Method for preparing silicon-carbon electrode material by using coal-to-hydrogen by-product metal-rich residual carbon

Abstract

The invention belongs to the field of high-value utilization of waste industrial products, and particularly relates to a method for preparing a silicon-carbon electrode material by using metal-rich residual carbon of a coal-to-hydrogen byproduct. According to the method disclosed by the invention, harmful light and heavy metal impurities in the metal-rich residual carbon can be removed, and meanwhile, the carbon-silicon composite porous structure and the endogenous graphene are synchronously generated. Due to the large surface specific surface area, the special hole structure and the enhanced conductivity of endogenous graphene, when the carbon structure is matched with hybrid silicon holes in the carbon structure to be used as electrodes of a super capacitor, a lithium ion battery and a sodium ion battery, the super capacitor, the lithium ion battery and the sodium ion battery can obtain very high electrochemical performance; and particularly, the material has excellent specific capacity and excellent rate capability.

Description

Technical Field

[0001] This invention belongs to the field of high-value utilization of waste industrial products, specifically relating to a method for preparing silicon-carbon electrode materials using metal-rich residual carbon from coal-to-hydrogen byproducts. Background Technology

[0002] Coal-to-hydrogen technology is widely used in energy conversion, but producing 1 ton of hydrogen generates approximately 8-10 tons of metal-rich residual carbon byproducts. This residual carbon has a complex composition, containing various heavy metals such as Fe, Ni, Cr, and As, and exhibits a highly disordered amorphous structure with low porosity and a small specific surface area (typically <50m²). 2 Currently, heavy metals are mainly disposed of through landfill or incineration, which not only wastes resources but also poses an environmental risk of heavy metal leakage.

[0003] In the field of electrochemical energy storage, silicon-carbon composite materials have become a research hotspot for next-generation electrode materials due to the ultra-high theoretical specific capacity of silicon (4200 mAh / g) and the good conductivity of carbon materials. However, existing technologies face three major bottlenecks: First, the volume expansion rate of silicon materials during charging and discharging is as high as 100%-300%, leading to electrode structure damage; second, the interfacial bonding between silicon and the carbon matrix is ​​weak, making it prone to delamination; and third, the preparation of traditional silicon-carbon materials relies on high-purity carbon and silicon sources, resulting in high costs and difficulty in achieving large-scale production.

[0004] Meanwhile, although coal-based carbon materials are considered ideal precursors due to their abundant reserves and low cost, the large number of amorphous components and aliphatic side chains in the macromolecular structure of coal leads to low ion transport efficiency and unstable electrochemical performance in their derived carbon materials. Existing modification methods mostly employ complex pretreatment processes or introduce expensive additives, failing to effectively solve the synergistic problem of "hazardous waste resource utilization" and "high-performance material preparation". Summary of the Invention

[0005] This invention addresses the technical problems mentioned in the background section by proposing a method for preparing silicon-carbon electrode materials using metal-rich residual carbon from coal-to-hydrogen byproducts. Through the synergistic effect of silane coupling agent modification, phosphorus source activation, and multi-stage hydrothermal grinding and washing processes, heavy metal removal, carbon-silicon interface optimization, and porous structure construction are achieved simultaneously, providing a new path for the high-value utilization of waste industrial products.

[0006] The raw material composition of this invention is as follows: Carbon source: Metal-rich residual carbon from coal-to-hydrogen byproducts, with fixed carbon content ≥60wt% and total heavy metal content ≤15wt% (including Fe 3-8wt%, Ni 1-3wt%, Cr 0.5-2wt%, etc.).

[0007] Silicon source: Silane coupling agent KH550, purity ≥98%. The amino groups in its molecular structure form chemical bonds with the functional groups on the carbon surface, and the siloxane groups can be hydrolyzed to generate silanol groups, which enhances the reactivity with phosphorus sources.

[0008] Phosphorus source: pyrophosphoric acid (85wt%) or oligophosphoric acid, preferably pyrophosphoric acid, whose fluidity and permeability at high temperatures ensure that it reacts fully with the metal components to form soluble phosphates.

[0009] Auxiliary reagents: anhydrous ethanol (purity ≥ 99.5%), deionized water (conductivity ≤ 10 μS / cm).

