CN117352711B - Preparation process of novel carbon-coated silicon and graphite composite negative electrode material - Google Patents
Preparation process of novel carbon-coated silicon and graphite composite negative electrode material Download PDFInfo
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- CN117352711B CN117352711B CN202311660675.4A CN202311660675A CN117352711B CN 117352711 B CN117352711 B CN 117352711B CN 202311660675 A CN202311660675 A CN 202311660675A CN 117352711 B CN117352711 B CN 117352711B
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- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 title claims abstract description 80
- 239000010703 silicon Substances 0.000 title claims abstract description 48
- 229910052710 silicon Inorganic materials 0.000 title claims abstract description 48
- 229910002804 graphite Inorganic materials 0.000 title claims abstract description 40
- 239000010439 graphite Substances 0.000 title claims abstract description 40
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- 239000007773 negative electrode material Substances 0.000 title claims abstract description 26
- 238000002360 preparation method Methods 0.000 title claims abstract description 23
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- 239000010405 anode material Substances 0.000 claims description 21
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- CZMRCDWAGMRECN-UGDNZRGBSA-N Sucrose Chemical compound O[C@H]1[C@H](O)[C@@H](CO)O[C@@]1(CO)O[C@@H]1[C@H](O)[C@@H](O)[C@H](O)[C@@H](CO)O1 CZMRCDWAGMRECN-UGDNZRGBSA-N 0.000 claims description 2
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- 229920001807 Urea-formaldehyde Polymers 0.000 claims description 2
- WQZGKKKJIJFFOK-VFUOTHLCSA-N beta-D-glucose Chemical compound OC[C@H]1O[C@@H](O)[C@H](O)[C@@H](O)[C@@H]1O WQZGKKKJIJFFOK-VFUOTHLCSA-N 0.000 claims description 2
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- 238000001035 drying Methods 0.000 description 8
- HBBGRARXTFLTSG-UHFFFAOYSA-N Lithium ion Chemical compound [Li+] HBBGRARXTFLTSG-UHFFFAOYSA-N 0.000 description 7
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- 239000011149 active material Substances 0.000 description 1
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- 230000004075 alteration Effects 0.000 description 1
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Classifications
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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
- H01M4/587—Carbonaceous material, e.g. graphite-intercalation compounds or CFx for inserting or intercalating light metals
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M4/00—Electrodes
- H01M4/02—Electrodes composed of, or comprising, active material
- H01M4/62—Selection of inactive substances as ingredients for active masses, e.g. binders, fillers
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M4/00—Electrodes
- H01M4/02—Electrodes composed of, or comprising, active material
- H01M2004/026—Electrodes composed of, or comprising, active material characterised by the polarity
- H01M2004/027—Negative electrodes
-
- 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 relates to the technical field of negative electrode materials, in particular to a novel preparation process of a carbon-coated silicon-graphite composite negative electrode material, which comprises the following components in parts by weight: 40 parts of modified graphite and 5-7 parts of carbon-coated silicon powder. The preparation process comprises the following steps: (1) graphite modification; (2) preparing a silicon suspension; (3) preparing a coating solution; (4) a cladding process; (5) carbonization treatment; (6) mixing procedure. The silicon-carbon composite anode material produced by the method has the advantages of simple process, low cost, suitability for mass production and excellent and stable product performance.
Description
Technical Field
The invention relates to the technical field of negative electrode materials, in particular to a preparation process of a novel carbon-coated silicon-graphite composite negative electrode material.
Background
Lithium batteries are a type of battery using a nonaqueous electrolyte solution with lithium metal or a lithium alloy as a positive/negative electrode material. Lithium metal batteries were first proposed and studied by Gilbert n.lewis in 1912. At 70 s of the 20 th century, m.s. Whittingham proposed and began to study lithium ion batteries. The chemical characteristics of lithium metal are very active, so that the processing, storage and use of lithium metal have very high requirements on environment. With the development of science and technology, lithium batteries have become the mainstream.
Lithium batteries can be broadly divided into two categories: lithium metal batteries and lithium ion batteries. Lithium ion batteries do not contain lithium in the metallic state and are rechargeable.
The lithium ion battery has the excellent performances of high working voltage, large energy density, long service life, wide application temperature range, no memory and the like, and is widely applied to the fields such as new energy automobiles and the like.
