CN113328058A - Preparation method and application of nitrogen-doped carbon/silicon nano composite material - Google Patents

Preparation method and application of nitrogen-doped carbon/silicon nano composite material Download PDF

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CN113328058A
CN113328058A CN202110580277.6A CN202110580277A CN113328058A CN 113328058 A CN113328058 A CN 113328058A CN 202110580277 A CN202110580277 A CN 202110580277A CN 113328058 A CN113328058 A CN 113328058A
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nitrogen
silicon
silicon powder
ball
composite material
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王�锋
陶君
覃彩芹
张贤
余链
杨宇航
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Hubei Engineering University
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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
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/04—Processes of manufacture in general
    • H01M4/0471—Processes of manufacture in general involving thermal treatment, e.g. firing, sintering, backing particulate active material, thermal decomposition, pyrolysis
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B82—NANOTECHNOLOGY
    • B82Y—SPECIFIC USES OR APPLICATIONS OF NANOSTRUCTURES; MEASUREMENT OR ANALYSIS OF NANOSTRUCTURES; MANUFACTURE OR TREATMENT OF NANOSTRUCTURES
    • B82Y30/00—Nanotechnology for materials or surface science, e.g. nanocomposites
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B82—NANOTECHNOLOGY
    • B82Y—SPECIFIC USES OR APPLICATIONS OF NANOSTRUCTURES; MEASUREMENT OR ANALYSIS OF NANOSTRUCTURES; MANUFACTURE OR TREATMENT OF NANOSTRUCTURES
    • B82Y40/00—Manufacture or treatment of nanostructures
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • 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
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/362—Composites
    • H01M4/366—Composites as layered products
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • 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
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • 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
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/62—Selection of inactive substances as ingredients for active masses, e.g. binders, fillers
    • H01M4/624—Electric conductive fillers
    • H01M4/625—Carbon or graphite
    • Y—GENERAL 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
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • 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

The invention relates to the technical field of lithium battery materials, and particularly discloses a preparation method and application of a nitrogen-doped carbon/silicon nano composite electrode material. The invention takes the commercial micron-sized silicon powder, carbon source and nitrogen source as raw materials and adopts in-situ polymerizationThe method obtains a polymer/silicon composite material precursor, and then obtains the nitrogen-doped carbon/silicon composite material through high-temperature carbonization. The nitrogen-doped carbon/silicon composite material shows excellent cycle performance after being assembled into a lithium ion half battery, and the cycle performance is 0.1 A.g‑1The current density is about 1000 mA-g after circulating for 100 circles‑1Specific capacity.

Description

Preparation method and application of nitrogen-doped carbon/silicon nano composite material
Technical Field
The invention relates to the technical field of lithium battery materials, in particular to a preparation method and application of a nitrogen-doped carbon/silicon nano composite material.
Background
In the information-oriented era of rapid development, the vigorous development of electronic devices and electric vehicles puts higher demands on the performance of lithium ion batteries, and the development of a new generation of high-energy-density and high-power lithium ion batteries is urgently needed. The commercial lithium ion battery graphite cathode material widely used at present has the advantages of stable cycle performance and good conductivity, but the theoretical capacity is too low and is only 372mAh g-1And the demand of the market for high-energy density batteries is far from being met. Therefore, there is a need to develop a new generation of high energy density lithium battery anode material. The theoretical capacity of the silicon negative electrode material is extremely high and reaches 4200 mAh.g-1However, it has poor conductivity and is accompanied by a severe volume expansion effect during charge and discharge, resulting in very poor cycle stability.
The preparation and electrochemical performance exploration of silicon/carbon composite materials are hot spots of research. Theoretically, the silicon/carbon negative electrode material has the advantages of both silicon and carbon materials, and the lithium battery negative electrode material with relatively high capacity and good cycle stability is obtained. However, many studies have found that these two materials exhibit poor compatibility during cycling. A large number of researches show that the performance of the nitrogen-doped carbon/silicon composite material is far superior to that of the common silicon/carbon composite material.
At present, the preparation of nitrogen-doped carbon/silicon composite materials mainly adopts: the material is prepared by mixing one or more methods such as a sol-gel method, a mechanical ball milling method, a chemical vapor deposition method and the like. The methods generally have the defects of complicated preparation process, poor product consistency, high energy consumption, high cost, limited large-scale preparation and the like.
