CN113871587B - Preparation method of silicon @ carbon nanotube @ carbon composite negative electrode material of lithium ion battery - Google Patents

Preparation method of silicon @ carbon nanotube @ carbon composite negative electrode material of lithium ion battery Download PDF

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CN113871587B
CN113871587B CN202111050658.XA CN202111050658A CN113871587B CN 113871587 B CN113871587 B CN 113871587B CN 202111050658 A CN202111050658 A CN 202111050658A CN 113871587 B CN113871587 B CN 113871587B
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silicon
carbon
ball milling
qsi
carbon nanotube
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CN113871587A (en
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闫小琴
王成登
顾有松
张文远
王东华
史浩锋
纪箴
王贯勇
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Guizhou Zhongshui Material Technology Co ltd
University of Science and Technology Beijing USTB
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University of Science and Technology Beijing USTB
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
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    • B82Y30/00—Nanotechnology for materials or surface science, e.g. nanocomposites
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    • B82—NANOTECHNOLOGY
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    • H—ELECTRICITY
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    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/052—Li-accumulators
    • H01M10/0525—Rocking-chair batteries, i.e. batteries with lithium insertion or intercalation in both electrodes; Lithium-ion batteries
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    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
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    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/38—Selection of substances as active materials, active masses, active liquids of elements or alloys
    • H01M4/386—Silicon or alloys based on silicon
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    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/58—Selection 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
    • H01M4/583—Carbonaceous material, e.g. graphite-intercalation compounds or CFx
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    • H—ELECTRICITY
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    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M2004/026—Electrodes composed of, or comprising, active material characterised by the polarity
    • H01M2004/027—Negative electrodes
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    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/10—Energy storage using batteries

Abstract

A preparation method of a silicon @ carbon nanotube @ carbon composite negative electrode material of a lithium ion battery is disclosed. Firstly, adopting polycrystalline silicon cutting silicon mud as a silicon source, obtaining high-purity micron-grade flaky silicon powder by means of acid washing and the like, and then refining a micron silicon chip to a nanometer size by dry ball milling; coating nano silicon by using starch and carbon nano tubes as carbon sources through a two-step ball milling method; and then carrying out high-temperature heat treatment to obtain the silicon @ carbon nanotube @ carbon composite anode material (QSi @ CNTs @ C). In the composite material, carbon nanotubes are mutually connected among nano-silicon to form a conductive network, so that a channel is provided for ion transmission, the conductive effect is achieved, and meanwhile sufficient vacancies can relieve the volume expansion of silicon; the carbon wraps the nano silicon and the carbon nano tubes in the microspheres, so that the nano silicon can be prevented from contacting with electrolyte, the consumption of the electrolyte is reduced, and the volume expansion of the silicon is inhibited. The composite material prepared by the invention has excellent rate capability and cycle performance, the preparation method is simple, the cost is low, and industrialization can be realized.

Description

Preparation method of silicon @ carbon nanotube @ carbon composite negative electrode material of lithium ion battery
Technical Field
The invention belongs to the field of lithium ion battery cathode materials, and particularly relates to a preparation method for constructing a silicon @ carbon nanotube @ carbon composite cathode material of a lithium ion battery. The method adopts low-cost polycrystalline silicon cutting silicon mud as a silicon source, prepares nano silicon by ball milling the polycrystalline silicon cutting silicon mud by a dry method, then prepares the silicon @ carbon nano tube @ starch composite material by two-step ball milling, and finally carries out high-temperature carbonization on the composite material to obtain the silicon @ carbon nano tube @ carbon lithium ion battery cathode material.
Background
With the continuous progress and rapid development of electronic technology, the demand of human beings for portable battery systems is increasing. Graphite is a poor choice for the current commercial lithium ion battery cathode material due to the advantages of good stability, low working voltage and the like. However, the theoretical specific capacity is lower and is only 372mAh g -1 The energy density of the lithium ion battery can not meet the requirement of human society on high energy density of the lithium ion battery. Therefore, finding an ideal anode material to replace graphite is the current research focus. Silicon has very high theoretical specific capacity, up to 4200mAh g -1 About ten times as much as graphite; and the working voltage is low, and the reserves in the crust are extremely abundant, so the lithium ion battery anode is the first choice material of the next generation of high energy density lithium ion battery. However, silicon alone as a negative electrode material has poor conductivity, and generates huge volume change during charging and discharging, so that the electrolyte is continuously consumed, and the capacity of the lithium ion battery is rapidly attenuated, and the coulombic efficiency is low. In response to these problems, reducing the size of silicon to the nanometer level can effectively reduce the volume expansion effect of silicon, and then further compounding with a carbon material having excellent conductivity can improve the conductivity and cycle performance thereof. However, the current silicon-carbon negative electrode material has poor conductivityThe ring performance is unstable, and the material cost is high and the process is complex. The key point for solving the problems is to develop the silicon-carbon negative electrode material with excellent performance.
