CN114937765A - Modified polyimide-coated silicon/lithium silicate negative electrode material, preparation method thereof and lithium ion battery - Google Patents
Modified polyimide-coated silicon/lithium silicate negative electrode material, preparation method thereof and lithium ion battery Download PDFInfo
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- CN114937765A CN114937765A CN202210588124.0A CN202210588124A CN114937765A CN 114937765 A CN114937765 A CN 114937765A CN 202210588124 A CN202210588124 A CN 202210588124A CN 114937765 A CN114937765 A CN 114937765A
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- lithium silicate
- conductive carbon
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- 229910052710 silicon Inorganic materials 0.000 title claims abstract description 157
- 239000010703 silicon Substances 0.000 title claims abstract description 157
- PAZHGORSDKKUPI-UHFFFAOYSA-N lithium metasilicate Chemical compound [Li+].[Li+].[O-][Si]([O-])=O PAZHGORSDKKUPI-UHFFFAOYSA-N 0.000 title claims abstract description 110
- 229910052912 lithium silicate Inorganic materials 0.000 title claims abstract description 110
- 239000004642 Polyimide Substances 0.000 title claims abstract description 78
- 229920001721 polyimide Polymers 0.000 title claims abstract description 78
- HBBGRARXTFLTSG-UHFFFAOYSA-N Lithium ion Chemical compound [Li+] HBBGRARXTFLTSG-UHFFFAOYSA-N 0.000 title claims abstract description 63
- 229910001416 lithium ion Inorganic materials 0.000 title claims abstract description 63
- 238000002360 preparation method Methods 0.000 title claims abstract description 30
- 239000007773 negative electrode material Substances 0.000 title claims description 25
- XUIMIQQOPSSXEZ-UHFFFAOYSA-N Silicon Chemical compound [Si] XUIMIQQOPSSXEZ-UHFFFAOYSA-N 0.000 claims abstract description 156
- 239000002131 composite material Substances 0.000 claims abstract description 123
- 239000011247 coating layer Substances 0.000 claims abstract description 33
- 238000000498 ball milling Methods 0.000 claims abstract description 22
- 238000000034 method Methods 0.000 claims abstract description 15
- 239000000463 material Substances 0.000 claims abstract description 13
- 239000005543 nano-size silicon particle Substances 0.000 claims abstract description 10
- 239000010405 anode material Substances 0.000 claims abstract description 9
- 239000000178 monomer Substances 0.000 claims description 71
- WMFOQBRAJBCJND-UHFFFAOYSA-M Lithium hydroxide Chemical compound [Li+].[OH-] WMFOQBRAJBCJND-UHFFFAOYSA-M 0.000 claims description 51
- GTDPSWPPOUPBNX-UHFFFAOYSA-N ac1mqpva Chemical compound CC12C(=O)OC(=O)C1(C)C1(C)C2(C)C(=O)OC1=O GTDPSWPPOUPBNX-UHFFFAOYSA-N 0.000 claims description 49
- 239000003575 carbonaceous material Substances 0.000 claims description 38
- LIVNPJMFVYWSIS-UHFFFAOYSA-N silicon monoxide Chemical compound [Si-]#[O+] LIVNPJMFVYWSIS-UHFFFAOYSA-N 0.000 claims description 38
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 claims description 37
- 150000004985 diamines Chemical class 0.000 claims description 30
- 238000010438 heat treatment Methods 0.000 claims description 22
- LFQSCWFLJHTTHZ-UHFFFAOYSA-N Ethanol Chemical compound CCO LFQSCWFLJHTTHZ-UHFFFAOYSA-N 0.000 claims description 19
- 239000011259 mixed solution Substances 0.000 claims description 18
- 238000001694 spray drying Methods 0.000 claims description 18
- CSCPPACGZOOCGX-UHFFFAOYSA-N Acetone Chemical compound CC(C)=O CSCPPACGZOOCGX-UHFFFAOYSA-N 0.000 claims description 15
- ZMXDDKWLCZADIW-UHFFFAOYSA-N N,N-Dimethylformamide Chemical compound CN(C)C=O ZMXDDKWLCZADIW-UHFFFAOYSA-N 0.000 claims description 15
- 239000002041 carbon nanotube Substances 0.000 claims description 15
- 229910021393 carbon nanotube Inorganic materials 0.000 claims description 15
- 229910003002 lithium salt Inorganic materials 0.000 claims description 15
- 159000000002 lithium salts Chemical class 0.000 claims description 15
- 229920000642 polymer Polymers 0.000 claims description 15
- 239000002904 solvent Substances 0.000 claims description 15
- 239000010406 cathode material Substances 0.000 claims description 14
- 238000006116 polymerization reaction Methods 0.000 claims description 14
- 239000002245 particle Substances 0.000 claims description 11
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims description 11
- 229910001868 water Inorganic materials 0.000 claims description 11
- IAZDPXIOMUYVGZ-UHFFFAOYSA-N Dimethylsulphoxide Chemical compound CS(C)=O IAZDPXIOMUYVGZ-UHFFFAOYSA-N 0.000 claims description 10
- ZUOUZKKEUPVFJK-UHFFFAOYSA-N diphenyl Chemical compound C1=CC=CC=C1C1=CC=CC=C1 ZUOUZKKEUPVFJK-UHFFFAOYSA-N 0.000 claims description 10
- USIUVYZYUHIAEV-UHFFFAOYSA-N diphenyl ether Chemical compound C=1C=CC=CC=1OC1=CC=CC=C1 USIUVYZYUHIAEV-UHFFFAOYSA-N 0.000 claims description 10
- 229920000049 Carbon (fiber) Polymers 0.000 claims description 9
- 229910010941 LiFSI Inorganic materials 0.000 claims description 9
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N Silicium dioxide Chemical compound O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 claims description 9
- 239000006230 acetylene black Substances 0.000 claims description 9
- 239000004917 carbon fiber Substances 0.000 claims description 9
- 229910021389 graphene Inorganic materials 0.000 claims description 9
- VDVLPSWVDYJFRW-UHFFFAOYSA-N lithium;bis(fluorosulfonyl)azanide Chemical compound [Li+].FS(=O)(=O)[N-]S(F)(=O)=O VDVLPSWVDYJFRW-UHFFFAOYSA-N 0.000 claims description 9
- VNWKTOKETHGBQD-UHFFFAOYSA-N methane Chemical compound C VNWKTOKETHGBQD-UHFFFAOYSA-N 0.000 claims description 9
- 238000002156 mixing Methods 0.000 claims description 7
- CBCKQZAAMUWICA-UHFFFAOYSA-N 1,4-phenylenediamine Chemical compound NC1=CC=C(N)C=C1 CBCKQZAAMUWICA-UHFFFAOYSA-N 0.000 claims description 5
- VLDPXPPHXDGHEW-UHFFFAOYSA-N 1-chloro-2-dichlorophosphoryloxybenzene Chemical compound ClC1=CC=CC=C1OP(Cl)(Cl)=O VLDPXPPHXDGHEW-UHFFFAOYSA-N 0.000 claims description 5
- NYJFVPGIOAESNA-UHFFFAOYSA-N 4-(4-propylphenoxy)benzene-1,3-diamine Chemical compound NC1=C(C=CC(=C1)N)OC1=CC=C(C=C1)CCC NYJFVPGIOAESNA-UHFFFAOYSA-N 0.000 claims description 5
- 229910013188 LiBOB Inorganic materials 0.000 claims description 5
- 239000012298 atmosphere Substances 0.000 claims description 5
- RWCCWEUUXYIKHB-UHFFFAOYSA-N benzophenone Chemical compound C=1C=CC=CC=1C(=O)C1=CC=CC=C1 RWCCWEUUXYIKHB-UHFFFAOYSA-N 0.000 claims description 5
- 239000012965 benzophenone Substances 0.000 claims description 5
- 235000010290 biphenyl Nutrition 0.000 claims description 5
- 239000004305 biphenyl Substances 0.000 claims description 5
- VKIRRGRTJUUZHS-UHFFFAOYSA-N cyclohexane-1,4-diamine Chemical compound NC1CCC(N)CC1 VKIRRGRTJUUZHS-UHFFFAOYSA-N 0.000 claims description 5
- 229910013870 LiPF 6 Inorganic materials 0.000 claims description 4
- 230000001681 protective effect Effects 0.000 claims description 4
- 239000000377 silicon dioxide Substances 0.000 claims description 4
- 230000035484 reaction time Effects 0.000 claims description 2
- 238000004519 manufacturing process Methods 0.000 claims 1
- 230000000694 effects Effects 0.000 abstract description 12