Disclosure of Invention
In view of the above-mentioned deficiencies of the prior art, a first object of the present invention is to provide a method for preparing a nitrogen-doped carbon/silicon nanocomposite, which achieves uniformity of polymer and silicon material at a molecular level by an in-situ polymerization method, and then obtains the nitrogen-doped carbon/silicon nanocomposite with uniform morphology by high-temperature carbonization.
The second purpose of the invention is to provide the application of the nitrogen-doped carbon/silicon nano composite material as a lithium ion battery cathode material.
The technical scheme adopted by the invention for solving the technical problems is as follows:
a preparation method of a nitrogen-doped carbon/silicon nano composite material comprises the steps of taking commercially available micron-sized silicon powder, a carbon source and a nitrogen source as raw materials, obtaining a polymer/silicon composite material precursor by adopting an in-situ polymerization method, and then carrying out high-temperature carbonization to obtain the nitrogen-doped carbon/silicon nano composite material.
The specific preparation method comprises the following steps:
s1, ball-milling the commercial micron-sized silicon powder for 6-48h at the ball-material ratio of (8-80):1 under the condition of 100-800rpm for later use;
s2, dispersing the silicon powder subjected to the ball milling in the S1 volume percent into deionized water, ultrasonically dispersing for 1-3 hours at 300-500W to obtain dispersion liquid, then adding a carbon source, a nitrogen source and a dispersing agent in a certain proportion into the dispersion liquid, and stirring; adding a certain amount of initiator into the mixture, stirring to obtain a mixed solution, transferring the mixed solution into a crucible, uniformly stirring, directly placing the crucible into a muffle furnace, heating the crucible to 60-120 ℃ at a heating rate of 1-5 ℃/min in the air atmosphere to perform polymerization reaction, and preserving heat for 1-4h to obtain a polymer/silicon composite material precursor;
and S3, continuously introducing nitrogen into the S2 muffle furnace, heating the polymer/silicon composite material precursor obtained in the S2 to 600-1000 ℃ at the heating rate of 1-5 ℃/min, carrying out high-temperature carbonization treatment, preserving the heat for 1-3h, cooling to room temperature, carrying out ball milling, and sieving with a 100-400-mesh sieve to obtain the nitrogen-doped carbon/silicon nanocomposite material.
Further, in the step S1, the silicon powder is AR grade and has a particle size of 40-100 μm.
Further, the ball milling conditions of the silicon powder in the step S1 are as follows: the silicon powder is ball milled for 6-12h under the conditions of 400-600rpm and the ball material ratio of (20-50): 1.
Preferably, the ball milling conditions of the silicon powder in the step S1 are as follows: the silicon powder is ball milled for 12 hours at the ball-to-material ratio of 40:1 and the speed of 500 rpm.
Further, in the step S2: the carbon source is acrylic acid, methacrylic acid, pyrrole or chitosan; the nitrogen source is melamine or urea; the dispersant is one or more of sodium dodecyl benzene sulfonate, sodium dodecyl sulfonate and sodium hexadecylbenzene sulfonate; the initiator is 3-5 wt% ammonium persulfate aqueous solution.
Preferably, in step S2: the carbon source is acrylic acid, the nitrogen source is melamine, the dispersing agent is sodium dodecyl benzene sulfonate, and the initiator is 5wt% ammonium persulfate aqueous solution.
Further, in the step S2: the mass ratio of the silicon powder to the carbon source to the nitrogen source is 1: (5-40): (2-10), preferably, the mass ratio of the silicon powder to the carbon source to the nitrogen source is 1: (8-10): (2-5), more preferably, the mass ratio of the silicon powder to the carbon source to the nitrogen source is 1: 9: 3; the addition amount of the dispersing agent is 10-30% of the mass of the silicon powder.
Further, in the step S2: silicon powder: the proportion of deionized water is 0.5g (40-200) mL, preferably 0.5g (80-120) mL.
Further, in the step S2: heating to 60-80 ℃ at the heating rate of 5 ℃/min to perform polymerization reaction, and keeping the temperature for 1-4 h.
