Preparation method of silicon-carbon electrode material, silicon-carbon electrode material and application of silicon-carbon electrode material

Abstract

The invention belongs to the field of preparation of electrode materials, and relates to a preparation method of a silicon-carbon electrode material, the silicon-carbon electrode material and application of the silicon-carbon electrode material. The invention provides a method for preparing a silicon-carbon electrode material. The method comprises the following steps: S1, cutting, crushing and screening a retired fan blade to obtain blade powder; s2, the leaf powder is subjected to acid pickling, filtering, washing and drying, and purified leaf powder is obtained; s3, pyrolyzing the purified leaf powder to obtain leaf pyrolytic carbon powder; s4, performing vacuum Joule heating on the blade pyrolytic carbon powder to obtain a solid product; s5, the solid product is subjected to ball milling and screening treatment, a silicon-carbon electrode material is prepared, specific Joule heating temperature, time and the like are selected, a silicon source and a carbon source in the retired fan blade are recovered and converted into the silicon-carbon electrode material, a recovered product with a high additional value is obtained, the resource value is increased, the whole process is simple, convenient and efficient, and the method is suitable for industrial production. Good application prospects are realized.

Description

Technical Field

[0001] The present invention belongs to the field of preparation of electrode materials, and particularly relates to a method for preparing a silicon-carbon electrode material, the silicon-carbon electrode material and its application. Background Art

[0002] The information disclosed in the background art of the present invention is only intended to increase the understanding of the overall background of the present invention, and is not necessarily regarded as an admission or an implication in any form that this information constitutes the prior art already known to those of ordinary skill in the art.

[0003] The wind power industry is booming, and old wind turbine blades are reaching the peak of retirement. How to achieve the efficient recycling and resource utilization of waste wind turbine blades has become a key issue affecting the green circular development and low-carbon footprint goals of the wind power industry. Wind turbine blades are mainly made of glass fiber reinforced resin composites (GFRP) based on organic resins. At present, the recycling methods of retired wind turbine blades mainly include mechanical processing, direct landfilling, chemical dissolution, incineration treatment and pyrolysis treatment, etc., but they generally have problems such as high recycling costs, low product value, and high environmental risks. Therefore, it is urgent to develop a new generation of recycling technologies with high efficiency, economy and environmental friendliness.

[0004] Due to its unique structural design, the silicon-carbon composite material exhibits excellent cycle stability, low expansion rate and high specific capacity, and is the focus of the research and development of negative electrode materials for future lithium-ion batteries. There are abundant silicon sources (glass fiber, 20%-30% SiO2) and carbon sources (matrix resin) in wind turbine blades. If the abundant silicon sources and carbon sources in retired wind turbine blades can be converted into high-performance silicon-carbon composite materials, it can not only solve the problem of blade recycling, but also provide low-cost and sustainable electrode raw materials for the battery industry, achieving the dual goals of "solid waste resource utilization" and "material high-endization". Summary of the Invention

[0005] The purpose of the present invention is to provide a method for preparing a silicon-carbon electrode material, the silicon-carbon electrode material and its application. Through the method of the present invention, retired wind turbine blades can be converted into silicon-carbon electrode materials, solving the problems of high recycling costs, low product value and high environmental risks of existing retired wind turbine blades.

[0006] To achieve the above purpose, the present invention provides the following solutions: In the first aspect, the present invention provides a method for preparing a silicon-carbon electrode material, comprising the following steps: S1. Cutting and crushing retired wind turbine blades, and screening to obtain blade powder; S2. Pickling the blade powder, filtering, washing and drying to obtain purified blade powder; S3. Pyrolyzing the purified blade powder to obtain blade pyrolysis carbon powder; S4. Vacuum Joule heating is carried out on the pyrolytic carbon powder of the blade to obtain a solid product; S5. The solid product is ball-milled and screened to prepare a silicon-carbon electrode material.

