Sulfur-doped carbon material, preparation method and application

Abstract

The invention relates to the technical field of electrochemical materials, in particular to a sulfur-doped carbon material, a preparation method and application. Based on a coprecipitation and high-temperature reaction method, a carbon source is deposited on the surface of a silicon molecular sieve, and the sulfur-doped carbon material is obtained through high-temperature vulcanization reaction, alkali liquor treatment, high-temperature carbonization treatment and acid liquor treatment. The preparation method disclosed by the invention has the characteristics of controllable operation and easiness in large-scale preparation, and meanwhile, the sulfur-doped carbon material prepared by the method has the characteristic of a controllable porous structure, and shows excellent performance and wide application prospect when being used as a sodium-ion battery negative electrode material.

Description

Technical Field

[0001] The present invention relates to the technical field of electrochemical materials, and in particular to a sulfur-doped carbon material, a preparation method and an application thereof. Background Art

[0002] Among the numerous anode materials for sodium-ion batteries, carbon-based materials have attracted widespread attention due to their excellent conductivity, low cost, and environmental friendliness. However, graphite, widely used in commercial lithium-ion batteries, cannot form stable intercalation compounds with sodium ions and, therefore, cannot be used in sodium-ion battery systems. Hard carbon materials, as the most promising carbon-based materials, are being extensively studied due to their high sodium storage capacity and abundant precursor sources.

[0003] Heteroatom doping of hard carbon materials is an important means to achieve the regulation of the properties and electronic structure of hard carbon materials and further improve their sodium storage capacity when used as sodium ion negative electrode materials. Li et al. synthesized sulfur-doped disordered carbon materials at 20mAg -1 A current density of 516 mAh g -1 Yang et al. synthesized sulfur-doped nitrogen-rich carbon nanosheets at 50 mA g -1 A current density of 350 mAh g -1 The sodium storage capacity of carbon materials is higher than that of nitrogen-doped materials (Adv. Mater. 29.1604108 (2017)). In addition, Qie et al. have shown through experiments that sulfur doping can increase the interlayer distance of carbon materials. At the same time, because the sulfur in the sulfur-doped materials can serve as an active reaction site with sodium ions, sulfur doping is more suitable for use as anode materials for sodium-ion batteries than nitrogen doping (Adv. Sci. 2.1500195 (2015)). However, the sulfur-doped carbon materials reported so far still have shortcomings when used as anode materials for sodium-ion batteries, such as low sodium storage capacity at high current density, poor rate performance, and inability to maintain long-term cycle stability. The development of new sulfur-doped carbon materials with high sodium storage performance is of great significance to promoting the practical application of carbon-based materials. Summary of the Invention

[0004] The present invention provides a method for preparing a sulfur-doped carbon material and its application. A carbon source is deposited on a silicon molecular sieve, followed by a high-temperature sulfurization reaction, alkaline solution treatment, carbonization reaction, and acid solution treatment to obtain the sulfur-doped carbon material. This method exhibits high reproducibility, wide applicability, and large-scale production. The resulting sulfur-doped carbon material can be manipulated using different silicon templates and exhibits excellent electrochemical performance as a negative electrode material for sodium-ion batteries.

[0005] In order to achieve the above object, the technical solution of the present invention is as follows:

[0006] In one aspect, the present invention provides a method for preparing a sulfur-doped carbon material, comprising the following steps:

[0007] A method for preparing a sulfur-doped carbon material comprises the following steps:

[0008] (1) A carbon source is deposited on a silicon molecular sieve using a co-precipitation method to obtain a mixture of a carbon source and a silicon molecular sieve precursor.

[0009] (2) transferring the precursor mixture and the sulfur source obtained in step (1) into a high-temperature reaction vessel under the protection of an inert atmosphere;

[0010] (3) performing a high-temperature vulcanization reaction in a high-temperature reactor;

[0011] (4) treating the product obtained in step (3) with alkali, washing, and drying to obtain a silicon molecular sieve / carbon intermediate composite material;

[0012] (5) Carrying out a carbonization reaction on the silicon molecular sieve / carbon intermediate composite material obtained in step (4) under the protection of an inert atmosphere II to obtain a silicon molecular sieve / carbon composite material.

