CN110797533A - Lignin hard carbon microsphere, hydrothermal preparation method and application of lignin hard carbon microsphere in alkali metal ion battery cathode - Google Patents

Abstract

The invention relates to a lignin hard carbon microsphere and a hydrothermal preparation method and its use in the negative electrode of an alkali metal ion battery; the lignin carbon microsphere is prepared by a hydrothermal method using lignin as a precursor. Firstly, the lignin is dissolved in water under sufficient stirring to obtain a lignin solution; the lignin solution is directly subjected to a hydrothermal reaction or is adjusted by adding acid and alkali to the pH value of the solution and then subjected to a hydrothermal reaction to obtain a lignin hydrothermal microarray. Ball precursor; after drying, the lignin microspheres are placed in a tube furnace, and carbonized at high temperature under the protection of inert gas to obtain lignin carbon microspheres. The lignin carbon microspheres have high sphericity, less adhesion, good structural stability and good dispersibility, and can maintain a high dispersion state. The invention studies the low-cost process synthesis of industrial waste lignin hydrothermal pelletization, and successfully applies it to the negative electrode material of alkali metal ion batteries, showing high capacity, good rate charge-discharge performance and cycle stability.

Description

A kind of lignin hard carbon microsphere and hydrothermal preparation method and its use in alkali metal ion electroporation battery negative

technical field

The invention belongs to the technical field of negative electrode materials for alkali metal (Li/Na/K) ion batteries, and in particular relates to a low-cost preparation method of lignin carbon microspheres with a hard carbon structure and high sphericity, and a preparation method thereof in alkali metal (Li/Na/K) ion batteries. /Na/K) ion battery anode.

Background technique

In the past few decades, social development has been heavily reliant on fossil energy, which has led to serious environmental pollution, such as the greenhouse effect and smog. Scientists around the world continue to develop green energy (solar energy, wind energy, tidal energy, etc.) to replace fossil energy to reduce the environmental burden and meet the energy demand for social development. However, the utilization of these new energy sources is limited due to their geographical and intermittent nature. For these reasons, the research and development of electrical energy storage has been promoted. Therefore, rechargeable and dischargeable secondary alkali metal ion batteries have attracted extensive attention. For example, lithium-ion batteries have the advantages of high energy density, long cycle life, small self-discharge, and good rate performance. At present, in addition to being widely used in portable electronic devices such as mobile phones, notebook computers, digital cameras, and power tools, they are also used in These developments have greatly promoted the development and application of anode materials and new technology systems with fast charging performance. While other alkali metal ion batteries, such as sodium-ion batteries, have a similar energy storage principle to lithium-ion batteries, although they have slightly lower electrochemical performance than lithium-ion batteries, due to the wide distribution and low price of sodium resources, their It has huge development potential in the fields of electric vehicles and energy storage batteries.

With the large-scale popularization of lithium-ion batteries in the field of electric vehicles, the shortcomings of existing lithium-ion batteries, such as short cruising range, slow charging speed, insufficient cycle life, and poor high and low temperature performance, have gradually been exposed, which has led to the urgent development of new electrode material systems. Require. For example, electrode material systems such as lithium iron phosphate and ternary cathode have been developed for fast-charging lithium-ion battery systems. In addition to continuing to optimize graphite for anode materials, research and development of hard carbon anode materials with large interlayer spacing and small crystallite size have been carried out. Development efforts are increasing. At the same time, since the radius of sodium ions is about 1.5 times that of lithium ions, the graphite structure with small interlayer spacing (about 0.336 nm) is not suitable for the insertion and extraction of sodium ions, while the hard carbon with large interlayer spacing (≥0.37 nm) The material is more suitable for storing sodium ions.