[0010] The process flow for preparing silicon-carbon electrode materials using metal-rich residual carbon as a byproduct of coal-to-hydrogen production is as follows: drying, grinding, and classifying the metal-rich residual carbon from coal-to-hydrogen production → silane coupling agent treatment → phosphorus source hot soaking → calcination activation → intermittent hydrothermal-hot water grinding and washing treatment → drying.

[0011] The specific steps are as follows: (1) Drying, grinding and grading The metal-rich residual carbon, a byproduct of coal-to-hydrogen production, was placed in a forced-air drying oven and dried at 150°C for 4 hours to remove free water and some adsorbed water. Subsequently, it was pulverized using a planetary ball mill with a ball-to-material ratio of 10:1, a rotation speed of 300 r / min, and a grinding time of 2 hours. The powder with a particle size ≤50 μm was collected by grading through a 250-mesh standard sieve to ensure the uniformity of subsequent reactions.

[0012] (2) Silane coupling agent treatment

[0013] Prepare an ethanol solution of 25-50 wt% KH550 or KH570 silane coupling agent, and pre-hydrolyze it for 30 minutes (hydrolysis temperature 25℃, pH value adjusted to 4-5) to generate an active intermediate containing silanol groups. The dried, ground, and graded coal-to-hydrogen byproduct, metal-rich residual carbon, was added to a high-speed mixer (1500 r / min). While stirring, an ethanol solution of the silane coupling agent was added through a high-pressure spray device (0.3 MPa) at a spray rate of 5 mL / min to ensure full contact between the powder and the silane solution. After mixing, stirring was continued for 30 minutes to allow KH550 or KH570 molecules to be loaded onto the carbon surface through both physical adsorption and chemical bonding. Finally, the mass ratio of silane to residual carbon was controlled within the range of 1:4.5-1:5.

[0014] (3) Phosphorus source heat immersion

[0015] The metal-rich residual carbon of the coal-to-hydrogen byproduct loaded with silane coupling agent was transferred to a reactor equipped with a stirrer, and a phosphorus source was added while it was hot. The reactor was stirred at 500 r / min for 2 hours, during which trace amounts of gas generated by the reaction were purged with nitrogen to ensure that the heavy metals and phosphorus source reacted fully to generate soluble salts such as FePO4 and Ni3(PO4)2.

[0016] The phosphorus source should be pyrophosphoric acid or oligophosphoric acid, with the standard being complete immersion of the solid. The amount used is generally 1-3 times the weight of the carbon source; the immersion temperature is 160-180℃.

[0017] (4) Calcination activation

[0018] Excess phosphorus source is removed by filtration. The material is extruded into long strips with a diameter of 30 mm and a length of 50 mm using a screw extruder and allowed to cool naturally to room temperature. The strips are then placed in a tube furnace and high-purity nitrogen (purity ≥ 99.99%) is introduced at a flow rate of 50 mL / min. The heating program is as follows: room temperature → 300-400℃: heating rate 5℃ / min, holding for 60 minutes to remove residual ethanol and low-molecular-weight volatiles; 300-400℃ → 700-900℃: heating rate 3℃ / min, holding for 120 minutes to achieve carbon-silicon composite and endogenous graphene (the carbon source generated by silane decomposition interacts with the carbon matrix to form a sheet-like graphene structure). After natural cooling to room temperature, a primary silicon-carbon composite material is obtained, in which the endogenous graphene content is ≥ 5 wt% and the specific surface area is ≥ 300 m² / g.

[0019] (5) Intermittent hydrothermal-hot water grinding and washing treatment

[0020] The primary composite material was placed in a hydrothermal reactor, and deionized water was added until it was completely submerged. After sealing, it was placed in a tiltable oven (20 r / min) and reacted at 130°C for 4 hours. After cooling to 80°C, the pressure was slowly released and the lid was opened. The slurry was transferred to an ultrasonic grinder (500W power, 20kHz frequency) and ground for 15 minutes to remove the phosphate adhering to the surface. Vacuum filtration (pressure -0.08MPa) was used to remove the acidic washing solution (pH≤2). The above hydrothermal-grinding-filtration process was repeated 4-6 times until the pH of the filtrate was 6.5-7.5, ensuring that the heavy metal removal rate was ≥98%. The final heavy metal content in the washing solution was: Fe≤0.01mg / L, Ni≤0.005mg / L, Cr≤0.003mg / L, which met the national integrated wastewater discharge standard (GB 8978-1996).

