Preparation method of ionic liquid assisted biomass derived hard carbon negative electrode material

Abstract

The invention discloses a method for preparing a biomass hard carbon negative electrode material with the assistance of ionic liquid. The preparation method of the biomass hard carbon negative electrode material comprises the following steps: (1) crushing and pre-sintering a biomass raw material to obtain a biomass hard carbon precursor; (2) soaking the precursor obtained in the step (1) in an ionic liquid solution, and stirring to obtain an ionic liquid coated intermediate product; and (3) carrying out segmented sintering on the intermediate product obtained in the step (2) in an inert atmosphere, and crushing to obtain the biomass hard carbon negative electrode material. The biomass hard carbon material obtained by the method is rich in heteroatom components, and has the advantages of high specific capacity, excellent high-rate charge-discharge performance and the like in the sodium ion battery.

Description

Technical Field

[0001] The present invention relates to the field of battery technology, and in particular to a preparation method and application of a carbon negative electrode material for a sodium ion battery. Background Art

[0002] With the widespread use of portable electronic devices and electric vehicles, energy storage technology is becoming increasingly important to social development. Lithium-ion batteries, currently the most widely used energy storage battery system, dominate the fields of portable electronic devices and electric vehicles due to their high energy density, excellent rate performance, and long cycle life. However, the scarcity and uneven distribution of lithium resources, as well as the high consumption of resource-based metals, have resulted in the high price of lithium-ion batteries, limiting their further large-scale application. The development of alternative, lower-cost energy storage battery systems is crucial.

[0003] In contrast, sodium is abundant and inexpensive, possessing similar physical and chemical properties to lithium, and the two batteries share similar charge and discharge mechanisms. While sodium-ion batteries have a lower energy density than lithium-ion batteries, they offer less stringent weight and volume requirements for power and energy storage, and are safer than lithium-ion batteries, making them the preferred choice for a new generation of energy storage batteries with superior overall performance.

[0004] Currently, the performance of sodium-ion batteries (SIBs) primarily depends on the properties of their positive and negative electrode materials. Compared to cathode materials, which offer a wide range of options, including layered metal oxides, polyanionic compounds, and Prussian blue analogs, the selection of negative electrode materials for SIBs is more limited. Carbon-based negative electrode materials are characterized by abundant raw materials, simple synthesis, low operating potential, and good cycling stability, making them ideal for constructing high-performance SIBs. In recent years, hard carbons with disordered structures have demonstrated excellent electrochemical properties, particularly those derived from various biomass precursors, which have been extensively studied. Currently, some biomass-derived hard carbon materials have been commercially produced and sold. However, the current preparation process for biomass-derived hard carbon materials generally suffers from complex preparation procedures, complex processes, long time periods, high pyrolysis temperatures, and high energy consumption, limiting their application in practical production. Summary of the Invention

[0005] The present invention aims to provide a method for preparing an ionic liquid-assisted carbon anode material for sodium-ion batteries. This method uses readily available biomass as the raw material and an ionic liquid as a heteroatom-rich precursor. The material is obtained through pulverization, soaking, and pyrolysis. The material exhibits circular and elliptical nanostructures and numerous irregularly distributed pores, which facilitate the rapid transport of ions and electrons. It exhibits advantages such as high reversible capacity and excellent high-rate charge-discharge performance, making it suitable as a highly active anode material for sodium-ion batteries.

[0006] The technical solution of the present invention includes the following contents:

[0007] A method for preparing a carbon negative electrode material for a sodium ion battery is provided, comprising the following steps:

[0008] (1) First, the biomass raw material is cleaned and dried, and then crushed and sieved to obtain a biomass hard carbon precursor;

[0009] (2) soaking the biomass hard carbon raw material obtained in step (1) in an ionic liquid solution, stirring in a container and then transferring it to a crucible, and drying the volatile matter in an oven to obtain a biomass hard carbon intermediate;

[0010] (3) The biomass hard carbon intermediate obtained in step (2) is subjected to a staged temperature-raising pyrolysis reaction in an inert atmosphere, and the product is crushed to obtain a biomass hard carbon negative electrode material.

