Biomass-based hard carbon material regulated and controlled by sulfonated aromatic hydrocarbon, preparation method of biomass-based hard carbon material and application of biomass-based hard carbon material in sodium-ion battery

Abstract

The invention discloses a sulfonated aromatic hydrocarbon regulated biomass-based hard carbon material, a preparation method thereof and application of the sulfonated aromatic hydrocarbon regulated biomass-based hard carbon material in a sodium-ion battery. The preparation method of the biomass-based hard carbon material comprises the following steps: (1) carrying out solid-liquid mixing on biomass and an aqueous solution of sulfonated aromatic hydrocarbon, drying, and uniformly mixing the sulfonated aromatic hydrocarbon and the biomass; the selected sulfonated aromatic hydrocarbon comprises at least one of benzenesulfonic acid, aminobenzene sulfonic acid, benzene disulfonic acid, carboxyl benzenesulfonic acid, methyl benzenesulfonic acid and tritoluenesulfonic acid. And (2) carrying out two-stage carbonization, low-temperature pre-carbonization and high-temperature re-carbonization on the mixed material to obtain hard carbon, and then sequentially carrying out crushing, acid pickling, water washing and drying. And the sulfonated aromatic hydrocarbon substance guides ordered arrangement of the carbon layer through pi-pi stacking. The obtained biomass-based hard carbon material not only has high yield, but also has a graphite microcrystalline structure beneficial to sodium storage. The hard carbon structure obtained through optimization provides a large number of sodium storage sites, so that the sodium storage performance of the battery is improved.

Description

Technical Field

[0001] The present invention relates to the field of battery technology, and in particular to a biomass-based hard carbon material regulated by sulfonated aromatic hydrocarbons, a preparation method thereof, and an application thereof in sodium ion batteries. Background Art

[0002] Faced with an increasingly severe environmental crisis and the depletion of non-renewable resources, finding safe, affordable, and large-scale renewable energy storage has become a top priority. Sodium and lithium belong to the same metal group, and sodium is abundant in nature, making sodium-ion batteries (Na-ion batteries) a promising alternative to lithium-ion batteries. In the field of battery materials technology, hard carbon materials, which are difficult to graphitize at high temperatures, exhibit enhanced sodium storage capacity and lower operating potentials, making them the most promising anode materials for Na-ion batteries.

[0003] Biomass-based hard carbon materials have become the most commercially promising candidate materials for sodium-ion battery negative electrode materials due to their wide source of precursors, low preparation costs, and high active sites brought by natural locally ordered graphite microcrystalline structures. However, the abundant oxygen-containing functional groups in biomass raw materials will trigger a violent release of small molecular volatile components during pyrolysis, leaving gas escape channels inside the material and inducing random and disordered accumulation of graphite microcrystals. Studies have shown that orderly arranged graphite microcrystalline domains can form stable platform sodium storage sites through an interlayer embedding mechanism, significantly improving the high potential area (less than 0.1Vvs.Na + / Na) storage capacity; however, highly disordered graphite microcrystal structures weaken the embedding sodium storage capacity, shifting the sodium storage mechanism from embedding to surface adsorption. This difference is directly reflected in the capacity changes over the charge-discharge curve. The disordered structure generally has a lower capacity, severely restricting the improvement of the material's sodium storage performance. Therefore, how to precisely control the orientation and size of graphite microcrystals in biomass-derived hard carbon has become a core technical bottleneck for improving the performance of sodium-ion battery anodes.

