CN113130868A - Composite material containing silicon monoxide, negative plate, lithium battery and preparation method thereof - Google Patents
Composite material containing silicon monoxide, negative plate, lithium battery and preparation method thereof Download PDFInfo
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- 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
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- C01—INORGANIC CHEMISTRY
- C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
- C01B32/00—Carbon; Compounds thereof
- C01B32/05—Preparation or purification of carbon not covered by groups C01B32/15, C01B32/20, C01B32/25, C01B32/30
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- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
- C01B33/00—Silicon; Compounds thereof
- C01B33/113—Silicon oxides; Hydrates thereof
- C01B33/12—Silica; Hydrates thereof, e.g. lepidoic silicic acid
- C01B33/18—Preparation of finely divided silica neither in sol nor in gel form; After-treatment thereof
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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
- H01M10/00—Secondary cells; Manufacture thereof
- H01M10/05—Accumulators with non-aqueous electrolyte
- H01M10/052—Li-accumulators
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- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M10/00—Secondary cells; Manufacture thereof
- H01M10/05—Accumulators with non-aqueous electrolyte
- H01M10/058—Construction or manufacture
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M4/00—Electrodes
- H01M4/02—Electrodes composed of, or comprising, active material
- H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
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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
- H01M4/38—Selection of substances as active materials, active masses, active liquids of elements or alloys
- H01M4/386—Silicon or alloys based on silicon
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- H—ELECTRICITY
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- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M4/00—Electrodes
- H01M4/02—Electrodes composed of, or comprising, active material
- H01M4/36—Selection of substances as active materials, active masses, active liquids
- H01M4/38—Selection of substances as active materials, active masses, active liquids of elements or alloys
- H01M4/40—Alloys based on alkali metals
- H01M4/405—Alloys based on lithium
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- H—ELECTRICITY
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- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M4/00—Electrodes
- H01M4/02—Electrodes composed of, or comprising, active material
- H01M4/36—Selection of substances as active materials, active masses, active liquids
- H01M4/48—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
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- H—ELECTRICITY
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- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M4/00—Electrodes
- H01M4/02—Electrodes composed of, or comprising, active material
- H01M4/62—Selection of inactive substances as ingredients for active masses, e.g. binders, fillers
- H01M4/624—Electric conductive fillers
- H01M4/625—Carbon or graphite
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- C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
- C01P2004/00—Particle morphology
- C01P2004/80—Particles consisting of a mixture of two or more inorganic phases
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- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
- Y02E60/10—Energy storage using batteries
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
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- Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
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- Y02P70/50—Manufacturing or production processes characterised by the final manufactured product
Abstract
The inventionDisclosed is a composite material containing silicon monoxide, which is a core-shell structure and comprises an inner core, a middle layer, a secondary outer layer and an outermost layer from inside to outside, wherein the inner core is made of silicon monoxide, the middle layer is made of lithium silicon composite material, the secondary outer layer is made of fluoride, the outermost layer is a carbon coating layer, and the silicon monoxide is SiOxWherein 0.5<x<1.5. The invention also discloses a preparation method of the composite material containing the silicon monoxide, which comprises the following steps: a. disproportionating the silicon monoxide; b. in a non-oxidizing atmosphere, mixing the disproportionated silicon monoxide, the metal lithium and a carbon source and then carrying out ball milling; c. carrying out fluorination treatment on the product obtained in the step b; d. and c, coating the product obtained in the step c with carbon. The invention also discloses a negative plate with the composite material containing the silicon monoxide. The invention also discloses a lithium battery with the negative plate.
Description
Technical Field
The invention relates to the technical field of lithium batteries, in particular to a composite material containing silicon monoxide, a negative plate, a lithium battery and a preparation method thereof.
Background
Because mileage anxiety often appears in the experience of using the electric motor car in the current consumer market, the research and development of the power battery are more and more developed towards the direction of quick charging. Current fast-charging batteries are primarily achieved by reduced areal and compacted densities, but also result in reduced energy density of the battery, a result that is not acceptable to the electric vehicle consumer market. If the energy density of the battery is further improved by changing the pure graphite into the silicon-based material and graphite composite, the energy density of the battery can be improved on the premise of ensuring the rate charging of the battery, so that the electric automobile has the quick charging performance and the long endurance.
