A modified lignin-derived hard carbon anode material and its preparation and application

Abstract

This invention discloses a modified lignin-derived hard carbon anode material and its preparation and application. The lignin-derived hard carbon material uses ammoniated or quaternized lignin as the carbon source, which is mixed with a dispersant and binder in an aqueous solution, dried, and then carbonized in stages at high temperature under an inert gas atmosphere to obtain the hard carbon material. The prepared hard carbon anode material has a small specific surface area and appropriate interlayer spacing, and as a sodium-ion battery anode, it exhibits high specific capacity, good rate performance, and cycle stability. This hard carbon preparation method is simple to operate and low in cost. It realizes the comprehensive utilization of industrial lignin resources and is beneficial for industrial promotion.

Description

Technical Field

[0001] This invention belongs to the fields of comprehensive resource utilization and sodium-ion battery technology, specifically relating to a modified lignin-derived hard carbon anode material and its preparation and application. Background Technology

[0002] The scarcity and high cost of lithium resources severely limit the widespread application of lithium-ion batteries in grid-scale energy storage. Due to the abundant reserves of sodium and its similar physical and chemical properties to lithium, sodium-ion batteries are considered one of the candidates for large-scale stationary energy storage. Designing and manufacturing reliable, high-capacity anode materials is a challenge for the commercialization of sodium-ion batteries. Sodium ions have a larger size than lithium ions. This makes it difficult to intercalate in graphite with its small interlayer spacing. Hard carbon anodes, due to their larger interlayer spacing (0.37-4.0 nm) and abundant defect sites, have become the optimal choice for sodium battery anodes. Hard carbon anodes are mainly prepared by carbonization of precursors such as biomass, resins, and polymers. They have many advantages such as wide availability, low cost, and no pollution, making them the most studied anode material. However, their relatively low sodium storage capacity and poor rate performance still limit the development of hard carbon anodes.

[0003] Biomass, as an economical and sustainable carbon source, has become one of the most commonly used precursors for preparing hard carbon anode materials for sodium-ion batteries. Lignin is the second most abundant biomass component in the plant kingdom after cellulose, mainly derived from pulping and papermaking processes and the alcohol production process in the cellulose industry. As an oxygen-rich natural aromatic polymer, lignin's amorphous disordered structure is a prerequisite for the formation of hard carbon. Therefore, lignin is a promising precursor for large-scale production of hard carbon.

[0004] Due to its abundant aromatic ring structure, lignin undergoes π-π stacking during carbonization, resulting in a large number of graphite-like domains in lignin-derived hard carbon. These numerous long-range ordered graphite domains not only hinder the formation of closed-cell structures but also restrict sodium ion diffusion, leading to relatively low sodium storage capacity and poor rate performance in lignin-derived hard carbon.

[0005] Patent application CN116514105A discloses a method for preparing hard carbon for sodium-ion battery negative electrodes. This method increases the sodium storage capacity by doping lignin with phosphorus atoms to increase the adsorption sites of lignin-derived hard carbon. However, the improvement effect is not significant, with a reversible sodium storage capacity of only 278 mAh·g. -1The reason is that the capacity provided by defect adsorption accounts for a relatively small proportion of the total capacity, making it difficult to increase sodium storage capacity by increasing adsorption sites. In the sodium storage capacity contribution of hard carbon, plateau capacity accounts for the largest proportion, mainly derived from the filling of near-metallic sodium within closed pores (Chemistry of Materials 2022, 34, 3489-3500). Controlling the pore volume of lignin-derived hard carbon through pore closure can regulate sodium storage capacity. Chinese patent CN110921647B discloses a method for preparing a hard carbon anode for sodium-ion batteries. This patent uses sodium lignin sulfonate as a self-template to control the pore structure of its derived hard carbon; however, the excessively large open pores make it difficult for the hard carbon to close at high temperatures to form a closed-pore structure, resulting in a minimal increase in the reversible sodium storage capacity of the hard carbon prepared by this method, with a capacity of only 303 mAh·g. -1 .

[0006] The main reason hindering the formation of closed-cell structures in lignin during pyrolysis is that the abundant aromatic rings in lignin cause π-π stacking during pyrolysis, making it difficult to form disordered short-range graphite domains. Excessive long-range graphite domains further hinder the formation of closed-cell structures in lignin-derived hard carbon. Therefore, how to enable lignin-derived hard carbon to generate a large number of closed-cell structures during pyrolysis is a technical problem that needs to be solved. Summary of the Invention

[0007] To address the shortcomings and deficiencies of existing technologies, the primary objective of this invention is to provide a method for preparing modified lignin-derived hard carbon anode materials.

