CN107959012B - Single-layer/double-layer coated silicon oxide composite negative electrode material and preparation method thereof - Google Patents

Single-layer/double-layer coated silicon oxide composite negative electrode material and preparation method thereof Download PDF

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CN107959012B
CN107959012B CN201711142093.1A CN201711142093A CN107959012B CN 107959012 B CN107959012 B CN 107959012B CN 201711142093 A CN201711142093 A CN 201711142093A CN 107959012 B CN107959012 B CN 107959012B
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negative electrode
silicon oxide
electrode material
oxide composite
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CN107959012A (en
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柳听前
刘灿
刘丰
邵乐强
程君
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Lixin Jiangsu Energy Technology Co ltd
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Etrust Power Group 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
    • 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
    • H01M4/62—Selection of inactive substances as ingredients for active masses, e.g. binders, fillers
    • 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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    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/10—Energy storage using batteries

Abstract

The invention provides a single-layer/double-layer coated silicon oxide composite negative electrode material and a preparation method thereof. According to the single-layer coated silicon oxide composite negative electrode material, the single-layer coated silicon oxide composite negative electrode material is a two-layer composite material with a core-shell structure, the inner core is a silica precursor, the outer layer is a lithium titanate layer, and the silica precursor is a material formed by silicon uniformly dispersed in silicon dioxide. According to the double-layer coated silicon oxide composite negative electrode material, the double-layer coated silicon oxide composite negative electrode material is a three-layer composite material with a core-shell structure, the inner core is a silica precursor, the middle layer is a lithium titanate layer, and the outermost layer is a carbon layer coated on the outer surface of the lithium titanate layer. The double-layer coated silicon oxide composite negative electrode material has a three-layer structure, the inner core is a silica precursor, the middle layer is a lithium titanate layer, and the outermost layer is a carbon layer, so that the volume effect of silicon oxide can be buffered well, and the double-layer coated silicon oxide composite negative electrode material has high specific capacity and excellent cycle performance.

Description

Single-layer/double-layer coated silicon oxide composite negative electrode material and preparation method thereof
Technical Field
The invention relates to the field of battery cathode materials, in particular to a single-layer/double-layer coated silicon oxide composite cathode material and a preparation method thereof.
Background
According to the planning of 'energy-saving and new energy automobile technical route map' in China, the single energy density target of the pure electric automobile power battery in China is 300Wh/kg by 2020. At present, the main approach to achieve this goal is to develop a high energy density electrode material, and it is very important to actively develop a novel negative electrode material to improve the energy density of a lithium ion battery. Silicon-based anode materials are one of the more studied high-capacity anode materials. Although the capacity of the silicon negative electrode is as high as 4200mAh/g, the silicon negative electrode material is accompanied by volume expansion of 300% when lithium is deintercalated, and the cycle performance is poor. At present, the performances of the material such as cycle, multiplying power and the like are generally improved by silicon nanocrystallization or preparation of a silicon-oxygen negative electrode material.
In patent CN102306759A, a composite negative electrode material of silicon oxide for lithium ion battery and a preparation method thereof are disclosed, the preparation of the material comprises the following steps: (1) sintering the silicon monoxide at high temperature in an inert atmosphere to generate nano silicon particles and amorphous silicon dioxide; (2) accurately weighing a certain amount of sintered silicon monoxide and a conductive agent, adding the weighed materials into a planetary ball mill, and mixing and ball-milling to obtain the silicon monoxide composite negative electrode material. However, since the silicon monoxide directly contacts the electrolyte, an SEI film is repeatedly formed, and cycle deterioration and overall performance are poor.
In patent CN101752547A, a process for preparing Si-SiO is disclosed2-C material preparation method. The method takes silicon monoxide, graphite and asphalt as raw materials to prepare the core-shell structure carbon-coated silicon oxide material with higher cycle performance and specific capacity. But the first coulombic efficiency of the material is lower than 70%.
In patent CN103022446A, a silicon oxide/carbon negative electrode material for lithium ion battery and a preparation method thereof are disclosed. The three-layer composite material takes graphite as an inner core, porous silicon oxide partially reduced by active metals such as lithium and the like as an intermediate layer, and organic pyrolytic carbon as an outermost coating layer, has good cycle performance and specific capacity, and the first coulombic efficiency can also reach 88%. However, the process is complex, high in cost, difficult to control and difficult to industrialize on a large scale.
