CN116741951A - Core-shell structure silicon oxide-based negative electrode composite material and preparation method thereof - Google Patents

Core-shell structure silicon oxide-based negative electrode composite material and preparation method thereof Download PDF

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CN116741951A
CN116741951A CN202210209063.2A CN202210209063A CN116741951A CN 116741951 A CN116741951 A CN 116741951A CN 202210209063 A CN202210209063 A CN 202210209063A CN 116741951 A CN116741951 A CN 116741951A
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silicon oxide
negative electrode
carbon
composite material
electrode composite
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卞灿灿
周旭峰
刘兆平
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Ningbo Institute of Material Technology and Engineering of CAS
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Ningbo Institute of Material Technology and Engineering of CAS
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/362—Composites
    • H01M4/366—Composites as layered products
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/052—Li-accumulators
    • H01M10/0525—Rocking-chair batteries, i.e. batteries with lithium insertion or intercalation in both electrodes; Lithium-ion batteries
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/38—Selection of substances as active materials, active masses, active liquids of elements or alloys
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/48—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides
    • H01M4/483—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides for non-aqueous cells
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/58—Selection of substances as active materials, active masses, active liquids of inorganic compounds other than oxides or hydroxides, e.g. sulfides, selenides, tellurides, halogenides or LiCoFy; of polyanionic structures, e.g. phosphates, silicates or borates
    • H01M4/583—Carbonaceous material, e.g. graphite-intercalation compounds or CFx
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M2004/026—Electrodes composed of, or comprising, active material characterised by the polarity
    • H01M2004/027—Negative electrodes
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/10—Energy storage using batteries

Abstract

A preparation method of a silicon oxide-based negative electrode composite material with a core-shell structure comprises the following steps: a) Mg is added with 2 Mixing Si, lithium oxide and silicon oxide, sequentially performing ball milling, sieving and first solid phase reaction, cooling, and performing first crushing and grading treatment to obtain a reaction product; b) Treating the reaction product obtained in the step a) by adopting a weak acid solution, filtering, and washing with water to obtain a non-carbon-coated material; c) Mixing the non-carbon-coated material obtained in the step b) with an organic carbon source water solution, drying, performing a second solid phase reaction, cooling, and performing second grinding and separationPerforming stage treatment to obtain a single-layer carbon-coated material; d) And c) carrying out chemical vapor deposition on the single-layer carbon-coated material obtained in the step c) by adopting carbon source gas, cooling, and carrying out third crushing and grading treatment to obtain the silicon oxide-based negative electrode composite material. The silicon oxide-based negative electrode composite material prepared by the preparation method provided by the invention has higher charge-discharge capacity and first coulombic efficiency.

Description

Core-shell structure silicon oxide-based negative electrode composite material and preparation method thereof
Technical Field
The invention relates to the technical field of lithium ion batteries, in particular to a silicon oxide-based negative electrode composite material with a core-shell structure and a preparation method thereof.
Background
With the rapid development of modern technology, people have higher requirements on energy storage and utilization, and in particular, the demand for high-capacity lithium ion batteries is growing. Most of the current commercial lithium battery cathode materials are graphite (theoretical specific capacity: 372 mAh/g), but the lower capacity can not meet the daily use of people, especially in the aspect of electric automobiles. The silicon cathode has high theoretical specific capacity (about 4200 mAh/g), low working potential (0.2-0.3V vs Li/Li) + ) And the content is rich, and the product is environment-friendly, so the product is expected to be a substitute of graphite. However, the silicon cathode has huge volume expansion (300%) in the lithiation/delithiation process, which is very easy to cause crushing of materials and irreversible damage to the battery caused by the separation of active substances from the current collector, thereby impeding practical application of Si.
The high theoretical specific capacity (about 2400 mAh/g) of the silicon oxide and the stronger cycling stability compared with silicon make the silicon oxide become one of the most promising choices for replacing the anode materials of the lithium ion batteries at present. However, the first coulombic efficiency of silica is low (about 70%) mainly because lithium reacts with silica to form an irreversible phase (Li during the first lithiation process 2 O and Li x SiO y ) Resulting in excessive consumption of lithium ions, resulting in first-time lower coulombic efficiency.
