Lignin hard carbon with high rate capability, preparation thereof and application of lignin hard carbon in sodium ion battery

Abstract

The invention discloses high-rate-performance lignin hard carbon as well as preparation and application thereof in a sodium-ion battery. The method comprises the following steps: directionally extracting guaiacol-based lignin based on a hydrothermal weak acid-alcohol system, performing catalytic reduction on the guaiacol-based lignin in an alkaline environment by using potassium borohydride to obtain lignin with high hydroxyl content, and finally carbonizing to obtain the lignin hard carbon with high graphite domain order degree, low specific surface area and high rate capability. The specific surface area of the obtained lignin hard carbon is smaller than 5 m < 2 > / g, and the graphite layer spacing is larger than 0.38 nm. Compared with lignin directly pyrolyzed hard carbon, the composite material has lower specific surface area, higher graphitization degree, graphite domain order degree and edge adsorption sites, has higher rate capability when being used as a sodium ion battery negative electrode material, meets the requirement of a rapid charging battery, and has a wide application prospect.

Description

Technical Field

[0001] The invention belongs to the technical field of negative electrode materials for sodium ion batteries, and in particular relates to a high-rate performance lignin hard carbon and its preparation and application in sodium ion batteries. Background Art

[0002] Sodium and lithium are in the same main group (Group IA) and have similar chemical properties. From the perspective of natural abundance, sodium is abundant in the earth's crust, and its content far exceeds that of lithium. The price of sodium salt is generally lower than that of lithium salt. At the same time, the working principle of sodium-ion batteries is similar to that of lithium-ion batteries. + / Na standard potential is -2.71V, and Li + / Li standard potential is similar to -3.02V, and both the positive and negative electrodes of sodium-ion batteries use aluminum as current collectors, which simplifies the battery recycling process and reduces costs. In summary, due to the abundant sodium resources and low cost, sodium-ion batteries are the most likely secondary batteries to replace lithium-ion batteries in the field of large-scale energy storage.

[0003] Graphite is the most common negative electrode material in commercial lithium-ion batteries and has a capacity of 372 mAh g -1 The theoretical lithium storage capacity corresponds to the formation of graphite intercalation compounds (GICs) LiC6. However, when graphite is used as the negative electrode material of sodium ion batteries, its sodium storage capacity is only 35 mAh g due to its inability to form stable intercalation compounds with sodium ions. -1 , and basically has no sodium storage activity. At the same time, compared with lithium ions, the larger radius of sodium ions leads to slow volume expansion and diffusion kinetics during charge and discharge, resulting in poor rate performance and cycle performance. Therefore, the development of negative electrode materials with good cycle performance, excellent rate performance and low cost is crucial for the development of sodium ion batteries.

[0004] Hard carbon is a disordered carbon material that cannot form a regular graphite structure even at a high temperature of 3000°C. Its precursors are generally resin-based, biomass-based, and carbohydrate-based. Among them, the biomass-based precursors are mainly coconut shells, straws, walnut shells, cellulose, lignin, etc. Hard carbon has the advantages of low price and environmental friendliness, and is considered to be a sodium storage negative electrode material with application prospects. However, the complex pore structure, graphite domains, and edge adsorption sites of hard carbon itself affect its sodium storage capacity and rate performance when used as a negative electrode for sodium ion batteries. Studying the sodium storage mechanism of hard carbon and clarifying the structure-activity relationship between its structure and performance will help the commercial application of hard carbon. The typical constant current charge and discharge curve of hard carbon is divided into two parts: a slope zone above 0.1V and a platform zone below 0.1V. The slope zone is for Na + Adsorbed at the edge adsorption site, the platform area corresponds to Na +First, the intercalation occurs in the graphite domains, and then the nanopores are filled. According to the sodium storage mechanism, the sodium storage behavior of hard carbon mainly includes: (1) adsorption at edge adsorption sites; (2) intercalation between carbon layers in graphite domains; and (3) filling in nanopores.

[0005] Increasing the edge adsorption sites of hard carbon can not only increase the slope capacity, but also improve the conductivity of hard carbon, reduce reaction and ion diffusion barriers, and improve rate performance. Commonly used methods include precursor pre-oxidation and heteroatom doping. Xia (ACS Applied Materials & Interfaces, 2021, 13 (40): 47728) et al. used pine wood as raw material and obtained hard carbon materials through sulfuric acid oxidation and two-step carbonization treatment. The concentrated sulfuric acid treatment process not only removes inorganic impurities and some organic extracts in the pine wood precursor, but also introduces oxygen-containing functional groups such as carbonyl into the derived hard carbon as an oxidant, which significantly improves the sodium storage performance of the hard carbon material. The pine wood derived hard carbon has a sodium storage capacity of 30 mAg -1 The sodium storage capacity at the current density is 354.6 mAh g -1 , the first coulombic efficiency is 88.7% at 1Ag -1 After 5000 cycles, the capacity remains at 243 mAh g -1 . The graphite domains of hard carbon are stacked in local areas, showing restricted stacking of 2-6 layers. This structure naturally constructs countless closed nanopores. Chou (Sustainable Materials and Technologies, 2022, 33: e00466) used hazelnut shells as raw materials and obtained hard carbon through simple purification and carbonization treatment. During the purification process, 36-38% hydrochloric acid was used to remove the inorganic impurities in the hazelnut shells, so that the hard carbon material obtained after carbonization has a larger interlayer spacing and more active sodium storage sites. The hard carbon is 20mAg -1 The reversible sodium storage capacity is 342 mAh g -1, the first Coulombic efficiency was as high as 91%. 2-3 layers of sodium atom adsorption structure can be formed inside the hard carbon nanopores, interacting with the carbon substrate, reducing the energy barrier of the system, and achieving an ideal state close to zero deposition potential. This microstructural feature ensures the formation of a stable contact interface between hard carbon and sodium ions during the electrochemical reaction, thereby increasing the sodium storage capacity of hard carbon. Wang (SusMat, 2022, 2(3): 357) used redwood waste as a precursor, chemically pretreated it with NaClO2 and NaOH, and then carbonized it at 1100°C to obtain hard carbon. The chemical treatment process reduces the content of lignin and hemicellulose in the raw materials, thereby achieving effective regulation of the closed-pore structure. The redwood-derived hard carbon structure contains more closed pores with thin pore walls. The thin and abundant closed pores provide more sodium storage sites, while allowing rapid transmission of sodium ions, thereby improving the platform capacity and rate performance of the material. The material has a high conductivity at 20 mAg -1 The reversible sodium storage capacity is 326 mAh g -1 And in 5Ag -1 It can still maintain 230mAh g at a high current density -1 .