In patent CN104617265A, a method for preparing a silicon-oxygen-carbon composite lithium ion battery anode material is disclosed, which comprises the following steps: in CO2And under the gas atmosphere, ball-milling the silicon-based material to obtain the silicon-oxygen-carbon composite material. However, the material prepared by the method has low first efficiency, and the cycle performance can not meet the requirement of a power battery.
In patent CN103682268A, a method for preparing a silicon negative electrode material coated with a carbon-lithium titanate double layer is provided. The silicon-based negative electrode material coated by the carbon and lithium titanate double layers is synthesized by a double-chelating agent sol-gel method by taking a chelating agent as a carbon source, a soluble Ti compound as a titanium source, a nano silicon source and various lithium compounds as lithium sources. But the agglomeration of the silicon source is not easy to control, and the prepared material has lower compaction density.
Disclosure of Invention
Therefore, a single-layer/double-layer coated silicon oxide composite negative electrode material with a silicon source which is not easy to agglomerate and good in cycling stability and a preparation method thereof are needed.
The single-layer coated silicon oxide composite negative electrode material is a two-layer composite material with a core-shell structure, wherein an inner core is a silica precursor, an outer layer is a lithium titanate layer, and the silica precursor is a material formed by uniformly dispersing nano-silicon in silicon dioxide. Preferably, the silicon oxide precursor is SiOxWherein, 0.5<x<1.5。
According to the technical scheme, as the inner core is a silica precursor and the nano-silicon is uniformly dispersed in the silicon dioxide, the single-layer coated silicon oxide composite negative electrode material performs self-absorption on the volume expansion effect of the silicon particles in the charging and discharging processes, so that the volume expansion effect of the silicon particles is greatly reduced, and the silicon source is not easy to agglomerate; and secondly, the lithium titanate layer coated on the outer layer of the silica precursor is beneficial to improving the cycle, multiplying power and low-temperature performance of the material, so that the cycle stability of the single-layer coated silicon oxide composite negative electrode material is better.
In one embodiment, the particle size of the silicon oxygen precursor is 0.5-15 μm. Preferably, the thickness of the lithium titanate layer is 5 to 500 nm.
A preparation method of a single-layer coated silicon oxide composite negative electrode material comprises the following steps:
1) uniformly mixing nano silicon and nano silicon dioxide to obtain a mixture, roasting the mixture at 1200-2200 ℃ under vacuum/argon gas, cooling, crushing, and performing ball milling to obtain a silica precursor;
2) dispersing a titanium source, the silica precursor and a lithium source into an organic solvent, uniformly stirring to form a gel, aging and drying the gel to obtain powder, and calcining the dried powder in a protective atmosphere to obtain the single-layer coated silicon oxide composite negative electrode material.
Preferably, the roasting time for preparing the silicon-oxygen precursor is 4-24 h. The ball milling can adopt planetary ball milling, vibration ball milling or horizontal planetary ball milling. When the ball milling is planetary ball milling or horizontal planetary ball milling, the ball milling condition is that the ball-material ratio is 20-100: 1, the ball milling rotating speed is 200-500 r/min, and the ball milling time is 0.5-24 h; when the ball milling is vibration ball milling, the ball milling conditions are as follows: the ball-material ratio is 20-100: 1, and the ball milling time is 0.5-24 h. The molar ratio of lithium ions in the lithium source to titanium ions in the titanium source is (0.8-1.2): 1.
according to the technical scheme, the nano silicon and the nano silicon dioxide are adopted to react at high temperature to generate the silicon monoxide, but the silicon monoxide is unstable and then decomposed into silicon and silicon dioxide, so that the nano silicon can be uniformly dispersed in the silicon dioxide to obtain the silicon-oxygen precursor, and then the surface of the silicon-oxygen precursor is coated with a single layer with high Li content by a sol-gel method+Conductive, well crystalline lithium titanate layers utilizing the stability of lithium titanate and high Li+The conductivity greatly improves the cyclicity of the single-layer coated silicon oxide composite negative electrode material, and simultaneously has promotion effect on the rate capability and the low-temperature performance.