[0004] Current technology usually uses acid (such as formic acid, acetic acid, etc.) to pretreat biomass, selectively remove hemicellulose / lignin, and regulate biomass components (such as increasing the relative content of cellulose). Existing patent CN 119118100 A discloses a biomass hard carbon negative electrode material and its preparation method and application. This patent uses waste biomass as raw material, and achieves the dissolution of hemicellulose in plants and the selective retention of cellulose and lignin components through organic acid pretreatment. After removing the organic acid, a high-performance biomass hard carbon negative electrode material can be obtained through two steps of carbonization and acid-base treatment. CN 117735518 A discloses a preparation method for corn cob-based hard carbon negative electrode material by hydrolyzing corn cobs with p-toluenesulfonic acid. The process uses p-toluenesulfonic acid as a hydrolysis agent to remove or partially remove lignin and hemicellulose. The purpose of using acid in the above patent is to selectively remove hemicellulose and lignin while retaining cellulose or other target components, thereby regulating the chemical composition and structure of biomass. The separation of acid and biomass is a key step in subsequent processing and directly affects the purity and performance of the material. However, the above methods have obvious limitations: first, the selective removal of a component not only increases processing time but also requires acid recovery treatment, which is costly; second, multiple washings must be performed after pretreatment to remove residual acid, which increases process steps and water consumption; and third, the removal of a component reduces carbon yield. The present invention provides a technical process for directly carbonizing a mixture of sulfonated aromatics and biomass. This process eliminates the need for selective removal of biomass components and separation of sulfonated aromatics. Instead, it utilizes the guiding effect of the carbon layer of sulfonated aromatics during the carbonization process to optimize the graphite microcrystalline structure of the hard carbon material and improve the material's sodium storage performance. Summary of the Invention

[0005] The purpose of the present invention is to overcome the problem in the prior art that the graphite microcrystal structure of biomass hard carbon is difficult to regulate, resulting in low sodium storage performance and low first coulombic efficiency of the hard carbon platform, and to provide a biomass-based hard carbon material regulated by sulfonated aromatic hydrocarbons and a preparation method thereof. The present invention introduces a sulfonated acidic aromatic hydrocarbon substance (Formula I: Ar-SO3H, Ar is a phenyl group or its derivatives), and guides the orderly arrangement of carbon layers through π-π stacking during the carbonization process, thereby achieving effective regulation of the graphite microcrystal structure (including size and order) of the hard carbon material and improving the degree of graphitization of the material. The locally ordered graphite microcrystal structure of the hard carbon after regulation and optimization provides abundant embedding and filling sites for sodium ion storage, significantly improving the platform capacity.

[0006] In order to achieve the above object, the present invention adopts the following technical solutions:

[0007] The first aspect of the present invention provides a method for preparing a biomass-based hard carbon material regulated by sulfonated aromatic hydrocarbons, comprising the following steps:

[0008] (1) solid-liquid mixing of biomass and sulfonated aromatic hydrocarbon aqueous solution, and drying, so as to uniformly mix the sulfonated aromatic hydrocarbon and biomass;

[0009] (2) The mixed material is subjected to two-stage carbonization, including low-temperature pre-carbonization and high-temperature re-carbonization, and then pulverized, acid-washed, water-washed and dried in sequence to obtain the hard carbon material.

[0010] Preferably, in step (1), the biomass is at least one of bamboo, pulp, lignin, cotton hulls, tea hulls, xylose residue, coconut shells, fruit cores, peanut shells, nut skins, corn cobs, straw and cellulose powder.

[0011] Preferably, in step (1), the sulfonated aromatic hydrocarbon is at least one of benzenesulfonic acid, aminobenzenesulfonic acid, benzenedisulfonic acid, carboxybenzenesulfonic acid, methylbenzenesulfonic acid and trimethylbenzenesulfonic acid.

[0012] Preferably, in step (1), the concentration of the sulfonated aromatic hydrocarbon aqueous solution is 1 to 20 wt% (mass fraction).

[0013] Preferably, in step (1), the mass ratio of the sulfonated aromatic hydrocarbon aqueous solution to the biomass is 0.01:1-0.5:1.

[0014] Preferably, in step (2), the low-temperature pre-carbonization is carried out under the protection of an inert atmosphere, and the carbonization conditions are: heating rate 2-20°C / min, temperature 400-900°C, and holding time 10-300min.

[0015] Preferably, in step (2), the high-temperature recarbonization is carried out under the protection of an inert atmosphere, and the carbonization conditions are: heating rate 2-20°C / min, temperature 1200-1600°C, and holding time 10-300min.

[0016] Preferably, the inert atmosphere is nitrogen or argon.

[0017] Preferably, in step (2), the pickling is carried out using an acidic solution comprising at least one of hydrochloric acid, sulfuric acid, phosphoric acid and nitric acid, wherein the acid concentration is 0.1-3 mol / L.

