CN116190621B - Silicon-based anode material, preparation method and application thereof - Google Patents

Silicon-based anode material, preparation method and application thereof Download PDF

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CN116190621B
CN116190621B CN202310468383.4A CN202310468383A CN116190621B CN 116190621 B CN116190621 B CN 116190621B CN 202310468383 A CN202310468383 A CN 202310468383A CN 116190621 B CN116190621 B CN 116190621B
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silicon
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carbon
graphite
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CN116190621A (en
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韩定宏
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Jiangsu Zenio New Energy Battery Technologies Co Ltd
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    • H01M4/583—Carbonaceous material, e.g. graphite-intercalation compounds or CFx
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Abstract

The invention relates to a silicon-based anode material, a preparation method and application thereof. The silicon-based anode material comprises a carbon matrix, a silicon-embedded layer, a silicon layer, a titanium nitride layer and a carbon sphere coating layer, wherein the silicon-embedded layer, the silicon layer, the titanium nitride layer and the carbon sphere coating layer are wrapped on the surface of the carbon matrix; the outer surface of the carbon matrix is provided with a porous structure, silicon is embedded into the porous structure, and the porous structure is combined with the carbon matrix to form a silicon-embedded layer of the carbon matrix; the outer coating layer of the embedded silicon layer is a silicon layer, a titanium nitride layer and a carbon pellet coating layer. The silicon-based anode material is a double-layer composite deposition layer, and has excellent compression resistance, good conductivity, high mechanical strength and large buffer space to relieve volume expansion; the comprehensive performance of the silicon-based carbon-containing anode material structure is optimized.

Description

Silicon-based anode material, preparation method and application thereof
Technical Field
The invention relates to the technical field of lithium ion batteries, in particular to a silicon-based negative electrode material, a preparation method and application thereof.
Background
Si material has 4200mAh/g ultrahigh theoretical capacity, which is more than 10 times of the existing commercial graphite negative electrode, and is recognized as the negative electrode material of the next generation high-energy density lithium ion battery by industry. However, the volume expansion is huge (> 300%) in the lithium intercalation process of the Si anode material, so that the problems of structural damage of the electrode active material, unstable electrochemical interface and the like are caused, and the cycle performance is poor; in addition, poor conductivity of Si results in poor rate performance.
The size of the silicon is reduced to the nanometer dimension, the absolute volume expansion of the silicon can be reduced, the structural pulverization caused by the stress in the process of lithium intercalation and deintercalation is reduced, and the circulation stability is improved. The porous micron Si can have the advantages of micron and nano materials at the same time, and the excellent porous structure can relieve the volume expansion, so that the porous micron Si is a key material for developing high-energy-density lithium ion batteries. Porous microsi also suffers from problems such as coating of the material into a pole piece, the huge pressure received on the porous microsi particles during calendaring of the pole piece can lead to structural cracking, leading to the generation of fresh interfaces and fine particles, which can form additional byproducts upon lithiation and electrical contact loss, which limits the application in the field of high energy density lithium ion batteries.
Disclosure of Invention
In order to solve the technical problems, the invention provides a silicon-based anode material, a preparation method and application thereof.
The invention is realized by the following scheme:
the first object of the invention is to provide a silicon-based anode material, which comprises a carbon matrix, a silicon-embedded layer, a silicon layer, a titanium nitride layer and a carbon pellet coating layer, wherein the silicon-embedded layer, the silicon layer, the titanium nitride layer and the carbon pellet coating layer are coated on the surface of the carbon matrix;
the outer surface of the carbon matrix is attached with a porous structure, and silicon is embedded into the porous structure to be combined with the carbon matrix to form a silicon-embedded layer of the carbon matrix; the outer coating layer of the embedded silicon layer is a silicon layer, a titanium nitride layer and a carbon pellet coating layer.
Further, the silicon-based anode material comprises a carbon matrix, and a silicon-embedded layer, a silicon layer, a titanium nitride layer and a carbon sphere coating layer which are sequentially coated on the surface of the carbon matrix.
In one embodiment of the invention, the carbon sphere coating layer surface is a plurality of carbon spheres.
In one embodiment of the invention, at least one of the following conditions is met:
a) The granularity of the silicon-based anode material is 2-25 mu m;
b) The carbon content of the silicon-based anode material is 22-85 wt% and the titanium content is 0.002-6 wt%.
In one embodiment of the invention, the following conditions are met:
the diameter of the carbon matrix is 2-19 mu m;
the thickness of the silicon-embedded layer is 0.01-0.5 mu m;
the thickness of the silicon layer is 0.05-5 mu m;
the thickness of the titanium nitride layer is 0.001-0.2 mu m;
the thickness of the carbon sphere coating layer is 0.001-0.3 mu m.
The second object of the present invention is to provide a method for preparing a silicon-based anode material, comprising the steps of:
(1) Mixing graphite material, alkaline material and water, performing hydrothermal reaction, washing and drying to obtain microporous graphite;
(2) Heating, washing, drying and sieving the microporous graphite obtained in the step (1) under the condition of mixed gas containing hydrogen to obtain porous graphite;
(3) Heating the porous graphite obtained in the step (2) for 20 min-5 h under the condition of inactive gas, and introducing mixed silane gas to perform silicon deposition to obtain a carbon matrix with a silicon layer on the surface;
(4) Heating the carbon matrix with the silicon layer on the surface obtained in the step (3) under the condition of inactive gas containing nitrogen, adding a titanium-containing load carrying hydrogen, and depositing a titanium nitride layer to obtain the carbon matrix with the silicon layer on the surface wrapped by the titanium nitride layer;
(5) Heating the carbon matrix with the silicon layer on the surface wrapped by the titanium nitride layer obtained in the step (4), introducing mixed gaseous carbon gas, and carrying out carbon deposition for a period of time; stopping introducing the mixed gaseous carbon gas, cooling to 400-700 ℃ and keeping the temperature constant to obtain the silicon-based anode material.
In one embodiment of the present invention, in step (1), at least one of the following conditions is satisfied:
(I) The particle size of the graphite material is 2-25 mu m;
(II) the mass ratio of the graphite material to the alkaline material is 100: 0.1-30;
(III) the mass concentration of the graphite material is 8-55 wt%;
(IV), hydrothermal reaction conditions: the heating temperature is 150-400 ℃ and the heating time is 4-24 hours;
And (V) the surface gap size of the microporous graphite is 0-15 nm.
In one embodiment of the present invention, in the step (1), the hydrothermal reaction is a conventional means in the art, preferably microwave heating is adopted, and the microwave heating has good controllability and better uniformity of material heating.
In one embodiment of the present invention, in the step (2), the heating temperature is 300 ℃ to 600 ℃ and the heating time is 6h to 24h; the particle size of the porous graphite is less than 6 mu m.
In one embodiment of the invention, in step (3), at least one of the following conditions is satisfied:
a) The mixed silane gas comprises silane gas and inactive mixed gas;
b) The heating temperature is 400-950 ℃;
c) The silicon content of the silicon-carbon precursor is 15-75wt%.
In one embodiment of the present invention, in the step (4), the flow ratio of the hydrogen gas to the inert gas containing nitrogen gas is 1 to 5:0.1 to 1.2.
In one embodiment of the present invention, in the step (4), the heating temperature is 720 ℃ to 1150 ℃.
