CN115377381A - Porous silicon-carbon composite electrode material for lithium ion battery and preparation method thereof - Google Patents

Porous silicon-carbon composite electrode material for lithium ion battery and preparation method thereof Download PDF

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CN115377381A
CN115377381A CN202211003754.3A CN202211003754A CN115377381A CN 115377381 A CN115377381 A CN 115377381A CN 202211003754 A CN202211003754 A CN 202211003754A CN 115377381 A CN115377381 A CN 115377381A
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silicon
electrode material
composite electrode
carbon
lithium ion
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王洁
高佳峰
王子奇
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Nanjing Forestry 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
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    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/362—Composites
    • 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
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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
    • 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
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    • 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
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    • 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
    • H01M4/587—Carbonaceous material, e.g. graphite-intercalation compounds or CFx for inserting or intercalating light metals
    • H—ELECTRICITY
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    • 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
    • H—ELECTRICITY
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    • 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
    • H01M4/628—Inhibitors, e.g. gassing inhibitors, corrosion inhibitors
    • 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 discloses a porous silicon-carbon composite electrode material for a lithium ion battery, which comprises the following components: silicon-carbon nano-particles and graphene, wherein nano-silicon wrapped by the inorganic carbon layer is uniformly dispersed in the graphene sheet layer. Meanwhile, the invention discloses a preparation method of the porous silicon-carbon composite electrode material for the lithium ion battery, which is characterized in that acid is utilized to simultaneously reduce the electronegativity of water-soluble silicic acid ions and the surface of a graphene oxide sheet layer, and the electrostatic repulsion force between the silicic acid ions and the graphene oxide sheet layer is weakened to form silicic acid and graphene oxide composite hydrogel, so that the silicic acid and the graphene oxide are uniformly compounded; introducing carbon source gas in the magnesiothermic reduction process of the silicon dioxide/graphene oxide compound to realize the reduction of the inorganic carbon layer coated nano silicon and graphene oxide, and finally obtaining the porous silicon-carbon composite electrode material with high compatibility of silicon and carbon interfaces and uniformly dispersed nano silicon particles; the preparation process is simple, high in controllability and suitable for industrial popularization.

Description

Porous silicon-carbon composite electrode material for lithium ion battery and preparation method thereof
Technical Field
The invention belongs to the technical field of preparation of battery cathode materials, and particularly relates to a porous silicon-carbon composite electrode material for a lithium ion battery and a preparation method thereof.
Background
The lithium ion battery has the advantages of high working voltage, high energy density, light weight, small volume, long service life and the like, and is widely applied to smart phones, notebook computers, electric automobiles and large-scale energy storage power stations. The current commercial graphite cathode material of the lithium ion battery has low theoretical capacity (372 mAh/g), and cannot meet the high energy density requirements of various electronic devices and new energy automobiles. Compared with commercial graphite negative electrodes, silicon has higher theoretical capacity (4200 mAh/g), abundant reserves and lower cost, and is considered to be one of the most potential candidate materials for replacing graphite in the next generation. However, the huge volume expansion (-400%) of silicon during the lithium ion intercalation and deintercalation process results in pulverization of electrodes and repeated formation of a Solid Electrolyte Interface (SEI) film, seriously affecting the cycle performance of the battery. In addition, silicon, as a semiconductor material, has very low electronic conductivity (6.7 × 10) - 2 S/m), which has prevented commercial application of silicon negative electrodes.
