CN111244414A - Method for preparing silicon-carbon negative electrode material by magnesiothermic reduction - Google Patents
Method for preparing silicon-carbon negative electrode material by magnesiothermic reduction Download PDFInfo
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- 238000000034 method Methods 0.000 title claims abstract description 27
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- HBBGRARXTFLTSG-UHFFFAOYSA-N Lithium ion Chemical compound [Li+] HBBGRARXTFLTSG-UHFFFAOYSA-N 0.000 abstract description 15
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- YTHCQFKNFVSQBC-UHFFFAOYSA-N magnesium silicide Chemical compound [Mg]=[Si]=[Mg] YTHCQFKNFVSQBC-UHFFFAOYSA-N 0.000 description 4
- 229910021338 magnesium silicide Inorganic materials 0.000 description 4
- AXZKOIWUVFPNLO-UHFFFAOYSA-N magnesium;oxygen(2-) Chemical compound [O-2].[Mg+2] AXZKOIWUVFPNLO-UHFFFAOYSA-N 0.000 description 4
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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
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B82—NANOTECHNOLOGY
- B82Y—SPECIFIC USES OR APPLICATIONS OF NANOSTRUCTURES; MEASUREMENT OR ANALYSIS OF NANOSTRUCTURES; MANUFACTURE OR TREATMENT OF NANOSTRUCTURES
- B82Y40/00—Manufacture or treatment of nanostructures
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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
- 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
- H01M4/62—Selection of inactive substances as ingredients for active masses, e.g. binders, fillers
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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
- H01M4/625—Carbon or graphite
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- 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 method for preparing a silicon-carbon negative electrode material by magnesiothermic reduction, which comprises the following steps: roasting the micro silicon powder, dispersing the micro silicon powder in an acid etching solution, heating in a water bath, and then performing suction filtration, washing and drying to obtain a pretreated sample; mixing a pretreated sample and magnesium powder by ball milling, placing the mixture in a sealed graphite crucible after natural drying, transferring the mixture to a tubular furnace of inert gas for magnesium thermal reaction, and carrying out acid washing, vacuum filtration, water washing and drying on the obtained product to obtain porous crystalline silicon; and uniformly mixing the prepared porous crystalline silicon and the organic matter precursor, drying, and then placing in protective gas for curing to obtain the silicon-based composite material. Porous crystalline silicon is obtained through acid etching pretreatment and magnesium thermal reduction treatment on micro silicon powder; the silicon material not only has higher specific capacity, but also has the function of buffering the volume expansion of the silicon material on the one hand; on the other hand, the depth of lithium ion deintercalation and the diffusion distance are shortened, so that the lithium ion deintercalation device shows excellent electrochemical performance.
Description
Technical Field
The invention relates to a method for preparing a silicon-carbon negative electrode material by magnesiothermic reduction, belonging to the technical field of silicon materials.
Background
The lithium ion battery has the advantages of high working voltage, high specific energy, long cycle life, light weight, small self-discharge and the like, and is widely applied to various portable electronic equipment, electric automobiles and other aspects. The negative electrode material is mainly made of carbon material as the main lithium storage body of the lithium ion battery. The carbon cathode has the defects of low specific capacity, low first charge-discharge efficiency and the like. Therefore, the search for a lithium ion battery cathode material with high specific capacity, low price and abundant raw materials becomes the focus of attention of people. The silicon material becomes the most promising next generation lithium ion battery cathode material by the theoretical capacity as high as 4200mAh/g and abundant materials. However, the silicon negative electrode has severe volume expansion (300%) in a fully lithium-intercalated state, which causes pulverization and falling-off of material particles, and also causes repeated growth of a surface SEI film, consumes an electrolyte and a lithium source, and seriously affects the electrochemical performance.
In order to solve the problem, many methods are proposed, such as methods for preparing multiphase composite materials, such as silicon nanoparticles, silicon nanowires, nanotubes, hollow spheres and the like, to relieve the volume effect of the multiphase composite materials, and meanwhile, the conductivity of the silicon cathode material is improved through carbon coating treatment; although the lithium ion battery cathode materials prepared by the methods show better performance, the preparation cost is higher, and the preparation process is complex.