Preferably, in step S2: the polymerization temperature is 80 ℃, and the holding time is 3 h.
Further, in the step S3: the flow rate of the introduced nitrogen is 0-40 mL/min, preferably 20 mL/min.
Preferably, the high-temperature carbonization step in step S3 is: heating to 800 ℃ at the heating rate of 2 ℃/min, and keeping the temperature for 2 h.
Preferably, in step S3: after ball milling, the mixture is sieved by a 200-mesh sieve.
Furthermore, the purity of the silicon powder, the carbon source, the nitrogen source, the dispersing agent and the initiator is not lower than the chemical purity.
The prepared nitrogen-doped carbon/silicon nano composite material is applied as a lithium ion battery cathode material. In the specific application, the steps are as follows: (1) preparing conductive carbon black (super-P) serving as a conductive agent, polyacrylic acid (PAA) serving as a binder and an active material (the nitrogen-doped carbon/silicon nano composite material) into slurry according to the mass ratio of 20:20:60 by using water as a solvent, coating the slurry on a copper foil, drying the copper foil at the temperature of 80 ℃ under a vacuum condition, and cutting the copper foil into electrode slices for later use; (2) sequentially stacking the positive electrode shell, the electrode plate obtained in the step (1), the diaphragm, the lithium plate, the foamed nickel and the negative electrode shell, adding a proper amount of electrolyte, and packaging to assemble the lithium ion half-cell, wherein the electrolyte can be 1mol/L LiPF6the/EC-DMC (1:1), the septum may be Celgard 2400.
Compared with the prior art, the invention has the advantages and beneficial effects that:
the synthesis method adopted by the invention is an in-situ polymerization method, and the polymer can uniformly wrap the silicon powder; in the polymer precursor, silicon powder can be uniformly dispersed in the polymer precursor, the nano nitrogen-doped carbon/silicon nano composite material with uniform size can be obtained through subsequent high-temperature carbonization treatment, and the proportion of each element in the product can be accurately controlled. During the polymerization reaction, a great deal of heat is released, and water vapor, generated carbon dioxide gas and part of acrylic acid are polymerized to cause the volume of a reaction body to expand violently to form a honeycomb-shaped solid polymer. The volume expansion makes the dispersion of metal ions more uniform, and the material with uniform size can be obtained after the subsequent heat treatment. Meanwhile, the method has the advantages of one-step in-place sectional type (grading) calcination and one-step molding, reduces the process flow, greatly reduces the energy consumption and labor cost, simplifies the experimental steps, avoids the traditional multi-step reaction, has excellent performance of the prepared material, and can realize large-scale production.
The nitrogen-doped carbon/silicon nano composite material prepared by the invention has good cycle stability of 0.1 A.g-1The theoretical capacity after 100 cycles of circulation under the current density is about 1000mAh g-1。
Drawings
FIG. 1 is an XRD diffractogram of a nitrogen-doped carbon/silicon nanocomposite prepared in example 1 of the present invention;
FIG. 2 is a Scanning Electron Microscope (SEM) image of a nitrogen-doped carbon/silicon nanocomposite prepared according to example 1 of the present invention;
FIG. 3 is a Scanning Electron Microscope (SEM) image of nitrogen-doped carbon/silicon nanocomposites prepared according to the present invention in comparative example 1 (left drawing) and comparative example 2 (right drawing);
FIG. 4 is an X-ray photoelectron diffraction (XPS) pattern of a nitrogen-doped carbon/silicon nanocomposite prepared in example 1 of the present invention;
FIG. 5 shows the nitrogen-doped carbon/silicon nanocomposite prepared in example 1 of the present invention assembled into a lithium ion battery at 0.1 A.g-1Cycling performance plot at current density.
Detailed Description
The technical solution of the present invention is further illustrated by the following embodiments in conjunction with the accompanying drawings.
In the following examples, the raw material silicon powder is purchased from Aladdin company, the Si purity is more than 99%, the AR grade is provided, and the particle size is 40-100 μm; other unexplained starting materials are commercially available and are all analytically pure.