- 230000002441 reversible effect Effects 0.000 abstract description 9
- 230000008569 process Effects 0.000 abstract description 8
- 238000007599 discharging Methods 0.000 abstract description 4
- 238000009776 industrial production Methods 0.000 abstract description 4
- 238000005265 energy consumption Methods 0.000 abstract description 3
- 230000007613 environmental effect Effects 0.000 abstract 1
- 239000000243 solution Substances 0.000 description 20
- 239000012299 nitrogen atmosphere Substances 0.000 description 14
- 238000003756 stirring Methods 0.000 description 12
- 238000001035 drying Methods 0.000 description 7
- HLBLWEWZXPIGSM-UHFFFAOYSA-N 4-Aminophenyl ether Chemical compound C1=CC(N)=CC=C1OC1=CC=C(N)C=C1 HLBLWEWZXPIGSM-UHFFFAOYSA-N 0.000 description 6
- WHXSMMKQMYFTQS-UHFFFAOYSA-N Lithium Chemical compound [Li] WHXSMMKQMYFTQS-UHFFFAOYSA-N 0.000 description 6
- 239000006185 dispersion Substances 0.000 description 6
- 229910052744 lithium Inorganic materials 0.000 description 6
- 238000012216 screening Methods 0.000 description 6
- 239000011343 solid material Substances 0.000 description 6
- 230000000052 comparative effect Effects 0.000 description 5
- 239000011159 matrix material Substances 0.000 description 5
- 239000002210 silicon-based material Substances 0.000 description 5
- 238000001132 ultrasonic dispersion Methods 0.000 description 5
- 239000007772 electrode material Substances 0.000 description 4
- 239000003792 electrolyte Substances 0.000 description 4
- 238000009830 intercalation Methods 0.000 description 4
- 230000002687 intercalation Effects 0.000 description 4
- 230000002829 reductive effect Effects 0.000 description 4
- HMDDXIMCDZRSNE-UHFFFAOYSA-N [C].[Si] Chemical compound [C].[Si] HMDDXIMCDZRSNE-UHFFFAOYSA-N 0.000 description 3
- 239000011248 coating agent Substances 0.000 description 3
- 238000000576 coating method Methods 0.000 description 3
- 238000013329 compounding Methods 0.000 description 3
- 125000005842 heteroatom Chemical group 0.000 description 3
- 230000000379 polymerizing effect Effects 0.000 description 3
- 238000011160 research Methods 0.000 description 3
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 description 2
- 229910001290 LiPF6 Inorganic materials 0.000 description 2
- 239000013543 active substance Substances 0.000 description 2
- 230000009286 beneficial effect Effects 0.000 description 2
- 239000011230 binding agent Substances 0.000 description 2
- 229910052799 carbon Inorganic materials 0.000 description 2
- 238000009831 deintercalation Methods 0.000 description 2
- 229910002804 graphite Inorganic materials 0.000 description 2
- 239000010439 graphite Substances 0.000 description 2
- 238000003837 high-temperature calcination Methods 0.000 description 2
- 230000002427 irreversible effect Effects 0.000 description 2
- 238000012986 modification Methods 0.000 description 2
- 230000004048 modification Effects 0.000 description 2
- 239000000843 powder Substances 0.000 description 2
- 239000002994 raw material Substances 0.000 description 2
- RYGMFSIKBFXOCR-UHFFFAOYSA-N Copper Chemical compound [Cu] RYGMFSIKBFXOCR-UHFFFAOYSA-N 0.000 description 1
- 229910013872 LiPF Inorganic materials 0.000 description 1
- 101150058243 Lipf gene Proteins 0.000 description 1
- 239000004743 Polypropylene Substances 0.000 description 1
- 230000008859 change Effects 0.000 description 1
- 238000006243 chemical reaction Methods 0.000 description 1
- 239000006258 conductive agent Substances 0.000 description 1
- 238000010276 construction Methods 0.000 description 1
- 238000007796 conventional method Methods 0.000 description 1
- 239000011889 copper foil Substances 0.000 description 1
- 238000005520 cutting process Methods 0.000 description 1
- 230000001351 cycling effect Effects 0.000 description 1
- 238000013461 design Methods 0.000 description 1
- 238000001514 detection method Methods 0.000 description 1
- 238000011161 development Methods 0.000 description 1
- 238000004146 energy storage Methods 0.000 description 1
- 238000003912 environmental pollution Methods 0.000 description 1
- 238000011065 in-situ storage Methods 0.000 description 1
- 238000011031 large-scale manufacturing process Methods 0.000 description 1
- 230000000670 limiting effect Effects 0.000 description 1
- 238000006138 lithiation reaction Methods 0.000 description 1
- 230000007774 longterm Effects 0.000 description 1
- 238000005259 measurement Methods 0.000 description 1
- 239000000203 mixture Substances 0.000 description 1
- 229910052757 nitrogen Inorganic materials 0.000 description 1
- HZBAVWLZSLOCFR-UHFFFAOYSA-N oxosilane Chemical compound [SiH2]=O HZBAVWLZSLOCFR-UHFFFAOYSA-N 0.000 description 1
- 229920000767 polyaniline Polymers 0.000 description 1
- 229920001690 polydopamine Polymers 0.000 description 1
- 239000002861 polymer material Substances 0.000 description 1
- 229920001155 polypropylene Polymers 0.000 description 1
- 229920000128 polypyrrole Polymers 0.000 description 1
- 238000010298 pulverizing process Methods 0.000 description 1
- 230000009467 reduction Effects 0.000 description 1
- 238000005096 rolling process Methods 0.000 description 1
- 238000000926 separation method Methods 0.000 description 1
- 229910052814 silicon oxide Inorganic materials 0.000 description 1
- 239000002002 slurry Substances 0.000 description 1
- 239000007787 solid Substances 0.000 description 1
- 239000007858 starting material Substances 0.000 description 1
- 230000002195 synergetic effect Effects 0.000 description 1
- 238000012360 testing method Methods 0.000 description 1
- 238000001291 vacuum drying Methods 0.000 description 1
Classifications
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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
-
- 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
- C01B33/02—Silicon
- C01B33/021—Preparation
- C01B33/023—Preparation by reduction of silica or free silica-containing material
-
- 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
- C01B33/20—Silicates
- C01B33/32—Alkali metal silicates
-
- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08G—MACROMOLECULAR COMPOUNDS OBTAINED OTHERWISE THAN BY REACTIONS ONLY INVOLVING UNSATURATED CARBON-TO-CARBON BONDS
- C08G73/00—Macromolecular compounds obtained by reactions forming a linkage containing nitrogen with or without oxygen or carbon in the main chain of the macromolecule, not provided for in groups C08G12/00 - C08G71/00
- C08G73/06—Polycondensates having nitrogen-containing heterocyclic rings in the main chain of the macromolecule
- C08G73/10—Polyimides; Polyester-imides; Polyamide-imides; Polyamide acids or similar polyimide precursors
- C08G73/1003—Preparatory processes
- C08G73/1007—Preparatory processes from tetracarboxylic acids or derivatives and diamines
- C08G73/1028—Preparatory processes from tetracarboxylic acids or derivatives and diamines characterised by the process itself, e.g. steps, continuous
- C08G73/1032—Preparatory processes from tetracarboxylic acids or derivatives and diamines characterised by the process itself, e.g. steps, continuous characterised by the solvent(s) used
-
- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08G—MACROMOLECULAR COMPOUNDS OBTAINED OTHERWISE THAN BY REACTIONS ONLY INVOLVING UNSATURATED CARBON-TO-CARBON BONDS
- C08G73/00—Macromolecular compounds obtained by reactions forming a linkage containing nitrogen with or without oxygen or carbon in the main chain of the macromolecule, not provided for in groups C08G12/00 - C08G71/00
- C08G73/06—Polycondensates having nitrogen-containing heterocyclic rings in the main chain of the macromolecule
- C08G73/10—Polyimides; Polyester-imides; Polyamide-imides; Polyamide acids or similar polyimide precursors
- C08G73/1067—Wholly aromatic polyimides, i.e. having both tetracarboxylic and diamino moieties aromatically bound
- C08G73/1071—Wholly aromatic polyimides containing oxygen in the form of ether bonds in the main chain
-
- 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
-
- 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
- H01M4/62—Selection of inactive substances as ingredients for active masses, e.g. binders, fillers
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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
- H01M4/62—Selection of inactive substances as ingredients for active masses, e.g. binders, fillers
- H01M4/624—Electric conductive fillers
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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
- H01M4/62—Selection of inactive substances as ingredients for active masses, e.g. binders, fillers
- H01M4/628—Inhibitors, e.g. gassing inhibitors, corrosion inhibitors
-
- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- 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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- 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 provides a silicon composite material, which comprises a silicon/lithium silicate composite material and a modified polyimide coating layer coated on the silicon/lithium silicate composite material; the modified polyimide is lithium ion doped polyimide. The modified polyimide with the specific structure coats the silicon/lithium silicate anode material, and the silicon/lithium silicate composite material has a structure that nano silicon particles are uniformly dispersed in a lithium silicate phase. The lithium silicate phase in the invention can improve the conductivity of lithium ion and buffer the volume expansion of silicon in the charging and discharging process. The polyimide coating layer has excellent mechanical properties, and the material is ensured to have higher first effect after being modified by lithium ions, high reversible capacity and excellent cycle performance. The preparation method provided by the invention is used for preparing the silicon/lithium silicate composite material by simple mechanical ball milling, has the advantages of low energy consumption, cost saving, environmental protection, simple preparation process, industrial production and high practicability, and has wide application prospect in the aspect of lithium ion battery cathodes.
Description
Technical Field
The invention belongs to the technical field of silicon composite materials, relates to a silicon composite material and a preparation method thereof, and a lithium ion battery, and particularly relates to a modified polyimide-coated silicon/lithium silicate negative electrode material and a preparation method thereof, and a lithium ion battery.
Background
The lithium ion battery has the advantages of high energy density, high output voltage, long cycle life, small environmental pollution and the like, and has extremely important application in the fields of electronic products, electric automobiles, energy storage and the like. The current commercialized lithium ion battery cathode material is mainly graphite cathode material, the theoretical capacity of which is only 372mAh/g, the actual capacity is 340-360 mAh/g, and the design requirement of high-specific energy battery cannot be met. Therefore, the development of a new-generation negative electrode material with high specific capacity, good cycle stability and rate capability for wide application in electronic products and electric vehicles has become a key issue for research in the field of batteries.
The silicon-based material has rich sources and higher specific capacity (4200mAh/g), and meanwhile, the lithium intercalation potential (0.4V) of the silicon-based material is close to the lithium intercalation potential (0.1V) of graphite, so that the silicon-based material is an ideal negative electrode material of a high-specific-energy battery. However, the silicon material has poor conductivity and serious volume effect generated during electrochemical lithium intercalation and deintercalation, which causes the damage of material structure and mechanical pulverization, leads to the separation between electrode materials and between the electrode materials and a current collector, and further loses electric contact, and leads to the rapid reduction of the cycle performance of the electrode. The current solution to this problem is to use materials with lower expansion coefficients as the matrix, and to inlay or encapsulate active silicon in these matrix materials to alleviate the volume change caused by the intercalation and deintercalation of lithium ions. The matrix material acts to cushion mechanical stresses. The more common matrix materials are carbon-based materials and polymer materials. However, compared with silicon, carbon-based materials have better mechanical properties and lower volume expansion rate (only 9%, which is much lower than 400% of silicon), but absolute volume expansion still exists, so the volume effect of silicon can be relieved to a certain extent by the construction method of the composite materials, but the long-term electrochemical cycling stability of the silicon-based materials is not remarkably improved. Moreover, in the subsequent cycle, as the cycle reaction continues, the interfacial bonding between the matrix material and the silicon active center is seriously damaged due to the mismatch of volume expansion, and the electrochemical cycle performance is reduced. For example, patent application with publication number CN108321368A discloses a polymer-coated silicon/lithium metasilicate negative electrode material and a preparation method thereof, which is to prepare a silicon/lithium metasilicate composite material by ball milling active lithium powder and silicon monoxide in an inert atmosphere, and polymerize polymers such as polyaniline, polypyrrole, polydopamine and the like in situ on the surface of the composite material. Firstly, lithium powder has high activity and strict requirements on environment, and is not suitable for industrial production. Meanwhile, polar heteroatoms in the polymer can consume lithium ions in the electrolyte, so that the first cycle efficiency is reduced, and the first efficiency of the electrode material prepared by the electrode material is only 70%, so that the requirement of a commercialized product of the cathode material is not met.