[0018] A second aspect of the present invention provides a biomass-based hard carbon material prepared by the aforementioned method using sulfonated aromatic hydrocarbons. The resulting biomass-based hard carbon material not only has a high yield but also possesses a graphite microcrystal structure that is favorable for sodium storage (including large graphite microcrystal size and low defect density). The optimized hard carbon structure provides a large number of sodium storage sites, thereby improving the battery's sodium storage capacity to 373 mAh g. -1 , especially the sodium storage platform capacity (246mAh g -1 ).

[0019] The third aspect of the present invention provides the use of the above-mentioned sulfonated aromatic hydrocarbon-regulated biomass-based hard carbon material as a negative electrode material for sodium ion batteries.

[0020] A fourth aspect of the present invention provides a sodium ion battery, the negative electrode of which contains the above-mentioned biomass-based hard carbon material regulated by sulfonated aromatic hydrocarbons.

[0021] Conventional technologies typically use acids (such as formic acid and acetic acid) to pretreat biomass (hydrolyze or remove hemicellulose / lignin) to change the composition of the biomass (such as increasing the cellulose content), followed by washing to prevent residual acid from affecting subsequent processes or product performance, thereby affecting the structure and properties of hard carbon. In contrast, the present invention has the following advantages and benefits:

[0022] The present invention is to guide the growth of graphite crystallites by sulfonated aromatics in the process of biomass pyrolysis, and the carbonized π-π stacking of aromatics in situ is used to achieve the effective regulation of the graphite crystal structure (including size and order) of hard carbon materials. Specifically, the benzenesulfonic acid and other sulfonated aromatic substances introduced, substances such as benzenesulfonic acid participate in the reaction during the pyrolysis process and can be converted into a part of the carbon structure. Unlike traditional pretreatment techniques, the present invention needs to retain the sulfonated aromatic substances in the biomass system without the need for additional washing steps. Its function is to provide a benzene ring structure during the biomass pyrolysis process to promote the orderly growth of graphite crystallites, rather than changing the initial components of biomass. After optimization, the locally ordered graphite crystal structure of hard carbon provides abundant embedding and filling sites for sodium ion storage, significantly improving the platform capacity. Comparative experiments show that when sulfonated aromatics are replaced by organic acids without benzene rings, such as phytic acid (Comparative Example 4), the electrochemical performance of the obtained hard carbon is significantly reduced. The charge and discharge curves show that the capacity and first coulomb efficiency of hard carbon are greatly reduced, which confirms the key role of the aromatic structure. On the one hand, organic acids without benzene rings cannot provide π-π stacking effects and cannot promote the orderly growth of graphite microcrystals. On the other hand, small molecule organic acids such as phytic acid may have adverse effects during the pyrolysis process and instead destroy the orderliness of graphite microcrystals. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 Graphs showing the charge and discharge curves of the hard carbon materials obtained in Example 5, Comparative Example 1, and Comparative Example 4.

[0024] Figure 2 The hard carbon materials prepared in Examples 1-8 and Comparative Examples 1-4 are samples, and a graph showing the relationship between graphite crystallite length and capacity.

[0025] Figure 3 The hard carbon prepared in Example 2, Example 3, Example 5 and Comparative Example 1 was used as a sample, and its XRD spectrum was measured.

[0026] Figure 4These are TEM images of the hard carbon material samples prepared in Example 5 and Comparative Example 1, where (a) is Comparative Example 1 and (b) is Example 5. DETAILED DESCRIPTION

[0027] To make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention are described clearly and completely below. Where specific conditions are not specified in the embodiments, conventional conditions were used. Where the manufacturer of the reagents or instruments is not specified, they are all conventional products that can be purchased commercially.

