CN111509217A - Silicon nano material and preparation method and application thereof - Google Patents

Silicon nano material and preparation method and application thereof Download PDF

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Publication number
CN111509217A
CN111509217A CN202010355603.9A CN202010355603A CN111509217A CN 111509217 A CN111509217 A CN 111509217A CN 202010355603 A CN202010355603 A CN 202010355603A CN 111509217 A CN111509217 A CN 111509217A
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silicon
preparation
acid
vermiculite
nano material
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王芳
于海峰
冯婷
肖远超
柴宏伟
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Luoyang Institute of Science and Technology
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Luoyang Institute of Science and Technology
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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
    • 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
    • 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 belongs to the technical field of electrode materials, and particularly relates to a silicon nano material, and a preparation method and application thereof. The preparation method of the silicon nano material provided by the invention comprises the following steps: mixing vermiculite and magnesium, and carrying out thermal reduction reaction to obtain a reduction product, wherein the reduction product comprises silicon and magnesium oxide; and carrying out acid leaching on the reduction product, and drying the product of the acid leaching to obtain the silicon nano material. The invention uses silicon dioxide and magnesium in vermiculite as raw materials, and adopts a thermal reduction method to reduce the silicon dioxide into silicon and oxidize the magnesium into magnesium oxide; and then, the 2D layered structure of vermiculite is still kept in the obtained silicon material by using an acid leaching method. Test results show that the silicon nano material prepared by the preparation method provided by the invention keeps the original 2D layered structure of vermiculite; after 100 cycles, the coulombic efficiency remained at 99.71%.

Description

Silicon nano material and preparation method and application thereof
Technical Field
The invention belongs to the technical field of electrode materials, and particularly relates to a silicon nano material, and a preparation method and application thereof.
Background
Currently, the research on the commercialized graphite-based material has reached theoretical capacity 372mAh/g, the performance improvement space is insufficient, and silicon has ultrahigh theoretical specific capacity of 4200mAh/g and lower discharge potential (about 0.1V vs, L i/L i)+) However, the capacity retention capacity of the silicon electrode is poor due to volume expansion during repeated L i insertion and extraction, resulting in pulverization of particles, deterioration of conductive network, and detachment of active material from the current collector, resulting in capacity fading and low coulombic efficiency, and in addition, the electrochemical activity of electrode reaction is reduced due to poor conductivity of silicon itself, resulting in low utilization of active material and excessively high polarization potential at high current density.
To overcome the above disadvantages of silicon, currently common technical means include the preparation of silicon nanostructures or silicon-carbon composites. Wherein, silicon nano structure, such as nano line, nano tube, porous nano silicon, etc. can not only adapt to volume change and maintain structural integrity, but also can accelerate charge transfer by shortening transport length, but the preparation process of conventional silicon nano structure is complex, and raw material SiH is4It is expensive. The preparation method of the silicon nano material has the advantages of cheap and easily obtained raw materials and simple preparation process, and has important significance for the energy industry.
Disclosure of Invention
In view of the above, the present invention aims to provide a method for preparing a silicon nanomaterial, wherein the method uses vermiculite as a raw material, the raw material is cheap and easy to obtain, and the preparation process is simple, and the silicon nanomaterial prepared by the method has the characteristic of excellent electrochemical performance; the invention also provides an application of the silicon nano material.
In order to achieve the purpose of the invention, the invention provides the following technical scheme:
the invention provides a preparation method of a silicon nano material, which comprises the following steps:
mixing vermiculite and magnesium, and carrying out thermal reduction reaction to obtain a reduction product, wherein the reduction product comprises silicon and magnesium oxide;
and carrying out acid leaching on the reduction product, and drying the product of the acid leaching to obtain the silicon nano material.
Preferably, the mass ratio of the vermiculite to the magnesium is 1: (0.5-2).
Preferably, the temperature of the thermal reduction reaction is 600-700 ℃, and the time is 6-8 h; the rate of heating to the temperature of the thermal reduction reaction is 2-8 ℃/min; the atmosphere of the thermal reduction reaction is inert atmosphere.
Preferably, the acid for acid leaching is hydrochloric acid, nitric acid or sulfuric acid, and the concentration of the acid for acid leaching is 1-3 mol/L.
Preferably, the mass ratio of the reduction product to the acid for acid leaching is 1: (8-12).
