CN111952559B - Silicon-carbon microsphere composite material self-assembled by two-dimensional silicon nanosheets, preparation method and application thereof in lithium ion battery cathode material - Google Patents
Silicon-carbon microsphere composite material self-assembled by two-dimensional silicon nanosheets, preparation method and application thereof in lithium ion battery cathode material Download PDFInfo
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- XUIMIQQOPSSXEZ-UHFFFAOYSA-N Silicon Chemical compound [Si] XUIMIQQOPSSXEZ-UHFFFAOYSA-N 0.000 title claims abstract description 100
- 229910052710 silicon Inorganic materials 0.000 title claims abstract description 100
- 239000010703 silicon Substances 0.000 title claims abstract description 100
- 239000004005 microsphere Substances 0.000 title claims abstract description 81
- 239000002131 composite material Substances 0.000 title claims abstract description 50
- 239000002135 nanosheet Substances 0.000 title claims abstract description 49
- HMDDXIMCDZRSNE-UHFFFAOYSA-N [C].[Si] Chemical compound [C].[Si] HMDDXIMCDZRSNE-UHFFFAOYSA-N 0.000 title claims abstract description 41
- HBBGRARXTFLTSG-UHFFFAOYSA-N Lithium ion Chemical compound [Li+] HBBGRARXTFLTSG-UHFFFAOYSA-N 0.000 title claims abstract description 25
- 229910001416 lithium ion Inorganic materials 0.000 title claims abstract description 25
- 238000002360 preparation method Methods 0.000 title claims abstract description 20
- 239000010406 cathode material Substances 0.000 title abstract description 12
- 239000000843 powder Substances 0.000 claims abstract description 49
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 claims abstract description 35
- 229910052799 carbon Inorganic materials 0.000 claims abstract description 34
- 229910021471 metal-silicon alloy Inorganic materials 0.000 claims abstract description 31
- 238000000034 method Methods 0.000 claims abstract description 21
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- LZZYPRNAOMGNLH-UHFFFAOYSA-M Cetrimonium bromide Chemical compound [Br-].CCCCCCCCCCCCCCCC[N+](C)(C)C LZZYPRNAOMGNLH-UHFFFAOYSA-M 0.000 claims description 7
- GVGUFUZHNYFZLC-UHFFFAOYSA-N dodecyl benzenesulfonate;sodium Chemical compound [Na].CCCCCCCCCCCCOS(=O)(=O)C1=CC=CC=C1 GVGUFUZHNYFZLC-UHFFFAOYSA-N 0.000 claims description 7
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- CSDREXVUYHZDNP-UHFFFAOYSA-N alumanylidynesilicon Chemical compound [Al].[Si] CSDREXVUYHZDNP-UHFFFAOYSA-N 0.000 claims description 6
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- XJWSAJYUBXQQDR-UHFFFAOYSA-M dodecyltrimethylammonium bromide Chemical compound [Br-].CCCCCCCCCCCC[N+](C)(C)C XJWSAJYUBXQQDR-UHFFFAOYSA-M 0.000 claims description 2
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- 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
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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
- 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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- 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
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Abstract
The invention discloses a silicon-carbon microsphere composite material self-assembled by two-dimensional silicon nanosheets, a preparation method and application thereof in a lithium ion battery cathode material, and belongs to the technical field of lithium ion batteries. The method comprises the following steps: corroding the silicon-metal alloy powder with acid, adding a carbon-containing compound to complete surface coating, and calcining to obtain the composite material. The two-dimensional silicon nanosheet is a core part of the composite material, and the key is that the surface of an eutectic silicon matrix frame is modified by a surfactant, a carbon-containing compound is coated on the surface of the eutectic silicon matrix frame, and after calcination, a surface organic matter is pyrolyzed into carbon to form a uniform coating layer, so that microspheres assembled by the carbon-coated two-dimensional silicon nanosheets are obtained. The carbon coating layer mainly plays a role in conducting electricity and inhibiting volume expansion of silicon, and the silicon serves as an electrochemical active material for storing energy. The composite material can be used as a lithium ion battery cathode material in the high-power field of new energy electric automobiles and the like, and has high specific capacity, good long-period cycle performance and excellent rate capability.
Description
Technical Field
The invention relates to the technical field of lithium ion batteries, in particular to a silicon-carbon microsphere composite material self-assembled by two-dimensional silicon nanosheets, a preparation method and application thereof in a lithium ion battery cathode material.
Background
With the shortage of global petroleum resources and the continuous deterioration of climate environment, the development of clean and energy-saving new energy automobiles is highly emphasized by all countries in the world, and a power supply is the key for the development of the new energy automobiles. At present, the commercial lithium ion battery mainly adopts graphite cathode materials, but has certain defects, and the theoretical capacity of the lithium ion battery is only 372mAh g -1 And the requirement of high energy density of the lithium ion battery in the future cannot be met, so that the development of a novel lithium ion battery cathode material becomes the key point of the current research. The silicon-based negative electrode material has high theoretical specific capacity (4200 mAh g) -1 ) And lower delithiation potential (<0.5V), environment-friendly and low in cost, and is favored by scientific research personnel.
