CN110844910B - Preparation method of silicon-based negative electrode material of lithium ion battery - Google Patents

Preparation method of silicon-based negative electrode material of lithium ion battery Download PDF

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CN110844910B
CN110844910B CN201911136192.8A CN201911136192A CN110844910B CN 110844910 B CN110844910 B CN 110844910B CN 201911136192 A CN201911136192 A CN 201911136192A CN 110844910 B CN110844910 B CN 110844910B
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silicon
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carbon material
electrode material
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CN110844910A (en
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王胜彬
张超
张臻
黄杰
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Beijing WeLion New Energy Technology Co ltd
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    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
    • C01B33/00—Silicon; Compounds thereof
    • C01B33/113—Silicon oxides; Hydrates thereof
    • C01B33/12—Silica; Hydrates thereof, e.g. lepidoic silicic acid
    • C01B33/18—Preparation of finely divided silica neither in sol nor in gel form; After-treatment thereof
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
    • C01B32/00—Carbon; Compounds thereof
    • C01B32/05—Preparation or purification of carbon not covered by groups C01B32/15, C01B32/20, C01B32/25, C01B32/30
    • 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
    • H01M4/48—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
    • H01M4/62—Selection of inactive substances as ingredients for active masses, e.g. binders, fillers
    • H01M4/624—Electric conductive fillers
    • H01M4/625—Carbon or graphite
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/10—Energy storage using batteries

Abstract

The invention discloses a preparation method of a silicon-based negative electrode material of a lithium ion battery, and belongs to the technical field of lithium ion batteries. Uniformly and completely mixing a silicon-based material, a pore-forming agent and a carbon precursor in deionized water to form a suspension, and then carrying out spray drying granulation to form spheroidal particles; sintering the spheroidal particles under the protection of inert atmosphere to obtain a silicon-based carbon material, washing to obtain a porous silicon-based carbon material, and coating the porous silicon-based carbon material with a solution containing an organic coating agent in a fluidized bed; and (3) carrying out high-temperature carbonization on the coated product under the protection of inert atmosphere, and taking out the product after cooling to room temperature to obtain the silicon-based negative electrode material. The preparation method has the advantages of simple process, low energy consumption and environmental protection, and the silicon-based negative electrode material prepared by the method has small volume expansion and excellent and stable cycle performance.

Description

Preparation method of silicon-based negative electrode material of lithium ion battery
Technical Field
The invention relates to the technical field of lithium ion batteries, in particular to a preparation method of a silicon-based negative electrode material of a lithium ion battery.
Background
The silicon material as the negative electrode of the lithium ion battery has the advantages of the highest theoretical specific capacity, a low lithium-intercalation platform, abundant resources and the like, and also has excellent rapid charge and discharge performance, which is very important for the application of the silicon material in power batteries. However, the silicon material has a very serious volume change problem in the electrochemical process, which not only causes the cracking and pulverization of silicon particles and the repeated generation of SEI film, but also causes the electrode material to be detached from the current collector. The phenomenon results in serious capacity attenuation and low coulombic efficiency of the silicon-based negative electrode material in the charge and discharge processes.
Chinese invention patent CN109671942A discloses a silicon-carbon three-dimensional composite material with a core-shell structure, in which nano-silicon particles are embedded in the gaps of graphite particles. The composite material relieves the pulverization of the silicon material to a certain degree and improves the electrochemical performance of the silicon material. However, since a certain space is not reserved for the expansion of silicon, the particles still break after a long period of cycling. CN109830673A is prepared by preparing silicon/silicon dioxide/conductive carbon black composite particles, and then etching away silicon dioxide by hydrofluoric acid to obtain the coated silicon @ carbon negative electrode material which is provided with a reserved space inside and can be used for silicon expansion. The method utilizes hydrofluoric acid with high risk to treat, is not beneficial to safety and environmental protection, and meanwhile, pore channels are generated in the coating layer in the etching process, so that the coating layer is not beneficial to blocking the electrolyte and influencing the electrochemical performance of the coating layer.
Therefore, the technical problem in the field is to develop a method for preparing the lithium ion battery cathode material with small volume expansion, excellent and stable cycle performance, simple process, low energy consumption and environmental protection.
