CN114937765B - 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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- 229910052710 silicon Inorganic materials 0.000 title claims abstract description 158
- 239000010703 silicon Substances 0.000 title claims abstract description 158
- PAZHGORSDKKUPI-UHFFFAOYSA-N lithium metasilicate Chemical compound [Li+].[Li+].[O-][Si]([O-])=O PAZHGORSDKKUPI-UHFFFAOYSA-N 0.000 title claims abstract description 105
- 229910052912 lithium silicate Inorganic materials 0.000 title claims abstract description 105
- 239000004642 Polyimide Substances 0.000 title claims abstract description 73
- 229920001721 polyimide Polymers 0.000 title claims abstract description 73
- HBBGRARXTFLTSG-UHFFFAOYSA-N Lithium ion Chemical compound [Li+] HBBGRARXTFLTSG-UHFFFAOYSA-N 0.000 title claims abstract description 62
- 229910001416 lithium ion Inorganic materials 0.000 title claims abstract description 62
- 238000002360 preparation method Methods 0.000 title claims abstract description 26
- 239000007773 negative electrode material Substances 0.000 title claims description 8
- XUIMIQQOPSSXEZ-UHFFFAOYSA-N Silicon Chemical compound [Si] XUIMIQQOPSSXEZ-UHFFFAOYSA-N 0.000 claims abstract description 157
- 239000002131 composite material Substances 0.000 claims abstract description 125
- 239000010405 anode material Substances 0.000 claims abstract description 34
- 239000011247 coating layer Substances 0.000 claims abstract description 29
- 238000000498 ball milling Methods 0.000 claims abstract description 22
- 239000000463 material Substances 0.000 claims abstract description 13
- 239000005543 nano-size silicon particle Substances 0.000 claims abstract description 10
- 239000000178 monomer Substances 0.000 claims description 67
- 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 47
- 239000003575 carbonaceous material Substances 0.000 claims description 36
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 claims description 34
- 150000004985 diamines Chemical class 0.000 claims description 29
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N Silicium dioxide Chemical compound O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 claims description 28
- 229910052814 silicon oxide Inorganic materials 0.000 claims description 22
- LFQSCWFLJHTTHZ-UHFFFAOYSA-N Ethanol Chemical compound CCO LFQSCWFLJHTTHZ-UHFFFAOYSA-N 0.000 claims description 19
- 238000010438 heat treatment Methods 0.000 claims description 18
- 239000011259 mixed solution Substances 0.000 claims description 18
- 238000001694 spray drying Methods 0.000 claims description 17
- 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 14
- 229910021393 carbon nanotube Inorganic materials 0.000 claims description 14
- 229910003002 lithium salt Inorganic materials 0.000 claims description 14
- 159000000002 lithium salts Chemical class 0.000 claims description 14
- 239000002904 solvent Substances 0.000 claims description 14
- 238000006116 polymerization reaction Methods 0.000 claims description 13
- 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
- USIUVYZYUHIAEV-UHFFFAOYSA-N diphenyl ether Chemical compound C=1C=CC=CC=1OC1=CC=CC=C1 USIUVYZYUHIAEV-UHFFFAOYSA-N 0.000 claims description 10
- 229910010941 LiFSI 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
- 239000002245 particle Substances 0.000 claims description 9
- 229920000049 Carbon (fiber) Polymers 0.000 claims description 8
- 239000006230 acetylene black Substances 0.000 claims description 8
- 239000004917 carbon fiber Substances 0.000 claims description 8
- ZUOUZKKEUPVFJK-UHFFFAOYSA-N diphenyl Chemical compound C1=CC=CC=C1C1=CC=CC=C1 ZUOUZKKEUPVFJK-UHFFFAOYSA-N 0.000 claims description 8
- 229910021389 graphene Inorganic materials 0.000 claims description 8
- VNWKTOKETHGBQD-UHFFFAOYSA-N methane Chemical compound C VNWKTOKETHGBQD-UHFFFAOYSA-N 0.000 claims description 8
- 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
- VKIRRGRTJUUZHS-UHFFFAOYSA-N cyclohexane-1,4-diamine Chemical compound NC1CCC(N)CC1 VKIRRGRTJUUZHS-UHFFFAOYSA-N 0.000 claims description 5
- 235000010290 biphenyl Nutrition 0.000 claims description 4
- 239000004305 biphenyl Substances 0.000 claims description 4
- 230000001681 protective effect Effects 0.000 claims description 4
- 101150058243 Lipf gene Proteins 0.000 claims description 3
- 239000000377 silicon dioxide Substances 0.000 claims description 3
- 230000035484 reaction time Effects 0.000 claims description 2
