CN112151769B - Method for preparing porous lithium battery silicon-carbon cathode by screw extruder - Google Patents

Method for preparing porous lithium battery silicon-carbon cathode by screw extruder Download PDF

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CN112151769B
CN112151769B CN202010984775.2A CN202010984775A CN112151769B CN 112151769 B CN112151769 B CN 112151769B CN 202010984775 A CN202010984775 A CN 202010984775A CN 112151769 B CN112151769 B CN 112151769B
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carbon
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陈庆
廖健淞
司文彬
李钧
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Sun Bin
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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
    • H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
    • H01M4/139—Processes of manufacture
    • H01M4/1395—Processes of manufacture of electrodes based on metals, Si or alloys
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B82—NANOTECHNOLOGY
    • B82Y—SPECIFIC USES OR APPLICATIONS OF NANOSTRUCTURES; MEASUREMENT OR ANALYSIS OF NANOSTRUCTURES; MANUFACTURE OR TREATMENT OF NANOSTRUCTURES
    • B82Y40/00—Manufacture or treatment of nanostructures
    • H—ELECTRICITY
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    • 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
    • H01M4/04—Processes of manufacture in general
    • H01M4/0402—Methods of deposition of the material
    • H01M4/0411—Methods of deposition of the material by extrusion
    • H—ELECTRICITY
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    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/38—Selection of substances as active materials, active masses, active liquids of elements or alloys
    • H01M4/386—Silicon or alloys based on silicon
    • 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
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    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/62—Selection of inactive substances as ingredients for active masses, e.g. binders, fillers
    • H01M4/628—Inhibitors, e.g. gassing inhibitors, corrosion inhibitors
    • H—ELECTRICITY
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    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M2004/021—Physical characteristics, e.g. porosity, surface area
    • H—ELECTRICITY
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    • 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
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    • 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 belongs to the technical field of lithium battery cathode preparation, and particularly relates to a method for preparing a porous lithium battery silicon-carbon cathode by using a screw extruder. The method comprises the following steps: ultrasonically dispersing styrene, methyl methacrylate and nano silicon powder in a mixed solvent of tetrahydrofuran and cyclohexane, adding n-butyllithium initiator, reacting under the protection of argon to form coated nano silicon particles, filtering, drying, adding deionized water, and adding an acetic acid solution under the irradiation of ultraviolet light to obtain porous PS membrane coated nano silicon particles; adding water-soluble inorganic filler into deionized water to prepare saturated solution, dispersing the porous PS film-coated nano silicon particles into the saturated solution, and evaporating to remove water to crystallize the inorganic filler in nano pores; the product obtained after evaporation is carbonized. And mixing the carbonized product with carbon powder, a binder and a paraffin lubricant, adding the mixture into a screw extruder, repeatedly extruding, soaking the extruded powder in deionized water, and drying to obtain the silicon-carbon composite material with the porous structure.

Description

Method for preparing porous lithium battery silicon-carbon cathode by screw extruder
Technical Field
The invention belongs to the technical field of lithium battery cathode preparation, and particularly relates to a method for preparing a porous lithium battery silicon-carbon cathode by using a screw extruder.
Background
At present, the development of new energy field is very vigorous, and in the field of mobile power supplies, a lead-acid battery and a nickel-hydrogen battery are gradually replaced by a lithium ion battery, so that the lithium ion battery becomes a leading character of the next generation of mobile power supplies. However, the lithium ion battery also has some unsolved 'pain points', such as the problems of low capacity, long charge and discharge time and poor cycle life, and the optimization of the negative electrode material is one of the keys for solving the problems. The negative electrode materials of the current commercial lithium ion battery are mainly artificial graphite and natural graphite, but the theoretical specific capacity of the negative electrode materials is relatively low, so that the requirement of the market on the high-capacity lithium ion battery is difficult to meet, and the silicon-based materials have high theoretical specific capacity and are one of the best substitute materials of the graphite.
However, the silicon-based material has natural defects which restrict the commercialization progress, such as large volume change in the cyclic process, poor conductivity of the silicon-based material itself, and the like. The existing solution mainly uses carbon as a framework to load and coat a silicon-based material so as to relieve the problems of volume effect and poor conductivity brought by the carbon.
