CN112086630B - Preparation method of silicon monoxide composite negative electrode material and product thereof - Google Patents

Preparation method of silicon monoxide composite negative electrode material and product thereof Download PDF

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CN112086630B
CN112086630B CN202010977062.3A CN202010977062A CN112086630B CN 112086630 B CN112086630 B CN 112086630B CN 202010977062 A CN202010977062 A CN 202010977062A CN 112086630 B CN112086630 B CN 112086630B
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carbon
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chemical vapor
silicon monoxide
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CN112086630A (en
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张亚光
王振
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Yunnan lichen New Material Technology Co.,Ltd.
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    • H01M4/02—Electrodes composed of, or comprising, active material
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Abstract

The invention discloses a preparation method of a silicon monoxide composite cathode material, which takes a silicon simple substance and silicon dioxide as initial raw materials and generates silicon monoxide through a centering reaction; vaporizing the silicon monoxide, introducing the vaporized silicon monoxide into a chemical vapor deposition furnace containing a carbon material, and performing chemical vapor deposition to obtain a primary product; and finally, carrying out carbon coating to obtain the silicon oxide composite negative electrode material. The prepared composite negative electrode material has a sandwich-type sandwich structure, the carbon material is used as a core, the outer surface of the carbon material is uniformly coated with the silicon monoxide, and the outermost layer of the carbon material is coated with a uniform carbon layer. The lithium ion battery assembled by the composite cathode material has higher capacity and better cycling stability, and particularly has ultrahigh first coulombic efficiency which can reach 90 percent at most.

Description

Preparation method of silicon monoxide composite negative electrode material and product thereof
Technical Field
The invention relates to the field of lithium battery cathode materials, in particular to a preparation method of a silicon monoxide composite cathode material and a product thereof.
Background
With the vigorous development of the new energy automobile industry, higher requirements are put forward on energy storage equipment such as a lithium battery, the battery is a power source of an automobile, and the safety performance, the cruising ability, the cycling stability and the like of the battery are closely related to the cathode material of the lithium battery, so that the preparation of the cathode material of the lithium battery with more excellent performance is particularly important. However, the most advanced lithium ion batteries at present have failed to meet the increasing demand for electric vehicles and large-scale energy batteries. Silicon is considered to be the most promising candidate for replacing graphite. It is the second most abundant element in the earth crust, is environment-friendly and has ultrahigh theoretical capacity (4200 mAh/g). However, the drastic changes in volume during lithium intercalation/deintercalation have serious adverse consequences, resulting in very poor cycling stability.
Compared with a silicon simple substance, the volume expansion of the silicon oxide material in the lithium intercalation process is greatly reduced, but the silicon oxide material also has higher theoretical specific capacity (more than 2000mAh/g) and low preparation cost, so the silicon oxide material becomes a negative electrode material with great potential. However, the silicon protoxide material will be inserted in the process of lithiumGeneration of Li2O and Li4SiO4And the like, so that part of Li loses activity, and the first charge-discharge efficiency is lower (less than 70 percent), thereby seriously influencing the practical application of the Li.
Disclosure of Invention
Aiming at the problems, the invention discloses a preparation method of a silicon monoxide composite negative electrode material, and the prepared negative electrode material has higher capacity and better cycling stability, particularly has ultrahigh first coulombic efficiency, and is expected to be used as a negative electrode material of a lithium ion battery.
The specific technical scheme is as follows:
a preparation method of a silicon monoxide composite cathode material comprises the steps of taking a silicon simple substance and silicon dioxide as initial raw materials, and generating silicon monoxide through a centering reaction; vaporizing the silicon monoxide, introducing the vaporized silicon monoxide into a chemical vapor deposition furnace containing a carbon material, and performing chemical vapor deposition to obtain a primary product; and finally, carrying out carbon coating to obtain the silicon oxide composite negative electrode material.
The preparation method disclosed by the invention has the advantages that the simple substance of silicon and silicon dioxide are used as initial raw materials, the silicon monoxide is generated through the centering reaction, then the silicon monoxide is vaporized and uniformly deposited and wrapped on the surface of a carbon material in the form of gas, the silicon monoxide has smaller volume expansion and uniformly deposits the surface of the carbon material, and the carbon-coated outer layer avoids the direct contact of the silicon monoxide and an SEI layer, so that the falling and pulverization of the silicon monoxide are avoided, the loss of the silicon monoxide is reduced, and the loss of the lithium ion re-embedding and extracting process is also reduced, thereby the first coulombic efficiency is obviously improved.
