CN114497518A - Negative active material, preparation method thereof and negative pole piece - Google Patents
Negative active material, preparation method thereof and negative pole piece Download PDFInfo
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- 239000007773 negative electrode material Substances 0.000 title claims abstract description 48
- 238000002360 preparation method Methods 0.000 title abstract description 15
- 239000002243 precursor Substances 0.000 claims abstract description 25
- 238000000034 method Methods 0.000 claims abstract description 21
- 239000010426 asphalt Substances 0.000 claims abstract description 19
- BLRPTPMANUNPDV-UHFFFAOYSA-N Silane Chemical compound [SiH4] BLRPTPMANUNPDV-UHFFFAOYSA-N 0.000 claims abstract description 12
- 229910000077 silane Inorganic materials 0.000 claims abstract description 12
- 150000001336 alkenes Chemical class 0.000 claims abstract description 8
- 150000001345 alkine derivatives Chemical class 0.000 claims abstract description 8
- 239000007770 graphite material Substances 0.000 claims abstract description 8
- JRZJOMJEPLMPRA-UHFFFAOYSA-N olefin Natural products CCCCCCCC=C JRZJOMJEPLMPRA-UHFFFAOYSA-N 0.000 claims abstract description 8
- 238000002156 mixing Methods 0.000 claims abstract description 7
- 239000006182 cathode active material Substances 0.000 claims abstract description 5
- 239000007789 gas Substances 0.000 claims description 25
- 238000005273 aeration Methods 0.000 claims description 20
- 239000002904 solvent Substances 0.000 claims description 14
- 239000006183 anode active material Substances 0.000 claims description 13
- XKRFYHLGVUSROY-UHFFFAOYSA-N Argon Chemical compound [Ar] XKRFYHLGVUSROY-UHFFFAOYSA-N 0.000 claims description 12
- 238000001035 drying Methods 0.000 claims description 12
- 239000011312 pitch solution Substances 0.000 claims description 9
- 238000003763 carbonization Methods 0.000 claims description 8
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- 229910052786 argon Inorganic materials 0.000 claims description 6
- 230000008569 process Effects 0.000 claims description 5
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- 239000000243 solution Substances 0.000 claims 2
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- 229910052710 silicon Inorganic materials 0.000 abstract description 20
- 239000010703 silicon Substances 0.000 abstract description 20
- HBBGRARXTFLTSG-UHFFFAOYSA-N Lithium ion Chemical compound [Li+] HBBGRARXTFLTSG-UHFFFAOYSA-N 0.000 abstract description 13
- 239000010439 graphite Substances 0.000 abstract description 13
- 229910002804 graphite Inorganic materials 0.000 abstract description 13
- 229910001416 lithium ion Inorganic materials 0.000 abstract description 13
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- 239000000919 ceramic Substances 0.000 description 7
- 238000000576 coating method Methods 0.000 description 6
- 230000000052 comparative effect Effects 0.000 description 6
- 229910052573 porcelain Inorganic materials 0.000 description 6
- YLQBMQCUIZJEEH-UHFFFAOYSA-N tetrahydrofuran Natural products C=1C=COC=1 YLQBMQCUIZJEEH-UHFFFAOYSA-N 0.000 description 6
- VGGSQFUCUMXWEO-UHFFFAOYSA-N Ethene Chemical compound C=C VGGSQFUCUMXWEO-UHFFFAOYSA-N 0.000 description 5
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- 239000011267 electrode slurry Substances 0.000 description 5
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- WHXSMMKQMYFTQS-UHFFFAOYSA-N Lithium Chemical compound [Li] WHXSMMKQMYFTQS-UHFFFAOYSA-N 0.000 description 2
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- DPXJVFZANSGRMM-UHFFFAOYSA-N acetic acid;2,3,4,5,6-pentahydroxyhexanal;sodium Chemical compound [Na].CC(O)=O.OCC(O)C(O)C(O)C(O)C=O DPXJVFZANSGRMM-UHFFFAOYSA-N 0.000 description 2
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- 238000005056 compaction Methods 0.000 description 2
- 239000006258 conductive agent Substances 0.000 description 2
- 238000005520 cutting process Methods 0.000 description 2
- 238000011161 development Methods 0.000 description 2
- 238000004146 energy storage Methods 0.000 description 2
- 238000010030 laminating Methods 0.000 description 2
- 229910052744 lithium Inorganic materials 0.000 description 2