- 238000000034 method Methods 0.000 abstract description 13
- 230000002441 reversible effect Effects 0.000 abstract description 9
- 230000000977 initiatory effect Effects 0.000 abstract description 7
- 230000007613 environmental effect Effects 0.000 abstract description 4
- 238000005265 energy consumption Methods 0.000 abstract description 3
- 238000009776 industrial production Methods 0.000 abstract description 2
- 239000000243 solution Substances 0.000 description 20
- 239000012299 nitrogen atmosphere Substances 0.000 description 14
- 229920000642 polymer Polymers 0.000 description 13
- 239000011343 solid material Substances 0.000 description 12
- 238000003756 stirring Methods 0.000 description 12
- WHXSMMKQMYFTQS-UHFFFAOYSA-N Lithium Chemical compound [Li] WHXSMMKQMYFTQS-UHFFFAOYSA-N 0.000 description 8
- 238000001723 curing Methods 0.000 description 8
- 229910052744 lithium Inorganic materials 0.000 description 8
- 238000001291 vacuum drying Methods 0.000 description 8
- 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
- 239000010406 cathode material Substances 0.000 description 6
- 239000006185 dispersion Substances 0.000 description 6
- 239000007788 liquid Substances 0.000 description 6
- 238000007873 sieving Methods 0.000 description 6
- 238000001132 ultrasonic dispersion Methods 0.000 description 6
- 230000000052 comparative effect Effects 0.000 description 5
- 238000004090 dissolution Methods 0.000 description 5
- 230000000694 effects Effects 0.000 description 5
- 239000003792 electrolyte Substances 0.000 description 4
- 238000009830 intercalation Methods 0.000 description 4
- 230000002687 intercalation Effects 0.000 description 4
- 239000002210 silicon-based material Substances 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
- 239000007772 electrode material Substances 0.000 description 3
- 238000013007 heat curing Methods 0.000 description 3
- 125000005842 heteroatom Chemical group 0.000 description 3
- 239000011159 matrix material Substances 0.000 description 3
- 238000012986 modification Methods 0.000 description 3
- 230000004048 modification Effects 0.000 description 3
- 230000000379 polymerizing effect Effects 0.000 description 3
- 239000002994 raw material Substances 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
- 229910013870 LiPF 6 Inorganic materials 0.000 description 2
- 239000013543 active substance Substances 0.000 description 2
- 230000006978 adaptation Effects 0.000 description 2
- 230000009286 beneficial effect Effects 0.000 description 2
- 229910052799 carbon Inorganic materials 0.000 description 2
- 238000009831 deintercalation Methods 0.000 description 2
- 238000013461 design Methods 0.000 description 2
- 238000001514 detection method 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
- 238000004519 manufacturing process Methods 0.000 description 2
- 238000002156 mixing Methods 0.000 description 2
- 239000000843 powder Substances 0.000 description 2
- 239000000758 substrate Substances 0.000 description 2
- RYGMFSIKBFXOCR-UHFFFAOYSA-N Copper Chemical compound [Cu] RYGMFSIKBFXOCR-UHFFFAOYSA-N 0.000 description 1
- 239000004743 Polypropylene Substances 0.000 description 1
- 238000013459 approach Methods 0.000 description 1
- 239000011230 binding agent Substances 0.000 description 1
- 230000015556 catabolic process Effects 0.000 description 1
- 238000006243 chemical reaction Methods 0.000 description 1
- 238000013329 compounding 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
- 230000006378 damage Effects 0.000 description 1
- 230000007423 decrease Effects 0.000 description 1
- 238000006731 degradation reaction 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
- 239000000203 mixture Substances 0.000 description 1
- 229910052757 nitrogen Inorganic materials 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
- 230000002829 reductive effect Effects 0.000 description 1
- 238000005096 rolling process Methods 0.000 description 1
- 238000000926 separation method Methods 0.000 description 1
- 239000002002 slurry Substances 0.000 description 1
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- 230000002195 synergetic effect Effects 0.000 description 1
- 238000012360 testing method 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
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- 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