[0008] Another object of the present invention is to provide a modified lignin-derived hard carbon anode material prepared by the above preparation method.

[0009] Another object of the present invention is to provide the application of the above-mentioned modified lignin-derived hard carbon anode material.

[0010] The combination of large interlayer spacing and high closed-pore volume in lignin-derived hard carbon is beneficial for providing more active sites for sodium storage, thereby improving the specific capacity and plateau capacity of the hard carbon anode. This invention utilizes ammoniated lignin or quaternized lignin as the lignin carbon source, at least one of hexadecyltrimethylammonium bromide and sodium dodecylbenzenesulfonate as a dispersant, and at least one of sodium carboxymethyl cellulose and sodium alginate as a binder. Lignin-derived hard carbon is prepared through carbonization, acid washing, water washing, filtration, drying, and carbonization. During the carbonization process, the modified ammoniated lignin and quaternized lignin, due to the presence of nitrogen-containing functional groups with low bond energy, can effectively break the π-π stacking of aromatic rings during pyrolysis, increasing the proportion of disordered short-range graphite domains. The disordered stacking of short-range graphite domains leads to abundant closed-pore structures. The lignin-derived hard carbon material of this invention can be used in electrochemical energy storage fields such as sodium-ion battery anodes.

[0011] The objective of this invention is achieved through the following technical solution:

[0012] A method for preparing a modified lignin-derived hard carbon anode material for sodium-ion batteries includes the following steps:

[0013] (1) Mix ammoniated lignin and / or quaternized lignin, dispersant and binder evenly to obtain a precursor;

[0014] (2) The precursor is carbonized for the first time in a protective gas atmosphere, then acid-washed, water-washed, dried, and then carbonized for the second time in a protective gas atmosphere to obtain the modified lignin-derived hard carbon anode material for sodium-ion batteries.

[0015] Preferably, the ammonia-oxidized lignin in step (1) is prepared by the following method: using water as the reaction medium, ammonia, lignin and hydrogen peroxide are subjected to a hydrothermal reaction in a hydrothermal reactor to remove water and obtain ammonia-oxidized lignin.

[0016] More preferably, the ammonia water is added in the form of an ammonia solution, the concentration of which is 10-30 wt.%; the mass ratio of the ammonia solution to lignin is (1-3):(2-5), more preferably (2.5-2.8):(2-5).

[0017] The hydrogen peroxide is added in the form of a hydrogen peroxide solution, the concentration of which is 8-50 wt.%; the mass ratio of the hydrogen peroxide solution to lignin is 1:(2-5), more preferably 1:2.

[0018] More preferably, the ammonia water is added in the form of an ammonia solution, the concentration of which is 10-30 wt.%; and the mass ratio of the ammonia solution to water is 1:10-20.

[0019] More preferably, the temperature of the hydrothermal reaction is 110-130°C, more preferably 130°C, and the time is 1-2 hours, more preferably 1 hour.

[0020] More preferably, the order of adding the ammonia solution, lignin, and hydrogen peroxide is as follows: first, add the ammonia solution to the water, then add the lignin and stir until evenly mixed, then add the hydrogen peroxide solution and continue stirring until evenly mixed.

[0021] More preferably, the time for stirring and mixing to achieve uniformity is 0.5 to 1 hour.

[0022] More preferably, the lignin is at least one of the following: enzymatically hydrolyzed lignin extracted from biorefining residues, organic solvent lignin obtained from solvent pulping, and alkali lignin extracted from black liquor from alkaline pulping.

[0023] Preferably, the quaternized lignin in step (2) is prepared by the following method: lignin and 3-chloro-2-hydroxypropyltrimethylammonium chloride are heated and reacted in an aqueous solution with a pH of 11 to 13, then dialyzed and dried to obtain quaternized lignin.

[0024] More preferably, the lignin is at least one of the following: enzymatically hydrolyzed lignin extracted from biorefining residues, organic solvent lignin obtained from solvent pulping, and alkali lignin extracted from black liquor from alkaline pulping.

[0025] More preferably, the mass ratio of the lignin to 3-chloro-2-hydroxypropyltrimethylammonium chloride is (1-2):1; more preferably, it is 1:1.

[0026] More preferably, the heating reaction temperature is 80-90°C, more preferably 80°C; and the time is 3-6 hours, more preferably 6 hours.

[0027] More preferably, the order of adding lignin and 3-chloro-2-hydroxypropyltrimethylammonium chloride is as follows: first, add lignin to water to adjust the pH to 11-13, and then add 3-chloro-2-hydroxypropyltrimethylammonium chloride; wherein the mass ratio of lignin to water is 1:(2-4), more preferably 1:4; the pH adjuster is a 10-20 wt.% sodium hydroxide solution, more preferably a 20 wt.% sodium hydroxide solution.