In one embodiment, the titanium source is titanium oxide sulfate, tetraethyl titanate, tetrabutyl titanate, titanium tetrachloride, or isopropyl titanate; the lithium source is lithium hydroxide, lithium chloride or lithium oxalate; the organic solvent is absolute ethyl alcohol, acetone or propanol.
In one embodiment, the mass of the titanium source is 1-15% of that of the silicon-oxygen precursor.
The double-layer coated silicon oxide composite negative electrode material is a three-layer composite material with a core-shell structure, wherein an inner core is a silica precursor, an intermediate layer is a lithium titanate layer, an outermost layer is a carbon layer coated on the outer surface of the lithium titanate layer, and the silica precursor is a material formed by uniformly dispersing nano-silicon in silicon dioxide. Preferably, the silicon oxide precursor is SiOxWherein, 0.5<x<1.5。
According to the technical scheme, the lithium-ion battery is of a three-layer structure, the inner core is a silica precursor, the middle layer is a lithium titanate layer, the outermost layer is a carbon layer, and the silica precursor is lithium oxide (Li) formed in the primary electrochemical discharge process2O) and lithium silicate (Li)4SiO4) The volume effect of the silicon oxide can be well buffered, so that the double-layer coated silicon oxide composite negative electrode material has high specific capacity and excellent cycle performance; the outermost coating carbon layer can play a supporting role and prevent lithium titanate flatulence.
In one embodiment, the lithium titanate layer has a thickness of 5 to 500nm, and the carbon layer has a thickness of 0.05 to 10 μm.
A preparation method of a double-layer coated silicon oxide composite negative electrode material comprises the following steps:
1) uniformly mixing nano silicon and nano silicon dioxide to obtain a mixture, roasting the mixture at 1200-2200 ℃ in a vacuum/argon atmosphere, cooling, and crushing to obtain a silica precursor;
2) dispersing a titanium source, the silica precursor and a lithium source into absolute ethyl alcohol serving as a solvent, uniformly stirring to form gel, aging and drying the gel to obtain powder, and calcining the dried powder in a protective atmosphere to obtain the single-layer coated silicon oxide composite negative electrode material;
3) and (2) uniformly mixing the single-layer coated silicon oxide composite negative electrode material with an organic carbon source and a solvent, drying to obtain a mixture, calcining the mixture at 500-1200 ℃ for 0.5-20 h in a protective atmosphere, and cooling to obtain the double-layer coated silicon oxide composite negative electrode material. Preferably, in the step 2), the molar ratio of lithium ions in the lithium source to titanium ions in the titanium source is (0.8-1.2): 1. in the step 3), the solvent is one or more of water, tetrahydrofuran, methanol, ethanol, ethylene glycol, propanol, acetone, methyl ethyl ketone, methyl propyl ketone, isopropanol, tetrahydrofuran, cyclohexane, petroleum ether, acetic acid and toluene. The protective atmosphere is argon or nitrogen.
According to the technical scheme, the carbon layer is formed by wrapping the outer surface of the single-layer coated silicon oxide composite anode material, and the preparation method is simple, easy to operate, low in cost, low in energy consumption and high in operability.
In one embodiment, the organic carbon source is one or more of phenolic resin, furfural resin, epoxy resin, urea resin, pitch, citric acid, glucose, sucrose, polyvinyl chloride, and polyvinyl butyral.
In one embodiment, the weight ratio of the single-layer coated silicon oxide composite anode material to the organic carbon source is 1: (0.5 to 20).
Has the advantages that: the invention has the advantages that:
1) according to the single-layer coated silicon oxide composite negative electrode material, as the inner core is a silicon oxide precursor and the nano silicon is uniformly dispersed in the silicon dioxide, the single-layer coated silicon oxide composite negative electrode material performs self-absorption on the volume expansion effect of silicon particles in the charging and discharging process, so that the volume expansion effect of the silicon particles is greatly reduced, and the silicon source is not easy to agglomerate; and secondly, the lithium titanate layer coated on the outer layer of the silica precursor enables the single-layer coated silicon oxide composite negative electrode material to have better cycling stability.
