CN112366301A - Silicon/silicon oxide/carbon composite negative electrode material for lithium ion battery and preparation method thereof - Google Patents

Silicon/silicon oxide/carbon composite negative electrode material for lithium ion battery and preparation method thereof Download PDF

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CN112366301A
CN112366301A CN202011251348.XA CN202011251348A CN112366301A CN 112366301 A CN112366301 A CN 112366301A CN 202011251348 A CN202011251348 A CN 202011251348A CN 112366301 A CN112366301 A CN 112366301A
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silicon
silicon oxide
sio
core
lithium ion
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CN112366301B (en
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杨丹
候佼
王兴蔚
贺超
孙永林
马少宁
马勇
候春平
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Ningxia Bolt Technology Co ltd
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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
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B82—NANOTECHNOLOGY
    • B82Y—SPECIFIC USES OR APPLICATIONS OF NANOSTRUCTURES; MEASUREMENT OR ANALYSIS OF NANOSTRUCTURES; MANUFACTURE OR TREATMENT OF NANOSTRUCTURES
    • B82Y30/00—Nanotechnology for materials or surface science, e.g. nanocomposites
    • 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
    • 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
    • H01M4/36—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

The invention relates to a negative electrode material for a lithium ion battery, a preparation method thereof and a battery, and discloses a preparation method of a silicon/silicon oxide/carbon composite negative electrode material for the lithium ion battery, a material and a batteryxAnd the amorphous pyrolytic carbon coating layer can well buffer the volume expansion of the nano silicon in the charge-discharge process on the premise of not remarkably reducing the capacity, and the high conductivity and stability of the pyrolytic carbon coating layer are beneficial to enhancing the Si @ SiOxAnd the stability of an SEI film at the interface of the composite material and an electrolyte solution enables the composite material to have high capacity, excellent rate capability and cycle performance.

Description

Silicon/silicon oxide/carbon composite negative electrode material for lithium ion battery and preparation method thereof
Technical Field
The invention relates to a preparation method of a negative electrode material for a lithium ion battery and the battery, in particular to a silicon/silicon oxide/carbon composite negative electrode material, a preparation method thereof and the lithium ion battery adopting the silicon/silicon oxide/carbon composite negative electrode material.
Background
At present, artificial graphite and natural graphite are mainly used as negative active materials of commercial lithium ion batteries, but the theoretical specific capacity of the graphite is only 372mAh/g and is lower, and the energy density of a battery system formed by the graphite and positive materials such as lithium iron phosphate, lithium manganate or nickel cobalt lithium manganate is generally 150 Wh/Kg; meanwhile, the lithium intercalation potential of graphite is close to the lithium deposition potential, and lithium is easily separated to generate lithium dendrite in the process of low-temperature charging or high-rate charging and discharging, so that the safety problem is caused. Therefore, the conventional graphite-based negative electrode material has difficulty in meeting the requirements of multifunctional electronic products on high power and high capacity of the lithium ion battery, and further research and development of a novel lithium ion battery negative electrode material with high energy density, high safety performance and long cycle life is needed.
Silicon as the lithium ion battery cathode material has the outstanding advantages that: the theoretical specific capacity is as high as 4200mAh/g (Li)4.4Si) more than 10 times that of commercial graphite; a slightly higher potential plateau than graphite (0.4V, Li/Li)+) The safety is good; excellent low temperature performance(ii) a The reserves are abundant.
However, the application of silicon as a negative electrode material of a lithium ion battery has great challenges: 1) during the charging and discharging process, the Li-Si alloying can generate serious volume expansion which can reach more than 300 percent (Li)4.4Si) which leads to the pulverization of silicon particles and the loss of activity, and poor cycle performance; 2) silicon particles are cracked in the charging and discharging process, the active particles and the poor electrical contact between the active particles and a current collector form an island effect, new SEI films are repeatedly formed on the cracked surfaces, and irreversible capacity loss and low coulombic efficiency are caused; 3) silicon is a semiconductor and exhibits low electrical conductivity (10)-5-10-3S cm-1) And ion diffusion coefficient (10)-14-10-13cm2s-1) Leading to the reduction of the dynamic performance of lithium ion diffusion; 4) large specific surface area, low tap density and the like caused by the nano structure effect. The above disadvantages severely restrict the industrial development and application.
In view of the above-mentioned disadvantages of silicon materials, researchers and industries have studied on the aspects of silicon nanostructure design, interface and surface structure design of nano silicon materials, and structural design using graphite as a stable carrier, and the modification methods adopted mainly include nano-modification and composite modification. The nano silicon-based material with special appearance and structure such as silicon nanoparticles, silicon nanowires, silicon nanotubes and silicon-based nano films is prepared, so that the volume change of the cathode active material is more uniform, the cathode material can obtain enough space to relieve the volume change of silicon, but the nano material is easy to agglomerate, a new volume effect can be generated in the circulation process, the problem of the cycling stability of the silicon material cannot be fundamentally solved by single nano treatment, and the nano silicon material with special structure and appearance has high preparation cost and complex process and is not beneficial to industrial popularization; the composite material introduces an active or inactive buffer matrix with good conductivity and small volume effect on the basis of reducing the volume effect of a silicon active phase through nanocrystallization, and improves the cycle stability of the silicon-based negative electrode material by adopting a volume compensation and conductivity increasing mode. The silicon-carbon composite material is the silicon-based material which is most expected to realize large-scale industrialization, but the problems of high cost, complex process and control of the nano silicon powder are urgently solvedDifficulty and poor batch stability. The research aiming at the silicon-based cathode material is mainly divided into a nano silicon cathode material and a nano silicon oxide SiOxTwo main categories of cathode materials. When the lithium ion size of the silicon is less than 150nm, the volume expansion of the silicon is obviously reduced, and the nano silicon negative electrode material has the characteristics of high capacity and high charging and discharging coulombic efficiency, but has poor rate capability and cycle performance; and SiOxThe capacity and the first coulombic efficiency of the material are lower than those of nano silicon, but the volume expansion of the material is smaller, and the cycle performance and the rate performance of the material are better.
The preparation of Si/SiO by liquid phase solidification-high temperature pyrolysis methodxthe/C composite material is prepared by mixing nano-silicon, crystalline flake graphite and SiO in carbon source solventxSi/SiO obtained after dispersionxThe composite material of the composite cathode material obtained by the method is easy to agglomerate, and Si and SiOxAre merely mixed together, no chemical bond is formed, and SiOxThe carbon layer is doped with a large amount of Si particles, HF is required for etching, and various factors enable the Si/SiO prepared by the methodxThe capacity performance, the cycle performance and the rate capability of the/C composite material are poor.
Chinese patent publication No. CN111164803A discloses a composite negative electrode material comprising a core, a first shell and a second shell, wherein the core of the negative electrode material disclosed in the patent is made of silicon and silicon oxide, the first shell is made of silicate substances and carbon particles, the second shell is made of an externally coated carbon film layer, the first shell is prepared in a mechanical mixing and dispersing way, the size of the core, the size of the first shell and the size of the second shell of the prepared composite negative electrode material are larger, the size of the core is between 1 and 10 mu m, the size of the first shell is between 0.01 and 2 mu m, the thickness of the second shell is between 0.01 and 1 mu m, the structural stability of the first shell is poor, the preparation method physically mixes and sinters the silicon particles, the uniformity of components is poor, the complete coating of the silicon particles by the silicon oxide cannot be realized, and the capacities of active substances of the silicon and the silicon oxide cannot be effectively exerted, the material also has poor rate capability.
