CN116759558A - Silicon anode material with sub-nano structure and preparation method and application thereof - Google Patents
Silicon anode material with sub-nano structure and preparation method and application thereof Download PDFInfo
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- XUIMIQQOPSSXEZ-UHFFFAOYSA-N Silicon Chemical compound [Si] XUIMIQQOPSSXEZ-UHFFFAOYSA-N 0.000 title claims abstract description 105
- 229910052710 silicon Inorganic materials 0.000 title claims abstract description 105
- 239000010703 silicon Substances 0.000 title claims abstract description 105
- 239000002086 nanomaterial Substances 0.000 title claims abstract description 32
- 239000010405 anode material Substances 0.000 title claims abstract description 18
- 238000002360 preparation method Methods 0.000 title claims abstract description 12
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 claims abstract description 107
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- 238000000034 method Methods 0.000 claims abstract description 28
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- 239000010410 layer Substances 0.000 claims abstract description 26
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- HBMJWWWQQXIZIP-UHFFFAOYSA-N silicon carbide Chemical compound [Si+]#[C-] HBMJWWWQQXIZIP-UHFFFAOYSA-N 0.000 claims abstract description 23
- 239000013078 crystal Substances 0.000 claims abstract description 19
- 239000000758 substrate Substances 0.000 claims abstract description 18
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- 238000000197 pyrolysis Methods 0.000 claims description 6
- WHXSMMKQMYFTQS-UHFFFAOYSA-N Lithium Chemical compound [Li] WHXSMMKQMYFTQS-UHFFFAOYSA-N 0.000 claims description 4
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- 239000005543 nano-size silicon particle Substances 0.000 claims description 4
- VGGSQFUCUMXWEO-UHFFFAOYSA-N Ethene Chemical compound C=C VGGSQFUCUMXWEO-UHFFFAOYSA-N 0.000 claims description 3
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- SWQJXJOGLNCZEY-UHFFFAOYSA-N helium atom Chemical compound [He] SWQJXJOGLNCZEY-UHFFFAOYSA-N 0.000 claims description 2
- NEXSMEBSBIABKL-UHFFFAOYSA-N hexamethyldisilane Chemical compound C[Si](C)(C)[Si](C)(C)C NEXSMEBSBIABKL-UHFFFAOYSA-N 0.000 claims description 2
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- 102000004310 Ion Channels Human genes 0.000 description 1
- 229910001290 LiPF6 Inorganic materials 0.000 description 1
- FKNQFGJONOIPTF-UHFFFAOYSA-N Sodium cation Chemical compound [Na+] FKNQFGJONOIPTF-UHFFFAOYSA-N 0.000 description 1
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Classifications
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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
- H01M4/362—Composites
- H01M4/366—Composites as layered products
-
- 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
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M4/00—Electrodes
- H01M4/02—Electrodes composed of, or comprising, active material
- H01M4/36—Selection of substances as active materials, active masses, active liquids
- H01M4/38—Selection of substances as active materials, active masses, active liquids of elements or alloys
- H01M4/386—Silicon or alloys based on silicon
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M4/00—Electrodes
- H01M4/02—Electrodes composed of, or comprising, active material
- H01M4/62—Selection of inactive substances as ingredients for active masses, e.g. binders, fillers
- H01M4/624—Electric conductive fillers
- H01M4/625—Carbon or graphite
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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
- H01M2004/026—Electrodes composed of, or comprising, active material characterised by the polarity
- H01M2004/027—Negative electrodes
Abstract
The invention belongs to the technical field of batteries, and provides a silicon anode material with a sub-nano structure, a preparation method and application thereof. The invention adopts a plasma gas phase method in-situ synthesis method to prepare a sub-nano structure silicon anode material consisting of a graphene/amorphous carbon substrate, a sub-nano structure silicon crystal grain, a carbon/silicon carbide composite material layer and a graphene/amorphous carbon coating layer; and introducing carbon source gas immediately after the nucleation of Si to prevent the growth of Si, so as to form sub-nanometer Si. And while forming a plurality of Si-C bonds, the Si-Si bonds are prevented from forming, and the finally formed sub-nano-scale silicon negative electrode composite material shows controllable high capacity and coulombic efficiency and excellent cycle stability. And the plasma gas phase synthesis method is simple and efficient, and is suitable for large-scale industrial production. Effectively solves the problem of silicon volume expansion.