In the existing silicon-carbon composite technology, relieving the volume expansion thereof through a porous structure is an ideal choice, and comprises two solving directions of porous silicon filled carbon or porous carbon coated silicon, and the patent application with the application number of CN201810998286.5 discloses a porous silicon-carbon negative electrode material, a preparation method thereof and a lithium ion battery, wherein the porous silicon-carbon negative electrode material comprises a porous silicon-carbon material and a graphite material; the porous silicon carbon material is of a core-shell type three-layer composite structure and comprises an inner core, an intermediate layer and an outermost layer, wherein the intermediate layer and the outermost layer are sequentially coated on the inner core, the inner core is made of an amorphous porous silicon oxygen material SiOx, the intermediate layer is a reticular conductive agent coating layer, and the outermost layer is an amorphous carbon coating layer. Compared with the prior art, the porous silicon-carbon material has the advantages that the volume expansion of the porous silicon-carbon material is greatly reduced, and the first efficiency and the cycle performance are remarkably improved through the design of a core-shell type three-layer composite structure; after the porous silicon-carbon negative electrode material is mixed with a graphite material, the first reversible specific capacity of the porous silicon-carbon negative electrode material is not less than 487.8mAh/g, the first efficiency is not less than 87.86%, the capacity retention rate is not less than 94.6% after 500 times of circulation, and the volume expansion rate is not more than 19.51%.
Patent application No. CN201811568780.4 discloses a silicon-carbon negative electrode material and a preparation method thereof. The invention discloses a preparation method of a silicon-carbon negative electrode material, which comprises the step of carbonizing a material coated with polyacrylate silicon by taking a nickel simple substance and/or a nickel-containing compound as a catalyst to obtain the silicon-carbon negative electrode material. The silicon-carbon negative electrode material prepared by the preparation method is a material with silicon uniformly coated by graphitized porous carbon and amorphous porous carbon. Because the graphitized porous carbon is contained, on the first hand, the conductivity of the silicon-carbon negative electrode material can be increased, which is beneficial to improving the rate capability of the lithium battery; in the second aspect, the mechanical property of the silicon-carbon negative electrode material can be improved; and in the third aspect, the pulverization and the volume expansion of silicon in the silicon-carbon negative electrode material in the use of the lithium ion battery can be relieved. However, such porous composite structures often need to be synthesized at a higher temperature, the process is generally complex, and the pore size and porosity of the porous composite structures are difficult to effectively control in the synthesis process, so that the production consistency of the negative electrode material is relatively poor. Therefore, the method has very important practical significance for improving the synthesis process of the porous silicon carbon cathode.
Patent application with application number CN201810396791.2 discloses a preparation method of a silicon-carbon negative electrode material, which comprises the following steps: and grinding the silicon powder slurry to obtain ground silicon powder slurry. And (3) carrying out graphitization treatment on the carbon micro powder to obtain graphitized carbon micro powder. Stirring the ground silicon powder slurry, continuously adding graphitized carbon micro powder into the ground silicon powder slurry in the stirring process, adding a coating carbon source, performing ultrasonic treatment, stirring simultaneously, and then performing spray drying to obtain the silicon carbon microspheres. And carbonizing the silicon-carbon microspheres to obtain the silicon-carbon microspheres. And etching the silicon carbide carbon microspheres, and then washing and drying the silicon carbide carbon microspheres to obtain the porous silicon carbon microsphere negative electrode material. A porous silicon carbon microsphere negative electrode material is manufactured by the method. The invention can produce the porous silicon carbon microsphere with high gram capacity and high capacity retention rate after multiple cycles.
The patent application with the application number of CN201910104110.5 discloses a porous silicon-carbon negative pole piece and a preparation method thereof, wherein the preparation method of the porous silicon-carbon negative pole piece comprises the following steps: etching the surface of the copper foil, then cleaning, drying and preheating; coating silicon-carbon negative electrode slurry on the surface of the dried copper foil by adopting a double-sided simultaneous extrusion coating machine; hard drying the coating pole piece; carrying out double-sided shot blasting treatment on the pole piece by using a pore-forming agent; carrying out pre-lithiation treatment on the surface of the pole piece; soft drying and drying the pole piece; rolling the pole piece; and finally coating an adhesion layer on the two sides of the silicon-carbon negative pole piece to obtain the silicon-carbon negative pole piece. The porous silicon-carbon cathode is obtained by online pore-forming and shot blasting through the shot blasting, the process is simple, the cost is low, and the porous structure effectively inhibits the expansion stress of the silicon-carbon cathode; meanwhile, the pole piece is subjected to pre-lithiation treatment and nano adhesion layer coating treatment, so that irreversible capacity loss of the silicon-carbon negative electrode is remarkably reduced, the peel strength and flexibility of the pole piece are enhanced, and the first coulomb efficiency and the cycle life of the silicon-carbon negative electrode are improved.