[0021] (6) Drying

[0022] The washed slurry was filtered, and the filter cake was placed in a vacuum drying oven and dried at 110°C for 8 hours until constant weight. It was then ground with a high-speed pulverizer to a particle size ≤20μm to obtain the finished silicon-carbon electrode material.

[0023] The silicon-carbon electrode material prepared using metal-rich residual carbon as a byproduct of coal-to-hydrogen production has a specific surface area of ​​300-600 m² / g, a total pore volume of 0.5-1.2 cm³ / g, an average pore diameter of 2-5 nm, a silicon content of 5-15 wt%, and a graphene content of 5-8 wt%.

[0024] The silicon-carbon electrode material prepared by this invention can be used to prepare supercapacitor electrodes, lithium-ion battery anode sheets, or sodium-ion battery anode sheets.

[0025] (1) Preparation of lithium-ion battery negative electrode: Weigh silicon carbon material, conductive carbon black and binder (PVDF) at a mass ratio of 8:1:1, add N-methylpyrrolidone (NMP) solvent, disperse in a planetary mixer for 2 hours to prepare a slurry with a solid content of 40wt%; coat the slurry on copper foil (wet film thickness 150μm), vacuum dry at 80℃ for 12 hours, roll to a thickness of 80μm, and cut into electrode sheets with a diameter of 12mm (area density 10-12mg / cm²). Pre-lithiation treatment of electrode sheets: In an argon glove box, the electrode sheets are paired with lithium metal sheets and charged to 0.01V at a rate of 0.05C. The charge is then maintained at this temperature for 2 hours to remove unstable components from the surface SEI film.

[0026] (2) Preparation of sodium-ion battery negative electrode: The electrode preparation process is the same as that of lithium-ion battery, and no pre-lithiation treatment is required; Electrochemical performance: In 1 mol / L NaClO4-EC / DMC electrolyte, the initial discharge capacity at 0.1C rate is ≥300mAh / g, and the capacity retention rate after 100 cycles is ≥80%.

[0027] (3) Preparation of supercapacitor electrodes: Weigh silicon carbide, conductive carbon black and binder (PTFE) in a mass ratio of 7:2:1, add a small amount of deionized water and grind into a uniform paste; roll the paste into a film with a thickness of 50μm, cut it into 10×10mm electrode sheets, vacuum dry at 120℃ for 6 hours, and assemble into a button supercapacitor (electrolyte is 6mol / L KOH).

[0028] Beneficial effects: (1) The metal-rich residual carbon (hazardous waste) byproduct of coal-to-hydrogen production is converted into high-value silicon-carbon electrode material with a heavy metal removal rate of ≥98%, which solves the environmental pollution problem of traditional treatment methods and realizes resource recycling; the entire preparation process has no toxic gas emissions, and the washing liquid can meet the emission standards after neutralization treatment; the raw material cost is only 1 / 3-1 / 2 of that of traditional silicon-carbon materials, and the process is simple and easy to scale up.

[0029] (2) By modifying silane to form a carbon-silicon chemical bonding interface, the volume expansion of silicon particles is effectively suppressed. At the same time, the endogenous graphene significantly improves the conductivity of the material (conductivity ≥100S / m), and the porous structure (pore size 2-5nm) provides channels for ion transport.

[0030] (3) The prepared silicon-carbon material has a coulombic efficiency of ≥90% for the first time in lithium-ion batteries and its cycle stability is better than that of traditional silicon-carbon materials; its specific capacitance in supercapacitors is ≥200F / g, which meets the requirements of high-performance energy storage devices. Attached Figure Description

[0031] Figure 1 The image shown is an electron microscope image of the silicon-carbon electrode material prepared in Example 3.

[0032] Figure 2 The energy spectrum mapping diagram and elemental composition table of the silicon-carbon electrode material prepared in Example 3 are shown. Detailed Implementation

[0033] Example 1: Raw materials: Residual metal-rich carbon from coal-to-hydrogen production (65wt% fixed carbon, 5wt% Fe, 2wt% Ni, 1wt% Cr), KH550 (98%), pyrophosphate (85wt%), anhydrous ethanol; The preparation process of silicon-carbon electrode material is as follows: (1) Drying, grinding and grading The metal-rich residual carbon, a byproduct of coal-to-hydrogen production, was placed in a forced-air drying oven and dried at 150°C for 4 hours to remove free water and some adsorbed water. Subsequently, it was pulverized using a planetary ball mill with a ball-to-material ratio of 10:1, a rotation speed of 300 r / min, and a grinding time of 2 hours. The powder with a particle size ≤50 μm was collected by grading through a 250-mesh standard sieve to ensure the uniformity of subsequent reactions.

