CN110931792B - Coated silicon-based material and preparation method thereof - Google Patents

Coated silicon-based material and preparation method thereof Download PDF

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CN110931792B
CN110931792B CN201911091055.7A CN201911091055A CN110931792B CN 110931792 B CN110931792 B CN 110931792B CN 201911091055 A CN201911091055 A CN 201911091055A CN 110931792 B CN110931792 B CN 110931792B
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silicon
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slurry
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CN110931792A (en
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伏萍萍
徐宁
宋英杰
马倩倩
吕菲
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Tianjin B&M Science and 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
    • H01M4/62—Selection of inactive substances as ingredients for active masses, e.g. binders, fillers
    • H01M4/624—Electric conductive fillers
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B82—NANOTECHNOLOGY
    • B82Y—SPECIFIC USES OR APPLICATIONS OF NANOSTRUCTURES; MEASUREMENT OR ANALYSIS OF NANOSTRUCTURES; MANUFACTURE OR TREATMENT OF NANOSTRUCTURES
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    • C01—INORGANIC CHEMISTRY
    • C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
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    • C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
    • C01B33/00—Silicon; Compounds thereof
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    • 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
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    • 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
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    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/58—Selection of substances as active materials, active masses, active liquids of inorganic compounds other than oxides or hydroxides, e.g. sulfides, selenides, tellurides, halogenides or LiCoFy; of polyanionic structures, e.g. phosphates, silicates or borates
    • H01M4/583—Carbonaceous material, e.g. graphite-intercalation compounds or CFx
    • H01M4/587—Carbonaceous material, e.g. graphite-intercalation compounds or CFx for inserting or intercalating light metals
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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

Li x Zr y O z The coated silicon-based negative electrode material is prepared by coating a layer of Li on the surface of a silicon-based material x Zr y O z To prepare, Li x Zr y O z May be Li 2+δ ZrO 3 、Li 6+3δ Zr 2 O 7 、Li 8+δ ZrO 6 δ is (0 to 0.1). The material forms a compact and uniform coating layer on the surface of the silicon-based material, so that the side reaction on the surface of the silicon-based material is effectively reduced, the expansion of the silicon-based material is effectively inhibited, and the multiplying power performance of the material is improved. The prepared coated silicon-based material has the characteristics of high reversible specific capacity and excellent coulombic efficiency, multiplying power and cycle performance.

Description

Coated silicon-based material and preparation method thereof
Technical Field
The invention relates to the field of lithium ion batteries, in particular to a coated silicon-based material and a preparation method thereof.
Background
The silicon material has specific capacity of 4200mAh/g, which is ten times of that of the graphite cathode material, so the silicon-based material becomes one of the most promising candidate materials for the cathode material of the high-specific energy density lithium ion battery. However, the silicon material is pulverized and dropped off in the charge and discharge process due to the volume expansion of 300%, so that the silicon material has very poor irreversible capacity loss and serious cycle life decay. In the development process of the silicon material, researchers can effectively prolong the cycle life of the material by preparing nano silicon wires, porous silicon, a shell-core structure, a synthetic silicon-metal material and other technical means.
At present, the technology of cladding silicon material and carbon material after compounding becomes common technology in the field. Common silicon-based composite materials adopt a core-shell structure, spherical artificial or natural graphite is used as a substrate, Si nano-particles are attached to the surface of the graphite, and a layer of amorphous carbon is coated on the surface of the graphite. However, the coated amorphous carbon layer has the characteristic of irreversible lithium absorption, so that the defect of reduced first coulomb efficiency is introduced; in addition, the problems of overlarge volume change, poor cycle performance, low first coulombic efficiency and the like always exist in charge-discharge cycles of the carbon coating layer and the silicon-based negative electrode material.
Researchers have attempted to replace carbon layers with other coating materials, with alloys as the coating in CN108682796A, fast-ion lithium salts as the coating in CN108493428A, and polymer electrolytes as the coating in CN 109950481A. However, the coating layers have the defects of complex preparation method, low strength of the coating layer, uneven coating thickness and the like, so that the development of a silicon-based material with good cyclicity and good stability is a technical problem in the field of lithium ion battery materials.
