500-600℃ for 1-2 hours, then maintain at 1500-1600℃ for 1-4 hours, and finally maintain at 500-600℃ for 1-2 hours.

[0044] Regulating the temperature of the second stage to 1500-1600℃ not only helps improve the capacity and rate performance of sodium-ion batteries, but also improves their cycle performance.

[0045] Preferably, the segmented high-temperature treatment is carried out in an inert gas atmosphere.

[0046] More preferably, the inert gas atmosphere is at least one of nitrogen atmosphere or argon atmosphere.

[0047] Preferably, after the segmented high-temperature treatment, a grinding step is also included.

[0048] More preferably, the grinding method is ball milling, the ball milling speed is 600-800 rad / min, and the time is 8-13 h.

[0049] A pine-based hard carbon material is prepared by any of the above-described preparation methods.

[0050] The application of the aforementioned pine-based hard carbon material in the preparation of sodium-ion battery anodes is also within the scope of protection of this invention.

[0051] A sodium-ion battery anode is prepared by the following steps: mixing a conductive agent, a binder, a solvent, and a pine-based hard carbon material to obtain a slurry; coating the obtained slurry onto a current collector; and drying to obtain the sodium-ion battery anode.

[0052] Preferably, the mass ratio of the conductive agent, binder and pine-based hard carbon material is (1-4):(1-8):94.

[0053] Preferably, the conductive agent is at least one of graphite black, carbon nanotubes, or graphene.

[0054] Preferably, the adhesive is at least one of polyvinylidene fluoride, styrene-butadiene rubber, polyacrylic acid, polyvinyl alcohol, or carboxymethyl cellulose.

[0055] Preferably, the solvent is water.

[0056] Preferably, the current collector is at least one of copper foil, aluminum foil, or silver foil.

[0057] Preferably, the drying temperature is 40–80°C and the drying time is 20–48 hours.

[0058] 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.

[0059] Preferably, the positive electrode is at least one of sodium sheet and sodium vanadium phosphate electrode.

[0060] Preferably, the diaphragm is made of at least one of glass fiber, polyethylene, or polyimide.

[0061] Preferably, the solvent of the electrolyte is at least one of ethylene glycol dimethyl ether, dimethyl carbonate, or ethylene carbonate.

[0062] Preferably, the electrolyte in the electrolyte solution is at least one of sodium trifluorocarbonate, sodium hexafluorophosphate, or sodium perchlorate.

[0063] Preferably, the concentration of the electrolyte in the electrolyte solution is 0.5 to 1 mol / L.

[0064] Compared with the prior art, the beneficial effects of the present invention are:

[0065] This invention involves carbonizing, acid washing, and segmented high-temperature treatment of pine wood to obtain a pine-based hard carbon material, which is used to prepare the negative electrode for sodium-ion batteries. This material enables sodium-ion batteries to have high specific capacity and good rate performance. In addition, it also enables sodium-ion batteries to have good cycle stability. Attached Figure Description

[0066] Figure 1 The image shows the XRD pattern of the pine-based hard carbon material prepared in Example 1 of this invention.

[0067] Figure 2 This is a SEM image of the pine-based hard carbon material prepared in Example 1 of the present invention.

[0068] Figure 3 A button battery made from the pine-based hard carbon material prepared in Example 5 of this invention has a 20 mAg performance. -1 Charging and discharging cycle performance at current density.

[0069] Figure 4 A button battery made from the pine-based hard carbon material prepared in Comparative Example 1 of this invention, at 20 mAg... -1 Charging and discharging cycle performance at current density.

[0070] Figure 5 A button battery made from the pine-based hard carbon material prepared in Example 5 of this invention has a performance of 300 mAg. -1 Charging and discharging cycle performance at current density.

[0071] Figure 6 A button battery made from the pine-based hard carbon material prepared in Example 6 of this invention has a performance of 300 mAg. -1 Charging and discharging cycle performance at current density.

[0072] Figure 7 A button battery made from the pine-based hard carbon material prepared in Example 7 of this invention has a performance of 300 mAg.-1 Charging and discharging cycle performance at current density.