[0034] (2) Silane coupling agent treatment

[0035] Prepare a 30wt% KH550 ethanol solution and pre-hydrolyze it for 30 minutes (hydrolysis temperature 25℃, pH adjusted to 4.5) to generate an active intermediate containing silanol groups. Add the dried, ground, and graded coal-to-hydrogen byproduct metal-rich residual carbon to a high-speed mixer (1500 r / min). While stirring, add the above-mentioned silane coupling agent ethanol solution through a high-pressure spray device (pressure 0.3 MPa) at a spray rate of 5 mL / min to ensure that the powder and the silane coupling agent ethanol solution are in full contact. After mixing, continue stirring for 30 minutes to allow KH550 molecules to be loaded onto the carbon surface through both physical adsorption and chemical bonding. Finally, the silane dosage to residual carbon mass ratio is controlled within the range of 1:5.

[0036] (3) Phosphorus source heat immersion

[0037] The metal-rich residual carbon from the coal-to-hydrogen byproduct loaded with silane coupling agent was transferred to a reactor equipped with a stirrer at 170°C. Pyrophosphoric acid was added while hot, with the solid completely submerged, at a rate of 1 times the weight of the carbon source. The mixture was stirred at 500 r / min for 2 hours, during which trace amounts of gas generated by the reaction were purged with nitrogen to ensure that the heavy metals and phosphorus source reacted fully to generate soluble salts such as FePO4 and Ni3(PO4)2.

[0038] (4) Calcination activation

[0039] Excess phosphorus source was removed by filtration. The material was extruded into long strips with a diameter of 30 mm and a length of 50 mm using a screw extruder and allowed to cool naturally to room temperature. The strips were then placed in a tube furnace and high-purity nitrogen (purity ≥ 99.99%) was introduced at a flow rate of 50 mL / min. The heating program was as follows: room temperature → 300℃: heating rate 5℃ / min, holding for 60 minutes to remove residual ethanol and low-molecular-weight volatiles; 300℃ → 900℃: heating rate 3℃ / min, holding for 120 minutes to achieve carbon-silicon composite and endogenous graphene (the carbon source generated by the decomposition of KH550 interacts with the carbon matrix to form a sheet-like graphene structure). After natural cooling to room temperature, a primary silicon-carbon composite material was obtained, in which the endogenous graphene content was ≥ 5 wt% and the specific surface area was ≥ 300 m² / g.

[0040] (5) Intermittent hydrothermal-hot water grinding and washing treatment

[0041] The primary composite material was placed in a hydrothermal reactor, and deionized water was added until it was completely submerged. After sealing, it was placed in a tiltable oven (20 r / min) and reacted at 130°C for 4 hours. After cooling to 80°C, the pressure was slowly released and the lid was opened. The slurry was transferred to an ultrasonic grinder (500W power, 20kHz frequency) and ground for 15 minutes to remove the phosphate adhering to the surface. Vacuum filtration (pressure -0.08MPa) was used to remove the acidic washing solution (pH≤2). The above hydrothermal-grinding-filtration process was repeated 5 times until the pH of the filtrate was 7.0, ensuring that the heavy metal removal rate was ≥98%. (6) Drying The washed slurry was filtered, and the filter cake was placed in a vacuum drying oven and dried at 110°C for 8 hours until constant weight. It was then ground with a high-speed pulverizer to a particle size ≤20μm to obtain the finished silicon-carbon electrode material.

[0042] Material performance testing: The physical properties of the silicon-carbon electrode material are as follows: specific surface area 420 m² / g, total pore volume 0.8 cm³ / g, silicon content 10 wt%, graphene content 6.5 wt%, and heavy metal removal rate 99.2%.

[0043] Preparation of lithium-ion test batteries: (1) Preparation of lithium-ion battery negative electrode: Weigh silicon carbon material, conductive carbon black and binder (PVDF) at a mass ratio of 8:1:1, add N-methylpyrrolidone (NMP) solvent, disperse in a planetary mixer for 2 hours to prepare a slurry with a solid content of 40wt%; coat the slurry on copper foil (wet film thickness 150μm), vacuum dry at 80℃ for 12 hours, roll to a thickness of 80μm, and cut into electrode sheets with a diameter of 12mm (area density 10-12mg / cm²). (2) Pre-lithiation treatment of electrode sheets: In an argon glove box, the electrode sheets are paired with lithium metal sheets and charged to 0.01V at a rate of 0.05C. The temperature is maintained for 2 hours to remove unstable components in the surface SEI film.