In one embodiment of the invention, in step (5), at least one of the following conditions is satisfied: the heating temperature is 700-950 ℃; the carbon deposition time is 2 min-45 min; the mixed gaseous carbon gas includes a gaseous carbon gas and an inert gas.
The third object of the invention is to provide a negative electrode plate, which comprises a first binder, a graphite material, a conductive material, a modified additive, the silicon-based negative electrode material or the silicon-based negative electrode material prepared by the preparation method.
In one embodiment of the invention, the mass ratio of the mixture of the silicon-based anode material and the graphite material, the first binding substance and the modifying additive is 85-99: 0.2-8: 0.2-10; the concentration of the graphite material in the mixture is 35-95 wt%.
The fourth object of the present invention is to provide a method for preparing a negative electrode sheet, comprising the steps of: mixing and stirring a silicon-based anode material, a graphite material mixture, a first binding substance and a modifying additive, adding water to adjust viscosity to obtain silicon-containing bottom layer homogenate, and coating the silicon-containing bottom layer homogenate on an anode current collector to obtain a silicon-containing bottom layer; mixing and stirring graphite material, first binding substance and conductive material, adding water to regulate viscosity to obtain graphite-containing upper layer homogenate, coating the graphite-containing upper layer homogenate on a silicon-containing bottom layer to obtain a graphite-containing upper layer, and drying and rolling to obtain the negative plate.
In one embodiment of the invention, the silicon-containing underlayer of the current collector has a areal weight of 40g/m 2 ~350g/m 2 The method comprises the steps of carrying out a first treatment on the surface of the The surface weight of the graphite-containing upper layer in the current collector is 40g/m 2 ~350g/m 2 。
In one embodiment of the invention, the modifying additive is prepared by the following method: adding a conductive material and a second binding substance into an organic solvent, stirring, reacting, adding ethanol to obtain a precipitate, and carrying out solid-liquid separation to obtain a solid phase (the material bonded by the conductive material and the second binding substance), wherein the solid phase is the modified additive.
A fifth object of the present invention is to provide a secondary battery including the negative electrode sheet.
A sixth object of the present invention is to provide a method for manufacturing a secondary battery, comprising the steps of: and sequentially stacking and winding the negative electrode plate, the isolating film and the positive electrode plate to obtain a bare cell and welding the electrode lugs, putting the bare cell into a battery aluminum shell/soft-package aluminum-plastic film, sealing the top side, drying to remove water, injecting electrolyte into the battery shell, forming, fixing the capacity, exhausting and sealing to finally obtain the secondary battery.
The reason for forming the carbon globules is as follows: when the titanium nitride layer is formed, the titanium nitride on the surface part of the titanium nitride layer is coagulated to generate stable crystal nuclei, the coagulated crystal can be gradually enlarged, when the grain size of the crystal exceeds a critical value, the crystal nuclei are aggregated to form small-grain titanium nitride nodules, so that more small-grain titanium nitride nodules are formed on the surface of the titanium nitride layer, and a plurality of carbon pellets are formed by gaseous carbon deposition and carbon grains cover the titanium nitride layer and the small-grain titanium nitride nodules.
Compared with the prior art, the technical scheme of the invention has the following advantages:
according to the invention, through secondary porosification treatment on the carbon matrix, silicon is conveniently deposited and embedded into the carbon matrix, a silicon embedded layer and a subsequent silicon layer are formed, the titanium nitride deposited layer and a unique carbon pellet coating layer improve the conductivity of silicon, and the high-dispersion inert phase in the high-hardness titanium nitride alloy phase is beneficial to effectively buffer the volume expansion of active silicon, and the complete coating of an outer carbon pellet layer, so that the capability of the material for resisting external force extrusion is improved, the structural cracking condition is reduced, and the adaptability and strength of the material in the pole piece manufacturing process are facilitated. The modified additive not only improves the conductivity of the silicon-based negative electrode material and limits the volume expansion of silicon, but also strengthens the structure of the pole piece, and the integrity of the silicon-based negative electrode material, the graphite material and the first binding substance in the negative electrode piece is improved.
In a word, the silicon-based negative electrode material is a double-layer composite deposition layer, and the composite layer has excellent compression resistance, good electric conductivity, higher mechanical strength and larger buffer space to relieve volume expansion; the comprehensive performance of the silicon-based carbon-containing anode material structure is optimized.
Drawings
In order that the invention may be more readily understood, a more particular description of the invention will be rendered by reference to specific embodiments thereof which are illustrated in the appended drawings, in which,
FIG. 1 is a schematic structural diagram of a silicon-based anode material obtained in example 1 of the present invention; wherein, 1, titanium nitride layer; 2. a carbon sphere coating layer; 3. carbon globules; 4. a carbon matrix; 5. a silicon-embedded layer; 6. a silicon layer;
fig. 2 is an SEM image of the silicon-based anode material obtained in example 1 of the present invention.
Detailed Description
In order to solve the problems of the prior art that the structure of an electrode active material is damaged, an electrochemical interface is unstable and the like due to huge volume expansion in the lithium intercalation process of the Si anode material, the cycle performance is poor; in addition, poor conductivity of Si causes technical problems such as poor rate performance. The invention provides a silicon-based anode material coated with carbon spheres, a preparation method and application thereof, and the carbon sphere-coated silicon-based anode material is realized by the following steps:
the first object of the invention is to provide a silicon-based anode material, which comprises a carbon matrix, a silicon-embedded layer, a silicon layer, a titanium nitride layer and a carbon pellet coating layer, wherein the silicon-embedded layer, the silicon layer, the titanium nitride layer and the carbon pellet coating layer are coated on the surface of the carbon matrix;
the outer surface of the carbon matrix is attached with a porous structure, and silicon is embedded into the porous structure to be combined with the carbon matrix to form a silicon-embedded layer of the carbon matrix; the outer coating layer of the embedded silicon layer is a silicon layer, a titanium nitride layer and a carbon pellet coating layer.
In one embodiment of the invention, the carbon sphere coating layer surface is a plurality of carbon spheres. The carbon globules are spherical or spheroid-like particles.
Further, the particle diameter of the carbon beads is 0.001 μm to 3 μm, and further 0.005 μm to 1.8 μm.
In one embodiment of the invention, at least one of the following conditions is met:
a) The granularity of the silicon-based anode material is 2-25 mu m;
b) The carbon content of the silicon-based anode material is 22-85 wt% and the titanium content is 0.002-6 wt%.
Further, the carbon content may vary from 22 to 25wt%, 25 to 30wt%, 30 to 33wt%, 33 to 40wt%, 40 to 48wt%, 48 to 56wt%, 56 to 60wt%, 60 to 63wt%, 64 to 69wt%, 69 to 70wt%, including but not limited to the concentration values listed above.
Further, the titanium content may be 0.002 to 0.01wt%, 0.01 to 0.05wt%, 0.05 to 0.08wt%, 0.08 to 0.1wt%, 0.1 to 0.2wt%, 0.2 to 0.3wt%, 0.3 to 0.5wt%, 0.5 to 0.6wt%, 0.6 to 0.8wt%, 0.8 to 1.0wt%, 1.0 to 1.5wt%, 1.5 to 2.0wt%, 2.0 to 2.5wt%, 2.5 to 3.0wt%, 3.0 to 4.0wt%, 4.0 to 5.0wt%, 5.0 to 6.0wt% different, including but not limited to the concentration values listed above.
