CN113206249B - Lithium battery silicon-oxygen composite anode material with good electrochemical performance and preparation method thereof - Google Patents

Lithium battery silicon-oxygen composite anode material with good electrochemical performance and preparation method thereof Download PDF

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CN113206249B
CN113206249B CN202110421855.1A CN202110421855A CN113206249B CN 113206249 B CN113206249 B CN 113206249B CN 202110421855 A CN202110421855 A CN 202110421855A CN 113206249 B CN113206249 B CN 113206249B
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silicon
solid electrolyte
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composite anode
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蔡新辉
胡博
徐梓炜
刘锐剑
金海侹
吕猛
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Huzhou Jincan New Energy Technology Co ltd
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    • HELECTRICITY
    • H01ELECTRIC ELEMENTS
    • H01MPROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
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    • H01M4/36Selection of substances as active materials, active masses, active liquids
    • H01M4/48Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides
    • H01M4/483Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides for non-aqueous cells
    • BPERFORMING OPERATIONS; TRANSPORTING
    • B82NANOTECHNOLOGY
    • B82YSPECIFIC USES OR APPLICATIONS OF NANOSTRUCTURES; MEASUREMENT OR ANALYSIS OF NANOSTRUCTURES; MANUFACTURE OR TREATMENT OF NANOSTRUCTURES
    • B82Y30/00Nanotechnology for materials or surface science, e.g. nanocomposites
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    • H01M10/052Li-accumulators
    • H01M10/0525Rocking-chair batteries, i.e. batteries with lithium insertion or intercalation in both electrodes; Lithium-ion batteries
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    • H01M2004/026Electrodes composed of, or comprising, active material characterised by the polarity
    • H01M2004/027Negative electrodes
    • YGENERAL 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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    • Y02EREDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/10Energy storage using batteries

Abstract

The invention relates to a lithium battery and discloses a silicon-oxygen composite negative electrode material with good electrochemical performance and a preparation method thereof. In addition, the solid electrolyte is introduced to improve lithium ion migration at the interface and reduce interface side reaction, so that the multiplying power and the cycle performance of the silicon-oxygen composite anode material are both considered.

Description

Lithium battery silicon-oxygen composite anode material with good electrochemical performance and preparation method thereof
Technical Field
The invention relates to the field of lithium batteries, in particular to a lithium battery silicon-oxygen composite anode material with good electrochemical performance and a preparation method thereof.
Background
In recent years, with the wide application of portable electronic devices and the increasing popularization of electric automobiles, the energy density of the traditional carbon anode material can not meet the demands of the existing market. The silicon-oxygen anode material is widely studied because of higher theoretical specific capacity (2680 mAh/g), but the silicon-oxygen anode material still has problems in the application of the silicon-oxygen anode material in the field of lithium battery anode:
1) The volume expansion of the silicon-oxygen anode material can reach 200% in the charge and discharge process, and the particle structure is extremely easy to damage, so that uncontrollable growth of the SEI film on the particle surface is caused. At this time, more side reactions occur at the interface between the silicon-oxygen negative electrode material and the electrolyte is consumed, so that the high electron ion transmission resistance caused by the side reactions obviously affects the circulation and the multiplying power performance;
2) The electronic conductivity and the ionic conductivity of the silicon-oxygen anode material are low, so that the electrochemical performances of the pure silicon-oxygen anode material such as first efficiency, circulation, multiplying power and the like are poor.
The prior research on the silicon-oxygen composite anode material mainly aims at reducing the particle size and coating an amorphous conductive carbon layer by solving the problems of volume expansion pulverization and low conductivity of the silicon-oxygen composite anode material. However, the single reduction of the particle size tends to result in a larger contact area between the silicone particles and the electrolyte, which is more consumed during charging and discharging. The amorphous carbon layer is coated to improve the electronic conductivity and relieve the problem of particle breakage, and the defects that the particles lose electrical contact after cyclic expansion, the ionic conductivity is improved to a limited extent and the like still exist.