In patent CN201610863902.7, a composite is obtained by condensing a metal reducing agent and SiO under a negative pressure environment by gasifying the two under high temperature heating and reacting them in a gas phase. The method needs to be in a high vacuum environment and reaches the gasification temperature of the material, so that the safety requirement on equipment is high, and the energy consumption caused by high temperature increases the cost, so that the production cost of the method is high, and the industrialized production is difficult to realize.
In patent CN201711318537.2, an inert atmosphere is invented for SiO x The material and the metal undergo oxidation-reduction reaction, the metal is oxidized to obtain a compound, and then the metal compound is etched by acid to realize SiO x The ratio x of O/Si of the material (0.5 < x < 1.5) is adjusted to y (0.2 < y < 0.9), and the oxygen content of the anode is reduced, so that the generation amount of an irreversible phase during the first lithium intercalation is reduced, namely the loss of the irreversible lithium is reduced, and the first coulomb efficiency of the material is improved. This approach is not environmentally friendly due to the use of acid to etch the metal oxide, which results in a large amount of acid waste, a large amount of waste liquid, and a large amount of cost for the subsequent treatment, which increases the production cost and is not conducive to large-scale application.
In patent CN201710193442.6, a method of forming a silicon oxide film by reacting Si/SiO 2 The raw material powder mixture and metallic magnesium are subjected to a gas phase reaction to form a mixture of a metal oxide and a metal oxide in the form of a silicon oxide (SiO x 0 < x < 2) contains silicon particles, mgSiO 3 (enstatite) and Mg2SiO 4 (magnesium silicate) crystal. The mode also utilizes gas phase reaction, has extremely high equipment requirement, directly uses magnesium powder, and can release a large amount of heat locally when carrying out the magnesian reduction reaction, thereby being unfavorable for safety. In addition, the charge-discharge capacity of the material in the mode is low (about 700 mAh/g), and the low capacity is difficult to realize large-scale application.
In patent CN201980006246.0, a silicon-based composite material with a pore structure is invented, in which a polymer with volume shrinkage occupies the pore structure, and a metal compound is distributed in SiO x (0.ltoreq.x.ltoreq.2) on the surface and inside. The pore canal structure required in the process is obtained after strong alkali treatment, a large amount of alkali liquor is used, a large amount of waste liquor is generated, a certain harm is caused to the environment due to improper treatment, the subsequent treatment is troublesome, and the production cost is greatly increased.
In patent CN201910621840.2, a method was invented which uses magnesium silicide as a reducing agent for improving the first coulombic efficiency of silicon oxide, but the first coulombic efficiency improvement of the prepared material is not obvious due to the lower content used; and the heat treatment temperature is higher, so that energy waste is caused.
In patent CN202110973237.8, a combination of one or more of a simple substance of silicon or a compound of silicon is invented, and a magnesium element is contained in the silicon oxide. The invention mainly utilizes magnesium silicide to improve the electrochemical performance of silicon oxide, and the magnesium silicide content is higher, and the magnesium silicide is atomized under the argon atmosphere with higher temperature and cooled in a wall-cooled vacuum cavity. This kind of harsh method causes a lot of energy waste, has raised the production cost.
In patent CN112331854a, a method of pre-lithiated silicon oxide negative electrode material of magnesium lithium silicate was invented, in which magnesium lithium silicate is formed mainly by using the reaction of magnesium oxide and lithium oxide with silicon oxide, thereby improving the coulombic efficiency of silicon oxide. However, the capacity of the material synthesized by the method is low, and the energy waste is caused by the same high heat treatment temperature. So a further intensive search is being conducted for such means.
In summary, the above-mentioned methods disclosed in the prior art have the major disadvantage of utilizing more gas phase reactions, which are extremely stringent in terms of production equipment; in the production and manufacturing process, strong acid and alkali (such as HCl and NaOH) are used, so that potential safety hazards exist, and the subsequent treatment cost is increased; in addition, these methods, while improving the first coulombic efficiency to some extent, result in materials having lower charge and discharge capacities. Therefore, developing a new technology with simple process flow, which is beneficial to large-scale production, has lower production cost and is environment-friendly, thereby improving the charge-discharge capacity and the first coulomb efficiency of the silicon oxide, and becoming a technical problem to be solved urgently by the technicians in the field.
Disclosure of Invention
In view of the above, the invention aims to provide the silicon oxide-based negative electrode composite material with the core-shell structure and the preparation method thereof, and the preparation method provided by the invention has the advantages of simple process flow, low cost, environmental friendliness and suitability for mass production; and the prepared silicon oxide-based negative electrode composite material with the core-shell structure has higher charge-discharge capacity and first coulombic efficiency.