In order to solve the problems of the silicon electrode described above, introduction of carbon material as a buffer, an isolation and a conductive layer on the surface of silicon particles is considered to be one of the most effective methods. The carbon material has small volume expansion (less than 10 percent) and relatively stable structure, has higher conductivity, good flexibility and lubricity and can effectively relieve the volume expansion of silicon in the charging and discharging processes. The graphene serving as a carbon material has high electronic conductivity, large specific surface area and excellent structure flexibility, and can effectively buffer the volume change of silicon particles and keep a stable conductive network. In the existing silicon and graphene composite technology, the method mainly comprises the steps of directly and physically mixing graphene and nano-silicon, carrying out Chemical Vapor Deposition (CVD) on nano-silicon on a graphene substrate, and carrying out a carbothermic reduction reaction on a silicon source and the graphene. Cho et al, which utilizes an ultrasonic means to mix nano-silicon with graphene oxide, and performs thermal decomposition reduction on the graphene oxide at 700 ℃ after drying to obtain a silicon/graphene composite, has poor interface compatibility between silicon and graphene, and causes poor cycle stability due to agglomeration of nano-silicon, and has a capacity retention rate of only 48.9% (Journal of electrochemical Chemistry 2020, 876, 114475). Liu et al disperse silicic acid powder and graphene powder into an ethanol solution, stir and mix, and then prepare a silicon/graphene composite by microwave radiation carbothermic reduction, wherein when the silicon/graphene composite is applied to a lithium ion battery, the specific capacity is 806mAh/g at a low current density of 100mA/g, the rate capability is poor, and the silicon/graphene composite is derived from silicon and graphene which are not uniformly dispersed (Carbon 2022, 196, 633-638). Therefore, in the prior art, the obtained silicon and graphene composite material has the problems of poor interface compatibility between silicon and graphene and serious agglomeration of silicon particles, so that the rate capability and the cycle performance are poor.
Disclosure of Invention
In view of the above, one of the objectives of the present invention is to provide a porous silicon-carbon composite electrode material for a lithium ion battery, which has the characteristics of high interface compatibility between silicon and carbon, uniform dispersion of nano-silicon particles in a carbon material, and the like, so as to obtain a high rate performance and high cycle stability. The second purpose of the invention is to provide a preparation method of the porous silicon-carbon composite electrode material for the lithium ion battery, which has the advantages of simple preparation process, high controllability and large-scale production capacity.
In order to achieve the purpose, the technical scheme of the invention is as follows:
a porous silicon-carbon composite electrode material for a lithium ion battery, comprising: silicon-carbon nano-particles and graphene, and nano-silicon wrapped by the inorganic carbon layer is uniformly dispersed in the graphene sheet layer.
The preparation method of the porous silicon-carbon composite electrode material for the lithium ion battery specifically comprises the following steps:
(1) Uniformly stirring and mixing a water-soluble silicate aqueous solution and a graphene oxide aqueous solution, then adding acid to react to obtain silicic acid/graphene oxide composite hydrogel, freeze-drying to obtain composite aerogel, washing the composite aerogel with a detergent, removing impurities, and drying to obtain a silicon dioxide/graphene oxide composite;
(2) Uniformly mixing the silicon dioxide/graphene oxide compound, magnesium oxide and magnesium powder, then placing the mixture in a tubular furnace, carrying out first-stage heating in an inert atmosphere, then introducing a carbon source gas under the load of inert gas, and carrying out second-stage heating to finally obtain a product 1;
(3) And (3) pickling and drying the product 1 to obtain the porous silicon-carbon composite electrode material.
Preferably, the water-soluble silicate in step (1) comprises one or more of sodium silicate, lithium silicate, potassium silicate and ammonium silicate.
Preferably, in the step (1), the mass fraction of the aqueous solution of silicate is 20-80 wt%, and the concentration of the aqueous solution of graphene oxide is 1-30 mg/mL.
Preferably, the volume ratio of the silicate solution to the graphene oxide aqueous solution in the step (1) is 1: 0.5-20.
Preferably, the stirring speed in the step (1) is 100-800 rpm, and the stirring time is more than or equal to 1h.
Preferably, the acid in the step (1) comprises one or more of sulfuric acid, hydrochloric acid and nitric acid, the concentration of the acid solution is 12-19 mol/mL, the volume of the acid is 1-10 mL, and the reaction time is more than or equal to 1h.
Preferably, the mass ratio of the silicon dioxide/graphene oxide compound to the magnesium oxide to the magnesium powder in the step (2) is 1: 0.5-10.
Preferably, the heating rate in the step (2) is 1-10 ℃/min, the heating temperature in the first stage is 500-1000 ℃, and the heating temperature in the second stage is 500-1000 ℃.
