CN117658107A - Bamboo-based hard carbon negative electrode material, preparation method thereof and sodium ion battery negative electrode - Google Patents

Abstract

The invention belongs to the technical field of sodium ion battery negative electrode materials, and provides a bamboo-based hard carbon negative electrode material, a preparation method thereof and a sodium ion battery negative electrode. The invention pre-carbonizes the bamboo-based biomass to make hydrogen atoms and other atoms (such as C, O, cl and N) in the bamboo-based biomass in volatile form (CH) ₄ 、CO ₂ 、CO、H ₂ O, HCl and NH ₃ ) Releasing to obtain pre-carbonized bamboo-based biomass; then acid leaching is carried out, so that metal or nonmetal impurity elements in the pre-carbonization treatment product are effectively reduced; ball milling is carried out to obtain a bamboo-based hard carbon precursor with proper granularity; finally, carbonizing the hard carbonized precursor, adjusting andand optimizing the microstructure of the material to obtain the bamboo-based hard carbon anode material. The bamboo-based hard carbon negative electrode material prepared by the preparation method provided by the invention is applied to sodium ion batteries, the initial coulomb efficiency can reach 89.8%, and the initial discharge specific capacity can reach 339.7mAh/g.

Description

Bamboo-based hard carbon negative electrode material and preparation method thereof and sodium ion battery negative electrode

Technical field

The invention relates to the technical field of sodium-ion battery negative electrode materials, and specifically relates to a bamboo-based hard carbon negative electrode material and a preparation method thereof and a sodium-ion battery negative electrode.

Background technique

Driven by the dual carbon goals, energy is accelerating its transformation to green development. Green energy such as wind energy, solar energy, tidal energy, and geothermal energy are developing rapidly. However, these intermittent power generation have a greater impact on the power grid, and there is an urgent need to be equipped with corresponding electrochemical equipment. Energy storage power stations are used to efficiently store and convert energy. At present, lithium-ion batteries have been successfully commercialized, but lithium resources are expensive. In this context, it is crucial to develop new energy storage systems with lower cost and excellent performance. Sodium-ion batteries are considered to be an ideal choice for the new generation of energy storage devices and conversion equipment due to their abundant sodium reserves, environmental friendliness, and similar electrochemical properties to lithium-ion batteries.

In the research process of sodium-ion batteries, carbon-based materials have become the preferred target for sodium storage anode materials due to their advantages such as wide sources, abundant resources, diverse structures, and long life. Hard carbon materials have larger interlayer spacing, more nanopores, and more defect sites, so they can store more sodium ions and exhibit higher specific capacities. Therefore, hard carbon materials are currently the most promising One of the negative electrode materials for sodium-ion batteries. However, battery anode materials made of hard carbon materials contain metal or non-metal impurity elements, which will consume sodium ions and reduce the cycle performance of sodium ion batteries; and the specific surface area of battery anode materials made of hard carbon materials is too large, causing pores The structure and interlayer spacing do not match the diameter of sodium ions, resulting in low first Coulombic efficiency, poor rate performance and unsatisfactory cycle performance of the sodium-ion battery, which affects the development of sodium-ion batteries.

Contents of the invention

The object of the present invention is to provide a bamboo-based hard carbon negative electrode material and its preparation method and application. The bamboo-based hard carbon negative electrode material provided by the invention has a moderate specific surface area, and the sodium ion battery prepared with the negative electrode material has a high specific capacity, high first Coulombic efficiency and good cycle stability.

In order to achieve the above-mentioned object of the invention, the present invention provides the following technical solutions:

The invention provides a preparation method of bamboo-based hard carbon negative electrode material, which includes the following steps:

1) Pre-carbonize bamboo-based biomass to obtain pre-carbonized bamboo-based biomass;

2) The pre-carbonized bamboo-based biomass obtained in step 1) is sequentially acid leached and ball milled to obtain a bamboo-based hard carbon precursor;

3) Carbonize the bamboo-based hard carbon precursor obtained in step 2) to obtain a bamboo-based hard carbon negative electrode material.

Preferably, the temperature of the pre-carbonization treatment in step 1) is 300-650°C; the time of the pre-carbonization treatment is 1-8 hours.

