A method for preparing sodium ion hard carbon from lignin modified phenol-formaldehyde resin doped with S in situ

Abstract

The application discloses a method for preparing sodium ion hard carbon by using lignin modified phenolic resin doped with S in situ, and belongs to the technical field of lignin modification, phenolic resin synthesis and sodium ion negative electrode hard carbon material preparation. In the method, anhydrous sodium sulfite is added by using a hydrothermal method, S elements are doped in lignin in situ, and then copolymerization is carried out with a phenolic prepolymer to obtain sulfonated lignin phenolic resin. After curing and high-temperature carbonization treatment, sulfonated lignin modified phenolic resin based hard carbon is prepared. In the method, S elements are doped in situ, the conductivity of the material can be improved, the specific surface area of the material can be influenced, and the characteristics of the electrochemical performance of the material can be improved, so that the directional regulation of the structure of the sulfonated lignin phenolic resin is realized. The method solves the problems of poor storage performance caused by small interlayer spacing, poor conductivity and large specific surface area of the lignin phenolic resin hard carbon.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of lignin modification, phenolic resin synthesis and sodium ion negative electrode hard carbon material preparation, and particularly relates to a method for preparing sodium ion hard carbon from lignin modified phenolic resin with in-situ S doping. BACKGROUND

[0002] The advantages of phenolic resin hard carbon include good application prospects, fast market growth, and good application in the field of sodium battery and lithium battery negative electrode doping. Phenolic resin hard carbon is expected to be applied first due to its relatively small production process difficulty. In addition, the demand for hard carbon material is expected to increase from 0.2 million tons / year in 2022 to 10.5 million tons / year in 2025, showing the rapid growth potential of the market. In terms of market space, it is expected that the market space of hard carbon material will reach 6.3 billion yuan by 2025. In summary, as a potential negative electrode material, phenolic resin hard carbon has broad application prospects and rapid market growth expectations, but it also faces technical difficulties and performance challenges. The main problem is that the oxygen content of the material is low, the interlayer spacing of the prepared hard carbon material is low, and the number of microcrystals is small, so it is necessary to further improve its performance and application range through technical innovation and material optimization.

[0003] The advantages of biomass modified phenolic resin mainly lie in improving mechanical properties, reducing free formaldehyde release, improving thermal stability, enhancing wear resistance and impact resistance, and improving dimensional stability, making it have wide application prospects in many fields. Lignin and its derivatives are representative substances of biological raw materials, which have rich oxygen-containing functional groups and can react with phenolic resin under certain conditions to improve the chemical properties of phenolic resin.

[0004] High S content of hard carbon material can improve the diffusion rate of Na+, cause the expansion of interlayer spacing, enhance porosity and form defects, which is beneficial to the improvement of sodium storage performance. Since lignin itself contains S element, in-situ doping of S on lignin molecules can be considered, and then the reactive sites are exposed by oxidation and reacted with phenolic resin prepolymer to modify the structure of phenolic resin, thereby changing the chemical structure and sodium storage performance of lignin phenolic resin hard carbon sodium ion negative electrode material and providing advantages for its application in the field of sodium ion battery. SUMMARY

[0005] The first object of the present application is to provide a method for preparing sodium ion hard carbon from lignin modified phenolic resin with in-situ S doping. The S content of lignin is regulated by in-situ doping technology, and the number of sulfur-containing groups on lignin is increased by sulfonation pretreatment. The sulfur-containing groups and oxygen-containing functional groups on sulfonated lignin are exposed by subsequent oxidation, which is beneficial to the modification of phenolic resin by sulfonated lignin, and realizes the controllable regulation of lignin with in-situ S doping on the molecular structure of phenolic resin.

[0006] The second object of the present application is to provide a sodium ion hard carbon prepared from a lignin modified phenolic resin in-situ doped with S, which has increased interlayer spacing of carbon microcrystals, increased number of ultramicropores and reduced specific surface area, so that a thinner and more uniform SEI film is formed during sodium storage.

[0007] The third object of the present application is to disclose an application of the sulfonated lignin phenolic resin based hard carbon in a sodium ion battery negative electrode material, which exhibits excellent initial efficiency and reversible capacity.

