CN116544381B - Pre-magnesium silicon-oxygen anode material, preparation method thereof and secondary battery - Google Patents

Pre-magnesium silicon-oxygen anode material, preparation method thereof and secondary battery Download PDF

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CN116544381B
CN116544381B CN202310627323.2A CN202310627323A CN116544381B CN 116544381 B CN116544381 B CN 116544381B CN 202310627323 A CN202310627323 A CN 202310627323A CN 116544381 B CN116544381 B CN 116544381B
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magnesium
anode material
silicon
latent heat
carbon
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CN116544381A (en
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刘春辉
李宁
傅儒生
余德馨
仰韻霖
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Guangdong Kaijin New Energy Technology Co Ltd
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/362—Composites
    • H01M4/366—Composites as layered products
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/052—Li-accumulators
    • H01M10/0525—Rocking-chair batteries, i.e. batteries with lithium insertion or intercalation in both electrodes; Lithium-ion batteries
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/38—Selection of substances as active materials, active masses, active liquids of elements or alloys
    • H01M4/386—Silicon or alloys based on silicon
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/48—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/58—Selection of substances as active materials, active masses, active liquids of inorganic compounds other than oxides or hydroxides, e.g. sulfides, selenides, tellurides, halogenides or LiCoFy; of polyanionic structures, e.g. phosphates, silicates or borates
    • H01M4/5825—Oxygenated metallic salts or polyanionic structures, e.g. borates, phosphates, silicates, olivines
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/58—Selection of substances as active materials, active masses, active liquids of inorganic compounds other than oxides or hydroxides, e.g. sulfides, selenides, tellurides, halogenides or LiCoFy; of polyanionic structures, e.g. phosphates, silicates or borates
    • H01M4/583—Carbonaceous material, e.g. graphite-intercalation compounds or CFx
    • H01M4/587—Carbonaceous material, e.g. graphite-intercalation compounds or CFx for inserting or intercalating light metals
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/10—Energy storage using batteries

Abstract

The invention relates to the technical field of material preparation, and discloses a pre-magnesium silicon-oxygen anode material, a preparation method thereof and a secondary battery. The pre-magnesium silica anode material comprises an inner core, a first coating layer and a second coating layer. XRD patterns were obtained by XRD testing, and the strongest intensity of the Si (111) diffraction peak before fitting was defined as I' 1 Then fitting the XRD patterns, and defining the strongest intensity of the Si (111) diffraction peak after fitting as I 1 ，(I` 1 ‑I 1 )/I 1 X is 100 percent or less than 6 percent. The preparation method of the pre-magnesium silicon oxygen anode material comprises the following steps of (I) coating SiO containing carbon x Mixing the preparation raw materials of the magnesium source and the latent heat agent, and roasting the mixture step by step from low to high in temperature to obtain a first material; step (II), pickling the first material to obtain a second material; and (III) coating the second material carbon and then carrying out post-treatment.

Description

Pre-magnesium silicon-oxygen anode material, preparation method thereof and secondary battery
Technical Field
The invention relates to the technical field of material preparation, in particular to a pre-magnesium silicon-oxygen anode material, a preparation method thereof and a secondary battery.
Background
In recent years, along with the rapid development of new energy automobiles and energy storage industries, the demand of people for high-energy density lithium ion batteries is higher and higher, and the graphite theoretical capacity of the traditional negative electrode material is only 372mAh/g, so that the application of the traditional negative electrode material in the high-energy density lithium ion batteries is severely limited. And the silicon serving as the novel anode material has a theoretical specific capacity of 4200mAh/g, so that the silicon anode material is an ideal anode material, but has an expansion rate of 300% in the lithium intercalation process, so that the cycle performance is poor, and the application of the silicon anode material is limited.
Compared with pure silicon negative electrode materials, the silicon oxide negative electrode material has higher theoretical specific capacity of 2615mAh/g, and the expansion rate is close to 150%, so that the silicon oxide negative electrode material is a novel ideal negative electrode material. However, silicon oxide forms lithium oxide and lithium silicate with lithium during the first lithium intercalation process, resulting in lower first coulombic efficiency. The current method for improving the first effect of the silicon oxide comprises prelithiation and prelithiation, and compared with prelithiation, the prelithiation has lower cost and is more advantageous in commercial application, and is one of the hot spots of current research.
The reaction type of magnesian reduction is SiO 2 +2mg=si+2mgo, Δh= -291.62kJ/mol, volume 1cm 3 The heat evolved by the magnesium reaction was 10.4kJ. It was reported that silica reacted with magnesium and that the instantaneous temperature measured by the thermocouple reached 1637 ℃ when the heating temperature reached 538 ℃. In conclusion, the magnesia reaction emits a large amount of heat, the reaction rate is high, the reaction is almost finished instantaneously, and if the reaction is not controlled, si grains are easily oversized due to high temperature, so that the recycling performance of the material is affected.
To solve this problem, it is mainly known in the art to add metal halides to the pre-magnesium reaction, for example: sodium chloride. However, at 1000K, sodium chloride has a specific heat capacity per unit volume of 2.69×10 -3 kJ/(cm 3 K) the temperature is rapidly increased by heat absorption by the heat of fusion of 1.04kJ/cm per unit volume of sodium chloride 3 The heat evolved by the reaction with the unit volume of magnesium reduced silica was 10.4kJ/cm 3 The difference is approximately 10 times. For example, in example 1 of CN110993900a, reducing 20g of carbon-coated silica powder with 1g of metal magnesium powder requires 40g of sodium chloride, and it can be seen from XRD pattern that silicon spikes still exist, which means that even if sodium chloride is 40 times of the mass of magnesium powder, the heat released instantaneously by the magnesia reduction reaction cannot be absorbed rapidly, resulting in local temperature being too high, so that part of Si grains are too large, resulting in silicon spikes.
Disclosure of Invention
In view of the above problems, an object of the present invention is to provide a pre-magnesium silicon oxide negative electrode material, a method for preparing the same, and a secondary battery. The preparation method of the pre-magnesium silicon-oxygen anode material can effectively and rapidly absorb heat generated by the magnesian reduction reaction so as to avoid overlarge part of Si grains caused by local overheating, and thus the pre-magnesium silicon-oxygen anode material with better cycle performance and multiplying power performance can be prepared.
To achieve the above object, the first aspect of the present invention provides a pre-magnesium silicon oxide anode material. The pre-magnesium silica anode material comprises an inner core, a first coating layer and a second coating layer. The first cladding layer is interposed between the inner core and the second cladding layer. The inner core comprises Si and a silicon oxygen compound, the first cladding comprises Si and a silicon oxygen magnesium compound, and the second cladding comprises a carbon cladding. XRD patterns were obtained by XRD testing, and the strongest intensity of the Si (111) diffraction peak before fitting was defined as I' 1 Then fitting the XRD patterns, and defining the strongest intensity of the Si (111) diffraction peak after fitting as I 1 ，(I` 1 -I 1 )/I 1 X is 100 percent or less than 6 percent. Optionally, XRD patterns in the range of 27.4 ° to 29.4 ° are fitted.
In the pre-magnesium silica anode material, the inner core is made of Si and silica compounds, and the first coating layer containing the Si and silica magnesium compounds coats the inner core, which is equivalent to the fact that the surface layer of the inner core is pre-magnesium, but the inner part of the inner core is not pre-magnesium. In addition, according to XRD test, (I 1 -I 1 )/I 1 The X is 100 percent or less and 6 percent, which shows that the sharpness of the diffraction peak of Si (111) is small, the Si content of large crystal grains is less, and the multiplying power and the cycle performance of the pre-magnesium silicon oxygen anode material are better. The second coating layer can further relieve volume expansion, and can be used as a carbon coating layer, so that not only can the conductivity of the material be increased, but also side reactions caused by contact of active silicon with electrolyte can be avoided.
In combination with the first aspect, the pre-magnesium-silicon-oxygen anode material includes a core, a first cladding layer, and a second cladding layer. Optionally, there may also be at least one (e.g., one, two, three, etc.) carbon coating layer on the outer layer of the second coating layer.
In some embodiments, the magnesium-silicon-oxygen compound comprises Mg SiO 3 Or, the silicon oxygen magnesium compound comprises MgSiO 3 And Mg (magnesium) 2 SiO 4 。
In some embodiments, the 28.4+ -0.2 ° Si (111) diffraction peak intensity is I as measured by XRD 1 MgSiO of 30.9+ -0.2 DEG 3 (610) Intensity of diffraction peak of I 2 ，0.1≤I 2 /I 1 ≤0.6。
In some embodiments, the Si (111) diffraction peak area of 28.4+ -0.2 DEG is A as tested by XRD 1 MgSiO of 30.9+ -0.2 DEG 3 (610) Diffraction peak area A 2 ，0.05≤A 2 /A 1 ≤0.30。
In some embodiments, the 28.4+ -0.2 ° Si (111) diffraction peak intensity is I as measured by XRD 1 Mg at 32.2±0.2° 2 SiO 4 (031) Intensity of diffraction peak of I 3 ，0≤I 3 /I 1 ≤0.20。
In some embodiments, the Si (111) diffraction peak area of 28.4+ -0.2 DEG is A as tested by XRD 1 Mg at 32.2±0.2° 2 SiO 4 (031) Diffraction peak area A 3 ，0≤A 3 /A 1 ≤0.10。
In some embodiments, mgSiO 3 Grain size D of (2) 1 ，8nm≤D 1 ≤15nm。
In some embodiments, mg 2 SiO 4 Grain size D of (2) 2 ，8nm≤D 2 ≤15nm。
In some embodiments, the specific surface area of the pre-magnesium silica anode material is 0.5m 2 /g to 10.0m 2 /g。
In some embodiments, the reversible capacity of the pre-magnesium silicon oxide negative electrode material is greater than or equal to 1400mAh/g.