The invention also improves the production equipment, connects the tubular furnace and the chemical vapor deposition furnace through a high-temperature resistant pipeline framework, leads the centering reaction to be carried out in the tubular furnace, leads the deposition of the gas phase silicon oxide to be carried out in the chemical vapor deposition furnace, leads the reactant to be fully reacted without introducing other interference impurities by respectively controlling the experimental temperature and the atmosphere and controlling the temperature rise and fall in a programmed manner, leads the silicon oxide to be introduced in a gas form and evenly deposits on the surface of the carbon material after cooling.
Experiments show that if all raw materials are put into a chemical vapor deposition furnace at one time, namely the centering reaction and the deposition of the gas-phase silicon oxide are carried out in the same equipment, the silicon oxide is mixed on the surface of the carbon material and is irregular, the formed carbon coating material has irregular shape and nonuniform thickness, is easy to pulverize and fall off to contact with an SEI film to be lost, and the first coulombic efficiency is reduced.
Preferably:
the silicon single substance is micron-grade high-purity silicon, the purity is not lower than 99.9%, and the D50 is 2-100 mu m;
the silicon dioxide is selected from micron-sized high-purity silicon dioxide, the purity is not lower than 99.9%, and the D50 is 2-100 mu m.
The raw materials with the preferred purity and particle size do not need further grinding processing, and the particles with too small size are easy to agglomerate, thus being not beneficial to the reaction.
The equation for the centering reaction is as follows:
SiO2+Si→SiOx，0＜x＜2；
preferably:
the molar ratio of the silicon simple substance to the silicon dioxide is 1-4: 1; the vaporization temperature of the silicon dioxide is close to that of the silicon monoxide, and experiments show that the molar ratio can ensure that the silicon dioxide completely reacts.
The temperature of the centering reaction is 1200-1400 ℃.
Compared with the method in the invention that the silicon simple substance and the silicon dioxide are used as raw materials, the neutral reaction in-situ preparation of the silicon oxide is used as the raw material, and the disproportionation reaction at high temperature can cause the generation of byproducts such as silicon or silicon dioxide.
The carbon material is selected from one or more of graphite, mesocarbon microbeads, soft carbon and hard carbon.
Preferably:
the molar ratio of the silica to the carbon material is 1: 5-10; experiments show that the composite material prepared under the molar ratio has the best comprehensive performance, has less silica, does not greatly help to improve the coulombic efficiency for the first time, and has reduced electrical performance due to excessive volume expansion of the silica. More preferably, the molar ratio of the silica to the carbon material is 1: 9.
the initial temperature in the chemical vapor deposition furnace is 1200-1500 ℃, and chemical vapor deposition is carried out after the temperature is reduced. Experiments show that the setting of the initial temperature is particularly critical, and the control of the temperature can adjust the deposition rate of the silicon oxide and further control the uniformity of the silicon oxide on the surface of the carbon material. The uniform coating of the silicon monoxide on the surface of the carbon material is not facilitated by too low or too high, so that the first coulombic efficiency of the lithium ion battery assembled by the finally prepared cathode material is not ideal.
The preparation method of the porous graphite composite silicon oxide negative electrode material specifically comprises the following steps:
(1) mixing and grinding a silicon simple substance and silicon dioxide to obtain a uniformly mixed raw material mixture;
(2) heating the raw material mixture to 1200-1400 ℃ under a protective atmosphere to perform a centering reaction to generate silicon monoxide; continuing to heat until the silicon monoxide is vaporized;
(3) mixing the vaporized silicon monoxide with inert gas, introducing the mixture into a chemical vapor deposition furnace containing a carbon material, and performing chemical vapor deposition to obtain a primary product;
(4) and under a protective atmosphere, taking hydrocarbon gas as a carbon source, and carrying out carbon coating treatment on the surface of the primary product to obtain the porous graphite composite silicon oxide negative electrode material.
In the step (1):
specifically, the silicon simple substance and silicon dioxide are mixed and ground in absolute ethyl alcohol until the mixture is uniform, and then the mixture is dried at 80-100 ℃ to remove the ethyl alcohol and sieved to obtain a raw material mixture.