2) According to the preparation method of the single-layer coated silicon oxide composite negative electrode material, the nano silicon and the nano silicon dioxide are adopted to react at high temperature to generate the silicon monoxide, but the silicon monoxide is unstable and then decomposed into the silicon and the silicon dioxide, so that the nano silicon can be uniformly dispersed in the silicon dioxide to obtain the silicon-oxygen precursor, and then the surface of the silicon-oxygen precursor is coated with a single layer with high Li content by a sol-gel method+Conductive, well crystalline lithium titanate layers utilizing the stability of lithium titanate and high Li+The conductivity greatly improves the cyclicity of the single-layer coated silicon oxide composite negative electrode material, and simultaneously has promotion effect on the rate capability and the low-temperature performance.
3) The double-layer coated silicon oxide composite negative electrode material has a three-layer structure, the inner core is a silica precursor, the middle layer is a lithium titanate layer, the outermost layer is a carbon layer, and the silica precursor is lithium oxide (Li) formed in the primary electrochemical discharge process2O) and lithium silicate (Li)4SiO4) Can be used forThe volume effect of the silicon oxide is well buffered, so that the double-layer coated silicon oxide composite negative electrode material has high specific capacity and excellent cycle performance.
4) According to the preparation method of the double-layer coated silicon oxide composite negative electrode material, the carbon layer is coated on the outer surface of the single-layer coated silicon oxide composite negative electrode material, and the preparation method is simple, easy to operate, low in cost, low in energy consumption and high in operability.
Drawings
FIG. 1 is a schematic structural diagram of a double-layer coated silicon oxide composite negative electrode material according to the present invention;
fig. 2 is a first charge-discharge curve diagram of the double-layer coated silicon oxide composite anode material of example 1 of the present invention;
fig. 3 is a cycle stability curve of the double-layered coated silicon oxide composite anode material of example 1 of the present invention;
fig. 4 is a cycle stability curve of the double-layered silicon oxide-coated composite anode material of example 2 of the present invention;
fig. 5 is a cycle stability curve of the double-layered coated silicon oxide composite anode material of example 3 of the present invention;
fig. 6 is a cycle stability curve of the double-layered coated silicon oxide composite anode material of example 4 of the present invention;
fig. 7 is a cycle stability curve of the single-layer coated silicon oxide composite anode material of example 5 of the present invention;
fig. 8 is a cycle stability curve of the single-layer coated silicon oxide composite anode material of example 6 of the present invention;
fig. 9 is a cycle stability curve of the negative electrode material for the lithium ion battery of comparative example 1 according to the present invention;
fig. 10 is a cycle stability curve of the negative electrode material for the lithium ion battery of comparative example 2 of the present invention.
Detailed Description
The following detailed description of the preferred embodiments of the present invention, taken in conjunction with the accompanying drawings, will make the advantages and features of the invention easier to understand by those skilled in the art, and thus will clearly and clearly define the scope of the invention.
Example 1
Referring to fig. 1, a double-layer coated silicon oxide composite negative electrode material 100 is a three-layer composite material having a core-shell structure, in which an inner core is a silica precursor 110, an intermediate layer is a lithium titanate layer 120, an outermost layer is a carbon layer 130 coated on an outer surface of the lithium titanate layer 120, and the silica precursor 110 is a material formed by uniformly dispersing nano-silicon 111 in silicon dioxide 112. Preferably, the silicon oxide precursor is SiOxWherein, 0.5<x<1.5. The lithium titanate layer has a thickness of 5 to 500nm, and the carbon layer has a thickness of 0.05 to 10 μm.
A preparation method of a double-layer coated silicon oxide composite negative electrode material comprises the following steps:
1) mixing 10g of nano silicon and 21.4g of nano silicon dioxide (the molar ratio is 1:1), performing ball milling for 3 hours at the rotating speed of 300rpm, uniformly mixing the materials to obtain a mixture, roasting the mixture for 6 hours at 1200 ℃ under the vacuum condition, cooling, and crushing the mixture by a crusher until the particle size is 5-20 microns; and performing ball milling for 6 hours to obtain a silica precursor, wherein the particle size of the silica precursor is 5-15 microns.
2) Taking 5g of silica precursor, putting the silica precursor into 50ml of absolute ethanol solution containing 0.5g of tetrabutyl titanate, stirring for 6 hours, adding 5ml of water, and stirring for 60 minutes; and then adding 50mL of anhydrous ethanol solution containing 0.08g of lithium oxalate, finally adding 1g of glacial acetic acid, uniformly stirring, stopping stirring when the sol becomes gel, aging the generated gel for 12h, then drying the gel in vacuum at 80 ℃ for 12h, and calcining the dried powder at the temperature rising speed of 5 ℃/min to 800 ℃ for 3h to obtain the single-layer coated silicon oxide composite negative electrode material.