[0006] Lignin is the second most abundant organic matter in plants and can be divided into three phenylpropane units with different methoxy content: syringylpropane unit (S-type lignin), guaiacylpropane unit (G-type lignin) and p-hydroxyphenylpropane unit (H-type lignin). These units are interconnected by ether bonds and carbon-carbon bonds to form a three-dimensional network structure of biopolymers, which contain abundant aromatic ring structures, aliphatic and aromatic hydrocarbon groups, and quinone groups and other active groups. These functional groups significantly affect the reaction characteristics of lignin. As the only aromatic compound that can be obtained from renewable resources in industry, lignin has been proven to be a substitute for petroleum phenol polymers and is widely used in the field of adhesives and dispersants. At the same time, the carbon content in lignin is as high as 60%, and it has abundant oxygen-containing functional groups. As a hard carbon precursor, it has broad application prospects in the field of sodium storage.

[0007] However, industrial lignin mainly comes from pulping and papermaking waste liquid or residues in the biorefining process. It has many impurities, complex components and insufficient active functional groups, which leads to poor sodium storage performance of hard carbon. For example, Ghimbeu (Carbon, 2019, 153: 634-647) used lignin sulfonate recovered from acid pulping waste liquid to prepare hard carbon with a storage capacity of only 205 mAh g -1 Therefore, it is very important to separate and purify industrial lignin or directly extract lignin from wood and then chemically modify it to improve the sodium storage performance.

[0008] Studies have shown that the molecular structural units and functional groups of different types of lignin have great applications in their hard carbon properties. The methoxy and phenolic hydroxyl groups on the side chains of lignin will significantly affect the reaction characteristics and pyrolysis process of lignin, thereby affecting the structure of lignin hard carbon. Zhang (Journal of Power Sources, 2023, 581: 233475) used pine wood as raw material and extracted pine wood lignin using ethanol and sulfuric acid system. Its molecules only contain G-type and a small amount of H-type structural units. During the pyrolysis process, micropores are first formed at low temperatures, and then the micropores are transformed into closed pores at high temperatures. The prepared pine wood lignin hard carbon has a high closed pore volume of 0.117cm 3 g -1 , reversible specific capacity up to 340mAh g -1 , but the rate performance is poor, such as in 2Ag -1 The reversible specific capacity is only 68 mAh g -1 This is because the lignin extracted using strong acid as a catalyst has a high degree of condensation and lacks functional groups such as hydroxyl groups, resulting in insufficient active sites for the prepared hard carbon and disordered graphite.

[0009] Carbonyl adsorption sites can provide reversible Na + adsorption sites, while increasing the electron transfer rate, synergistically and effectively improving the reaction kinetics and enhancing the electrochemical performance. Li (Electrochimica Acta, 2019, 313: 109) prepared grapefruit peel-derived hard carbon by hydrothermal pretreatment and high-temperature carbonization has a high carbonyl content, which improves its rate performance. -1 The sodium storage capacity is 124 mAh g -1 Yu Xiaochen (Structural Regulation and Energy Storage Performance of Lignin Carbon [D]. Tianjin University, 2019.) used the organic solvent acetone to extract high-purity lignin from corn cobs and reacted it in a sodium borohydride aqueous solution to obtain reduced lignin, increase the carbonyl content and remove heteroatoms. The hard carbon obtained by carbonization has a sodium storage capacity of 308.6 mAh g -1 , but its rate performance is poor (at 500mAg -1 The sodium storage capacity is only 52 mAh g -1 ). This is because corncob lignin is a GSH type lignin with a complex structure, which leads to low order of graphite domains in the hard carbon obtained by pyrolysis; and in the absence of a catalyst, the reaction between sodium borohydride and lignin is incomplete, and the obtained lignin has a low hydroxyl content, which cannot be pyrolyzed to generate a large amount of carbonyl content in lignin hard carbon.

[0010] In summary, lignin hard carbon has broad application prospects as a sodium storage negative electrode, but the industrial lignin derived from the pulping and papermaking and bioethanol refining processes has low purity and complex components. The prepared lignin hard carbon has poor rate performance, which makes it difficult to use under high current, limiting its application in the field of fast charging batteries. Summary of the invention

[0011] In order to overcome the shortcomings and deficiencies of the above-mentioned prior art lignin hard carbon having low carbonyl content and low graphite disorder leading to poor rate performance, the primary purpose of the present invention is to provide a method for preparing lignin hard carbon with high rate performance.

[0012] Another object of the present invention is to provide high-rate performance lignin hard carbon prepared by the above method.

[0013] Another object of the present invention is to provide the application of the above-mentioned high-rate performance lignin hard carbon in the negative electrode of sodium ion battery.

[0014] In the present invention, the specific surface area of ​​the lignin hard carbon is less than 5m 2 / g, the graphite interlayer spacing is greater than 0.38nm.

[0015] The method of the present invention utilizes potassium borohydride to catalytically reduce guaiacyl lignin to obtain high-hydroxy lignin and prepare lignin hard carbon. First, guaiacyl lignin is extracted based on the hydrothermal weak acid-alcohol water system, and ash is removed at the same time. Pine wood is used as the raw material because more than 90% of its structural units are G-type, which ensures that the structure of the prepared hard carbon component is uniform. The alcohol water system separates lignin under weak acid conditions, and its purpose is to reduce the condensation degree of lignin, which is beneficial to improve the subsequent lignin reduction reaction activity. Potassium borohydride is further used to catalytically reduce guaiacyl lignin in a normal pressure and alkaline environment, break the β-O-4 bond between lignin, and further increase the hydroxyl content. During the carbonization process, the reduction of the condensation degree of lignin can increase the graphitization degree of lignin hard carbon. The carbonization process retains hydroxyl groups and generates abundant edge adsorption sites, thereby obtaining lignin hard carbon with high graphitization degree, low specific surface area and high rate performance.

[0016] The purpose of the present invention is achieved through the following technical solutions:

[0017] A method for preparing high-rate performance lignin hard carbon comprises the following steps:

[0018] (1) mixing pine wood powder with weak acid, alcohol and water, heating and reacting in a reactor, filtering after the reaction, adding water to the filtrate to separate lignin, washing, and drying to obtain guaiacyl lignin;

[0019] (2) preparing an aqueous solution of guaiacyl lignin, adding a catalyst, then adding an alkaline regulator to a pH of 10 to 13, then adding potassium borohydride for reduction reaction, and finally adding an acidic regulator to a pH of 1 to 3, precipitating a precipitate, filtering, washing, and drying to obtain high-hydroxy lignin;

[0020] (3) The high-hydroxy lignin is carbonized, washed, and dried to obtain lignin hard carbon.