[0008] To solve the above problems, the technical solution adopted by the present application is as follows:

[0009] A method for preparing a sodium ion hard carbon from a lignin modified phenolic resin in-situ doped with S, first preparing a sulfonated lignin by hydrothermal method using sodium lignosulfonate and anhydrous sodium sulfite, then oxidizing the sulfonated lignin and condensing it with a phenolic resin prepolymer to obtain a sulfonated lignin phenolic resin; and then curing and carbonizing the sulfonated lignin phenolic resin to obtain a sulfonated lignin modified phenolic resin based hard carbon.

[0010] Further, the mass ratio of the sodium lignosulfonate to the anhydrous sodium sulfite is 1:2 to 2:1.

[0011] Further, the mass ratio of the sodium lignosulfonate to the anhydrous sodium sulfite is 1:1.225.

[0012] Further, the preparation method of the sulfonated lignin is as follows: dissolving the sodium lignosulfonate and the anhydrous sodium sulfite in a NaOH aqueous solution, stirring for 1 h, and then heating to prepare the sulfonated lignin; and after separation, water washing, drying and grinding treatment, the sulfonated lignin powder is obtained.

[0013] Further, the heating temperature is 100-200 DEG C.

[0014] Further, the heating temperature is 160 DEG C.

[0015] Further, the heating time is 2-6 h.

[0016] Further, the heating time is 4 h.

[0017] Further, the sulfonated lignin phenolic resin based hard carbon prepared by any of the above methods.

[0018] Further, the application of the sulfonated lignin phenolic resin based hard carbon in a sodium ion battery negative electrode material.

[0019] Compared with the prior art, the present application has the following advantages:

[0020] 1) The present application utilizes the sulfonation of in-situ doping S to expose more oxygen functional groups and sulfur-containing groups on lignin by increasing the sulfur-containing groups of lignin and subsequent oxidation, realizes the directional regulation of sulfonated lignin on the molecular structure of phenolic resin, and solves the problems of regulating S and O elements on the molecular structure of lignin, increasing the qualitative content of sulfur and oxygen-containing groups on phenolic resin, and the unfavorable storage performance of the interlayer spacing and pore structure of modified phenolic resin and hard carbon.

[0021] 2) The present application utilizes the sulfonated lignin pretreatment to modify the phenolic resin raw material to prepare hard carbon, which has excellent sodium storage performance and low toxicity compared to the traditional phenolic resin-based hard carbon preparation method, and the molecular structure of the sulfonated lignin modified phenolic resin hard carbon precursor is modified, the interlayer spacing of the sulfonated lignin phenolic resin-based hard carbon is increased, the specific surface area is reduced, and the number of ultramicropore area is increased, which is beneficial to improve the electrochemical performance of the sodium ion battery negative material.

[0022] 3) The preparation method disclosed by the present application is simple in operation, low in energy consumption, and low in requirement for equipment, and has reference significance for other types of biomass modified phenolic resin and the preparation of hard carbon materials. BRIEF DESCRIPTION OF DRAWINGS

[0023] Figure 1 XRD patterns of sulfonated lignin reactions under different optimization conditions in Examples 2-5 of the present application;

[0024] Figure 2 XRD patterns of sulfonated lignin reactions under different optimization conditions in Examples 3 and 8-10 of the present application;

[0025] Figure 3 XRD patterns of sulfonated lignin reactions under different optimization conditions in Examples 3 and 11-13 of the present application. DETAILED DESCRIPTION

[0026] In order to make the above-mentioned purposes, features and advantages of the present application more obvious and easy to understand, the specific embodiments of the present application will be described in detail below.

[0027] In the following examples, unless otherwise specified, the technical means used are conventional means known to those skilled in the art. If no specific conditions are noted in the examples, the conventional conditions or the conditions recommended by the manufacturer are used. If no manufacturer of the reagent or instrument is noted, it is a conventional product that can be obtained by market purchase.

[0028] The test methods used in the present application are as follows:

[0029] 1. Molecular structure property test

[0030] X-ray diffraction (XRD) was used to analyze the structure of the hard carbon using Cu Ka radiation at a scan rate of 5 ° / min; the molecular weight of the sample (GPC) was tested using a waters 1525 & Agilent PL-GPC220, and the solvent was water and chloroform.