Example 1: a preparation method of a nitrogen-doped carbon/silicon nano composite material comprises the following steps:
1) ball-milling silicon powder (40-100 mu m) for 12 hours at a ball-to-material ratio of 40:1 under the condition of 500 rpm;
2) dispersing 0.5g of silicon powder subjected to ball milling in the step 1) into 80mL of deionized water, performing ultrasonic dispersion for 2 hours at 400W to obtain dispersion liquid, adding 4.5g of acrylic acid, 1.5g of melamine and 0.10g of sodium dodecyl benzene sulfonate into the dispersion liquid, and stirring for 3 hours; adding 2mL of 5 mass percent ammonium persulfate aqueous solution into the mixture, stirring to obtain a mixed solution, transferring the mixed solution into a large crucible, uniformly stirring, placing the large crucible into a small-sized movable muffle furnace, heating to 80 ℃ at a heating rate of 5 ℃/min under the air condition to perform polymerization reaction, and preserving heat for 3 hours to obtain a polymer/silicon composite material precursor;
3) and continuously introducing nitrogen into the S2 small-sized movable muffle furnace at the flow rate of 20mL/min, after 5min, heating the precursor of the polymer/silicon composite material obtained in the S2 large crucible to 800 ℃ at the heating rate of 2 ℃/min from 80 ℃, preserving the temperature for 2h, cooling to room temperature, performing ball milling, and sieving with a 200-mesh sieve to obtain the nitrogen-doped carbon/silicon nanocomposite material.
Fig. 1 and 2 are an XRD chart and an SEM chart, respectively, of the nitrogen-doped carbon/silicon nanocomposite material prepared in example 1. As can be seen from FIG. 1, no impurity peak appears on the XRD spectrum of the nitrogen-doped carbon/silicon nano composite material, each diffraction peak is completely matched with JCPDS standard card (JCPDS No.27-1402) of Si, and no obvious spectrum peak appears on the XRD spectrum because the nitrogen-containing carbon material is an amorphous material.
As can be seen from FIG. 2, the synthesized N-doped carbon/silicon nanocomposites are all uniform particles with uniform particle size distribution and particle size of 2-10 μm. Fig. 4 is an XPS graph of the nitrogen-doped carbon/silicon nanocomposite prepared in example 1, which confirms that the carbon material contains nitrogen element, thereby obtaining a product of the nitrogen-doped carbon/silicon nanocomposite.
Example 2: a preparation method of a nitrogen-doped carbon/silicon nano composite material comprises the following steps:
1) ball-milling silicon powder (40-100 mu m) for 12 hours at a ball-to-material ratio of 40:1 under the condition of 500 rpm;
2) dispersing 0.5g of silicon powder subjected to ball milling in the step 1) into 80mL of deionized water, performing ultrasonic dispersion for 2h at 400W to obtain dispersion liquid, adding 5.0g of acrylic acid, 1.0g of urea and 0.12g of sodium dodecyl benzene sulfonate into the dispersion liquid, and stirring for 3 h; adding 2mL of 5 mass percent ammonium persulfate aqueous solution into the mixture, stirring to obtain a mixed solution, transferring the mixed solution into a large crucible, uniformly stirring, placing the large crucible into a small-sized movable muffle furnace, heating to 80 ℃ at a heating rate of 5 ℃/min under the air condition to perform polymerization reaction, and preserving heat for 3 hours to obtain a polymer/silicon composite material precursor;
3) and continuously introducing nitrogen into the S2 small-sized movable muffle furnace at the flow rate of 20mL/min, after 5min, heating the precursor of the polymer/silicon composite material obtained in the S2 large crucible to 800 ℃ at the heating rate of 2 ℃/min from 80 ℃, preserving the temperature for 2h, cooling to room temperature, performing ball milling, and sieving with a 200-mesh sieve to obtain the nitrogen-doped carbon/silicon nanocomposite material.
