CN108923037B

CN108923037B - Silicon-rich SiOx-C material and preparation method and application thereof

Info

Publication number: CN108923037B
Application number: CN201811191738.5A
Authority: CN
Inventors: 王庆莉; 王辉; 李道聪; 夏昕; 杨茂萍
Original assignee: Hefei Guoxuan High Tech Power Energy Co Ltd
Current assignee: Hefei Gotion High Tech Power Energy Co Ltd
Priority date: 2018-10-12
Filing date: 2018-10-12
Publication date: 2020-12-11
Anticipated expiration: 2038-10-12
Also published as: CN108923037A

Abstract

The invention discloses silicon-rich SiO_xThe preparation method of the-C material takes SiO as a raw material, and the SiO is generated by etching SiO disproportionation reaction and has the composition of SiO₂SiO of @ SiO @ Si_xObtaining a porous silicon-based material, and then depositing Si in the pore structure of the porous silicon-based material by CVD (chemical vapor deposition) to obtain a silicon-rich SiO_xA material, and further a carbon coating layer formed by CVD deposition. Silicon-rich SiO prepared by the preparation method of the invention_xThe gram capacity and the first coulombic efficiency of the-C material are higher than those of commercial SiO, the circulation stability is relatively good, and the defect of low first effect of the SiO material is overcome.

Description

Silicon-rich SiOx-C material and preparation method and application thereof

Technical Field

The invention belongs to the field of lithium ion batteries, and particularly relates to silicon-rich SiO_x-C material and preparation method and application thereof.

Background

In recent years, with the continuous expansion of lithium ion batteries in the application of high-power devices such as electric tools, electric/hybrid vehicles, energy storage power stations and the like, the traditional graphite cathode (with a specific capacity of 372 mAh/g) is difficult to meet the requirements of human beings on high-energy density batteries, so that the search for the next generation of lithium ion battery anode materials capable of replacing graphite becomes one of the hot spots of the related researches of the current lithium ion batteries. The theoretical specific capacity of the silicon material is 4200mAh/g, the resource is rich, the phenomenon of solvent co-intercalation with electrolyte can not occur, and meanwhile, the lithium intercalation potential is higher and the silicon material is safer. However, the silicon anode material undergoes a volume change of up to 300% during charging and discharging, and such a high volume expansion and contraction easily causes crushing of the electrode material, and the electrode material is separated from contact with a current collector and an electrode conductive network, and at the same time, a new surface is generated due to the volume change, so that a new solid-electrolyte interface (SEI) needs to be formed, thereby causing a large amount of consumption of electrolyte, and further causing a substantial reduction in cycle life. On the other hand, the electrical conductivity and lithium ion diffusion speed of silicon are lower than those of graphite, which limits the performance of silicon under high-current and high-power conditions.

Due to the above problems, the academia and industry have moved some attention to the field of silicon oxide. Although the silicon monoxide sacrifices partial capacity, the silicon monoxide has relatively small expansion compared with nano silicon, and byproducts such as lithium oxide, lithium silicate and lithium metasilicate generated in the charging and discharging processes can provide a buffering effect, so that the cycle performance of the material is greatly improved. But the conductivity of the material is relatively poor, and the first effect is low.

Disclosure of Invention

Aiming at the defects, the invention provides silicon-rich SiO_xThe preparation method of the-C material integrates the advantages and the disadvantages of Si and SiO, takes SiO as a raw material, and generates SiO by etching SiO disproportionation reaction₂SiO of @ SiO @ Si_xObtaining a porous silicon-based material, and then depositing Si in the pore structure of the porous silicon-based material by a CVD (chemical vapor deposition) method to obtain a silicon-rich SiO_xThe material is silicon generated through disproportionation reaction and silicon deposited by CVD, so that silicon grains are small and have the grain diameter of about 3 nm-20 nm, and the electronic conductivity of the material can be improved by a carbon coating layer formed through CVD deposition. Silicon-rich SiO prepared by the preparation method of the invention_xThe gram capacity and the first coulombic efficiency of the-C material are higher than those of commercial SiO, the circulation stability is relatively good, and the defect of low first effect of the SiO material is overcome.

