Bagasse hard carbon negative electrode material and preparation method and application thereof

Abstract

The invention discloses a bagasse hard carbon negative electrode material as well as a preparation method and application thereof, and the preparation method comprises the following steps: sequentially carrying out granulation treatment, pre-carbonization treatment at 400-800 DEG C, acid pickling treatment and hard carbonization treatment at 1350-1550 DEG C on bagasse to obtain the bagasse hard carbon negative electrode material. According to the preparation method disclosed by the invention, through a preparation strategy of pre-carbonization treatment at 400-800 DEG C, acid pickling and hard carbonization treatment at 1350-1550 DEG C, the bagasse hard carbon negative electrode material with high first discharge specific capacity, high first coulombic efficiency and excellent cycle performance can be obtained.

Description

Technical Field

[0001] The present invention belongs to the technical field of sodium-ion batteries, and particularly relates to a bagasse hard carbon negative electrode material, a preparation method thereof, and an application thereof. Background Art

[0002] Restricted by the limitation of lithium metal resources and high cost, the application of lithium-ion batteries in the current energy storage system field is being gradually replaced. Compared with lithium metal, sodium metal is rich in reserves and low in price in the earth's crust, and sodium and lithium belong to the same group of elements, and they have similar physical and chemical properties. Therefore, sodium-ion batteries for energy storage systems have attracted wide attention from the public.

[0003] Currently, the positive electrode materials of sodium-ion batteries include transition metal oxides, polyanion compounds, Prussian blue compounds, etc., and great progress has been made. However, the commonly used graphite negative electrode material of lithium-ion batteries is not suitable for the insertion / extraction of sodium ions. Finding a suitable negative electrode material has become the key to the rapid development of sodium-ion batteries. Hard carbon materials have rich pore structures, large interlayer spacings, and nano-graphite crystals, which are suitable for the insertion / extraction of sodium ions, showing high specific capacity and low potential advantages, and having a very broad application prospect, attracting wide attention from people.

[0004] There are three types of commonly used precursor materials in sodium-ion battery hard carbon negative electrode materials: resin types (such as polyglycol, epoxy resin, phenolic resin, etc.), asphalt types (such as petroleum, tar, and natural asphalt, etc.), and biomass types (such as cellulose, lignin, and biomass waste, etc.). Biomass-derived hard carbon materials have the advantages of wide sources and low cost, and they have rich pore structures and complex functional groups, showing high capacity and good rate performance. However, the existing biomass hard carbon materials have disadvantages such as low initial Coulomb efficiency and poor long-cycle performance. Therefore, how to obtain a biomass hard carbon negative electrode material with high initial discharge specific capacity, high initial Coulomb efficiency, and excellent cycle performance has become a problem to be solved in the field of sodium-ion batteries. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to overcome the deficiencies of the prior art and provide a bagasse hard carbon negative electrode material with high initial discharge specific capacity, high initial Coulomb efficiency, and excellent cycle performance, a preparation method thereof, and an application thereof.

[0006] To solve the above technical problems, the present invention adopts the following technical solutions.

[0007] A preparation method of a bagasse hard carbon negative electrode material includes the following steps:

[0008] (1) Granulate bagasse to obtain bagasse particles;

[0009] (2) Under a protective atmosphere or in a vacuum condition, pre-carbonize the bagasse particles obtained in step (1) at 400°C to 800°C to obtain bagasse carbon material;

[0010] (3) Perform pickling treatment on the bagasse carbon material obtained in step (2), and after cleaning and drying, obtain the treated bagasse carbon material;

[0011] (4) Under a protective atmosphere, perform hard carbonization treatment on the treated bagasse carbon material obtained in step (3) at 1350°C to 1550°C to obtain a bagasse hard carbon negative electrode material.

[0012] In the above preparation method, further improved, in step (4), the temperature of the hard carbonization treatment is 1400°C to 1500°C.

[0013] In the above preparation method, further improved, in step (2), the time of the pre-carbonization treatment is 1 h to 8 h.

[0014] In the above preparation method, further improved, in step (4), the time of the hard carbonization treatment is 0.5 h to 8 h.

