CN111785948B - Silica negative electrode material, preparation method thereof and negative electrode for secondary battery - Google Patents

Silica negative electrode material, preparation method thereof and negative electrode for secondary battery Download PDF

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CN111785948B
CN111785948B CN202010735517.0A CN202010735517A CN111785948B CN 111785948 B CN111785948 B CN 111785948B CN 202010735517 A CN202010735517 A CN 202010735517A CN 111785948 B CN111785948 B CN 111785948B
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carbon
oxygen
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CN111785948A (en
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陈松
王志勇
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Hunan Shinzoom Technology Co ltd
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    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
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    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
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    • H—ELECTRICITY
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    • 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
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    • H01M4/5825—Oxygenated metallic salts or polyanionic structures, e.g. borates, phosphates, silicates, olivines
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    • H01M2004/026—Electrodes composed of, or comprising, active material characterised by the polarity
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Abstract

The application relates to the field of lithium batteries, in particular to a silica anode material, a preparation method thereof and an anode for a secondary battery. And (2) carrying out heat treatment on the carbon-coated silicon monoxide and a metal material, so that at least part of silicon monoxide in the carbon-coated silicon monoxide reacts with the metal material to generate silicate and a silicon simple substance, thereby obtaining the silicon-oxygen cathode material. The silicate does not have lithium intercalation capacity, can inhibit the volume expansion of the material and can improve the first effect of the silicon-oxygen negative electrode material. In addition, in the reaction process of the metal material and the silicon monoxide, the carbon layer can enable the reaction process to be carried out slowly due to the existence of the carbon layer, the phenomenon that the silicon crystal grain size is too large due to the generation of a large amount of heat is avoided, and the silicon-oxygen negative electrode material can show better cycle performance due to the smaller silicon crystal grain size.

Description

Silica negative electrode material, preparation method thereof and negative electrode for secondary battery
Technical Field
The application relates to the field of lithium batteries, in particular to a silica negative electrode material, a preparation method thereof and a negative electrode for a secondary battery.
Background
With the rapid development of new energy industries, lithium ion batteries are required to have higher energy density and cycle life. The capacity of the silicon-oxygen cathode material is 1500-1800mAh/g, and the silicon-oxygen cathode material has lower volume expansion (160%) compared with a silicon cathode, and has larger application potential. Lithium silicon oxide compounds formed in the lithium embedding process of the silicon-oxygen material can effectively inhibit volume expansion and improve the cycle life of the material, but excessive lithium silicon oxide compounds can cause the first effect (the first coulombic efficiency of the battery, referred to as the first effect) to be reduced; the first effect of the current commercial silicon oxygen materials is generally 75 percent.
The silicon grain size of the existing silicon-oxygen cathode material is larger, and the silicon-oxygen cathode material shows poorer cycle performance.
Disclosure of Invention
An object of the embodiments of the present application is to provide a silica negative electrode material, a preparation method thereof, and a negative electrode for a secondary battery, which aim to improve the first efficiency and cycle performance of a negative electrode material for a lithium battery.
The application provides a preparation method of a silicon-oxygen anode material, which comprises the following steps:
and (3) carrying out heat treatment on the carbon-coated silicon monoxide and the metal material, so that at least part of silicon monoxide in the carbon-coated silicon monoxide reacts with the metal material to generate silicate and a silicon simple substance, thereby obtaining the silicon-oxygen cathode material.
Reducing silicon monoxide coated by carbon by using metal to enable at least one part of silicon monoxide to react to generate silicate, wherein the silicate does not have the lithium intercalation capacity, so that the volume expansion of the material can be inhibited, and the first effect of the silicon-oxygen cathode material can be improved; in addition, in the reaction process of the metal and the silicon monoxide, the carbon layer can enable the reaction process to be carried out slowly due to the existence of the carbon layer, the phenomenon that the silicon crystal grain size is larger due to the generation of a large amount of heat is avoided, and the silicon-oxygen negative electrode material shows better cycle performance due to the smaller silicon crystal grain size.
In some embodiments of the first aspect of the present application, the metallic material comprises at least one of Mg, Li, Na, K, Ca, Sr, Ba, Ti, Zr, B, Al, Co, and alloys thereof.