Preferably, the acid leaching temperature is 20-30 ℃, and the time is 10-14 h.
Preferably, the drying temperature is 50-70 ℃, and the drying time is 10-14 h.
Preferably, the drying further comprises the steps of carrying out hydrofluoric acid washing, solid-liquid separation and final drying on the dried product in sequence.
The invention also provides the silicon nano material prepared by the preparation method in the technical scheme, wherein the silicon nano material has a 2D layered structure; the single-layer thickness of the nano material is 4-10 nm.
The invention also provides the application of the silicon nano material in the technical scheme as a negative electrode material in a lithium ion battery.
The invention provides a preparation method of a silicon nano material, which comprises the following steps: mixing vermiculite and magnesium, and carrying out thermal reduction reaction to obtain a reduction product, wherein the reduction product comprises silicon and magnesium oxide; to the reduction productThe invention uses silicon dioxide and magnesium in vermiculite as raw materials, adopts a thermal reduction method to reduce the silicon dioxide into silicon and oxidize the magnesium into magnesium oxide, and then uses the acid leaching method to ensure that the obtained silicon material still retains the 2D layered structure of the vermiculite, and the 2D layered structure is beneficial to ensuring L i in the circulation of a lithium ion battery+While the volume change of the electrode can be mitigated by relieving the mechanical stress during cycling. Therefore, the silicon nano material prepared by the invention has a 2D layered structure and has good coulombic efficiency.
The test results of the embodiment show that the silicon nano material prepared by the preparation method provided by the invention keeps the original 2D layered structure of vermiculite; after 100 cycles, the coulombic efficiency remained at 99.71%.
Drawings
FIG. 1 is an SEM image of a silicon nanomaterial prepared in example 1;
fig. 2 is a cyclic voltammogram of the button cell prepared in application example 1;
fig. 3 is a cyclic voltammogram of the button cell prepared in comparative example 1;
fig. 4 is a charge-discharge curve diagram of the button cell prepared in application example 1;
fig. 5 is a charge-discharge curve diagram of the button cell prepared in comparative example 1;
fig. 6 is a cycle stability test chart of the button cell prepared in application example 1;
fig. 7 is a graph showing the cycling stability test of the button cell prepared in comparative example 1;
FIG. 8 is an SEM image of a silicon nanomaterial prepared in example 2;
FIG. 9 is an XRD pattern of the silicon nanomaterial prepared in example 2;
FIG. 10 is a cyclic voltammogram of the silicon nanomaterial prepared in example 2;
fig. 11 is a graph of the ac impedance of a button cell prepared in application example 2;
fig. 12 is a graph of the ac impedance of the button cell prepared in comparative example 1;
fig. 13 is a graph of the ac impedance after 10 charges and discharges for the button cell prepared in example 2 and the button cell prepared in comparative example 1;
fig. 14 is a charge and discharge graph of the button cell prepared in example 2;
fig. 15 is a graph of the cycling stability test of the button cell prepared in example 2;
fig. 16 is a charge and discharge graph of the button cell prepared in example 3;
fig. 17 is a graph of the cycling stability test of the button cells prepared in example 3.
Detailed Description
The invention provides a preparation method of a silicon nano material, which comprises the following steps:
mixing vermiculite and magnesium, and carrying out thermal reduction reaction to obtain a reduction product, wherein the reduction product comprises silicon and magnesium oxide;
and carrying out acid leaching on the reduction product, and drying the product of the acid leaching to obtain the silicon nano material.
In the present invention, the components are commercially available products well known to those skilled in the art unless otherwise specified.
The method mixes vermiculite with magnesium, and carries out thermal reduction reaction to obtain a reduction product, wherein the reduction product comprises silicon and magnesium oxide.
