CN116864653B - 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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CN116864653B
CN116864653B CN202311028032.8A CN202311028032A CN116864653B CN 116864653 B CN116864653 B CN 116864653B CN 202311028032 A CN202311028032 A CN 202311028032A CN 116864653 B CN116864653 B CN 116864653B
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magnesium
silicon
anode material
equal
oxygen
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CN116864653A (en
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李宁
傅儒生
余德馨
刘春辉
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
    • H01M4/483—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides for non-aqueous cells
    • 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
    • H01M4/485—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of mixed oxides or hydroxides for inserting or intercalating light metals, e.g. LiTi2O4 or LiTi2OxFy
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/62—Selection of inactive substances as ingredients for active masses, e.g. binders, fillers
    • H01M4/624—Electric conductive fillers
    • H01M4/625—Carbon or graphite
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/62—Selection of inactive substances as ingredients for active masses, e.g. binders, fillers
    • H01M4/628—Inhibitors, e.g. gassing inhibitors, corrosion inhibitors
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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, a second coating layer and a third coating layer from inside to outside. The core includes Si and a silicon oxygen compound, the first cladding includes Si and a silicon oxygen magnesium compound, the second cladding includes MgAl 2O4, and the third cladding includes a carbon layer. The pre-magnesium silicon-oxygen anode material adopted by the invention has better alkali resistance and cycle performance.

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.
Silicon oxide material SiO x (0 < x < 2) has received extensive attention due to its higher theoretical specific capacity 2615mAh/g, lower volume expansion (about 160%) and suitable lithium removal/intercalation potential compared with Si, and the oxygen-containing medium inside the SiO x material can maintain the structural integrity of the material and avoid particle rupture, which is beneficial to the cycle performance of the material. However, the first intercalation of SiO x with lithium results in lithium silicate and lithium oxide, which, because of the irreversibility of lithium oxide and most of lithium silicate, results in a lower first coulombic efficiency.
The first coulombic efficiency of SiO x materials is usually improved by pre-magnesium or pre-lithium, and pre-lithium SiO x materials have limited their wide application due to their high cost. And the pre-lithium SiO x material and the carbon-coated SiO x material or the pre-magnesium SiO x material are used in a composite manner, so that the cost can be reduced, and the use scene can be enhanced. Because the pre-lithium SiO x material contains soluble Li 2 O and lithium silicate, the pH is generally 11 to 13, the material compounded with the pre-lithium SiO x material needs higher alkali resistance, and the general carbon-coated SiO x material and the pre-magnesium SiO x material have poorer alkali resistance, are easy to generate gas in alkali solution, and reduce the processing performance.
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 pre-magnesium silicon oxide anode material adopted by the invention has better alkali resistance and cycle performance, not only can be independently used as an anode active material, but also can be used in combination with a pre-lithium SiO x material so as to reduce the cost.
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, a second coating layer and a third coating layer from inside to outside. The core includes Si and a silicon oxygen compound, the first cladding includes Si and a silicon oxygen magnesium compound, the second cladding includes MgAl 2O4, and the third cladding includes a carbon layer.
The pre-magnesium silicon-oxygen anode material has at least the following technical effects.
(1) In the pre-magnesium silica anode material, the inner core is made of Si and silica compounds, the first coating layer containing the Si and the silica compounds coats the inner core, and the silica compounds can form an internal bonding network, so that Young modulus is enhanced, and volume expansion is inhibited.
(2) The second coating layer comprises MgAl 2O4,MgAl2O4 with higher Young's modulus (about 180 GPa), can inhibit the volume expansion of the SiO x material, increase the integrity and structural stability of the material, and can inhibit side reaction in the charge-discharge cycle process of the battery, thereby improving the cycle performance of the pre-magnesium silicon oxygen anode material.
(3) MgAl 2O4 has stronger alkali resistance, and can be used as a coating layer to improve the alkali resistance of the pre-magnesium silicon oxygen anode material, so that the pre-magnesium silicon oxygen anode material can be used in combination with a pre-lithium SiO x material, and the cost is reduced.
(4) The third coating layer can further relieve volume expansion, and can be used as a carbon layer to not only increase the conductivity of the material, but also avoid side reactions caused by contact of active silicon with electrolyte.
In combination with the first aspect, the pre-magnesium-silicon-oxygen anode material includes a core, a first cladding layer, a second cladding layer, and a third cladding layer. Optionally, the outer layer of the third coating layer may also have at least one (e.g., one, two, three, etc.) carbon layer.
In some embodiments, the magnesium-silicon oxide compound comprises MgSiO 3.
In some embodiments, the 28.4+ -0.2 deg. Si (111) diffraction peak intensity is I 1, and the 30.9+ -0.2 deg. MgSiO 3 (610) diffraction peak intensity is I 2,0.1≤I2/I1.ltoreq.0.4 as tested by XRD.
In some embodiments, the 28.4+ -0.2 ° Si (111) diffraction peak area is A 1, and the 30.9+ -0.2 ° MgSiO 3 (610) diffraction peak area is A 2,0.05≤A2/A1 +.ltoreq.0.20 as tested by XRD.
In some embodiments, the 28.4+ -0.2 ° Si (111) diffraction peak intensity is I 1, and the 44.8+ -0.2 ° MgAl 2O4 (400) diffraction peak intensity is I 3,0.03≤I3/I1 +.ltoreq.0.10 as tested by XRD.
In some embodiments, the 28.4+ -0.2 ° Si (111) diffraction peak area is A 1, and the 44.8+ -0.2 ° MgAl 2O4 (400) diffraction peak area is A 3,0.01≤A3/A1 +.ltoreq.0.05 as tested by XRD.
In some embodiments, the diffraction peak intensity of MgAl 2O4 (400) of 44.8+ -0.2 DEG is I 3, and the diffraction peak intensity of Si (220) of 47.4+ -0.2 DEG is I 4,0.06≤I3/I4.ltoreq.0.20 as tested by XRD.
In some embodiments, the 28.4+ -0.2 deg. Si (111) diffraction peak intensity is I 1 and the 36.85 deg. MgAl 2O4 (311) diffraction peak intensity is I 5,0.05≤I5/I1.ltoreq.0.15 as tested by XRD.
In some embodiments, the diffraction peak area of MgAl 2O4 (400) of 44.8+ -0.2 DEG is A 3, and the diffraction peak area of Si (220) of 47.4+ -0.2 DEG is A 4,0.03≤A3/A4.ltoreq.0.15 as tested by XRD.
In some embodiments, the Si has a grain size of D.ltoreq.7.0 nm.
In some embodiments, the specific surface area of the pre-magnesium silicon oxygen anode material is from 0.5m 2/g to 5.0m 2/g.
In some embodiments, the D50 of the pre-magnesium silicon oxide negative electrode material is 1 μm to 10 μm.
In some embodiments, the pre-magnesium silicon oxide negative electrode material has a 1.5 week lithium intercalation expansion of 45% or less.
In some embodiments, the reversible capacity of the pre-magnesium silicon oxide negative electrode material is greater than or equal to 1450mAh/g.
In some embodiments, the first coulombic efficiency of the pre-magnesium siloxy anode material is greater than or equal to 83%.
In some embodiments, the pre-magnesium silicon oxygen anode material has a 50 cycle lithium intercalation expansion of 50% or less.
In some embodiments, the pre-magnesium silicon oxygen anode material has a 50 cycle lithium intercalation expansion growth rate of less than or equal to 5%.
In some embodiments, the capacity retention of the pre-magnesium silicon oxide anode material is greater than or equal to 90% after 50 weeks of cycling.
In some embodiments, the oxygen content in the pre-magnesium silicon oxygen anode material is 15wt.% to 30wt.%.
In some embodiments, the carbon content in the pre-magnesium silicon oxygen anode material is from 2wt.% to 10wt.%.
In some embodiments, the magnesium content in the pre-magnesium silicon oxide negative electrode material is 5wt.% to 10wt.%.
In some embodiments, the aluminum content in the pre-magnesium silicon oxygen anode material is 0.4wt.% to 2.0wt.%.
In some embodiments, the silicon oxide compound comprises silicon oxide and/or silicon dioxide.
In some embodiments, the diameter of the inner core is greater than 0 and less than or equal to 3.0 μm.
In some embodiments, the thickness of the first cladding layer is from 0.1 μm to 5.0 μm.
In some embodiments, the second cladding layer has a thickness of 5nm to 25nm.
In some embodiments, the thickness of the third cladding layer is from 10nm to 100nm.
In some embodiments, the pre-magnesium silicon oxide anode material is free of Mg 2SiO4.
In some embodiments, the pre-magnesium silicon oxygen anode material begins to produce gas at 45 ℃ for more than or equal to 240 hours and at 60 ℃ for more than or equal to 170 hours in an alkaline solution with a pH of 13.