Therefore, how to find a more suitable way to solve the above problems of the existing silicon negative electrode, and to obtain a silicon carbon negative electrode product with high reversible capacity, excellent cycle performance, commercialization suitability for industrial popularization and application, has become one of the problems to be solved by many front-line researchers and scientific research type enterprises.
Disclosure of Invention
In view of the above, the technical problem to be solved by the present invention is to provide a silicon composite material, a preparation method thereof, and a lithium ion battery, in particular, a lithium ion battery modified polyimide-coated silicon/lithium silicate negative electrode material. The silicon composite material provided by the invention has the characteristics of high reversible capacity, excellent cycle performance and the like, and the process is simple and feasible, is convenient for large-scale production, has high practicability, and has wide application prospect in the aspect of lithium ion battery cathodes.
The invention provides a silicon composite material, which comprises a silicon/lithium silicate composite material and a modified polyimide coating layer coated on the silicon/lithium silicate composite material;
the modified polyimide is lithium ion doped polyimide.
Preferably, in the silicon/lithium silicate composite material, nano silicon particles are dispersed in the lithium silicate material;
the particle size of the nano silicon particles is more than or equal to 10 nm;
the lithium ion doped polyimide comprises a lithium ion modified polyimide.
Preferably, in the silicon composite material, the mass content of the silicon/lithium silicate composite material is 93-99%;
the D50 particle size of the silicon composite material is 1-10 mu m;
the silicon composite material is a lithium ion battery cathode material.
Preferably, the silicon composite material further comprises a conductive carbon material;
the conductive carbon material comprises one or more of conductive carbon black, acetylene black, carbon nanotubes, graphene and carbon fibers;
the conductive carbon material comprises one or more of a conductive carbon material compounded on the silicon/lithium silicate composite material, a conductive carbon material coated on the silicon/lithium silicate composite material, a conductive carbon material doped in the modified polyimide coating layer and a conductive carbon material compounded on the modified polyimide coating layer.
The invention provides a preparation method of a silicon composite material, which comprises the following steps:
1) under protective atmosphere, carrying out ball milling on the silicon monoxide, the lithium hydroxide and the mixed solution to obtain a silicon/lithium silicate composite material;
2) and mixing the silicon/lithium silicate composite material obtained in the step, a polymer monomer and a solvent containing lithium salt, carrying out polymerization reaction, and carrying out spray drying and heating curing to obtain the silicon composite material.
Preferably, the particle size of the silicon monoxide is 3-10 μm;
the atomic ratio of Si to O in the silicon monoxide is n, wherein n is more than or equal to 0.8 and less than 1.6;
the molar ratio of the silicon monoxide to the lithium hydroxide is (6-9): 1;
the mixed solution comprises a mixed solution of water and alcohol;
the ball milling time is 6-10 h.
Preferably, the polymer monomers include dianhydride monomers and diamine monomers;
the dianhydride monomer comprises one or more of pyromellitic dianhydride, benzophenone dianhydride, biphenyl dianhydride, diphenyl ether dianhydride and 1,2,4, 5-pyromellitic dianhydride;
the diamine monomer comprises one or more of p-phenylenediamine, 4' -diamino-3, 3 ' -dimethyl biphenyl, 4' -diamino diphenyl sulfone, 2-bis [4- (2, 4-diamino phenoxy) phenyl ] propane and 1, 4-diaminocyclohexane;
the molar ratio of the dianhydride monomer to the diamine monomer is (1-1.05): 1;
the step 2) also comprises a conductive carbon material.
Preferably, the conductive carbon material comprises one or more of conductive carbon black, acetylene black, carbon nanotubes, graphene and carbon fibers;
the lithium salt comprises LiBOB and LiPF 6 And one or more of LiFSI;
the molar ratio of the lithium salt to the dianhydride monomer is (1-15): 100, respectively;
the solvent comprises one or more of acetone, dimethyl sulfoxide and N, N-dimethylformamide;
the step 2) is specifically as follows:
mixing a conductive carbon material, a lithium salt, a dianhydride monomer and a solvent, adding a diamine monomer for polymerization, adding the silicon/lithium silicate composite material obtained in the step, and finally performing spray drying and heating curing to obtain the silicon composite material.
Preferably, the temperature of the polymerization reaction is 40-70 ℃;
the polymerization reaction time is 1-4 h;
the temperature of the spray drying is 150-200 ℃;
the temperature of the heating and curing is 300-450 ℃;
the heating and curing time is 2-6 h.
The invention also provides a lithium ion battery, which comprises a positive electrode and a negative electrode;
the anode comprises a silicon composite anode material;
the silicon composite negative electrode material comprises the silicon composite material in any one of the technical schemes or the silicon composite material prepared by the preparation method in any one of the technical schemes.
The invention provides a silicon composite material, which comprises a silicon/lithium silicate composite material and a modified polyimide coating layer coated on the silicon/lithium silicate composite material; the modified polyimide is lithium ion doped polyimide. Compared with the prior art, the invention aims at improving the battery performance by the pre-lithiation process after the existing silicon-carbon cathode material is modified by mainly carbon coating, so that the cost is higher, and the carbon coating layer and the active substance are easy to mismatch in the circulation process to influence the electrochemical performance; and the polymer adopted in the prior stage is coated with the silicon-carbon negative electrode material, and polar heteroatoms in the polymer can consume lithium ions in electrolyte, so that the first cycle efficiency of the battery is influenced, and the like. The invention is based on the research that the heteroatom contained in the polymer coating layer can consume lithium ions in the electrolyte, thereby leading to the first irreversible capacity increase.
Based on the silicon composite material with a specific structure, the modified polyimide-coated silicon/lithium silicate negative electrode material comprises the silicon/lithium silicate composite material and a modified polyimide coating layer coated outside the composite material, the silicon/lithium silicate composite material has a structure that nano silicon particles (less than 10nm) are uniformly dispersed in a lithium silicate phase, and the modified polyimide coating layer is obtained by polymerizing a dianhydride monomer and a diamine monomer in a solvent containing lithium ions. The lithium silicate phase in the invention can improve the conductivity of lithium ion and buffer the volume expansion of silicon in the charging and discharging process. The polyimide coating layer has excellent mechanical properties, and the lithium ion modified polyimide coating layer ensures that the material has high first effect, high reversible capacity and excellent cycle performance.
The invention also provides a preparation method of the modified polyimide coated silicon/lithium silicate cathode material, the silicon/lithium silicate composite material is prepared by simple mechanical ball milling, high-temperature calcination in the traditional preparation method is abandoned, the energy consumption is greatly reduced, the cost is saved, the preparation method is green and environment-friendly, and the preparation method has the characteristics of simple preparation process, low requirement on environment, industrial production, high practicability and the like, and has wide application prospect in the aspect of lithium ion battery cathodes.