The mixed grinding mode is one or two of wet ball milling and sand milling.
Preferably, the mixing and grinding is selected from sanding, the rotating speed is 2000-2880 r/min, the discharging rate is 300-500L/h, and the sanding time is 2-4 h.
Preferably, the mesh number of the screen is 100-800 meshes.
In the step (2):
the protective atmosphere is selected from one or more of helium, neon, argon, krypton, xenon and radon;
heating at the rate of 3-10 ℃/min;
and continuously heating at the speed of 2-5 ℃/min to 1500-1600 ℃.
In the step (3):
preferably, the carbon material is selected from graphite, which has good electrical conductivity. More preferably porous graphite having a porous structure, which can deposit more silica, thereby further increasing the capacity.
Preferably, the porous graphite is micron-sized, D50 is 2-100 mu m, and the specific surface area is more than or equal to 50m2(ii)/g; still more preferably, the porous graphite has a D50 of 5 to 50 μm. Tests show that the porous graphite with the size is more suitable for vapor deposition of silicon monoxide, and the lithium ion battery assembled by the prepared cathode material has higher first coulombic efficiency.
The inert gas is one or more of helium, neon, argon, krypton, xenon and radon.
In order to ensure that the chemical vapor deposition is carried out under an inert atmosphere, the inert gas is only required to be excessive in the vaporized silicon monoxide.
In order to simplify the operation process and reduce the energy consumption, the temperature in the chemical vapor deposition furnace is reduced to 700-800 ℃ for chemical vapor deposition; the temperature can ensure the full proceeding of the chemical vapor deposition, and meanwhile, the temperature adjustment is not needed when the subsequent carbon coating operation is carried out. And performing chemical vapor deposition under the constant pressure of 0.1-0.3 Mpa. The pressure at this point is more favorable for deposition.
Further preferably:
in the step (2):
heating to 1300-1400 ℃ at the rate of 5-10 ℃/min;
and continuously heating at the speed of 5 ℃/min to 1550-1600 ℃.
In the step (3):
the D50 of the porous graphite is 5-20 μm, and is specifically selected from D50 ═ 15.6 μm.
The initial temperature in the chemical vapor deposition furnace is 1350-1500 ℃.
Tests show that the lithium ion battery assembled by the negative electrode material prepared under the further optimized process conditions has the initial coulombic efficiency of not less than 86 percent and can reach more than 90 percent at most. Meanwhile, the reversible specific capacity of 0.2C multiplying power discharge is close to a theoretical value.
In the step (4):
the hydrocarbon gas is selected from one or more of methane, ethane, propane, ethylene, propylene and acetylene;
the mass ratio of the hydrocarbon gas to the protective atmosphere is 1: 2-4;
the temperature of the carbon coating treatment is 700-800 ℃.
The invention also discloses the silicon monoxide composite negative electrode material prepared by the method, which has a sandwich type sandwich structure, takes a carbon material as a core, uniformly coats silicon monoxide on the outer surface of the carbon material, and coats a uniform carbon layer on the outermost layer.
Compared with the prior art, the invention has the following beneficial effects:
the invention discloses a preparation method of a silicon monoxide composite cathode material, which comprises the steps of taking a silicon simple substance and silicon dioxide as initial raw materials, generating silicon monoxide through a centering reaction, vaporizing the silicon monoxide, uniformly settling and wrapping the silicon dioxide on the surface of a carbon material in a gas form, and finally coating carbon. The prepared composite negative electrode material has a sandwich-type sandwich structure, the carbon material is used as a core, the outer surface of the carbon material is uniformly coated with the silicon monoxide, and the outermost layer of the carbon material is coated with a uniform carbon layer. The lithium ion battery assembled by the composite cathode material has higher capacity and better cycling stability, and particularly has ultrahigh first coulombic efficiency which can reach 90 percent at most.
Drawings
FIG. 1 is a Scanning Electron Microscope (SEM) picture of a primary product of porous graphite composited with silica prepared in example 1, wherein a further enlarged view is shown in the small figure;
fig. 2 is a projection electron microscope (TEM) photograph of the silica composite anode material prepared in example 1;
fig. 3 is an XRD (X-ray diffraction powder diffractometer) graph of the anode materials respectively prepared in example 1 (curve a) and comparative example 1 (curve b).