In some embodiments, the pre-magnesium silicon oxygen anode material begins to produce gas at 45 ℃ for more than or equal to 400 hours and at 60 ℃ for more than or equal to 310 hours in an alkaline solution with a pH of 11.
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) first cladding: stirring SiO x, an aluminum-containing compound, a binder and a solvent, then performing spray drying to obtain a first mixture, mixing the first mixture with a carbon source, and then sequentially performing first roasting and first post-treatment to obtain a first roasting material, wherein x is 0< 2, and the aluminum-containing compound accounts for 1-10% of the mass of SiO x.
Step (II) magnesian reduction reaction: and mixing the first roasting material, a magnesium source and molten salt to obtain a second mixture, and sequentially carrying out second roasting and second post-treatment on the second mixture under an inert atmosphere to obtain a second roasting material, wherein the highest temperature of the second roasting is 800-1000 ℃.
Step (III) second coating: and (3) carrying out acid washing on the second roasting material, and then carrying out carbon coating.
With reference to the second aspect, the carbon layer of the pre-magnesium silicon oxygen anode material of the present invention at least comprises the carbon source in step (I) and the carbon coating in step (III). Optionally, a carbon coating layer can be further provided on the basis of the carbon coating in the second coating in the step (III). 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 at least the following technical effects.
1. SiO x, aluminum-containing compound, binder and solvent are stirred and then spray-dried to obtain particles with uniformly distributed components, and the particles are mixed with a carbon source and then are roasted for the first time. The aluminum-containing compound is converted into aluminum oxide by roasting, the binder is decomposed to form voids, and the carbon source forms a loose carbon layer. Magnesium is derived from molten salt, passes through a gap formed by a carbon layer and a binder to react with alumina and SiO x, and respectively generates MgAl 2O4 and a magnesium-silicon oxide compound, and Mg 2SiO4 is removed by acid washing to retain acid-alkali-resistant MgAl 2O4, so that the alkali resistance and the cycle performance of the pre-magnesium-silicon oxide negative electrode material are improved.
2. SiO x is coated by alumina and carbon, then a magnesium source is added for carrying out a magnesian reduction reaction, the embedding rate of magnesium can be restrained through double coating layers, the intensity of magnesian reduction is reduced, and the size of silicon crystal grains can be controlled so as to improve the cycle performance of the material.
In some embodiments, the aluminum-containing compound includes at least one of aluminum carbonate, aluminum chloride, aluminum sulfate, aluminum nitrate, aluminum hydroxide, aluminum oxide, aluminum phosphate, aluminum acetate, aluminum isopropoxide, and tert-butyl aluminum oxide.
In some embodiments, the binder includes at least one of polyvinyl alcohol, polyacrylic acid, carboxymethyl cellulose, phenolic resin, epoxy resin, polyamide resin, and neoprene.
In some embodiments, the solvent comprises at least one of deionized water, ethanol, methanol, isopropanol, and ethyl acetate.
In some embodiments, the mass ratio of SiO x, aluminum-containing compound, binder, and solvent is 100:1 to 10:1 to 10:200 to 2000.
In some embodiments, the carbon source comprises at least one of pitch, phenolic resin, starch, polyvinyl alcohol, epoxy resin, polydopamine, lignin, citric acid, glucose, and sucrose.
In some embodiments, the magnesium source comprises metallic magnesium and/or magnesium alloy.
In some embodiments, the magnesium source has a D50 of 100 μm or less.
In some embodiments, the molten salt includes at least one of NaCl, KCl, rbCl, csCl, caCl 2、MgCl2、SrCl2 and BaCl 2.
In some embodiments, the melting point of the molten salt is > 650 ℃.
In some embodiments, the mass ratio of the first calcine to the magnesium source, the molten salt, is 100:5 to 15:20 to 100.
In some embodiments, the carbon source comprises 1% to 5% of the mass of the first mixture.
In some embodiments, the molar ratio of Mg element in the second calcine to hydrogen element in the acid solution employed for pickling is 1:1.2 to 2.2.
In some embodiments, the time for pickling is from 1h to 6h.
In some embodiments, the acid solution used for pickling has a concentration of 0.1mol/L to 1.0mol/L.
In some embodiments, the means employed for mixing in step (I) and step (II) independently of each other comprises VC mixing, fusion machine mixing, or ball mill mixing.
In some embodiments, the time of mixing in step (I) and step (II) is each independently 1h to 10h.
In some embodiments, the first calcination is performed under an inert atmosphere.
In some embodiments, the spray drying temperature is from 80 ℃ to 200 ℃.
In some embodiments, the first firing is at a temperature of 600 ℃ to 700 ℃ for a time of 2 hours to 12 hours at a rate of 1 ℃/min to 10 ℃/min.
In some embodiments, the first post-treatment and the second post-treatment comprise cooling to room temperature and breaking up sequentially after firing.
In some embodiments, the inert atmosphere comprises at least one of nitrogen, argon, and helium.
In some embodiments, the second calcine is washed with water, dried, and then filtered, washed with water, dried, and broken up.
In some embodiments, the carbon coating comprises at least one of a gas phase coating, a solid phase coating, and a liquid phase coating.
In some embodiments, the second firing is a step firing.
In some embodiments, the step firing includes incubating the mixture at a temperature ramp rate of 1 ℃/min to 6 ℃/min for 2 hours to 12 hours at 500 ℃ to 650 ℃ and then at a temperature ramp rate of 1 ℃/min to 10 ℃/min for 880 ℃ to 1000 ℃ for 1 hour to 10 hours.
The third aspect of the invention provides the pre-magnesium silicon oxygen anode material or the application of the pre-magnesium silicon oxygen anode material prepared by the preparation method of the pre-magnesium silicon oxygen anode material in the anode material. The invention provides a secondary battery comprising a positive electrode material and a negative electrode material, wherein the negative electrode material comprises the pre-magnesia silica anode material or the pre-magnesia silica anode material prepared by the preparation method of the pre-magnesia silica anode 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.
Drawings
FIG. 1 is a schematic structural diagram of a pre-magnesia silica anode material of the invention;
FIG. 2 is an XRD pattern of the pre-magnesium silica anode material of example 1;
FIG. 3 is a single particle EDS diagram of the pre-magnesium silicon oxide negative electrode material of example 1;
Fig. 4 is an XRD pattern of the pre-magnesium silicon oxygen anode material of comparative example 1.
Detailed Description
The pre-magnesium silicon oxygen anode material can be independently 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 as an anode active material alone, can be mixed with other anode active materials (such as natural graphite, artificial graphite, soft carbon, hard carbon and the like), and further can be mixed with a pre-lithium silicon-oxygen anode material to be used as an anode active material in a secondary battery, so that the requirements of high performance and low cost are met.