In some embodiments, the first coulombic efficiency of the pre-magnesium siloxy anode material is greater than or equal to 84%.
In some embodiments, the pre-magnesium silicon oxygen anode material has a rate discharge of 3C/0.2C ≡93.0%.
In some embodiments, the capacity retention of the pre-magnesium silicon oxide negative electrode material is greater than or equal to 90.0% after 50 weeks of cycling.
In some embodiments, the oxygen content in the pre-magnesium silicon oxygen anode material is 22wt.% to 30wt.% and the carbon content is 2wt.% to 10wt.%.
In some embodiments, the particle size D50 of the pre-magnesium silicon oxide anode material is 2 μm to 14 μm.
In some embodiments, the Si has a grain size of D 3 ，4nm≤D 3 ≤8nm。
In some embodiments, the silicon oxide compound comprises silicon oxide and/or silicon dioxide.
In some embodiments, the diameter of the inner core is 0.1 μm to 10.0 μm.
In some embodiments, the thickness of the first cladding layer is from 0.1 μm to 6.0 μm.
In some embodiments, the first coating layer is porous in structure and the average pore size of the pre-magnesium silicon oxide anode material is from 1nm to 20nm.
In some embodiments, the first coating layer is porous and the pore volume of the pre-magnesium-silicon-oxygen anode material is 0.01cm 3 /g to 0.2cm 3 /g。
In some embodiments, the second cladding layer has a thickness of 10nm to 300nm.
In some embodiments, XRD patterns in the range of 27.4 ° to 29.4 ° are fitted.
The second aspect of the invention provides a preparation method of the pre-magnesium silicon-oxygen anode material, which comprises the steps (I), (II) and (III).
Step (I): will contain carbon-coated SiO x After mixing the preparation raw materials of the magnesium source and the latent heat agent, roasting the mixture step by step from low to high in temperature to obtain a first material. Wherein 0 is <x<2, the vaporization heat of the latent heat agent is more than or equal to 5kJ/cm in unit volume 3 And contains a substance having a boiling point of 500 ℃ to 1000 ℃ and the latent heat agent does not reduce SiO x Or does not participate in the magnesia reduction of SiO x Is a reaction of (a). The step firing includes at least a first firing stage to melt the latent heat agent and a step firing step to sinter the carbon-coated SiO x And a second roasting stage for reacting with the magnesium source.
Step (II): and (3) pickling the first material to obtain a second material.
Step (III): and coating the second material carbon, and then carrying out post-treatment.
With reference to the second aspect, carbon-coated SiO is used x In this case, the second coating layer may be carbon-coated SiO x A carbon layer thereon. Optionally, a carbon coating layer may be further provided on the outer layer of the second coating layer. Optionally, at least one (e.g., one, two, three, etc.) carbon layer may be additionally coated on this basis by means of carbon coating.
In combination with the second aspect, the invention provides the pre-magnesium silicon oxygen anode material prepared by the preparation method of the pre-magnesium silicon oxygen anode material.
The preparation method of the pre-magnesium silicon-oxygen anode material has the following technical effects:
1. the invention adopts the method that the vaporization heat per unit volume is more than or equal to 5kJ/cm 3 And contains a substance having a boiling point of 500 ℃ to 1000 ℃ as a latent heat agent, and the latent heat agent does not reduce SiO x Or does not participate in the magnesia reduction of SiO x The reaction of (2) can absorb more heat under the same volume, can effectively inhibit local overheating during the magnesium thermal reaction, thereby inhibiting Si and MgSiO 3 And Mg (magnesium) 2 SiO 4 The grains grow up. Once the heat is too high, si, mgSiO 3 And Mg (magnesium) 2 SiO 4 The grains generally grow in a very short time.
2. The latent heat agent and the magnesium source can be mutually dissolved in a molten state, the contact area of the latent heat agent and the magnesium source can be increased, mass transfer and heat transfer are facilitated, diffraction peaks caused by overlarge part of Si grains due to local reaction overheating are reduced, the magnesium thermal reduction is more uniform, and the cycle performance and the multiplying power performance of the pre-magnesium silicon-oxygen anode material are improved.
3. After the raw materials are mixed, the raw materials are roasted step by step from low to high in temperature, and the latent heat agent is melted in the first roasting stage in the step roasting, so that the liquid latent heat agent can wrap the magnesium source, the contact area of the latent heat agent and the magnesium source is increased, and the subsequent uniform magnesium pre-preparation is facilitated. A great amount of heat released instantaneously in the magnesium thermal reaction in the second roasting stage is easily absorbed by vaporization of the latent heat agent, which is beneficial to controlling overgrowth of Si crystal grains.
In some embodiments, the preparation feedstock further comprises a metal halide.
In some embodiments, the metal halide comprises NaF, KF, caF 2 、MgF 2 、NaCl、KCl、CaCl 2 、MgCl 2 、FeCl 2 、FeCl 3 、CuCl 2 、AlCl 3 、ZnCl 2 、ZnBr 2 And MgI 2 At least one of them.
In some embodiments, when the starting material for the preparation of step (I) contains a metal halide, then the SiO is carbon coated x The mass ratio of the magnesium source, the latent heat agent and the metal halide is 100:5-50:50-500:0-200, and the content of the metal halide is not 0. When the raw material for the step (I) does not contain a metal halide, then the SiO is coated with carbon x The mass ratio of the magnesium source to the latent heat agent is 100:5-50:50-500.
In some embodiments, the carbon-coated SiO x D50 of (2) is from 2 μm to 14 μm.
In some embodiments, the magnesium source comprises metallic magnesium and/or magnesium alloy.
In some embodiments, the D50 of the magnesium source is 10 μm to 200 μm.
In some embodiments, D100.ltoreq.500 μm for the magnesium source.
In some embodiments, the latent heat agent has a melting point of 500 ℃ or less.
In some embodiments, the latent heat agent comprises at least one of cadmium, a cadmium alloy, selenium, and a selenium alloy.
In some embodiments, the D50 of the latent heat agent is from 10 μm to 100 μm.
In some embodiments, D100 of the latent heat agent is less than or equal to 300 μm.
In some embodiments, the volume ratio of the latent heat agent to the magnesium source is 2 to 6:1.
In some embodiments, the latent heat agent does not include lithium, sodium, potassium, magnesium, calcium, aluminum, sodium chloride, or potassium chloride.
In some embodiments, the carbon-coated SiO x The mass ratio of the magnesium source to the latent heat agent is 100:5-50:50-500.
In some embodiments, the step firing is performed under an inert atmosphere comprising at least one of nitrogen, argon, and helium.
In some embodiments, the step firing is performed in a rotary kiln at a rotational speed of 0.5rpm to 5.0rpm.
In some embodiments, the firing temperature in the first firing stage is 300 ℃ to 500 ℃, the holding time is 1h to 4h, and the ramp rate is 1 ℃/min to 10 ℃/min.
In some embodiments, the firing temperature in the second firing stage is 500 ℃ to 1000 ℃, the holding time is 1h to 12h, and the ramp rate is 1 ℃/min to 10 ℃/min.
In some embodiments, the first material is cooled to room temperature and then acid washed.
In some embodiments, the acid solution employed for the acid wash is at least one of hydrochloric acid, sulfuric acid, nitric acid, and hydrofluoric acid.
In some embodiments, the acid solution used for pickling has a concentration of 0.1mol/L to 5.0mol/L.
In some embodiments, the acid solution employed for the acid wash and the first material are in a mass ratio of 3 to 15:1.
In some embodiments, the time for pickling is from 1h to 10h.
In some embodiments, the number of pickling is from 1 to 5.
In some embodiments, the stirring is performed during the pickling, and the stirring speed is 100rpm to 600rpm.
In some embodiments, the means employed for mixing includes VC mixing, fusion machine mixing, or ball milling mixing.
In some embodiments, the first material is washed with acid and then sequentially filtered, washed with water, and dried to obtain a second material.
In some embodiments, the carbon coating is performed with an organic carbon source, and the mass ratio of the second material to the organic carbon source is 100:1-10.
In some embodiments, the carbon coating is at a temperature of 700 ℃ to 1000 ℃, a soak time of 1h to 12h, and a ramp rate of 1 ℃/min to 10 ℃/min.
In some embodiments, the post-treatment comprises at least one of crushing, pulverizing, and sieving.
The invention also provides a secondary battery, which comprises a positive electrode material and a negative electrode material, wherein the negative electrode material comprises the pre-magnesium silicon-oxygen negative electrode material or the pre-magnesium silicon-oxygen negative electrode material prepared by the preparation method of the pre-magnesium silicon-oxygen negative electrode material.
In some embodiments, the positive electrode material includes at least one of a lithium cobaltate-based positive electrode material, a lithium iron phosphate-based positive electrode material, a lithium nickel cobalt manganate-based positive electrode material, and a lithium nickel cobalt aluminate-based positive electrode material.
The invention prepares the pre-magnesium silicon oxygen cathode material with a brand new structure or component by controlling local reaction overheat to avoid oversized Si crystal grains and corresponding process, and the XRD characterization shows that the pre-magnesium silicon oxygen cathode material has small or no sharp degree of Si (111) diffraction peak, especially (I') 1 -I 1 )/I 1 The X is 100 percent or less than or equal to 6 percent, which is obviously different from the pre-magnesium silicon oxygen anode materials prepared by other processes, and shows that the structure or the composition of the pre-magnesium silicon oxygen anode material is different from the pre-magnesium silicon oxygen anode materials prepared by other processes. The invention is fitted by means of XRD patterns (I') 1 -I 1 )/I 1 The difference of the structure or the composition of the pre-magnesium silica anode material and other anode silica materials is verified by the X100 percent to 6 percent. In addition, it is the difference in material structure or composition that brings about the obvious different technical effects.