The invention provides a preparation method of a silicon oxide-based negative electrode composite material with a core-shell structure, which comprises the following steps:
a) Mg is added with 2 Si, oxygenMixing lithium oxide and silicon oxide, sequentially performing ball milling, sieving and first solid phase reaction, cooling, and performing first crushing and grading treatment to obtain a reaction product;
b) Treating the reaction product obtained in the step a) by adopting a weak acid solution, filtering, and washing with water to obtain a non-carbon-coated material;
c) Mixing the non-carbon-coated material obtained in the step b) with an organic carbon source aqueous solution, drying, carrying out a second solid phase reaction, cooling, and carrying out a second crushing and grading treatment to obtain a single-layer carbon-coated material;
d) And c) carrying out chemical vapor deposition on the single-layer carbon coated material obtained in the step c) by adopting carbon source gas, cooling, and carrying out third crushing and grading treatment to obtain the silicon oxide-based negative electrode composite material with the core-shell structure.
Preferably, the Mg in step a) 2 The mass ratio of Si, lithium oxide and silicon oxide is 1: (0.5-2): (3-9).
Preferably, the ball milling in the step a) adopts planetary ball milling, and the ball-to-material ratio is (5-20): 1, ball milling time is 1-4 h; the mesh number of the sieving is 300-500 meshes.
Preferably, the first solid phase reaction in step a) is specifically performed by:
placing the sieved product into a tube furnace, sealing, vacuumizing to below 0.01Pa, heating to 500-900 ℃ at a heating speed of 5-10 ℃ per minute under inert atmosphere, and preserving heat for 1-6 h.
Preferably, the weak acid solution in step b) is an acetic acid solution; the treatment process by adopting the weak acid solution comprises the following steps:
uniformly mixing the reaction product obtained in the step a) with a weak acid solution, and magnetically stirring for 1-2 h after sealing.
Preferably, the aqueous organic carbon source solution in step c) is an aqueous glucose solution, and the mass ratio of glucose to water in the aqueous glucose solution is 1: (5-7); the drying temperature is 60-80 ℃.
Preferably, the second solid phase reaction in step c) is performed by:
and (3) placing the dried product into a tubular furnace, sealing, vacuumizing to below 0.01Pa, heating to 700-900 ℃ at a heating speed of 5-10 ℃ per minute under an inert atmosphere, and preserving heat for 1-4 h.
Preferably, the carbon source gas in step d) is selected from one or more of ethylene gas, acetylene gas and methane gas; the chemical vapor deposition process specifically comprises the following steps:
placing the single-layer carbon-coated material obtained in the step c) into a chemical vapor deposition furnace, sealing, vacuumizing to below 0.01Pa, heating to 700-1000 ℃ at a heating speed of 5-10 ℃/min under an inert atmosphere, and then introducing carbon source gas for heat preservation for 0.5-4 h; the flow ratio of the inert gas and the carbon source gas in the inert atmosphere is (5-15): 1.
preferably, the average particle diameter of the first pulverization and classification treatment is 1 μm to 3 μm; the average grain diameter of the second crushing and grading treatment is 2-4 mu m; the average particle diameter of the third crushing and grading treatment is 4-6 mu m.
The invention also provides a silicon oxide-based negative electrode composite material with a core-shell structure, which is prepared by adopting the preparation method of the technical scheme.
The invention provides a preparation method of a silicon oxide-based negative electrode composite material with a core-shell structure, which comprises the following steps: a) Mg is added with 2 Mixing Si, lithium oxide and silicon oxide, sequentially performing ball milling, sieving and first solid phase reaction, cooling, and performing first crushing and grading treatment to obtain a reaction product; b) Treating the reaction product obtained in the step a) by adopting a weak acid solution, filtering, and washing with water to obtain a non-carbon-coated material; c) Mixing the non-carbon-coated material obtained in the step b) with an organic carbon source aqueous solution, drying, carrying out a second solid phase reaction, cooling, and carrying out a second crushing and grading treatment to obtain a single-layer carbon-coated material; d) And c) carrying out chemical vapor deposition on the single-layer carbon coated material obtained in the step c) by adopting carbon source gas, cooling, and carrying out third crushing and grading treatment to obtain the silicon oxide-based negative electrode composite material with the core-shell structure. Compared with the prior art, the preparation method provided by the inventionThe method adopts specific process steps to realize better overall interaction, and prepares the double-layer carbon-coated silicon oxide-based anode composite material with a core-shell structure containing metal elements; the silicon oxide-based negative electrode composite material has high charge-discharge capacity and first coulombic efficiency.