Description
Technical Field
The invention belongs to the technical field of batteries, relates to a negative electrode material of a sodium ion battery, and particularly relates to a silicon negative electrode material with a sub-nano structure, and a preparation method and application thereof.
Background
The disclosure of this background section is only intended to increase the understanding of the general background of the invention and is not necessarily to be construed as an admission or any form of suggestion that this information forms the prior art already known to those of ordinary skill in the art.
Replacement of conventional graphite anodes with high capacity materials is the most promising approach to achieve higher energy high density lithium ion batteries. Silicon (Si) reacts with lithium through an alloying reaction and is considered as a viable candidate due to its high specific capacity (3592 mAh/g), however, silicon suffers from serious structural degradation and instability of Solid Electrolyte Interphase (SEI) during lithiation or delithiation due to a large volume fluctuation. These can not only cause the particles to break and lose electrical contact with the electrode system, but can also mechanically disrupt the stable formation of the SEI layer and constantly expose new surfaces of the material to the electrolyte.
The atmospheric thermal plasma is a magnetically rotating dispersed arc plasma in which the high temperature region of the arc is an ionized gas in a thermodynamic equilibrium state. Such an environment provides unique heat flow, including electrons and heavy particles. The nanometer material synthesized by the plasmas has the advantages of simple synthesis steps, economic synthesis raw materials, high synthesis efficiency and the like, and is extremely suitable for industrial production or exploration of industrial production. The nano materials which are prepared in large scale by the method at present are carbon black, graphene, fullerene, carbon nano tube, silicon carbide and the like.
To alleviate the problem of silicon volume expansion, over the last decade of research has shown that reducing the silicon feature size to the nanometer scale can subject silicon to tremendous dimensional strain without fracturing. Also, combining silicon with other elements into a carbon material substrate is not a strategy for synthesizing small-sized silicon, and various carbonaceous materials including graphite, graphene and amorphous carbon have been used as buffer matrices for silicon composite materials to mitigate volume changes, prevent direct exposure of Si surfaces to electrolytes and provide conductive paths. However, their structure is not strong enough to withstand severe volume fluctuations and is prone to fracture during long-term cycling.
The silicon-based material adopted in the industry is compounded with two modes, one is as in patent CN114388770A, silicon simple substance and silicon dioxide are used as initial raw materials, gas silicon oxide is generated through a centering reaction, the gas silicon oxide reacts with reducing gas at high temperature to obtain silicon oxide with high silicon-oxygen ratio, the silicon oxide is processed through a grinding process to obtain micron-sized silicon oxide powder with concentrated and uniform granularity, and a uniform carbon layer is coated by carbon coating. Also, as in patent CN116154141a, a silicon-carbon material is obtained by depositing silane on a porous carbon skeleton by vapor deposition reaction using a silicon-containing gas as a raw material; alternatively, as in patent CN115732666a, in a thermal plasma processing apparatus, silicon vapor is deposited in the pores of the through-holes of porous carbon microspheres to obtain a precursor material.
In the above patent documents, a silicon-oxygen-based negative electrode material is synthesized by synthesizing a silicon-oxygen precursor and carbon-coating, and a silicon-carbon-based negative electrode material is synthesized by vapor phase silane deposition of a porous carbon precursor. Although the intrinsic volume expansion of silicon is alleviated to some extent, the high specific surface area does not solve the problem that when the silicon volume is reduced, serious interface side reaction occurs, the consumption of active lithium ions causes the reduction of specific capacity, the ion and electron conductivity is hindered, and the irreversible phase is induced.
Disclosure of Invention
In order to solve the problems, the invention provides a silicon anode material with a sub-nano structure and a preparation method thereof. According to the invention, after the nucleation of Si, carbon source gas is immediately introduced to prevent the growth of Si, so that sub-nanometer Si is formed. And while forming a plurality of Si-C bonds, the Si-Si bonds are prevented from forming, and the finally formed sub-nano-scale silicon negative electrode composite material shows controllable high capacity and coulombic efficiency and excellent cycle stability. And the plasma gas phase synthesis method is simple and efficient, and is suitable for large-scale industrial production.