In one embodiment of the invention, at least one of the following conditions is met:
The diameter of the carbon matrix is 2-19 mu m;
the thickness of the silicon-embedded layer is 0.01-0.5 mu m;
the thickness of the silicon layer is 0.05-5 mu m;
the thickness of the titanium nitride layer is 0.001-0.2 mu m;
the thickness of the carbon sphere coating layer is 0.001-0.3 mu m.
The second object of the present invention is to provide a method for preparing a silicon-based anode material, comprising the steps of:
(1) Mixing graphite material, alkaline material and water, performing hydrothermal reaction, washing and drying to obtain microporous graphite;
(2) Heating, washing, drying and sieving the microporous graphite obtained in the step (1) under the condition of mixed gas containing hydrogen to obtain porous graphite;
(3) Heating the porous graphite obtained in the step (2) for 20 min-5 h under the condition of inactive gas, and introducing mixed silane gas to perform silicon deposition to obtain a carbon matrix with a silicon layer on the surface;
(4) Heating the carbon matrix with the silicon layer on the surface obtained in the step (3) under the condition of inactive gas containing nitrogen, adding a titanium-containing load carrying hydrogen, and depositing a titanium nitride layer to obtain the carbon matrix with the silicon layer on the surface wrapped by the titanium nitride layer;
(5) Heating the carbon matrix with the silicon layer on the surface wrapped by the titanium nitride layer obtained in the step (4), introducing mixed gaseous carbon gas, and carrying out carbon deposition for a period of time; stopping introducing the mixed gaseous carbon gas, cooling to 400-700 ℃ and keeping the temperature constant to obtain the silicon-based anode material.
In one embodiment of the present invention, in step (1), at least one of the following conditions is satisfied:
(I) The particle size of the graphite material is 2-25 mu m;
(II) the graphite material is selected from one or more of artificial graphite flakes, artificial graphite spheres, artificial graphite blocks, modified natural flaky graphite, modified natural crystalline graphite, modified natural graphite spheres and modified natural graphite blocks;
(III) the alkaline material is a conventional alkaline material in the art, and is not limited thereto, and is preferably one or more of sodium metaaluminate, aluminum hydroxide, potassium hydroxide, lithium hydroxide, magnesium carbonate, lithium carbonate, magnesium metaaluminate, lithium metaaluminate and potassium metaaluminate;
(IV) the mass ratio of the graphite material to the alkaline material is 100: 0.1-30;
(V) the mass concentration of the graphite material is 8-55 wt%.
In one embodiment of the present invention, in step (1), at least one of the following conditions is satisfied:
(a) Hydrothermal reaction conditions: the heating temperature is 150-400 ℃ and the heating time is 4-24 hours;
(b) And the surface gap size of the microporous graphite is 0 nm-15 nm.
Further, in the step (1), after the graphite surface is activated under the hydrothermal condition, the electron distribution of carbon is affected by the inorganic salt generated on the surface, and etching is further formed, so that the surface microporation is realized.
In one embodiment of the present invention, in the step (2), the volume concentration of the hydrogen in the mixed gas containing hydrogen is 0.2vt% -3vt%.
Further, the volume concentration of hydrogen is 0.2vt, 0.5vt, 1.0vt, 1.5vt, 2.0vt, 2.3vt, 2.4vt, 2.5vt, 2.6vt, 2.7vt, 2.8vt, 2.9vt, 3.0vt, or any value between any two concentration values; including but not limited to the concentration values listed above.
In one embodiment of the present invention, in the step (2), the heating temperature is 300 ℃ to 600 ℃ and the heating time is 6h to 24h; the particle size of the porous graphite is less than 6 mu m.
Further, in the step (2), on the surface enriched by the micropores, oxygen-containing substances generated by the microporous graphite or oxygen-containing gas carried by the airflow react with surface carbon at high temperature to obtain carbon monoxide and carbon dioxide, the carbon monoxide and the carbon dioxide are consumed by hydrogenation, the reaction is promoted to continuously occur, the carbon consumption in the micropores is increased, and the micropores are gradually enlarged.
In one embodiment of the present invention, in the step (3), the inert gas is selected from one or more of nitrogen, helium, xenon, radon, neon and argon.
In one embodiment of the present invention, in the step (4), the inert gas containing nitrogen further includes one or more of helium, xenon, radon, neon and argon.
In one embodiment of the present invention, in step (3), the mixed silane gas includes a silane gas and an inert mixed gas.
In one embodiment of the present invention, the silane gas is selected from one or more of monosilane, disilane, trisilane, dimethylsilane, dichlorosilane, trichlorosilane and silicon tetrachloride; the inactive mixed gas is selected from one or more of nitrogen, helium, xenon, radon, neon, argon and the like; the airflow ratio of the silane gas to the inactive mixed gas is 1-5: 0.1 to 2.
In one embodiment of the present invention, in the step (3), the heating temperature is 400 ℃ to 950 ℃.
In one embodiment of the present invention, in the step (3), the silicon content in the carbon substrate containing the silicon layer is 15wt% to 75wt%.
In one embodiment of the present invention, in the step (4), the gas flow ratio of the hydrogen gas to the inactive gas is 1 to 5:0.1 to 1.2.
In one embodiment of the present invention, in the step (4), the heating temperature is 720 ℃ to 1150 ℃.
In one embodiment of the invention, in step (4), the titanium-containing support is selected from at least one of titanium tetrachloride, titanium tetrabromide and titanium tetraiodide, preferably titanium tetrachloride.
In one embodiment of the present invention, in the step (5), the heating temperature is 700 ℃ to 950 ℃; the carbon deposition time is 2 min-45 min.
In one embodiment of the present invention, in step (5), the mixed gaseous carbon gas includes a gaseous carbon gas and an inert gas; the gaseous carbon gas is selected from one or more of methane, ethane, propane, acetylene, propyne, butyne and ethylene; the inactive gas is selected from one or more of nitrogen, helium, xenon, radon, neon, argon and the like.
In one embodiment of the present invention, in the step (5), the gas flow ratio of the gaseous carbon gas to the inactive gas is 1 to 5:0.1 to 1.0.
Further, in the step (5), when the temperature is reduced to 400-700 ℃, silicon can be amorphized, and particles are finer silicon crystal particles, so that the electrical property of the material is improved.
The third object of the invention is to provide a negative electrode plate, which comprises a first binder, a graphite material, a conductive material, a modified additive, the silicon-based negative electrode material or the silicon-based negative electrode material prepared by the preparation method.
In one embodiment of the invention, the mass ratio of the mixture of the silicon-based anode material and the graphite material, the first binding substance and the modifying additive is 85-99: 0.2-8: 0.2-10; the concentration of the graphite material in the mixture is 35-95 wt%.
The fourth object of the present invention is to provide a method for preparing a negative electrode sheet, comprising the steps of: mixing and stirring a silicon-based anode material, a graphite material mixture, a first binding substance and a modifying additive, adding water to adjust viscosity to obtain silicon-containing bottom layer homogenate, and coating the silicon-containing bottom layer homogenate on an anode current collector to obtain a silicon-containing bottom layer; mixing and stirring graphite material, first binding substance and conductive material, adding water to regulate viscosity to obtain graphite-containing upper layer homogenate, coating the graphite-containing upper layer homogenate on a silicon-containing bottom layer to obtain a graphite-containing upper layer, and drying and rolling to obtain the negative plate.