The energy density of the power battery can be obviously improved by converting the negative electrode material from graphite to a silicon-based material. However, the cycle life of the battery is drastically reduced due to the severe volume effect of the pure silicon carbon material during charging and discharging. Currently, the industry is more inclined to use silicon-oxygen materials as the negative electrode materials of power batteries. However, the use of a silica material as a battery anode material also has intrinsic defects, mainly due to the presence of a large amount of oxygen in the material, and the consumption of a large amount of Li source during the formation process due to the SEI film formation and the lithium silicate/lithium oxide species, which results in low first-time efficiency of such materials. How to improve the first effect of such materials becomes the focus of research in the industry and academia at present.
Disclosure of Invention
Based on this, it is necessary to provide a composite material containing silicon oxide, a negative plate, a lithium battery and a preparation method thereof, aiming at the problems that the silicon oxide material is used as a negative active material, so that the first efficiency of the battery is low and the cycle life is poor.
The composite material containing the silicon oxide is of a core-shell structure and comprises an inner core, an intermediate layer, a secondary outer layer and an outermost layer from inside to outside, wherein the inner core is made of the silicon oxide, the intermediate layer is made of a lithium silicon composite material, the secondary outer layer is made of fluoride, the outermost layer is a carbon coating layer, and the silicon oxide is SiOxWherein 0.5<x<1.5。
A method for preparing a composite material containing silicon monoxide comprises the following steps:
a. disproportionating the silicon monoxide at 750-1100 deg.c for 1-5 hr;
b. in a non-oxidizing atmosphere, mixing the disproportionated silicon monoxide, the metal lithium and a carbon source and then carrying out ball milling;
c. carrying out fluorination treatment on the product obtained in the step b;
d. and c, coating the product obtained in the step c with carbon.
A negative plate comprises a current collector and a negative active layer arranged on the current collector, wherein the negative active layer is provided with the composite material containing the silicon oxide in any embodiment or the composite material containing the silicon oxide prepared by the preparation method of the composite material containing the silicon oxide in any embodiment.
A lithium battery comprises a positive plate, the negative plate, a diaphragm and a non-aqueous electrolyte.
In order to solve the problems of low energy density and poor cycle life of a battery caused by low first-effect of the silicon oxide and improve the adverse effect caused by volume expansion of silicon oxide particles, exogenous lithium is introduced into the silicon oxide material from the material end, a lithium-silicon compound is formed on the outer layer of the inner core of the silicon oxide to serve as an intermediate layer, and carbon is coated on the outer layer and the outermost layer of the inner core of the silicon oxide, so that the stability of the lithium-silicon compound is improved, the lithium-silicon compound has synergistic effect with the silicon oxide and the lithium-silicon compound layer, the first-effect efficiency of the silicon oxide is improved from 75% to about 90%, the cycle life is further improved, and the situation that a pre-lithiation process is carried out after a silicon-oxygen negative electrode sheet is manufactured to obtain higher first-effect and cycle life is avoided. In addition, the invention is improved from the aspect of negative electrode materials, and compared with the improvement on a current collector or a pole piece end, the invention does not need special factory building transformation and is beneficial to large-scale production and cost control.
Detailed Description
In order that the invention may be more fully understood, reference will now be made to the following description. The present invention may be embodied in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete.
Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. The terminology used in the description of the invention herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. As used herein, the term "and/or" includes any and all combinations of one or more of the associated listed items.
The embodiment of the invention provides a silicon oxide composite material which is of a core-shell structure and comprises an inner core, an intermediate layer, a secondary outer layer and an outermost layer from inside to outside, wherein the inner core is made of silicon oxide, the intermediate layer is made of a lithium silicon composite material, the secondary outer layer is made of fluoride, and the outermost layer is a carbon coating layer.