Example 3: a preparation method of a nitrogen-doped carbon/silicon nano composite material comprises the following steps:
1) ball-milling silicon powder (40-100 mu m) for 12 hours at a ball-to-material ratio of 40:1 under the condition of 500 rpm;
2) dispersing 0.5g of silicon powder subjected to ball milling in the step 1) into 80mL of deionized water, performing 400W ultrasonic dispersion for 2 hours to obtain dispersion liquid, adding 20.0g of acrylic acid, 5.0g of melamine and 0.15g of sodium dodecyl benzene sulfonate into the dispersion liquid, and stirring for 3 hours; adding 2mL of 5 mass percent ammonium persulfate aqueous solution into the mixture, stirring to obtain a mixed solution, transferring the mixed solution into a large crucible, uniformly stirring, placing the large crucible into a small-sized movable muffle furnace, heating to 80 ℃ at a heating rate of 5 ℃/min under the air condition to perform polymerization reaction, and preserving heat for 3 hours to obtain a polymer/silicon composite material precursor;
3) and continuously introducing nitrogen into the S2 small-sized movable muffle furnace at the flow rate of 20mL/min, after 5min, heating the precursor of the polymer/silicon composite material obtained in the S2 large crucible to 800 ℃ at the heating rate of 2 ℃/min from 80 ℃, preserving the temperature for 2h, cooling to room temperature, performing ball milling, and sieving with a 200-mesh sieve to obtain the nitrogen-doped carbon/silicon nanocomposite material.
Example 4: a preparation method of a nitrogen-doped carbon/silicon nano composite material comprises the following steps:
1) ball-milling silicon powder (40-100 mu m) for 12 hours at a ball-to-material ratio of 40:1 under the condition of 500 rpm;
2) dispersing 0.5g of silicon powder subjected to ball milling in the step 1) into 80mL of deionized water, performing 400W ultrasonic dispersion for 2 hours to obtain dispersion liquid, adding 3.0g of pyrrole, 3.0g of melamine and 0.12g of sodium dodecyl benzene sulfonate into the dispersion liquid, and stirring for 3 hours; adding 2mL of 5 mass percent ammonium persulfate aqueous solution into the mixture, stirring to obtain a mixed solution, transferring the mixed solution into a large crucible, uniformly stirring, placing the large crucible into a small-sized movable muffle furnace, heating to 80 ℃ at a heating rate of 5 ℃/min under the air condition to perform polymerization reaction, and preserving heat for 3 hours to obtain a polymer/silicon composite material precursor;
3) and continuously introducing nitrogen into the S2 small-sized movable muffle furnace at the flow rate of 20mL/min, after 5min, heating the precursor of the polymer/silicon composite material obtained in the S2 large crucible to 800 ℃ at the heating rate of 2 ℃/min from 80 ℃, preserving the temperature for 2h, cooling to room temperature, performing ball milling, and sieving with a 200-mesh sieve to obtain the nitrogen-doped carbon/silicon nanocomposite material.
Comparative example 1: a preparation method of a nitrogen-doped carbon/silicon nano composite material comprises the following steps:
1) ball-milling silicon powder (40-100 mu m) for 12 hours at a ball-to-material ratio of 40:1 under the condition of 500 rpm;
2) dispersing 0.5g of silicon powder subjected to ball milling in the step 1) into 80mL of deionized water, performing ultrasonic dispersion for 2 hours at 400W to obtain dispersion liquid, adding 4.5g of acrylic acid, 1.5g of melamine and 0.12g of sodium dodecyl benzene sulfonate into the dispersion liquid, and stirring for 3 hours; and then adding 2mL of 5 mass percent ammonium persulfate aqueous solution into the mixture, stirring to obtain a mixed solution, transferring the mixed solution into a large crucible, uniformly stirring, placing the large crucible into a small-sized movable muffle furnace, continuously introducing nitrogen into an S2 small-sized movable muffle furnace at the flow rate of 20mL/min, keeping the temperature for 2h after 5min until the atmosphere is in the muffle furnace, quickly heating the temperature to 800 ℃ from the room temperature at the heating rate of 5 ℃/min, cooling to the room temperature, performing ball milling, and sieving with a 200-mesh sieve to obtain the nitrogen-doped carbon/silicon nanocomposite.
Comparative example 1 the product obtained by one-step calcination, as shown in the SEM image of FIG. 3 (left image), has serious particle agglomeration, large particle size distribution, and non-uniform overall structure.