3) Sequentially weighing the single-layer coated silicon oxide composite negative electrode material, asphalt, acetic acid and distilled water according to the mass ratio of the single-layer coated silicon oxide composite negative electrode material to the asphalt to the acetic acid to the distilled water of 5:1:2:0.5:2, putting the single-layer coated silicon oxide composite negative electrode material, the asphalt, the acetic acid and the distilled water into a ball mill for ball milling for 3 hours, and then heating and evaporating to dryness at 100 ℃; calcining for 10h at the temperature rising speed of 5 ℃/min to 1000 ℃ in the nitrogen atmosphere, and cooling to obtain the double-layer coated silicon oxide composite negative electrode material.
In the embodiment, in the prepared double-layer coated silicon oxide composite negative electrode material, the thickness of the lithium titanate layer is 150-300 nm, and the thickness of the carbon layer is 0.5-1.5 μm.
Example 2
A preparation method of a double-layer coated silicon oxide composite negative electrode material comprises the following steps:
1) mixing 7.5g of nano silicon and 21.4g of nano silicon dioxide, then carrying out ball milling for 3h at the rotating speed of 300rpm, uniformly mixing the materials to obtain a mixture, roasting the mixture for 6h at 1500 ℃ under a vacuum condition, cooling, and crushing the mixture by using a crusher until the particle size is 10-50 mu m; and performing ball milling for 6 hours to obtain a silica precursor, wherein the particle size of the silica precursor is 2-10 mu m.
2) Taking 5g of silica precursor, putting the silica precursor into 50ml of absolute ethanol solution containing 0.5g of tetrabutyl titanate, stirring for 6 hours, adding 5ml of water, and stirring for 60 minutes; and then adding 50mL of acetone solution containing 0.11g of lithium oxalate, finally adding 1g of glacial acetic acid, uniformly stirring, stopping stirring when the sol becomes gel, aging the generated gel for 12h, then drying in vacuum at 80 ℃ for 12h, and calcining the dried powder at the temperature rising speed of 5 ℃/min to 700 ℃ for 2h to obtain the single-layer coated silicon oxide composite negative electrode material.
3) Weighing the single-layer coated silicon oxide composite negative electrode material, asphalt, acetic acid and distilled water according to the mass ratio of the single-layer coated silicon oxide composite negative electrode material to the asphalt to the acetic acid to the distilled water of 5:1:1.5:0.5:2, putting the single-layer coated silicon oxide composite negative electrode material, the asphalt to the acetic acid and the distilled water into a ball mill for ball milling for 3 hours, and then heating and evaporating to dryness at 100 ℃; calcining for 3h at the heating speed of 5 ℃/min to 900 ℃ in the nitrogen atmosphere, and cooling to obtain the double-layer coated silicon oxide composite negative electrode material.
In the embodiment, in the prepared double-layer coated silicon oxide composite negative electrode material, the thickness of the lithium titanate layer is 10-200 nm, and the thickness of the carbon layer is 3-7 μm.
Example 3
A preparation method of a double-layer coated silicon oxide composite negative electrode material comprises the following steps:
1) mixing 10g of nano silicon and 21.4g of nano silicon dioxide (the molar ratio is 1:1), performing ball milling for 3 hours at the rotating speed of 300rpm, uniformly mixing the materials to obtain a mixture, roasting the mixture for 8 hours at 2000 ℃ under a vacuum condition, cooling, and crushing the mixture by using a crusher until the particle size is 10-50 mu m; and performing ball milling for 6 hours to obtain a silica precursor, wherein the particle size of the silica precursor is 2-10 mu m.
2) Taking 5g of silica precursor, putting the silica precursor into 50ml of absolute ethanol solution containing 0.25g of tetrabutyl titanate, stirring for 6 hours, adding 5ml of water, and stirring for 60 minutes; and then adding 50mL of anhydrous ethanol solution containing 0.1g of lithium chloride, finally adding 1g of glacial acetic acid, uniformly stirring, stopping stirring when the sol becomes gel, aging the generated gel for 12h, then drying the gel in vacuum at 80 ℃ for 12h, and calcining the dried powder at the temperature rising speed of 5 ℃/min to 900 ℃ for 5h to obtain the single-layer coated silicon oxide composite negative electrode material.