Disclosure of Invention
In order to solve the technical problems, the invention aims to provide a method for preparing a silicon-carbon anode material by magnesiothermic reduction, porous crystalline silicon is prepared by utilizing the characteristic of a primary particle structure of silica fume sub-meter, and the porous crystalline silicon is subjected to carbon-coated surface modification treatment to show excellent electrochemical performance; the process is low in preparation cost and simple and feasible in process, and the aim of the invention is achieved through the following technical scheme:
a method for preparing a silicon-carbon negative electrode material by magnesiothermic reduction specifically comprises the following steps:
(1) pretreating the micro silicon powder: roasting the micro silicon powder, dispersing the micro silicon powder in acid etching liquid, heating the micro silicon powder to 60-90 ℃ in a water bath, performing dynamic stirring for 1-6 hours, performing suction filtration, washing with water, and drying to obtain a pretreated sample.
(2) Ball milling, mixing and magnesium thermal reduction acid etching: mixing the pretreated micro silicon powder and magnesium powder by ball milling, placing the mixture in a sealed graphite crucible after natural drying, transferring the mixture to a tubular furnace of inert gas for magnesium thermal reaction, and carrying out acid washing, vacuum filtration, water washing and drying on the obtained product to obtain the porous crystalline silicon.
(3) Coating of the surface carbon layer: and uniformly mixing the prepared porous crystalline silicon and the organic matter precursor, drying, placing in inert gas, and curing at the temperature of 800-1100 ℃ to obtain the silicon-based composite material.
Preferably, the acid etching solution in step (1) of the present invention is one or a mixture of several of hydrochloric acid, sulfuric acid, nitric acid, oxalic acid and acetic acid, and the concentration of the acid etching solution is 3.26 mol/L.
Preferably, the calcination conditions in step (1) of the present invention are calcination at 500-1100 ℃ for 4-10 hours.
Preferably, the mass ratio of the pretreated micro silicon powder to the magnesium powder is 1 (0.8-1.2).
Preferably, the ball milling parameters in step (2) of the present invention are: the rotating speed is 100-.
Preferably, the temperature of the magnesium thermal reaction in the step (2) of the invention is 600-800 ℃ and the time is 1-10 hours.
Preferably, the inert gas in step (2) of the present invention is a mixture of one or more of air, argon and nitrogen.
Preferably, the acid used in the acid washing in step (2) of the present invention is hydrochloric acid, and the concentration of the hydrochloric acid is 0.5 to 5 mol/L.
Preferably, the organic matter in the step (3) is one or more of sucrose, asphalt, polyaniline, phenolic resin and PVDF; the mass ratio of the porous crystalline silicon to the organic precursor is 1 (0.1-1).
The invention has the beneficial effects that:
(1) the invention prepares the nano-porous crystalline silicon by carrying out magnesium thermal reduction acid etching treatment on the silicon micro-waste in the silicon metallurgy industry; the pore structure not only buffers the volume expansion of the porous structure, but also shortens the de-intercalation depth and the diffusion distance of lithium ions, and the preparation method is low in cost and simple and easy to implement.
(2) A carbon layer is coated on the surface of a silicon material by utilizing an organic matter high-temperature pyrolysis method to form a silicon/carbon composite structure, and the electrical conductivity and the cycling stability of the silicon cathode material are greatly improved by the composite structure.
Drawings
FIG. 1 is a diagram showing nitrogen adsorption-desorption of porous silicon prepared in example 1.
FIG. 2 is a scanning electron microscope image of the porous silicon-based composite material prepared in example 2.
FIG. 3 is a transmission electron microscope image of the porous silicon-based composite material prepared in example 2.
FIG. 4 is a graph of the electrochemical cycling of the silicon-based composite material at a current density of 0.5A/g in example 2.
Detailed Description
The invention will be described in more detail with reference to the following figures and examples, but the scope of the invention is not limited thereto.
Example 1
A method for preparing a silicon-carbon negative electrode material by magnesiothermic reduction specifically comprises the following steps:
(1) pretreating the micro silicon powder: roasting the micro silicon powder at 500 ℃ for 10 hours, then dispersing the micro silicon powder in a sulfuric acid solution with the concentration of 3.26mol/L, heating the micro silicon powder to 60 ℃ in a water bath, stirring the micro silicon powder for 6 hours under power, and then carrying out suction filtration, water washing and drying to obtain a pretreated sample.