Disclosure of Invention
In order to solve the technical problems, the invention provides Li x Zr y O z Coating the silicon-based negative electrode material to obtain a layer of Li-containing material uniformly coated on the surface of the silicon-based material by designing a coating synthesis process x Zr y O z The coating not only improves the first coulombic efficiency and the cycle performance of the silicon-based negative electrode material, but also improves the rate capability of the material.
In order to solve the technical problems, the invention adopts the technical scheme that:
the coated silica-based material comprises silica-based particles as an inner core, and nano-films coated on the surfaces of the silica-based particles and Li as the nano-films x Zr y O z 。
Preferably, the Li x Zr y O z Is Li 2+δ ZrO 3 、Li 6+3δ Zr 2 O 7 、Li 8+δ ZrO 6 Wherein δ is 0 to 0.1.
Preferably, the Li x Zr y O z From Li 2+δ ZrO 3 And Li 8+δ ZrO 6 Composition in which, in terms of mole ratios, Li 2+δ ZrO 3 ：Li 8+δ ZrO 6 1: 0.5 to 2, wherein δ is 0 to 0.1.
Preferably, the Li x Zr y O z From Li 2+δ ZrO 3 And Li 6+3δ Zr 2 O 7 Composition in which, in terms of mole ratios, Li 2+δ ZrO 3 ：Li 6+3δ Zr 2 O 7 1: 0.1 to 1, wherein δ is 0 to 0.1.
Preferably, the silicon-based particles are a composite material of graphite and a silicon material, wherein the silicon material is elemental silicon (Si) and/or silica oxide (SiO).
A preparation method of a coated silicon-based material comprises the following steps:
1) according to the chemical formula Li x Zr y O z Weighing a certain amount of lithium hydroxide (LiOH) and zirconium dioxide (ZrO) according to a molar ratio 2 ) Mixing and grinding the powder, and placing the powder in a high-temperature reaction furnace for high-temperature reaction to generate Li x Zr y O z ；
2) Subjecting the Li obtained in step 1) x Zr y O z Adding a silicon material and mixing uniformly to obtain a mixture I; the silicon material is simple substance silicon (Si) and/or silicon monoxide (SiO) material, and Li is calculated by mass ratio x Zr y O z 0.1 to 5 percent of silicon material;
3) placing the mixture I in a sand mill, adding a dispersing agent, and fully grinding to obtain slurry S1, wherein the particle size D50 of the slurry S1 is less than or equal to 200 nm; the dispersing agent is volatile liquid organic matter;
4) placing the slurry S1 into a dispersing bucket, slowly supplementing a dispersing agent to enable the solid content to be less than or equal to 50%, then adding graphite, and dispersing at a low speed until the mixture is uniform to obtain slurry S2;
5) drying and grinding the slurry S2 to obtain a powdery material II;
6) and (3) placing the powdery material II in a high-temperature reaction furnace, and carrying out high-temperature reaction for a certain time under the protection of inert atmosphere to obtain the coated silicon-based material.
Preferably, the reaction temperature of the high-temperature reaction in the step 1) is 600-1000 ℃, and the reaction time is 1-24 h.
Preferably, the mass ratio of silicon material/(silicon material + graphite) is 1% to 10%.
Preferably, the solid content of the slurry S1 in the step 4) is 5-30%, and the solid content of the slurry S2 is less than or equal to 50%.
Preferably, the reaction temperature of the high-temperature reaction in the step 6) is 400-900 ℃, the reaction time is 2-24 h, and the inert atmosphere is nitrogen, argon or the mixed gas thereof.
The coated silicon-based material can be directly used as a negative electrode material to be applied to a lithium ion battery, and the coated silicon-based material prepared by the preparation method can also be directly used as a negative electrode material to be applied to the lithium ion battery.
The invention has the beneficial effects that: the invention uniformly coats a layer of Li-containing silicon-based material on the surface by designing a coating material and a coating synthesis process x Zr y O z Thereby obtaining a Li x Zr y O z Coated silicon-based negative electrode materials, Li x Zr y O z The material has the characteristics of lithium storage and fast ion conduction, and Li is creatively designed x Zr y O z The composition and the proportion of the silicon-based negative electrode material optimize the lithium storage capacity and the lithium ion conductivity of the material to the maximum extent, ensure the overall stability of the material, reduce the loss of active substances caused by coating, improve the first coulombic efficiency and the cycle performance of the silicon-based negative electrode material, and improve the rate capability of the material.