Preferably, the carbon source gas in step (2) includes CO 2 、CH 4 、C 2 H 2 And C 2 H 4 The inert gas is argon; the flow rate of the inert gas is 5-200 sccm, and the flow rate of the carbon source gas is 5-150 sccm.
Preferably, the concentration of the hydrochloric acid aqueous solution in the step (3) is 0.01-2.0 mol/L, the drying temperature is 60-150 ℃, and the drying time is more than 1h.
The invention also relates to a lithium ion battery with the electrode material of the porous silicon-carbon composite electrode material.
According to the technical scheme, compared with the prior art, the porous silicon-carbon composite electrode material for the lithium ion battery and the preparation method thereof provided by the invention have the following excellent effects:
(1) The invention provides a porous silicon-carbon composite electrode material for a lithium ion battery, wherein nano silicon wrapped by an inorganic carbon layer is uniformly dispersed in a graphene sheet layer, and a formed porous hierarchical structure is beneficial to full contact of electrolyte and the electrode material and complete permeation of the electrolyte; the silicon-carbon particles and the graphene interface have high compatibility, the inorganic carbon coating layer and the graphene sheet cooperate to reduce the volume expansion of silicon and prevent the agglomeration of nano silicon particles, the conductivity of the electrode material is improved, the advantages of ultrahigh capacity of silicon and stable circulation of carbon are fully utilized, and the high gram capacity, high rate performance and excellent circulation performance of the silicon-carbon composite electrode material are ensured;
(2) According to the preparation method of the porous silicon-carbon composite electrode material, the electronegativity of water-soluble silicic acid ions and the surface of the graphene oxide sheet layer is reduced by using acid at the same time, and the mutual electrostatic repulsion force is weakened, so that the silicic acid and graphene oxide composite hydrogel is formed, and uniform compounding of the silicic acid and the graphene oxide is realized. The interior of the composite hydrogel is connected through hydrogen bonds formed by silicic acid and hydroxyl functional groups of graphene oxide, so that the structural stability of the material is ensured;
(3) According to the preparation method of the porous silicon-carbon composite electrode material, carbon source gas is introduced in the magnesiothermic reduction process of the silicon dioxide/graphene oxide composite so as to realize reduction of the inorganic carbon layer coated with nano silicon and graphene oxide, and the porous silicon-carbon composite electrode material with high compatibility of silicon and carbon interfaces and uniformly dispersed nano silicon particles is prepared; the raw materials of the preparation method belong to cheap materials commonly applied in industry, and the preparation process is safe and controllable.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, it is obvious that the drawings in the following description are only embodiments of the present invention, and for those skilled in the art, other drawings can be obtained according to the provided drawings without creative efforts.
FIG. 1 is an X-ray diffraction pattern of a silicon-carbon composite electrode material obtained in example 1.
FIG. 2 is an X-ray diffraction pattern of the silicon-carbon composite electrode material obtained in example 2.
FIG. 3 is an X-ray diffraction pattern of the silicon-carbon composite electrode material obtained in example 3.
FIG. 4 is an X-ray diffraction pattern of the silicon-carbon composite electrode material obtained in example 4.
FIG. 5 is an X-ray diffraction pattern of the silicon-carbon composite electrode material obtained in comparative example 1.
FIG. 6 is a scanning electron micrograph of a silicon-carbon composite electrode material obtained in example 1.
FIG. 7 is a scanning electron micrograph of a silicon carbon composite electrode material obtained in example 2.
FIG. 8 is a scanning electron micrograph of a silicon carbon composite electrode material obtained in example 3.
FIG. 9 is a scanning electron micrograph of a silicon carbon composite electrode material obtained in example 4.
FIG. 10 is a scanning electron micrograph of the Si-C composite electrode material obtained in comparative example 1.