Meanwhile, the preparation method provided by the invention has the advantages of simple process flow, low cost, environmental friendliness and contribution to large-scale production, so that the preparation method has good application prospect and potential in the technical field of lithium ion batteries.
Drawings
FIG. 1 is a schematic structural diagram of a core-shell structure silica-based negative electrode composite material prepared by the preparation method provided in example 1 of the present invention;
FIG. 2 is a cross-sectional SEM image of a core-shell structure silica-based negative electrode composite material prepared by the preparation method of example 1 of the present invention;
FIG. 3 is a thermogravimetric graph of a core-shell structure silica-based negative electrode composite material prepared by the preparation method provided in example 1 of the present invention;
fig. 4 is an XRD phase diagram of the core-shell structure silica-based negative electrode composite material prepared by the preparation method provided in example 1 of the present invention.
Detailed Description
The technical solutions of the present invention will be clearly and completely described in conjunction with the embodiments of the present invention, and it is apparent that the described embodiments are only some embodiments of the present invention, but not all embodiments. All other embodiments, which can be made by those skilled in the art based on the embodiments of the invention without making any inventive effort, are intended to be within the scope of the invention.
The invention provides a preparation method of a silicon oxide-based negative electrode composite material with a core-shell structure, which comprises the following steps:
a) Mg is added with 2 Mixing Si, lithium oxide and silicon oxide, sequentially performing ball milling, sieving and first solid phase reaction, cooling, and performing first crushing and grading treatment to obtain a reaction product;
b) Treating the reaction product obtained in the step a) by adopting a weak acid solution, filtering, and washing with water to obtain a non-carbon-coated material;
c) Mixing the non-carbon-coated material obtained in the step b) with an organic carbon source aqueous solution, drying, carrying out a second solid phase reaction, cooling, and carrying out a second crushing and grading treatment to obtain a single-layer carbon-coated material;
d) And c) carrying out chemical vapor deposition on the single-layer carbon coated material obtained in the step c) by adopting carbon source gas, cooling, and carrying out third crushing and grading treatment to obtain the silicon oxide-based negative electrode composite material with the core-shell structure.
The invention firstly uses Mg 2 Mixing Si, lithium oxide and silicon oxide, sequentially ball milling, sieving, performing a first solid phase reaction, cooling, and performing a first crushing and grading treatment to obtain a reaction product.
The invention aims at the Mg 2 Si, lithium oxide (Li) 2 The source of O) and silicon oxide (SiO) is not particularly limited, and commercially available products or self-made products known to those skilled in the art may be used. In the present invention, the Mg 2 The mass ratio of Si, lithium oxide and silicon oxide is preferably 1: (0.5-2): (3-9), more preferably 1: (0.5-2): (3-7).
In the present invention, the ball milling is preferably planetary ball milling, wherein the balls used are preferably agate balls, and the ball-to-material ratio is preferably (5-20): 1, more preferably 10: the ball milling time is preferably 1 to 4 hours, more preferably 2 hours.
In the present invention, the mesh number of the screen is preferably 300 to 500 mesh, more preferably 400 mesh.
In the present invention, the process of the first solid phase reaction is preferably specifically:
placing the sieved product into a tube furnace, sealing, vacuumizing to below 0.01Pa, heating to 500-900 ℃ at a heating speed of 5-10 ℃/min under inert atmosphere, and preserving heat for 1-6 h;
more preferably:
and (3) placing the sieved product into a tube furnace, sealing, vacuumizing to below 0.01Pa, heating to 550-850 ℃ at a heating speed of 5 ℃/min under an argon atmosphere, and preserving heat for 2h.
In the invention, the cooling temperature is room temperature; the average particle diameter of the first pulverization and classification treatment is preferably 1 μm to 3 μm, more preferably 2 μm (D50).
After the reaction product is obtained, the obtained reaction product is treated by adopting weak acid solution and then filtered, and the non-carbon-coated material is obtained after water washing.
In the present invention, the weak acid solution is preferably an acetic acid solution; the source of the acetic acid solution is not particularly limited in the present invention, and commercially available products known to those skilled in the art may be used.