(2) Mixing the pretreated sample and magnesium powder according to the mass ratio of 1:0.8 by using a planetary ball mill, wherein the mass ratio of ball materials is 1:2, the rotating speed is 150 r/m, and naturally drying after ball milling for 12 hours to obtain a reaction material.
(3) Placing the reaction materials in a sealed graphite crucible, transferring the sealed graphite crucible to a tubular furnace under the argon atmosphere, and preserving the heat for 10 hours at 600 ℃; and (3) acid etching the obtained product with 0.5mol/L hydrochloric acid for 12 hours to remove the byproducts of the magnesium oxide and the magnesium silicide, and performing suction filtration and drying to obtain the porous crystalline silicon.
(4) And mixing the dried porous crystalline silicon with phenolic resin according to the mass ratio of 1:0.1, drying, and then placing the dried product in an argon gas environment at the temperature of 800 ℃ for curing treatment to obtain the porous crystalline silicon composite material.
(5) And (3) taking the obtained porous silicon-based composite material as a silicon negative electrode material of the lithium ion battery to perform electrochemical performance test. The pole piece ratio is: preparing a CR2025 type button battery by using a porous silicon composite material, namely acetylene black and PVDF (polyvinylidene fluoride) in a ratio of 7:2:2 and taking a lithium sheet as a reference electrode; under the current density of 0.5A/g, the first discharge specific capacity is 2766 mAh/g. Compared with a commercial silicon composite negative electrode, the silicon negative electrode composite material prepared by the invention has higher capacity (see attached table I).
FIG. 1 is a nitrogen adsorption-desorption graph of crystalline silicon prepared by magnesiothermic reduction and acid etching in the present example, from which it can be seen that crystalline silicon has rich mesoporous structure and large specific surface area (127.0 m)2And/g) shows that porous crystalline silicon is obtained after magnesiothermic reduction acid etching.
Example 2
A method for preparing a silicon-carbon negative electrode material by magnesiothermic reduction specifically comprises the following steps:
(1) pretreating the micro silicon powder: roasting the micro silicon powder at 800 ℃ for 6 hours, then dispersing the micro silicon powder in hydrochloric acid solution with the concentration of 3.26mol/L, heating the micro silicon powder to 80 ℃ in water bath, and preserving the heat for 3 hours to obtain a pretreated sample.
(2) Mixing the pretreated sample and magnesium powder according to the mass ratio of 1:0.85 by using a planetary ball mill, wherein the mass ratio of ball materials is 1:2, the rotating speed is 150 r/m, and naturally drying the mixture after ball milling for 12 hours to obtain a reaction material;
(3) placing the reaction materials in a sealed graphite crucible, transferring the sealed graphite crucible into a tubular furnace under the argon atmosphere, and preserving the temperature for 5 hours at 700 ℃; acid etching the obtained product with 1mol/L hydrochloric acid for 12 hours to remove the byproducts of magnesium oxide and magnesium silicide, and performing suction filtration and drying to obtain porous crystalline silicon;
(4) and mixing the dried porous crystalline silicon with phenolic resin according to the mass ratio of 1:0.25, drying, and then placing the dried product in an argon gas environment at the temperature of 1000 ℃ for curing treatment to obtain the porous crystalline silicon composite material.
(5) And (3) taking the obtained porous silicon-based composite material as a silicon negative electrode material of the lithium ion battery to perform electrochemical performance test. The pole piece ratio is: the porous silicon composite material is acetylene black and PVDF (polyvinylidene fluoride) in a ratio of 7:2:2, and a lithium sheet is used as a reference electrode to prepare the CR2025 type button cell. The first discharge specific capacity is 3078mAh/g under the current density of 0.5A/g. Compared with a commercial silicon composite negative electrode, the silicon negative electrode composite material prepared by the invention has higher capacity (see attached table I).
FIG. 2 is a scanning electron microscope image of the porous silicon-based composite material according to the present embodiment, from which it can be seen that the size of the crystalline silicon is still maintained at submicron level after the reducing acid etching, and the crystalline silicon is in a spherical or quasi-spherical nanostructure; some particles are slightly sintered due to the high temperature. After pyrolysis with organic phenolic resin, a carbon layer is formed on the surface of the organic phenolic resin by curing, and the structure of the carbon layer coated around the organic phenolic resin can be obviously observed from the figure.