[0007] In one or more embodiments, in step S1, the cutting size of the retired wind turbine blade is ≤ 10 cm, and the particle size range of crushing and screening is 50 - 200 mesh. The above-mentioned particle size of crushing and screening can ensure uniform heat and mass transfer in subsequent reactions.

[0008] In one or more embodiments, in step S2, the acid is selected from any one of hydrochloric acid, sulfuric acid, and nitric acid; preferably hydrochloric acid, and the concentration range of the acid solution is 1 - 3 mol / L; the solid-liquid mass ratio during pickling is 1:5 - 1:10, and it is stirred at room temperature for 2 - 8 hours; the drying temperature is 80 - 100 °C, and the drying time is 12 - 24 hours.

[0009] The pickling process can effectively remove metal impurities such as calcium, magnesium, aluminum, and iron in the wind turbine blade, and the above pickling conditions can effectively avoid the corrosion loss of glass fiber and excessive wastewater treatment load; the above drying conditions can ensure the full removal of moisture in the raw material and lower energy consumption.

[0010] In one or more embodiments, in step S3, the pyrolysis atmosphere can be one or a mixture of nitrogen, argon, carbon dioxide, and helium. The pyrolysis heating rate is 5 - 20 °C / min, the pyrolysis temperature is 600 - 900 °C, the holding time is 0.5 - 2 h, and the gas flow rate is 50 - 200 mL / min. When the temperature and holding time are lower than the above range, or the heating rate is higher than the above range, the volatile matter is not released sufficiently, and the conductivity of the pyrolytic carbon is poor and the pore structure is not developed. On the contrary, the pores of the carbon matrix may close or collapse and increase energy consumption.

[0011] In one or more embodiments, in step S4, the temperature range of Joule heating is 1400 - 1800 °C, the power-on time is 10 - 60 seconds, and the vacuum degree is 10 -2 -10 -3 Pa. By controlling the above parameters, the relative contents of SiO2, SiC, and Si, the particle size, as well as the pore structure, graphitization degree, and grain size of the carbon matrix can be regulated. When the temperature and power-on time exceed the upper limit, electrode ablation will occur, and the silicon particles will melt and agglomerate or volatilize and be lost. On the contrary, the carbothermal reduction reaction of SiO2 cannot occur, and the graphitization degree of the carbon matrix is relatively low. The vacuum environment can inhibit the oxidation reaction and promote the progress of the carbothermal reduction reaction.

[0012] In one or more embodiments, in step S5, the ball milling rotation speed is 400 - 600 rpm, the ball milling time is 4 - 8 hours, and then it is sieved to 300 - 600 mesh. At too low ball milling rotation speed and ball milling time, the particle size cannot meet the requirements of electrode coating, while too high ball milling rotation speed and ball milling time will result in too fine particles, increase the slurry viscosity, reduce the coating efficiency, and increase the energy consumption.

[0013] In a second aspect, a silicon-carbon electrode material is prepared by the method described in the first aspect of the present invention.

[0014] In a third aspect, there is an application of the silicon-carbon electrode material described in the second aspect of the present invention in a lithium-ion battery or a sodium-ion battery.

[0015] The beneficial effects of the present invention are as follows: 1. Through a series of operations such as crushing, sieving, pickling, pyrolysis, vacuum Joule heating, and ball milling of retired wind turbine blades, the present invention recovers the silicon source and carbon source in the retired wind turbine blades and converts them into a silicon-carbon electrode material, obtaining a recycled product with high added value, improving the resource utilization value, and the overall process is simple and efficient, having good application prospects.

[0016] 2. In the present invention, the method of vacuum rapid Joule heating is used to heat the blade powder to ultra-high temperature in an extremely short time, promoting the carbothermal reduction reaction of SiO2 in the matrix to generate nano-silicon particles or silicon carbide, while the amorphous carbon is transformed into graphitized carbon and serves as a conductive coating layer for the silicon particles. In addition, the ultra-high heating and cooling rate can inhibit the melting and agglomeration of silicon particles; further ball milling and sieving of the solid product can ensure the obtaining of a uniform nano-scale silicon-carbon electrode material.