[0028] More preferably, the drying temperature is 65–80°C and the time is 8–12 hours.

[0029] Preferably, in step (1), the mass ratio of lignin, dispersant and binder is 10:(0.5-1):(0.5-1), more preferably 10:0.5:0.5, wherein lignin refers to ammoniated lignin and / or quaternized lignin.

[0030] Preferably, the dispersant in step (1) is at least one of hexadecyltrimethylammonium bromide and sodium dodecylbenzenesulfonate.

[0031] Preferably, the adhesive in step (1) is at least one of sodium carboxymethyl cellulose and sodium alginate.

[0032] Preferably, the method for uniform mixing in step (1) is as follows: add ammoniated lignin and / or quaternized lignin and dispersant to water and stir evenly, then add binder and continue stirring evenly, and dry to obtain precursor.

[0033] More preferably, the drying temperature is 60–80°C and the time is 12–24 hours.

[0034] More preferably, the ratio of lignin to water is (10-20) g: (100-500) mL, even more preferably 20 g: (100-250) mL, wherein lignin refers to ammoniated lignin and / or quaternized lignin.

[0035] More preferably, the time for mixing is 2 to 5 hours.

[0036] Preferably, the protective gas in step (2) is at least one of nitrogen, argon and helium.

[0037] Preferably, the temperature of the first carbonization in step (2) is 400-800℃, more preferably 600-700℃, and the time is 0.5-5h, more preferably 2h; the temperature of the second carbonization is 1000-1500℃, more preferably 1200-1500℃, and the time is 2-6h, more preferably 2-5h.

[0038] Preferably, the heating rate of the two carbonization processes in step (2) is 1 to 10 °C / min, more preferably 5 °C / min, and the flow rate of the protective gas is 2 to 100 mL / min, more preferably 60 mL / min.

[0039] Preferably, the acid used for pickling in step (2) is at least one of dilute hydrochloric acid (0.5-2 mol / L), sulfuric acid (0.5-2 mol / L), and nitric acid (0.5-2 mol / L). Pickling refers to immersing the carbonized material in the acid and stirring for 2-48 hours.

[0040] Preferably, the water washing in step (2) refers to immersing the carbonized material in water and stirring for 12-48 hours, followed by filtration. The acid washing is followed by water washing and then drying; the drying temperature is 60-80℃ and the time is 8-12 hours.

[0041] A modified lignin-derived hard carbon anode material for sodium-ion batteries was prepared by the above method.

[0042] The specific surface area of ​​the modified lignin-derived hard carbon anode material used in the sodium-ion battery is 5–30 m². 2 It has the characteristics of few open pores and many closed pores; sodium metal half-cells assembled in 1 mol / L NaPF6 in DME electrolyte were tested at different current densities, and their specific capacity was 300–360 mAh·g. -1 .

[0043] The above-mentioned modified lignin-derived hard carbon anode material for sodium-ion batteries is used in sodium-ion batteries.

[0044] This invention aims to prepare hard carbon anodes for sodium-ion batteries using inexpensive lignin through modification. Traditional preparation methods typically use alkali metal salts as templates to create pores. The high mass ratio of template to carbon results in excessive open pores in the hard carbon, leading to a large specific surface area and poor sodium storage performance. This invention modifies lignin, adds a dispersant and mixes it uniformly with the lignin carbon source, and adds a binder to make the lignin carbon source structure dense, reducing preparation costs and achieving comprehensive resource utilization. The resulting hard carbon anode material has a small specific surface area and a high number of closed-pore structures, and also exhibits good electrochemical performance.

[0045] Furthermore, the preparation method of the modified lignin-derived hard carbon anode material for sodium-ion batteries proposed in this invention has advantages such as no corrosion to equipment, simple preparation process, and low preparation cost, which is conducive to large-scale production.

[0046] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0047] (1) This invention utilizes lignin, which is abundant and inexpensive, as a matrix. The lignin is modified by ammonia oxidation or quaternization to alter its pyrolysis behavior. The lignin carbon source is dispersed using a dispersant, and then a binder is used to densify the lignin carbon source structure. Finally, lignin-derived hard carbon for sodium-ion batteries is obtained through low-temperature carbonization, acid washing, and high-temperature carbonization. Therefore, this invention has the advantages of being environmentally friendly, having a simple preparation process, and being low-cost.

[0048] (2) The carbon material obtained in this invention has a small specific surface area and abundant closed-pore structure. The abundant closed-pore structure can provide pore-filled sodium storage micro-points for the platform capacity, thereby improving the capacity and rate performance of sodium-ion batteries.

