Method for preparing bamboo-based hard carbon material by using ethanol solvothermal pretreatment process, bamboo-based hard carbon material and application of bamboo-based hard carbon material

Abstract

The invention discloses a method for preparing a bamboo-based hard carbon material by using an ethanol solvent thermal pretreatment process, the bamboo-based hard carbon material and application of the bamboo-based hard carbon material, the method comprises the following steps: step 1, pouring dry bamboo pulp powder into an ethanol solution, and uniformly stirring to obtain a mixed suspension; step 2, transferring the mixed suspension into a hydrothermal reaction kettle, putting the hydrothermal reaction kettle into a drying oven, keeping the temperature at 60-100 DEG C for 8-24 hours, cooling to room temperature after the reaction is finished, and sequentially drying and grinding to obtain a pretreated bamboo fiber precursor; and step 3, placing the pretreated bamboo fiber precursor in a tubular furnace, heating from room temperature to 600-1200 DEG C at a heating rate of 2-10 DEG C / min in a nitrogen atmosphere, and keeping the temperature for 1-4 hours to obtain the bamboo-based hard carbon material. The method is short in technological process and low in energy consumption, and the prepared bamboo-based hard carbon material has large interlayer spacing and specific surface area and can endow the sodium ion battery with excellent electrochemical performance.

Description

Technical Field

[0001] The invention relates to a sodium ion battery negative electrode material, in particular to a method for preparing a bamboo-based hard carbon material by utilizing an ethanol solvent thermal pretreatment process, the bamboo-based hard carbon material and applications thereof. Background Art

[0002] As a negative electrode material for sodium ion batteries, hard carbon has a larger interlayer spacing and richer pore structure than graphite, and has a lower sodium storage potential (~0.1V) and stable cycle performance. It is considered to be the most promising negative electrode material for sodium ion batteries.

[0003] As a natural biomass material, bamboo is mainly composed of organic macromolecules with high carbon content, such as cellulose, hemicellulose and lignin. It has natural advantages such as short growth cycle and high yield. It is one of the important raw materials for the papermaking industry. Using bamboo as a carbon source to prepare hard carbon is expected to significantly reduce corporate production costs and effectively improve the performance stability of hard carbon, which has positive significance for the development of the hard carbon industry.

[0004] In recent years, the research on preparing hard carbon materials using bamboo as a precursor has attracted the attention of researchers. There are also occasional reports on the preparation of hard carbon using bamboo pulp as raw material. However, the existing preparation method generally adopts secondary sintering, which is to pretreat the bamboo pulp at a temperature of 500-700 ° C under alkaline / acidic conditions or mixed with P / N salts, and then sinter it at a temperature above 1000 ° C. The whole process has high energy consumption and a long process. In addition, when the prepared bamboo-based hard carbon material is used in sodium batteries, the fast charging performance is poor. At 1Ag -1 At high current density, the platform capacity can only reach 220mA·hg -1 , and when the current density is from 100mA·g -1 Increased to 1000mA·g -1 When the capacity is reduced, the capacity loss rate is as high as 40%.

[0005] Therefore, it is necessary to develop a new method for preparing bamboo-based hard carbon materials using bamboo pulp as a precursor, so as to reduce energy consumption and improve the performance of bamboo-based hard carbon materials. Summary of the Invention

[0006] The present invention aims to provide a method for preparing a bamboo-based hard carbon material using an ethanol solvent thermal pretreatment process, a bamboo-based hard carbon material and its application. The method not only has a short process flow and low energy consumption, but also the prepared bamboo-based hard carbon material has a large interlayer spacing and specific surface area, which can give sodium ion batteries excellent electrochemical properties.

[0007] The present invention is achieved through the following technical solutions:

[0008] The method for preparing bamboo-based hard carbon material by using ethanol solvent thermal pretreatment process comprises the following steps:

[0009] Step 1: Pour the dry bamboo pulp powder into the ethanol solution and stir evenly to obtain a mixed suspension;

[0010] Step 2: transferring the mixed suspension to a hydrothermal reactor and placing it in an oven, keeping the temperature at 60-100° C. for 8-24 hours, cooling to room temperature after the reaction, drying and grinding in sequence to obtain a pretreated bamboo fiber precursor;

[0011] Step 3: Place the pretreated bamboo fiber precursor in a tubular furnace, and heat it from room temperature to 600-1200° C. at a heating rate of 2-10° C. / min under a nitrogen atmosphere, and keep it warm for 1-4 hours to obtain a bamboo-based hard carbon material.