- 239000000203 mixture Substances 0.000 description 2
- 238000012986 modification Methods 0.000 description 2
- 230000004048 modification Effects 0.000 description 2
- 229920002981 polyvinylidene fluoride Polymers 0.000 description 2
- 238000005096 rolling process Methods 0.000 description 2
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- 239000002002 slurry Substances 0.000 description 2
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 2
- 238000003466 welding Methods 0.000 description 2
- RYGMFSIKBFXOCR-UHFFFAOYSA-N Copper Chemical compound [Cu] RYGMFSIKBFXOCR-UHFFFAOYSA-N 0.000 description 1
- 229910018540 Si C Inorganic materials 0.000 description 1
- 229910008045 Si-Si Inorganic materials 0.000 description 1
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N Silicium dioxide Chemical compound O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 description 1
- 229910006411 Si—Si Inorganic materials 0.000 description 1
- 229910052782 aluminium Inorganic materials 0.000 description 1
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 description 1
- PNEYBMLMFCGWSK-UHFFFAOYSA-N aluminium oxide Inorganic materials [O-2].[O-2].[O-2].[Al+3].[Al+3] PNEYBMLMFCGWSK-UHFFFAOYSA-N 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
- 235000010948 carboxy methyl cellulose Nutrition 0.000 description 1
- 239000010406 cathode material Substances 0.000 description 1
- 238000005229 chemical vapour deposition Methods 0.000 description 1
- 239000002131 composite material Substances 0.000 description 1
- 238000013329 compounding Methods 0.000 description 1
- 238000001816 cooling Methods 0.000 description 1
- 239000011889 copper foil Substances 0.000 description 1
- 239000011258 core-shell material Substances 0.000 description 1
- 230000001351 cycling effect Effects 0.000 description 1
- 238000001514 detection method Methods 0.000 description 1
- 239000002270 dispersing agent Substances 0.000 description 1
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- 239000007788 liquid Substances 0.000 description 1
- GELKBWJHTRAYNV-UHFFFAOYSA-K lithium iron phosphate Chemical compound [Li+].[Fe+2].[O-]P([O-])([O-])=O GELKBWJHTRAYNV-UHFFFAOYSA-K 0.000 description 1
- 229910052751 metal Inorganic materials 0.000 description 1
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- 239000002135 nanosheet Substances 0.000 description 1
- 239000002071 nanotube Substances 0.000 description 1
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- 238000011056 performance test Methods 0.000 description 1
- 239000011295 pitch Substances 0.000 description 1
- 239000002985 plastic film Substances 0.000 description 1
- 229920006255 plastic film Polymers 0.000 description 1
- 239000007774 positive electrode material Substances 0.000 description 1
- 230000009467 reduction Effects 0.000 description 1
- 229910010271 silicon carbide Inorganic materials 0.000 description 1
- 229910052814 silicon oxide Inorganic materials 0.000 description 1
- 239000007784 solid electrolyte Substances 0.000 description 1
- 229920003048 styrene butadiene rubber Polymers 0.000 description 1
- 238000005979 thermal decomposition reaction Methods 0.000 description 1
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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
- H01M4/38—Selection of substances as active materials, active masses, active liquids of elements or alloys
- H01M4/386—Silicon or alloys based on silicon
-
- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
- C01B32/00—Carbon; Compounds thereof
- C01B32/05—Preparation or purification of carbon not covered by groups C01B32/15, C01B32/20, C01B32/25, C01B32/30
-
- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
- C01B33/00—Silicon; Compounds thereof
- C01B33/02—Silicon
- C01B33/021—Preparation
- C01B33/027—Preparation by decomposition or reduction of gaseous or vaporised silicon compounds other than silica or silica-containing material
-
- 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
- H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
- H01M4/134—Electrodes based on metals, Si or alloys
-
- 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