Drawings
FIG. 1 is a scanning electron microscope topography of the pre-magnesium silicon oxygen anode material of example 1;
FIG. 2 is an XRD pattern of the pre-magnesium silica anode material of example 1;
FIG. 3 is a schematic fit of the XRD pattern obtained in FIG. 2;
FIG. 4 is an XRD pattern of the pre-magnesium silica anode material of comparative example 1;
fig. 5 is a schematic fit of the XRD pattern obtained in fig. 4.
Detailed Description
The pre-magnesium silicon oxygen anode material can be used as an anode active material to be applied to a secondary battery. The secondary battery includes a positive electrode material and a negative electrode material. The positive electrode material comprises at least one of a lithium cobalt oxide positive electrode material, a lithium iron phosphate positive electrode material, a nickel cobalt lithium manganate positive electrode material and a nickel cobalt lithium aluminate positive electrode material. The pre-magnesium silicon oxygen anode material can be used alone as an anode active material, or can be mixed with other anode active materials (such as natural graphite, artificial graphite, soft carbon, hard carbon and the like).
The pre-magnesium silica anode material comprises an inner core, a first coating layer and a second coating layer.
The specific surface area of the pre-magnesium silica anode material is 0.5m 2 /g to 10.0m 2 /g, which may be, but is not limited to, 0.5m 2 /g、1.0m 2 /g、2.0m 2 /g、3.0m 2 /g、4.0m 2 /g、5.0m 2 /g、6.0m 2 /g、7.0m 2 /g、8.0m 2 /g、9.0m 2 /g、10.0m 2 And/g. The reversible capacity of the pre-magnesium silicon oxygen anode material is more than or equal to 1400mAh/g, and can be more than or equal to 1400mAh/g, more than or equal to 1420mAh/g, more than or equal to 1440mAh/g, more than or equal to 1460mAh/g, more than or equal to 1480mAh/g, more than or equal to 1500mAh/g, more than or equal to 1530mAh/g, more than or equal to 1550mAh/g and more than or equal to 1600mAh/g. The first coulombic efficiency of the pre-magnesium silicon oxygen anode material is more than or equal to 84 percent, can be more than or equal to 84 percent, more than or equal to 85 percent, more than or equal to 86 percent, more than or equal to 87 percent, more than or equal to 88 percent, more than or equal to 89 percent, more than or equal to 90 percent, more than or equal to 91 percent and more than or equal to 92 percent. The multiplying power discharge of the pre-magnesium silicon oxygen anode material is more than or equal to 93.0 percent and 3C/0.2C, which can be more than or equal to 93.0 percent, more than or equal to 94.0 percent, more than or equal to 95.0 percent, more than or equal to 96.0 percent, more than or equal to 97.0 percent, more than or equal to 98.0 percent and more than or equal to 99.0 percent. The capacity retention rate of the magnesium-pre-silicon-oxygen anode material at 50 weeks is more than or equal to 90.0 percent, can be more than or equal to 91.0 percent, more than or equal to 92.0 percent, more than or equal to 93.0 percent, more than or equal to 94.0 percent, more than or equal to 95.0 percent, more than or equal to 96.0 percent, more than or equal to 97.0 percent and more than or equal to 98.0 percent without limitation. The oxygen content in the pre-magnesium silicon oxygen anode material is 22wt.% to 30wt.%, and may be, but is not limited to, 22wt.%, 23wt.%, 24wt.%, 25wt.%, 26wt.%, 27wt.%, 28wt.%, 29wt.%, 30wt.%. The carbon content in the pre-magnesium silico negative electrode material is 2wt.% to 10wt.%, and may be, but is not limited to, 2wt.%, 3wt.%, 4wt.%, 5wt.%, 6wt.%, 7wt.% 8wt.%, 9wt.%, 10wt.%. The particle size D50 of the pre-magnesium silicon oxygen anode material is 2 μm to 14 μm, and may be, but is not limited to, 2 μm, 3 μm, 4 μm, 5 μm, 6 μm, 7 μm, 8 μm, 9 μm, 10 μm, 11 μm, 12 μm, 13 μm, 14 μm.
The core includes Si and silicon oxide. The diameter of the core is 0.1 μm to 10.0 μm and may be, but is not limited to, 0.1 μm, 0.5 μm, 1.0 μm, 1.5 μm, 2.0 μm, 2.5 μm, 3.0 μm, 3.5 μm, 4.0 μm, 4.5 μm, 5.0 μm, 5.5 μm, 6.0 μm, 6.5 μm, 7.0 μm, 7.5 μm, 8.0 μm, 8.5 μm, 9.0 μm, 9.5 μm, 10.0 μm. Si grain size D 3 ，4nm≤D 3 ≤8nm，D 3 May be, but is not limited to, 4 μm, 5 μm, 6 μm, 7 μm, 8 μm. As one embodiment, 4 nm.ltoreq.D 3 And the wavelength is less than or equal to 6nm. The silicon oxygen compound includes silicon oxide and/or silicon dioxide.
The first cladding layer is interposed between the inner core and the second cladding layer and includes Si and a magnesium-silicon oxide compound. The thickness of the first coating layer is 0.1 μm to 6.0 μm, and may be, but not limited to, 0.1 μm, 0.5 μm, 1.0 μm, 1.5 μm, 2.0 μm, 2.5 μm, 3.0 μm, 3.5 μm, 4.0 μm, 4.5 μm, 5.0 μm, 5.5 μm, 6.0 μm. The first coating layer is of a porous structure. The average pore diameter of the pre-magnesium silicon oxygen anode material is 1nm to 20nm, and can be 1nm, 2nm, 3nm, 4nm, 5nm, 6nm, 7nm, 8nm, 9nm, 10nm, 11nm, 12nm, 13nm, 14nm, 15nm, 16nm, 17nm, 18nm, 19nm and 20nm. Pore volume of the pre-magnesium silica anode material is 0.01cm 3 /g to 0.20cm 3 Per g, may be, but is not limited to, 0.01cm 3 /g、0.03cm 3 /g、0.05cm 3 /g、0.07cm 3 /g、0.10cm 3 /g、0.12cm 3 /g、0.15cm 3 /g、0.17cm 3 /g、0.19cm 3 /g、0.20cm 3 /g。
XRD test shows that the strongest intensity of Si (111) diffraction peak before fitting is defined as I' 1 Then fitting the XRD patterns, and defining the strongest intensity of the Si (111) diffraction peak after fitting as I 1 ，(I` 1 -I 1 )/I 1 ×100％≤6％。(I` 1 -I 1 )/I 1 Values of x 100% may be, but are not limited to, 6% >, 5% >, 4% >, 3% >, or less2% or less than or equal to 1%.
The intensity of the diffraction peak of Si (111) with the angle of 28.4 plus or minus 0.2 degrees can be used for fitting an XRD spectrum by software, and the fitted XRD spectrum can be selected from 27.4 degrees to 29.4 degrees. As an example, XRD patterns were fit analyzed, e.g. using X' pert High Score (version 2.1.0 2004) software, which comprises the steps of: removing Ka2, smoothing, defining background, finding peak, fitting Si spectral peak, finding I 1 And I 1 Calculation (I') 1 -I 1 )/I 1 Values x 100%.
(1) Go Ka2: the XRD pattern to be analyzed is opened, the blank of the pattern is clicked on "Strip K-Alpha2", the "Strip K-Alpha2" is clicked on in a pop-up dialog box, and then "replay" is clicked again (parameter setting: method is Rachinger, K-A2/K-A1 integrity ratio is 0.5).
(2) Smoothing: right click on spectrogram blank, click on "smoth" in menu, click on "smoth" in pop-up dialog, and then click on "Replace" (parameter setting: polynominal type is Quintic, fast Fourier Degree of smoothing is 1).
(3) Definition of background: right click on spectrogram blank, "Determine Background," click on "Background" in pop-up dialog, and then click on "Accept" (parameter setting: granular is 20,Bending factor is 1).
(4) Peak searching: the peak blank of the spectrum is right-clicked, the "Search Peaks" is clicked in the pop-up dialog, and then the "Accept" is clicked. ( Peak finding parameters: minimum significant is 1.0-2.0,minimum tip width, 0.1-0.5,maximum tip width is 2.0-6.0,peak base width is 10.0 )
(5) Si spectral peak fitting: right clicking the blank of the spectrogram, clicking 'Set Manual Ranges', inputting an angle range '27.4-29.4' in a pop-up dialog box, clicking 'OK', right clicking the blank of the spectrogram, clicking 'Fit Profile', and fitting once.
(6) Find I 1 And I 1 : the Anchor Scan Date is turned on, and the maximum value I' is found in the Iobs column, 27.4-29.4 DEG 1 The highest intensity of the diffraction peak of Si (111) comprises a diffraction backgroundStrength; find the maximum I in Icalc column, 27.4-29.4 DEG 1 The strongest intensities after fitting the Si (111) diffraction peak included the diffraction back intensities.
(7) Calculation (I') 1 -I 1 )/I 1 Values x 100%.
In addition, the XRD patterns can be fit analyzed using MDI Jade or Origin software.
The silicon-oxygen-magnesium compound comprises MgSiO 3 Or, the silicon oxygen magnesium compound comprises MgSiO 3 And Mg (magnesium) 2 SiO 4 . The magnesium-silicon oxide compound in the pre-magnesium silicon oxide anode material prepared after acid washing is mainly MgSiO 3 . XRD test shows that the diffraction peak intensity of Si (111) with the angle of 28.4+/-0.2 DEG is I 1 MgSiO of 30.9+ -0.2 DEG 3 (610) Intensity of diffraction peak of I 2 ，0.1≤I 2 /I 1 ≤0.6。I 2 /I 1 The values of (2) may be, but are not limited to, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6. As one embodiment, 0.1.ltoreq.I 2 /I 1 Less than or equal to 0.4. Si (111) diffraction peak area of 28.4+ -0.2 DEG A 1 MgSiO of 30.9+ -0.2 DEG 3 (610) Diffraction peak area A 2 ，0.05≤A 2 /A 1 ≤0.30。A 2 /A 1 The values of (c) may be, but are not limited to, 0.05, 0.10, 0.15, 0.20, 0.25, 0.30. As one embodiment, 0.05.ltoreq.A 2 /A 1 ≤0.20。MgSiO 3 Grain size D of (2) 1 ，8nm≤D 1 15nm or less, alternatively 8nm or less D 1 ≤13.5nm。D 1 May be, but is not limited to, 8nm, 9nm, 10nm, 11nm, 12nm, 13nm, 14nm, 15nm.