Patent application with the application number of CN201710356888.6 discloses a porous silicon-carbon composite material and a preparation method and application thereof. The porous silicon-carbon composite material is formed by compounding porous silicon and a carbon material, wherein the carbon material is coated on the surface of the porous silicon, the particle size of the porous silicon-carbon composite material is 1-10 mu m, and the specific surface area of the porous silicon-carbon composite material is 10-30m2(ii) in terms of/g. The material is prepared by firstly obtaining porous silicon from iron-silicon alloy through mechanical ball milling and acid etching, compounding the porous silicon with an organic carbon source through a spray pelletizing method, and then carbonizing at high temperature. The porous silicon-carbon composite material can be used for preparing a battery cathode active material, and shows high coulombic efficiency, high capacity and excellent cycle stability when being applied to a lithium ion battery.
The patent application with the application number of CN201710915041.7 discloses a silicon-carbon composite negative electrode material, which has a core-shell structure and comprises an inner core part and a shell part coated on the inner core part, wherein the inner core part is nano-silicon, and the shell part is a composite structure containing a porous carbon material and lithium salt. The invention also provides a preparation method of the silicon-carbon composite negative electrode material.
The patent application with the application number of CN201910231094.6 discloses a porous silicon carbon negative electrode material and a preparation method and application thereof, nano silicon microspheres are used as raw materials, a certain amount of white carbon black, conductive carbon black and adhesive water emulsion are added through a spray drying granulation technology to obtain silicon/silicon dioxide/conductive carbon black composite particles, the particles are placed in hydrofluoric acid to be stirred and soaked, silicon dioxide components are etched away, and precipitation and filtration are carried out to obtain the coated silicon @ carbon negative electrode material (the porous silicon carbon negative electrode material). The method can accurately regulate and control the size, the aperture size and the morphology of particles, reserve space for the expansion of silicon in the electrochemical process, slow down the negative influence of the volume expansion of the silicon on the cathode, and greatly improve the service life and the safety of the battery; and volatile gas is not generated in the preparation process, so that the pollution is small, the energy is saved, the environment is protected, the cost is low, the process is simple, and the method has great market potential and generates good social benefit.
The patent application with the application number of CN201410227442.X discloses a silicon-carbon multi-element composite negative electrode material which mainly comprises 30-60% of flexible graphite, 30-50% of nano silicon and 10-30% of amorphous carbon by mass; the amorphous carbon is obtained by high-temperature pyrolysis of an organic carbon source, and the flexible graphite is obtained by applying pressure to expanded graphite; the preparation method of the product comprises the following steps: firstly, preparing an expanded graphite/silicon-silicon dioxide/carbon composite negative electrode material by a high-temperature pyrolysis method; pouring the mixture into a mould and pressing to obtain a flexible graphite/silicon-silicon dioxide/carbon composite anode material; etching the silicon dioxide by using corrosive liquid to obtain a flexible graphite/silicon/carbon composite negative electrode material; and finally, penetrating the asphalt into the gaps of the flexible graphite/silicon/carbon composite negative electrode material in a protective atmosphere, performing high-temperature heat treatment, and repeating the steps for multiple times to obtain the product. The product of the invention has the advantages of high capacity, high coulombic efficiency, good cycle performance, stable structure, large reversible capacity and the like.