In order to achieve the purpose, the invention adopts the following technical scheme:

silicon-rich SiO_x-C material preparation method comprising the steps of:

a. SiO is put in inert atmosphere for disproportionation reaction to obtain SiO with the composition₂SiO of @ SiO @ Si_x；

b. SiO in step a_xEtching to obtain porous silicon-based material;

c. adding silicon source gas, and depositing silicon in the porous silicon-based material by a chemical vapor deposition method to obtain silicon-rich SiO_xA material; the reaction apparatus of the chemical vapor deposition method is not particularly limited, and a rotary kiln is preferable, and the rotary kiln is used in the present invention in the specific embodiment;

d. replacing the silicon source gas with a carbon source gas and then performing chemical vapor deposition on the silicon-rich SiO_xForming a carbon coating layer on the pore structure and the surface of the material to obtain the silicon-rich SiO_x-a material C;

the SiO is used as raw material and is generated by etching SiO disproportionation reaction_xPreparing a porous silicon-based material, and then depositing silicon in the porous silicon-based material by a CVD method to obtain silicon-rich SiO_xThe Si generated after disproportionation reaction and the Si obtained by CVD deposition are small in grain size of about 3 nm-20 nm, so that the volume expansion of the material is small, and the cycle performance of the material is greatly improved; further processing the silicon-rich SiO by CVD method_xThe carbon coating layers are uniformly deposited in and on the material, so that the electronic conductivity of the material can be improved. Thus, the silicon-rich SiO prepared by the present invention_xthe-C material overcomes the defects of the commercial SiO material, and improves the capacity and the first coulombic efficiency of the material.

In addition, the preparation method provided by the invention has simple process steps, and because the chemical vapor deposition of the silicon and the carbon material only needs to replace the gas source, the silicon does not need to be deposited, cooled, discharged, mixed with the carbon source and heated for carbonization, the control is easy and the large-scale production is realized.

Further, in the step a, the inert atmosphere is one or more of nitrogen, argon, helium and neon;

the disproportionation reaction is carried out at the temperature of 900-1200 ℃ for 2-12 h to obtain SiO with proper grain size of silicon grains in the structure_xA material.

Further, in the step b, the etching process is to use HF solution, KOH solution or NaOH solution for etching to remove SiO generated by disproportionation reaction₂Reducing the irreversible capacity loss of the material, and then filtering, washing and vacuum drying, wherein the temperature of the vacuum drying is 80-100 ℃, and the vacuum degree is-0.8 MPa-1 MPa.

Preferably, the etching adopts an HF solution, wherein the mass fraction of the HF solution is 35% -44%, and the SiO solution is_xThe mass ratio of the etching solution to the HF solution is 2: 1-1: 2, and the etching time is 0.5-2 hours;

further, in the step c, the silicon source gas is one or more of silane, dichlorosilane, trichlorosilane and tetrachlorosilane, and the flow rate is 1mL/min to 4 mL/min; the chemical vapor deposition is carried out at the deposition temperature of 600-1000 ℃ for 2-12 h.

Further, in the step d, the carbon source gas is one or more of methane or homologues thereof, acetylene or homologues thereof, toluene or homologues thereof, and ethanol or homologues thereof, and the flow rate is 1mL/min to 4 mL/min; the chemical vapor deposition method has the deposition temperature of 700-1000 ℃ and the deposition time of 2-12 h.

Furthermore, in the step d, the thickness of the carbon coating layer is 10 nm-100 nm, the carbon coating layer formed by a chemical vapor phase method is compact and uniform, the electronic conductivity of the material is improved, and in addition, the excessive thickness of the carbon coating layer can cause the reduction of the mass specific capacity of the material and lose the advantage of high capacity of the silicon-based material; the carbon coating layer is too thin, so that the coating of the material is not uniform or complete, and the coulombic efficiency and the cycle performance of the material are reduced, therefore, the thickness of the carbon coating layer is preferably 10 nm-100 nm.