[0011] According to the above scheme, in step (1), the biomass raw material is at least one of corn stalks, corn cobs, straw, sugarcane bagasse, reeds, bamboo, coffee shells, nut shells, waste pulp, leaves, and wood.

[0012] According to the above scheme, in step (2), the drying temperature is 60-200° C., and the drying time is 1-48 hours.

[0013] According to the above scheme, in step (2), the average particle size of the biomass precursor is 10-100 μm.

[0014] According to the above scheme, in step (2), the ionic liquid is an ionic liquid containing at least one of nitrogen, sulfur, boron, phosphorus and fluorine elements, and the mass ratio of the biomass precursor to the ionic liquid is 0.1-2:1.

[0015] According to the above scheme, in step (2), the stirring time is 1-12 hours.

[0016] According to the above scheme, in step (2), the drying temperature is 60-200° C., and the drying time is 1-24 hours.

[0017] According to the above scheme, in step (2), the protective atmosphere is an inert atmosphere such as Ar, N2, etc.

[0018] According to the above scheme, in step (3), the pyrolysis conditions of the first stage are: heating rate of 0.5-10°C / min, pyrolysis temperature of 200-400°C, and pyrolysis time of 1-4h.

[0019] According to the above scheme, in step (3), the pyrolysis conditions of the second stage are: heating rate of 0.5-10°C / min, pyrolysis temperature of 600-1000°C, and pyrolysis time of 1-12h.

[0020] Provided is an application of the hard carbon negative electrode material prepared by the above scheme in sodium ion batteries.

[0021] The benefits of the present invention are as follows: the process flow is simple and the product performance is excellent. In the above technical solution, the crushed biomass raw material precursor is soaked in an ionic liquid and then pyrolyzed to obtain a biomass hard carbon negative electrode material. The ionic liquid plays multiple roles such as a pore former and a heteroatom source. The carbonized sample has carbon nanostructures of different shapes, a layered structure and a rich pore structure. These structural features enable the liquid electrolyte to fully infiltrate the sample, provide more diffusion channels and active sites for sodium ions, shorten the transmission path of sodium ions, and are beneficial to improving the electrochemical performance of the material. The introduction of heteroatoms brings multiple beneficial effects. Negatively charged pyridinic nitrogen and pyrrolic nitrogen are usually highly reactive, which can improve sodium ion dynamics and promote capacitive reactions on the carbon surface, thereby improving its sodium storage performance. The addition of boron can improve the conductivity of the negative electrode material and increase the electron transfer rate because the electron-deficient boron in the boron-carbon bond carries positively charged holes. The fluorine element may change the crystal structure or surface chemical properties of the negative electrode material and optimize the ion transmission channels inside the material. More importantly, the electronegativity of fluorine can significantly increase the specific capacity of the material, thereby improving battery performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 This is a scanning electron microscope image of the biomass hard carbon prepared by the present invention.

[0023] Figure 2 This is the X-ray diffraction pattern of the biomass hard carbon prepared in the present invention,

[0024] Figure 3 This is the Raman spectrum of the biomass hard carbon prepared by the present invention.

[0025] Figure 4 N2 adsorption-desorption isotherm of the biomass hard carbon prepared in the present invention,

[0026] Figure 5 This is the pore size distribution diagram of the biomass hard carbon prepared by the present invention,

[0027] Figure 6 This is the first charge and discharge specific capacity diagram of the biomass hard carbon prepared by the present invention at a rate of 30 mA / g.

[0028] Figure 7 This is a long cycle performance diagram of the biomass hard carbon prepared in the present invention at a charge and discharge current density of 100 mA / g. DETAILED DESCRIPTION

[0029] In order to further understand the invention content and characteristics of the present invention, the present invention will be described more comprehensively below in conjunction with specific embodiments, but these embodiments do not limit the full content of the present invention. The purpose of providing these embodiments is to make the disclosure of the present invention understood more thoroughly and comprehensively. Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those generally understood by those skilled in the art of the present invention. The terms used in this specification of the present invention are only for the purpose of describing specific embodiments and are not intended to limit the present invention.