Drawings
FIG. 1 is a flow chart of a process for preparing a silicon-based material according to the present invention;
FIG. 2 shows example 1 of the present inventionProvided Li x Zr y O z SEM photograph of coated silicon-based material.
Detailed Description
The invention is further illustrated by the following examples in conjunction with the drawings.
The coated silicon-based material is characterized in that the inner core of the coated silicon-based material is silicon-based particles, the surfaces of the silicon-based particles are coated with nano films, and the nano films are Li x Zr y O z . The invention adopts Li x Zr y O z As a coating, compared with the traditional amorphous carbon coating material or other coating materials, the material has the advantages of fast ion conductor and lithium storage material, has good stability, can promote the insertion and extraction of lithium ions, and does not influence Li + And (4) mass transfer.
Preferably, the Li x Zr y O z Is Li 2+δ ZrO 3 、Li 6+3δ Zr 2 O 7 、Li 8+δ ZrO 6 Wherein δ is 0 to 0.1.
Preferably, the Li x Zr y O z From Li 2+δ ZrO 3 And Li 8+δ ZrO 6 Composition in which, in terms of mole ratios, Li 2+δ ZrO 3 ：Li 8+δ ZrO 6 1: 0.5 to 2, wherein δ is 0 to 0.1.
Preferably, the Li x Zr y O z From Li 2+δ ZrO 3 And Li 6+3δ Zr 2 O 7 Composition in which, in terms of mole ratios, Li 2+δ ZrO 3 ：Li 6+3δ Zr 2 O 7 1: 0.1 to 1, wherein δ is 0 to 0.1.
In many Li x Zr y O z Among the compounds, Li is preferably used 2+δ ZrO 3 、Li 6+3δ Zr 2 O 7 、Li 8+δ ZrO 6 One or a combination of several compounds, and the compounds have lithium-rich characteristics, so that the prepared material is more excellent than other Li x Zr y O z Has better electrochemical performanceAnd (4) chemical properties.
Especially when combinations of specific proportions are used, e.g. Li 2+δ ZrO 3 ：Li 8+δ ZrO 6 1: 0.5 to 2 or Li 2+δ ZrO 3 ：Li 6+3δ Zr 2 O 7 1: 0.1-1, obtaining a coating with reasonable element ratio through thermodynamic calculation and design ratio, forming stronger bonding force among coating components, forming more Li-Zr bonds, constructing a lithium ion channel network, and strengthening Li + The prepared nano film has better thermal stability and electrochemical performance.
Preferably, the silicon-based particles are a composite material of graphite and a silicon material, wherein the silicon material is elemental silicon (Si) and/or silicon monoxide (SiO).
A preparation method of a coated silicon-based material comprises the following steps:
1) according to the chemical formula Li x Zr y O z Weighing a certain amount of lithium hydroxide (LiOH) and zirconium dioxide (ZrO) according to the molar ratio 2 ) Mixing and grinding the powder, and placing the powder in a high-temperature reaction furnace for high-temperature reaction to generate Li x Zr y O z ；
2) Subjecting the Li obtained in step 1) x Zr y O z Adding a silicon material and uniformly mixing to obtain a mixture I; the silicon material is simple substance silicon (Si) and/or silicon monoxide (SiO) material, and Li is calculated by mass ratio x Zr y O z 0.1 to 5 percent of silicon material; li x Zr y O z The coating has excessive content, which may cause the disadvantage of specific capacity loss; li x Zr y O z The coating content is too low, the coating effect cannot be achieved, and the invention discovers that when the proportion of 0.1-5% is adopted, the prepared coating has stability and conductivity and has the best comprehensive performance.
3) Placing the mixture I in a sand mill, adding a dispersing agent, and fully grinding to obtain slurry S1, wherein the particle size D50 of the slurry S1 is not more than 200 nm; the dispersing agent is a volatile liquid organic matter;
4) placing the slurry S1 into a dispersing bucket, slowly supplementing a dispersing agent to enable the solid content to be less than or equal to 50%, then adding graphite, and dispersing at a low speed until the mixture is uniform to obtain slurry S2;
5) drying and grinding the slurry S2 to obtain a powdery material II;
6) and (3) placing the powdery material II in a high-temperature reaction furnace, and carrying out high-temperature reaction for a certain time under the protection of inert atmosphere to obtain the coated silicon-based material.