Experimental results show that the compounding of lithium silicate in the modified polyimide-coated silicon/lithium silicate negative electrode material prepared by the invention can obviously improve the ionic conductivity of the material, and simultaneously can buffer the volume effect (volume expansion) of silicon in the charge and discharge processes, thereby being beneficial to improving the conductivity of lithium ion; the polyimide coating layer has excellent mechanical properties, and the lithium ion modified polyimide coating layer ensures that the material has high first effect, reversible capacity and good cycle performance.
Detailed Description
For a further understanding of the invention, reference will now be made to the preferred embodiments of the invention by way of example, and it is to be understood that the description is intended to further illustrate features and advantages of the invention, and not to limit the scope of the claims.
All starting materials for the present invention, without particular limitation as to their source, may be purchased commercially or prepared according to conventional methods well known to those skilled in the art.
All the raw materials of the present invention are not particularly limited in their purity, and the present invention preferably employs an analytical grade or a conventional purity used in the field of lithium ion negative electrode preparation.
The invention provides a silicon composite material, which comprises a silicon/lithium silicate composite material and a modified polyimide coating layer coated on the silicon/lithium silicate composite material;
the modified polyimide is lithium ion doped polyimide.
In the present invention, the lithium ion doped polyimide preferably comprises a lithium ion modified polyimide.
In the present invention, in the silicon/lithium silicate composite material, the nano-silicon particles are preferably dispersed in the lithium silicate material.
In the present invention, the particle diameter of the nano-silicon particles is preferably 10nm or more, more preferably 12nm or more, and still more preferably 14nm or more.
In the present invention, the silicon/lithium silicate composite material has a mass content of preferably 93% to 99%, more preferably 94% to 98%, and still more preferably 95% to 97%.
In the invention, the D50 particle size of the silicon composite material is preferably 1-10 μm, more preferably 3-8 μm, and more preferably 5-6 μm.
In the present invention, the silicon composite material is preferably a lithium ion battery negative electrode material.
In the present invention, the silicon composite material preferably includes a conductive carbon material.
In the present invention, the conductive carbon material preferably includes one or more of conductive carbon black, acetylene black, carbon nanotubes, graphene, and carbon fibers, and more preferably conductive carbon black, acetylene black, carbon nanotubes, graphene, or carbon fibers.
In the present invention, the conductive carbon material preferably includes one or more of a conductive carbon material composited on the silicon/lithium silicate composite, a conductive carbon material coated on the silicon/lithium silicate composite, a conductive carbon material doped in the modified polyimide coating layer, and a conductive carbon material composited on the modified polyimide coating layer, and more preferably a conductive carbon material composited on the silicon/lithium silicate composite, a conductive carbon material coated on the silicon/lithium silicate composite, a conductive carbon material doped in the modified polyimide coating layer, and a conductive carbon material composited on the modified polyimide coating layer.
The invention is a complete and refined integral technical scheme, better ensures the specific structure and morphology of the composite material, better inhibits the silicon volume expansion, and further improves the first effect, reversible capacity and cycle performance of the battery, and the modified polyimide coated silicon/lithium silicate cathode material can be specifically as follows:
the silicon/lithium silicate composite material consists of a silicon/lithium silicate composite material and a modified polyimide coating layer coated outside the composite material. The silicon/lithium silicate composite material has a structure that nano silicon particles (less than 10nm) are uniformly dispersed in a lithium silicate phase, and the modified polyimide coating layer is obtained by polymerizing a dianhydride monomer and a diamine monomer in a solvent containing lithium ions.
Specifically, the weight content of the silicon/lithium silicate composite material in the negative electrode material is 93-99%, and the weight content of the modified polyimide coating layer in the negative electrode material is 0.5-7%.
Specifically, the particle size D50 of the modified polyimide coated silicon/lithium silicate negative electrode material is 1-10 μm, and preferably 3-7 μm.
The invention provides a preparation method of a silicon composite material, which comprises the following steps:
1) under protective atmosphere, carrying out ball milling on the silicon monoxide, the lithium hydroxide and the mixed solution to obtain a silicon/lithium silicate composite material;
2) and mixing the silicon/lithium silicate composite material obtained in the step, a polymer monomer and a solvent containing lithium salt, carrying out polymerization reaction, and carrying out spray drying and heating curing to obtain the silicon composite material.
In the invention, the silicon oxide, the lithium hydroxide and the mixed solution are ball-milled in a protective atmosphere to obtain the silicon/lithium silicate composite material.
In the present invention, the particle size of the silica is preferably 3 to 10 μm, more preferably 5 to 9 μm, and still more preferably 6 to 8 μm.
In the present invention, the atomic ratio of Si to O in the silylene oxide is n, preferably 0.8. ltoreq. n < 1.6, more preferably 0.9. ltoreq. n.ltoreq.1.5, more preferably 1.0. ltoreq. n.ltoreq.1.4, more preferably 1.1. ltoreq. n.ltoreq.1.3.
In the present invention, the molar ratio of the silicon monoxide to the lithium hydroxide is preferably (6 to 9): 1, more preferably (6.5 to 8.5): 1, more preferably (7-8): 1.
in the present invention, the mixed solution preferably includes a mixed solution of water and alcohol.
In the invention, the time for ball milling is preferably 6-10 h, more preferably 6.5-9.5 h, more preferably 7-9 h, and more preferably 7.5-8.5 h.
The silicon/lithium silicate composite material obtained in the step, a polymer monomer and a solvent containing lithium salt are mixed, then polymerization reaction is carried out, and the silicon/lithium silicate composite material is obtained after spray drying and heating curing.
In the present invention, the polymer monomer preferably includes a dianhydride monomer and a diamine monomer.
In the present invention, the dianhydride monomer preferably includes one or more of pyromellitic dianhydride, benzophenone dianhydride, biphenyl dianhydride, diphenyl ether dianhydride, and 1,2,4, 5-pyromellitic dianhydride, and more preferably pyromellitic dianhydride, benzophenone dianhydride, biphenyl dianhydride, diphenyl ether dianhydride, or 1,2,4, 5-pyromellitic dianhydride.
In the present invention, the diamine monomer preferably includes one or more of p-phenylenediamine, 4 '-diamino-3, 3' -dimethylbiphenyl, 4 '-diaminodiphenyl sulfone, 2-bis [4- (2, 4-diaminophenoxy) phenyl ] propane and 1, 4-diaminocyclohexane, and more preferably p-phenylenediamine, 4' -diamino-3, 3 '-dimethylbiphenyl, 4' -diaminodiphenyl sulfone, 2-bis [4- (2, 4-diaminophenoxy) phenyl ] propane or 1, 4-diaminocyclohexane.
In the present invention, the molar ratio of the dianhydride monomer to the diamine monomer is preferably (1 to 1.05): 1, more preferably (1.01 to 1.04): 1, more preferably (1.02 to 1.03): 1.
in the present invention, the step 2) preferably includes a conductive carbon material.
In the present invention, the conductive carbon material preferably includes one or more of conductive carbon black, acetylene black, carbon nanotubes, graphene, and carbon fibers, and more preferably conductive carbon black, acetylene black, carbon nanotubes, graphene, or carbon fibers.
In the present invention, the lithium salt preferably includes one or more of LiBOB, LiPF6, and LiFSI, and more preferably LiBOB, LiPF6, or LiFSI.