[0049] (3) This invention uses inexpensive lignin resources to prepare hard carbon materials that can be used as anodes of sodium-ion batteries, realizing the comprehensive utilization of resources in the material preparation process, which is conducive to industrial promotion and application. Attached Figure Description

[0050] Figure 1 This is a flowchart illustrating the preparation process of lignin-derived hard carbon for sodium-ion batteries according to this application.

[0051] Figure 2 The image shows the XRD pattern of quaternized lignin-derived hard carbon (QALHC) from Example 1.

[0052] Figure 3 Raman diagram of quaternized lignin-derived hard carbon (QALHC) from Example 1.

[0053] Figure 4 The image shows the SAXS diagram of quaternized lignin-derived hard carbon (QALHC) from Example 1.

[0054] Figure 5 The image shows a SEM image (magnification 10,000x) of quaternized lignin-derived hard carbon (QALHC) from Example 1.

[0055] Figure 6 The nitrogen adsorption-desorption isotherm curve of quaternized lignin-derived hard carbon (QALHC) in Example 1 is shown.

[0056] Figure 7 This is a pore size distribution diagram of quaternized lignin-derived hard carbon (QALHC) from Example 1.

[0057] Figure 8 Example 1: Quaternized lignin-derived hard carbon (QALHC) used as the negative electrode in a sodium-ion battery. The specific capacity of QALHC is shown as a line graph of current density.

[0058] Figure 9 Example 1: Quaternized lignin-derived hard carbon (QALHC) was used as the negative electrode in a sodium-ion battery at 1 A·g -1 Cyclic performance at current density.

[0059] Figure 10 SAXS plot of lignin-derived hard carbon (QALHC) for Comparative Example 1. Detailed Implementation

[0060] The present invention will be further described in detail below with reference to the embodiments and accompanying drawings, but the implementation of the present invention is not limited thereto.

[0061] Unless otherwise specified in the embodiments of this invention, the conditions shall be performed according to conventional conditions or conditions recommended by the manufacturer. All raw materials and reagents used, unless otherwise specified, are commercially available conventional products.

[0062] Example 1

[0063] (1) Dissolve 50g of dried enzymatically hydrolyzed lignin in 200mL of deionized water and adjust the pH to 12.0 with 20wt.% NaOH. Add 50g of 3-chloro-2-hydroxypropyltrimethylammonium chloride and react at 80℃ for 6h. Use a dialysis bag (1000Da MWCO) to remove unreacted small molecules and inorganic salts and purify the solution by dialysis. After drying, grind to obtain quaternized lignin (QAL).

[0064] (2) Add 20g of quaternized lignin, 1g of hexadecyltrimethylammonium bromide and 250mL of ultrapure water to a 500mL beaker in sequence, stir to mix the quaternized lignin and hexadecyltrimethylammonium bromide thoroughly, and continue stirring for 3h.

[0065] (3) Add 1g of sodium carboxymethyl cellulose to the solution in step (2) and stir for 3 hours.

[0066] (4) Place the solution from step (3) in a 75°C oven to dry the solution and obtain a solid.

[0067] (5) The solid from step (4) was heated to 700℃ for 2h under a nitrogen atmosphere and a gas flow rate of 60mL / min at a heating rate of 5℃ / min. After the reaction was completed, it was soaked in 1mol / L hydrochloric acid for 12h, washed with deionized water for 12h, vacuum filtered and dried at 75℃ for 10h to obtain quaternized lignin-derived porous carbon, named QAL-700.

[0068] (6) QAL-700 was heated to 1400℃ for 2h in a nitrogen atmosphere at a gas flow rate of 60mL / min and a heating rate of 5℃ / min to obtain quaternized lignin-derived hard carbon, named QALHC.

[0069] The prepared QALHC has a 7.1m... 2 The QALHC hard carbon anode has a relatively small specific surface area per g. X-ray diffraction (XRD) and Raman spectroscopy patterns are shown below. Figure 2 and Figure 3 As shown, Figure 2 Two broad peaks appear near 23° and 44°, corresponding to the (002) and (100) crystal planes of the carbon material. The interlayer spacing of QALHC was calculated to be 0.380 nm, and the ID1 / IG value was calculated to be 2.40. This indicates that QALHC has a disordered carbon layer structure and a large interlayer spacing, which is conducive to the intercalation of sodium ions.

[0070] QALHC, conductive carbon black and PVDF (polyvinylidene fluoride) were mixed in a mass ratio of 8:1:1 and coated onto copper foil. After drying, the mixture was cut into circular electrode sheets with a radius of 6 mm for later use.