The silicon-carbon anode material is an anode material with great application potential, and has become a technical hot spot in the field of lithium ion batteries due to the fact that the theoretical ratio is high, the energy density is high and the safety is high. However, the current silicon carbon negative electrode has some problems that limit practical applications, such as electrode breakage due to volume expansion, electrode loss conductivity due to active material peeling from the surface of the current collector, capacity degradation and cycle life reduction due to continuous exposure of fresh surfaces and repeated growth of the SEI film.
Based on the above, we propose a novel carbon-coated silicon and natural graphite composite anode material and preparation process, hopefully solving the defects in the prior art.
Disclosure of Invention
Aiming at the defects of the prior art, the invention provides a preparation process of a novel carbon-coated silicon and graphite composite anode material.
In order to achieve the above purpose, the invention provides a preparation process of a novel carbon-coated silicon and graphite composite anode material, which comprises the following steps:
(1) Modification of graphite: placing 40 parts of dried graphite in electromagnetic microwave or light wave equipment, modifying the graphite by electromagnetic microwave or light wave, and introducing nitrogen for protection in the process to obtain modified graphite;
(2) Preparation of a silicon suspension: dispersing 4-6 parts by weight of dried silicon nano powder in a mixed solvent with the mass of 6-9 times of that of the silicon nano powder, and obtaining silicon suspension through magnetic stirring and ultrasonic dispersion;
(3) Preparing a coating solution: taking 3-30 parts by weight of coating material, and dissolving the coating material by using a solvent with the mass being 3-5 times that of the coating material to obtain a coating solution;
(4) The coating process comprises the following steps: mixing the silicon suspension with the coating solution, uniformly stirring, and then spraying and drying the mixture to obtain silicon powder coated by the coating material;
(5) Carbonizing: placing the silicon powder coated by the coating material into a tube furnace, and simultaneously introducing inert atmosphere for protection for carbonization to obtain carbonized silicon powder;
(6) Mixing: putting modified graphite in the anode material into a ball mill, performing ball milling treatment, and then uniformly mixing the modified graphite with carbonized silicon powder, silicon carbide or silicon boride to finally prepare the anode material;
the negative electrode material comprises the following components in parts by mass:
40 parts of modified graphite;
5-7 parts of carbonized silicon powder;
1-2 parts of silicon carbide or 1-2 parts of silicon boride.
The negative electrode material comprises 1-2 parts by weight of silicon carbide or 1-2 parts by weight of silicon boride, wherein the addition of the silicon carbide can improve the service life of the negative electrode material due to high temperature resistance, wear resistance and good heat conductivity of the silicon carbide, and the addition of the silicon boride can improve the performance of a battery and enhance the capacity retention rate of the battery due to the combination of excellent performances of boron atoms and silicon atoms.
Further, in the step (1), the graphite is one of natural graphite or spherical graphite, the graphite is dried for 3-4 hours at the temperature of 60-90 ℃, the nitrogen flow rate is 100-110 mL/min, the electromagnetic microwave or light wave modification power is 800-1000 w, and the modification time is 40-60 s.
Further, in the step (2), the particle size of the silicon nano powder is 50-500nm, the silicon nano powder contains 10wt% of fumed silica, the particle size of the fumed silica is 7-40nm, the mixed solvent is ethanol, isopropanol, acetone or a mixed solution of one organic solvent of ethanol, isopropanol and acetone and water, the volume ratio of the organic solvent to the water is 9:1, the rotating speed of a magnetic stirrer is 400-2000r/min, the stirring time is 30-90min, the ultrasonic frequency is 10-40kHz, and the ultrasonic time is 30-90min. After the fumed silica component is added, the particle size of the fumed silica is smaller, the dispersibility is better, and the fumed silica can be used as crystal nucleus in the step (4) micron spraying and drying process, so that the silicon powder coated by the coating material obtained in the drying process is better and uniform, the particles are smaller, and the fumed silica can resist caking, so that the silicon powder coated by the coating material is prevented from caking.
Further, the coating material in the step (3) is at least one of phenolic resin, epoxy resin, urea-formaldehyde resin, furfural resin, polyvinyl alcohol, polyethylene glycol, polyethylene oxide, polyvinylidene fluoride, acrylic resin, polyvinyl chloride, coal pitch, petroleum pitch, mesophase pitch, coal tar, glucose, sucrose, citric acid and chitosan, and the solvent is one of acetone, ethanol, xylene, ethyl acetate, tetrahydrofuran, ethyl acetate, methyl butyl ketone and xylene.