However, the silicon-based negative electrode material also meets some challenges in the industrial process, and the volume expansion effect of silicon reaches up to 300% in the charging and discharging processes, so that the problems of structural collapse, pulverization and the like are caused, and the application of silicon as the negative electrode material of the lithium battery is severely restricted. Therefore, it is critical to study the problems of suppressing the volume expansion effect in the silicon reaction and improving the silicon conductivity. The method for combining silicon and carbon to form the silicon-carbon composite material is a commonly adopted method in the research of silicon cathode materials at present. The silicon-carbon negative electrode material has small volume change in the charge-discharge process and better circulation stability, and the carbonaceous negative electrode material is a mixed conductor of ions and electrons. In addition, silicon has similar chemical properties to carbon, which can be tightly bound, and thus carbon is often used as the substrate of choice for compounding with silicon. In a silicon-carbon composite system, silicon particles are used as active substances to provide lithium storage capacity; the carbon can buffer the volume change of the silicon cathode in the charging and discharging process, improve the conductivity of the siliceous material and avoid the agglomeration of silicon particles in the charging and discharging cycle.
For example, chinese patent application with publication number CN 105226285A discloses a porous silicon-carbon composite material and a preparation method thereof, wherein the preparation process comprises: firstly, providing a silicon-active metal alloy, reacting with a pore-forming agent through a liquid phase method to remove the active metal, then cleaning the porous silicon nano material with hydrofluoric acid solution to remove silicon oxide, then performing ball milling, coating a polymer, and carbonizing to finally obtain the porous silicon-carbon composite material. Although the expansion rate of the material is reduced and the specific capacity is improved, the preparation process is complex by adopting the method, the hydrofluoric acid has strong corrosivity to equipment and is easy to cause safety hidden danger, and the first efficiency of the prepared material is low, so that the application and popularization of the material in the field of lithium ion batteries are influenced.
Disclosure of Invention
In order to overcome the defects in the prior art, the invention aims to provide a silicon-carbon microsphere composite material self-assembled by two-dimensional silicon nanosheets, a preparation method and application thereof in a lithium ion battery cathode material.
The invention provides a method for solving the problem of serious volume expansion of a silicon-based material in the application of a lithium ion battery, and a high-performance silicon-carbon composite material with a microsphere structure is synthesized.
The invention also aims to provide a preparation method of the silicon-carbon composite material, which has the advantages of simple process, low cost, high safety and environmental friendliness.
The invention further aims to provide a high-performance silicon-carbon composite material with a unique microsphere structure assembled by two-dimensional silicon nanosheets, and application of the high-performance silicon-carbon composite material to the negative electrode of a lithium ion battery and commercial application of the high-performance silicon-carbon composite material.
The silicon-carbon microsphere composite material self-assembled by the two-dimensional silicon nanosheets is formed by assembling carbon-coated silicon-carbon microspheres and the two-dimensional silicon nanosheets. The carbon coating layer can effectively relieve the volume change of silicon particles in the lithiation and delithiation processes, increase the conductivity of the material and improve the electrochemical performance stability of the material. The microsphere assembled by the two-dimensional silicon nanosheets has a stable structure and can exert the advantage of capacity.
The invention fully combines the advantages of silicon materials and carbon materials, starts from the space structure, firstly synthesizes the microspheres assembled by unique silicon frames, and introduces the carbon coating layer on the basis of the silicon frame microspheres. The silicon frame can support the whole microsphere structure, so that the stability of the composite material structure is ensured, the capacity is improved, the cycle life is prolonged, and the development prospect is good.
The invention successfully synthesizes a unique microsphere structure composite material assembled by two-dimensional silicon nanosheets by adopting a low-price silicon-metal alloy raw material and combining a simple coating strategy. When the material is applied to a lithium ion battery cathode, excellent cycle stability and rate capability are shown. At 500mA g -1 Is circulated for 150 cycles, the composite material can maintain about 1100mAh g -1 ～1500mAh g -1 The reversible capacity of (a). And 2A g -1 The current density of the electrode is 200 cycles, and 650mAh g can still be maintained -1 ～800mAh g -1 The reversible capacity of (a). The method has the advantages of easy process, low cost, high safety, environmental friendliness and the like, and can be applied to large scale in industry.
The purpose of the invention is realized by at least one of the following technical solutions.
The invention provides a preparation method of a silicon-carbon microsphere composite material self-assembled by two-dimensional silicon nanosheets, which comprises the following steps:
(1) Soaking the silicon-metal alloy powder in an acidic substance for corrosion, and taking out to obtain corroded powder; dispersing the corroded powder in a solvent, adding a surfactant, uniformly mixing, and carrying out surface modification treatment to obtain a modified mixed solution;
(2) Adding a carbon-containing compound (a precursor serving as a carbon source) and an alkaline substance into the modified mixed solution obtained in the step (1), uniformly mixing, performing polycondensation reaction at room temperature, then coating the surface of the alloy powder through hydrothermal reaction, centrifuging to obtain a precipitate, washing, and drying to obtain coated alloy powder;
(3) And (3) heating the coated alloy powder obtained in the step (2) and calcining the alloy powder to obtain the silicon-carbon microsphere composite material (the high-performance silicon-carbon composite material with a microsphere structure) self-assembled by two-dimensional silicon nanosheets.
Further, the silicon-metal alloy powder in the step (1) is one or more of silicon-aluminum alloy, silicon-iron alloy, silicon-magnesium alloy, silicon-manganese alloy and silicon-calcium alloy powder; in the silicon-metal alloy powder, the mass ratio of silicon to metal is 80 to 5; the size of the silicon-metal alloy powder is 0.5 to 5 microns.
