CN109301228B - Silicon material for lithium ion battery and preparation method thereof - Google Patents

Silicon material for lithium ion battery and preparation method thereof Download PDF

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CN109301228B
CN109301228B CN201811293432.0A CN201811293432A CN109301228B CN 109301228 B CN109301228 B CN 109301228B CN 201811293432 A CN201811293432 A CN 201811293432A CN 109301228 B CN109301228 B CN 109301228B
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silicon
porous
lithium ion
ion battery
silicon material
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CN109301228A (en
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尚伟丽
孔令涌
李洁凤
任望保
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Shenzhen Dynanonic Co ltd
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Shenzhen Dynanonic 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
    • H01M4/58—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
    • 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
    • H01M2004/021—Physical characteristics, e.g. porosity, surface area
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/10—Energy storage using batteries

Abstract

The invention discloses a silicon material for a lithium ion battery, which comprises a silicon-containing substrate, wherein the silicon-containing substrate comprises a main body and irregular bulges which are arranged on the surface of the main body and extend outwards, at least one of the surface and the inside of the main body is provided with a porous structure, and the average pore diameter of the porous structure is 10-500 nm; the silicon-containing matrix is obtained by expanding a porous silicon-containing material. The silicon material for the lithium ion battery provided by the invention has a unique structure, the cycle performance of the silicon material as a negative electrode material is improved, and the compaction density of the silicon material is improved. The invention also provides a preparation method of the silicon material for the lithium ion battery, which comprises the following steps: (1) carrying out pore etching or construction on the silicon-containing material to obtain a porous silicon-containing material; (2) adding the porous silicon-containing material into a reaction kettle, and reacting for 0.5-2h under the pressure of 0.5-5.0Mpa and the temperature of 200-400 ℃ to obtain the silicon material for the lithium ion battery. The preparation method is simple and easy to operate.

Description

Silicon material for lithium ion battery and preparation method thereof
Technical Field
The invention relates to the technical field of batteries, in particular to a silicon material for a lithium ion battery and a preparation method thereof.
Background
At present, various novel silicon negative electrode materials are concerned due to the ultrahigh capacity and rate (the theoretical capacity of silicon is 4200mAh/g), and in addition, silicon is one of the important elements of the earth, and provides inherent advantages for large-scale preparation. However, the volume expansion and contraction of the material can reach more than 300% in the charging and discharging processes, so that electroactive substances on the electrode are pulverized and fall off, the specific capacity of the material is attenuated, and even the accidents of piercing of a diaphragm, bursting of a battery, burning of the battery, even explosion and the like can be caused. Therefore, how to prepare silicon negative electrode materials with low expansion rate, high conductivity and stability has become an important issue in the scientific research and industry.
Disclosure of Invention
In order to solve the defects in the prior art, the invention provides a silicon material for a lithium ion battery and a preparation method thereof, the production process is simple and efficient, the silicon material for the lithium ion battery is prepared at low cost, and simultaneously, the high conductivity and stability of the silicon material for the lithium ion battery and the low expansion in the charging and discharging process are realized.
Specifically, in a first aspect, the invention provides a silicon material for a lithium ion battery, which comprises a silicon-containing substrate, wherein the silicon-containing substrate comprises a main body and irregular protrusions which are arranged on the surface of the main body and extend outwards, at least one of the surface and the inside of the main body is provided with a porous structure, and the average pore diameter of the porous structure is 10-500 nm; the silicon-containing matrix is obtained by expanding a porous silicon-containing material.
Wherein the silicon-containing matrix is a primary particle or a secondary particle constructed by a plurality of nano-scale particles.
Wherein the shape of the silicon-containing matrix is popcorn.
The silicon material for the lithium ion battery further comprises a carbon layer coated on the surface of the silicon-containing substrate, and the surface appearance of the carbon layer is consistent with that of the silicon-containing substrate.
Wherein the average size of the silicon material for the lithium ion battery is 1-200 mu m, and the specific surface area is 5-60m2(ii) a compacted density of 1.6-2.0g/cm3。
Wherein, the length that the arch extends outward from the main part is 10-500nm, and the clearance size between the arch is 10-500 nm.