The specific surface area of the pre-magnesium silicon oxide anode material is 0.5m 2/g to 5.0m 2/g, which can be, but is not limited to, 0.5m 2/g、1.0m2/g、2.0m2/g、3.0m2/g、4.0m2/g、5.0m2/g. The particle size D50 of the pre-magnesium silicon oxide negative electrode material is 1 μm to 10 μm, and may be, but is not limited to, 1 μm, 2 μm, 3 μm, 4 μm, 5 μm, 6 μm, 7 μm, 8 μm, 9 μm, 10 μm. The expansion rate of the pre-magnesium silicon oxygen negative electrode material for 1.5 weeks is less than or equal to 45 percent, less than or equal to 44 percent, less than or equal to 43 percent, less than or equal to 42 percent, less than or equal to 41 percent, less than or equal to 40 percent, less than or equal to 39 percent, less than or equal to 38 percent, less than or equal to 37 percent, less than or equal to 36 percent, less than or equal to 35 percent, less than or equal to 34 percent, less than or equal to 33 percent, less than or equal to 32 percent, less than or equal to 31 percent, and less than or equal to 30 percent. The reversible capacity of the pre-magnesium silicon-oxygen anode material is more than or equal to 1450mAh/g, the first coulombic efficiency of the pre-magnesium silicon-oxygen anode material is more than or equal to 83 percent, which is more than or equal to 83 percent, 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 expansion rate of the pre-magnesium silicon oxygen anode material after 50 weeks is less than or equal to 50 percent, can be not limited to less than or equal to 50 percent, less than or equal to 49 percent, less than or equal to 48 percent, less than or equal to 47 percent, less than or equal to 46 percent, less than or equal to 45 percent, less than or equal to 44 percent, less than or equal to 43 percent, less than or equal to 42 percent, less than or equal to 41 percent and less than or equal to 40 percent. The expansion and growth rate of the magnesium-doped silicon oxygen anode material after 50 weeks is less than or equal to 5 percent, which can be, but is not limited to, less than or equal to 5 percent, less than or equal to 4 percent, less than or equal to 3 percent, less than or equal to 2 percent and less than or equal to 1 percent. The capacity retention rate of the magnesium-pre-silicon-oxygen anode material after 50 weeks is more than or equal to 90 percent, can be more than or equal to 90 percent, more than or equal to 91 percent, more than or equal to 92 percent, more than or equal to 93 percent, more than or equal to 94 percent, more than or equal to 95 percent, more than or equal to 96 percent, more than or equal to 97 percent and more than or equal to 98 percent. The oxygen content in the pre-magnesium-silicon-oxygen anode material is 15wt.% to 30wt.%, can be, but is not limited to, 15wt.％、16wt.％、17wt.％、18wt.％、19wt.％、20wt.％、21wt.％、22wt.％、23wt.％、24wt.％、25wt.％、26wt.％、27wt.％、28wt.％、29wt.％、30wt.％. wt.% and the carbon content in the pre-magnesium-silicon-oxygen anode material is 2wt.% to 10wt.%, can be, but is not limited to, 2wt.%, 3wt.%, 4wt.%, 5wt.%, 6wt.%, 7wt.%, 8wt.%, 9wt.%, 10wt.%. The magnesium content in the pre-magnesium silico negative electrode material is 5wt.% to 10wt.%, and may be, but is not limited to, 5wt.%, 6wt.%, 7wt.%, 8wt.%, 9wt.%, 10wt.%. The aluminum content in the pre-magnesium silicon oxygen anode material is 0.4wt.% to 2.0wt.%, and may be, but is not limited to, 0.4wt.%, 0.6wt.%, 0.8wt.%, 1.0wt.%, 1.2wt.%, 1.4wt.%, 1.6wt.%, 1.8wt.%, 2.0wt.%. In an alkaline solution with the pH value of 13, the pre-magnesium silicon oxygen anode material starts to produce gas at 45 ℃ for more than or equal to 240 hours, and starts to produce gas at 60 ℃ for more than or equal to 170 hours. In an alkaline solution with the pH value of 11, the pre-magnesium silicon oxygen anode material starts to produce gas at 45 ℃ for more than or equal to 400 hours, and starts to produce gas at 60 ℃ for more than or equal to 310 hours. The pre-magnesium silica anode material has stable performance at pH of 11-13, so that the pre-magnesium silica anode material can be mixed for use with the pre-lithium silica anode material. The alkaline solution may be a sodium hydroxide or potassium hydroxide solution.
As shown in fig. 1, the pre-magnesium silicon oxygen anode material 100 of the present invention includes an inner core 10, a first clad layer 30, a second clad layer 50, and a third clad layer 70.
The core includes Si and silicon oxide. The diameter of the inner core is greater than 0 and less than or equal to 3.0 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. The grain size of Si is D.ltoreq.7nm, and D may be, but is not limited to, 4 μm, 5 μm, 6 μm, 7 μm. As an embodiment, D.ltoreq.6 nm. The silicon oxygen compound includes silicon oxide and/or silicon dioxide.
The first cladding layer includes Si and a magnesium-silicon oxide compound. The thickness of the first cladding layer is 0.1 μm to 5.0 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.
The magnesium-silicon oxide compound comprises MgSiO 3, or comprises MgSiO 3 and Mg 2SiO4.Mg2SiO4 which are in a single molecular structure, mgSiO 3 is in a polymerization chain structure, mg 2SiO4 and molten salt are easy to form a eutectic compound, and the eutectic compound is precipitated in the molten salt and is easy to be removed by acid washing, so that the magnesium-silicon oxide compound in the magnesium-silicon oxide anode material prepared after acid washing is mainly MgSiO 3. The values of 28.4+ -0.2 ° Si (111) diffraction peak intensity of I 1, 30.9+ -0.2 ° MgSiO 3 (610) diffraction peak intensity of I 2,0.1≤I2/I1≤0.4.I2/I1 by XRD test can be, but are not limited to, 0.1, 0.2, 0.3, 0.4. Values of 28.4±0.2° Si (111) diffraction peak area a 1, 30.9±0.2° MgSiO 3 (610) diffraction peak area a 2,0.05≤A2/A1≤0.20.A2/A1 may be, but are not limited to, 0.05, 0.10, 0.15, 0.20.
The second cladding layer includes MgAl 2O4. Magnesium is derived from molten salt and reacts with alumina through voids formed by the loose carbon layer and binder and forms MgAl 2O4. The thickness of the second coating layer is 5nm to 25nm, and may be, but not limited to, 5nm, 7nm, 9nm, 11nm, 13nm, 15nm, 17nm, 19nm, 21nm, 23nm, 25nm.
The values of the diffraction peak intensities of the MgAl 2O4 (400) of 44.8+ -0.2 deg. of I 3,0.03≤I3/I1≤0.10,I3/I1 can be, but are not limited to, 0.03, 0.04, 0.05, 0.06, 0.07, 0.08, 0.09, 0.10 as measured by XRD. The value of the Si (220) diffraction peak intensity of 47.4+ -0.2 DEG, I 4,0.06≤I3/I4≤0.20,I3/I4, can be, but is not limited to, 0.06, 0.07, 0.08, 0.09, 0.10, 0.11, 0.12, 0.13, 0.14, 0.15, 0.16, 0.17, 0.18, 0.19, 0.20. Values of 36.85 ° MgAl 2O4 (311) diffraction peak intensity of I 5,0.05≤I5/I1≤0.15,I5/I1 may be, but are not limited to, 0.05, 0.06, 0.07, 0.08, 0.09, 0.10, 0.11, 0.12, 0.13, 0.14, 0.15. Values of the diffraction peak area of MgAl 2O4 (400) of 44.8±0.2° as a 3,0.01≤A3/A1≤0.05,A3/A1 may be, but are not limited to, 0.01, 0.02, 0.03, 0.04, 0.05. The value of the Si (220) diffraction peak area of 47.4+ -0.2 DEG, A 4,0.03≤A3/A4≤0.15,A3/A4, can be, but is not limited to, 0.03, 0.04, 0.05, 0.06, 0.07, 0.08, 0.09, 0.10, 0.11, 0.12, 0.13, 0.14, 0.15.
The third cladding layer includes a carbon layer. The thickness of the third coating layer is 10nm to 100nm, and may be, but not limited to, 10nm, 20nm, 30nm, 40nm, 50nm, 60nm, 70nm, 80nm, 90nm, 100nm.
The preparation method of the pre-magnesium silicon-oxygen anode material comprises the steps of (I), (II) and (III).
The first coating in the step (I) comprises stirring SiO x, an aluminum-containing compound, a binder and a solvent, then performing spray drying to obtain a first mixture, mixing the first mixture with a carbon source, and then sequentially performing first roasting and first post-treatment to obtain a first roasting substance.
Where 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. The D50 of SiO x is 2 μm to 10 μm, and the D50 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. The aluminum-containing compound includes at least one of aluminum carbonate, aluminum chloride, aluminum sulfate, aluminum nitrate, aluminum hydroxide, aluminum oxide, aluminum phosphate, aluminum acetate, aluminum isopropoxide, and tert-butyl aluminum oxide. The aluminum salt is decomposed into aluminum hydroxide under the action of a solvent and then baked to generate aluminum oxide or directly baked and decomposed to generate aluminum oxide. The binder comprises at least one of polyvinyl alcohol, polyacrylic acid, carboxymethyl cellulose, phenolic resin, epoxy resin, polyamide resin and chloroprene rubber, the binder is favorable for coating the aluminum-containing compound on the surface of SiO x, and the solvent comprises at least one of deionized water, ethanol, methanol, isopropanol and ethyl acetate, and the solvent is favorable for uniformly dispersing the components. The aluminum-containing compound is 1 to 10% by mass of SiO x, and may be, but not limited to, 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%. Further, the mass ratio of SiO x, aluminum-containing compound, binder and solvent is 100:1-10:1-10:200-2000, and the mass ratio of the four can be, but not limited to, 100:1:1:200、100:3:5:300、100:5:3:400、100:3:7:500、100:3:10:800、100:5:5:500、100:5:7:600、100:5:9:800、100:5:10:1000、100:7:5:500、100:7:2:300、100:7:7:700、100:7:9:900、100:9:2:400、100:9:5:600、100:9:7:800、100:9:10:500、100:9:5:1500、100:4:2:1200、100:10:6:1900. carbon source including at least one of asphalt, phenolic resin, starch, polyvinyl alcohol, epoxy resin, polydopamine, lignin, citric acid, glucose and sucrose. The carbon source accounts for 1 to 5% of the mass of the first mixture, and may be, but is not limited to, 1%, 2%, 3%, 4%, 5%.