Disclosure of Invention
In order to overcome the defects of the prior art, the invention aims to provide the preparation method of the silicon-based negative electrode material of the lithium ion battery, the method has the advantages of simple process, low energy consumption and environmental protection, and the silicon-based negative electrode material prepared by the method has small volume expansion and excellent and stable cycle performance.
In order to solve the problems, the technical scheme adopted by the invention is as follows:
a preparation method of a silicon-based negative electrode material of a lithium ion battery comprises the following steps:
s1, granulating: uniformly and completely mixing a silicon-based material, a pore-forming agent and a carbon precursor in deionized water to form a suspension, and then carrying out spray drying granulation to form spheroidal particles with the particle size of D50 being 5-30 mu m;
s2, sintering: heating the spheroidal particles obtained in the step S1 to 600-1200 ℃ under the protection of inert atmosphere, preserving the heat for 1-6h, and taking out the spheroidal particles after cooling to room temperature to obtain a silicon-based carbon material;
s3, washing: placing the silicon-based carbon material obtained in the step S2 in deionized water, stirring for 1-6h, and taking out the solid to obtain a porous silicon-based carbon material;
s4, surface coating: placing the porous silicon-based carbon material obtained in the step S3 in a cavity of fluidized bed equipment, spraying a solution containing an organic coating agent into a fluidized bed for coating, wherein the coating reaction time is 0.5-2 h, and taking out the porous silicon-based carbon material for later use after cooling to room temperature;
s5, high-temperature carbonization: and (5) heating the product obtained in the step (S4) to 600-1200 ℃ under the protection of inert atmosphere, preserving heat for 1-6h, and taking out after cooling to room temperature to obtain the silicon-based negative electrode material.
In a preferred embodiment of the present invention, a carbon material is further added to the step S1 to form a suspension; the mass ratio of the silicon-based material to the pore-forming agent to the carbon precursor to the carbon material is 1: 0.1-10: 0.5-20: 0-10.
In a preferred embodiment of the present invention, the carbon material is at least one of graphite, carbon nanotubes, and graphene.
As a preferred embodiment of the present invention, the chemical formula of the Si-based material in the step S1 is SiOxOr SiOx@ C, wherein x is more than or equal to 0 and less than or equal to 1, and the content of C is less than or equal to 20 percent; the D50 size of the silicon-based material is 0.1-5 mu m.
In a preferred embodiment of the present invention, the pore-forming agent in step S1 is a soluble salt, and the soluble salt is at least one of chloride, nitrate and sulfate of main group metal elements, and includes but is not limited to soluble salts such as sodium chloride, calcium chloride, potassium nitrate and sodium sulfate.
In a preferred embodiment of the present invention, the carbon precursor in step S1 is at least one of sodium carboxymethylcellulose, polyvinylpyrrolidone, glucose, sucrose, melamine, and polyethylene glycol.
In a preferred embodiment of the present invention, the deionized water content in the suspension of step S1 is 35 to 80%.
In a preferred embodiment of the present invention, the mass ratio of the silicon-based carbon material to the deionized water in step S3 is 1: 0.5-10.
In a preferred embodiment of the present invention, the organic coating agent in step S4 is at least one of glucose, sucrose, phenolic resin, polyethylene glycol, and asphalt; the solvent is at least one of deionized water, methanol, ethanol and tetrahydrofuran.
As a preferred embodiment of the present invention, the mass ratio of the organic coating agent to the porous silicon-based carbon material in step S4 is 0.001 to 0.1: 1; the mass fraction of the organic coating agent solution is 1-65%.
Preferably, the air inlet temperature of the fluidized bed in the step S4 is 60-150 ℃.
Preferably, the inert atmosphere in step S2 and step S5 is nitrogen, argon or helium.
Compared with the prior art, the invention has the beneficial effects that:
(1) according to the invention, the pore-forming agent is added in the granulation process, so that the process steps of independently coating the pore-forming agent are reduced, the flow is simplified, and the efficiency is improved; soluble salt is used as a pore-forming agent, and the pore-forming agent can be ablated by water, so that toxic and harmful hydrofluoric acid used by the traditional etching pore-forming agent is avoided, and the method is safe and environment-friendly;
(2) compared with the traditional coating process, the novel coating process of the fluidized bed can realize the uniform coating of the extremely thin coating layer, avoid the side reaction of the electrolyte and the surface of the silicon-based material caused by the nonuniform coating and improve the circulation stability.