Preferably, the pre-carbonization treatment in step 1) is performed in an air atmosphere.

Preferably, the concentration of the acid solution used in the acid leaching in step 2) is 1 to 8 mol/L.

Preferably, the rotation speed of the ball mill in step 2) is 300-600 rpm; the ball milling time is 1-6 hours.

Preferably, the particle size of the bamboo-based hard carbon precursor in step 2) is 100 to 600 mesh.

Preferably, the temperature of the carbonization treatment in step 3) is 800-1600°C; the time of the carbonization treatment is preferably 2-6 hours.

Preferably, the carbonization treatment in step 3) is performed under an inert atmosphere.

The invention also provides a bamboo-based hard carbon negative electrode material prepared by the preparation method described in the above technical solution.

The present invention also provides a sodium-ion battery negative electrode. The negative electrode material in the sodium-ion battery negative electrode is the bamboo-based hard carbon negative electrode material described in the above technical solution.

The invention provides a method for preparing a bamboo-based hard carbon negative electrode material, which includes the following steps: 1) pre-carbonizing bamboo-based biomass to obtain pre-carbonized bamboo-based biomass; 2) pre-carbonizing the bamboo-based biomass obtained in step 1). The carbonized bamboo-based biomass is acid leached and ball milled sequentially to obtain a bamboo-based hard carbon precursor; 3) Carbonize the bamboo-based hard carbon precursor obtained in step 2) to obtain a bamboo-based hard carbon negative electrode material. By pre-carbonizing the bamboo-based biomass, the present invention converts hydrogen atoms and other atoms (such as C, O, Cl and N) in the bamboo-based biomass into the form of volatiles (CH ₄ , CO ₂ , CO, H ₂ O, HCl and NH ₃ , etc.) are released, increasing the active sites on the surface of the material, promoting organic cross-linking between molecules, increasing the disorder of the structure, and conducive to the migration and diffusion of Na ⁺ , making it have a slope ratio The capacity also has a platform specific capacity, and the sodium storage specific capacity is increased; by acid leaching the pre-carbonized bamboo-based biomass, the metal or non-metal impurity elements in the pre-carbonized bamboo-based biomass can be effectively reduced, and the consumption of sodium ions can be reduced. Reduce the risk of micro-short circuits in the produced battery during the charge and discharge process, and improve battery cycle and safety performance; by ball milling the pre-carbonized bamboo-based biomass after acid leaching to obtain a bamboo-based hard carbon precursor with suitable particle size , while adjusting its defect concentration, increasing its sodium storage capacity, and conducive to full and uniform reaction in the subsequent carbonization process; by carbonizing the bamboo-based hard carbon precursor, the microstructure of the material can be adjusted and optimized to obtain a Bamboo-based hard carbon anode materials with appropriate layer spacing can increase the degree of graphitization of bamboo-based hard carbon anode materials, gradually closing the open pores, increasing the closed pores, reducing the specific surface area, and reducing the formation of more SEI films in the first cycle. Avoid more defect sites causing irreversible storage of sodium ions, and achieve high first Coulombic efficiency and high specific capacity of the material. The results of the examples show that the specific surface area of the bamboo-based hard carbon negative electrode material prepared by the preparation method provided by the present invention is 13.5m ² /g. When used in sodium-ion batteries, the first Coulombic efficiency can reach 89.8%, and the first discharge specific capacity can reach 89.8%. 339.7mAh/g.

Description of drawings

Figure 1 is a scanning electron microscope image of the bamboo-based hard carbon negative electrode material prepared in Example 2 of the present invention;

Figure 2 is a charge-discharge curve of a sodium-ion battery made of bamboo-based hard carbon negative electrode material prepared in Example 2 of the present invention;

Figure 3 is a cycle performance diagram of a sodium-ion battery made of the bamboo-based hard carbon negative electrode material prepared in Example 2 of the present invention.

Detailed ways

The invention provides a preparation method of bamboo-based hard carbon negative electrode material, which includes the following steps:

1) Pre-carbonize bamboo-based biomass to obtain pre-carbonized bamboo-based biomass;

2) The pre-carbonized bamboo-based biomass obtained in step 1) is sequentially acid leached and ball milled to obtain a bamboo-based hard carbon precursor;

3) Carbonize the bamboo-based hard carbon precursor obtained in step 2) to obtain a bamboo-based hard carbon negative electrode material.