Chinese patent publication CN105406050A discloses a silicon/silicon oxide/metal/carbon anode material with a core-shell structure. The method is characterized in that a silicon oxide layer is prepared on the surface of silicon particles directly in a physical mixing and dispersing mode, the process is not controllable, but the silicon oxide layer prepared by a physical method has a collapse structure of the silicon oxide layer due to poor stability in a large-charge and discharge process, so that metal nanoparticles are added in the silicon oxide layer to form a nano composite layer. However, the lithium ions are influenced by a certain resistance during the migration and diffusion on the negative electrode material, the rate capability and the cycle performance of the material are influenced, and the capacity of the negative electrode material silicon active substance in the patent cannot be effectively exerted, after the negative electrode material in the patent is prepared into a complete 18650 full cell, the capacity of the cell is only about 1500mAh/g, and the cell is not suitable for large-rate charge and discharge, and because the influencing factors of the 18650 full cell capacity performance and the cycle performance include a positive electrode material, an electrolyte and the like, if the negative electrode material prepared in the patent is simply prepared into a half cell, the cycle performance and the rate performance of the negative electrode material are poorer when the research on the performance of the negative electrode material is carried out.
Based on the problems in the prior art, a new silicon/silicon oxide/carbon composite negative electrode material for lithium ion batteries, a preparation method thereof and a battery are needed to be invented, and the characteristics of high capacity performance of silicon particles and high cycle performance of silicon oxides are further exerted.
Disclosure of Invention
In order to solve the problems of serious agglomeration and SiO existing in the composite cathode material prepared by the prior art in the background technologyxThe invention provides a silicon/silicon oxide/carbon composite cathode material, a preparation method thereof and a battery, aiming at improving the capacity, the cycle performance and the rate performance of a cathode material of a lithium ion battery.
The silicon/silicon oxide/carbon composite cathode material for the lithium ion battery has a core-shell structure, and is a dual-core shell structure.
The core of the core-shell structure is composed of nano silicon particles;
the shell layer has a multilayer structure, and the inner layer is silicon oxide SiOxThe buffer layer is 1-50nm thick, and the outer layer is composed of a carbon layer coated outside the silicon oxide layer;
the outer coating carbon layer is formed by carbonizing a carbonizable organic substance at a high temperature of 600-1250 ℃, and the nano Si @ SiOxThe mass ratio of the core-shell structure material to the carbonizable organic carbon source is 50: 5.0 to 200.0;
the shell is a carbon coating layer coated outside the nano silicon particles and the silicon oxide inner layer thereof, and the mass of the coating layer is 2-200% of the mass of silicon.
The other purpose of the invention is to prepare the silicon/silicon oxide/carbon composite anode material, and the preparation method is realized by the following steps:
preparation of S1 nano-silicon particles: preparing nano silicon powder by one of a solid-phase ball milling method, a liquid-phase ball milling method, a chemical vapor deposition method, a laser sputtering method and a plasma chemical vapor deposition method, wherein the particle size of the prepared silicon powder is 20-300 nm;
in this step, silicon powder particles of different sizes of 20-300 nm, such as 20nm, 50nm, 100nm, 150nm, 200nm, 300nm, etc., can be obtained by a solid phase ball milling method, a liquid phase ball milling method, a chemical vapor deposition method, a laser sputtering method, or a plasma chemical vapor deposition method, and the obtained nanoparticles are in a shape of a sphere, a quasi-sphere, a strip, a flake, a cone, a rhombus, or a form disorder distribution of two or more shapes.
S2 nanometer Si @ SiOxPreparation of core-shell structure material: the prepared nano silicon powder and an oxidant are subjected to in-situ oxidation treatment to prepare Si @ SiOxCore-shell materials, Si @ SiOxSiO of core-shell materialsxThe thickness of the buffer shell layer is controllable, and is 1-50nm, such as 1nm, 10nm, 20nm, 30nm, 50nm and the like;
in the step, the adopted oxidant is a mixed oxidant consisting of one or more than two of oxygen, potassium permanganate, potassium dichromate, sodium dichromate, nitric acid, potassium chlorate, sodium chlorate, potassium perchlorate, sodium perchlorate, hydrogen peroxide and peroxyacetic acid;
in the step, a layer of SiO is formed on the surface of the nano silicon ions obtained in the step S1 through in-situ oxidation treatmentxLithium storage phase buffer layer and SiO prepared by using methodxThe coating layer is firmly combined on the surface of the nano silicon particles through chemical bonds, and the volume expansion and contraction of the nano silicon in the charge and discharge process can be well buffered on the premise of not remarkably reducing the capacity. Can well maintain SiO in the process of heavy current charging and dischargingxStructural stability of the layer, no structural collapse occurs.
S3 purification treatment: the Si @ SiO prepared in the above wayxAcidifying the core-shell structure material by using acid to remove soluble metal ions, and then washing the core-shell structure material by using pure water for at least 3 times for later use;
in the step, the acid used for purification is mixed acid consisting of one or more than two of hydrochloric acid, acetic acid, oxalic acid and phosphoric acid;
the purpose of this step is to remove the SiOxSoluble metal ions incorporated during the layer process to work well on SiOxThe surface of the layer is coated with a pyrolytic carbon layer.
S4 mixing and dispersing: the purified Si @ SiOxThe mass ratio of the core-shell structure material to the carbonizable organic carbon source is 50: 5.0-200.0, performing ultrasonic pre-dispersion in a solvent, performing the dispersion process in protective gas with a certain flow velocity, and setting parameters of the rotation speed, frequency, power density and dispersion time of the ultrasonic dispersion to obtain mixed slurry with the solid content of 20-60%;
in the step, the organic carbon source capable of being carbonized is one or more of emulsified asphalt, polyglycol ether, diethyl phthalate, polyethylene glycol, modified alkyd resin, furan resin, phenolic resin, polyvinyl alcohol, methyl cellulose, styrene-butadiene rubber, polymethacrylate, sucrose, glucose, polyvinylpyrrolidone, fatty alcohol-polyoxyethylene ether, alkylphenol ethoxylate, polyoxyethylene alkylamide, fatty acid-polyoxyethylene ester and polyoxyethylene alkylammonium, and the solvent is one or more of deionized water, methanol, ethanol, propanol, isopropanol, acetone, isopropyl ketone, N-hexane, N-methylpyrrolidone, tetrahydrofuran and ethyl acetate;
s5 drying treatment: drying the mixed slurry at 105-300 ℃ by adopting a stirring drying, or fluidized bed drying, or spray drying mode to prepare a precursor;
s6 carbonization: heating the precursor to 350-550 ℃ at a heating rate of 1-10 ℃/min under the protective gas atmosphere, and preserving the heat for 60-180 min to obtain a silicon/silicon oxide/carbon composite anode material precursor;
s7 high-temperature sintering treatment: heating the precursor of the silicon/silicon oxide/carbon composite negative electrode material to the calcining temperature of 600-1250 ℃ at the heating rate of 1-10 ℃/min under the protective gas atmosphere, calcining for 1-10.0 h, and naturally cooling to the room temperature after sintering to obtain the silicon/silicon oxide/carbon composite negative electrode material for the lithium ion battery;
in the steps S4, S5, S6 and S7, the protective gas is one of nitrogen, helium, neon, argon, krypton or xenon, and the flow rate is 0.2-1.0 m3/h。
By utilizing the steps, the core-shell structure silicon/silicon oxide/carbon composite negative electrode material with a stable structure can be obtained.
Another object of the present invention is to produce a battery using the silicon/silicon oxide/carbon composite negative electrode material for a lithium ion battery of the present invention.