[0013] (6) The silicon molecular sieve / carbon composite material obtained in step (5) is subjected to acid treatment, washed, and dried to obtain a sulfur-doped carbon material.

[0014] Furthermore, in step (1), the carbon source is any one of maltose, soluble starch, sucrose, anhydrous glucose, fructose, lactose, dopamine hydrochloride, melamine, dicyandiamide, urea or pyridine; and the silicon molecular sieve is any one of silicon spheres, silicon nanopowder, silica sol, SBA-15 or MCM-41, or a mixture of two or more thereof.

[0015] Furthermore, in step (1), the coprecipitation temperature is 25 to 100° C., preferably 25 to 60° C., and the coprecipitation time is 6 to 72 hours, preferably 48 to 72 hours. The addition ratio of the carbon source to the silicon molecular sieve is a mass fraction ratio (M (carbon source): M (silicon molecular sieve)) of 10% to 60%, preferably 30% to 50%.

[0016] Furthermore, in step (2), the inert atmosphere is one or a mixture of two or more of argon, nitrogen, and helium, preferably high-purity argon; the sulfur source is any one of carbon disulfide, thiourea, sodium sulfide, potassium sulfide, ammonium sulfide, or thioacetamide; and the addition ratio of the precursor mixture and the sulfur source is a mass fraction ratio (M (precursor mixture): M (sulfur source)) of 10% to 100%, preferably 15% to 50%.

[0017] Furthermore, in the step (3), the heating rate of the high-temperature vulcanization reaction is in the range of 1 to 20°C / min, preferably 10 to 20°C / min; the temperature is raised to an end point temperature of 200 to 500°C, preferably 250 to 400°C; and the constant temperature time at the end point temperature is 2 to 6 hours, preferably 3 to 5 hours.

[0018] Furthermore, in step (4), the alkali solution in the alkali treatment is a sodium hydroxide solution with a concentration of 1 to 8 mol / L or a potassium hydroxide solution with a concentration of 1 to 8 mol / L, the alkali treatment time is 2 to 6 hours, the alkali treatment temperature is 60 to 100°C, the drying temperature is 25 to 80°C, and the drying time is 6 to 72 hours. The alkali solution is preferably a 4 to 6 mol / L NaOH solution; the alkali treatment temperature is preferably 60 to 80°C; the alkali treatment time is preferably 3 to 5 hours; the drying temperature is preferably 60 to 80°C; and the drying time is preferably 8 to 24 hours.

[0019] Furthermore, in step (5), the second inert atmosphere is one or a mixture of two or more of argon, nitrogen, and helium; the carbonization reaction is heated at a rate of 1 to 20°C / min to an end point temperature of 600 to 1000°C, and the temperature is maintained at the end point temperature for 1 to 6 hours. The second inert atmosphere is preferably high-purity argon; the programmed heating rate is preferably 1 to 10°C / min; the end point temperature is preferably 600 to 800°C; and the reaction time is preferably 2 to 4 hours.

[0020] Furthermore, in step (6), the acid in the acid treatment is a hydrofluoric acid solution with a mass fraction of 5 to 20%, the acid treatment time is 6 to 48 hours, and the acid treatment temperature is 25 to 60°C; the drying temperature is 25 to 80°C, and the drying time is 6 to 72 hours. The acid solution is preferably a hydrofluoric acid solution with a mass fraction of 10 to 15%, the acid treatment temperature is preferably 25 to 40°C, and the acid treatment time is preferably 12 to 24 hours. The drying temperature is preferably 60 to 80°C; and the drying time is preferably 8 to 24 hours.

[0021] Another aspect of the present invention provides a sulfur-doped carbon material obtained by the above preparation method. The sulfur-doped carbon material can realize the regulation of different material structures according to the use of different templates.