[0044] (3) Battery assembly: Take a positive electrode shell in an argon glove box, and place a standard lithium manganese oxide positive electrode sheet (coating facing up) and a separator (completely covering the electrode sheet) in sequence; add 4 drops of LiPF6 electrolyte with a dropper to wet the separator and positive electrode sheet, and let stand for 5 minutes; then place the negative electrode sheet (coating facing down, aligned with the positive electrode sheet), and finally place the gasket and spring sheet (convex side of the spring sheet facing up). Cover the negative electrode shell on the spring sheet, ensuring that the battery shell is aligned without misalignment, place it in a button cell sealing machine, adjust the pressure to 8~12MPa, and seal for 3 seconds. After sealing, remove the glove box and check for any leakage before testing.

[0045] Fabrication of supercapacitor testing devices: Weigh silicon carbide material, conductive carbon black, and binder (PTFE) in a mass ratio of 7:2:1, add a small amount of deionized water, and grind into a uniform paste. Roll the paste into a 50μm thick film, cut it into 10×10mm electrode sheets, vacuum dry at 120℃ for 6 hours, and assemble into a button-type supercapacitor (electrolyte is 6mol / L KOH).

[0046] Preparation of sodium-ion test batteries: (1) Preparation of sodium-ion battery negative electrode: The electrode sheet preparation process is the same as that of lithium-ion battery, and no pre-lithiation treatment is required; (2) Battery assembly: Take a positive electrode shell in an argon glove box, and place a standard sodium manganate layered oxide positive electrode sheet (coating facing up) and a separator (completely covering the electrode sheet) in sequence; add 4 drops of 1mol / L NaClO4-EC / DMC electrolyte with a dropper to wet the separator and positive electrode sheet, and let stand for 5 min; then place the negative electrode sheet (coating facing down, aligned with the positive electrode sheet), and finally place the gasket and spring sheet (convex side of the spring sheet facing up). Cover the negative electrode shell on the spring sheet, ensuring that the battery shell is aligned without misalignment, place it in a button battery sealing machine, adjust the pressure to 8~12 MPa, and seal for 3 s. After sealing, remove the glove box and check for leakage before testing.

[0047] Electrochemical performance of lithium-ion batteries: initial discharge capacity 1680mAh / g, initial charge capacity 1520mAh / g, initial coulombic efficiency 90.5%; capacity retention after 100 cycles 87%; 1C rate discharge capacity 850mAh / g.

[0048] Supercapacitor performance: Specific capacitance of 215 F / g at a current density of 1 A / g, and capacitance retention of 92% after 10,000 cycles at a current density of 10 A / g.

[0049] Sodium-ion battery performance: initial charge capacity 925mAh / g, initial discharge capacity 915mAh / g, initial coulombic efficiency 98.9%; capacity retention after 100 cycles 99%; 1C rate discharge capacity 850mAh / g.

[0050] Example 2: The raw materials are the same as in Example 1, and the preparation process is the same as in Example 1, except that the mass ratio of silane coupling agent to residual carbon is 1:4.5. The preparation of lithium-ion batteries, sodium-ion batteries, and supercapacitors is the same as in Example 1.

[0051] Carbon material performance testing: specific surface area 380 m² / g, total pore volume 0.7 cm³ / g, silicon content 8 wt%, graphene content 7.6 wt%, heavy metal removal rate 98.5%; Electrochemical performance of lithium-ion batteries: initial discharge capacity 1750mAh / g, initial charge capacity 1620mAh / g, initial coulombic efficiency 92.5%; capacity retention after 100 cycles 85%; 1C rate discharge capacity 1050mAh / g.

[0052] Supercapacitor performance: Specific capacitance of 220F / g at a current density of 1A / g, and capacitance retention of 92% after 10,000 cycles at a current density of 10A / g.

[0053] Sodium-ion battery performance: initial charge capacity 1150mAh / g, initial discharge capacity 1030mAh / g, initial coulombic efficiency 89.6%; capacity retention after 100 cycles 99%; 1C rate discharge capacity 970mAh / g.