In a second aspect, the invention provides a preparation method of a silicon material for a lithium ion battery, which comprises the following steps:
(1) carrying out pore etching or construction on the silicon-containing material to obtain a porous silicon-containing material;
(2) and (2) adding the porous silicon-containing material in the step (1) into a reaction kettle, and reacting for 0.5-2h under the pressure of 0.5-5.0Mpa and the temperature of 200-400 ℃ to obtain the silicon material for the lithium ion battery.
In the step (1), the porous silicon-containing material is porous micron-sized primary particles or porous secondary particles, and the preparation method of the porous silicon-containing material specifically comprises the following steps:
carrying out pore etching on the micron-sized silicon-containing particles to obtain porous micron-sized primary particles; or
And (3) placing a plurality of nano-scale silicon-containing particles in water or emulsion, stirring, then agglomerating the nano-scale silicon-containing particles, and drying to obtain the porous secondary particles.
In the step (2), the porous silicon-containing material and a carbon source are mixed according to a mass ratio of 1:0.05-0.5 to obtain a mixture, and the mixture is added into a reaction kettle to react to obtain the silicon material for the lithium ion battery.
Wherein the porous silicon-containing material obtained in the step (1) is expanded after reaction in the reaction kettle, and the expansion rate is more than 5 times.
By adopting the scheme, the invention has the following beneficial effects:
(1) the silicon material for the lithium ion battery comprises a silicon-containing substrate, wherein the silicon-containing substrate comprises a main body and irregular bulges which are arranged on the surface of the main body and extend outwards;
(2) in the invention, the surface of the silicon-containing matrix is coated by adopting a carbon coating means, so that the conductivity and the stability of the composite material can be obviously improved;
(3) the preparation method of the silicon material for the lithium ion battery provided by the invention has the advantages of simple and efficient preparation process and lower cost.
Drawings
Fig. 1 is a schematic structural diagram of a silicon material for a lithium ion battery according to an embodiment of the present invention;
fig. 2 is a schematic diagram of a process for preparing a silicon material for a lithium ion battery according to an embodiment of the present invention;
FIG. 3 is a schematic diagram illustrating a process for preparing a silicon material for a lithium ion battery according to another embodiment of the present invention;
fig. 4 is a schematic diagram of a process for preparing a silicon material for a lithium ion battery according to another embodiment of the present invention.
Detailed Description
While the following is a preferred embodiment of the present invention, it should be noted that, for those skilled in the art, various modifications and improvements can be made without departing from the principle of the present invention, and such modifications and improvements are considered to be within the scope of the present invention.
Referring to fig. 1, fig. 1 is a schematic structural diagram of a silicon material for a lithium ion battery prepared in embodiment 1 of the present invention. The invention provides a silicon material for a lithium ion battery, which comprises a silicon-containing substrate 10, wherein the silicon-containing substrate comprises a main body 1 and irregular bulges 2 which are arranged on the surface of the main body 1 and extend outwards, at least one position of the surface and the inner part of the main body 1 is provided with a porous structure 3, and the average pore diameter of the porous structure 3 is 10-500 nm; the silicon-containing matrix 1 is obtained by expanding a porous silicon-containing material.
In the present invention, the silicon-containing substrate includes a body and a random protrusion disposed on a surface of the body and extending outward, the body generally refers to a middle portion of the silicon substrate, and the protrusion is disposed around the body. The size of the body may be micro-scale or nano-scale. The fact that at least one of the surface and the interior of the body is provided with a porous structure means that: the surface or the inside of the main body is provided with a porous structure, or the surface and the inside of the main body are provided with a porous structure.
In the invention, the silicon-containing matrix is obtained by expanding a porous silicon-containing material. At least one of the surface and the interior of the porous silicon-containing material contains holes, after subsequent expansion, the pore diameter of some holes is enlarged, some holes even expand and crack, and the cracked silicon material protrudes outwards, so that a silicon-containing substrate with a three-dimensional flower-shaped porous structure is finally formed. Optionally, the porous silicon-containing material comprises a porous primary particle or a porous secondary particle constructed from a plurality of nanoscale particles. Further optionally, the size of the primary particle is 1 μm to 30 μm, the porous primary particle contains nano-scale pores, the pore diameter of the nano-scale pores is 10nm to 100nm, and the porosity of the primary particle is 60% to 90%. Further optionally, the secondary particles have a size of 1 μm to 20 μm. The size of the nano-scale particles is 10-100 nm. The porous structure in the secondary particles refers to the voids between the nano-sized particles in the secondary particles. The pore diameter of the porous secondary particles is 10-100nm, and the porosity of the porous secondary particles is 50% -90%.