The patent application with the application number of CN202010092820.3 discloses a preparation method of a silicon-carbon cathode, which is characterized in that a plasma platform is used, a silicon-containing material is used as a silicon source, a nitrogen-containing atmosphere is used as a gas source, nitrogen element doping is carried out on a carbon material, and silicon-based nanoparticles are deposited to obtain the silicon-carbon cathode. According to the preparation method of the silicon-carbon cathode, the porous carbon material is adopted, so that the conductivity of the material can be increased, the multiplying power performance and the stability of the material are improved, and the pulverization and the volume expansion of silicon can be inhibited by gaps; silicon-based nanoparticles reduce direct participation of silicon in reaction through multiple reactions in the reaction process, and the material circulation stability is improved.
Disclosure of Invention
The invention provides a method for preparing a porous lithium battery silicon-carbon negative electrode by using a screw extruder, aiming at the problem that the porous structure is difficult to effectively control in the preparation process of the existing porous silicon-carbon negative electrode material.
In order to achieve the purpose, the method for preparing the porous lithium battery silicon-carbon cathode by using the screw extruder comprises the following steps:
(1) ultrasonically dispersing styrene, methyl methacrylate and nano silicon powder in a mixed solvent of tetrahydrofuran and cyclohexane to prepare turbid liquid, adding an n-butyl lithium initiator, reacting under the protection of argon to form PS-b-PMMA block polymer coated nano silicon particles, filtering and drying the PS-b-PMMA block polymer coated nano silicon particles, adding deionized water, and slowly dropwise adding 38% wt acetic acid solution under the irradiation of ultraviolet light to obtain porous PS film coated nano silicon particles;
(2) adding a water-soluble inorganic filler into deionized water to prepare a saturated solution, dispersing the porous PS film-coated nano silicon particles prepared in the step (1) into the saturated solution, heating to 80-100 ℃, and evaporating to remove the deionized water to crystallize the inorganic filler in nano holes;
(3) carbonizing the product obtained after evaporation in the step (2) at the high temperature of 800-1000 ℃ for 4-6 h in a vacuum environment;
(4) mixing the product obtained after carbonization in the step (3) with carbon powder, a binder and a paraffin lubricant, adding the mixture into a screw extruder, repeatedly extruding for 5-10 times, soaking the extruded powder in deionized water for 1-2 hours, and then carrying out vacuum drying for 3-6 hours to obtain the silicon-carbon composite material with the porous structure.
Further preferably, in the step (1), 30-50 parts by weight of styrene, 40-60 parts by weight of methyl methacrylate, 30-50 parts by weight of nano silicon powder, 5-10 parts by weight of n-butyllithium, 90-100 parts by weight of tetrahydrofuran, 90-100 parts by weight of cyclohexane, and an excess of deionized water and 38wt% acetic acid solution are used. More preferably, in the step (1), the styrene accounts for 30-40 parts by weight, the methyl methacrylate accounts for 40-50 parts by weight, the nano silicon powder accounts for 40-50 parts by weight, the n-butyllithium accounts for 6-8 parts by weight, the tetrahydrofuran accounts for 95-100 parts by weight, and the cyclohexane accounts for 90-94 parts by weight.
Further preferably, the water-soluble inorganic filler in step (2) is sodium chloride.
Further preferably, the binder in the step (4) is a mixed powder of CMC and SBR in a mass ratio of 1: 1. CMC is sodium carboxymethyl cellulose; SBR is styrene butadiene rubber.
Further preferably, the temperature of the screw extruder in the step (4) is 50-80 ℃, and the rotation speed is 40-100 rpm.
Further preferably, the raw materials in the step (4) are in parts by weight: 40-60 parts of carbonized product, 1-5 parts of paraffin, 40-60 parts of carbon powder and 3-5 parts of binder.
Further preferably, the particle size of the carbon powder in step (4) is less than 100 nm.
Has the advantages that:
according to the invention, organic phase with nano-pores is coated with silicon powder in advance, saturated solution of inorganic filler is heated to separate out crystals to fill the nano-pores, so that the porosity in the carbonization process is ensured, and particles are coated by a screw extruder for the second time after carbonization, so that the porous material with a controllable surface structure is obtained.
The main process is that a coating layer is formed on the surface of the nanometer silicon by self-assembly of block polymers, the block polymer layer on the surface of the particles has the property of a semipermeable membrane, acetic acid permeates into the particles, so that internal pressure expansion is initiated, meanwhile, ultraviolet light initiates PMMA block fracture and PS section crosslinking, nanopores are formed on a block polymer film, PS particles are vitrified while being precipitated and crystallized through inorganic filler and embedded into the nanopores in the hydrothermal treatment process, finally, secondary coating is carried out by using a screw extruder after high-temperature carbonization, and the inorganic filler is washed away, so that the silicon-carbon negative electrode material with a controllable porous structure is obtained.