[0015] In the above preparation method, further improved, in step (3), the pickling treatment is specifically: immerse the bagasse carbon material in a mixed acid solution for soaking, and the mixed acid solution is composed of a hydrofluoric acid solution and an oxygen-containing acid; the volume ratio of the hydrofluoric acid solution to the oxygen-containing acid in the mixed acid solution is 1 to 2:1 to 2, the concentration of the hydrofluoric acid solution is 0.1 mol / L to 25 mol / L, the concentration of the oxygen-containing acid is 0.1 mol / L to 25 mol / L, and the oxygen-containing acid is at least one of sulfuric acid solution, hydrochloric acid solution and phosphoric acid solution; the cleaning is specifically: wash the bagasse carbon material after pickling treatment with water until the pH value of the filtrate is 7.

[0016] In the above preparation method, further improved, in step (3), the concentration of the hydrofluoric acid solution is 5 mol / L to 25 mol / L.

[0017] In the above preparation method, further improved, in step (1), the average particle size of the bagasse particles is 5 mm to 10 mm, and the moisture content of the bagasse particles is 1% to 25%; before using the bagasse, the following treatments are also included: screen and crush the bagasse in sequence; the aperture of the sieve used for screening is 5 mm to 8 mm.

[0018] In the above preparation method, further improved, in step (2), the heating rate during the pre-carbonization treatment is 3°C / min to 15°C / min, the protective atmosphere includes nitrogen or an inert atmosphere, and the inert atmosphere includes argon;

[0019] In step (4), during the hard carbonization treatment, the heating rate is 2°C / min to 15°C / min. The protective atmosphere includes nitrogen or an inert atmosphere, and the inert atmosphere includes argon. After the hard carbonization treatment, the following treatments are also included: pulverizing the product of the hard carbonization treatment and sieving it. The pulverization is successively carried out using a mechanical pulverizer and a jet mill, and the sieve mesh for sieving is 300 mesh to 1000 mesh.

[0020] As a general technical concept, the present invention also provides a bagasse hard carbon anode material prepared by the above preparation method.

[0021] As a general technical concept, the present invention also provides an application of the above bagasse hard carbon anode material in a sodium-ion battery.

[0022] Compared with the prior art, the advantages of the present invention are as follows:

[0023] (1) The present invention provides a preparation method for a bagasse hard carbon anode material. Using bagasse as a biomass raw material and adopting a preparation strategy of "400°C to 800°C pre-carbonization treatment + pickling + 1350°C to 1550°C hard carbonization treatment", a bagasse hard carbon anode material with a high initial discharge specific capacity, a high initial Coulombic efficiency, and excellent cycling performance can be obtained. Specifically: on the one hand, bagasse contains abundant hemicellulose, lignin, and cellulose, which can induce bagasse to be transformed into highly disordered carbon during the hard carbonization treatment, effectively inhibiting the transformation of bagasse into highly graphitized carbon, so that the bagasse hard carbon anode material has a wider crystal plane spacing, which is beneficial to the rapid transmission and storage of sodium ions; on the other hand, it can achieve the directional transformation of the hard carbon material from a porous structure to a less porous structure, and the fine regulation of the macropores and open pores to closed pores. The less porous and closed pore structures can reduce the specific surface area of the bagasse hard carbon anode material, improve its initial discharge specific capacity and initial Coulombic efficiency, and improve the cycling performance. In addition, the bagasse used in the present invention, as a waste product in sugar factory production, has a very low utilization rate. Using bagasse as the raw material for the hard carbon anode material of a sodium-ion battery can further increase its added value. The preparation method of the present invention has the advantages of simple operation, environmental friendliness, etc., and is suitable for large-scale industrial production.

[0024] (2) The preparation method of the present invention uses a mixed acid solution to perform pickling treatment on the bagasse carbon material. The mixed acid solution is composed of a hydrofluoric acid solution and an oxygen-containing acid, which can further improve the initial discharge specific capacity and initial Coulomb efficiency of the bagasse hard carbon negative electrode material. Specifically, since a large amount of silicon dioxide impurities (5% - 20%) are contained in bagasse, the presence of these impurities will significantly reduce the capacity of the material. Using a mixed acid solution of hydrofluoric acid solution and oxygen-containing acid to perform pickling treatment on the bagasse carbon material can not only completely remove the silicon dioxide impurities in the bagasse carbon material, improve the material purity, but also perform preliminary pore formation on the bagasse carbon material, which helps the transformation of the pore structure of the subsequent hard carbon material. Brief Description of the Drawings

[0025] Figure 1 XRD pattern of the bagasse hard carbon negative electrode material prepared in Example 1 of the present invention.