[0017] 3. The silicon-carbon electrode material prepared by the present invention is a composite structure of graphite carbon layers wrapping nano-particles, with adjustable particle size, having a relatively high specific surface area, relatively high specific capacity, cycle stability, and excellent rate performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] The schematic diagrams of the specification forming a part of the present invention are used to provide a further understanding of the present invention. The schematic embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation to the present invention.

[0019] Figure 1 It is a process flow chart of the method for preparing a silicon-carbon electrode material from retired wind turbine blades in Example 1 of the present invention; Figure 2 It is a microscopic morphology diagram of the silicon-carbon electrode material prepared in Example 1 of the present invention; Figure 3 It is a microscopic morphology diagram of the silicon-carbon electrode material prepared in Example 2 of the present invention; Figure 4The first charge-discharge curves of the silicon-carbon electrode materials prepared in Examples 1-4 and Comparative Examples 1-2 of the present invention at 0.1C; Figure 5 The rate performance test diagrams of the silicon-carbon electrode materials prepared in Examples 1-4 and Comparative Examples 1-2 of the present invention; Figure 6 The 200-cycle performance test diagrams of the silicon-carbon electrode materials prepared in Examples 1-4 and Comparative Examples 1-2 of the present invention at 0.5C. Detailed implementation manners

[0020] It should be noted that the following detailed descriptions are all exemplary and are intended to provide further explanations of the present invention. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by those of ordinary skill in the technical field to which the present invention belongs.

[0021] The technical solution of the present invention will be further described below in conjunction with specific embodiments.

[0022] Example 1 S1. Cut, crush, and screen the retired wind turbine blades to obtain blade powder. Specifically, the cutting size of the retired wind turbine blades is ≤ 10 cm, and the particle size range of crushing and screening is 200 mesh.

[0023] S2. Immerse the blade powder in a dilute hydrochloric acid solution, stir at room temperature to remove metal impurities in the raw materials, then filter, wash, and dry to obtain purified blade powder. Specifically, the concentration range of the hydrochloric acid solution is 1 mol / L, the solid-liquid mass ratio is 1:10, stir at room temperature for 2 hours, the drying temperature is 80°C, and the drying time is 24 hours.

[0024] S3. Slowly pyrolyze the purified blade powder in a tube furnace to obtain blade pyrolysis carbon powder. Specifically, the pyrolysis temperature is 900°C, the heating rate is 5°C / min, the heat preservation time is 2 h, and the nitrogen flow rate is 200 mL / min.

[0025] S4. Perform vacuum Joule heating on the blade pyrolysis carbon powder to obtain a solid product. Specifically, the heating temperature is 1800°C, the power-on time is 10 seconds, and the vacuum degree is 10 -3 Pa.

[0026] S5. Perform high-speed ball milling and screening on the solid product to prepare a silicon-carbon electrode material. Specifically, the ball milling speed is 400 rpm, the ball milling time is 8 hours, and screen to 500 mesh.

[0027] The process flow chart of the method for preparing a silicon-carbon electrode material from retired wind turbine blades in this example is as Figure 1 shown. The microscopic morphology diagram of the silicon-carbon electrode material prepared in this example is as Figure 2As shown, the specific surface area of the silicon-carbon electrode material prepared in this example is 220.1 m 2 / g, and I D / I G is 0.75. The average size of the silicon particles is about 180 nm. When this material is used as the negative electrode of a lithium battery, the initial charge-discharge Coulomb efficiency is 84% at a current density of 0.1C, the discharge specific capacity is 1483 mAh / g, the 1C capacity retention rate is 90%, and the capacity retention rate is 79.9% after 200 cycles at 0.5C.

[0028] Example 2 S1. Cut, crush, and screen the retired wind turbine blades to obtain blade powder. Specifically, the cutting size of the retired wind turbine blades is ≤10 cm, and the particle size range of crushing and screening is 100 mesh.