[0022] The present invention also provides an application of the sulfur-doped carbon material, wherein the material is used as a negative electrode material in a sodium ion battery system.

[0023] Compared with the prior art, the present invention has the following beneficial effects:

[0024] 1. The technical route provided by the present invention has better battery performance than the sulfur-doped carbon materials prepared by the common one-step high-temperature vulcanization, and has potential application prospects in the field of energy storage.

[0025] 2. The technical route provided by the present invention realizes the efficient preparation of sulfur-doped carbon materials. The preparation method can realize the batch preparation of such materials and has universal applicability. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments or comparative examples of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative labor.

[0027] Figure 1 This is a high-resolution transmission electron microscopy (HRTEM) image of the sulfur-doped carbon material in Example 1;

[0028] Figure 2 This is a high-resolution scanning electron microscope (HRSEM) image of the sulfur-doped carbon material in Example 1;

[0029] Figure 3 The sulfur-doped carbon material in Example 1 is used as the negative electrode material for sodium ion batteries in a test voltage range of 0.01 to 3 V and a current density of 100 mA·g -1 Performance diagram when

[0030] Figure 4 The sulfur-doped carbon material in Example 1 is used as the negative electrode material for sodium ion batteries in a test voltage range of 0.01 to 3 V and a current density of 2000 mA·g -1 Performance diagram when

[0031] Figure 5 The sulfur-doped carbon material in Example 2 is used as the negative electrode material for sodium ion batteries in a test voltage range of 0.01 to 3 V and a current density of 100 mA·g -1 Performance diagram when

[0032] Figure 6 The sulfur-doped carbon material in Example 3 is used as the negative electrode material for sodium ion batteries in a test voltage range of 0.01 to 3 V and a current density of 100 mA·g -1 Performance diagram when

[0033] Figure 7 The comparative material in Comparative Example 1 was used as the negative electrode material for sodium ion batteries in a test voltage range of 0.01 to 3 V and a current density of 100 mA g -1 Performance diagram when

[0034] Figure 8The comparative material in Comparative Example 2 was used as the negative electrode material for sodium ion batteries in a test voltage range of 0.01 to 3 V and a current density of 100 mA g -1 Performance diagram when

[0035] Figure 9 The comparative material in Comparative Example 3 was used as the negative electrode material for sodium ion batteries in a test voltage range of 0.01 to 3 V and a current density of 100 mA g -1 Performance diagram when DETAILED DESCRIPTION

[0036] The entire material preparation process is described in detail below through examples.

[0037] Unless otherwise specified, the materials used in the examples of the present invention can be obtained from commercial sources or prepared according to conventional methods well known to those skilled in the art.

[0038] Example 1

[0039] (1) 500 mg of glucose and 1.6 g of SBA-15 (M (carbon source): M (silicon molecular sieve) = 31%) were ultrasonically dispersed and dissolved in 20 mL of deionized water. The mixture was stirred at 25°C for 48 h until the solvent was completely evaporated to obtain a precursor mixture of glucose and SBA-15.

[0040] (2) The precursor mixture obtained in (1) and 8 mL of CS2 (M (precursor mixture): M (sulfur source) = 21%) were transferred and packaged into a high-temperature reactor under an argon atmosphere.

[0041] (3) Place the medium- and high-temperature reactor (2) in a muffle furnace, heat it to 200°C at a heating rate of 10°C / min, and keep the temperature constant for 4 hours.

[0042] (4) The sample obtained in (3) was treated with 6 mol / L sodium hydroxide solution at 60°C for 3 h, filtered, washed with water and ethanol until the filtrate was neutral, and then transferred to a drying oven at 80°C for 12 h.

[0043] (5) The dried sample in (4) was transferred to a tube furnace and heated to 600 °C at a heating rate of 5 °C / min under argon atmosphere and kept at this temperature for 2 h.