In order to achieve the above purpose, the present invention adopts the following technical scheme:
in a first aspect of the present invention, there is provided a sub-nanostructure silicon negative electrode material comprising:
a graphene/amorphous carbon substrate;
the graphene/amorphous carbon substrate is loaded with sub-nano structure silicon grains and a carbon/silicon carbide composite material layer, wherein the sub-nano silicon grains are distributed on the graphene/amorphous carbon substrate, the silicon grain size is between 0.8 and 4nm, the thickness of the silicon layer is between 15 and 25nm, and the silicon carbide and the carbon composite material are distributed in gaps between the silicon grains;
and the sub-nano structure silicon crystal grain and the carbon/silicon carbide composite material layer are loaded with a graphene/amorphous carbon coating layer.
The graphene/amorphous carbon outer coating layer provided by the structure provides a good lithium ion channel and rich conductive paths, so that the material has good ion conductivity and electron conductivity while the silicon crystal grains are not in direct contact with electrolyte; the distribution of the silicon crystal grains at the sub-nanometer level ensures the expansion space of silicon-lithium alloying, and avoids cracks or crushing caused by volume expansion in the circulation process; the silicon carbide/carbon skeleton dispersed between the silicon layers not only isolates and inhibits the growth of silicon sub-nano grains, but also forms a good plane conductive network, enhances the electronic conductivity of the material and reduces the internal resistance.
In a second aspect of the present invention, there is provided a method for preparing a silicon anode material having a sub-nanostructure, comprising:
introducing carbon source gas into the plasma region for pyrolysis, and depositing the formed solid in a collecting chamber to obtain the graphene/amorphous carbon substrate;
stopping introducing the carbon source gas, introducing the silicon source gas into the plasma region for pyrolysis, starting to gradually reduce the flow of the silicon-containing gas after 15-20 min of operation, simultaneously introducing the carbon source gas, and gradually increasing the flow of the carbon source gas until the silicon source gas is not introduced any more and the flow of the carbon source gas reaches the maximum value, wherein the formed solid is deposited on the graphene/amorphous carbon substrate, namely: a sub-nanostructured silicon grain and a carbon/silicon carbide composite layer;
continuously sending carbon source gas into a plasma region for pyrolysis, and depositing formed solid on the silicon crystal grains with the sub-nano structure and the carbon/silicon carbide composite material layer, wherein the method comprises the following steps: and (5) coating the graphene/amorphous carbon coating layer to obtain the graphene/amorphous carbon coating layer.
In some embodiments, the plasma current parameter is set in the range of 60A to 150A, the plasma voltage is in the range of 30-70V, and the input power is 4-10 kW.
In some embodiments, the plasma current parameter is 120-150A, the voltage range is 55-70V, and the input power is 7-9 kW when the graphene/amorphous carbon substrate and the graphene/amorphous carbon coating are formed.
In some embodiments, when forming the sub-nanostructure silicon grains and carbon/silicon carbide composite layer, the plasma current parameter is 90-120A, the voltage range is 35-50V, and the input power is 4-5 kW.
In some embodiments, before the carbon source gas or the silicon source gas is introduced for the first time, a buffer gas is introduced, and the flow rate of the buffer gas is 30-40 slm; purifying for 5-8 min.
In some embodiments, the flow rate of the carbon source gas is 5 to 10slm for 15 to 20 minutes during the preparation of the graphene/amorphous carbon substrate.
In some embodiments, in the process of preparing the silicon crystal grains with the sub-nano structure and the carbon/silicon carbide composite material layer, firstly, introducing silicon source gas, wherein the flow is 5-10 slm, and keeping for 15-20 minutes; and then, within 15-20 minutes, gradually reducing the flow rate of the silicon source gas to 0slm, and gradually increasing the flow rate of the carbon source gas from 0 to 5-10 slm.
In some embodiments, the carbon source gas flow is 5-10 slm and is maintained for 15-20 minutes during the preparation of the graphene/amorphous carbon coating.