In some embodiments of the first aspect of the present application, the mass ratio of the metallic material to the carbon-coated silicon monoxide is 1: 5-9;
optionally, a mass ratio of the metal material to the carbon-coated silicon monoxide is 1: 6.5-7.5.
In some embodiments of the first aspect of the present application, the step of heat treating the carbon coated silicon monoxide with a metallic material comprises:
preserving the heat of the carbon-coated SiO and the metal material at 300-600 ℃ for 1-10 h; then preserving the heat for 0.5-10 h at 850-1100 ℃;
optionally, the carbon-coated silicon monoxide and the metal material are subjected to heat preservation for 1-10 hours at the temperature of 300-600 ℃, and then are heated to 850-1100 ℃ at the heating rate of 5-20 ℃/min and are subjected to heat preservation for 0.5-10 hours;
optionally, the heat treatment is carried out under a pressure of 1 to 140 Pa; optionally, the heat treatment is carried out at a pressure of 8 to 30 Pa.
In some embodiments of the first aspect of the present application, the step of heat treating the carbon coated silicon monoxide with the metal material further comprises:
coating a carbon layer on the surface of the silicon monoxide to obtain the carbon-coated silicon monoxide;
optionally, coating a carbon layer on the surface of the silicon monoxide by adopting a chemical vapor deposition method;
optionally, the carbon layer with the thickness of 10-1000nm is coated on the outer surface of the silicon monoxide.
In some embodiments of the first aspect of the present application, the particle size distribution of the SiO is:
D10：≥3μm；
D50：5-8μm；
D100：＜15μm。
in some embodiments of the first aspect of the present application, the mass fraction of carbon in the carbon-coated silicon monoxide is between 0.2 and 20%;
optionally, the mass fraction of carbon in the carbon-coated SiO is 1-8%.
In a second aspect of the present application, a silicon-oxygen negative electrode material is provided, and is prepared by the preparation method of the silicon-oxygen negative electrode material.
The silicate can inhibit volume expansion, and the first effect is improved while the cycle life is prolonged. The carbon layer on the surface can improve the conductivity and inhibit the volume expansion to a certain extent, and is beneficial to forming a stable SEI film.
A third aspect of the present application provides a silicon oxygen anode material, comprising: a core and a carbon layer coated outside the core, the core including Mg 2 SiO 4 、MgSiO 3 And dispersed in Mg 2 SiO 4 、MgSiO 3 Silicon crystal grains in between;
Mg 2 SiO 4 with MgSiO 3 Does not have the lithium embedding capacity, can effectively inhibit the expansion of the material, improve the cycle life and simultaneously improve the first effect.
In a fourth aspect, the present application provides an anode for a secondary battery, which comprises the above-described silica anode material.
The negative electrode for a secondary battery has the advantages of the silicon-oxygen negative electrode material. Has better electrical performance.
Drawings
In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings that are required to be used in the embodiments will be briefly described below, it should be understood that the following drawings only illustrate some embodiments of the present application and therefore should not be considered as limiting the scope, and for those skilled in the art, other related drawings can be obtained from the drawings without inventive effort.
Fig. 1 is a scanning electron microscope image of the silicon-oxygen negative electrode material provided in example 1.
Fig. 2 is an XRD spectrum of the silicon oxygen anode material provided in example 1.
Fig. 3 is a scanning electron microscope image of a CP cross section of the silicon oxygen negative electrode material provided in example 1.
Fig. 4 is a distribution curve of each element in the cross section of the silicon oxygen anode material provided in example 1 from the inside of the particle to the outside.
Fig. 5 is a scanning electron microscope image of a CP cross section of the silicon-oxygen negative electrode material provided in example 2.
Fig. 6 is a cross-sectional distribution curve of each element from the inside to the outside of the particle of the silicon-oxygen anode material provided in example 2.
Fig. 7 is a scanning electron microscope image of the silicon oxide negative electrode material provided in comparative example 1.
Fig. 8 is an XRD pattern of the silicon oxygen anode material provided in comparative example 1.
Fig. 9 shows charge and discharge curves of the button cells obtained in example 1 and comparative example 1 of the present application.
Detailed Description
In order to make the objects, technical solutions and advantages of the embodiments of the present application clearer, the technical solutions of the embodiments of the present application will be clearly and completely described below. The examples, in which specific conditions are not specified, were conducted under conventional conditions or conditions recommended by the manufacturer. The reagents or instruments used are conventional products which are not indicated by manufacturers and are commercially available.