In one embodiment of the invention, the silicon-containing underlayer of the current collector has a areal weight of 40g/m 2 ~350g/m 2 The method comprises the steps of carrying out a first treatment on the surface of the The surface weight of the graphite-containing upper layer in the current collector is 40g/m 2 ~350g/m 2 。
In one embodiment of the invention, the mass ratio of the mixture of the silicon-based anode material and the graphite material, the first binding substance and the modifying additive is 85-99: 0.2-8: 0.2-10; the mass ratio of the graphite material to the first bonding substance to the conductive material is 85-99: 0.5-8: 0.5 to 10.
In one embodiment of the present invention, the first binding substance is a binding substance conventional in the art, and is not limited thereto, and is preferably one or more of styrene-butadiene rubber, sodium alginate, polyvinylidene fluoride, sodium carboxymethyl cellulose, lithium carboxymethyl cellulose, polymethacrylate, polyamide and polyimide.
In one embodiment of the present invention, the conductive material is a conductive material conventional in the art, and is not limited herein, and is preferably one or more of an oligowall carbon nanotube, a single-wall carbon nanotube, a double-wall carbon nanotube, a multiwall carbon nanotube, a conductive carbon black, a conductive graphite, and graphene.
In one embodiment of the present invention, the negative electrode current collector is a negative electrode current collector conventional in the art, and is not limited herein, but is preferably one or more of copper foil, nickel-plated copper foil.
In one embodiment of the invention, the modifying additive is prepared by the following method: the modified additive is prepared by the following method: and adding the conductive material and the second binding substance into an organic solvent, stirring, reacting, adding ethanol to obtain a precipitate, and carrying out solid-liquid separation to obtain a solid phase, thereby obtaining the material bonded by the conductive material and the second binding substance, which is the modified additive.
In one embodiment of the present invention, the organic solvent is a conventional organic solvent in the art, and is not limited thereto, and is preferably selected from N, N-dimethylformamide.
In one embodiment of the present invention, the liquid-solid ratio of the organic solvent, the conductive material, and the second binding substance is 2 to 60: 1-30: 1 to 20 (L: kg or mL: g: g).
In one embodiment of the present invention, the second binding substance is a binding substance conventional in the art, and is not limited herein, and is preferably one or more of lithium polyacrylate, polyacrylic acid, polyacrylamide, carboxymethyl cellulose, sodium carboxymethyl cellulose, lithium carboxymethyl cellulose, sodium alginate and lithium alginate.
In one embodiment of the invention, the reaction time is 4-24 hours.
A fifth object of the present invention is to provide a secondary battery including the above-described negative electrode sheet.
A sixth object of the present invention is to provide a method for manufacturing a secondary battery, comprising the steps of: and sequentially stacking and winding the negative electrode plate, the isolating film and the positive electrode plate to obtain a bare cell and welding the electrode lugs, putting the bare cell into a battery aluminum shell/soft-package aluminum-plastic film, sealing the top side, drying to remove water, injecting electrolyte into the battery shell, forming, fixing the capacity, exhausting and sealing to finally obtain the secondary battery.
The present invention will be further described with reference to the accompanying drawings and specific examples, which are not intended to be limiting, so that those skilled in the art will better understand the invention and practice it.
Example 1:
the embodiment of the invention provides a silicon-based anode material, and a preparation method and application thereof:
(I), a silicon-based anode material and a preparation method thereof:
1. silicon-based anode material:
the titanium content is 0.13wt%, the nitrogen content is 0.46%, the diameter of the carbon matrix is 5-8 mu m, the thickness of the silicon embedded layer is 0.3 mu m, the thickness of the silicon layer is 0.07 mu m, the titanium nitride layer is 0.02 mu m, and the coating layer of the carbon globules is 0.3 mu m.
2. The preparation method of the silicon-based anode material comprises the following steps:
2.1 microporation treatment: the mass ratio of the graphite material (2-25 mu m artificial graphite sheet) to the alkaline material (magnesium metaaluminate) is 100: adding water to the mass concentration of the graphite material in the equipment of 20wt%, mixing, adding water, placing in a microwave heating equipment, carrying out microwave hydrothermal treatment for 16h at 210 ℃ (under the hydrothermal condition, after the graphite surface is activated, inorganic salt generated on the surface can influence the electron distribution of carbon, further etching can be formed, surface microporation is realized), washing the obtained material with deionized water, and drying to obtain the microporous graphite with the surface pores of 0-3 nm.
2.2 reaming: delivering microporous graphite into a heating pipe, introducing mixed gas (air containing hydrogen with volume concentration of 2.3 vt%) into the heating pipe, heating at 500deg.C for 7 hr, washing the obtained material with deionized water, drying, and sieving to obtain porous graphite (micropore enriched surface with carbon atoms easily oxidized to generate CO and CO at high temperature) 2 The expansion treatment of the pores is completed).
2.3 one deposition: and (3) delivering the porous graphite into a reaction furnace of a fluidized furnace, controlling the temperature of the reaction furnace at 780 ℃, introducing nitrogen inert gas, and then introducing mixed silane gas (wherein the airflow ratio of monosilane to helium is 2:0.4) to perform silicon deposition, so as to obtain a silicon-carbon precursor, wherein the silicon content of the deposited silicon is 52wt% of the silicon-carbon precursor.
2.4 secondary deposition: the preparation method comprises the steps of (1) conveying a silicon-carbon precursor into a reaction furnace in a fluidized furnace, controlling the temperature of the reaction furnace at 950 ℃, introducing nitrogen inert gas, introducing load gas hydrogen (the gas flow ratio of the hydrogen to the argon is 3:0.5, and the hydrogen is loaded with gaseous titanium tetrachloride) for deposition for 36min, and obtaining a titanium nitride layer;
2.5 three depositions: after stopping introducing nitrogen and loading gas hydrogen, controlling the temperature of the reaction furnace at 850 ℃, introducing mixed gaseous carbon gas (the mixed gaseous carbon gas is obtained by mixing acetylene and nitrogen in a gas flow ratio of 2:0.3), depositing for 20min, stopping introducing the mixed gaseous carbon gas, cooling to 500 ℃ and staying for 30min (at low temperature of 400-700 ℃, silicon can be amorphized, particles show silicon crystal particles, the particle size is finer, and the electrical property of the material is improved), and obtaining the silicon-based anode material, wherein the characterization result of the obtained silicon-based anode material is shown in figure 2.
(II) application of silicon-based anode materials:
3. the negative plate and the preparation method thereof are as follows:
3.1 negative electrode sheet: silicon-based anode material and graphite material (graphite mass ratio 80 wt%)The adhesive comprises a first adhesive substance (90 wt% of sodium carboxymethyl cellulose and 10wt% of styrene-butadiene rubber) and a modifying additive according to a mass ratio of 92:4:4 mixing, stirring, adding deionized water, stirring, regulating viscosity to obtain silicon-containing bottom layer homogenate, coating the silicon-containing bottom layer homogenate on the cathode current collector copper foil to obtain silicon-containing bottom layer (surface weight of 75 g/m) 2 ) The method comprises the steps of carrying out a first treatment on the surface of the And then the graphite material (graphite material in the step 2.1), the first bonding substance and the conductive material are mixed according to the mass ratio of 95:2:3 mixing, stirring, adding deionized water, stirring, and regulating viscosity to obtain graphite-containing upper layer homogenate, coating the graphite-containing upper layer homogenate on the silicon-containing bottom layer to obtain graphite-containing upper layer (surface weight of 30 g/m) 2 ) And (5) drying and rolling to obtain the negative plate.