Further, in the silicon-rich SiO_x-C material, 0 < x < 1, the silicon-rich SiO_xThe grain size of silicon crystal grains in the-C material is 3 nm-20 nm. The grain size of the silicon crystal grains prepared by the method is 3 nm-20 nm, and when the grain size is larger, the stress distribution in the grains is uneven along with the penetration of lithium intercalation, so that cracks are generated, the electric contact between the silicon crystal grains and a conductive network is lost, and the internal resistance of a battery is increased; the silicon crystal grains with smaller grain sizes have large contact area with the conductive network in the electrode due to large specific surface area and small influence on the silicon crystal grains by volume effect in the lithium deintercalation process, thereby being beneficial to the electrochemical cycle performance of the electrode

Another object of the present invention is to provide a silicon-rich SiO_x-a material C.

The third purpose of the invention is to provide silicon-rich SiO_x-use of a C material for the preparation of a lithium ion battery. The silicon-rich SiO of the invention_xAnd the-C material is used as a negative electrode material to prepare the lithium ion battery, and the prepared lithium ion battery is tested for electrochemical performance, so that the specific capacity and the cycling stability of the prepared lithium ion battery are improved.

Drawings

FIG. 1 is a silicon-rich SiO as prepared in example 1_x-SEM image of material C;

FIG. 2 shows the Si-rich SiO prepared in example 1_xEDS profile of material C;

FIG. 3 shows the Si-rich SiO prepared in example 1_x-local TEM images of material C;

FIG. 4 shows a silicon-rich SiO prepared in example 1_x-TEM images of material C;

FIG. 5 shows silicon-rich SiO in example 1 and comparative example_xFirst charge-discharge curve at 0.1C current density for button cell assembled with-C material.

Detailed Description

In order to facilitate understanding of the present invention, the technical solutions of the present invention are further clearly and completely described below with reference to the accompanying drawings and examples, but the scope of the present invention is not limited to the following specific examples.

Unless otherwise defined, all terms of art used hereinafter have the same meaning as commonly understood by one of ordinary skill in the art. The terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the scope of the present invention.

It is to be understood that the reagents and materials used in the present invention are commercially available products or products that can be produced by known methods.

Example 1

Putting 10g of SiO into a porcelain boat, then placing the porcelain boat into a tube furnace in an argon protective atmosphere, heating the tube furnace to 900 ℃ at the heating rate of 5 ℃/min, preserving heat for 2h, cooling and taking out the prepared SiO_x. Mixing SiO_xAnd mixing the silicon substrate with an HF aqueous solution with the mass fraction of 40% according to the mass ratio of 2:1, soaking for 0.5h, filtering, washing for 3 times by using deionized water until a washing liquid is neutral, and then placing in a vacuum drying box with the vacuum degree of-0.8 MPa, and drying at the temperature of 80 ℃ to obtain the porous silicon-based material. Placing 5g of porous silicon-based material in a CVD furnace, introducing argon to discharge air in the CVD furnace, subsequently introducing silane gas with the gas flow rate of 4mL/min, heating the tube furnace to 600 ℃ at the heating rate of 5 ℃/min, preserving the temperature for 2h, stopping introducing silane, heating the tube furnace to 800 ℃, introducing acetylene gas with the gas flow rate of 4mL/min, preserving the temperature for 2h at 800 ℃, stopping introducing acetylene gas, and cooling to obtain the silicon-rich SiO_x-C material, wherein, SiO is rich in silicon_xThe grain size of silicon crystal grains of the-C material is 3 nm-20 nm, and the thickness of the carbon coating layer is 10 nm-100 nm.

