CN115863600A - Silicon-carbon negative electrode material and preparation method and application thereof - Google Patents
Silicon-carbon negative electrode material and preparation method and application thereof Download PDFInfo
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Abstract
The invention belongs to the technical field of secondary batteries, and particularly relates to a silicon-carbon negative electrode material and a preparation method and application thereof. The invention provides a preparation method of a silicon-carbon anode material, which comprises the following steps: performing first carbon coating on a metal compound by adopting a chemical vapor deposition method to obtain a porous carbon matrix precursor; the metal compound comprises one or more of potassium oxide, calcium oxide, magnesium oxide, aluminum oxide, zinc oxide, sodium carbonate, magnesium carbonate and calcium carbonate; pickling the porous carbon matrix precursor to obtain a porous carbon matrix; performing silicon deposition on the porous carbon substrate by adopting a chemical vapor deposition method to obtain a silicon-carbon precursor; and carrying out second carbon coating on the silicon-carbon precursor by adopting an organic carbon source cracking mode to obtain the silicon-carbon cathode material. The silicon-carbon negative electrode material prepared by the preparation method provided by the invention has excellent specific capacity and cycling stability when being used for a lithium ion battery.
Description
Technical Field
The invention belongs to the technical field of secondary batteries, and particularly relates to a silicon-carbon negative electrode material and a preparation method and application thereof.
Background
The current lithium ion battery technology is limited by energy density to cause the problem of limited endurance mileage of the electric automobile, thus bringing endurance anxiety to users and severely restricting the market share of the electric automobile. The energy density of the battery is improved mainly by two ways of optimizing the battery structure and improving the energy density of materials, the mass proportion of the negative electrode material in the battery is about 16%, and the use of the high-capacity negative electrode material is one of effective means for improving the energy density of the battery.
The traditional lithium ion battery cathode material is a graphite material, but the theoretical capacity of the traditional lithium ion battery cathode material is lower (372 mAh/g), and the market demand cannot be met. The silicon-based negative electrode material has a lithium removal potential similar to that of graphite and has a high theoretical specific capacity (4200 mAh/g), and has a huge application potential in improving the performance of a power battery when being used as a lithium battery negative electrode, but the silicon-based material has a huge volume effect (more than 300%) in the charging and discharging process, so that a formed solid electrolyte interface film is unstable, particles are easy to crack and pulverize, the electric contact with a current collector is lost, and finally, the rapid attenuation of electrode capacity and low coulombic efficiency are caused, and the rapid reduction of cycle performance is caused. Therefore, how to improve the cycle performance is of great significance to the application of silicon materials in lithium ion batteries.
Disclosure of Invention
The invention aims to provide a silicon-carbon negative electrode material and a preparation method thereof.
In order to achieve the above purpose, the invention provides the following technical scheme:
the invention provides a preparation method of a silicon-carbon anode material, which comprises the following steps:
performing first carbon coating on a metal compound by adopting a chemical vapor deposition method to obtain a porous carbon matrix precursor; the metal compound comprises one or more of potassium oxide, calcium oxide, magnesium oxide, aluminum oxide, zinc oxide, sodium carbonate, magnesium carbonate and calcium carbonate;
pickling the porous carbon matrix precursor to obtain a porous carbon matrix;
performing silicon deposition on the porous carbon substrate by adopting a chemical vapor deposition method to obtain a silicon-carbon precursor;
and carrying out second carbon coating on the silicon-carbon precursor by adopting an organic carbon source cracking mode to obtain the silicon-carbon negative electrode material.
Preferably, the median particle diameter of the metal compound is 10nm to 100 μm;
the carbon source adopted by the first carbon coating comprises one or more of methane, ethane, propane, ethylene and acetylene; the gas flow of the carbon source is 0.1-5L/min;
the temperature of the first carbon coating is 700-900 ℃, and the time is 0.5-12 h; the first carbon coating is performed in an inert gas.
Preferably, the acid adopted by the acid washing is one or more of dilute hydrochloric acid, dilute sulfuric acid and dilute nitric acid;
the concentration of the acid is 0.5-5 mol/L; the molar ratio of the acid to the metal compound is greater than 1.2:1;
the pickling time is 1-12 h, and the temperature is 25-100 ℃.
Preferably, the porous carbon matrix has a porosity of greater than 50% and an average pore size of 10 to 100nm.
Preferably, the silicon source used for silicon deposition comprises one or more of monosilane, dimethylsilane, chlorosilane, chloromethylsilane and dichlorosilane; the gas flow of the silicon source is 0.3-2L/min;
the temperature of the silicon deposition is 400-700 ℃, and the time is 0.5-24 h; the silicon deposition is carried out in an inert gas.
Preferably, the organic carbon source used for the second carbon coating comprises one or more of methane, acetylene, toluene, glucose, petroleum asphalt, mesophase asphalt, phenolic resin and polyacrylonitrile;
the temperature of the second carbon coating is 300-900 ℃, and the time is 0.5-12 h; the second carbon coating is performed in an inert gas.
The invention also provides the silicon-carbon cathode material obtained by the preparation method in the technical scheme, wherein the silicon-carbon cathode material is of a core-shell structure;
the inner core of the core-shell structure comprises a porous carbon matrix and nano silicon particles; the nano silicon particles are distributed in the pores and on the surface of the porous carbon matrix;
the shell of the core-shell structure is a carbon coating layer.
Preferably, the specific surface area of the silicon-carbon negative electrode material is 1-10 m 2 (ii)/g, the median particle diameter is 3-20 μm;
the silicon-carbon negative electrode material comprises 25-75% by mass of silicon element and 25-75% by mass of carbon element.
Preferably, the nano silicon particles comprise amorphous silicon and/or crystalline silicon; the median particle diameter of the nano silicon particles is less than 50 nm;
the mass percentage of the carbon coating layer in the silicon-carbon negative electrode material is 1-10%.