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M4/00—Electrodes
- H01M4/02—Electrodes composed of, or comprising, active material
- H01M4/62—Selection of inactive substances as ingredients for active masses, e.g. binders, fillers
- H01M4/628—Inhibitors, e.g. gassing inhibitors, corrosion inhibitors
-
- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
- C01P2004/00—Particle morphology
- C01P2004/80—Particles consisting of a mixture of two or more inorganic phases
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- Chemical & Material Sciences (AREA)
- Chemical Kinetics & Catalysis (AREA)
- Electrochemistry (AREA)
- General Chemical & Material Sciences (AREA)
- Organic Chemistry (AREA)
- Engineering & Computer Science (AREA)
- Materials Engineering (AREA)
- Inorganic Chemistry (AREA)
- Manufacturing & Machinery (AREA)
- Battery Electrode And Active Subsutance (AREA)
Abstract
The invention relates to the technical field of lithium ion batteries, in particular to a negative active material, a preparation method thereof and a negative pole piece. The method comprises the following steps of putting a graphite material into a tubular furnace, and introducing silane gas; introducing olefin or alkyne gas on the basis to obtain a precursor of the cathode active material; finally, uniformly mixing the anode active substance precursor with the asphalt solution, and performing post-treatment to obtain an anode active substance; and further using the prepared negative active material for preparing a negative pole piece. After the negative active material is embedded into the sub-nanometer silicon clusters on the graphite surface, the carbon layer is coated on the particle surface, so that the direct exposure of the silicon surface to the electrolyte is reduced to the maximum extent, the side reaction is reduced, the particle conductivity is increased, and the performance of the lithium ion battery is improved.
Description
Technical Field
The invention relates to the technical field of lithium ion batteries, in particular to a negative active material, a preparation method thereof and a negative pole piece.
Background
Lithium ion battery as energy storage equipment with highest energy conversion efficiency at presentThe method plays an important role in the new energy industry. In recent decades, with the popularization of portable electronic products and power batteries, the demand for higher energy density of the batteries has increased, and among them, the development of high-capacity negative electrode materials instead of the conventional graphite anode is the most effective way to achieve higher energy density. Silicon (Si) has extremely high theoretical specific capacity (3592 mAh) through alloying reaction with lithium ions-1) It is considered as a material with great development potential. Most of the silicon negative electrodes are prepared by methods such as metal alloying, silicon oxide reduction, sol-gel, chemical vapor deposition, mechanical crushing and the like to obtain larger shapes (nanowires, nanosheets, nanotubes, hollow structures and core-shell structures). In commercial use, the composite material is generally prepared by compounding the carbon-based material with the carbon-based material due to the combination of cost and performance.
Since silicon expands in volume during lithium intercalation, the structure of silicon is severely collapsed and a Solid Electrolyte Interphase (SEI) is unstable, which not only causes particles to lose contact with a current collector due to expansion and fracture, but also constantly exposes new surfaces generated after fracture to an electrolyte, and affects stable formation of an SEI film. To alleviate the negative effects of volume expansion, efforts by many researchers have demonstrated that reducing the particle size to the nanometer scale allows silicon to withstand the tremendous strains and provide its high capacity electrochemical performance. Silicon inevitably produces an oxide layer, and although it is only 2-3nm thick, it occupies a significant weight for sub-nanometer sized (about 1nm) silicon, thereby reducing the gram capacity of the material and hindering electron conduction.