In some embodiments, the carbon source is comprised of a carbon-containing gas consisting essentially of one or both of methane, ethylene, ethane, propane, and acetylene gas (99.99% purity); preferably, a high hydrocarbon ratio feed gas such as ethane will produce a more planar morphology of the carbon structure and a low hydrocarbon ratio feed gas such as acetylene will produce a more irregular carbon structure.
In some embodiments, the silicon source is comprised of a silicon-containing gas consisting essentially of one or both of silane or hexamethyldisilane gas (99.99% purity); preferably, the silane should be used in the production of silicon grains to avoid carbon-silicon bond formation.
In some embodiments, the buffer gas is used to remove residual feedstock atmosphere and impurity gases in the plasma reactor, and the arc plasma is ignited, consisting of one of helium or argon (99.99% purity).
More specifically, the method comprises the following steps:
preparation of graphene/amorphous carbon substrate: first, the plasma generator and the collection chamber are purged with a buffer gas. Then, an arc plasma was ignited in a pure buffer gas, and after the plasma was operated for 5 minutes, a carbon source gas was continuously fed into the plasma region. The gas pyrolyzes in the plasma zone to form solid and gaseous products. The solid powder precipitated in the collection chamber is a graphene/amorphous carbon substrate and the gaseous by-products are vented to the atmosphere.
Preparing a silicon crystal grain with a sub-nano structure and a carbon/silicon carbide composite material: and continuously introducing buffer gas into the plasma generator, igniting arc plasma in the pure buffer gas after the purification is finished, introducing silicon-containing precursor gas after the plasma is operated for 5 minutes, pyrolyzing the silicon-containing precursor gas in a plasma region to form solid and gas products, gradually reducing the flow rate of the silicon-containing gas after the plasma is operated for a period of time, starting to introduce a small amount of carbon source gas, gradually increasing the flow rate of the gas, and finally, not introducing the silicon-containing gas and enabling the flow rate of the carbon source gas to reach the maximum value.
Preparing an outer layer graphene/amorphous carbon coating: and continuously introducing carbon source gas into the plasma generator, closing the plasma after the reactor is operated for a period of time, and collecting the product of the collecting chamber.
In a third aspect, the invention provides an application of the sub-nanostructure silicon negative electrode material or the sub-nanostructure silicon negative electrode material prepared by the method in preparation of a lithium battery.
The beneficial effects of the invention are that
(1) The invention provides an in-situ synthesis method by a plasma gas phase method, which is characterized in that carbon source gas is immediately introduced after Si is nucleated to prevent the growth of Si, so that sub-nanometer Si is formed. And the formation of Si-Si bonds is prevented while a plurality of Si-C bonds are formed, and the finally formed sub-nano silicon anode composite material.
(2) The synthesized sub-nano silicon anode composite material provided by the invention has controllable high capacity and coulombic efficiency and excellent cycle stability. And the plasma gas phase synthesis method is simple and efficient, and is suitable for large-scale industrial production.
Drawings
The accompanying drawings, which are included to provide a further understanding of the invention and are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and together with the description serve to explain the invention.
Fig. 1 is a schematic diagram showing the structure of a sub-nano-scale silicon anode material of the present invention.
Fig. 2 is a schematic diagram showing a magnetic rotating arc plasma generator used in the present invention.
Detailed Description
It should be noted that the following detailed description is exemplary and is intended to provide further explanation of the invention. Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs.
The invention will now be described in further detail with reference to the following specific examples, which should be construed as illustrative rather than limiting.
Example 1
And (3) combining the plasma reactor and the collecting chamber, introducing buffer gas argon, and setting the flow to be 30slm, and continuing until the experiment is finished. After the chamber was sufficiently purged, the arc plasma was ignited, current 120A was set, then ethane gas was flowed, the flow rate was set to 10slm, for 15 minutes and then stopped. The plasma generator was turned off, the plasma was ignited after resting for 5 minutes, the current level was set to 90A, then 5slm silane was introduced and stopped after 15 minutes. The plasma generator was turned off, the plasma was ignited after 5 minutes of rest, then 10slm of ethane gas was vented, and stopped after 15 minutes. The plasma generator was turned off and the chamber was cooled by argon flow for 5 minutes. The collection chamber is then opened and the product is collected to yield a silicon composite.