[0030] Implementation Example 1

[0031] A method for preparing an ionic liquid-derived biomass hard carbon negative electrode material is provided, comprising the following steps:

[0032] (1) First, 100 g of peanut shells were mechanically crushed, washed repeatedly with deionized water, and dried in an oven at 80°C for 12 hours;

[0033] (2) crushing the peanut shell raw material in step (1) in a wall breaking machine and sieving it with a 200-mesh sieve to obtain a biomass hard carbon precursor with a particle size of less than 74 μm;

[0034] (3) 10 g of the biomass hard carbon precursor obtained in step (2) was immersed in 20 g of 1-butyl-3-methylimidazolium tetrafluoroborate ionic liquid solution, and after magnetic stirring in a beaker for 2 hours, it was transferred to a crucible and dried in an oven at 80° C. for 12 hours to obtain a biomass hard carbon intermediate;

[0035] (4) The biomass hard carbon intermediate obtained in step (3) is subjected to a staged heating pyrolysis reaction in a tubular furnace in an N2 atmosphere: in the first stage, the tubular furnace is heated from room temperature to 400°C at a rate of 5°C per minute and maintained at 400°C for 1 hour; in the second stage, it is further heated to 800°C at a rate of 5°C per minute and maintained for 1 hour, and then cooled to room temperature in an N2 atmosphere, the product is taken out, and a planetary ball mill is used to mill the product at a speed of 100 rpm for 30 minutes to obtain a biomass hard carbon negative electrode material. Its microscopic morphology is as follows Figure 1 Its crystal structure is shown in Figure 2 Its Raman spectrum is shown in Figure 3 As shown, its specific surface area N2 adsorption-desorption isotherm is as follows Figure 4 As shown, Figure 5 This is the pore size distribution diagram of the biomass hard carbon prepared in the present invention.

[0036] The prepared biomass hard carbon negative electrode material, conductive agent (Super P), and binder (PVDF) were weighed in a clean mortar at a mass ratio of 8:1:1, mixed, and coated. After drying and cutting, they were assembled into CR2025 button-type sodium ion batteries in a glove box. A 15mm sodium sheet was used as the counter electrode, and 1.0M NaClO4 was dissolved in ethyl carbonate (EC) and diethyl carbonate (DEC) (volume ratio of 1:1:1), and 5.0% fluoroethyl carbonate (FEC) was used as the electrolyte. The battery was tested for charge and discharge performance on the Neware battery test platform, and the results are as follows: Figure 6 As shown in the figure, at a charge and discharge current density of 30mA / g, its reversible charge and discharge capacity is 300.5mAh / g. At a charge and discharge current density of 100mA / g, its capacity retention rate is still above 280mAh / g after 200 cycles, showing a high capacity retention rate.

[0037] Implementation Example 2

[0038] A method for preparing an ionic liquid-derived biomass hard carbon negative electrode material is provided, comprising the following steps:

[0039] (1) First, 100 g of corn cobs were mechanically crushed and dried in an oven at 80°C for 12 hours;

[0040] (2) crushing the corn cob raw material in step (1) in a wall breaking machine and sieving it with a 200-mesh sieve to obtain a biomass hard carbon precursor with a particle size of less than 74 μm;

[0041] (3) 10 g of the biomass hard carbon precursor obtained in step (2) was immersed in 10 g of 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide ionic liquid solution, and after magnetic stirring in a beaker for 3 hours, it was transferred to a crucible and dried in an oven at 80° C. for 12 hours to obtain a biomass hard carbon intermediate;

[0042] (4) The biomass hard carbon intermediate obtained in step (3) is subjected to a staged heating pyrolysis reaction in a tubular furnace in an Ar atmosphere: in the first stage, the tubular furnace is heated from room temperature to 350°C at a rate of 5°C per minute, and maintained at 350°C for 1 hour; in the second stage, it is further heated to 700°C at a rate of 5°C per minute, maintained for 2 hours, and then cooled to room temperature in an Ar atmosphere. The product is taken out and ball-milled in a planetary ball mill at a speed of 100 revolutions per minute for 30 minutes to obtain a biomass hard carbon negative electrode material.

[0043] The battery was assembled according to the method of Example 1 and tested under the same conditions. At a charge and discharge current density of 30 mA / g, the initial charge and discharge capacity was 286.1 mAh / g and 425.5 mAh / g.