Drawings
FIG. 1: the process flow diagram of the invention;
FIG. 2: example 1 desorption profile of specific surface area test for preparing silicon carbon negative electrode;
FIG. 3: desorption profile of the specific surface area test of the silicon carbon cathode prepared in comparative example 1.
Detailed Description
The present invention will be described in further detail with reference to specific embodiments, but it should not be construed that the scope of the present invention is limited to the following examples. Various substitutions and alterations can be made by those skilled in the art and by conventional means without departing from the spirit of the method of the invention described above.
Example 1
A preparation method of a porous lithium battery silicon-carbon negative electrode by using a screw extruder comprises the following steps:
(1) ultrasonically dispersing 40 parts by weight of styrene, 50 parts by weight of methyl methacrylate and 40 parts by weight of nano silicon powder in a mixed solvent of 100 parts by weight of tetrahydrofuran and 100 parts by weight of cyclohexane to prepare a suspension, adding 10 parts by weight of n-butyllithium initiator, reacting under the protection of argon to form PS-b-PMMA block polymer coated nano silicon particles, filtering and drying the PS-b-PMMA block polymer coated nano silicon particles, adding deionized water, and slowly dropwise adding 38% wt of acetic acid solution under the irradiation of ultraviolet light to obtain porous PS membrane coated nano silicon particles;
(2) adding inorganic filler sodium chloride into deionized water to prepare a saturated solution, dispersing 200 parts by weight of the porous PS film-coated nano silicon particles prepared in the step (1) into the saturated solution, heating to 100 ℃, and evaporating to remove the deionized water to crystallize the inorganic filler in the nano holes;
(3) carbonizing the product obtained after evaporation in the step (2) at the high temperature of 900 ℃ for 5 hours in a vacuum environment;
(4) mixing CMC and SBR according to the mass ratio of 1:1 to obtain a binder; and (3) mixing 40 parts by weight of the product carbonized in the step (3) with 250 parts by weight of carbon powder with the granularity of 50-100 nm, 20 parts by weight of binder and 20 parts by weight of paraffin lubricant, adding the mixture into a screw extruder, repeatedly extruding the mixture for 8 times at 70 ℃ and the rotating speed of 80rpm, placing the extruded powder into deionized water, soaking the powder for 2 hours, and performing vacuum drying for 4 hours to obtain the silicon-carbon composite material with the porous structure.
Example 2
A preparation method of a porous lithium battery silicon-carbon negative electrode by using a screw extruder comprises the following steps:
(1) ultrasonically dispersing 40 parts by weight of styrene, 50 parts by weight of methyl methacrylate and 50 parts by weight of nano silicon powder in a mixed solvent of 100 parts by weight of tetrahydrofuran and 100 parts by weight of cyclohexane to prepare a suspension, adding 10 parts by weight of n-butyllithium initiator, reacting under the protection of argon to form PS-b-PMMA block polymer coated nano silicon particles, filtering and drying the PS-b-PMMA block polymer coated nano silicon particles, adding deionized water, and slowly dropwise adding 38% wt of acetic acid solution under the irradiation of ultraviolet light to obtain porous PS membrane coated nano silicon particles;
(2) adding water-soluble inorganic filler sodium chloride into deionized water to prepare a saturated solution, dispersing 200 parts by weight of the porous PS film-coated nano silicon particles prepared in the step (1) into the saturated solution, heating to 100 ℃, and evaporating to remove the deionized water to crystallize the inorganic filler in the nano holes;
(3) carbonizing the product obtained after evaporation in the step (2) at the high temperature of 900 ℃ for 5 hours in a vacuum environment;
(4) mixing CMC and SBR according to the mass ratio of 1:1 to obtain a binder;
and (3) mixing 50 parts by weight of the product carbonized in the step (3) with 250 parts by weight of carbon powder with the granularity of 50-100 nm, 20 parts by weight of binder and 20 parts by weight of paraffin lubricant, adding the mixture into a screw extruder, repeatedly extruding the mixture for 8 times at 80 ℃ and the rotating speed of 50rpm, placing the extruded powder into deionized water, soaking the powder for 2 hours, and performing vacuum drying for 4 hours to obtain the silicon-carbon composite material with the porous structure.