According to the invention, exogenous lithium is introduced into the surface of the silicon oxide to form a lithium-silicon alloy/lithium silicate composite layer (intermediate layer) on the outer layer of the silicon oxide inner core, and on one hand, the intermediate layer is present, so that part of exogenous lithium stored on the surface of silicon oxide particles in advance can be used as supplement for effective lithium in the battery during lithium intercalation for the first time, and the first coulomb efficiency and cycle life of the battery are improved; on the other hand, the existence of the intermediate layer can generate a pre-expansion effect on the silicon monoxide so as to reduce the volume effect of the cell; on the other hand, the existence of the intermediate layer is more favorable for forming an SEI film on the surface of the silicon monoxide particles and is favorable for the maturity of the SEI film of the negative electrode. In order to further stabilize the pre-lithiated silicon oxide composite material, a secondary outer layer is formed by surface fluorination, the secondary outer layer is an inert layer and can be used as a barrier to separate direct contact between silicon oxide and electrolyte, and the inert layer is also used as an artificial SEI film to ensure that the cycle performance of a silicon-oxygen cathode is improved; the surface of the secondary outer layer is coated with a carbon layer, so that the outermost layer prevents the middle layer from being interfered by external environment (water and oxygen), and prevents a silicon monoxide core in the battery from directly contacting with electrolyte, the conductivity of the pole piece can be improved, the multiplying power performance of the battery can be improved, and meanwhile, the silicon monoxide composite material coated with the outermost layer can be used for synthesizing aqueous slurry by using an aqueous binder to obtain a silicon dioxide negative pole piece by adopting a traditional coating process.
In some embodiments, the silica is SiOxWherein 0.5<x<1.5. Specifically, x may be 0.5, 0.6, 0.7, 0.8, 0.9, 1.0, 1.1, 1.2, 1.3, 1.4, 1.5.
In some embodiments, the particle size D50 of the inner core is between 0.5 μm and 20 μm. Specifically, D50 is 0.5. mu.m, 1. mu.m, 2. mu.m, 3. mu.m, 4. mu.m, 5. mu.m, 6. mu.m, 7. mu.m, 8. mu.m, 9. mu.m, 10. mu.m, 11. mu.m, 12. mu.m, 13. mu.m, 14. mu.m, 15. mu.m, 16. mu.m, 17. mu.m, 18. mu.m, 19. mu.m, or 20. mu.m.
In some embodiments, the intermediate layer has a thickness of 0.01 μm to 2 μm, the secondary outer layer has a thickness of 2nm to 200nm, and the outermost layer has a thickness of 0.01 μm to 1 μm.
In some embodiments, the outermost layer may comprise 1% to 15% by weight of the composite material containing silicon oxide. Specifically, the concentration may be 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12%, 13%, 14%, 15%.
The embodiment of the invention also provides a preparation method of the composite material containing the silicon monoxide, which comprises the following steps:
a. disproportionating the silicon monoxide;
b. in a non-oxidizing atmosphere, mixing the disproportionated silicon monoxide, the metal lithium and a carbon source and then carrying out ball milling;
c. carrying out fluorination treatment on the product obtained in the step b;
d. and c, coating the product obtained in the step c with carbon.
In some embodiments, the disproportionation temperature in step a is 750-1100 ℃ and the disproportionation time is 1-5 h. Specifically, the disproportionation temperature may be 750 deg.C, 800 deg.C, 850 deg.C, 900 deg.C, 950 deg.C, 1000 deg.C, 1050 deg.C, 1100 deg.C, and the disproportionation time may be adaptively adjusted according to the disproportionation temperature. Preferably, the disproportionation temperature is 850-1000 ℃, and the disproportionation time is 1-5 h.
In some embodiments, the structure of the disproportionated silicon monoxide of step a is silicon nano-domain, SiO2Cluster and between silicon nano crystal domain and SiO2A sub-oxidized interfacial region between the two clusters.
In some embodiments, in step b, the mass ratio of the disproportionated silicon monoxide, the metallic lithium and the carbon source is (100-x-y): x: y, wherein 1< x <5, 2< y < 10.
In some embodiments, in step b, the carbon source is selected from at least one of a carbon-containing organic substance, a carbon-containing inorganic substance; preferably, the carbon source is selected from one or more of small molecular saccharides, carbon black, acetylene black, carbon nanotubes, pitch, graphene and carbon nanofibers.
In some embodiments, in step b, the non-oxidizing atmosphere is an inert gas. So as to effectively avoid safety accidents such as ignition and the like caused by violent oxidation reaction of the lithium metal or the lithium silicon alloy contacting with oxygen or water.