The following specifically describes the silicon-oxygen negative electrode material, the method for producing the same, and a negative electrode for a secondary battery according to the examples of the present application.
A preparation method of a silicon-oxygen anode material comprises the following steps: and (2) carrying out heat treatment on the carbon-coated silicon monoxide and a metal material, so that at least part of silicon monoxide in the carbon-coated silicon monoxide reacts with the metal material to generate silicate and a silicon simple substance, thereby obtaining the silicon-oxygen cathode material.
In the application, metal is adopted to reduce silicon monoxide (SiO) coated by carbon, so that at least a part of the silicon monoxide reacts to generate silicate, the silicate does not have lithium embedding capacity, the volume expansion of the material can be inhibited, the first effect of the silicon-oxygen cathode material can be improved, in addition, in the reaction process of the metal and the silicon monoxide, the carbon layer can enable the reaction to be slowly carried out due to the existence of the carbon layer, the phenomenon that the silicon grain size is larger due to the generation of a large amount of heat is avoided, and the silicon grain size is smaller so that the silicon-oxygen cathode material shows better cycle performance.
In this application, the reaction of at least a portion of the SiO to form the silicate includes the reaction of a portion of the SiO to form the silicate and the reaction of all of the SiO to form the silicate. In the example of the partial silicon monoxide reaction, the finally obtained silicon monoxide negative electrode material contains partial silicon monoxide, so that the volume expansion of the material can be inhibited, and the first effect of the silicon monoxide negative electrode material is improved.
In an embodiment of the present application, the metallic material is selected from materials that can form a silicate with silicon monoxide, for example, the metallic material includes at least one of Mg, Li, Na, K, Ca, Sr, Ba, Ti, Zr, B, Al, Co, and alloys thereof.
The alloy may contain at least two of Mg, Li, Na, K, Ca, Sr, Ba, Ti, Zr, B, Al, and Co.
Further, in some embodiments, the mass ratio of the metal material to the carbon-coated silicon monoxide is 1:5 to 9, and may be, for example, 1:5, 1:6, 1:6.5, 1:6.9, 1:7, 1:7.2, 1:7.5, 1:8, or 1:9, and so forth. The ratio of the metal material to the carbon-coated SiO is in the above range, so that the SiO can be reduced more sufficiently, and the over-low first effect is avoided; meanwhile, the phenomenon that the crystal grain size is too large and the cycle performance is poor due to too high proportion is avoided;
it should be noted that in other embodiments of the present application, the mass ratio of the metal material to the carbon-coated SiO may not be in the above range, if the material utilization and yield are not taken into consideration.
In this embodiment, the step of heat-treating the carbon-coated SiO and metal material includes:
preserving the heat of the carbon-coated SiO and the metal material at 300-600 ℃ for 1-10 h; then preserving the heat for 0.5 to 10 hours at 850 to 1100 ℃.
The metal material and the carbon-coated silicon monoxide react for a period of time at a low temperature (300-600 ℃) so that the metal material is doped into the carbon layer and reacts with the silicon monoxide to generate metal oxide, which is beneficial to inhibiting the increase of the size of silicon crystal. And then reacting for a period of time at a high temperature (850-1100 ℃) to react the metal oxide with the silicon monoxide to generate silicate.
Illustratively, the temperature of the low temperature section may be 300 ℃, 350 ℃, 400 ℃, 450 ℃, 500 ℃, 546 ℃ or 600 ℃, and so on.
The temperature of the high temperature section may be 850 deg.C, 895 deg.C, 920 deg.C, 970 deg.C, 1005 deg.C, 1058 deg.C, 1100 deg.C, etc.
Accordingly, the temperatures of the low temperature section and the high temperature section may be set according to the height of the reaction temperature of the metal material and SiO.
Further, in some embodiments of the present application, the reaction temperature is increased from the low temperature stage to the high temperature stage at a ramp rate of 5-20 ℃/min. For example, the temperature ramp rate can be 5 deg.C/min, 10 deg.C/min, 15 deg.C/min, 20 deg.C/min, and the like. The temperature is slowly raised, which is beneficial to avoiding the growth of the grain size of silicon crystal.