In the step (4), the mixed solution of the silicon suspension and the coating solution is sprayed out through 1-10 mu m micropores, and the silicon powder coated by the coating material is obtained by hot air drying at the temperature of 100-200 ℃.
Further, in the step (5), during the carbonization treatment, the carbonization treatment temperature is 600-1200 ℃, the heating rate is 1-5 ℃/min, the carbonization time is 3.5-5h, and the inert atmosphere is one of nitrogen, argon and helium, preferably helium. When helium is adopted, the helium can enter the material for internal protection because the radius is smaller, the effect is better, and the helium can be recycled.
Further, in the step (6), the ball milling rotating speed is 500-2000r/min, and the time is 0-2h.
Further, in the negative electrode material, the silicon content is 5-15%, the grain diameter is 10-15 mu m, and the tap density is 0.9-1.2g/cm 3 The true density is 2.9-3.2g/cm 3 。
Compared with the prior art, the invention provides a novel carbon-coated silicon and graphite composite negative electrode material and a preparation process thereof, and the novel carbon-coated silicon and graphite composite negative electrode material has the following beneficial effects:
the invention does not limit the sources and equipment of the raw materials, and the silicon-carbon composite anode material produced by the method has simple process, low cost, suitability for mass production and excellent and stable product performance.
The invention provides a novel simple and efficient preparation method, which improves the performance of the silicon-carbon composite anode material. The preparation process and the silicon-carbon material are suitable for the negative electrode material of the lithium ion battery, can effectively improve the cycle performance and the multiplying power performance of the lithium ion battery, and have wide application prospects.
According to the preparation method, the carbon material is coated on the surface of the silicon by using a carbon coating technology, the cycling stability of the silicon negative electrode is improved after the carbon material is compounded with graphite, the preparation technology can realize low-cost modified graphite negative electrode and is compounded with the carbon-coated silicon material, and a technical path of the silicon-carbon negative electrode material is provided.
In conclusion, the novel preparation process of the silicon-carbon composite anode material has the advantages of simplicity, high efficiency and low cost, and has great practical application potential and market value.
Detailed Description
The technical solutions of the embodiments of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention, and it is apparent that the described embodiments are only some embodiments of the present invention, not all embodiments. All other embodiments, which can be made by those skilled in the art based on the embodiments of the invention without making any inventive effort, are intended to be within the scope of the invention.
Embodiment 1, a novel carbon-coated silicon and graphite composite anode material comprises the following components in parts by mass: 40 parts of modified graphite; 6 parts of carbonized silicon powder.
The preparation method comprises the following steps:
(1) Modification of graphite: placing 40 parts of dried natural graphite in electromagnetic microwave equipment for electromagnetic microwave modification, and introducing nitrogen for protection in the process to obtain modified graphite, wherein the graphite is dried for 3 hours at the temperature of 60-70 ℃, the flow rate of the nitrogen is 100-110 mL/min, the electromagnetic microwave modification power is 800w, and the modification time is 40s;
(2) Preparation of a silicon suspension: dispersing 4.5 parts by mass of dried silicon nano powder and 0.5 part by mass of fumed silica in a mixed solvent of ethanol and water, wherein the mass ratio of the ethanol to the water is 9:1, and carrying out magnetic stirring and ultrasonic dispersion to obtain a silicon suspension, wherein the particle size of the silicon nano powder is 50-500nm, the particle size of the fumed silica is 7-40nm, the rotating speed of a magnetic stirrer is 800r/min, the stirring time is 40min, the ultrasonic frequency is 20kHz, and the ultrasonic time is 40min;
(3) Preparing a coating solution: taking 6 parts by weight of phenolic resin, and dissolving the phenolic resin by adopting acetone with the mass being 4 times of that of the phenolic resin to obtain silicon powder coated by a coating material;
(4) The coating process comprises the following steps: mixing the silicon suspension with the coating solution, stirring uniformly, spraying out through 1-10 mu m micropores, and drying at 100-120 ℃ by hot air to obtain silicon powder coated by the coating material;
(5) Carbonizing: placing the silicon powder coated by the coating material in a tube furnace, and simultaneously introducing nitrogen for protection for carbonization, wherein in the carbonization treatment process, the carbonization treatment temperature is 600-900 ℃, the heating rate is 2 ℃/min, and the carbonization time is 4 hours, so as to obtain carbonized silicon powder;
(6) Mixing: putting modified graphite in the anode material into a ball mill, performing ball milling treatment at the ball milling speed of 500r/min for 1h, and uniformly mixing with other components to obtain the anode material, wherein the silicon content is 11.2%, the particle size is 10-15 mu m, and the tap density is 1.01g/cm 3 The true density is 2.9g/cm 3 。
Embodiment 2, a novel carbon-coated silicon and graphite composite anode material comprises the following components in parts by mass: 40 parts of modified graphite; 7 parts of carbonized silicon powder; 1 part of silicon carbide.