The invention also provides the application of the silicon-carbon negative electrode material in the technical scheme in a lithium ion battery.
The invention provides a preparation method of a silicon-carbon anode material, which comprises the following steps: performing first carbon coating on a metal compound by adopting a chemical vapor deposition method to obtain a porous carbon matrix precursor; the metal compound comprises one or more of potassium oxide, calcium oxide, magnesium oxide, aluminum oxide, zinc oxide, sodium carbonate, magnesium carbonate and calcium carbonate; acid washing is carried out on the porous carbon matrix precursor to obtain a porous carbon matrix; performing silicon deposition on the porous carbon substrate by adopting a chemical vapor deposition method to obtain a silicon-carbon precursor; and carrying out second carbon coating on the silicon-carbon precursor by adopting an organic carbon source cracking mode to obtain the silicon-carbon negative electrode material. According to the invention, metal compound particles are used as a template, a porous carbon material is prepared by using chemical vapor deposition carbon and acid washing technologies and is used as a matrix, and by utilizing the advantages of excellent mechanical property, good conductivity, stable chemical property, larger pore volume and the like, the porous carbon material can be used as a silicon-based material carrier to effectively buffer volume expansion, and the particle size of silicon particles can be reduced by depositing silicon on porous carbon through chemical vapor, and finally, a silicon-carbon cathode material is prepared by performing second carbon coating. The porous carbon substrate obtained by the preparation method provided by the invention has higher porosity, the silicon-carbon negative electrode material has smaller specific surface area and excellent conductivity, and the silicon-carbon negative electrode material shows excellent specific capacity and cycling stability when being used for a lithium ion battery.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings needed to be used in the embodiments will be briefly described below, and it is obvious that the drawings in the following description are only some embodiments of the present invention, and it is obvious for those skilled in the art to obtain other drawings without inventive exercise.
FIG. 1 is an SEM photograph of a porous carbon matrix obtained in example 1;
FIG. 2 is a pore size distribution diagram of the porous carbon matrix obtained in example 1;
FIG. 3 is an SEM image of the silicon-carbon anode material obtained in example 1;
FIG. 4 is an XRD diffraction pattern of the silicon-carbon anode material obtained in example 1;
FIG. 5 is a charge-discharge curve diagram of the silicon-carbon negative electrode material obtained in example 1.
Detailed Description
The invention provides a preparation method of a silicon-carbon anode material, which comprises the following steps:
performing first carbon coating on a metal compound by adopting a chemical vapor deposition method to obtain a porous carbon matrix precursor; the metal compound comprises one or more of potassium oxide, calcium oxide, magnesium oxide, aluminum oxide, zinc oxide, sodium carbonate, magnesium carbonate and calcium carbonate;
acid washing is carried out on the porous carbon matrix precursor to obtain a porous carbon matrix;
performing silicon deposition on the porous carbon substrate by adopting a chemical vapor deposition method to obtain a silicon-carbon precursor;
and carrying out second carbon coating on the silicon-carbon precursor by adopting an organic carbon source cracking mode to obtain the silicon-carbon negative electrode material.
In the present invention, the starting components are all commercially available products well known to those skilled in the art unless otherwise specified.
According to the invention, a chemical vapor deposition method is adopted to carry out first carbon coating on a metal compound to obtain a porous carbon matrix precursor.
In the present invention, the metal compound includes one or more of potassium oxide, calcium oxide, magnesium oxide, aluminum oxide, zinc oxide, sodium carbonate, magnesium carbonate and calcium carbonate, preferably includes one or more of potassium oxide, calcium oxide, magnesium oxide, zinc oxide, sodium carbonate and calcium carbonate, more preferably includes one or more of calcium oxide, zinc oxide, sodium carbonate and calcium carbonate; when the metal compounds are more than two of the above specific choices, the present invention does not have any special limitation on the proportion of the specific substances, and the specific substances can be mixed according to any proportion. The median particle diameter of the metal compound is preferably from 10nm to 100 μm, more preferably from 100nm to 50 μm, and most preferably from 1 to 10 μm.
In the present invention, the carbon source used for the first carbon coating preferably comprises one or more of methane, ethane, propane, ethylene and acetylene, more preferably comprises one or more of methane, ethane, ethylene and acetylene, and most preferably comprises one or more of methane, ethane and acetylene; when the carbon source is more than two of the above specific choices, the invention does not have any special limitation on the proportion of the specific substances, and the specific substances are mixed according to any proportion. The gas flow rate of the carbon source is preferably 0.1 to 5L/min, more preferably 0.5 to 4L/min, and most preferably 0.8 to 3L/min.
In the present invention, the temperature increase rate of the first carbon coating is preferably 1 to 10 ℃/min, more preferably 2 to 8 ℃/min, and most preferably 4 to 7 ℃/min; the temperature is preferably 700 to 900 ℃, more preferably 750 to 870 ℃, and most preferably 800 to 850 ℃; the time is preferably 0.5 to 12 hours, more preferably 1 to 10 hours, and most preferably 3 to 8 hours; the first carbon coating is preferably carried out in an inert gas; the inert gas preferably comprises nitrogen, helium, neon or argon, more preferably comprises nitrogen, helium or argon, most preferably comprises nitrogen or argon; the flow rate of the inert gas is preferably 0.3 to 2L/min, more preferably 0.5 to 1.8L/min, and most preferably 1 to 1.5L/min.
In the present invention, the first carbon coating is preferably performed using a chemical vapor deposition furnace; the rotating speed of the chemical vapor deposition furnace is preferably 0.2-2 r/min, more preferably 0.5-1.5 r/min, and most preferably 0.8-1.3 r/min; the pressure in the furnace is preferably 0 to 0.3MPa, more preferably 0.1 to 0.3MPa, and most preferably 0.1 to 0.2MPa.