Further, in some embodiments of the present application, the above heat treatment is performed under a pressure of 1 to 140Pa, for example, a pressure of 1Pa, 10Pa, 20Pa, 30Pa, 60Pa, 80Pa, 110Pa, 140Pa, or the like. The pressure of 1-140Pa is beneficial to the sublimation of the metal material under lower pressure, and the sublimed gas-phase metal material reacts with the carbon-coated silicon monoxide, so that the reaction is more uniform.
In the present embodiment, description is made taking a metal material including Mg as an example.
The carbon-coated SiO reacts with Mg, which reacts with COThe silicon reacts to generate magnesium silicate and silicon simple substance (silicon crystal grains), and tests of the inventor show that the silicon-oxygen negative electrode material contains Mg 2 SiO 4 With MgSiO 3 . The obtained silicon-oxygen cathode material can improve the first effect and the cycle performance; and the silicon crystal grains of the obtained silicon-oxygen cathode material are small.
Correspondingly, the inventor uses silicon monoxide which is not coated with a carbon layer to react with metal magnesium, and then coats the carbon layer after the reaction, and the test of the inventor finds that the obtained material contains Mg 2 SiO 4 No MgSiO was detected 3 The silicon crystal grain of the silicon-oxygen cathode material in the material is larger, and the first efficiency is lower.
Further, in the examples of the present application, the carbon-coated silicon monoxide may be directly commercially available or prepared.
The embodiments of the present application provide a method for preparing carbon-coated silicon monoxide, which mainly includes coating a carbon layer on the outer surface of the silicon monoxide. It is understood that the carbon layer can be coated on the SiO layer by various methods, for example, in this embodiment, the carbon layer is coated on the SiO layer by chemical vapor deposition.
Illustratively, one or more small molecular organic substances with certain ring structures in a vaporizable molecular structure are used as a carbon source to carry out vapor deposition on a carbon layer on the surface of the silicon monoxide.
For example, the carbon source can be selected from alkanes, alkenes, alkynes and derivatives thereof having a certain cyclic structure, heterocyclic compounds, pyridines, pyrimidines, complexes containing benzene rings and nitrogen, benzene derivatives, amide derivatives, heterocyclic aromatic hydrocarbons, and the like.
In some embodiments, the particle size distribution of the SiO is:
D10：≥3μm；
D50：5-8μm；
D100：＜15μm。
the particle size of the silicon monoxide is favorable for improving the first effect of the silicon-oxygen negative electrode material and is favorable for manufacturing a pole piece in the later period.
Further, in some embodiments herein, the mass fraction of carbon in the carbon-coated SiO is 0.2-20%; for example, it may be 0.2%, 0.5%, 1%, 5%, 6%, 9%, 13%, 17%, 19%, or 20%, etc.
Further, a carbon layer with the thickness of 10-1000nm is coated on the outer surface of the silicon monoxide. The carbon layer is too thin to relieve the reduction speed, and too thick can influence the contact effect of metal and SiO, so that the generated silicate is too little, and the expansion inhibiting effect is not good.
The preparation method of the silicon-oxygen anode material provided by the embodiment of the application has the following advantages that:
the carbon-coated SiO and metal heat treatment only needs a simple solid-phase mixing process of carbon-coated SiO and metal, and the shape of the material after metal modification has no obvious change. The surface carbon layer of the silicon monoxide can effectively slow down the reduction reaction of SiO and metal, and is beneficial to controlling the size of silicon crystal grains. The increase of the size of silicon crystal grains can be effectively inhibited in the whole reaction process, and the silicon-oxygen cathode material with better cycle life and first effect is obtained.
The embodiment of the application also provides a silicon-oxygen anode material, which is prepared by the preparation method of the silicon-oxygen anode material.
The silicon oxygen cathode material silicon crystal grain size that this application embodiment provided is less, and silicate can restrain and lead to volume expansion, improves the first effect when improving cycle life. The carbon layer on the surface can improve the conductivity and inhibit the volume expansion to a certain extent, and is beneficial to forming a stable SEI (solid electrolyte interphase) film.
Embodiments of the present application also provide a silicon oxygen anode material, the silicon oxygen anode material includes: a core and a carbon layer coated outside the core, wherein the core comprises Mg 2 SiO 4 With MgSiO 3 And silicon crystal grains dispersed therein.