[0026] Figure 2 Nitrogen adsorption and desorption curve of the bagasse hard carbon negative electrode material prepared in Example 1 of the present invention.

[0027] Figure 3 Pore size distribution of the bagasse hard carbon negative electrode material prepared in Example 1 of the present invention.

[0028] Figure 4 Charge-discharge curve of the bagasse hard carbon negative electrode material prepared in Example 1 of the present invention.

[0029] Figure 5 Cycling performance graph of the bagasse hard carbon negative electrode material prepared in Example 1 of the present invention. Detailed Description of the Invention

[0030] The present invention will be further described below in conjunction with the accompanying drawings of the specification and specific preferred embodiments, but the protection scope of the present invention is not limited thereby. The materials and instruments used in the following embodiments are all commercially available.

[0031] Example 1:

[0032] A preparation method of the bagasse hard carbon negative electrode material of the present invention includes the following steps:

[0033] (1) Using 15 kg of bagasse as raw material, it is placed on a vibrating sieve for vibrating screening. The sieve aperture of the vibrating screening is 5 mm to remove the obvious distinguishable impurities in the bagasse, and then mechanical coarse crushing is carried out to obtain bagasse granulation powder.

[0034] (2) Granulation treatment is carried out on the bagasse granulation powder obtained in step (1) to obtain bagasse particles; among them, the average particle size of the bagasse particles is 5 mm, and the moisture content is 1% - 10%.

[0035] (3) Place the bagasse particles obtained in step (2) in a low-temperature atmosphere furnace and perform pre-carbonization treatment under a nitrogen atmosphere, that is, heat up to 500 °C at a rate of 5 °C / min and hold for 3 h. After natural cooling, bagasse carbon materials are obtained.

[0036] (4) Immerse the bagasse carbon materials obtained in step (3) in a mixed acid solution of hydrofluoric acid and hydrochloric acid for pickling treatment to remove impurities in the carbon materials; then wash the pickled bagasse carbon materials with deionized water until the pH value of the filtrate is 7, and after drying treatment, treated bagasse carbon materials are obtained. Among them, the mixed acid solution of hydrofluoric acid and hydrochloric acid is prepared by the following method: Mix the hydrofluoric acid solution and the hydrochloric acid solution according to the volume ratio of the hydrofluoric acid solution to the hydrochloric acid solution of 1:1 to obtain a mixed acid solution of hydrofluoric acid and hydrochloric acid; the concentration of the hydrofluoric acid solution is 22.5 mol / L, and the concentration of the hydrochloric acid solution is 3 mol / L.

[0037] (5) Place the treated bagasse carbon materials obtained in step (4) in a high-temperature atmosphere furnace and perform hard carbonization treatment under a nitrogen atmosphere, that is, heat up to 1400 °C at a rate of 5 °C / min and hold for 2 h. After natural cooling, collect the bagasse hard carbon materials; then, perform fine crushing treatment successively with a mechanical crusher and a jet mill, and pass through a 300-mesh sieve to obtain bagasse hard carbon anode materials.

[0038] Figure 1 XRD pattern of the bagasse hard carbon anode material prepared in Example 1 of the present invention. From Figure 1 It can be seen that the bagasse hard carbon anode material has high purity and no impurities. According to Bragg's formula, its interlayer spacing d 002 is 0.397 nm.

[0039] Figure 2 Nitrogen adsorption and desorption isotherm curve of the bagasse hard carbon anode material prepared in Example 1 of the present invention. From Figure 2 It can be seen that the specific surface area of the bagasse hard carbon anode material is 19.2 m 2 / g.

[0040] Figure 3 Pore size distribution diagram of the bagasse hard carbon anode material prepared in Example 1 of the present invention. From Figure 3 It can be seen that the bagasse hard carbon anode material is a mesoporous material, and its pore size distribution range is 1.5 nm to 30 nm, concentrated at a pore size of 5 nm.

[0041] A negative electrode sheet is prepared by using the bagasse hard carbon anode material prepared in this embodiment, and includes the following steps:

[0042] Mix the bagasse hard carbon anode material and sodium alginate evenly according to the mass ratio of 9:1, add deionized water to make a slurry, coat it on the copper foil, and put it into a vacuum drying oven at 80 °C for vacuum drying for 12 h to obtain the negative electrode sheet.