Disclosure of Invention
The invention provides a lithium battery silicon-oxygen composite anode material with good electrochemical performance and a preparation method thereof, and aims to solve the technical problems of volume expansion pulverization, low electron conductivity and low ion conductivity of the existing silicon-oxygen anode material. The silicon oxide composite negative electrode material takes the silicon oxide with the surface distributed with the carbon nano material and the solid electrolyte (in two forms) as the inner core, and the inner core is coated with a layer of amorphous carbon, so that the amorphous carbon coating layer can relieve the expansion and pulverization of silicon oxide particles in the charge and discharge process of the material, and forms a conductive framework with the carbon nano material, and the electron conductivity and the ion conductivity are high, so that the problem of electric contact failure caused in the repeated lithium intercalation and deintercalation process is solved. In addition, the solid electrolyte is introduced to improve lithium ion migration at the interface and reduce interface side reaction, so that the multiplying power and the cycle performance of the silicon-oxygen composite anode material are both considered.
The specific technical scheme of the invention is as follows:
in a first aspect, the invention provides a silicon-oxygen composite anode material with good electrochemical performance for a lithium battery, which takes silicon oxide with carbon nanomaterial and solid electrolyte distributed on the surface as an inner core, and amorphous carbon coated on the surface of the silicon oxide as a coating layer; the carbon nano material and the solid electrolyte are distributed on the surface of the silicon oxide in a dispersed form or in a form of modifying the solid electrolyte by the carbon nano material; wherein the silicon oxide accounts for 70-98wt%, the carbon nanomaterial accounts for 0.01-5%, the solid electrolyte accounts for 0.01-10%, and the amorphous carbon accounts for 1-15%. The silicon-oxygen composite anode material has unique structural design, the carbon nano material and the solid electrolyte are introduced on the basis of amorphous carbon coated silicon oxide particles, and the carbon nano material and the solid electrolyte are firmly and uniformly combined on the surfaces of the silicon oxide particles through the chemical bond action of an amorphous carbon coating layer, so that the problems of particle pulverization, low electronic conductivity and low ionic conductivity of the silicon-oxygen material can be solved. The limiting effect of the amorphous carbon coating layer can avoid the structural pulverization failure problem caused by the lithium intercalation and deintercalation of silicon oxygen particles, and the carbon nano material and the amorphous carbon can form a conductive framework, so that the electron transmission problem among particles and between particles and a current collector can be solved by the synergistic effect, and the electrical contact failure caused in the repeated lithium intercalation and deintercalation process is avoided. The interface stability of the silicon-oxygen negative electrode and the electrolyte can be obviously improved by the combined action of the solid electrolyte and the amorphous carbon, the interface side reaction of lithium ion intercalation and deintercalation and the electrolyte is reduced, and the problems of too fast electrolyte consumption and gas production are avoided, so that the material has excellent multiplying power performance and cycle performance.
The lithium ion conductivity of the LLZO, LLZTO and other ceramic solid electrolytes is as high as 1 -4 ~10 -3 S cm -1 Ion conductivity of near commercial liquid electrolyte 10 -3 S cm -1 By coating solid electrolytes such as LLZTO, LLZO and the like on the surface of the silicon-oxygen negative electrode, the solid electrolytes can be cooperated with an amorphous carbon layer and a carbon nano material to form an artificial SEI film coating layer with high lithium ion conductivity and high mechanical stability, and the coating layer improves the coulombic efficiency and the cycle stability of the silicon-oxygen negative electrode by weakening the decomposition of electrolyte. In addition, the excellent lithium ion transmission capability of the coating layer can be obviously improvedHigh silicon oxygen negative electrode rate capability.
Further, the carbon nanomaterial and the solid electrolyte can be distributed on the surface of the silicon oxide in the form of the carbon nanomaterial modified solid electrolyte. The carbon nano material such as graphene, carbon nano tube and the like has ultrahigh electron conductivity, and the modified solid electrolyte which simultaneously takes account of ion conductivity and electron conductivity can be obtained by modifying the solid electrolyte by utilizing the carbon nano material, and compared with the carbon nano material and the solid electrolyte which are distributed on the surface of silicon oxide in a dispersion form, the modified solid electrolyte has the following advantages: 1) The liquid phase modification process utilizes the advantage of large surface area of the carbon nano material to uniformly load the solid electrolyte particles, so that the aggregation of the nano solid electrolyte particles in a large quantity can be avoided, and the advantage of the ultrahigh ion conductivity of the solid electrolyte can not be exerted; 2) When the solid electrolyte is dispersed on the surface of the silicon oxide in a dispersion form, the volume effect of the silicon oxide anode particles is easy to cause the falling-off failure of the solid electrolyte during charging and discharging, and the solid electrolyte is loaded on the surface of the carbon nano material through pre-modification, so that the falling-off problem of the solid electrolyte can be solved; 3) The modified solid electrolyte can coordinate with the carbon nano material, has ultrahigh electronic conductivity and lithium ion conductivity, and is more beneficial to improving the coulomb efficiency, the cycle stability and the multiplying power performance of the silicon-oxygen negative electrode.