The precursors of hard carbon mainly include fossil fuels, polymer materials and biomass. Among them, biomass-based precursors have the advantages of wide sources, diverse structures, renewable, low cost, and environmental friendliness, and are expected to become key anode materials for the industrialization of alkali metal ion batteries. Tingzhou Yang et al. [Advanced Materials, 2016, 28(3):539-545] used nitrogen-rich bean dregs as raw material to prepare nitrogen-doped carbon flakes, and the specific capacity remained at 247.5mAh/g after 50 cycles of cycling. Chinese patent CN 108059144A discloses a preparation method of bagasse hard carbon. The bagasse is used as raw material, and the hard carbon is prepared by mechanical ball milling and then high temperature treatment; when used as the negative electrode of sodium ion battery and potassium ion battery, it shows excellent electrochemical performance. Chinese patent CN 106299365A discloses a method for preparing a hard carbon negative electrode material for sodium ion batteries based on biomass such as pine nuts, walnut shells, rice husks, etc. The solution is treated with acid solution, and then activated by microwave to obtain a hard carbon negative electrode material suitable for sodium ion batteries. Chinese patent CN 107068997 discloses a method for preparing a hard carbon/graphite negative electrode composite material for sodium ion batteries based on mangosteen shell biomass shell, which is to add carbon-containing biomass shell powder to an alkaline solution, seal with water and heat, and pickle it. , Mixed with graphite powder after washing, ball milled for refinement, high-temperature carbonization, pickling, drying, and grinding to obtain hard carbon/graphene composite material, which can be used in sodium ion batteries. However, the above methods all use biomass precursors as a whole for pretreatment and carbonization to prepare hard carbon negative electrodes without finely dividing their lignin, cellulose and hemicellulose components, which is not conducive to the uniform control of hard carbon structures. Therefore, it is necessary to develop a process technology to determine the biomass component as a precursor to prepare hard carbon.

Lignin is the second most abundant biomass in nature after cellulose, and it is an inexpensive, green and renewable biomass material. Lignin is composed of three basic structural units: p-hydroxyphenylpropane units (H), guaiacylpropane units (G), and syringylpropane units (S). The three basic structural units of lignin are mainly connected by C-O-C and C-C, and the connection site can occur between the hydroxyl groups on the benzene ring, or between the three carbon atoms of the structural unit, or between the benzene ring A complex three-dimensional network macromolecular structure is formed between the side chains. For example, when lignin is used as a precursor to directly conduct carbonization heat treatment to prepare carbon materials, it mainly undergoes dehydration, thermal cracking and polycondensation aromatization processes. The prepared carbon materials have low yield, large specific surface area and developed pores. The prepared negative electrode material The capacity is small and the first charge and discharge efficiency is low. However, when the lignin precursor is subjected to hydrothermal carbonization under high temperature and high pressure in advance, the cleavage of benzene and surrounding side chains and functional groups, polycondensation aromatization and hydrothermal treatment of the lignin precursor occur in the hydrothermal carbonization stage. self-assembly process, resulting in the formation of lignin hydrothermal microspheres. When the lignin hydrothermal microspheres continue to undergo carbonization heat treatment, the carbonization yield will be significantly higher than that of the direct carbonization of the lignin precursor, and lignin carbon microspheres with small specific surface area, high density and good electrical conductivity can be prepared. ball.

Compared with traditional carbon materials, carbon microspheres have the advantages of high filling density, good fluidity, high mechanical strength, and large specific surface area that other carbon materials cannot match due to their unique spherical structure. Adsorbents, drug delivery and other fields. Spherical carbon materials, as electrode materials for alkali metal ion batteries, have high electrode density, small specific surface area, good castability, and isotropy, which are beneficial to obtain high initial efficiency, high capacity, high rate performance and long cycle life.

SUMMARY OF THE INVENTION

The purpose of the present invention is to provide a simple method for preparing lignin carbon microspheres with hard carbon structure. In the present invention, lignin is used as a precursor, and lignin carbon microspheres are prepared by a hydrothermal method. The preparation method of the lignin carbon microspheres provided by the present invention is as follows: firstly, the lignin is dissolved in water under sufficient stirring to obtain a lignin solution; the lignin solution is directly subjected to a hydrothermal reaction or is adjusted by adding acid and alkali to the solution. The pH value is then subjected to a hydrothermal reaction to obtain the lignin hydrothermal microsphere precursor; after drying, the lignin microspheres are placed in a tube furnace, and carbonized at high temperature under the protection of an inert gas to obtain the lignin carbon microspheres. The lignin carbon microspheres have high sphericity, less adhesion, good structural stability and good dispersibility, and can maintain a high dispersion state. The invention studies the low-cost process synthesis of industrial waste lignin hydrothermal pelletization, and successfully applies it to the negative electrode material of alkali metal ion batteries, showing high capacity, good rate charge-discharge performance and cycle stability.

The specific technical scheme involved in the present invention is as follows:

A lignin hard carbon microsphere, wherein the lignin hard carbon microsphere is spherical, and the graphite-like crystallite interlayer spacing (d ₀₀₂ ) of the lignin hard carbon microsphere is 0.36-0.40 nm;

Preferably, the specific surface area of the lignin hard carbon microspheres is 0.5-300 m ² /g, and the pore volume is 0.01-0.25 cm 3 /g.

Preferably, the particle size distribution of the lignin hard carbon microspheres is 1-15 μm.