[0073] Figure 8 A button cell made from the pine-based hard carbon material prepared in Comparative Example 1 of this invention has a performance of 300 mAg. -1 Charging and discharging cycle performance at current density.

[0074] Figure 9 Button batteries made from the pine-based hard carbon material prepared in Example 5 of this invention have an energy density of 20-1500 mAg. -1 Charging / discharging rate performance at current density;

[0075] Figure 10 The button cell made from the pine-based hard carbon material prepared in Comparative Example 1 of this invention has an energy density of 20-1500 mAg. -1 Charging / discharging rate performance at current density; Detailed Implementation

[0076] 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.

[0077] Example 1

[0078] This embodiment provides a method for preparing pine-based hard carbon material, including the following steps:

[0079] 1) Pine wood was dried at 80℃ for 24 hours, then 20g was weighed and placed in a ball mill, and 5g of phosphoric acid solution (concentration of 5mol / L) was added. The mixture was ball-milled at 600rad / min for 10 hours (with a 30min pause after every 30min during the ball milling process) to obtain a mixture. The mixture was then placed in a nitrogen atmosphere and heated from 25℃ to 600℃ at a rate of 2℃ / min for 3 hours to obtain a black substance.

[0080] 2) The black substance obtained in step 1) was immersed in 1 mol / L hydrochloric acid solution, stirred at 60°C for 24 h, filtered and washed with deionized water until neutral, and dried at 80°C for 48 h to obtain black powder.

[0081] 3) Place the black powder obtained in step 2) under a nitrogen atmosphere, raise the temperature from 25°C to 600°C at a rate of 2°C / min and hold for 1 hour, then raise the temperature to 1500°C (denoted as temperature T) at a rate of 2°C / min and hold for 2 hours, and finally lower the temperature to 600°C at a rate of 2°C / min and hold for 1 hour. Allow it to cool naturally to room temperature, and then place the obtained material in a ball mill and ball mill it at a speed of 800 rad / min for 12 hours (during the ball milling process, stop for 30 minutes after every 30 minutes) to obtain pine wood-based hard carbon material.

[0082] Example 2

[0083] This embodiment provides a method for preparing pine-based hard carbon material, which is basically the same as that in Example 1, except that the temperature T in step 3) is 1300℃.

[0084] Example 3

[0085] This embodiment provides a method for preparing pine-based hard carbon material, which is basically the same as that in Example 1, except that the temperature T in step 3) is 1600℃.

[0086] Example 4

[0087] This embodiment provides a method for preparing pine-based hard carbon material, which is basically the same as that in Example 1, except that in step 1), the temperature is increased from 25°C to 500°C at a rate of 2°C / min and held for 3 hours.

[0088] In step 3), the temperature is increased from 25°C to 500°C at a rate of 2°C / min and held for 2 hours, then increased to 1500°C at a rate of 2°C / min and held for 4 hours, and finally decreased to 500°C at a rate of 2°C / min and held for 2 hours.

[0089] Example 5

[0090] This embodiment provides a sodium-ion battery negative electrode and a sodium-ion battery prepared therefrom, the preparation process of which is as follows:

[0091] 1) Polyvinylidene fluoride, graphite carbon black, styrene-butadiene rubber and pine-based hard carbon material from Example 1 were mixed in water at a mass ratio of 4:2:2:95 to obtain a slurry. The slurry was coated on copper foil and dried under vacuum at 60°C for 24 hours to obtain the sodium-ion battery negative electrode.

[0092] 2) The battery is assembled in a glove box filled with argon gas. The negative electrode is the sodium-ion battery obtained in step 1), the positive electrode is a sodium sheet, the separator is glass fiber, and the electrolyte is a 1 mol / L NaCFSO3 ethylene glycol dimethyl ether solution to obtain the sodium-ion battery.

[0093] Example 6

[0094] This embodiment provides a sodium-ion battery negative electrode and a sodium-ion battery prepared therefrom, which is basically the same as that in embodiment 5, except that the pine-based hard carbon material in step 1) is the same as that in embodiment 2.

[0095] Example 7

[0096] This embodiment provides a sodium-ion battery negative electrode and a sodium-ion battery prepared therefrom, which is basically the same as that in Example 5, except that the pine-based hard carbon material in step 1) is the same as that in Example 3.