The mixing in step (I) may be performed by means of VC mixing, fusion machine mixing or ball milling mixing. The mixing time is 1h to 10h, and may be, but is not limited to, 1h, 2h, 3h, 4h, 5h, 6h, 7h, 8h, 9h, 10h. 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 stirring time is 1h to 10h, and can be, but not limited to, 1h, 2h, 3h, 4h, 5h, 6h, 7h, 8h, 9h, 10h. The spray drying temperature is 80 to 200 ℃, and may be, but not limited to, 80 ℃, 90 ℃, 100 ℃, 110 ℃, 120 ℃, 130 ℃, 140 ℃, 150 ℃, 160 ℃, 170 ℃, 180 ℃, 190 ℃, 200 ℃. The first firing is performed under an inert atmosphere, which may be, but is not limited to, at least one of nitrogen, argon, and helium. The temperature of the first firing is 600 to 700 ℃, and may be, but not limited to, 600 ℃, 610 ℃, 620 ℃, 630 ℃, 640 ℃, 650 ℃, 660 ℃, 670 ℃, 680 ℃, 690 ℃, 700 ℃. The time for the first firing is 2h to 12h, and may be, but not limited to, 2h, 3h, 4h, 5h, 6h, 7h, 8h, 9h, 10h, 11h, 12h. The temperature rising rate of the first roasting is 1 ℃/min to 10 ℃/min, and can 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 first post-treatment comprises the steps of cooling to room temperature and scattering after roasting.
The step (II) of magnesian reduction reaction comprises the steps of mixing the first roasting material, a magnesium source and molten salt to obtain a second mixture, and sequentially carrying out second roasting and second post-treatment on the second mixture in an inert atmosphere to obtain a second roasting material.
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 100 μm or less, and may be, but is not limited to, 100 μm or less, 90 μm or less, 80 μm or less, 70 μm or less, 60 μm or less, 50 μm or less, 40 μm or less, 30 μm or less, 20 μm or less, or 10 μm or less. The molten salt includes at least one of NaCl, KCl, rbCl, csCl, caCl 2、MgCl2、SrCl2 and BaCl 2. The melting point of the molten salt is more than 650 ℃, and the melting point can be more than or equal to 660 ℃, more than or equal to 670 ℃, more than or equal to 680 ℃, more than or equal to 690 ℃, more than or equal to 700 ℃, more than or equal to 750 ℃, more than or equal to 800 ℃ and more than or equal to 850 ℃. The mass ratio of the first roasting material to the magnesium source to the molten salt is 100:5-15:20-100, and the mass ratio of the magnesium source to the molten salt is 1: 4-20, which may be, but is not limited to, 100:5:20、100:5:50、100:5:70、100:5:100、100:7:35、100:7:45、100:7:55、100:7:65、100:10:80、100:10:90、100:10:100、100:15:70、100:15:80、100:15:90、100:15:100. inert atmospheres including at least one of nitrogen, argon, and helium.
The mixing in step (II) may be performed by a method comprising VC mixing, fusion machine mixing or ball milling mixing. The mixing time is 1h to 10h, and can be 1h, 2h, 3h, 4h, 5h, 6h, 7h, 8h, 9h and 10h. The second roasting is step roasting. The maximum temperature of the second firing is 800 to 1000 ℃, and may be, but not limited to, 800 ℃, 820 ℃, 840 ℃, 860 ℃, 880 ℃, 900 ℃, 920 ℃, 940 ℃, 960 ℃, 980 ℃, 1000 ℃. Further, the step-by-step roasting comprises the steps of firstly preserving the temperature of the mixture at the temperature rising rate of 1 ℃/min to 6 ℃/min for 2 hours to 12 hours at the temperature rising rate of 500 ℃ to 650 ℃, and then preserving the temperature of the mixture at the temperature rising rate of 880 ℃ to 1000 ℃ for 1 hour to 10 hours at the temperature rising rate of 1 ℃/min to 10 ℃/min. The molten salt is subjected to composite roasting with a magnesium source to form a composite material, and then subjected to a magnesia reduction reaction with SiO x. The firing temperature in the first step of the step firing may be, but not limited to, 500 ℃, 520 ℃, 540 ℃, 560 ℃, 580 ℃, 600 ℃, 620 ℃, 640 ℃, 650 ℃. The incubation time of the first step may be, but is not limited to, 2h, 4h, 6h, 8h, 10h, 12h. The temperature rise rate of the first step of the step firing may be, but is not limited to, 1 ℃/min, 2 ℃/min, 3 ℃/min, 4 ℃/min, 5 ℃/min, 6 ℃/min. The firing temperature in the second step of the step firing may be, but not limited to, 880 ℃, 900 ℃, 920 ℃, 940 ℃, 960 ℃, 980 ℃, 1000 ℃. The heat preservation time of the second step of the step roasting can be, but is not limited to, 1h, 2h, 3h, 4h, 5h, 6h, 7h, 8h, 9h and 10h. The rate of heating in the second step of the step firing 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 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 second post-treatment comprises cooling to room temperature and scattering after roasting.
The second coating in the step (III) comprises the step of carrying out carbon coating on the second roasting material after acid washing.
As an embodiment, the second calcined product is sequentially subjected to first water washing and first drying before acid washing. The mass ratio of the second roasting material to the water in the first water washing is 1:3-10, and can be but is not limited to 1:3, 1:4, 1:5, 1:6, 1:7, 1:8, 1:9 and 1:10. The temperature of the first drying is 45-150 ℃ and the drying time is 6-36 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 ℃,110 ℃, 120 ℃, 130 ℃, 140 ℃, 150 ℃. By way of example, the time of drying may be, but is not limited to, 6h, 8h, 10h, 12h, 14h, 16h, 18h, 20h, 22h, 24h, 28h, 30h, 33h, 36h. The drying may be, but is not limited to, vacuum drying, inert atmosphere protection drying or forced air drying.
Acid washing with an acid solution is adopted, and Mg 2SiO4 is subjected to acidolysis to generate silicic acid for removal. 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 1.0mol/L, and may be, but not limited to, 0.1mol/L, 0.2mol/L, 0.3mol/L, 0.4mol/L, 0.5mol/L, 0.6mol/L, 0.7mol/L, 0.8mol/L, 0.9mol/L, 1.0mol/L. The pickling time is 1h to 6h, and can be, but is not limited to, 1h, 2h, 3h, 4h, 5h, 6h. The number of pickling times is 1 to 5, and may be, but not limited to, 1, 2, 3, 4, 5 times to remove Mg 2SiO4 as much as possible, 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 molar ratio of Mg element in the second roasting material to hydrogen element in the acid solution used for acid washing is 1:1.2-2.2, and may be, but not limited to, 1:1.2, 1:1.3, 1:1.4, 1:1.5, 1:1.6, 1:1.7, 1:1.8, 1:1.9, 1:2.0, 1:2.1, 1:2.2.
As an implementation scheme, the acid washing is followed by filtration, secondary water washing, secondary drying and scattering. The filtration mode can be, but is not limited to, filter pressing or suction filtration. And washing the filtered material to be neutral by adopting water washing. The mass ratio of the material to water after acid washing in the second water washing is 1:3-10, and can be but is not limited to 1:3, 1:4, 1:5, 1:6, 1:7, 1:8, 1:9 and 1:10. The temperature of the second drying is 45-150 ℃ and the drying time is 6-36 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 ℃, 110 ℃, 120 ℃, 130 ℃, 140 ℃, 150 ℃. By way of example, the time of drying may be, but is not limited to, 6h, 8h, 10h, 12h, 14h, 16h, 18h, 20h, 22h, 24h, 28h, 30h, 33h, 36h. The drying may be, but is not limited to, vacuum drying, inert atmosphere protection drying or forced air drying.
The carbon coating includes at least one of a gas phase coating, a solid phase coating, and a liquid phase coating.
As an embodiment, the carbon coating is performed using an organic carbon source. The carbon coating amount is 2wt.% to 10wt.%, and may be, but is not limited to, 2wt.%, 3wt.%, 4wt.%, 5wt.%, 6wt.%, 7wt.%, 8wt.%, 9wt.%, 10wt.%. 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 methane, ethane, ethylene, acetylene, propane, propylene, i.e. be gas phase coated. 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.
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, which comprises the following steps.
(I) First coating
Stirring SiO (D50 is 5.4 mu m), alCl 3, 10wt.% polyvinyl alcohol aqueous solution and deionized water according to a mass ratio of 100:6:5:800 to obtain a first mixture, stirring at a speed of 300rpm for 5 hours, spray-drying the first mixture at 120 ℃, mixing with asphalt according to a mass ratio of 100:4 for 3 hours, then roasting at a heating rate of3 ℃/min to 650 ℃ for 8 hours under an argon atmosphere, cooling to room temperature, and scattering to obtain a first roasting material.