Comparative example 2: a preparation method of a nitrogen-doped carbon/silicon nano composite material comprises the following steps:
1) ball-milling silicon powder (40-100 mu m) for 12 hours at a ball-to-material ratio of 40:1 under the condition of 500 rpm;
2) taking 0.5g of silicon powder subjected to ball milling in the step 1), dispersing in 80mL of deionized water, performing 400W ultrasonic dispersion for 2h to obtain dispersion liquid, adding 9.0g of acrylic acid, 3.0g of melamine and 0.15g of sodium dodecyl benzene sulfonate into the dispersion liquid, transferring into a 250mL three-neck round-bottom flask, stirring for 3h to obtain a mixed solution, adding 2mL of 5 mass percent aqueous solution of ammonium persulfate into the three-neck round-bottom flask, placing the three-neck round-bottom flask into an electric heating jacket, stirring, heating to 80 ℃, performing polymerization reaction, and preserving heat for 30min to obtain a polymer/silicon composite material precursor;
3) and (3) drying the precursor of the polymer/silicon composite material obtained in the step 2) in a 100 ℃ oven for 1h, then ball-milling for 3h at a ball-to-material ratio of 40:1 under the condition of 500rpm, then sieving by a 200-mesh sieve, then heating to 800 ℃ from room temperature at a heating rate of 2 ℃/min in a muffle furnace under the protection of 20mL/min nitrogen, and preserving heat for 2h to obtain the nitrogen-doped carbon/silicon nanocomposite.
Comparative example 2 the product obtained by the conventional agitation polymerization calcination, as shown in the SEM picture of fig. 3 (right picture), has serious particle agglomeration, large particle size distribution, and non-uniform overall structure.
An electrode was formed using the nitrogen-doped carbon/silicon nanocomposite material obtained in example 1 in the following manner.
The preparation method comprises the steps of mixing conductive carbon black (super-P) serving as a conductive agent, polyacrylic acid (PAA) serving as a binder and an active material (the nitrogen-doped carbon/silicon nano composite material prepared in the embodiment 1) in a mass ratio of 20:20:60 by using water as a solvent, adding the mixture into the water to prepare slurry, coating the slurry on a copper foil, drying the copper foil at 80 ℃ under a vacuum condition, and cutting the copper foil into electrode plates for later use.
And then assembling the prepared electrode slices into the lithium ion half-cell in a glove box. Firstly, the positive electrode can, the electrode sheet, the separator,And the lithium sheet, the foamed nickel and the negative electrode shell are sequentially stacked, and are packaged after a proper amount of electrolyte is added. Wherein the battery case is CR2016 type, the diaphragm is Celgard2400, and the electrolyte is 1mol/L LiPF6/EC-DMC (1:1) (LiPF6Dissolving ethylene carbonate and dimethyl carbonate according to a volume ratio of 1:1) in the mixed solution).
The lithium ion half cell is set at 0.1 A.g-1The current density was cycled for 100 cycles to obtain a cycle performance chart, as shown in FIG. 5, from FIG. 5, it can be seen that the material was at 0.1A · g-1The electrochemical performance is stable under the current density of (1), and the specific capacity is still kept at 1000mAh g after the circulation for 100 weeks-1Coulombic efficiency was close to 100%, representing excellent electrochemical stability.
The same performance test as in example 1 was performed after the nitrogen-doped carbon/silicon nanocomposites prepared in examples 2-4 and comparative examples 1-2 were also prepared into electrodes and lithium-ion half cells according to the method for preparing electrodes and lithium-ion half cells from the nitrogen-doped carbon/silicon nanocomposite prepared in example 1, and the electrochemical performance of the lithium-ion half cells composed of the nitrogen-doped carbon/silicon nanocomposites prepared in examples 1-4 and comparative examples 1-2 is shown in the following table 1:
TABLE 1
Figure BDA0003085891680000081
As can be seen from table 1, the composite materials prepared in examples 1 to 4 through the integration of staged calcination have excellent electrochemical properties, high specific charge-discharge capacity, and coulombic efficiency close to 100%, and have great advantages compared with materials prepared by the conventional method.