[0097] Example 8

[0098] This embodiment provides a sodium-ion battery negative electrode and a sodium-ion battery prepared therefrom, which is basically the same as that in Example 5, except that the pine-based hard carbon material in step 1) is the same as that in Example 4.

[0099] Comparative Example 1

[0100] This comparative example provides a comparison of pine-based hard carbon material and sodium-ion batteries, including the following steps:

[0101] 1) First, process according to steps 1) and 2) of Example 1 to obtain black powder; then place the black powder under a nitrogen atmosphere and raise it from 25°C to 1500°C at a rate of 2°C / min and keep it for 2 hours, then let it cool naturally to room temperature. The resulting material is placed in a ball mill and ball-milled at a speed of 800 rad / min for 12 hours (during the ball milling process, stop for 30 minutes after every 30 minutes) to obtain the comparative pine wood-based hard carbon material.

[0102] 2) The difference from Example 5 is that the pine-based hard carbon material of Example 5 is replaced with the comparative pine-based hard carbon material of this comparative example in step 1), and a sodium-ion battery is obtained.

[0103] Performance testing

[0104] 1. XRD testing and morphological characterization

[0105] The pine-based hard carbon material from Example 1 was subjected to X-ray diffraction and scanning electron microscopy tests, respectively. The test results are as follows: Figure 1 and Figure 2 As shown. Figure 1 The XRD pattern of Example 1 is shown below. Figure 1 Two distinct broad peaks can be observed near 23.5° and 43°, which belong to the (002) and (100) peaks of amorphous carbon materials. The formation of amorphous carbon materials is the basis for the good sodium storage performance and cycle stability of the pine-based hard carbon materials prepared in this invention. Figure 2 The image shown is a scanning electron microscope image of Example 1. Figure 2The surface of the pine-based hard carbon material observed in the study exhibits numerous porous structures, which effectively enhance its sodium storage capacity. The XRD test and morphology characterization results of the pine-based hard carbon materials in Examples 2-4 are similar to those in Example 1.

[0106] 2. Electrochemical performance

[0107] The sodium-ion batteries from Examples 5-7 and the comparative sodium-ion battery from Comparative Example 1 were subjected to rate performance tests and cycle stability tests, respectively. The test results are as follows: Figures 3-7 As shown.

[0108] Figure 3 and Figure 4 The sodium-ion battery of Example 5 and the comparative sodium-ion battery of Comparative Example 1 were respectively tested at 20 mAg. -1 Charge-discharge cycle performance at current density. From... Figure 3 It can be seen that the initial specific capacity of Example 5 is 354 mAhg. -1 After 50 cycles, its capacity is 350mAhg. -1 The capacity retention rate is 98%. Figure 4 It can be seen that the initial specific capacity of Comparative Example 1 is 298 mAh g. -1 After 50 cycles, its capacity is 290 mAh g. -1 Its capacity retention rate is 97%. Furthermore, at 20 mAg... -1 At current density, Example 5 has a first coulomb efficiency of 93%, while Comparative Example 1 has only 82%.

[0109] Figures 5-8 The sodium-ion batteries of Examples 5-7 and the comparative sodium-ion battery of Comparative Example 1 were tested at 300 mAg. -1 Charge-discharge cycle performance at current density. From... Figure 5 It can be seen that the initial specific capacity of Example 5 is 286.8 mAh g. -1 After 300 cycles, its capacity still reaches 280mAh. -1 Its capacity retention rate is 98%. Figure 6 It can be seen that the initial specific capacity of Example 6 is 310.5 mAh g. -1 After 300 cycles, its capacity still reaches 240mAh. -1 Its capacity retention rate is 77%, and the battery tends to stabilize after 60 cycles, maintaining a specific capacity of 240 mAh g. -1 Left and right. From Figure 7 It can be seen that the initial specific capacity of Example 7 is 286.7 mAh g. -1 After 300 cycles, its capacity still reaches 244 mAh. -1Its capacity retention rate is 85%, and the battery tends to stabilize after 20 cycles, maintaining a specific capacity of 244 mAh g. -1 Left and right. From Figure 8 It can be seen that the initial specific capacity of Comparative Example 1 is 281 mAh g. -1 After 300 cycles, its capacity decreased to 218 mAh g. -1 Its capacity retention rate is 77%. This indicates that the pine-based hard carbon material obtained through the segmented high-temperature treatment of the present invention, when used to prepare the anode of a sodium-ion battery, enables the sodium-ion battery to have a (initial) high specific capacity, and, due to the high initial specific capacity, the sodium-ion battery still maintains a high specific capacity after multiple cycles.