Preferably, the nanoscale particles may be solid or porous. When the nano-scale particles are in a porous structure, the pore diameter of the porous structure is 1-5 nm.
In the present invention, the silicon-containing matrix is a primary particle or a secondary particle constructed of a plurality of nano-sized particles. The silicon-containing matrix obtained by expanding the porous primary particles is a primary particle, and the silicon-containing matrix obtained by expanding the secondary particles constructed from a plurality of nano-sized particles is a secondary particle. When the secondary particles are expanded, the voids between the plurality of nano-sized particles are expanded and broken as holes, thereby forming a silicon substrate. As used herein, "build" refers to the agglomeration or packing of a plurality of nanoscale particles to form secondary particles. Optionally, when the silicon-containing matrix is a primary particle, the size of the silicon-containing matrix is 30-150 μm. When the silicon-containing matrix is a secondary particle constructed of a plurality of nano-sized particles, the size of the silicon-containing matrix is 20 to 100 μm.
Alternatively, the porous structure can provide space for the expansion of the silicon material. The average pore diameter of the porous structure is 10-500 nm. Further optionally, the average pore size of the porous structure is 10-50nm, 50-100nm, or 100-500 nm. Optionally, the shape of the porous structure is not limited, and may be circular, elliptical, polygonal, irregular, or the like.
In the invention, the surface of the silicon-containing substrate is in a random bulge shape, and the silicon-containing substrate is in a popcorn shape. The silicon-containing substrate is obtained by expanding a porous silicon-containing material, wherein holes in the porous silicon-containing material even expand and crack, and the cracked silicon material bulges outwards to form bulges, and the bulges can be further curled, twisted or overturned, so that a popcorn structure is formed. Optionally, the silicon-containing substrate comprises a body and a protrusion disposed on a surface of the body. Further alternatively, the convex shape may be a sheet, a column, a dendrite, or a line. The length of the protrusion is 10-500nm, namely the length of the protrusion extending outwards from the main body is 10-500 nm. Further alternatively, the protrusions may be crimped, twisted or flipped. Further alternatively, the protrusions may also have a porous structure therein, as shown in fig. 1. Further optionally, the size of the gap existing between the adjacent protrusions is 10-500 nm. These porous structures and gaps further provide a buffer space for the silicon volume expansion.
In the present invention, the silicon material for a lithium ion battery further includes a carbon layer 20 coated on the surface of the silicon-containing substrate 10, and the surface topography of the carbon layer 20 is consistent with the surface topography of the silicon-containing substrate 10. Optionally, when the silicon-containing substrate is popcorn-shaped, the carbon layer coated on the surface of the popcorn-shaped silicon-containing substrate follows the surface topography of the silicon-containing substrate and is also popcorn-shaped. Therefore, the surface appearance of the carbon layer is basically consistent with that of the silicon-containing substrate, and the finally obtained silicon material for the lithium ion battery is also popcorn. Alternatively, the carbon layer may be a porous structure, thereby contributing to further suppressing the volume expansion of silicon. Optionally, the porous pore size of the carbon layer is 20-100 nm. Optionally, the carbon layer has a thickness of 10nm to 2000 nm. Further optionally, the carbon layer has a thickness of 10-200nm, 200nm-700nm, or 700nm-2000 nm. In the invention, the surface of the silicon-containing substrate is coated by adopting a carbon coating means, so that the conductivity and the stability of the silicon material can be obviously improved.
In the present invention, the material of the carbon layer is at least one selected from the group consisting of activated carbon, graphite, graphene, carbon nanotubes, carbon nanofibers, and carbon black.
In the invention, the mass ratio of the silicon-containing matrix to the carbon layer is 1: 0.03-0.3.
In the invention, the average size of the silicon material for the lithium ion battery is 1-200 μm. Alternatively, the average size is 1-5 μm, 5-10 μm, 10-50 μm, or 50-200 μm.
In the invention, the specific surface area of the silicon material for the lithium ion battery is 5-60m2(ii) in terms of/g. Alternatively, the specific surface area is 50 to 60m2(ii) in terms of/g. The silicon material for the lithium ion battery obtained by the invention has larger specific surface area.