[0012] Furthermore, the particle size of the dry bamboo pulp powder in step 1 is 50-200 μm.

[0013] Furthermore, the ethanol solution in step 1 is an industrial ethanol solution with a mass fraction of 95%.

[0014] Furthermore, the ratio of the dry bamboo pulp powder and the ethanol solution in step 1 is (80-200 g): (50-100 mL).

[0015] Furthermore, the filling ratio of the hydrothermal reactor in step 2 is 40-70%.

[0016] Furthermore, the drying in step 2 is carried out in a forced air drying oven at 60-100° C. for 10-24 hours.

[0017] Furthermore, the grinding in step 2 is performed using a mortar for 1 to 3 hours.

[0018] Furthermore, the particle size of the bamboo fiber precursor after the pretreatment in step 2 is 5 to 100 μm.

[0019] A bamboo-based hard carbon material with an interlayer spacing of 0.37-0.45nm, a particle size of 5-50μm, and a specific surface area of ​​15-50m 2 ·g -1 .

[0020] Application of a bamboo-based hard carbon material as a negative electrode material for sodium ion batteries.

[0021] The present invention has the following beneficial technical effects:

[0022] 1) The present invention adopts a two-step method of ethanol pretreatment-high-temperature carbonization to synthesize bamboo-based hard carbon materials, which has the advantages of short process, simple process, no need for large-scale equipment and harsh reaction conditions, easy availability of raw materials, low cost and no need for post-processing. It is also environmentally friendly and suitable for large-scale production. In addition, the present invention does not involve acid and alkali corrosion and high-temperature sintering in the pretreatment stage of dry bamboo pulp powder, which reduces raw material loss and energy consumption, improves yield and saves production costs.

[0023] 2) The bamboo-based hard carbon material prepared by the present invention as the negative electrode material of sodium ion battery not only has a large interlayer spacing of 0.37-0.45nm, which helps to accelerate the transmission and diffusion of ions, thereby improving the rate performance and capacity of sodium ion battery; but also has a large interlayer spacing of 15-50nm. 2 ·g -1 The large specific surface area provides more storage space and surface active sites for sodium ions, thereby increasing the capacity of the battery; in short, the bamboo-based hard carbon material prepared by the present invention can increase the sodium storage capacity of the platform and the sodium storage capacity under high current, thereby giving the sodium ion battery excellent electrochemical performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 This is an SEM image of the bamboo-based hard carbon material prepared in Example 1 of the present invention;

[0025] Figure 2 Rate curve of a sodium ion battery when the bamboo-based hard carbon material prepared in Example 1 of the present invention is used as the negative electrode material of the sodium ion battery. DETAILED DESCRIPTION

[0026] The present invention will be further described in detail below with reference to specific embodiments, which are intended to explain the present invention rather than to limit it.

[0027] Example 1

[0028] Step 1: Weigh 90 g of dry bamboo pulp powder and place it in a beaker containing 60 mL of 95% industrial ethanol solution, and stir with a glass rod for 15 minutes to obtain a mixed suspension A;

[0029] Step 2: Transfer the mixed suspension A to a hydrothermal reactor with a filling ratio of 55%, place the hydrothermal reactor in an oven at 90°C, and keep it warm for 12 hours to obtain a reaction product B;

[0030] Step 3: After the reaction product B is cooled to room temperature, it is placed in a blast drying oven at 80° C. and dried for 12 hours. After cooling, it is placed in a mortar and ground for 1 hour to obtain a pretreated bamboo fiber precursor C with a particle size range of 40 to 100 μm.

[0031] Step 4: Place the pretreated bamboo fiber precursor C in a tubular furnace, and heat it from room temperature to 950° C. at a heating rate of 3° C. / min under a nitrogen atmosphere, and keep it warm for 3 hours to carbonize it to obtain a bamboo-based hard carbon material.