The mass ratio of the metal compound to the carbon in the porous carbon matrix precursor is preferably 1:1 to 5, more preferably 1:2 to 4, most preferably 1:2 to 3.
After the first carbon coating is finished, the porous carbon matrix precursor is subjected to acid washing to obtain the porous carbon matrix.
In the invention, the acid used for acid washing is preferably one or more of dilute hydrochloric acid, dilute sulfuric acid and dilute nitric acid, more preferably dilute hydrochloric acid and/or dilute nitric acid, and most preferably dilute hydrochloric acid; when the acid is more than two of the specific choices, the proportion of the specific substances is not limited in any way, and the specific substances can be mixed according to any proportion. The concentration of the acid is preferably 0.5 to 5mol/L, more preferably 1 to 4mol/L, and most preferably 2 to 3mol/L; the molar ratio of acid to metal compound is preferably greater than 1.2:1, more preferably 1.2 to 5:1, most preferably from 2 to 4:1.
in the present invention, the time for the acid washing is preferably 1 to 12 hours, more preferably 2 to 10 hours, and most preferably 4 to 8 hours; the temperature is preferably from 25 to 100 deg.C, more preferably from 40 to 90 deg.C, most preferably from 50 to 80 deg.C.
In the invention, the equipment used for pickling is preferably a magnetic stirrer and/or a mechanical stirrer, and more preferably a magnetic stirrer; the rotation speed of the equipment for acid washing is preferably 100-1000 r/min, more preferably 200-800 r/min, and most preferably 400-600 r/min.
After the acid washing is finished, the method also comprises the steps of washing, drying and screening in sequence.
In the present invention, the solvent used for the water washing is preferably pure water; the equipment adopted by the water washing is preferably a magnetic stirrer and/or a mechanical stirrer, and more preferably a magnetic stirrer; the rotating speed of the equipment adopted by the water washing is preferably 100-1000 r/min, more preferably 200-800 r/min, and most preferably 400-600 r/min; the washing time is preferably 0.5 to 5 hours, more preferably 1 to 4 hours, and most preferably 2 to 3 hours; the temperature is preferably from 25 to 100 deg.C, more preferably from 40 to 90 deg.C, most preferably from 50 to 80 deg.C.
In the invention, the drying equipment is preferably an air-blast drying oven; the drying temperature is preferably 100 to 200 ℃, more preferably 120 to 180 ℃, and most preferably 140 to 160 ℃.
In the invention, the equipment adopted for screening is preferably an ultrasonic vibration screen; the screening device preferably has a mesh size of 20 to 2000 mesh, more preferably 100 to 1500 mesh, and most preferably 200 to 1000 mesh.
In the present invention, the porosity of the porous carbon matrix is preferably greater than 50%, more preferably from 50 to 90%, most preferably from 60 to 80%; the average pore size is preferably 10 to 100nm, more preferably 20 to 80nm, and most preferably 40 to 60nm; the porous carbon matrix preferably has a center particle size of 6 to 100. Mu.m, more preferably 10 to 80 μm, and most preferably 40 to 60 μm.
In the invention, the special pore-forming technology (acid washing) causes the pore-size distribution of the porous carbon matrix material to mainly exist as mesopores, and the average pore-size is 10-100 nm. The pore diameter and the porosity of the porous carbon matrix are increased, so that the deposition of nano silicon particles is facilitated, the volume expansion effect in the charge and discharge process of the lithium ion battery can be effectively relieved, and the material has better dynamic performance.
After the porous carbon matrix is obtained, the porous carbon matrix is subjected to silicon deposition by adopting a chemical vapor deposition method to obtain a silicon-carbon precursor.
In the present invention, the silicon source used for silicon deposition preferably comprises one or more of monosilane, dimethylsilane, chlorosilane, chloromethylsilane and dichlorosilane, more preferably comprises one or more of monosilane, dimethylsilane, chlorosilane and dichlorosilane, and most preferably comprises one or more of monosilane, dimethylsilane and dichlorosilane; when the silicon source is more than two of the above specific choices, the invention does not have any special limitation on the proportion of the specific substances, and the specific substances are mixed according to any proportion. The flow rate of the silicon source gas is preferably 0.3 to 2L/min, more preferably 0.5 to 1.8L/min, and most preferably 1 to 1.5L/min.
In the invention, the heating rate of the silicon deposition is preferably 1-10 ℃/min, more preferably 2-8 ℃/min, and most preferably 4-7 ℃/min; the temperature is preferably 400 to 700 ℃, more preferably 450 to 650 ℃, and most preferably 500 to 600 ℃; the time is preferably 0.5 to 24 hours, more preferably 3 to 20 hours, and most preferably 5 to 15 hours; the silicon deposition is preferably carried out in an inert gas; the inert gas preferably comprises nitrogen, helium, neon or argon, more preferably comprises nitrogen, helium or argon, most preferably comprises nitrogen or argon; the gas flow rate of the inert gas is preferably 0.3 to 2L/min, more preferably 0.5 to 1.8L/min, and most preferably 1 to 1.5L/min.
In the present invention, the silicon deposition is preferably performed using a chemical vapor deposition furnace; the rotating speed of the chemical vapor deposition furnace is preferably 0.2-2 r/min, more preferably 0.5-1.5 r/min, and most preferably 0.8-1.3 r/min; the pressure in the furnace is preferably 0 to 0.3MPa, more preferably 0.1 to 0.3MPa, and most preferably 0.1 to 0.2MPa.