3) Weighing the single-layer coated silicon oxide composite negative electrode material, glucose and distilled water according to the mass ratio of 3:1:5, putting the single-layer coated silicon oxide composite negative electrode material, the glucose and the distilled water into a ball mill for ball milling for 3 hours, and then heating and evaporating at 100 ℃ to dryness; calcining for 3h at the heating speed of 3 ℃/min to 1000 ℃ in the nitrogen atmosphere, and cooling to obtain the double-layer coated silicon oxide composite negative electrode material.
In the embodiment, in the prepared double-layer coated silicon oxide composite negative electrode material, the thickness of the lithium titanate layer is 200-350 nm, and the thickness of the carbon layer is 0.1-2 μm.
Example 4
A preparation method of a double-layer coated silicon oxide composite negative electrode material comprises the following steps:
1) mixing 13g of nano silicon and 21.4g of nano silicon dioxide, then carrying out ball milling, carrying out ball milling at the rotating speed of 300rpm for 3h, uniformly mixing the materials to obtain a mixture, roasting the mixture at 1200 ℃ for 6h under a vacuum condition, cooling, and crushing the mixture by using a crusher until the particle size is 10-50 mu m; and performing ball milling for 6 hours to obtain a silica precursor, wherein the particle size of the silica precursor is 2-10 mu m.
2) Taking 5g of silica precursor, putting the silica precursor into 50ml of absolute ethanol solution containing 0.25g of tetrabutyl titanate, stirring for 6 hours, adding 5ml of water, and stirring for 60 minutes; and then adding 50mL of anhydrous ethanol solution containing 0.15g of lithium chloride, finally adding 1g of glacial acetic acid, uniformly stirring, stopping stirring when the sol becomes gel, aging the generated gel for 12h, then drying the gel in vacuum at 80 ℃ for 12h, and calcining the dried powder at the temperature rising speed of 5 ℃/min to 1000 ℃ for 2h to obtain the single-layer coated silicon oxide composite negative electrode material.
3) Weighing the single-layer coated silicon oxide composite negative electrode material, phenolic resin, acetone and petroleum ether according to the mass ratio of 2:3:1:0.5, putting the single-layer coated silicon oxide composite negative electrode material, the phenolic resin, the acetone and the petroleum ether into a ball mill, ball-milling for 5 hours, and then heating and evaporating at 100 ℃ to dryness; calcining for 4h at the heating speed of 3 ℃/min to 850 ℃ in the nitrogen atmosphere, and cooling to obtain the double-layer coated silicon oxide composite negative electrode material.
In the embodiment, in the prepared double-layer coated silicon oxide composite negative electrode material, the thickness of the lithium titanate layer is 20-50 nm, and the thickness of the carbon layer is 5-8 μm.
Example 5
A preparation method of a single-layer coated silicon oxide composite negative electrode material comprises the following steps:
1) mixing 8.5g of nano silicon and 21.4g of nano silicon dioxide, then carrying out ball milling, carrying out ball milling at the rotating speed of 300rpm for 3h, uniformly mixing the materials to obtain a mixture, roasting the mixture at 1200 ℃ for 6h under the vacuum condition, cooling, and crushing by using a crusher until the particle size is 10-50 mu m; and performing ball milling for 6 hours to obtain a silica precursor, wherein the particle size of the silica precursor is 2-10 mu m.
2) Taking 5g of silica precursor, putting the silica precursor into 50ml of absolute ethanol solution containing 0.25g of tetrabutyl titanate, stirring for 6 hours, adding 5ml of water, and stirring for 60 minutes; and then adding 50mL of acetone solution of 0.12g of lithium oxalate, finally adding 1g of glacial acetic acid, uniformly stirring, stopping stirring when the sol becomes gel, aging the generated gel for 12h, then drying in vacuum at 80 ℃ for 12h, and calcining the dried powder at the temperature rising speed of 5 ℃/min to 700 ℃ for 2h to obtain the single-layer coated silicon oxide composite negative electrode material.
In the embodiment, in the prepared single-layer coated silicon oxide composite negative electrode material, the thickness of the lithium titanate layer is 50-150 nm.