The preparation method comprises the following steps:
(1) Modification of graphite: placing 40 parts of dried natural crystalline flake graphite into electro-optical wave equipment for light wave modification, and introducing nitrogen for protection in the process to obtain modified graphite, wherein the graphite is dried for 3 hours at the temperature of 70-90 ℃, the flow rate of the nitrogen is 100-110 mL/min, the light wave modification power is 1000w, and the modification time is 1min;
(2) Preparation of a silicon suspension: dispersing 5.4 parts by mass of dried silicon nano powder and 0.6 part by mass of fumed silica in isopropanol which is 8 times by mass of the silicon nano powder, and magnetically stirring and ultrasonically dispersing to obtain a silicon suspension, wherein the particle size of the silicon nano powder is 50-500nm, the particle size of the fumed silica is 7-40nm, the rotating speed of a magnetic stirrer is 1500r/min, the stirring time is 60min, the ultrasonic frequency is 30kHz, and the ultrasonic time is 60min;
(3) Preparing a coating solution: taking 12 parts by weight of polyethylene oxide, and dissolving the polyethylene oxide by using dimethylbenzene with the mass being 5 times that of the polyethylene oxide to obtain a coating solution;
(4) The coating process comprises the following steps: mixing the silicon suspension with the coating solution, stirring uniformly, spraying out through 1-10 mu m micropores, and drying at the temperature of 150-200 ℃ by hot air to obtain silicon powder coated by the coating material;
(5) Carbonizing: placing the silicon powder coated by the coating material in a tube furnace, and simultaneously introducing argon for protection for carbonization, wherein in the carbonization treatment process, the carbonization treatment temperature is 900-1100 ℃, the heating rate is 4 ℃/min, and the carbonization time is 5 hours, so as to obtain carbonized silicon powder;
(6) Mixing: putting modified graphite and silicon boride in the anode material into a ball mill, performing ball milling treatment at the ball milling speed of 1000r/min for 2 hours, and then uniformly mixing with other components to finally obtain the anode material, wherein the silicon content is 13.4%, the particle size is 10-15 mu m, and the tap density is 1.11g/cm 3 The true density is 3.0g/cm 3 。
Embodiment 3, a novel carbon-coated silicon and graphite composite anode material comprises the following components in parts by mass: 40 parts of modified graphite; 7 parts of carbonized silicon powder; 1 part of silicon boride.
The preparation method comprises the following steps:
(1) Modification of graphite: putting 40 parts of dried spherical graphite into electromagnetic microwave equipment for electromagnetic microwave modification, and introducing nitrogen for protection in the process to obtain modified graphite, wherein the graphite is dried for 3 hours at the temperature of 70-90 ℃, the flow rate of the nitrogen is 100-110 mL/min, the electromagnetic microwave modification power is 1000w, and the modification time is 1min;
(2) Preparation of a silicon suspension: dispersing 5.4 parts by mass of dried silicon nano powder and 0.6 part by mass of fumed silica in a mixed solvent of isopropanol and water, wherein the mass ratio of the isopropanol to the water is 9:1, and carrying out magnetic stirring and ultrasonic dispersion to obtain a silicon suspension, wherein the particle size of the silicon nano powder is 50-500nm, the particle size of the fumed silica is 7-40nm, the rotating speed of a magnetic stirrer is 1500r/min, the stirring time is 60min, the ultrasonic frequency is 30KHz, and the ultrasonic time is 60min;
(3) Preparing a coating solution: taking 15 parts by weight of glucose, and dissolving the glucose by adopting methyl butyl ketone with the mass being 5 times that of the glucose to obtain a coating solution;
(4) The coating process comprises the following steps: mixing the silicon suspension with the coating solution, stirring uniformly, spraying out through 1-10 mu m micropores, and drying at the temperature of 150-200 ℃ by hot air to obtain silicon powder coated by the coating material;
(5) Carbonizing: placing the silicon powder coated by the coating material in a tube furnace, and simultaneously introducing helium for protection for carbonization, wherein in the carbonization treatment process, the carbonization treatment temperature is 900-1100 ℃, the heating rate is 3 ℃/min, and the carbonization time is 5 hours, so as to obtain carbonized silicon powder;
(6) Mixing: putting modified graphite and silicon boride in the anode material into a ball mill, performing ball milling treatment at a ball milling speed of 1500r/min for 2 hours, and then uniformly mixing with other components to obtain the anode material, wherein the silicon content is 13.6%, the particle size is 10-15 mu m, and the tap density is 1.13g/cm 3 The true density is 3.10g/cm 3 。
In example 4, 1 part of silicon boride was added to the negative electrode material of example 1, and the other steps are the same as in example 1, and are not repeated.