In the present invention, bamboo-based biomass is pre-carbonized to obtain pre-carbonized bamboo-based biomass.

In the present invention, the preparation method of the bamboo-based biomass is preferably: washing the bamboo raw materials with deionized water and drying them in sequence to obtain the bamboo-based biomass.

In the present invention, the bamboo raw material is preferably one or more types of bamboo, moso bamboo, moso bamboo, purple bamboo and water bamboo.

The present invention has no special limitation on the method of washing with deionized water, and any washing method well known in the art can be used. In the present invention, the deionized water washing can remove solid particles, dust and dirt on the surface of bamboo raw materials.

In the present invention, the drying temperature is preferably 60-160°C, more preferably 70-110°C, further preferably 80-100°C; the drying time is preferably 12-48h, more preferably 14 ~36h, more preferably 16~24h. The present invention removes moisture from bamboo raw materials by limiting the drying temperature and time to obtain bamboo-based biomass. The present invention has no special limitations on the drying equipment, and drying equipment well known in the art can be used. In the present invention, the drying equipment is preferably a blast drying box.

In the present invention, the temperature of the pre-carbonization treatment is preferably 300-650°C, more preferably 350-600°C, further preferably 400-500°C; the time of the pre-carbonization treatment is preferably 1-8 hours, more preferably It is 1.5-7.5h, More preferably, it is 3-6h. In the present invention, the rate of heating to the pre-carbonization treatment temperature is preferably 3 to 15°C/min, and more preferably 5 to 10°C/min. The present invention uses pre-carbonization treatment to convert hydrogen atoms and other atoms (such as C, O, Cl and N, etc.) in the bamboo-based biomass into the form of volatiles (CH ₄ , CO ₂ , CO, H ₂ O, HCl and NH ₃ ) is released, increasing the active sites on the surface of the material, promoting organic cross-linking between molecules, increasing the disorder of the structure, and facilitating the migration and diffusion of Na ⁺ , giving it both a slope specific capacity and a plateau specific capacity. , the sodium storage specific capacity increases; by limiting the temperature, time and heating rate of the pre-carbonization treatment, the disorder of the structure can be further increased, which is more conducive to the migration and diffusion of Na ⁺ and further increases the sodium storage specific capacity.

In the present invention, the pre-carbonization treatment is preferably performed in an air atmosphere. The present invention has no special limitations on the pre-carbonization equipment, and pre-carbonization equipment well known in the art can be used. In the present invention, the pre-carbonization equipment is preferably a muffle furnace.

After the pre-carbonization treatment is completed, the present invention preferably cools and crushes the pre-carbonization product in sequence to obtain pre-carbonized bamboo-based biomass.

In the present invention, the cooling is preferably cooling to room temperature along with the furnace. In the present invention, the particle size of the pre-carbonized bamboo-based biomass is preferably 1 to 50 μm, more preferably 2 to 40 μm, and even more preferably 5 to 30 μm. The present invention obtains powdery pre-carbonized bamboo-based biomass by limiting the crushing particle size, so that it is easier to remove impurities in the subsequent acid leaching process, and the subsequent ball milling is easier and more uniform, which is beneficial to the subsequent process. The present invention has no special limitations on the crushing equipment, and crushing equipment well known in the art can be used. In the present invention, the crushing equipment is preferably a jet mill.

After obtaining the pre-carbonized bamboo-based biomass, the present invention preferably acid-leaches and ball-mills the pre-carbonized bamboo-based biomass in sequence to obtain a bamboo-based hard carbon precursor.

In the present invention, the concentration of the acid solution used in the acid leaching is preferably 1 to 8 mol/L, more preferably 1.5 to 7 mol/L, and even more preferably 3 to 5 mol/L. In the present invention, the acid solution used in the acid leaching is preferably one or more of hydrochloric acid, sulfuric acid and nitric acid. In the present invention, the acid leaching time is preferably 3 to 12 hours, more preferably 4 to 10 hours, and even more preferably 5 to 8 hours. The invention promotes the full dissolution of metal or non-metal impurities in the acid solution through acid leaching, effectively reduces the metal or non-metal impurity elements in the pre-carbonization product, reduces the consumption of sodium ions, and at the same time can reduce micro-short circuits in the battery during charging and discharging. risk, improve battery cycle and safety performance.