[0029] S2. Immerse the blade powder in a dilute hydrochloric acid solution and stir at room temperature to remove metal impurities in the raw materials, then filter, wash, and dry to obtain purified blade powder. Specifically, the concentration range of the hydrochloric acid solution is 3 mol / L, the solid-liquid mass ratio is 1:5, stir at room temperature for 8 hours, the drying temperature is 100°C, and the drying time is 12 hours.

[0030] S3. Slowly pyrolyze the purified blade powder in a tube furnace to obtain blade pyrolytic carbon powder. Specifically, the pyrolysis temperature is 700°C, the heating rate is 5°C / min, the holding time is 1 h, and the nitrogen flow rate is 200 mL / min.

[0031] S4. Perform vacuum Joule heating on the blade pyrolytic carbon powder to obtain a solid product. Specifically, the heating temperature is 1600°C, the energization time is 20 seconds, and the vacuum degree is 10 -3 Pa.

[0032] S5. Perform high-speed ball milling and screening on the solid product to prepare a silicon-carbon electrode material. Specifically, the ball milling speed is 400 rpm, the ball milling time is 4 hours, and screen to 400 mesh.

[0033] The microscopic morphology diagram of the silicon-carbon electrode material prepared in this example is as Figure 3 shown. The specific surface area of the silicon-carbon electrode material prepared in this example is 284.5 m 2 / g, and I D / I G is 0.65. The average size of the silicon particles is about 140 nm. When this material is used as the negative electrode of a lithium battery, the initial charge-discharge Coulomb efficiency is 82% at a current density of 0.1C, the discharge specific capacity is 1569 mAh / g, the 1C capacity retention rate is 88%, and the capacity retention rate is 70.2% after 200 cycles at 0.5C.

[0034] Example 3 S1. Cut, crush, and screen the retired wind turbine blades to obtain blade powder. Specifically, the cutting size of the retired wind turbine blades is ≤ 10 cm, and the particle size range for crushing and screening is 150 mesh.

[0035] S2. Immerse the blade powder in a dilute hydrochloric acid solution, stir at room temperature to remove metal impurities in the raw material, then filter, wash, and dry to obtain purified blade powder. Specifically, the concentration range of the hydrochloric acid solution is 2 mol / L, the solid-liquid mass ratio is 1:8, stir at room temperature for 6 hours, the drying temperature is 80 °C, and the drying time is 24 hours.

[0036] S3. Slowly pyrolyze the purified blade powder in a tube furnace to obtain blade pyrolytic carbon powder. Specifically, the pyrolysis temperature is 800 °C, the heating rate is 5 °C / min, the holding time is 1 h, and the nitrogen flow rate is 200 mL / min.

[0037] S4. Conduct vacuum Joule heating on the blade pyrolytic carbon powder to obtain a solid product. Specifically, the heating temperature is 1400 °C, the energization time is 15 s, and the vacuum degree is 10 -3 Pa.

[0038] S5. Conduct high-speed ball milling and screening on the solid product to prepare a silicon-carbon electrode material. Specifically, the ball milling speed is 600 rpm, the ball milling time is 8 hours, and screen to 600 mesh.

[0039] The specific surface area of the silicon-carbon electrode material prepared in this example is 189.7 m 2 / g, I D / I G is 0.82, the average size of the silicon particles is about 120 nm. Using this material as the negative electrode of a lithium battery, the initial charge-discharge Coulomb efficiency is 86% at a current density of 0.1C, the discharge specific capacity is 1431 mAh / g, the 1C capacity retention rate is 93%, and the capacity retention rate is 85.0% after 200 cycles at 0.5C.

[0040] Example 4 S1. Cut, crush, and screen the retired wind turbine blades to obtain blade powder. Specifically, the cutting size of the retired wind turbine blades is ≤ 10 cm, and the particle size range for crushing and screening is 200 mesh.

[0041] S2. Immerse the blade powder in a dilute hydrochloric acid solution, stir at room temperature to remove metal impurities in the raw material, then filter, wash, and dry to obtain purified blade powder. Specifically, the concentration range of the hydrochloric acid solution is 2 mol / L, the solid-liquid mass ratio is 1:10, stir at room temperature for 4 hours, the drying temperature is 80 °C, and the drying time is 24 hours.