In the invention, the vermiculite is a nonmetallic mineral and has a two-dimensional layered structure of aluminosilicate containing iron and magnesium. In the present invention, the chemical composition of the vermiculite is preferably XM3Q4O10(OH)2Wherein X is an interlayer cation, preferably Ca2+、Na+、Mg2+And K+One or more of; m is an octahedral cation, preferably Mg2+、Fe3+、Fe2+、Al3+、Ti4+、Mn2+And Cr3+One or more of; q is a tetrahedral cation, preferably Si4+、Al3+、Fe3+And Ti4+One or more of; water molecules exist among molecular layers of the vermiculite.The chemical composition of the vermiculite disclosed by the invention preferably comprises the following components in percentage by mass: 14 to 18% of MgO and Fe2O35～17％、CaO 1～3％、SiO237～42％、Al2O310～13％、H2O 4～8％、K2O6.5 percent and trace L i, Ti, Cr and Ni elements, the source of the vermiculite is not particularly limited, and the source is known to a person skilled in the art, and in the embodiment of the invention, the vermiculite is from Yuli Xinjiang.
In the present invention, the particle size of the vermiculite particles is preferably 80 mesh or less.
The present invention preferably subjects the vermiculite to thermal expansion and pretreatment in sequence prior to mixing with magnesium.
In the invention, the temperature of the thermal expansion is preferably 600-900 ℃, and more preferably 700-850 ℃; the time is preferably 5 to 15min, and more preferably 7 to 13 min. In the present invention, the thermal expansion device is preferably a muffle furnace. The invention ensures that the vermiculite presents a 2D layered structure appearance through thermal expansion.
In the present invention, the pretreatment preferably comprises the steps of:
and (3) carrying out acid washing, water washing and drying on the vermiculite particles obtained by crushing the vermiculite in sequence to obtain blocky vermiculite.
The pickling solution is preferably hydrochloric acid, sulfuric acid or nitric acid, the concentration of the pickling solution is preferably 0.5-4 mol/L, more preferably 1-3.5 mol/L, the ratio of the mass of the vermiculite particles to the volume of the pickling solution is preferably 6.25 g: 250m L, the pickling temperature is preferably 80 ℃, the time is preferably 2-16 h, more preferably 4-14 h, and more preferably 6-12 h, the pickling is preferably carried out under the condition of stirring, the stirring rate is not particularly limited, and a stirring rate well known to a person skilled in the art can be adopted.
In the present invention, the pH of the water-washed product obtained by the water-washing is preferably 6.5. In the present invention, the washing with water is preferably performed by suction filtration. The invention removes the redundant hydrochloric acid through water washing. In the present invention, the drying temperature is preferably 100 ℃ and the drying time is preferably 10 hours.
In the present invention, the magnesium is preferably magnesium powder; the particle size of the magnesium powder is not particularly limited in the present invention, and the particle size of the magnesium powder known to those skilled in the art may be used.
In the present invention, the mass ratio of vermiculite to magnesium is preferably 1: (0.5 to 2), more preferably 1: (0.7 to 1.5), most preferably 1: 1. in the invention, the temperature of the thermal reduction reaction is preferably 600-700 ℃, more preferably 620-680 ℃, and further preferably 640-660 ℃; the time is preferably 6 to 8 hours, more preferably 6.2 to 7.8 hours, and still more preferably 6.5 to 7.5 hours. In the invention, the rate of raising the temperature to the temperature of the thermal reduction reaction is preferably 2-8 ℃/min, more preferably 3-7 ℃/min, and still more preferably 4-6 ℃/min. In the present invention, the atmosphere of the thermal reduction reaction is preferably an inert atmosphere. In the present invention, the inert atmosphere is preferably argon or nitrogen. In the invention, the purity of the argon or nitrogen is preferably 99-99.999%.
According to the invention, silicon dioxide in vermiculite reacts with magnesium through thermal reduction reaction, the silicon dioxide is reduced into silicon, and the magnesium is oxidized into magnesium oxide.
After the reduction product is obtained, the invention carries out acid leaching on the reduction product, and the product of the acid leaching is dried to obtain the silicon nano material.
In the invention, the acid for acid leaching is preferably hydrochloric acid, nitric acid or sulfuric acid, the concentration of the acid for acid leaching is preferably 1-3 mol/L, more preferably 1.3-2.7 mol/L, and even more preferably 1.8-2.2 mol/L, the mass ratio of the reduction product to the acid for acid leaching is preferably 1 (8-12), more preferably 1 (9-11), and most preferably 1: 10, in the invention, the temperature of the acid leaching is preferably 20-30 ℃, more preferably 22-28 ℃, even more preferably 24-26 ℃, the time is preferably 10-14 h, and even more preferably 11-13 h, in the invention, the acid leaching is preferably to add the acid into the reduction product, the adding mode is preferably dropwise adding, in the invention, the dropwise adding speed is preferably 0.02m L/s, and through the dropwise adding, the invention, the reaction system solution caused by the heat release of the thermal reduction reaction can be avoided.