[0043] Using the above negative electrode sheet, with sodium metal as the counter electrode, Celgard 2400 polypropylene film as the separator, and 0.5 M NaPF6 / DIG solution as the electrolyte, assemble a coin-type sodium-ion battery in a glove box under an argon atmosphere. Let the assembled battery stand for 24 h, and use a LAND electrochemical tester for testing. The test voltage range is 0.01 V to 2 V, and the current density is 30 mA / g.

[0044] Figure 4 This is the charge-discharge curve of the bagasse hard carbon anode material prepared in Example 1 of the present invention. Figure 5 This is the cycle performance diagram of the bagasse hard carbon anode material prepared in Example 1 of the present invention. From Figure 4 、 Figure 5 It can be seen that the initial Coulombic efficiency of the bagasse hard carbon anode material as the negative electrode is 91.6%, the initial discharge specific capacity is 284.6 mAh / g, and the discharge specific capacity after 30 cycles is 282.0 mAh / g.

[0045] Example 2:

[0046] A bagasse hard carbon anode material of the present invention has a preparation method basically the same as that of the bagasse hard carbon anode material in Example 1, except that: in step (4), the volume ratio of the hydrofluoric acid solution to the hydrochloric acid solution is 1:1, the concentration of the hydrofluoric acid solution is 5 mol / L, and the concentration of the hydrochloric acid solution is 5 mol / L.

[0047] Assemble according to the negative electrode sheet and battery assembly method of the bagasse hard carbon anode material in Example 1, and keep its test conditions consistent with those in Example 1 to test its electrochemical performance.

[0048] In this example, the initial discharge specific capacity of the bagasse hard carbon anode material as the negative electrode is 286.5 mAh / g, and the initial Coulombic efficiency is 95.5%.

[0049] Example 3:

[0050] A preparation method of a bagasse hard carbon anode material of the present invention includes the following steps:

[0051] (1) Using 15 kg of bagasse as raw material, put it on a vibrating sieve for vibrating screening. The screen aperture of the vibrating screening is 5 mm to remove the obvious distinguishable impurities in the bagasse, and then carry out mechanical coarse crushing to obtain bagasse granulation powder.

[0052] (2) Granulate the bagasse granulating powder obtained in step (1) to obtain bagasse particles; wherein, the average particle size of the bagasse particles is 5 mm and the moisture content is 1% - 10%.

[0053] (3) Place the bagasse particles obtained in step (2) in a low-temperature atmosphere furnace and perform pre-carbonization treatment under a nitrogen atmosphere, that is, heat up to 500 °C at a rate of 5 °C / min and hold for 2 h, and after natural cooling, obtain bagasse carbon materials.

[0054] (4) Immerse the bagasse carbon materials obtained in step (3) in a mixed acid solution of hydrofluoric acid and sulfuric acid for soaking to perform pickling treatment to remove impurities in the carbon materials; then wash the pickled bagasse carbon materials with deionized water until the pH value of the filtrate is 7, and after drying treatment, obtain the treated bagasse carbon materials. Among them, the mixed acid solution of hydrofluoric acid and sulfuric acid is prepared by the following method: Mix the hydrofluoric acid solution and the sulfuric acid solution according to the volume ratio of the hydrofluoric acid solution to the sulfuric acid solution of 2:1 to obtain the mixed acid solution of hydrofluoric acid and sulfuric acid; the concentration of the hydrofluoric acid solution is 2 mol / L, and the concentration of the sulfuric acid solution is 1 mol / L.

[0055] (5) Place the treated bagasse carbon materials obtained in step (4) in a high-temperature atmosphere furnace and perform hard carbonization treatment under a nitrogen atmosphere, that is, heat up to 1400 °C at a rate of 5 °C / min and hold for 3.5 h, and collect the bagasse hard carbon materials after natural cooling; then, perform fine crushing treatment successively with a crusher and a jet mill, and pass through a 300-mesh sieve to obtain the bagasse hard carbon negative electrode material.

[0056] Assemble according to the negative electrode sheet and battery assembly method of the bagasse hard carbon negative electrode material in Example 1, and keep the test conditions consistent with those in Example 1 to test its electrochemical performance.