[0042] S3. Slowly pyrolyze the purified leaf powder in a tube furnace to obtain leaf pyrolysis carbon powder. Specifically, the pyrolysis temperature is 800 °C, the heating rate is 5 °C / min, the holding time is 1 h, carbon dioxide is used as the carrier gas, and the flow rate is 50 mL / min.

[0043] S4. Vacuum Joule heat the leaf pyrolysis carbon powder to obtain a solid product. Specifically, the heating temperature is 1600 °C, the energization time is 10 s, and the vacuum degree is 10 -3 Pa.

[0044] S5. Perform high-speed ball milling and screening on the solid product to prepare a silicon-carbon electrode material. Specifically, the ball milling speed is 400 rpm, the ball milling time is 8 h, and the screening is to 500 mesh.

[0045] The specific surface area of the silicon-carbon electrode material prepared in this example is 386.3 m 2 / g, I D / I G is 0.78, the average size of the silicon particles is about 170 nm. Using this material as the anode of a lithium battery, the initial charge-discharge Coulomb efficiency is 76% at a current density of 0.1C, the discharge specific capacity is 1514 mAh / g, the 1C capacity retention rate is 85%, and the capacity retention rate is 80.0% after 200 cycles at 0.5C.

[0046] Comparative Example 1 S1. Cut, crush, and screen the retired wind turbine blades to obtain blade powder. Specifically, the cutting size of the retired wind turbine blades is ≤10 cm, and the crushing and screening particle size range is 200 mesh.

[0047] S2. Immerse the blade powder in a dilute hydrochloric acid solution and stir at room temperature to remove metal impurities in the raw materials, then filter, wash, and dry to obtain purified leaf powder. Specifically, the concentration range of the hydrochloric acid solution is 1 mol / L, the solid-liquid mass ratio is 1:10, stir at room temperature for 2 h, the drying temperature is 80 °C, and the drying time is 24 h.

[0048] S3. Slowly pyrolyze the purified leaf powder in a tube furnace to obtain leaf pyrolysis carbon powder. Specifically, the pyrolysis temperature is 900 °C, the heating rate is 5 °C / min, the holding time is 2 h, and the nitrogen flow rate is 200 mL / min.

[0049] S4. Vacuum Joule heat the leaf pyrolysis carbon powder to obtain a solid product. Specifically, the heating temperature is 1200 °C, the energization time is 10 s, and the vacuum degree is 10 -3 Pa.

[0050] S5. The solid product is subjected to high-speed ball milling and screening to obtain the silicon-carbon electrode material. Specifically, the ball milling speed is 400 rpm, the ball milling time is 8 hours, and the screening is carried out to 500 mesh.

[0051] The specific surface area of the silicon-carbon electrode material prepared in this comparative example is 243.2 m 2 / g, I D / I G is 1.12, the average size of the silicon particles is about 160 nm. When this material is used as the negative electrode of a lithium battery, the initial charge-discharge Coulomb efficiency is 70% at a current density of 0.1C, the discharge specific capacity is 853 mAh / g, the 1C capacity retention rate is 55%, and the capacity retention rate is 67.2% after 200 cycles at 0.5C.

[0052] Comparative Example 2 S1. The retired wind turbine blade is cut, crushed and screened to obtain blade powder. Specifically, the cutting size of the retired wind turbine blade is ≤10 cm, and the particle size range of crushing and screening is 200 mesh.

[0053] S2. The blade powder is immersed in a dilute hydrochloric acid solution, stirred at room temperature to remove metal impurities in the raw material, and then filtered, washed and dried to obtain purified blade powder. Specifically, the concentration range of the hydrochloric acid solution is 1 mol / L, the solid-liquid mass ratio is 1:10, stirred at room temperature for 2 hours, the drying temperature is 80°C, and the drying time is 24 hours.