The thickness of the carbon layer in the sample is 10-20 nm, the thickness of the silicon layer is 30-50 nm, the size of silicon crystal grains is 10-20 nm, the arrangement is disordered, and the size distribution is uneven.
Example 2
And (3) combining the plasma reactor and the collecting chamber, introducing buffer gas argon, and setting the flow to be 30slm, and continuing until the experiment is finished. After the chamber was sufficiently purged, the arc plasma was ignited, current 120A was set, then ethane gas was vented, the flow rate was set to 10slm, and then stopped for 5 minutes. The plasma generator was turned off, plasma was ignited after 5 minutes of rest, current level 90A was set, then 10slm silane was introduced, after 5 minutes of duration, silane gas flow was reduced while ethane was introduced, silane flow was reduced from 10slm to 0slm, ethane flow was increased from 0slm to 10slm, and acceleration and deceleration were maintained constant. The ethane flow was then maintained at 10slm for 5 minutes, the plasma generator was turned off, and the chamber was cooled by argon flow for 5 minutes. The collection chamber is then opened and the product is collected to yield a silicon composite.
The process of ethane inhibition of silicon grain growth was increased compared to example 1. The thickness of the carbon layer is 2-8 nm, the thickness of the silicon layer is 10-20 nm, the size of the silicon crystal grains is 0.8-2.5 nm, the arrangement is uniform, and amorphous phase silicon carbide and carbon structures are distributed among the silicon crystal grains.
Example 3
And (3) combining the plasma reactor and the collecting chamber, introducing buffer gas argon, and setting the flow to be 30slm, and continuing until the experiment is finished. After the chamber was sufficiently purged, the arc plasma was ignited, the current 150A was set, then ethane gas was introduced, the flow rate was set to 10slm, and then stopped for 5 minutes. The plasma generator was turned off, plasma was ignited after resting for 5 minutes, current level 120A was set, then 10slm silane was introduced, after 5 minutes, silane gas flow was reduced while ethane was introduced, silane flow was reduced from 10slm to 0slm, ethane flow was increased from 0slm to 10slm, and acceleration and deceleration were maintained constant. The ethane flow was then maintained at 10slm for 5 minutes, the plasma generator was turned off, and the chamber was cooled by argon flow for 5 minutes. The collection chamber is then opened and the product is collected to yield a silicon composite.
Compared with example 2, the plasma discharge current and discharge power were increased. At this time, the thickness of the carbon layer is 10-15 nm, the thickness of the silicon layer is 15-25 nm, the size of the silicon crystal grains is 2-5 nm, the arrangement is uniform, and amorphous phase silicon carbide and carbon structures are distributed among the silicon crystal grains.
Example 4
And (3) combining the plasma reactor and the collecting chamber, introducing buffer gas argon, and setting the flow to be 30slm, and continuing until the experiment is finished. After the cavity is fully purified, the arc plasma is ignited, the current 90A is set, then 10slm silane is introduced, after 5 minutes, the silane gas flow is reduced, and simultaneously ethane is introduced, in 10 minutes, the silane flow is reduced from 10slm to 0slm, the ethane flow is increased from 0slm to 10slm, and the speed-up and the speed-down are kept constant. The plasma generator was turned off and the chamber was cooled by argon flow for 5 minutes. The collection chamber is then opened and the product is collected to yield a silicon composite.
The process of carbon interlayer formation was subtracted compared to example 2. The thickness of a silicon layer in a high-definition transmission electron microscope image of the tested silicon/silicon carbide/carbon structure is 15-25 nm, the size of silicon crystal grains is 1.5-3 nm, the arrangement is uniform, and amorphous phase silicon carbide and carbon structures are distributed among the silicon crystal grains.