In the present invention, the treatment with a weak acid solution is preferably specifically:
uniformly mixing the reaction product obtained in the step a) with a weak acid solution, and magnetically stirring for 1-2 h after sealing;
more preferably:
uniformly mixing the reaction product obtained in the step a) with a weak acid solution, and magnetically stirring for 1h after sealing.
In the present invention, the number of times of the water washing is preferably 1 to 3 times, more preferably 2 times; and (3) washing the filtered solid product with water to obtain a non-carbon-coated material which can be directly used as a negative electrode material.
In the present invention, the specific reaction formula of the above steps is as follows:
Mg 2 Si+Li 2 O+SiO→MgO+Li 2 SiO 3 +Si；
after weak acid treatment, all MgO is removed, and part of the residual Mg 2 Si and Li 2 O, it is obvious that the material is composed of Li 2 SiO 3 And Si, and mainly Si participates in the charge-discharge process, the first coulomb efficiency of the material can be theoretically high.
After the non-carbon-coated material is obtained, the obtained non-carbon-coated material is mixed with an organic carbon source aqueous solution and then dried, a second solid phase reaction is carried out, and after cooling, a second crushing and grading treatment is carried out, so that the single-layer carbon-coated material is obtained.
In the present invention, the aqueous organic carbon source solution is preferably an aqueous glucose solution, and the mass ratio of glucose to water in the aqueous glucose solution is preferably 1: (5-7), more preferably 1:6. the source of the organic carbon source is not particularly limited in the present invention, and commercially available products known to those skilled in the art may be used.
In the present invention, the drying temperature is preferably 60 to 80 ℃, more preferably 80 ℃; drying is carried out by means of ovens known to those skilled in the art.
In the present invention, the process of the second solid phase reaction is preferably specifically:
placing the dried product into a tubular furnace, sealing, vacuumizing to below 0.01Pa, heating to 700-900 ℃ at a heating speed of 5-10 ℃/min under inert atmosphere, and preserving heat for 1-4 h;
more preferably:
and (3) placing the dried product into a tubular furnace, sealing, vacuumizing to below 0.01Pa, heating to 800 ℃ at a heating speed of 10 ℃/min under an argon atmosphere, and preserving heat for 1h.
In the invention, the cooling temperature is room temperature; the average particle diameter of the second pulverization and classification treatment is preferably 2 μm to 4 μm, more preferably 3 μm (D50).
After the single-layer carbon-coated material is obtained, the single-layer carbon-coated material is subjected to chemical vapor deposition by adopting carbon source gas, and is subjected to third crushing and grading treatment after being cooled, so that the silicon oxide-based negative electrode composite material with the core-shell structure is obtained.
In the present invention, the carbon source gas is preferably one or more selected from the group consisting of ethylene gas, acetylene gas and methane gas, more preferably ethylene gas; the source of the carbon source gas is not particularly limited, and commercially available products known to those skilled in the art may be used.
In the present invention, the chemical vapor Deposition (CVD, chemicalVapor Deposition) process is preferably specifically:
placing the single-layer carbon-coated material obtained in the step c) into a chemical vapor deposition furnace, sealing, vacuumizing to below 0.01Pa, heating to 700-1000 ℃ at a heating speed of 5-10 ℃/min under an inert atmosphere, and then introducing carbon source gas for heat preservation for 0.5-4 h;
more preferably:
placing the single-layer carbon-coated material obtained in the step c) into a chemical vapor deposition furnace, sealing, vacuumizing to below 0.01Pa, heating to 850 ℃ at a heating rate of 10 ℃/min under an inert atmosphere, and then introducing carbon source gas for heat preservation for 2 hours.
In the present invention, the flow ratio of the inert gas to the carbon source gas in the inert atmosphere is preferably (5 to 15): 1, more preferably 10:1. in a preferred embodiment of the present invention, the inert gas is argon, the gas flow rate is 200scc, the carbon source gas is ethylene, and the gas flow rate is 20scc.
In the invention, the cooling temperature is room temperature; the average particle diameter of the third pulverization and classification treatment is preferably 4 μm to 6 μm, more preferably 5 μm (D50).