Compared with the prior art that the composite material obtained by liquid phase solidification is easy to agglomerate, and the surface of the coating layer of the composite material obtained by the method is doped with a large amount of Si particles to cause serious capacity loss, the invention adopts an oxidant in-situ oxidation method and a high-temperature pyrolysis method to grow and coat SiO outside the silicon nano particles in situ from inside to outside of the core-shell structure in sequencexLayer of Si @ SiOxThe outer is coated with a pyrolytic carbon layer, and the obtained cathode material does not generateThe problem of agglomeration is solved, Si particles cannot be doped on the surface of a coating layer of the composite material, and the obtained composite material has the advantages of low capacity loss, high specific capacity and high coulombic efficiency for the first time.
The silicon nanoparticle core and the silicon oxide shell of the silicon/silicon oxide/carbon composite negative electrode material prepared by adopting the oxide agent in-situ oxidation-high temperature pyrolysis method have small sizes, the size of the silicon nanoparticle is smaller than 300nm, and the size of the silicon oxide shell is smaller than 50nm, so that the volume expansion of silicon can be obviously reduced, the capacity exertion of active substances is greatly improved, the specific capacity of the obtained negative electrode material is higher than 2800mAh/g, and the silicon oxide layer prepared by adopting the oxide agent in-situ oxidation is combined with the silicon nanoparticles by chemical bonds, so that the structure is stable, and the defects that the conventional SiO obtained by adopting physical mixing and dispersion is overcomexThe coating layer is easy to generate structural collapse under the condition of large-current charge and dischargexThe coating layer keeps stable structure in the heavy current charging and discharging process, and well buffers the volume expansion of the nano silicon in the charging and discharging process, so that the Si @ SiOxSimultaneously has high capacity of nano silicon cathode material, higher charging and discharging coulombic efficiency and SiOxThe material has the characteristics of excellent cycle performance and rate capability.
The composite cathode material provided by the invention has the high capacity characteristic of the nano-silicon cathode material and the SiOxThe material has the characteristics of high cycle performance and excellent rate capability.
In the preparation process of the silicon/silicon oxide/carbon composite anode material, Si @ SiOxAfter preparation, acid is used for purification, soluble metal ions are blended in silicon oxide in the previous steps for preparing the composite negative electrode material, so that the pyrolytic carbon coating layer can be firmly arranged on SiOxThe surface of the layer also avoids the prior art on SiOxThe high conductivity and stability of the pyrolytic carbon coating layer in the present invention contribute to the enhancement of Si @ SiOxStability of an SEI film at an interface with an electrolyte.
After the composite cathode material prepared by the invention is prepared into a button type half cell, the capacity retention rate can be more than 90% after 1C high rate circulation for 100 weeks, the capacity retention rate can be more than 95% after 0.2C rate circulation for 100 weeks, the capacity retention rate can be more than 85% after 0.2C rate circulation for 300 weeks,
the composite material has high capacity, excellent rate performance and cycle performance, and the method for preparing the composite cathode material has the advantages of simple process, environmental friendliness, low production cost and the like, and is suitable for industrial production of the silicon/silicon oxide/carbon composite cathode material for the lithium ion battery and the battery.
Drawings
Fig. 1 is a TEM photograph of the silicon/silicon oxide/carbon composite anode material for a lithium ion battery prepared in example 1, with a scale bar of 100 nm.
Fig. 2 is an HRTEM photograph of the silicon/silicon oxide/carbon composite anode material for the lithium ion battery prepared in example 1, with a scale bar of 5 nm.
Fig. 3 is an X-ray diffraction spectrum of the silicon/silicon oxide/carbon composite anode material for a lithium ion battery prepared in example 1.
Fig. 4 is a charge and discharge curve of a battery made of a silicon/silicon oxide/carbon composite anode material for a lithium ion battery prepared in example 1.
Detailed Description
The present invention will be described in further detail with reference to the accompanying drawings and examples.
The silicon/silicon oxide/carbon composite cathode material for the lithium ion battery is of a double-core shell structure. The core of the core-shell structure is composed of nano silicon particles, the size of the nano silicon particles is 20-300 nm, and the nano silicon particles are spherical, quasi-spherical, elongated, flaky, conical or rhombic and the like; the shell layer has a multilayer structure, and the inner layer is silicon oxide SiOxThe buffer layer is 1-50nm thick, and the outer layer is composed of a carbon layer coated outside the silicon oxide layer; the outer coating carbon layer is formed by carbonizing a carbonizable organic substance at a high temperature of 600-1250 ℃, and the nano Si @ SiOxThe mass ratio of the core-shell structure material to the carbonizable organic carbon source is 50: 5.0-200.0%; the shell is a carbon coating layer coated outside the nano silicon particles and the silicon oxide inner layer thereof, and the carbon coating layer is coated on the nano silicon particles and the silicon oxide inner layerThe mass of the coating layer is 2-200% of the mass of silicon.
The preparation method of the silicon/silicon oxide/carbon composite negative electrode material for the lithium ion battery, which is the silicon/silicon oxide/carbon composite negative electrode material for the lithium ion battery, comprises the following steps:
s1, preparing nano silicon particles: preparing nano silicon ions with the size of 20-300 nm;
s2, nanometer Si @ SiOxPreparation of core-shell structure material:
the prepared nano silicon powder is subjected to in-situ oxidation treatment in an oxidant to prepare Si @ SiO with controllable thicknessxCore-shell materials, SiOxThe thickness of the shell layer is controllable, and the size of the shell layer can be 1-50 nm;
s3, purification treatment:
the Si @ SiO prepared in the above wayxRemoving soluble metal ions from the core-shell structure material by acidification treatment, and then washing the core-shell structure material for at least 3 times by pure water for later use;
s4, mixing and dispersing:
the purified Si @ SiOxThe mass ratio of the core-shell structure material to the carbonizable organic carbon source is 50: 5.0-200.0, the ultrasonic pre-dispersion is carried out in a solvent, the rotating speed is 150-600 r/min, the frequency is 10-20 kHz, and the power density is 0.25-0.45W/cm2After the ultrasonic pre-dispersion time is 30-120 min, obtaining mixed slurry with the solid content of 20-60%;
step S5, drying treatment:
drying the mixed slurry at 105-300 ℃ to prepare a precursor;
s6, carbonizing treatment:
carbonizing the precursor in a protective gas atmosphere to obtain a silicon/silicon oxide/carbon composite anode material precursor;
s7, high-temperature sintering treatment:
sintering the silicon/silicon oxide/carbon composite anode material precursor in a protective gas atmosphere, and naturally cooling to room temperature after sintering to obtain the silicon/silicon oxide/carbon composite anode material for the lithium ion battery;
in some embodiments, the method of preparing the nano silicon powder in step S1 is a solid phase ball milling method, a liquid phase ball milling method, a chemical vapor deposition method, a laser sputtering method, a plasma chemical vapor deposition method, or the like, and the silicon nanoparticles are spherical, or quasi-spherical, or elongated, or thin sheet, or conical, or rhombic, or the like;
in some embodiments, step S2 prepares the nano Si @ SiOxThe oxidant adopted by the inner cladding layer of the core-shell structural material is one of oxygen, potassium permanganate, potassium dichromate, sodium dichromate, nitric acid, potassium chlorate, sodium chlorate, potassium perchlorate, sodium perchlorate, hydrogen peroxide, peroxyacetic acid and the like, or a mixed oxidant consisting of more than two of the oxygen, the potassium permanganate, the potassium dichromate, the sodium dichromate, the nitric acid, the potassium chlorate, the sodium chlorate, the potassium perchlorate, the sodium perchlorate, the hydrogen peroxide, the peroxyacetic acid;
in some embodiments, the acid used in step S3 is a mixed acid of one or more of hydrochloric acid, acetic acid, oxalic acid, or phosphoric acid;
in some embodiments, the carbonizable organic carbon source used in step S4 is one or more of emulsified asphalt, polyethylene glycol ether, diethyl phthalate, polyethylene glycol, modified alkyd resin, furan resin, phenolic resin, polyvinyl alcohol, methyl cellulose, styrene butadiene rubber, polymethacrylate, sucrose, glucose, polyvinylpyrrolidone, fatty alcohol polyoxyethylene ether, alkylphenol ethoxylates, polyoxyethylene alkylamides, fatty acid polyoxyethylene esters, and polyoxyethylene alkylammonium; the solvent is more than one of deionized water, methanol, ethanol, propanol, isopropanol, acetone, isopropanol, N-hexane, N-methylpyrrolidone, tetrahydrofuran and ethyl acetate;
in some embodiments, the drying manner adopted in step S5 is one of stirring drying, fluidized bed drying, or spray drying, and the drying temperature is 105-300 ℃;
the atomization rotating speed of spray drying is 8000-20000 r/min;
in some embodiments, the temperature rising rate used in step S6 is 1-10 ℃/min, and the temperature is maintained at 350-550 ℃ for 60-180 min;
in some embodiments, the temperature rising rate used in step S7 is 1-10 ℃/min, and the calcination time at 600-1250 ℃ is 1-10.0 h;
in some embodiments, the protective gas employed in the present invention is nitrogen, helium, neon, argon, krypton, or xenon.