Detailed Description
The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
The embodiment of the invention discloses a preparation method of a porous silicon-carbon composite electrode material of a lithium ion battery, which comprises the following specific steps:
(1) Uniformly stirring and mixing a water-soluble silicate aqueous solution with the mass fraction of 20-80 wt% and a graphene oxide aqueous solution with the concentration of 1-30 mg/mL according to the volume ratio of 1: 0.5-20, wherein the stirring speed is 100-800 rpm, the stirring time is more than or equal to 1h, then adding an acid solution with the volume of 1-10 mL and the concentration of 12-19 mol/mL for reaction, the reaction time is more than or equal to 1h, obtaining silicic acid/graphene oxide composite hydrogel, performing freeze drying to obtain composite aerogel, washing the composite aerogel by using a detergent, removing impurities, and then drying at the temperature of 60-150 ℃ for more than 1h to obtain a silicon dioxide/graphene oxide composite;
(2) Uniformly mixing the silicon dioxide/graphene oxide compound, magnesium oxide and magnesium powder according to the mass ratio of 1: 0.5-10, then placing the mixture in a tubular furnace, heating at the rate of 1-10 ℃/min, carrying out first-stage heating under the inert gas argon at the temperature of 500-1000 ℃, then introducing a carbon source gas under the load of the inert gas, wherein the flow rate of the inert gas is 5-200 sccm, the flow rate of the carbon source gas is 5-150 sccm, carrying out second-stage heating at the temperature of 500-1000 ℃, and finally obtaining a product 1;
(3) And (3) cleaning the product 1 by using a hydrochloric acid aqueous solution with the concentration of 0.01-2.0 mol/L, and then drying at the temperature of 60-150 ℃ for more than 1h to obtain the porous silicon-carbon composite electrode material.
In order to further optimize the technical scheme, the water-soluble silicate in the step (1) comprises one or more of sodium silicate, lithium silicate, potassium silicate and ammonium silicate; the acid comprises one or more of sulfuric acid, hydrochloric acid and nitric acid; the detergent comprises water or ethanol;
in order to further optimize the technical scheme, the carbon source gas in the step (2) comprises CO 2 、CH 4 、C 2 H 2 And C 2 H 4 One or more of;
the technical solution of the present invention will be further described with reference to the following specific examples.
Example 1
The embodiment comprises the following specific steps:
(1) Stirring and mixing 20mL of water-soluble sodium silicate solution with the mass fraction of 42wt% and 10mL of graphene oxide aqueous solution with the concentration of 4mg/mL, placing the mixture in a reaction container with the rotating speed of 800rpm, adding 5mL of sulfuric acid with the concentration of 18.4mol/mL, stirring and reacting to obtain silicic acid/graphene oxide composite hydrogel, freeze-drying to obtain composite aerogel, washing the aerogel with deionized water and ethanol, removing impurities, and drying in an oven at 80 ℃ for 14 hours to obtain a silicon dioxide/graphene oxide composite with the carbon content of 3 wt%;
(2) Uniformly mixing the silicon dioxide/graphene oxide compound, magnesium oxide and magnesium powder according to the mass ratio of 1: 2: 1.3, then placing the mixture into a tubular furnace, introducing argon gas at the flow rate of 40sccm, starting to heat to 750 ℃ at the heating rate of 5 ℃/min after 0.5h, keeping the temperature for 4h at a constant temperature, and then introducing CO at the flow rate of 30sccm 2 Keeping the temperature at 750 ℃ for 4h to obtain a product 1;
(3) And washing the product 1 with an excessive 1.0mol/L HCl aqueous solution for 12h, then washing the product to be neutral by deionized water, and drying the product in an oven at 80 ℃ for 14h to obtain the porous silicon-carbon composite electrode material with the carbon content of 6 wt%.
Example 2
The embodiment comprises the following specific steps:
(1) Stirring and mixing 20mL of water-soluble lithium silicate solution with the mass fraction of 42wt% and 20mL of graphene oxide aqueous solution with the concentration of 4mg/mL, placing the mixture in a reaction container with the rotation speed of 700rpm, adding 7mL of nitric acid with the concentration of 15.3mol/mL, stirring and reacting to obtain silicic acid/graphene oxide composite hydrogel, freezing and drying to obtain composite aerogel, washing the aerogel with deionized water and ethanol, removing impurities, and drying in an oven at 100 ℃ for 12 hours to obtain a silicon dioxide/graphene oxide composite with the carbon content of 4 wt%;
(2) Uniformly mixing the silicon dioxide/graphene oxide compound, magnesium oxide and magnesium powder according to the mass ratio of 1: 2: 1.3, then placing the mixture into a tubular furnace, introducing argon gas with the flow of 60sccm, starting to heat to 850 ℃ at the heating rate of 5 ℃/min after 0.5h, keeping the temperature for 4h, and then introducing CH with the flow of 50sccm 4 Continuously keeping the constant temperature at 850 ℃ for 4h to obtain a product 2;
(3) And washing the product 2 with an excessive 1.5mol/L HCl aqueous solution for 12h, then washing the product to be neutral by deionized water, and drying the product in an oven at 100 ℃ for 12h to obtain the porous silicon-carbon composite electrode material with the carbon content of 8 wt%.