The preparation method provided by the invention adopts specific process steps, utilizes silicon elements introduced by silicide to make up for the defect of the capacity of silicon oxide caused by the generation of inactive lithium silicate, and simultaneously utilizes lithium oxide to modify the silicon oxide under the action of the silicide to realize overall better interaction, so as to prepare the double-layer carbon-coated silicon oxide negative electrode composite material with a core-shell structure containing metal elements, which has a unique core-shell structure, wherein the shell is lithium silicate, the inner core is disproportionated silicon oxide, and the lithium silicate coats the disproportionated silicon oxide; the silicon oxide-based negative electrode composite material has high charge-discharge capacity and first coulombic efficiency.
The invention also provides a silicon oxide-based negative electrode composite material with a core-shell structure, which is prepared by adopting the preparation method of the technical scheme. The invention provides a double-layer carbon-coated silicon oxide-based negative electrode composite material with a core-shell structure containing metal elements, wherein the core is disproportionated silicon oxide, the shell is lithium silicate crystal, a unique core-shell structure is formed, and the surface of the composite material is coated with double-layer carbon, so that the first coulomb efficiency, the charge-discharge capacity and the cycle stability of the silicon oxide are improved.
In the present invention, if silicide is not added, li is directly used 2 O, would result in a decrease in the capacity of the material; if nano silicon is added, the capacity of the material can be increased, but the cost is increased; for a material system, nano silicon is added into a silicon oxide system in a mixture, and is not primary particles of a silicon-based anode material with a unique core-shell structure, which are expressed in the system.
The invention provides a preparation method of a silicon oxide-based negative electrode composite material with a core-shell structure, which comprises the following steps: a) Mg is added with 2 Mixing Si, lithium oxide and silicon oxide, sequentially performing ball milling, sieving and first solid phase reaction, cooling, and performing first crushing and grading treatment to obtain a reaction product; b) Treating the reaction product obtained in the step a) by adopting a weak acid solution, filtering, and washing with water to obtain a non-carbon-coated material; c) Mixing the non-carbon-coated material obtained in the step b) with an organic carbon source aqueous solution, drying, carrying out a second solid phase reaction, cooling, and carrying out a second crushing and grading treatment to obtain a single-layer carbon-coated material; d) And c) carrying out chemical vapor deposition on the single-layer carbon coated material obtained in the step c) by adopting carbon source gas, cooling, and carrying out third crushing and grading treatment to obtain the silicon oxide-based negative electrode composite material with the core-shell structure. Compared with the prior art, the preparation method provided by the invention adopts specific process steps to realize better overall interaction, and prepares the double-layer carbon-coated silicon oxide-based negative electrode composite material with a core-shell structure containing metal elements; the silicon oxide-based negative electrode composite material has high charge-discharge capacity and first coulombic efficiency.
Meanwhile, the preparation method provided by the invention has the advantages of simple process flow, low cost, environmental friendliness and contribution to large-scale production, so that the preparation method has good application prospect and potential in the technical field of lithium ion batteries.
In order to further illustrate the present invention, the following examples are provided. The raw materials used in the following examples of the present invention are all commercially available.
Example 1
(1) Preparation of a negative electrode material:
1) The mass ratio of the weighed substances is 1:1:3 Mg of 2 After uniformly mixing Si, lithium oxide and silicon oxide raw materials, carrying out planetary ball milling, wherein the ball-to-material ratio is 10:1 ball milling for 2 hours, sieving by a 400-mesh sieve, collecting the sieved product, placing into a tube furnace, sealing, vacuumizing to below 0.01Pa, heating to 550 ℃ at a heating speed of 5 ℃/min under argon atmosphere, preserving heat for 2 hours, cooling to room temperature, and carrying out crushing and grading treatment, wherein the average particle size is 2 mu m (D50).
2) And (3) uniformly mixing the product obtained in the step (1) with acetic acid solution, sealing, magnetically stirring for 1h, filtering, and washing with water twice to obtain the non-carbon-coated material.
3) Taking the product of the step 2) and glucose aqueous solution (the mass ratio is glucose: water = 1: 6) Mixing uniformly, drying in an oven at 80 ℃, placing into a tube furnace, sealing, vacuumizing to below 0.01Pa, heating to 800 ℃ at a heating speed of 10 ℃/min under argon atmosphere, preserving heat for 1h, cooling to room temperature, crushing and grading, and obtaining the single-layer carbon-coated (carbon content 4 wt%) material with an average particle size of 3 mu m (D50).