[0057] In this example, the initial discharge specific capacity of the bagasse hard carbon negative electrode material as the negative electrode is 261.4 mAh / g, and the initial Coulomb efficiency is 90.5%.

[0058] Example 4:

[0059] A preparation method of the bagasse hard carbon negative electrode material of the present invention includes the following steps:

[0060] (1) Using 15 kg of bagasse as raw materials, place it on a vibrating sieve for vibrating screening. The aperture of the vibrating screening sieve is 5 mm to remove the obvious distinguishable impurities in the bagasse, and then perform mechanical coarse crushing to obtain bagasse granulating powder.

[0061] (2) Granulate the bagasse granulating powder obtained in step (1) to obtain bagasse particles; wherein, the average particle size of the bagasse particles is 5 mm and the moisture content is 1% - 10%.

[0062] (3) Place the bagasse particles obtained in step (2) in a low-temperature atmosphere furnace and perform pre-carbonization treatment under a nitrogen atmosphere, that is, heat up to 400 °C at a rate of 5 °C / min and hold for 3 h, and after natural cooling, obtain bagasse carbon material.

[0063] (4) Immerse the bagasse carbon material obtained in step (3) in a mixed acid solution of hydrofluoric acid and sulfuric acid for pickling treatment to remove impurities in the carbon material; then wash the pickled bagasse carbon material with deionized water until the pH value of the filtrate is 7, and after drying treatment, obtain the treated bagasse carbon material. Among them, the mixed acid solution of hydrofluoric acid and sulfuric acid is prepared by the following method: Mix the hydrofluoric acid solution and the sulfuric acid solution according to the volume ratio of the hydrofluoric acid solution to the sulfuric acid solution of 1:1 to obtain the mixed acid solution of hydrofluoric acid and sulfuric acid; the concentration of the hydrofluoric acid solution is 20 mol / L, and the concentration of the sulfuric acid solution is 1 mol / L.

[0064] (5) Place the treated bagasse carbon material obtained in step (4) in a high-temperature atmosphere furnace and perform hard carbonization treatment under a nitrogen atmosphere, that is, heat up to 1450 °C at a rate of 10 °C / min and hold for 3 h, and collect the bagasse hard carbon material after natural cooling; then, perform fine crushing treatment successively with a pulverizer and a jet mill, and pass through a 300-mesh sieve to obtain the bagasse hard carbon negative electrode material.

[0065] Assemble according to the negative electrode sheet and battery assembly method of the bagasse hard carbon negative electrode material in Example 1, and keep its test conditions consistent with those in Example 1, and test its electrochemical performance.

[0066] In this example, the initial discharge specific capacity of the bagasse hard carbon negative electrode material as the negative electrode is 285.1 mAh / g, and the initial Coulomb efficiency is 92.4%.

[0067] Example 5:

[0068] A preparation method of the bagasse hard carbon negative electrode material of the present invention includes the following steps:

[0069] (1) Take 15 kg of bagasse as raw material, put it on a vibrating sieve for vibrating screening, the screen aperture of the vibrating screening is 5 mm, remove the obvious distinguishable impurities in the bagasse, and then perform mechanical coarse crushing to obtain bagasse granulation powder.

[0070] (2) Perform granulation treatment on the bagasse granulation powder obtained in step (1) to obtain bagasse particles; among them, the average particle size of the bagasse particles is 5 mm, and the moisture content is 1% - 10%.

[0071] (3) Place the bagasse particles obtained in step (2) in a low-temperature atmosphere furnace and carry out pre-carbonization treatment under a nitrogen atmosphere, that is, heat up to 400 °C at a rate of 5 °C / min and hold for 3 h, and after natural cooling, bagasse carbon materials are obtained.

[0072] (4) Immerse the bagasse carbon materials obtained in step (3) in a mixed acid solution of hydrofluoric acid and sulfuric acid for soaking to carry out pickling treatment to remove impurities in the carbon materials; then wash the pickled bagasse carbon materials with deionized water until the pH value of the filtrate is 7, and after drying treatment, treated bagasse carbon materials are obtained. Among them, the mixed acid solution of hydrofluoric acid and sulfuric acid is prepared by the following method: Mix the hydrofluoric acid solution and the sulfuric acid solution according to the volume ratio of the hydrofluoric acid solution to the sulfuric acid solution of 1:2 to obtain a mixed acid solution of hydrofluoric acid and sulfuric acid; the concentration of the hydrofluoric acid solution is 22.5 mol / L, and the concentration of the sulfuric acid solution is 1 mol / L.