Disclosure of Invention
In order to improve the capacity of the lithium ion battery, have higher safety stability and longer cycle life, and simultaneously have higher energy density to meet higher requirements of mobile equipment, power batteries and energy storage equipment, the invention aims to provide a negative electrode active material, a preparation method thereof and a negative electrode plate. The method comprises the following steps of putting a graphite material into a tubular furnace, and introducing silane gas; introducing olefin or alkyne gas on the basis to obtain a precursor of the cathode active material; finally, uniformly mixing the anode active substance precursor with the asphalt solution, and performing post-treatment to obtain an anode active substance; and further using the prepared negative active material for preparing a negative pole piece. After the negative active material is embedded into the sub-nanometer silicon clusters on the graphite surface, the carbon layer is coated on the particle surface, so that the direct exposure of the silicon surface to the electrolyte is reduced to the maximum extent, the side reaction is reduced, the particle conductivity is increased, and the performance of the lithium ion battery is improved.
The purpose of the invention can be realized by the following technical scheme:
a first object of the present invention is to provide a method for preparing an anode active material, comprising the steps of:
(1) putting a graphite material into a tubular furnace, and introducing silane gas;
(2) introducing olefin or alkyne gas on the basis of the step (1) to obtain a precursor of the cathode active material;
(3) and (3) uniformly mixing the anode active material precursor obtained in the step (2) with an asphalt solution, and carrying out post-treatment to obtain the anode active material.
In one embodiment of the present invention, in the step (1), the aeration rate is 10 to 100cm during the silane gas aeration3 min-1The aeration temperature is 400-600 ℃, and the aeration time is 10-120 min.
In one embodiment of the present invention, in the step (2), the aeration rate is 10 to 100cm during the aeration of the olefin or alkyne gas3 min-1The ventilation time is 10-120 min.
In one embodiment of the present invention, in the step (3), the anode active material precursor cooled to room temperature is mixed with the pitch solution.
In one embodiment of the invention, the bitumen solution is obtained by dissolving bitumen in a hydrocarbon solvent.
In one embodiment of the present invention, in the step (3), the mass ratio of the negative electrode active material precursor to the pitch solution is 1: 10-10: 1.
in one embodiment of the present invention, in the step (3), the post-treatment is carbonization after drying.
In one embodiment of the invention, in the drying process, the drying temperature is 50-200 ℃ under a vacuum state; in the carbonization process, the reactor is in an argon state and the carbonization temperature is 500-1000 ℃.
A second object of the present invention is to provide a negative electrode active material prepared by the above method.
The third purpose of the invention is to provide a negative pole piece, and the negative active material for preparing the negative pole piece is the negative active material.
Compared with the prior art, the invention has the following beneficial effects:
(1) according to the preparation method of the negative active material, silicon nuclei are generated on the surface of graphite by silicon in the process of heating and decomposing silane gas into silicon, and a silicon layer is formed on the basis; in the gas phase, ethylene is combined with silicon molecules into Si-C bonds to inhibit the formation of Si-Si bonds, thereby preventing the continuous growth of silicon nuclei, and finally leading to the formation of sub-nanometer-sized silicon clusters in the silane gas during thermal decomposition.
(2) According to the negative active material, after the sub-nanometer-sized silicon clusters are embedded in the graphite surface, the carbon layer is coated on the surface of the graphite, so that the direct exposure of the silicon surface to the electrolyte is reduced to the maximum extent, the side reaction is reduced, and the conductivity of graphite particles is increased.
Drawings
FIG. 1 is a graph of 1C/1C cycle performance at 25 ℃ of lithium ion batteries prepared in example 1 and comparative examples 1 and 2 of the present invention.
Detailed Description
The invention provides a preparation method of a negative active material, which comprises the following steps:
(1) putting a graphite material into a tubular furnace, and introducing silane gas;
(2) introducing olefin or alkyne gas on the basis of the step (1) to obtain a precursor of the cathode active material;
(3) and (3) uniformly mixing the anode active material precursor obtained in the step (2) with an asphalt solution, and carrying out post-treatment to obtain the anode active material.
