CN110474032B - Silicon-carbon negative electrode material based on photovoltaic waste silicon and preparation method thereof - Google Patents

Silicon-carbon negative electrode material based on photovoltaic waste silicon and preparation method thereof Download PDF

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CN110474032B
CN110474032B CN201910775618.8A CN201910775618A CN110474032B CN 110474032 B CN110474032 B CN 110474032B CN 201910775618 A CN201910775618 A CN 201910775618A CN 110474032 B CN110474032 B CN 110474032B
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CN110474032A (en
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刘艳侠
范亚蒙
刘凡
王璞
张锁江
阮晶晶
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Institute of Process Engineering of CAS
Zhengzhou Institute of Emerging Industrial Technology
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Zhengzhou Institute of Emerging Industrial Technology
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    • BPERFORMING OPERATIONS; TRANSPORTING
    • B82NANOTECHNOLOGY
    • B82YSPECIFIC USES OR APPLICATIONS OF NANOSTRUCTURES; MEASUREMENT OR ANALYSIS OF NANOSTRUCTURES; MANUFACTURE OR TREATMENT OF NANOSTRUCTURES
    • B82Y30/00Nanotechnology for materials or surface science, e.g. nanocomposites
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    • H01ELECTRIC ELEMENTS
    • H01MPROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00Secondary cells; Manufacture thereof
    • H01M10/05Accumulators with non-aqueous electrolyte
    • H01M10/052Li-accumulators
    • H01M10/0525Rocking-chair batteries, i.e. batteries with lithium insertion or intercalation in both electrodes; Lithium-ion batteries
    • HELECTRICITY
    • H01ELECTRIC ELEMENTS
    • H01MPROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
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    • H01M4/36Selection of substances as active materials, active masses, active liquids
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    • H01M4/366Composites as layered products
    • HELECTRICITY
    • H01ELECTRIC ELEMENTS
    • H01MPROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
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    • H01M4/02Electrodes composed of, or comprising, active material
    • H01M4/36Selection of substances as active materials, active masses, active liquids
    • H01M4/38Selection of substances as active materials, active masses, active liquids of elements or alloys
    • H01M4/386Silicon or alloys based on silicon
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    • H01M4/02Electrodes composed of, or comprising, active material
    • H01M4/36Selection of substances as active materials, active masses, active liquids
    • H01M4/58Selection of substances as active materials, active masses, active liquids of inorganic compounds other than oxides or hydroxides, e.g. sulfides, selenides, tellurides, halogenides or LiCoFy; of polyanionic structures, e.g. phosphates, silicates or borates
    • H01M4/583Carbonaceous material, e.g. graphite-intercalation compounds or CFx
    • HELECTRICITY
    • H01ELECTRIC ELEMENTS
    • H01MPROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
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    • H01M4/02Electrodes composed of, or comprising, active material
    • H01M4/62Selection of inactive substances as ingredients for active masses, e.g. binders, fillers
    • H01M4/624Electric conductive fillers
    • YGENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
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    • Y02EREDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/10Energy storage using batteries

Abstract

The invention provides a silicon-carbon cathode material based on photovoltaic waste silicon and a preparation method thereof. The preparation method comprises the following steps: (1) crushing and drying the collected waste silicon materials to obtain waste silicon powder; (2) placing the waste silicon powder in an inert atmosphere for high-temperature impurity removal, and performing acid cleaning purification and drying to obtain high-purity silicon powder; (3) adding high-purity silicon powder into a dispersion medium, and performing high-speed ball milling to obtain a nano silicon solution; (4) collecting the nano silicon solution, adjusting the solid content, adding an organic carbon source, a conductive agent and a dispersing agent according to a certain proportion, and then sanding and mixing uniformly; (5) and (4) spray-drying and calcining the mixed solution to obtain the silicon-carbon negative electrode material. The silicon-carbon cathode material prepared by the method has high first-efficiency and good cycling stability, and the preparation method has the advantages of cost advantage and simple operation and is suitable for industrial production.