Further, the acidic substance in the step (1) is one or more of hydrochloric acid, sulfuric acid and oxalic acid; the concentration of the acidic substance is 1-4mol/L; the time for soaking the silicon-metal alloy powder in the acidic substance is 12-48h; the solvent in the step (1) is one or more of water and ethanol; the mass volume ratio of the silicon-metal alloy powder to the solvent is 1.
Preferably, the solvent in step (1) is an ethanol solution.
Further, the surfactant in the step (1) is one or more of cetyl trimethyl ammonium bromide, dodecyl trimethyl ammonium bromide and sodium dodecyl benzene sulfonate; the mass ratio of the surfactant to the silicon-metal alloy powder is (0.001-0.1); the time of the surface modification treatment in the step (1) is 2-6h.
Further, the carbon-containing compound in the step (2) is one or more of dopamine, sucrose, glucose, resorcinol and formaldehyde; the mass ratio of the carbon-containing compound in the step (2) to the silicon-metal alloy powder in the step (1) is 1.
Preferably, the carbon-containing compound in step (2) is resorcinol and formaldehyde, and the resorcinol and the formaldehyde can perform polycondensation reaction to form a coating layer on the surface of the silicon framework, and the ratio of the mass of the resorcinol to the mass of the formaldehyde is 0.5-1.5.
Further, the alkaline substance in the step (2) is ammonia water, and the concentration of the alkaline substance is 0.01-0.5 mol/L; the volume ratio of the ammonia water in the step (2) to the solvent in the step (1) is 1:100 to 1:10..
Further, the reaction time of the step (2) at room temperature is 12-48h; the temperature of the hydrothermal reaction is 50-100 ℃, and the time of the hydrothermal reaction is 12-48h.
Further, the temperature of the calcination treatment in the step (3) is 500-650 ℃, and the time of the calcination treatment is 2-6h.
The invention provides a silicon-carbon microsphere composite material self-assembled by two-dimensional silicon nanosheets, which is prepared by the preparation method, wherein the mass fraction of silicon is 10% -80%, and the carbon content is 20% -90%.
The invention provides an application of a silicon-carbon microsphere composite material self-assembled by two-dimensional silicon nanosheets in preparation of a lithium ion battery cathode material, which is characterized by comprising the following steps:
mixing the silicon-carbon microsphere composite material self-assembled by two-dimensional silicon nanosheets, carbon black and PVDF, pulping, and then coating the mixture on a copper foil to obtain the lithium ion battery negative electrode material; the mass ratio of the silicon-carbon microsphere composite material self-assembled by the two-dimensional silicon nanosheets, the carbon black and the PVDF is (5-8).
In the preparation process, the surfactant mainly plays a role in improving the surface of the silicon-metal alloy, and charges are carried on the surface of the silicon-metal alloy, so that the carbon layer can be conveniently coated.
The microsphere silicon-carbon composite material (namely the high-performance silicon-carbon composite material with a microsphere structure) assembled by the two-dimensional silicon nanosheets is prepared by the preparation method.
Preferably, the high-performance silicon-carbon composite material with the microsphere structure comprises 10-80% of silicon by mass and 20-90% of carbon by mass.
Further preferably, in the high-performance silicon-carbon composite material with the microsphere structure, the mass fraction of silicon is 40-75%, and the mass fraction of carbon is 25-60%.
Most preferably, the mass fraction of silicon in the high-performance silicon-carbon composite material with the microsphere structure is 55.4%, and the mass fraction of carbon is 44.6%.
Preferably, the above specific application process is: and mixing the high-performance silicon-carbon composite material with the microsphere structure, carbon black and PVDF to prepare pulp, and coating the pulp on copper foil to obtain the lithium ion battery cathode.
Further preferably, the application process is: weighing 0.16g of high-performance silicon-carbon composite material with a microsphere structure, 0.02g of PVDF and 0.02g of carbon black, mixing and grinding the materials, transferring the materials into a small glass bottle, adding 2mL of NMP, magnetically stirring the materials for 1h, coating the materials on copper foil to prepare an electrode, and assembling the electrode in a glove box by taking a metal lithium sheet as a counter electrode to form the CR2016 type button cell.
Compared with the prior art, the invention has the following advantages and beneficial effects:
(1) The raw materials used by the invention are silicon-metal alloy powder (such as silicon-aluminum, silicon-iron, silicon-magnesium, silicon-calcium and the like) which is low in price, the silicon-metal alloy powder consists of original silicon and eutectic silicon, and after metal is corroded by acid, a silicon frame is generated; the silicon frame provides a template for the growth of carbon compounds (such as phenolic resin), and can also play a certain supporting role on the final microsphere structure, thereby being beneficial to ensuring the integrity of the whole structure. In addition, the invention also has the advantages of high safety, environmental protection and the like; thus, the present invention has the potential for large-scale commercial applications.
(2) The carbon coating method adopted by the invention is simple, the carbon-containing compound is directly coated on the surface of the silicon frame by a one-step method, and the microspheres assembled by the two-dimensional carbon-coated silicon nanosheets are formed after high-temperature calcination. When the carbon coating layer is applied to a lithium ion battery cathode material, the change of the volume of silicon particles in the lithiation and delithiation processes can be effectively relieved by the carbon coating layer, the conductivity of the material is increased, and the electrochemical stability of the material is improved; the microspheres assembled by the two-dimensional silicon nanosheets are stable in structure and can exert the advantage of capacity.