Example 3
A preparation method of a porous lithium battery silicon-carbon negative electrode by using a screw extruder comprises the following steps:
(1) ultrasonically dispersing 40 parts by weight of styrene, 50 parts by weight of methyl methacrylate and 40 parts by weight of nano silicon powder in a mixed solvent of 100 parts by weight of tetrahydrofuran and 100 parts by weight of cyclohexane to prepare a suspension, adding 10 parts by weight of n-butyllithium initiator, reacting under the protection of argon to form PS-b-PMMA block polymer coated nano silicon particles, filtering and drying the PS-b-PMMA block polymer coated nano silicon particles, adding deionized water, and slowly dropwise adding 38% wt of acetic acid solution under the irradiation of ultraviolet light to obtain porous PS membrane coated nano silicon particles;
(2) adding water-soluble inorganic filler sodium chloride into deionized water to prepare a saturated solution, dispersing 200 parts by weight of the porous PS film-coated nano silicon particles prepared in the step (1) into the saturated solution, heating to 100 ℃, and evaporating to remove the deionized water to crystallize the inorganic filler in the nano holes;
(3) carbonizing the product obtained after evaporation in the step (2) at the high temperature of 900 ℃ for 5 hours in a vacuum environment;
(4) mixing CMC and SBR according to the mass ratio of 1:1 to obtain a binder;
and (3) mixing 60 parts by weight of the product carbonized in the step (3) with 200 parts by weight of carbon powder with the granularity of 50-100 nm, 20 parts by weight of binder and 20 parts by weight of paraffin lubricant, adding the mixture into a screw extruder, repeatedly extruding the mixture for 8 times at the temperature of 60 ℃ and the rotating speed of 100rpm, placing the extruded powder into deionized water, soaking the powder for 2 hours, and performing vacuum drying for 4 hours to obtain the silicon-carbon composite material with the porous structure.
Example 4
A preparation method of a porous lithium battery silicon-carbon negative electrode by using a screw extruder comprises the following steps:
(1) ultrasonically dispersing 40 parts by weight of styrene, 50 parts by weight of methyl methacrylate and 40 parts by weight of nano silicon powder in a mixed solvent of 100 parts by weight of tetrahydrofuran and 100 parts by weight of cyclohexane to prepare a suspension, adding 10 parts by weight of n-butyllithium initiator, reacting under the protection of argon to form PS-b-PMMA block polymer coated nano silicon particles, filtering and drying the PS-b-PMMA block polymer coated nano silicon particles, adding deionized water, and slowly dropwise adding 38% wt of acetic acid solution under the irradiation of ultraviolet light to obtain porous PS membrane coated nano silicon particles;
(2) adding water-soluble inorganic filler sodium chloride into deionized water to prepare a saturated solution, dispersing 200 parts by weight of the porous PS film-coated nano silicon particles prepared in the step (1) into the saturated solution, heating to 100 ℃, and evaporating to remove the deionized water to crystallize the inorganic filler in the nano holes;
(3) carbonizing the product obtained after evaporation in the step (2) at the high temperature of 900 ℃ for 5 hours in a vacuum environment;
(4) mixing CMC and SBR according to the mass ratio of 1:1 to obtain a binder;
and (3) mixing 60 parts by weight of the carbonized product obtained in the step (3) with 220 parts by weight of carbon powder with the granularity of less than 100nm, 20 parts by weight of binder and 20 parts by weight of paraffin lubricant, adding the mixture into a screw extruder, repeatedly extruding the mixture for 8 times at 50 ℃ and 80rpm, placing the extruded powder into deionized water, soaking the powder for 2 hours, and performing vacuum drying for 4 hours to obtain the silicon-carbon composite material with the porous structure.