Description

Silicon-carbon negative electrode material based on photovoltaic waste silicon and preparation method thereof
Technical Field
The invention relates to the field of battery materials, in particular to a silicon-carbon negative electrode material based on photovoltaic waste silicon and a preparation method thereof.
Background
With the rapid development of mobile electronic products and new energy automobile industries, on one hand, the requirement of the market for the energy density of lithium ion batteries is increasing day by day, and on the other hand, the national policy is also promoting the development of high energy density batteries, so that a scheme for promoting the development action of automobile power batteries (2017) is proposed definitely, and the specific energy per unit of lithium ion power batteries is more than 300 Wh/kg in 2020. As a key material of lithium ion batteries, the selection of the negative electrode material plays a crucial role in the exertion of battery energy. The theoretical specific capacity of the traditional negative electrode material graphite is only 372 mAh/g, and the use requirement of the high-energy density lithium ion battery cannot be met. The theoretical capacity of silicon is up to 4200 mAh/g, which is more than ten times of the theoretical capacity of graphite. To achieve the goal of 300 Wh/kg, a material system for silicon-based negative electrodes matching high nickel positive electrodes has been a consensus in the industry.
Although the silicon-based negative electrode material has a wide application prospect, the silicon material still has technical barriers in the actual use process and needs to be broken through, wherein the main problems are as follows: 1) the volume expansion reaches 320% after lithium intercalation, and the volume expansion further causes material pulverization, electrode structure change and continuous formation of a Solid Electrolyte Interface (SEI) film; 2) intrinsic to the semiconductor material, is poorly conductive. Because of the limitation of the bottleneck problem, silicon materials are not used as anode materials alone, and at present, the battery material enterprises mainly use silicon together with graphite, a conductive agent and other carbon materials, and the introduction of the carbon materials can improve the conductivity of silicon-carbon anodes. Aiming at the problem of volume expansion of silicon, nanocrystallization is an effective solution. Research shows that when the size of the silicon material is less than 150 nm in at least one dimension, the problem of volume expansion can be effectively relieved, and the material is prevented from being pulverized and broken.
At present, most of battery-grade nano silicon powder on the market is prepared by adopting a plasma method and a laser method, and mainly by utilizing SiH4The gas is used as a reaction raw material and is prepared by vapor deposition, and the nano silicon powder prepared by the method has high purity and controllable particle size, but has high production cost and seriously restricts the development of downstream silicon-carbon material industry. In recent years, the photovoltaic industry is rapidly developed, the global polycrystalline silicon yield reaches 43.0 ten thousand tons in 2018, and the yield of China exceeds 50 percent. In the process of processing a solar silicon wafer, high-purity crystalline silicon with the purity of 99.9999 percent can be cut into a specific size and a specific shape, and in the process, about 40 percent of the high-purity crystalline silicon can become waste silicon blocks and submicron-grade waste materials mixed in cutting fluid, so that more than 10 ten thousand tons of cutting waste silicon are generated in China every year, wherein the submicron-grade waste silicon materials accounting for about 50 percent are discarded due to difficulty in recycling in the photovoltaic industry. The battery-grade nano silicon prepared by purifying and refining the submicron grade produced in the cutting process of the photovoltaic industry can realize resource recycling, greatly reduce the production cost of the nano silicon and promote the development of silicon-carbon cathode materials and lithium ion battery industries.
Chinese patent CN104112850 provides a preparation method of lithium ion battery cathode material based on photovoltaic industry silicon waste, which is to mix purified and modified micron or submicron silicon with graphite simply, match with a specific binder system and apply the mixture to the lithium ion battery cathode material. The silicon and graphite are mixed for use, so that the volume expansion of the silicon can be relieved to a certain extent, and the conductivity of the composite material is improved. Chinese patent CN104701491 uses waste silicon slurry in the production process of silicon chips as raw material, and prepares nano-silicon porous silicon by drying, acid washing, ball milling and strong acid corrosion, and directly uses the nano-silicon porous silicon as the negative electrode material of lithium ion batteries. The nano silicon porous silicon can relieve the volume expansion of silicon to a certain extent, but a large amount of strong acid corrosion preparation method adopted by the nano silicon porous silicon can cause pollution to the environment and is not suitable for large-scale production.