Fig. 3 is a transmission electron microscope image of the porous silicon-based composite material of the embodiment, and it can be seen from the image that the crystalline silicon surface is coated with a carbon layer structure, which further improves the conductivity of the crystalline silicon.
Fig. 4 is an electrochemical cycle curve of the porous silicon-based composite material of the present embodiment at a current density of 0.5A/g, and it can be seen from the graph that the porous silicon-based composite material exhibits excellent cycle stability, the first coulombic efficiency of the porous silicon-based composite material reaches 77.6%, the capacity retention rate of the porous silicon-based composite material after 300 charge-discharge cycles is 62.8%, and the porous silicon-based composite material has excellent electrochemical performance.
Example 3
A method for preparing a silicon-carbon negative electrode material by magnesiothermic reduction comprises the following steps:
(1) pretreating the micro silicon powder: roasting the micro silicon powder at 900 ℃ for 8 hours, then dispersing the micro silicon powder in nitric acid solution with the concentration of 3.26mol/L, heating the micro silicon powder to 70 ℃ in water bath, and preserving the heat for 5 hours to obtain a pretreated sample.
(2) Mixing the pretreated sample and magnesium powder according to the mass ratio of 1:0.9 by using a planetary ball mill, wherein the mass ratio of ball materials is 1:2, the rotating speed is 150 r/m, and naturally drying the mixture after ball milling for 8 hours to obtain a reaction material;
(3) placing the reaction materials in a sealed graphite crucible, transferring the sealed graphite crucible to a tubular furnace under the argon atmosphere, and preserving the temperature for 10 hours at 700 ℃; acid etching the obtained product with 5mol/L hydrochloric acid for 12 hours to remove the byproducts of magnesium oxide and magnesium silicide, and performing suction filtration and drying to obtain porous crystalline silicon;
(4) and mixing the dried porous crystalline silicon with phenolic resin according to the mass ratio of 1:0.5, drying, and then placing the dried product in an argon gas 1100 ℃ temperature environment for curing treatment to obtain the porous crystalline silicon composite material.
(5) And (3) taking the obtained porous silicon-based composite material as a silicon negative electrode material of the lithium ion battery to perform electrochemical performance test. The pole piece ratio is: the porous silicon composite material is acetylene black and PVDF (polyvinylidene fluoride) in a ratio of 7:2:2, and a lithium sheet is used as a reference electrode to prepare the CR2025 type button cell. Under the current density of 0.5A/g, the first discharge specific capacity is 2796 mAh/g. Compared with a commercial silicon composite negative electrode, the silicon negative electrode composite material prepared by the invention has higher capacity (see attached table I).
Example 4
A method for preparing a silicon-carbon negative electrode material by magnesiothermic reduction comprises the following steps:
(1) pretreating the micro silicon powder: the micro silicon powder is roasted for 4 hours at 1100 ℃, then dispersed in oxalic acid solution with the concentration of 3.26mol/L, heated to 90 ℃ in water bath, and kept warm for 1 hour to obtain a pretreatment sample.
(2) Mixing the pretreated sample and magnesium powder according to the mass ratio of 1:1.2 by using a planetary ball mill, wherein the mass ratio of ball materials is 1:2, the rotating speed is 150 r/m, and naturally drying the mixture after ball milling for 12 hours to obtain a reaction material;
(3) placing the reaction material in a sealed graphite crucible, transferring the reaction material into a tubular furnace under the argon atmosphere, and preserving the heat at 800 ℃ for 1 hour; acid etching the obtained product with 1mol/L hydrochloric acid for 12 hours to remove the byproducts of magnesium oxide and magnesium silicide, and performing suction filtration and drying to obtain porous crystalline silicon;
(4) and mixing the dried porous crystalline silicon with phenolic resin according to the mass ratio of 1:1, drying, and then placing the dried product in an argon gas environment at the temperature of 800 ℃ for curing treatment to obtain the porous crystalline silicon composite material.