After the acid leaching is completed, the present invention preferably washes and vacuum-dries the product obtained by the acid leaching in sequence.

In the present invention, the washing is preferably carried out by first washing with deionized water and then washing with ethanol. In the present invention, the deionized water washing is preferably stopped when the washing liquid is neutral.

In the present invention, the vacuum drying temperature is preferably 60 to 110°C, more preferably 75 to 105°C, and even more preferably 90 to 100°C. In the present invention, the vacuum drying time is preferably 6 to 16 hours, more preferably 8 to 12 hours. The present invention removes moisture from washed pre-carbonized bamboo-based biomass by limiting the temperature and time of vacuum drying. The present invention has no special limitations on the vacuum drying equipment, and vacuum drying equipment well known in the art can be used.

After the vacuum drying is completed, the present invention preferably ball-mills the vacuum-dried product to obtain a bamboo-based hard carbon precursor.

In the present invention, the rotation speed of the ball mill is preferably 300 to 600 rpm, and more preferably 350 to 500 rpm. In the present invention, the ball milling time is preferably 1 to 6 hours, more preferably 1.5 to 5.5 hours, and even more preferably 3 to 4 hours. The present invention obtains a hard carbon precursor with suitable particle size by limiting the rotation speed, time and particle size of the ball mill, and at the same time adjusts its defect concentration and increases its sodium storage capacity, which is conducive to a sufficient and uniform reaction in the subsequent carbonization process.

In the present invention, the particle size of the bamboo-based hard carbon precursor is preferably 100 to 600 mesh, and more preferably 150 to 450 mesh. In the present invention, when the particle size of the bamboo-based hard carbon precursor is not in the above range, the present invention preferably sieves the ball milled product. The present invention has no special limitations on the screening equipment, and screening equipment well known in the art can be used.

The present invention has no special limitations on the ball milling equipment, and ball milling equipment well known in the art can be used. In the present invention, the ball milling equipment is preferably a planetary ball mill.

After obtaining the bamboo-based hard carbon precursor, the present invention carbonizes the bamboo-based hard carbon precursor to obtain the bamboo-based hard carbon negative electrode material.

In the present invention, the temperature of the carbonization treatment is preferably 800 to 1600°C, more preferably 900 to 1500°C, and even more preferably 1000 to 1300°C. In the present invention, the rate of heating to the temperature of the carbonization treatment is preferably 1 to 10°C/min, and more preferably 2 to 8°C/min. In the present invention, the carbonization treatment time is preferably 2 to 6 hours, more preferably 2 to 4 hours. The present invention adjusts and optimizes the microstructure of the bamboo-based hard carbon precursor through carbonization treatment, obtains bamboo-based hard carbon negative electrode materials with suitable layer spacing, improves the graphitization degree of the bamboo-based hard carbon negative electrode material, and gradually closes the openings. The pores increase and the specific surface area decreases, which reduces the formation of more SEI films in the first cycle, avoids more defect sites causing irreversible storage of sodium ions, and achieves high first Coulombic efficiency and high specific capacity of the material; through limited carbonization treatment Temperature, time and heating rate, further adjust and optimize the microstructure of the bamboo-based hard carbon precursor, thereby obtaining a bamboo-based hard carbon anode material with suitable layer spacing.

In the present invention, the pre-carbonization treatment is preferably performed in an inert atmosphere. The present invention has no special limitations on the inert atmosphere, and any inert gas well known in the art can be used. In the present invention, the inert atmosphere is preferably nitrogen or argon. The present invention has no special limitations on the carbonization treatment equipment, and carbonization treatment equipment well known in the art can be used. In the present invention, the equipment for carbonization treatment is preferably a high-temperature tube furnace.