[0028] Example 1

[0029] This embodiment provides a method for preparing a biomass-based hard carbon material regulated by sulfonated aromatics, and the specific steps are as follows:

[0030] Add methylbenzenesulfonic acid and an appropriate amount of deionized water to the reaction vessel to dissolve the methylbenzenesulfonic acid, then add cellulose powder to make the methylbenzenesulfonic acid: cellulose powder = 20wt.%, and stir mechanically until the two are completely mixed; transfer the obtained mixture to a heater for drying for 12 hours at a temperature of 80°C. The dried mixture is pre-carbonized at low temperature under a nitrogen atmosphere: the heating rate is 5°C / min, the carbonization temperature is 900°C, and the insulation time is 2 hours. After natural cooling, the pre-carbonized product is re-carbonized at high temperature: the heating rate is 5°C / min, the carbonization temperature is 1600°C, and the insulation time is 2 hours. Then cool naturally to room temperature, take out the material, crush it and sieve it to a mesh size of 400. Use 0.1mol / L hydrochloric acid to wash it, and then use deionized water to wash the residual hydrochloric acid in the hard carbon to obtain hard carbon.

[0031] Example 2

[0032] This embodiment provides a method for preparing a biomass-based hard carbon material regulated by sulfonated aromatics, and the specific steps are as follows:

[0033] Add benzenesulfonic acid and an appropriate amount of deionized water to the reaction vessel to dissolve the benzenesulfonic acid, then add cellulose powder so that the benzenesulfonic acid: cellulose powder = 10wt.%, and stir mechanically until the two are completely mixed; transfer the obtained mixture to a heater for drying for 12 hours at a temperature of 80°C. The dried mixture is pre-carbonized at low temperature under a nitrogen atmosphere: the heating rate is 5°C / min, the carbonization temperature is 900°C, and the insulation time is 2 hours. After natural cooling, the pre-carbonized product is re-carbonized at high temperature: the heating rate is 5°C / min, the carbonization temperature is 1400°C, and the insulation time is 2 hours. Then cool naturally to room temperature, take out the material, crush it and sieve it to a mesh size of 400 mesh. Wash it with 0.1mol / L hydrochloric acid, and then use deionized water to wash the residual hydrochloric acid in the hard carbon to obtain hard carbon.

[0034] Example 3

[0035] This embodiment provides a method for preparing a biomass-based hard carbon material regulated by sulfonated aromatics, and the specific steps are as follows:

[0036] Add methylbenzenesulfonic acid and an appropriate amount of deionized water to the reaction vessel to dissolve the methylbenzenesulfonic acid, then add cellulose powder so that the methylbenzenesulfonic acid: cellulose powder = 50wt.%, and stir mechanically until the two are completely mixed; transfer the obtained mixture to a heater for drying for 12 hours at a temperature of 80°C. The dried mixture is pre-carbonized at low temperature under a nitrogen atmosphere: the heating rate is 5°C / min, the carbonization temperature is 900°C, and the insulation time is 2 hours. After natural cooling, the pre-carbonized product is re-carbonized at high temperature: the heating rate is 5°C / min, the carbonization temperature is 1400°C, and the insulation time is 2 hours. Then cool naturally to room temperature, take out the material, crush it and sieve it to a mesh size of 400 mesh. Wash it with 0.1mol / L hydrochloric acid, and then use deionized water to wash the residual hydrochloric acid in the hard carbon to obtain hard carbon.

[0037] Example 4

[0038] This embodiment provides a method for preparing a biomass-based hard carbon material regulated by sulfonated aromatics, and the specific steps are as follows:

[0039] Add aminobenzenesulfonic acid and an appropriate amount of deionized water to the reaction vessel to dissolve the aminobenzenesulfonic acid, then add cellulose powder to make the aminobenzenesulfonic acid: cellulose powder = 20wt.%, and stir mechanically until the two are completely mixed; transfer the obtained mixture to a heater for drying for 12 hours at a temperature of 80°C. The dried mixture is pre-carbonized at low temperature under a nitrogen atmosphere: the heating rate is 5°C / min, the carbonization temperature is 900°C, and the insulation time is 2 hours. After natural cooling, the pre-carbonized product is re-carbonized at high temperature: the heating rate is 5°C / min, the carbonization temperature is 1400°C, and the insulation time is 4 hours. Then cool naturally to room temperature, take out the material, crush it and sieve it to a mesh size of 400. Use 0.1mol / L hydrochloric acid to wash it, and then use deionized water to wash the residual hydrochloric acid in the hard carbon to obtain hard carbon.