Example 3
The embodiment comprises the following specific steps:
(1) Stirring and mixing 20mL of water-soluble potassium silicate solution with the mass fraction of 42wt% and 40mL of graphene oxide aqueous solution with the concentration of 4mg/mL, placing the mixture in a reaction container with the rotation speed of 500rpm, adding 10mL of hydrochloric acid with the concentration of 12mol/mL, stirring and reacting to obtain silicic acid/graphene oxide composite hydrogel, freezing and drying to obtain composite aerogel, washing the aerogel with deionized water and ethanol, removing impurities, and drying in an oven at 120 ℃ for 10 hours to obtain a silicon dioxide/graphene oxide composite with the carbon content of 6 wt%;
(2) Uniformly mixing the silicon dioxide/graphene oxide compound, magnesium oxide and magnesium powder according to the mass ratio of 1: 2: 1.3, then placing the mixture into a tubular furnace, introducing argon gas at the flow rate of 80sccm, starting to heat to 950 ℃ at the heating rate of 5 ℃/min after 0.5h, keeping the temperature for 4h at a constant temperature, and then introducing C at the flow rate of 60sccm 2 H 2 Continuously keeping the constant temperature at 950 ℃ for 4 hours to obtain a product 3;
(3) And washing the product 3 with an excessive 2mol/L HCl aqueous solution for 12h, then washing the product to be neutral by deionized water, and drying the product in an oven at 120 ℃ for 10h to obtain the porous silicon-carbon composite electrode material with the carbon content of 9 wt%.
Example 4
The embodiment comprises the following specific steps:
(1) Stirring and mixing 20mL of water-soluble ammonium silicate solution with the mass fraction of 42wt% and 80mL of graphene oxide aqueous solution with the concentration of 4mg/mL, placing the mixture in a reaction container with the rotation speed of 400rpm, adding 10mL of sulfuric acid with the concentration of 18.4mol/mL, stirring and reacting to obtain silicic acid/graphene oxide composite hydrogel, freeze-drying to obtain composite aerogel, washing the aerogel with deionized water and ethanol, removing impurities, and drying in an oven at 140 ℃ for 8 hours to obtain a silicon dioxide/graphene oxide composite with the carbon content of 9 wt%;
(2) Mixing the above silicon dioxide/graphene oxide compositeMagnesium oxide and magnesium powder are uniformly mixed according to the mass ratio of 1: 2: 1.3, then the mixture is placed in a tubular furnace, argon is introduced at the flow rate of 50sccm, the temperature is raised to 1000 ℃ at the heating rate of 5 ℃/min after half an hour, the temperature is kept for 4 hours at constant temperature, and then C is introduced at the flow rate of 50sccm 2 H 4 Keeping the temperature at 1000 ℃ for 4 hours to obtain a product 4;
(3) And washing the product 4 with an excessive 0.5mol/L HCl aqueous solution for 12h, then washing the product to be neutral by deionized water, and drying the product in an oven at 140 ℃ for 8h to obtain the porous silicon-carbon composite electrode material with the carbon content of 11 wt%.