After the silicon deposition, the present invention also preferably includes oxidation. In the present invention, the temperature of the oxidation is preferably 25 to 100 ℃, more preferably 40 to 90 ℃, and most preferably 50 to 80 ℃; the time is preferably 0.5 to 10 hours, more preferably 2 to 8 hours, and most preferably 4 to 6 hours; the oxidation is preferably carried out in air; the air is preferably dry compressed air; the humidity of the air is 0 to 20%, more preferably 3 to 18%, most preferably 5 to 15%; the flow rate is preferably 0.1 to 20L/min, more preferably 1 to 15L/min, and most preferably 5 to 10L/min.
In the invention, the oxidation has the function of forming a small amount of silicon oxide on the surface of the nano silicon and preventing the high-activity nano silicon from being exposed in the air and violently oxidized and spontaneously ignited.
In the invention, the silicon deposition adopts a chemical vapor deposition technology, so that the median particle diameter of the prepared nano silicon particles is not more than 50nm, and good cycle performance can be achieved in the charging and discharging process, and on the other hand, the particle size, the crystal structure and the deposited nano silicon quality of the nano silicon particles can be adjusted by changing the process parameters of the vapor deposition furnace.
After the silicon-carbon precursor is obtained, the silicon-carbon precursor is subjected to second carbon coating by adopting an organic carbon source cracking mode to obtain the silicon-carbon negative electrode material.
In the present invention, the organic carbon source used for the second carbon coating preferably includes one or more of methane, acetylene, toluene, glucose, petroleum pitch, mesophase pitch, phenolic resin, and polyacrylonitrile, more preferably includes one or more of methane, acetylene, toluene, glucose, petroleum pitch, phenolic resin, and polyacrylonitrile, and most preferably includes one or more of methane, acetylene, toluene, petroleum pitch, and polyacrylonitrile; when the organic carbon source is more than two of the above specific choices, the invention has no special limitation on the proportion of the specific substances, and the specific substances are mixed according to any proportion. The second carbon coating preferably comprises a gas phase coating, a liquid phase coating or a solid phase coating, more preferably comprises a gas phase coating or a liquid phase coating, and most preferably comprises a gas phase coating.
In the invention, the heating rate of the second carbon coating is preferably 1-10 ℃/min, more preferably 2-8 ℃/min, and most preferably 4-7 ℃/min; the temperature is preferably 300 to 900 ℃, more preferably 400 to 800 ℃, and most preferably 500 to 700 ℃; the time is preferably 0.5 to 12 hours, more preferably 3 to 10 hours, and most preferably 5 to 8 hours; the second carbon coating is preferably carried out in an inert gas. The inert gas preferably comprises nitrogen, helium, neon or argon, more preferably comprises nitrogen, helium or argon, most preferably comprises nitrogen or argon; the flow rate of the inert gas is preferably 0.1 to 20L/min, more preferably 1 to 15L/min, and most preferably 5 to 10L/min.
In the invention, the second carbon coating is preferably a gas-phase organic carbon source coating, and the gas-phase organic carbon source coating is preferably carried out by adopting a chemical vapor deposition furnace; the flow rate of the gas-phase organic carbon source is preferably 0.1-20L/min, more preferably 1-15L/min, and most preferably 5-10L/min; the rotating speed of the chemical vapor deposition furnace is preferably 0.2-2 r/min, more preferably 0.5-1.5 r/min, and most preferably 0.8-1.3 r/min; the pressure in the furnace is preferably 0 to 0.3MPa, more preferably 0.1 to 0.3MPa, and most preferably 0.1 to 0.2MPa.
In the present invention, the second carbon coating process is preferably: and fully contacting the silicon-carbon precursor with an organic carbon source, and cracking the organic carbon source at high temperature to obtain the silicon-carbon cathode material.
In the invention, the second carbon coating can isolate the contact between the nano silicon particles and water, can avoid water system homogenization and gas generation in the battery preparation process, has a good homogenization process, can avoid the direct contact with electrolyte to generate an excessive SEI film in the charge-discharge process, and can keep good cycle performance and other electrochemical performances in the battery charge-discharge process.
The preparation method of the silicon-carbon cathode material provided by the invention takes metal compound particles as a template, uses chemical vapor deposition carbon and acid washing technology to prepare a porous carbon material as a substrate, utilizes the advantages of excellent mechanical property, good conductivity, stable chemical property, larger pore volume and the like of the porous carbon material as a silicon-based material carrier to effectively buffer volume expansion, can reduce the granularity of silicon particles by chemical vapor deposition silicon on the porous carbon, and finally carries out second carbon coating to prepare the silicon-carbon cathode material. The porous carbon substrate obtained by the preparation method provided by the invention has higher porosity, the silicon-carbon negative electrode material has smaller specific surface area and excellent conductivity, and the silicon-carbon negative electrode material shows excellent specific capacity and cycling stability when being used for a lithium ion battery.
The invention also provides the silicon-carbon cathode material obtained by the preparation method in the technical scheme, wherein the silicon-carbon cathode material is of a core-shell structure;
the inner core of the core-shell structure comprises a porous carbon matrix and nano silicon particles; the nano silicon particles are distributed in the pores and on the surface of the porous carbon matrix;
the shell of the core-shell structure is a carbon coating layer.
In the present invention, the specific surface area of the silicon-carbon negative electrode material is preferably 1 to 10m 2 (ii) g, more preferably 2 to 8m 2 Per g, most preferably from 4 to 6m 2 (ii)/g; the median particle diameter is preferably from 3 to 20 μm, more preferably from 5 to 18 μm, most preferably from 10 to 15 μm; the mass percentage content of the silicon element in the silicon-carbon negative electrode material is preferably 25-75%, more preferably 35-65%, and most preferably 45-55%; the content of carbon is preferably 25 to 75% by mass, more preferably 35 to 65% by mass, and most preferably 45 to 55% by mass.