Comparative example 1
A preparation method of a porous lithium battery silicon-carbon negative electrode by using a screw extruder comprises the following steps:
(1) ultrasonically dispersing 40 parts by weight of styrene, 50 parts by weight of methyl methacrylate and 40 parts by weight of nano silicon powder in a mixed solvent of 100 parts by weight of tetrahydrofuran and 100 parts by weight of cyclohexane to prepare a suspension, adding 10 parts by weight of n-butyllithium initiator, reacting under the protection of argon to form PS-b-PMMA block polymer coated nano silicon particles, filtering and drying the PS-b-PMMA block polymer coated nano silicon particles, adding deionized water, and slowly dropwise adding 38% wt of acetic acid solution under the irradiation of ultraviolet light to obtain porous PS membrane coated nano silicon particles;
(2) carbonizing the porous PS film-coated nano silicon particles in the step (1) at the high temperature of 900 ℃ for 5 hours in a vacuum environment;
(3) mixing CMC and SBR according to the mass ratio of 1:1 to obtain a binder; and (3) mixing 40 parts by weight of the product carbonized in the step (2) with 250 parts by weight of carbon powder with the granularity of 50-100 nm, 20 parts by weight of binder and 20 parts by weight of paraffin lubricant, adding the mixture into a screw extruder, repeatedly extruding the mixture for 8 times at 70 ℃ and the rotating speed of 80rpm, placing the extruded powder into deionized water, soaking the powder for 2 hours, and performing vacuum drying for 4 hours to obtain the silicon-carbon composite material with the porous structure.
Comparative example 2
A preparation method of a porous lithium battery silicon-carbon negative electrode by using a screw extruder comprises the following steps:
(1) ultrasonically dispersing 40 parts by weight of styrene, 50 parts by weight of methyl methacrylate and 40 parts by weight of nano silicon powder in a mixed solvent of 100 parts by weight of tetrahydrofuran and 100 parts by weight of cyclohexane to prepare a suspension, adding 10 parts by weight of n-butyllithium initiator, reacting under the protection of argon to form PS-b-PMMA block polymer coated nano silicon particles, filtering and drying the PS-b-PMMA block polymer coated nano silicon particles, adding deionized water, and slowly dropwise adding 38% wt of acetic acid solution under the irradiation of ultraviolet light to obtain porous PS membrane coated nano silicon particles;
(2) adding inorganic filler sodium chloride into deionized water to prepare a saturated solution, dispersing 200 parts by weight of the porous PS film-coated nano silicon particles prepared in the step (1) into the saturated solution, heating to 100 ℃, and evaporating to remove the deionized water to crystallize the inorganic filler in the nano holes;
(3) carbonizing the product obtained after evaporation in the step (2) at the high temperature of 900 ℃ for 5 hours in a vacuum environment; eluting the soluble salt to obtain the silicon-carbon composite material with the porous structure.
And (3) correlation detection:
the specific surface areas of example 1 and comparative example 2 were tested using the low temperature nitrogen adsorption method (BET).
The samples of example 1, comparative example 1 and comparative example 2 were mixed with PVDF and Super-P respectively in a ratio of 8:1:1 to form a slurry, the slurry was coated on the surface of copper foil to serve as a positive electrode, a lithium sheet was used as a negative electrode, lithium hexafluorophosphate and carbonate were used as electrolytes to prepare a CR2032 button cell, and the button cell was subjected to a cycle performance test at a test current of 0.4ma/g and a cycle number of 50 times, with the test results shown in Table 1.
Table 1 results of cycle performance test of example 1 and comparative examples 1 and 2
First circulation capacity (mah/g) First cycle efficiency (%) 50-circle circulation residual capacity (mah/g)
Example 1 467.4 82.7 448.8
Example 2 470.1 83.2 453.2
Example 3 468.8 82.9 451.3
Example 4 465.3 82.1 435.7
Comparative example 1 473.8 84.9 312.7
Comparative example 2 458.9 81.3 305.4
Through detection, the first circulation capacity and efficiency difference between examples 1-4 and comparative examples 1-2 is not large, and the examples have no attenuation after 50 cycles of circulation, because the inorganic filler effectively ensures that the pore channels are not blocked in the melting carbonization process of organic matters at high temperature in the carbonization process after the inorganic filler is filled in the nanopores, the specific surface area is large, and fig. 2 is a desorption curve of example 1. While comparative example 1 does not fill the micropores with a soluble salt, it is difficult to form porous silicon carbon, and the volume expansion relieving property for silicon is poor, as shown in fig. 3, which is the desorption curve of comparative example 1. Comparative example 2, although having nano-pores, was inferior in volume expansion relieving property because secondary coating was not performed in the screw extruder.