[0040] Example 5

[0041] This embodiment provides a method for preparing a biomass-based hard carbon material regulated by sulfonated aromatics, the specific contents of which are as follows:

[0042] Add methylbenzenesulfonic acid and an appropriate amount of deionized water to the reaction vessel to dissolve the methylbenzenesulfonic acid, then add cellulose powder to make the methylbenzenesulfonic acid: cellulose powder = 20wt.%, and stir mechanically until the two are completely mixed; transfer the obtained mixture to a heater for drying for 12 hours at a temperature of 80°C. The dried mixture is pre-carbonized at low temperature under a nitrogen atmosphere: the heating rate is 5°C / min, the carbonization temperature is 900°C, and the insulation time is 2 hours. After natural cooling, the pre-carbonized product is re-carbonized at high temperature: the heating rate is 5°C / min, the carbonization temperature is 1400°C, and the insulation time is 2 hours. Then cool naturally to room temperature, take out the material, crush it and sieve it to a mesh size of 400 mesh. Wash it with 0.1mol / L hydrochloric acid, and then use deionized water to wash the residual hydrochloric acid in the hard carbon to obtain hard carbon.

[0043] Example 6

[0044] This embodiment provides a method for preparing a biomass-based hard carbon material regulated by sulfonated aromatics, and the specific steps are as follows:

[0045] Add carboxybenzenesulfonic acid and an appropriate amount of deionized water to the reaction vessel to dissolve the carboxybenzenesulfonic acid, then add cellulose powder so that the carboxybenzenesulfonic acid: cellulose powder = 20wt.%, and stir mechanically until the two are completely mixed; transfer the obtained mixture to a heater for drying for 12 hours at a temperature of 80°C. The dried mixture is pre-carbonized at low temperature under a nitrogen atmosphere: the heating rate is 5°C / min, the carbonization temperature is 500°C, and the insulation time is 2 hours. After natural cooling, the pre-carbonized product is re-carbonized at high temperature: the heating rate is 5°C / min, the carbonization temperature is 1400°C, and the insulation time is 2 hours. Then cool naturally to room temperature, take out the material, crush it and sieve it to a mesh size of 400. Use 0.1mol / L hydrochloric acid to wash it, and then use deionized water to wash the residual hydrochloric acid in the hard carbon to obtain hard carbon.

[0046] Example 7

[0047] This embodiment provides a method for preparing a biomass-based hard carbon material regulated by sulfonated aromatics, and the specific steps are as follows:

[0048] Toluenesulfonic acid and an appropriate amount of deionized water were added to a reaction vessel to dissolve the toluenesulfonic acid. Bamboo powder was then added to achieve a ratio of 20 wt.% of toluenesulfonic acid to bamboo powder. The mixture was mechanically stirred until thoroughly mixed. The resulting mixture was transferred to a heater for drying at 80°C for 12 hours. The dried mixture was pre-carbonized at low temperature under a nitrogen atmosphere: heating rate of 5°C / min, carbonization temperature of 900°C, and heat preservation time of 2 hours. After natural cooling, the pre-carbonized product was re-carbonized at high temperature: heating rate of 5°C / min, carbonization temperature of 1400°C, and heat preservation time of 2 hours. The product was then naturally cooled to room temperature, and the product was removed, crushed, and sieved to a mesh size of 400. The product was washed with 0.1 mol / L hydrochloric acid, and then the residual hydrochloric acid in the hard carbon was washed with deionized water to obtain hard carbon.