In conclusion, the preparation method disclosed by the invention is simple in process, low in energy consumption, environment-friendly and easy for industrial production, the silicon-based negative electrode material prepared by the method is small in volume expansion and excellent and stable in cycle performance, and the first coulomb efficiency of the silicon-based negative electrode material is effectively improved.
Detailed Description
The present invention will be described in further detail with reference to specific embodiments.
A preparation method of a silicon-based negative electrode material of a lithium ion battery comprises the following steps:
s1, granulating: silicon-based material, pore-forming agent, carbon precursor and carbon material are mixed according to the mass ratio of 1: 0.1-10: 0.5-20: 0-10, uniformly mixing the mixture in deionized water to form a suspension, wherein the content of the deionized water in the suspension is 35-80%, and then carrying out spray drying granulation to form spheroidal particles with the particle size of D50 being 5-30 mu m;
wherein the chemical formula of the silicon-based material is SiOxOr SiOx@ C, wherein x is more than or equal to 0 and less than or equal to 1, the content of C is less than or equal to 20 percent, and the size of D50 is 0.1-5 mu m; the pore-forming agent is soluble salt, and the soluble salt is at least one of chloride, nitrate and sulfate of main group metal elements, including but not limited to soluble salts such as sodium chloride, calcium chloride, potassium nitrate, sodium sulfate and the like;the carbon precursor is at least one of sodium carboxymethylcellulose, polyvinylpyrrolidone, glucose, sucrose, melamine and polyethylene glycol; the carbon material is at least one of graphite, carbon nano tube and graphene.
S2, sintering: heating the spheroidal particles obtained in the step S1 to 600-1200 ℃ under the protection of the inert atmosphere of nitrogen or argon or helium, preserving the heat for 1-6h, and taking out the spheroidal particles after cooling to the room temperature to obtain the silicon-based carbon material;
s3, washing: placing the silicon-based carbon material obtained in the step S2 in deionized water, stirring for 1-6h, and taking out the solid to obtain a porous silicon-based carbon material; wherein the mass ratio of the silicon-based carbon material to the deionized water is 1: 0.5-10.
S4, surface coating: placing the porous silicon-based carbon material obtained in the step S3 in a cavity of fluidized bed equipment, spraying a solution containing an organic coating agent into a fluidized bed for coating, wherein the air inlet temperature is 60-150 ℃, the coating reaction time is 0.5-2 h, and taking out the porous silicon-based carbon material for later use after cooling to room temperature; wherein the organic coating agent is at least one of glucose, sucrose, phenolic resin, polyethylene glycol and asphalt; the solvent adopted by the organic coating agent solution is at least one of deionized water, methanol, ethanol and tetrahydrofuran; the mass ratio of the organic coating agent to the porous silicon-based carbon material is 0.001-0.1: 1; the mass fraction of the organic coating agent solution is 1-65%.
S5, high-temperature carbonization: and (5) heating the product obtained in the step (S4) to 600-1200 ℃ under the protection of the inert atmosphere of nitrogen or argon or helium, preserving the heat for 1-6h, and taking out the product after cooling to room temperature to obtain the silicon-based negative electrode material.