[0031] 2. Battery performance test (discharge specific capacity (mAh g -1 ) and initial efficiency)

[0032] 2.1 Battery production

[0033] Preparation of electrodes: hard carbon material, conductive agent (super-P) and binder (PVDF) were mixed in a mass ratio of 7:1:1, and a slurry was prepared using NMP as a dispersant. The slurry was coated on a copper foil and dried in a forced air drying oven at 80°C for 12h. The dried electrode sheet was punched into a circular electrode sheet with a diameter of 15mm for standby use.

[0034] Assembling of button half-cell: the battery was assembled in an argon glove box with moisture and oxygen content less than 0.01ppm, using a CR2032 specification battery shell, and the electrolyte was 1mol / L NaPF6 (solvent was a mixed solution of ethylene carbonate: dimethyl carbonate: methyl ethyl carbonate in a volume ratio of 1:1:1), and a metal sodium sheet was used as both the counter electrode and the reference electrode, and the separator was a GF / D glass fiber separator. The battery was assembled in the order of positive shell, electrode sheet, separator, sodium sheet, gasket, spring and negative shell from bottom to top.

[0035] 2.2 Performance test

[0036] Constant current charge-discharge test (GCD) was tested on CT-4008Tn battery detection system.

[0037] Comparative example

[0038] 5g of lignin was oxidized, and then condensed with phenolic resin prepolymer to prepare sulfonated lignin modified phenolic resin, and finally carbonized and high-temperature refined to obtain sulfonated lignin modified phenolic resin hard carbon.

[0039] Example 1

[0040] A method for preparing sodium ion hard carbon by in-situ doping S modified lignin phenolic resin, the steps are as follows:

[0041] (1) First, 5g of sodium lignosulfonate and 2.5g of anhydrous sodium sulfite were dissolved in 30mL of 3mol / L NaOH aqueous solution, stirred for 1h, and then transferred to a high-pressure reaction kettle at 160°C for 3h to prepare a sulfonated lignin mixture;

[0042] (2) The sulfonated lignin mixture prepared in step (1) is separated, washed with water, dried, and ground to obtain sulfonated lignin powder;

[0043] (3) 5g of the sulfonated lignin powder obtained in step (2) is first oxidized, then subjected to polycondensation with phenolic resin prepolymer to prepare sulfonated lignin modified phenolic resin, and finally carbonized and high-temperature refined to obtain sulfonated lignin modified phenolic resin hard carbon.

[0044] Example 2

[0045] A method for preparing sodium ion hard carbon by in-situ doping S of lignin modified phenolic resin, the steps are as follows:

[0046] (1) First, 5g of lignin sodium sulfonate and 5g of anhydrous sodium sulfite are dissolved in 30mL of 3mol / L NaOH aqueous solution, stirred for 1h, and transferred to a high-pressure reaction kettle at 160℃ for 3h to prepare a sulfonated lignin mixture;

[0047] (2) The sulfonated lignin mixture prepared in step (1) is separated, washed with water, dried, and ground to obtain sulfonated lignin powder;

[0048] (3) 5g of the sulfonated lignin powder obtained in step (2) is first oxidized, then subjected to polycondensation with phenolic resin prepolymer to prepare sulfonated lignin modified phenolic resin, and finally carbonized and high-temperature refined to obtain sulfonated lignin modified phenolic resin hard carbon.

[0049] Example 3

[0050] A method for preparing sodium ion hard carbon by in-situ doping S of lignin modified phenolic resin, the steps are as follows:

[0051] (1) First, 5g of lignin sodium sulfonate and 6.125g of anhydrous sodium sulfite are dissolved in 30mL of 3mol / L NaOH aqueous solution, stirred for 1h, and transferred to a high-pressure reaction kettle at 160℃ for 3h to prepare a sulfonated lignin mixture;

[0052] (2) The sulfonated lignin mixture prepared in step (1) is separated, washed with water, dried, and ground to obtain sulfonated lignin powder;

[0053] (3) 5g of the sulfonated lignin powder obtained in step (2) is first oxidized, then subjected to polycondensation with phenolic resin prepolymer to prepare sulfonated lignin modified phenolic resin, and finally carbonized and high-temperature refined to obtain sulfonated lignin modified phenolic resin hard carbon.