[0021] Preferably, the weight ratio of the pine wood powder, weak acid, alcohol and water in step (1) is 1:1-2:8-10:2-5.

[0022] Preferably, in step (2), the weight ratio of the guaiacyl lignin, the catalyst, potassium borohydride and water is 10:4-10:10-30:80-150.

[0023] Preferably, the particle size of the pine wood powder in step (1) is ≤250 microns.

[0024] Preferably, the weak acid in step (1) is at least one of acetic acid and citric acid.

[0025] Preferably, the alcohol in step (1) is at least one of methanol, ethanol and n-propanol.

[0026] Preferably, the heating reaction temperature in step (1) is 60 to 100° C. and the time is 1 to 3 hours.

[0027] Preferably, the filtrate in step (1) is added with water to precipitate lignin, and then the lignin is separated by vacuum filtration.

[0028] Preferably, the washing in step (1) refers to washing with water until it becomes neutral.

[0029] Preferably, the drying in step (1) is at least one of forced air drying, vacuum drying and infrared drying, the drying temperature is 80 to 110° C., and the drying time is 8 to 12 hours.

[0030] Preferably, the catalyst in step (2) is at least one of cupric chloride, ferric bromide and potassium iodide.

[0031] Preferably, the reduction reaction in step (2) is carried out at a temperature of 40 to 60° C. and for a period of 8 to 12 hours.

[0032] Preferably, the alkaline regulator in step (2) is a 50-70wt.% alkaline solution; the alkali is at least one of sodium hydroxide, potassium hydroxide and ammonia water; the acidic regulator is a 10-30wt.% acid solution; the acid is at least one of hydrochloric acid, acetic acid, nitric acid and sulfuric acid.

[0033] Preferably, the drying in step (2) is at least one of forced air drying, vacuum drying and infrared drying, the drying temperature is 80 to 110° C., and the drying time is 8 to 12 hours.

[0034] Preferably, the carbonization in step (3) is carried out under an inert gas atmosphere, and the inert gas is at least one of nitrogen, argon and helium.

[0035] Preferably, the carbonization procedure in step (3) is: heating to 1200-1500°C at 3-10°C / min and maintaining for 60-180min; more preferably: heating to 1200-1500°C at 4-6°C / min and maintaining for 120-150min.

[0036] Preferably, the drying in step (3) is at least one of forced air drying, vacuum drying and infrared drying, the drying temperature is 80 to 110° C., and the drying time is 8 to 12 hours.

[0037] Preferably, the carbonization process in step (3) is preferably carried out in a tubular furnace.

[0038] Preferably, the washing in step (3) refers to immersing the carbonized product in a dilute acid solution to wash away the residual pyrolysis products therein, and the washing time is 10 to 12 hours; the concentration of the dilute acid solution is 0.5 to 1.5 mol / L; and the acid is at least one of hydrochloric acid, acetic acid, nitric acid and sulfuric acid.

[0039] A high-rate performance lignin hard carbon prepared by the above method.

[0040] The above-mentioned high-rate performance lignin hard carbon is used as a negative electrode material for sodium ion batteries.

[0041] The present invention will be described in more detail below:

[0042] (1) Weighing pine wood powder with a particle size of less than 250 μm, adding weak acid, alcohol and water, fully mixing, reacting in a reactor at a certain temperature for 1 to 3 hours, filtering after the reaction, adding a certain amount of water to the filtrate, separating lignin by vacuum filtration, washing until the pH reaches 7, and drying the filter cake to obtain guaiacyl lignin;

[0043] This step is to obtain guaiacyl lignin with uniform structure. The content of guaiacyl lignin G type accounts for 90%, which is beneficial to reduce the thermal stability of subsequent high-temperature carbonization and promote the rearrangement of graphite domains.

[0044] This step utilizes a weak acid-alcohol water system to effectively extract lignin while reducing the ash content. The obtained guaiacyl lignin has high purity and regular composition, which is beneficial to improving the subsequent reaction activity and the graphitization degree of the lignin hard carbon after carbonization.

[0045] The hydrothermal reaction temperature in this step is 60-100°C and the time is 1-3 hours. If the hydrothermal reaction temperature is too low or the time is too short, it is not conducive to the removal of hemicellulose; if the hydrothermal reaction temperature is too high or the time is too long, it will inhibit the delignification of ethanol and increase energy consumption.

[0046] (2) adding guaiacyl lignin to water to dissolve it into a solution of a certain mass concentration, adding a catalyst, adding an alkaline regulator to adjust the pH of the solution to 10-13, then adding potassium borohydride, reacting at 40-60° C. for 8-12 hours, adding an acidic regulator to adjust the pH of the solution to 1-3, precipitating a precipitate, filtering and washing until the pH reaches 7, and then drying the filter cake to obtain high-hydroxy lignin;

[0047] This step is to obtain high-hydroxyl lignin. The strong reducing property of potassium borohydride in alkaline aqueous solution is used to catalyze the reduction of the β-O-4 bonds in the lignin polymer to generate single benzene ring compounds, increase the phenolic hydroxyl content, and reduce the molecular weight of lignin.

[0048] This step breaks β-O-4 and increases the phenolic hydroxyl content of lignin, which is not only beneficial to increase the edge adsorption sites of lignin hard carbon after carbonization, but also the smaller molecular weight is beneficial to the uniform molecular weight of the obtained high hydroxyl lignin, promoting the formation of regular graphite domains after carbonization. The increase in graphitization degree is beneficial to the improvement of lignin hard carbon conductivity and thus the sodium storage capacity; the edge adsorption sites enable lignin hard carbon to store more sodium ions, thereby improving the rate performance of the hard carbon negative electrode.

[0049] In this step, an alkaline regulator must be added in advance to create an alkaline environment and maintain the solution pH at 10-13, so that the guaiacyl lignin can be fully dissolved, which is also conducive to improving the solubility of potassium borohydride. Lignin cannot be directly reacted with potassium borohydride in water because potassium borohydride is unstable in an environment with a pH value less than 7 and generates a large amount of hydrogen when it comes into contact with water.

[0050] This step must be preceded by the addition of a catalyst (electrophilic reagent), and potassium borohydride cannot be used directly in an alkaline environment for the reaction. Because potassium borohydride is less stable in water, the addition of an electrophilic reagent can promote the stability of potassium borohydride, while accelerating the reaction rate, improving efficiency, and allowing the reaction to proceed fully.