Comparative example 1
The comparative example provides a preparation method of a silicon-carbon anode material, which specifically comprises the following steps:
s1, depositing mixed gas of silane gas and olefin gas on porous carbon, particularly on a pore wall by adopting a chemical vapor deposition method to obtain powder I;
s2, discharging mixed gas remained in the deposition equipment after deposition by using argon, then introducing methane gas to coat the powder I with carbon for the first time, crushing and grading, and then introducing methane or acetylene gas to coat the powder II with carbon for the second time;
s3, uniformly coating the high molecular polymer on the surface of the powder II by using a spray drying method to form a continuous, uniform and compact high molecular polymer coating layer, and thus obtaining the silicon-carbon anode material.
Wherein the olefin gas is ethylene.
Wherein the addition amount of the olefin gas is 0.5% of the volume of the silane gas.
Wherein, in step S1, the processing temperature of the mixed gas deposition is 850 ℃.
Wherein in step S1, the gas flow rate of the mixed gas deposition is 2m 3 /min。
In step S1, the process time of the mixed gas deposition is 10 hours.
Wherein, in step S1 and step S2, a chemical vapor deposition furnace is adopted for deposition.
Wherein, in step S1, the volume of the porous carbon accounts for 65% of the volume of the furnace chamber of the chemical vapor deposition furnace.
Wherein, in step S2, the treatment temperature of the first carbon coating is 950 ℃.
Wherein in step S2, the gas flow rate of the first carbon-coated gas is 3m 3 /min。
In step S2, the treatment time for the first carbon coating is 4h.
Wherein, in step S2, the crushing classification is performed at room temperature in air.
Wherein, in step S2, the particle size obtained by crushing and classifying is 3 μm.
Wherein, in step S2, the treatment temperature of the second carbon coating is 850 ℃.
Wherein in step S2, the gas flow rate of the second carbon coating is 3m 3 /min。
In step S2, the second carbon-coated treatment time is 8h.
Wherein, in step S3, the spray drying temperature is 350 ℃.
Comparative example 2
The difference from example 1 is that no ethane was fed during the silane feed. The method comprises the following specific steps: and (3) combining the plasma reactor and the collecting chamber, introducing buffer gas argon, and setting the flow to be 30slm, and continuing until the experiment is finished. After the chamber was sufficiently purged, the arc plasma was ignited, current 120A was set, then ethane gas was vented, the flow rate was set to 10slm, and then stopped for 5 minutes. The plasma generator was turned off, the plasma was ignited after resting for 5 minutes, the current level was set at 90A, then 10slm silane was introduced, after 5 minutes, the silane gas flow was reduced, and within 10 minutes, the silane flow was reduced from 10slm to 0slm, keeping the deceleration constant. Then 10slm of ethane was introduced for 5 minutes, the plasma generator was turned off, and the chamber was cooled by argon flow for 5 minutes. The collection chamber is then opened and the product is collected to yield a silicon composite.
Test examples
Batteries were prepared by using the silicon anode materials provided in examples 1 to 4 and comparative example 1, and specific steps for preparing batteries include:
mixing and dissolving a silicon negative electrode material, a conductive agent and a binder in a solvent according to a mass ratio of 94:2:4, controlling the solid content to be 50%, coating the mixture on a copper foil current collector, and vacuum drying to prepare a button cell assembled by a negative electrode plate, an electrolyte, an SK diaphragm, a lithium plate and a shell by adopting a conventional production process; wherein, the solvent of the electrolyte is Ethylene Carbonate (EC) and dimethyl carbonate (DMC) and ethylene carbonate (EMC) in the volume ratio of 1:1:1; the solute is LiPF6, and the concentration of the solute is 1mol/L; on the battery test system, the electrical performance of the battery is tested. The test conditions were: at normal temperature, 0.1C constant current charge and discharge, the charge and discharge cut-off voltage is 0.01V-1.5V, and the test results are shown in Table 1.
Table 1 comparison of the comparative properties of examples and comparative examples
As can be seen from table 1, the electrical properties of the silicon carbon negative electrode materials prepared in examples 1 to 4 are superior to those of comparative example 1, and the silicon crystal grain size is small. The silicon of examples 2 to 4, which underwent carbon inhibition, had smaller sub-nanocrystalline grains, and examples 1 to 3, which had carbon interlayer coating, had higher initial effects. As is evident from comparative example 2 and example 4, the composite material having sub-nanostructure silicon grains and carbon/silicon carbide has higher capacity and initial efficiency.