By pre-carbonizing the bamboo-based biomass, the present invention converts hydrogen atoms and other atoms (such as C, O, Cl and N) in the bamboo-based biomass into volatile forms (CH ₄ , CO ₂ , CO, H ₂ O, HCl and NH ₃ , etc.) are released, increasing the active sites on the surface of the material, promoting organic cross-linking between molecules, increasing the disorder of the structure, and conducive to the migration and diffusion of Na ⁺ , making it have a slope ratio The capacity also has a platform specific capacity, and the sodium storage specific capacity is increased; by acid leaching the pre-carbonized bamboo-based biomass, the metal or non-metal impurity elements in the pre-carbonized product can be effectively reduced, and the consumption of sodium ions can be reduced, thereby reducing the production cost. The risk of micro-short circuit in the battery obtained during the charge and discharge process is improved, and the battery cycle and safety performance are improved; by ball milling the pre-carbonized bamboo-based biomass after acid leaching, a bamboo-based hard carbon precursor with suitable particle size is obtained, and at the same time Adjusting its defect concentration increases its sodium storage capacity, and is conducive to full and uniform reaction in the subsequent carbonization process; by carbonizing the bamboo-based hard carbon precursor, the microstructure of the material can be adjusted and optimized to obtain a suitable layer The spacing of the bamboo-based hard carbon anode material increases the degree of graphitization of the bamboo-based hard carbon anode material, gradually closing the open pores, increasing the closed pores, and reducing the specific surface area, thereby reducing the generation of more SEI films in the first cycle and avoiding More defect sites cause irreversible storage of sodium ions, achieving high first Coulombic efficiency and high specific capacity of the material.

The invention also provides a bamboo-based hard carbon negative electrode material prepared by the preparation method described in the above technical solution.

In the present invention, the specific surface area of the bamboo-based hard carbon negative electrode material is preferably 1 to 30 m ² /g, more preferably 3 to 25 m ² /g; the layer spacing of the bamboo-based hard carbon negative electrode material is preferably 0.36 to 0.36 m 2 /g. 0.50 nm, more preferably 0.37 to 0.42 nm. By limiting the specific surface area and interlayer spacing of the bamboo-based hard carbon negative electrode material, the present invention can further reduce the generation of more SEI films in the first cycle and avoid more defective sites causing irreversible storage of sodium ions.

The bamboo-based hard carbon negative electrode material prepared by the invention has a small specific surface area and a suitable layer spacing, which can reduce the generation of more SEI films in the first cycle, avoid more defective sites causing irreversible storage of sodium ions, and achieve high first-time performance of the material. Coulombic efficiency and high specific capacity.

The present invention also provides a sodium-ion battery negative electrode. The negative electrode material in the sodium-ion battery negative electrode is the bamboo-based hard carbon negative electrode material described in the above technical solution.

In the present invention, the sodium ion battery negative electrode preferably includes a current collector and a negative electrode material layer coated on the current collector; the negative electrode material layer includes the bamboo-based hard carbon negative electrode material and conductive agent described in the above technical solution. and adhesive.

In the present invention, the mass ratio of the bamboo-based hard carbon negative electrode material, conductive agent and binder is preferably 93:3:4. In the present invention, the conductive additive is preferably one or more of acetylene black, SuperP and carbon nanotubes; in the present invention, the binder is polyvinylidene fluoride and sodium carboxymethyl cellulose.

In the present invention, the thickness of the negative electrode material layer is preferably 100 to 300 μm, and more preferably 150 to 250 μm. The present invention controls the load of the pole piece by limiting the thickness of the negative electrode material layer to prevent the load of the pole piece from being too high or too low, affecting the transmission speed of sodium ions and causing poor electrochemical performance.

The preparation method of the sodium ion battery negative electrode is preferably: grind the bamboo-based hard carbon material, conductive agent and binder evenly according to the mass ratio of 93:3:4, and then add an appropriate amount of NMP to adjust the solid content to 40~ 50% of the slurry is evenly coated on the aluminum foil with a coating machine. The loading capacity is 4.5~5.0 mg/cm ² . Place it in a vacuum drying box and vacuum dry it at 80°C for 12 hours. Then use a punching machine to prepare sodium oxide with a diameter of 10 mm. Ion battery negative electrode.

The sodium-ion battery negative electrode prepared from the bamboo-based hard carbon negative electrode material prepared by the present invention is used in sodium-ion batteries. The first Coulombic efficiency can reach 89.8%, and the first discharge specific capacity can reach 339.7mAh/g.