Disclosure of Invention
Aiming at the technical problems, the invention provides a silicon-carbon cathode material based on photovoltaic waste silicon and a preparation method thereof, which take waste silicon mud in the photovoltaic industry as a raw material, effectively reduce the production cost, have simple preparation process and are suitable for industrial amplification. The step-by-step refining is adopted, the particle size of the silicon powder is controlled within a reasonable range, and the particle size and the specific surface area are balanced, so that the nano silicon can exert better performance. In addition, an organic carbon source is introduced in the sanding process, and a stable and uniform amorphous carbon coating layer can be formed on the surface of the silicon material through high-temperature calcination, so that the silicon material is prevented from being directly contacted with electrolyte, a stable SEI (solid electrolyte interphase) film is favorably formed, and the coulombic efficiency and the cycling stability of the material are improved.
In order to solve the technical problems, the technical scheme of the invention is as follows:
a silicon-carbon negative electrode material based on photovoltaic waste silicon is a sphere-like silicon-carbon composite negative electrode material, amorphous carbon formed by organic matter pyrolysis is coated on the surface layer of flaky nano silicon, and the interior of the material is composed of the coated flaky nano silicon and a conductive agent; the flaky nano silicon is obtained by processing leftover materials generated in the process of cutting a crystal silicon wafer in the photovoltaic industry, the particle size of the flaky nano silicon is 50-200 nm, and the thickness of the flaky nano silicon is 10-50 nm; the mass ratio of each component is respectively as follows: 50-90% of flaky nano silicon, 5-20% of conductive agent and 10-30% of organic matter cracking carbon.
The preparation method of the silicon-carbon cathode material based on the photovoltaic waste silicon comprises the following steps:
(1) crushing and drying the photovoltaic waste silicon material to obtain waste silicon powder, placing the waste silicon powder in an inert atmosphere for high-temperature impurity removal, and then carrying out acid washing and drying to obtain high-purity silicon powder;
(2) adding high-purity silicon powder and zirconia balls into a solvent according to a certain proportion, and carrying out high-speed ball milling in an inert atmosphere to obtain a nano-silicon suspension;
(3) collecting the nano-silicon suspension, adjusting the solid content, adding an organic carbon source, a conductive agent and a dispersing agent, and then sealing, sanding and uniformly mixing to obtain mixed slurry;
(4) and carrying out spray drying on the mixed slurry and calcining in an inert atmosphere to finally obtain the silicon-carbon negative electrode material.
Further, in the step (1), the photovoltaic waste silicon is a waste silicon material generated in the process of cutting the solar crystalline silicon wafer by the diamond wire, wherein the purity of the cut crystalline silicon is more than 99.9999% or more, and the silicon content of the waste silicon material is more than 80%.
Further, in the step (1), high-temperature calcination is carried out to remove most organic impurities, and then acid washing is carried out; the pickling comprises two pickling purifications, wherein one or more of dilute hydrochloric acid, dilute nitric acid and dilute sulfuric acid are used for pickling, and after cleaning, hydrofluoric acid is used for carrying out the second pickling, wherein the pickling temperature is 20-95 ℃, and the pickling time is 0.5-24 hours.
Further, during high-speed ball milling in the step (2), a solvent is one or more of deionized water, ethanol, butanol, methanol, isopropanol, cyclohexanone, acetone, butanone or cyclohexane, and the solid content is 5-50%.
Further, during high-speed ball milling in the step (2), the mass ratio of the high-purity silicon powder to the zirconia balls is 10 (5-30), the particle size of the zirconia is 0.1-3 mm, and the ball milling speed is 100-800 rpm.