In the invention, the molar ratio of the lithium salt to the dianhydride monomer is preferably (1-15): 100, more preferably (4-12): 100, more preferably (7-9): 100.
in the present invention, the solvent preferably includes one or more of acetone, dimethyl sulfoxide and N, N-dimethylformamide, and more preferably acetone, dimethyl sulfoxide or N, N-dimethylformamide.
In the present invention, the step 2) is particularly preferably:
mixing a conductive carbon material, a lithium salt, a dianhydride monomer and a solvent, adding a diamine monomer for polymerization, adding the silicon/lithium silicate composite material obtained in the step, and finally performing spray drying and heating curing to obtain the silicon composite material.
In the invention, the polymerization reaction temperature is preferably 40-70 ℃, more preferably 45-65 ℃, and more preferably 50-60 ℃.
In the invention, the time of the polymerization reaction is preferably 1-4 h, more preferably 1.5-3.5 h, and more preferably 2-3 h.
In the invention, the temperature of the spray drying is preferably 150-200 ℃, more preferably 160-190 ℃, and more preferably 170-180 ℃.
In the invention, the heating and curing temperature is preferably 300-450 ℃, more preferably 330-420 ℃, and more preferably 360-390 ℃.
In the invention, the time for heating and curing is preferably 2-6 h, more preferably 2.5-5.5 h, more preferably 3-5 h, and more preferably 3.5-4.5 h.
The invention is a complete and refined integral preparation process, better ensures the specific structure and morphology of the composite material, better inhibits the silicon volume expansion, and further improves the first effect, reversible capacity and cycle performance of the battery, and the preparation method of the modified polyimide coated silicon/lithium silicate cathode material can specifically comprise the following steps:
the preparation method of the modified polyimide coated silicon/lithium silicate anode material comprises the following steps:
s1, preparing a silicon/lithium silicate composite material: taking a mixed solution (2:3) of silicon monoxide, lithium hydroxide and water/ethanol, and carrying out ball milling in a nitrogen atmosphere to obtain a silicon/lithium silicate composite material;
s2, preparing a modified polyimide coating layer: and uniformly dispersing the silicon/lithium metasilicate composite material, the conductive carbon material and the polymer monomer in the S1 in a lithium salt-containing solvent, carrying out polymerization reaction, and carrying out spray drying and heating curing to obtain the modified polyimide-coated silicon/lithium metasilicate negative electrode material.
Specifically, in the S1, the particle size of the silicon monoxide is 3-10 μm; the concentration of the lithium hydroxide is 1moL/L, and the purity of the nitrogen is 99.99%; the atomic ratio of Si to O in the silicon monoxide is n, wherein n is more than or equal to 0.8 and less than 1.6.
Specifically, in S1, the molar ratio of the silicon monoxide to the lithium hydroxide is 9:1 to 6: 1. The ball milling time is 6-10 h, and the ball milling is mechanical ball milling.
Specifically, in S2, the conductive carbon material is one or a mixture of more of conductive carbon black, acetylene black, carbon nanotubes, graphene, and carbon fibers; the lithium salt is LiBOB or LiPF 6 And one of LiFSI, the addition amount is 1% -15% of dianhydride monomer.
Specifically, in S2, the polymer monomers are dianhydride monomers and diamine monomers, and the ratio of dianhydride to diamine is 1-1.05: 1-1. The needed solvent is at least one of acetone, dimethyl sulfoxide and N, N-dimethylformamide.
Specifically, the dianhydride monomer comprises at least one of pyromellitic dianhydride, benzophenone dianhydride, biphenyl dianhydride, diphenyl ether dianhydride and 1,2,4, 5-pyromellitic dianhydride. The diamine monomer is at least one of p-phenylenediamine, 4' -diamino-3, 3 ' -dimethyl biphenyl, 4' -diamino diphenyl sulfone, 2-bis [4- (2, 4-diamino phenoxy) phenyl ] propane and 1, 4-diaminocyclohexane.
Specifically, in S2, the spray drying temperature is 150-200 ℃, the heating and curing conditions are 300-450 ℃, and the heating time is 2-6 hours.
The invention provides a lithium ion battery, which comprises a positive electrode and a negative electrode;
in the present invention, the anode preferably includes a silicon composite anode material
In the present invention, the silicon composite negative electrode material preferably includes the silicon composite material described in any one of the above technical schemes or the silicon composite material prepared by the preparation method described in any one of the above technical schemes.
The invention provides a modified polyimide-coated silicon/lithium silicate negative electrode material, a preparation method thereof and a lithium ion battery. The silicon/lithium silicate negative electrode material with the modified polyimide coating with the specific structure comprises a silicon/lithium silicate composite material and a modified polyimide coating layer coated outside the composite material, wherein the silicon/lithium silicate composite material has a structure that nano silicon particles (less than 10nm) are uniformly dispersed in a lithium silicate phase, and the modified polyimide coating layer is obtained by polymerizing a dianhydride monomer and a diamine monomer in a solvent containing lithium ions. The lithium silicate phase in the invention can improve the conductivity of lithium ion and buffer the volume expansion of silicon in the charging and discharging process. The polyimide coating layer has excellent mechanical properties, and the lithium ion modified polyimide coating layer ensures that the material has high first effect, high reversible capacity and excellent cycle performance.
The invention also provides a preparation method of the modified polyimide coated silicon/lithium silicate cathode material, the silicon/lithium silicate composite material is prepared by simple mechanical ball milling, high-temperature calcination in the traditional preparation method is abandoned, the energy consumption is greatly reduced, the cost is saved, the preparation method is green and environment-friendly, and the preparation method has the characteristics of simple preparation process, low requirement on environment, industrial production, high practicability and the like, and has wide application prospect in the aspect of lithium ion battery cathodes.
Experimental results show that the compounding of lithium silicate in the modified polyimide-coated silicon/lithium silicate negative electrode material prepared by the invention can obviously improve the ionic conductivity of the material, and simultaneously can buffer the volume effect (volume expansion) of silicon in the charge and discharge processes, thereby being beneficial to improving the conductivity of lithium ion; the polyimide coating layer has excellent mechanical properties, and the lithium ion modified polyimide coating layer ensures that the material has high first effect, reversible capacity and good cycle performance.
In order to further illustrate the present invention, a silicon composite material, a preparation method thereof, and a lithium ion battery provided by the present invention are described in detail below with reference to examples, but it should be understood that the examples are implemented on the premise of the technical solution of the present invention, and detailed embodiments and specific operation procedures are given, which are only for further illustrating the features and advantages of the present invention, but not for limiting the claims of the present invention, and the scope of protection of the present invention is not limited to the following examples.