The above descriptions are only preferred embodiments of the present invention and do not limit the present invention in any form. It should be pointed out that for those of ordinary skill in the art, several improvements and modifications can be made without departing from the principles of the present invention, and these improvements and modifications should also be regarded as the protection scope of the present invention.

Example 1

A preparation method of bamboo-based hard carbon negative electrode material, consisting of the following steps:

1) First wash the bamboo raw materials with deionized water, and then dry them in a blast drying oven at 80°C for 16 hours to obtain bamboo-based biomass, which is then transferred to a muffle furnace and pre-carbonized in an air atmosphere. The heating rate of the pre-carbonization treatment is 5°C/min, the temperature of the pre-carbonization treatment is 450°C, and the time of the pre-carbonization treatment is 2 hours. After the pre-carbonization treatment is completed, the product is naturally cooled, and then placed in a pulverizer and crushed to 30 mesh to obtain pre-carbonized bamboo-based biomass;

2) Dip the pre-carbonized bamboo-based biomass obtained in step 1) into a hydrochloric acid solution with a concentration of 2 mol/L for 6 hours. After acid leaching, first wash with deionized water until neutral, then wash with ethanol, and then place Dry in a vacuum drying oven at 100°C for 10 hours, and then place the dried pre-carbonized bamboo-based biomass in a planetary ball mill and ball-mill at a speed of 400 rpm. The ball-milling time is 2 hours. After ball-milling, 200-mesh bamboo-based hard carbon is obtained by screening. Precursor;

3) Transfer the bamboo-based hard carbon precursor obtained in step 2) to a high-temperature tube furnace, and perform carbonization treatment under an argon atmosphere. The temperature rise rate of the carbonization treatment is 3°C/min, and the temperature of the carbonization treatment is The temperature is 1200°C, and the carbonization treatment time is 2 hours. After the carbonization treatment is completed, the temperature is naturally cooled to obtain the bamboo-based hard carbon negative electrode material.

Example 2

The difference between this embodiment and Example 1 is that the temperature of the carbonization treatment is 1300°C, and the rest is the same as Example 1.

Example 3

The difference between this embodiment and Example 1 is that the temperature of the carbonization treatment is 1400°C, and the rest is the same as Example 1.

Example 4

The difference between this embodiment and Example 2 is that the concentration of the hydrochloric acid solution is 4 mol/L, and the rest is the same as Example 2.

Example 5

The difference between this embodiment and Example 4 is that the ball milling time is 4 hours, and the rest is the same as Example 4.

Example 6

The difference between this embodiment and Example 5 is that the concentration of the hydrochloric acid solution is 2 mol/L, the temperature of the carbonization treatment is 1100°C, and the rest is the same as Example 5.

Comparative example 1

The difference between this comparative example and Example 1 is that the acid leaching step in step 2) is omitted, and the pre-carbonized bamboo-based biomass obtained in step 1) is directly placed in a planetary ball mill and ball milled at a rotation speed of 400 rpm. The ball milling time is 2 hours. After ball milling, the bamboo-based hard carbon precursor of 200 mesh is obtained by sieving. The rest is the same as in Example 1.

Comparative example 2

The difference between this comparative example and Example 1 is that the ball milling step in step 2) is omitted, and the pre-carbonized bamboo-based biomass obtained in step 1) is immersed in a hydrochloric acid solution with a concentration of 2 mol/L for 6 hours. First wash with deionized water until neutral, then wash with ethanol, and then dry in a vacuum drying oven at 100°C for 10 hours to obtain a 200-mesh bamboo-based hard carbon precursor. The rest is the same as Example 1.

Application examples 1 to 6

The bamboo-based hard carbon negative electrode materials prepared in Examples 1 to 6, SuperP and polyvinylidene fluoride were ground evenly according to the mass ratio of 93:3:4, and then an appropriate amount of NMP was added to prepare a slurry with a solid content of 45%. The material is evenly coated on the aluminum foil with a coating machine, and placed in a vacuum drying oven for vacuum drying at 80°C for 12 hours. Then, a punching machine is used to prepare a sodium ion battery negative electrode with a diameter of 10 mm, and the sodium ion battery negative electrodes of application examples 1 to 6 are obtained. .