[0054] Example 4

[0055] A method for preparing sodium ion hard carbon by in-situ doping S of lignin modified phenolic resin, the steps are as follows:

[0056] (1) First, 5g of sodium lignosulfonate and 7.5g of anhydrous sodium sulfite are dissolved in 30mL of 3mol / L NaOH aqueous solution, stirred for 1h, transferred to a high-pressure reaction kettle at 160℃ and reacted for 3h to prepare a sulfonated lignin mixed solution;

[0057] (2) The sulfonated lignin mixed solution prepared in step (1) is separated, washed with water, dried, and ground to obtain sulfonated lignin powder;

[0058] (3) 5g of the sulfonated lignin powder obtained in step (2) is first oxidized, then polycondensed with phenolic resin prepolymer to prepare sulfonated lignin modified phenolic resin, and finally carbonized and high-temperature refined to obtain sulfonated lignin modified phenolic resin hard carbon.

[0059] Example 5

[0060] A method for preparing sodium ion hard carbon by in-situ doping S of lignin modified phenolic resin, the steps are as follows:

[0061] (1) First, 5g of sodium lignosulfonate and 8.125g of anhydrous sodium sulfite are dissolved in 30mL of 3mol / L NaOH aqueous solution, stirred for 1h, transferred to a high-pressure reaction kettle at 160℃ and reacted for 3h to prepare a sulfonated lignin mixed solution;

[0062] (2) The sulfonated lignin mixed solution prepared in step (1) is separated, washed with water, dried, and ground to obtain sulfonated lignin powder;

[0063] (3) 5g of the sulfonated lignin powder obtained in step (2) is first oxidized, then polycondensed with phenolic resin prepolymer to prepare sulfonated lignin modified phenolic resin, and finally carbonized and high-temperature refined to obtain sulfonated lignin modified phenolic resin hard carbon.

[0064] Example 6

[0065] A method for preparing sodium ion hard carbon by in-situ doping S of lignin modified phenolic resin, the steps are as follows:

[0066] (1) First, 5g of sodium lignosulfonate and 10g of anhydrous sodium sulfite are dissolved in 30mL of 3mol / L NaOH aqueous solution, stirred for 1h, transferred to a high-pressure reaction kettle at 160℃ and reacted for 3h to prepare a sulfonated lignin mixed solution;

[0067] (2) The sulfonated lignin mixed solution prepared in step (1) is separated, washed with water, dried, and ground to obtain sulfonated lignin powder;

[0068] (3) Take 5 g of the sulfonated lignin powder obtained in step (2), first perform oxidation, then perform polycondensation with the phenolic resin prepolymer, to obtain a sulfonated lignin modified phenolic resin, and finally perform carbonization and high-temperature refining, to obtain a sulfonated lignin modified phenolic resin hard carbon.

[0069] The samples prepared in the above examples 1-6 and the comparative example were respectively subjected to molecular structure property and battery performance tests, and the test results are shown in Table 1.

[0070] Table 1 Comparison of sodium storage performance of sulfonated lignin modified phenolic resin hard carbon without different anhydrous sodium sulfite in examples 1-6 and the comparative example

[0071]

[0072] It can be seen from the comparison of the data in Table 1 that when the water addition amount of anhydrous sodium sulfite is 6.125 g, the discharge specific capacity is the highest.

[0073] Example 7

[0074] A method for preparing a sodium ion hard carbon from a lignin modified phenolic resin doped with S in situ, comprising the following steps:

[0075] (1) First, 5 g of sodium lignosulfonate and 6.125 g of anhydrous sodium sulfite are dissolved in 30 mL of 3 mol / L NaOH aqueous solution, stirred for 1 h, and then transferred to a high-pressure reaction kettle at 120°C for reaction for 3 h, to obtain a sulfonated lignin mixture;

[0076] (2) The sulfonated lignin mixture prepared in step (1) is subjected to separation, water washing, drying, and grinding, to obtain a sulfonated lignin powder;

[0077] (3) Take 5 g of the sulfonated lignin powder obtained in step (2), first perform oxidation, then perform polycondensation with the phenolic resin prepolymer, to obtain a sulfonated lignin modified phenolic resin, and finally perform carbonization and high-temperature refining, to obtain a sulfonated lignin modified phenolic resin hard carbon.