In one embodiment of the present invention, in the step (1), the aeration rate is 10 to 100cm during the silane gas aeration3 min-1The aeration temperature is 400-600 ℃, and the aeration time is 10-120 min.
In one embodiment of the present invention, in the step (2), the aeration rate is 10-100cm during the introduction of the olefin or alkyne gas3 min-1The ventilation time is 10-120 min.
In one embodiment of the present invention, in the step (3), the anode active material precursor cooled to room temperature is mixed with the pitch solution.
In one embodiment of the invention, the bitumen solution is obtained by dissolving bitumen in a hydrocarbon solvent.
In one embodiment of the present invention, in the step (3), the mass ratio of the negative electrode active material precursor to the pitch solution is 1: 10-10: 1.
in one embodiment of the present invention, in the step (3), the post-treatment is carbonization after drying.
In one embodiment of the invention, in the drying process, the drying temperature is 50-200 ℃ under a vacuum state; in the carbonization process, the reactor is in an argon state and the carbonization temperature is 500-1000 ℃.
The present invention provides a negative electrode active material prepared by the above method.
The invention provides a negative pole piece, and a negative active material for preparing the negative pole piece is the negative active material.
The invention is described in detail below with reference to the figures and specific embodiments.
In the following examples, materials used are commercially available unless otherwise specified; the cycle performance test of the prepared lithium ion battery is a conventional detection means in the field.
Example 1
The embodiment provides a preparation method of a lithium ion battery.
(1) Preparation of negative electrode active material: placing 2g of commercial graphite material in a porcelain boat, placing the porcelain boat in a tube furnace, and introducing high-purity siliconAlkane gas at 400 deg.C for 100cm3 min-1Aeration at the rate of (3) for 10 minutes; then high-purity ethylene gas is introduced on the basis of the reaction pressure, and the concentration is 15cm3 min-1Ventilating for 60 minutes at the speed of (2) to obtain a precursor of the cathode active substance; after the mixture is cooled to room temperature, stirring the negative active material precursor and a pitch solution (the pitch solution takes tetrahydrofuran as a solvent, the mass ratio of pitch to tetrahydrofuran is 80: 20, and the mass ratio of the negative active material precursor to the pitch solution is 5: 1) at room temperature for 2 hours, and then drying the solvent in a vacuum oven at 60 ℃. Finally, carbonizing the mixture at 800 ℃ under argon to obtain the negative active material.
(2) Preparing positive active material slurry: 16.044kg of lithium iron phosphate (LFP), 0.42kg of superconducting carbon black conductive agent (SP) and 0.336kg of binding agent polyvinylidene fluoride (PVDF) are dry-mixed and stirred for 30 minutes, and then 13.2kg of solvent N-methyl pyrrolidone (NMP) is added and stirred for 6 hours, so that the positive electrode slurry with the viscosity of about 8000 mPas is finally obtained.
(3) Manufacturing a positive plate: and uniformly coating the positive electrode slurry on the front surface and the back surface of an aluminum foil with the thickness of 8 mm. The surface density is controlled at 24mg/cm in the coating process2Meanwhile, pole lug areas of 20mm are reserved on two sides; the coated pole piece passes through a 110 ℃ oven with the length of 20 meters at the speed of 3m/s to remove the solvent NMP, so as to obtain a positive pole piece; rolling the pole piece by a roller press to ensure that the compaction density reaches 2.85g/cm3Then, equally dividing the pole piece coil into an upper coil and a lower coil by laser slitting; and finally, cutting the anode plate into a 60cm long and 30cm wide anode plate by using a die.
(4) Preparation of negative electrode active material slurry: 16.044kg of the negative electrode active material prepared in the step (1), 0.35kg of superconducting carbon black conductive agent (SP) and 0.336kg of carboxymethyl cellulose sodium (CMC) as a dispersing agent are dry-mixed and stirred for 30 minutes, and then 13.2kg of solvent water and 0.336kg of Styrene Butadiene Rubber (SBR) as a binding agent are added and stirred for 6 hours, and finally negative electrode slurry with the viscosity of about 5000 mPas is obtained.