(II) magnesium reduction reaction
Mixing the first roasting material, magnesium powder (D50=30μm) and anhydrous CaCl 2 (melting point 772 ℃) in VC for 5 hours according to the mass ratio of 100:14:80 to obtain a second mixture, heating the second mixture under argon atmosphere, heating the second mixture from room temperature to 600 ℃ at the heating rate of 2 ℃/min for 4 hours, heating the second mixture to 900 ℃ at the heating rate of 4 ℃/min for 4 hours, and scattering the second mixture after natural cooling to obtain the second roasting material.
(III) second coating
Washing the second roasting material with water for 1h according to the mass ratio of the second roasting material to water of 1:6 to remove CaCl 2, drying in vacuum at 80 ℃ for 8h, scattering, washing with hydrochloric acid with the concentration of 0.7mol/L for 2h, washing with deionized water to neutrality according to the mol ratio of Mg element to hydrogen element in hydrochloric acid of 1:1.5, washing with filter pressing after washing, drying in vacuum at 100 ℃ for 6h, scattering, mixing with asphalt according to the mass ratio of 100:4, and heating to 900 ℃ for 3h at the heating rate of 5 ℃/min in nitrogen atmosphere to obtain the pre-magnesium silicon-oxygen anode material.
The prepared pre-magnesium silica anode material adopts XRD test to carry out crystal structure characterization, and is shown in figure 2. The prepared pre-magnesium silicon oxygen cathode material is subjected to a single particle EDS test, as shown in figure 3.
Characterization of the crystal structure: XRD test is carried out on the prepared pre-magnesium silica anode material by adopting a PANalytical panaceae Powder diffractometer and Xpert3Powder, wherein 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. The average size of Si grains was calculated using the scherrer equation. Meanwhile, the Si (111) diffraction peak intensity I 1,MgSiO3 (610) diffraction peak intensity I 2,MgAl2O4 (400) diffraction peak intensity I 3, the Si (220) diffraction peak intensity I 4,MgAl2O4 (311) diffraction peak intensity I 5, the Si (111) diffraction peak area A 1,MgSiO3 (610) diffraction peak area, the MgAl 2O4 (400) diffraction peak area A 3 and the Si (220) diffraction peak area A 4 are recorded.
The pre-magnesium silica anode material comprises an inner core, a first coating layer, a second coating layer and a third coating layer. The average diameter of the core was about 1.5 μm and comprised of Si and silicon oxygen compounds, the average thickness of the first cladding layer was about 2.0 μm and comprised of Si and silicon oxygen magnesium compounds, the average thickness of the second cladding layer was about 15nm and comprised of uniformly distributed MgAl 2O4, and the average thickness of the third cladding layer was about 45nm.
Example 2
The difference between example 2 and example 1 is that the mass ratio of SiO (D50 of 5.4 μm), alCl 3, 10wt.% aqueous polyvinyl alcohol solution and deionized water is replaced by 100:2:5:800.
Example 3
The difference between example 3 and example 1 is that the mass ratio of SiO (D50 of 5.4 μm), alCl 3, 10wt.% aqueous polyvinyl alcohol solution and deionized water is replaced by 100:10:5:800.
Example 4
The difference between example 4 and example 1 is that 10wt.% of the aqueous polyvinyl alcohol solution is exchanged for polyacrylic acid.
Example 5
The difference between example 5 and example 1 is that the mass of bitumen in the second coating of step (III) is changed from 100:4 to 100:6.
Example 6
The difference between example 6 and example 1 is that AlCl 3 is exchanged for Al (NO 3)3.
Example 7
The difference between example 7 and example 1 is that AlCl 3 is replaced by Al (OH) 3.
Example 8
The difference between example 8 and example 1 is that 900℃is replaced by 950℃in the step (II) magnesian reduction reaction.
Example 9
The difference between example 9 and example 1 is that the mass ratio of the first calcine, magnesium powder (d50=30μm) and anhydrous CaCl 2 (melting point 772 ℃) is replaced by 100:12:80.
Example 10
The difference between example 10 and example 1 is that the temperature of the spray drying in the first coating of step (I) was changed to 150 ℃.
Example 11
The embodiment is a preparation method of a pre-magnesium silicon-oxygen anode material, which comprises the following steps.
(I) First coating
SiO 0.8 (D50 is 5.8 mu m), alCl 3, 10wt.% of polyvinyl alcohol aqueous solution and ethanol are stirred according to a mass ratio of 100:5:3:1500 to obtain a first mixture, the stirring speed is 300rpm, the time is 5 hours, the first mixture is spray-dried at 120 ℃, VC is mixed with asphalt according to a mass ratio of 100:4 for 3 hours, the mixture is baked for 8 hours under argon atmosphere at a heating rate of 3 ℃/min to 650 ℃, and the mixture is cooled to room temperature and scattered to obtain a first baked product.
Step (II) and step (III) are the same as in example 1.
Example 12
The embodiment is a preparation method of a pre-magnesium silicon-oxygen anode material, which comprises the following steps.
(I) First coating
Stirring SiO (D50 is 5.4 mu m), alCl 3, 10wt.% polyvinyl alcohol aqueous solution and deionized water according to a mass ratio of 100:6:5:800 to obtain a first mixture, stirring at 300rpm for 5 hours, spray-drying the first mixture at 120 ℃, mixing with lignin according to a mass ratio of 100:3 for 3 hours, then roasting at a heating rate of 3 ℃/min to 650 ℃ for 8 hours under argon atmosphere, cooling to room temperature, and scattering to obtain a first roasting material.
Step (II) and step (III) are the same as in example 1.
Example 13
The embodiment is a preparation method of a pre-magnesium silicon-oxygen anode material, which comprises the following steps.
(I) First coating
Stirring SiO (D50 is 5.4 mu m), alCl 3, 10wt.% polyvinyl alcohol aqueous solution and deionized water according to a mass ratio of 100:6:5:800 to obtain a first mixture, wherein the stirring speed is 500rpm during mixing for 4 hours, spray-drying the first mixture at 120 ℃, VC-mixing with asphalt according to a mass ratio of 100:4 for 3 hours, then baking for 12 hours under nitrogen atmosphere at a heating rate of 6 ℃/min to 600 ℃, cooling to room temperature, and scattering to obtain a first baked product.
Step (II) and step (III) are the same as in example 1.
Example 14
The embodiment is a preparation method of a pre-magnesium silicon-oxygen anode material, which comprises the following steps.
Step (I) and step (III) are the same as in example 1.
(II) magnesium reduction reaction
Mixing the first roasting material, magnesium powder (D50=50μm) and KCl (melting point is 770 ℃) in a fusion machine according to a mass ratio of 100:14:80 for 6 hours to obtain a second mixture, heating the second mixture under a nitrogen atmosphere from room temperature, heating to 550 ℃ at a heating rate of 5 ℃/min for 6 hours, heating to 1000 ℃ at a heating rate of 8 ℃/min for 2 hours, and naturally cooling to obtain the second roasting material.
Example 15
The embodiment is a preparation method of a pre-magnesium silicon-oxygen anode material, which comprises the following steps.
Step (I) and step (II) are the same as in example 1.
(III) second coating
Washing the second roasting material with water for 2 hours according to the mass ratio of the second roasting material to water of 1:4 to remove CaCl 2, drying by blowing at 100 ℃ for 14 hours, scattering, pickling with dilute nitric acid with the concentration of 0.4mol/L for 3 hours, washing with water for neutral according to the mol ratio of Mg element to hydrogen element in hydrochloric acid of 1:1.8, washing with deionized water for filtering after pickling, scattering after vacuum drying at 100 ℃ for 8 hours, heating to 700 ℃ at the heating rate of 3 ℃/min, introducing acetylene in an inert atmosphere of nitrogen, reacting for 1.5 hours after heat preservation, closing the introduction of acetylene, and naturally cooling to room temperature to obtain the pre-magnesium silicon-oxygen anode material.
Comparative example 1
The comparative example is a preparation method of a pre-magnesium silicon oxygen anode material, comprising the following steps.
(I) First coating
Stirring SiO (D50 is 5.4 mu m), 10wt.% polyvinyl alcohol aqueous solution and deionized water according to a mass ratio of 100:5:800 to obtain a first mixture, spray-drying the first mixture at 120 ℃, VC-mixing the first mixture with asphalt according to a mass ratio of 100:4 for 3 hours, then baking the mixture for 8 hours under argon atmosphere at a temperature rising rate of 3 ℃/min to 650 ℃, cooling the mixture to room temperature, and scattering the mixture to obtain a first baked product.