In some embodiments, in step b, the temperature of the ball milling process is 150 ℃ to 250 ℃. Specifically, the ball milling temperature may be 150 deg.C, 160 deg.C, 170 deg.C, 180 deg.C, 190 deg.C, 200 deg.C, 210 deg.C, 220 deg.C, 230 deg.C, 240 deg.C, 250 deg.C. The ball milling system is properly heated, the temperature is kept at 150-250 ℃, the lithium metal can be melted by increasing the temperature of the ball milling system, so that the lithium metal can be rapidly and uniformly dispersed on the surface of the silicon oxide, in addition, the alloying reaction between the silicon oxide and the lithium metal can be accelerated by increasing the temperature, and thus the efficiency of the ball milling process and the quality of the silicon oxide composite material can be improved, and a better pre-lithiation effect can be achieved.
In some embodiments, in step b, the ball milling media has a particle size of 3mm to 20 mm.
In some embodiments, in the step b, the ball-to-material ratio of the ball milling process is (20-40): 1, the ball milling speed is 300-700 rpm, and the ball milling time is 1-8 h.
In some embodiments, in step b, the ball milling process is conducted at an ambient dew point of-30 ℃ or less. The ball milling process is in a dry environment, the dew point of the ball milling process is below-30 ℃, the dry environment can ensure that the obtained silicon oxide composite material cannot be subjected to safety accidents such as fire and the like when the ball milling process is opened after the ball milling process is finished, the failure of the obtained silicon oxide composite material due to oxidation can be reduced, and the generation of side reaction products on the surface of the material can be avoided, so that the slurry combination and the battery performance of the silicon oxide material are influenced.
In some embodiments, in step c, the step of fluorination treatment is to fluorinate the product obtained in step b with a fluorine-containing compound.
Preferably, the fluorine-containing compound is selected from one or more of fluorine-containing inorganic salts, fluorine-containing gas and fluorine-containing non-gaseous organic substances.
Optionally, the fluorine-containing inorganic salts are selected from one or more of copper trifluoromethanesulfonate, copper hexafluorophosphate, copper tetrafluoroborate, nickel tetrafluoroborate, iron trifluoromethanesulfonate, iron tetrafluoroborate, zinc tetrafluoroborate, silver trifluoromethanesulfonate, cobalt tetrafluoroborate, lithium hexafluorophosphate, lithium hexafluoroarsenate, lithium tetrafluoroborate, litsffi, LiSFI, lidfo, lithium fluoride, sodium fluoride, ammonium bifluoride, sodium hydrogen fluoride, potassium hydrogen fluoride, and lithium trifluoromethanesulfonate;
optionally, the fluorine-containing gas is selected from fluorine gas, HF, SiF4、SnF4、SF6One or more of perfluorohexanone, and a perfluorocarbon compound;
optionally, the fluorine-containing non-gaseous organic substance is selected from one or more of perfluoro resin, polytetrafluoroethylene, polyvinylidene fluoride, polyhexafluoropropylene, fluoroethylene carbonate and fluoropropylene carbonate.
The state of the fluorine-containing compound is different, and the fluorination method is also different. The fluorine-containing gas can be directly contacted with the silicon oxide material particles to complete fluorination, and fluorine-containing solid organic matters need to be heated to release fluorine carbon free radicals and then contacted with the silicon oxide composite material particles to complete fluorination.
In some embodiments, the fluorine-containing compound is selected from fluorine-containing inorganic salts or liquid fluorine-containing organics, and in step c, the fluorination treatment is a liquid phase reaction.
In some embodiments, the fluorine-containing compound is selected from solid fluorine-containing organics, and the fluorination treatment is a reaction of releasing fluorocarbon radicals by heating with the product obtained in step b.
In some embodiments, the fluorine-containing compound is selected from fluorine-containing gases, and in the step c, the fluorination treatment is to place the product obtained in the step b in a reaction kettle and introduce fluorine-containing gases for reaction. This method is the preferred fluorination treatment method.
In some embodiments, the carbon coating process in step d is liquid phase coating or gas phase coating.