Comparative example 1 in step (6) of example 3, silicon powder after carbonization was also added to the ball mill and mixed during the ball milling process, and the other steps are the same as in example 3, and are not repeated.
Comparative example 2 in step (2) of example 3, "5.4 parts of silicon nano-powder and 0.6 parts of fumed silica" was changed to 6 parts of silicon nano-powder, and the other steps are the same as in example 3, and are not repeated.
Comparative example 3 in step (6) of example 1, "hot air drying at 100-120℃through 1-10 μm micropores" was changed to direct solvent evaporation drying, and the other steps are the same as in example 1, and are not described in detail.
In comparative example 4, the modified graphite in example 1 was replaced with unmodified graphite, and the other matters in example 1 are not described in detail.
The negative electrode materials prepared in examples and comparative examples were used as a negative electrode active material according to the following: conductive agent: binder = 94.8:2.2: and 3, uniformly mixing the materials in a mass ratio, coating the materials on a copper foil current collector, and drying to obtain a negative electrode plate for standby.
The obtained battery assembled by the stage sheets was tested, with lithium sheets as a counter electrode, with a polymer porous membrane PP as a separator, and with LiPF 6 Dissolved in a mixed solvent EC: DEC: the solution in DMC (1:1:1) was used as an electrolyte in an argon glove box (oxygen and water values were controlled to be the same as those in the argon glove box<Less than 1 ppm) to form a button cell. The battery manufactured by using the basic conditions is subjected to capacity and first coulombic efficiency test by adopting a blue electric system, the charging current is 0.1C, the discharging current is 0.1C, the charging and discharging voltage range is 5mV-2.0V, and the first discharging specific capacity and the first efficiency test result are shown in table 1.
TABLE 1 results of Performance test of the above examples and comparative examples
| Sequence number | Specific capacity of first discharge, mAh/g | First time efficiency, percent |
| Example 1 | 645 | 95.1 |
| Example 2 | 646 | 95.3 |
| Example 3 | 648 | 95.4 |
| Example 4 | 659 | 96.1 |
| Comparative example 1 | 621 | 92.2 |
| Comparative example 2 | 631 | 93.0 |
| Comparative example 3 | 613 | 90.2 |
| Comparative example 4 | 590 | 89.3 |
As can be seen from the data in the table, the test data of the examples 1-4 are all good, the specific capacity of the first discharge is more than or equal to 645mAh/g, and the first efficiency is more than 95%; comparison of the test data of example 1 and example 4 shows that the addition of silicon boride can improve cell performance; the data of comparative example 1 show that if carbonized silicon powder is ball milled together, the original coating layer is destroyed, and the battery performance is affected; the data of comparative example 2 shows that fumed silica can improve battery performance; the data of comparative example 3 shows that the coating mode has a large influence on the final battery performance; the data of comparative example 4 shows that the negative electrode material prepared from unmodified graphite has poor final properties.
Although embodiments of the present invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made therein without departing from the principles and spirit of the invention, the scope of which is defined in the appended claims and their equivalents.