Step (II) and step (III) are the same as in example 1.
The crystal structure of the pre-magnesium silicon oxygen anode material obtained in comparative example 1 was measured by an X-ray diffractometer, and the result is shown in fig. 4. As can be seen from the results of FIG. 4, the pre-magnesium silicon-oxygen anode material does not contain MgAl 2O4 phase, and has higher silicon peak, large silicon crystal grain and adverse cycle performance.
Comparative example 2
The comparative example is a preparation method of a pre-magnesium silicon oxygen anode material, comprising the following steps.
(I) First coating
Stirring SiO (D50 is 5.4 mu m), alCl 3, 10wt.% polyvinyl alcohol aqueous solution and deionized water according to a mass ratio of 100:0.5:5:800 to obtain a first mixture, stirring at 300rpm for 5 hours, spray-drying the first mixture at 120 ℃, mixing with asphalt according to a mass ratio of 100:4 for 3 hours, then roasting at a heating rate of 3 ℃/min to 650 ℃ for 8 hours under argon atmosphere, cooling to room temperature, and scattering to obtain a first roasted product.
Step (II) and step (III) are the same as in example 1.
Comparative example 3
The comparative example is a preparation method of a pre-magnesium silicon oxygen anode material, comprising the following steps.
(I) First coating
Stirring SiO (D50 is 5.4 mu m), alCl 3, 10wt.% polyvinyl alcohol aqueous solution and deionized water according to a mass ratio of 100:20:5:800 to obtain a first mixture, stirring at a speed of 300rpm for 5 hours, spray-drying the first mixture at 120 ℃, mixing the first mixture with asphalt according to a mass ratio of 100:4 for 3 hours, then roasting at a temperature rising rate of 3 ℃/min to 650 ℃ for 8 hours under an argon atmosphere, cooling to room temperature, and scattering to obtain a first roasting material.
Step (II) and step (III) are the same as in example 1.
Comparative example 4
The comparative example is a preparation method of a pre-magnesium silicon oxygen anode material, comprising the following steps.
(I) First coating
Stirring SiO (D50 is 5.4 mu m), mgCl 2, 10wt.% polyvinyl alcohol aqueous solution and deionized water according to a mass ratio of 100:6:5:800 to obtain a first mixture, stirring at a speed of 300rpm for 5 hours, spray-drying the first mixture at 120 ℃, mixing with asphalt according to a mass ratio of 100:4 for 3 hours, then roasting at a temperature rising rate of 3 ℃/min to 650 ℃ for 8 hours under an argon atmosphere, cooling to room temperature, and scattering to obtain a first roasting material.
Step (II) and step (III) are the same as in example 1.
Comparative example 5
The comparative example is a preparation method of a pre-magnesium silicon oxygen anode material, comprising the following steps.
(I) Magnesian reduction reaction
Mixing carbon-coated SiO (D50 is 5.4 mu m, carbon content is 3.0 wt.%), alCl 3, magnesium powder (D50=30mu m) and anhydrous CaCl 2 (melting point is 772 ℃) in a mass ratio of 100:6:14:80 for 5 hours to obtain a mixture, heating the mixture from room temperature under argon atmosphere, heating to 600 ℃ at a heating rate of 2 ℃/min for 4 hours, heating to 900 ℃ at a heating rate of 4 ℃/min for 4 hours, and naturally cooling and scattering to obtain a roasted product.
(II) carbon coating
Washing the roasted material with water for 1h according to the mass ratio of 1:6 to remove CaCl 2, vacuum drying at 80 ℃ for 8h, scattering, pickling with hydrochloric acid with the concentration of 0.7mol/L for 2h, carrying out filter pressing after pickling, washing with deionized water to be neutral, vacuum drying at 100 ℃ for 6h, scattering, mixing with asphalt according to the mass ratio of 100:4, and heating to 900 ℃ at the heating rate of 5 ℃/min in nitrogen atmosphere for 3h to obtain the pre-magnesium silicon-oxygen negative electrode material.
Comparative example 6
The comparative example is a preparation method of a pre-magnesium silicon oxygen anode material, comprising the following steps.
Step (I) and step (III) are the same as in example 1.
(II) magnesium reduction reaction
Mixing the first roasting material, magnesium powder (D50=30μm) and anhydrous CaCl 2 (melting point 772 ℃) in VC for 5 hours according to the mass ratio of 100:14:80 to obtain a second mixture, heating the second mixture under argon atmosphere, heating the second mixture to 600 ℃ at the heating rate of 2 ℃/min for 4 hours, heating the second mixture to 700 ℃ at the heating rate of 4 ℃/min for 4 hours, and naturally cooling the second mixture to obtain the second roasting material.
Comparative example 7
The comparative example is a preparation method of a pre-magnesium silicon oxygen anode material, comprising the following steps.
Step (I) and step (III) are the same as in example 1.
(II) magnesium reduction reaction
Mixing the first roasting material, magnesium powder (D50=30μm) and anhydrous CaCl 2 (melting point 772 ℃) in VC for 5 hours according to the mass ratio of 100:14:80 to obtain a second mixture, heating the second mixture under argon atmosphere, heating the second mixture from room temperature to 600 ℃ at the heating rate of 2 ℃/min for 4 hours, heating the second mixture to 1100 ℃ at the heating rate of 4 ℃/min for 4 hours, and scattering the second mixture after natural cooling to obtain the second roasting material.
Comparative example 8
The comparative example is a preparation method of a pre-magnesium silicon oxygen anode material, comprising the following steps.
(I) First coating
Stirring SiO (D50 is 5.4 mu m), aluminum powder, 10wt.% polyvinyl alcohol aqueous solution and deionized water according to a mass ratio of 100:6:5:800 to obtain a first mixture, stirring at 300rpm for 5 hours, spray-drying the first mixture at 120 ℃, mixing the first mixture with asphalt according to a mass ratio of 100:4 for 3 hours, then heating to 650 ℃ for 8 hours at a heating rate of 3 ℃/min under argon atmosphere, cooling to room temperature, and scattering to obtain a first roasting product.
Step (II) and step (III) are the same as in example 1.
The pre-magnesium silicon oxygen anode materials prepared in examples 1 to 15 and comparative examples 1 to 8 were subjected to physical properties and chemical composition tests under the following conditions, and the results are shown in tables 1 and 2.
The pre-magnesium silicon oxygen anode materials prepared in examples 1 to 15 and comparative examples 1 to 8 were subjected to alkali resistance test, and the results thereof are shown in table 3.
The pre-magnesium silicon oxygen anode materials prepared in examples 1 to 15 and comparative examples 1 to 8 were respectively prepared into button cells for electrochemical performance test, the button cell preparation process and test conditions thereof were as follows, and the test results are shown in table 4.
The test conditions are described below.
(1) Physical Properties
And testing the particle size distribution of the pre-magnesium silicon-oxygen anode material by adopting a laser particle sizer.
And testing the specific surface area of the pre-magnesium silicon oxygen anode material by adopting a nitrogen isothermal adsorption-desorption curve.
Testing the crystal form structure of the pre-magnesium silicon oxygen cathode material by adopting an X-ray diffractometer to obtain the grain size of the nano silicon, and calculating I2/I1、I3/I1、I3/I4、I5/I1、A2/A1、A3/A1、A3/A4.
(2) Chemical composition testing
Testing magnesium element and aluminum element of the pre-magnesium silicon oxygen anode material by adopting an inductive coupling plasma atomic emission spectrometry; an oxygen-nitrogen analyzer is adopted to test the content of oxygen element; and testing the content of the carbon element by adopting a carbon-sulfur analyzer.
(3) Alkali resistance test
300ML of 0.001mol/L NaOH solution (pH=11.0) is weighed and added into a special alkali-resistant test container, the special test container is placed into a water bath kettle with the temperature of 45 ℃ and is sealed and placed for 1h, so that the temperature of 0.001mol/L NaOH reaches 45 ℃. The special container for testing was opened, 3g of the pre-magnesium silicon oxygen anode materials prepared in examples 1 to 15 and comparative examples 1 to 8 were added respectively, immediately sealed, stirred continuously in a water bath at 45℃and the gas production was recorded by a custom-made device MC-BMP-II.
300ML of 0.001mol/L NaOH solution (PH=11.0) is weighed and added into a special alkali-resistant test container, the special test container is placed into a water bath kettle with the temperature of 60 ℃ and is sealed and placed for 1h, so that the temperature of 0.001mol/L NaOH reaches 60 ℃. The special container for testing was opened, 3g of the pre-magnesium silicon oxygen anode materials prepared in examples 1 to 15 and comparative examples 1 to 8 were added respectively, immediately sealed, stirred continuously in a water bath at 60℃and the gas production was recorded by a custom-made device MC-BMP-II.