(5) Manufacturing a negative pole piece: and uniformly coating the negative electrode slurry on the front surface and the back surface of a copper foil with the thickness of 8 mm. The surface density is controlled to be 17mg/cm in the coating process2Meanwhile, pole lug areas of 20mm are reserved on two sides; will be coated withThe pole piece passes through a 110 ℃ oven with the length of 20m at the speed of 3m/s to remove solvent water, so as to obtain a negative pole piece; rolling the pole piece by a roller press to ensure that the compaction density reaches 1.7g/cm3Then, equally dividing the pole piece coil into an upper coil and a lower coil by laser slitting; then cutting the anode plate into a cathode plate with the length of 65cm and the width of 35cm by using a die to complete the manufacture.
(6) Manufacturing a ceramic diaphragm: the front and back surfaces of the diaphragm are coated with nano alumina coatings, and the solvent is removed through drying in a vacuum oven, so that the porous ceramic diaphragm with high porosity and high wettability is formed.
(7) Manufacturing a dry battery core: and (3) repeatedly laminating the positive plate, the negative plate and the ceramic diaphragm in the steps (3), (5) and (6) in sequence according to the sequence of ceramic diaphragm-negative plate-ceramic diaphragm-positive plate-ceramic diaphragm, wherein in the laminating process: firstly, the directions of the lugs of the positive electrode and the negative electrode are opposite; and the positive plate is completely arranged in the middle of the negative plate. And then welding the laminated anode tab and the laminated cathode tab together to form a full tab.
(8) Assembling a battery, namely applying 500N pressure on a dry battery core at a certain temperature to enable a positive plate, a negative plate and a ceramic diaphragm to be in close contact with each other, then placing the dry battery core into a shell of an aluminum-plastic film, respectively welding external lugs on all lugs of a positive electrode and a negative electrode, carrying out top sealing and side sealing on the shell, baking and injecting liquid into the battery core, and then manufacturing the battery according to a conventional manufacturing process of a soft package battery, thereby finally obtaining the method for improving the cycle performance by nanocrystallizing a silicon layer and coating surface carbon.
Example 2
Compared with the embodiment 1, the embodiment has the same steps except the step (1); the step (1) of the invention is as follows:
(1) preparation of negative electrode active material: placing 2g of commercial graphite material in a porcelain boat, placing the porcelain boat in a tube furnace, introducing high-purity silane gas, and heating at 400 deg.C for 100cm3 min-1Aeration at the rate of (3) for 10 minutes; then introducing high-purity ethylene gas with the volume of 10cm on the basis3 min-1Ventilating for 120 minutes at the speed of the anode active material to obtain a precursor of the anode active material; after it is cooled to room temperatureMixing a negative active material precursor and an asphalt solution (wherein tetrahydrofuran is used as a solvent in the asphalt solution, the mass ratio of asphalt to tetrahydrofuran is 80: 20, the mass ratio of the negative active material precursor to the asphalt solution is 1: 10, stirring at room temperature for 2 hours, drying the solvent in a vacuum oven at 50 ℃, and finally carbonizing at 500 ℃ under argon to obtain the negative active material.
Example 3
Compared with the embodiment 1, the embodiment has the same steps except the step (1); the step (1) of the invention is as follows:
(1) preparation of negative electrode active material: placing 2g of commercial graphite material in a porcelain boat, placing the porcelain boat in a tube furnace, introducing high-purity silane gas, and heating at 600 deg.C for 10cm3 min-1Aeration at a rate of (3) for 120 minutes; then high-purity ethylene gas is introduced on the basis of the above reaction pressure, and the gas flow rate is 100cm3 min-1Ventilating for 10 minutes at the speed of the anode active material to obtain a precursor of the anode active material; and cooling to room temperature, mixing the negative active material precursor with an asphalt solution (tetrahydrofuran is used as a solvent in the asphalt solution, the mass ratio of the asphalt to the tetrahydrofuran is 80: 20, the mass ratio of the negative active material precursor to the asphalt solution is 10: 1, stirring for 2 hours at room temperature, drying the solvent in a vacuum oven at 200 ℃, and finally carbonizing at 1000 ℃ under argon to obtain the negative active material.