[0078] Example 8

[0079] A method for preparing a sodium ion hard carbon from a lignin modified phenolic resin doped with S in situ, comprising the following steps:

[0080] (1) First, 5 g of sodium lignosulfonate and 6.125 g of anhydrous sodium sulfite are dissolved in 30 mL of 3 mol / L NaOH aqueous solution, stirred for 1 h, and then transferred to a high-pressure reaction kettle at 140°C for reaction for 3 h, to obtain a sulfonated lignin mixture;

[0081] (2) The sulfonated lignin mixture prepared in step (1) is subjected to separation, water washing, drying, and grinding, to obtain a sulfonated lignin powder;

[0082] (3) Take 5 g of the sulfonated lignin powder obtained in step (2), first perform oxidation, then perform polycondensation with phenolic resin prepolymer, to prepare sulfonated lignin modified phenolic resin, and finally perform carbonization and high-temperature refining, to obtain sulfonated lignin modified phenolic resin hard carbon.

[0083] Example 9

[0084] A method for preparing sodium ion hard carbon from lignin modified phenolic resin in-situ doped with S, comprising the following steps:

[0085] (1) First, dissolve 5 g of sodium lignosulfonate and 6.125 g of anhydrous sodium sulfite in 30 mL of 3 mol / L NaOH aqueous solution, stir for 1 h, and then transfer to a high-pressure reaction kettle at 180°C for reaction for 3 h, to prepare a sulfonated lignin mixture;

[0086] (2) Perform separation, water washing, drying, and grinding on the sulfonated lignin mixture prepared in step (1), to obtain sulfonated lignin powder;

[0087] (3) Take 5 g of the sulfonated lignin powder obtained in step (2), first perform oxidation, then perform polycondensation with phenolic resin prepolymer, to prepare sulfonated lignin modified phenolic resin, and finally perform carbonization and high-temperature refining, to obtain sulfonated lignin modified phenolic resin hard carbon.

[0088] Example 10

[0089] A method for preparing sodium ion hard carbon from lignin modified phenolic resin in-situ doped with S, comprising the following steps:

[0090] (1) First, dissolve 5 g of sodium lignosulfonate and 6.125 g of anhydrous sodium sulfite in 30 mL of 3 mol / L NaOH aqueous solution, stir for 1 h, and then transfer to a high-pressure reaction kettle at 200°C for reaction for 3 h, to prepare a sulfonated lignin mixture;

[0091] (2) Perform separation, water washing, drying, and grinding on the sulfonated lignin mixture prepared in step (1), to obtain sulfonated lignin powder;

[0092] (3) Take 5 g of the sulfonated lignin powder obtained in step (2), first perform oxidation, then perform polycondensation with phenolic resin prepolymer, to prepare sulfonated lignin modified phenolic resin, and finally perform carbonization and high-temperature refining, to obtain sulfonated lignin modified phenolic resin hard carbon.

[0093] The molecular structure properties and battery performance of the samples prepared in the above-mentioned Example 3, Examples 7-10, and Comparative Examples were tested, and the test results are shown in Table 2 below.

[0094] Table 2. Comparison of sodium storage performance of sulfonated lignin modified phenolic resin hard carbon with different sulfonation reaction temperatures of example 3, example 7-10 and comparative examples

[0095]

[0096] From the above table, it can be seen that when the reaction temperature of sulfonated lignin is 160℃, the specific discharge capacity is the highest.

[0097] Example 11

[0098] A method for preparing sodium ion hard carbon from lignin modified phenolic resin doped with S in situ, the steps are as follows:

[0099] (1) First, 5g of sodium lignosulfonate and 6.125g of anhydrous sodium sulfite are dissolved in 30mL of 3mol / L NaOH aqueous solution, stirred for 1h, and then transferred to a high-pressure reaction kettle at 160℃ for reaction for 2h to prepare a sulfonated lignin mixture;

[0100] (2) The sulfonated lignin mixture prepared in step (1) is separated, washed with water, dried, and ground to obtain sulfonated lignin powder;

[0101] (3) Take 5g of the sulfonated lignin powder obtained in step (2), first perform oxidation, then perform polycondensation with phenolic resin prepolymer to prepare sulfonated lignin modified phenolic resin, and finally perform carbonization and high-temperature refining to obtain sulfonated lignin modified phenolic resin hard carbon.