Detailed Description
The present invention will now be described in detail with reference to specific embodiments thereof, but the invention is not limited thereto.
Example 1
Mixing a high-purity silicon simple substance and high-purity silicon dioxide according to the proportion of 1: weighing 1 mol ratio, sanding for 2h in absolute ethyl alcohol at the rotating speed of 2400r/min, drying at 90 ℃ to remove the ethyl alcohol, and sieving to obtain the precursor of the mixture of the high-purity silicon simple substance and the high-purity silicon dioxide with uniform texture. And placing the mixture precursor in a high-temperature tube furnace, filling inert protective gas in the cavity under the protection of the inert gas, maintaining the pressure gauge at a constant normal pressure, heating at the speed of 5 ℃/min, heating to 1400 ℃, and keeping the temperature for 8 hours. After the reaction is completed, generating silicon monoxide, heating to 1600 ℃ at the speed of 5 ℃/min, opening an inert gas valve switch, controlling the gas flow to be 60L/h, conveying the mixed gas of the inert gas and the silicon monoxide into a chemical vapor deposition furnace with the initial temperature of 1500 ℃ and the vacuum state, and placing porous graphite (15.6 mu m for D50 and 50.2m for the specific surface area) in the chemical vapor deposition furnace2/g) the molar ratio of the high-purity silicon dioxide to the porous graphite is 1: 9, when the reading of the pressure gauge is stable, closing the gas valve of the conveying pipeline, opening the rotary switch, setting the rotating speed to be 100r/min, setting the program to enter cooling treatment, cooling to 800 ℃, closing the valve switch of the silicon oxide gas valve to obtain a porous graphite and silicon oxide composite initial product, opening the acetylene gas valve and continuously opening the inert gas protection, wherein the mass ratio of the acetylene gas to the inert gas is 1: and 2, coating the primary product with carbon, performing carbon deposition coating at 800 ℃, keeping for 4h, closing an acetylene gas valve, continuously introducing inert gas, cooling to room temperature, and taking out to obtain the porous graphite composite silicon oxide negative electrode material.
Fig. 1 is a Scanning Electron Microscope (SEM) image of the primary product prepared in this example, and it can be seen from the image that the porous graphite surface is uniformly coated with a silica layer, and the thickness is about 200nm by testing. Fig. 2 is a TEM image of the final product prepared in this example, and it can be seen from the observation of the image that the outermost side of the primary product is coated with a uniform carbon layer having a thickness of about 8 nm.
Fig. 3 is an XRD pattern of the product prepared in this example, and an XRD pattern of the product prepared in comparative example 1 is given as a comparison, and it can be seen that the comparative example 1 has a large number of phases due to the large amount of impurities and incomplete reaction.
Example 2
Mixing a high-purity silicon simple substance and high-purity silicon dioxide according to a molar ratio of 2: 1, sanding for 2 hours in absolute ethyl alcohol at a rotating speed of 2200r/min, drying at 90 ℃ to remove the ethyl alcohol, and sieving to obtain a high-purity silicon simple substance and high-purity silicon dioxide mixture precursor with uniform texture. And placing the mixture precursor in a high-temperature tube furnace, filling inert protective gas in the cavity under the protection of the inert gas, maintaining the pressure gauge at a constant normal pressure, heating at the speed of 10 ℃/min, heating to 1300 ℃, and keeping for 4 hours. After the reaction is completed, generating the silicon monoxide, heating to 1600 ℃ at the speed of 5 ℃/min, opening a gas valve switch, controlling the gas flow to be 60L/h, conveying the mixed gas of the inert gas and the silicon monoxide into a chemical vapor deposition furnace with the initial temperature of 1350 ℃ and the vacuum state, and placing the chemical vapor deposition furnace and the porous graphite (D50 is 15.6 mu m, the specific surface area reaches 50.2 m)2/g) the molar ratio of the high-purity silicon dioxide to the porous graphite is 1: 9, when the reading of the pressure gauge is stable, closing the gas valve of the conveying pipeline, opening the rotary switch, setting the rotating speed to be 100r/min, setting the program to enter cooling treatment, cooling to 800 ℃, closing the valve switch of the silicon oxide gas valve to obtain a porous graphite and silicon oxide composite initial product, opening the acetylene gas valve and continuously opening the inert gas protection, wherein the volume ratio of the acetylene gas to the inert gas is 1: 2, coating the primary product with carbon, performing carbon deposition coating at 800 ℃, keeping for 4h, closing an acetylene gas valve, continuously introducing inert gas, cooling to room temperature, and taking out to obtain the porous graphite composite silicon oxide cathodeA material.