[0051] In this step, the reaction temperature is controlled at 40-60°C. If the temperature is too low, it is not conducive to the borohydride reduction reaction, and the reaction rate is slow, the efficiency is low, and the reaction is incomplete; if the temperature is too high, potassium borohydride will decompose and generate by-products; and energy consumption will be increased, which will increase costs.

[0052] (3) The high-hydroxy lignin in step (2) is carbonized, washed, and dried to obtain lignin hard carbon.

[0053] This step is to carbonize lignin to generate hard carbon. The G type accounts for up to 90% of high hydroxyl lignin, which increases the thermal instability of the carbonization process and promotes the formation of uniform graphite domains and edge adsorption sites (C=O) during pyrolysis.

[0054] The carbonization gas atmosphere in this step does not necessarily need to be nitrogen, and can be replaced by other inert gases such as argon. The carbonization temperature is required to be in the range of 1200-1500°C and the time is 120-150 minutes. If the temperature is too low and the time is too short, the carbonization will be incomplete and the material conductivity will be poor; if the temperature is too high and the time is too long, the material structure will be unstable and partially collapsed, and energy consumption will increase, raising production costs.

[0055] This step requires that the concentration of the dilute acid solution be 0.5-1.5 mol / L; the acid is at least one of hydrochloric acid, acetic acid, nitric acid and sulfuric acid, and the washing time is 10-12 hours. If the acid concentration is too low or the soaking time is too short, byproducts will remain in the carbonization process, reducing the conductivity of the product; if the acid concentration is too high or the soaking time is too long, the pore structure of the product will be destroyed.

[0056] The specific surface area of ​​the lignin hard carbon prepared by the present invention is less than 5m 2 / g, the graphite interlayer spacing is greater than 0.38nm.

[0057] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0058] (1) Compared with the hard carbon prepared by direct pyrolysis of lignin, the hard carbon prepared by the present invention has a lower specific surface area, a higher degree of graphitization and edge adsorption sites. As a negative electrode material for sodium ion batteries, it has a higher rate performance and meets the requirements of fast charging batteries, and has broad application prospects.

[0059] (2) The present invention increases the phenolic hydroxyl content and reduces the molecular weight through the strong catalytic reducing property of potassium borohydride in an alkaline environment, thereby obtaining high-hydroxyl lignin with uniform structure, promoting the formation of graphite domains, and significantly improving the degree of graphitization. The reaction is green and environmentally friendly, which is conducive to industrial production. BRIEF DESCRIPTION OF THE DRAWINGS

[0060] Figure 1 This is a scanning electron microscope image of the lignin hard carbon obtained in Example 1 of the present invention.

[0061] Figure 2 This is a transmission electron microscope picture of the lignin hard carbon obtained in Example 1 of the present invention.

[0062] Figure 3 This is the nitrogen adsorption-desorption isotherm diagram of the lignin hard carbon obtained in Example 1 of the present invention.

[0063] Figure 4This is the X-ray photoelectron spectrum of the lignin hard carbon obtained in Example 1 of the present invention.

[0064] Figure 5 This is the X-ray diffraction spectrum of the lignin hard carbon obtained in Example 1 of the present invention.

[0065] Figure 6 This is the Raman spectrum of the lignin hard carbon obtained in Example 1 of the present invention. DETAILED DESCRIPTION

[0066] The present invention is further described in detail below in conjunction with embodiments and drawings, but the embodiments of the present invention are not limited thereto.

[0067] If no specific conditions are specified in the examples of the present invention, the experiments were carried out under conventional conditions or conditions recommended by the manufacturer. All raw materials, reagents, etc., whose manufacturers are not specified, are conventional products that can be purchased commercially.

[0068] Example 1

[0069] Add 5 g of pine wood powder with a particle size of less than 250 μm, 5 g of acetic acid, 40 g of ethanol, and 10 g of deionized water to a reactor, mix thoroughly, and react at 60° C. for 1 hour in the reactor. After the reaction is completed, filter, add water to the filtrate, and separate the lignin by vacuum filtration, and wash until the pH is 7. Dry the filter cake to obtain guaiacyl lignin;

[0070] 5 g of guaiacyl lignin was added to 40 g of water to dissolve and prepare a solution, 2 g of copper chloride was added, a sodium hydroxide solution with a mass concentration of 60% was added to adjust the pH to 12, and then 5 g of potassium borohydride was added, reacted at 40° C. for 8 hours, a hydrochloric acid solution with a mass concentration of 20% was added to adjust the pH to 3, a precipitate was precipitated, filtered and washed until the pH reached 7, and then the filter cake was vacuum dried at 100° C. for 12 hours to obtain high hydroxyl lignin;

[0071] The high hydroxyl lignin was placed in a tube furnace under argon protection at 5 °C min -1 The temperature was raised to 1400°C at a rate of 1000 °C and carbonized for 2 h.

[0072] The sample obtained after carbonization was immersed in 100 ml of 1 mol / L hydrochloric acid solution, stirred for 12 h, filtered and washed with deionized water, and dried in a vacuum oven at 100° C. for 12 h to obtain lignin hard carbon.

[0073] Example 2

[0074] Add 5 g of pine wood powder with a particle size of less than 250 μm, 10 g of acetic acid, 50 g of ethanol, and 25 g of deionized water to a reactor, mix thoroughly, and react at 100° C. for 3 hours in the reactor. After the reaction is completed, filter, add water to the filtrate, and separate the lignin by vacuum filtration, and wash until the pH is 7. Dry the filter cake to obtain guaiacyl lignin;

[0075] 5 g of guaiacyl lignin was added to 75 g of water to dissolve and prepare a solution, 5 g of copper chloride was added, a sodium hydroxide solution with a mass concentration of 60% was added to adjust the pH to 12, and then 15 g of potassium borohydride was added, reacted at 60° C. for 12 hours, a hydrochloric acid solution with a mass concentration of 20% was added to adjust the pH to 3, a precipitate was precipitated, filtered and washed until the pH reached 7, and then the filter cake was vacuum dried at 100° C. for 12 hours to obtain high hydroxyl lignin;

[0076] The high hydroxyl lignin was placed in a tube furnace under argon protection at 5 °C min -1 The temperature was raised to 1400°C at a rate of 1000 °C and carbonized for 2 h.

[0077] The sample obtained after carbonization was immersed in 100 ml of 1 mol / L hydrochloric acid solution, stirred for 12 h, filtered and washed with deionized water, and dried in a vacuum oven at 100° C. for 12 h to obtain lignin hard carbon.