Testing the composite negative electrode material prepared by the method, and determining an XRD (X-ray diffraction) pattern by using an XRD-7000X-ray diffractometer of Shimadzu corporation; observing the morphology and the particle size of the composite material by using a Zeiss Gemini SEM500 field emission scanning electron microscope; observing the thickness of the coating layer by using a FEITalos 200F transmission electron microscope; testing the specific surface area of the composite material by using a JW-DX type specific surface area tester of the Jingwei Gaobao company;
the silicon/silicon oxide/carbon composite negative electrode material prepared by the method is used for electrochemical performance test, and the composite negative electrode materials of examples 1-6 and the silicon-carbon negative electrode material of a comparative example are used as negative electrode active materials for button cell test. Weighing negative active substances, namely conductive carbon black SP, sodium carboxymethylcellulose CMC and styrene butadiene rubber SBR (styrene butadiene rubber) in a ratio of 85:8:3:4 by mass, mixing and pulping, coating the mixture with a solid content of 40% on a Cu foil, drying the mixture for 12 hours at 85 ℃, rolling and punching the mixture, using a metal lithium sheet as a counter electrode, and adding fluoroethylene carbonate FEC: ethylene carbonate EC: ethyl methyl carbonate EMC ═ 1: 2: 7 preparing electrolyte, adopting a polypropylene PP, polyethylene PE and polypropylene PP multilayer composite film (laminated structure) as a diaphragm, and preparing the electrolyte into 2 groups of CR2032 button cells in a German Braun MBRAUN glove box protected by high-purity argon. The method comprises the steps of testing the electrical performance of a button cell by using a CT2001A type cell testing system of blue-electricity electronic products Limited company in Wuhan City, wherein the charging and discharging voltage range is 0.003-2.0V, the first discharging capacity mAh/g of 0.1C and the first efficiency are measured, after 3 weeks of charging and discharging activation of 0.1C are measured, the first group is subjected to 1C charging and discharging cycle testing, the cycle capacity retention rate of 100 weeks is calculated by using the ratio of the 1C discharging capacity of 100 weeks to the 1C discharging capacity of 1 week, the second group is subjected to 0.2C multiplying power charging and discharging cycle, and the cycle capacity retention rates of 100 weeks and 300 weeks are calculated.
Example 1
S1, preparation of nano silicon particles
Adopting a QM-3SP04 planetary ball mill, taking zirconia balls as a ball milling medium, taking micron-sized silicon powder as a raw material, and mixing the raw materials in a ratio of 20: 1, ball milling for 12 hours at the rotating speed of 500r/min to prepare spherical nano silicon powder, wherein the particle size of the silicon powder is 100 nm.
S2, nanometer Si @ SiOxPreparation of core-shell materials
Treating the prepared nano silicon powder for 3 hours at 500 ℃ in an oxygen atmosphere to obtain Si @ SiO with the silicon oxide inner layer thickness of 14nmxA core-shell structured material.
S3, purifying
The Si @ SiO prepared in the above wayxThe core-shell structure material is acidified by 1mol/L hydrochloric acid for 1h to remove soluble metal ions, and then washed by pure water for 3 times.
S4, mixing and dispersing
The purified Si @ SiOxThe mass ratio of the core-shell structure material to the sucrose is 50:50 is subjected to ultrasonic pre-dispersion in water solution, the rotating speed is 300r/min, the frequency is 15kHz, and the power density is 0.35W/cm2After the ultrasonic pre-dispersion time is 60min, mixed slurry with the solid content of 45% is obtained;
s5, drying treatment
And stirring and drying the mixed slurry in a beaker at the temperature of 120 ℃ to obtain a precursor.
S6, carbonizing treatment
And (3) heating the precursor to 400 ℃ at the heating rate of 5 ℃/min under the protection of a nitrogen atmosphere, and preserving the temperature for 120min to obtain the silicon/silicon oxide/carbon composite anode material precursor.
S7, high-temperature sintering treatment
Heating the precursor of the silicon/silicon oxide/carbon composite negative electrode material to the calcining temperature of 700 ℃ at the heating rate of 3 ℃/min under the nitrogen atmosphere, calcining for 8h, naturally cooling to the room temperature after sintering to obtain the silicon/silicon oxide/carbon composite negative electrode material for the lithium ion battery, wherein the size of a nano silicon particle core of the obtained composite negative electrode material is 100nm, and the SiO particle core of the obtained composite negative electrode material is SiOxThe size of the shell is 14nm, and the size of the shell is nano Si @ SiOxThe mass ratio of the core-shell structure material to the pyrolytic carbon coating layer is 50: 50.
And (3) after the silicon/silicon oxide/carbon composite negative electrode material for the lithium ion battery obtained in the embodiment 1 is sieved by a 250-mesh sieve, structure and appearance characterization and electrochemical performance test are carried out. The 0.1C first discharge capacity of the composite negative electrode material is 2834.3mAh/g, the first efficiency is 80.42%, the cycle capacity retention rate of the first group of batteries 1C in 100 charge-discharge cycles is 90.20%, the capacity retention rate of the second group of batteries 0.2C in 100 charge-discharge cycles is 96.30%, and the capacity retention rate of the second group of batteries 0.2C in 300 charge-discharge cycles is 86.50%, and the test results are summarized in Table 1.
As shown in fig. 3, is the XRD diffraction pattern of the composite material of example 1. By comparison with diffraction peaks of standard PDF cards (PDF #27-1402) of single crystal silicon, strong diffraction peaks observed near 28.4 °, 47.3 ° and 56.1 ° correspond to the (111), (220) and (311) crystal planes of crystalline silicon, respectively. The main components of the composite material can be determined to be Si and amorphous carbon through the analysis of an XRD pattern.
As shown in FIGS. 1 to 2, TEM photographs of the silicon/silicon oxide/carbon composite negative electrode material for lithium ion batteries prepared in example 1 were taken. As can be seen from the photo, the shape of the nano-silicon is spherical, the size of the particle is about 100nm, the particle has a core-shell structure, the core is a nano-silicon particle, the surface of the particle is provided with double coating layers, the inner coating layer is silicon oxide, the thickness is about 14nm, and the outer coating layer is an amorphous carbon coating layer.