Example 1:
a preparation method of a silicon-based negative electrode material of a lithium ion battery comprises the following steps:
s1, granulating: mixing Si particles with the D50 size of 0.1 mu m, sodium chloride, glucose and polyvinylpyrrolidone according to the mass ratio of 1: 0.1: 20, uniformly mixing in deionized water, wherein the deionized water accounts for 35% of the total mass; pumping the obtained suspension into a spray dryer for granulation to obtain spheroidal particle powder with the D50 size of 5 mu m;
s2, sintering: heating the sphere-like particle powder with the D50 size of 5 microns obtained in the step S1 to 600 ℃ under the protection of nitrogen atmosphere, preserving heat for 6 hours, and taking out after cooling to room temperature to obtain a saliferous silicon-based carbon material;
s3, washing: and (4) mixing the saliferous silicon-based carbon material obtained in the step S2 with deionized water according to the mass ratio of 1:0.5, mixing for 6 hours, taking out the solid, and drying to obtain the porous silicon-based carbon material;
s4, surface coating: placing the porous silicon-based carbon material obtained in the step S3 in a cavity of fluidized bed equipment, adjusting the air inlet temperature to 120 ℃, spraying a deionized water solution of sucrose into the fluidized bed, carrying out coating reaction for 0.5h, cooling to room temperature, and taking out; wherein the mass of the sucrose accounts for 10% of that of the porous silicon-based carbon material, and the mass fraction of the deionized water solution of the sucrose accounts for 10%;
s5, high-temperature carbonization: and (5) heating the product obtained in the step (S4) to 600 ℃ under the protection of nitrogen gas, performing carbonization heat treatment for 6 hours, cooling to room temperature, and taking out to obtain the silicon-carbon negative electrode material with a cavity and a coating layer outside the cavity.
Example 2:
a preparation method of a silicon-based negative electrode material of a lithium ion battery comprises the following steps:
s1, granulating: SiO with a D50 size of 0.2 μm0.8Calcium chloride, melamine, sodium carboxymethylcellulose and graphene are uniformly mixed in deionized water according to the mass ratio of 1:2:5:1, wherein the deionized water accounts for 80% of the total mass; pumping the obtained suspension into a spray dryer for granulation to obtain spheroidal particle powder with the D50 size of 10 mu m;
s2, sintering: heating the D50-size 10 mu m spherical particle powder obtained in the step S1 to 1200 ℃ under the protection of nitrogen atmosphere, preserving heat for 1h, cooling to room temperature, and taking out to obtain a saliferous silicon-oxygen-carbon material;
s3, washing: and (4) mixing the saliferous silicon-based carbon material obtained in the step S2 with deionized water according to the mass ratio of 1:1, mixing and stirring for 4 hours, taking out the solid, and drying to obtain a porous silica carbon material;
s4, surface coating: placing the porous silica carbon material obtained in the step S3 in a cavity of fluidized bed equipment, adjusting the air inlet temperature to 80 ℃, spraying a methanol solution of phenolic resin into a fluidized bed, carrying out coating reaction for 2 hours, cooling to room temperature, and taking out; wherein the mass of the phenolic resin is 0.1 percent of that of the porous silica carbon material, and the mass fraction of the methanol solution of the phenolic resin is 1 percent;
s5, high-temperature carbonization: and (5) heating the product obtained in the step (S4) to 800 ℃ under the protection of argon gas, carrying out carbonization heat treatment for 4 hours, cooling to room temperature, and taking out to obtain the silicon-oxygen-carbon negative electrode material with a cavity and a coating layer outside the cavity.
Example 3:
a preparation method of a silicon-based negative electrode material of a lithium ion battery comprises the following steps:
s1, granulating: uniformly mixing SiO @ C with the size of D50 being 3 mu m, sodium sulfate, polyethylene glycol and carbon nano tubes in deionized water according to the mass ratio of 1:1:0.5:5, wherein the deionized water accounts for 50% of the total mass; pumping the obtained suspension into a spray dryer for granulation to obtain spheroidal particle powder with the D50 size of 30 mu m;
s2, sintering: heating the spherical-like particle powder with the D50 size of 30 microns obtained in the step S1 to 1000 ℃ under the protection of helium atmosphere, preserving heat for 2 hours, and taking out after cooling to room temperature to obtain a saliferous siloxycarbon material;
s3, washing: and (4) mixing the saliferous silica-carbon material obtained in the step S2 with deionized water according to the mass ratio of 1: 5, mixing and stirring for 3 hours, taking out the solid, and drying to obtain the porous silica carbon material;
s4, surface coating: placing the porous silica carbon material obtained in the step S3 in a cavity of fluidized bed equipment, adjusting the air inlet temperature to 150 ℃, spraying a deionized water solution of glucose into the fluidized bed, carrying out coating reaction for 1 hour, cooling to room temperature, and taking out; wherein the mass of the glucose is 5% of that of the porous silica carbon material, and the mass fraction of the deionized water solution of the glucose is 65%;
s5, high-temperature carbonization: and (5) heating the product obtained in the step (S4) to 1000 ℃ under the protection of argon gas, carrying out carbonization heat treatment for 2h, cooling to room temperature, and taking out to obtain the silicon-oxygen-carbon negative electrode material with a cavity and a coating layer outside the cavity.