300ML of 0.1mol/L NaOH solution (PH=13.0) is weighed and added into a special container for alkali resistance test, the special container for test is put into a water bath kettle with the temperature of 45 ℃ and is sealed and placed for 1h, so that the temperature of 0.1mol/L NaOH reaches 45 ℃. The special container for testing was opened, 3g of the pre-magnesium silicon oxygen anode materials prepared in examples 1 to 15 and comparative examples 1 to 8 were added respectively, immediately sealed, stirred continuously in a water bath at 45℃and the gas production was recorded by a custom-made device MC-BMP-II.
300ML of 0.1mol/L NaOH solution (PH=13.0) is weighed and added into a special container for alkali resistance test, the special container for test is put into a water bath kettle with the temperature of 60 ℃ and is sealed and placed for 1h, so that the temperature of 0.1mol/L NaOH reaches 60 ℃. The special container for testing was opened, 3g of the pre-magnesium silicon oxygen anode materials prepared in examples 1 to 15 and comparative examples 1 to 8 were added respectively, immediately sealed, stirred continuously in a water bath at 60℃and the gas production was recorded by a custom-made device MC-BMP-II.
(4) Electrochemical performance test
First charge and discharge performance test: the pre-magnesium silicon oxide anode materials prepared in examples 1 to15 and comparative examples 1 to 8 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 rolled to prepare an anode sheet. The lithium metal sheet is used as a counter electrode, 1mol/L LiPF 6 and a three-component mixed solvent according to the ratio of EC to DMC to EMC=1:1:1 (v/v/v) are mixed to form electrolyte, a polypropylene microporous membrane is used as a diaphragm, and the CR2032 button cell is assembled in a glove box filled with inert gas. The charge and discharge test of the button cell was performed on a blue electronic company LANHE battery test system. Under normal temperature conditions, the first reversible specific capacity and the first coulombic efficiency are obtained by discharging with a constant current of 0.1C to a voltage of 0.01V, then discharging with a constant current of 0.02C to a voltage of 0.005V, and charging with a constant current of 0.1C to a voltage of 1.5V.
And (3) testing the cycle performance: the pre-magnesium silicon oxygen cathode materials, the pre-lithium silicon oxygen cathode materials (which can be conventional products on the market) prepared in examples 1 to 15 and comparative examples 1 to 8 are uniformly mixed with graphite according to the mass ratio of 0.5:0.5:9 to be used as an active substance, and are mixed with an aqueous dispersion liquid (LA 132, solid content 15%) of an acrylonitrile multipolymer binder and a conductive agent (Super P) according to the mass ratio of 70:10:20, and then a proper amount of water is added to be used as a solvent to prepare slurry, and the slurry is coated on copper foil and is subjected to vacuum drying and rolling to prepare the cathode sheet. The metal lithium is used as a counter electrode, a 1mol/L LiPF 6 three-component mixed solvent is used for preparing a CR2032 button cell by adopting a polypropylene microporous membrane as a diaphragm according to electrolyte mixed by EC: DMC: EMC=1:1:1 (volume ratio), and the button cell is assembled in a glove box filled with inert gas. The charge and discharge test of the button cell is carried out on a cell test system of blue electronic Co., ltd, and the charge and discharge voltage is limited to 0.005-1.5V under the constant current charge and discharge at normal temperature. The initial and 50-week-after-cycle thickness of the negative electrode was measured, and the 50-week lithium intercalation expansion rate H2 was calculated. Under normal temperature conditions, 0.1C is charged and discharged for one week at constant current, then 0.1C is fully charged, the initial and full-charge thickness of the cathode after 1.5 weeks of circulation is tested, the expansion rate H1 of 1.5 Zhou Qianli is calculated, and the expansion and growth rate H3 = H2-H1 of lithium intercalation after 50 weeks of circulation is carried out. 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.
Table 1 physical properties and chemical composition test results of the pre-magnesium-silicon-oxygen anode materials prepared in each example and comparative example
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TABLE 2 XRD parameters of the pre-magnesium silica anode materials prepared in examples and comparative examples
TABLE 3 alkali resistance test results of the pre-magnesium silica anode materials prepared in examples and comparative examples
Table 4 electrochemical performance test results of the pre-magnesium-silicon-oxygen anode materials prepared in each example and comparative example
As can be seen from the results in Table 1, the pre-magnesium-silicon-oxygen anode materials prepared in examples 1 to 15 of the present invention have a certain content of aluminum element and magnesium element, and have a low D50 and specific surface area, so that the electrochemical properties of the pre-magnesium-silicon-oxygen anode materials prepared in examples 1 to 15 are better as can be seen from the physical properties and chemical compositions of the materials. From the results of Table 4, it was also confirmed that the reversible capacity of the pre-magnesium-silicon-oxygen anode materials prepared in examples 1 to 15 was not less than 1450mAh/g, the initial coulombic efficiency was not less than 83%, the lithium intercalation expansion rate at 1.5 weeks was not more than 45%, the lithium intercalation expansion rate after 50 weeks of circulation was not more than 50%, the lithium intercalation expansion increase rate was not more than 5%, and the capacity retention rate was not less than 90%. This is mainly because MgAl 2O4 (as shown in XRD test results of table 2) is included in the pre-magnesium silicon oxide negative electrode material of the present invention, and the circulation performance of the pre-magnesium silicon oxide negative electrode material can be effectively improved by the contained MgAl 2O4. Meanwhile, as shown in the results of table 3, the inclusion of MgAl 2O4 in the pre-magnesium silicon oxygen anode material can also effectively improve the alkali resistance of the material.
Comparative example 1 and comparative examples 1 to 4, in which an aluminum-containing compound was not added during the preparation, or the content of the aluminum-containing compound was too high or too low, resulted in failure to form a MgAl 2O4 -containing coating layer, or the coating layer was too thin and too thick, resulting in deterioration of cycle performance.
In comparative example 5, the aluminum-containing compound and the magnesium source were baked together, and MgAl 2O4 formed was doped in the layer formed of the magnesium-silicon oxide compound, instead of forming a special coating layer, which corresponds to simple doping of aluminum element, so that the cycle performance and alkali resistance of the material were not improved much.
The magnesium reduction reaction in comparative example 6 was too low in temperature to produce Mg 2AlO4, so that the material performance was poor. The magnesium reduction reaction in comparative example 7 was too high in temperature, resulting in a large silicon grain size, which is disadvantageous in cycle performance.
In comparative example 8, aluminum powder, which has the same effect as the magnesium source, diffuses into the SiO x material and reacts with SiO x to form a silicon aluminum compound instead of MgAl 2O4, so that the material properties are also poor.
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. The preparation method of the pre-magnesium silicon-oxygen anode material is characterized by comprising the following steps:
(I) First coating
Stirring SiO x, an aluminum-containing compound, a binder and a solvent, then performing spray drying to obtain a first mixture, mixing the first mixture with a carbon source, then sequentially performing first roasting and first post-treatment to obtain a first roasting product, wherein 0< x <2, the aluminum-containing compound accounts for 1-10% of the mass of SiO x, the aluminum-containing compound comprises at least one of aluminum carbonate, aluminum chloride, aluminum sulfate, aluminum nitrate, aluminum hydroxide, aluminum oxide, aluminum phosphate, aluminum acetate, aluminum isopropoxide and tert-butyl aluminum oxide, the binder comprises at least one of polyvinyl alcohol, polyacrylic acid, carboxymethyl cellulose, phenolic resin, epoxy resin, polyamide resin and chloroprene rubber, and the solvent comprises at least one of deionized water, ethanol, methanol, isopropanol and ethyl acetate, wherein the mass ratio of SiO x, the aluminum-containing compound, the binder and the solvent is 100:1-10:1-10:200-2000;
(II) magnesium reduction reaction
Mixing the first roasting material, a magnesium source and molten salt to obtain a second mixture, and sequentially carrying out second roasting and second post-treatment on the second mixture under inert atmosphere to obtain a second roasting material, wherein the highest temperature of the second roasting is 800-1000 ℃;
(III) second coating
And (3) carrying out carbon coating on the second roasting material after acid washing.