Wherein the modified additive is prepared by the following method: placing N, N-dimethylformamide in a container, removing air, introducing nitrogen, sequentially adding a conductive material (single-walled carbon nano tube), a second binder (polyacrylamide, N, N-dimethylformamide, a modified conductive material and the second binder according to a liquid-solid ratio (L: kg: kg) of 20:2:12), fully stirring, reacting at room temperature for 12h, adding ethanol to obtain a precipitate, and filtering to obtain the modified additive.
3.2 a secondary battery: the secondary battery prepared by the negative electrode plate comprises the following preparation steps:
and sequentially stacking and winding the negative electrode plate, the isolating film and the positive electrode plate to obtain a bare cell and welding the electrode lugs, putting the bare cell into a battery aluminum shell/soft-package aluminum-plastic film, sealing the top side, drying to remove water, injecting electrolyte into the battery shell, forming, fixing the capacity, exhausting and sealing to obtain the secondary battery.
Example 2:
the embodiment of the invention provides a silicon-based anode material, and a preparation method and application thereof:
(I), a silicon-based anode material and a preparation method thereof:
1. silicon-based anode material:
the titanium content is 0.15wt%, the nitrogen content is 0.34%, the diameter of the carbon matrix is 5-8 mu m, the thickness of the silicon embedded layer is 0.3 mu m, the thickness of the silicon layer is 0.07 mu m, the titanium nitride layer is 0.02 mu m, and the coating layer of the carbon globules is 0.3 mu m.
2. The preparation method of the silicon-based anode material comprises the following steps:
2.1 microporation treatment: the mass ratio of the graphite material (2-25 mu m artificial graphite sheet) to the alkaline material (magnesium metaaluminate) is 100: adding water until the mass concentration of the graphite material in the equipment is 20wt%, mixing, adding water, placing in microwave heating equipment, carrying out microwave hydrothermal treatment for 16h at 210 ℃, washing the obtained material with deionized water, and drying to obtain microporous graphite with surface pores of 0-3 nm;
2.2 reaming: and (3) delivering the microporous graphite into a heating pipe, introducing mixed gas (air containing hydrogen with the volume concentration of 2.3vt percent), heating for 7 hours at the temperature of 500 ℃, washing the obtained material with deionized water, drying, and sieving to obtain the porous graphite with the particle size of less than 6 mu m.
2.3 one deposition: and (3) delivering the porous graphite into a reaction furnace in a fluidized furnace, controlling the temperature of the reaction furnace at 780 ℃, introducing nitrogen inert gas, and then introducing mixed silane gas (the gas flow ratio of monosilane to helium is 2:0.4) to perform silicon deposition, so as to obtain a silicon-carbon precursor, wherein the silicon content of the deposited silicon is 54wt% of the silicon-carbon precursor.
2.4 secondary deposition: the silicon-carbon precursor is sent into a reaction furnace in a fluidization furnace (fluidization tube), the temperature of the reaction furnace is controlled at 950 ℃, nitrogen inert gas is introduced, and then hydrogen gas with load gas (the gas flow ratio of the hydrogen gas to the argon gas is 3:0.5, and the hydrogen gas loads gaseous titanium tetrachloride) is introduced for deposition for 36min, so that a titanium nitride layer is obtained;
2.5 three depositions: and after stopping introducing nitrogen and loading gas hydrogen, controlling the temperature of the reaction furnace at 850 ℃, introducing mixed gaseous carbon gas (the mixed gaseous carbon gas is obtained by mixing acetylene and nitrogen in a gas flow ratio of 2:0.3), depositing for 20min, stopping introducing the mixed gaseous carbon gas, and cooling to 500 ℃ for 30min to obtain the silicon-based anode material.
Application of (II) silicon-based anode material
3. The negative plate and the preparation method thereof are as follows:
3.1 negative electrode sheet: silicon-based negative electrode material and graphite material (graphite mass ratio 80wt%) First binding substance (90 wt% sodium carboxymethyl cellulose and 10wt% styrene butadiene rubber), modifying additive according to the mass ratio 93:3:4 mixing, stirring, adding deionized water, stirring, regulating viscosity to obtain silicon-containing bottom layer homogenate, coating the silicon-containing bottom layer homogenate on the cathode current collector copper foil to obtain silicon-containing bottom layer (surface weight of 75 g/m) 2 ) The method comprises the steps of carrying out a first treatment on the surface of the And then the graphite material (graphite material in the step 2.1), the first bonding substance and the conductive material are mixed according to the mass ratio of 95:2:3 mixing, stirring, adding deionized water, stirring, and regulating viscosity to obtain graphite-containing upper layer homogenate, coating the graphite-containing upper layer homogenate on the silicon-containing bottom layer to obtain graphite-containing upper layer (surface weight of 30 g/m) 2 ) And (5) drying and rolling to obtain the negative plate.
Wherein the modified additive is prepared by the following method: placing N, N-dimethylformamide in a container, removing air, introducing nitrogen, sequentially adding a conductive material (single-walled carbon nano tube), a second binder (polyacrylamide, N, N-dimethylformamide, a modified conductive material and the second binder according to a liquid-solid ratio (L: kg: kg) of 20:2:12), fully stirring, reacting at room temperature for 12h, adding ethanol to obtain a precipitate, and filtering to obtain the modified additive.
3.2 a secondary battery: the secondary battery prepared by the negative electrode plate comprises the following preparation steps:
and sequentially stacking and winding the negative electrode plate, the isolating film and the positive electrode plate to obtain a bare cell and welding the electrode lugs, putting the bare cell into a battery aluminum shell/soft-package aluminum-plastic film, sealing the top side, drying to remove water, injecting electrolyte into the battery shell, forming, fixing the capacity, exhausting and sealing to obtain the secondary battery.
Example 3:
the embodiment of the invention provides a silicon-based anode material, and a preparation method and application thereof:
(I), a silicon-based anode material and a preparation method thereof:
1. silicon-based anode material:
the titanium content is 0.17wt%, the nitrogen content is 0.61%, the diameter of the carbon matrix is 5-9 mu m, the thickness of the silicon embedded layer is 0.3 mu m, the thickness of the silicon layer is 0.07 mu m, the thickness of the titanium nitride layer is 0.04 mu m, and the thickness of the carbon sphere coating layer is 0.07 mu m.
2. The preparation method of the silicon-based anode material comprises the following steps:
2.1 microporation treatment: the mass ratio of the graphite material (2-25 mu m artificial graphite sheet) to the alkaline material (magnesium metaaluminate) is 100: adding water until the mass concentration of the graphite material in the equipment is 20wt%, mixing, adding water, placing in a microwave heating equipment, carrying out microwave hydrothermal treatment for 12 hours at 270 ℃, washing the obtained material with deionized water, and drying to obtain microporous graphite with surface pores of 1-4 nm;
2.2 reaming: and (3) delivering the microporous graphite into a heating pipe, introducing mixed gas (air containing hydrogen with the volume concentration of 2.3vt percent), heating for 7 hours at the temperature of 500 ℃, washing the obtained material with deionized water, drying, and sieving to obtain the porous graphite with the particle size of less than 6 mu m.