[0032] from Figure 1 It can be seen that the particle size of the bamboo-based hard carbon material prepared in the embodiment is between 5 and 50 μm. Referring to the enlarged picture in the upper right corner, it can be clearly observed that the circular pits on the surface of the bamboo-based hard carbon material after ethanol treatment are not only increased, but also provide more sodium storage active sites, which is of great benefit to improving the capacity of the battery.

[0033] The bamboo-based hard carbon material prepared in Example 1 was used as the negative electrode material for sodium ion batteries, and sodium ion button batteries were assembled and their charge and discharge capacities were tested. The results were as follows: Figure 2 As shown, it can be seen that the sodium ion battery at 0.1A·g -1 The capacity can reach 370mA·hg at the current density -1 After 30 cycles, at 0.1A·g -1 At this current density, the capacity can still reach 350mAh g -1 Above, it has a very high capacity retention rate; In addition, at 1A·g -1 At the current density, the capacity can reach 290mA·hg -1 , which is much higher than the 220mA·hg of existing bamboo-based hard carbon materials. -1 ; It shows that the bamboo-based hard carbon material prepared in Example 1 has excellent rate performance and can give sodium ion batteries excellent electrochemical properties.

[0034] Example 2

[0035] Step 1: Weigh 120 g of dry bamboo pulp powder and place it in a beaker containing 80 mL of 95% industrial ethanol solution, and stir with a glass rod for 18 minutes to obtain a mixed suspension A;

[0036] Step 2: Transfer the mixed suspension A to a hydrothermal reactor with a filling ratio of 65%, place the hydrothermal reactor in an oven at 100° C., and keep the temperature for 18 hours to obtain a reaction product B;

[0037] Step 3: After the reaction product B is cooled to room temperature, it is placed in a 60° C. forced air drying oven and dried for 24 hours. After cooling, it is placed in a mortar and ground for 1.5 hours to obtain a pretreated bamboo fiber precursor C with a particle size range of 10 to 80 μm.

[0038] Step 4: Place the pretreated bamboo fiber precursor C in a tubular furnace, and heat it from room temperature to 850°C at a heating rate of 2°C / min under a nitrogen atmosphere, and keep it warm for 2 hours to carbonize it to obtain a bamboo-based hard carbon material.

[0039] Example 3

[0040] Step 1: Weigh 140 g of dry bamboo pulp powder and place it in a beaker containing 90 mL of 95% industrial ethanol solution, and stir with a glass rod for 10 minutes to obtain a mixed suspension A;

[0041] Step 2: Transfer the mixed suspension A to a hydrothermal reactor with a filling ratio of 40%, place the hydrothermal reactor in an oven at 80°C, and keep the temperature for 9 hours to obtain a reaction product B;

[0042] Step 3: After the reaction product B is cooled to room temperature, it is placed in a blast drying oven at 70° C. and dried for 20 hours. After cooling, it is placed in a mortar and ground for 1 hour to obtain a pretreated bamboo fiber precursor C with a particle size range of 30 to 90 μm.

[0043] Step 4: Place the pretreated bamboo fiber precursor C in a tubular furnace, and heat it from room temperature to 1100° C. at a heating rate of 5° C. / min under a nitrogen atmosphere, and keep it warm for 4 hours to carbonize it to obtain a bamboo-based hard carbon material.

[0044] Example 4

[0045] Step 1: Weigh 170 g of dry bamboo pulp powder and place it in a beaker containing 75 mL of 95% industrial ethanol solution, and stir with a glass rod for 12 minutes to obtain a mixed suspension A;

[0046] Step 2: Transfer the mixed suspension A to a hydrothermal reactor with a filling ratio of 70%, place the hydrothermal reactor in an oven at 60°C, and keep warm for 24 hours to obtain a reaction product B;

[0047] Step 3: After the reaction product B is cooled to room temperature, it is placed in a 90° C. forced air drying oven and dried for 16 hours. After cooling, it is placed in a mortar and ground for 2 hours to obtain a pretreated bamboo fiber precursor C with a particle size range of 15 to 70 μm.