Further, the organic carbon source in the step (3) is one or more of phenolic resin, epoxy resin, sucrose, starch, chitosan or glucose.
Further, the dispersant in the step (3) is one or more of polyvinylpyrrolidone, polyethyleneimine, sodium carboxymethylcellulose or sodium dodecylbenzenesulfonate.
Further, the solid content of the sand in the step (3) is 5-50%, the sand grinding speed is 1000-3000 rpm, and the sand grinding time is 0.5-10 h.
Further, in the step (4), the calcining is to heat the spray-dried material to 600-1000 ℃ at a heating rate of 1-20 ℃/min, and preserve the heat for 1-4 hours, wherein the inert atmosphere is one or more of nitrogen, argon or hydrogen.
The invention has the beneficial effects that:
(1) according to the invention, photovoltaic waste silicon is used as a raw material, and waste silicon powder mixed in cutting fluid and generated during silicon wafer cutting is purified and refined to obtain the silicon-carbon negative electrode material, so that resource recycling of the waste silicon can be realized, and the development of circular economy is facilitated.
(2) The silicon-carbon cathode material prepared by the invention has obvious cost advantage. The price of the nano silicon prepared by the plasma method and the laser method is too high, and the cost of the nano silicon accounts for about 50 percent of the overall cost of the silicon-carbon material. The invention can obtain the nano silicon solution by treating the waste silicon through a simple process, thereby greatly reducing the cost. The silicon-carbon cathode material can be obtained by mixing the nano solution with a certain proportion of organic carbon source and conductive agent, and then drying and calcining, and the step of drying the nano silicon solution is omitted, so that the process flow is simplified, and the production cost is further reduced.
(3) The wet ball milling refining process provided by the invention can control the particle size of the silicon powder within a reasonable range, and finally obtain the flaky nano silicon with uniform particle size.
(4) The invention provides a sphere-like silicon carbon negative electrode material with the surface uniformly coated by amorphous carbon. An organic carbon source and a conductive agent are introduced in the sanding process, amorphous carbon can be uniformly coated on the surface of the flaky nano silicon after the material is calcined, and the amorphous carbon layer can effectively prevent the silicon material from being directly contacted with electrolyte, so that a stable SEI film can be formed, and the stability of the material is improved; on the other hand, the addition of the carbon material and the conductive agent can improve the overall conductivity of the material and improve the electrochemical performance of the material.
Drawings
Fig. 1 is an SEM image of the silicon carbon negative electrode material obtained by the present invention.
Fig. 2 is a graph of the cycling stability of the silicon-carbon negative electrode material obtained by the invention.
Detailed Description
The present invention is further illustrated by the following examples, but the present invention is not limited to the following examples.
The experimental drugs and methods in the following examples were used according to conventional conditions or according to the commercial instructions.
The prepared silicon-carbon negative electrode material is assembled into a half cell and is subjected to electrochemical performance test: silicon-carbon negative electrode material: super P: and (3) homogenizing and smearing the adhesive according to the mass ratio of 8:1: 1. Wherein the binder is a solution of sodium carboxymethylcellulose (CMC), Styrene Butadiene Rubber (SBR) and polyacrylic acid (PAA) in a mass ratio of 1:1:1, and the electrolyte is LiPF6A conventional electrolyte. The lithium plate is used as a counter electrode and assembled into a CR2025 button cell. Under the condition of normal temperature, a charge-discharge test is carried out by utilizing a LANHE CT2001A blue test system under the current density of 100 mA/g, and the voltage range is 0.005-2.0V.
Example 1
The preparation method of the silicon-carbon negative electrode material based on the photovoltaic waste silicon comprises the following steps:
(1) photovoltaic waste silicon is crushed to an average particle size of less than 2 mm by a crusher and then dried in an air-blast drying oven until the moisture content is less than 2%. And (3) placing the dried waste silicon powder in a horizontal tube furnace, heating to 900 ℃ at the speed of 5 ℃/min under the nitrogen atmosphere, and preserving heat for 2h to remove impurities at high temperature.