2.3 one deposition: and (3) delivering the porous graphite into a reaction furnace in a fluidized furnace, controlling the temperature of the reaction furnace at 720 ℃, introducing nitrogen inert gas, and then introducing mixed silane gas (wherein the airflow ratio of monosilane to helium is 2:0.4) for silicon deposition, so as to obtain a silicon-carbon precursor, wherein the silicon content of the deposited silicon is 48wt% of the silicon-carbon precursor.
2.4 secondary deposition: the preparation method comprises the steps of (1) conveying a silicon-carbon precursor into a reaction furnace in a fluidized furnace, controlling the temperature of the reaction furnace at 950 ℃, introducing nitrogen inert gas, and then introducing load gas hydrogen (the gas flow ratio of the hydrogen to the argon is 3:0.5, and the hydrogen is loaded with titanium tetrachloride) for deposition for 36min to obtain a titanium nitride layer;
2.5 three depositions: and after stopping introducing nitrogen and loading gas hydrogen, controlling the temperature of the reaction furnace at 850 ℃, introducing mixed gaseous carbon gas (the mixed gaseous carbon gas is obtained by mixing acetylene and inactive gas nitrogen in a gas flow ratio of 2:0.3), depositing for 20min, stopping introducing the mixed gaseous carbon gas, and cooling to 500 ℃ for 30min to obtain the silicon-based anode material.
Application of (II) silicon-based anode material
3. The negative plate and the preparation method thereof are as follows:
3.1 negative electrode sheet: silicon-based negative electrode material and graphite material (graphite mass80 wt.%), a first binding substance (90 wt.% sodium carboxymethylcellulose and 10 wt.% styrene-butadiene rubber), and a modifying additive according to a mass ratio of 94:1.5:4.5 mixing, stirring, adding deionized water, stirring, adjusting viscosity to obtain silicon-containing bottom layer homogenate, coating the silicon-containing bottom layer homogenate on the cathode current collector copper foil to obtain silicon-containing bottom layer (surface weight of 75 g/m) 2 ) The method comprises the steps of carrying out a first treatment on the surface of the And then the graphite material (graphite material in the step 2.1), the first bonding substance and the conductive material are mixed according to the mass ratio of 95:2:3 mixing, stirring, adding deionized water, stirring, and regulating viscosity to obtain graphite-containing upper layer homogenate, coating the graphite-containing upper layer homogenate on the silicon-containing bottom layer to obtain graphite-containing upper layer (surface weight of 30 g/m) 2 ) And (5) drying and rolling to obtain the negative plate.
Wherein the modified additive is prepared by the following method: placing N, N-dimethylformamide in a container, removing air, introducing nitrogen, sequentially adding a conductive material (single-walled carbon nano tube), a second binder (polyacrylamide, N, N-dimethylformamide, a modified conductive material and the second binder according to a liquid-solid ratio (L: kg: kg) of 20:2:12), fully stirring, reacting at room temperature for 12h, adding ethanol to obtain a precipitate, and filtering to obtain the modified additive.
3.2 a secondary battery: the secondary battery prepared by the negative electrode plate comprises the following preparation steps: and sequentially stacking and winding the negative electrode plate, the isolating film and the positive electrode plate to obtain a bare cell and welding the electrode lugs, putting the bare cell into an electric aluminum shell/soft-package aluminum-plastic film, sealing the top side, drying to remove water, injecting electrolyte into the battery shell, forming, fixing the capacity, exhausting and sealing to obtain the secondary battery.
Example 4:
the embodiment of the invention provides a silicon-based anode material, and a preparation method and application thereof:
(I), a silicon-based anode material and a preparation method thereof:
1. silicon-based anode material:
the titanium content is 0.08wt%, the nitrogen content is 0.29%, the diameter of the carbon matrix is 5-8 mu m, the thickness of the silicon embedded layer is 0.3 mu m, the thickness of the silicon layer is 0.07 mu m, the titanium nitride layer is 0.04 mu m, and the coating layer of the carbon globules is 0.08 mu m.
2. The preparation method of the silicon-based anode material comprises the following steps:
2.1 microporation treatment: graphite material (artificial graphite sheet with the thickness of 2-25 μm) and alkaline material (potassium hydroxide) according to the mass ratio of 100:2, adding water to the mass concentration of the graphite material in the equipment of 20wt%, mixing, adding water, placing in a microwave heating equipment, carrying out microwave hydrothermal treatment for 12 hours at 270 ℃, washing the obtained material with deionized water, and drying to obtain the microporous graphite with the surface pores of 1-4 nm.
2.2 reaming: and (3) delivering the microporous graphite into a heating pipe, introducing mixed gas (air containing hydrogen with the volume concentration of 2.8vt percent), heating for 12 hours at the temperature of 450 ℃, washing the obtained material with deionized water, drying, and sieving to obtain the porous graphite with the particle size of less than 6 mu m.
2.3 one deposition: and (3) delivering the porous graphite into a reaction furnace in a fluidized furnace, controlling the temperature of the reaction furnace at 650 ℃, introducing nitrogen inert gas, and then introducing mixed silane gas (wherein the airflow ratio of monosilane to helium is 2:0.3) for silicon deposition, so as to obtain a silicon-carbon precursor, wherein the silicon content of the deposited silicon is 49wt% of the silicon-carbon precursor.
2.4 secondary deposition: the preparation method comprises the steps of (1) conveying a silicon-carbon precursor into a reaction furnace in a fluidized furnace, controlling the temperature of the reaction furnace to 1080 ℃, introducing nitrogen inert gas, and then introducing load gas hydrogen (the gas flow ratio of the hydrogen to the argon is 3:0.5, and the hydrogen is loaded with gaseous titanium tetrachloride) for deposition for 30min to obtain a titanium nitride layer;
2.5 three depositions: and after stopping introducing nitrogen and loading gas hydrogen, controlling the temperature of the reaction furnace at 850 ℃, introducing mixed gaseous carbon gas (the mixed gaseous carbon gas is obtained by mixing acetylene and nitrogen in a gas flow ratio of 2:0.3), depositing for 25min, stopping introducing the mixed gaseous carbon gas, and cooling to 480 ℃ and staying for 45min to obtain the silicon-based anode material.
Application of (II) silicon-based anode material
3. The negative plate and the preparation method thereof are as follows:
3.1 negative electrode sheet: silicon-based negative electrode material, graphite material (graphite mass ratio 90 wt.%), firstBinding substances (90 wt% of sodium carboxymethyl cellulose and 10wt% of styrene-butadiene rubber) and modifying additives according to the mass ratio of 95.5:1.5:3 mixing, stirring, adding deionized water, stirring, regulating viscosity to obtain silicon-containing bottom layer homogenate, coating the silicon-containing bottom layer homogenate on the cathode current collector copper foil to obtain silicon-containing bottom layer (surface weight of 75 g/m) 2 ) The method comprises the steps of carrying out a first treatment on the surface of the And then the graphite material (graphite material in the step 2.1), the first bonding substance and the conductive material are mixed according to the mass ratio of 95:2:3 mixing, stirring, adding deionized water, stirring, and regulating viscosity to obtain graphite-containing upper layer homogenate, coating the graphite-containing upper layer homogenate on the silicon-containing bottom layer to obtain graphite-containing upper layer (surface weight of 30 g/m) 2 ) And (5) drying and rolling to obtain the negative plate.