The preparation method of lignin hard carbon microspheres of the present invention at least comprises the following steps:

(1) Dissolving the lignin precursor into deionized water, stirring at room temperature until completely dissolved, to obtain a lignin solution;

(2) The above lignin aqueous solution is directly subjected to hydrothermal reaction, or after adding acid or alkali substances, to obtain a neutral solution (pH≈7) or an acidic solution (pH<7) or an alkaline solution (pH>7), respectively ;

(3) using the lignin solution obtained in step (2) as a reaction solution, and performing hydrothermal carbonization by hydrothermal reaction to obtain a lignin hydrothermal product;

(4) after the lignin hydrothermal product obtained in step (3) is separated and dried, lignin carbon microspheres are obtained;

(5) carbonizing the lignin microspheres obtained in step (4) under the protection of inert gas at high temperature to obtain the lignin hard carbon microspheres.

Preferably, the lignin precursor described in step (1) is sodium lignosulfonate, ammonium lignosulfonate, calcium lignosulfonate, or lignocellulose.

Preferably, the acid described in step (2) is an inorganic acid such as hydrochloric acid, sulfuric acid, nitric acid or boric acid, etc.; an organic acid such as formic acid, acetic acid, propionic acid or butyric acid, etc.

Preferably, the base described in step (2) is an inorganic base such as potassium hydroxide, sodium hydroxide, lithium hydroxide, ammonium hydroxide, anhydrous sodium carbonate, sodium bicarbonate, potassium carbonate or potassium bicarbonate and the like.

Preferably, the solid content of the solution in step (2) is 1wt%-30wt%.

Preferably, the conditions of the hydrothermal reaction in step (3) are 150-350° C., the hydrothermal treatment time is 3h-60h, and the filling degree of the reaction kettle is 20-75%.

Preferably, the separation method described in step (4) is one of filtration, centrifugation, spray drying and the like.

Preferably, the inert gas in step (5) is one or more of nitrogen gas, argon gas, hydrogen gas, and carbon monoxide gas.

Preferably, the high-temperature carbonization temperature in step (5) is 900° C.˜1800° C., and the time is 1 h˜5 h.

The lignin hard carbon microspheres of the present invention are used for the negative electrode of the alkali metal ion battery; the negative electrode material for the lithium ion battery, the sodium ion battery and the potassium ion battery is used for the alkali metal ion battery.

The invention also relates to a negative electrode material of an alkali metal battery, the negative electrode material contains the lignin hard carbon microspheres of the present application.

Preferably, the alkali metal battery is a lithium ion battery or a sodium ion battery or a potassium ion battery.

The technical solution of the present application has at least the following beneficial effects:

The preparation process of the invention is simple, the source of raw materials is abundant, the preparation efficiency is high, the sphericity of the product is good, and the particle size is controllable.

The lignin hard carbon microspheres prepared by the invention can be directly carbonized without pre-oxidation treatment, the particles are not bonded, and the dispersibility is good; and it is beneficial to coating and film formation in the electrode preparation process and improving the surface smoothness of the electrode. Spend.

The lignin hard carbon microspheres prepared by the invention have large interlayer spacing, provide more alkali metal ion storage space when used as the negative electrode material of alkali metal (Li/Na/K) ion batteries, have high capacity and rate performance;

The lignin hard carbon microspheres prepared by the invention have low specific surface area and structural stability, and the spherical microcrystalline structure is conducive to the insertion and extraction of sodium ions, lithium ions or potassium ions from all directions, and has more stable cycle performance.

Description of drawings

1 is a scanning electron microscope photograph of the hydrothermal lignin carbon microspheres prepared in Example 1.

FIG. 2 is a scanning electron microscope photograph of the lignin hard carbon microspheres prepared in Example 2. FIG.

FIG. 3 is a scanning electron microscope photograph of the lignin hard carbon microspheres prepared in Example 3. FIG.

FIG. 4 is a scanning electron microscope photograph of the lignin hard carbon microspheres prepared in Example 4. FIG.

5 is the first three charge-discharge curves of the lithium storage of the lignin hard carbon microsphere negative electrode prepared in Example 3.

6 is the first three charge-discharge curves of the sodium storage of the lignin hard carbon microsphere negative electrode prepared in Example 9.

Detailed ways

The present invention will be further described below in conjunction with specific embodiments. It should be understood that these examples are only used to illustrate the present invention and not to limit the scope of the present invention.