After the acid leaching, the invention preferably further comprises carrying out solid-liquid separation on a system obtained by the acid leaching; the solid-liquid separation method is not particularly limited, and a solid-liquid separation method known to those skilled in the art, specifically, centrifugal separation, may be used. In the present invention, the rotation speed of the centrifugal separation is preferably 10000rpm, and the time is preferably 10 min.
In the invention, the drying temperature is preferably 50-70 ℃, more preferably 55-65 ℃, and further preferably 57-63 ℃; the time is preferably 10 to 14 hours, more preferably 10.5 to 13.5 hours, and still more preferably 11 to 13 hours.
After the drying, the invention preferably further comprises the steps of sequentially carrying out hydrofluoric acid cleaning, solid-liquid separation and final drying on the dried product to obtain the silicon nano material. In the invention, the mass percentage concentration of the hydrofluoric acid cleaning is preferably 1-5%, more preferably 1.5-4.5%, and still more preferably 2-4%. According to the invention, unreduced silicon dioxide in the dried product is removed through hydrofluoric acid washing, which is beneficial to improving the purity of the silicon nano material. In the present invention, the solid-liquid separation is preferably centrifugal separation; the centrifugation in the present invention is not particularly limited, and centrifugation well known to those skilled in the art may be used. In the present invention, the rotation speed of the centrifugal separation is preferably 10000rpm, and the time is preferably 10 min. In the invention, the final drying temperature is preferably 50-70 ℃, more preferably 55-65 ℃, and further preferably 57-63 ℃; the time is preferably 10 to 14 hours, more preferably 11 to 13 hours, and still more preferably 11.5 to 12.5 hours.
The invention also provides the silicon nano material prepared by the preparation method of the technical scheme, and the silicon nano material has a 2D layered structure. In the present invention, the thickness of the single layer of the silicon nanomaterial is preferably4-10 nm, the silicon nano material provided by the invention keeps the original 2D layered structure of vermiculite, and the unique 2D layered structure is favorable for L i in the electrochemical cycle of a lithium ion battery+While the volume change of the electrode can be mitigated by relieving the mechanical stress during cycling. .
The invention also provides the application of the silicon nano material in the technical scheme as a negative electrode material in a lithium ion battery. In the invention, the nano silicon material has a two-dimensional layered structure, and can promote the diffusion of lithium ions and relieve the volume change of an electrode by releasing mechanical stress in a circulating process as a negative electrode material of a lithium ion battery.
In the present invention, the application specifically comprises the following steps: mixing the silicon nano material, the conductive agent, the binder and water to obtain slurry; sequentially coating, drying and tabletting the slurry to obtain an electrode plate; and assembling the button type half cell by taking the electrode plate as a positive electrode and a lithium plate as a negative electrode.
The conductive agent is not particularly limited in the present invention, and any conductive agent known to those skilled in the art may be used, specifically, for example, SuperP; the binder used in the present invention is not particularly limited, and binders well known to those skilled in the art, specifically, CMC; the mass dispersion of the CMC is preferably 3%; the solvent is preferably water. In the invention, the mass ratio of the silicon nano material to the conductive agent to the binder is preferably (60-80): (15-35): (4-6). The coating, drying and tabletting are not particularly limited in the present invention, and may be performed by coating, drying and tabletting, which are well known to those skilled in the art. In the present invention, the apparatus for coating the sheet is preferably a coater. In the present invention, the counter electrode is preferably a lithium sheet. The invention has no special limitation on the assembly of the battery, and the battery assembly known by the technicians in the field can be adopted; in the present invention, the assembly of the cell is preferably performed in a glove box filled with argon gas.
In order to further illustrate the present invention, the following will describe a silicon nanomaterial provided by the present invention, and a preparation method and application thereof in detail with reference to examples, but they should not be construed as limiting the scope of the present invention.