It is understood that in some embodiments of the present application, the inner core may also comprise SiO.
Mg 2 SiO 4 With MgSiO 3 Does not have the lithium embedding capacity, can effectively inhibit expansion, improve the cycle life and simultaneously improve the first effect.
Further, in the examples of the present application, all of the SiO reacts with Mg to form Si crystal grains and Mg 2 SiO 4 With MgSiO 3 (ii) a Part of the SiO reacts with Mg to form Si grains and Mg 2 SiO 4 With MgSiO 3 The remaining portion of the SiO continues to remain in the core.
Embodiments of the present application also provide a negative electrode for a secondary battery including any one of the above-described silicon-oxygen negative electrode materials.
Accordingly, the negative electrode for a secondary battery has the advantages of the above-described silicon-oxygen negative electrode material.
Dispersing a negative electrode active material, optional conductive agents (such as carbon materials such as carbon black and metal particles), binders (such as SBR), additives (such as PTC thermistor materials) and the like in a solvent (such as deionized water), uniformly stirring, uniformly coating on a negative electrode current collector, and drying to obtain the negative electrode piece containing the negative electrode diaphragm.
The negative electrode provided by the embodiment of the application is beneficial to improving the first coulombic efficiency and the cycle performance of the battery.
The features and properties of the present application are described in further detail below with reference to examples.
Example 1
The embodiment provides a silicon-oxygen anode material which is mainly prepared by the following steps:
placing 5kg of SiO powder in a CVD furnace, heating to 900 ℃, introducing an acetylene carbon source, preserving heat for 1h, cooling and sieving with a 325-mesh sieve. The amount of acetylene was controlled so that the carbon layer thickness of the carbon-coated SiO was 10 nm.
And (3) mixing the carbon-coated SiO and the magnesium powder in a solid phase at a mixing ratio of 6:1 (mass ratio) by using a VC mixer. Mixing, placing in a stainless steel vacuum rotary furnace, vacuumizing to 10Pa, and sealing. Heating to 400 ℃ at the speed of 5 ℃/min, preserving heat for 8h, and then continuously heating to 950 ℃ and preserving heat for 4 h.
Fig. 1 is a scanning electron microscope image of the silicon-oxygen negative electrode material provided in example 1, from fig. 1, it can be observed that the particles are dispersed uniformly, no obvious agglomeration phenomenon occurs, and the particle size D50 of the sample measured by a malvern 3000 laser particle sizer is 6.1 μm.
FIG. 2 is an XRD spectrum of the silicon-oxygen anode material provided in example 1, and peaks corresponding to the calibration of a PDF card can be found, wherein a sample prepared in the example contains Si, SiO and Mg 2 SiO 4 、MgSiO 3 The crystal grain size of the Si (111) crystal face is 10nm calculated by the Sherler equation.
Fig. 3 is a scanning electron microscope image of a CP cross section of the silicon-oxygen negative electrode material provided in example 1. Fig. 4 is a distribution curve of each element in the cross section of the silicon oxygen anode material provided in example 1 from the inside of the particle to the outside.
As can be seen from fig. 3 and 4, magnesium can penetrate into the particles and react with the particles, and the silicon crystal grains are uniformly dispersed in the silicate framework, so that the silicate inhibits the volume expansion of the silicon crystal grains, which is beneficial to improving the cycle life of the material.
Example 2
This example provides a silicon-oxygen anode material, and the difference between the preparation of the silicon-oxygen anode material in the examples of the present application and the example 1 is:
and (3) mixing the carbon-coated SiO with the magnesium powder in a solid phase, and then preserving the heat for 4 hours at 400 ℃.
Fig. 5 is a scanning electron microscope image of a CP cross section of the silicon-oxygen negative electrode material provided in example 2. Fig. 6 is a cross-sectional distribution curve of each element from the inside to the outside of the particle of the silicon-oxygen anode material provided in example 2.
As can be seen from FIGS. 5 and 6, only the surface layer is doped with metal to form metal silicate in part of the reaction process, and the inner layer is SiO.
Example 3
This example provides a silicon-oxygen anode material, and the difference between the preparation of the silicon-oxygen anode material in the examples of the present application and the example 1 is:
the mass ratio of the carbon-coated SiO to the magnesium powder is 8: 1.