[0054] S3. The purified blade powder is slowly pyrolyzed in a tubular furnace to obtain blade pyrolytic carbon powder. Specifically, the pyrolysis temperature is 900°C, the heating rate is 5°C / min, the holding time is 2h, and the nitrogen flow rate is 200 mL / min.

[0055] S4. The blade pyrolytic carbon powder is subjected to vacuum Joule heating to obtain a solid product. Specifically, the heating temperature is 2000°C, the energization time is 10 seconds, and the vacuum degree is 10 -3 Pa.

[0056] S5. The solid product is subjected to high-speed ball milling and screening to obtain the silicon-carbon electrode material. Specifically, the ball milling speed is 400 rpm, the ball milling time is 8 hours, and the screening is carried out to 500 mesh.

[0057] The specific surface area of the silicon-carbon electrode material prepared in this comparative example is 152.1m 2 / g, I D / I GIt is 0.34, the average size of the silicon particles is about 240 nm. When this material is used as the negative electrode of a lithium battery, the first charge-discharge Coulombic efficiency is 65% at a current density of 0.1C, the discharge specific capacity is 1124 mAh / g, the 1C capacity retention rate is 40%, and the capacity retention rate is 54.7% after 200 cycles at 0.5C.

[0058] The first charge-discharge curves of the silicon-carbon electrode materials prepared in Examples 1-4 and Comparative Examples 1-2 of the present invention at 0.1C are as shown in Figure 4 ; the rate performance test diagrams of the silicon-carbon electrode materials are as shown in Figure 5 ; the 200-cycle performance test diagrams of the silicon-carbon electrode materials at 0.5C are as shown in Figure 6 .

[0059] The effect data of Examples 1-4 and Comparative Examples 1-2 are shown in Table 1 below: Table 1 Effect data tables of each example and comparative example

[0060] The above are only the preferred embodiments of the present invention and are not used to limit the present invention. For those skilled in the art, the present invention can have various changes and modifications. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A preparation method of a silicon-carbon electrode material, characterized in that, It includes the following steps: S1. Cut and crush the retired wind turbine blades, and screen to obtain blade powder; S2. Pickle the blade powder, filter, wash and dry to obtain purified blade powder; S3. Pyrolyze the purified blade powder to obtain blade pyrolytic carbon powder; S4. Conduct vacuum Joule heating on the blade pyrolytic carbon powder to obtain a solid product; S5. Conduct ball milling and screening on the solid product to prepare a silicon-carbon electrode material; In the step S4, the temperature of Joule heating is 1400~1800 °C, the power-on time is 10~60 seconds, and the vacuum degree is 10 -2 -10 -3 Pa.

2. The preparation method according to claim 1, characterized in that, In the step S1, the particle size range of crushing and screening of the retired wind turbine blades is 50-200 mesh.

3. The preparation method according to claim 1, characterized in that, In the step 2, the acid is selected from any one of hydrochloric acid, sulfuric acid, and nitric acid.

4. The preparation method according to claim 1, wherein In the step 2, the concentration range of the acid solution is 1-3 mol / L, the solid-liquid mass ratio is 1:5-1:10, and the pickling time is 2-8 hours.

5. The preparation method according to claim 1, characterized in that, In the step 2, the drying temperature is 80-100 °C, and the drying time is 12-24 hours.

6. The preparation method according to claim 1, wherein In the step S3, the pyrolysis atmosphere is one or a mixture of several of nitrogen, argon, carbon dioxide, and helium.

7. The preparation method according to claim 1, wherein In the step S3, the heating rate is 5-20 °C / min, the pyrolysis temperature is 600-900 °C, the holding time is 0.5-2 h, and the gas flow rate is 50-200 mL / min.

8. The preparation method according to claim 1, characterized in that, In the step S5, the ball milling speed is 400-600 rpm, the ball milling time is 4-8 hours, and then it is screened to 300-600 mesh.

9. A silicon-carbon electrode material prepared by the preparation method according to any one of claims 1-8.

10. An application of the silicon-carbon electrode material according to claim 9 in a lithium-ion battery or a sodium-ion battery.

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