[0054] Example 3: Raw materials: Metal-rich residual carbon from coal-to-hydrogen production (65wt% fixed carbon, 5wt% Fe, 2wt% Ni, 1wt% Cr), KH570 (97%), pyrophosphate (85wt%), anhydrous ethanol; The preparation process is the same as in Example 1, except that KH570 is used as the silane coupling agent.

[0055] The preparation of lithium-ion batteries, sodium-ion batteries, and supercapacitors is the same as in Example 1.

[0056] Carbon material performance testing: The physical properties of the silicon-carbon electrode material are as follows: specific surface area 410 m² / g, total pore volume 0.78 cm³ / g, silicon content 9.8 wt%, graphene content 6.2 wt%, and heavy metal removal rate 99.3%.

[0057] Electrochemical performance of lithium-ion batteries: initial discharge capacity 1580mAh / g, initial charge capacity 1420mAh / g, initial coulombic efficiency 89.9%; capacity retention after 100 cycles 90%; 1C rate discharge capacity 1090mAh / g.

[0058] Supercapacitor performance: Specific capacitance of 280F / g at a current density of 1A / g, and capacitance retention of 94% after 10,000 cycles at a current density of 10A / g.

[0059] Sodium-ion battery performance: initial charge capacity 850mAh / g, initial discharge capacity 810mAh / g, initial coulombic efficiency 95.3%; capacity retention after 100 cycles 99%; 1C rate discharge capacity 760mAh / g.

[0060] Example 4: Raw materials: Residual carbon rich in metals from coal-to-hydrogen production (65wt% fixed carbon, 5wt% Fe, 2wt% Ni, 1wt% Cr), KH550 (98%), oligophosphoric acid (free phosphoric acid <1%), anhydrous ethanol; The preparation process is the same as in Example 1, except that the phosphorus source is changed to oligophosphoric acid, and the amount used is 3 times the weight of carbon.

[0061] The preparation of lithium-ion batteries, sodium-ion batteries, and supercapacitors is the same as in Example 1.

[0062] Carbon material performance testing: The physical properties of the silicon-carbon electrode material are as follows: specific surface area 370 m² / g, total pore volume 0.77 cm³ / g, silicon content 10 wt%, graphene content 5.6 wt%, and heavy metal removal rate 98.5%.

[0063] Electrochemical performance of lithium-ion batteries: initial discharge capacity 1480mAh / g, initial charge capacity 1320mAh / g, initial coulombic efficiency 89.2%; capacity retention after 100 cycles 90%; 1C rate discharge capacity 880mAh / g.

[0064] Supercapacitor performance: Specific capacitance of 212 F / g at a current density of 1 A / g, and capacitance retention of 93% after 10,000 cycles at a current density of 10 A / g.

[0065] Sodium-ion battery performance: initial charge capacity 890mAh / g, initial discharge capacity 830mAh / g, initial coulombic efficiency 93.3%; capacity retention after 100 cycles 96%; 1C rate discharge capacity 730mAh / g.

[0066] Example 5: The raw materials are the same as in Example 1; The preparation process is the same as in Example 1, except that the heating program is as follows: room temperature → 400℃: heating rate 5℃ / min, holding for 60 minutes to remove residual ethanol and low molecular weight volatiles; 400℃ → 700℃: heating rate 3℃ / min, holding for 120 minutes. The preparation of lithium-ion batteries, sodium-ion batteries, and supercapacitors is the same as in Example 1.

[0067] Carbon material performance testing: The physical properties of the silicon-carbon electrode material are as follows: specific surface area 280 m² / g, total pore volume 0.72 cm³ / g, silicon content 14 wt%, graphene content 5.1 wt%, and heavy metal removal rate 99.9%.

[0068] Electrochemical performance of lithium-ion batteries: initial discharge capacity 1980mAh / g, initial charge capacity 1920mAh / g, initial coulombic efficiency 97.0%; capacity retention after 100 cycles 84%; 1C rate discharge capacity 1750mAh / g.

[0069] Supercapacitor performance: Specific capacitance of 202 F / g at a current density of 1 A / g, and capacitance retention of 89% after 10,000 cycles at a current density of 10 A / g.

[0070] Sodium-ion battery performance: initial charge capacity 1150mAh / g, initial discharge capacity 1110mAh / g, initial coulombic efficiency 96.5%; capacity retention after 100 cycles 91%; 1C rate discharge capacity 960mAh / g.