(3) When the high-performance silicon-carbon composite material with the microsphere structure is used for a lithium ion battery cathode, when the silicon content is 40-70%, the result shows excellent performance through the test of electrochemical performance; at a current density of 500mAg -1 The lower circulation is 150 circles, and 1100mAh g can be kept -1 ～1500mAh g -1 Can be reversedAn amount; and in 2Ag -1 The current density of the current is 200 cycles, and 650mAhg can still be maintained -1 ～800mAh g -1 The reversible capacity of the lithium ion battery cathode material synthesized by the invention is proved to have good cycle performance and good performance under a large current density, and the application of the lithium ion battery in high-power occasions such as new energy electric vehicles and the like is guaranteed.
Drawings
Fig. 1 is an XRD chart of a two-dimensional silicon nanosheet self-assembled silicon-carbon microsphere composite material prepared in example 5 of the present invention.
Fig. 2 is an SEM image of a microspherical silicon composite material assembled by two-dimensional silicon nanosheets obtained in the embodiment of the present invention.
Fig. 3 is a raman spectrum of a microsphere silicon composite material assembled by two-dimensional silicon nanosheets obtained in example 5 of the present invention.
Fig. 4a is a charging/discharging specific capacity curve and coulombic efficiency chart of the two-dimensional silicon nanosheet self-assembled silicon carbon microsphere composite material obtained in embodiment 5 of the present invention.
Fig. 4b is a charge-discharge specific capacity curve of the two-dimensional silicon nanosheet self-assembled silicon carbon microsphere composite material obtained in embodiment 2 of the present invention.
Fig. 4c is a coulombic efficiency chart of the two-dimensional silicon nanosheet self-assembled silicon carbon microsphere composite material obtained in the embodiment of the present invention.
Detailed Description
The following examples are presented to further illustrate the practice of the invention, but the practice and protection of the invention is not limited thereto. It is noted that the processes described below, if not specifically detailed, are all those that can be realized or understood by those skilled in the art with reference to the prior art. The reagents or apparatus used are not indicated to the manufacturer, and are considered to be conventional products available by commercial purchase.
Example 1
1. Silicon-metal alloy surface modification treatment: weighing 10g of ferrosilicon alloy powder (the content of silicon is 20 percent, and the size of the alloy powder is 3 microns), and corroding for 12 hours by using 1mol/L hydrochloric acid to obtain silicon particles; 1.62g of silicon particles are taken and dispersed in 81mL of ethanol water solution (the volume percentage concentration of the ethanol solution is 28 percent), 0.0162g of surfactant cetyl trimethyl ammonium bromide is added for surface modification, and the surface modification time is 2 hours, so that the modified silicon particles are obtained.
2. Preparing a high-performance silicon-carbon composite material with a microsphere structure: sequentially measuring 5mL of ammonia water (with the concentration of 0.01 mol/L) and 0.44g of glucose, reacting for 12 hours at room temperature, transferring to a polytetrafluoroethylene reaction kettle, carrying out hydrothermal reaction for 24 hours at 100 ℃, centrifuging, washing, drying, and calcining for 5 hours at 600 ℃ to obtain the high-performance silicon-carbon composite material (the silicon-carbon microsphere composite material self-assembled by two-dimensional silicon nanosheets).
Taking 0.16g of the high-performance silicon-carbon composite material with the microsphere structure prepared in the embodiment, 0.02g of PVDF and 0.02g of carbon black, mixing and grinding the materials, transferring the materials into a small glass bottle, adding 2mLNMP (N-methyl pyrrolidone), magnetically stirring the materials for 1h, coating the materials on a copper foil to prepare an electrode (the size of the copper foil is 13 mm), and assembling the electrode in a glove box by taking metal lithium as a counter electrode to form a CR2016 type button battery for carrying out an electrochemical performance test.
Example 2
1. Silicon-metal alloy surface modification treatment: weighing 10g of ferrosilicon alloy powder (the content of silicon is 10 percent, and the size of the alloy powder is 5 microns), and corroding for 48 hours by using 2mol/L sulfuric acid to obtain silicon particles; 0.8g of silicon particles are taken and dispersed in 81mL of ethanol water solution (the volume percentage concentration of ethanol is 28 percent), 0.008g of surfactant sodium dodecyl benzene sulfonate is added for surface modification, and the surface modification time is 4 hours, thus obtaining the modified silicon particles.
2. Preparing a high-performance silicon-carbon composite material with a microsphere structure: sequentially measuring 5mL of ammonia water (with the concentration of 0.001 mol/L) and 0.82g of dopamine, reacting for 24 hours at room temperature, transferring to a polytetrafluoroethylene reaction kettle, carrying out hydrothermal reaction for 36 hours at 80 ℃, centrifugally washing, drying, and calcining for 5 hours at 650 ℃ to obtain the high-performance silicon-carbon composite material (the silicon-carbon microsphere composite material self-assembled by two-dimensional silicon nanosheets).