Preferably, the mass ratio of silicon material/(silicon material + graphite) is 1% to 10%. Too much silicon material and poor conductivity; the silicon content is too low and the core is unstable.
Preferably, the reaction temperature of the high-temperature reaction in the step 1) is 600-1000 ℃, and the reaction time is 1-24 h. The reaction temperature is too low, the reaction time is too short, and Li cannot be synthesized x Zr y O z A target product; the reaction temperature is too high, the reaction time is too long, and the generated Li x Zr y O z It is easy to break.
Preferably, the solid content of the slurry S1 in the step 4) is 5-30%, and the solid content of the slurry S2 is less than or equal to 50%.
Preferably, the reaction temperature of the high-temperature reaction in the step 6) is 400-900 ℃, the reaction time is 2-24 h, and the inert atmosphere is nitrogen, argon or the mixed gas thereof.
In the preparation process, the optimization of the roasting preparation conditions is also important. The defects of incomplete synthesis of a coating layer and low bonding force with a matrix material can be caused by excessively low roasting temperature and excessively short time; the disadvantages of excessive sintering of silicon materials, poor cycle performance and the like can be caused by overhigh roasting temperature and overlong roasting time. The invention further optimizes the roasting condition to obtain the material with better performance.
The following examples are provided to further illustrate the embodiments of the present invention, but the scope of the present invention is not limited thereto.
Example 1
The preparation method of the coated silicon-based material comprises the following steps:
1) 0.0088g of lithium hydroxide (LiOH) and 0.0226g of zirconium oxide (ZrO) were weighed 2 ) Grinding, mixing, placing in a high-temperature reaction furnace, introducing oxygen, reacting at 600 ℃ for 4h to generate Li 2.01 ZrO 3 ；
2) The Li obtained in the step 1) 2.01 ZrO 3 Adding 28.09g of simple substance silicon (Si) powder and 140g of absolute ethyl alcohol, and dispersing for 10min to obtain a mixture I;
3) putting the mixture I into a sand mill, and sanding the mixture I at the rotating speed of 2000 r/min until the granularity D50 of the slurry is less than or equal to 200 nm; closing the sand mill, discharging the slurry into a dispersion barrel, slowly adding 449g of absolute ethyl alcohol while stirring, adding 533.7g of natural graphite, and dispersing for 30 min.
4) And 2) discharging the slurry, placing the slurry in a forced air drying oven, drying the slurry for 12 hours at the temperature of 80 ℃ to obtain a fully dried material, and grinding the fully dried material into powder.
5) The powder material is placed in nitrogen atmosphere for roasting at the roasting temperature of 400 ℃ for 24 hours to obtain Li 2.01 ZrO 3 Coated Li 2.01 ZrO 3 @ Si/C negative electrode material.
Comparative example 1
The preparation of an uncoated silicon-based material comprises the following steps:
1) weighing 28.09g of simple substance silicon (Si) powder, adding 140g of absolute ethyl alcohol, and dispersing for 10 min;
2) the dispersed slurry is put into a sand mill, and is sanded until the granularity D50 of the slurry is less than or equal to 200nm at the rotating speed of 2000 r/min; closing the sand mill, discharging the slurry into a dispersion barrel, slowly adding 449g of absolute ethyl alcohol while stirring, adding 533.7g of natural graphite, and dispersing for 30 min.
3) Discharging the slurry, drying in a forced air drying oven at 80 deg.C for 12 hr to obtain fully dried material, and grinding into powder.
4) And roasting the powder material in a nitrogen atmosphere at the roasting temperature of 400 ℃ for 24 hours. Thus obtaining the silicon-based material without coating.