Claims (10)

1. A preparation method of a nitrogen-doped carbon/silicon nano composite material is characterized by comprising the following steps:
s1, ball-milling the micron-sized silicon powder for 6-48h at the ball-material ratio of (8-80):1 under the condition of 100-800rpm for later use;
s2, dispersing the silicon powder subjected to the ball milling in the S1 volume percent into deionized water, ultrasonically dispersing for 1-3h at 300-500W to obtain dispersion liquid, then adding a carbon source, a nitrogen source and a dispersing agent into the dispersion liquid, and stirring; adding an initiator into the mixture, stirring the mixture to obtain a mixed solution, transferring the mixed solution into a crucible, uniformly stirring the mixed solution, directly putting the crucible into a muffle furnace, heating the crucible to 60-120 ℃ in an air atmosphere to perform a polymerization reaction, and preserving the temperature for 1-4 hours to obtain a polymer/silicon composite material precursor;
the mass ratio of the silicon powder to the carbon source to the nitrogen source is 1: (5-40): (2-10); the addition amount of the dispersing agent is 10-30% of the mass of the silicon powder;
and S3, continuously introducing nitrogen into the S2 muffle furnace, heating the polymer/silicon composite material precursor obtained in the S2 to 600-1000 ℃, carrying out high-temperature carbonization treatment, preserving the temperature for 1-3h, cooling to room temperature, carrying out ball milling, and sieving with a 100-400-mesh sieve to obtain the nitrogen-doped carbon/silicon nanocomposite material.
2. The preparation method according to claim 1, wherein the ball milling conditions of the silicon powder in the step S1 are as follows: the silicon powder is ball milled for 6-12h under the conditions of 400-600rpm and the ball material ratio of (20-50): 1.
3. The preparation method according to claim 2, wherein the ball milling conditions of the silicon powder in the step S1 are as follows: the silicon powder is ball milled for 12 hours at the ball-to-material ratio of 40:1 and the speed of 500 rpm.
4. The preparation method according to claim 1, characterized in that the particle size of the micron-sized silicon powder in the step S1 is 40-100 μm; in the step S2: the carbon source is acrylic acid, methacrylic acid, pyrrole or chitosan; the nitrogen source is melamine or urea; the dispersant is one or more of sodium dodecyl benzene sulfonate, sodium dodecyl sulfonate and sodium hexadecylbenzene sulfonate; the initiator is 3-5 wt% ammonium persulfate aqueous solution.
5. The method according to claim 4, wherein in the step S2: the carbon source is acrylic acid, the nitrogen source is melamine, the dispersing agent is sodium dodecyl benzene sulfonate, and the initiator is 5wt% ammonium persulfate aqueous solution.
6. The method according to claim 1, wherein in the step S2: the mass ratio of the silicon powder to the carbon source to the nitrogen source is 1: (8-10): (2-5).
7. The method according to claim 1, wherein in the step S2: the mass ratio of the silicon powder to the carbon source to the nitrogen source is 1: 9: 3.
8. the method according to claim 1, wherein in the step S2: heating to 60-80 ℃ at the heating rate of 5 ℃/min to perform polymerization reaction, and keeping the temperature for 1-4 h.
9. The method according to claim 8, wherein in step S2: the polymerization temperature is 80 ℃, and the holding time is 3 h.
10. The production method according to claim 1, wherein the high-temperature carbonization step in step S3 is: heating to 800 ℃ at the heating rate of 2 ℃/min, and keeping the temperature for 2 h;
the method according to claim 1, wherein in the step S3: after ball milling, sieving the mixture by a 200-mesh sieve;
the method according to claim 1, wherein in the step S2: silicon powder: the proportion of the deionized water is 0.5g (40-200) mL;
the method according to claim 11, wherein in step S2: silicon powder: the proportion of the deionized water is 0.5g (80-120) mL;
the use of the nitrogen-doped carbon/silicon nanocomposite material prepared by the preparation method according to any one of claims 1 to 13 as a negative electrode material of a lithium ion battery.
CN202110580277.6A 2021-03-15 2021-05-26 Preparation method and application of nitrogen-doped carbon/silicon nano composite material Pending CN113328058A (en)

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CN112110448A (en) * 2020-09-21 2020-12-22 中山大学 Nitrogen-doped carbon and nano-silicon composite anode material and preparation method thereof

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WO2013010346A1 (en) * 2011-07-15 2013-01-24 中国科学院广州能源研究所 Lithium-ion battery negative electrode-use silicon-carbon composite material and preparation method therefor
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