Comparative example 1
The comparative example comprises the following specific steps:
(1) Placing 20mL of water-soluble sodium silicate solution with the mass fraction of 42wt% in a reaction container with the rotating speed of 800rpm, adding 5mL of sulfuric acid with the concentration of 18.4mol/mL, stirring, reacting to obtain silicic acid hydrogel, freeze-drying to obtain aerogel, washing the aerogel with deionized water and ethanol, removing impurities, and drying in an oven at 120 ℃ for 10 hours to obtain silicon dioxide;
(2) Weighing and uniformly mixing the silicon dioxide, the magnesium oxide and the magnesium powder according to the mass ratio of 1: 2: 1.3, then placing the mixture into a tube furnace, introducing argon gas with the flow of 70sccm, starting to heat up to 750 ℃ at the heating rate of 5 ℃/min after half an hour, keeping the temperature for 4 hours at constant temperature, and then introducing CO with the flow of 60sccm 2 Continuously keeping the constant temperature at 750 ℃ for 4 hours to obtain a product 5;
(3) And washing the product 5 with an excessive 1.0mol/L HCl aqueous solution for 12h, then washing the product to be neutral by deionized water, and drying the product in an oven at 120 ℃ for 10h to obtain the porous silicon-carbon composite electrode material with the carbon content of 2 wt%.
The embodiments in the present description are described in a progressive manner, each embodiment focuses on differences from other embodiments, and the same and similar parts among the embodiments are referred to each other.
(1) X-ray diffraction (XRD) test:
using an X-ray powder diffractometer model Rigaku-D/max-2550pc from Hitachi, japanTest using Cu-Ka as radiation source at a wavelength of
Figure BSA0000281940960000101
A Ni filter plate is adopted, the pipe flow is 40mA, the pipe pressure is 40KV, the scanning range is 10-90 degrees, the scanning speed is 10 degrees/min, and the step length is 0.08 degrees. Placing the material into a glass slide, flattening, embedding the glass slide into the center of an instrument experiment groove, and testing; phase identification and crystal structure information were analyzed by the JADE5.0 software, with specific test results as follows:
fig. 1 is an X-ray diffraction pattern of the porous silicon-carbon composite electrode material for a lithium ion battery prepared in example 1, wherein the ordinate is intensity of ray diffraction, the abscissa is an X-ray scanning angle, distinct silicon characteristic peaks appear at 2 θ of 28.36 °, 47.22 °, 56.04 °, 69.04 °, 76.30 ° and 87.94 °, which correspond to silicon crystal planes (111), (220), (311), (400), (331) and (422), respectively, and the X-ray diffraction pattern is consistent with standard card PDF # 27-1402.
Fig. 2 is an X-ray diffraction pattern of the porous silicon-carbon composite electrode material for lithium ion batteries prepared in example 2, wherein the ordinate is the intensity of X-ray diffraction, the abscissa is the X-ray scanning angle, distinct silicon characteristic peaks appear at 28.28 °, 47.14 °, 55.98 °, 68.98 °, 76.22 ° and 87.88 of 2 θ, which correspond to the silicon crystal faces (111), (220), (311), (400), (331) and (422), respectively, and the X-ray diffraction pattern is consistent with standard card PDF # 27-1402.
Fig. 3 is an X-ray diffraction pattern of the porous silicon-carbon composite electrode material for lithium ion batteries prepared in example 3, wherein the ordinate is the intensity of X-ray diffraction, the abscissa is the X-ray scanning angle, distinct silicon characteristic peaks appear at 28.30 °, 47.18 °, 56.00 °, 68.96 °, 76.26 ° and 87.92 ° of 2 θ, which correspond to the silicon crystal faces (111), (220), (311), (400), (331) and (422), respectively, and the X-ray diffraction pattern is consistent with standard card PDF # 27-1402.
Fig. 4 is an X-ray diffraction pattern of the porous silicon-carbon composite electrode material for a lithium ion battery prepared in example 4, wherein the ordinate is the intensity of the X-ray diffraction, the abscissa is the X-ray scanning angle, and distinct silicon characteristic peaks appear at 28.28 °, 47.20 °, 56.04 °, 69.08 °, 76.30 ° and 87.98 ° of 2 θ, which correspond to the silicon crystal faces (111), (220), (311), (400), (331) and (422), respectively, and the X-ray diffraction pattern is consistent with standard card PDF # 27-1402.