In the present invention, the nano silicon particles preferably include amorphous silicon and/or crystalline silicon, more preferably include amorphous silicon; when the nano silicon particles are more than two of the specific choices, the proportion of the specific substances is not limited in any way, and the nano silicon particles can be mixed according to any proportion. The median particle diameter of the nano-silicon particles is preferably 50nm or less, more preferably 0.1 to 40nm, and most preferably 10 to 30nm.
In the present invention, the number of carbon coating layers is preferably at least one, more preferably 1 to 5, and most preferably 2 to 3; the monolayer thickness is preferably 100nm or more, more preferably 100nm to 10 μm, most preferably 500nm to 5 μm; the mass percentage content of the carbon coating layer in the silicon-carbon negative electrode material is preferably 1-10%, more preferably 2-8%, and most preferably 4-6%; the carbon coating layer is also preferably filled in pores of the porous carbon matrix.
When the silicon-carbon negative electrode material provided by the invention is used as a negative electrode active material of a secondary battery, the energy density of the battery can be obviously improved, and the silicon-carbon negative electrode material has excellent electrochemical performance and dynamic performance.
The invention also provides the application of the silicon-carbon negative electrode material in the technical scheme in a lithium ion battery.
The present invention is not limited to any particular process, and may be applied in a manner known to those skilled in the art.
For further illustration of the present invention, the following detailed description of the silicon carbon anode material provided by the present invention, its preparation method and application are provided in conjunction with the accompanying drawings and examples, which should not be construed as limiting the scope of the present invention.
Example 1
(1) Preparation of porous carbon matrix: putting 1kg of magnesium oxide powder in a CVD (chemical vapor deposition) furnace, wherein the median particle size of magnesium oxide is 4 mu m, introducing nitrogen with the flow rate of 1L/min to keep the pressure in the furnace at 0.15MPa and the rotating speed of the furnace body at 1.0r/min until the oxygen content in the CVD furnace is less than 100ppm, heating to 800 ℃ at the speed of 5 ℃/min, introducing 0.8L/min of acetylene, preserving heat for 12h to ensure that deposited carbon is uniformly coated in the magnesium oxide powder, and cooling to room temperature. Adding 1 mol/L100L dilute hydrochloric acid into carbon-coated magnesium oxide, performing acid-washing pore-forming in a magnetic stirrer at 80 ℃ for 10h at 400r/min, performing water-washing at 80 ℃ for 2h to neutrality at 400r/min, drying at 140 ℃, and sieving by a 325-mesh sieve to obtain the porous carbon matrix.
(2) Silicon deposition: placing the porous carbon substrate in a CVD furnace, introducing nitrogen with the flow rate of 1L/min to keep the pressure in the furnace at 0.15MPa and the rotating speed of the furnace body at 1.0r/min until the oxygen content in the CVD furnace is less than 100ppm, heating to 500 ℃ at the speed of 5 ℃/min, introducing 0.8L/min of silane, preserving the temperature for 20h to deposit nano silicon on the surface and in the pores of the porous carbon substrate, and cooling to room temperature to obtain the silicon-carbon precursor.
(3) Preparing a silicon-carbon negative electrode material: and (3) placing the silicon-carbon precursor in the step (2) in a CVD furnace, introducing nitrogen with the flow rate of 1L/min to keep the pressure in the furnace at 0.15MPa and the rotating speed of the furnace body at 1.0r/min until the oxygen content in the CVD furnace is less than 100ppm, heating to 700 ℃ at the speed of 5 ℃/min, introducing 0.8L/min of acetylene, keeping the temperature at 700 ℃ for 6h to uniformly coat deposited carbon on the surface and pores of the silicon-carbon precursor, and cooling to room temperature to obtain the silicon-carbon cathode material.
Example 2
(1) Preparation of porous carbon substrate: 1kg of calcium carbonate powder is placed in a CVD furnace, the median particle size of the calcium carbonate is 10 mu m, nitrogen is introduced, the flow rate of the nitrogen is 1L/min, the pressure in the CVD furnace is kept at 0.15MPa, the rotating speed of the furnace body is 1.0r/min until the oxygen content in the CVD furnace is less than 100ppm, the temperature is raised to 850 ℃ at the speed of 5 ℃/min, 1L/min of acetylene is introduced, the temperature is kept for 10h, deposited carbon is uniformly coated in the calcium carbonate powder, and the temperature is lowered to the room temperature. Adding 20L of dilute hydrochloric acid of 2mol/L into carbon-coated calcium carbonate, carrying out acid washing and pore forming at 80 ℃ for 8h in a magnetic stirrer at 600r/min, carrying out water washing at 80 ℃ for 2h to neutrality at 400r/min, drying at 140 ℃, and sieving by a 325-mesh sieve to obtain the porous carbon matrix.
(2) Silicon deposition: placing the porous carbon substrate in a CVD furnace, introducing nitrogen with the flow rate of 1L/min to keep the pressure in the furnace at 0.15MPa and the rotating speed of the furnace body at 1.0r/min until the oxygen content in the CVD furnace is less than 100ppm, heating to 550 ℃ at the speed of 6 ℃/min, introducing 3L/min of silane, preserving heat for 6h to deposit nano silicon particles on the surface and in pores of the porous carbon substrate, and cooling to room temperature to obtain the silicon-carbon precursor.
(3) Preparing a silicon-carbon negative electrode material: and (3) placing the silicon-carbon precursor in the step (2) in a CVD furnace, introducing nitrogen with the flow rate of 1L/min to keep the pressure in the furnace at 0.15MPa and the rotating speed of the furnace body at 1.0r/min until the oxygen content in the CVD furnace is less than 100ppm, heating to 700 ℃ at the speed of 7 ℃/min, introducing 1.5L/min of acetylene, keeping the temperature at 700 ℃ for 5h to enable deposited carbon to be uniformly coated on the surface of the silicon-carbon precursor, and cooling to room temperature to obtain the silicon-carbon cathode material.