Preferably, the solid electrolyte is Li 7-x La 3 Ta x Zr 2-x O 12 (LLZTO) and/or LiLa 3 Zr 2 O 12 (LLZO);x=0-2。
Preferably, the silicon oxide is a block particle, the amorphous carbon is soft carbon or hard carbon, and the carbon nanomaterial is a sheet-like or tubular structure.
The flaky or tubular carbon nano material such as graphene, carbon nano tube and the like is introduced into the anode material, the long-range ordered structure of the flaky or tubular carbon nano material can cooperate with the amorphous carbon coating layer, a conductive network is constructed on the particle and electrode layers, and the problem of low silicon-oxygen conductivity is solved.
Preferably, the silica has a silica ratio of 1-1.08:1, and the median particle diameter of the particles is 0.5-10 μm.
Preferably, the carbon nanomaterial is one of carbon nanotubes and graphene.
In a second aspect, the invention provides a preparation method of a silicon-oxygen composite anode material, which comprises the following two schemes:
for the carbon nanomaterial and the solid electrolyte to be distributed on the surface of the silicon oxide in a dispersed form, the preparation method comprises the following steps:
1) Mixing and dispersing silica powder, carbon nano material slurry, solid electrolyte powder and solvent uniformly, and then performing ultrasonic dispersion to obtain uniform slurry;
2) Drying, granulating and depolymerizing the uniform slurry to obtain powder particles;
3) Adopting a carbon source to carry out solid-phase or liquid-phase coating treatment on the powder particles, and cooling to obtain a precursor;
4) And transferring the precursor into carbonization equipment, heating to 600-1200 ℃ under protective atmosphere, preserving heat for 2-24h, cooling, taking out, and screening to obtain the silicon-oxygen composite anode material.
In the scheme, the silicon-oxygen composite anode material is prepared by dispersing solid electrolyte, silica powder and carbon nano material, performing ultrasonic treatment to form a uniform mixture, drying and granulating, and then coating a carbon source through a solid phase or a liquid phase, and carbonizing to form amorphous carbon.
The preparation method is characterized in that the carbon nanomaterial modified solid electrolyte is distributed on the surface of silicon oxide, and the preparation method comprises the following steps:
1) Uniformly mixing and dispersing the carbon nano material slurry, the solid electrolyte powder and the solvent, and then performing ultrasonic dispersion to obtain uniform slurry;
2) Drying, granulating and depolymerizing the uniform slurry, and performing heat treatment at 250-350 ℃ for 1-3 hours to obtain a carbon nanomaterial modified solid electrolyte;
3) Uniformly mixing the obtained carbon nanomaterial modified solid electrolyte with silica powder to obtain powder particles, carrying out solid-phase or liquid-phase coating treatment by adopting a carbon source, and cooling to obtain a precursor;
4) And transferring the precursor into carbonization equipment, heating to 600-1200 ℃ under protective atmosphere, preserving heat for 2-24h, cooling, taking out, and screening to obtain the silicon-oxygen composite anode material.
In the scheme, the solid electrolyte and the carbon nano material are dispersed and ultrasonically formed into a uniform mixture, the uniform mixture is dried, granulated and depolymerized, the carbon nano material modified solid electrolyte is obtained after low-temperature heat treatment, carbon source cladding is carried out through a solid phase or a liquid phase, amorphous carbon is formed through carbonization, and finally the silicon-oxygen composite anode material is obtained.
Preferably, in step 1), the carbon nanomaterial slurry contains a thickener; the thickener is one or more of sodium carboxymethyl cellulose, polytetrafluoroethylene, polyacrylic acid and polyvinylidene fluoride; the solvent is one or more of isopropanol, deionized water, N-methyl pyrrolidone, ethanol and ethylene glycol; the ultrasonic dispersion time is 0.2-1h.
Preferably, in step 2), the method of drying and granulating is vacuum drying, freeze drying or spray drying. The depolymerization mode is one or more of rolling mill, mechanical mill, air flow mill and ball mill. The equipment for low-temperature heat treatment is a vertical kettle or a heating VC mixer.