[0073] (5) Place the treated bagasse carbon materials obtained in step (4) in a high-temperature atmosphere furnace and carry out hard carbonization treatment under a nitrogen atmosphere, that is, heat up to 1500 °C at a rate of 5 °C / min and hold for 3 h, and collect the bagasse hard carbon materials after natural cooling; then, carry out fine crushing treatment successively with a crusher and a jet mill, and pass through a 300-mesh sieve to obtain bagasse hard carbon negative electrode materials.

[0074] Assemble according to the negative electrode sheet and battery assembly method of the bagasse hard carbon negative electrode material in Example 1, and keep the test conditions consistent with those in Example 1 to test its electrochemical performance.

[0075] In this example, the initial discharge specific capacity of the bagasse hard carbon negative electrode material as the negative electrode is 274.2 mAh / g, and the initial Coulomb efficiency is 92.5%.

[0076] Comparative Example 1:

[0077] A preparation method of bagasse hard carbon negative electrode materials includes the following steps:

[0078] (1) Use 20 kg of bagasse as raw material, carry out mechanical coarse crushing to obtain bagasse powder.

[0079] (2) Carry out granulation treatment on the bagasse powder obtained in step (1) to obtain bagasse particles; among them, the particle size of the bagasse particles is 5 mm to 10 mm, and the moisture content is 3% to 7%.

[0080] (3) Place the bagasse particles obtained in step (2) in a low-temperature atmosphere furnace and carry out pre-carbonization treatment under a nitrogen atmosphere, that is, heat up to 400 °C at a rate of 5 °C / min and hold for 3 h, and after natural cooling, bagasse carbon materials are obtained.

[0081] (4) Place the bagasse carbon material obtained in step (3) in a high-temperature atmosphere furnace and perform hard carbonization treatment under a nitrogen atmosphere, that is, heat it to 1300 °C at a rate of 5 °C / min and hold for 3 h. After natural cooling, perform fine crushing treatment with a pulverizer to obtain a bagasse hard carbon negative electrode material.

[0082] The specific surface area of the hard carbon material of the bagasse hard carbon negative electrode material prepared in Comparative Example 1 is 36.2 m 2 / g, and its pore size distribution range is 1 - 60 nm, concentrated at a pore size of 4 nm.

[0083] Assemble according to the negative electrode sheet and battery assembly method of the bagasse hard carbon negative electrode material in Example 1, and keep the test conditions consistent with those in Example 1 to test its electrochemical performance.

[0084] The initial discharge specific capacity of the battery using the bagasse hard carbon negative electrode material in Comparative Example 1 as the negative electrode is 201.6 mAh / g, and the initial Coulomb efficiency is 83.6%.

[0085] Table 1 Electrochemical performance of the bagasse hard carbon negative electrode materials in Examples 1 - 5 and Comparative Example 1

[0086]

[0087] As can be seen from Table 1, since the bagasse carbon material prepared in Comparative Example 1 was not subjected to pickling treatment and the temperature of the hard carbonization treatment was too low, its initial discharge specific capacity and initial Coulomb efficiency were not ideal. Compared with Comparative Example 1, the bagasse hard carbon negative electrode material prepared in Example 1 has high purity, a narrower pore size distribution range, a smaller specific surface area, and higher initial discharge specific capacity and initial Coulomb efficiency. This is because: performing hard carbonization treatment in the temperature range of 1350 °C to 1550 °C can achieve the transformation of the hard carbon material from a porous structure to a less porous structure, and the transformation of macropores and open pores to closed pores, thereby reducing the surface area and improving the initial discharge specific capacity and initial Coulomb efficiency; similarly, the bagasse hard carbon negative electrode materials prepared in Examples 2 - 5 have excellent initial discharge specific capacity and initial Coulomb efficiency. In addition, compared with the bagasse hard carbon negative electrode materials prepared in Examples 1 and 2, the initial discharge specific capacity of the bagasse hard carbon negative electrode material prepared in Example 3 decreased because: the concentration of hydrofluoric acid in the pickling treatment process was low, resulting in the failure to remove some silica impurities in the bagasse carbon material, which caused the decrease in the initial discharge specific capacity of the prepared bagasse hard carbon negative electrode material. It can be seen that through the preparation strategy of "400 °C - 800 °C pre-carbonization treatment + pickling + 1350 °C - 1550 °C hard carbonization treatment", the present invention can obtain a bagasse hard carbon negative electrode material with high initial discharge specific capacity, high initial Coulomb efficiency, and excellent cycle performance.