Comparative example 1
In step 1 of example 1, the preparation process and materials used were the same as in example 1 except that ethylene gas was introduced.
Comparative example 2
In step 4 of example 1, the negative electrode active material used for the preparation of the negative electrode slurry was untreated commercial graphite, and the other preparation processes and materials used were the same as those of example 1.
FIG. 1 is a graph of 1C/1C cycle performance at 25 ℃ of lithium ion batteries prepared in example 1 and comparative examples 1 and 2; it can be seen from fig. 1 that the cycle performance of the lithium ion battery prepared in example 1 (the graphite surface is coated with nano-silicon and the surface is carbon-coated) is significantly better than that of the lithium ion battery prepared in comparative example 1 (only the graphite surface is coated with nano-silicon and carbon-coated) and comparative example 2 (the graphite is not treated).
This indicates that: after the graphite surface is coated with the nano silicon and the surface of the graphite surface is coated with carbon, the direct contact between the nano silicon and electrolyte can be reduced while lithium ion migration is not influenced, so that the side reaction on the silicon surface is reduced, the side reaction on a new interface generated by silicon volume expansion is avoided, the structural collapse of silicon is relieved, and the structural stability and the capacity cycling stability of the cathode material are improved.
The embodiments described above are described to facilitate an understanding and use of the invention by those skilled in the art. It will be readily apparent to those skilled in the art that various modifications to these embodiments may be made, and the generic principles described herein may be applied to other embodiments without the use of the inventive faculty. Therefore, the present invention is not limited to the above embodiments, and those skilled in the art should make improvements and modifications within the scope of the present invention based on the disclosure of the present invention.
Claims (10)
1. A method for producing a negative electrode active material, characterized by comprising the steps of:
(1) putting a graphite material into a tubular furnace, and introducing silane gas;
(2) introducing olefin or alkyne gas on the basis of the step (1) to obtain a precursor of the cathode active material;
(3) and (3) uniformly mixing the anode active material precursor obtained in the step (2) with an asphalt solution, and carrying out post-treatment to obtain the anode active material.
2. The method for preparing a negative electrode active material according to claim 1, wherein the aeration rate in the step (1) is 10 to 100cm during the aeration of the silane gas3 min-1The aeration temperature is 400-600 ℃, and the aeration time is 10-120 min.
3. The method for preparing a negative electrode active material according to claim 1, wherein in the step (2), the aeration rate is 10 to 100cm during the aeration of the olefin or alkyne gas3 min-1The ventilation time is 10-120 min.
4. The method for preparing the negative active material according to claim 1, wherein in the step (3), the negative active material precursor cooled to room temperature is mixed with the pitch solution.
5. The method according to claim 4, wherein the asphalt solution is a mixed solution obtained by mixing asphalt and a hydrocarbon solvent.
6. The method for preparing the negative electrode active material according to claim 1, wherein in the step (3), the mass ratio of the negative electrode active material precursor to the pitch solution is 1: 10-10: 1.
7. the method for preparing a negative electrode active material according to claim 1, wherein the post-treatment in the step (3) is drying and then carbonizing.
8. The method for preparing a negative active material according to claim 7, wherein the drying is performed under vacuum at a temperature of 50 to 200 ℃; in the carbonization process, the reactor is in an argon state and the carbonization temperature is 500-1000 ℃.
9. A negative electrode active material prepared by the method according to any one of claims 1 to 8.
10. A negative electrode sheet, characterized in that the negative electrode active material for producing the negative electrode sheet is the negative electrode active material according to claim 9.
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