Example 4:
a preparation method of a silicon-based negative electrode material of a lithium ion battery comprises the following steps:
s1, granulating: si @ C with the D50 size of 1 mu m, potassium nitrate, sucrose, polyvinylpyrrolidone and graphite in a mass ratio of 1: 10: 10: 6, uniformly mixing in deionized water, wherein the deionized water accounts for 60% of the total mass; pumping the obtained suspension into a spray dryer for granulation to obtain spheroidal particle powder with the D50 size of 15 mu m;
s2, sintering: heating the D50 spherical-like particle powder with the size of 15 microns obtained in the step S1 to 800 ℃ under the protection of argon atmosphere, preserving heat for 3 hours, and taking out the powder after cooling to room temperature to obtain a saliferous silicon-carbon material;
s3, washing: and (4) mixing the saliferous silicon-carbon material obtained in the step S2 with deionized water according to the mass ratio of 1: 10, mixing and stirring for 1h, taking out the solid, and drying to obtain a porous silicon-carbon material;
s4, surface coating: placing the porous silicon-carbon material obtained in the step S3 in a cavity of fluidized bed equipment, adjusting the air inlet temperature to 60 ℃, spraying a methanol solution of polyethylene glycol into the fluidized bed, carrying out coating reaction for 2 hours, cooling to room temperature, and taking out; wherein the mass of the polyethylene glycol is 8% of that of the porous silicon-carbon material, and the mass fraction of the methanol solution of the polyethylene glycol is 40%;
s5, high-temperature carbonization: and (5) heating the product obtained in the step (S4) to 1200 ℃ under the protection of helium gas, performing carbonization heat treatment for 1h, cooling to room temperature, and taking out to obtain the silicon-carbon anode material with a cavity and a coating layer outside the cavity.
Example 5:
a preparation method of a silicon-based negative electrode material of a lithium ion battery comprises the following steps:
s1, granulating: SiO with the D50 size of 0.15 mu m, potassium nitrate and sodium chloride, glucose and polyethylene glycol, carbon nano-tubes and graphene are mixed according to the mass ratio of 1: 8: 15: 4, uniformly mixing in deionized water, wherein the deionized water accounts for 70% of the total mass; pumping the obtained suspension into a spray dryer for granulation to obtain spheroidal particle powder with the D50 size of 12 mu m;
s2, sintering: heating the D50 spherical-like particle powder with the size of 12 microns obtained in the step S1 to 800 ℃ under the protection of argon atmosphere, preserving heat for 4 hours, and taking out after cooling to room temperature to obtain a saliferous silicon-carbon material;
s3, washing: and (4) mixing the saliferous silicon-carbon material obtained in the step S2 with deionized water according to the mass ratio of 1: 8, mixing and stirring for 1h, taking out the solid, and drying to obtain a porous silicon-carbon material;
s4, surface coating: placing the porous silicon-carbon material obtained in the step S3 in a cavity of fluidized bed equipment, adjusting the air inlet temperature to 80 ℃, spraying a tetrahydrofuran solution of asphalt into a fluidized bed, carrying out coating reaction for 1h, cooling to room temperature, and taking out; wherein the mass of the asphalt is 2% of that of the porous silicon-carbon material, and the mass fraction of the tetrahydrofuran solution of the asphalt is 10%;
s5, high-temperature carbonization: and (4) heating the product obtained in the step (S4) to 1200 ℃ under the protection of helium gas, performing carbonization heat treatment for 2h, cooling to room temperature, and taking out to obtain the silicon-carbon negative electrode material with a cavity and a coating layer outside the cavity.
Comparative example 1:
si particles having a D50 size of 100nm used in example 1 were used as comparative example 1.