Example 1: 2 g of sodium lignosulfonate powder was added to 60 mL of deionized water, and stirred until it was completely dissolved to obtain a neutral lignin solution with a solid content of about 3%. The lignin solution prepared above was transferred to a reaction kettle with a volume of 100 mL and sealed. The temperature of the reaction kettle was raised to 250°C, and after the holding time was 12 h, the temperature was naturally lowered to room temperature. After being taken out, the hydrothermal reaction product was centrifuged to obtain the bottom sediment; it was continued to be dried in a blast oven at 80° C. to obtain lignin hydrothermal microspheres. Its scanning electron micrograph is shown in Figure 1. It can be seen from Fig. 1 that spherical lignin particles are obtained, the surface of the particle sphere is smooth, and the particle size is 2-3 μm. The lignin hydrothermal microspheres were placed in a corundum crucible and placed in a high-temperature tube furnace, heated to 900°C at a heating rate of 5°C/min, and carbonized at high temperature for 3 hours under nitrogen protection at 900°C to obtain 900°C carbonized lignin. Hard carbon microspheres.

Example 2: 2 g of sodium lignosulfonate powder was added to 60 mL of deionized water, and stirred until it was completely dissolved to obtain a lignin solution. Then 20 mL of 2 mol/L sodium hydroxide solution was added to obtain an alkaline solution with a solid content of 3%. The alkaline lignin solution prepared above was transferred to a hydrothermal reactor with a volume of 100 mL and sealed. The temperature of the reaction kettle was raised to 250°C, and after the holding time was 12 h, the temperature was naturally lowered to room temperature. After taking out, centrifuge the solution, take the bottom sediment, and dry it in a blast oven at 80 °C to obtain lignin hydrothermal gel microspheres; its scanning electron micrograph is shown in Figure 2, and its particles are spherical , the primary particle size is less than 1 μm, and there is a small amount of fusion and agglomeration. The lignin hydrothermal gel microspheres were placed in a corundum crucible and placed in a high-temperature tube furnace, heated to 900°C at a heating rate of 5°C/min, and carbonized at a high temperature at 900°C under nitrogen protection for 3 hours to obtain 900°C carbonized microspheres. Lignin hard carbon microspheres.

Example 3: 2 g of sodium lignosulfonate powder was added to 60 mL of deionized water, and stirred until it was completely dissolved to obtain a lignin solution. Then 20 mL of 1 mol/L hydrochloric acid solution was added to obtain an acidic solution with a solid content of 3%. The lignin solution prepared above was transferred to a hydrothermal reactor with a volume of 100 mL and sealed. The temperature of the reaction kettle was gradually raised to 250°C, and after a holding time of 60h, the temperature was naturally lowered to room temperature. After taking out, the solution was centrifuged, and the bottom sediment was taken out and dried in a blast oven at 80° C. to obtain lignin hydrothermal microspheres. The lignin hydrothermal microspheres were placed in a corundum crucible and placed in a high-temperature tube furnace, heated to 900°C at a heating rate of 5°C/min, and carbonized at high temperature for 3 hours under nitrogen protection at 900°C to obtain 900°C carbonized lignin. Hard carbon microspheres; their scanning electron micrographs are shown in Figure 3. It can be seen from Fig. 3 that the lignin hard carbon microspheres have high sphericity, the particle size is 2-10 microns, and the dispersibility is good.

Example 4: The preparation conditions of the hydrothermal lignin microspheres are the same as those in Example 3; High-temperature carbonization at 1100 °C under nitrogen protection for 3 h, the lignin hard carbon microspheres carbonized at 1100 °C were obtained; the scanning electron micrograph is shown in Figure 4. It can be seen from Figure 4 that the samples prepared under this process condition have high sphericity, relatively uniform particle size distribution, and good dispersibility.

Example 5: The preparation conditions of the hydrothermal lignin microspheres were the same as those in Example 3; the lignin hydrothermal microspheres were placed in a corundum crucible and placed in a high-temperature tube furnace, and the temperature was raised to 1300°C at a heating rate of 5°C/min, and the temperature was Carbonized at high temperature at 1300℃ for 3h under nitrogen protection to obtain lignin hard carbon microspheres carbonized at 1300℃.

Example 6: The preparation conditions of hydrothermal lignin microspheres are the same as those in Example 3; Carbonized at high temperature for 3 h under nitrogen protection at ℃ to obtain lignin hard carbon microspheres carbonized at 1500 ℃.

Example 7: The preparation conditions of the hydrothermal lignin microspheres were the same as those in Example 3; Carbonized at high temperature for 3 h under nitrogen protection at ℃ to obtain lignin hard carbon microspheres carbonized at 1800 ℃.