[0049] Example 8

[0050] This embodiment provides a method for preparing a biomass-based hard carbon material regulated by sulfonated aromatics, and the specific steps are as follows:

[0051] Add methylbenzenesulfonic acid and an appropriate amount of deionized water to the reaction vessel to dissolve the methylbenzenesulfonic acid, then add cotton hull powder to make the methylbenzenesulfonic acid: cotton hull powder = 20wt.%, and stir mechanically until the two are completely mixed; transfer the obtained mixture to a heater for drying for 12 hours at a temperature of 80°C. The dried mixture is pre-carbonized at low temperature under a nitrogen atmosphere: the heating rate is 5°C / min, the carbonization temperature is 900°C, and the insulation time is 2 hours. After natural cooling, the pre-carbonized product is re-carbonized at high temperature: the heating rate is 5°C / min, the carbonization temperature is 1400°C, and the insulation time is 2 hours. Then cool naturally to room temperature, take out the material, crush it and sieve it to a mesh size of 400. Use 0.1mol / L hydrochloric acid to wash it, and then use deionized water to wash the residual hydrochloric acid in the hard carbon to obtain hard carbon.

[0052] Comparative Example 1

[0053] The cellulose powder is dried in a heater for 12 hours at a temperature of 80°C. The dried cellulose powder is pre-carbonized at low temperature under a nitrogen atmosphere: the heating rate is 5°C / min, the carbonization temperature is 900°C, and the insulation time is 2 hours. After natural cooling, the pre-carbonized product is re-carbonized at high temperature: the heating rate is 5°C / min, the carbonization temperature is 1400°C, and the insulation time is 2 hours. It is then naturally cooled to room temperature, the material is taken out, crushed and sieved, and the mesh size is 400 mesh. It is washed with 0.1 mol / L hydrochloric acid, and then the residual hydrochloric acid in the hard carbon is washed with deionized water to obtain hard carbon.

[0054] Comparative Example 2

[0055] The bamboo powder is dried in a heater for 12 hours at a temperature of 80°C. The dried bamboo powder is pre-carbonized at low temperature under a nitrogen atmosphere: the heating rate is 5°C / min, the carbonization temperature is 900°C, and the insulation time is 2 hours. After natural cooling, the pre-carbonized product is re-carbonized at high temperature: the heating rate is 5°C / min, the carbonization temperature is 1400°C, and the insulation time is 2 hours. It is then naturally cooled to room temperature, the material is taken out, crushed and sieved, and the mesh size is 400 mesh. It is washed with 0.1 mol / L hydrochloric acid, and then the residual hydrochloric acid in the hard carbon is washed with deionized water to obtain hard carbon.

[0056] Comparative Example 3

[0057] The cotton hull powder is dried in a heater for 12 hours at a temperature of 80°C. The dried cotton hull powder is pre-carbonized at low temperature under a nitrogen atmosphere: the heating rate is 5°C / min, the carbonization temperature is 900°C, and the insulation time is 2 hours. After natural cooling, the pre-carbonized product is re-carbonized at high temperature: the heating rate is 5°C / min, the carbonization temperature is 1400°C, and the insulation time is 2 hours. It is then naturally cooled to room temperature, the material is taken out, crushed and sieved, and the mesh size is 400 mesh. It is washed with 0.1 mol / L hydrochloric acid, and then the residual hydrochloric acid in the hard carbon is washed with deionized water to obtain hard carbon.

[0058] Comparative Example 4

[0059] Add an appropriate amount of 10wt% phytic acid solution to the reaction vessel, and then add cellulose powder so that the mass ratio of phytic acid: cellulose powder = 10wt.%, and stir mechanically until the two are completely mixed; transfer the obtained mixture to a heater for drying for 12 hours at a temperature of 80°C. The dried mixture is pre-carbonized at low temperature under a nitrogen atmosphere: the heating rate is 5°C / min, the carbonization temperature is 900°C, and the insulation time is 2 hours. After natural cooling, the pre-carbonized product is re-carbonized at high temperature: the heating rate is 5°C / min, the carbonization temperature is 1400°C, and the insulation time is 2 hours. Then cool naturally to room temperature, take out the material, crush it and sieve it to a mesh size of 400. Wash it with 0.1mol / L hydrochloric acid, and then use deionized water to wash the residual hydrochloric acid in the hard carbon to obtain hard carbon.