Preferably, the liquid phase coated carbon source is selected from one or more of coal tar, paraffin, liquid hydrocarbons, heavy oil, sucrose, glucose, pitch, and PVDF.
Optionally, the gas phase coating is selected from chemical gas phase coating or physical gas phase coating.
Preferably, the chemical vapor-coated gas source is selected from one or more of propyne, propylene, methane, ethane, propane, ethylene, acetylene, benzene, toluene, xylene, styrene, and ethylbenzene.
The preparation method provided by the embodiment of the invention is a preparation method of the silicon oxide composite material capable of realizing large-scale production, and the silicon oxide composite material with high specific capacity and high first-time efficiency in batches can be obtained by the process, so that an optional material is provided for commercialization of a high-energy density battery.
The embodiment of the invention also provides a negative electrode sheet, which comprises a current collector and a negative electrode active layer on the current collector, wherein the negative electrode active layer is provided with the composite material containing the silicon oxide in any embodiment or the composite material containing the silicon oxide prepared by the preparation method of the composite material containing the silicon oxide in any embodiment.
The negative active layer may further include a conductive agent and a binder, and is uniformly mixed with the negative active material. The conductive agent may be one or more of acetylene black, carbon fiber, carbon nanotube, and graphite. The binder may be one or more of polyvinylidene fluoride (PVDF), Polytetrafluoroethylene (PTFE), and Styrene Butadiene Rubber (SBR).
The embodiment of the invention also provides a lithium battery which comprises a positive plate, a negative plate, a diaphragm and a non-aqueous electrolyte. The negative electrode plate is the negative electrode plate in any one of the above embodiments.
The nonaqueous electrolyte may be a nonaqueous electrolyte solution or a solid electrolyte membrane. The lithium ion battery using the nonaqueous electrolyte solution further includes a separator disposed between the positive electrode material layer and the negative electrode material layer. The lithium battery adopting the solid electrolyte membrane arranges a diaphragm between the positive pole piece and the negative pole piece. The non-aqueous electrolyte comprises a solvent and a solute dissolved in the solvent, and the solvent can be one or more of cyclic carbonate, chain carbonate, cyclic ether, chain ether, nitrile and amide, such as ethylene carbonate, propylene carbonate, diethyl carbonate, dimethyl carbonate, methyl ethyl carbonate, methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, gamma-butyrolactone, tetrahydrofuran, 1, 2-dimethoxyethane, acetonitrile and dimethylformamide. The solute may be exemplified by LiPF6、LiBF4、LiCF3SO3、LiAsF6、LiCIO4And LiBOB.
The material of the separator may be selected from polyolefin based polymer materials.
The positive electrode tab may include a current collector and a positive active layer on the current collector. The positive active layer may be a conventional positive active material for a lithium battery, and will not be described herein.
Example 1
(1) Disproportionating the micron-sized silicon oxide material at the high temperature of 1000 ℃ for 2 h.
(2) The obtained disproportionated silica, metallic lithium and sucrose were added in a sealed Ar gas-filled ball mill at 95:2:3 and ball-milled at 190 ℃ and a dew point of-35 ℃ at a high speed of 500rpm for 1.5 hours to obtain a composite material coated with a lithium silicon alloy/lithium silicate composite layer (lithium silicon composite layer).
(3) Dissolving ammonium bifluoride in ethyl methyl carbonate to form 0.2M fluorine-containing inorganic salt solution, adding the silicon monoxide composite material obtained in the step (2) into the fluorine-containing inorganic salt solution, performing fluorination for 15min, separating solid from liquid, cleaning with an organic solvent, and drying.
(4) And (3) performing liquid phase coating on the silicon oxide composite material obtained in the step (3) by using coal tar as a carbon source, and carbonizing for 2 hours at 800 ℃ to obtain the final silicon oxide composite material. The carbon coating layer accounts for 2 percent of the mass and has the thickness of 1.5 mu m.
Example 2
The difference from example 1 is that the disproportionation temperature in step (1) was 750 ℃.
Example 3
The difference from example 1 is that the disproportionation temperature in step (1) was 1100 ℃.
Example 4
The difference from example 1 is that the disproportionation time in step (1) was 1 h.
Example 5
The difference from example 1 is that the disproportionation time in step (1) was 5 h.