Example 4
This example provides a silicon-oxygen anode material, and the difference between the preparation of the silicon-oxygen anode material in the examples of the present application and the example 1 is:
the mass ratio of SiO to magnesium powder after carbon coating is 5: 1.
Example 5
This example provides a silicon-oxygen anode material, and the difference between the preparation of the silicon-oxygen anode material in the examples of the present application and the example 1 is:
the mass ratio of the carbon-coated SiO to the magnesium powder is 9: 1.
Example 6
The present embodiment provides a silicon-oxygen anode material, and the difference between the preparation of the silicon-oxygen anode material in the embodiments of the present application and the embodiment 1 is that:
the amount of acetylene was controlled so that the carbon layer thickness of the carbon-coated SiO was 50 nm.
Example 7
This example provides a silicon-oxygen anode material, and the difference between the preparation of the silicon-oxygen anode material in the examples of the present application and the example 1 is:
the amount of acetylene was controlled so that the carbon layer thickness of the carbon-coated SiO was 100 nm.
Example 8
This example provides a silicon-oxygen anode material, and the difference between the preparation of the silicon-oxygen anode material in the examples of the present application and the example 1 is:
the amount of acetylene was controlled so that the carbon layer thickness of the carbon-coated SiO was 200 nm.
Comparative example 1
The comparative example provides a silicon-oxygen anode material, which is mainly prepared by the following steps:
5kg of SiO powder and magnesium powder were mixed in a solid phase in a ratio of 6:1 (mass ratio) in a VC mixer. Mixing, placing in a stainless steel vacuum rotary furnace, vacuumizing to 10Pa, and sealing. Heating to 400 ℃ at the speed of 5 ℃/min, preserving heat for 4h, then continuously heating to 900 ℃, preserving heat for 4h, cooling, and sieving with a 325-mesh sieve.
And (3) placing the metal modified SiO powder in a CVD furnace, heating to 900 ℃, introducing an acetylene carbon source, preserving heat for 1h, cooling and sieving with a 325-mesh sieve.
Fig. 7 is a scanning electron microscope image of the silicon-oxygen cathode material provided in comparative example 1, from fig. 7, a remarkable particle agglomeration phenomenon can be observed, and the particle size D50 of the sample measured by a malvern 3000 laser particle sizer is 16.0 μm.
FIG. 8 is an XRD pattern of the silicon-oxygen anode material provided by comparative example 1, and only Si, SiO and Mg in the XRD pattern can be seen from FIG. 8 2 SiO 4 And the Si peak intensity is very high, and the grain size of the Si (111) crystal face is calculated to be 35.5nm through the Scherrer equation.
Test examples
The silicon-oxygen negative electrode materials prepared in examples 1-8 and comparative example 1 were assembled into 2032 button cells, and the performance thereof was tested, and the results thereof are summarized in fig. 9 and table 1:
the prepared cathode material is assembled by adopting a 2032 button cell, and the specific assembling method is as follows:
1. material blending and homogenizing: according to the active substance: conductive agent: the binder is 94:2.5:3.5, the binder is water-based binder, and the wet stirring is carried out uniformly.
2. And uniformly coating the slurry on a copper foil, and then drying.
3. Assembling the battery: and (4) stacking the lithium sheet, the diaphragm and the pole piece in sequence in the glove box, and adding a certain amount of electrolyte to complete the assembly of the button cell.
The specific discharge capacity and the specific charge capacity in table 1 are the specific lithium intercalation capacity and the specific lithium deintercalation capacity of the anode in the button type half cell.
The testing method of the grain size comprises the following steps: the crystal structure of the composite material is measured by CuK alpha radioactive source XRD, a characteristic peak of Si (111) is obtained in an X-ray diffraction pattern corresponding to the 2 theta range of 27.5-29.5 degrees, the half-peak width of the peak is measured, and the peak is substituted into the Shele equation to obtain the crystal grain size of the Si (111) crystal face, wherein the crystal grain size is the crystal grain size of the silicon crystal in the application.
TABLE 1 electrochemical characteristics of negative electrode materials obtained in examples 1 to 8 and comparative example 1
Figure BDA0002604038540000121
Fig. 9 shows charge and discharge curves of the button cells obtained in example 1 and comparative example 1 of the present application. Experimental results show that 2032 button cells assembled by the negative electrode materials provided by the embodiments 1-8 have excellent electrochemical performance, the first charge specific capacity is 1200-1500 mAh/g, the first charge-discharge coulombic efficiency is 83% -90%, and the capacity retention rate is more than 87% after 200 circles.