XRD test shows that the diffraction peak intensity of Si (111) with the angle of 28.4+/-0.2 DEG is I 1 Mg at 32.2±0.2° 2 SiO 4 (031) Intensity of diffraction peak of I 3 ，0≤I 3 /I 1 ≤0.20。I 3 /I 1 The values of (c) may be, but are not limited to, 0, 0.01, 0.03, 0.05, 0.07, 0.09, 0.11, 0.13, 0.15, 0.17, 0.19, 0.20. As one embodiment, 0.ltoreq.I 3 /I 1 Less than or equal to 0.10. XRD test shows that the diffraction peak area of Si (111) with the angle of 28.4+/-0.2 DEG is A 1 Mg at 32.2±0.2° 2 SiO 4 (031 Diffraction peak area A 3 ，0≤A 3 /A 1 ≤0.10。A 3 /A 1 The values of (c) may be, but are not limited to, 0, 0.01, 0.02, 0.03, 0.04, 0.05, 0.06, 0.07, 0.08, 0.09, 0.10. As one embodiment, 0.ltoreq.A 3 /A 1 Less than or equal to 0.05. By way of example, I 3 /I 1 Has a value of 0, and indicates that the magnesium-silicon oxide compound does not contain Mg 2 SiO 4 。Mg 2 SiO 4 Grain size D of (2) 2 ，8nm≤D 2 15nm or less, alternatively 8nm or less D 2 ≤13.5nm。D 2 May be, but is not limited to, 8nm, 9nm, 10nm, 11nm, 12nm, 13nm, 14nm, 15nm.
The second cladding layer includes a carbon cladding layer. The thickness of the second coating layer is 10nm to 300nm, and may be, but not limited to, 10nm, 30nm, 50nm, 70nm, 100nm, 150nm, 170nm, 200nm, 220nm, 240nm, 260nm, 280nm, 300nm. The carbon content of the second cladding layer is 2% to 10% of the sum of the mass of the core, the first cladding layer and the second cladding layer, and may be, but not limited to, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%.
The preparation method of the pre-magnesium silicon-oxygen anode material comprises the steps of (I), (II) and (III).
Step (I): will contain carbon-coated SiO x After mixing the preparation raw materials of the magnesium source and the latent heat agent, roasting the mixture step by step from low to high in temperature to obtain a first material.
Wherein the carbon coats SiO x 0 in (0)<x<2, x may be, but is not limited to, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1.0, 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 1.7. As an example, x is 1. As an embodiment, 0.5.ltoreq.x.ltoreq.1.5. Carbon coated SiO x The amount of medium carbon coating is 1wt.% to 5wt.%, and may be, but is not limited to, 1wt.%, 2wt.%, 3wt.%, 4wt.%, 5wt.%. Carbon coated SiO x The D50 of (2) is 2 μm to 14. Mu.m, which may be, but is not limited to, 2 μm, 3 μm, 4 μm, 5 μm, 6 μm, 7 μm, 8 μm, 9 μm, 10 μm, 11 μm, 12 μm, 13 μm, 14 μm.
The magnesium source comprises metallic magnesium and/or magnesium alloys. The magnesium alloy may be at least one of magnesium zinc alloy, magnesium aluminum alloy and magnesium tin alloy. The magnesium source has a D50 of 10 μm to 200 μm and may be, but is not limited to, 10 μm, 20 μm, 30 μm, 40 μm, 50 μm, 60 μm, 70 μm, 80 μm, 90 μm, 100 μm, 110 μm, 120 μm, 130 μm, 140 μm, 150 μm, 160 μm, 170 μm, 180 μm, 190 μm, 200 μm. The magnesium source has a D100 of 500 μm or less, and may be, but is not limited to 500 μm or less, 480 μm or less, 450 μm or less, 430 μm or less, 400 μm or less, 370 μm or less, 350 μm or less, 330 μm or less, 300 μm or less, 270 μm or less, or 250 μm or less.
The vaporization heat of the latent heat agent is more than or equal to 5kJ/cm in unit volume 3 And contains a substance having a boiling point of 500 ℃ to 1000 ℃ and the latent heat agent does not reduce SiO x Or does not participate in the magnesia reduction of SiO x Is carried out by a reaction; the latent heat agent may be simple substance, compound or mixture; when the latent heat agent is an element and/or a compound, the boiling point of the element and/or the compound is 500-1000 ℃; when the latent heat agent is a mixture, the latent heat agent contains more than or equal to 50wt.%, more than or equal to 60wt.%, more than or equal to 70wt.%, and,
80wt.%, 90wt.% or more, or 95wt.% or more (based on the latent heat agent) of a substance having a boiling point of 500 ℃ to 1000 ℃. Heat of vaporization per unit volume = heat of vaporization per mole mass x density. The heat of vaporization per unit volume of the inventive latent heat agent can be, but is not limited to, 5kJ/cm or more 3 、≥6kJ/cm 3 、≥7kJ/cm 3 、≥8kJ/cm 3 、≥9kJ/cm 3 、
≥10kJ/cm 3 . The boiling point of the latent heat agent may be, but is not limited to, 500 ℃, 550 ℃, 600 ℃, 650 ℃, 700 ℃, 750 ℃, 800 ℃, 850 ℃, 900 ℃, 950 ℃, 1000 ℃. The latent heat agent at this boiling point is vaporized in the magnesium thermal reaction to absorb heat. The melting point of the latent heat agent is less than or equal to 500 ℃, and can be, but is not limited to, less than or equal to 500 ℃, less than or equal to 450 ℃, less than or equal to 400 ℃, less than or equal to 350 ℃, less than or equal to 300 ℃, less than or equal to 250 ℃, less than or equal to 200 ℃ and less than or equal to 150 ℃. The lower melting point of the latent heat agent can be melted at low temperature to improve SiO coating with carbon x The contact area of the magnesium source to achieve uniform magnesium pre-production. The latent heat agent includes at least one of cadmium, a cadmium alloy, selenium and a selenium alloy, which may be, but is not limited to, selected from the group consisting of cadmium tin alloy, cadmium lead alloy, selenium tin alloy, or selenium cadmium alloy. The D50 of the latent heat agent is 10 μm to 100 μm, and may be, but not limited to, 10 μm, 20 μm, 30 μm,40 μm, 50 μm, 60 μm, 70 μm, 80 μm, 90 μm, 100 μm. D100 of the latent heat agent is 300 μm or less, and may be, but is not limited to 300 μm or less, 270 μm or less, 250 μm or less, 200 μm or less, 180 μm or less, 150 μm or less. The volume ratio of the latent heat agent to the magnesium source is 2-6:1, which can be but is not limited to 2:1, 3:1, 4:1, 5:1, 6:1.
Carbon coated SiO x The mass ratio of the magnesium source and the latent heat agent is 100:5-50:50-500, and can be, but is not limited to, 100:5:50, 100:5:100, 100:5:300, 100:5:500, 100:15:50, 100:15:70, 100:15:200, 100:15:400, 100:25:75, 100:25:200, 100:25:350, 100:25:500, 100:35:70, 100:35:200, 100:35:300, 100:35:500, 100:50:50, 100:50:200, 100:50:300, 100:50:500).
The latent heat agent is not melted and then directly reacts with SiO x The metal or compound that is reacted (such as Al, K, li, na, mg, ca, etc.) is not a high boiling elemental metal or compound that has a boiling point above the thermal reaction temperature of magnesium (such as bismuth, indium, gallium, sodium chloride, potassium chloride, all having a boiling point above 1000 ℃). Physical properties of the inventive latent heat agent and conventional molten salt are shown in table 1 as examples. Wherein, cadmium and selenium have lower boiling points and higher vaporization heat per unit volume, and sodium chloride and potassium chloride have too high boiling points and are higher than the magnesium thermal reaction temperature, so that the cadmium and the selenium are difficult to vaporize in the magnesium thermal reaction process to absorb heat rapidly. Although the boiling point of zinc chloride is not high, the vaporization heat per unit volume is low, the heat absorption effect is limited, a large amount of heat cannot be absorbed in a short time, and once the heat is too high, si and MgSiO 3 And Mg (magnesium) 2 SiO 4 The grains generally grow in a very short time.
TABLE 1 physical Properties parameters of the latent heat agent and conventional molten salt
As an embodiment, the preparation feedstock further comprises a metal halide. The metal halides include NaF, KF, caF 2 、MgF 2 、NaCl、KCl、CaCl 2 、MgCl 2 、FeCl 2 、FeCl 3 、CuCl 2 、AlCl 3 、ZnCl 2 、ZnBr 2 And MgI 2 At least one of them. Carbon coated SiO x The mass ratio of the magnesium source, the latent heat agent and the metal halide is 100:5-50:50-500:0-200, and can be but not limited to 100:5:50:10, 100:5:100:10, 100:5:300:10, 100:5:500:25, 100:15:50: 35. 100:15:70:45, 100:15:200:55, 100:15:400:65, 100:25:75:80, 100:25:200:90, 100:25:350:100, 100:25:500:125, 100:35:70:150, 100:35:200:180, 100:35:300:40, 100:35:500:70, 100:50:50:30, 100:50:200:40, 100:50:300:50, 100:50:500:50.