Example 2
The preparation method of the coated silicon-based material comprises the following steps:
1) 0.6145g of lithium hydroxide (LiOH) were weighed,0.4791g of zirconium oxide (ZrO) 2 ) Grinding, mixing, placing in a high-temperature reaction furnace, introducing oxygen, reacting at 800 ℃ for 8h to generate Li 6.6 Zr 2 O 7 ；
2) The Li obtained in the step 1) 6.6 Zr 2 O 7 44.10g of a powder of Silica (SiO) and
dispersing 150g of acetone for 10min to obtain a mixture I;
3) putting the mixture I into a sand mill, and sanding the mixture I at the rotating speed of 2000 r/min until the granularity D50 of the slurry is less than or equal to 200 nm; the sand mill was turned off, the slurry was discharged into a dispersion tank, 734g of acetone was slowly added with stirring, 837.9g of natural graphite was added, and dispersion was carried out for 30 min.
4) And 2) discharging the slurry, placing the slurry in a microwave oven, performing microwave drying for 2 hours to obtain a fully dried material, and grinding the fully dried material into powder.
5) And roasting the powder material in a nitrogen atmosphere at the roasting temperature of 750 ℃ for 8 hours. Namely to obtain Li 6.6 Zr 2 O 7 Coated Li 6.6 Zr 2 O 7 @ SiO/C negative electrode material.
Example 3
The preparation method of the coated silicon-based material comprises the following steps:
1) 1.4378g of lithium hydroxide (LiOH), 0.9135g of zirconium oxide (ZrO) were weighed out 2 ) Grinding, mixing, placing in a high-temperature reaction furnace, introducing oxygen, reacting at 800 ℃ for 8h to generate Li 8.1 ZrO 6 ；
2) Subjecting the Li obtained in step 1) 8.1 ZrO 6 Adding 14.05g of simple substance silicon (Si) and 22.05 g of silicon monoxide (SiO) powder, adding 150g of diethyl ether, and dispersing for 10min to obtain a mixture I;
3) putting the mixture I into a sand mill, and sanding the mixture I at the rotating speed of 2000 r/min until the granularity D50 of the slurry is less than or equal to 200 nm; the sand mill is closed, the slurry is discharged into a dispersion bucket, 1461g of diethyl ether is slowly added while stirring, 1768.7g of natural graphite is added, and the dispersion is carried out for 30 min.
4) And 2) discharging the slurry, placing the slurry in a forced air drying oven, drying for 12 hours at the drying temperature of 120 ℃ to obtain a fully dried material, and grinding the fully dried material into powder.
5) And roasting the powder material in a nitrogen atmosphere at the roasting temperature of 750 ℃ for 8 hours. Namely to obtain Li 8.1 ZrO 6 Coated Li 8.1 ZrO 6 @ Si/SiO/C negative electrode material.
Comparative example 2
The preparation method of the coated silicon-based material comprises the following steps:
1) preparation of Li 6 Zr 2 O 7 : 0.9211g of lithium hydroxide (LiOH) and 1.5800g of zirconium oxide (ZrO) were weighed 2 ) Grinding, mixing, placing in a high-temperature reaction furnace, introducing oxygen, and reacting at 750 ℃ for 8 h; preparation of Li 2 ZrO 3 : 0.0768g of lithium hydroxide (LiOH) and 0.3950g of zirconium oxide (ZrO) were weighed 2 ) Grinding, mixing, placing in a high-temperature reaction furnace, introducing air, and reacting at 800 ℃ for 8 h;
2) weighing Li prepared in step 1) 6 Zr 2 O 7 ：1.0776g、Li 2 ZrO 3 : 0.2454g, weighing 44.10g of silicon monoxide (SiO) powder, adding 105g of acetone, and dispersing for 10 min;
3) the dispersed slurry is put into a sand mill, and is sanded until the granularity D50 of the slurry is less than or equal to 200nm at the rotating speed of 2000 r/min; the sand mill was turned off, the slurry was discharged into a dispersion tank, 735g of acetone was slowly added while stirring, 837.9g of natural graphite was added, and dispersion was carried out for 30 min.
4) And 3) discharging the slurry, placing the slurry in a microwave oven, performing microwave drying for 2 hours to obtain a fully dried material, and grinding the fully dried material into powder.