Fig. 4 shows the charge/discharge curves of the silicon/silicon oxide/carbon composite negative electrode material for the lithium ion battery obtained in example 1. The specific capacity of the composite material can be calculated to be 2830mAh/g, and the first efficiency is 80.30%.
Example 2
S1, preparation of nano silicon particles
Adopting a QM-3SP04 planetary ball mill, taking zirconia balls as a ball milling medium, taking micron-sized silicon powder as a raw material, and mixing the materials in a ball-material ratio of 20: 1, ball milling for 24 hours at the rotating speed of 300r/min by using a solution of ethanol and water (the volume ratio is 50:50) to prepare slurry of nano silicon powder, wherein the particle size of the silicon is 300 nm.
S2, nanometer Si @ SiOxPreparation of core-shell materials
Treating the prepared nano silicon powder with 0.5mol/L potassium permanganate solution for 0.5h to prepare Si @ SiO with the thickness of 2nmxA core-shell structured material.
S3, purifying
The Si @ SiO prepared in the above wayxThe core-shell structure material was treated with 2mol/L acetic acid solution to remove soluble metal ions, and then washed with pure water 4 times.
S4, mixing and dispersing
The purified Si @ SiOxThe mass ratio of the core-shell structure material to the methyl cellulose is 50: 5.0 ultrasonic pre-dispersion in water, 150r/min of rotation speed, 20kHz of frequency and 0.25W/cm of power density2And obtaining mixed slurry with the solid content of 20% after the ultrasonic pre-dispersion time is 30 min.
S5, drying treatment
Drying the mixed slurry at 105 ℃ by adopting a fluidized bed drying mode to prepare a precursor.
S6, carbonizing treatment
Heating the precursor to 350 ℃ at the heating rate of 1 ℃/min in the helium atmosphere, and preserving the temperature for 180min to prepare a silicon/silicon oxide/carbon composite anode material precursor;
s7, high-temperature sintering treatment
Heating the precursor of the silicon/silicon oxide/carbon composite negative electrode material to 600 ℃ at the heating rate of 1 ℃/min in the helium atmosphere, calcining for 10h, naturally cooling to room temperature after sintering to obtain the silicon/silicon oxide/carbon composite negative electrode material for the lithium ion battery, wherein the size of a nano silicon particle core of the obtained composite negative electrode material is 300nm, and the SiO particle core of the obtained composite negative electrode material is SiOxThe size of the shell is 2nm, and the size of the shell is nano Si @ SiOxThe mass ratio of the core-shell structure material to the pyrolytic carbon coating layer is 50: 5.
And (3) screening the silicon/silicon oxide/carbon composite negative electrode material for the lithium ion battery obtained in the example 2 through a 250-mesh sieve, and then carrying out electrochemical performance test. The 0.1C first discharge capacity of the composite negative electrode material is 3250.8mAh/g, the first efficiency is 78.50%, the 1C charge-discharge capacity retention rate in 100 weeks is 88.70%, the 0.2C charge-discharge capacity retention rate in 100 weeks is 95.70%, and the 0.2C charge-discharge capacity retention rate in 300 weeks is 86.10%, and the test results are summarized in Table 1.
Example 3
S1, preparation of nano silicon particles
Adopts chemical vapor deposition method, uses RTL1200 type rotary tube furnace as synthesis equipment, uses SiH4Is silicon source, argon gas is protective gas, the pressure of the reaction chamber is 0.2MPa, SiH4The flow rate of the reaction is 180ml/min, the reaction temperature is 750 ℃, and spherical nano silicon powder is prepared, and the particle size of the silicon powder is 40 nm;
s2, nanometer Si @ SiOxPreparation of core-shell materials
Treating the prepared nano silicon powder with 0.02mol/L potassium dichromate solution for 5 hours to obtain Si @ SiO with the thickness of 5nmxA core-shell structured material.
S3, purifying
The Si @ SiO prepared in the above wayxThe core-shell structure material is stirred and treated with 0.1mol/L oxalic acid for 3 hours to remove soluble metal ions, and then is washed and treated with pure water for 4 times.
S4, mixing and dispersing
The purified Si @ SiOxThe mass ratio of the core-shell structure material to the polyvinyl alcohol is 50:200 is pre-dispersed in ethanol water solution (volume ratio 50:50) with the rotation speed of 600r/min, frequency of 10kHz and power density of 0.45W/cm2And obtaining mixed slurry with solid content of 60% after the ultrasonic pre-dispersion time is 120 min.
S5, drying treatment
Drying the mixed slurry at 300 deg.C by spray drying at 8000r/min under nitrogen protection with flow rate of 0.2m to obtain precursor3/h。
S6, carbonizing treatment
Heating the precursor to 550 ℃ at a heating rate of 10 ℃/min under an argon atmosphere, and preserving the temperature for 60min to obtain a silicon/silicon oxide/carbon composite anode material precursor;
s7, high-temperature sintering treatment
Heating the precursor of the silicon/silicon oxide/carbon composite anode material to the calcination temperature of 1250 ℃ at the heating rate of 10 ℃/min under the argon atmosphere, calcining for 1h, naturally cooling to room temperature after sintering is finished to obtain the silicon/silicon oxide/carbon composite anode material for the lithium ion battery, wherein the size of a nano silicon particle core of the obtained composite anode material is 40nm，SiOxThe size of the shell is 5nm, and the size of the shell is nano Si @ SiOxThe mass ratio of the core-shell structure material to the pyrolytic carbon coating layer is 50: 200.
And (3) screening the silicon/silicon oxide/carbon composite negative electrode material for the lithium ion battery obtained in the embodiment 3 through a 250-mesh sieve, and then carrying out electrochemical performance test. The 0.1C first discharge capacity of the composite negative electrode material is 3030.50mAh/g, the first efficiency is 79.80%, the 1C charge-discharge 100-week cycle capacity retention rate is 89.50%, the 0.2C charge-discharge 100-week capacity retention rate is 95.80%, and the 0.2C charge-discharge 300-week capacity retention rate is 86.30%, and the test results are summarized in Table 1.
Example 4
S1, preparation of nano silicon particles
Preparing nanometer silicon powder by laser sputtering method with NPD-4000(A) full-automatic PLD pulsed laser deposition system, laser wavelength of 800nm and power density of 105W/cm2Silicon with the purity of 5N is used as a target material, argon is used as protective gas, the vacuum degree is less than 133Pa, the temperature is 800 ℃, the deposition time is 4 hours, and the particle size of the prepared silicon powder is 20 nm.
S2, nanometer Si @ SiOxPreparation of core-shell materials
Treating the prepared nano silicon powder with 0.02mol/L sodium dichromate solution for 8h to obtain Si @ SiO with the thickness of 10nmxA core-shell structured material.
S3, purifying
The Si @ SiO prepared in the above wayxThe core-shell structure material is acidified by 0.5mol/L phosphoric acid for 2h to remove soluble metal ions, and then washed by pure water for 5 times.
S4, mixing and dispersing
The purified Si @ SiOxThe core-shell structure material and the phenolic resin are mixed according to the mass ratio of 50:20 in a mixed solvent of ethanol and acetone (volume ratio of 50:50) at a rotation speed of 300r/min, a frequency of 15kHz and a power density of 0.30W/cm2And obtaining mixed slurry with the solid content of 30% after the ultrasonic pre-dispersion time is 60 min.
S5, drying treatment
And drying the mixed slurry at 110 ℃ by adopting a stirring and drying mode to obtain a precursor.