Preferably, in step 3), the carbon source is at least one of pitch, resin, and tar; further, the softening point of the asphalt is 100-300 ℃; the resin is one or more of phenolic resin, acrylonitrile resin, furan resin and polyethylene oxide resin; the tar is one or more of phenol oil, wash oil and anthracene oil.
Preferably, in the step 3), the ratio of the carbon source to the ground particles is 3-25:100. If the carbon source ratio is too high, the capacity of the composite material is low, and if the carbon source ratio is too low, the first effect of the material is low.
Preferably, the solid phase or liquid phase coating is realized by one or more of a roller furnace, a vertical kettle, a mechanical fusion machine and a heating VC mixer.
Preferably, in the step 4), the carbonization equipment is a box carbonization furnace, a roller kiln, a tubular carbonization furnace or a pusher kiln.
Compared with the prior art, the invention has the beneficial effects that: the negative electrode material has unique structural design, and the amorphous carbon, the carbon nano material and the solid electrolyte (in two distribution forms) are coated on the surface of the silicon oxide particles to form the artificial SEI film coating layer with high lithium ion conductivity and high mechanical stability, and the coating layer plays a role of a surface SEI film, so that the decomposition of electrolyte can be effectively reduced, the coulombic efficiency and the circulation stability of a silicon negative electrode are improved, the lithium ion transmission rate of the Si negative electrode is improved, and the rate capability of the silicon negative electrode is remarkably improved.
Drawings
Fig. 1 is an XRD pattern of the silicon oxide composite anode material prepared in example one (upper curve) and comparative example one (lower curve).
Fig. 2 is an SEM image of the silicon oxide composite anode material prepared in example one.
Fig. 3 is a comparative graph of the buckling cycle curves of the silicon oxide composite anode materials prepared in the first embodiment, the second embodiment and the first comparative embodiment.
Fig. 4 is a graph showing the comparison of the full-electric cycle curves of the silicon-oxygen composite anode materials prepared in the first example (upper curve), the second example (middle curve) and the first comparative example (lower curve) and the artificial graphite compound sample.
Detailed Description
The invention is further described below with reference to examples.
General examples
A silicon-oxygen composite negative electrode material of a lithium battery with good electrochemical performance takes silicon oxide with carbon nanomaterial and solid electrolyte distributed on the surface as an inner core, and amorphous carbon coated on the surface of the silicon oxide as a coating layer; the carbon nano material and the solid electrolyte are distributed on the surface of the silicon oxide in a dispersed form or in a form of modifying the solid electrolyte by the carbon nano material; wherein the silicon oxide accounts for 70-98wt%, the carbon nanomaterial accounts for 0.01-5%, the solid electrolyte accounts for 0.01-10%, and the amorphous carbon accounts for 1-15%. Wherein the silicon oxide is blocky particles with the silicon-oxygen ratio of 1 to 1.08:1, the median diameter of the particles is 0.5-10 mu m. The amorphous carbon is soft carbon or hard carbon, and the solid electrolyte is Li 7-x La 3 Ta x Zr 2-x O 12 (LLZTO) and/or Li 7 La 3 Zr 2 O 12 (LLZO); x=0-2. The carbon nanomaterial is in a sheet-like or tubular structure, and is further preferably one of a carbon nanotube and graphene.
A preparation method of a silicon-oxygen composite anode material comprises two schemes:
for the carbon nanomaterial and the solid electrolyte to be distributed on the surface of the silicon oxide in a dispersed form, the preparation method comprises the following steps:
1) Mixing and dispersing silica powder, carbon nano material slurry, solid electrolyte powder and solvent uniformly, and then carrying out ultrasonic dispersion for 0.2-1h to obtain uniform slurry. Wherein the carbon nanomaterial slurry contains a thickener; the thickener is one or more of sodium carboxymethyl cellulose, polytetrafluoroethylene, polyacrylic acid and polyvinylidene fluoride; the solvent is one or more of isopropanol, deionized water, N-methyl pyrrolidone, ethanol and ethylene glycol.
2) And drying and granulating (vacuum drying, freeze drying or spray drying) the uniform slurry, depolymerizing (one or more of roller mill, mechanical mill, air flow mill and ball mill), and obtaining powder particles after depolymerizing.