[0048] Step 4: Place the pretreated bamboo fiber precursor C in a tubular furnace, and heat it from room temperature to 600°C at a heating rate of 8°C / min under a nitrogen atmosphere, and keep it warm for 2 hours to carbonize it to obtain a bamboo-based hard carbon material.

[0049] Example 5

[0050] Step 1: Weigh 200 g of dry bamboo pulp powder and place it in a beaker containing 100 mL of 95% industrial ethanol solution, and stir with a glass rod for 20 minutes to obtain a mixed suspension A;

[0051] Step 2: Transfer the mixed suspension A to a hydrothermal reactor with a filling ratio of 60%, place the hydrothermal reactor in an oven at 70°C, and keep the temperature for 8 hours to obtain a reaction product B;

[0052] Step 3: After the reaction product B is cooled to room temperature, it is placed in a blast drying oven at 100° C. and dried for 10 hours. After cooling, it is placed in a mortar and ground for 3 hours to obtain a pretreated bamboo fiber precursor C with a particle size range of 5 to 70 μm.

[0053] Step 4: Place the pretreated bamboo fiber precursor C in a tubular furnace, and heat it from room temperature to 1200° C. at a heating rate of 10° C. / min under a nitrogen atmosphere, and keep it warm for 1 hour to carbonize it to obtain a bamboo-based hard carbon material.

Claims

1. A method for preparing bamboo-based hard carbon materials using an ethanol solvent thermal pretreatment process, characterized in that: The steps include: Step 1: Pour the dry bamboo pulp powder into the ethanol solution and stir evenly to obtain a mixed suspension; Step 2: transferring the mixed suspension to a hydrothermal reactor and placing it in an oven, keeping the temperature at 60-100° C. for 8-24 hours, cooling to room temperature after the reaction, drying and grinding in sequence to obtain a pretreated bamboo fiber precursor; Step 3: Place the pretreated bamboo fiber precursor in a tubular furnace, and heat it from room temperature to 600-1200° C. at a heating rate of 2-10° C. / min under a nitrogen atmosphere, and keep it warm for 1-4 hours to obtain a bamboo-based hard carbon material.

2. The method for preparing bamboo-based hard carbon materials using an ethanol solvent thermal pretreatment process according to claim 1, characterized in that: The particle size of the dry bamboo pulp powder in step 1 is 50-200 μm.

3. The method for preparing bamboo-based hard carbon material by utilizing ethanol solvent thermal pretreatment process according to claim 1, characterized in that: The ethanol solution in step 1 is an industrial ethanol solution with a mass fraction of 95%.

4. The method for preparing bamboo-based hard carbon material by utilizing ethanol solvent thermal pretreatment process according to claim 3, characterized in that: The ratio of the dry bamboo pulp powder and the ethanol solution in step 1 is (80-200 g): (50-100 mL).

5. The method for preparing bamboo-based hard carbon material by utilizing ethanol solvent thermal pretreatment process according to claim 1, characterized in that: The filling ratio of the hydrothermal reaction kettle in step 2 is 40-70%.

6. The method for preparing bamboo-based hard carbon materials using an ethanol solvent thermal pretreatment process according to claim 1, characterized in that: The drying in step 2 is carried out in a forced air drying oven at 60-100° C. for 10-24 hours.

7. The method for preparing bamboo-based hard carbon materials using an ethanol solvent thermal pretreatment process according to claim 1, wherein: The grinding in step 2 is performed by using a mortar and pestle for 1 to 3 hours.

8. The method for preparing bamboo-based hard carbon materials using an ethanol solvent thermal pretreatment process according to claim 1, wherein: The particle size of the bamboo fiber precursor after the pretreatment in step 2 is 5 to 100 μm.

9. A bamboo-based hard carbon material prepared by the method according to any one of claims 1 to 8, characterized in that: The interlayer distance is 0.37-0.45nm, the particle size is 5-50μm, and the specific surface area is 15-50m 2 ·g -1 .

10. Use of the bamboo-based hard carbon material according to claim 9 as a negative electrode material for sodium ion batteries.

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