Example 3
Mixing a high-purity silicon simple substance and high-purity silicon dioxide according to a molar ratio of 2: 1, sanding for 2 hours in absolute ethyl alcohol at a rotating speed of 2200r/min, drying at 90 ℃ to remove the ethyl alcohol, and sieving to obtain a high-purity silicon simple substance and high-purity silicon dioxide mixture precursor with uniform texture. And placing the mixture precursor in a high-temperature tube furnace, filling inert protective gas in the cavity under the protection of the inert gas, maintaining the pressure gauge at a constant normal pressure, heating at the speed of 10 ℃/min, heating to 1300 ℃, and keeping for 4 hours. After the reaction is completed, generating the silicon monoxide, heating to 1600 ℃ at the speed of 5 ℃/min, opening a gas valve switch, controlling the gas flow to be 60L/h, conveying the mixed gas of the inert gas and the silicon monoxide into a chemical vapor deposition furnace with the initial temperature of 1200 ℃ and the vacuum state, and placing the chemical vapor deposition furnace and the porous graphite (D50 is 15.6 mu m, the specific surface area reaches 50.2 m)2Per g), the mass ratio of the high-purity silicon dioxide to the porous graphite is 1: 9, when the reading of the pressure gauge is stable, closing the gas valve of the conveying pipeline, opening the rotary switch, setting the rotating speed to be 100r/min, setting the program to enter cooling treatment, cooling to 800 ℃, closing the valve switch of the silicon oxide gas valve to obtain a porous graphite and silicon oxide composite initial product, opening the acetylene gas valve and continuously opening the inert gas protection, wherein the volume ratio of the acetylene gas to the inert gas is 1: and 2, coating the primary product with carbon, performing carbon deposition coating at 800 ℃, keeping for 4h, closing an acetylene gas valve, continuously introducing inert gas, cooling to room temperature, and taking out to obtain the porous graphite composite silicon oxide negative electrode material.
Example 4
Mixing a high-purity silicon simple substance and high-purity silicon dioxide according to a molar ratio of 1: 1, sanding for 2 hours in absolute ethyl alcohol at the rotating speed of 2400r/min, drying at 90 ℃ to remove the ethyl alcohol, and sieving to obtain a high-purity silicon simple substance and high-purity silicon dioxide mixture precursor with uniform texture. And placing the mixture precursor in a high-temperature tube furnace, filling inert protective gas in the cavity under the protection of the inert gas, maintaining the pressure gauge at a constant normal pressure, heating at the speed of 5 ℃/min, heating to 1400 ℃, and keeping the temperature for 8 hours. When the reaction is complete, the silicon monoxide is generatedHeating to 1600 deg.C at 5 deg.C/min, opening gas valve with gas flow of 60L/h, delivering the mixed gas of inert gas and silicon monoxide into a chemical vapor deposition furnace with initial temperature of 1500 deg.C and vacuum state, and placing porous graphite (D50 is 30.6 μm, and specific surface area is 61.2 m)2/g) mixing, wherein the mass ratio of the silicon dioxide to the porous graphite is 1: 9, when the reading of the pressure gauge is stable, closing the gas valve of the conveying pipeline, opening the rotary switch, setting the rotating speed to be 100r/min, setting the program to enter cooling treatment, cooling to 800 ℃, closing the valve switch of the silicon oxide gas valve to obtain a porous graphite and silicon oxide composite initial product, opening the acetylene gas valve and continuously opening the inert gas protection, wherein the mass ratio of the acetylene gas to the inert gas is 1: and 2, coating the primary product with carbon, performing carbon deposition coating at 800 ℃, keeping for 4h, closing an acetylene gas valve, continuously introducing inert gas, cooling to room temperature, and taking out to obtain the porous graphite composite silicon oxide negative electrode material.