3) Adopting a carbon source, carrying out solid-phase or liquid-phase coating treatment on powder particles according to the mass ratio of 3-25:100 by one or more of a roller furnace, a vertical kettle, a mechanical fusion machine and a heating VC mixer, and cooling to obtain a precursor. The carbon source is at least one of asphalt, resin and tar; further, the softening point of the asphalt is 100-300 ℃; the resin is one or more of phenolic resin, acrylonitrile resin, furan resin and polyethylene oxide resin; the tar is one or more of phenol oil, wash oil and anthracene oil.
4) And transferring the precursor into carbonization equipment (a box-type carbonization furnace, a roller kiln, a tubular carbonization furnace or a pusher kiln), heating to 600-1200 ℃ under a protective atmosphere, preserving heat for 2-24 hours, cooling, taking out, and screening to obtain the silicon-oxygen composite anode material.
The preparation method is characterized in that the carbon nanomaterial modified solid electrolyte is distributed on the surface of silicon oxide, and the preparation method comprises the following steps:
1) Uniformly mixing and dispersing the carbon nano material slurry, the solid electrolyte powder and the solvent, and then performing ultrasonic dispersion for 0.2-1h to obtain uniform slurry; wherein the carbon nanomaterial slurry contains a thickener; the thickener is one or more of sodium carboxymethyl cellulose, polytetrafluoroethylene, polyacrylic acid and polyvinylidene fluoride; the solvent is one or more of isopropanol, deionized water, N-methyl pyrrolidone, ethanol and ethylene glycol.
2) And (3) drying and granulating (vacuum drying, freeze drying or spray drying) the uniform slurry, depolymerizing (one or more of roller mill, mechanical mill, air flow mill and ball mill), and performing heat treatment at 250-350 ℃ for 1-3 hours, thereby obtaining the carbon nanomaterial modified solid electrolyte.
3) Uniformly mixing the obtained carbon nanomaterial modified solid electrolyte with silica powder to obtain powder particles, carrying out solid-phase or liquid-phase coating treatment on a carbon source (the mass ratio of the powder particles to the carbon source is 3-25:100) by one or more of a roller furnace, a vertical kettle, a mechanical fusion machine and a heating VC mixer, and cooling to obtain a precursor. The carbon source is at least one of asphalt, resin and tar; further, the softening point of the asphalt is 100-300 ℃; the resin is one or more of phenolic resin, acrylonitrile resin, furan resin and polyethylene oxide resin; the tar is one or more of phenol oil, wash oil and anthracene oil.
4) And transferring the precursor into carbonization equipment (a box-type carbonization furnace, a roller kiln, a tubular carbonization furnace or a pusher kiln), heating to 600-1200 ℃ under a protective atmosphere, preserving heat for 2-24 hours, cooling, taking out, and screening to obtain the silicon-oxygen composite anode material.
Example one (distribution of carbon nanomaterial-modified solid electrolyte on silica surface)
Taking 0.2kg graphene slurry (solid content 5% and solvent NMP) and 0.05kg solid state electricityElectrolyte (Li) 6.9 La 3 Ta 0.1 Zr 1.9 O 12 200 nm) and 1.5kg of isopropanol, adding into a 5L dispersion sand mill, dispersing at high speed for 2 hours uniformly to obtain uniform slurry, and then inserting an ultrasonic generator into the slurry for 1 hour by ultrasonic treatment. And (3) carrying out spray drying granulation on the slurry to obtain a solid mixture, carrying out air flow grinding on the depolymerized material, transferring the depolymerized material into a heating VC mixer, and carrying out heat treatment at 300 ℃ for 2 hours to obtain the graphene modified solid electrolyte. Mixing the obtained modified solid electrolyte, 1.88kg of silica powder (SiO, median particle diameter is 5 mu m) and 0.1kg of petroleum asphalt (softening point at 200 ℃) for 1h by a three-dimensional mixer, transferring into an experimental roller furnace, carrying out solid-phase coating treatment, mixing and heating to 550 ℃ under protective atmosphere, preserving heat for 2h, and naturally cooling to obtain a precursor. And transferring the precursor material into a roller kiln, heating to 1050 ℃ in nitrogen atmosphere, carbonizing for 20 hours and preserving for 5 hours. And (3) naturally cooling, and screening by a 250-mesh screen to obtain the silica composite anode material.