0.12g of the high-performance silicon-carbon composite material with the microsphere structure prepared in the embodiment, 0.04g of PVDF and 0.04g of carbon black are mixed and groundTransferring into a small glass bottle, adding 2mLNMP (N-methyl pyrrolidone), magnetically stirring for 1h, coating the material on a copper foil to prepare an electrode (the size of the copper foil is 13 mm), assembling the electrode into a CR2016 type button cell in a glove box by taking metal lithium as a counter electrode, and carrying out electrochemical performance test. As shown in FIG. 4b, at 200mA g -1 The current density of the current is 120 circles, and 550mAh g can still be kept -1 The reversible capacity of (a).
Example 3
1. Silicon-metal alloy surface modification treatment: weighing 10g of silicon-manganese alloy powder (the content of silicon is 15 percent, and the size of the alloy powder is 2 microns), and corroding for 48 hours by using 3mol/L oxalic acid to obtain silicon particles; 1.2g of silicon particles are taken and dispersed in 48mL of ethanol water solution (the volume percentage concentration of ethanol is 28 percent), 0.024g of surfactant cetyl trimethyl ammonium bromide is added for surface modification, and the surface modification time is 6 hours, thus obtaining the modified silicon particles.
2. Preparing a high-performance silicon-carbon composite material with a microsphere structure: sequentially measuring 1mL of ammonia water (with the concentration of 0.01 mol/L), 0.91g of resorcinol and 1.19mL of formaldehyde, reacting for 48h at room temperature, then transferring to a polytetrafluoroethylene reaction kettle, carrying out hydrothermal reaction for 48h at 100 ℃, carrying out centrifugal washing, drying, and calcining for 6h at 650 ℃ to obtain the high-performance silicon-carbon composite material (the silicon-carbon microsphere composite material self-assembled by two-dimensional silicon nanosheets).
Taking 0.1g of the high-performance silicon-carbon composite material with the microsphere structure prepared in the embodiment, 0.06g of PVDF and 0.04g of carbon black, mixing and grinding the materials, transferring the materials into a small glass bottle, adding 2mLNMP (N-methyl pyrrolidone), magnetically stirring the materials for 1h, coating the materials on a copper foil to prepare an electrode (the size of the copper foil is 13 mm), and assembling the electrode in a glove box by taking metal lithium as a counter electrode to obtain a CR2016 type button battery for carrying out an electrochemical performance test.
Example 4
1. Silicon-metal alloy surface modification treatment: weighing 10g of silicon-manganese alloy powder (the content of silicon is 30 percent, and the size of the alloy powder is 2 microns), and corroding for 24 hours by using 4mol/L sulfuric acid to obtain silicon particles; 0.89g of silicon particles are taken and dispersed in 44.5mL of ethanol water solution (the volume percentage concentration of ethanol is 28 percent), 0.008g of surfactant sodium dodecyl benzene sulfonate is added for surface modification, and the surface modification time is 4 hours, thus obtaining the modified silicon particles.
2. Preparing a high-performance silicon-carbon composite material with a microsphere structure: sequentially measuring 1mL of ammonia water (with the concentration of 0.1 mol/L), reacting 0.92g of glucose at room temperature for 12 hours, transferring to a polytetrafluoroethylene reaction kettle, carrying out hydrothermal reaction at 70 ℃ for 48 hours, carrying out centrifugal washing, drying, and calcining at 500 ℃ for 6 hours to obtain the high-performance silicon-carbon composite material. As shown in part (a) of fig. 2, the composite material is a silicon carbon microsphere composite material self-assembled by two-dimensional silicon nanosheets.
Taking 0.16g of the high-performance silicon-carbon composite material with the microsphere structure prepared in the embodiment, 0.02g of PVDF and 0.02g of carbon black, mixing and grinding the materials, transferring the materials into a small glass bottle, adding 2mL of NMP (N-methylpyrrolidone), magnetically stirring the materials for 1h, coating the materials on a copper foil to prepare an electrode (the size of the copper foil is 13 mm), and assembling the electrode in a glove box by taking metal lithium as a counter electrode to form a CR2016 type button battery to perform an electrochemical performance test.
Example 5
1. Silicon-metal alloy surface modification treatment: weighing 10g of silicon-aluminum alloy powder (the content of silicon is 20 percent, and the size of the alloy powder is 2 microns), and corroding for 24 hours by using 3mol/L hydrochloric acid to obtain silicon particles; 0.60g of silicon particles are taken and dispersed in 70mL of ethanol water solution (the volume percentage concentration of the ethanol is 28 percent), 0.024g of hexadecyl trimethyl ammonium bromide surfactant is added for surface modification, and the surface modification time is 3 hours, thus obtaining the modified silicon particles.
2. Preparing a high-performance silicon-carbon composite material with a microsphere structure: sequentially measuring 3mL of ammonia water (with the concentration of 0.05 mol/L), 1.15g of resorcinol and 1.61mL of formaldehyde, reacting for 36h at room temperature, then transferring to a polytetrafluoroethylene reaction kettle, carrying out hydrothermal reaction for 24h at 100 ℃, carrying out centrifugal washing, drying, and calcining for 5h at 650 ℃ to obtain the high-performance silicon-carbon composite material (the silicon-carbon microsphere composite material self-assembled by two-dimensional silicon nanosheets). The XRD pattern of FIG. 1 clearly shows that the silicon in the composite material corresponds to its standard spectrum (JCPDS No. 27-1402), and the Raman spectrum of FIG. 3 shows that it is in the spectrum500cm -1 There appears a strong peak, also indicating the presence of silicon, at 1340cm -1 And 1573cm -1 The strong peaks appeared there correspond to the D and G peaks of carbon, respectively, indicating successful coating of carbon on the surface of silicon. From the scanning electron microscope (b) part of fig. 2, it can also be seen that the material is a silicon carbon microsphere composite material self-assembled by two-dimensional silicon nanosheets.