[0044] (6) The sample in (5) was treated with a 10% by mass hydrofluoric acid solution at 30°C for 12 h, filtered and washed with water and ethanol until the filtrate was neutral, and dried in a forced air drying oven at 80°C for 12 h to obtain a sulfur-doped carbon material.

[0045] High-resolution transmission electron microscopy images ( Figure 1 ) and high-resolution scanning electron microscopy images ( Figure 2) showed that the sulfur-doped carbon material prepared by this technical route well retained the pore structure of the silicon template.

[0046] Example 2

[0047] (1) 500 mg of glucose and 1.6 g of SBA-15 (M (carbon source): M (silicon molecular sieve) = 31%) were ultrasonically dispersed and dissolved in 20 mL of deionized water. The mixture was stirred at 25°C for 48 h until the solvent was completely evaporated to obtain a precursor mixture of glucose and SBA-15.

[0048] (2) The precursor mixture obtained in (1) and 8 mL of CS2 (M (precursor mixture): M (sulfur source) = 21%) were transferred and packaged into a high-temperature reactor under an argon atmosphere.

[0049] (3) Place the medium- and high-temperature reactor (2) in a muffle furnace, heat it to 400°C at a heating rate of 10°C / min, and keep the temperature constant for 4 hours.

[0050] (4) The sample obtained in (3) was treated with 6 mol / L sodium hydroxide solution at 60°C for 3 h, filtered, washed with water and ethanol until the filtrate was neutral, and then transferred to a drying oven at 80°C for 12 h.

[0051] (5) The dried sample in (4) was transferred to a tube furnace and heated to 800 °C at a heating rate of 5 °C / min under argon atmosphere and kept at this temperature for 2 h.

[0052] (6) The sample in (5) was treated with a 10% by mass hydrofluoric acid solution at 30°C for 12 h, filtered and washed with water and ethanol until the filtrate was neutral, and dried in a forced air drying oven at 80°C for 12 h to obtain a sulfur-doped carbon material.

[0053] Example 3

[0054] (1) 500 mg of glucose and 1.6 g of SBA-15 (M (carbon source): M (silicon molecular sieve) = 31%) were ultrasonically dispersed and dissolved in 20 mL of deionized water. The mixture was stirred at 25°C for 48 h until the solvent was completely evaporated to obtain a precursor mixture of glucose and SBA-15.

[0055] (2) The precursor mixture obtained in (1) and 8 mL of CS2 (M (precursor mixture): M (sulfur source) = 21%) were transferred and packaged into a high-temperature reactor under an argon atmosphere.

[0056] (3) Place the medium- and high-temperature reactor (2) in a muffle furnace, heat it to 500°C at a heating rate of 10°C / min, and keep the temperature constant for 4 h.

[0057] (4) The sample obtained in (3) was treated with 6 mol / L sodium hydroxide solution at 60°C for 3 h, filtered, washed with water and ethanol until the filtrate was neutral, and then transferred to a drying oven at 80°C for 12 h.

[0058] (5) The dried sample in (4) was transferred to a tube furnace and heated to 1000°C at a heating rate of 5°C / min under argon atmosphere and kept at this temperature for 2 h.

[0059] (6) The sample in (5) was treated with a 10% by mass hydrofluoric acid solution at 30°C for 12 h, filtered and washed with water and ethanol until the filtrate was neutral, and dried in a forced air drying oven at 80°C for 12 h to obtain a sulfur-doped carbon material.

[0060] Comparative Example 1

[0061] (1) 500 mg of glucose and 1.6 g of SBA-15 (M (carbon source): M (silicon molecular sieve) = 31%) were ultrasonically dispersed and dissolved in 20 mL of deionized water. The mixture was stirred at 25°C for 48 h until the solvent was completely evaporated to obtain a precursor mixture of glucose and SBA-15.

[0062] (2) The sample in (1) was transferred to a tube furnace, and an argon atmosphere containing bubbling CS2 (M (precursor mixture): M (sulfur source) = 21%) was introduced. The temperature was increased to 600°C at a heating rate of 5°C / min and kept constant for 2h.