Example 6
The difference from example 1 is that in step (2), the disproportionated silicon monoxide, metallic lithium and sucrose are added according to a ratio of 97:1:2 and are ball milled at a high speed of 300rpm for 8h at a temperature of 150 ℃, so as to obtain the composite material coated with the lithium silicon alloy/lithium silicate composite layer.
Example 7
The difference from example 1 is that in step (2), the disproportionated silicon monoxide, lithium metal and graphene are added according to a ratio of 85:5:10 and are subjected to high-speed ball milling at a speed of 700rpm and a temperature of 250 ℃ for 1h to obtain the composite material coated with the lithium silicon alloy/lithium silicate composite layer.
Example 8
The difference from example 1 is that in step (3), lithium tetrafluoroborate was dissolved in ethyl methyl carbonate to form a 0.5M fluorine-containing inorganic salt solution, the silica composite material obtained in step (2) was put into the fluorine-containing inorganic salt solution, and subjected to fluorination for 30min, solid-liquid separation, washing with an organic solvent, and drying.
Example 9
The difference from the example 1 is that in the step (3), the sealed reactor is filled with the silicon oxide composite material obtained in the step (2), SiF4 is introduced, and the reaction is carried out for 30min, so as to obtain the fluorinated silicon oxide composite material.
Example 10
The difference from example 1 is that in step (3), a perfluoro resin is used as a fluorine source, and the perfluoro resin and the silica composite material obtained in step (2) are heated to 300 ℃ for 15min under the condition of being separated, so as to obtain the fluorinated silica composite material.
Example 11
The difference from the embodiment 1 is that in the step (4), the fluorinated silica composite material obtained in the step (3) is subjected to liquid phase coating by using paraffin as a carbon source, and is carbonized to obtain the final silica composite material. The carbon coating layer accounts for 2.2 percent of the mass and has the thickness of 1.2 mu m.
Example 12
The difference from the embodiment 1 is that in the step (4), the fluorinated silica composite material obtained in the step (3) is subjected to liquid phase coating by using heavy oil as a carbon source, and is carbonized to obtain the final silica composite material. The carbon coating layer accounts for 1.1 percent of the mass and has the thickness of 0.8 mu m.
Example 13
The difference from the embodiment 1 is that in the step (4), acetylene is used as a carbon source to perform chemical vapor coating on the silica composite material obtained in the step (3), and the final silica composite material is obtained after coating. The carbon coating layer accounts for 1.0 percent of the mass and has a thickness of 0.7 mu m.
Example 14
The difference from the embodiment 1 is that in the step (4), styrene is used as a carbon source to perform chemical vapor phase coating on the silica composite material obtained in the step (3), and the final silica composite material is obtained after coating. The carbon coating layer accounts for 1.3 percent of the mass and has a thickness of 1.0 mu m.
Comparative example 1
(1) Disproportionating the micron-sized silicon oxide material at the high temperature of 1000 ℃ for 2 h.
(2) And (2) performing liquid phase coating on the silicon oxide material obtained in the step (1) by using coal tar as a carbon source, and carbonizing for 2 hours at 800 ℃ to obtain the final silicon oxide composite material. The carbon coating layer accounts for 2 percent of the mass and has the thickness of 1.0 mu m.
Comparative example 2
(1) Disproportionating the micron-sized silicon oxide material at the high temperature of 1000 ℃ for 2 h.
(2) The obtained disproportionated silica, metallic lithium and sucrose were added at a ratio of 95:2:3 and ball-milled at 190 ℃ for 1.5h at a high speed of 500rpm in a sealed Ar gas-filled ball mill to obtain a composite material coated with a lithium silicon alloy/lithium silicate composite layer.
Comparative example 3
(1) Disproportionating the micron-sized silicon oxide material at the high temperature of 1000 ℃ for 2 h.
(2) The obtained disproportionated silica, metallic lithium and sucrose were added at a ratio of 95:2:3 and ball-milled at 190 ℃ for 1.5h at a high speed of 500rpm in a sealed Ar gas-filled ball mill to obtain a composite material coated with a lithium silicon alloy/lithium silicate composite layer.