Example 8: 2 g of sodium lignosulfonate powder was added to 20 mL of deionized water, and stirred until it was completely dissolved to obtain a lignin solution. Then 20 mL of 1 mol/L hydrochloric acid solution was added to obtain an acidic solution with a solid content of 3%. The lignin solution prepared above was transferred to a hydrothermal reactor with a volume of 100 mL and sealed. The temperature of the reaction kettle was gradually raised to 150°C, and after a holding time of 3h, the temperature was naturally lowered to room temperature. After taking out, the solution was centrifuged, and the bottom sediment was taken out and dried in a blast oven at 80° C. to obtain lignin hydrothermal microspheres. The lignin hydrothermal microspheres were placed in a corundum crucible and placed in a high-temperature tube furnace, heated to 900°C at a heating rate of 5°C/min, and carbonized at high temperature for 3 hours under nitrogen protection at 900°C to obtain 900°C carbonized lignin. Hard carbon microspheres.

Example 9: 2 g of ammonium lignosulfonate powder was added to 40 mL of deionized water, and stirred until it was completely dissolved to obtain a lignin solution. Then 20 mL of 1 mol/L hydrochloric acid solution was added to obtain an acidic solution with a solid content of 3%. The lignin solution prepared above was transferred to a hydrothermal reactor with a volume of 100 mL and sealed. The temperature of the reaction kettle was gradually raised to 250°C, and after a holding time of 60h, the temperature was naturally lowered to room temperature. After taking out, the solution was centrifuged, and the bottom sediment was taken out and dried in a blast oven at 80° C. to obtain lignin hydrothermal microspheres. The lignin hydrothermal microspheres were placed in a corundum crucible and placed in a high-temperature tube furnace, heated to 1100°C at a heating rate of 5°C/min, and carbonized at high temperature for 3 hours under nitrogen protection at 1100°C to obtain 1100°C carbonized lignin. Hard carbon microspheres

Example 10: 2 g of calcium lignosulfonate powder was added to 60 mL of deionized water, and stirred until it was completely dissolved to obtain a lignin solution. Then 20 mL of 1 mol/L hydrochloric acid solution was added to obtain an acidic solution with a solid content of 3%. The lignin solution prepared above was transferred to a hydrothermal reactor with a volume of 100 mL and sealed. The temperature of the reaction kettle was gradually raised to 250°C, and after a holding time of 30h, the temperature was naturally lowered to room temperature. After taking out, the solution was centrifuged, the bottom sediment was taken, and dried in a blast oven at 60° C. to obtain lignin hydrothermal microspheres. The lignin hydrothermal microspheres were placed in a corundum crucible and placed in a high-temperature tube furnace, heated to 1300°C at a heating rate of 5°C/min, and carbonized at a high temperature at 900°C under nitrogen protection for 3 hours to obtain 1300°C carbonized lignin. Hard carbon microspheres.

Example 11: 2 g of ammonium lignosulfonate powder was added to 75 mL of deionized water, and stirred until it was completely dissolved to obtain a lignin solution. Then 20 mL of 1 mol/L hydrochloric acid solution was added to obtain an acidic solution with a solid content of 3%. The lignin solution prepared above was transferred to a hydrothermal reactor with a volume of 100 mL and sealed. The temperature of the reaction kettle was gradually raised to 200°C, and after a holding time of 30h, the temperature was naturally lowered to room temperature. After taking out, the solution was centrifuged, and the bottom sediment was taken out and dried in a blast oven at 80° C. to obtain lignin hydrothermal microspheres. The lignin hydrothermal microspheres were placed in a corundum crucible and placed in a high-temperature tube furnace, heated to 1500°C at a heating rate of 5°C/min, and carbonized at a high temperature at 1500°C under nitrogen protection for 3 hours to obtain 1500°C carbonized lignin. Hard carbon microspheres.

Example 12: 2 g of ammonium lignosulfonate powder was added to 75 mL of deionized water, and stirred until it was completely dissolved to obtain a lignin solution. Then 20 mL of 1 mol/L hydrochloric acid solution was added to obtain an acidic solution with a solid content of 3%. The lignin solution prepared above was transferred to a hydrothermal reactor with a volume of 100 mL and sealed. The temperature of the reaction kettle was gradually raised to 350°C, and after a holding time of 20h, the temperature was naturally lowered to room temperature. After taking out, the solution was centrifuged, and the bottom sediment was taken out and dried in a blast oven at 80° C. to obtain lignin hydrothermal microspheres. The lignin hydrothermal microspheres were placed in a corundum crucible and placed in a high-temperature tube furnace, heated to 1800°C at a heating rate of 5°C/min, and carbonized at a high temperature at 1800°C under nitrogen protection for 3 hours to obtain 1800°C carbonized lignin. Hard carbon microspheres.