[0063] (3) The sample obtained in (2) was treated with a 6 mol / L sodium hydroxide solution at 60°C for 3 h, filtered and washed with water and ethanol until the filtrate was neutral. The sample was then treated with a 10% by mass hydrofluoric acid solution at 30°C for 12 h, filtered and washed with water and ethanol until the filtrate was neutral, and dried in a forced air drying oven at 80°C for 12 h to obtain a comparative material prepared by a one-step high-temperature reaction.

[0064] Comparative Example 2

[0065] (1) 500 mg of glucose and 1.6 g of SBA-15 (M (carbon source): M (silicon molecular sieve) = 31%) were ultrasonically dispersed and dissolved in 20 mL of deionized water. The mixture was stirred at 25°C for 48 h until the solvent was completely evaporated to obtain a precursor mixture of glucose and SBA-15.

[0066] (2) The sample in (1) was transferred to a tube furnace, and an argon atmosphere containing bubbling CS2 (M (precursor mixture): M (sulfur source) = 21%) was introduced. The temperature was increased to 800°C at a heating rate of 5°C / min and kept constant for 2 h.

[0067] (3) The sample obtained in (2) was treated with a 6 mol / L sodium hydroxide solution at 60°C for 3 h, filtered and washed with water and ethanol until the filtrate was neutral. The sample was then treated with a 10% by mass hydrofluoric acid solution at 30°C for 12 h, filtered and washed with water and ethanol until the filtrate was neutral, and dried in a forced air drying oven at 80°C for 12 h to obtain a comparative material prepared by a one-step high-temperature reaction.

[0068] Comparative Example 3

[0069] (1) 500 mg of glucose and 1.6 g of SBA-15 (M (carbon source): M (silicon molecular sieve) = 31%) were ultrasonically dispersed and dissolved in 20 mL of deionized water. The mixture was stirred at 25°C for 48 h until the solvent was completely evaporated to obtain a precursor mixture of glucose and SBA-15.

[0070] (2) The sample in (1) was transferred to a tube furnace, and an argon atmosphere containing bubbling CS2 (M (precursor mixture): M (sulfur source) = 21%) was introduced. The temperature was increased to 1000°C at a heating rate of 5°C / min and kept constant for 2 h.

[0071] (3) The sample obtained in (2) was treated with a 6 mol / L sodium hydroxide solution at 60°C for 3 h, filtered and washed with water and ethanol until the filtrate was neutral. The sample was then treated with a 10% by mass hydrofluoric acid solution at 30°C for 12 h, filtered and washed with water and ethanol until the filtrate was neutral, and dried in a forced air drying oven at 80°C for 12 h to obtain a comparative material prepared by a one-step high-temperature reaction.

[0072] Application Example 1

[0073] The sulfur-doped carbon material obtained in Example 1 was used in a sodium ion battery system to investigate its electrochemical performance as a negative electrode material of the battery.

[0074] 1.Battery preparation:

[0075] Active material, acetylene black and binder (PVDF) were weighed in a mass ratio of 7:2:1 in sequence and added to an appropriate amount of 1-methyl-2-pyrrolidone to form a uniform active material slurry. The active material slurry was coated on a copper foil using a coating machine and then dried in an oven at 60°C for 24 hours. CR2032 batteries were assembled in an argon-filled glove box (ensuring that the water and oxygen values were all below 0.1 ppm), using metallic sodium as the counter electrode, Whatman glass fiber as the separator, and 1.0 M NaClO4 dissolved in ethylene carbonate and propylene carbonate with 5 wt% fluoroethylene carbonate added and a volume ratio of 1:1 as the electrolyte.

[0076] 2.Electrochemical performance evaluation:

[0077] Test conditions:

[0078] Temperature: 30°C; Voltage range: 0.01-3V; Current density: 100mA·g -1 and 2000mAg -1 .