Disclosure of Invention
The invention aims to provide a preparation method of a silicon @ carbon nanotube @ carbon negative electrode material, which has economic benefits, is simple to prepare and can realize industrialization. The carbon nano tubes are mutually connected between the nano silicon to form a three-dimensional conductive network which is electron and Li + The ion transmission provides a channel, on one hand, the channel plays a role in conducting electricity, and on the other hand, the sufficient vacancy can relieve the volume expansion of silicon; the carbon wraps the nano silicon and the carbon nano tubes in the microspheres, so that the nano silicon can be prevented from contacting with electrolyte, the consumption of the electrolyte is reduced, and the volume expansion of the silicon is inhibited. The prepared composite material shows good rate performance and excellent cycle stability, and is considered as an ideal lithium ion battery cathode material.
The preparation method of the lithium ion battery silicon @ carbon nanotube @ carbon negative electrode material is shown in figure 1.
The preparation steps are as follows:
step one, preparing nano silicon: putting the pickled polycrystalline silicon cutting silicon mud into a zirconia ball milling tank, wherein the ratio of ball milling beads to materials (polycrystalline silicon cutting silicon mud) is 50. And performing dry ball milling for 10-12h at the rotating speed of 500-600r/min, and sieving the ball-milled silicon powder to obtain the nano-silicon powder.
Step two, preparing the silicon @ carbon nanotube composite material: sequentially adding nano silicon, carbon nano tubes and polyvinylpyrrolidone into deionized water, and carrying out ultrasonic treatment for 1-2h to obtain a mixed solution; dividing the mixed solution into N equal parts, respectively placing the N equal parts into zirconia ball milling tanks, and then placing the ball milling tanks on a planetary ball mill. Regulating the rotating speed to 500-600r/min, carrying out wet ball milling for 2-4h, centrifuging and cleaning the obtained solution, and finally placing the solution in a drying box for treatment at 60 ℃ for 10-12h to obtain the silicon @ carbon nanotube composite material, wherein the label is QSi @ CNTs.
Step three, preparing the silicon @ carbon nanotube @ starch composite material: and (3) weighing a proper amount of starch and QSi @ CNTs prepared in the step two, adding into a zirconia ball milling tank, and then placing the ball milling tank on a planetary ball mill. Regulating the rotating speed to 500-600r/min, carrying out dry ball milling for 10-12h, and sieving the ball-milled composite material to obtain silicon @ carbon nano tube @ starch composite material powder marked as QSi @ CNTs @ starch.
Step four, preparing the silicon @ carbon nanotube @ carbon composite material: grinding the QSi @ CNTs @ starch composite material prepared in the third step, placing the ground QSi @ CNTs @ starch composite material in a quartz boat, and adding N 2 And (2) carrying out high-temperature carbonization in the atmosphere, and then naturally cooling to room temperature to obtain the silicon @ carbon nanotube @ carbon composite material marked as QSi @ CNTs @ C.
Further, in the first step, the number of the N equal parts of the mixed solution is 2 parts or 4 parts, and the corresponding number of the zirconia ball milling tanks is 2 or 4.
Further, in the step one, the diameters of the zirconia ball milling beads are respectively 5mm, 8 mm, 10 mm and 15mm, the mass ratio of the correspondingly added milling beads is 2.
Further, in the second step, the content of the nano silicon in the mixed solution prepared by every 100ml of deionized water is 0.5-1g; the content of the carbon nano tube is 0.25-0.5g; the content of polyvinylpyrrolidone is 0.25-0.5g, and the total mass of substances added in per 100ml of deionized water is 1-2g.
Further, the centrifugation and washing processes in the second step are repeated for 2-4 times.
Furthermore, the adding amount of QSi/CNTs in the zirconia ball-milling tank in the third step is 0.6-1g, and the corresponding adding amount of starch is 1.6-10g.
Further, the heat treatment in the fourth step is sectional heating, the heating is carried out at the heating rate of 3-5 ℃/min to 300-400 ℃ and the heat preservation is carried out for 1-2h, then the heating is carried out at the same heating rate to 700-900 ℃ and the heat preservation is carried out for 2-3h, and the gas flow rate is 80-100sccm.
The technical key points of the preparation process of the silicon @ carbon nanotube @ carbon anode material are as follows: the dosage of nano silicon, carbon nano tube and starch, ball milling time, annealing temperature, heat preservation time and the like.
The mass ratio range of the nano silicon to the carbon nano tube to the starch is 1:0.25:4-1:0.5:10, the wet ball milling time is 2-4h, the dry ball milling time is 10-12h, and the annealing temperature is 700-900 ℃, because the nano silicon and the carbon nano tube can be coated in the carbon ball within the parameter range.