S6, carbonizing treatment
And heating the precursor to 450 ℃ at the heating rate of 3 ℃/min under the argon atmosphere, and preserving the temperature for 90min to obtain the silicon/silicon oxide/carbon composite anode material precursor.
S7, high-temperature sintering treatment
Heating the precursor of the silicon/silicon oxide/carbon composite negative electrode material to a calcination temperature of 750 ℃ at a heating rate of 3 ℃/min under an argon atmosphere, calcining for 3h, naturally cooling to room temperature after sintering is finished, obtaining the silicon/silicon oxide/carbon composite negative electrode material for the lithium ion battery, wherein the size of a nano silicon particle core of the obtained composite negative electrode material is 20nm, and the size of SiO is 20nmxThe size of the shell is 10nm, and the size of the shell is nano Si @ SiOxThe mass ratio of the core-shell structure material to the pyrolytic carbon coating layer is 50: 20.
The lithium ion battery obtained in example 4 was subjected to electrochemical performance testing after passing through a 250 mesh sieve using a silicon/silicon oxide/carbon composite negative electrode material. The 0.1C first discharge capacity of the composite negative electrode material is 2790.10mAh/g, the first efficiency is 81.20%, the 1C charge-discharge capacity retention rate in 100 weeks is 91.20%, the 0.2C charge-discharge capacity retention rate in 100 weeks is 96.50%, and the 0.2C charge-discharge capacity retention rate in 300 weeks is 86.70%, and the test results are summarized in Table 1.
Example 5
S1, preparation of nano silicon particles
Adopting a plasma chemical vapor deposition method, taking a German CYRANNUS plasma chemical vapor deposition system as synthesis equipment, the frequency is 2.45GHz, the power is 3kW, and SiH is used4Is silicon source, argon gas is protective gas, the pressure of the reaction chamber is 0.15MPa, SiH4The flow rate of the reaction is 300ml/min, the reaction temperature is 800 ℃, and the nano silicon powder is prepared, and the particle size of the silicon powder is 50 nm.
S2, nanometer Si @ SiOxPreparation of core-shell materials
Treating the prepared nano silicon powder with 0.05mol/L potassium perchlorate to prepare Si @ SiO with the thickness of 15nmxA core-shell structured material.
S3, purifying
The Si @ SiO prepared in the above wayxThe core-shell structure material was acidified with 0.5mol/L hydrochloric acid for 5 hours to remove soluble metal ions, and then washed with pure water 3 times.
S4, mixing and dispersing
The purified Si @ SiOxThe core-shell structure material and the styrene butadiene rubber are mixed according to the mass ratio of 50:20 ultrasonic pre-dispersion in water at a rotation speed of 200r/min, a frequency of 15kHz and a power density of 0.30W/cm2And after the ultrasonic pre-dispersion time is 90min, obtaining mixed slurry with the solid content of 50%.
S5, drying treatment
And drying the mixed slurry at 150 ℃ by adopting a stirring and drying mode to obtain a precursor.
S6, carbonizing treatment
And heating the precursor to 500 ℃ at the heating rate of 5 ℃/min under the nitrogen atmosphere, and preserving the temperature for 90min to obtain the silicon/silicon oxide/carbon composite anode material precursor.
S7, high-temperature sintering treatment
Heating the precursor of the silicon/silicon oxide/carbon composite negative electrode material to the calcining temperature of 1000 ℃ at the heating rate of 5 ℃/min under the nitrogen atmosphere, calcining for 3h, naturally cooling to the room temperature after sintering is finished to obtain the silicon/silicon oxide/carbon composite negative electrode material for the lithium ion battery, wherein the size of a nano silicon particle core of the obtained composite negative electrode material is 50nm, and the SiO particle core of the obtained composite negative electrode material is SiOxThe size of the shell is 15nm, and the size of the shell is nano Si @ SiOxThe mass ratio of the core-shell structure material to the pyrolytic carbon coating layer is 50: 20.
The lithium ion battery obtained in example 5 was subjected to electrochemical performance testing after passing through a 250 mesh sieve using a silicon/silicon oxide/carbon composite negative electrode material. The 0.1C first discharge capacity of the composite negative electrode material is 2870.90mAh/g, the first efficiency is 80.90%, the cycle capacity retention rate of 1C charge-discharge 100 weeks is 88.60%, the capacity retention rate of 0.2C charge-discharge 100 weeks is 96.02%, and the capacity retention rate of 0.2C charge-discharge 300 weeks is 86.50%, and the test results are summarized in Table 1.
Example 6
S1, preparation of nano silicon particles
Adopting a QM-3SP04 planetary ball mill, taking zirconia balls as a ball milling medium, taking micron-sized silicon powder as a raw material, and mixing the raw materials in a ratio of 20: ball milling is carried out for 24 hours at the rotating speed of 600r/min according to the ball material ratio of 1 to obtain the sphere-like nano silicon powder, and the particle size of the silicon powder is 20 nm.
S2, nanometer Si @ SiOxPreparation of core-shell materials
Treating the prepared nano silicon powder with 3% hydrogen peroxide for 12h to obtain Si @ SiO with the thickness of 50nmxA core-shell structured material.
S3, purifying
The Si @ SiO prepared in the above wayxThe core-shell structure material is acidified by 0.5mol/L hydrochloric acid for 4h to remove soluble metal ions, and then washed by pure water for 3 times.
S4, mixing and dispersing
The purified Si @ SiOxThe mass ratio of the core-shell structure material to the polyvinyl alcohol is 50:50 in an ethanol water solution (volume ratio is 1: 1), the rotating speed is 300r/min, the frequency is 20kHz, and the power density is 0.25W/cm2And obtaining mixed slurry with the solid content of 30% after the ultrasonic pre-dispersion time is 120 min.
S5, drying treatment
Drying the mixed slurry at 260 deg.C by spray drying to obtain precursor, wherein the atomization rotation speed is 20000r/min, the flow is 1.0m under nitrogen protection3/h。
S6, carbonizing treatment
And heating the precursor to 400 ℃ at the heating rate of 2 ℃/min under the argon atmosphere, and preserving the temperature for 100min to obtain the silicon/silicon oxide/carbon composite anode material precursor.
S7, high-temperature sintering treatment
Heating the precursor of the silicon/silicon oxide/carbon composite negative electrode material to a calcination temperature of 650 ℃ at a heating rate of 2 ℃/min under an argon atmosphere, calcining for 8h, naturally cooling to room temperature after sintering to obtain the silicon/silicon oxide/carbon composite negative electrode material for the lithium ion battery, wherein the size of a nano silicon particle core of the obtained composite negative electrode material is 20nm, and the SiO particle core of the obtained composite negative electrode material is SiOxThe size of the shell is 20nm, and the size of the shell is nano Si @ SiOxThe mass ratio of the core-shell structure material to the pyrolytic carbon coating layer is 50: 50.
The silicon/silicon oxide/carbon composite negative electrode material for the lithium ion battery obtained in example 6 was sieved with a 250 mesh sieve, and then subjected to electrochemical performance test. The 0.1C first discharge capacity of the composite negative electrode material is 2950.60mAh/g, the first efficiency is 80.10%, the 1C charge-discharge 100-week cycle capacity retention rate is 89.90%, the 0.2C charge-discharge 100-week capacity retention rate is 96.80%, and the 0.2C charge-discharge 300-week capacity retention rate is 86.90%, and the test results are summarized in Table 1.