The step-firing is performed under an inert atmosphere including at least one of nitrogen, argon and helium. The step firing is performed in a rotary kiln at a rotational speed of 0.5rpm to 5.0rpm, which may be, but is not limited to, 0.5rpm, 1.0rpm, 1.5rpm, 2.0rpm, 2.5rpm, 3.0rpm, 3.5rpm, 4.0rpm, 4.5rpm, 5.0rpm. The mixing mode includes VC mixing, fusion machine mixing or ball milling mixing.
The step firing includes at least a first firing stage to melt the latent heat agent and a step firing step to sinter the carbon-coated SiO x And a second roasting stage for reacting with the magnesium source. The roasting temperature in the first roasting stage is 300-500 ℃, the heat preservation time is 1-4 h, and the heating rate is 1-10 ℃/min. As an example, the firing temperature of the first firing stage may be, but is not limited to, 300 ℃, 320 ℃, 340 ℃, 360 ℃, 380 ℃, 400 ℃, 420 ℃, 440 ℃, 460 ℃, 480 ℃, 500 ℃. The incubation time for the first firing stage may be, but is not limited to, 1h, 2h, 3h, 4h. The temperature rise rate of the first firing stage may be, but is not limited to, 1 ℃/min, 2 ℃/min, 3 ℃/min, 4 ℃/min, 5 ℃/min, 6 ℃/min, 7 ℃/min, 8 ℃/min, 9 ℃/min, 10 ℃/min. The roasting temperature of the second roasting stage is 500-1000 ℃, the heat preservation time is 1-12 h, and the heating rate is 1-10 ℃/min. As an example, the firing temperature in the second firing stage may be, but is not limited to, 500 ℃, 520 ℃, 540 ℃, 560 ℃, 580 ℃, 600 ℃, 620 ℃, 640 ℃, 660 ℃, 680 ℃, 700 ℃, 720 ℃, 740 ℃, 760 ℃, 780 ℃, 800 ℃, 820 ℃, 840 ℃, 860 ℃, 880 ℃, 900 ℃, 920 ℃,940 ℃, 960 ℃, 980 ℃, 1000 ℃. The holding time of the second firing stage may be, but is not limited to, 1h, 2h, 3h, 4h, 5h, 6h, 7h, 8h, 9h, 10h, 11h, 12h. The rate of heating up in the second firing stage may be, but is not limited to, 1 ℃/min, 2 ℃/min, 3 ℃/min, 4 ℃/min, 5 ℃/min, 6 ℃/min, 7 ℃/min, 8 ℃/min, 9 ℃/min, 10 ℃/min.
Step (II): and (3) pickling the first material to obtain a second material.
As an embodiment, the first material is cooled to room temperature and then pickled. Surface-generated Mg of the inner core 2 SiO 4 It is insoluble in water and it is integral with the silicon material, closely connected. Acid solution is adopted for acid washing, mg 2 SiO 4 Acid hydrolysis to silicic acid is carried out to remove the silicic acid.
As an embodiment, the acid solution used for the acid washing is at least one of hydrochloric acid, sulfuric acid, nitric acid and hydrofluoric acid. The acid solution used for the acid washing has a concentration of 0.1mol/L to 5.0mol/L, and may be, but not limited to, 0.1mol/L, 0.5mol/L, 1.0mol/L, 1.5mol/L, 2.0mol/L, 2.5mol/L, 3.0mol/L, 3.5mol/L, 4.0mol/L, 4.5mol/L, 5.0mol/L. The pickling time is 1h to 10h, and can be, but is not limited to, 1h, 2h, 3h, 4h, 5h, 6h, 7h, 8h, 9h, 10h. The number of pickling times is 1 to 5, and may be, but not limited to, 1, 2, 3, 4, 5 to remove Mg as much as possible 2 SiO 4 Thereby increasing the capacity of the material. Stirring is performed during pickling, and the stirring speed is 100rpm to 600rpm, and may be, but not limited to, 100rpm, 150rpm, 200rpm, 250rpm, 300rpm, 350rpm, 400rpm, 450rpm, 500rpm, 550rpm, 600rpm. The mass ratio of the acid solution to the first material used for pickling is 3-15:1, which can be, but is not limited to, 3:1, 4:1, 5:1, 6:1, 7:1, 8:1, 9:1, 10:1, 11:1, 12:1, 13:1, 14:1, 15:1.
As an implementation scheme, the first material is subjected to acid washing and then is sequentially filtered, washed and dried to obtain the second material. The filtration mode can be, but is not limited to, filter pressing or suction filtration. Washing the filtered material to be neutral by adopting water, wherein the weight ratio of the water amount of the water to the filtered material is 2-20:1, and the water amount of the water to the filtered material can be, but is not limited to, 2:1, 3:1, 4:1, 5:1, 6:1, 7:1, 8:1, 9:1, 10:1, 11:1, 12:1, 13:1, 14:1, 15:1, 16:1, 17:1, 18:1, 19:1 and 20:1. The water washing time is 0.1h to 2h, and can be, but not limited to, 0.1h, 0.3h, 0.5h, 0.7h, 0.9h, 1.0h, 1.3h, 1.5h, 1.7h, 1.9h, 2.0h. The temperature of drying after water washing is 45-100 ℃ and the drying time is 12-36 h. As an example, the temperature of drying may be, but is not limited to, 45 ℃, 50 ℃, 55 ℃, 60 ℃, 65 ℃, 70 ℃, 75 ℃, 80 ℃, 85 ℃, 90 ℃, 95 ℃, 100 ℃. By way of example, the time of drying may be, but is not limited to, 12h, 14h, 16h, 18h, 20h, 22h, 24h, 28h, 30h, 33h, 36h. The drying is vacuum drying or air drying.
Step (III): and coating the second material carbon, and then carrying out post-treatment.
As an embodiment, the carbon coating is performed using an organic carbon source. The mass ratio of the second material to the organic carbon source is 100:1-10, and can be, but is not limited to, 100:1, 100:2, 100:3, 100:4, 100:5, 100:6, 100:7, 100:8, 100:9, 100:10. The organic carbon source may be, but is not limited to, a gaseous organic carbon source, a liquid organic carbon source, or a solid organic carbon source. The carbon coating may be gas phase coating, solid phase coating or liquid phase coating. Of course, other coating methods such as plasma may be used as long as the coating forms a carbon-coated outer layer. The carbon-coated outer layer formed by the method can be one layer, two layers, three layers and the like. The pre-magnesium silicon oxygen anode material is not limited by a carbon coating mode, and is also not limited by the number of layers of the carbon coating outer layer. In some embodiments, the organic carbon source may be at least one of methane, ethane, ethylene, acetylene, propane, propylene, pitch, phenolic, starch, polyvinyl alcohol, epoxy, polydopamine, lignin, citric acid, glucose, and sucrose. As an example, the organic carbon source may be pitch. As an embodiment of the present invention, the carbon coating temperature is 700 to 1000 ℃, and may be, but not limited to, 700 ℃, 750 ℃, 800 ℃, 850 ℃, 900 ℃, 950 ℃, 1000 ℃. The incubation time is 1h to 12h, and may be, but is not limited to, 1h, 2h, 3h, 4h, 5h, 6h, 7h, 8h, 9h, 10h, 11h, 12h. The heating rate of the carbon coating is 1 to 10 ℃ per minute, and may be, but is not limited to, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10 ℃/min.
As an embodiment of the present invention, the post-treatment includes at least one of crushing, pulverizing, and sieving. The crushing may be performed by a twin roll crusher at a rotation speed of 6r/min to 10r/min, but not limited to 6r/min, 7r/min, 8r/min, 9r/min, 10r/min. The comminution may be performed, but is not limited to, using a pulverizer. The screen mesh used for sieving is 100 mesh to 500 mesh, and can be, but not limited to, 100 mesh, 130 mesh, 150 mesh, 170 mesh, 200 mesh, 230 mesh, 250 mesh, 300 mesh, 350 mesh, 400 mesh, 450 mesh, 500 mesh.
For a better description of the objects, technical solutions and advantageous effects of the present invention, the present invention will be further described with reference to specific examples. It should be noted that the following implementation of the method is a further explanation of the present invention and should not be taken as limiting the present invention.
Example 1
The embodiment is a preparation method of a pre-magnesium silicon-oxygen anode material, comprising the following steps:
step (I): 1.00kg of carbon-coated SiO (carbon coating amount: 3wt.%, D50: 6.3 μm), 0.15kg of metal magnesium powder (D50: 62 μm, D100: 177 μm) and 2.24kg of cadmium powder (cadmium powder volume: 3 times the magnesium powder volume, heat of vaporization per unit volume: 7.69 kJ/cm) 3 The method comprises the steps of mixing VC with the boiling point of 765 ℃, the melting point of 321 ℃, the D50 of 55 mu m and the D100 of 152 mu m in a rotary furnace, heating to 430 ℃ at a heating rate of 5 ℃/min under the protection of argon, preserving heat for 4 hours, heating to 880 ℃ at a heating rate of 1 ℃/min, preserving heat for 6 hours, and cooling to room temperature to obtain a first material.
Step (II): the first material and hydrochloric acid are mixed and stirred (hydrochloric acid concentration is 1.0 mol/L) for 2h according to the mass ratio of 1:5, and the acid is washed for 2 times, and the stirring is carried out while the acid is washed, and the stirring speed is 300rpm. And (3) filtering by a filter press, washing with deionized water to neutrality, and vacuum drying at 80 ℃ for 20 hours to obtain a second material.
Step (III): and heating the second material to 900 ℃ at a heating rate of 5 ℃/min under an argon atmosphere by adopting asphalt (5 wt.%), preserving heat for 6 hours, cooling, and then crushing, crushing and sieving sequentially.