[0110] Compare Figure 3 and Figure 4 , Figure 5 and Figure 8 It can be seen that the specific capacity and cycle retention rate of Example 5 are excellent under different current densities, while the cycle stability of Comparative Example 1 under high current density is not as good as that of Example 5.

[0111] Figure 9 and Figure 10 The sodium-ion battery of Example 5 and the comparative sodium-ion battery of Comparative Example 1 have performance values ​​ranging from 20 to 1500 mAg. -1 Charge-discharge rate performance at current density. From... Figure 9 It can be seen that the sodium-ion battery of Example 5 performs well at 20, 30, 60, 120, 240, 300, 600, 900, 1500 and 20 mAg. -1 The reversible capacities at different current densities (each cycle being 10 times) were 315.4, 298.5, 292.3, 280.5, 261.6, 252.6, 229.2, 206.5, 166.2, and 301.4 mAh g, respectively. -1 .from Figure 10 It can be seen that the sodium-ion battery in Comparative Example 1 performs better at 20, 30, 60, 120, 240, 300, 600, 900, 1500 and 20 mAg. -1 The reversible capacities at different current densities (each cycled 10 times) were 312.5, 284.2, 275.2, 233.3, 169.7, 149.6, 85.3, 61.4, 42.2, and 290.1 ​​mAh g. -1 The comparison of the two figures shows that Example 5 has a higher specific capacity than Comparative Example 1 at different current densities, and the specific capacity fluctuation of Comparative Example 1 is smaller than that of the Comparative Example 1 under the rate performance test, indicating that the hard carbon material of Example 1 is more stable.

[0112] Comparing the experimental data of Example 5 and Comparative Example 1, it can be seen that the specific capacity, cycle stability, and rate performance of Example 5 are all superior to those of Comparative Example 1. This indicates that the pine-based hard carbon material treated by segmented high temperature in this invention, when used to prepare sodium-ion batteries, improves their specific capacity, cycle stability (especially cycle stability at high current densities), and charge / discharge capacity.

[0113] The performance of the sodium-ion battery in Example 8 is similar to that in Example 5.

[0114] 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 a pine-based hard carbon material, characterized in that, Includes the following steps: The pine wood is carbonized, then acid-washed, and finally subjected to segmented high-temperature treatment to obtain the pine wood-based hard carbon material. The segmented high-temperature treatment process is as follows: first, maintain at 500~600℃ for 1~2 hours, then maintain at 1500~1600℃ for 2~4 hours, and finally maintain at 500~600℃ for 1~2 hours.

2. The preparation method according to claim 1, characterized in that, Prior to the carbonization process, the method also includes a step of mixing pine wood and a pore-forming agent.

3. The preparation method according to claim 2, characterized in that, The pore-forming agent is at least one of phosphoric acid, citric acid, or potassium hydroxide.

4. The preparation method according to claim 1, characterized in that, The carbonization process is carried out at a temperature of 400-800℃ for 1-5 hours.

5. A pine-based hard carbon material, characterized in that, It is prepared by any of the preparation methods described in claims 1 to 4.

6. The application of the pine-based hard carbon material of claim 5 in the preparation of sodium-ion battery anodes.

7. A sodium-ion battery negative electrode, characterized in that, The sodium-ion battery negative electrode is prepared by the following steps: a conductive agent, a binder, a solvent, and the pine-based hard carbon material of claim 5 are mixed to obtain a slurry, the obtained slurry is coated on a current collector, and dried to obtain the sodium-ion battery negative electrode.

8. The sodium-ion battery negative electrode according to claim 7, characterized in that, The mass ratio of the conductive agent, binder and pine-based hard carbon material is (1~4):(1~8):

94.

9. 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 any one of claims 7 to 8.

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