[0079] 3. Discussion of results

[0080] Regardless of the low current density of 100mA·g -1 Or high current density 2000mAg -1 Under the test conditions, the material showed good cycle stability and high reversible specific capacity. -1 After 100 test cycles, the current density still maintains 410mAh g -1 The reversible capacity ( Figure 3 ), at a high current density of 2000mAg -1 After 1500 cycles test, there is still 270mAh g -1 The reversible capacity ( Figure 4 ), the test results show that the sulfur-doped carbon material prepared by the inventive technology shows great application potential as a sodium ion electrode material.

[0081] Application Example 2

[0082] The sulfur-doped carbon material obtained in Example 2 was applied to a sodium ion battery system to investigate its electrochemical performance as a negative electrode material of the battery.

[0083] 1.Battery preparation:

[0084] Active material, acetylene black and binder (PVDF) were weighed in a mass ratio of 7:2:1 in sequence and added to an appropriate amount of 1-methyl-2-pyrrolidone to form a uniform active material slurry. The active material slurry was coated on a copper foil using a coating machine and then dried in an oven at 60°C for 24 hours. CR2032 batteries were assembled in an argon-filled glove box (ensuring that the water and oxygen values were all below 0.1 ppm), using metallic sodium as the counter electrode, Whatman glass fiber as the separator, and 1.0 M NaClO4 dissolved in ethylene carbonate and propylene carbonate with 5 wt% fluoroethylene carbonate added and a volume ratio of 1:1 as the electrolyte.

[0085] 2.Electrochemical performance evaluation:

[0086] Test conditions:

[0087] Temperature: 30°C; Voltage range: 0.01-3V; Current density: 100mA·g -1 .

[0088] 3. Discussion of the results

[0089] The sulfur-doped carbon material prepared by changing the synthesis temperature of the preparation process within the scope of the claims has a high conductivity at 100 mA·g -1 After 100 test cycles at the same current density, the capacity remains at 400 mAh g -1 ( Figure 5 ), the test results show that the sulfur-doped carbon material prepared by the inventive technology shows great application potential as a sodium ion electrode material.

[0090] Application Example 3

[0091] The sulfur-doped carbon material obtained in Example 3 was used in a sodium ion battery system to investigate its electrochemical performance as a negative electrode material of the battery.

[0092] 1.Battery preparation:

[0093] Active material, acetylene black and binder (PVDF) were weighed in a mass ratio of 7:2:1 in sequence and added to an appropriate amount of 1-methyl-2-pyrrolidone to form a uniform active material slurry. The active material slurry was coated on a copper foil using a coating machine and then dried in an oven at 60°C for 24 hours. CR2032 batteries were assembled in an argon-filled glove box (ensuring that the water and oxygen values were all below 0.1 ppm), using metallic sodium as the counter electrode, Whatman glass fiber as the separator, and 1.0 M NaClO4 dissolved in ethylene carbonate and propylene carbonate with 5 wt% fluoroethylene carbonate added and a volume ratio of 1:1 as the electrolyte.

[0094] 2.Electrochemical performance evaluation:

[0095] Test conditions:

[0096] Temperature: 30°C; Voltage range: 0.01-3V; Current density: 100mA·g -1 .

[0097] 3. Discussion of the results

[0098] The sulfur-doped carbon material prepared by changing the synthesis temperature of the preparation process within the scope of the claims has a high conductivity at 100 mA·g -1 After 100 test cycles at the same current density, the capacity remains at 393 mAh g -1 ( Figure 6 ), the test results show that the sulfur-doped carbon material prepared by this invention technology has great application potential as a sodium ion electrode material.

[0099] Application Example 4

[0100] The comparative material obtained in Comparative Example 1 was used in a sodium ion battery system to examine its electrochemical performance as a negative electrode material of the battery.