The lithium ion battery silicon @ carbon nanotube @ carbon anode material and the preparation method thereof have the following specific preparation steps:
step one, preparing nano silicon: putting equal parts of the pickled polycrystalline silicon cutting silicon mud into 2 or 4 zirconia ball milling tanks of 100ml, adding zirconia ball milling beads into the ball milling tanks, wherein the diameters of the ball milling beads are respectively 5mm, 8 mm, 10 mm and 15mm, the mass ratio of the ball milling beads to the materials (polycrystalline silicon cutting silicon mud) is 2. And performing dry ball milling for 10-12h at the rotating speed of 500-600r/min, and sieving the ball-milled silicon powder to obtain the nano-silicon powder.
Step two, preparing the silicon @ carbon nanotube composite material: sequentially adding nano silicon, a carbon nano tube and polyvinylpyrrolidone into 100-200ml of deionized water, wherein the content of the added nano silicon is 0.5-1g; the content of the carbon nano tube is 0.25-0.5g. Performing ultrasonic treatment for 1-2h to obtain a mixed solution, wherein the content of polyvinylpyrrolidone is 0.25-0.5g; dividing the mixed solution into 2 equal parts or 4 equal parts, putting the 2 equal parts or 4 equal parts into a zirconia ball milling tank with the volume of 100ml, adding ball milling beads into the ball milling tank, wherein the diameters of the ball milling beads are respectively 5mm, 8 mm, 10 mm and 15mm, the mass ratio of the added ball milling beads to the material (mixed solution) is 2. And (2) carrying out wet ball milling for 2-4h at the rotating speed of 500-600r/min, centrifuging and cleaning the obtained solution for 2-4 times, and finally treating the solution for 10-12h in a drying box at the temperature of 60 ℃ to obtain silicon @ carbon nanotube composite powder which is marked as QSi @ CNTs.
Step three, preparing the silicon @ carbon nanotube @ starch composite material: weighing 1.6-10g of starch and 0.6-1g of QSi @ CNTs prepared in the second step (namely, controlling the ratio of silicon, carbon nanotubes and starch to be 1: 4-1: 0.5), adding the mixture into two zirconia ball milling tanks with the volume of 100ml, adding ball milling beads into the ball milling tanks, wherein the diameters of the ball milling beads are respectively 5, 8, 10 and 15mm, the mass ratio of the ball milling beads to the materials is 2. Performing dry ball milling for 10-12h at the rotation speed of 500-600r/min, and sieving the ball-milled composite material to obtain silicon @ carbon nanotube @ starch composite material powder marked as QSi @ CNTs @ starch.
Step four, preparing the silicon @ carbon nanotube @ carbon composite material: taking QSi @ CNTs @ starch composite powder prepared in the third step, grinding the QSi @ CNTs @ starch composite powder, and placing the powder in a quartz boat, wherein N is 2 Under the atmosphere, the gas flow rate is 90sccm, the silicon @ carbon nanotube @ carbon composite material is firstly heated to 300 ℃ at the heating rate of 5 ℃/min and is kept for 1-2h, then is heated to 800 ℃ at the same heating rate and is kept for 2-3h, and then is naturally cooled to room temperature along with the furnace to obtain the silicon @ carbon nanotube @ carbon composite material, wherein the label is QSi @ CNTs @ C.
Has the advantages that:
(1) The method takes the polysilicon cutting silicon mud as a silicon source, reduces the size of silicon particles by a dry ball milling method, and has the advantages of low cost, simple operation, environmental protection and realization of large-scale industrial production.
(2) The ball milling method is used for coating carbon on the prepared nano silicon, and the carbon nano tubes are mutually connected among the nano silicon to form a three-dimensional conductive network, so that the conductive effect is achieved on one hand, and the sufficient vacant sites can effectively relieve the volume expansion of the silicon on the other hand; the carbon wraps the nano silicon and the carbon nano tubes in the microspheres, so that the nano silicon can be prevented from contacting with the electrolyte, the consumption of the electrolyte is reduced, and the volume expansion of the silicon is inhibited; part of the carbon nano tubes extend out of the micro-spheres to provide channels for ion transmission, thereby playing a good role in electric conduction. The conductivity in the negative electrode material is enhanced, and the transmission rate of lithium ions in the material is accelerated, so that the cycle stability and the rate capability of the lithium ion battery are improved.
(3) The silicon @ carbon nanotube @ carbon anode material prepared by the method has the advantages of simplicity in operation, low cost, capability of realizing industrial production and the like.
Drawings
Fig. 1 is a preparation flow chart of a silicon @ carbon nanotube @ carbon composite anode material.
Fig. 2a and b are scanning electron microscope images of the silicon @ carbon nanotube @ carbon composite anode material.