Claims (8)
1. The preparation process of the carbon-coated silicon-graphite composite anode material is characterized by comprising the following steps of:
(1) Modification of graphite: placing 40 parts of dried graphite in electromagnetic microwave equipment for electromagnetic microwave modification, and introducing nitrogen for protection in the process to obtain modified graphite;
(2) Preparation of a silicon suspension: dispersing 4-6 parts by weight of dried silicon nano powder in a mixed solvent with the mass of 6-9 times of that of the silicon nano powder, and magnetically stirring and ultrasonically dispersing to obtain a silicon suspension, wherein the silicon nano powder contains 10wt% of fumed silica;
(3) Preparing a coating solution: taking 3-30 parts by weight of coating material, and dissolving the coating material by using a solvent with the mass being 3-5 times that of the coating material to obtain a coating solution;
(4) The coating process comprises the following steps: mixing the silicon suspension with the coating solution, uniformly stirring, and then carrying out micron spray drying to obtain silicon powder coated by the coating material;
(5) Carbonizing: placing the silicon powder coated by the coating material in a tube furnace, and simultaneously introducing inert atmosphere for protection and carbonizing to obtain carbon-coated silicon powder;
(6) Mixing: putting the modified graphite into a ball mill, performing ball milling treatment, and then uniformly mixing the modified graphite with carbon-coated silicon powder, silicon carbide or silicon boride to finally prepare a negative electrode material;
the negative electrode material comprises the following components in parts by mass:
40 parts of modified graphite;
5-7 parts of carbon-coated silicon powder;
1-2 parts of silicon carbide or 1-2 parts of silicon boride.
2. The process for preparing the negative electrode material by compounding carbon-coated silicon and graphite according to claim 1, wherein in the step (1), the graphite is one of natural graphite or spherical graphite, the graphite is dried for 3-4 hours at the temperature of 60-90 ℃, the nitrogen flow rate is 100-110 mL/min, the electromagnetic microwave modification power is 800-1000 w, and the modification time is 40-60 s.
3. The process for preparing the carbon-coated silicon-graphite composite anode material according to claim 1, wherein in the step (2), the silicon nano powder has a particle size of 50-500nm, the fumed silica has a particle size of 7-40nm, the mixed solvent is a mixture of ethanol, isopropanol and acetone or a mixed solution of one of ethanol, isopropanol and acetone and water, the volume ratio of the organic solvent to the water is 9:1, the rotation speed of a magnetic stirrer is 400-2000r/min, the stirring time is 30-90min, the ultrasonic frequency is 10-40kHz, and the ultrasonic time is 30-90min.
4. The process for preparing the carbon-coated silicon-graphite composite anode material according to claim 1, wherein the coating material in the step (3) is at least one of phenolic resin, epoxy resin, urea resin, furfural resin, polyvinyl alcohol, polyethylene glycol, polyethylene oxide, polyvinylidene fluoride, acrylic resin, polyvinyl chloride, coal pitch, petroleum pitch, mesophase pitch, coal tar, glucose, sucrose, citric acid and chitosan, and the solvent is one of acetone, ethanol, xylene, ethyl acetate, tetrahydrofuran, methyl butyl ketone and xylene.
5. The process for preparing a carbon-coated silicon-graphite composite negative electrode material according to claim 1, wherein in the step (4), the micron spraying process is to spray the mixed solution of the silicon suspension and the coating solution through 1-10 μm micropores, and hot air drying is performed at a temperature of 100-200 ℃ to obtain the silicon powder coated by the coating material.
6. The process for preparing the carbon-coated silicon-graphite composite anode material according to claim 1, wherein in the step (5), the carbonization treatment temperature is 600-1200 ℃, the heating rate is 1-5 ℃/min, and the carbonization time is 3.5-5h in the carbonization treatment process, and the inert atmosphere is one of nitrogen, argon and helium.
7. The process for preparing the carbon-coated silicon-graphite composite anode material according to claim 1, wherein in the step (6), the ball milling speed is 500-2000r/min for 1-2h.
8. The process for preparing a negative electrode material composited by carbon-coated silicon and graphite as claimed in claim 1, wherein the silicon mass content in the negative electrode material is 5% -15%, the particle size of the negative electrode material is 10-15 μm, and the tap density is 0.9-1.2g/cm 3 The true density is 2.9-3.2g/cm 3 。
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| CN110085842A (en) * | 2019-05-10 | 2019-08-02 | 山西大学 | A kind of silicon-carbon composite cathode material and preparation method thereof |
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| CN110085842A (en) * | 2019-05-10 | 2019-08-02 | 山西大学 | A kind of silicon-carbon composite cathode material and preparation method thereof |
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