5) And roasting the powder material in a nitrogen atmosphere at the roasting temperature of 750 ℃ for 8 hours. Namely to obtain Li x Zr y O z Coated SiO/C negative electrode material, Li x Zr y O z Has a design composition of Li 6 Zr 2 O 7 :Li 2 ZrO 3 ＝2:1。
Example 4
The preparation method of the coated silicon-based material comprises the following steps:
1) preparation of Li 6 Zr 2 O 7 : 0.7769g of lithium hydroxide (LiOH) and 1.333g of zirconium oxide (ZrO) were weighed 2 ) Grinding, mixing, placing in a high-temperature reaction furnace, introducing oxygen, and reacting at 750 ℃ for 8 h; preparation of Li 2 ZrO 3 : 0.1295g of lithium hydroxide (LiOH) and 0.6664g of zirconium oxide (ZrO) were weighed 2 ) Grinding, mixing, placing in a high-temperature reaction furnace, introducing air, and reacting at 800 ℃ for 8 h;
2) weighing Li prepared in step 1) 6 Zr 2 O 7 ：0.9090g、Li 2 ZrO 3 : 0.4140g, weighing 44.10g of silicon monoxide (SiO) powder, adding 105g of acetone, and dispersing for 10 min;
3) the dispersed slurry is put into a sand mill, and is sanded until the granularity D50 of the slurry is less than or equal to 200nm at the rotating speed of 2000 r/min; closing the sand mill, discharging the slurry into a dispersion barrel, slowly adding 735g of acetone while stirring, adding 837.9g of natural graphite, and dispersing for 30 min;
4) and 3) discharging the slurry, placing the slurry in a microwave oven, performing microwave drying for 2 hours to obtain a fully dried material, and grinding the fully dried material into powder.
5) And roasting the powder material in a nitrogen atmosphere at the roasting temperature of 750 ℃ for 8 hours. Namely to obtain Li x Zr y O z Coated SiO/C negative electrode material, Li x Zr y O z Has a design composition of Li 6 Zr 2 O 7 :Li 2 ZrO 3 ＝1:1。
Example 5
The preparation method of the coated silicon-based material comprises the following steps:
1) preparation of Li 2 ZrO 3 : 0.2718g of lithium hydroxide (LiOH) and 0.6995g of zirconium oxide (ZrO) were weighed 2 ) Grinding, mixing, placing in a high-temperature reaction furnace, introducing oxygen, and reacting at 400 ℃ for 24 hours; preparation of Li 8 ZrO 6 : 1.0874g of lithium hydroxide (LiOH) and 0.6995g of zirconium oxide (ZrO) were weighed 2 ) Grinding, mixing, placing in a high-temperature reaction furnace, introducing oxygen, and reacting at 400 ℃ for 24 hours;
2) weighing Li prepared in step 1) 2 ZrO 3 ：0.4346g、Li 8 ZrO 6 ：0.6890g, weighing 28.01g of simple substance silicon (Si) powder, adding 560g of acetone, and dispersing for 10 min;
3) the dispersed slurry is put into a sand mill, and is milled until the granularity D50 of the slurry is less than or equal to 200nm at the rotating speed of 2000 revolutions per minute; closing the sand mill, discharging the slurry into a dispersion barrel, slowly adding 2250g of acetone while stirring, adding 2780.9g of natural graphite, and dispersing for 30 min;
4) and 3) discharging the slurry, placing the slurry in a microwave oven, performing microwave drying for 2 hours to obtain a fully dried material, and grinding the fully dried material into powder.
5) And roasting the powder material in a nitrogen atmosphere at the roasting temperature of 750 ℃ for 8 hours. Namely to obtain Li x Zr y O z Coated SiO/C negative electrode material, Li x Zr y O z Has a design composition of Li 2 ZrO 3 :Li 8 ZrO 6 ＝1:1。
Example 6
The preparation method of the coated silicon-based material comprises the following steps:
1) preparation of Li 2 ZrO 3 : 0.0980g of lithium hydroxide (LiOH) and 0.2522g of zirconium oxide (ZrO) were weighed 2 ) Grinding, mixing, placing in a high-temperature reaction furnace, introducing oxygen, and reacting at 900 ℃ for 2 h;
preparation of Li 8 ZrO 6 : 0.1960g of lithium hydroxide (LiOH) and 0.1261g of zirconium oxide (ZrO) were weighed 2 ) Grinding, mixing, placing in a high-temperature reaction furnace, introducing oxygen, and reacting at 900 ℃ for 2 h;
2) weighing Li prepared in step 1) 2 ZrO 3 ：0.1567g、Li 8 ZrO 6 : 0.1242g, weighing 28.01g of simple substance silicon (Si) powder, adding 540g of diethyl ether, and dispersing for 10 min;
3) the dispersed slurry is put into a sand mill, and is sanded until the granularity D50 of the slurry is less than or equal to 200nm at the rotating speed of 2000 r/min; turning off the sand mill, discharging the slurry into a dispersion bucket, slowly adding 2270g of diethyl ether while stirring, adding 2780.9g of natural graphite, and dispersing for 30 min.