FIGS. 3a and b are X-ray diffraction patterns and Raman spectra of the silicon @ carbon nanotube @ carbon composite anode material, respectively.
FIG. 4a is 0.1mV s -1 And b is a constant current charging and discharging curve chart of the silicon @ carbon nano tube @ carbon composite negative electrode material at 0.05 ℃.
FIG. 5 is a graph showing the stability of the cycle of 300 cycles before Si, QSi @ C-4, QSi @ C-10 and QSi @ CNTs @ C at 0.2C.
FIG. 6 is the graph of the stability of 300 cycles before QSi @ C-10 and QSi @ CNTs @ C at 0.2C.
Detailed Description
The technical solutions in the comparative examples and examples of the present invention will be described in detail and completely with reference to the comparative examples and examples of the present invention, but are not limited thereto.
Comparative example 1
Step one, equally putting the pickled polycrystalline silicon cutting silicon mud into 2 or 4 100ml zirconia ball milling tanks, adding zirconia ball milling beads into the ball milling tanks, wherein the diameters of the ball milling beads are respectively 5, 8, 10 and 15mm, the mass ratio of the ball milling beads to the materials (polycrystalline silicon cutting silicon mud) is 2. Dry ball milling is carried out for 10-12h at the rotating speed of 500-600 r/min.
And step two, screening the ball-milled silicon powder through a sieve to obtain the nano silicon powder electrode material marked as Si.
Step three, mixing QSi @ CNTs @ C with conductive carbon black (super P) and polyacrylic acid (PAA) according to the ratio of 8. Stirring and mixing to form the electrode slurry. The electrode slurry was uniformly coated on a copper foil and vacuum dried, and the electrolyte was 90% (1 m lipfd/DEC (volume ratio 1)) +10% fec, to make a coin cell.
Testing the electrochemical performance of Si, wherein the discharge specific capacity of the first ring is 3983.8mAh/g, the charge specific capacity of the first ring is 2931.4mAh/g, and the coulombic efficiency of the first ring is 73.5%; after 300 cycles, the capacity remained at 2.916mAh/g.
Comparative example 2
Step one, weighing 2-4g of starch, equally dividing the starch into 2 or 4 zirconia ball milling tanks of 100ml, adding zirconia ball milling beads into the ball milling tanks, wherein the diameters of the ball milling beads are 5mm, 8 mm, 10 mm and 15mm respectively, the corresponding addition amount is 2. Dry ball milling is carried out for 10-12h at the rotating speed of 500-600r/min, and the ball milled starch is taken to pass through a sieve.
Step two, taking 1-2g of the starch after ball milling, grinding and placing in a quartz boat, and adding N 2 And under the atmosphere, the gas flow rate is 80-100sccm, the carbon sheet electrode material is firstly heated to 300-400 ℃ at the heating rate of 3-5 ℃/min and is kept warm for 1-2h, then is heated to 700-900 ℃ at the same heating rate and is kept warm for 2-3h, and then is naturally cooled to room temperature along with the furnace to obtain the carbon sheet electrode material which is marked as C.
Step three, mixing C with conductive carbon black (super P) and polyacrylic acid (PAA) according to 1. Stirring and mixing to form the electrode slurry. The electrode slurry was uniformly coated on a copper foil and vacuum dried, and the electrolyte was 90% (1 m lipfd/DEC (volume ratio 1)) +10% fec, to make a coin cell.
Testing the electrochemical performance of C, wherein the discharge specific capacity of the first ring is 415mAh/g, the charge specific capacity of the first ring is 178.4mAh/g, and the coulomb efficiency of the first ring is 42%; after 300 cycles, the capacity remained at 127.7mAh/g.
Example 1
Step one, equally putting the pickled polycrystalline silicon cutting silicon mud into 2 or 4 100ml zirconia ball milling tanks, adding zirconia ball milling beads into the ball milling tanks, wherein the diameters of the ball milling beads are respectively 5, 8, 10 and 15mm, the mass ratio of the ball milling beads to the materials (polycrystalline silicon cutting silicon mud) is 2. And (3) performing dry ball milling for 10-12 hours at the rotating speed of 500-600r/min, and sieving the ball-milled silicon powder through a sieve to obtain the nano-silicon powder.
Step two, sequentially adding nano-silicon, carbon nano-tubes and polyvinylpyrrolidone into 100-200ml of deionized water, wherein the content of the added nano-silicon is 0.5-1g; the content of the carbon nano tube is 0.25-0.5g. Performing ultrasonic treatment for 1-2h to obtain a mixed solution, wherein the content of polyvinylpyrrolidone is 0.25-0.5g; dividing the mixed solution into 2 equal parts and 4 equal parts, putting the solution into 2 or 4 zirconia ball milling tanks with the volume of 100ml, adding ball milling beads into the ball milling tanks, wherein the diameters of the ball milling beads are respectively 5mm, 8 mm, 10 mm and 15mm, the mass ratio of the ball milling beads to the material (mixed solution) is 2. And (2) carrying out wet ball milling for 2-4h at the rotating speed of 500-600r/min, centrifuging and cleaning the obtained solution for 2-4 times, and finally treating the solution in a drying box at the temperature of 60 ℃ for 10-12h to obtain the silicon @ carbon nanotube composite material powder.