The above description is only of the preferred embodiments of the present invention and is not intended to limit the present invention, but various modifications and variations can be made to the present invention by those skilled in the art. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.
Claims (10)
1. A sub-nanostructured silicon anode material, comprising:
a graphene/amorphous carbon substrate;
the graphene/amorphous carbon substrate is loaded with sub-nano structure silicon grains and a carbon/silicon carbide composite material layer, wherein the sub-nano silicon grains are distributed on the graphene/amorphous carbon substrate, the silicon grain size is between 0.8 and 4nm, the thickness of the silicon layer is between 15 and 25nm, and the silicon carbide and the carbon composite material are distributed in gaps between the silicon grains;
and the sub-nano structure silicon crystal grain and the carbon/silicon carbide composite material layer are loaded with a graphene/amorphous carbon coating layer.
2. The preparation method of the silicon anode material with the sub-nano structure is characterized by comprising the following steps of:
introducing carbon source gas into the plasma region for pyrolysis, and depositing the formed solid in a collecting chamber to obtain the graphene/amorphous carbon substrate;
stopping introducing the carbon source gas, introducing the silicon source gas into the plasma region for pyrolysis, starting to gradually reduce the flow of the silicon-containing gas after 15-20 min of operation, simultaneously introducing the carbon source gas, and gradually increasing the flow of the carbon source gas until the silicon source gas is not introduced any more and the flow of the carbon source gas reaches the maximum value, wherein the formed solid is deposited on the graphene/amorphous carbon substrate, namely: a sub-nanostructured silicon grain and a carbon/silicon carbide composite layer;
continuously sending carbon source gas into a plasma region for pyrolysis, and depositing formed solid on the silicon crystal grains with the sub-nano structure and the carbon/silicon carbide composite material layer, wherein the method comprises the following steps: and (5) coating the graphene/amorphous carbon coating layer to obtain the graphene/amorphous carbon coating layer.
3. The method for preparing a silicon anode material with a sub-nano structure according to claim 2, wherein when the graphene/amorphous carbon substrate and the graphene/amorphous carbon coating layer are formed, the plasma current parameter is 120-150A, the voltage range is 55-70V, and the input power is 7-9 kW.
4. The method for preparing a silicon negative electrode material with a sub-nano structure according to claim 2, wherein when the silicon crystal grain with the sub-nano structure and the carbon/silicon carbide composite material layer are formed, the plasma current parameter is 90-120A, the voltage range is 35-50V, and the input power is 4-5 kW.
5. The method for preparing the silicon anode material with the sub-nano structure according to claim 1, wherein before the carbon source gas or the silicon source gas is introduced for the first time, buffer gas is introduced, and the flow rate of the buffer gas is 30-40 slm; purifying for 5-8 min.
6. The method for preparing a silicon anode material with a sub-nano structure according to claim 1, wherein the flow rate of the carbon source gas is 5-10 slm and the time is 15-20 minutes in the process of preparing the graphene/amorphous carbon substrate.
7. The method for preparing a silicon negative electrode material with a sub-nano structure according to claim 1, wherein in the process of preparing the silicon crystal grain with the sub-nano structure and the carbon/silicon carbide composite material layer, firstly, introducing silicon source gas with the flow rate of 5-10 slm for 15-20 minutes; and then, within 15-20 minutes, gradually reducing the flow rate of the silicon source gas to 0slm, and gradually increasing the flow rate of the carbon source gas from 0 to 5-10 slm.
8. The method for preparing a silicon anode material with a sub-nano structure according to claim 1, wherein the flow rate of carbon source gas is 5-10 slm and is kept for 15-20 minutes in the process of preparing the graphene/amorphous carbon coating layer.
9. The method for preparing a silicon negative electrode material with a sub-nano structure according to claim 1, wherein the carbon source is one or two selected from the group consisting of methane, ethylene, ethane, propane and acetylene gas;
or the silicon source is one or two of silane or hexamethyldisilane gas;
or, the buffer gas is helium or argon.
10. Use of the sub-nanostructured silicon anode material of claim 1 or the sub-nanostructured silicon anode material prepared by the method of any one of claims 2-9 in the preparation of a lithium battery.
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