In the invention, the compacted density of the silicon material for the lithium ion battery is 1.6-2.0g/cm3. Optionally, the compacted density is 1.7-1.9g/cm3。
In the present invention, the material of the silicon-containing matrix includes at least one of silicon and silicon monoxide.
In the present invention, lithium metal is attached to the surface of the silicon-containing substrate or to the porous structure. The silicon-containing matrix is compounded with the metal lithium, so that a lithium source can be supplemented to the silicon material, lithium consumed by the lithium ion battery in the first charging process can be effectively compensated, lithium ions can be separated from the silicon material during discharging, and the first charging and discharging efficiency is improved. Optionally, the molar ratio of the lithium metal to the silicon-containing matrix is 0.1-4: 1. Preferably, the molar ratio of the metallic lithium to the silicon-containing matrix is 0.5-3: 1. More preferably, the molar ratio of the metallic lithium to the silicon-containing matrix is 1-2: 1.
The silicon-containing matrix in the silicon material for the lithium ion battery provided by the first aspect of the invention is a three-dimensional flower-shaped porous structure, and due to the unique structure, free space buffering can be provided for expansion of silicon during energy storage, and large expansion of the volume of the silicon material for the lithium ion battery in the charging and discharging process when the silicon material is applied to a negative electrode material can not be caused, so that the negative electrode material has excellent cycle performance, and in addition, the silicon material also has high compaction density.
The second aspect of the invention provides a preparation method of a silicon material for a lithium ion battery, which comprises the following steps:
(1) carrying out pore etching or construction on the silicon-containing material to obtain a porous silicon-containing material;
(2) and (2) adding the porous silicon-containing material in the step (1) into a reaction kettle, and reacting for 0.5-2h under the pressure of 0.5-5.0Mpa and the temperature of 200-400 ℃ to obtain the silicon material for the lithium ion battery.
In step (1) of the present invention, the silicon-containing material is at least one of silicon and silica. Alternatively, the silicon-containing material may be micro-scale silicon-containing particles, such as micro-scale silicon-containing particles having a particle size of 1-30 μm, or nano-scale silicon-containing particles, such as nano-scale silicon-containing particles having a particle size of 10-100 nm. The shape of the silicon-containing material is not particularly limited, and may be spherical or other shapes.
Referring to fig. 2, in one embodiment of step (1) of the present invention, the porous silicon-containing material is porous micron-sized primary particles, and the preparation method of the porous micron-sized primary particles comprises the following steps:
and carrying out pore etching on the micron-sized silicon-containing particles 31 to obtain the porous micron-sized primary particles 32.
The invention adopts a cavitation method to corrode the silicon-containing material to obtain a porous structure. Optionally, the method of pitting employed includes HF-HNO3Corrosion, electrochemical anodic corrosion or hydrothermal corrosion. Specifically, the hole etching method adopted in the step (1) of the invention is HF-HNO3The etching method comprises the following specific processes:
adding a silicon-containing material to HF-HNO3And adding an additive into the system, reacting for 1-4h at the temperature of 20-40 ℃, filtering, and washing to obtain the porous silicon-containing material.
In step (1) of the present invention, the HF-HNO3In the system, HF and HNO3The molar concentration ratio of (A) to (B) is 1.5-5: 1.
In step (1) of the present invention, the additive is at least one of oxalic acid, urea, sodium nitrite, acetic acid, methanol and ethanol.
In step (1) of the present invention, the additive is used in an amount of HNO35-20% of the mass.
In step (1) of the present invention, the porous, micron-sized primary particles 32 contain many pores 33 on the surface and inside thereof. Alternatively, the holes may be holes penetrating through the silicon material or holes not penetrating through the silicon material. Optionally, the pore size of the porous, micron-sized primary particles 32 obtained in step (1) is 10-100 nm. Optionally, the porous, micron-sized primary particles 32 have a pore size of 20-80 nm.
In the present invention, the porosity of the porous, micron-sized primary particles 32 obtained in step (1) is 60% to 90%.