[0102] Example 12

[0103] A method for preparing sodium ion hard carbon from lignin modified phenolic resin doped with S in situ, the steps are as follows:

[0104] (1) First, 5g of sodium lignosulfonate and 6.125g of anhydrous sodium sulfite are dissolved in 30mL of 3mol / L NaOH aqueous solution, stirred for 1h, and then transferred to a high-pressure reaction kettle at 160℃ for reaction for 4h to prepare a sulfonated lignin mixture;

[0105] (2) The sulfonated lignin mixture prepared in step (1) is separated, washed with water, dried, and ground to obtain sulfonated lignin powder;

[0106] (3) Take 5g of the sulfonated lignin powder obtained in step (2), first perform oxidation, then perform polycondensation with phenolic resin prepolymer to prepare sulfonated lignin modified phenolic resin, and finally perform carbonization and high-temperature refining to obtain sulfonated lignin modified phenolic resin hard carbon.

[0107] Example 13

[0108] A method for preparing sodium ion hard carbon from lignin modified phenolic resin doped with S in situ, the steps are as follows:

[0109] (1) First, 5 g of sodium lignosulfonate and 6.125 g of anhydrous sodium sulfite were dissolved in 30 mL of 3 mol / L NaOH aqueous solution, stirred for 1 h, and transferred to a high-pressure reaction kettle at 160℃ for reaction for 5 h to prepare a sulfonated lignin mixture;

[0110] (2) The sulfonated lignin mixture prepared in step (1) was separated, washed with water, dried, and ground to obtain sulfonated lignin powder;

[0111] (3) 5 g of the sulfonated lignin powder obtained in step (2) was first oxidized, then subjected to polycondensation with a phenolic resin prepolymer to prepare a sulfonated lignin modified phenolic resin, and finally carbonized and high-temperature refined to obtain a sulfonated lignin modified phenolic resin hard carbon.

[0112] Example 14

[0113] A method for preparing a sodium ion hard carbon from a lignin modified phenolic resin doped with S in situ, comprising the following steps:

[0114] (1) First, 5 g of sodium lignosulfonate and 6.125 g of anhydrous sodium sulfite were dissolved in 30 mL of 3 mol / L NaOH aqueous solution, stirred for 1 h, and transferred to a high-pressure reaction kettle at 160℃ for reaction for 6 h to prepare a sulfonated lignin mixture;

[0115] (2) The sulfonated lignin mixture prepared in step (1) was separated, washed with water, dried, and ground to obtain sulfonated lignin powder;

[0116] (3) 5 g of the sulfonated lignin powder obtained in step (2) was first oxidized, then subjected to polycondensation with a phenolic resin prepolymer to prepare a sulfonated lignin modified phenolic resin, and finally carbonized and high-temperature refined to obtain a sulfonated lignin modified phenolic resin hard carbon.

[0117] The molecular structure properties and battery performance of the samples prepared in the above-mentioned Example 3, Examples 11-14 and Comparative Examples were tested, and the test results are shown in Table 3.

[0118] Table 3 Comparison of sodium storage performance of sulfonated lignin modified phenolic resin hard carbon with different reaction times in Example 3, Examples 11-14 and Comparative Examples

[0119]

[0120] From the comparison of the data in the above table, it can be seen that when the reaction time of the sulfonated lignin is 4 h, the discharge specific capacity is the highest.