Comparative example 1
High-purity silicon simple substance and high-purity silicon dioxide are mixed according to a molar ratio of 1: 1, sanding for 2 hours in absolute ethyl alcohol at a rotating speed of 2200r/min, drying at 95 ℃ to remove the ethyl alcohol, and sieving to obtain a high-purity silicon simple substance and high-purity silicon dioxide mixture precursor with uniform texture. Placing the mixture precursor in a chemical vapor deposition furnace with the initial temperature of 1500 ℃ and the vacuum state, and mixing the mixture precursor with the porous graphite placed in the chemical vapor deposition furnace, wherein the molar ratio of silicon dioxide to the porous graphite is 1: 9, when the indication of the pressure gauge is stable, turning on a rotary switch, keeping the rotating speed at 100r/min for 2h to obtain a secondary precursor, setting a program to perform cooling treatment, cooling to 800 ℃, turning on an acetylene gas valve and continuously turning on inert gas protection, wherein the gas proportion is 1: and 2, coating the secondary precursor with carbon, performing carbon deposition coating at 800 ℃, keeping for 4h, continuously introducing inert gas, cooling to room temperature, and taking out.
Comparative example 2
High-purity silicon simple substance and high-purity silicon dioxide are mixed according to a molar ratio of 2: 1, sanding for 2 hours in absolute ethyl alcohol at a rotating speed of 2200r/min, drying at 95 ℃ to remove the ethyl alcohol, and sieving to obtain a high-purity silicon simple substance and high-purity silicon dioxide mixture precursor with uniform texture. Placing the mixture precursor in a chemical vapor deposition furnace with the initial temperature of 1350 ℃ and the vacuum state, and mixing the mixture precursor with the porous graphite placed in the chemical vapor deposition furnace, wherein the molar ratio of the silicon dioxide to the porous graphite is 1: 9, when the indication of the pressure gauge is stable, turning on a rotary switch, keeping the rotating speed at 100r/min for 2h to obtain a secondary precursor, setting a program to perform cooling treatment, cooling to 800 ℃, turning on an acetylene gas valve and continuously turning on inert gas protection, wherein the gas proportion is 1: and 2, coating the secondary precursor with carbon, performing carbon deposition coating at 800 ℃, keeping for 4h, continuously introducing inert gas, cooling to room temperature, and taking out.
Comparative example 3
High-purity silicon simple substance and high-purity silicon dioxide are mixed according to a molar ratio of 3: 1, sanding for 2 hours in absolute ethyl alcohol at a rotating speed of 2200r/min, drying at 95 ℃ to remove the ethyl alcohol, and sieving to obtain a high-purity silicon simple substance and high-purity silicon dioxide mixture precursor with uniform texture. Placing the mixture precursor in a chemical vapor deposition furnace with the initial temperature of 1350 ℃ and the vacuum state, and mixing the mixture precursor with the porous graphite placed in the chemical vapor deposition furnace, wherein the molar ratio of the silicon dioxide to the porous graphite is 1: 9, when the indication of the pressure gauge is stable, turning on a rotary switch, keeping the rotating speed at 100r/min for 2h to obtain a secondary precursor, setting a program to perform cooling treatment, cooling to 800 ℃, turning on an acetylene gas valve and continuously turning on inert gas protection, wherein the gas proportion is 1: and 2, coating the secondary precursor with carbon, performing carbon deposition coating at 800 ℃, keeping for 4h, continuously introducing inert gas, cooling to room temperature, and taking out.
Application example
In the preparation of all pole pieces, carbon black (SP) is used as a conductive agent, sodium carboxymethyl cellulose (CMC) is used as a binder, and the mass ratio of the conductive agent to the synthesized negative electrode material is 1: 1: 8, mixing and dissolving the mixture in deionized water and a small amount of alcohol, and magnetically stirring for more than 8 hours to prepare uniformly dispersed battery slurry for later use. And (3) uniformly coating the battery slurry on the surface of an electrode (the cut foam copper or copper foil), carrying out vacuum drying at 85 ℃ for 12h, tabletting and weighing for later use. Utilizing a German Labstar company glove box (model number)Mbraun) were assembled to obtain a button-type half cell (CR2025), and the electrochemical performance of the electrode was tested. The button half cell assembly completely adopts a lithium sheet as a counter electrode, a foam nickel sheet as a buffer gasket, and the water oxygen content of the manufacturing environment is respectively as follows: water concentration<2ppm, oxygen concentration<2 ppm. The adopted electrolyte component is 1M LiPF6Dissolved in EC and DMC organic solvents.
Examples 1-4 and comparative examples 1-3 were characterized using the following methods.