[0071] Scanning electron microscope (SEM) image of QALHC as shown below Figure 5 As shown, the morphology of quaternized lignin-derived hard carbon is blocky with a relatively smooth surface and some micropores.

[0072] Figure 6 and Figure 7 The nitrogen adsorption-desorption curves and pore size distribution diagrams for QALHC are shown. Figure 6 The increase in nitrogen adsorption at low adsorption pressure indicates the presence of micropores, while the significant increase in nitrogen adsorption and the lag adsorption ring at high adsorption pressure indicate the presence of mesopores. Figure 7 The aperture distribution map also verifies this conclusion.

[0073] The prepared sodium-ion battery electrode sheet was used as the negative electrode, the sodium metal sheet was used as the positive electrode, and 1 mol / L NaPF6 inDME was used as the electrolyte to assemble a sodium-ion button cell, and the electrochemical performance of the QALHC was tested.

[0074] Figure 8 A dotted graph showing the specific capacity of QALHC as the negative electrode in a sodium-ion battery as a function of current density. (At 0.05 A·g) -1 At a current density of 354 mAh·g, the QALHC has a capacity of 354 mAh·g. -1 The specific capacity is at 5 A·g -1 It still has 134mAh·g -1 The specific capacity indicates that QALHC has excellent rate performance when applied to the anode of sodium-ion batteries. Figure 9 This indicates that the half-cell operates at 1 A·g -1 After 1000 cycles, it has a capacity retention rate of 87.1%.

[0075] Example 2

[0076] (1) Add 10g of commercially available ammonia solution (25-28wt.%) to 200mL of deionized water; slowly add 10g of dried enzymatically hydrolyzed lignin and stir for 30 minutes; add 5g of a quantitative amount of commercially available hydrogen peroxide solution (30wt.%), continue stirring for 30 minutes, and then transfer to a hydrothermal reactor; hydrothermally react at 130℃ for 1h; after the hydrothermal reactor cools down, remove water and unreacted substances by rotary evaporation of the reaction solution, and then vacuum dry at 80℃ and grind to obtain ammonia-oxidized lignin (AOL).

[0077] (2) Add 20g of ammonia-oxidized lignin, 1g of hexadecyltrimethylammonium bromide and 100mL of ultrapure water to a 500mL beaker in sequence, stir to mix the ammonia-oxidized lignin and hexadecyltrimethylammonium bromide thoroughly, and continue stirring for 3h.

[0078] (3) Add 1g of sodium carboxymethyl cellulose to the solution in step (2) and stir for 3 hours.

[0079] (4) Place the solution from step (3) in a 75°C oven to dry the solution and obtain a solid.

[0080] (5) The solid from step (4) was heated to 700℃ for 2h under a nitrogen atmosphere and a gas flow rate of 60mL / min at a heating rate of 5℃ / min. After the reaction was completed, it was soaked in 1mol / L hydrochloric acid for 12h, washed with deionized water for 12h, vacuum filtered and dried at 75℃ for 10h to obtain ammonia-oxidized lignin-derived porous carbon, named AOL-700.

[0081] (6) AOL-700 was heated to 1500℃ for 4h in a nitrogen atmosphere at a gas flow rate of 60mL / min and a heating rate of 5℃ / min to obtain ammonia-oxidized lignin-derived hard carbon, which was named AOLHC.

[0082] (6) The prepared AOLHC has a 20.3m 2 Smaller specific surface area per g.

[0083] AOLHC, conductive carbon black, and PVDF (polyvinylidene fluoride) were mixed in a mass ratio of 8:1:1 and coated onto copper foil. After drying, the mixture was cut into circular electrode sheets with a radius of 6 mm for later use.

[0084] The prepared sodium-ion battery electrode sheet was used as the negative electrode, the sodium metal sheet was used as the positive electrode, and 1 mol / L NaPF6 inDME was used as the electrolyte to assemble a sodium-ion button cell, and the electrochemical performance of AOLHC was tested.

[0085] AOLHC at 0.05 A·g -1 At a current density, AOLHC has 339 mAh·g -1 The specific capacity is at 5 A·g -1 It still has 131mAh·g -1 The specific capacity indicates that AOLHC has excellent rate performance when applied to the anode of sodium-ion batteries.

[0086] Example 3

[0087] (1) Dissolve 100g of dried enzymatically hydrolyzed lignin in 200mL of deionized water and adjust the pH to 12.0 with 20wt.% NaOH. Add 50g of 3-chloro-2-hydroxypropyltrimethylammonium chloride and react at 90℃ for 3h. Use a dialysis bag (1000Da MWCO) to remove unreacted small molecules and inorganic salts and purify the solution by dialysis. After drying, grind to obtain quaternized lignin (QAL).