[0121] In order to analyze the structure-activity relationship of OLPRC, the microstructure thereof was analyzed by X-ray diffraction (XRD) spectrum. As shown in Figure 1 ,Figure 2 and Figure 3 As shown, two distinct diffraction peaks were observed at approximately 23.60° and 43.10°, corresponding to the (002) and (100) crystal planes of the carbon material, respectively. All the samples were prepared under the same pyrolysis conditions to obtain hard carbon, and the characteristic peak positions did not show significant shifts. With the in-situ S-doped lignin sulfonation reaction proceeding, the hard carbon obtained from the sulfonated lignin-modified phenolic resin under the optimal conditions (6.125 g sodium sulfite, 160°C, 4 h) exhibited relatively broad diffraction peaks. This indicates that the sulfonated lignin phenolic resin hard carbon prepared from the precursor synthesized under optimal conditions has a better disordered structure. Some characteristic parameters of each hard carbon during the synthesis process are shown in Table 4 below. The interlayer spacing and carbon crystallite size and number of the samples were calculated using the Bragg equation and Scherrer equation, respectively. Example 12 is the optimal sulfonated lignin phenolic resin hard carbon, and the calculation results show its interlayer spacing (d...). 002 The maximum is Its carbon crystallite size (La) is relatively small, and the number of crystallites is relatively high. Combined with the specific surface area results, it can be seen that in-situ doping with sulfur alters the molecular structure of lignin, affecting the structure of subsequent lignin resins. The sulfonated lignin-phenolic resin with a special structure exhibits increased interlayer spacing and altered carbon crystallite size and number during pyrolysis due to sulfur doping, without increasing the specific surface area of ​​the hard carbon material. This phenomenon may be because sulfur doping, while increasing the interlayer spacing, also works synergistically with other functional groups in the sulfonated lignin-phenolic resin to promote pore shrinkage, thereby giving the hard carbon a certain number of micropores or closed-pore structures, improving the sodium storage performance of sodium-ion batteries.

[0122] Table 4 shows the d-peak data in the XRD patterns.

[0123]

[0124] The sodium storage performance of unsulfonated oxidized lignin resin hard carbon and sulfonated lignin phenolic resin hard carbon obtained in Examples 1-14 was tested (Tables 1-3). It was found that with the optimization of the sulfonation reaction of in-situ doping of lignin with S, the reversible capacity and initial efficiency of the sulfonated lignin phenolic resin hard carbon gradually increased. The resulting phenolic resin-based hard carbon exhibited increased micropore volume while maintaining stable and excellent sodium storage performance. Among these phenolic resin-based hard carbon materials, the hard carbon prepared under optimal conditions (6.125 g sodium sulfite, 160 °C, 4 h) had a sodium storage capacity of 0.05 A g. -1 It can exhibit the highest reversible capacity of 400mAh g. -1The initial coulombic efficiency is 81% on both sides. The above method reduces the raw material cost of phenolic resin-based hard carbon materials to some extent, improves the sodium storage performance of biomass-based resin, and provides a new way for the industrial application of biomass-based phenolic resin hard carbon.

[0125] The above only describes the preferred embodiments of the present application and is not intended to limit the present application. The present application can have various modifications and changes for those skilled in the art. Any modification, equivalent replacement, improvement, etc. within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A method for preparing sodium-ion hard carbon from lignin-modified phenolic resin doped with sulfur in situ, characterized in that, First, sulfonated lignin is prepared by hydrothermal method using sodium lignin sulfonate and anhydrous sodium sulfite. Then, the sulfonated lignin is oxidized and polycondensed with phenolic resin prepolymer to obtain sulfonated lignin phenolic resin. The sulfonated lignin phenolic resin is then cured and carbonized to obtain sulfonated lignin-modified phenolic resin-based hard carbon. The mass ratio of sodium lignin sulfonate to anhydrous sodium sulfite is 1:2 to 2:

1. The preparation method of sulfonated lignin is as follows: sodium lignin sulfonate and anhydrous sodium sulfite are dissolved in NaOH aqueous solution, stirred for 1 h, and then heated to prepare sulfonated lignin. After separation, washing, drying, and grinding, sulfonated lignin powder is obtained. The heating temperature is 100-200 ℃, and the heating time is 2-6 h.

2. The method for preparing sodium-ion hard carbon from lignin-modified phenolic resin with in-situ S doping according to claim 1, characterized in that, The mass ratio of sodium lignosulfonate to anhydrous sodium sulfite is 1:1.

225.

3. The method for preparing sodium-ion hard carbon from lignin-modified phenolic resin with in-situ S doping according to claim 1, characterized in that, The temperature for the heating reaction is 160 °C.

4. The method for preparing sodium-ion hard carbon from lignin-modified phenolic resin with in-situ S doping according to claim 1, characterized in that, The heating reaction time was 4 hours.

5. A sulfonated lignin phenolic resin-based hard carbon prepared by the method described in any one of claims 1 to 4.

6. The application of the sulfonated lignin phenolic resin-based hard carbon according to claim 5 in sodium-ion battery anode materials.

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