Homogenizing, coating and rolling the prepared silicon-oxygen composite anode material, carbon black, CMC and SBR according to the proportion of 94.5:1.5:2.0:2.0 to prepare a working electrode, taking a lithium sheet as a counter electrode to prepare a button cell, carrying out charge and discharge test, and taking lithium cobaltate as a positive electrode to carry out full cell test.
Example two (distribution of carbon nanomaterial and solid electrolyte in dispersed form on silica surface)
0.2kg of graphene slurry (solid content 5% and solvent NMP) and 0.05kg of solid electrolyte (Li 6.9 La 3 Ta 0.1 Zr 1.9 O 12 200 nm), 1.88kg of silica powder (SiO, median particle diameter of 5 μm) and 1.5kg of isopropyl alcohol were added into a 5L dispersion sand mill, and after being dispersed at high speed for 2 hours uniformly, uniform slurry was obtained, and then an ultrasonic generator was inserted into the slurry, and ultrasonic was conducted for 1 hour. The slurry is subjected to spray drying and granulation to obtain a solid mixture, and the solid mixture is subjected to pneumatic grinding and deagglomeration to obtain powder particles. Transferring the depolymerized powder particles and 0.1kg petroleum asphalt (softening point of 200 ℃) into an experimental roller furnace, performing solid-phase coating treatment, mixing and heating to 550 ℃ under protective atmosphere, preserving heat for 2 hours, and naturally cooling to obtain a precursor. And transferring the precursor material into a roller kiln, heating to 1050 ℃ in nitrogen atmosphere, carbonizing for 20 hours and preserving for 5 hours. And (3) naturally cooling, and screening by a 250-mesh screen to obtain the silica composite anode material.
Homogenizing, coating and rolling the prepared silicon-oxygen composite anode material, carbon black, CMC and SBR according to the proportion of 94.5:1.5:2.0:2.0 to prepare a working electrode, taking a lithium sheet as a counter electrode to prepare a button cell, carrying out charge and discharge test, and taking lithium cobaltate as a positive electrode to carry out full cell test.
Through tests, the reversible discharge specific capacity of the silicon-oxygen composite anode material reaches 1295.8mAh/g, the first efficiency is 80.1%, and the reversible capacity of 1171.1mAh/g is still obtained after 50 weeks of circulation.
Example III
0.8kg of carbon nanotube slurry (solid content 1% and NMP as solvent) and 0.5kg of solid electrolyte (Li 6.8 La 3 Ta 0.2 Zr 1.8 O 12 500 nm), 15.0kg of silica powder (SiO, with a median particle diameter of 4 μm) and 10kg of isopropanol, and then adding into a 30L dispersion sand mill, dispersing at high speed for 2 hours uniformly to obtain uniform slurry, and then inserting an ultrasonic generator into the slurry for ultrasonic treatment for 2 hours. And (3) transferring the slurry into an electric heating constant temperature drying oven for drying at 90 ℃, and mechanically grinding and grading to obtain powder particles. . Transferring the obtained powder particles and lkg phenol oil into a mechanical fusion machine, and carrying out low-temperature liquid phase coating treatment to obtain a precursor. And transferring the precursor material into a roller kiln, heating to 1050 ℃ in nitrogen atmosphere, carbonizing for 24 hours and preserving for 6 hours. And (3) naturally cooling, and screening by a 250-mesh screen to obtain the silica composite anode material.
Through tests, the reversible discharge specific capacity of the silicon-oxygen composite anode material reaches 1328.9mAh/g, the first efficiency is 79.6%, and the reversible capacity of 1139.1mAh/g is still obtained after 50 weeks of circulation.
Example IV
0.5kg of carbon nanotube slurry (solid content 1% and NMP as solvent) and 0.02kg of solid electrolyte (Li 6.9 La 3 Ta 0.1 Zr 1.9 O 12 500 nm), 2kg of silica powder (SiO, median particle diameter 4 μm) and 2kgAdding NMP into a 5L dispersion sand mill, dispersing at high speed for 2h to obtain uniform slurry, and then inserting an ultrasonic generator into the slurry for 0.5h. And (3) transferring the slurry into an electric heating constant temperature drying oven or a muffle furnace for drying at 90 ℃, and then grinding and grading by airflow to obtain powder particles. Transferring the obtained powder particles, 0.3kg of petroleum asphalt and 0.5kg of anthracene oil into a mechanical fusion machine, transferring the materials subjected to low-temperature liquid phase coating treatment into VC thermal compounding equipment, and preserving heat at 500 ℃ for 2 hours to obtain a precursor. And transferring the precursor material into a roller kiln, heating to 1000 ℃ under the nitrogen atmosphere, carbonizing for 18 hours and preserving for 5 hours. And (3) naturally cooling, and screening by a 250-mesh screen to obtain the silica composite anode material.