And (3) performance testing:
the morphology test is carried out by adopting American Saimer Feishale Phenom Generation 5, and the test result is shown in figure 1;
the physical phase analysis detection is carried out by adopting XRD-D2 PHASER of Bruker company, and the test result is shown in figure 2;
the specific surface area is tested by adopting a Tristar3020 full-automatic specific surface area and a porosity analyzer of the American Michel instruments company; the cycling performance of the cells was tested on the novice apparatus. The test results are shown in table 1 below.
TABLE 1
Figure BDA0002686112030000111
Figure BDA0002686112030000121
As can be seen from the above table, the first coulombic efficiencies of the examples are higher than those of the comparative examples, which indicates that the surface texture of the composite graphite in the form of the silicon monoxide gas is more uniform, the thickness is uniform, the formed sandwich structure is more regular, the layers are more distinct, the first charge-discharge efficiency is higher than that of the comparative example, and the 0.2C-rate discharge reversible specific capacity example 1 is up to 498mAh/g and is close to a theoretical value, and in addition, the initial particle size of the porous graphite is related to the first coulombic efficiency, which causes the change of the first coulombic efficiency as compared with the examples 1 and 4.
The invention is well implemented in accordance with the above-described embodiments. It should be noted that, based on the above design, even if some insubstantial modifications or colorings are made on the present invention to solve the same technical problems, the adopted technical solution is still the same as the present invention, and therefore, the technical solution should be within the protection scope of the present invention.

Claims (7)

1. The preparation method of the silicon monoxide composite negative electrode material is characterized by specifically comprising the following steps:
(1) mixing and grinding a silicon simple substance and silicon dioxide to obtain a uniformly mixed raw material mixture;
(2) heating the raw material mixture to 1200-1400 ℃ under a protective atmosphere to perform a centering reaction to generate silicon monoxide; continuing to heat until the silicon monoxide is vaporized;
(3) mixing the vaporized silicon monoxide with inert gas, introducing the mixture into a chemical vapor deposition furnace containing a carbon material, and performing chemical vapor deposition to obtain a primary product;
the carbon material is selected from porous graphite, and D50 is 5-20 mu m;
the molar ratio of the silica to the carbon material is 1: 5-10;
the initial temperature in the chemical vapor deposition furnace is 1350-1500 ℃, and the chemical vapor deposition is carried out after the temperature is reduced to 700-800 ℃;
(4) and under a protective atmosphere, taking hydrocarbon gas as a carbon source, and carrying out carbon coating treatment on the surface of the primary product to obtain the silicon monoxide composite negative electrode material.
2. The method for producing the silica composite anode material according to claim 1, wherein in the step (1):
the silicon single substance is micron-grade high-purity silicon, the purity is not lower than 99.9%, and the D50 is 2-100 mu m;
the silicon dioxide is selected from micron-sized high-purity silicon dioxide, the purity is not lower than 99.9%, and the D50 is 2-100 mu m;
the molar ratio of the silicon simple substance to the silicon dioxide is 1-4: 1.
3. the method for producing the silica composite anode material according to claim 1, wherein in the step (2):
heating at the rate of 3-10 ℃/min;
and continuously heating at the speed of 2-5 ℃/min to 1500-1600 ℃.
4. The method for producing the silica composite anode material according to claim 1, wherein in the step (3):
and performing chemical vapor deposition under the constant pressure of 0.1-0.3 Mpa.
5. The method for producing the silica composite anode material according to claim 1, characterized in that:
in the step (2):
heating to 1300-1400 ℃ at the rate of 5-10 ℃/min;
and continuously heating at the speed of 5 ℃/min to 1550-1600 ℃.
6. The method for producing the silica composite anode material according to claim 1, wherein in the step (4):
the hydrocarbon gas is selected from one or more of methane, ethane, propane, ethylene, propylene and acetylene;
the volume ratio of the hydrocarbon gas to the protective atmosphere is 1: 2-4;
the temperature of the carbon coating treatment is 700-800 ℃.
7. The negative electrode material of silicon oxide composite prepared by the method of any one of claims 1 to 6, wherein the negative electrode material has a sandwich-type sandwich structure, a carbon material is used as a core, the outer surface of the carbon material is uniformly coated with silicon oxide, and the outermost layer is coated with a uniform carbon layer.
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