Referring to fig. 3, in another embodiment of step (1) of the present invention, the porous silicon-containing material is a porous secondary particle, and the preparation method of the porous secondary particle is as follows:
placing a plurality of nano-scale silicon-containing particles 41 in water or emulsion, stirring, then agglomerating the nano-scale silicon-containing particles 41, and drying to obtain the porous secondary particles 44.
In the present invention, the pore diameter of the porous secondary particle is 10 to 100 nm. By "porous" is meant the voids between the nano-scale silicon-containing particles after agglomeration or packing of the nano-scale silicon-containing particles, as shown at 46 in figure 3. Optionally, the size of the porous secondary particles is in the micron range, such as the size of the porous secondary particles is 1-20 μm. Optionally, the porous secondary particle has a porosity of 50% to 90%. Preferably, the nanoscale particles may be solid or porous. When the nano-scale particles are in a porous structure, the size of the porous structure is 1-5 nm.
Referring to fig. 4, in another embodiment of step (1) of the present invention, the porous secondary particle is prepared by the following steps:
and (2) taking the nano-scale particles 41, carrying out pore etching on the nano-scale particles 41 by adopting the pore etching method, wherein a plurality of pores 43 are etched on the surfaces and the inside of the nano-scale particles, and in the pore etching process, the porous nano-scale particles are agglomerated, washed and dried to construct porous secondary particles 42.
In the step (2), the porous silicon-containing material and a carbon source are mixed according to a mass ratio of 1:0.05-0.5 to obtain a mixture, and the mixture is added into a reaction kettle to react to obtain the silicon material for the lithium ion battery. Optionally, the carbon source comprises at least one of sucrose, lactose, glucose, starch, cellulose, high polymer cracked carbon, pitch cracked carbon, graphene, and graphene oxide. Optionally, the mass ratio of the porous silicon-containing material to the carbon source is 1:0.05-0.1 or 1: 0.1-0.5. In the invention, the surface of the silicon-containing substrate is coated by adopting a carbon coating means, so that the conductivity and the stability of the silicon material can be obviously improved.
In the step (2) of the present invention, the reaction is carried out under a pressure of 0.5 to 1.5MPa or a pressure of 1.5 to 5.0 MPa.
In step (2) of the present invention, the reaction time is 0.5 to 1 hour or 1 to 2 hours.
In the step (2) of the invention, the porous silicon-containing material obtained in the step (1) expands after reaction in the reaction kettle, and the expansion rate is more than 5 times. Specifically, the expansion ratio is 5 to 10 times. The "expansion ratio" refers to the volume ratio of the silicon-containing material after expansion to the silicon-containing material before non-expansion.
In the step (2) of the invention, the explosion rate of the porous silicon-containing material obtained in the step (1) in the reaction kettle is greater than or equal to 95%. The "popcorn ratio" refers to the weight ratio of the porous silicon-containing material forming the popcorn composite material to the total porous silicon-containing material.
In step (2) of the present invention, the volume of the porous silicon-containing material or the mixture in step (1) is 5 to 30% of the volume of the reaction vessel. At this volume fraction, the reaction is safe and efficient.
In the step (2), after the reaction is finished, the temperature of the reaction kettle is reduced to 100 ℃ and 150 ℃, and the silicon material for the lithium ion battery is taken out.
In the invention, the porous silicon-containing material prepared in the step (1) contains a plurality of pores. Alternatively, the holes may be holes penetrating through the silicon material or holes not penetrating through the silicon material. Under high temperature and high pressure, the porous silicon-containing material expands, wherein the pore diameter of some pores expands and becomes larger, some pores even expand and crack, and the cracked silicon material bulges outwards and can be rolled, twisted or overturned, and finally, the silicon-containing matrix with the three-dimensional flower-shaped porous structure is formed. And coating a carbon material formed by a carbon source on the surface of the silicon-containing matrix to form a carbon layer, thereby obtaining the silicon-carbon composite material.
In the invention, metallic lithium can be added in the step (2) to be reacted to compound the metallic lithium with the silicon-containing material.
The preparation method of the silicon material for the lithium ion battery provided by the second aspect of the invention has the advantages of simple and efficient preparation process and lower cost, and the prepared silicon material for the lithium ion battery has a special structure which reserves a large enough expansion space for the silicon material in the charging and discharging process, prolongs the charging and discharging cycle life of the silicon material and improves the cycle performance of the silicon material.