Step three, taking the composite material powder prepared in the step three, grinding the composite material powder, placing the ground composite material powder in a quartz boat, and putting the quartz boat in a reactor N 2 And under the atmosphere, the gas flow rate is 80-100sccm, the silicon @ carbon nanotube composite electrode material is firstly heated to 300-400 ℃ at the heating rate of 3-5 ℃/min and is kept for 1-2h, then is heated to 700-900 ℃ at the same heating rate and is kept for 2-3h, and then is naturally cooled to room temperature along with the furnace to obtain the silicon @ carbon nanotube composite electrode material which is marked as QSi @ CNTs.
Step four, mixing QSi @ CNTs with conductive carbon black (super P) and polyacrylic acid (PAA) according to the ratio of 8. Stirring and mixing to form the electrode slurry. The electrode slurry was uniformly coated on a copper foil and vacuum dried, and the electrolyte was 90% (1 m lipfd/DEC (volume ratio 1)) +10% fec, to make a coin cell.
The electrochemical performance of QSi @ CNTs is tested, the discharge specific capacity of the first circle is 2107.4mAh/g, the charge specific capacity of the first circle is 1635.3mAh/g, and the coulombic efficiency of the first circle is 77.6 percent; after 300 cycles, the capacity remained at 341.5mAh/g.
Example 2
Step one, equally putting the pickled polycrystalline silicon cutting silicon mud into 2 or 4 100ml zirconia ball milling tanks, adding zirconia ball milling beads into the ball milling tanks, wherein the diameters of the ball milling beads are respectively 5, 8, 10 and 15mm, the mass ratio of the ball milling beads to the materials (polycrystalline silicon cutting silicon mud) is 2. And performing dry ball milling for 10-12h at the rotating speed of 500-600r/min, and sieving the ball-milled silicon powder to obtain the nano-silicon powder.
Step two, weighing 0.2-0.5g of starch and 0.8-2g of the nano silicon powder prepared in the step one (namely, controlling the ratio of silicon to starch to be 1. Dry ball milling is carried out for 10-12h at the rotating speed of 500-600r/min, the ball milled composite material is sieved, and silicon @ starch composite material powder is obtained and is marked as QSi @ starch-4.
Step three, taking the QSi @ starch composite material powder prepared in the step two, grinding the QSi @ starch composite material powder, placing the QSi @ starch composite material powder in a quartz boat, and placing the quartz boat in a reactor with N 2 Under the atmosphere, the gas flow rate is 80-100sccm, the silicon @ carbon composite electrode material is firstly heated to 300-400 ℃ at the heating rate of 3-5 ℃/min and is kept for 1-2h, then is heated to 700-900 ℃ at the same heating rate and is kept for 2-3h, and then is naturally cooled to room temperature along with the furnace to obtain the silicon @ carbon composite electrode material, which is marked as QSi @ C-4.
Step four, mixing QSi @ C-4 with conductive carbon black (super P) and polyacrylic acid (PAA) according to the ratio of 8. Stirring and mixing to form the electrode slurry. The electrode slurry was uniformly coated on a copper foil and vacuum dried, and the electrolyte was 90% (1 m lipfd/DEC (volume ratio 1)) +10% fec, to make a coin cell.
The electrochemical performance of QSi @ C-4 is tested, the discharge specific capacity of the first ring is 1697.9mAh/g, the charge specific capacity of the first ring is 1301.5mAh/g, and the coulombic efficiency of the first ring is 76.65%; after 300 cycles, the capacity remained at 229.6mAh/g.
Example 3
Step one, equally putting the pickled polycrystalline silicon cutting silicon mud into 2 or 4 100ml zirconia ball milling tanks, adding zirconia ball milling beads into the ball milling tanks, wherein the diameters of the ball milling beads are respectively 5, 8, 10 and 15mm, the mass ratio of the ball milling beads to the materials (polycrystalline silicon cutting silicon mud) is 2. And (3) performing dry ball milling for 10-12 hours at the rotating speed of 500-600r/min, and sieving the ball-milled silicon powder through a sieve to obtain the nano-silicon powder.
Step two, weighing 0.2-0.5g of starch and 1.2-3g of the nano silicon powder prepared in the step one (namely, controlling the ratio of silicon to starch to be 1. And (3) carrying out dry ball milling for 10-12h at the rotating speed of 500-600r/min, and sieving the ball-milled composite material to obtain silicon @ starch composite material powder marked as QSi @ starch-6.