Example 13: 2 g of ammonium lignosulfonate powder was added to 60 mL of deionized water, and stirred until it was completely dissolved to obtain a lignin solution. Then 20 mL of 1 mol/L boric acid solution was added to obtain an acidic solution with a solid content of 3%. The lignin solution prepared above was transferred to a hydrothermal reactor with a volume of 100 mL and sealed. The temperature of the reaction kettle was gradually raised to 250°C, and after a holding time of 60h, the temperature was naturally lowered to room temperature. After taking out, the solution was centrifuged, the bottom sediment was taken, and dried in a blast oven at 60° C. to obtain lignin hydrothermal microspheres. The lignin hydrothermal microspheres were placed in a corundum crucible and placed in a high-temperature tube furnace, heated to 900°C at a heating rate of 5°C/min, and carbonized at high temperature for 3 hours under nitrogen protection at 900°C to obtain 900°C carbonized lignin. Hard carbon microspheres.

Example 14: 2 g of ammonium lignosulfonate powder was added to 60 mL of deionized water, and stirred until it was completely dissolved to obtain a lignin solution. Then 20 mL of 1 mol/L acetic acid solution was added to obtain an acidic solution with a solid content of 3%. The lignin solution prepared above was transferred to a hydrothermal reactor with a volume of 100 mL and sealed. The temperature of the reaction kettle was gradually raised to 250°C, and after a holding time of 60h, the temperature was naturally lowered to room temperature. After taking out, the solution was centrifuged, and the bottom sediment was taken out and dried in a blast oven at 80° C. to obtain lignin hydrothermal microspheres. The lignin hydrothermal microspheres were placed in a corundum crucible and placed in a high-temperature tube furnace, heated to 1100°C at a heating rate of 5°C/min, and carbonized at high temperature for 3 hours under nitrogen protection at 1100°C to obtain 1100°C carbonized lignin. Hard carbon microspheres.

Example 15: 2 g of sodium lignosulfonate powder was added to 60 mL of deionized water, and stirred until it was completely dissolved to obtain a lignin solution. Then 20 mL of 2mol/L potassium hydroxide solution was added to obtain an alkaline solution with a solid content of 3%. The alkaline lignin solution prepared above was transferred to a hydrothermal reactor with a volume of 100 mL and sealed. The temperature of the reaction kettle was gradually raised to 250°C, and after a holding time of 12 h, the temperature was naturally lowered to room temperature. After taking out, the solution was centrifuged, and the bottom sediment was taken out and dried in a forced air oven at 80°C to obtain lignin hydrothermal gel microspheres. The lignin hydrothermal gel microspheres were placed in a corundum crucible and placed in a high-temperature tube furnace, heated to 1300°C at a heating rate of 5°C/min, and carbonized at a high temperature at 1300°C under nitrogen protection for 3 hours to obtain 1300°C carbonized microspheres. Lignin hard carbon microspheres.

Example 16: 2 g of sodium lignosulfonate powder was added to 60 mL of deionized water, and stirred until it was completely dissolved to obtain a lignin solution. Then 20 mL of 2 mol/L potassium bicarbonate solution was added to obtain an alkaline solution with a solid content of 3%. The alkaline lignin solution prepared above was transferred to a hydrothermal reactor with a volume of 100 mL and sealed. The temperature of the reaction kettle was gradually raised to 250°C, and after a holding time of 30h, the temperature was naturally lowered to room temperature. After taking out, centrifuge the solution, take the bottom sediment, and dry it in a blast oven at 60°C to obtain lignin hydrothermal gel microspheres; the particle size is less than 1 μm. The lignin hydrothermal gel microspheres were placed in a corundum crucible and placed in a high-temperature tube furnace, heated to 900°C at a heating rate of 5°C/min, and carbonized at a high temperature at 900°C under nitrogen protection for 3 hours to obtain 900°C carbonized microspheres. Lignin hard carbon microspheres.

Example 17: 2 g of sodium lignosulfonate powder was added to 60 mL of deionized water, and stirred until it was completely dissolved to obtain a lignin solution. Then 20 mL of 2mol/L sodium carbonate solution was added to obtain an alkaline solution with a solid content of 3%. The alkaline lignin solution prepared above was transferred to a hydrothermal reactor with a volume of 100 mL and sealed. The temperature of the reaction kettle was gradually raised to 250°C, and after a holding time of 60h, the temperature was naturally lowered to room temperature. After taking out, the solution was centrifuged, and the bottom sediment was taken out and dried in a forced air oven at 80°C to obtain lignin hydrothermal gel microspheres. The lignin hydrothermal gel microspheres were placed in a corundum crucible and placed in a high-temperature tube furnace, heated to 1100°C at a heating rate of 5°C/min, and carbonized at a high temperature at 1100°C under nitrogen protection for 3 hours to obtain 1100°C carbonized microspheres. Lignin hard carbon microspheres.