4) Placing the product obtained in the step 3) into a CVD chemical vapor deposition furnace, sealing, vacuumizing to below 0.01Pa, heating to 850 ℃ at a heating speed of 10 ℃/min under an argon atmosphere (the air flow is 200 scc), introducing ethylene gas, preserving heat for 2 hours (the air flow is 20 scc), cooling to room temperature, and carrying out crushing and grading treatment to obtain a silicon oxide-based negative electrode composite material with a double-layer carbon coating (the carbon content is 8 wt%) and containing a core-shell structure of metal elements, wherein the average grain diameter is 5 mu m (D50); the schematic structure is shown in fig. 1.
The cross-section characterization diagram of the obtained material is shown in the following figure 2, and a unique core-shell structure is obviously shown; and FIG. 3 also shows that after carbon coating, the carbon content of the material is about 8% and the material is eventually composed of Si and Li 2 SiO 3 Two phase composition, see figure 4.
(2) Manufacturing of the battery:
and (3) preparing the anode material prepared in the step (1): conductive carbon black (Super-P): styrene Butadiene Rubber (SBR, styrene-Butadiene Rubber) and carboxymethyl cellulose (CMC, carboxymethyl Cellulose) at 6:2:2, uniformly mixing the mixture with deionized water with a certain mass ratio to prepare negative electrode mixture slurry; the electrode plate is uniformly coated on a copper foil current collector and dried for 5 hours at a drying temperature of 80 ℃ to obtain the electrode plate. The button cell is assembled by using lithium foil as a counter electrode.
Example 2
The preparation method provided in the embodiment 1 is adopted to obtain a silicon oxide-based negative electrode composite material with a core-shell structure, and a battery is further manufactured; the difference is that: mg of 2 The mass ratio of Si, lithium oxide and silicon oxide raw materials is 1:1:4.
example 3
The preparation method provided in the embodiment 1 is adopted to obtain a silicon oxide-based negative electrode composite material with a core-shell structure, and a battery is further manufactured; the difference is that: mg of 2 The mass ratio of Si, lithium oxide and silicon oxide raw materials is 1:1:5, a step of; the heat treatment temperature in step 1) was increased to 650 ℃.
Example 4
The preparation method provided in the embodiment 1 is adopted to obtain a silicon oxide-based negative electrode composite material with a core-shell structure, and a battery is further manufactured; the difference is that: mg of 2 The mass ratio of Si, lithium oxide and silicon oxide raw materials is 1:1:6, preparing a base material; the heat treatment temperature in step 1) was increased to 650 ℃.
Example 5
The preparation method provided in the embodiment 1 is adopted to obtain a silicon oxide-based negative electrode composite material with a core-shell structure, and a battery is further manufactured; the difference is that: mg of 2 The mass ratio of Si, lithium oxide and silicon oxide raw materials is 2:1:6, preparing a base material; the heat treatment temperature in step 1) was increased to 750 ℃.
Example 6
The preparation method provided in the embodiment 1 is adopted to obtain a silicon oxide-based negative electrode composite material with a core-shell structure, and a battery is further manufactured; the difference is that: mg of 2 Si, lithium oxide and silicon oxideThe mass ratio of the materials of the raw materials is 2:1:7, preparing a base material; the heat treatment temperature in step 1) was increased to 750 ℃.
Example 7
The preparation method provided in the embodiment 1 is adopted to obtain a silicon oxide-based negative electrode composite material with a core-shell structure, and a battery is further manufactured; the difference is that: mg of 2 The mass ratio of Si, lithium oxide and silicon oxide raw materials is 1:2:6, preparing a base material; the heat treatment temperature in step 1) was increased to 850 ℃.
Example 8
The preparation method provided in the embodiment 1 is adopted to obtain a silicon oxide-based negative electrode composite material with a core-shell structure, and a battery is further manufactured; the difference is that: mg of 2 The mass ratio of Si, lithium oxide and silicon oxide raw materials is 1:2:7, preparing a base material; the heat treatment temperature in step 1) was increased to 850 ℃.
Comparative example 1
A button cell was prepared according to the procedure of step (2) of example 1 using the non-carbon coated material prepared in step 2) of example 1 as a negative electrode material.
Comparative example 2
A button cell was prepared according to the procedure of step (2) of example 1 using a silicon oxide raw material as a negative electrode material.