Through tests, the reversible discharge specific capacity of the silicon-oxygen composite anode material reaches 1226.0mAh/g, the first efficiency is 80.1%, and the reversible capacity of 1071.7mAh/g is still obtained after 50 weeks of circulation.
Comparative example one (without addition of solid electrolyte)
1.88kg of silica powder (with the median particle diameter of 5 mu m) and 0.1kg of petroleum asphalt (with the softening point of 200 ℃) are transferred into VC thermal compounding equipment to be subjected to solid phase coating treatment, and then are mixed and heated to 550 ℃ under protective atmosphere, heat preservation is carried out for 2 hours, and a precursor is obtained after natural cooling. And transferring the precursor material into a roller kiln, heating to 1050 ℃ in nitrogen atmosphere, carbonizing for 20 hours and preserving for 5 hours. And (3) naturally cooling, and screening by a 250-mesh screen to obtain the silica composite anode material.
Through tests, the reversible capacity of the composite anode material purely coated with amorphous carbon and silicon oxide reaches 1299.0mAh/g, the first efficiency is 77.8%, but the half cell has the reversible capacity of only 788.0mAh/g after 50 weeks of circulation at 0.1C/0.1C.
Performance comparison
(1) The first embodiment differs from the second embodiment only in the combination form of the carbon nanomaterial and the solid electrolyte; while comparative example one differs in that no solid electrolyte was added. FIG. 1 shows XRD patterns of the silica composite anode materials prepared in example one and comparative example one, from which it can be seen that the silica composite anode material was successfully prepared in example one, without significant impurity peaks, and thatSiO x Typical diffraction peaks of LLZTO, and (002) plane peaks of carbon can be observed at 26.8 °, indicating the presence of an amorphous carbon coating on the surface. While the XRD pattern of comparative example one does not observe diffraction peaks of LLZTO. The morphology is shown in the SEM of figure 2, the lamellar graphene material is modified by the solid electrolyte nano particles, and the lamellar graphene material is compounded on the surfaces of silicon oxide particles or filled between the particles, so that an excellent conductive network can be constructed when the electrode is manufactured.
(2) Physical property test and electrochemical test of the silicon oxide composite anode materials prepared in examples one and two and comparative example one are shown in the following table:
Figure BDA0003027480880000081
as can be seen from the comparison chart of the buckling cycle of FIG. 3 and the data in the table above, the silicon-oxygen composite anode material prepared in the first embodiment comprises 0.5% of graphene, 2.5% of LLZTO and 5% of 200 ℃ softening point asphalt carbon source coating proportion, D 50 The reversible capacity of the composite material reaches 1282.7mAh/g, the primary efficiency is 80.3%, the reversible capacity of the button cell still reaches 1203.2mAh/g after 50 weeks of circulation at 0.1C/0.1C, and the capacity retention rate of 93.8% is better than that of the second embodiment, wherein the specific surface area is 7.21 mu m and 2.97m 2/g. The fact that graphene is adopted to carry out pre-modification on the solid electrolyte can enable the electrical performance to be further improved. The second embodiment is superior to the first embodiment, and the introduction of the solid electrolyte can significantly improve the electrical performance.
(3) The silicon-oxygen composite anode material and artificial graphite are mixed to prepare a silicon-carbon anode material with the capacity of 450mAh/g, and the silicon-carbon anode material is manufactured into a soft-package full battery, and the full battery test results are shown in the following table:
Figure BDA0003027480880000082
as can be seen from fig. 4 and the table above, the retention rate of the silicon-carbon anode material obtained by the first embodiment after 300 weeks of circulation at 1C/1C still remains 91.2%, the 4C charging constant current section accounts for 65.2%, and the 4C discharge capacity retention rate is 76.3%. Each performance index is better than that of the mixed sample of the second embodiment and the first comparative embodiment. The comparison of the three can show that the multiplying power and the cycle performance of the silicon-oxygen composite anode material obtained by adopting the carbon nano material for pre-modifying the solid electrolyte and then coating the amorphous carbon are obviously improved.