Example 18: 2 g of sodium lignosulfonate powder was added to 60 mL of deionized water, and stirred until it was completely dissolved to obtain a lignin solution. Then 20 mL of 2mol/L sodium bicarbonate solution was added to obtain an alkaline solution with a solid content of 3%. Transfer the alkaline lignin solution prepared above to a hydrothermal reaction kettle with a volume of 100 mL, and tighten the seal. Then put the hydrothermal reaction kettle into the oven, set the oven temperature to 250°C, after 12 hours of reaction time, set the oven temperature to 20°C, and slowly cool down to room temperature. After taking out, centrifuge the solution, take the bottom sediment, and dry it in a blast oven at 60°C to obtain lignin hydrothermal gel microspheres; the particle size is less than 1 μm. The lignin hydrothermal gel microspheres were placed in a corundum crucible and placed in a high-temperature tube furnace, heated to 1300°C at a heating rate of 5°C/min, and carbonized at a high temperature at 1300°C under nitrogen protection for 3 hours to obtain 1300°C carbonized microspheres. Lignin hard carbon microspheres.

Comparative Example 1: In the patent CN102956876B, glucose was used as the precursor, and the temperature was raised to 750°C in an Ar-8% H2 (the volume percentage of H2 in the Ar-H2 mixture was 8%) and kept at 750°C for 15h. After natural cooling , to obtain flake pyrolysis hard carbon material. Its specific surface area is 623m2/g, and the graphite-like crystallite spacing (d ₀₀₂ ) is 0.37nm; with sodium hydroxymethyl cellulose (CMC) as the binder, the ratio of flake pyrolysis hard carbon to CMC is 9:1 An electrode sheet was made, and a button battery was assembled with metal lithium as the counter electrode. The electrolyte of the battery is: 1.0mol/L LiPF6 (EC:DMC=1:1, v/v), assembled in an argon-protected glove box, and galvanostatic charge-discharge was performed at a current density of 37mA/g , the charging voltage range is 0 ~ 3.0V.

Comparative Example 2: In patent CN106099109B, medium-temperature coal tar pitch was used as raw material, dissolved in nitrogen methyl pyrrolidone (NMP), mixed with sodium chloride template according to a certain proportion, and NMP was evaporated to dryness in an oil bath at 200°C. The obtained mixture was carbonized, heated to 750 °C at 5 °C/min under the protection of inert gas in a tube furnace and maintained for 2 h, taken out after cooling, and washed with water to obtain pitch-based hard carbon nanosheets. The 002 interlayer spacing of hard carbon nanosheets can reach 0.342 nm.

The negative electrode material was prepared by combining hard carbon nanosheets with acetylene black and PVDF (polyvinylidene fluoride) in a mass ratio of 7:2:1, the current collector was copper foil, and a sodium-ion battery was assembled in a glove box. The electrochemical performance of the battery was tested on the Land CT2001A battery test system. The charge-discharge voltage ranged from 0.01 to 3V. The pitch-based hard carbon nanosheets were measured to have a reversible capacity of 168.3mAh g for the first time under the condition of a charge-discharge rate of 0.1Ag ^-1 . ^-1 .

Lithium-ion battery applications:

Example 1 to Example 7 and Comparative Example 1 are applied to the negative electrode material of lithium ion battery, and the preparation process of negative electrode of lithium ion battery is as follows: negative electrode active material, conductive carbon black (VXC72), polyvinylidene fluoride with a mass of 87:5:8 The ratio is mixed to form a slurry, and an appropriate amount of NMP is added to adjust the viscosity of the slurry to a suitable range. Adjust the stirring speed to 6000 rpm, and after stirring the slurry for 30 minutes, apply the slurry to the copper foil. After drying the coated pole pieces in a vacuum oven at 120° C. for 12 hours, the pieces were cut to obtain electrode pieces of lignin hard carbon microspheres. The above-mentioned lignin hard carbon microsphere electrode sheet is used as the working electrode, the metal lithium sheet is used as the counter electrode, and the electrolyte is 1.2mol/L LiPF ₆ (EC:DMC:EMC=1:1:1, v/v), The separator adopts polypropylene (PP) separator, which is assembled into a CR-2430 button lithium battery in an argon gas glove box (H2O<1ppm, O2<1ppm), and is charged and discharged with a constant current at a current density of 20mA/g. The charging voltage The range is 0 to 3.0V. FIG. 5 shows the first three charge-discharge curves of the lithium storage of the lignin hard carbon microsphere negative electrode prepared in Example 3.