[0088] (2) Add 20g of quaternized lignin, 2g of hexadecyltrimethylammonium bromide and 250mL of ultrapure water to a 500mL beaker in sequence, stir to mix the quaternized lignin and hexadecyltrimethylammonium bromide thoroughly, and continue stirring for 3h.

[0089] (3) Add 2g of sodium carboxymethyl cellulose to the solution in step (2) and stir for 3 hours.

[0090] (4) Place the solution from step (3) in a 75°C oven to dry the solution and obtain a solid.

[0091] (5) The solid from step (4) was heated to 600℃ for 2h under a nitrogen atmosphere and a gas flow rate of 60mL / min at a heating rate of 5℃ / min. After the reaction was completed, it was soaked in 1mol / L hydrochloric acid for 12h, washed with deionized water for 12h, vacuum filtered and dried at 75℃ for 10h to obtain quaternized lignin-derived porous carbon, named QAL-600.

[0092] (6) QAL-600 was heated to 1200℃ for 6h in a nitrogen atmosphere at a gas flow rate of 60mL / min and a heating rate of 5℃ / min to obtain quaternized lignin-derived hard carbon, named QALHC-2.

[0093] QALHC-2 at 0.05 A·g -1 At a current density of 348 mAh·g, QALHC-2 has a capacity of 348 mAh·g. -1 The specific capacity is at 5 A·g -1 It still has 123mAh·g -1 The specific capacity indicates that QALHC-2 has excellent rate performance when applied as a negative electrode in sodium-ion batteries.

[0094] Example 4

[0095] (1) Add 20g of commercially available ammonia solution (25-28wt.%) to 200mL of deionized water; slowly add 40g of dried enzymatically hydrolyzed lignin and stir for 30 minutes; add 8g of a quantitative amount of commercially available hydrogen peroxide solution (30wt.%), continue stirring for 30 minutes, and then transfer to a hydrothermal reactor; hydrothermally react at 110℃ for 2 hours; after the hydrothermal reactor cools down, remove water and unreacted substances by rotary evaporation of the reaction solution, and then vacuum dry at 80℃ and grind to obtain ammonia-oxidized lignin (AOL).

[0096] (2) Add 20g of ammonia-oxidized lignin, 2g of hexadecyltrimethylammonium bromide and 100mL of ultrapure water to a 500mL beaker in sequence, stir to mix the ammonia-oxidized lignin and hexadecyltrimethylammonium bromide thoroughly, and continue stirring for 3h.

[0097] (3) Add 2g of sodium carboxymethyl cellulose to the solution in step (2) and stir for 3 hours.

[0098] (4) Place the solution from step (3) in a 75°C oven to dry the solution and obtain a solid.

[0099] (5) The solid from step (4) was heated to 600℃ for 2h under a nitrogen atmosphere and a gas flow rate of 60mL / min at a heating rate of 5℃ / min. After the reaction was completed, it was soaked in 1mol / L hydrochloric acid for 12h, washed with deionized water for 12h, vacuum filtered and dried at 75℃ for 10h to obtain ammonia-oxidized lignin-derived porous carbon, named AOL-600.

[0100] (6) AOL-600 was heated to 1300℃ for 5h in a nitrogen atmosphere at a gas flow rate of 60mL / min and a heating rate of 5℃ / min to obtain ammonia-oxidized lignin-derived hard carbon, named AOLHC-2.

[0101] AOLHC-2 at 0.05 A·g -1 At a current density of 344 mAh·g, the AOLHC has a current density of 344 mAh·g. -1 The specific capacity is at 5 A·g -1 It still has 118mAh·g -1 The specific capacity indicates that AOLHC has excellent rate performance when applied to the anode of sodium-ion batteries.

[0102] Comparative Example 1

[0103] (1) Add 20g of enzymatically hydrolyzed lignin, 1g of hexadecyltrimethylammonium bromide and 250mL of ultrapure water to a 500mL beaker in sequence. Stir to mix the lignin and hexadecyltrimethylammonium bromide thoroughly, and continue stirring for 3h.

[0104] (2) Add 1g of sodium carboxymethyl cellulose to the solution in step (1) and stir for 3h.

[0105] (3) The solution from step (2) was placed in an oven at 75°C to dry the solution and obtain a solid.

[0106] (4) The solid from step (3) was heated to 700℃ for 2h under a nitrogen atmosphere and a gas flow rate of 60mL / min at a heating rate of 5℃ / min. After the reaction was completed, it was soaked in 1mol / L hydrochloric acid for 12h, washed with deionized water for 12h, vacuum filtered and dried at 75℃ for 10h to obtain lignin-derived porous carbon, named AL-700.