[0060] Comparative Example 5

[0061] Add methylbenzenesulfonic acid and an appropriate amount of deionized water to the reaction vessel to dissolve the methylbenzenesulfonic acid, then add cellulose powder to make the methylbenzenesulfonic acid: cellulose powder = 70wt.%, and stir mechanically until the two are completely mixed; transfer the obtained mixture to a heater for drying for 12 hours at a temperature of 80°C. The dried mixture is pre-carbonized at low temperature under a nitrogen atmosphere: the heating rate is 5°C / min, the carbonization temperature is 900°C, and the insulation time is 2 hours. After natural cooling, the pre-carbonized product is re-carbonized at high temperature: the heating rate is 5°C / min, the carbonization temperature is 1400°C, and the insulation time is 2 hours. Then cool naturally to room temperature, take out the material, crush it and sieve it to a mesh size of 400 mesh. Wash it with 0.1mol / L hydrochloric acid, and then use deionized water to wash the residual hydrochloric acid in the hard carbon to obtain hard carbon.

[0062] Test Example 1

[0063] The electrochemical performance of the finished product was tested using the half-cell test method:

[0064] Hard carbon negative electrode active material samples (Examples 1-8, Comparative Examples 1-5), a conductive agent (SP), and a binder (CMC) were mixed uniformly with a certain amount of deionized water in a mass ratio of 85:12:3 and then coated on a current collector to prepare the sodium ion battery negative electrode sheet. The sheet was pressed into a circular sheet with a diameter of 12 mm and dried at 105°C for 12 hours. In a glove box, button cells were assembled using a sodium metal sheet as the counter electrode, an electrolyte of 1M NaPF6 in DME (100 vol%), and a Whatman GF / D ultrafine glass fiber as the separator. Testing was performed using a LANHE CT3002A battery tester at a current density of 20 mA / g and a voltage range of 0.005-3 V. The cellulose-based hard carbon negative electrode material prepared in Example 5 exhibited a first-cycle capacity of 373 mAh / g at 20 mA / g, a platform capacity increased to 245 mAh / g, and a first coulombic efficiency of 85%.

[0065] The electrochemical performance of the batteries assembled from Examples 1-8 and Comparative Examples 1-5 was tested at a current density of 20 mA / g and a voltage range of 0.005-3 V. The test results are shown in Table 1.

[0066] Table 1

[0067] sample Graphite crystallite length (La) (nm) Capacity (mAh / g) Platform capacity (mAh / g) First coulombic efficiency (%) Example 1 6.02 367 220 84 Example 2 5.49 334 223 86 Example 3 6.36 337 208 78 Example 4 6.12 370 243 88 Example 5 6.28 373 245 85 Example 6 5.82 353 232 85 Example 7 5.51 345 205 83 Example 8 5.64 344 217 88 Comparative Example 1 5.12 314 194 77 Comparative Example 2 3.91 225 117 66 Comparative Example 3 3.15 170 55 38 Comparative Example 4 3.83 220 129 68 Comparative Example 5 5.19 322 199 81

[0068] It can be seen from the results in Table 1 that the π-π stacking effect of the aromatic substance guides the orderly arrangement of the hard carbon carbon layer, realizes the increase of the graphite crystallites of the hard carbon material, and finally provides abundant embedding sites for sodium ion storage, which significantly improves the sodium storage performance of the hard carbon material. Specifically, the graphite crystallite length of Example 5 reaches 6.28nm, and the capacity reaches 373mAh / g. In Comparative Example 5, excessive sulfonated aromatics are introduced, and the strong polar sulfonic acid groups thereof interfere with the synergistic effect of π-π stacking, causing disordered arrangement of the carbon layer and reduced length of the graphite crystallite. For example, the graphite crystallite length of Comparative Example 5 is 5.19nm, which is lower than 6.28nm of Example 5. Excessive sulfonic acid groups may generate unstable sulfur-containing substances during the carbonization process, increase the side reactions at the electrode / electrolyte interface, and cause the first efficiency of Comparative Example 5 to be reduced to 81%.

[0069] The charge and discharge curves of Example 5, Comparative Example 1 and Comparative Example 4 are shown in FIG. Figure 1 As shown. Figure 1 The results show that the material's charge-discharge curve exhibits typical hard carbon characteristics, with a slope above 0.1V and a plateau below 0.1V. This plateau is associated with the embedding of sodium ions within the graphite microcrystal structure. The π-π stacking of the aromatics significantly increases the graphite microcrystal structure, leading to a significant increase in the plateau.