[0101] 1.Battery preparation:

[0102] Active material, acetylene black and binder (PVDF) were weighed in a mass ratio of 7:2:1 in sequence and added to an appropriate amount of 1-methyl-2-pyrrolidone to form a uniform active material slurry. The active material slurry was coated on a copper foil using a coating machine and then dried in an oven at 60°C for 24 hours. CR2032 batteries were assembled in an argon-filled glove box (ensuring that the water and oxygen values were all below 0.1 ppm), using metallic sodium as the counter electrode, Whatman glass fiber as the separator, and 1.0 M NaClO4 dissolved in ethylene carbonate and propylene carbonate with 5 wt% fluoroethylene carbonate added and a volume ratio of 1:1 as the electrolyte.

[0103] 2.Electrochemical performance evaluation:

[0104] Test conditions:

[0105] Temperature: 30°C; Voltage range: 0.01-3V; Current density: 100mA·g -1 .

[0106] 3. Discussion of the results

[0107] The comparative material prepared by a one-step high temperature reaction was -1 After 100 test cycles at the current density, the capacity is only 210 mAh g -1 ( Figure 7 ), the comparative test results show that the sulfur-doped carbon material prepared by the synthesis technology route in the claims has superior performance when used as a negative electrode material for sodium ion batteries.

[0108] Application Example 5

[0109] The comparative material obtained in Comparative Example 2 was used in a sodium ion battery system to examine its electrochemical performance as a negative electrode material of the battery.

[0110] 1.Battery preparation:

[0111] Active material, acetylene black and binder (PVDF) were weighed in a mass ratio of 7:2:1 in sequence and added to an appropriate amount of 1-methyl-2-pyrrolidone to form a uniform active material slurry. The active material slurry was coated on a copper foil using a coating machine and then dried in an oven at 60°C for 24 hours. CR2032 batteries were assembled in an argon-filled glove box (ensuring that the water and oxygen values were all below 0.1 ppm), using metallic sodium as the counter electrode, Whatman glass fiber as the separator, and 1.0 M NaClO4 dissolved in ethylene carbonate and propylene carbonate with 5 wt% fluoroethylene carbonate added and a volume ratio of 1:1 as the electrolyte.

[0112] 2.Electrochemical performance evaluation:

[0113] Test conditions:

[0114] Temperature: 30°C; Voltage range: 0.01-3V; Current density: 100mA·g -1 .

[0115] 3. Discussion of the results

[0116] The comparative materials obtained by changing the temperature in the one-step high-temperature reaction process were -1 After 50 cycles of testing at the current density, the cycle capacity is only 149 mAh g -1 ( Figure 8 ), the comparative test results show that the sulfur-doped carbon material prepared by the synthesis technology route in the claims has superior performance when used as a negative electrode material for sodium ion batteries.

[0117] Application Example 6

[0118] The comparative material obtained in Comparative Example 3 was used in a sodium ion battery system to examine its electrochemical performance as a negative electrode material of the battery.

[0119] 1.Battery preparation:

[0120] Active material, acetylene black and binder (PVDF) were weighed in a mass ratio of 7:2:1 in sequence and added to an appropriate amount of 1-methyl-2-pyrrolidone to form a uniform active material slurry. The active material slurry was coated on a copper foil using a coating machine and then dried in an oven at 60°C for 24 hours. CR2032 batteries were assembled in an argon-filled glove box (ensuring that the water and oxygen values were all below 0.1 ppm), using metallic sodium as the counter electrode, Whatman glass fiber as the separator, and 1.0 M NaClO4 dissolved in ethylene carbonate and propylene carbonate with 5 wt% fluoroethylene carbonate added and a volume ratio of 1:1 as the electrolyte.

[0121] 2.Electrochemical performance evaluation:

[0122] Test conditions:

[0123] Temperature: 30°C; Voltage range: 0.01-3V; Current density: 100mA·g -1 .

[0124] 3. Discussion of the results

[0125] The comparative materials obtained by changing the temperature in the one-step high-temperature reaction process were -1 After 70 cycles of testing at the current density, the cycle capacity is only 98 mAh g -1 ( Figure 9 ), the comparative test results show that the sulfur-doped carbon material prepared by the synthesis technology route in the claims has superior performance when used as a negative electrode material for sodium ion batteries.