Comparative example 2:
a preparation method of a silicon-based negative electrode material of a lithium ion battery comprises the following steps:
s1, granulating: si particles with the D50 size of 0.1 mu m and glucose are mixed according to the mass ratio of 1: 20, uniformly mixing in deionized water, wherein the deionized water accounts for 35% of the total mass; pumping the obtained suspension into a spray dryer for granulation to obtain spheroidal particle powder with the D50 size of 5 mu m;
s2, sintering: heating the sphere-like particle powder with the D50 size of 5 microns obtained in the step S1 to 600 ℃ under the protection of nitrogen atmosphere, preserving heat for 6 hours, and taking out after cooling to room temperature to obtain a saliferous silicon-carbon material;
s3, surface coating: placing the porous silicon-carbon material obtained in the step S2 in a cavity of fluidized bed equipment, adjusting the air inlet temperature to 120 ℃, spraying a deionized water solution of sucrose into the fluidized bed, carrying out coating reaction for 0.5h, cooling to room temperature, and taking out; wherein the mass of the sucrose is 10% of that of the silicon-carbon material, and the mass fraction of the deionized water solution of the sucrose is 10%;
s4, high-temperature carbonization: and (5) heating the product obtained in the step (S3) to 600 ℃ under the protection of helium gas, performing carbonization heat treatment for 6 hours, cooling to room temperature, and taking out to obtain the silicon-carbon anode material with the coating layer.
Comparative example 3:
a preparation method of a silicon-based negative electrode material of a lithium ion battery comprises the following steps:
s1, granulating: si particles with the D50 size of 0.1 mu m, sodium chloride and glucose are mixed according to the mass ratio of 1: 0.1: 20, uniformly mixing in deionized water, wherein the deionized water accounts for 35% of the total mass; pumping the obtained suspension into a spray dryer for granulation to obtain spheroidal particle powder with the D50 size of 5 mu m;
s2, sintering: heating the sphere-like particle powder with the D50 size of 5 microns obtained in the step S1 to 600 ℃ under the protection of nitrogen atmosphere, preserving heat for 6 hours, and taking out after cooling to room temperature to obtain a saliferous silicon-carbon material;
s3, washing: and (4) mixing the saliferous silicon-carbon material obtained in the step S2 with deionized water according to the mass ratio of 1: and 0.5, mixing and stirring for 6 hours, taking out the solid, and drying to obtain the porous silicon-carbon negative electrode material.
Performance comparison experiment:
the silicon-based negative electrode materials prepared in the five embodiments and the silicon-based negative electrode materials of the three comparative examples are respectively manufactured into pole pieces, the pole pieces are used as working electrodes, and LiPF is used6The method comprises the steps of assembling a button cell by using/DMC + EC + DEC (1: 1: 1) as an electrolyte, carrying out charging and discharging until the voltage is 0.01-1.5V, and measuring the first charging specific capacity, the first coulombic efficiency and the 50-week cycle retention rate, wherein the results are shown in Table 1.
TABLE 1 comparison of initial specific charge capacity, initial coulombic efficiency, 50 cycle retention
0.1C specific first charge capacity (mAh/g) 0.1C first coulombic efficiency (%) 0.1C, 100-week cycle maintenance (%)
Example 1 643 91 96
Example 2 526 89 97
Example 3 512 89 97
Example 4 675 90 95
Example 5 658 90 96
Comparison ofExample 1 2527 62 0
Comparative example 2 648 91 92
Comparative example 3 652 76 86
As can be seen from table 1, the silicon-based negative electrode materials with the cavities inside and the coating layers outside all prepared in the five embodiments of the present invention exhibit high first coulombic efficiency and excellent cycling stability. The silicon materials used in the example 1 are the same as those used in the comparative examples 1, 2 and 3, and the first coulombic efficiency and the cycle performance of the example 1 are greatly improved compared with those of the untreated comparative example 1; comparative example 2 has no space for volume expansion of silicon inside although it has surface coating, and compared with example 1, the first coulombic efficiency is basically consistent, but the cycle performance is deteriorated; in comparative example 3, which has a cavity for volume expansion of silicon but no surface coating, although the contact area between the electrode and the electrolyte is increased, side reactions are increased, the first coulombic efficiency is low and the cycle performance is further deteriorated, as compared with examples 1 and 2.