Taking 0.16g of the high-performance silicon-carbon composite material with the microsphere structure prepared in the embodiment, 0.02g of PVDF and 0.02g of carbon black, mixing and grinding the materials, transferring the materials into a small glass bottle, adding 2mLNMP (N-methyl pyrrolidone), magnetically stirring the materials for 1h, coating the materials on a copper foil to prepare an electrode (the size of the copper foil is 13 mm), and assembling the electrode in a glove box by taking metal lithium as a counter electrode to form a CR2016 type button battery for carrying out an electrochemical performance test. As shown in FIG. 4a, at 500mAg -1 The current density of the alloy is 150 cycles, and 1200mAh g can still be kept -1 The reversible capacity of (a). The composite material is shown to have good cycling stability and higher reversible capacity.
Example 6
1. Silicon-metal alloy surface modification treatment: weighing 10g of silicon-aluminum alloy powder (the content of silicon is 10 percent, and the size of the alloy powder is 5 microns), and corroding for 24 hours by using 3mol/L oxalic acid to obtain silicon particles; 0.80g of silicon particles are taken and dispersed in 120mL of ethanol water solution (the volume percentage concentration of ethanol is 28 percent), 0.004g of surfactant sodium dodecyl benzene sulfonate is added for surface modification, and the surface modification time is 6 hours, so that the modified silicon particles are obtained.
2. Preparing a high-performance silicon-carbon composite material with a microsphere structure: sequentially measuring 3mL of ammonia water (with the concentration of 0.1 mol/L) and 1.38g of glucose, reacting for 48 hours at room temperature, transferring to a polytetrafluoroethylene reaction kettle, carrying out hydrothermal reaction for 48 hours at 100 ℃, centrifugally washing, drying, and calcining for 5 hours at 650 ℃ to obtain the high-performance silicon-carbon composite material (the silicon-carbon microsphere composite material self-assembled by two-dimensional silicon nanosheets).
Taking 0.10g of the high-performance silicon-carbon composite material with the microsphere structure prepared in the embodiment, 0.06g of PVDF and 0.04g of carbon black, mixing and grinding the materials, transferring the materials into a small glass bottle, adding 2mLNMP (N-methyl pyrrolidone), magnetically stirring the materials for 1h, coating the materials on a copper foil to prepare an electrode (the size of the copper foil is 13 mm), and assembling the electrode in a glove box by taking metal lithium as a counter electrode to form a CR2016 type button battery for carrying out an electrochemical performance test.
Example 7
1. Silicon-metal alloy surface modification treatment: weighing 10g of silicon-aluminum alloy powder (the content of silicon is 5 percent, and the size of the alloy powder is 5 microns), and corroding for 24 hours by using 3mol/L sulfuric acid to obtain silicon particles; 0.80g of silicon particles are taken and dispersed in 120mL of ethanol water solution (the volume percentage concentration of ethanol is 28 percent), 0.016g of surfactant cetyl trimethyl ammonium bromide is added for surface modification, and the surface modification time is 2 hours, so that the modified silicon particles are obtained.
2. Preparing a high-performance silicon-carbon composite material with a microsphere structure: sequentially measuring 3mL of ammonia water (with the concentration of 0.5 mol/L), 1.55g of resorcinol and 2.17mL of formaldehyde, reacting for 48 hours at room temperature, then transferring to a polytetrafluoroethylene reaction kettle, carrying out hydrothermal reaction for 12 hours at 50 ℃, carrying out centrifugal washing, drying, and calcining for 5 hours at 500 ℃ to obtain the high-performance silicon-carbon composite material, wherein the high-performance silicon-carbon composite material can also be seen from a scanning electron microscope (c) diagram of fig. 2.
Taking 0.14g of the high-performance silicon-carbon composite material with the microsphere structure prepared in the embodiment, 0.04g of PVDF and 0.02g of carbon black, mixing and grinding the materials, transferring the materials into a small glass bottle, adding 2mLNMP (N-methyl pyrrolidone), magnetically stirring the materials for 1h, coating the materials on a copper foil to prepare an electrode (the size of the copper foil is 13 mm), and assembling the electrode in a glove box by taking metal lithium as a counter electrode to form a CR2016 type button battery for carrying out an electrochemical performance test. As shown in fig. 4c, at 500mAg -1 The current density of the current is 120 circles, and 1000mAh g can still be kept -1 The reversible capacity of (a). The composite material is shown to have good cycling stability and higher reversible capacity.
Example 8
1. Silicon-metal alloy surface modification treatment: weighing 10g of silicon-magnesium alloy powder (the content of silicon is 5 percent, and the size of the alloy powder is 4 microns), and corroding for 48 hours by using 4mol/L sulfuric acid to obtain silicon particles; 0.40g of silicon particles are taken and dispersed in 40mL of ethanol water solution (the volume percentage concentration of ethanol is 28 percent), 0.004g of surfactant sodium dodecyl benzene sulfonate is added for surface modification, and the surface modification time is 4 hours, so that the modified silicon particles are obtained.