Example 3
(1) Preparation of porous carbon substrate: putting 1kg of magnesium oxide powder in a CVD furnace, leading nitrogen into the CVD furnace with the medium particle size of the magnesium oxide being 4 mu m and the flow rate of the nitrogen being 1L/min to keep the pressure in the CVD furnace at 0.15MPa and the rotating speed of the furnace body at 1.0r/min until the oxygen content in the CVD furnace is less than 100ppm, heating to 900 ℃ at the speed of 5 ℃/min, leading in 0.8L/min of acetylene, preserving the heat for 5h to ensure that deposited carbon is uniformly coated in the magnesium oxide powder, and cooling to the room temperature. Adding 120L of dilute hydrochloric acid of 1mol/L into the carbon-coated magnesium oxide, carrying out acid washing and pore forming at 80 ℃ for 15h in a magnetic stirrer at 400r/min, washing to be neutral, drying at 140 ℃, and sieving by a 325-mesh sieve to obtain the porous carbon matrix.
(2) Silicon deposition: placing the porous carbon substrate in a CVD furnace, introducing nitrogen with the flow rate of 1L/min to keep the pressure in the furnace at 0.15MPa and the rotating speed of the furnace body at 1.0r/min until the oxygen content in the CVD furnace is less than 100ppm, heating to 500 ℃ at the speed of 5 ℃/min, introducing 1L/min of silane, preserving heat for 15h to deposit nano silicon on the surface and in the pores of the porous carbon substrate, cooling to 50 ℃, introducing air with the flow rate of 5L/min and the humidity of 15% to carry out surface oxidation for 3h to obtain the silicon-carbon precursor.
(3) Preparing a silicon-carbon negative electrode material: and (3) placing the silicon-carbon precursor in the step (2) in a CVD furnace, introducing nitrogen until the oxygen content in the CVD furnace is less than 100ppm, heating to 700 ℃ at the speed of 5 ℃/min, introducing 0.8L/min of acetylene, preserving the temperature for 5h at 700 ℃, uniformly coating deposited carbon on the surface and pores of the silicon-carbon precursor, and cooling to room temperature to obtain the silicon-carbon cathode material.
Example 4
(1) Preparation of porous carbon substrate: putting 1kg of magnesium oxide powder in a CVD furnace, leading nitrogen into the CVD furnace with the medium particle size of the magnesium oxide being 8 mu m and the flow rate of the nitrogen being 1L/min to keep the pressure in the CVD furnace at 0.15MPa and the rotating speed of the furnace body at 1.0r/min until the oxygen content in the CVD furnace is less than 100ppm, heating to 900 ℃ at the speed of 5 ℃/min, leading 5L/min of acetylene, preserving the heat for 5h to ensure that deposited carbon is uniformly coated in the magnesium oxide powder, and cooling to the room temperature. Adding 2 mol/L100L of dilute hydrochloric acid into carbon-coated magnesium oxide, performing acid-washing pore-forming in a magnetic stirrer at 80 ℃ for 15h at 400r/min, washing to neutrality, drying at 140 ℃, and sieving by a 325-mesh sieve to obtain the porous carbon matrix.
(2) Silicon deposition: placing a porous carbon substrate in a CVD furnace, introducing nitrogen with the flow rate of 1L/min to keep the pressure in the furnace at 0.15MPa and the rotating speed of the furnace body at 1.0r/min until the oxygen content in the CVD furnace is less than 100ppm, heating to 650 ℃ at the speed of 5 ℃/min, introducing 4L/min of silane, preserving the temperature for 5h to deposit nano silicon on the surface and in the pores of the porous carbon substrate, cooling to room temperature, and introducing air with the flow rate of 4L/min and the humidity of 20% to carry out surface oxidation for 2h to obtain the silicon-carbon precursor.
(3) Preparing a silicon-carbon negative electrode material: and (3) placing the silicon-carbon precursor in the step (2) in a CVD furnace, introducing nitrogen with the flow rate of 1L/min to keep the pressure in the furnace at 0.15MPa and the rotating speed of the furnace body at 1.0r/min until the oxygen content in the CVD furnace is less than 100ppm, heating to 650 ℃ at the speed of 5 ℃/min, introducing 0.8L/min of acetylene, keeping the temperature at 650 ℃ for 4h to ensure that deposited carbon is uniformly coated on the surface and pores of the silicon-carbon precursor, and cooling to room temperature to obtain the silicon-carbon cathode material.
Example 5
(1) Preparation of porous carbon substrate: 1kg of magnesium oxide powder is placed in a CVD furnace, the median particle size of the magnesium oxide is 4 mu m, nitrogen is introduced with the flow rate of 1L/min, the pressure in the furnace is kept at 0.15MPa, the rotating speed of the furnace body is 1.0r/min until the oxygen content in the CVD furnace is less than 100ppm, the temperature is raised to 800 ℃ at the speed of 5 ℃/min, 1L/min of acetylene is introduced, the temperature is kept for 6h, deposited carbon is uniformly coated in the magnesium oxide powder, and the temperature is reduced to room temperature. Adding 1 mol/L100L dilute hydrochloric acid into carbon-coated magnesium oxide, performing acid-washing pore-forming in a magnetic stirrer at the temperature of 80 ℃ for 24h at the speed of 400r/min, washing to be neutral, drying at the temperature of 140 ℃, and sieving by a 325-mesh sieve to obtain the porous carbon matrix.
(2) Silicon deposition: placing the porous carbon substrate in a CVD furnace, introducing nitrogen with the flow rate of 1L/min to keep the pressure in the furnace at 0.15MPa and the rotating speed of the furnace body at 1.0r/min until the oxygen content in the CVD furnace is less than 100ppm, heating to 600 ℃ at the speed of 5 ℃/min, introducing silane with the flow rate of 0.3L/min, preserving the temperature for 36h, and depositing nano silicon on the surface and in pores of the porous carbon substrate to obtain the silicon-carbon precursor.