(3) And (3) performing liquid phase coating on the silicon oxide composite material obtained in the step (3) by using coal tar as a carbon source, and carbonizing for 2 hours at 800 ℃ to obtain the final silicon oxide composite material. The carbon coating layer accounts for 2 percent of the mass and has the thickness of 1.5 mu m.
Comparative example 4
(1) Adding micron-sized silicon monoxide material obtained without disproportionation and pulverization, lithium metal and cane sugar according to a ratio of 95:2:3 in a sealed Ar gas-filled ball mill, and carrying out high-speed ball milling at 500rpm for 1.5h at 190 ℃ to obtain the composite material coated with the lithium silicon alloy/lithium silicate composite layer.
(2) Dissolving ammonium bifluoride in ethyl methyl carbonate to form 0.2M fluorine-containing inorganic salt solution, adding the silica composite material obtained in the step (1) into the fluorine-containing inorganic salt solution, performing fluorination for 15min, separating solid from liquid, cleaning with an organic solvent, and drying.
(3) And (3) performing liquid phase coating on the silicon oxide composite material obtained in the step (3) by using coal tar as a carbon source, and carbonizing for 2 hours at 800 ℃ to obtain the final silicon oxide composite material. The carbon coating layer accounts for 2 percent of the mass and has the thickness of 1.5 mu m.
Comparative example 5
Comparative example 5 differs from example 1 only in step (2), step (2) of comparative example 5 and no carbon source was added during the ball milling process.
(2) In a sealed ball mill filled with Ar gas, the obtained disproportionated silicon monoxide and metallic lithium are added according to a ratio of 95:2 and are subjected to high-speed ball milling for 1.5h at a speed of 500rpm under the condition of 190 ℃, and a composite material coated with a lithium silicon alloy/lithium silicate composite layer (lithium silicon composite layer) is obtained.
Comparative example 6
Comparative example 6 differs from example 1 only in step (2), and the ball milling temperature in step (2) of comparative example 6 is 100 ℃.
Comparative example 7
Comparative example 7 differs from example 1 only in step (2), and the ball milling temperature in step (2) of comparative example 7 is 400 ℃.
Comparative example 8
Comparative example 8 differs from example 1 only in step (2), the dew point of the ball mill in step (2) of comparative example 8 being-20 ℃.
Electrochemical testing:
1) preparation of negative plate
Mixing the silica composite material finally prepared in the examples and the comparative examples with graphite according to the mass ratio of 1:10 to prepare a negative electrode active material with the specific capacity of 450mAh/g, mixing the negative electrode active material, conductive carbon black (SP) serving as a conductive agent and a binder (CMC-SBR,1/1wt) according to the mass ratio of 95:2:3, adding a proper amount of deionized water to obtain negative electrode active slurry, coating the negative electrode active slurry on two functional surfaces of a Cu foil, and dryingAnd obtaining the negative plate. The surface density of the negative plate is 10mg/cm2The compacted density is 1.5g/cm3。
2) Preparation of Positive plate
Mixing Li (Ni)0.5Co0.2Mn0.3)O2Mixing the positive electrode active material, SP and PVDF binder at a mass ratio of 94:3:3, adding N-methylpyrrolidone (NMP) to obtain positive electrode active slurry, and coating the positive electrode active slurry on the functional surface of the carbon-coated Al foil to obtain a positive electrode sheet.
3) Electricity buckling preparation method for lithium ion battery
Cutting the negative electrode piece obtained in the step 1) into a circular piece with the diameter of 14mm, and assembling into a 2032 type buckling battery.
4) Preparation of lithium ion soft package full battery
Assembling the negative plate obtained in the step 1), the positive plate obtained in the step 2) and the diaphragm into a battery, and injecting electrolyte to prepare the soft package full battery.
Assembling the negative plate obtained in the step 1), the positive plate obtained in the step 2) and the diaphragm into a battery, and injecting electrolyte to prepare the soft package full battery.
Electrochemical tests were performed under the same conditions on the batteries prepared in the examples and comparative examples, and the results are shown in table 1 below.
TABLE 1
The technical features of the embodiments described above may be arbitrarily combined, and for the sake of brevity, all possible combinations of the technical features in the embodiments described above are not described, but should be considered as being within the scope of the present specification as long as there is no contradiction between the combinations of the technical features.