Example 1
(1) Mechanically ball-milling 15.0g of silica, 5.4g of lithium hydroxide and 15g of water/ethanol mixed solution (2:3) in a nitrogen atmosphere for 8 hours, and drying in vacuum to obtain a silicon/lithium silicate composite material;
(2) dispersing 0.2g of carbon nanotubes in 100mL of NMP solution, ultrasonically dispersing, adding 0.02mmoL of LiPF 6 After dissolving, adding 1mmol of 1,2,4, 5-pyromellitic dianhydride, and stirring for 2 hours at normal temperature;
(3) heating the solution, keeping the temperature at 50 ℃, dropwise adding 4,4' -diaminodiphenyl ether into an NMP solution containing lithium ions according to the molar ratio of diamine monomer to dianhydride monomer of 1:1.01, and reacting for 2 hours;
(4) adding the silicon/lithium silicate composite material prepared in the step (1) into the obtained mixed system, wherein the weight ratio of the sum of the polyimide monomer dianhydride and the monomer diamine to the silicon/lithium silicate composite material is 0.02:1, and stirring for 1 h;
(5) and (3) screening a solid material obtained by spray drying the dispersion, and treating for 2 hours at 400 ℃ in a nitrogen atmosphere. Finally obtaining the lithium ion doped polyimide coated silicon/lithium silicate cathode material.
Example 2
(1) Mechanically ball-milling 15.0g of silicon monoxide, 5.4g of lithium hydroxide and 15g of water/ethanol mixed solution (2:3) for 8 hours in a nitrogen atmosphere, and drying in vacuum to obtain a silicon/lithium silicate composite material;
(2) dispersing 0.2g of carbon nano tube in 100mL of NMP solution, performing ultrasonic dispersion, adding 0.02mmoL of LiFSI to dissolve, adding 1mmoL of 1,2,4, 5-pyromellitic dianhydride, and stirring at normal temperature for 2 hours;
(3) heating the solution, keeping the temperature at 50 ℃, dropwise adding 4,4' -diaminodiphenyl ether into an NMP solution containing lithium ions according to the molar ratio of diamine monomer to dianhydride monomer of 1:1.01, and reacting for 2 hours;
(4) adding the silicon/lithium silicate composite material prepared in the step (1) into the obtained mixed system, wherein the weight ratio of the sum of the polyimide monomer dianhydride and the monomer diamine to the silicon/lithium silicate composite material is 0.02:1, and stirring for 1 h;
(5) and (3) screening the solid material obtained by spray drying the dispersion, and treating for 2 hours at 400 ℃ in a nitrogen atmosphere. Finally, the lithium ion doped polyimide coated silicon/lithium silicate anode material is obtained.
Example 3
(1) Mechanically ball-milling 15.0g of silicon monoxide, 5.4g of lithium hydroxide and 15g of water/ethanol mixed solution (2:3) for 8 hours in a nitrogen atmosphere, and drying in vacuum to obtain a silicon/lithium silicate composite material;
(2) dispersing 0.2g of carbon nano tube in 100mL of NMP solution, performing ultrasonic dispersion, adding 0.04mmoL of LiFSI to dissolve, adding 1mmoL of 1,2,4, 5-pyromellitic dianhydride, and stirring at normal temperature for 2 hours;
(3) heating the solution, keeping the temperature at 50 ℃, dropwise adding 4,4' -diaminodiphenyl ether into an NMP solution containing lithium ions according to the molar ratio of diamine monomer to dianhydride monomer of 1:1.01, and reacting for 2 hours;
(4) adding the silicon/lithium silicate composite material prepared in the step (1) into the obtained mixed system, wherein the weight ratio of the sum of the polyimide monomer dianhydride and the monomer diamine to the silicon/lithium silicate composite material is 0.02:1, and stirring for 1 h;
(5) and (3) screening a solid material obtained by spray drying the dispersion, and treating for 2 hours at 400 ℃ in a nitrogen atmosphere. Finally obtaining the lithium ion doped polyimide coated silicon/lithium silicate cathode material.
Example 4
(1) Mechanically ball-milling 15.0g of silicon monoxide, 5.4g of lithium hydroxide and 15g of water/ethanol mixed solution (2:3) for 8 hours in a nitrogen atmosphere, and drying in vacuum to obtain a silicon/lithium silicate composite material;
(2) dispersing 0.2g of carbon nano tube in 100mL of NMP solution, performing ultrasonic dispersion, adding 0.04mmoL of LiFSI to dissolve, adding 1mmoL of 1,2,4, 5-pyromellitic dianhydride, and stirring at normal temperature for 2 hours;
(3) heating the solution, keeping the temperature at 50 ℃, dropwise adding 4,4' -diaminodiphenyl ether into an NMP solution containing lithium ions according to the molar ratio of diamine monomer to dianhydride monomer of 1:1.01, and reacting for 2 hours;
(4) adding the silicon/lithium silicate composite material prepared in the step (1) into the obtained mixed system, wherein the weight ratio of the sum of the polyimide monomer dianhydride and the monomer diamine to the silicon/lithium silicate composite material is 0.04:1, and stirring for 1 h;
(5) and (3) screening a solid material obtained by spray drying the dispersion, and treating for 2 hours at 400 ℃ in a nitrogen atmosphere. Finally obtaining the lithium ion doped polyimide coated silicon/lithium silicate cathode material.
Example 5
(1) Mechanically ball-milling 15.0g of silicon monoxide, 5.4g of lithium hydroxide and 15g of water/ethanol mixed solution (2:3) for 8 hours in a nitrogen atmosphere, and drying in vacuum to obtain a silicon/lithium silicate composite material;
(2) dispersing 0.4g of carbon nano tube in 100mL of NMP solution, performing ultrasonic dispersion, adding 0.04mmoL of LiFSI to dissolve, adding 1mmoL of 1,2,4, 5-pyromellitic dianhydride, and stirring at normal temperature for 2 hours;
(3) heating and preserving heat in the solution for 50 ℃, dropwise adding 4,4' -diaminodiphenyl ether into an NMP solution containing lithium ions according to the molar ratio of diamine monomer to dianhydride monomer of 1:1.01, and reacting for 2 hours;
(4) adding the silicon/lithium silicate composite material prepared in the step (1) into the obtained mixed system, wherein the weight ratio of the sum of the polyimide monomer dianhydride and the monomer diamine to the silicon/lithium silicate composite material is 0.04:1, and stirring for 1 h;
(5) and (3) screening a solid material obtained by spray drying the dispersion, and treating for 2 hours at 400 ℃ in a nitrogen atmosphere. Finally obtaining the lithium ion doped polyimide coated silicon/lithium silicate cathode material.
Comparative example 1
Ball-milling raw material silicon is selected as a negative electrode material.