4) And 3) discharging the slurry, placing the slurry in an air-blast drying oven, drying at 70 ℃ to obtain a fully dried material, and grinding the fully dried material into powder.
5) And roasting the powder material in a nitrogen atmosphere at the roasting temperature of 900 ℃ for 12 hours. Namely to obtain Li x Zr y O z Coated SiO/C negative electrode material, Li x Zr y O z Has a design composition of Li 2 ZrO 3 :Li 8 ZrO 6 ＝2:1。
Experimental conditions
FIG. 1 is a flow chart of a process for preparing a silicon-based material according to the present invention, and FIG. 2 is a flow chart of Li according to example 1 of the present invention x Zr y O z SEM photograph of the coated silica-based material shows that the present invention successfully prepares Li having a complete structure and no crushed small particles x Zr y O z A coated silicon-based material.
Table 1 lists the reversible specific capacity and first coulombic efficiency of 0.1C lithium-ion button cells assembled from samples prepared in the above examples. The testing conditions of the button cell are LR 2032, 0.05C 0.01-2.0V, vs + and/Li. The charging and discharging equipment is a blue-electricity charging and discharging instrument.
Table 1 comparison table of first charge and discharge performance
Figure BDA0002268935620000111
As can be seen from the data in the table, Li prepared in the examples of the present invention is compared with the blank comparative example 1 without coating x Zr y O z The reversible specific capacity and the first coulombic efficiency of the coated silicon-based material are obviously improved, and 6 groups of embodiments show that the reversible capacity of the product can be further improved along with the increase of the coating proportion. This is due to Li x Zr y O z The coating layer covers the surface of the silicon material, so that the side effects of pulverization, shedding and the like on the surface of the silicon material are reduced, and Li is used x Zr y O z Has certain lithium storage capacity, so that the material of the invention keeps ideal coulombic efficiency.
It can also be seen from the table that in Li x Zr y O z The optimized examples 4, 5 and 6 of the surface coating component have higher reversible specific capacity and first coulombic efficiency under the condition of the same or less coating capacity. This is probably because the ratio of Li to Zr is proper, more Li-Zr bonds are formed, and Li is strengthened + The conductive force is built up to form a more smooth lithium ion passage.
However, when the Li ion content is too large, the lithium ion path is blocked. Comparative example 2 increased Li compared with example 4 6 Zr 2 O 7 It can be seen that the capacity and first efficiency of the lithium secondary battery are obviously reduced, probably because the mass transfer of the lithium ions is hindered due to the excessive content of the lithium ions.
Table 2 lists the rate performance of lithium ion button cells assembled from samples made in the above examples. The test condition of the battery is LR 2032, 0.01-2.0V vs. Li + [ Li ]: 0.05DC/0.05CC for one cycle of charge and discharge; 0.1DC/0.05CC is charged and discharged for one cycle; 1.0DC/0.05CC was charged and discharged for one cycle. The charging and discharging device used is a blue charging and discharging instrument.
Table 2 comparison table of large multiplying power charging and discharging performance
Figure BDA0002268935620000121
As can be seen from the data in the table, Li prepared by the invention x Zr y O z The rate capability of the coated silicon-based negative electrode material is improved compared with that of the corresponding uncoated comparative example, on the one hand, the Li is used for improving the rate capability of the coated silicon-based negative electrode material x Zr y O z The coating layer has higher electronic conductivity, thus improving the conductivity of the product, and on the other hand, the coating layer is made of Li x Zr y O z The coating layer can effectively prevent the nano particles of the silicon-based negative electrode material from sintering in the electrochemical charge-discharge process. The same rules are shown in table 2 and table 1, which proves the importance of selecting a proper coating proportion and a coating material proportion, and a more smooth lithium ion channel can be built by a proper Li-Zr proportion and a proper raw material selection, thereby being beneficial to the improvement of electrochemical performance.