And carrying out section morphology characterization on the prepared pre-magnesium silicon-oxygen anode material by adopting a scanning electron microscope, as shown in figure 1. The prepared pre-magnesium silica anode material adopts XRD test to carry out crystal structure characterization, and is shown in figure 2. The resulting XRD patterns were fitted using X' pert High Score (version 2.1.0 2004) software as shown in figure 3. The procedure for fitting analysis of XRD patterns using X' pert High Score software was performed as described in detail above, and includes the steps of: removing Ka2, smoothing, defining background, finding peak, fitting Si spectral peak, finding I 1 And I 1 Calculation (I') 1 -I 1 )/I 1 Values x 100%.
Characterization of the crystal structure: XRD test is carried out on the prepared pre-magnesium silica anode material by adopting a Powder diffractometer of Panalytical panaceae, the Netherlands, the Xpert3Powder, the test voltage is 40KV, the test current is 40mA, the scanning range is 10-90 DEG, the scanning step length is 0.008 DEG, and the scanning time of each step is 12s. Average size of Si grains, mg, calculated using the Shelle formula 2 SiO 4 Average size of crystal grains, mgSiO 3 Average size of grains. Simultaneous recording of Si (111) diffraction peak intensity I 1 ，MgSiO 3 (610) Intensity of diffraction peak I 2 ，Mg 2 SiO 4 (031) Intensity of diffraction peak I 3 Si (111) diffraction peak area A 1 ，MgSiO 3 (610) Diffraction peak area, mg 2 SiO 4 (031) Diffraction peak area A 3 。
As can be seen in conjunction with fig. 1 and 2, the pre-magnesium silicon oxide negative electrode material includes a core, a first cladding layer, and a second cladding layer. The first cladding layer is interposed between the core and the second cladding layer, the core includes Si and a silicon oxygen compound, the first cladding layer is of a porous structure and includes Si and a silicon oxygen magnesium compound, and the second cladding layer includes a carbon cladding layer. The oxygen content in the pre-magnesium silicon oxygen anode material was 27.9wt.%, and the carbon content was 5.3wt.%. The particle size D50 of the pre-magnesium silica anode material was 5.8 μm. The specific surface area of the pre-magnesium silica anode material is 2.4m 2 /g。I 2 /I 1 0.52, A 2 /A 1 0.15.
Example 2
In the preparation method of the pre-magnesium silicon oxygen anode material, the same volume of selenium-tin alloy powder is used for replacing cadmium powder, the mass percentage of selenium in the selenium-tin alloy powder is 90 percent, the volume of the selenium-tin alloy powder is 3 times that of magnesium powder, and the vaporization heat per unit volume is 5.42kJ/cm 3 Selenium has a boiling point of 685 ℃, a melting point of 221 ℃, a D50 of 57 μm, a D100 of 163 μm, and the remainder of the procedure in example 1.
The oxygen content of the pre-magnesium silicon oxygen anode material in this example was 27.6wt.%, and the carbon content was 5.3wt.%. The particle size D50 of the pre-magnesium silica anode material was 5.9 μm. The specific surface area of the pre-magnesium silica anode material is 2.9m 2 /g。I 2 /I 1 0.545, A 2 /A 1 0.11, I 3 /I 1 0.05, A 3 /A 1 0.06.
Example 3
In the preparation method of the pre-magnesium silicon oxygen anode material, the same volume of selenium powder is used for replacing cadmium powder, the volume of the selenium powder is 3 times of that of the magnesium powder, and the vaporization heat per unit volume is 5.82kJ/cm 3 The remainder of example 1 was followed with a boiling point of 685 ℃, a melting point of 221 ℃, a D50 of 46 μm and a D100 of 133. Mu.m.
The oxygen content of the pre-magnesium silicon oxygen anode material in this example was 28.2wt.%, and the carbon content was 5.4wt.%. The particle size D50 of the pre-magnesium silica anode material was 5.7 μm. The specific surface area of the pre-magnesium silica anode material is 3.8m 2 /g。I 2 /I 1 0.46, A 2 /A 1 0.12, I 3 /I 1 0.08, A 3 /A 1 0.07.
Example 4
In the preparation method of the pre-magnesium silicon-oxygen anode material of the embodiment, the magnesium source is magnesium-zinc alloy powder (D50 is 37 mu m, D100 is 92 mu m), the mass percentage of magnesium in the magnesium-zinc alloy powder is 50%, the mass percentage of the magnesium-zinc alloy powder is 0.32kg, the latent heat agent is cadmium powder, and the rest is the same as the embodiment 1.
The oxygen content of the pre-magnesium silicon oxygen anode material in this example was 27.3wt.%, and the carbon content was 5.2wt.%. Particle size D50 of the pre-magnesium silica anode material is 5.5 mu m . The specific surface area of the pre-magnesium silica anode material is 2.3m 2 /g。I 2 /I 1 0.57, A 2 /A 1 0.21, I 3 /I 1 0.05, A 3 /A 1 0.05.
Example 5
The preparation raw materials in the preparation method of the pre-magnesium silicon oxygen cathode material of the embodiment also comprise 0.56kg of sodium chloride, wherein the volume of the sodium chloride is 3 times that of the magnesium powder, and the rest is the same as the embodiment 1.
The oxygen content of the pre-magnesium silicon oxygen anode material in this example was 28.3wt.%, and the carbon content was 5.3wt.%. The particle size D50 of the pre-magnesium silica anode material was 6.0 μm. The specific surface area of the pre-magnesium silica anode material is 4.5m 2 /g。I 2 /I 1 0.42, A 2 /A 1 0.11, I 3 /I 1 0.08, A 3 /A 1 0.06.
Example 6
In the preparation method of the pre-magnesium silicon oxygen anode material, the acid solution adopted in the acid washing is nitric acid, the concentration is 3.0mol/L, and the rest is the same as that in the embodiment 1.
The oxygen content of the pre-magnesium silicon oxygen anode material in this example was 27.8wt.%, and the carbon content was 5.3wt.%. The particle size D50 of the pre-magnesium silica anode material was 5.6 μm. The specific surface area of the pre-magnesium silica anode material is 2.4m 2 /g。I 2 /I 1 0.50, A 2 /A 1 0.15.
Example 7
In the step (I) of the preparation method of the pre-magnesium silicon-oxygen anode material, heating to 380 ℃ at the heating rate of 8 ℃/min, preserving heat for 1.5h, then heating to 750 ℃ at the heating rate of 3 ℃/min, preserving heat for 9h, and cooling to room temperature to obtain a first material. The remainder is the same as in example 1.
The oxygen content of the pre-magnesium silicon oxygen anode material in this example was 27.9wt.%, and the carbon content was 5.4wt.%. The particle size D50 of the pre-magnesium silica anode material was 5.7 μm. The specific surface area of the pre-magnesium silica anode material is 3.3m 2 /g。I 2 /I 1 0.53, A 2 /A 1 0.16, I 3 /I 1 Is 0 to.06，A 3 /A 1 0.07.
Example 8
In the preparation method of the pre-magnesium silicon oxygen anode material, inert atmosphere is nitrogen, ball milling is adopted for mixing, and the rest is the same as in the embodiment 1.
The oxygen content of the pre-magnesium silicon oxygen anode material in this example was 28.1wt.%, and the carbon content was 5.2wt.%. The particle size D50 of the pre-magnesium silica anode material was 5.6 μm. The specific surface area of the pre-magnesium silica anode material is 1.7m 2 /g。I 2 /I 1 0.49, A 2 /A 1 0.14.
Example 9
In the preparation method of the pre-magnesium silicon oxygen anode material of the embodiment, 1.00kg of carbon coated SiO x (D50 is 8.2 μm, x is 0.8, carbon coating amount is 4 wt.%), 0.35kg of metal magnesium powder and 3.28kg of cadmium powder (the volume of the cadmium powder is 4 times that of the magnesium powder) VC are mixed and then placed in a rotary kiln, and the rest is the same as in example 1.
The oxygen content of the pre-magnesium silicon oxygen anode material in this example was 24.4wt.%, and the carbon content was 6.2wt.%. The particle size D50 of the pre-magnesium silica anode material was 8.4 μm. The specific surface area of the pre-magnesium silica anode material is 3.1m 2 /g。I 2 /I 1 0.38, A 2 /A 1 0.09, I 3 /I 1 0.09, A 3 /A 1 0.08.
Example 10
In the preparation method of the pre-magnesium silicon oxide anode material, the mass ratio of the first material to the hydrochloric acid is 1:8; the pickling time was 1.5 hours, the pickling times were 4 times, the stirring speed at the same time as the pickling was 200rpm, the stirring time was 3.0 hours, and the rest was the same as in example 1.
The oxygen content of the pre-magnesium silicon oxygen anode material in this example was 26.8wt.%, and the carbon content was 5.4wt.%. The particle size D50 of the pre-magnesium silica anode material was 5.8 μm. The specific surface area of the pre-magnesium silica anode material is 7.6m 2 /g。I 2 /I 1 0.51, A 2 /A 1 0.14.
Example 11
In the preparation method of the pre-magnesium silicon oxide anode material, the following step (III): and heating the second material to 850 ℃ at a heating rate of 8 ℃/min under an argon atmosphere by adopting asphalt (3.5 wt.%), preserving heat for 10 hours, cooling, and then crushing, crushing and sieving sequentially.
The oxygen content of the pre-magnesium silicon oxygen anode material in this example was 28.4wt.%, and the carbon content was 5.7wt.%. The particle size D50 of the pre-magnesium silica anode material was 5.8 μm. The specific surface area of the pre-magnesium silica anode material is 1.9m 2 /g。I 2 /I 1 0.47, A 2 /A 1 0.09.
As in example 1, XRD patterns obtained in examples 2 to 11 were fitted using X 'pert High Score (version 2.1.0 of 2004) software, respectively, and the fitting procedure was as described above, and (I' was calculated 1 -I 1 )/I 1 Values of x 100% and the results are listed in table 2.