The sodium ion battery negative electrode prepared in Application Examples 1 to 6 was used as the negative electrode, the glass fiber disc was used as the separator, the sodium metal sheet was used as the counter electrode and the reference electrode, and the electrolyte was 1 mol/L sodium perchlorate/ethylene carbonate/ Diethyl carbonate solution, assemble a sodium-ion battery according to the structure of a CR2025 standard button cell in a high-purity argon-filled glove box, and conduct charge and discharge tests on the battery on a battery test platform with a current density of 30 mA/g. The results are as follows As shown in Table 1.

Table 1 Specific surface areas of the bamboo-based hard carbon negative electrode materials prepared in Examples 1 to 6 and Comparative Examples 1 to 2 and electrochemical properties of the prepared sodium ion batteries

It can be seen from Table 1 that the specific surface area of the bamboo-based hard carbon negative electrode material prepared by the present invention is small, and the first Coulombic efficiency and first discharge specific capacity of the sodium-ion battery prepared are both high.

Figure 1 is a scanning electron microscope image of the bamboo-based hard carbon negative electrode material prepared in Example 2 of the present invention. As shown in the figure: the bamboo-based hard carbon negative electrode material prepared in Example 2 of the present invention has an irregular shape and a small particle size. Uneven, ranging from 2 to 25 μm, the surface is relatively smooth, and the pores are visible to be small.

Figure 2 is a charge-discharge curve diagram of a sodium-ion battery made from the bamboo-based hard carbon negative electrode material in Example 2 of the present invention. As shown in the figure: a sodium-ion battery made from the bamboo-based hard carbon negative electrode material in Example 2 of the present invention. It has a high specific discharge capacity of 323.2mAh/g.

Figure 3 is a cycle performance diagram of a sodium-ion battery made from the bamboo-based hard carbon negative electrode material in Example 2 of the present invention. As shown in the figure: the cycle performance of a sodium-ion battery made from the bamboo-based hard carbon negative electrode material in Example 2 of the present invention. After 120 times, it still shows a high reversible specific capacity of 289.9mAh/g, a capacity retention rate of 89.7%, good cycle stability, and good electrochemical performance.

The above descriptions are only preferred embodiments of the present invention and do not limit the present invention in any form. It should be noted that for those of ordinary skill in the art, several improvements and modifications can be made without departing from the principles of the present invention, and these improvements and modifications should also be regarded as the protection scope of the present invention.

Claims (10)

1. A preparation method of a bamboo-based hard carbon anode material comprises the following steps:

1) Pre-carbonizing the bamboo-based biomass to obtain pre-carbonized bamboo-based biomass;

2) Sequentially carrying out acid leaching and ball milling on the pre-carbonized bamboo-based biomass obtained in the step 1) to obtain a bamboo-based hard carbon precursor;

3) And 2) carbonizing the bamboo-based hard carbon precursor obtained in the step 2) to obtain the bamboo-based hard carbon anode material.

2. The method according to claim 1, wherein the temperature of the pre-carbonization treatment in step 1) is 300 to 650 ℃; the pre-carbonization treatment time is 1-8 h.

3. The preparation method according to claim 1 or 2, wherein the pre-carbonization treatment in step 1) is performed under an air atmosphere.

4. The method according to claim 1, wherein the acid solution used for acid leaching in step 2) has a concentration of 1 to 8mol/L.

5. The method according to claim 1, wherein the rotational speed of the ball mill in step 2) is 300 to 600rpm; the ball milling time is 1-6 h.

6. The method according to claim 1, wherein the particle size of the bamboo-based hard carbon precursor in the step 2) is 100 to 600 mesh.

7. The method according to claim 1, wherein the temperature of the carbonization treatment in the step 3) is 800 to 1600 ℃; the carbonization treatment time is 2-6 h.

8. The preparation method according to claims 1 and 7, characterized in that the carbonization treatment in step 3) is performed under an inert atmosphere.

9. The bamboo-based hard carbon negative electrode material produced by the production method of any one of claims 1 to 8.

10. A negative electrode of a sodium ion battery, wherein the negative electrode material in the negative electrode of the sodium ion battery is the bamboo-based hard carbon negative electrode material according to claim 9.