Wherein the modified additive is prepared by the following method: placing N, N-dimethylformamide in a container, removing air, introducing nitrogen, sequentially adding a conductive material (single-walled carbon nano tube), a second binder (polyacrylamide, N, N-dimethylformamide, a modified conductive material and the second binder according to a liquid-solid ratio (L: kg: kg) of 35:3:15), fully stirring, reacting at room temperature for 15h, adding ethanol to obtain a precipitate, and filtering to obtain the modified additive.
3.2 a secondary battery: the secondary battery prepared by the negative electrode plate comprises the following preparation steps:
and sequentially stacking and winding the negative electrode plate, the isolating film and the positive electrode plate to obtain a bare cell and welding the electrode lugs, putting the bare cell into a battery aluminum shell/soft-package aluminum-plastic film, sealing the top side, drying to remove water, injecting electrolyte into the battery shell, forming, fixing the capacity, exhausting and sealing to obtain the secondary battery.
Example 5:
the embodiment of the invention provides a silicon-based anode material, and a preparation method and application thereof:
(I), a silicon-based anode material and a preparation method thereof:
1. silicon-based anode material:
the titanium content is 0.05wt%, the nitrogen content is 0.21%, the diameter of the carbon matrix is 5-8 mu m, the thickness of the silicon embedded layer is 0.3 mu m, the thickness of the silicon layer is 0.07 mu m, the titanium nitride layer is 0.03 mu m, and the coating layer of the carbon globules is 0.08 mu m.
2. The preparation method of the silicon-based anode material comprises the following steps:
2.1 microporation treatment: graphite material (artificial graphite sheet with the thickness of 2-25 μm) and alkaline material (potassium hydroxide) according to the mass ratio of 100:2 adding water until the mass concentration of the graphite material in the equipment is 20wt%, mixing, adding water, placing in microwave heating equipment, carrying out microwave hydrothermal treatment for 14h at 340 ℃, washing the obtained material with deionized water, and drying to obtain microporous graphite with surface pores of 1-4 nm;
2.2 reaming: and (3) delivering the microporous graphite into a heating pipe, introducing mixed gas (air containing hydrogen with the volume concentration of 2.8vt percent), heating for 7 hours at the temperature of 500 ℃, washing the obtained material with deionized water, drying, and sieving to obtain the porous graphite with the particle size of less than 6 mu m.
2.3 one deposition: delivering porous graphite into a reaction furnace in a fluidized furnace, controlling the temperature of the reaction furnace at 720 ℃, introducing nitrogen inert gas, and introducing mixed silane gas (the airflow ratio of monosilane to helium is 2:0.3) to perform silicon deposition, so as to obtain a silicon-carbon precursor, wherein the silicon content of deposited silicon is 51wt% of the silicon-carbon precursor;
2.4 secondary deposition: the preparation method comprises the steps of (1) conveying a silicon-carbon precursor into a reaction furnace in a fluidized furnace, controlling the temperature of the reaction furnace to 1080 ℃, introducing nitrogen inactive gas, and then introducing load gas hydrogen (the gas flow ratio of the hydrogen to the argon is 3:0.5, and the hydrogen is loaded with gaseous titanium tetrachloride) for deposition for 30min to obtain a titanium nitride layer;
2.5 three depositions: and after stopping introducing nitrogen and loading gas hydrogen, controlling the temperature of the reaction furnace at 850 ℃, introducing mixed gaseous carbon gas (the mixed gaseous carbon gas is obtained by mixing acetylene and nitrogen inactive gas in a gas flow ratio of 2:0.3), depositing for 28min, stopping introducing the mixed gaseous carbon gas, cooling to 480 ℃, and standing for 45min to obtain the silicon-based anode material.
(II) application of silicon-based anode materials:
3. the negative plate and the preparation method thereof are as follows:
3.1 negative electrode sheet: silicon-based negative electrode material, graphite material (graphite mass ratio)90 wt.%), a first binding substance (90 wt.% sodium carboxymethylcellulose and 10 wt.% styrene-butadiene rubber), and a modifying additive according to a mass ratio of 96:1.5:2.5 mixing, stirring, adding deionized water, stirring, and adjusting viscosity to obtain silicon-containing bottom layer homogenate, coating the silicon-containing bottom layer homogenate on a negative current collector copper foil to obtain silicon-containing bottom layer (surface weight of 75 g/m) 2 ) The method comprises the steps of carrying out a first treatment on the surface of the And then the graphite material (graphite material in the step 2.1), the first bonding substance and the conductive material are mixed according to the mass ratio of 95:2:3 mixing, stirring, adding deionized water, stirring, and regulating viscosity to obtain graphite-containing upper layer homogenate, coating the graphite-containing upper layer homogenate on the silicon-containing bottom layer to obtain graphite-containing upper layer (surface weight of 30 g/m) 2 ) And (5) drying and rolling to obtain the negative plate.
Wherein the modified additive is prepared by the following method: placing N, N-dimethylformamide in a container, removing air, introducing nitrogen, sequentially adding a conductive material (single-walled carbon nano tube), a second binder (polyacrylamide, N, N-dimethylformamide, a modified conductive material and the second binder according to a liquid-solid ratio (L: kg: kg) of 35:3:15), fully stirring, reacting at room temperature for 15h, adding ethanol to obtain a precipitate, and filtering to obtain the modified additive.
3.2 a secondary battery: the secondary battery prepared by the negative electrode plate comprises the following preparation steps:
and sequentially stacking and winding the negative electrode plate, the isolating film and the positive electrode plate to obtain a bare cell and welding the electrode lugs, putting the bare cell into a battery aluminum shell/soft-package aluminum-plastic film, sealing the top side, drying to remove water, injecting electrolyte into the battery shell, forming, fixing the capacity, exhausting and sealing to obtain the secondary battery.
Comparative example 1:
the difference from example 1 is that the silicon-based negative electrode material preparation was not subjected to secondary deposition.
Comparative example 2:
the difference from example 1 is that the silicon-based negative electrode material preparation was not subjected to three depositions.
Comparative example 3:
the difference from example 1 is that the modifying additive is replaced by a conductive material (single-walled carbon nanotubes).
Test example:
1. rebound rate under full charge of the negative electrode plate and cracking condition of silicon-based negative electrode material:
powder resistance of the negative electrode materials of each example and comparative example was measured by a resistance meter; measuring the thickness of the graphite-silicon negative electrode plate after drying in the step 1.2 and the thickness of the graphite-silicon negative electrode plate in a full charge state of the battery by using a ten-thousandth spiral ruler, wherein the expansion rate of the negative electrode plate is = (the thickness of the graphite-silicon negative electrode plate in the full charge state of the battery-the thickness of the graphite-silicon negative electrode plate after drying)/the thickness of the graphite-silicon negative electrode plate after drying is multiplied by 100%; and observing the cracking condition of the silicon-based anode materials on the surface of the anode piece after 400 th cycle of battery cycles of examples 1-5 and comparative examples 1-3 by using an electron microscope. The experimental results are shown in Table 1.