Example 1
Mixing 6.25g of vermiculite particles with hydrochloric acid with the concentration of 250m L of 0.5 mol/L, stirring the obtained mixed system for 2 hours at the constant temperature of 80 ℃ by using a heat collection type magnetic stirrer, cooling to room temperature, filtering and washing the solid for a plurality of times by using deionized water until the pH value is 6.5, and placing the solid in a vacuum drying oven for vacuum drying for 12 hours at the temperature of 100 ℃ to obtain blocky vermiculite;
cooling 1.0g of the obtained blocky vermiculite to room temperature, uniformly mixing the blocky vermiculite with 1.0g of magnesium powder, placing the mixture in a quartz tube furnace, heating the mixture from the room temperature to 650 ℃ at the speed of 5 ℃/min in a high-purity argon atmosphere with the purity of 99.999%, and then preserving the heat for 7 hours to obtain 1.3g of powdery reduction product;
dropwise adding hydrochloric acid with the concentration of 2 mol/L into the obtained reduction product at the dropwise adding rate of 0.02m L/s until the reduction product is completely soaked (the use amount of the hydrochloric acid is 30m L), then stirring for 12h at room temperature by using a magnetic stirrer, pouring into a centrifuge tube, carrying out high-speed centrifugal separation for 10min at the rotation speed of 10000prm, carrying out vacuum drying for 12h at the temperature of 60 ℃ on the obtained solid product, washing for several times by using hydrofluoric acid with the mass percentage content of 1%, carrying out centrifugal separation for 10min at the rotation speed of 10000rpm, and carrying out vacuum drying for 12h at the temperature of 60 ℃ in sequence to obtain the silicon nano material.
SEM test of the obtained silicon nano material was carried out by using a scanning electron microscope of Thermo scientific type Apreo S, and the obtained SEM picture is shown in FIG. 1. As can be seen from FIG. 1, the silicon nanomaterial provided by the invention maintains the original 2D layered structure of vermiculite.
Application example 1
The silicon nanomaterial prepared in example 1 was used as an active material, Super P was used as a conductive agent, and CMC was used
(3 percent by mass) is binder, water is used as solvent, and the mass ratio of the silicon nano material to the conductive agent to the binder is 70: 25: 5, preparing slurry, coating by a coating machine, drying, tabletting and weighing to obtain the electrode slice. And placing the electrode plates in a glove box filled with argon, and assembling the button cell by taking the lithium plate as a counter electrode.
The electrochemical performance of the button cell obtained in the application example 1 is measured by adopting a blue cell test system under the test conditions of 0.1mV/s and 0.02-2V (vs. L i)+/L i), the cyclic voltammogram obtained is shown in FIG. 2. it can be seen from FIG. 2 that the cyclic voltammogram is 0.75-1.25V (vs. L i)+L i), a broad peak appears in three cycles, the peak is the decomposition of electrolyte and the formation of SEI film, a sharp peak is at about 0.1V in the first cycle, the peak is gradually converted into a broad peak at about 0.25V along with the increase of the cycle times, and is the lithium insertion process for converting crystalline silicon and lithium into silicon-lithium alloy, meanwhile, two obvious oxidation peaks appearing at 0.3V and 0.5V are the lithium removal process for converting silicon-lithium alloy into amorphous silicon, and the intensity of the two oxidation peaks is gradually increased along with the increase of the cycle times, which indicates the continuous activation process of the electrode material.
Comparative example 1
A button cell was obtained by using commercial silicon (purchased from jiang violet light in technologies ltd.) in place of the silicon nanomaterial and performing the same procedure as in application example 1.
The button cell obtained in comparative example 1 was tested for cyclic voltammograms as in application example 1 and the cyclic voltammograms are shown in figure 3. As can be seen from fig. 3, at the 1 st cycle, two reduction peaks occurring between 0.5 and 1.2V are electrolyte decomposition and SEI film formation, a broad peak formed around 0.25V is a lithium intercalation process, an oxidation peak corresponding to around 0.5V is a lithium deintercalation process, and the intensity of the oxidation peak in the subsequent cycle increases, indicating that the electrode material is sufficiently activated.