Comparative example 2
Mechanically ball-milling 15.0g of silicon monoxide, 5.4g of lithium hydroxide and 15g of water/ethanol mixed solution (2:3) for 8 hours in a nitrogen atmosphere, and drying in vacuum to obtain a silicon/lithium silicate composite material;
comparative example 3
(1) Mechanically ball-milling 15.0g of silica, 5.4g of lithium hydroxide and 15g of water/ethanol mixed solution (2:3) in a nitrogen atmosphere for 8 hours, and drying in vacuum to obtain a silicon/lithium silicate composite material;
(2) dispersing 0.2g of carbon nano tube in 100mL of NMP solution, performing ultrasonic dispersion, adding 1mmol of 1,2,4, 5-pyromellitic dianhydride, and stirring at normal temperature for 2 h;
(3) heating the solution, keeping the temperature at 50 ℃, dropwise adding 4,4' -diaminodiphenyl ether into an NMP solution containing lithium ions according to the molar ratio of diamine monomer to dianhydride monomer of 1:1.01, and reacting for 2 hours;
(4) adding the silicon/lithium silicate composite material prepared in the step (1) into the obtained mixed system, wherein the weight ratio of the sum of the polyimide monomer dianhydride and the monomer diamine to the silicon/lithium silicate composite material is 0.02:1, and stirring for 1 h;
(5) and (3) screening the solid material obtained by spray drying the dispersion, and treating for 2 hours at 400 ℃ in a nitrogen atmosphere. Finally, the lithium ion doped polyimide coated silicon/lithium silicate anode material is obtained.
Example 6
The silicon anode materials prepared in the examples 1-5 and the comparative examples 1-3 are subjected to electrical property detection, and the main steps comprise:
according to the active substance: conductive agent: mixing the binder with the binder in a mass ratio of 8:1:1 (solid content is 40-45%); coating the slurry on a copper foil, and preparing a pole piece through vacuum drying, rolling and cutting; a lithium sheet is used as a counter electrode, a polyethylene-polypropylene composite diaphragm is used as a diaphragm, and the content of 1.0mol/L LiPF containing 5% of FEC 6 And (EC/DMC/EMC ═ 1:1:1) is used as an electrolyte, and the button cell is assembled. The charging and discharging current is 0.1C, and the voltage range is 0.002-2.0V.
Referring to table 1, table 1 shows data of electrical property measurements of silicon anode materials prepared in examples of the present invention and comparative examples.
TABLE 1
The test results in table 1 show that the modified polyimide-coated silicon/lithium silicate negative electrode material improves the ionic conductivity of the negative electrode material through the compounding of lithium silicate, and the polyimide coating layer has excellent mechanical properties and reduces the release of irreversible capacity after being modified by lithium ions. The first efficiency and the cycle performance of the material are improved through the mutual synergistic effect.
The above detailed description of a modified polyimide-coated silicon/lithium silicate negative electrode material, a method for preparing the same, and a lithium ion battery provided by the present invention are provided herein, and specific examples are used to illustrate the principles and embodiments of the present invention, and the above description of the examples is only provided to help understand the method and the core ideas of the present invention, including the best mode, and also to enable any person skilled in the art to practice the present invention, including making and using any devices or systems and performing any combination of the methods. It should be noted that, for those skilled in the art, it is possible to make various improvements and modifications to the present invention without departing from the principle of the present invention, and those improvements and modifications also fall within the scope of the claims of the present invention. The scope of the invention is defined by the claims and may include other embodiments that occur to those skilled in the art. Such other embodiments are intended to be within the scope of the claims if they have structural elements that do not differ from the literal language of the claims, or if they include equivalent structural elements with insubstantial differences from the literal languages of the claims.
Claims (10)
1. The silicon composite material is characterized by comprising a silicon/lithium silicate composite material and a modified polyimide coating layer coated on the silicon/lithium silicate composite material;
the modified polyimide is lithium ion doped polyimide.
2. The silicon composite of claim 1, wherein in the silicon/lithium silicate composite, nano-silicon particles are dispersed in a lithium silicate material;
the particle size of the nano silicon particles is more than or equal to 10 nm;
the lithium ion doped polyimide comprises a lithium ion modified polyimide.
3. The silicon composite material according to claim 1, wherein the silicon/lithium silicate composite material is contained in an amount of 93 to 99% by mass;
the D50 particle size of the silicon composite material is 1-10 mu m;
the silicon composite material is a lithium ion battery cathode material.
4. The silicon composite material according to claim 1, further comprising a conductive carbon material;
the conductive carbon material comprises one or more of conductive carbon black, acetylene black, carbon nanotubes, graphene and carbon fibers;
the conductive carbon material comprises one or more of a conductive carbon material compounded on the silicon/lithium silicate composite material, a conductive carbon material coated on the silicon/lithium silicate composite material, a conductive carbon material doped in the modified polyimide coating layer and a conductive carbon material compounded on the modified polyimide coating layer.
5. A preparation method of a silicon composite material is characterized by comprising the following steps:
1) under protective atmosphere, carrying out ball milling on the silicon monoxide, the lithium hydroxide and the mixed solution to obtain a silicon/lithium silicate composite material;
2) and mixing the silicon/lithium silicate composite material obtained in the step, a polymer monomer and a solvent containing lithium salt, carrying out polymerization reaction, and carrying out spray drying and heating curing to obtain the silicon composite material.
6. The method according to claim 5, wherein the particle size of the silica is 3 to 10 μm;
the atomic ratio of Si to O in the silicon monoxide is n, wherein n is more than or equal to 0.8 and less than 1.6;
the molar ratio of the silicon monoxide to the lithium hydroxide is (6-9): 1;
the mixed solution comprises a mixed solution of water and alcohol;
the ball milling time is 6-10 h.
7. The method of claim 5, wherein the polymer monomers comprise dianhydride monomers and diamine monomers;
the dianhydride monomer comprises one or more of pyromellitic dianhydride, benzophenone dianhydride, biphenyl dianhydride, diphenyl ether dianhydride and 1,2,4, 5-pyromellitic dianhydride;
the diamine monomer comprises one or more of p-phenylenediamine, 4' -diamino-3, 3 ' -dimethyl biphenyl, 4' -diamino diphenyl sulfone, 2-bis [4- (2, 4-diamino phenoxy) phenyl ] propane and 1, 4-diaminocyclohexane;
the molar ratio of the dianhydride monomer to the diamine monomer is (1-1.05): 1;
the step 2) also comprises a conductive carbon material.
8. The production method according to claim 7, wherein the conductive carbon material includes one or more of conductive carbon black, acetylene black, carbon nanotubes, graphene, and carbon fibers;
the lithium salt comprises LiBOB and LiPF 6 And one or more of LiFSI;
the molar ratio of the lithium salt to the dianhydride monomer is (1-15): 100, respectively;
the solvent comprises one or more of acetone, dimethyl sulfoxide and N, N-dimethylformamide;
the step 2) is specifically as follows:
mixing a conductive carbon material, a lithium salt, a dianhydride monomer and a solvent, adding a diamine monomer for polymerization, adding the silicon/lithium silicate composite material obtained in the step, and finally performing spray drying and heating curing to obtain the silicon composite material.
9. The method according to claim 7, wherein the polymerization reaction temperature is 40 to 70 ℃;
the polymerization reaction time is 1-4 h;
the temperature of the spray drying is 150-200 ℃;
the temperature of the heating and curing is 300-450 ℃;
the heating and curing time is 2-6 h.
10. A lithium ion battery is characterized by comprising a positive electrode and a negative electrode;
the anode comprises a silicon composite anode material;
the silicon composite negative electrode material comprises the silicon composite material as defined in any one of claims 1 to 4 or the silicon composite material prepared by the preparation method as defined in any one of claims 5 to 9.
Priority Applications (1)
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