Example 2

Putting 10g of SiO into a porcelain boat, then placing the porcelain boat into a tube furnace in a nitrogen protective atmosphere, heating the tube furnace to 900 ℃ at the heating rate of 5 ℃/min, preserving heat for 12h, cooling and taking out the prepared SiO_x. Mixing SiO_xAnd mixing with 35% of HF aqueous solution according to the mass ratio of 1:2, soaking for 2h, filtering, washing for 3 times by using deionized water until the washing liquid is neutral, then placing in a vacuum drying oven with the vacuum degree of-1 MPa, and drying at 80 ℃ to obtain the porous silicon-based material. 5g of porous silicon-based material was placed in a CVD furnace, nitrogen gas was introduced to discharge the air in the CVD furnace, and then silane gas was introduced,the gas flow is 1mL/min, the tubular furnace is heated to 600 ℃ at the heating rate of 5 ℃/min, the temperature is kept for 12h, the silane gas is stopped being introduced, the tubular furnace is heated to 700 ℃, the acetylene gas is introduced, the gas flow is 1mL/min, the temperature is kept at 700 ℃ for 12h, the acetylene gas is stopped being introduced, and the silicon-rich SiO is prepared after the temperature is reduced_x-C material, wherein, SiO is rich in silicon_xThe grain size of silicon crystal grains of the-C material is 3 nm-20 nm, and the thickness of the carbon coating layer is 10 nm-100 nm.

Example 3

Putting 10g of SiO into a porcelain boat, then placing the porcelain boat into a tube furnace in a nitrogen protective atmosphere, heating the tube furnace to 1200 ℃ at a heating rate of 5 ℃/min, preserving heat for 2h, cooling and taking out the prepared SiO_x. Mixing SiO_xAnd HF aqueous solution with the mass fraction of 44% is mixed according to the mass ratio of 2:1, soaked for 0.5h, filtered, washed for 3 times by deionized water until the washing liquid is neutral, and then placed in a vacuum drying box with the vacuum degree of-0.8 MPa, and dried at the temperature of 100 ℃ to obtain the porous silicon-based material. Placing 5g of porous silicon-based material in a CVD furnace, introducing nitrogen to discharge air in the CVD furnace, subsequently introducing mixed gas of dichlorosilane and silane, wherein the gas flow is 4mL/min, heating the tubular furnace to 1000 ℃ at the heating rate of 5 ℃/min, preserving the temperature for 2h, stopping introducing the mixed gas of dichlorosilane and silane, keeping the temperature of the tubular furnace to 1000 ℃, introducing methane gas, wherein the gas flow is 4mL/min, preserving the temperature for 2h at 1000 ℃, stopping introducing the methane gas, and cooling to obtain the silicon-rich SiO_x-C material, wherein, SiO is rich in silicon_xThe grain size of silicon crystal grains of the-C material is 3 nm-20 nm, and the thickness of the carbon coating layer is 10 nm-100 nm.

Example 4

Putting 10g of SiO into a porcelain boat, then placing the porcelain boat into a tube furnace in helium protective atmosphere, heating the tube furnace to 1100 ℃ at the heating rate of 5 ℃/min, preserving heat for 8h, cooling and taking out the prepared SiO_x. Mixing SiO_xAnd mixing the porous silicon-based material with an HF aqueous solution with the mass fraction of 40% according to the mass ratio of 1:1, soaking for 1.5h, filtering, washing for 3 times by using deionized water until a washing solution is neutral, then placing in a vacuum drying box with the vacuum degree of-1 MPa, and drying at 90 ℃ to obtain the porous silicon-based material. 5g of porous silicon-based material is placed in a CVD furnace, and a helium exhaust is introducedTaking out the air in the CVD furnace, introducing trichlorosilane gas with the gas flow of 2.5mL/min, heating the tubular furnace to 800 ℃ at the heating rate of 5 ℃/min, preserving the temperature for 8h, stopping introducing trichlorosilane gas, keeping the tubular furnace to 800 ℃, introducing toluene gas with the gas flow of 2.5mL/min, preserving the temperature for 8h at 800 ℃, stopping introducing toluene gas, cooling to obtain the silicon-rich SiO_x-C material, wherein, SiO is rich in silicon_xThe grain size of silicon crystal grains of the-C material is 3 nm-20 nm, and the thickness of the carbon coating layer is 10 nm-100 nm.