2. And (3) electrical property detection:
at normal temperature of 25 ℃, the initial and cut-off voltages are 2.8V, 4.25V,1C is charged to 4.25V, then 4.25V constant voltage is charged until the current is reduced to 0.05C, 0.1C is discharged to 2.8V, and the capacity retention rate is recorded when the battery is charged and discharged for the 100 th circle and the 500 th circle. The experimental results are shown in Table 2.
TABLE 1 composite layer negative electrode sheet case
Table 2 battery electrical performance in examples and comparative examples
As can be seen from Table 1, the titanium nitride deposition layers and the unique carbon pellet coating layers of examples 1-5 increased conductivity and reduced the electrical resistance of the materials. The composite layer negative electrode sheets of the comparative examples 1 and 2 have higher full charge rebound rate, obvious cracking and clearer cracking, and the silicon-based negative electrode material of the comparative example 3 has few microcracks and clearer cracking, wherein the composite layer negative electrode sheet of the comparative example 2 has the highest full charge rebound rate, the silicon-based negative electrode material has the most serious cracking, the titanium nitride deposition layer obtained by secondary deposition, the carbon sphere coating layer obtained by tertiary deposition and the compressive resistance and the higher mechanical strength of the silicon-based negative electrode material are improved by adding the modifying additive.
In Table 2, the 100-turn capacity retention rates of examples 1 to 5 are 90.8% -91.9%, the 100-turn capacity retention rates of comparative examples 1 to 3 are 88.2% -91.6%, the difference between the 100-turn capacity retention rates of examples 1 to 5 and comparative examples 3 is not large, but from the 600 th turn, the battery attenuation of comparative examples 1 to 2 is relatively fast, the attenuation is respectively reduced to 83.6% and 82.2%, the capacity retention rates of examples 1 to 5 are between 85.4% -87.6%, and the capacity retention rate is relatively good, which indicates that the capacity attenuation is most obvious and the circulation stability is the worst when the carbon pellet coating layer is not formed in comparative example 2 in the invention.
It is apparent that the above examples are given by way of illustration only and are not limiting of the embodiments. Other variations and modifications of the present invention will be apparent to those of ordinary skill in the art in light of the foregoing description. It is not necessary here nor is it exhaustive of all embodiments. And obvious variations or modifications thereof are contemplated as falling within the scope of the present invention.

Claims (13)

1. The silicon-based anode material of the lithium ion battery is characterized by comprising a carbon matrix, a silicon-embedded layer, a silicon layer, a titanium nitride layer and a carbon sphere coating layer, wherein the silicon-embedded layer, the silicon layer, the titanium nitride layer and the carbon sphere coating layer are wrapped on the surface of the carbon matrix;
the outer surface of the carbon matrix is attached with a porous structure, and silicon is embedded into the porous structure to be combined with the carbon matrix to form a silicon-embedded layer of the carbon matrix; the outer coating layer of the embedded silicon layer is a silicon layer, a titanium nitride layer and a carbon pellet coating layer.
2. The silicon-based anode material according to claim 1, wherein the carbon sphere coating layer is formed of a plurality of carbon spheres.
3. The silicon-based anode material according to claim 1, wherein at least one of the following conditions is satisfied:
a) The granularity of the silicon-based anode material is 2-25 mu m;
b) The carbon content of the silicon-based anode material is 22-85 wt% and the titanium content is 0.002-6 wt%.
4. The silicon-based anode material according to claim 1, wherein the following condition is satisfied:
the diameter of the carbon matrix is 2-19 mu m;
the thickness of the silicon-embedded layer is 0.01-0.5 mu m;
the thickness of the silicon layer is 0.05-5 mu m;
the thickness of the titanium nitride layer is 0.001-0.2 mu m;
the thickness of the carbon sphere coating layer is 0.001-0.3 mu m.
5. A method for preparing a silicon-based anode material of a lithium ion battery according to any one of claims 1 to 4, comprising the steps of:
(1) Mixing graphite material, alkaline material and water, performing hydrothermal reaction, washing and drying to obtain microporous graphite;
(2) Heating, washing, drying and sieving the microporous graphite obtained in the step (1) under the condition of mixed gas containing hydrogen to obtain porous graphite;
(3) Heating the porous graphite obtained in the step (2) for 20 min-5 h under the condition of inactive gas, and introducing mixed silane gas to perform silicon deposition to obtain a carbon matrix with a silicon layer on the surface;
(4) Heating the carbon matrix with the silicon layer on the surface obtained in the step (3) under the condition of inactive gas containing nitrogen, adding a titanium-containing load carrying hydrogen, and depositing a titanium nitride layer to obtain the carbon matrix with the silicon layer on the surface wrapped by the titanium nitride layer;
(5) Heating the carbon matrix with the silicon layer on the surface wrapped by the titanium nitride layer obtained in the step (4), introducing mixed gaseous carbon gas, and carrying out carbon deposition for a period of time; stopping introducing the mixed gaseous carbon gas, cooling to 400-700 ℃ and keeping the temperature constant to obtain the silicon-based anode material.
6. The method according to claim 5, wherein in the step (1), at least one of the following conditions is satisfied:
(I) The particle size of the graphite material is 2-25 mu m;
(II), the mass ratio of the graphite material to the alkaline material is 100: 0.1-30;
(III) the mass concentration of the graphite material is 8-55 wt%;
(IV), conditions of hydrothermal reaction: the heating temperature is 150-400 ℃ and the heating time is 4-24 hours;
and (V) the surface gap size of the microporous graphite is 0-15 nm.
7. The method according to claim 5, wherein in the step (2), at least one of the following conditions is satisfied:
the heating temperature is 300-600 ℃;
the heating time is 6-24 hours;
the particle size of the porous graphite is less than 6 mu m.
8. The method according to claim 5, wherein in the step (3), at least one of the following conditions is satisfied:
A) The mixed silane gas comprises silane gas and inactive mixed gas;
b) The heating temperature is 400-950 ℃;
c) The silicon content of the carbon matrix containing the silicon layer is 15-75wt%.
9. The method according to claim 5, wherein in the step (4), at least one of the following conditions is satisfied:
the airflow ratio of the hydrogen to the inactive gas containing nitrogen is 1-5: 0.1 to 1.2;
the heating temperature is 720-1150 ℃.
10. The method according to claim 5, wherein in step (5), at least one of the following conditions is satisfied:
the heating temperature is 700-950 ℃;
the carbon deposition time is 2 min-45 min;
the mixed gaseous carbon gas includes a gaseous carbon gas and an inert gas.
11. A negative electrode sheet comprising a first binder, a graphite material, and a conductive material, and further comprising a modifying additive, the silicon-based negative electrode material of any one of claims 1 to 4, or the silicon-based negative electrode material prepared by the preparation method of any one of claims 5 to 10.
12. The negative plate according to claim 11, wherein the mass ratio of the mixture of the silicon-based negative electrode material and the graphite material, the first binding substance and the modifying additive is 85-99: 0.2-8: 0.2-10; the concentration of the graphite material in the mixture is 35-95 wt%.
13. A secondary battery comprising the negative electrode sheet according to claim 11 or 12.
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CN110993931A (en) * 2019-12-23 2020-04-10 上海纳米技术及应用国家工程研究中心有限公司 Modification method of silicon negative electrode material for lithium ion battery
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CN109671942A (en) * 2018-12-24 2019-04-23 成都硅宝科技股份有限公司 A kind of lithium-ion battery silicon-carbon anode material and preparation method thereof
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