Example 1
A preparation method of a silicon material for a lithium ion battery comprises the following steps:
(1) preparation of porous silicon material
10g of micron-sized silicon material was added to HF-HNO3Etching holes in the mixed solution, wherein HF and HNO3The molar concentration ratio of (1.5: 1), adding 4g of oxalic acid, reacting at 20 ℃ for 4 hours at constant temperature, filtering and washing to obtain the porous silicon material, wherein the pore diameter of the porous silicon material is 10-50nm, and the porosity is 60-80%.
(2) Preparation of silicon material for lithium ion battery
And (2) adding the porous silicon material obtained in the step (1) into a reaction kettle, wherein the volume of reactants accounts for 20% of the volume of the reaction kettle, heating to 300 ℃, reacting for 1h, cooling to 100 ℃, and quickly opening a valve of the reaction kettle in a safe material bin to obtain the silicon material for the lithium ion battery. The explosion rate of the porous silicon material in the reaction kettle is more than 95 percent.
The silicon material for the lithium ion battery prepared in the embodiment 1 has the size of 1-10 μm, the pore diameter of the porous structure is 50-100nm, the length of the bulge is 100-200nm, and the specific surface area is 50-60m2(ii) a compacted density of 1.7 to 2.0g/cm3。
Example 2
A preparation method of a silicon material for a lithium ion battery comprises the following steps:
(1) preparation of porous silicon material
10g of micron-sized silica material was added to HF-HNO3Etching holes in the mixed solution, wherein HF and HNO3The molar concentration ratio of (1) is 5:1, 2.5g of urea is added, after the reaction is carried out for 1 hour at the constant temperature of 80 ℃, the porous silica material is obtained by filtration and washing, the aperture of the porous silica material is 20-70nm, and the porosity is 70-85%.
(2) Preparation of silicon material for lithium ion battery
Mixing the porous silica material obtained in the step (1) according to a mass ratio of 1:0.5 to obtain a mixture, adding the mixture into a reaction kettle, heating the mixture to 200 ℃, reacting for 2 hours, cooling to 150 ℃, and quickly opening a valve of the reaction kettle in a safe material bin to obtain the silicon material for the lithium ion battery. The explosion rate of the porous silica material in the reaction kettle is more than 95 percent.
The silicon material for lithium ion battery prepared in example 2 has a size of 5-10 μm, a porous structure with a pore diameter of 100-300nm, a protrusion length of 300-400nm, and a specific surface area of 50-60m2(ii) a compacted density of 1.7 to 2.0g/cm3。
Example 3
A preparation method of a silicon material for a lithium ion battery comprises the following steps:
(1) preparation of porous silicon material
10g of micron-sized silicon material was added to HF-HNO3Etching holes in the mixed solution, wherein HF and HNO3The molar concentration ratio of the porous silicon material is 3:1, 7g of sodium nitrite is added, the reaction is carried out for 2 hours at the constant temperature of 40 ℃, and then the porous silicon material is obtained by filtering and washing. The pore diameter of the porous silicon material is 70-100nm, and the porosity is 80-90%.
(2) Preparation of silicon material for lithium ion battery
And (2) adding the porous silicon material obtained in the step (1) into a reaction kettle, wherein the volume of reactants accounts for 30% of the volume of the reaction kettle, heating to 400 ℃, reacting for 0.5h, cooling to 120 ℃, and quickly opening a valve of the reaction kettle in a safe material bin to obtain the silicon material for the lithium ion battery. The explosion rate of the porous silicon material in the reaction kettle is more than 95 percent.
The silicon material for the lithium ion battery prepared in the embodiment 3 has the size of 10-30 μm, the pore diameter of the porous structure is 300-500nm, the length of the bulge is 400-500nm, and the specific surface area is 50-60m2(ii) a compacted density of 1.7 to 2.0g/cm3。
Example 4
A preparation method of a silicon material for a lithium ion battery comprises the following steps:
(1) preparation of porous silicon material
And (2) putting 10g of nano-scale silicon material into water, stirring and standing, then agglomerating a plurality of nano-scale silicon-containing particles, and drying to obtain the porous silicon material. The porous silicon material has a pore diameter of 10-20nm and a porosity of 50-70%.