(5) Taking the obtained porous silicon-based composite material as a silicon negative electrode material of a lithium ion battery, and carrying out electrochemical performance test; the pole piece ratio is: preparing a CR2025 type button battery by using a porous silicon composite material, namely acetylene black and PVDF (polyvinylidene fluoride) in a ratio of 7:2:2 and taking a lithium sheet as a reference electrode; under the current density of 0.5A/g, the first discharge specific capacity is 3287 mAh/g. The silicon anode composite prepared by the present invention has higher capacity compared to commercial silicon composite anodes (see attached table 1).
TABLE 1 Charge and discharge Properties of silicon negative electrode composites in examples
In conclusion, the invention carries out magnesium thermal reduction and acid etching on the micro silicon powder from the silicon metallurgy industrial waste, carries out surface modification, and is used for the electrode material of the lithium ion battery after being coated with the conductive carbon layer; the structural characteristics of the submicron primary particles of the micro silicon powder and the shape-preserving effect of the magnesiothermic reduction are fully utilized to prepare the porous crystalline silicon. The formation of the silicon body pore channel not only buffers the volume expansion of the silicon cathode in the lithium removal/insertion process; meanwhile, the impregnation of the electrolyte is promoted, the de-intercalation depth and diffusion distance of lithium ions are shortened, and excellent electrochemical performance is shown. Not only provides excellent electrode material for lithium ion battery, but also realizes high value-added utilization of micro silicon powder. And the whole preparation process is simple and feasible in process, low in cost and simple in equipment.
Claims (9)
1. The method for preparing the silicon-carbon cathode material by magnesiothermic reduction is characterized by comprising the following steps:
(1) pretreating the micro silicon powder: roasting the micro silicon powder, dispersing the micro silicon powder in acid etching liquid, heating the micro silicon powder to 60-90 ℃ in a water bath, performing dynamic stirring for 1-6 hours, performing suction filtration, washing with water, and drying to obtain a pretreated sample;
(2) ball milling, mixing and magnesium thermal reduction acid etching: mixing the pretreated micro silicon powder and magnesium powder by ball milling, placing the mixture in a sealed graphite crucible after natural drying, transferring the mixture to a tubular furnace of inert gas for magnesium thermal reaction, and carrying out acid washing, vacuum filtration, water washing and drying on the obtained product to obtain porous crystalline silicon;
(3) coating of the surface carbon layer: and uniformly mixing the prepared porous crystalline silicon and the organic matter precursor, drying, placing in inert gas, and curing at the temperature of 800-1100 ℃ to obtain the silicon-based composite material.
2. The method for preparing the silicon-carbon anode material by the magnesiothermic reduction according to claim 1, wherein: the acid etching solution in the step (1) is one or a mixture of more of hydrochloric acid, sulfuric acid, nitric acid, oxalic acid and acetic acid, and the concentration of the acid etching solution is 3.26 mol/L.
3. The method for preparing the silicon-carbon anode material by the magnesiothermic reduction according to claim 1, wherein: the roasting condition in the step (1) is that the roasting is carried out for 4 to 10 hours at the temperature of 500 ℃ and 1100 ℃.
4. The method for preparing the silicon-carbon anode material by the magnesiothermic reduction according to claim 1, wherein: the mass ratio of the pretreated micro silicon powder to the magnesium powder is 1 (0.8-1.2).
5. The method for preparing the silicon-carbon anode material by the magnesiothermic reduction according to claim 1, wherein: the ball milling parameters in the step (2) are as follows: the rotating speed is 100-.
6. The method for preparing the silicon-carbon anode material by the magnesiothermic reduction according to claim 1, wherein: the temperature of the magnesium thermal reaction in the step (2) is 600-800 ℃, and the time is 1-10 hours.
7. The method for preparing the silicon-carbon anode material by the magnesiothermic reduction according to claim 1, wherein: the inert gas in the step (2) is one or a mixture of air, argon and nitrogen.
8. The method for preparing the silicon-carbon anode material by the magnesiothermic reduction according to claim 1, wherein: the acid used in the acid washing in the step (2) is hydrochloric acid, and the concentration of the hydrochloric acid is 0.5-5 mol/L.
9. The method for preparing the silicon-carbon anode material by the magnesiothermic reduction according to claim 1, wherein: the organic matter in the step (3) is one or more of sucrose, asphalt, polyaniline, phenolic resin and PVDF; the mass ratio of the porous crystalline silicon to the organic precursor is 1 (0.1-1).
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