[0078] Example 3

[0079] Add 5 g of pine wood powder with a particle size of less than 250 μm, 5 g of acetic acid, 45 g of ethanol, and 20 g of deionized water to a reactor, mix thoroughly, and react at 80° C. for 2 hours in the reactor. After the reaction is completed, filter, add water to the filtrate, and separate the lignin by vacuum filtration, and wash until the pH is 7. Dry the filter cake to obtain guaiacyl lignin;

[0080] 5 g of guaiacyl lignin was added to 50 g of water to dissolve and prepare a solution, 3 g of copper chloride was added, a sodium hydroxide solution with a mass concentration of 60% was added to adjust the pH to 12, and then 10 g of potassium borohydride was added, reacted at 50° C. for 12 hours, a hydrochloric acid solution with a mass concentration of 20% was added to adjust the pH to 3, a precipitate was precipitated, filtered and washed until the pH reached 7, and then the filter cake was vacuum dried at 100° C. for 12 hours to obtain high hydroxyl lignin;

[0081] The high hydroxyl lignin was placed in a tube furnace under argon protection at 5 °C min -1 The temperature was raised to 1400°C at a rate of 1000 °C and carbonized for 2 h.

[0082] The sample obtained after carbonization was immersed in 100 ml of 1 mol / L hydrochloric acid solution, stirred for 12 h, filtered and washed with deionized water, and dried in a vacuum oven at 100° C. for 12 h to obtain lignin hard carbon.

[0083] Example 4

[0084] Add 5 g of pine wood powder with a particle size of less than 250 μm, 5 g of acetic acid, 50 g of ethanol, and 10 g of deionized water to a reactor, mix thoroughly, and react at 80° C. in the reactor for 1 hour. After the reaction is completed, filter, add water to the filtrate, and separate the lignin by vacuum filtration, and wash until the pH is 7. Dry the filter cake to obtain guaiacyl lignin;

[0085] 5 g of guaiacyl lignin was added to 50 g of water to dissolve and prepare a solution, 5 g of ferric bromide was added, a sodium hydroxide solution with a mass concentration of 60% was added to adjust the pH to 12, and then 5 g of potassium borohydride was added, reacted at 50° C. for 12 hours, a hydrochloric acid solution with a mass concentration of 20% was added to adjust the pH to 3, a precipitate was precipitated, filtered and washed until the pH reached 7, and then the filter cake was vacuum dried at 100° C. for 12 hours to obtain high hydroxyl lignin;

[0086] The high hydroxyl lignin was placed in a tube furnace under argon protection at 5 °C min -1 The temperature was raised to 1400°C at a rate of 1000 °C and carbonized for 2 h.

[0087] The sample obtained after carbonization was immersed in 100 ml of 1 mol / L hydrochloric acid solution, stirred for 12 h, filtered and washed with deionized water, and dried in a vacuum oven at 100° C. for 12 h to obtain lignin hard carbon.

[0088] Example 5

[0089] Add 5 g of pine wood powder with a particle size of less than 250 μm, 5 g of acetic acid, 50 g of n-propanol, and 10 g of deionized water to a reactor, mix thoroughly, and react at 80° C. for 1 hour in the reactor. After the reaction is completed, filter, add water to the filtrate, and separate the lignin by vacuum filtration, and wash until the pH is 7. Dry the filter cake to obtain guaiacyl lignin;

[0090] 5 g of guaiacyl lignin was added to 50 g of water to dissolve and prepare a solution, 5 g of copper chloride was added, a sodium hydroxide solution with a mass concentration of 60% was added to adjust the pH to 12, and then 5 g of potassium borohydride was added, reacted at 50° C. for 12 hours, a hydrochloric acid solution with a mass concentration of 20% was added to adjust the pH to 3, a precipitate was precipitated, filtered and washed until the pH reached 7, and then the filter cake was vacuum dried at 100° C. for 12 hours to obtain high hydroxyl lignin;

[0091] The high hydroxyl lignin was placed in a tube furnace under argon protection at 5 °C min -1 The temperature was raised to 1400°C at a rate of 1000 °C and carbonized for 2 h.

[0092] The sample obtained after carbonization was immersed in 100 ml of 1 mol / L hydrochloric acid solution, stirred for 12 h, filtered and washed with deionized water, and dried in a vacuum oven at 100° C. for 12 h to obtain lignin hard carbon.

[0093] Comparative Example 1 (Compared with Example 1, directly using alkali lignin to react with potassium borohydride)

[0094] 5 g of alkali lignin was added to 40 g of water to dissolve and prepare a solution, 2 g of copper chloride was added, a sodium hydroxide solution with a mass concentration of 60% was added to adjust the pH to 12, and then 5 g of potassium borohydride was added, reacted at 40° C. for 8 hours, a hydrochloric acid solution with a mass concentration of 20% was added to adjust the pH to 3, a precipitate was precipitated, filtered and washed until the pH reached 7, and then the filter cake was vacuum dried at 100° C. for 12 hours to obtain high hydroxyl lignin;

[0095] The high hydroxyl lignin was placed in a tube furnace under argon protection at 5 °C min -1 The temperature was raised to 1400°C at a rate of 1000 °C and carbonized for 2 h.

[0096] The sample obtained after carbonization was immersed in 100 ml of 1 mol / L hydrochloric acid solution, stirred for 12 h, filtered and washed with deionized water, and dried in a vacuum oven at 100° C. for 12 h to obtain lignin hard carbon.

[0097] Comparative Example 2 (Compared with Example 1, extraction of poplar lignin for catalytic reduction reaction)

[0098] Add 5 g of poplar wood powder with a particle size of less than 250 μm, 5 g of acetic acid, 40 g of ethanol, and 10 g of deionized water to a reactor, mix thoroughly, and react at 60° C. in the reactor for 1 hour. After the reaction is completed, filter, add water to the filtrate, and separate the lignin by vacuum filtration, and wash until the pH is 7. Dry the filter cake to obtain guaiacyl lignin;

[0099] 5 g of guaiacyl lignin was added to 40 g of water to dissolve and prepare a solution, 2 g of copper chloride was added, a sodium hydroxide solution with a mass concentration of 60% was added to adjust the pH to 12, and then 5 g of potassium borohydride was added, reacted at 40° C. for 8 hours, a hydrochloric acid solution with a mass concentration of 20% was added to adjust the pH to 3, a precipitate was precipitated, filtered and washed until the pH reached 7, and then the filter cake was vacuum dried at 100° C. for 12 hours to obtain high hydroxyl lignin;

[0100] The high hydroxyl lignin was placed in a tube furnace under argon protection at 5 °C min -1 The temperature was raised to 1400°C at a rate of 1000 °C and carbonized for 2 h.