2. The method for producing a pre-magnesium silica anode material according to claim 1, characterized by comprising at least one of the following features (1) to (19):
(1) The carbon source comprises at least one of asphalt, phenolic resin, starch, polyvinyl alcohol, epoxy resin, polydopamine, lignin, citric acid, glucose and sucrose;
(2) The magnesium source comprises metallic magnesium and/or magnesium alloy;
(3) The D50 of the magnesium source is less than or equal to 100 mu m;
(4) The molten salt includes at least one of NaCl, KCl, rbCl, csCl, caCl 2、MgCl2、SrCl2 and BaCl 2;
(5) The melting point of the molten salt is more than 650 ℃;
(6) The mass ratio of the first roasting material to the magnesium source to the molten salt is 100:5-15:20-100;
(7) The carbon source accounts for 1 to 5 percent of the mass of the first mixture;
(8) The molar ratio of the Mg element in the second roasting material to the hydrogen element in the acid solution adopted by the acid washing is 1:1.2-2.2;
(9) The pickling time is 1 to 6 hours;
(10) The concentration of the acid solution adopted by the acid washing is 0.1mol/L to 1.0mol/L;
(11) The mode adopted by the mixing in the step (I) and the step (II) independently comprises VC mixing, fusion machine mixing or ball milling mixing;
(12) The mixing times in step (I) and step (II) are each independently 1h to 10h;
(13) The first roasting is carried out under inert atmosphere;
(14) The spray drying temperature is 80 ℃ to 200 ℃;
(15) The temperature of the first roasting is 600-700 ℃, the time is 2-12 h, and the heating rate is 1-10 ℃/min;
(16) The first post-treatment and the second post-treatment comprise the steps of cooling to room temperature and scattering after roasting in sequence;
(17) The inert atmosphere comprises at least one of nitrogen, argon and helium;
(18) The second roasting material is sequentially subjected to first water washing and first drying before acid washing, and is sequentially subjected to filtration, second water washing, second drying and scattering after acid washing;
(19) The carbon coating includes at least one of a gas phase coating, a solid phase coating, and a liquid phase coating.
3. The method for preparing a pre-magnesium silicon oxygen anode material according to claim 1, wherein the second firing is a step firing.
4. The method of preparing a pre-magnesium silicon-oxygen anode material according to claim 3, wherein the step-by-step baking comprises the steps of firstly keeping the temperature of the mixture at 500 ℃ to 650 ℃ for 2 hours to 12 hours at a heating rate of 1 ℃/min to 6 ℃/min, and then keeping the temperature of the mixture at 880 ℃ to 1000 ℃ for 1 hour to 10 hours at a heating rate of 1 ℃/min to 10 ℃/min.
5. The pre-magnesium silica anode material according to any one of claims 1 to 4, comprising an inner core, a first coating layer, a second coating layer and a third coating layer from inside to outside, wherein the inner core comprises Si and a silica compound, the first coating layer comprises Si and a silica-magnesium compound, the second coating layer comprises MgAl 2O4, and the third coating layer comprises a carbon layer.
6. The pre-magnesium, silicon-oxygen anode material according to claim 5, wherein the silicon-oxygen-magnesium compound comprises MgSiO 3.
7. The pre-magnesium, silicon-oxygen anode material according to claim 6, comprising at least one of the following features ① to ⑧:
① XRD tests prove that the diffraction peak intensity of Si (111) with the angle of 28.4 plus or minus 0.2 degrees is I 1, and the diffraction peak intensity of MgSiO 3 (610) with the angle of 30.9 plus or minus 0.2 degrees is I 2,0.1≤I2/I1 which is less than or equal to 0.4;
② XRD tests prove that the diffraction peak area of Si (111) with the angle of 28.4+/-0.2 ℃ is A 1, and the diffraction peak area of MgSiO 3 (610) with the angle of 30.9+/-0.2 ℃ is A 2,0.05≤A2/A1 which is less than or equal to 0.20;
③ XRD tests prove that the diffraction peak intensity of Si (111) with the angle of 28.4+/-0.2 ℃ is I 1, and the diffraction peak intensity of MgAl 2O4 (400) with the angle of 44.8+/-0.2 ℃ is I 3,0.03≤I3/I1 which is less than or equal to 0.10;
④ XRD tests prove that the diffraction peak area of Si (111) with the angle of 28.4+/-0.2 ℃ is A 1, and the diffraction peak area of MgAl 2O4 (400) with the angle of 44.8+/-0.2 ℃ is A 3,0.01≤A3/A1 which is less than or equal to 0.05;
⑤ XRD tests prove that the diffraction peak intensity of MgAl 2O4 (400) with the angle of 44.8 plus or minus 0.2 degrees is I 3, and the diffraction peak intensity of Si (220) with the angle of 47.4 plus or minus 0.2 degrees is I 4,0.06≤I3/I4 which is less than or equal to 0.20;
⑥ XRD tests prove that the diffraction peak intensity of Si (111) of 28.4+/-0.2 degrees is I 1, and the diffraction peak intensity of MgAl 2O4 (311) of 36.85 degrees is I 5,0.05≤I5/I1 which is less than or equal to 0.15;
⑦ XRD tests prove that the diffraction peak area of MgAl 2O4 (400) with the angle of 44.8 plus or minus 0.2 degrees is A 3, and the diffraction peak area of Si (220) with the angle of 47.4 plus or minus 0.2 degrees is A 4,0.03≤A3/A4 which is less than or equal to 0.15;
⑧ The grain size of Si is D, and D is less than or equal to 7.0nm.
8. The pre-magnesium, silicon-oxygen anode material according to claim 5, comprising at least one of the following features (one) to (twenty):
The specific surface area of the pre-magnesium silicon oxygen anode material is 0.5m 2/g to 5.0m 2/g;
(II) the D50 of the pre-magnesium silicon oxide anode material is 1-10 μm;
(III) the expansion rate of lithium intercalation of the pre-magnesium silicon oxide anode material for 1.5 weeks is less than or equal to 45%;
Fourthly, the reversible capacity of the pre-magnesium silicon oxide anode material is more than or equal to 1450mAh/g;
(V) the first coulombic efficiency of the pre-magnesium silicon oxide anode material is more than or equal to 83%;
(VI) the expansion rate of the lithium intercalation of the pre-magnesium silicon oxide anode material after 50 cycles is less than or equal to 50 percent;
(seventh), the expansion and growth rate of the lithium intercalation of the pre-magnesium silicon oxygen cathode material is less than or equal to 5% after 50 weeks of circulation;
(eight) the capacity retention rate of the magnesium-silicon-oxygen anode material is more than or equal to 90% after 50 weeks of circulation;
(nine) the oxygen content in the pre-magnesium-silicon-oxygen anode material is 15wt.% to 30wt.%;
(ten) the carbon content in the pre-magnesium silicon oxide negative electrode material is 2wt.% to 10wt.%;
(eleven) the magnesium content in the pre-magnesium-silicon-oxygen anode material is 5wt.% to 10wt.%;
(twelve) the aluminum content in the pre-magnesium silicon oxygen anode material is 0.4wt.% to 2.0wt.%;
(thirteen) the silicon oxide compound comprises silicon oxide and/or silicon dioxide;
(fourteen) the diameter of the inner core is greater than 0 and less than or equal to 3.0 μm;
(fifteen) the first clad layer has a thickness of 0.1 μm to 5.0 μm;
sixteenth, the second coating layer has a thickness of 5nm to 25nm;
(seventeen) the thickness of the third coating layer is 10nm to 100nm;
Eighteen, the pre-magnesium silicon oxygen anode material does not contain Mg 2SiO4;
(nineteenth) in an alkaline solution with the pH value of 13, the pre-magnesium silicon oxygen anode material starts to produce gas at the temperature of 45 ℃ for more than or equal to 240 hours, and starts to produce gas at the temperature of 60 ℃ for more than or equal to 170 hours;
And (twenty) in the alkaline solution with the pH value of 11, the pre-magnesium silicon oxygen anode material starts to produce gas at the temperature of 45 ℃ for more than or equal to 400 hours, and starts to produce gas at the temperature of 60 ℃ for more than or equal to 310 hours.
9. Use of the pre-magnesium-silicon-oxygen anode material prepared by the preparation method of the pre-magnesium-silicon-oxygen anode material according to any one of claims 1 to 4 or the pre-magnesium-silicon-oxygen anode material according to any one of claims 5 to 8 in an anode material.
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 prepared by the method for preparing a 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 according to any one of claims 5 to 8.
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Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN112289985A (en) * 2020-09-22 2021-01-29 合肥国轩高科动力能源有限公司 C @ MgAl2O4Composite coating modified silicon-based negative electrode material and preparation method thereof
CN116565170A (en) * 2023-05-26 2023-08-08 广东凯金新能源科技股份有限公司 Silicon-based anode material, preparation method thereof and secondary battery

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* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN112289985A (en) * 2020-09-22 2021-01-29 合肥国轩高科动力能源有限公司 C @ MgAl2O4Composite coating modified silicon-based negative electrode material and preparation method thereof
CN116565170A (en) * 2023-05-26 2023-08-08 广东凯金新能源科技股份有限公司 Silicon-based anode material, preparation method thereof and secondary battery

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