(3) Preparing a silicon-carbon negative electrode material: and (3) placing the silicon-carbon precursor in the step (2) in a CVD furnace, introducing nitrogen with the flow rate of 1L/min to keep the pressure in the furnace at 0.15MPa and the rotating speed of the furnace body at 1.0r/min until the oxygen content in the CVD furnace is less than 100ppm, heating to 600 ℃ at the speed of 5 ℃/min, introducing 0.8L/min of acetylene, keeping the temperature at 600 ℃ for 6h to ensure that deposited carbon is uniformly coated on the surface and pores of the silicon-carbon precursor, and cooling to room temperature to obtain the silicon-carbon cathode material.
Comparative example 1
A silicon carbon anode material was prepared in the manner described in example 1, except that a commercially available porous carbon substrate was used.
Comparative example 2
A silicon carbon negative electrode material was prepared in the manner described in example 1, except that a porous carbon matrix prepared using a phenolic resin was used.
Comparative example 3
A silicon carbon anode material was prepared in the manner described in example 1, except that a porous carbon matrix prepared using polymethyl methacrylate was used.
Comparative example 4
A silicon carbon anode material was prepared in the manner described in example 1, except that a porous carbon matrix prepared with a polystyrene resin was used.
Comparative example 5
A silicon carbon anode material was prepared in the manner described in example 1, except that a porous carbon matrix prepared using an acrylic resin was used.
Test example 1
The particle size ranges of the silicon-carbon negative electrode materials obtained in examples 1 to 5 and comparative examples 1 to 5 were measured by a malvern laser particle size analyzer Mastersizer 3000, and the specific surface area of the silicon-carbon negative electrode material was measured by a fine gaobo JW-DX type dynamic adsorption specific surface area analyzer. The test results are shown in Table 1.
TABLE 1 particle size and specific surface area of silicon carbon anode materials obtained in examples 1 to 5 and comparative examples 1 to 5
As can be seen from Table 1, the silicon-carbon negative electrode material prepared by the method has the characteristics of easy regulation and control of particle size, moderate median particle size and small specific surface area, and can reduce the occurrence of side reactions when used in a lithium ion battery system.
Test example 2
The silicon carbon anode materials obtained in examples 1 to 5 and comparative examples 1 to 5 were tested for conductivity, first reversible capacity and first efficiency.
And (3) lithium battery electricity tapping test: the silicon-carbon negative electrode materials obtained in the examples 1 to 5 and the comparative examples 1 to 5 are mixed in pure water according to a mass ratio of the silicon-carbon material, the conductive carbon black and the binder of 96. A button half cell is assembled in a glove box filled with argon, a counter electrode is a metal lithium sheet, a diaphragm is PE, and an electrolyte is 1mol/L EC/DMC (Vol 1: 1) of LiPF 6. The charge and discharge test of the button cell was carried out by test procedures 0.2C DC to 0V,0.05C DC to 0V,0V CV 50uA,0.01C DC to 0V,0V CV 20uA, rest 10min, and 0.2C CC to 2V. The first reversible capacity and efficiency of the silicon carbon anode materials in the examples and comparative examples were measured. The test equipment of the button cell is a LAND cell test system of blue electronic corporation of Wuhan city.
And (3) conductivity test: the resistivity of the powder is tested by adopting a Chinese micro-nano (GEST-126), the compactness of the powder material is different, the powder material is tested under different pressures, and the obtained data are different, so that when the powder resistance of the sample is tested, the fixed pressure condition is 5T, and then the conversion is carried out according to the resistivity data to obtain the conductivity data. Conductivity and resistivity are inverse to each other, i.e. conductivity = 1/resistivity. The test results are shown in Table 2.
TABLE 2 conductivity, first reversible capacity and first efficiency of silicon carbon anode materials obtained in examples 1 to 5 and comparative examples 1 to 5
As can be seen from Table 2, the silicon-carbon negative electrode material prepared by the method has high conductivity and specific capacity, the first reversible capacity is greater than 2000mAh/g in a lithium ion battery test system, and the first coulombic efficiency is greater than 85%.
The morphology of the porous carbon matrix and the silicon carbon anode material obtained in example 1 was analyzed using a field emission Scanning Electron Microscope (SEM) (JSM-7800F), and the results are shown in fig. 1 and 3. As can be seen from fig. 1 and 3, the porous carbon matrix obtained in example 1 has a rich porous structure, and the surface of the obtained silicon-carbon negative electrode material has a dense carbon coating layer, so that water and electrolyte can be isolated.
The grain size of the material was determined by phase analysis of the material using an XRD diffractometer (Panalytical X' PERT PRO MPD, the Netherlands), and the results are shown in FIG. 4. As can be seen from fig. 4, the deposited nano-silicon in example 1 is amorphous silicon.
As can be seen from fig. 5, the silicon carbon negative electrode material obtained in example 1 has a high first reversible capacity.
According to the embodiment, the preparation method of the silicon-carbon negative electrode material provided by the invention takes the metal compound particles as the template, the porous carbon material is prepared by using the chemical vapor deposition carbon and the acid washing technology as the matrix, the porous carbon material can effectively buffer the volume expansion by using the advantages of excellent mechanical property, good conductivity, stable chemical property, larger pore volume and the like as a silicon-based material carrier, the particle size of the silicon particles can be reduced by depositing silicon on the porous carbon through the chemical vapor, and finally, the silicon-carbon negative electrode material is prepared by performing second carbon coating. The porous carbon substrate obtained by the preparation method provided by the invention has higher porosity, the silicon-carbon negative electrode material has smaller specific surface area and excellent conductivity, and the silicon-carbon negative electrode material shows excellent specific capacity and cycling stability when being used for a lithium ion battery.