[0101] The sample obtained after carbonization was immersed in 100 ml of 1 mol / L hydrochloric acid solution, stirred for 12 h, filtered and washed with deionized water, and dried in a vacuum oven at 100° C. for 12 h to obtain lignin hard carbon.

[0102] Comparative Example 3 (Compared with Example 1, extracting corncob lignin for catalytic reduction reaction)

[0103] Add 5 g corn cob wood powder with a particle size of less than 250 μm, 5 g acetic acid, 40 g ethanol, and 10 g deionized water to a reactor, mix thoroughly, and react at 60° C. for 1 hour in the reactor. After the reaction is completed, filter, add water to the filtrate, separate lignin by vacuum filtration, and wash until the pH is 7. Dry the filter cake to obtain guaiacyl lignin;

[0104] 5 g of guaiacyl lignin was added to 40 g of water to dissolve and prepare a solution, 2 g of copper chloride was added, a sodium hydroxide solution with a mass concentration of 60% was added to adjust the pH to 12, and then 5 g of potassium borohydride was added, reacted at 40° C. for 8 hours, a hydrochloric acid solution with a mass concentration of 20% was added to adjust the pH to 3, a precipitate was precipitated, filtered and washed until the pH reached 7, and then the filter cake was vacuum dried at 100° C. for 12 hours to obtain high hydroxyl lignin;

[0105] The high hydroxyl lignin was placed in a tube furnace under argon protection at 5 °C min -1 The temperature was raised to 1400°C at a rate of 1000 °C and carbonized for 2 h.

[0106] The sample obtained after carbonization was immersed in 100 ml of 1 mol / L hydrochloric acid solution, stirred for 12 h, filtered and washed with deionized water, and dried in a vacuum oven at 100° C. for 12 h to obtain lignin hard carbon.

[0107] Comparative Example 4 (Compared with Example 1, no catalytic reduction catalyst was added)

[0108] Add 5 g of pine wood powder with a particle size of less than 250 μm, 5 g of acetic acid, 40 g of ethanol, and 10 g of deionized water to a reactor, mix thoroughly, and react at 60° C. for 1 hour in the reactor. After the reaction is completed, filter, add water to the filtrate, and separate the lignin by vacuum filtration, and wash until the pH is 7. Dry the filter cake to obtain guaiacyl lignin;

[0109] 5 g of guaiacyl lignin was added to 40 g of water to dissolve and prepare a solution, a sodium hydroxide solution with a mass concentration of 60% was added to adjust the pH to 12, and then 5 g of potassium borohydride was added, reacted at 40° C. for 8 hours, a hydrochloric acid solution with a mass concentration of 20% was added to adjust the pH to 3, a precipitate was precipitated, filtered and washed until the pH reached 7, and then the filter cake was vacuum dried at 100° C. for 12 hours to obtain high hydroxyl lignin;

[0110] The high hydroxyl lignin was placed in a tube furnace under argon protection at 5 °C min -1 The temperature was raised to 1400°C at a rate of 1000 °C and carbonized for 2 h.

[0111] The sample obtained after carbonization was immersed in 100 ml of 1 mol / L hydrochloric acid solution, stirred for 12 h, filtered and washed with deionized water, and dried in a vacuum oven at 100° C. for 12 h to obtain lignin hard carbon.

[0112] Comparative Example 5 (Compared with Example 1, the catalytic reducing agent uses sodium borohydride instead of potassium borohydride)

[0113] Add 5 g of pine wood powder with a particle size of less than 250 μm, 5 g of acetic acid, 40 g of ethanol, and 10 g of deionized water to a reactor, mix thoroughly, and react at 60° C. for 1 hour in the reactor. After the reaction is completed, filter, add water to the filtrate, and separate the lignin by vacuum filtration, and wash until the pH is 7. Dry the filter cake to obtain guaiacyl lignin;

[0114] 5 g of guaiacyl lignin was added to 40 g of water to dissolve and prepare a solution, 2 g of copper chloride was added, a sodium hydroxide solution with a mass concentration of 60% was added to adjust the pH to 12, and then 5 g of sodium borohydride was added, reacted at 40° C. for 8 hours, a hydrochloric acid solution with a mass concentration of 20% was added to adjust the pH to 3, a precipitate was precipitated, filtered and washed until the pH reached 7, and then the filter cake was vacuum dried at 100° C. for 12 hours to obtain high hydroxyl lignin;

[0115] The high hydroxyl lignin was placed in a tube furnace under argon protection at 5 °C min -1 The temperature was raised to 1400°C at a rate of 1000 °C and carbonized for 2 h.

[0116] The sample obtained after carbonization was immersed in 100 ml of 1 mol / L hydrochloric acid solution, stirred for 12 h, filtered and washed with deionized water, and dried in a vacuum oven at 100° C. for 12 h to obtain lignin hard carbon.

[0117] Comparative Example 6 (Compared with Example 1, no alkaline regulator was added to the catalytic reduction reaction)

[0118] Add 5 g of pine wood powder with a particle size of less than 250 μm, 5 g of acetic acid, 40 g of ethanol, and 10 g of deionized water to a reactor, mix thoroughly, and react at 60° C. for 1 hour in the reactor. After the reaction is completed, filter, add water to the filtrate, and separate the lignin by vacuum filtration, and wash until the pH is 7. Dry the filter cake to obtain guaiacyl lignin;

[0119] 5 g of guaiacyl lignin was added to 40 g of water to dissolve and prepare a solution, 2 g of copper chloride was added, and then 5 g of potassium borohydride was added, and the reaction was carried out at 40° C. for 8 hours, and a hydrochloric acid solution with a mass concentration of 20% was added to adjust the pH to 3, and the precipitate was precipitated, filtered and washed until the pH reached 7, and then the filter cake was vacuum dried at 100° C. for 12 hours to obtain high hydroxyl lignin;

[0120] The high hydroxyl lignin was placed in a tube furnace under argon protection at 5 °C min -1 The temperature was raised to 1400°C at a rate of 1000 °C and carbonized for 2 h.

[0121] The sample obtained after carbonization was immersed in 100 ml of 1 mol / L hydrochloric acid solution, stirred for 12 h, filtered and washed with deionized water, and dried in a vacuum oven at 100° C. for 12 h to obtain lignin hard carbon.