(2) And (3) immersing the silicon material subjected to high-temperature impurity removal into 1M diluted hydrochloric acid, stirring for 4 hours at 40 ℃, filtering, and washing with deionized water to be neutral. And then, carrying out acid cleaning for the second time, immersing the cleaned silicon material into 1M hydrofluoric acid solution, stirring for 2 hours at room temperature, filtering again, and cleaning with deionized water to be neutral. And then drying the cleaned silicon powder in vacuum to obtain high-purity silicon powder with the purity of more than 99.5 percent.
(3) 50g of high-purity silicon powder and 150g of zirconia beads are weighed and added into 75 g of absolute ethyl alcohol, and ball milling is carried out at the speed of 300 rpm for 5 hours to obtain the nano silicon solution. Adding absolute ethyl alcohol into the nano-silicon solution to adjust the solid content to 20%, then weighing 300 g of the nano-silicon solution, and respectively adding 30 g of phenolic resin, 10 g of graphene and 20 g of polyethyleneimine to obtain mixed slurry. The mixed slurry was poured into a sand mill and sanded at 2000 rpm for 3 h. And then, spray drying the sanded slurry, calcining the dried slurry in a nitrogen atmosphere, heating to 900 ℃ at the speed of 5 ℃/min, and preserving heat for 2h to obtain the silicon-carbon negative electrode material with the spherical shape in the micro-morphology.
Example 2
The preparation method of the silicon-carbon negative electrode material based on the photovoltaic waste silicon comprises the following steps:
(1) photovoltaic waste silicon is crushed to an average particle size of less than 2 mm by a crusher and then dried in a vacuum drying oven until the moisture content is less than 2%. And (3) placing the dried waste silicon powder in a horizontal tube furnace, heating to 700 ℃ at the speed of 5 ℃/min under the nitrogen atmosphere, and preserving heat for 2h to remove impurities at high temperature.
(2) And (3) immersing the silicon material subjected to high-temperature impurity removal into 1M dilute nitric acid, stirring for 5 hours at 70 ℃, centrifuging, and repeatedly cleaning with deionized water to be neutral. And then, carrying out acid cleaning for the second time, immersing the cleaned silicon material into 0.5M hydrofluoric acid solution, stirring for 10h at room temperature, centrifuging, and cleaning with deionized water to be neutral. And then drying the cleaned silicon powder in vacuum to obtain high-purity silicon powder with the purity of more than 99.5 percent.
(3) 50g of high-purity silicon powder and 80 g of zirconia beads are weighed and added into 80 g of deionized water, and the mixture is ball-milled for 3 hours at the speed of 400 rpm to obtain the nano silicon solution. Deionized water is added into the nano-silicon suspension to adjust the solid content to 20%, then 300 g of nano-silicon solution is weighed, 35 g of glucose, 10 g of graphene and 20 g of polyvinylpyrrolidone are respectively added to obtain mixed slurry. The mixed slurry was poured into a sand mill and sanded at 2500 rpm for 2 h. And then, spray drying the sanded slurry, calcining the dried slurry in an argon atmosphere, heating to 700 ℃ at the speed of 5 ℃/min, and preserving heat for 2h to obtain the silicon-carbon negative electrode material with the spherical-like micro-morphology.
Example 3
The preparation method of the silicon-carbon negative electrode material based on the photovoltaic waste silicon comprises the following steps:
(1) photovoltaic waste silicon is crushed to an average particle size of less than 2 mm by a crusher and then dried in an air-blast drying oven until the moisture content is less than 2%. And (3) placing the dried waste silicon powder in a horizontal tube furnace, heating to 700 ℃ at the speed of 5 ℃/min under the nitrogen atmosphere, and preserving heat for 2h to remove impurities at high temperature.