Meanwhile, when the silicon-carbon negative electrode material provided by the invention is used as a negative electrode active material of a secondary battery, the energy density of the battery can be obviously improved, and the silicon-carbon negative electrode material has excellent electrochemical performance and dynamic performance.
Although the above embodiments have been described in detail, they are only a part of the embodiments of the present invention, not all of the embodiments, and other embodiments can be obtained without inventive step according to the embodiments, and all of the embodiments belong to the protection scope of the present invention.
Claims (10)
1. The preparation method of the silicon-carbon negative electrode material is characterized by comprising the following steps of:
performing first carbon coating on a metal compound by adopting a chemical vapor deposition method to obtain a porous carbon matrix precursor; the metal compound comprises one or more of potassium oxide, calcium oxide, magnesium oxide, aluminum oxide, zinc oxide, sodium carbonate, magnesium carbonate and calcium carbonate;
pickling the porous carbon matrix precursor to obtain a porous carbon matrix;
performing silicon deposition on the porous carbon substrate by adopting a chemical vapor deposition method to obtain a silicon-carbon precursor;
and carrying out second carbon coating on the silicon-carbon precursor by adopting an organic carbon source cracking mode to obtain the silicon-carbon negative electrode material.
2. The production method according to claim 1, wherein the metal compound has a median particle diameter of 10nm to 100 μm;
the carbon source adopted by the first carbon coating comprises one or more of methane, ethane, propane, ethylene and acetylene; the gas flow of the carbon source is 0.1-5L/min;
the temperature of the first carbon coating is 700-900 ℃, and the time is 0.5-12 h; the first carbon coating is performed in an inert gas.
3. The preparation method according to claim 1, wherein the acid used for the acid washing is one or more of dilute hydrochloric acid, dilute sulfuric acid and dilute nitric acid;
the concentration of the acid is 0.5-5 mol/L; the molar ratio of the acid to the metal compound is greater than 1.2:1;
the pickling time is 1-12 h, and the temperature is 25-100 ℃.
4. The method according to claim 1 or 3, wherein the porous carbon matrix has a porosity of more than 50% and an average pore size of 10 to 100nm.
5. The method of claim 1, wherein the silicon source used for silicon deposition comprises one or more of monosilane, dimethylsilane, chlorosilane, chloromethylsilane, and dichlorosilane; the gas flow of the silicon source is 0.3-2L/min;
the temperature of the silicon deposition is 400-700 ℃, and the time is 0.5-24 h; the silicon deposition is carried out in an inert gas.
6. The preparation method of claim 1, wherein the organic carbon source used for the second carbon coating comprises one or more of methane, acetylene, toluene, glucose, petroleum pitch, mesophase pitch, phenolic resin and polyacrylonitrile;
the temperature of the second carbon coating is 300-900 ℃, and the time is 0.5-12 h; the second carbon coating is performed in an inert gas.
7. The silicon-carbon negative electrode material prepared by the preparation method of any one of claims 1 to 6, wherein the silicon-carbon negative electrode material has a core-shell structure;
the inner core of the core-shell structure comprises a porous carbon matrix and nano silicon particles; the nano silicon particles are distributed on the pores and the surface of the porous carbon matrix by 5;
the shell of the core-shell structure is a carbon coating layer.
8. The silicon-carbon anode material as claimed in claim 7, wherein the specific surface area of the silicon-carbon anode material is 1 to 10m 2 Per g, median particle diameterIs 3-20 μm;
the silicon-carbon negative electrode material comprises 25-75% by mass of silicon element and 25-75% by mass of carbon element, wherein the mass percentage of the silicon element in the silicon-carbon negative electrode material is 0%.
9. The silicon-carbon anode material as claimed in claim 7 or 8, wherein the nano-silicon particles comprise amorphous silicon and/or crystalline silicon; the median particle diameter of the nano silicon particles is less than 50 nm;
the mass percentage of the carbon coating layer in the silicon-carbon negative electrode material is 1-10%.
10. Use of the silicon carbon negative electrode material of any one of claims 7 to 9 in a lithium ion battery.
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| CN116454255A (en) * | 2023-06-15 | 2023-07-18 | 江苏正力新能电池技术有限公司 | Silicon-carbon negative electrode material and application thereof |
| CN116598452A (en) * | 2023-05-15 | 2023-08-15 | 江门市和创新能源材料有限公司 | Silicon-carbon negative electrode material and preparation method and application thereof |
| CN116885158A (en) * | 2023-09-08 | 2023-10-13 | 琥崧智能装备(太仓)有限公司 | Carbon-silicon composite anode active material and preparation method and application thereof |
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| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN116598452A (en) * | 2023-05-15 | 2023-08-15 | 江门市和创新能源材料有限公司 | Silicon-carbon negative electrode material and preparation method and application thereof |
| CN116598452B (en) * | 2023-05-15 | 2024-03-12 | 江门市和创新能源材料有限公司 | Silicon-carbon negative electrode material and preparation method and application thereof |
| CN116454255A (en) * | 2023-06-15 | 2023-07-18 | 江苏正力新能电池技术有限公司 | Silicon-carbon negative electrode material and application thereof |
| CN116454255B (en) * | 2023-06-15 | 2023-09-08 | 江苏正力新能电池技术有限公司 | Silicon-carbon negative electrode material and application thereof |
| CN116885158A (en) * | 2023-09-08 | 2023-10-13 | 琥崧智能装备(太仓)有限公司 | Carbon-silicon composite anode active material and preparation method and application thereof |
| CN116885158B (en) * | 2023-09-08 | 2023-12-01 | 琥崧智能装备(太仓)有限公司 | Carbon-silicon composite anode active material and preparation method and application thereof |
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