[0122] Comparative Example 7 (Compared with Example 1, the catalytic reduction reaction temperature is lowered)

[0123] Add 5 g of pine wood powder with a particle size of less than 250 μm, 5 g of acetic acid, 40 g of ethanol, and 10 g of deionized water to a reactor, mix thoroughly, and react at 60° C. for 1 hour in the reactor. After the reaction is completed, filter, add water to the filtrate, and separate the lignin by vacuum filtration, and wash until the pH is 7. Dry the filter cake to obtain guaiacyl lignin;

[0124] 5 g of guaiacyl lignin was added to 40 g of water to dissolve and prepare a solution, 2 g of copper chloride was added, a sodium hydroxide solution with a mass concentration of 60% was added to adjust the pH to 12, and then 5 g of potassium borohydride was added, and the reaction was carried out under ice bath for 8 hours, and a hydrochloric acid solution with a mass concentration of 20% was added to adjust the pH to 3, and a precipitate was precipitated, filtered and washed until the pH reached 7, and then the filter cake was vacuum dried at 100° C. for 12 hours to obtain high hydroxyl lignin;

[0125] The high hydroxyl lignin was placed in a tube furnace under argon protection at 5 °C min -1 The temperature was raised to 1400°C at a rate of 1000 °C and carbonized for 2 h.

[0126] The sample obtained after carbonization was immersed in 100 ml of 1 mol / L hydrochloric acid solution, stirred for 12 h, filtered and washed with deionized water, and dried in a vacuum oven at 100° C. for 12 h to obtain lignin hard carbon.

[0127] The lignin hard carbon prepared in the above examples and comparative examples was used in the following applications:

[0128] Test method:

[0129] The morphology and size of the samples of the present invention were tested by field emission scanning electron microscopy (SEM, Hitachi S-550).

[0130] The microstructure and crystal phase information of the sample of the present invention are tested by transmission electron microscopy (TEM, JEM-2100Plus).

[0131] The crystal information and composition of the samples of the present invention were tested by X-ray diffraction (MiniFlex 600).

[0132] The carbonyl content of the samples of the present invention was measured by X-ray photoelectron spectrometer (Thermo Scientific).

[0133] The specific surface area and average pore size of the samples of the present invention were tested by a fully automatic specific surface area and pore analyzer (ASAP2020).

[0134] The graphitization degree of the sample of the present invention is tested by a micro Raman tester (Raman, XploRA PLUS), and the intensity ratio of the G peak to the D peak represents the graphitization degree, and the larger the value, the greater the graphitization degree.

[0135] The electrochemical test is carried out after the battery is assembled. First, the lignin hard carbon prepared in the embodiment and the comparative example is put into a ball mill and milled with superconducting carbon black for 2 hours, and the speed is set to 200r / min. Then the binder polyvinylidene fluoride (PVDF) is dissolved in N-methylpyrrolidone (NMP). After complete dissolution, the ground sample is transferred to the solution and stirred for 4 hours. The mass ratio of lignin hard carbon, superconducting carbon black and PVDF is 8:1:1, and appropriate NMP is added to make the slurry have a certain fluidity. The slurry is coated on the copper foil with a coater, and after drying, it is transferred to a vacuum drying oven at 110°C and dried for 12 hours. The copper foil with the coated sample is rolled and cut into electrode sheets with a diameter of 12 mm. After weighing and recording the mass of each electrode sheet, it is transferred to a vacuum oven and baked at 110°C for 12 hours. After cooling to room temperature, the electrode sheet is quickly placed in the glove box for standby use. The sodium ion battery was assembled in a glove box filled with high-purity argon gas, and the oxygen and water content in the box was controlled to be less than 0.1ppm during operation. In the half-cell, the sodium sheet was used as the counter electrode, and a 1mol / L NaPF6 solution (the solvent was ethylene glycol dimethyl ether (DME)) was used as the electrolyte. The negative electrode shell, sodium sheet, diaphragm, electrolyte, pole piece, gasket, shrapnel, and positive electrode shell were packaged in sequence and assembled into a LIR2032 button battery for electrochemical performance testing, testing the charge and discharge capacity at a current density of 50mA / g and the rate performance at 5A / g.

[0136] Table 1 Structural characteristics of lignin hard carbon

[0137]

[0138] Table 2 Electrochemical properties of lignin hard carbon

[0139]

[0140] right Figure 1 to Figure 6 To explain:

[0141] Figure 1 This is a scanning electron microscope picture of the lignin hard carbon prepared in Example 1 of the present invention. It can be seen that it is a block-shaped three-dimensional structure with a dense surface and fewer pores.

[0142] Figure 2 This is a transmission electron microscope picture of the lignin hard carbon prepared in Example 1 of the present invention. It can be seen that the internal graphite domain structure is uniform, the carbon layers are stacked in large numbers, and the interlayer spacing is large.

[0143] Figure 3 The nitrogen adsorption-desorption curve and pore size distribution curve of the lignin hard carbon prepared in Example 1 of the present invention. The adsorption amount of the nitrogen adsorption-desorption curve increases significantly in the low-pressure zone, and obvious hysteresis loops appear in the medium-pressure zone and the high-pressure zone, indicating that the material has both micropores and mesopores, and the pore structure is small. The pore size distribution curve shows that the micropore distribution is concentrated at 1.3nm, the mesopore distribution is concentrated at 3nm, and the macropores are concentrated at 20-60nm, thus resulting in a lower specific surface area. The micropores and mesopores are attributed to the increase in the hydroxyl content, which reduces the thermal stability.

[0144] Figure 4 This is the X-ray photoelectron spectrum of lignin hard carbon prepared in Example 1 of the present invention. Information such as the elemental composition, chemical state and molecular structure of the sample surface can be obtained from the peak position and peak shape of the spectrum. Information on the elemental content of the sample surface can be obtained from the peak intensity. It can be seen that Example 1 has a higher carbon content. After further calculation, the carbonyl content is 75%.

[0145] Figure 5 This is the X-ray diffraction pattern of the lignin hard carbon prepared in Example 1 of the present invention. The graphite interlayer spacing can be calculated based on the half peak width at (002). The graphite interlayer spacing of Example 1 is 0.387 nm, which is conducive to the storage of sodium ions and the improvement of electronic conductivity.

[0146] Figure 6 This is the Raman spectrum of the lignin hard carbon of Example 1 of the present invention. The ratio of the peak intensity of the G peak and the D peak is usually used to represent the graphitization degree of the material. The ratio of the peak intensity of the G peak and the D peak of Example 1 is larger, indicating a higher degree of graphitization, which is consistent with the characterization results of the X-ray diffraction spectrum.