[0044] Implementation Example 3

[0045] A method for preparing an ionic liquid-derived biomass hard carbon negative electrode material is provided, comprising the following steps:

[0046] (1) First, 100 g of camellia oleifera shells were mechanically crushed, repeatedly washed with deionized water, and dried in an oven at 80°C for 12 hours;

[0047] (2) crushing the camellia shell raw material in step (1) in a wall breaking machine and sieving it with a 250-mesh sieve to obtain a biomass hard carbon precursor with a particle size of less than 41 μm;

[0048] (3) 10 g of the biomass hard carbon precursor obtained in step (2) was immersed in 10 g of 1-vinyl-3-methylimidazolium tetrafluoroborate ionic liquid solution, and after magnetic stirring in a beaker for 1 hour, it was transferred to a crucible and dried in an oven at 80° C. for 24 hours to obtain a biomass hard carbon intermediate;

[0049] (4) The biomass hard carbon intermediate obtained in step (3) is subjected to a staged heating pyrolysis reaction in a tubular furnace in an N2 atmosphere: in the first stage, the tubular furnace is heated from room temperature to 400°C at a rate of 5°C per minute and maintained at 400°C for 1 hour; in the second stage, it is further heated to 700°C at a rate of 5°C per minute and maintained for 2 hours, and then cooled to room temperature in an N2 atmosphere, the product is taken out, and a planetary ball mill is used to mill the product at a speed of 100 revolutions per minute for 30 minutes to obtain a biomass hard carbon negative electrode material.

[0050] The battery was assembled according to the method of Example 1 and tested under the same conditions. At a charge and discharge current density of 30 mA / g, the initial charge and discharge capacity was 297.6 mAh / g and 485.2 mAh / g.

Claims

1. A method for preparing a carbon negative electrode material for a sodium ion battery, characterized in that: The steps include: (1) Biomass raw material pretreatment First, the biomass raw material is cleaned and dried, and then crushed and sieved to obtain a biomass hard carbon precursor; (2) Preparation of biomass hard carbon intermediates The biomass hard carbon raw material obtained in step (1) is immersed in an ionic liquid solution, stirred in a container, and then transferred to a crucible, and volatile matter is dried in an oven to obtain a biomass hard carbon intermediate; (3) Preparation of biomass hard carbon negative electrode materials by pyrolysis The biomass hard carbon intermediate obtained in step (2) is subjected to a staged temperature-raising pyrolysis reaction in an inert atmosphere, and the product is crushed to obtain a biomass hard carbon negative electrode material.

2. The preparation method according to claim 1, characterized in that The biomass raw material in step (1) is at least one of corn stalks, corn cobs, straw, sugarcane bagasse, reeds, bamboo, coffee shells, nut shells, waste paper pulp, leaves, and wood.

3. The preparation method according to claim 1, characterized in that In the step (1), the drying temperature is 60-200° C., and the drying time is 1-48 hours.

4. The preparation method according to claim 1, characterized in that In the step (1), the average particle size of the biomass precursor is 10-100 μm.

5. The preparation method according to claim 1, characterized in that In the step (2), the ionic liquid is an ionic liquid containing at least one of nitrogen, sulfur, boron, phosphorus and fluorine, and the mass ratio of the biomass precursor to the ionic liquid is 0.1-2:

1.

6. The preparation method according to claim 1, characterized in that In the step (2), the stirring time is 1-12 hours.

7. The preparation method according to claim 1, characterized in that In the step (2), the drying temperature is 60-200° C., and the drying time is 1-24 hours.

8. The preparation method according to claim 1, characterized in that In the step (2), the protective atmosphere is an inert atmosphere such as Ar, N2, etc.

9. The preparation method according to claim 1, characterized in that In the step (3), the pyrolysis conditions of the first stage are: a heating rate of 0.5-10°C / min, a pyrolysis temperature of 200-400°C, and a pyrolysis time of 1-4h; in the step (3), the pyrolysis conditions of the second stage are: a heating rate of 0.5-10°C / min, a pyrolysis temperature of 600-1000°C, and a pyrolysis time of 1-12h.

10. An application, characterized in that: The hard carbon negative electrode material according to claim 1 is applied to a sodium ion battery.

Images