2. Preparing a high-performance silicon-carbon composite material with a microsphere structure: sequentially measuring 3mL of ammonia water (with the concentration of 0.2 mol/L) and 1.07g of glucose, reacting for 48 hours at room temperature, then transferring to a polytetrafluoroethylene reaction kettle, carrying out hydrothermal reaction for 48 hours at 100 ℃, centrifugally washing, drying, and calcining for 5 hours at 650 ℃ to obtain the high-performance silicon-carbon composite material, wherein the material can also be seen to be a silicon-carbon microsphere composite material self-assembled by two-dimensional silicon nanosheets from a scanning electron microscope (d) diagram of fig. 2.
Taking 0.16g of the high-performance silicon-carbon composite material with the microsphere structure prepared in the embodiment, 0.02g of PVDF and 0.02g of carbon black, mixing and grinding the materials, transferring the mixture into a small glass bottle, adding 2mL of NMP (N-methylpyrrolidone), magnetically stirring the mixture for 1h, coating the material on a copper foil to prepare an electrode (the size of the copper foil is 13 mm), and assembling the electrode into a CR2016 type button cell in a glove box by using metal lithium as a counter electrode to perform an electrochemical performance test.
Example 9
1. Silicon-metal alloy surface modification treatment: weighing 10g of silicon-magnesium alloy powder (the content of silicon is 30 percent, and the size of the alloy powder is 3 microns), and corroding for 16 hours by using 3mol/L hydrochloric acid to obtain silicon particles; 0.40g of silicon particles are taken and dispersed in 40mL of ethanol water solution (the volume percentage concentration of the ethanol is 28 percent), 0.008g of sodium dodecyl benzene sulfonate surfactant is added for surface modification, the surface modification time is 3 hours, and the modified silicon particles are obtained.
2. Preparing a high-performance silicon-carbon composite material with a microsphere structure: sequentially measuring 3mL of ammonia water (with the concentration of 0.5 mol/L) and 1.07g of dopamine, reacting for 48 hours at room temperature, transferring to a polytetrafluoroethylene reaction kettle, carrying out hydrothermal reaction for 48 hours at 80 ℃, centrifugally washing, drying, and calcining for 5 hours at 650 ℃ to obtain the high-performance silicon-carbon composite material (silicon-carbon microsphere composite material self-assembled by two-dimensional silicon nanosheets).
0.14g of the high performance silicon carbon composite with microsphere structure prepared in this example was takenMixing the materials, 0.04g of PVDF and 0.02g of carbon black, grinding, transferring into a small glass bottle, adding 2ml of NMP (N-methyl pyrrolidone), magnetically stirring for 1h, coating the materials on a copper foil to prepare an electrode (the size of the copper foil is 13 mm), assembling the electrode serving as a counter electrode in a glove box to form a CR2016 type button cell, and carrying out electrochemical performance test. As shown in FIG. 4c, at 300mAg -1 The current density of the current is 120 circles, and 600mAh g can still be kept -1 The reversible capacity of (a).
Example 10
1. Silicon-metal alloy surface modification treatment: weighing 10g of silicon-magnesium alloy powder (the content of silicon is 5 percent, and the size is 3 microns), and corroding for 28 hours by using 2mol/L hydrochloric acid to obtain silicon particles; 0.20g of silicon particles are taken and dispersed in 28mL of ethanol water solution (the volume percentage concentration of ethanol is 28 percent), 0.016g of surfactant cetyl trimethyl ammonium bromide is added for surface modification, and the surface modification time is 3 hours, so that the modified silicon particles are obtained.
2. Preparing a high-performance silicon-carbon composite material with a microsphere structure: sequentially measuring 3mL of ammonia water (with the concentration of 0.01 mol/L), 1.29g of resorcinol and 1.68mL of formaldehyde, reacting for 48 hours at room temperature, then transferring to a polytetrafluoroethylene reaction kettle, carrying out hydrothermal reaction for 48 hours at 80 ℃, carrying out centrifugal washing, drying, and calcining for 5 hours at 600 ℃ to obtain the high-performance silicon-carbon composite material (the silicon-carbon microsphere composite material self-assembled by two-dimensional silicon nanosheets).
Taking 0.10g of the high-performance silicon-carbon composite material with the microsphere structure prepared in the embodiment, 0.06g of PVDF and 0.04g of carbon black, mixing and grinding the materials, transferring the materials into a small glass bottle, adding 2mLNMP (N-methyl pyrrolidone), magnetically stirring the materials for 1h, coating the materials on a copper foil to prepare an electrode (the size of the copper foil is 13 mm), and assembling the electrode in a glove box by taking metal lithium as a counter electrode to form a CR2016 type button battery for carrying out an electrochemical performance test.
Performance testing
The material prepared in the above embodiment is characterized by using X-ray diffraction (XRD), raman spectroscopy (Raman spectroscopy) and Scanning Electron Microscope (SEM) as characterization means, and fully analyzing the morphology, composition and carbon content thereof.
After the battery prepared in the embodiment is placed for 12 hours, a battery tester (Shenzhen Xinwei) and BTS7.5.5 software are adopted, the test temperature is room temperature, and the current density is 200mAg -1 ～2000mAg -1 In the case of the battery, constant current charging and discharging (discharge cutoff voltage of 0.01V and charging voltage of 3V) was performed, and the cycle performance and rate performance (expressed by different current densities) of the battery were tested. The electrical properties of the samples are detailed in table 1.