Step three, taking the QSi @ starch composite material powder prepared in the step two, grinding the QSi @ starch composite material powder, placing the QSi @ starch composite material powder in a quartz boat, and placing the quartz boat in a reactor with N 2 Under the atmosphere, the gas flow rate is 80-100sccm, the silicon @ carbon composite electrode material is firstly heated to 300-400 ℃ at the heating rate of 3-5 ℃/min and is kept for 1-2h, then is heated to 700-900 ℃ at the same heating rate and is kept for 2-3h, and then is naturally cooled to room temperature along with the furnace to obtain the silicon @ carbon composite electrode material, which is marked as QSi @ C-6.
Step four, mixing QSi @ C-6 with conductive carbon black (super P) and polyacrylic acid (PAA) according to the ratio of 8. Stirring and mixing to form the electrode slurry. The electrode slurry was uniformly coated on copper foil and vacuum dried, the electrolyte was 90% (1M lipfd 6 ED/DEC (1 volume ratio)) +10% fec, and coin cells were made.
The electrochemical performance of QSi @ C-6 is tested, the discharge specific capacity of the first ring is 1301.5mAh/g, the charge specific capacity of the first ring is 929.6mAh/g, and the coulombic efficiency of the first ring is 71.43 percent; after 300 cycles, the capacity remained at 313.4mAh/g.
Example 4
Step one, equally putting the pickled polycrystalline silicon cutting silicon mud into 2 or 4 100ml zirconia ball milling tanks, adding zirconia ball milling beads into the ball milling tanks, wherein the diameters of the ball milling beads are respectively 5mm, 8 mm, 10 mm and 15mm, the mass ratio of the ball milling beads to the materials (polycrystalline silicon cutting silicon mud) is 2. And (3) performing dry ball milling for 10-12 hours at the rotating speed of 500-600r/min, and sieving the ball-milled silicon powder through a sieve to obtain the nano-silicon powder.
Step two, weighing 0.2-0.5g of starch and 1.6-4g of the nano silicon powder prepared in the step one (namely, controlling the ratio of silicon to starch to be 1. And (2) carrying out dry ball milling for 10-12h at the rotating speed of 500-600r/min, and sieving the ball-milled composite material to obtain silicon @ starch composite material powder marked as QSi @ starch-8.
Step three, taking the QSi @ starch-8 composite material powder prepared in the step two, grinding the composite material powder, placing the ground composite material powder in a quartz boat, and putting the quartz boat in a reactor with N 2 Under the atmosphere, the gas flow rate is 80-100sccm, the silicon @ carbon composite electrode material is firstly heated to 300-400 ℃ at the heating rate of 3-5 ℃/min and is kept for 1-2h, then is heated to 700-900 ℃ at the same heating rate and is kept for 2-3h, and then is naturally cooled to room temperature along with the furnace to obtain the silicon @ carbon composite electrode material, which is marked as QSi @ C-8.
Step four, mixing QSi @ C-8 with conductive carbon black (super P) and polyacrylic acid (PAA) according to the ratio of 8. Stirring and mixing to form the electrode slurry. The electrode slurry was uniformly coated on a copper foil and vacuum dried with 90% electrolyte (1M LiPF) 6 ED/DEC (volume ratio 1)) +10% fec, and was made into coin cells.
The electrochemical performance of QSi @ C-8 is tested, the discharge specific capacity of the first turn is 1014.2mAh/g, the charge specific capacity of the first turn is 661.3mAh/g, and the coulombic efficiency of the first turn is 65.2%; after 300 cycles, the capacity remained at 402.6mAh/g.
Example 5
Step one, equally putting the pickled polycrystalline silicon cutting silicon mud into 2 or 4 100ml zirconia ball milling tanks, adding zirconia ball milling beads into the ball milling tanks, wherein the diameters of the ball milling beads are respectively 5mm, 8 mm, 10 mm and 15mm, the mass ratio of the ball milling beads to the materials (polycrystalline silicon cutting silicon mud) is 2. And performing dry ball milling for 10-12h at the rotating speed of 500-600r/min, and sieving the ball-milled silicon powder to obtain the nano-silicon powder.
Step two, weighing 0.2-0.5g of starch and 2-5g of the nano silicon powder prepared in the step one (namely controlling the ratio of silicon to starch to be 1. Dry ball milling is carried out for 10-12h at the rotating speed of 500-600r/min, the ball milled composite material is sieved, and silicon @ starch composite material powder is obtained and is marked as QSi @ starch-10.