Further, the electrochemical performance of example 1 is better than that of example 2, the electrochemical performance of examples 1 and 3 is better than that of examples 4 and 5, and the electrochemical performance of examples 1, 6 and 7 is better than that of example 8.
The above description is only a preferred embodiment of the present application and is not intended to limit the present application, and various modifications and changes may be made by those skilled in the art. Any modification, equivalent replacement, improvement and the like made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims (16)

1. A preparation method of a silicon-oxygen anode material is characterized by comprising the following steps:
carrying out heat treatment on a raw material only containing carbon-coated silicon monoxide and a metal material, so that at least part of silicon monoxide in the carbon-coated silicon monoxide reacts with the metal material to generate silicate and a silicon simple substance, and obtaining a silicon-oxygen cathode material; the metallic material comprises Mg, and the silicate comprises Mg 2 SiO 4 、MgSiO 3 ；
The mass ratio of the metal material to the carbon-coated silicon monoxide is 1: 5-9; the heat treatment comprises: preserving the heat of the carbon-coated SiO and the metal material at 300-600 ℃ for 1-10 h; then preserving the heat for 0.5-10 h at 850-1100 ℃; the heat treatment is carried out under the condition that the pressure is 1-140 Pa.
2. The method for producing a silicon oxygen anode material according to claim 1,
the metal material also comprises at least one of Li, Na, K, Ca, Sr, Ba, Ti, Zr, Al, Co and the alloy of the above metal elements.
3. The method for producing a silicon oxygen anode material according to claim 1,
the mass ratio of the metal material to the carbon-coated silicon monoxide is 1: 6-8.
4. The method for preparing a silicon-oxygen anode material according to claim 1,
and (3) preserving the heat of the carbon-coated SiO and the metal material at 300-600 ℃ for 1-10 h, then heating to 850-1100 ℃ at a heating rate of 5-20 ℃/min, and preserving the heat for 0.5-10 h.
5. The method for preparing a silicon-oxygen anode material according to claim 4,
the heat treatment is carried out under the condition that the pressure is 8-30 Pa.
6. The method for preparing a silicon-oxygen anode material according to any one of claims 1 to 5,
the step of heat treatment of the carbon-coated SiO and metal material further comprises:
coating a carbon layer on the surface of the silicon monoxide to obtain the carbon-coated silicon monoxide.
7. The method for preparing a silicon-oxygen anode material according to claim 6,
the carbon layer is coated on the surface of the silicon monoxide by adopting a chemical vapor deposition method.
8. The method for preparing a silicon-oxygen anode material according to claim 6,
the carbon layer with the thickness of 10-1000nm is coated on the outer surface of the silicon monoxide.
9. The method for preparing a silicon-oxygen anode material according to claim 6,
the particle size distribution of the silicon monoxide is as follows:
D10：≥3μm；
D50：5～8μm；
D100：＜15μm。
10. the method for preparing a silicon-oxygen anode material according to claim 6,
the mass fraction of carbon in the carbon-coated silicon monoxide is 0.2-20%.
11. The method for preparing a silicon-oxygen anode material according to claim 10,
the mass fraction of carbon in the carbon-coated SiO is 1-8%.
12. A silicon-oxygen negative electrode material, which is characterized in that the silicon-oxygen negative electrode material is prepared by the preparation method of the silicon-oxygen negative electrode material of any one of claims 1 to 11.
13. A silicon oxygen anode material, wherein the silicon oxygen anode material comprises: a core and a carbon layer coated outside the core, the core including Mg 2 SiO 4 、MgSiO 3 And dispersed in said Mg 2 SiO 4 、MgSiO 3 Silicon crystal grains in between.
14. The silicon-oxygen anode material as claimed in claim 13, wherein the carbon layer has a thickness of 10nm to 1000 nm.
15. The silicon-oxygen anode material as claimed in claim 14, wherein the carbon layer has a thickness of 10 to 100 nm.
16. A negative electrode for a secondary battery, characterized by comprising the silicon oxide negative electrode material according to any one of claims 12 to 15.
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