Comparative example 1
The preparation method of the pre-magnesium silicon oxygen cathode material of the comparative example is based on the example 1, 2.24kg of cadmium powder is replaced by 0.56kg of sodium chloride with equal volume (the vaporization heat per unit volume is 6.34 kJ/cm) 3 Boiling point 1465 ℃, melting point 801 ℃, D50 60 μm, D100 172 μm), sodium chloride volume 3 times the magnesium powder volume, the remainder being the same as in example 1. The prepared pre-magnesium silica anode material is subjected to crystal structure characterization by XRD test, and is shown in figure 4. The resulting XRD patterns were fitted using X' pert High Score (version 2.1.0 2004) software as in example 1, as shown in figure 5.
The oxygen content of the pre-magnesium silicon oxygen anode material in this comparative example was 28.0wt.%, and the carbon content was 5.4wt.%. The particle size D50 of the pre-magnesium silica anode material was 5.9 μm. The specific surface area of the pre-magnesium silica anode material is 2.7m 2 /g。I 2 /I 1 0.38, A 2 /A 1 0.08, I 3 /I 1 0.11, A 3 /A 1 0.09.
Comparative example 2
The preparation method of the pre-magnesium silica anode material of the comparative example replaces 2.24kg of cadmium powder with 1.87kg of sodium chloride (1.87 kg of sodium chloride volume is 0.15kg of magnesium powder) on the basis of the example 110 times the product, the heat of vaporization per unit volume was 6.34kJ/cm 3 Boiling point 1465 ℃, melting point 801 ℃, D50 60 μm, D100 172 μm), the remainder being the same as in example 1.
The oxygen content of the pre-magnesium silicon oxygen anode material in this comparative example was 28.2wt.%, and the carbon content was 5.6wt.%. The particle size D50 of the pre-magnesium silica anode material was 5.6 μm. The specific surface area of the pre-magnesium silica anode material is 2.2m 2 /g。I 2 /I 1 0.34, A 2 /A 1 0.13, I 3 /I 1 0.07, A 3 /A 1 0.05.
Comparative example 3
The preparation method of the pre-magnesium silica anode material of the comparative example replaces 2.24kg of cadmium powder with 0.56kg of zinc chloride with equal volume (the vaporization heat per unit volume is 2.69 kJ/cm) based on the example 1 3 Boiling point 732 ℃, melting point 283 ℃, D50 76 μm, D100 226 μm), the remainder being the same as in example 1.
The oxygen content of the pre-magnesium silicon oxygen anode material in this comparative example was 29.6wt.%, and the carbon content was 5.7wt.%. The particle size D50 of the pre-magnesium silica anode material was 6.1 μm. The specific surface area of the pre-magnesium silica anode material is 4.3m 2 /g。I 2 /I 1 0.32, A 2 /A 1 0.11, I 3 /I 1 0.23, A 3 /A 1 0.12.
Comparative example 4
The preparation method of the pre-magnesium silicon-oxygen anode material of the comparative example is based on the example 5, 2.24kg of cadmium powder is replaced by cadmium magnesium alloy powder with the same volume (wherein the mass percent of cadmium is 90%) and the rest is the same as the example 5.
The oxygen content of the pre-magnesium silicon oxygen anode material in this comparative example was 23.5wt.%, and the carbon content was 5.7wt.%. The particle size D50 of the pre-magnesium silica anode material was 5.3 μm. The specific surface area of the pre-magnesium silica anode material is 8.7m 2 /g。I 2 /I 1 0.48, A 2 /A 1 0.14, I 3 /I 1 0.06, A 3 /A 1 0.03.
Comparative example 5
The comparative example is a preparation method of a pre-magnesium silicon oxygen anode material, comprising the following steps:
step (I): 1.00kg of carbon-coated SiO (carbon coating amount: 3wt.%, D50: 6.1 μm), 0.15kg of metal magnesium powder (D50: 62 μm, D100: 177 μm) and 2.24kg of cadmium powder (cadmium powder volume: 3 times the magnesium powder volume, heat of vaporization per unit volume: 7.69 kJ/cm) 3 The VC with the boiling point of 765 ℃, the melting point of 321 ℃, the D50 of 55 mu m and the D100 of 152 mu m) is mixed and then placed in a rotary furnace, the rotating speed of a cylinder body is 1.0rpm, the mixture is heated to 880 ℃ at the heating rate of 5 ℃/min under the protection of argon, the temperature is kept for 6 hours, and the first material is obtained after cooling to the room temperature. The remainder is the same as in example 1.
The oxygen content of the pre-magnesium silicon oxygen anode material in this comparative example was 27.8wt.%, and the carbon content was 5.5wt.%. The particle size D50 of the pre-magnesium silica anode material was 5.6 μm. The specific surface area of the pre-magnesium silica anode material is 3.2m 2 /g。I 2 /I 1 0.62, A 2 /A 1 0.18, I 3 /I 1 0.07, A 3 /A 1 0.05.
As in example 1, XRD patterns obtained in comparative examples 2 to 5 were fitted using X 'pert High Score (version 2.1.0 in 2004) software, respectively, and the fitting procedure was as described above, and (I' was calculated 1 -I 1 )/I 1 Values of x 100% and the results are listed in table 2.
Referring to example 1, the pre-magnesium silicon oxygen anode materials prepared in examples 2 to 11 and comparative examples 1 to 5 were respectively subjected to crystal structure characterization by XRD test, and the results thereof are shown in table 2.
The pre-magnesium silicon oxygen anode materials prepared in examples 1 to 11 and comparative examples 1 to 5 were respectively prepared into half cells for electrochemical performance test, and the cell preparation process and test conditions thereof are as follows, and the test results are shown in table 2.
Half cell preparation: the pre-magnesium silica anode materials prepared in examples 1 to 11 and comparative examples 1 to 5 were used as active materials, respectively, mixed with an aqueous dispersion of an acrylonitrile copolymer binder (LA 132, solid content 15%) and a conductive agent (Super-P) in a mass ratio of 70:10:20, added with an appropriate amount of water as a solvent to prepare a slurry, coated on a copper foil, and vacuum-dried and roll-pressed to preparePreparing a negative plate. Lithium metal was used as a counter electrode, and 1mol/L LiPF was used 6 And mixing the three components of mixed solvents according to the ratio of EC to DMC to emc=1:1:1 (v/v) to form an electrolyte, and adopting a polypropylene microporous membrane as a diaphragm to assemble the CR2032 button cell in a glove box filled with inert gas.
First charge and discharge performance test: the prepared CR2032 type button cell was performed on a cell test system of blue electronic company, inc. Under normal temperature conditions, discharging is carried out with constant current of 0.1C until the voltage reaches 0.01V, then discharging is carried out with constant current of 0.02C until the voltage reaches 0.005V, the first lithium intercalation specific capacity is obtained, and charging is carried out with constant current of 0.1C until the voltage reaches 1.5V, so that the first lithium deintercalation specific capacity and the first coulombic efficiency are obtained.
And (3) multiplying power performance test: the prepared CR2032 type button cell was tested using a battery test system from blue electronics, inc. Under normal temperature, discharging with constant current of 0.1C to voltage of 0.01V, discharging with constant current of 0.02C to voltage of 0.005V, and charging with constant current of 0.2C to voltage of 1.5V to obtain lithium removal specific capacity of 0.2C; discharging with constant current of 0.1C to reach 0.01V, discharging with constant current of 0.02C to reach 0.005V, charging with constant current of 3C to reach 1.5V to obtain lithium removing specific capacity of 3C, and calculating capacity retention rate.
And (3) testing the cycle performance: the prepared CR2032 type button cell was tested using a battery test system from blue electronics, inc. Under normal temperature, 1C constant current charge and discharge is carried out to 0.01V, then 0.05C constant current discharge is carried out to 0.005V, and finally 1C constant current charge is carried out to 1.5V, thereby obtaining the lithium removal specific capacity, and the cycle is carried out for 50 times, and the capacity retention rate of 50 weeks of the cycle is calculated. The capacity retention rate at 50 weeks was the ratio of the lithium removal specific capacity at 50 weeks to the lithium removal specific capacity at 1 week.
Table 2 test results of the pre-magnesium-silicon-oxygen anode materials prepared in each example and comparative example
As can be seen from the results of Table 2, the Si grain size, mgSiO, of the pre-magnesium silica anode materials prepared in examples 1 to 11 of the present invention 3 Grain size, mg 2 SiO 4 The grain size is smaller, and the prepared material has higher capacity and better cycle and multiplying power performance. Meanwhile, in the pre-magnesium silica anode materials prepared in examples 1 to 11 (I 1 ’-I 1 )/I 1 The lower value indicates that the Si (111) diffraction peak of the pre-magnesium silicon oxygen anode material prepared by the invention has small sharpness or no peak, and the Si (111) diffraction peak of the comparative example 1 is more sharp in combination with fig. 3 and 5, which indicates that a large amount of large-grain Si exists.
Comparative example 1 and comparative examples 1 to 2, which use sodium chloride as a latent heat agent, do not absorb heat rapidly in the magnesium thermal reaction because of its high boiling point, and cannot prevent the growth of Si grains in a short time, even though the improvement effect of increasing the amount of sodium chloride on Si grains is still limited.
In comparative examples 1 and 3, zinc chloride was used as a latent heat agent, but the vaporization heat per unit volume was low although the boiling point was not high, and the heat absorption was limited in the magnesium thermal reaction, and the preferable effect was not obtained.
Comparative example 5 and comparative example 4, the substitution of cadmium powder for cadmium magnesium alloy powder, since comparative example 4 contains magnesium as a reducing component, the reduction of SiO is participated x And the heat generation is increased, and the Si crystal grain has no obvious improvement effect.
Comparative example 1 and comparative example 5, the step firing helps to improve the pre-magnesium uniformity and control the overgrowth of Si grains.