Step three, taking the QSi @ starch-10 composite material powder prepared in the step two, grinding the composite material powder, placing the ground composite material powder in a quartz boat, and putting the quartz boat in a reactor with N 2 Under the atmosphere, the gas flow rate is 80-100sccm, the silicon @ carbon composite electrode material is firstly heated to 300-400 ℃ at the heating rate of 3-5 ℃/min and is kept warm for 1-2h, then is heated to 700-900 ℃ at the same heating rate and is kept warm for 2-3h, and then is naturally cooled to room temperature along with the furnace to obtain the silicon @ carbon composite electrode material, which is marked as QSi @ C-10.
Step four, mixing QSi @ C-10 with conductive carbon black (super P) and polyacrylic acid (PAA) according to the ratio of 8. Stirring and mixing to form the electrode slurry. The electrode slurry was uniformly coated on a copper foil and vacuum dried, and the electrolyte was 90% (1 m lipfd/DEC (volume ratio 1)) +10% fec, to make a coin cell.
The electrochemical performance of QSi @ C-10 is tested, the discharge specific capacity of the first ring is 810.5mAh/g, the charge specific capacity of the first ring is 512.8mAh/g, and the coulomb efficiency of the first ring is 62.3 percent; after 300 cycles, the capacity remained at 601.4mAh/g.
Example 6
Step one, equally putting the pickled polycrystalline silicon cutting silicon mud into 2 or 4 100ml zirconia ball milling tanks, adding zirconia ball milling beads into the ball milling tanks, wherein the diameters of the ball milling beads are respectively 5, 8, 10 and 15mm, the mass ratio of the ball milling beads to the materials (polycrystalline silicon cutting silicon mud) is 2. And (3) performing dry ball milling for 10-12 hours at the rotating speed of 500-600r/min, and sieving the ball-milled silicon powder through a sieve to obtain the nano-silicon powder.
Step two, sequentially adding nano-silicon, carbon nano-tubes and polyvinylpyrrolidone into 100-200ml of deionized water, wherein the content of the added nano-silicon is 0.5-1g; the content of the carbon nano tube is 0.25-0.5g. Performing ultrasonic treatment for 1-2h to obtain a mixed solution, wherein the content of polyvinylpyrrolidone is 0.25-0.5g; dividing the mixed solution into 2 equal parts or 4 equal parts, putting the 2 equal parts or 4 equal parts into a zirconia ball milling tank with the volume of 100ml, adding zirconia ball milling beads into the ball milling tank, wherein the diameters of the ball milling beads are respectively 5mm, 8 mm, 10 mm and 15mm, the mass ratio of the corresponding addition amounts is 2. And (2) carrying out wet ball milling for 2-4h at the rotating speed of 500-600r/min, centrifuging and cleaning the obtained solution for 2-4 times, and finally treating the solution for 10-12h in a drying box at the temperature of 60 ℃ to obtain the silicon @ carbon nanotube composite material which is marked as QSi @ CNTs.
Step three, weighing 1.6-10g of starch and 0.6-1g of QSi @ CNTs prepared in the step two (namely, controlling the ratio of silicon, carbon nanotubes and starch to be 1. Performing dry ball milling for 10-12h at the rotation speed of 500-600r/min, and sieving the ball-milled composite material to obtain silicon @ carbon nanotube @ starch composite material powder marked as QSi @ CNTs @ starch.
Step four, taking the QSi @ CNTs @ starch composite powder prepared in the step three, grinding the QSi @ CNTs @ starch composite powder, then placing the QSi @ CNTs @ starch composite powder in a quartz boat, and grinding the QSi @ CNTs @ starch composite powder in a quartz boat 2 Under the atmosphere, the gas flow rate is 80-100sccm, and the temperature is raised by 3-5 ℃/minHeating to 300-400 ℃ at a speed, keeping the temperature for 1-2h, then heating to 700-900 ℃ at the same heating rate, keeping the temperature for 2-3h, and then naturally cooling to room temperature along with the furnace to obtain the silicon @ carbon nanotube @ carbon composite electrode material, which is marked as QSi @ CNTs @ C.
Step five, mixing QSi @ CNTs @ C with conductive carbon black (super P) and polyacrylic acid (PAA) according to the ratio of 8. Stirring and mixing to form the electrode slurry. The electrode slurry was uniformly coated on a copper foil and vacuum dried with 90% electrolyte (1M LiPF) 6 ED/DEC (volume ratio 1)) +10% fec, and was made into coin cells.
The electrochemical performance of QSi @ CNTs @ C is tested, the discharge specific capacity of the first ring is 1013.8mAh/g, the charge specific capacity of the first ring is 809.9mAh/g, and the coulombic efficiency of the first ring is 79.88%; after 300 cycles, the capacity remained at 720mAh/g.