The button cell obtained in the example 1 and the comparative example 1 were subjected to charge and discharge tests, and the obtained charge and discharge curves are shown in fig. 4 and 5, wherein fig. 4 is a charge and discharge curve chart of the button cell prepared in the example 1 and fig. 5 is a charge and discharge curve chart of the button cell prepared in the comparative example 1. As can be seen from fig. 4 and 5, in fig. 4, in the first discharge curve, the plateau in the range of 1.0-0.05V corresponds to the formation of SEI film, and in the subsequent longer plateau is the conversion of crystalline silicon to amorphous silicon, and in fig. 5, the first discharge curve of the button cell made of commercial silicon also has two voltage plateaus. In the first circulation, the discharge specific capacity and the charge specific capacity of the button cell obtained by applying the silicon nano material prepared from vermiculite in example 1 are 674.3mAh/g and 445.2mAh/g respectively, and the first coulombic efficiency is 66%; the first charge-discharge specific capacity of the button cell prepared from the commercial silicon in the comparative example 1 is 1510.2Ah/g and 1692.3mAh/g respectively, the coulombic efficiency is 89.24%, the first discharge specific capacity, the charge specific capacity and the coulombic efficiency of the silicon nano material obtained from vermiculite in the application example 1 respectively reach 39.8%, 29.5% and 73.96% of those of the commercial silicon in the comparative example 1, and the button cell is superior to the first discharge specific capacity, the charge specific capacity and the coulombic efficiency of other non-commercial silicon at present, and has huge research and application prospects.
The cycling stability tests of the button cells obtained in the application example 1 and the button cell obtained in the comparative example 1 are shown in fig. 6 and 7, wherein fig. 6 is a graph of the cycling performance of the button cell prepared in the application example 1, and fig. 7 is a graph of the cycling performance of the button cell prepared in the comparative example 1. As can be seen from fig. 6 and 7, after 10 charge-discharge cycles, the specific capacity of the silicon nanomaterial provided in application example 1 is almost unchanged, the curve is relatively stable, and the coulombic efficiency is maintained at about 99.7%; the commercial silicon provided in comparative example 1 was in a slow decreasing trend of specific capacity in the first 60 cycles and was maintained in a steady state after 60 cycles. The test result shows that the silicon nano material obtained by the preparation method provided by the invention has good lithium storage performance and cycling stability.
Example 2
Mixing 6.25g of vermiculite particles with hydrochloric acid with the concentration of 2 mol/L of 250m L, stirring the obtained mixed system for 8 hours at the constant temperature of 80 ℃ by using a heat collection type magnetic stirrer, cooling to the room temperature, filtering and washing solids for a plurality of times by using deionized water until the pH value is 6.5, and putting the mixed system in a vacuum drying oven for vacuum drying for 12 hours at the temperature of 100 ℃ to obtain blocky vermiculite;
cooling 1.0g of the obtained blocky vermiculite to room temperature, uniformly mixing the blocky vermiculite with 1.0g of magnesium powder, placing the mixture in a quartz tube furnace, heating the mixture from the room temperature to 650 ℃ at the speed of 5 ℃/min in a high-purity argon atmosphere with the purity of 99.999%, and then preserving the heat for 7 hours to obtain 1.4g of powdery reduction product;
dropwise adding hydrochloric acid with the concentration of 2 mol/L into the obtained reduction product at the dropwise adding rate of 0.02m L/s until the reduction product is completely soaked (the use amount of the hydrochloric acid is 40m L), then stirring for 12h at room temperature by using a magnetic stirrer, pouring into a centrifuge tube, carrying out high-speed centrifugal separation for 10min at the rotation speed of 10000prm, carrying out vacuum drying on the obtained solid product for 12h at the temperature of 60 ℃, washing for several times by using hydrofluoric acid with the mass percentage of 1%, carrying out centrifugal separation for 10min at the rotation speed of 10000rpm, and carrying out vacuum drying for 12h at the temperature of 60 ℃ to obtain the silicon nano material.
SEM test of the obtained silicon nano material was carried out by using a scanning electron microscope of Thermo scientific type Apreo S, and the SEM image is shown in FIG. 8. As can be seen from FIG. 8, the silicon nanomaterial provided by the invention maintains the original 2D layered structure of vermiculite.
The obtained silicon nanomaterial was subjected to XRD measurement using an X-ray diffractometer (D8Advance) of Bruker, Germany, and the obtained XRD pattern was shown in FIG. 9. As can be seen from fig. 9, both the diffraction peak intensity and the peak position of the silicon nanomaterial prepared in this example 2 are consistent with those of standard silicon (standard card number: PDF #27-1402), wherein the diffraction peaks at 28.5 °, 47.2 °, 56.1 °, 69.2 °, and 76.5 ° are respectively attributed to the (111), (220), (311), (400), and (331) crystal planes of the cubic Si phase, which proves that silicon with higher purity is obtained based on the above preparation method.