Finally, it should be noted that the above embodiments are only for illustrating the technical solution of the present invention and not for limiting the scope of the present invention, and although the present invention has been described in detail with reference to the preferred embodiments, it should be understood by those skilled in the art that the present invention can be modified or substituted without departing from the spirit and scope of the technical solution of the present invention.

Claims (10)

1. Pre-magnesium silicon oxygen cathodeThe material is characterized by comprising a core, a first coating layer and a second coating layer, wherein the first coating layer is arranged between the core and the second coating layer, the core comprises Si and silicon oxygen compounds, the first coating layer comprises Si and silicon oxygen magnesium compounds, the second coating layer comprises a carbon coating layer, an XRD pattern is obtained through XRD test, and the strongest intensity of a Si (111) diffraction peak before fitting is defined as I' 1 XRD patterns in the range of 27.4 DEG to 29.4 DEG were then fitted, and the strongest intensity of the Si (111) diffraction peak after fitting was defined as I 1 ，(I` 1 -I 1 )/I 1 The preparation of the inner core and the first coating layer comprises the following steps of: will contain carbon-coated SiO x After mixing the raw materials for preparing the magnesium source and the latent heat agent, roasting the raw materials in steps from low temperature to high temperature, wherein the step roasting at least comprises a first roasting stage for melting the latent heat agent and a step roasting step for coating the SiO with carbon x A second roasting stage of reaction with said magnesium source, 0<x<2, the latent heat agent is a substance with the vaporization heat of more than or equal to 5kJ/cm < 3 > per unit volume and the boiling point of 500-1000 ℃, the latent heat agent comprises at least one of cadmium, cadmium alloy, selenium and selenium alloy, the latent heat agent does not comprise lithium, sodium, potassium, magnesium, calcium, aluminum, sodium chloride or potassium chloride, the roasting temperature of the first roasting stage is 300-500 ℃, and the roasting temperature of the second roasting stage is 500-1000 ℃.
2. The pre-magnesium siloxy anode material of claim 1, wherein said siloxy magnesium compound comprises MgSiO 3 Or, the magnesium-silicon oxide compound comprises MgSiO 3 And Mg (magnesium) 2 SiO 4 。
3. The pre-magnesium siloxy anode material of claim 2, comprising at least one of the following features (1) to (6):
(1) XRD test shows that the diffraction peak intensity of Si (111) with the angle of 28.4+/-0.2 DEG is I 1 MgSiO of 30.9+ -0.2 DEG 3 (610) Intensity of diffraction peak of I 2 ，0.1≤I 2 /I 1 ≤0.6；
(2) XRD test shows that the diffraction peak area of Si (111) with the angle of 28.4+/-0.2 DEG is A 1 MgSiO of 30.9+ -0.2 DEG 3 (610) Diffraction peak area A 2 ，0.05≤A 2 /A 1 ≤0.30；
(3) XRD test shows that the diffraction peak intensity of Si (111) with the angle of 28.4+/-0.2 DEG is I 1 Mg at 32.2±0.2° 2 SiO 4 (031) Intensity of diffraction peak of I 3 ，0≤I 3 /I 1 ≤0.20；
(4) XRD test shows that the diffraction peak area of Si (111) with the angle of 28.4+/-0.2 DEG is A 1 Mg at 32.2±0.2° 2 SiO 4 (031) Diffraction peak area A 3 ，0≤A 3 /A 1 ≤0.10；
⑤MgSiO 3 Grain size D of (2) 1 ，8nm≤D 1 ≤15nm；
⑥Mg 2 SiO 4 Grain size D of (2) 2 ，8nm≤D 2 ≤15nm。
4. The pre-magnesium, silicon-oxygen anode material according to claim 1, comprising at least one of the following features (one) to (fourteen):
the specific surface area of the pre-magnesium silica anode material is 0.5m 2 /g to 10.0m 2 /g；
The reversible capacity of the pre-magnesium silicon oxide anode material is more than or equal to 1400mAh/g;
(III) the first coulombic efficiency of the pre-magnesium silicon oxide anode material is more than or equal to 84%;
fourthly, the multiplying power discharge of the pre-magnesium silicon oxygen anode material is 3C/0.2C or more than 93.0%;
(V) the capacity retention rate of the magnesium-silicon-oxygen anode material after 50 weeks circulation is more than or equal to 90.0%;
(six) the oxygen content in the pre-magnesium silicon oxygen anode material is 22wt.% to 30wt.% and the carbon content is 2wt.% to 10wt.%;
(seventh) the particle size D50 of the pre-magnesium silicon oxide anode material is 2 μm to 14 μm;
(eight) Si grain size D 3 ，4nm≤D 3 ≤8nm；
(nine) the silicon oxide compound comprises silicon oxide and/or silicon dioxide;
(ten) the diameter of the inner core is 0.1 μm to 10.0 μm;
(eleventh) the thickness of the first clad layer is 0.1 μm to 6.0 μm;
(twelve) the first coating layer is of a porous structure, and the average pore diameter of the pre-magnesium silicon oxygen anode material is 1nm to 20nm;
thirteenth, the first coating layer is of a porous structure, and the pore volume of the pre-magnesium silica anode material is 0.01cm 3 /g to 0.2cm 3 /g；
(fourteen) the thickness of the second coating layer is 10nm to 300nm.
5. The preparation method of the pre-magnesium silicon-oxygen anode material is characterized by comprising the following steps:
(I) Will contain carbon-coated SiO x Mixing the raw materials, magnesium source and latent heat agent, and roasting to obtain a first material, wherein 0<x<2, the heat of vaporization of the latent heat agent is more than or equal to 5kJ/cm per unit volume 3 And contains a substance having a boiling point of 500 ℃ to 1000 ℃ and the latent heat agent does not reduce SiO x Or does not participate in the magnesia reduction of SiO x The latent heat agent including at least one of cadmium, cadmium alloy, selenium and selenium alloy, the latent heat agent excluding lithium, sodium, potassium, magnesium, calcium, aluminum, sodium chloride or potassium chloride, the step firing including at least a first firing stage to melt the latent heat agent and a step firing step to melt the carbon-coated SiO x The second roasting stage reacts with the magnesium source, the roasting temperature of the first roasting stage is 300-500 ℃, the heat preservation time is 1-4 h, the heating rate is 1-10 ℃/min, the roasting temperature of the second roasting stage is 500-1000 ℃, the heat preservation time is 1-12 h, and the heating rate is 1-10 ℃/min;
(II) pickling the first material to obtain a second material;
(III) coating the second material with carbon, and then performing post-treatment.
6. The method for preparing a pre-magnesium silicon oxygen anode material according to claim 5, wherein the preparation raw material further comprises a metal halide.
7. The method for preparing a pre-magnesium silicon oxygen anode material according to claim 6, wherein the metal halide comprises NaF, KF, caF 2 、MgF 2 、NaCl、KCl、CaCl 2 、MgCl 2 、FeCl 2 、FeCl 3 、CuCl 2 、AlCl 3 、ZnCl 2 、ZnBr 2 And MgI 2 At least one of them.
8. The method for preparing a pre-magnesium silicon oxygen anode material according to claim 6, wherein the carbon is coated with SiO x The mass ratio of the magnesium source to the heat-latent agent to the metal halide is 100:5-50:50-500:0-200, and the content of the metal halide is not 0.
9. The method for producing a pre-magnesium silica anode material according to claim 5, characterized by comprising at least one of the following features (1) to (23):
(1) The carbon coats SiO x D50 of (2) to 14 μm;
(2) The magnesium source comprises metallic magnesium and/or magnesium alloy;
(3) The magnesium source has a D50 of 10 μm to 200 μm;
(4) D100 of the magnesium source is less than or equal to 500 mu m;
(5) The melting point of the latent heat agent is less than or equal to 500 ℃;
(6) The D50 of the latent heat agent is 10 μm to 100 μm;
(7) D100 of the latent heat agent is less than or equal to 300 mu m;
(8) The volume ratio of the latent heat agent to the magnesium source is 2-6:1;
(9) The carbon coats SiO x The mass ratio of the magnesium source to the latent heat agent is 100:5-50:50-500;
(10) The step-by-step roasting is performed under an inert atmosphere, wherein the inert atmosphere comprises at least one of nitrogen, argon and helium;
(11) The step-by-step roasting is carried out in a rotary furnace, and the rotating speed of the rotary furnace is 0.5rpm to 5.0rpm;
(12) Cooling the first material to room temperature and then carrying out acid washing;
(13) The acid solution adopted in the acid washing is at least one of hydrochloric acid, sulfuric acid, nitric acid and hydrofluoric acid;
(14) The concentration of the acid solution adopted by the acid washing is 0.1mol/L to 5.0mol/L;
(15) The mass ratio of the acid solution adopted by the acid washing to the first material is 3-15:1;
(16) The pickling time is 1 to 10 hours;
(17) The number of times of acid washing is 1 to 5 times;
(18) Stirring is carried out during pickling, and the stirring speed is 100rpm to 600rpm;
(19) The mixing mode comprises VC mixing, fusion machine mixing or ball milling mixing;
(20) The first material is subjected to acid washing, and then is sequentially filtered, washed and dried to obtain the second material;
(21) The carbon coating is carried out by adopting an organic carbon source, and the mass ratio of the second material to the organic carbon source is 100:1-10;
(22) The temperature of the carbon coating is 700-1000 ℃, the heat preservation time is 1-12 h, and the heating rate is 1-10 ℃/min;
(23) The post-treatment includes at least one of crushing, pulverizing, and sieving.
10. A secondary battery comprising a positive electrode material and a negative electrode material, wherein the negative electrode material comprises the pre-magnesium-silicon-oxygen negative electrode material according to any one of claims 1 to 4, or the pre-magnesium-silicon-oxygen negative electrode material prepared by the method for preparing the pre-magnesium-silicon-oxygen negative electrode material according to any one of claims 5 to 9.
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