The raw materials and equipment used in the invention are common raw materials and equipment in the field unless specified otherwise; the methods used in the present invention are conventional in the art unless otherwise specified.
The foregoing description is only a preferred embodiment of the present invention, and is not intended to limit the present invention, and any simple modification, variation and equivalent transformation of the above embodiment according to the technical substance of the present invention still fall within the scope of the technical solution of the present invention.

Claims (10)

1. A preparation method of a lithium battery silicon-oxygen composite anode material with good electrochemical performance is characterized by comprising the following steps: the method comprises the following steps:
1) Uniformly mixing and dispersing the carbon nano material slurry, the solid electrolyte powder and the solvent, and then performing ultrasonic dispersion to obtain uniform slurry;
2) Drying, granulating and depolymerizing the uniform slurry, and performing heat treatment at 250-350 ℃ for 1-3 hours to obtain a carbon nanomaterial modified solid electrolyte;
3) Uniformly mixing the obtained carbon nanomaterial modified solid electrolyte with silica powder to obtain powder particles, carrying out solid-phase or liquid-phase coating treatment by adopting a carbon source, and cooling to obtain a precursor;
4) Transferring the precursor into carbonization equipment, heating to 600-1200 ℃ under protective atmosphere, preserving heat for 2-24h, cooling, taking out, and screening to obtain a silicon-oxygen composite anode material of the lithium battery;
the silicon-oxygen composite negative electrode material of the lithium battery takes silicon oxide with carbon nanomaterial modified solid electrolyte distributed on the surface as an inner core, and amorphous carbon coated on the surface of the silicon oxide as a coating layer; the carbon nanomaterial modified solid electrolyte is a carbon nanomaterial loaded with the solid electrolyte; wherein the silicon oxide accounts for 70-98wt%, the carbon nanomaterial accounts for 0.01-5%, the solid electrolyte accounts for 0.01-10%, and the amorphous carbon accounts for 1-15%.
2. The method for producing a silicon-oxygen composite anode material according to claim 1, wherein the solid electrolyte is Li 7-x La 3 Ta x Zr 2-x O 12 And/or LiLa 3 Zr 2 O 12 ;x=0-2。
3. The method for preparing a silicon-oxygen composite anode material according to claim 1, wherein the silicon oxide is a block particle, the amorphous carbon is soft carbon or hard carbon, and the carbon nanomaterial is a sheet-like or tubular structure.
4. The method for producing a silicon oxide composite negative electrode material according to claim 3, wherein the silicon oxide has a silicon-oxygen ratio of 1-1.08:1 and a median particle diameter of 0.5-10 μm.
5. The method for preparing a silicon-oxygen composite anode material according to claim 1, wherein the carbon nanomaterial is one of carbon nanotubes and graphene.
6. The method according to claim 1, wherein in step 1), the carbon nanomaterial slurry contains a thickener; the thickening agent is one or more of sodium carboxymethyl cellulose, polytetrafluoroethylene, polyacrylic acid and polyvinylidene fluoride.
7. The preparation method according to claim 1, wherein in the step 1), the solvent is one or more of isopropanol, deionized water, N-methylpyrrolidone, ethanol and ethylene glycol;
the ultrasonic dispersion time is 0.2-1h.
8. The process according to claim 1, wherein in step 2),
the drying and granulating method is vacuum drying, freeze drying or spray drying;
the depolymerization mode is one or more of rolling mill, mechanical mill, air flow mill and ball mill;
the heat treatment equipment is a vertical kettle or a heating VC mixer.
9. The process according to claim 1, wherein in step 3),
the carbon source is at least one of asphalt, resin and tar;
the softening point of the asphalt is 100-300 ℃;
the resin is one or more of phenolic resin, acrylonitrile resin, furan resin and polyethylene oxide resin;
the tar is one or more of phenol oil, wash oil and anthracene oil;
the ratio of the carbon source to the powder particles is 3-25:100;
the solid phase or liquid phase coating is realized by one or more of a roller furnace, a vertical kettle, a mechanical fusion machine and a heating VC mixer.
10. The method of claim 1, wherein in step 4), the carbonization device is a box carbonization furnace, a roller kiln, a tube carbonization furnace, or a pusher kiln.
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