Table 3 lists the capacity retention for 50 weeks of reversible capacity of lithium ion button cells assembled from samples prepared in the above examples. The test conditions of the battery are LR 2032, 1C 0.01-2.0V and vs. The charging and discharging equipment is a blue-electricity charging and discharging instrument.
TABLE 3 comparison of cycle performance
Figure BDA0002268935620000131
As can be seen from the data in the table, Li prepared by the invention x Zr y O z The coated silicon-based negative electrode material has good capacity retention rate. Visible Li x Zr y O z The coating layer plays a role in inhibiting pulverization of the silicon-based material, so that the cycle performance of the coating layer is greatly improved. The optimized coating layer of the double components has better stability because more Li-Zr bonds are formed.
In summary, the disclosure of the present invention is not limited to the above-mentioned embodiments, and those skilled in the art can easily set other embodiments within the technical teaching of the present invention, but such embodiments are included in the scope of the present invention.

Claims (7)

1. A coated silicon-based material, which is characterized in that: the inner core of the coated silicon-based material is silicon-based particles, the surfaces of the silicon-based particles are coated with nano films, and the nano films are Li x Zr y O z (ii) a The Li x Zr y O z From Li 2+δ ZrO 3 And Li 8+δ ZrO 6 Composition in which, in terms of mole ratios, Li 2+δ ZrO 3 ：Li 8+δ ZrO 6 1: 0.5 to 2, δ is 0 to 0.1, or the above Li x Zr y O z From Li 2+δ ZrO 3 And Li 6+3δ Zr 2 O 7 Composition in which, in terms of mole ratios, Li 2+δ ZrO 3 ：Li 6+3δ Zr 2 O 7 ＝1：0.1~1，δ＝0~0.1。
2. The clad silicon-based material as recited in claim 1, wherein: the silicon-based particles are a composite material of graphite and a silicon material, wherein the silicon material is simple substance silicon (Si) and/or silicon monoxide (SiO).
3. A method for preparing the coated silicon-based material according to claim 1 or 2, comprising the steps of:
1) according to the chemical formula Li x Zr y O z Weighing a certain amount of lithium hydroxide (LiOH) and zirconium dioxide (ZrO) according to a molar ratio 2 ) Mixing and grinding the powder, placing the powder in a high-temperature reaction furnace for high-temperature reaction to generate Li x Zr y O z ；
2) Subjecting the Li obtained in step 1) x Zr y O z Adding a silicon material and mixing uniformly to obtain a mixture I; the silicon material is simple substance silicon (Si) and/or silicon monoxide (SiO) material, and Li is calculated by mass ratio x Zr y O z 0.1% -5% of silicon material;
3) placing the mixture I in a sand mill, adding a dispersing agent, and fully grinding to obtain slurry S1, wherein the particle size D50 of the slurry S1 is less than or equal to 200 nm; the dispersing agent is volatile liquid organic matter;
4) placing the slurry S1 into a dispersing bucket, slowly supplementing a dispersing agent to ensure that the solid content is less than or equal to 50%, and then adding graphite to disperse at a low speed until the mixture is uniform to obtain slurry S2;
5) drying and grinding the slurry S2 to obtain a powdery material II;
6) and (3) placing the powdery material II in a high-temperature reaction furnace, and carrying out high-temperature reaction for a certain time under the protection of inert atmosphere to obtain the coated silicon-based material.
4. The method for preparing the coated silicon-based material according to claim 3, wherein: the reaction temperature of the high-temperature reaction in the step 1) is 600-1000 ℃, and the reaction time is 1-24 h.
5. The method for preparing the coated silicon-based material according to claim 3, wherein the coating comprises the following steps: the mass ratio of the silicon material/(silicon material + graphite) is 1% -10%.
6. The method for preparing the coated silicon-based material according to claim 3, wherein: in the step 4), the solid content of the slurry S1 is 5-30%, and the solid content of the slurry S2 is less than or equal to 50%.
7. The method for preparing the coated silicon-based material according to claim 3, wherein: the reaction temperature of the high-temperature reaction in the step 6) is 400-900 ℃, the reaction time is 2-24 h, and the inert atmosphere is nitrogen, argon or a mixed gas thereof.
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