(2) And (3) immersing the silicon material subjected to high-temperature impurity removal into 2M dilute sulfuric acid, stirring for 5 hours at 60 ℃, centrifuging, and repeatedly cleaning with deionized water to be neutral. And then, carrying out acid cleaning for the second time, immersing the cleaned silicon material into 1M hydrofluoric acid solution, stirring for 5 hours at room temperature, centrifuging, and cleaning with deionized water to be neutral. And then drying the cleaned silicon powder in a forced air drying oven to obtain high-purity silicon powder with the purity of more than 99.5 percent.
(3) 50g of high-purity silicon powder and 150g of zirconia beads are weighed and added into 50g of acetone, and the mixture is ball-milled for 3 hours at the speed of 400 rpm to obtain the nano silicon solution. Acetone is added into the nano-silicon suspension to adjust the solid content to 50%, then 200 g of nano-silicon solution is weighed, and 50g of epoxy resin, 10 g of carbon nano-tube and 40 g of sodium carboxymethylcellulose aqueous solution with the mass fraction of 30% are respectively added to obtain mixed slurry. The mixed slurry was poured into a sand mill and sanded at 3000 rpm for 1 h. And then, spray drying the sanded slurry, calcining the dried slurry in a hydrogen atmosphere, heating to 900 ℃ at the speed of 5 ℃/min, and preserving heat for 2h to obtain the silicon-carbon negative electrode material with the spherical shape in the micro-morphology.
Example 4
The preparation method of the silicon-carbon negative electrode material based on the photovoltaic waste silicon comprises the following steps:
(1) photovoltaic waste silicon is crushed to an average particle size of less than 2 mm by a crusher and then dried in an air-blast drying oven until the moisture content is less than 2%. And (3) placing the dried waste silicon powder in a horizontal tube furnace, heating to 900 ℃ at the speed of 5 ℃/min under the nitrogen atmosphere, and preserving heat for 2h to remove impurities at high temperature.
(2) And (3) immersing the silicon material subjected to high-temperature impurity removal into a 2M mixed solution of dilute sulfuric acid and alkene hydrochloric acid, stirring for 5 hours at 70 ℃, filtering, and repeatedly cleaning with deionized water until the silicon material is neutral. And then, carrying out acid cleaning for the second time, immersing the cleaned silicon material into 1M hydrofluoric acid solution, stirring for 4 hours at room temperature, centrifuging, and cleaning with deionized water to be neutral. And then drying the cleaned silicon powder in a forced air drying oven to obtain high-purity silicon powder with the purity of more than 99.5 percent.
(3) 50g of high-purity silicon powder and 120 g of zirconia beads are weighed and added into 50g of methanol, and the mixture is ball-milled for 2 hours at the speed of 500 rpm to obtain the nano silicon solution. And weighing 200 g of nano silicon solution, and respectively adding 50g of sucrose, 5 g of carbon nano tube, 5 g of graphene and 40 g of polyvinylpyrrolidone aqueous solution with the mass fraction of 30% to obtain mixed slurry. The mixed slurry was poured into a sand mill and sanded at 2500 rpm for 2 h. And then, spray drying the sanded slurry, calcining the dried slurry in an argon atmosphere, heating to 900 ℃ at the speed of 5 ℃/min, and preserving heat for 2h to obtain the silicon-carbon negative electrode material with the spherical-like micro-morphology.
Example 5
The preparation method of the silicon-carbon negative electrode material based on the photovoltaic waste silicon comprises the following steps:
(1) photovoltaic waste silicon is crushed to an average particle size of less than 2 mm by a crusher and then dried in an air-blast drying oven until the moisture content is less than 2%. And (3) placing the dried waste silicon powder in a horizontal tube furnace, heating to 900 ℃ at the speed of 5 ℃/min under the nitrogen atmosphere, and preserving heat for 2h to remove impurities at high temperature.
(2) And (3) immersing the silicon material subjected to high-temperature impurity removal into a 2M mixed solution of dilute nitric acid and alkene hydrochloric acid, stirring at 50 ℃ for 5 hours, centrifuging, and repeatedly cleaning with deionized water to be neutral. And then, carrying out acid cleaning for the second time, immersing the cleaned silicon material into 1M hydrofluoric acid solution, stirring for 4 hours at room temperature, filtering, and cleaning with deionized water to be neutral. And then drying the cleaned silicon powder in a drying box to obtain high-purity silicon powder with the purity of more than 99.5 percent.