[0147] The specific surface area of ​​the lignin hard carbon prepared in Examples 1-5 is less than 5m2 / g, the graphite interlayer spacing is greater than 0.380nm, and the graphitization degree is greater than 0.65. The graphitization degree of Example 1 is 0.65, and the specific surface area is 3.5m 2 / g, and the graphite interlayer spacing is 0.387nm, which is much better than the hard carbon material obtained by alkaline lignin borohydride reduction in Comparative Example 1. The electrochemical performance test results of lignin hard carbon in Table 2 show that the lignin hard carbon obtained in Example 1 has excellent charge and discharge performance and rate performance. At a current density of 50mA / g, the first charge capacity is 331mAh / g, the charge capacity after 100 cycles is 325mAh / g, and the rate performance at a current density of 5A / g is 157mAh / g. The charge capacity is better, and the rate performance is significantly better than that of Comparative Example 1, indicating that the lignin hard carbon prepared by the technology of the present invention is better than industrial lignin hard carbon.

[0148] Compared with Example 1, Comparative Examples 2 and 3 respectively extract poplar lignin and corncob lignin, wherein the basic unit composition of poplar lignin is G-type lignin, and the basic unit composition of corncob lignin is G-type, S-type and H-type. Therefore, the extracted guaiacyl lignin component is uneven and has a low content of phenolic hydroxyl groups. The lignin hard carbon generated after carbonization has a low degree of graphitization and a low carbonyl content, resulting in poor charge and discharge performance and rate performance.

[0149] Compared with Example 1, Comparative Example 4 did not add a catalytic reduction reaction catalyst, which reduced the reaction rate. The interaction between lignin and potassium borohydride was weak, which weakened the catalytic reduction effect of potassium borohydride, resulting in a lower degree of graphitization, a lower carbonyl content and a lower graphite interlayer spacing.

[0150] Compared with Example 1, Comparative Example 5 uses sodium borohydride to catalyze the reduction of lignin. Sodium borohydride has poor stability in water and cannot fully react with lignin, resulting in the inability to completely reduce guaiacyl lignin. The resulting high-hydroxyl lignin has a low phenolic hydroxyl content, resulting in a significant reduction in the hard carbonyl content of lignin.

[0151] Compared with Example 1, Comparative Example 6 did not add an alkaline regulator, and was unable to fully dissolve the guaiacyl lignin. At the same time, the stability of potassium borohydride was reduced, which weakened the catalytic reduction effect, resulting in the inability to completely reduce the guaiacyl lignin, and the resulting lignin had a low hard carbon carbonyl content.

[0152] Compared with Example 1, Comparative Example 7 lowers the catalytic reduction reaction temperature and reduces the catalytic reduction reaction activity, resulting in failure to completely reduce the guaiacyl lignin, and the resulting lignin has a low hard carbonyl content.

[0153] In summary, the weak acid-alcohol extraction of pine wood powder and the potassium borohydride catalytic reduction reaction described in the method of the present invention can prepare lignin hard carbon with uniform graphite domain structure and high carbonyl content. As a sodium ion battery electrode material, it shows significantly better performance than industrial lignin hard carbon and the lignin hard carbon prepared in Comparative Examples 1 to 7.

[0154] The above embodiments are preferred implementation modes of the present invention, but the implementation modes of the present invention are not limited to the above embodiments. Any other changes, modifications, substitutions, combinations, and simplifications that do not deviate from the spirit and principles of the present invention should be equivalent replacement methods and are included in the protection scope of the present invention.

Claims

1. A method for preparing high-rate performance lignin hard carbon, characterized in that: The following steps are involved: (1) mixing pine wood powder with weak acid, alcohol and water, heating and reacting in a reactor, filtering after the reaction, adding water to the filtrate to separate lignin, washing, and drying to obtain guaiacyl lignin; (2) preparing an aqueous solution of guaiacyl lignin, adding a catalyst, then adding an alkaline regulator to a pH of 10 to 13, then adding potassium borohydride for reduction reaction, and finally adding an acidic regulator to a pH of 1 to 3, precipitating a precipitate, filtering, washing, and drying to obtain high-hydroxy lignin; (3) The high-hydroxy lignin is carbonized, washed, and dried to obtain lignin hard carbon.

2. The method for preparing a high-rate performance lignin hard carbon according to claim 1, characterized in that: In step (1), the weight ratio of the pine wood powder, weak acid, alcohol and water is 1:1-2:8-10:2-5; And / or, the temperature of the heating reaction in step (1) is 60-100° C. and the time is 1-3 hours.

3. A method for preparing a high-rate performance lignin hard carbon according to claim 1 or 2, characterized in that: In step (2), the weight ratio of the guaiacyl lignin, the catalyst, potassium borohydride and water is 10:4-10:10-30:80-150; And / or, the temperature of the reduction reaction in step (2) is 40-60° C. and the time is 8-12 hours.

4. A method for preparing a high rate performance lignin hard carbon according to claim 1, 2 or 3, characterized in that: The weak acid in step (1) is at least one of acetic acid and citric acid; And / or, the alcohol in step (1) is at least one of methanol, ethanol and n-propanol; And / or, the catalyst in step (2) is at least one of cupric chloride, ferric bromide and potassium iodide.

5. A method for preparing a high rate performance lignin hard carbon according to claim 1, 2 or 3, characterized in that: The carbonization procedure in step (3) is: heating to 1200-1500° C. at 3-10° C. / min and maintaining for 60-180 min; And / or, the carbonization in step (3) is carried out under an inert gas atmosphere.

6. The method for preparing a high-rate performance lignin hard carbon according to claim 5, characterized in that: The carbonization procedure in step (3) is: heating to 1200-1500° C. at 4-6° C. / min and maintaining for 120-150 min; And / or, the inert gas is at least one of nitrogen, argon and helium.

7. A method for preparing a high rate performance lignin hard carbon according to claim 1, 2 or 3, characterized in that: The particle size of the pine wood powder in step (1) is ≤250 μm; And / or, the alkaline regulator in step (2) is a 50-70 wt.% alkaline solution; wherein the alkali is at least one of sodium hydroxide, potassium hydroxide and ammonia water; And / or, the acidic regulator in step (2) is a 10-30 wt.% acid solution; wherein the acid is at least one of hydrochloric acid, acetic acid, nitric acid and sulfuric acid.

8. A method for preparing high rate performance lignin hard carbon according to claim 1, 2 or 3, characterized in that: The washing in step (3) refers to immersing the carbonized product in a dilute acid solution to wash away the residual pyrolysis products therein, and the washing time is 10 to 12 hours; the concentration of the dilute acid solution is 0.5 to 1.5 mol / L; the acid is at least one of hydrochloric acid, acetic acid, nitric acid and sulfuric acid.

9. A high-rate performance lignin hard carbon obtained by the preparation method according to any one of claims 1 to 8.

10. Use of the high-rate performance lignin hard carbon described in claim 9 in a negative electrode material for sodium ion batteries.

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