Fig. 5 is an X-ray diffraction pattern of the porous silicon-carbon composite electrode material for lithium ion batteries prepared in comparative example 1, wherein the ordinate is the intensity of the X-ray diffraction, the abscissa is the X-ray scanning angle, and distinct silicon characteristic peaks appear at 2 θ of 28.28 °, 47.14 °, 56.04 °, 68.98 °, 76.22 ° and 87.88 °, which correspond to the silicon crystal faces (111), (220), (311), (400), (331) and (422), respectively, and the X-ray diffraction pattern is consistent with standard card PDF # 27-1402.
(2) Scanning electron microscopy characterization:
the morphology of the lithium ion battery electrode materials prepared in each of examples 1 to 4 and comparative example 1 was respectively observed using a JSM-7600F scanning electron microscope tester manufactured by HITACHI corporation at an acceleration voltage of 3KV, and the specific test results were analyzed as follows:
fig. 6 is a scanning electron microscope image of the porous silicon-carbon composite electrode material for the lithium ion battery prepared in example 1, and it is apparent that a plurality of sheets of graphene load silicon particles and present a porous structure.
Fig. 7 is a scanning electron microscope image of the porous silicon-carbon composite electrode material for the lithium ion battery prepared in example 2, and it is apparent that a plurality of sheets of graphene load silicon particles and present a porous structure.
Fig. 8 is a scanning electron microscope image of the porous silicon-carbon composite electrode material for the lithium ion battery prepared in example 3, and it is apparent that a plurality of sheets of graphene load silicon particles and present a porous structure.
Fig. 9 is a scanning electron microscope image of the porous silicon-carbon composite electrode material for the lithium ion battery prepared in example 4, and it is apparent that a plurality of sheets of graphene load silicon particles and present a porous structure.
Fig. 10 is a scanning electron microscope image of the porous silicon-carbon composite electrode material for the lithium ion battery prepared in comparative example 1, and it can be obviously seen that the composite material has a porous structure.
(3) The silicon-carbon negative electrode materials prepared in examples 1 to 4 and comparative example 1 were used as a positive electrode, a metal lithium plate was used as a negative electrode, and 1.0mol/L LiPF was used 6 EC (ethylene carbonate) + DMC (dimethyl carbonate) + FEC (fluoroethylene carbonate) (EC, DMC and FEC volume ratio 4.5: 1) as electrolyte, assembled into CR2032 coin cells in argon glove boxes respectively.
The button cell is tested by a blue battery tester produced by Jinnuo electronics, inc. in Wuhan, the test conditions and results are as follows:
the button cell is sequentially subjected to constant-current charge and discharge tests at current densities of 100, 200, 500, 1000, 2000, 3000 and 100mA/g, and the voltage interval is 0-1.5V. The button half cells of the silicon-carbon composite electrode materials obtained in the embodiments 1 to 4 all have initial discharge capacities higher than 1600mAh/g, and the initial coulomb efficiencies are all higher than 75%, while the button half cells of the silicon-carbon composite electrode materials obtained in the comparative example 1 have lower initial discharge capacities, only 1366.9mAh/g, and 71.2% of initial coulomb efficiency, and the specific values are detailed in table 1 (the initial discharge capacities and the initial coulomb efficiencies of the silicon-carbon composite electrode materials obtained in the embodiments 1 to 4 and the comparative example 1). The button half-cell of the silicon-carbon composite electrode material obtained in the embodiment 1-4 has better capacity retention rate under different current densities, and shows good multiplying power cycle performance; and the silicon-carbon composite electrode material obtained in the comparative example 1 has poorer rate cycle performance of the button half cell and low discharge capacity, and specific numerical values are detailed in a table 2 (the rate cycle capacity of the button half cell of the silicon-carbon composite electrode material obtained in the embodiment examples 1 to 4 and the comparative example 1).
TABLE 1
Figure BSA0000281940960000141
TABLE 2
Figure BSA0000281940960000142
The inventive content is not limited to the content of the above-mentioned embodiments, wherein combinations of one or several of the embodiments may also achieve the object of the invention.
In the present specification, the embodiments are described in a progressive manner, each embodiment focuses on differences from other embodiments, and the same and similar parts among the embodiments are referred to each other. The method disclosed by the embodiment corresponds to the method disclosed by the embodiment, so that the description is simple, and the relevant points can be referred to the description of the method part.