Claims (8)

1. A method for preparing a porous lithium battery silicon-carbon composite material by using a screw extruder is characterized by comprising the following steps:
(1) ultrasonically dispersing styrene, methyl methacrylate and nano silicon powder in a mixed solvent of tetrahydrofuran and cyclohexane to prepare turbid liquid, adding an n-butyllithium initiator, reacting under the protection of argon to form PS-b-PMMA block polymer coated nano silicon particles, filtering and drying the PS-b-PMMA block polymer coated nano silicon particles, adding deionized water, and slowly dropwise adding 38wt% acetic acid solution under the irradiation of ultraviolet light to obtain porous PS film coated nano silicon particles;
(2) adding a water-soluble inorganic filler into deionized water to prepare a saturated solution, dispersing the porous PS film-coated nano silicon particles prepared in the step (1) into the saturated solution, heating to 80-100 ℃, and evaporating to remove the deionized water to crystallize the inorganic filler in nano holes;
(3) carbonizing the product obtained after evaporation in the step (2) at a high temperature of 800-1000 ℃ for 4-6 h in a vacuum environment;
(4) and (3) mixing the product obtained after carbonization in the step (3), carbon powder, a binder and a paraffin lubricant, adding the mixture into a screw extruder, repeatedly extruding for 5-10 times, soaking the extruded powder in deionized water for 1-2 hours, and then carrying out vacuum drying for 3-6 hours to obtain the silicon-carbon composite material with the porous structure.
2. The method for preparing the porous lithium battery silicon-carbon composite material by using the screw extruder as claimed in claim 1, wherein in the step (1), 30-50 parts by weight of styrene, 40-60 parts by weight of methyl methacrylate, 30-50 parts by weight of nano silicon powder, 5-10 parts by weight of n-butyllithium, 90-100 parts by weight of tetrahydrofuran, 90-100 parts by weight of cyclohexane, and the excess of deionized water and 38wt% acetic acid solution are adopted.
3. The method for preparing the porous lithium battery silicon-carbon composite material by using the screw extruder as claimed in claim 1, wherein in the step (1), 30 to 40 parts by weight of styrene, 40 to 50 parts by weight of methyl methacrylate, 40 to 50 parts by weight of nano silicon powder, 6 to 8 parts by weight of n-butyl lithium, 95 to 100 parts by weight of tetrahydrofuran and 90 to 94 parts by weight of cyclohexane are used.
4. The method for preparing the porous lithium battery silicon-carbon composite material by the screw extruder as claimed in claim 1, wherein the water-soluble inorganic filler in the step (2) is sodium chloride.
5. The method for preparing the porous lithium battery silicon-carbon composite material by the screw extruder in claim 1, wherein the binder in the step (4) is a mixed powder of CMC and SBR in a mass ratio of 1: 1.
6. The method for preparing the porous lithium battery silicon-carbon composite material by using the screw extruder as claimed in claim 1, wherein the temperature of the screw extruder in the step (4) is 50-80 ℃, and the rotation speed is 40-100 rpm.
7. The method for preparing the porous lithium battery silicon-carbon composite material by using the screw extruder as claimed in claim 1, wherein the raw materials in the step (4) comprise the following components in parts by weight: 40-60 parts of carbonized product, 10-20 parts of nano inorganic filler, 1-5 parts of paraffin, 40-60 parts of carbon powder and 3-5 parts of binder.
8. The method for preparing the porous lithium battery silicon-carbon composite material by the screw extruder as claimed in claim 1, wherein the particle size of the carbon powder in the step (4) is less than 100 nm.
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CN106898756A (en) * 2017-04-24 2017-06-27 广东烛光新能源科技有限公司 A kind of silicon-carbon cathode material and preparation method thereof
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CN106898756A (en) * 2017-04-24 2017-06-27 广东烛光新能源科技有限公司 A kind of silicon-carbon cathode material and preparation method thereof
CN109830673A (en) * 2019-03-26 2019-05-31 南京大学射阳高新技术研究院 A kind of porous silicon-carbon cathode material and the preparation method and application thereof

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