Comparative example 1
A composite silicon negative electrode material is prepared by the following method:
s1, selecting silicon powder with the median particle size of 50-80 nm as nano silicon, placing the nano silicon in a rotary furnace at the rotating speed of 20r/min, introducing mixed gas of argon and oxygen with the volume ratio of 1:0.5 at the gas flow of 0.5L/min, and carrying out heat treatment for 1h at 500 ℃ to obtain primary heat-treated silicon powder;
s2, mixing the primary heat-treated silicon powder, bismuth powder and tin powder according to the mass ratio of 100:5:5, then loading the mixture into a high-energy ball mill, loading zirconium balls with the diameter of 0.5mm, then introducing argon protective gas, and carrying out high-energy ball milling, wherein the rotating speed of the ball mill is 3000r/min, the mass ratio of the grinding balls to the powder is 10:1, and carrying out ball milling for 20 hours to obtain ball-milled mixed powder; then placing the ball-milled mixed powder in a rotary furnace with the rotating speed of 50r/min, introducing argon, and carrying out heat treatment for 2h at 800 ℃ to obtain a first precursor;
s3, proportioning the first precursor and asphalt powder with the particle size of 3 mu m according to a mass ratio of 70:30, uniformly mixing, placing in a VC mixer, adjusting the frequency to 50Hz, and mixing for 60min to obtain a second precursor;
and S4, adding the second precursor into a fusion machine, adjusting the rotation speed to 2000rpm, fusing for 5 hours, then placing the second precursor into a high-temperature box-type furnace, introducing nitrogen protective gas, heating to 800 ℃, preserving heat for 3 hours, cooling to room temperature, crushing, screening and demagnetizing to obtain the composite silicon cathode material.
The composite silicon negative electrode material obtained in comparative example 1 had a nano-silicon content of 50 wt%, a nano-composite coating thickness of 20nm, and the nano-composite coating was SiO1.5With Bi-Sn alloy, nanocomposite coatingsCoated with a conductive carbon layer.
And (3) screening the silicon/carbon composite negative electrode material for the lithium ion battery obtained in the comparative example 1 through a 250-mesh sieve, and then carrying out electrochemical performance test. The first discharge capacity of the composite negative electrode material at 0.1C is 1683.2mAh/g, the first efficiency is 86.6%, the cycle capacity retention rate of the composite negative electrode material at 1C after 100 weeks of charge and discharge is 63.8%, the cycle capacity retention rate of the composite negative electrode material at 0.2C after 100 weeks of charge and discharge is 92.90%, the cycle capacity retention rate of the composite negative electrode material at 0.2C after 300 weeks of charge and discharge is 73.60%, and the test results of the comparative example are summarized in Table 1.
According to the silicon/silicon oxide/carbon composite cathode material, the preparation method and the battery, a compact silicon oxide inner buffer layer is formed on the surface of the nano silicon particles and a compact carbon coating layer is formed outside the compact silicon oxide inner buffer layer by constructing the structural design of a core-double shell structure. Li is formed by the silicon oxide inner cladding layer in the first charge-discharge process2O and Li4SiO4The buffer layer can effectively inhibit the volume expansion and contraction of the nano silicon, and the amorphous carbon outer coating layer is beneficial to improving the electron transmission of an interface and enhancing the stability of an SEI film of the interface, so that the structural stability and the electrochemical performance of the composite material are improved by improving the structural stability and the electrochemical performance of the nano silicon.
Compared with the prior art, the method generates the lithium storage active phase SiO on the surface of the nanometer silicon by the double-nucleocapsid structurexAnd the amorphous pyrolytic carbon coating layer can well buffer the volume expansion of nano silicon in the charge-discharge process on the premise of not remarkably reducing the capacity, and the high conductivity and stability of the pyrolytic carbon coating layer are favorable for enhancing the Si @ SiOxAnd the stability of an SEI film on an electrolyte interface, so that the composite material has the advantages of high capacity, excellent rate capability and cycle performance, environmental friendliness, low production cost and the like, and is suitable for industrial silicon/silicon oxide/carbon composite cathode materials for lithium ion batteries, preparation methods thereof and batteries.
The preparation method is simple, environment-friendly, easy to control process conditions, low in production cost and easy for industrial production.
Table 1: EXAMPLES summary of test results
Figure BDA0002771712030000201
Finally, it should be noted that: the above examples are only intended to illustrate the technical solution of the present invention, but not to limit it; although the present invention has been described in detail with reference to the foregoing embodiments, it will be understood by those of ordinary skill in the art that: the technical solutions described in the foregoing embodiments may still be modified, or some or all of the technical features may be equivalently replaced; and the modifications or the substitutions do not make the essence of the corresponding technical solutions depart from the scope of the technical solutions of the embodiments of the present invention.

Claims (10)

1. The silicon/silicon oxide/carbon composite negative electrode material for the lithium ion battery is characterized in that the structure of the silicon/silicon oxide/carbon composite negative electrode material for the lithium ion battery is a core-shell structure,
the core is composed of nano silicon particles;
the inner layer of the shell structure is SiOxThe buffer layer, the outer cover is formed by the pyrolytic carbon layer coated outside the silicon oxide layer;
silicon oxide SiO coated outside the nano silicon particle kernelxThe thickness of the buffer layer structure is 1-50nm, SiOxThe mass of the buffer layer is 2-200% of that of the silicon particle core; nano Si @ SiOxThe mass ratio of the core-shell structure material to the pyrolytic carbon coating layer is 50: 5.0 to 200.0.
2. The silicon/silicon oxide/carbon composite negative electrode material for a lithium ion battery according to claim 1, wherein: the size of the core-shell structure core nano silicon particles is 20-300 nm, and the shape of the core-shell structure core nano silicon particles is spherical, quasi-spherical, long strip, thin sheet, conical or rhombic.
3. The method for preparing the silicon/silicon oxide/carbon composite negative electrode material for the lithium ion battery according to any one of claims 1 to 2, comprising the following steps:
s1: preparing nano silicon particles;
s2: nano Si @ SiOxPreparing a core-shell structure material;
s3: purifying to remove impurities mixed in the step;
s4: mixing and dispersing the organic carbon source capable of being carbonized and the Si @ SiO treated in the step S3xMixing and dispersing;
s5: drying, namely drying the product processed in the step S4;
s6: carbonizing, namely carbonizing the product dried in the step S5 to obtain a silicon/silicon oxide/carbon composite anode material precursor;
s7: sintering at high temperature, namely sintering the silicon/silicon oxide/carbon composite anode material precursor prepared in the step S6, and cooling to obtain the silicon/silicon oxide/carbon composite anode material for the lithium ion battery;
the method is characterized in that:
the step S2 of preparing the nano Si @ SiOxThe method for preparing the core-shell structure material comprises the step of carrying out in-situ oxidation treatment on the nano silicon particles prepared in the step S1 by using an oxidant to obtain Si @ SiO with the thickness of 1nm to 50nmxA core-shell structured material.
4. The method for producing a silicon/silicon oxide/carbon composite negative electrode material for a lithium ion battery according to claim 3, wherein the purification treatment method of step S3 is: the Si @ SiO prepared by the stepsxThe core-shell structure material is acidified by acid to remove soluble metal ions, and then washed by pure water for at least 3 times.
5. The method for preparing a silicon/silicon oxide/carbon composite anode material for a lithium ion battery according to claim 3 or 4, wherein: the step S2 of preparing the nano Si @ SiOxThe core-shell structure material adopts mixed oxygen composed of one or more than two of oxygen, potassium permanganate, potassium dichromate, sodium dichromate, nitric acid, potassium chlorate, sodium chlorate, potassium perchlorate, sodium perchlorate, hydrogen peroxide and peroxyacetic acid as oxidantAn oxidizing agent.