(2) Preparation of silicon material for lithium ion battery
And (2) adding the porous silicon material obtained in the step (1) into a reaction kettle, wherein the volume of reactants accounts for 30% of the volume of the reaction kettle, heating to 400 ℃, reacting for 0.5h, cooling to 120 ℃, and quickly opening a valve of the reaction kettle in a safe material bin to obtain the silicon material for the lithium ion battery. The explosion rate of the porous silicon material in the reaction kettle is more than 95 percent.
The silicon material for the lithium ion battery prepared in the embodiment 4 has the size of 1-20 μm, the pore diameter of the porous structure is 100-200nm, the length of the bulge is 100-200nm, and the specific surface area is 50-60m2(ii) a compacted density of 1.7 to 2.0g/cm3。
Example 5
A preparation method of a silicon material for a lithium ion battery comprises the following steps:
mixing the porous silicon material obtained in the step (1) in the embodiment 1 with sucrose according to a mass ratio of 1:0.05 to obtain a mixture, adding the mixture into a reaction kettle, heating the mixture to 300 ℃, reacting for 1 hour, cooling to 100 ℃, and quickly opening a valve of the reaction kettle in a safe material bin to obtain the silicon material for the lithium ion battery. The explosion rate of the porous silicon material in the reaction kettle is more than 95 percent.
Example 6
A preparation method of a silicon material for a lithium ion battery comprises the following steps:
mixing the porous silica material obtained in the step (1) in the embodiment 2 with glucose according to the mass ratio of 1:0.5 to obtain a mixture, adding the mixture into a reaction kettle, wherein the volume of a reactant accounts for 5% of the volume of the reaction kettle, heating to 200 ℃, reacting for 2 hours, cooling to 150 ℃, and quickly opening a valve of the reaction kettle in a safe material bin to obtain the silicon material for the lithium ion battery. The explosion rate of the porous silica material in the reaction kettle is more than 95 percent.
Example 7
A preparation method of a silicon material for a lithium ion battery comprises the following steps:
mixing the porous silicon material obtained in the step (1) in the embodiment 3 with asphalt cracking carbon according to the mass ratio of 1:0.1 to obtain a mixture, adding the mixture into a reaction kettle, heating the mixture to 400 ℃, reacting for 0.5h, cooling to 120 ℃, and quickly opening a valve of the reaction kettle in a safe material bin to obtain the silicon material for the lithium ion battery. The explosion rate of the porous silicon material in the reaction kettle is more than 95 percent.
Example 8
A preparation method of a silicon material for a lithium ion battery comprises the following steps:
mixing the porous silicon material obtained in the step (1) in the embodiment 4 with asphalt cracking carbon according to the mass ratio of 1:0.1 to obtain a mixture, adding the mixture into a reaction kettle, heating the mixture to 400 ℃, reacting for 0.5h, cooling to 120 ℃, and quickly opening a valve of the reaction kettle in a safe material bin to obtain the silicon material for the lithium ion battery. The explosion rate of the porous silicon material in the reaction kettle is more than 95 percent.
Effects of the embodiment
The invention also provides a comparative example to show the effect of the silicon material for the lithium ion battery.
Comparative example 1
The preparation method of the silicon-carbon composite material comprises the following steps:
(1) preparation of porous silicon material
10g of micron-sized silicon material was added to HF-HNO3Etching holes in the mixed solution, wherein HF and HNO3The molar concentration ratio of (1.5: 1), adding 4g of oxalic acid, reacting at 20 ℃ for 4 hours at constant temperature, filtering and washing to obtain the porous silicon material, wherein the pore diameter of the obtained porous silicon material is 10-50nm, and the porosity is 60-80%.
(2) Preparation of silicon-carbon composite material
And (2) mixing the porous silicon material obtained in the step (1) with cane sugar according to the mass ratio of 1:0.05 to obtain a mixture, putting the mixture into a tubular furnace, introducing nitrogen, and carbonizing for 6 hours at 700 ℃ to obtain a carbon-coated porous silicon material, namely the silicon-carbon composite material.
The silicon material for lithium ion batteries prepared in example 5 and the silicon-carbon composite material prepared in comparative example 1 were assembled into a button half cell, and the electrochemical performance was further verified. Wherein the material is tested under the condition of 1C, the voltage range of charging and discharging is 0.01-2V, and the capacity retention rate after 100 and 300 cycles is tested.