In conclusion, the soluble salt is used as the pore-forming agent, and the pore-forming agent can be ablated by water, so that toxic and harmful hydrofluoric acid used in the traditional etching pore-forming agent is avoided, and the method is safe and environment-friendly; by adopting the fluidized bed coating process, the uniform coating of the extremely thin coating layer can be realized, the side reaction of the electrolyte and the surface of the silicon-based material caused by nonuniform coating is avoided, and the circulation stability is improved. Therefore, the preparation method provided by the invention has the advantages of simple process, low energy consumption, environmental protection and easiness in industrial production, and the silicon-based negative electrode material prepared by the method has small volume expansion and excellent and stable cycle performance, and effectively improves the first coulomb efficiency of the silicon-based negative electrode material.
The above embodiments are only preferred embodiments of the present invention, and the protection scope of the present invention is not limited thereby, and any insubstantial changes and substitutions made by those skilled in the art based on the present invention are within the protection scope of the present invention.

Claims (6)

1. A preparation method of a silicon-based negative electrode material of a lithium ion battery is characterized by comprising the following steps: the method comprises the following steps:
s1, granulating: uniformly and completely mixing a silicon-based material, a pore-forming agent and a carbon precursor in deionized water to form a suspension, and then carrying out spray drying granulation to form spheroidal particles with the particle size of D50 being 5-30 mu m; wherein the chemical formula of the silicon-based material is SiOxWherein x is more than or equal to 0 and less than or equal to 1; the D50 size of the silicon-based material is 0.1-5 mu m; the carbon precursor is at least one of sodium carboxymethylcellulose, polyvinylpyrrolidone, glucose, sucrose, melamine and polyethylene glycol;
s2, sintering: heating the spheroidal particles obtained in the step S1 to 600-1200 ℃ under the protection of inert atmosphere, preserving the heat for 1-6h, and taking out the spheroidal particles after cooling to room temperature to obtain a silicon-based carbon material;
s3, washing: placing the silicon-based carbon material obtained in the step S2 in deionized water, stirring for 1-6h, and taking out the solid to obtain a porous silicon-based carbon material;
s4, surface coating: placing the porous silicon-based carbon material obtained in the step S3 in a cavity of fluidized bed equipment, spraying a solution containing an organic coating agent into a fluidized bed for coating, wherein the coating reaction time is 0.5-2 h, and taking out the porous silicon-based carbon material for later use after cooling to room temperature; wherein the mass ratio of the organic coating agent to the porous silicon-based carbon material is 0.001-0.1: 1; the mass fraction of the organic coating agent solution is 1-65%;
s5, high-temperature carbonization: and (5) heating the product obtained in the step (S4) to 600-1200 ℃ under the protection of inert atmosphere, preserving heat for 1-6h, and taking out after cooling to room temperature to obtain the silicon-based negative electrode material.
2. The preparation method of the silicon-based negative electrode material of the lithium ion battery as claimed in claim 1, wherein the preparation method comprises the following steps: a carbon material is also added in the step S1 to prepare a suspension; the mass ratio of the silicon-based material to the pore-forming agent to the carbon precursor to the carbon material is 1: 0.1-10: 0.5-20: 0-10, and the amount of the carbon material is not 0; the carbon material is at least one of graphite, carbon nano tube and graphene.
3. The preparation method of the silicon-based negative electrode material of the lithium ion battery as claimed in claim 1 or 2, wherein: the pore-forming agent in the step S1 is a soluble salt, and the soluble salt is at least one of chloride, nitrate and sulfate of main group metal elements.
4. The preparation method of the silicon-based negative electrode material of the lithium ion battery as claimed in claim 1 or 2, wherein: the content of deionized water in the suspension of the step S1 is 35-80 wt%.
5. The preparation method of the silicon-based negative electrode material of the lithium ion battery as claimed in claim 1 or 2, wherein: the mass ratio of the silicon-based carbon material to the deionized water in the step S3 is 1: 0.5-10.
6. The preparation method of the silicon-based negative electrode material of the lithium ion battery as claimed in claim 1 or 2, wherein: the organic coating agent in the step S4 is at least one of glucose, sucrose, phenolic resin, polyethylene glycol and asphalt; the solvent is at least one of deionized water, methanol, ethanol and tetrahydrofuran.
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