TABLE 1
The invention utilizes a hydrothermal method to prepare the high-performance silicon-carbon composite material with the microsphere structure, the silicon-carbon composite material with the optimal silicon content is found by changing the proportion of silicon-carbon raw materials, and the electrochemical properties of the corresponding materials are also researched: cycle performance, rate performance, and the like. By comparing ten examples, it was found that samples with a silicon weight fraction of 48.4% to 55.2% had good cycling performance, all at 500mA g -1 The current density is kept at 1000mAh g after circulating for 150 circles -1 The above reversible capacity; sample with 37.6% silicon weight fraction at 500mAg -1 After 200 cycles of circulation, the reversible capacity reaches 784mAg -1 (ii) a Sample with 61.7% silicon weight fraction at 300mAg -1 After circulating for 100 circles, the reversible capacity reaches 902mAh g -1 。
The above examples are only preferred embodiments of the present invention, which are intended to illustrate the present invention, but not to limit the present invention, and those skilled in the art should be able to make changes, substitutions, modifications, etc. without departing from the spirit of the present invention.
Claims (9)
1. A preparation method of a silicon-carbon microsphere composite material self-assembled by two-dimensional silicon nanosheets is characterized by comprising the following steps:
(1) Corroding the silicon-metal alloy powder with an acidic substance, and centrifugally washing to obtain corroded powder; dispersing the corroded powder in a solvent, adding a surfactant, and carrying out surface modification treatment to obtain a modified mixed solution, wherein the silicon-metal alloy powder is one or more of silicon-aluminum alloy, silicon-iron alloy, silicon-magnesium alloy, silicon-manganese alloy and silicon-calcium alloy powder, the mass ratio of silicon to metal in the silicon-metal alloy powder is (30;
(2) Adding a carbon-containing compound and an alkaline substance into the modified mixed solution obtained in the step (1), uniformly mixing, performing a polycondensation reaction at room temperature, performing a hydrothermal reaction, centrifuging to obtain a precipitate, washing, and drying to obtain coated alloy powder, wherein the hydrothermal reaction temperature is 50-100 ℃, the hydrothermal reaction time is 12-48h, and the mass ratio of the carbon-containing compound to the silicon-metal alloy powder obtained in the step (1) is (1);
(3) And (3) heating the coated alloy powder obtained in the step (2) for calcining to obtain the silicon-carbon microsphere composite material self-assembled by the two-dimensional silicon nanosheets.
2. The method for preparing the silicon-carbon microsphere composite material self-assembled by two-dimensional silicon nano sheets according to claim 1, wherein the acidic substance in the step (1) is one or more of hydrochloric acid, sulfuric acid and oxalic acid; the concentration of the acidic substance is 1-4mol/L; the time for soaking the silicon-metal alloy powder in the acidic substance is 12-48h; the solvent in the step (1) is one or more of water and ethanol; the mass volume ratio of the silicon-metal alloy powder to the solvent is 1.
3. The method for preparing the silicon-carbon microsphere composite material self-assembled by two-dimensional silicon nano sheets according to claim 1, wherein the surfactant in the step (1) is one or more of cetyl trimethyl ammonium bromide, dodecyl trimethyl ammonium bromide and sodium dodecyl benzene sulfonate; the mass ratio of the surfactant to the silicon-metal alloy powder is (0.001-0.1); the time of the surface modification treatment in the step (1) is 2-6h.
4. The method for preparing the silicon-carbon microsphere composite material self-assembled by two-dimensional silicon nano sheets according to claim 1, wherein the carbon-containing compound in the step (2) is one or more of dopamine, sucrose, glucose, resorcinol and formaldehyde.
5. The preparation method of the silicon-carbon microsphere composite material self-assembled by two-dimensional silicon nano sheets according to claim 1, wherein the alkaline substance in the step (2) is ammonia water, the concentration of the alkaline substance is 0.01-0.5mol/L, and the volume ratio of the alkaline substance in the step (2) to the solvent in the step (1) is 1.
6. The preparation method of the silicon-carbon microsphere composite material self-assembled by two-dimensional silicon nano sheets according to claim 1, wherein the time for the polycondensation reaction at room temperature in the step (2) is 12-48h.
7. The preparation method of the silicon-carbon microsphere composite material self-assembled by two-dimensional silicon nano sheets as claimed in claim 1, wherein the temperature of the calcination treatment in the step (3) is 500-650 ℃, and the time of the calcination treatment is 2-6h.
8. The two-dimensional silicon nanosheet self-assembled silicon-carbon microsphere composite material prepared by the preparation method of any one of claims 1 to 7, wherein the mass fraction of silicon is 10% -80%, and the carbon content is 20% -90%.
9. The application of the silicon-carbon microsphere composite material self-assembled by two-dimensional silicon nanosheets as defined in claim 8 in the preparation of a lithium ion battery negative electrode material is characterized by comprising the following steps:
mixing the silicon-carbon microsphere composite material self-assembled by the two-dimensional silicon nanosheets, carbon black and PVDF, pulping, and coating on copper foil to obtain the lithium ion battery negative electrode material; the mass ratio of the silicon-carbon microsphere composite material self-assembled by the two-dimensional silicon nanosheets, the carbon black and the PVDF is 5:3:2-8:1:1.
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