Sodium-ion battery applications:

Example 8 to Example 18 and Comparative Example 2 are applied to the negative electrode material of sodium ion battery, and the preparation process of negative electrode of sodium ion battery is as follows: negative electrode active material, conductive carbon black (VXC72), polyvinylidene fluoride with a mass of 87:5:8 The ratio is mixed to form a slurry, and an appropriate amount of NMP is added to adjust the viscosity of the slurry to a suitable range. Adjust the stirring speed to 6000 rpm, and after stirring the slurry for 30 minutes, apply the slurry to the copper foil. After drying the coated pole pieces in a vacuum oven at 120° C. for 12 hours, the pieces were cut to obtain electrode pieces of lignin hard carbon microspheres. The above lignin hard carbon microsphere electrode sheet is used as the working electrode, the metal sodium sheet is used as the counter electrode, the electrolyte is 1mol/L NaClO ₄ /(EC:DEC=1:1, v/v), and the diaphragm is made of glass fiber The separator (GF/F, D=125mm, Whatman) was assembled into a CR-2430 button sodium battery in an argon gas glove box, and was charged and discharged with constant current at a current density of 20mA/g, and the charging voltage ranged from 0 to 3.0 V. FIG. 6 shows the first three charge-discharge curves of the sodium storage of the lignin hard carbon microspheres prepared in Example 9.

Schedule Description

Table 1 Comparison of the structure and first charge-discharge performance of lignin hard carbon microspheres obtained in the inventive example and the carbon material of the comparative example

The technical solutions disclosed and proposed in the present invention can be realized by those skilled in the art by referring to the content of this article and appropriately changing the conditions, routes and other links. The methods and technical routes described herein can be modified or recombined without departing from the content, spirit and scope of the present invention to achieve the final preparation technology. It should be particularly pointed out that all similar substitutions and modifications apparent to those skilled in the art are deemed to be included in the spirit, scope and content of the present invention.

Claims (10)

1. The lignin hard carbon microsphere is characterized in that the lignin hard carbon microsphere is spherical, and the graphite-like microcrystalline interlayer spacing of the lignin hard carbon microsphere is 0.36-0.40 nm.

2. The lignin hard charcoal microsphere according to claim 1, wherein the specific surface area of the lignin hard charcoal microsphere is 0.5-300 m²A pore volume of 0.01 to 0.25 cm/g³/g。

3. The lignin hard charcoal microsphere according to claim 1, wherein the particle size of the lignin hard charcoal microsphere is 1-15 μm.

4. The hydrothermal preparation method of lignin hard carbon microspheres of claim 1, which is characterized by comprising the following steps:

(1) dissolving lignin in deionized water, and fully stirring at room temperature until the lignin is completely dissolved to obtain a lignin solution;

(2) directly carrying out hydrothermal reaction on the lignin aqueous solution; or adding acid or alkali substances, and then carrying out hydrothermal reaction to obtain a lignin hydrothermal microsphere precursor;

(3) and (3) carrying out high-temperature carbonization on the lignin microsphere precursor obtained in the step (2) under the protection of inert atmosphere to obtain the lignin hard carbon microsphere.

5. The method of claim 4, wherein: the lignin in the step (1) is sodium lignosulfonate, ammonium lignosulfonate, calcium lignosulfonate or lignocellulose.

6. The method of claim 4, wherein: the acid used in the step (2) is inorganic acid of hydrochloric acid, sulfuric acid, nitric acid or boric acid; or an organic acid of formic acid, acetic acid, propionic acid or butyric acid.

7. The method of claim 4, wherein: the alkali used in the step (2) is inorganic alkali of potassium hydroxide, sodium hydroxide, lithium hydroxide, ammonium hydroxide, anhydrous sodium carbonate, sodium bicarbonate, potassium carbonate or potassium bicarbonate.

8. The process according to claim 4, wherein: the hydrothermal reaction in the step (3) is carried out under the conditions of 150-350 ℃, the hydrothermal treatment time is 3-60 h, and the filling degree of the reaction kettle is 20-75%.

9. The preparation method of claim 4, wherein the high-temperature carbonization temperature in the step (3) is 900-1800 ℃ and the time is 1-5 h.

10. The lignin hard carbon microspheres of claim 1 are used for the negative electrode of an alkali metal ion battery; the alkali metal ion battery is a negative electrode material of a lithium ion battery, a sodium ion battery and a potassium ion battery.

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