Example 6
A preparation method of a single-layer coated silicon oxide composite negative electrode material comprises the following steps:
1) mixing 10g of nano silicon and 21.4g of nano silicon dioxide (the molar ratio is 1:1), performing ball milling for 3 hours at the rotating speed of 300rpm, uniformly mixing the materials to obtain a mixture, roasting the mixture for 6 hours at 1200 ℃ under the argon condition, cooling, and crushing the mixture by a crusher until the particle size is 10-50 mu m; and performing ball milling for 6 hours to obtain a silica precursor, wherein the particle size of the silica precursor is 2-10 mu m.
2) Taking 5g of silica precursor, putting the silica precursor into 50mL of absolute ethanol solution containing 0.8g of tetrabutyl titanate, stirring for 6h, adding 5mL of water, and stirring for 60 min; and then adding 50mL of anhydrous ethanol solution of 0.10g of lithium oxalate, finally adding 1g of glacial acetic acid, uniformly stirring, stopping stirring when the sol becomes gel, aging the generated gel for 10h, then drying in vacuum at 80 ℃ for 12h, and calcining the dried precipitate at the temperature rising speed of 5 ℃/min to 700 ℃ for 2h to obtain the single-layer coated silicon oxide composite negative electrode material.
In the embodiment, in the prepared single-layer coated silicon oxide composite negative electrode material, the thickness of the lithium titanate layer is 100-200 nm.
Comparative example 1
A preparation method of a lithium ion battery negative electrode material comprises the following steps:
mixing 10g of nano silicon and 21.4g of nano silicon dioxide (the molar ratio is 1:1), performing ball milling for 3 hours at the rotating speed of 300rpm, uniformly mixing the materials to obtain a mixture, roasting the mixture for 6 hours at 1200 ℃ under the vacuum condition, cooling, and crushing the mixture by a crusher until the particle size is 10-50 mu m; and performing ball milling for 6 hours to obtain the silica precursor lithium ion battery cathode material, wherein the silica precursor has a particle size of 2-10 microns.
Comparative example 2
A preparation method of a lithium ion battery negative electrode material comprises the following steps:
1) mixing 10g of nano silicon and 21.4g of nano silicon dioxide (the molar ratio is 1:1), performing ball milling for 3 hours at the rotating speed of 300rpm, uniformly mixing the materials to obtain a mixture, roasting the mixture for 6 hours at 1200 ℃ under the vacuum condition, cooling, and crushing the mixture by a crusher until the particle size is 10-50 mu m; and performing ball milling for 6 hours to obtain a silica precursor, wherein the particle size of the silica precursor is 2-10 mu m.
2) Weighing the single-layer coated silicon oxide composite negative electrode material, asphalt, acetic acid and distilled water according to the mass ratio of the single-layer coated silicon oxide composite negative electrode material to the asphalt to the acetic acid to the distilled water of 2:1:1:0.5, putting the single-layer coated silicon oxide composite negative electrode material, the asphalt to the acetic acid to the distilled water into a ball mill for ball milling for 5 hours, and then heating and evaporating to dryness at 100 ℃; calcining for 4h at the heating speed of 3 ℃/min to 850 ℃ in the nitrogen atmosphere, and cooling to obtain the lithium ion battery cathode material.
Performance testing
The single-layer/double-layer coated silicon oxide composite negative electrode materials obtained in the examples 1-6 and the lithium ion battery negative electrode materials obtained in the comparative examples 1-2 are tested for various performances such as circulation, low temperature, multiplying power and the like in the button cell. Wherein, the electrode material composition is: the mass ratio of the active material to the conductive agent to the PVDF (polyvinylidene fluoride) is 92:4: 4; the positive electrode is metallic lithium; the electrolyte is 1mol/L LiPF6EC of (1: 1:1) solution of EMC, EC is ethylene carbonate; the membrane thickness was 20 μm. The cycle, low temperature and rate performance of each example and each comparative example were tested with a blue tester, and the experimental data obtained are shown in table 1 and fig. 2 to 10.