Example 5

Putting 10g of SiO into a porcelain boat, then placing the porcelain boat into a tube furnace in a nitrogen protective atmosphere, heating the tube furnace to 1200 ℃ at a heating rate of 5 ℃/min, preserving heat for 2h, cooling and taking out the prepared SiO_x. Mixing SiO_xSoaking in KOH aqueous solution for 1.5h, filtering, washing for 3 times by using deionized water until the washing liquid is neutral, and then placing in a vacuum drying oven with the vacuum degree of-1 MPa, and drying at the temperature of 80 ℃ to obtain the porous silicon-based material. Placing 5g of porous silicon-based material in a CVD furnace, introducing nitrogen to discharge air in the CVD furnace, subsequently introducing silane gas with the gas flow rate of 4mL/min, heating the tubular furnace to 600 ℃ at the heating rate of 5 ℃/min, preserving the temperature for 2h, stopping introducing the silane gas, heating the tubular furnace to 1000 ℃, introducing acetylene gas with the gas flow rate of 4mL/min, preserving the temperature for 2h at 1000 ℃, stopping introducing the acetylene gas, cooling to room temperature, discharging, and preparing the silicon-rich SiO_x-C material, wherein, SiO is rich in silicon_xThe grain size of silicon crystal grains of the-C material is 3 nm-20 nm, and the thickness of the carbon coating layer is 10 nm-100 nm.

Example 6

Putting 10g of SiO into a porcelain boat, then placing the porcelain boat into a tube furnace in a nitrogen protective atmosphere, heating the tube furnace to 1200 ℃ at a heating rate of 5 ℃/min, preserving heat for 2h, cooling and taking out the prepared SiO_x. Mixing SiO_xSoaking in NaOH aqueous solution for 1.5h, filtering, washing for 3 times by using deionized water until the washing liquid is neutral, and then placing in a vacuum drying oven with the vacuum degree of-1 MPa, and drying at 80 ℃ to obtain the porous silicon-based material. 5g of porous silicon-based material was placed in a CVD furnace, and nitrogen gas was introduced to discharge the air in the CVD furnace, followed by introduction of tetrachlorosilaneThe flow rate of alkane gas is 4mL/min, the temperature of the tubular furnace is increased to 600 ℃ at the temperature increase rate of 5 ℃/min, the temperature is maintained for 2h, the introduction of tetrachlorosilane gas is stopped, the temperature of the tubular furnace is increased to 1000 ℃, ethanol gas is introduced, the flow rate of gas is 4mL/min, the temperature is maintained at 1000 ℃ for 2h, the introduction of ethanol gas is stopped, the temperature is reduced to room temperature, and discharging is carried out to obtain silicon-rich SiO_x-C material, wherein, SiO is rich in silicon_xThe grain size of silicon crystal grains of the-C material is 3 nm-20 nm, and the thickness of the carbon coating layer is 10 nm-100 nm.

Comparative example

Placing 5g of unprocessed SiO in a CVD furnace, introducing argon to discharge air in the CVD furnace, introducing acetylene gas with the gas flow of 4mL/min, raising the temperature of the CVD furnace to 800 ℃ according to the temperature rise rate of 5 ℃/min, preserving the temperature for 2h, stopping introducing the acetylene gas, and cooling to obtain the carbon-coated SiO material.

The silicon-rich SiO prepared in example 1_xAnd (4) carrying out material characterization on the-C material, wherein the results are shown in FIGS. 1-4. FIG. 1 is a silicon-rich SiO_xAnd SEM images of the-C material, and the prepared material can be observed to have a bulk morphology basically similar to that of the SiO raw material. FIG. 2 is a silicon-rich SiO_xEDS diagram of-C material, it can be found that the material has three element distributions, Si, O and C, wherein O is mainly derived from SiO which is the raw material, and the carbon material is distributed on the surface of Si and relatively uniformly distributed. FIG. 3 is a silicon-rich SiO_x-local TEM images of C material, it can be observed that after high temperature, lattice fringes of Si appear in the material, where the D (111) lattice spacing is 3.183 a, and the resulting silicon grains have a particle size around 20nm, indicating that the high temperature partial disproportionation of SiO and CVD deposited Si is crystalline silicon. FIG. 4 is a silicon-rich SiO_xTEM image of-C material, carbon coated homogeneously on SiO after CVD deposition_xThe thickness of the coating layer is about 20 nm.