Application example 2
The button cell was prepared by using the silicon nanomaterial obtained in example 2 instead of the silicon nanomaterial obtained in application example 1.
The electrochemical performance of the button cell obtained in application example 2 was tested in the same manner as in application example 1, and the cyclic voltammogram obtained is shown in FIG. 10. As can be seen from fig. 10, the button cell obtained from the silicon nanomaterial obtained in example 2 of the present invention has an obvious reduction peak at 0.65V, and disappears in subsequent cycles, indicating that it is electrolyte decomposition and SEI film formation, and the oxidation peak appearing at about 0.25 to 0.52V is gradually clear with the increase of cycle number, indicating that it has good reversibility.
The ac impedance test was performed on the button cell obtained in example 2 and comparative example 1, and the test results are shown in fig. 11 to 13, where fig. 11 is an ac impedance graph of the button cell prepared in application example 2, fig. 12 is an ac impedance graph of the button cell prepared in comparative example 1, and fig. 13 is an ac impedance graph of the button cell prepared in example 2 and the button cell prepared in comparative example 1 after 10 times of charging and discharging, and it can be seen from fig. 11 to 13 that the button cells obtained in application example 2 and comparative example 1 both show a decreasing trend in resistance value with increasing number of charging and discharging times, mainly because the electrode is fully activated after many cycles, L i is increased+The de-intercalation rate, wherein the button cell prepared from the silicon nanomaterial of example 2 has a resistance value of 133 Ω after 10 charge-discharge cycles and the button cell of comparative example 1 has a resistance value of 204 Ω, indicates that the silicon nanomaterial provided by the present invention has a lower resistance and a faster charge transfer rate than commercial silicon.
The button cell obtained in example 2 was subjected to a charge and discharge test, and the charge and discharge curves obtained are shown in fig. 14. As can be seen from fig. 14, the initial charge and discharge capacities of the button cell obtained from the silicon nanomaterial prepared according to the present invention were 210.1mAh/g and 297.5mAh/g, respectively, and the initial charge and discharge capacities reached 13.9% and 17.6% of the button cell prepared from commercial silicon of comparative example 1, respectively; the initial coulombic efficiency of the button cell obtained from the silicon nanomaterial prepared by the invention is 70.63%, which reaches 79.15% of the button cell obtained from commercial silicon of comparative example 1.
The button cell obtained in the application example 2 was subjected to a cycle performance test, and the test results are shown in fig. 15. As can be seen from fig. 15, after 100 cycles, the charge and discharge capacities of the button cell obtained from the silicon nanomaterial prepared by the present invention are 111.4mAh/g and 111.7mAh/g, respectively, and the coulomb efficiency is 99.71%.
Example 3
Mixing 6.25g of vermiculite particles with hydrochloric acid with the concentration of 250m L of 4 mol/L, stirring the obtained mixed system for 16 hours at the constant temperature of 80 ℃ by using a heat collection type magnetic stirrer, cooling to the room temperature, filtering and washing solids for a plurality of times by using deionized water until the pH value is 6.5, and putting the mixed system in a vacuum drying oven for vacuum drying for 12 hours at the temperature of 100 ℃ to obtain blocky vermiculite;
cooling 1.0g of the obtained blocky vermiculite to room temperature, uniformly mixing the blocky vermiculite with 1.0g of magnesium powder, placing the mixture in a quartz tube furnace, heating the mixture from the room temperature to 650 ℃ at the speed of 5 ℃/min in a high-purity argon atmosphere with the purity of 99.999%, and then preserving the heat for 7 hours to obtain 1.35g of powdery reduction product;
dropwise adding hydrochloric acid with the concentration of 2 mol/L into the obtained reduction product at the dropwise adding rate of 0.02m L/s until the reduction product is completely soaked (the use amount of the hydrochloric acid is 50m L), then stirring for 12h at room temperature by using a magnetic stirrer, pouring into a centrifuge tube, carrying out high-speed centrifugal separation for 10min at the rotation speed of 10000prm, carrying out vacuum drying on the obtained solid product for 12h at the temperature of 60 ℃, washing for several times by using hydrofluoric acid with the mass percentage of 1%, carrying out centrifugal separation for 10min at the rotation speed of 10000rpm, and carrying out vacuum drying for 12h at the temperature of 60 ℃ to obtain the silicon nano material.