The silicon material for a lithium ion battery having a three-dimensional flower-like porous structure in example 5 had a discharge capacity of 2030mAh/g at 1C for the first time, and the silicon-carbon composite material of comparative example 1 had a discharge capacity of 1950mAh/g at 1C for the first time. In addition, the capacity retention rate of the silicon material for a lithium ion battery in example 5 was 85% or more after 300 cycles. The silicon-carbon composite material in comparative example 1 has a capacity retention rate of only about 80% after being cycled for 100 cycles, and has a capacity retention rate of about 55% after being cycled for 300 cycles. As can be seen from the above, the silicon material for lithium ion batteries of the examples of the present invention has better cycle performance than that of comparative example 1. Furthermore, comparative example 1 had a compacted density of only 1.6g/cm3On the other hand, the silicon material for lithium ion batteries of example 5 of the present invention had a higher compacted density.
The above-mentioned embodiments only express one embodiment of the present invention, and the description thereof is more detailed and specific, but not to be 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 (10)

1. The silicon material for the lithium ion battery is characterized by comprising a silicon-containing substrate, wherein the silicon-containing substrate is prepared by the following method: (1) carrying out pore etching or construction on the silicon-containing material to obtain a porous silicon-containing material; (2) adding the porous silicon-containing material in the step (1) into a reaction kettle, and reacting for 0.5-2h under the pressure of 0.5-5.0Mpa and the temperature of 200-400 ℃; the silicon-containing matrix comprises a main body and irregular bulges which are arranged on the surface of the main body and extend outwards, and the bulges can be folded, twisted or turned over to form the silicon-containing matrix with a three-dimensional flower-shaped porous structure; at least one of the surface and the interior of the main body is provided with a porous structure, and the average pore diameter of the porous structure is 10-500 nm; the compacted density of the silicon material for the lithium ion battery is 1.6-2.0g/cm3。
2. The silicon material for lithium ion batteries according to claim 1, wherein the silicon-containing matrix is a primary particle or a secondary particle constructed from a plurality of nano-sized particles.
3. The silicon material for lithium ion batteries according to claim 1, wherein the morphology of the silicon-containing matrix is popcorn-like.
4. The silicon material for lithium ion batteries according to claim 1, further comprising a carbon layer coated on the surface of the silicon-containing substrate, wherein the surface topography of the carbon layer is consistent with the surface topography of the silicon-containing substrate.
5. The silicon material for lithium ion batteries according to claim 1, wherein the average scale of the silicon material for lithium ion batteriesInch of 1-200 μm, and specific surface area of 5-60m2/g。
6. The silicon material for lithium ion batteries according to claim 1, wherein the protrusions extend outward from the main body by a length of 10-500nm, and the size of the gaps between the protrusions is 10-500 nm.
7. A preparation method of a silicon material for a lithium ion battery is characterized by comprising the following steps:
(1) carrying out pore etching or construction on the silicon-containing material to obtain a porous silicon-containing material;
(2) adding the porous silicon-containing material in the step (1) into a reaction kettle, and reacting for 0.5-2h under the pressure of 0.5-5.0Mpa and the temperature of 200-400 ℃ to obtain the silicon material for the lithium ion battery as defined in any one of claims 1-6.
8. The method for preparing a silicon material for a lithium ion battery according to claim 7, wherein in the step (1), the porous silicon-containing material is porous micron-sized primary particles or porous secondary particles, and the method for preparing the porous silicon-containing material specifically comprises the following steps:
carrying out pore etching on the micron-sized silicon-containing particles to obtain porous micron-sized primary particles; or
And (3) placing a plurality of nano-scale silicon-containing particles in water or emulsion, stirring, then agglomerating the nano-scale silicon-containing particles, and drying to obtain the porous secondary particles.
9. The preparation method of the silicon material for the lithium ion battery according to claim 7, wherein in the step (2), the porous silicon-containing material and the carbon source are mixed according to a mass ratio of 1:0.05-0.5 to obtain a mixture, and the mixture is added into a reaction kettle to react to obtain the silicon material for the lithium ion battery.
10. The method for preparing the silicon material for the lithium ion battery according to claim 7, wherein the porous silicon-containing material obtained in the step (1) expands after reaction in the reaction kettle, and the expansion rate is 5 times or more.
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