The previous description of the disclosed embodiments is provided to enable any person skilled in the art to make or use the present invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other embodiments without departing from the spirit or scope of the invention. Thus, the present invention is not intended to be limited to the embodiments shown herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims (10)

1. A porous silicon-carbon composite electrode material for a lithium ion battery is characterized by comprising: silicon carbon nanoparticles and graphene; the nano silicon wrapped by the inorganic carbon layer is uniformly dispersed in the graphene sheet layer.
2. The preparation method of the porous silicon-carbon composite electrode material for the lithium ion battery according to claim 1, which is characterized by comprising the following steps:
(1) Uniformly stirring and mixing a water-soluble silicate aqueous solution and a graphene oxide aqueous solution, adding acid for reaction to obtain silicic acid/graphene oxide composite hydrogel, freeze-drying to obtain composite aerogel, washing the composite aerogel by using a detergent, removing impurities, and drying to obtain a silicon dioxide/graphene oxide composite;
(2) Uniformly mixing the silicon dioxide/graphene oxide compound, magnesium oxide and magnesium powder, then placing the mixture in a tubular furnace, carrying out first-stage heating in an inert atmosphere, then introducing a carbon source gas under the load of inert gas, and carrying out second-stage heating to finally obtain a product 1;
(3) And (3) pickling and drying the product 1 to obtain the porous silicon-carbon composite electrode material.
3. The method for preparing the porous silicon-carbon composite electrode material for the lithium ion battery according to claim 2, wherein the water-soluble silicate in the step (1) comprises one or more of sodium silicate, lithium silicate, potassium silicate and ammonium silicate; the mass fraction of the silicate solution is 20-80 wt%, the concentration of the graphene oxide solution is 1-30 mg/mL, and the volume ratio of the silicate solution to the graphene oxide solution is 1: 0.5-20.
4. The preparation method of the porous silicon-carbon composite electrode material for the lithium ion battery according to claim 2, wherein the stirring speed in the step (1) is 100-800 rpm, and the stirring time is more than or equal to 1h; the acid comprises one or more of sulfuric acid, hydrochloric acid and nitric acid, the concentration of the acid solution is 12-19 mol/mL, the volume of the acid is 1-10 mL, and the reaction time is more than or equal to 1h.
5. The method for preparing the porous silicon-carbon composite electrode material for the lithium ion battery according to claim 2, wherein the detergent in the step (1) comprises water or ethanol; the drying temperature is 60-150 ℃, and the drying time is more than 1h.
6. The method for preparing the porous silicon-carbon composite electrode material for the lithium ion battery according to claim 2, wherein the mass ratio of the silicon dioxide/graphene oxide composite, the magnesium oxide and the magnesium powder in the step (2) is 1: 0.5-10.
7. The preparation method of the porous silicon-carbon composite electrode material for the lithium ion battery according to claim 2, wherein the temperature rise rate in the step (2) is 1-10 ℃/min, the first-stage heating temperature is 500-1000 ℃, and the second-stage heating temperature is 500-1000 ℃.
8. The method for preparing the porous Si-C composite electrode material for lithium ion batteries according to claim 2, wherein the carbon source gas in the step (2) comprises CO 2 、CH 4 、C 2 H 2 And C 2 H 4 The inert gas is argon; the flow rate of the inert gas is 5-200 sccm, and the flow rate of the carbon source gas is 5-150 sccm.
9. The preparation method of the porous silicon-carbon composite electrode material for the lithium ion battery according to claim 2, wherein the concentration of the hydrochloric acid aqueous solution in the step (3) is 0.01-2.0 mol/L, the drying temperature is 60-150 ℃, and the drying time is more than 1h.
10. A lithium ion battery comprising the porous silicon-carbon composite electrode material for a lithium ion battery according to any one of claims 1 to 9.
CN202211003754.3A 2022-08-22 2022-08-22 Porous silicon-carbon composite electrode material for lithium ion battery and preparation method thereof Pending CN115377381A (en)

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