Application example 3
The button cell was prepared by using the silicon nanomaterial obtained in example 3 instead of the silicon nanomaterial obtained in application example 1.
And (3) carrying out charge and discharge tests on the button cell obtained in the example 3, wherein the obtained charge and discharge curve is shown in figure 16. As can be seen from fig. 16, the initial charge and discharge capacities of the button cell obtained from the silicon nanomaterial prepared according to the present invention were 488.2mAh/g and 721.5mAh/g, respectively, and the initial charge and discharge capacities reached 32.3% and 42.6% of the button cell prepared from commercial silicon of comparative example 1, respectively; the initial coulombic efficiency of the button cell obtained from the silicon nanomaterial prepared by the invention is 67.66%, which reaches 75.8% of the button cell obtained from commercial silicon of comparative example 1.
The button cell obtained in the application example 3 was subjected to a cycle performance test, and the test result is shown in fig. 17. As can be seen from fig. 17, after 100 cycles, the charge and discharge capacities of the button cell obtained from the silicon nanomaterial prepared by the present invention were 77.8mAh/g and 77.6mAh/g, respectively, and the coulombic efficiency was 99.7%. After 10 cycles, the charge-discharge specific capacity of the button cell obtained in the application example 3 tends to be in a stable state, and the button cell has certain cycle stability.
The foregoing is only a preferred embodiment of the present invention, and it should be noted that, for those skilled in the art, various modifications and decorations can be made without departing from the principle of the present invention, and these modifications and decorations should also be regarded as the protection scope of the present invention.

Claims (10)

1. A preparation method of a silicon nano material is characterized by comprising the following steps:
mixing vermiculite and magnesium, and carrying out thermal reduction reaction to obtain a reduction product, wherein the reduction product comprises silicon and magnesium oxide;
and carrying out acid leaching on the reduction product, and drying the product of the acid leaching to obtain the silicon nano material.
2. The preparation method according to claim 1, wherein the mass ratio of the vermiculite to the magnesium is 1: (0.5-2).
3. The preparation method according to claim 1 or 2, wherein the temperature of the thermal reduction reaction is 600-700 ℃ and the time is 6-8 h; the rate of heating to the temperature of the thermal reduction reaction is 2-8 ℃/min; the atmosphere of the thermal reduction reaction is inert atmosphere.
4. The preparation method according to claim 1, wherein the acid used for acid leaching is hydrochloric acid, nitric acid or sulfuric acid, and the concentration of the acid used for acid leaching is 1-3 mol/L.
5. The production method according to claim 1 or 4, wherein the mass ratio of the reduced product to the acid for acid leaching is 1: (8-12).
6. The preparation method according to claim 1 or 4, wherein the acid leaching temperature is 20-30 ℃ and the time is 10-14 h.
7. The preparation method according to claim 1, wherein the drying temperature is 50-70 ℃ and the drying time is 12-14 h.
8. The production method according to claim 1, wherein the drying further comprises subjecting the dried product to hydrofluoric acid washing, solid-liquid separation, and final drying in this order.
9. The silicon nanomaterial prepared by the preparation method of any one of claims 1 to 8, wherein the silicon nanomaterial has a 2D layered structure; the single-layer thickness of the nano material is 4-10 nm.
10. Use of the silicon nanomaterial of claim 9 as an anode material in a lithium ion battery.
CN202010355603.9A 2020-04-29 2020-04-29 Silicon nano material and preparation method and application thereof Pending CN111509217A (en)

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Citations (3)

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Publication number Priority date Publication date Assignee Title
JP2010100442A (en) * 2008-10-21 2010-05-06 Nozawa Corp Method for producing cordierite
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Publication number Priority date Publication date Assignee Title
JP2010100442A (en) * 2008-10-21 2010-05-06 Nozawa Corp Method for producing cordierite
CN104577082A (en) * 2015-01-09 2015-04-29 南京大学 Nano-silicon material and application thereof
CN110534710A (en) * 2019-07-15 2019-12-03 同济大学 Silicon/carbon composite and its preparation method and application

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