[0071] Comparative Example 1

[0072] The residual carbon from coal-to-hydrogen production is ground to a particle size of ≤20μm using a high-speed pulverizer. The resulting material is then used to manufacture lithium-ion batteries, sodium-ion batteries, and supercapacitors, following the same steps as in Example 1.

[0073] Carbon material performance testing: The physical properties of the electrode material obtained are: specific surface area 25 m² / g, total pore volume 0.06 cm³. 3 / g, silicon content 1wt%, heavy metal content 13%.

[0074] Electrochemical performance of lithium-ion batteries: Cannot be tested by direct short circuit.

[0075] Supercapacitor performance: Specific capacitance of 11 F / g at a current density of 1 A / g, and capacitance retention of 15% after 10,000 cycles at a current density of 10 A / g.

[0076] Sodium-ion battery performance: initial discharge capacity 110mAh / g, initial charge capacity 80mAh / g, initial coulombic efficiency 72.7%; short-circuit failure after 100 cycles.

[0077] Comparative Example 2

[0078] (1) Drying, grinding and grading

[0079] The metal-rich residual carbon, a byproduct of coal-to-hydrogen production, was placed in a forced-air drying oven and dried at 150°C for 4 hours to remove free water and some adsorbed water. Subsequently, it was pulverized using a planetary ball mill with a ball-to-material ratio of 10:1, a rotation speed of 300 r / min, and a grinding time of 2 hours. The powder with a particle size ≤50 μm was collected by grading through a 250-mesh standard sieve to ensure the uniformity of subsequent reactions.

[0080] (2) Phosphorus source heat immersion

[0081] The metal-rich residual carbon byproduct of coal-to-hydrogen production is transferred to a 170°C reactor equipped with a stirrer. Pyrophosphoric acid is added while hot, with the solid completely submerged, and the amount added is 1 times the weight of the carbon source. The reactor is stirred at 500 r / min for 2 hours, during which trace amounts of gas generated by the reaction are purged with nitrogen to ensure that the heavy metals and phosphorus source react fully to generate soluble salts such as FePO4 and Ni3(PO4)2.

[0082] (3) Intermittent hydrothermal-hot water grinding and washing treatment

[0083] The primary composite material was placed in a hydrothermal reactor, and deionized water was added until it was completely submerged. After sealing, it was placed in a tiltable oven (20 r / min) and reacted at 130°C for 4 hours. After cooling to 80°C, the pressure was slowly released and the lid was opened. The slurry was transferred to an ultrasonic grinder (500W power, 20kHz frequency) and ground for 15 minutes to remove the phosphate adhering to the surface. Vacuum filtration (pressure -0.08MPa) was used to remove the acidic washing solution (pH≤2). The above hydrothermal-grinding-filtration process was repeated 5 times until the pH of the filtrate was 7.0, ensuring that the heavy metal removal rate was ≥98%. (4) Drying The washed slurry was filtered, and the filter cake was placed in a vacuum drying oven and dried at 110°C for 8 hours until constant weight. It was then ground with a high-speed pulverizer to a particle size of ≤20μm to obtain the finished comparative material.

[0084] The obtained materials were used to make lithium-ion batteries, sodium-ion batteries, and supercapacitors in the same manner as in Example 1.

[0085] Carbon material performance testing: The physical properties of the electrode material obtained are: specific surface area 50 m² / g, total pore volume 0.1 cm³. 3 / g, silicon content 0.5wt%, heavy metal removal rate 99.9%.

[0086] Electrochemical performance of lithium-ion batteries: initial discharge capacity 480mAh / g, initial charge capacity 320mAh / g, initial coulombic efficiency 66.7%; capacity retention after 100 cycles 32%; 1C rate discharge capacity 110mAh / g.

[0087] Supercapacitor performance: Specific capacitance of 35 F / g at a current density of 1 A / g, and capacitance retention of 12% after 10,000 cycles at a current density of 10 A / g.

[0088] Sodium-ion battery performance: initial charge capacity 230mAh / g, initial discharge capacity 110mAh / g, initial coulombic efficiency 47.8%; capacity retention after 100 cycles 50%; 1C rate discharge capacity 96mAh / g.

Claims

1. A method for preparing silicon-carbon electrode materials using metal-rich residual carbon as a byproduct of coal-to-hydrogen production, characterized in that, The process flow for preparing the electrode material is as follows: drying, grinding and classifying residual carbon from coal-to-hydrogen production rich in metals → silane coupling agent treatment → phosphorus source hot soaking → calcination activation → intermittent hydrothermal-hot water grinding and washing treatment → drying.