The silicon-rich SiO prepared in example 1_xThe material-C, the conductive agent SP and the binder LA133 are combined and coated according to the mass ratio of 8:1:1 to assemble the CR2016 button cell, wherein 1mol/L LiPF is used as electrolyte₆The Ethylene Carbonate (EC) + dimethyl carbonate (DMC) solution of (iv) and tested for electrochemical performance, the results are shown in fig. 5. At a current density of 0.1C, the head of the materialThe specific discharge capacity is 2305.6mAh/g, the specific charge capacity is 1851.7mAh/g, and the first coulombic efficiency is 80.3%.

The carbon-coated SiO materials prepared in the comparative example were assembled into a CR2016 button cell in the same manner as in example 1, and subjected to electrochemical performance test, with the results shown in fig. 5. Under the current density of 0.1C, the first discharge specific capacity of the material is 2210.9mAh/g, the charge specific capacity is 1647.2mAh/g, and the first coulombic efficiency is 74.5%.

From example 1 and comparative example, it can be seen that the silicon-rich SiO prepared by the invention_xthe-C material can not only improve the first charge specific capacity of the material, but also improve the first coulombic efficiency of the material, which is exactly due to the fact that part of SiO in the SiO matrix is used₂Etching and filling the cause of Si, and disproportionation reaction of SiO to produce Si and CVD-deposited Si (limited by disproportionation of produced SiO)₂Particle size) is 3 nm-20 nm, the volume expansion is relatively small, and the SiO matrix is arranged around the material for buffering expansion, so that the first effect and the cycle performance of the material are improved.

The above description is only for the preferred embodiment of the present invention, but the scope of the present invention is not limited thereto, and any person skilled in the art should be able to cover the technical scope of the present invention and the equivalent alternatives or modifications according to the technical solution and the inventive concept of the present invention within the technical scope of the present invention.

Claims

1. A preparation method of a silicon-rich SiOx-C material is characterized by comprising the following steps: the method comprises the following steps:

a. SiO is put into inert gas or nitrogen for disproportionation reaction to obtain the SiO composition₂SiOx @ SiO @ Si, wherein x is more than 0 and less than 1;

b. etching the SiOx in the step a for 0.5-2 h by adopting 35-44% of HF solution by mass percent to obtain a porous silicon-based material, wherein the mass ratio of the SiOx to the HF solution is 2: 1-1: 2;

c. controlling the flow rate of silicon source gas to be 1-4 mL/min, and depositing silicon in the porous silicon-based material by a chemical vapor deposition method to obtain a silicon-rich SiOx material;

d. and replacing the silicon source gas with a carbon source gas, controlling the flow rate of the carbon source gas to be 1-4 mL/min, and forming a carbon coating layer with the thickness of 10-100 nm on the pore structure and the surface of the silicon-rich SiOx material by a chemical vapor deposition method to obtain the silicon-rich SiOx-C material, wherein the grain size of silicon grains in the silicon-rich SiOx-C material is 3-20 nm.

2. The method of claim 1, wherein: in the step a, the inert gas is one or more of argon, helium and neon;

the disproportionation reaction temperature is 900-1200 ℃, and the reaction time is 2-12 h.

3. The method of claim 1, wherein: in the step b, the etching process specifically comprises the steps of adopting an HF solution for etching, filtering, washing and vacuum drying, wherein the temperature of the vacuum drying is 80-100 ℃, and the vacuum degree is-0.8 MPa to-1 MPa.

4. The method of claim 1, wherein: in the step c, the silicon source gas is one or more of silane, dichlorosilane, trichlorosilane and tetrachlorosilane; the chemical vapor deposition method has the deposition temperature of 600-1000 ℃ and the deposition time of 2-12 h.

5. The method of claim 1, wherein: in step d, the carbon source gas is one or more of methane or homologues thereof, acetylene or homologues thereof, toluene or homologues thereof, and ethanol or homologues thereof; the chemical vapor deposition method has the deposition temperature of 700-1000 ℃ and the deposition time of 2-12 h.

6. A silicon-rich SiOx-C material produced by the production method according to any one of claims 1 to 5.

7. Use of the silicon-rich SiOx-C material of claim 6 for the preparation of a lithium ion battery.