[0088] The above are only the preferred embodiments of the present invention, and do not impose any form of limitation on the present invention. Although the present invention has been disclosed as above with the preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make many possible changes and modifications to the technical solution of the present invention by using the methods and technical contents disclosed above, or modify it into equivalent embodiments with equivalent changes. Therefore, any simple modification, equivalent replacement, equivalent change and modification made to the above embodiments based on the technical essence of the present invention without departing from the technical solution of the present invention still fall within the scope of protection of the technical solution of the present invention.

Claims

1. A preparation method of a bagasse hard carbon anode material, characterized in that It includes the following steps: (1) Granulate bagasse to obtain bagasse particles; (2) Under a protective atmosphere or in a vacuum condition, pre-carbonize the bagasse particles obtained in step (1) at 400°C to 800°C to obtain a bagasse carbon material; (3) Perform pickling treatment on the bagasse carbon material obtained in step (2), and after washing and drying, obtain a treated bagasse carbon material; (4) Under a protective atmosphere, perform hard carbonization treatment on the treated bagasse carbon material obtained in step (3) at 1350°C to 1550°C to obtain a bagasse hard carbon anode material.

2. The preparation method of the bagasse hard carbon negative electrode material according to claim 1, wherein, In step (4), the temperature of the hard carbonization treatment is 1400°C to 1500°C.

3. The preparation method of the bagasse hard carbon negative electrode material according to claim 1, characterized in that, In step (2), the time of the pre-carbonization treatment is 1h to 8h.

4. The preparation method of the bagasse hard carbon negative electrode material according to claim 1, characterized in that, In step (4), the time of the hard carbonization treatment is 0.5h to 8h.

5. The preparation method of the bagasse hard carbon negative electrode material according to any one of claims 1 to 4, characterized in that, In step (3), the pickling treatment specifically is: Immerse the bagasse carbon material in a mixed acid solution for soaking. The mixed acid solution is composed of a hydrofluoric acid solution and an oxyacid; the volume ratio of the hydrofluoric acid solution to the oxyacid in the mixed acid solution is 1 to 2:1 to 2, the concentration of the hydrofluoric acid solution is 0.1mol / L to 25mol / L, the concentration of the oxyacid is 0.1mol / L to 25mol / L, and the oxyacid is at least one of a sulfuric acid solution, a hydrochloric acid solution, and a phosphoric acid solution; the washing specifically is: Wash the bagasse carbon material after pickling treatment with water until the pH value of the filtrate is 7.

6. The preparation method of the bagasse hard carbon negative electrode material according to claim 5, characterized in that, In step (3), the concentration of the hydrofluoric acid solution is 5mol / L to 25mol / L.

7. The preparation method of the bagasse hard carbon anode material according to any one of claims 1 to 4, characterized in that, In step (1), the average particle size of the bagasse particles is 5mm to 10mm, and the moisture content of the bagasse particles is 1% to 25%; before using the bagasse, the following treatments are also included: Screen and crush the bagasse in sequence; the aperture of the sieve used for screening is 5mm to 8mm.

8. The preparation method of the bagasse hard carbon negative electrode material according to any one of claims 1 to 4, characterized in that, In step (2), the heating rate during the pre-carbonization treatment is 3°C / min to 15°C / min, the protective atmosphere includes nitrogen or an inert atmosphere, and the inert atmosphere includes argon; In step (4), the heating rate during the hard carbonization treatment is 2°C / min to 15°C / min, the protective atmosphere includes nitrogen or an inert atmosphere, and the inert atmosphere includes argon; after the hard carbonization treatment, the following treatments are also included: Crush and sieve the product of the hard carbonization treatment; the crushing is sequentially performed with a mechanical crusher and a jet mill, and the sieve for sieving is 300 mesh to 1000 mesh.

9. A bagasse hard carbon anode material prepared by the preparation method of the bagasse hard carbon anode material according to any one of claims 1 to 8.

10. An application of the bagasse hard carbon anode material according to claim 9 in a sodium ion battery.

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