2. The method for preparing silicon-carbon electrode materials using metal-rich residual carbon as a byproduct of coal-to-hydrogen production according to claim 1, characterized in that, The method steps are as follows: (1) Drying, grinding and grading: The metal-rich coal hydrogen production residual carbon is fully dried at 150°C and then pulverized in a pulverizer until the average particle size is ≤50μm; (2) Silane coupling agent treatment: The metal-rich coal hydrogen production residue carbon dried in step (1) is ground in a high-speed mixer while an ethanol solution of silane coupling agent is added by spraying, so that the metal-rich coal hydrogen production residue carbon can fully absorb the silane coupling agent. (3) Hot soaking with phosphorus source: The metal-rich coal-to-hydrogen residual carbon obtained in step (2) that has fully absorbed the silane coupling agent is added to the phosphorus source that can keep it submerged while hot and stirred and mixed for soaking. (4) Calcination and activation: After filtering out excess phosphorus source from the metal-rich coal-to-hydrogen residual carbon that has been soaked in phosphorus source in step (3) and fully absorbed silane coupling agent, it is extruded into strips and activated in a tube furnace under nitrogen atmosphere to obtain strip-shaped silicon-carbon composite material. (5) Intermittent hydrothermal-hot water grinding and washing treatment: The activated strip-shaped silicon-carbon composite material is placed in a hydrothermal reactor, filled with pure water and sealed. After the hydrothermal reaction, it is cooled to 80°C and the lid is opened. The acidic washing liquid is filtered out after grinding with an ultrasonic grinding gun for 15 minutes. The above steps are repeated until the filtrate is neutral. (6) Drying: After filtering the slurry prepared in step (5), dry it at 110°C to constant weight, and grind it to obtain silicon-carbon composite material.

3. The method for preparing silicon-carbon electrode materials using metal-rich residual carbon as a byproduct of coal-to-hydrogen production according to claim 2, characterized in that, In step (2), the silane coupling agent is KH550 or KH570, the concentration of the ethanol solution of the silane coupling agent is 25-50%wt, and the final mass ratio of the amount of silane coupling agent to the residual carbon of the metal-rich coal-to-hydrogen is 1:4.5-1:

5.

4. The method for preparing silicon-carbon electrode materials using metal-rich residual carbon as a byproduct of coal-to-hydrogen production according to claim 2, characterized in that, In step (3), the phosphorus source is selected as pyrophosphoric acid or oligophosphoric acid, and the soaking temperature is 160-180℃.

5. The method for preparing silicon-carbon electrode materials using metal-rich residual carbon as a byproduct of coal-to-hydrogen production according to claim 2, characterized in that, In step (4), activation is to first heat the temperature to 300-400℃ for 60 minutes, and then heat the temperature to 700-900℃ for 120 minutes.

6. The method for preparing silicon-carbon electrode materials using metal-rich residual carbon as a byproduct of coal-to-hydrogen production according to claim 2, characterized in that, In step (5), the hydrothermal reaction is carried out at 130°C for 4 hours in a rotatable oven.

7. A silicon-carbon electrode material prepared by the method according to any one of claims 1-6, characterized in that, Silicon-carbon electrode materials have a specific surface area of ​​300-600 m². 2 / g, silicon content 5-15wt%, graphene content 5-8wt%, heavy metal removal rate ≥98%.

8. An application of a silicon-carbon electrode material prepared by the method according to any one of claims 1-6, characterized in that, The silicon-carbon electrode material is used to prepare negative electrodes for supercapacitors, lithium-ion batteries, or sodium-ion batteries.

9. The application of the silicon-carbon electrode material according to claim 8, characterized in that, The negative electrode sheet is made by grinding silicon carbide electrode material with conductive carbon black and binder in a solvent to form a slurry, which is then coated or rolled onto a conductive substrate to form an electrode sheet.

10. The application of the silicon-carbon electrode material according to claim 8, characterized in that, The electrolyte for the supercapacitor electrode is 6 mol / L KOH; the lithium-ion battery anode needs to be pre-lithiated, specifically under the following conditions: charged at a rate of 0.05C to 0.01V and kept at that temperature for 2 hours; the electrolyte for the sodium-ion battery is 1 mol / L NaClO4-EC / DMC.

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