The above-mentioned embodiments only express several embodiments of the present invention, and the description thereof is more specific and detailed, but not construed as limiting the scope of the invention. It should be noted that, for a person skilled in the art, several variations and modifications can be made without departing from the inventive concept, which falls within the scope of the present invention. Therefore, the protection scope of the present patent shall be subject to the appended claims.
Claims (10)
1. The composite material containing the silicon monoxide is characterized by being of a core-shell structure and comprising an inner core, an intermediate layer, a secondary outer layer and an outermost layer from inside to outside, wherein the inner core is made of the silicon monoxide, the intermediate layer is made of a lithium silicon composite material, the secondary outer layer is made of fluoride, the outermost layer is a carbon coating layer, and the silicon monoxide is SiOxWherein 0.5<x<1.5。
2. The composite material containing silica according to claim 1, wherein the particle size D50 of the inner core is 0.5 to 20 μm, the thickness of the intermediate layer is 0.01 to 2 μm, the thickness of the secondary outer layer is 2 to 200nm, the thickness of the outermost layer is 0.01 to 1 μm, and the weight ratio of the outermost layer to the silica-containing composite material is 1 to 15%.
3. The method for producing a composite material containing a silicon oxide according to any one of claims 1 to 2, comprising the steps of:
a. disproportionating the silicon monoxide at 750-1100 deg.c for 1-5 hr;
b. in a non-oxidizing atmosphere, mixing the disproportionated silicon monoxide, the metal lithium and a carbon source and then carrying out ball milling;
c. carrying out fluorination treatment on the product obtained in the step b;
d. and c, coating the product obtained in the step c with carbon.
4. The method for preparing a composite material containing silicon monoxide according to claim 3, wherein the disproportionation temperature in step a is 750-1000 ℃ and the disproportionation time is 1-5 h.
5. The composite comprising siliconoxide of claim 4The preparation method of the material is characterized in that the structure of the disproportionated silicon monoxide in the step a is the coexistence of the following three structures: silicon nano-domain, SiO2Cluster and between silicon nano crystal domain and SiO2A sub-oxidized interfacial region between the two clusters.
6. The method for preparing a composite material containing silicon monoxide according to claim 3, wherein in the step b, the mass ratio of the disproportionated silicon monoxide, the metallic lithium and the carbon source is (100-x-y): x: y, wherein 1< x <5, and 2< y < 10.
7. The method for preparing the composite material containing the silicon monoxide according to claim 3, wherein in the step b, the temperature of the ball milling process is 150 ℃ to 250 ℃, and the dew point of the environment in which the ball milling process is carried out is below-30 ℃; and/or the presence of a gas in the gas,
in the step b, the ball-material ratio in the ball milling process is (20-40): 1, the ball milling speed is 300-700 rpm, the ball milling time is 1-8 h, and the particle size of the ball milling medium is 3-20 mm.
8. The method for preparing a composite material containing silicon monoxide according to any one of claims 3 to 7, wherein in the step c, the step of fluorination treatment is to fluorinate the product obtained in the step b by using a fluorine-containing compound;
the fluorine-containing compound is selected from fluorine-containing inorganic salts or liquid fluorine-containing organic matters, and in the step c, the fluorination treatment is liquid phase reaction; alternatively, the first and second electrodes may be,
the fluorine-containing compound is selected from solid fluorine-containing organic matters, and in the step c, the fluorination treatment is to release fluorine carbon free radicals in a heating mode to react with the product obtained in the step b; alternatively, the first and second electrodes may be,
and in the step c, the fluoridation treatment is to place the product obtained in the step b in a reaction kettle and introduce fluorine-containing gas for reaction.
9. A negative electrode sheet comprising a current collector and a negative electrode active layer provided on the current collector, wherein the negative electrode active layer has the composite material containing silicon oxide according to any one of claims 1 to 2 or the composite material containing silicon oxide prepared by the method for preparing the composite material containing silicon oxide according to any one of claims 3 to 8.
10. A lithium battery comprising a positive electrode sheet, the negative electrode sheet according to claim 9, a separator, and a nonaqueous electrolyte.
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