[0107] (5) AL-700 was heated to 1400℃ for 2h in a nitrogen atmosphere at a gas flow rate of 60mL / min and a heating rate of 5℃ / min to obtain lignin-derived hard carbon, which was named ALHC.

[0108] The prepared ALHC has a 2.9m... 2 The sodium-ion battery has a relatively small specific surface area. ALHC, conductive carbon black, and PVDF (polyvinylidene fluoride) were mixed in a mass ratio of 8:1:1 and coated onto copper foil. After drying, the mixture was cut into circular electrode sheets with a radius of 6 mm. The prepared sodium-ion battery electrode sheet was used as the negative electrode, a sodium metal sheet as the positive electrode, and 1 mol / L NaPF6 in DME as the electrolyte to assemble a sodium-ion button cell. The electrochemical performance of the ALHC was then tested.

[0109] At 0.05 A·g -1 At a current density of 301 mAh·g -1 The specific capacity is at 5 A·g -1 It has a capacity of 99mAh·g -1 The specific capacity indicates that the rate performance of ALHC applied to the negative electrode of sodium-ion batteries is worse than that in Examples 1 and 2.

[0110] Comparative Example 2

[0111] (1) Add 20g of ammoniated lignin (obtained in Example 2), 1g of hexadecyltrimethylammonium bromide and 100mL of ultrapure water to a 500mL beaker in sequence, stir to mix the ammoniated lignin and hexadecyltrimethylammonium bromide thoroughly, and continue stirring for 3h.

[0112] (3) Add 1g of sodium carboxymethyl cellulose to the solution in step (2) and stir for 3 hours.

[0113] (4) Place the solution from step (3) in a 75°C oven to dry the solution and obtain a solid.

[0114] (5) The solid from step (4) was heated to 700℃ for 2h under a nitrogen atmosphere and a gas flow rate of 60mL / min at a heating rate of 5℃ / min. After the reaction was completed, it was soaked in 1mol / L hydrochloric acid for 12h, washed with deionized water for 12h, vacuum filtered and dried at 75℃ for 10h to obtain ammonia-oxidized lignin-derived porous carbon, named AOL-700.

[0115] (6) AOL-700 was heated to 900℃ for 2h in a nitrogen atmosphere at a gas flow rate of 60mL / min and a heating rate of 5℃ / min to obtain ammonia-oxidized lignin-derived hard carbon, named AOLHC-3.

[0116] Comparative Example 3

[0117] (1) Add 20g of quaternized lignin (obtained in Example 1), 1g of hexadecyltrimethylammonium bromide and 250mL of ultrapure water to a 500mL beaker in sequence, stir to mix the quaternized lignin and hexadecyltrimethylammonium bromide thoroughly, and continue stirring for 3h.

[0118] (3) Add 1g of sodium carboxymethyl cellulose to the solution in step (2) and stir for 3 hours.

[0119] (4) Place the solution from step (3) in a 75°C oven to dry the solution and obtain a solid.

[0120] (5) The solid from step (4) was heated to 700℃ for 2h under a nitrogen atmosphere and a gas flow rate of 60mL / min at a heating rate of 5℃ / min. After the reaction was completed, it was soaked in 1mol / L hydrochloric acid for 12h, washed with deionized water for 12h, vacuum filtered and dried at 75℃ for 10h to obtain quaternized lignin-derived porous carbon, named QAL-700.

[0121] (6) QAL-700 was heated to 1700℃ for 2h in a nitrogen atmosphere at a gas flow rate of 60mL / min and a heating rate of 5℃ / min to obtain quaternized lignin-derived hard carbon, named QALHC-3.

[0122] Table 1. Capacity of the negative electrode materials in Examples 1-4 and Comparative Examples 1-3

[0123]

[0124] The above embodiments are preferred embodiments of the present invention, but the embodiments of the present invention are not limited to the above embodiments. Any changes, modifications, substitutions, combinations, or simplifications made without departing from the spirit and principle of the present invention shall be considered equivalent substitutions and shall be included within the protection scope of the present invention.

Claims

1. A method for preparing a modified lignin-derived hard carbon negative electrode material, characterized in that, The method comprises the following steps: (1) uniformly mixing aminated lignin and / or quaternary ammonium lignin, a dispersing agent and a binder to obtain a precursor; (2) performing first carbonization on the precursor in a protective gas atmosphere, then performing acid washing, water washing and drying, and then performing second carbonization on the precursor in a protective gas atmosphere to obtain a modified lignin-derived hard carbon negative electrode material; In step (1), the aminated lignin is obtained by the following method: hydrothermal reaction of ammonia, lignin and hydrogen peroxide in a hydrothermal kettle in water as a reaction medium, and then removing water; In step (1), the quaternary ammonium lignin is obtained by the following method: heating reaction of lignin and 3-chloro-2-hydroxypropyl trimethyl ammonium chloride in an aqueous solution with a pH of 11-13, dialysis and drying to obtain the quaternary ammonium lignin; The temperature of the second carbonization is 1000-1500 ℃, and the time is 2-6 h.