TABLE 1 test data of negative electrode materials of examples 1 to 6 and comparative examples 1 to 2
Figure BDA0001471621100000101
As can be seen from table 1 and fig. 2 to 10, the first coulombic efficiency and the cycle residual capacity of the dual-layer coated silicon oxide composite negative electrode materials of examples 1 to 4 of the present invention are higher than those of examples 5 to 6 and comparative examples 1 to 2, and the discharge capacity rate at-10 ℃ of examples 1 to 4 is also higher, which indicates that the dual-layer coated silicon oxide composite negative electrode materials of the present invention have good cycle, low temperature and rate capability. Meanwhile, the first coulombic efficiency and the circulating residual capacity of the embodiments 5 to 6 are also higher than those of the comparative examples 1 to 2, which shows that the single-layer coated silicon oxide composite negative electrode material of the invention has better performance than the comparative examples and has good performances.
The above-mentioned embodiments only express several embodiments of the present invention, and the description thereof is more specific and detailed, but not construed as limiting the scope of the present invention. It should be noted that, for a person skilled in the art, several variations and modifications can be made without departing from the inventive concept, which falls within the scope of the present invention. Therefore, the protection scope of the present patent shall be subject to the appended claims.

Claims (4)

1. The preparation method of the single-layer coated silicon oxide composite negative electrode material is characterized by comprising the following steps of:
1) uniformly mixing nano silicon and nano silicon dioxide to obtain a mixture, roasting the mixture at 1200-2200 ℃ in a vacuum/argon atmosphere, cooling, crushing, and performing ball milling to obtain a silica precursor; the silica precursor is a material formed by uniformly dispersing and distributing nano silicon on silicon dioxide;
2) dispersing a titanium source, the silica precursor and a lithium source into an organic solvent, uniformly stirring to form a gel, aging and drying the gel to obtain powder, and calcining the dried powder in a protective atmosphere to obtain the single-layer coated silicon oxide composite negative electrode material;
the titanium source is sulfuric acid titanium oxide, tetraethyl titanate, tetrabutyl titanate, titanium tetrachloride or isopropyl titanate; the lithium source is lithium hydroxide, lithium chloride or lithium oxalate; the organic solvent is absolute ethyl alcohol, acetone or propanol; the mass of the titanium source is 1-15% of that of the silica precursor.
2. The single-layer coated silicon oxide composite negative electrode material prepared by the preparation method of claim 1 is characterized in that the single-layer coated silicon oxide composite negative electrode material is a two-layer composite material with a core-shell structure, wherein an inner core is a silica precursor, an outer layer is a lithium titanate layer, and the silica precursor is a material formed by uniformly dispersing nano-silicon in silicon dioxide; the particle size of the silica precursor is 0.5-15 mu m.
3. The preparation method of the double-layer coated silicon oxide composite negative electrode material is characterized by comprising the following steps of:
1) uniformly mixing nano silicon and nano silicon dioxide to obtain a mixture, roasting the mixture at 1200-2200 ℃ in a vacuum/argon atmosphere, cooling, and crushing to obtain a silica precursor; the silica precursor is a material formed by uniformly dispersing and distributing nano silicon on silicon dioxide;
2) dispersing a titanium source, the silica precursor and a lithium source into absolute ethyl alcohol serving as a solvent, uniformly stirring to form gel, aging and drying the gel to obtain powder, and calcining the dried powder in a protective atmosphere to obtain the single-layer coated silicon oxide composite negative electrode material;
3) uniformly mixing the single-layer coated silicon oxide composite negative electrode material with an organic carbon source and a solvent, drying to obtain a mixture, calcining the mixture at 500-1200 ℃ for 0.5-20 h in a protective atmosphere, and cooling to obtain a double-layer coated silicon oxide composite negative electrode material; the organic carbon source is one or more of phenolic resin, furfural resin, epoxy resin, urea resin, asphalt, citric acid, glucose, sucrose, polyvinyl chloride and polyvinyl butyral; the weight ratio of the single-layer coated silicon oxide composite negative electrode material to the organic carbon source is 1 (0.5-20).
4. The double-layer coated silicon oxide composite negative electrode material prepared by the preparation method of claim 3 is characterized in that the double-layer coated silicon oxide composite negative electrode material is a three-layer composite material with a core-shell structure, wherein an inner core is a silica precursor, an intermediate layer is a lithium titanate layer, an outermost layer is a carbon layer coated on the outer surface of the lithium titanate layer, and the silica precursor is a material formed by uniformly dispersing nano-silicon in silicon dioxide; the thickness of the lithium titanate layer is 5-500 nm, and the thickness of the carbon layer is 0.05-10 mu m.
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