(3) 50g of high-purity silicon powder and 100 g of zirconia beads are weighed and added into a mixed solution of 80 g of ethanol and deionized water, and the nano silicon solution is obtained after ball milling for 2 hours at the speed of 500 rpm. Deionized water is added into the nano-silicon solution to adjust the solid content to 30%, then 200 g of nano-silicon suspension is weighed, and 50g of sucrose, 10 g of carbon nano-tube, 20 g of polyvinylpyrrolidone and 20 g of sodium carboxymethylcellulose are respectively added to obtain mixed slurry. The mixed slurry was poured into a sand mill and sanded at 3000 rpm for 2.5 h. And then, spray drying the sanded slurry, calcining the dried slurry in a nitrogen atmosphere, heating to 850 ℃ at the speed of 5 ℃/min, and preserving heat for 2h to obtain the silicon-carbon negative electrode material with the spherical-like micro-morphology.
Example 6
The preparation method of the silicon-carbon negative electrode material based on the photovoltaic waste silicon comprises the following steps:
(1) photovoltaic waste silicon is crushed to an average particle size of less than 2 mm by a crusher and then dried in an air-blast drying oven until the moisture content is less than 2%. And (3) placing the dried waste silicon powder in a horizontal tube furnace, heating to 850 ℃ at the speed of 5 ℃/min under the nitrogen atmosphere, and preserving heat for 2h to remove impurities at high temperature.
(2) And (3) immersing the silicon material subjected to high-temperature impurity removal into a 2M mixed solution of dilute nitric acid and alkene sulfuric acid, stirring at room temperature for 10 hours, filtering, and repeatedly washing with deionized water until the mixture is neutral. And then, carrying out acid cleaning for the second time, immersing the cleaned silicon material into 0.5M hydrofluoric acid solution, stirring at room temperature for 12h, centrifuging, and cleaning with deionized water to be neutral. And then drying the cleaned silicon powder in a drying box to obtain high-purity silicon powder with the purity of more than 99.5 percent.
(3) 50g of high-purity silicon powder and 150g of zirconia beads are weighed and added into 80 g of acetone, and the mixture is ball-milled for 2.5 hours at the speed of 450 rpm to obtain the nano-silicon solution. Deionized water is added into the nano-silicon solution to adjust the solid content to 10%, then 600 g of nano-silicon suspension is weighed, and 50g of glucose, 10 g of carbon nano-tube, 20 g of polyethyleneimine and 20 g of sodium carboxymethylcellulose are respectively added to obtain mixed slurry. The mixed slurry was poured into a sand mill and sanded at 1500 rpm for 8 h. And then, spray drying the sanded slurry, calcining the dried slurry in a nitrogen atmosphere, heating to 650 ℃ at the speed of 5 ℃/min, and preserving heat for 2h to obtain the silicon-carbon negative electrode material with the spherical-like micro-morphology.
The above description is only for the purpose of illustrating the preferred embodiments of the present invention and is not to be construed as limiting the invention, and any modifications, equivalents, improvements and the like made within the spirit and principle of the present invention should be included in the scope of the present invention.