Electrochemical performance:
discharging the prepared button cell to a voltage of 0.005V at a rate of 0.1C and charging to a voltage of 2.0V at a rate of 0.05C to obtain a specific discharge capacity (mAh/g), a specific charge capacity (mAh/g) and an initial coulombic efficiency (specific charge capacity/specific discharge capacity); after the first charge and discharge, the battery was subjected to a cycle test at a rate of 0.2C from the second charge and discharge.
The analysis results of the obtained specific charge-discharge capacity and first coulombic efficiency are shown in table 1.
TABLE 1 specific charge-discharge capacity, first coulombic efficiency data
The previous description of the disclosed embodiments is provided to enable any person skilled in the art to make or use the present invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other embodiments without departing from the spirit or scope of the invention. Thus, the present invention is not intended to be limited to the embodiments shown herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims (10)

1. A preparation method of a silicon oxide-based negative electrode composite material with a core-shell structure comprises the following steps:
a) Mg is added with 2 Mixing Si, lithium oxide and silicon oxide, sequentially performing ball milling, sieving and first solid phase reaction, cooling, and performing first crushing and grading treatment to obtain a reaction product;
b) Treating the reaction product obtained in the step a) by adopting a weak acid solution, filtering, and washing with water to obtain a non-carbon-coated material;
c) Mixing the non-carbon-coated material obtained in the step b) with an organic carbon source aqueous solution, drying, carrying out a second solid phase reaction, cooling, and carrying out a second crushing and grading treatment to obtain a single-layer carbon-coated material;
d) And c) carrying out chemical vapor deposition on the single-layer carbon coated material obtained in the step c) by adopting carbon source gas, cooling, and carrying out third crushing and grading treatment to obtain the silicon oxide-based negative electrode composite material with the core-shell structure.
2. The method according to claim 1, wherein the Mg in step a) 2 The mass ratio of Si, lithium oxide and silicon oxide is 1: (0.5-2): (3-9).
3. The method according to claim 1, wherein the ball milling in step a) is planetary ball milling, and the ball-to-material ratio is (5-20): 1, ball milling time is 1-4 h; the mesh number of the sieving is 300-500 meshes.
4. The method according to claim 1, wherein the first solid phase reaction in step a) is performed by:
placing the sieved product into a tube furnace, sealing, vacuumizing to below 0.01Pa, heating to 500-900 ℃ at a heating speed of 5-10 ℃ per minute under inert atmosphere, and preserving heat for 1-6 h.
5. The method of claim 1, wherein the weak acid solution in step b) is an acetic acid solution; the treatment process by adopting the weak acid solution comprises the following steps:
uniformly mixing the reaction product obtained in the step a) with a weak acid solution, and magnetically stirring for 1-2 h after sealing.
6. The method according to claim 1, wherein the aqueous organic carbon source solution in step c) is an aqueous glucose solution having a mass ratio of glucose to water of 1: (5-7); the drying temperature is 60-80 ℃.
7. The method according to claim 1, wherein the second solid phase reaction in step c) is performed by:
and (3) placing the dried product into a tubular furnace, sealing, vacuumizing to below 0.01Pa, heating to 700-900 ℃ at a heating speed of 5-10 ℃ per minute under an inert atmosphere, and preserving heat for 1-4 h.
8. The production method according to claim 1, wherein the carbon source gas in step d) is selected from one or more of ethylene gas, acetylene gas and methane gas; the chemical vapor deposition process specifically comprises the following steps:
placing the single-layer carbon-coated material obtained in the step c) into a chemical vapor deposition furnace, sealing, vacuumizing to below 0.01Pa, heating to 700-1000 ℃ at a heating speed of 5-10 ℃/min under an inert atmosphere, and then introducing carbon source gas for heat preservation for 0.5-4 h; the flow ratio of the inert gas and the carbon source gas in the inert atmosphere is (5-15): 1.
9. the method according to claim 1, wherein the average particle diameter of the first pulverization and classification treatment is 1 μm to 3 μm; the average grain diameter of the second crushing and grading treatment is 2-4 mu m; the average particle diameter of the third crushing and grading treatment is 4-6 mu m.
10. A core-shell structured silica-based negative electrode composite material, characterized in that it is prepared by the preparation method according to any one of claims 1 to 9.
CN202210209063.2A 2022-03-03 2022-03-03 Core-shell structure silicon oxide-based negative electrode composite material and preparation method thereof Pending CN116741951A (en)

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