[0126] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the above embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for preparing a sulfur-doped carbon material, characterized in that: The following steps are involved: (1) depositing a carbon source on a silicon molecular sieve by a co-precipitation method to obtain a mixture of a carbon source and a silicon molecular sieve precursor; (2) transferring the precursor mixture and the sulfur source obtained in step (1) into a high-temperature reaction vessel under the protection of an inert atmosphere; (3) performing a high-temperature vulcanization reaction in a high-temperature reactor; (4) treating the product obtained in step (3) with alkali, washing, and drying to obtain a silicon molecular sieve / carbon intermediate composite material; (5) performing a carbonization reaction on the silicon molecular sieve / carbon intermediate composite material obtained in step (4) under the protection of an inert atmosphere 2 to obtain a silicon molecular sieve / carbon composite material; (6) The silicon molecular sieve / carbon composite material obtained in step (5) is subjected to acid treatment, washed, and dried to obtain a sulfur-doped carbon material.

2. The preparation method according to claim 1, wherein: In the step (1), the carbon source is any one of maltose, soluble starch, sucrose, anhydrous glucose, fructose, lactose, dopamine hydrochloride, melamine, dicyandiamide, urea or pyridine; and the silicon molecular sieve is any one of silicon spheres, silicon nanopowder, silica sol, SBA-15 or MCM-41, or a mixture of two or more thereof.

3. The preparation method according to claim 1, wherein: In the step (1), the coprecipitation temperature is 25-100° C. and the time is 6-72 hours. The addition ratio of the carbon source to the silicon molecular sieve is 10% to 60% by mass.

4. The preparation method according to claim 1, wherein: In the step (2), the inert atmosphere is one of argon, nitrogen, and helium, or a mixture of two or more thereof; the sulfur source is any one of carbon disulfide, thiourea, sodium sulfide, potassium sulfide, ammonium sulfide, or thioacetamide; and the addition ratio of the precursor mixture and the sulfur source is a mass fraction ratio of 10% to 100%.

5. The preparation method according to claim 1, wherein: In the step (3), the temperature rise rate of the high-temperature vulcanization reaction is in the range of 1 to 20°C / min; the temperature is raised to an end point temperature of 200 to 500°C; and the constant temperature time at the end point temperature is 2 to 6 hours.

6. The preparation method according to claim 1, wherein: In the step (4), the alkali solution in the alkali treatment is a sodium hydroxide solution with a concentration of 1 to 8 mol / L or a potassium hydroxide solution with a concentration of 1 to 8 mol / L, the alkali treatment time is 2 to 6 hours, the alkali treatment temperature is 60 to 100° C.; the drying temperature is 25 to 80° C., and the drying time is 6 to 72 hours.

7. The preparation method according to claim 1, wherein: In the step (5), the second inert atmosphere is one or a mixture of two or more of argon, nitrogen, and helium; the heating rate of the carbonization reaction is in the range of 1 to 20°C / min, the temperature is raised to 600 to 1000°C at the end point, and the constant temperature time at the end point temperature is 1 to 6 hours.

8. The preparation method according to claim 1, wherein: In the step (6), the acid in the acid treatment is a hydrofluoric acid solution with a mass fraction of 5 to 20%, the acid treatment time is 6 to 48 hours, the acid treatment temperature is 25 to 60° C.; the drying temperature is 25 to 80° C., and the drying time is 6 to 72 hours.

9. The sulfur-doped carbon material prepared by the preparation method according to any one of claims 1 to 8, characterized in that: The structure of the prepared sulfur-doped carbon material can be controlled according to the template used.

10. An application of the sulfur-doped carbon material prepared by the preparation method according to any one of claims 1 to 8, characterized in that: The material is used as a negative electrode material in a sodium ion battery system.

Images