6. The method for preparing a silicon/silicon oxide/carbon composite anode material for a lithium ion battery according to claim 3 or 4, wherein: the acid adopted for purification in the step S3 is a mixed acid consisting of one or more than two of hydrochloric acid, acetic acid, oxalic acid and phosphoric acid.
7. The method for preparing a silicon/silicon oxide/carbon composite anode material for a lithium ion battery according to claim 3 or 4, wherein: the organic carbon source capable of being carbonized adopted in the step S4 is one or a combination of more than two of emulsified asphalt, polyglycol ether, diethyl phthalate, polyethylene glycol, modified alkyd resin, furan resin, phenolic resin, polyvinyl alcohol, methyl cellulose, styrene-butadiene rubber, polymethacrylate, sucrose, glucose, polyvinylpyrrolidone, fatty alcohol-polyoxyethylene ether, alkylphenol ethoxylate, polyoxyethylene alkylamide, fatty acid-polyoxyethylene ester and polyoxyethylene alkylammonium; the solvent is one or more of deionized water, methanol, ethanol, propanol, isopropanol, acetone, isopropanol, N-hexane, N-methylpyrrolidone, tetrahydrofuran and ethyl acetate.
8. The method for preparing a silicon/silicon oxide/carbon composite anode material for a lithium ion battery according to claim 3 or 4, wherein: the Si @ SiO purified by S3 in the step S4xThe mass ratio of the core-shell structure material to the carbonizable organic carbon source is 50: 5.0-200.0, performing ultrasonic pre-dispersion in a solvent, performing the dispersion process in protective gas with a certain flow velocity, and setting parameters of the rotation speed, frequency, power density and dispersion time of the ultrasonic dispersion to obtain mixed slurry with the solid content of 20-60%.
9. The method for preparing a silicon/silicon oxide/carbon composite anode material for a lithium ion battery according to claim 3 or 4, wherein: the steps S4, S5, S6 and S7 are carried out in protective gas, and the protective gas is mixed gas consisting of one or more than two of nitrogen, helium, neon, argon, krypton or xenon.
10. A lithium ion battery, characterized by: the lithium ion battery comprises the silicon/silicon oxide/carbon composite negative electrode material according to any one of claims 1 to 2 or the silicon/silicon oxide/carbon composite negative electrode material prepared by the preparation method according to any one of claims 3 to 9.
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CN113644243A (en) * 2021-07-30 2021-11-12 清华大学 Nitrogen-doped hollow-structure graphite microsphere, composite negative electrode material and preparation method of composite negative electrode material
CN114050226A (en) * 2021-10-26 2022-02-15 惠州锂威新能源科技有限公司 Negative electrode material and preparation method thereof, negative plate and lithium ion battery
CN114068869A (en) * 2021-11-23 2022-02-18 安徽大学 Core-shell structure silicon @ silicon monoxide/carbon anode material and preparation method and application thereof
CN114684825A (en) * 2022-04-19 2022-07-01 河北工业大学 Preparation method and application of silica-carbon composite nanoparticles with core-shell structure
CN115196641A (en) * 2022-09-11 2022-10-18 隆能科技(南通)有限公司 Preparation process of porous SiOx negative electrode material with high lithium storage performance
WO2022247893A1 (en) * 2021-05-27 2022-12-01 泛亚应用科技股份有限公司 Anode active substance and preparation method therefor, and lithium secondary battery prepared on basis of same
CN115747760A (en) * 2022-11-30 2023-03-07 中国科学院兰州化学物理研究所 Composite coating coated silicon-based material and preparation method and application thereof
CN116387483A (en) * 2023-03-31 2023-07-04 重庆太蓝新能源有限公司 Si@C@MOFs composite material and preparation method thereof, negative electrode material, negative electrode plate and lithium battery
CN116516522A (en) * 2023-04-03 2023-08-01 苏州大学 Lithium ion self-supporting silicon-carbon composite nanofiber negative electrode material and preparation method and application thereof
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CN117374261A (en) * 2023-12-08 2024-01-09 深圳市本征方程石墨烯技术股份有限公司 Negative electrode material and preparation method and application thereof
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CN113113606A (en) * 2021-04-08 2021-07-13 昆山宝创新能源科技有限公司 Negative electrode material, preparation method thereof, pole piece and lithium ion battery
CN113113606B (en) * 2021-04-08 2023-04-07 昆山宝创新能源科技有限公司 Negative electrode material, preparation method thereof, pole piece and lithium ion battery
WO2022247893A1 (en) * 2021-05-27 2022-12-01 泛亚应用科技股份有限公司 Anode active substance and preparation method therefor, and lithium secondary battery prepared on basis of same
CN113644243A (en) * 2021-07-30 2021-11-12 清华大学 Nitrogen-doped hollow-structure graphite microsphere, composite negative electrode material and preparation method of composite negative electrode material
CN114050226A (en) * 2021-10-26 2022-02-15 惠州锂威新能源科技有限公司 Negative electrode material and preparation method thereof, negative plate and lithium ion battery
CN114050226B (en) * 2021-10-26 2023-10-31 惠州锂威新能源科技有限公司 Negative electrode material, preparation method thereof, negative electrode plate and lithium ion battery
CN114068869B (en) * 2021-11-23 2023-08-29 安徽大学 Core-shell structure silicon @ silicon oxide/carbon anode material and preparation method and application thereof
CN114068869A (en) * 2021-11-23 2022-02-18 安徽大学 Core-shell structure silicon @ silicon monoxide/carbon anode material and preparation method and application thereof
CN114684825A (en) * 2022-04-19 2022-07-01 河北工业大学 Preparation method and application of silica-carbon composite nanoparticles with core-shell structure
CN114684825B (en) * 2022-04-19 2022-12-06 河北工业大学 Preparation method and application of silica-carbon composite nanoparticles with core-shell structure
WO2024002041A1 (en) * 2022-06-27 2024-01-04 贝特瑞新材料集团股份有限公司 Negative electrode material, preparation method therefor and secondary battery
WO2024050799A1 (en) * 2022-09-09 2024-03-14 宁德时代新能源科技股份有限公司 Negative electrode active material, preparation method therefor, secondary battery, battery module, battery pack and electric apparatus
CN115196641A (en) * 2022-09-11 2022-10-18 隆能科技(南通)有限公司 Preparation process of porous SiOx negative electrode material with high lithium storage performance
CN115747760B (en) * 2022-11-30 2023-11-28 中国科学院兰州化学物理研究所 Composite coating coated silicon-based material, preparation method and application thereof
CN115747760A (en) * 2022-11-30 2023-03-07 中国科学院兰州化学物理研究所 Composite coating coated silicon-based material and preparation method and application thereof
CN116387483A (en) * 2023-03-31 2023-07-04 重庆太蓝新能源有限公司 Si@C@MOFs composite material and preparation method thereof, negative electrode material, negative electrode plate and lithium battery
CN116387483B (en) * 2023-03-31 2024-04-02 重庆太蓝新能源有限公司 Si@C@MOFs composite material and preparation method thereof, negative electrode material, negative electrode plate and lithium battery
CN116516522A (en) * 2023-04-03 2023-08-01 苏州大学 Lithium ion self-supporting silicon-carbon composite nanofiber negative electrode material and preparation method and application thereof
CN117374261A (en) * 2023-12-08 2024-01-09 深圳市本征方程石墨烯技术股份有限公司 Negative electrode material and preparation method and application thereof
CN117374261B (en) * 2023-12-08 2024-04-16 深圳市本征方程石墨烯技术股份有限公司 Negative electrode material and preparation method and application thereof

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