Claims (9)

1. A preparation method of a silicon-carbon negative electrode material based on photovoltaic waste silicon is characterized by comprising the following steps:
(1) crushing and drying the photovoltaic waste silicon material to obtain waste silicon powder, placing the waste silicon powder in an inert atmosphere for high-temperature impurity removal, and then carrying out acid washing and drying to obtain high-purity silicon powder;
(2) adding high-purity silicon powder and zirconia balls into a solvent according to a certain proportion, and carrying out high-speed ball milling in an inert atmosphere to obtain a nano-silicon suspension;
(3) collecting the nano-silicon suspension, adjusting the solid content, adding an organic carbon source, a conductive agent and a dispersing agent, and then sealing, sanding and uniformly mixing to obtain mixed slurry;
(4) spray drying the mixed slurry and calcining in an inert atmosphere to finally obtain a silicon-carbon negative electrode material;
the silicon-carbon negative electrode material is a sphere-like silicon-carbon composite negative electrode material, amorphous carbon formed by organic matter pyrolysis is coated on the surface layer of the flaky nano silicon, and the interior of the flaky nano silicon is composed of the coated flaky nano silicon and a conductive agent; the flaky nano silicon is obtained by processing leftover materials generated in the process of cutting a crystal silicon wafer in the photovoltaic industry, the particle size of the flaky nano silicon is 50-200 nm, and the thickness of the flaky nano silicon is 10-50 nm; the mass ratio of each component is respectively as follows: 50-90% of flaky nano silicon, 5-20% of conductive agent and 10-30% of organic matter cracking carbon.
2. The preparation method of the silicon-carbon anode material based on the photovoltaic waste silicon as claimed in claim 1, wherein the preparation method comprises the following steps: the photovoltaic waste silicon in the step (1) is a waste silicon material generated when the diamond wire cuts the solar crystal silicon wafer, wherein the purity of the cut crystalline silicon is more than 99.9999 percent or more, and the silicon content of the waste silicon material is more than 80 percent.
3. The preparation method of the silicon-carbon anode material based on the photovoltaic waste silicon as claimed in claim 1, wherein the preparation method comprises the following steps: in the step (1), high-temperature calcination is carried out to remove most organic impurities, and then acid washing is carried out; the pickling comprises two pickling purifications, wherein one or more of dilute hydrochloric acid, dilute nitric acid and dilute sulfuric acid are used for pickling, and after cleaning, hydrofluoric acid is used for carrying out the second pickling, wherein the pickling temperature is 20-95 ℃, and the pickling time is 0.5-24 hours.
4. The preparation method of the silicon-carbon anode material based on the photovoltaic waste silicon as claimed in claim 1, wherein the preparation method comprises the following steps: during high-speed ball milling in the step (2), the solvent is one or more of deionized water, ethanol, butanol, methanol, isopropanol, cyclohexanone, acetone, butanone or cyclohexane, and the solid content is 5-50%.
5. The preparation method of the silicon-carbon anode material based on the photovoltaic waste silicon as claimed in claim 1, wherein the preparation method comprises the following steps: during high-speed ball milling in the step (2), the mass ratio of the high-purity silicon powder to the zirconia balls is 10 (5-30), the particle size of the zirconia is 0.1-3 mm, and the ball milling speed is 100-.
6. The preparation method of the silicon-carbon anode material based on the photovoltaic waste silicon as claimed in claim 1, wherein the preparation method comprises the following steps: the organic carbon source in the step (3) is one or more of phenolic resin, epoxy resin, sucrose, starch, chitosan or glucose.
7. The preparation method of the silicon-carbon anode material based on the photovoltaic waste silicon as claimed in claim 1, wherein the preparation method comprises the following steps: the dispersant in the step (3) is one or more of polyvinylpyrrolidone, polyethyleneimine, sodium carboxymethylcellulose or sodium dodecyl benzene sulfonate.
8. The preparation method of the silicon-carbon anode material based on the photovoltaic waste silicon as claimed in claim 1, wherein the preparation method comprises the following steps: and (3) in the step (3), the solid content is 5-50% during sanding, the sanding speed is 1000-3000 rpm, and the sanding time is 0.5-10 h.
9. The preparation method of the silicon-carbon anode material based on the photovoltaic waste silicon as claimed in claim 1, wherein the preparation method comprises the following steps: in the step (4), the calcination is to heat the spray-dried material to 600-1000 ℃ at a heating rate of 1-20 ℃/min and preserve the heat for 1-4 h, wherein the inert atmosphere is one or more of nitrogen, argon or hydrogen.
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