The following table summarizes the performance parameters of the silicon-carbon composite anode material
Figure BDA0003252627750000101
As can be seen from the table above, the reversible capacity after 300 cycles is higher for all six examples than for the two comparative examples. Particularly, the high capacity is kept after 300 circles for QSi @ C-10 and QSi @ CNTs @ C, and in addition, the first-circle coulombic efficiency of the QSi @ CNTs @ C is up to 79.88 percent, which shows that the silicon-carbon composite negative electrode material has better cycle stability and the advantage of the silicon-carbon negative electrode material in the preparation of the lithium ion battery. The characteristics of simple preparation process and low cost of the used raw materials are integrated, and the fact that QSi @ CNTs @ C has a great application prospect as the lithium ion battery anode material is explained.
The above embodiments are only examples of the present invention, and should not be construed as limiting the present invention, and any modifications, equivalent substitutions, improvements and the like made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims (7)

1. A preparation method of a silicon @ carbon nanotube @ carbon composite anode material of a lithium ion battery is characterized by comprising the following preparation steps:
step one, preparing nano silicon: placing the pickled polycrystalline silicon cutting silicon mud into a zirconia ball milling tank, wherein the ratio of ball milling beads to the polycrystalline silicon cutting silicon mud is 50; performing dry ball milling for 10-12h at the rotating speed of 500-600r/min, and sieving the ball-milled silicon powder to obtain nano silicon powder;
step two, preparing the silicon @ carbon nanotube composite material: sequentially adding nano silicon, carbon nano tubes and polyvinylpyrrolidone into deionized water, and carrying out ultrasonic treatment for 1-2h to obtain a mixed solution; dividing the mixed solution into N equal parts, respectively putting the N equal parts into zirconia ball milling tanks, and then putting the ball milling tanks on a planetary ball mill; regulating the rotating speed to 500-600r/min, carrying out wet ball milling for 2-4h, centrifuging and cleaning the obtained solution, and finally placing the solution in a drying box for treatment at 60 ℃ for 10-12h to obtain the silicon @ carbon nanotube composite material which is marked as QSi @ CNTs;
step three, preparing the silicon @ carbon nanotube @ starch composite material: weighing a proper amount of starch and QSi @ CNTs prepared in the second step, adding the starch and the QSi @ CNTs into a zirconia ball milling tank, then placing the ball milling tank on a planetary ball mill, adjusting the rotating speed to 500-600r/min, carrying out dry ball milling for 10-12h, and sieving the ball-milled composite material to obtain silicon @ carbon nanotube @ starch composite material powder marked as QSi @ CNTs @ starch;
step four, preparing the silicon @ carbon nanotube @ carbon composite material: grinding the QSi @ CNTs @ starch composite material prepared in the third step, placing the ground QSi @ CNTs @ starch composite material in a quartz boat, and adding N 2 And (2) carrying out high-temperature carbonization in the atmosphere, and then naturally cooling to room temperature to obtain the silicon @ carbon nanotube @ carbon composite material marked as QSi @ CNTs @ C.
2. The method for preparing the silicon @ carbon nanotube @ carbon composite anode material for the lithium ion battery as defined in claim 1, wherein in the first step, the number of the N equal parts of the mixed solution is 2 or 4, and the number of the corresponding zirconia ball milling tanks is 2 or 4.
3. The preparation method of the lithium ion battery silicon @ carbon nanotube @ carbon composite anode material as claimed in claim 1, wherein in the step one, the diameters of the zirconia ball milling beads are 5mm, 8 mm, 10 mm and 15mm respectively, the mass ratio of the added zirconia ball milling beads to the polysilicon cutting silicon slurry is 2.
4. The method for preparing the silicon @ carbon nanotube @ carbon composite anode material of the lithium ion battery as claimed in claim 1, wherein the content of the nano-silicon in the mixed solution prepared by every 100ml of deionized water in the second step is 0.5-1g; the content of the carbon nano tube is 0.25-0.5g; the content of polyvinylpyrrolidone is 0.25-0.5g, and the total mass of substances added in per 100ml of deionized water is 1-2g.
5. The preparation method of the lithium ion battery silicon @ carbon nanotube @ carbon composite anode material as defined in claim 1, wherein the centrifugation and cleaning processes in the second step are repeated for 2-4 times.
6. The method for preparing the silicon @ carbon nanotube @ carbon composite anode material for the lithium ion battery as defined in claim 1, wherein the QSi/CNTs in the zirconia ball-milling pot in the third step is added in an amount of 0.6 to 1g, and the corresponding starch is added in an amount of 1.6 to 10g.
7. The preparation method of the silicon @ carbon nanotube @ carbon composite anode material for the lithium ion battery as claimed in claim 1, wherein the heat treatment mode in the fourth step is sectional heating, the heating is carried out at a heating rate of 3-5 ℃/min to 300-400 ℃ and the heat preservation is carried out for 1-2h, then the heating is carried out at the same heating rate to 700-900 ℃ and the heat preservation is carried out for 2-3h 2 The flow rate is 80-100sccm.
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