2. The method for preparing a modified lignin-derived hard carbon anode material according to claim 1, characterized in that, The ammonia is added in the form of an ammonia solution, the concentration of the ammonia solution is 10-30 wt.%, and the mass ratio of the ammonia solution to the lignin is (1-3):(2-5); The hydrogen peroxide is added in the form of a hydrogen peroxide solution, the concentration of the hydrogen peroxide solution is 8-50 wt.%, and the mass ratio of the hydrogen peroxide solution to the lignin is 1:(2-5); The temperature of the hydrothermal reaction is 110-130 ℃, and the time is 1-2 h; The lignin is at least one of enzymatic hydrolysis lignin extracted from a bio-refinery residue, organic solvent lignin obtained by solvent pulping and alkali lignin extracted from black liquor of alkali pulping.

3. The method for preparing a modified lignin-derived hard carbon anode material according to claim 1, characterized in that, The mass ratio of the lignin to 3-chloro-2-hydroxypropyl trimethyl ammonium chloride is (1-2):1, the heating reaction temperature is 80-90 ℃, and the time is 3-6 h; The lignin is at least one of enzymatic hydrolysis lignin extracted from a bio-refinery residue, organic solvent lignin obtained by solvent pulping and alkali lignin extracted from black liquor of alkali pulping.

4. The method for preparing a modified lignin-derived hard carbon anode material according to claim 1, characterized in that, In step (1), the mass ratio of the lignin, the dispersing agent and the binder is 10:(0.5-1):(0.5-1), wherein the lignin refers to aminated lignin and / or quaternary ammonium lignin; In step (1), the dispersing agent is at least one of cetyl trimethyl ammonium bromide and sodium dodecyl benzene sulfonate; In step (1), the binder is at least one of sodium carboxymethyl cellulose and sodium alginate.

5. The method for preparing a modified lignin-derived hard carbon anode material according to claim 1, characterized in that, In step (2), the temperature of the first carbonization is 400-800 ℃, and the time is 0.5-5 h.

6. The method for preparing a modified lignin-derived hard carbon anode material according to claim 1, characterized in that, In step (1), the method for uniformly mixing is as follows: the aminated lignin and / or quaternary ammonium lignin and the dispersing agent are added into water and stirred uniformly, then the binder is added and stirred uniformly, and then drying is performed to obtain the precursor; the ratio of the lignin to water is (10-20) g:(100-500) mL, wherein the lignin refers to aminated lignin and / or quaternary ammonium lignin; In step (2), the protective gas is at least one of nitrogen, argon and helium; In step (2), the temperature rising rate of the two carbonizations is 1-10 ℃ / min, and the flow rate of the protective gas is 2-100 mL / min. The acid used in the pickling in step (2) is at least one of 0.5-2 mol / L dilute hydrochloric acid, 0.5-2 mol / L sulfuric acid and 0.5-2 mol / L nitric acid, and the pickling refers to immersing the carbonized material in the acid and stirring for 2-48 h.

7. The method for preparing a modified lignin-derived hard carbon anode material according to claim 1, characterized in that, The ammonia water is added in the form of an ammonia water solution, the concentration of the ammonia water solution is 10-30 wt.%, and the ratio of the ammonia water solution to water is 1:(5-20). The feeding sequence of the ammonia water, the lignin and the hydrogen peroxide is: first adding the ammonia water solution into water, then adding the lignin and stirring to mix uniformly, and then adding the hydrogen peroxide solution and continuing to stir to mix uniformly.

8. The method for preparing a modified lignin-derived hard carbon anode material according to claim 1, characterized in that, The feeding sequence of the lignin and 3-chloro-2-hydroxypropyltrimethylammonium chloride is: first adding the lignin into water, adjusting the pH to 11-13, and then adding 3-chloro-2-hydroxypropyltrimethylammonium chloride; wherein the mass ratio of the lignin to water is 1:(2-4), and the adjusting agent used for adjusting the pH is a 10-20 wt.% sodium hydroxide solution.

9. A modified lignin derivative hard carbon negative electrode material prepared by the preparation method in any one of claims 1-8.

10. The use of the modified lignin derivative hard carbon negative electrode material in claim 9 in the field of batteries.

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