[0070] The hard carbon materials prepared in Examples 1-8 and Comparative Examples 1-4 were used as samples, and the graph showing the relationship between graphite crystallite length and capacity was shown in Figure 1. Figure 2 As shown. Figure 2 The results show that the sodium storage capacity is positively correlated with the length of graphite crystallites.

[0071] The hard carbon materials prepared in Examples 2, 3, 5 and Comparative Example 1 were used as samples, and the XRD patterns were as follows: Figure 3 The hard carbon materials prepared in Example 5 and Comparative Example 1 were used as samples, and the TEM images were as follows. Figure 4 As shown. Figure 3 and Figure 4 It can be seen that all hard carbon samples present a locally ordered structure. The introduction of sulfonated aromatics effectively increases the length of graphite crystallites, increases the degree of order of the hard carbon structure, and slightly increases the interlayer spacing.

[0072] This invention introduces a sulfonated acidic aromatic hydrocarbon (Formula I: Ar-SO3H, where Ar is a phenyl group or its derivative) to guide the orderly arrangement of carbon layers through π-π stacking, effectively controlling the graphite microcrystal structure (including size and order) of the hard carbon material and improving the material's degree of graphitization. The optimized, locally ordered graphite microcrystal structure of the hard carbon provides abundant embedding and filling sites for sodium ion storage, significantly increasing the platform capacity.

[0073] The above embodiments are preferred implementations of the present invention, but the implementations 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 considered as equivalent replacement methods and are included in the scope of protection of the present invention.

Claims

1. A method for preparing a biomass-based hard carbon material regulated by sulfonated aromatics, characterized in that: The following steps are involved: (1) solid-liquid mixing of biomass and sulfonated aromatic hydrocarbon aqueous solution, and drying, so as to uniformly mix the sulfonated aromatic hydrocarbon and biomass; (2) The mixed material is subjected to two-stage carbonization, including low-temperature pre-carbonization and high-temperature re-carbonization, and then pulverized, acid-washed, water-washed and dried in sequence to obtain the hard carbon material.

2. The preparation method according to claim 1, characterized in that In step (1), the biomass is at least one of bamboo, pulp, lignin, cotton hulls, tea oil shells, xylose residue, coconut shells, fruit cores, peanut shells, nut skins, corn cobs, straw and cellulose powder; and the sulfonated aromatic hydrocarbons are at least one of benzenesulfonic acid, aminobenzenesulfonic acid, benzene disulfonic acid, carboxybenzenesulfonic acid, methylbenzenesulfonic acid and trimethylbenzenesulfonic acid.

3. The preparation method according to claim 1, characterized in that In step (1), the concentration of the sulfonated aromatic hydrocarbon aqueous solution is 1 to 20 wt %; and the mass ratio of the sulfonated aromatic hydrocarbon aqueous solution to the biomass is 0.01:1 to 0.5:

1.

4. The preparation method according to claim 1, characterized in that In step (2), the low-temperature pre-carbonization is carried out under the protection of an inert atmosphere, and the carbonization conditions are: heating rate 2-20°C / min, temperature 400-900°C, and holding time 10-300min.

5. The preparation method according to claim 1, characterized in that In step (2), the high-temperature recarbonization is carried out under the protection of an inert atmosphere, and the carbonization conditions are: a heating rate of 2-20°C / min, a temperature of 1200-1600°C, and a holding time of 10-300min.

6. The preparation method according to claim 4 or 5, characterized in that The inert atmosphere is nitrogen or argon.

7. The preparation method according to claim 1, characterized in that In step (2), the pickling adopts an acidic solution including at least one of hydrochloric acid, sulfuric acid, phosphoric acid and nitric acid.

8. The preparation method according to claim 7, characterized in that The acid concentration is 0.1-3 mol / L.

9. A biomass-based hard carbon material regulated by sulfonated aromatic hydrocarbons obtained by the preparation method according to any one of claims 1 to 7.

10. Use of the biomass-based hard carbon material regulated by sulfonated aromatics according to claim 9 as a negative electrode material for sodium ion batteries.

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