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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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- 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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- 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
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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 coated silicon/lithium silicate anode material with the specific structure has the structure that nano silicon particles are uniformly dispersed in a lithium silicate phase. The lithium silicate phase in the invention can improve lithium ion conductivity and buffer the volume expansion of silicon in the charge and discharge process. The polyimide coating layer has excellent mechanical properties, ensures that the material has higher initial effect after being modified by lithium ions, and has high reversible capacity and excellent cycle performance. The preparation method provided by the invention prepares 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 the negative electrode of the lithium ion battery.
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 anode 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 commercial lithium ion battery cathode material is mainly graphite cathode material, the theoretical capacity of the current commercial lithium ion battery cathode material is 372mAh/g, the actual capacity is 340-360 mAh/g, and the design requirement of a high specific energy battery can not be met. Therefore, development of a new negative electrode material of the next generation, which has high specific capacity and good cycle stability and rate capability, to realize wide use in electronic products and electric automobiles has become a key subject of research in the battery field.
The silicon-based material has rich sources and higher specific capacity (4200 mAh/g), and meanwhile, the lithium intercalation potential (0.4V) 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 itself has poor conductivity, and the serious volume effect generated during electrochemical lithium intercalation and deintercalation causes the destruction of the material structure and mechanical pulverization, which leads to the separation of electrode materials and the electrode material from the current collector, and further to the loss of electrical contact, resulting in the rapid decline of the cycle performance of the electrode. Current approaches to this problem have employed materials with lower expansion coefficients as substrates, with active silicon embedded or encapsulated in these substrates to mitigate volume changes due to lithium ion intercalation and deintercalation. The matrix material acts to buffer mechanical stresses. The common matrix materials are carbon materials and polymer materials. However, compared with silicon, the carbon material has better mechanical property and lower volume expansion rate (only 9 percent and far lower than 400 percent of silicon), but the absolute volume expansion still exists, so the construction method of the composite material can relieve the volume effect of the silicon to a certain extent, but the long-term electrochemical cycle stability of the silicon material is not obviously improved. In the subsequent cycle, as the cycle reaction proceeds, the interface between the matrix material and the silicon active center is severely damaged due to the mismatch of volume expansion, resulting in the degradation of electrochemical cycle performance. For example, patent application publication No. CN108321368A discloses a polymer coated silicon/lithium metasilicate negative electrode material and a preparation method thereof, wherein active lithium powder and silicon oxide are ball-milled under inert atmosphere to prepare a silicon/lithium silicate composite material, and polymers such as polyaniline, polypyrrole, polydopamine and the like are polymerized on the surface of the composite material in situ. Firstly, the lithium powder has higher activity, has severe environmental requirements and is not suitable for industrial production. Meanwhile, the polar hetero atoms in the polymer consume lithium ions in the electrolyte, so that the first cycle efficiency is reduced, the first efficiency of the prepared electrode material is only 70%, and the requirements of commercial products of the cathode material are not met.
Therefore, how to find a more suitable way to solve the problems existing in the existing silicon negative electrode, to a silicon-carbon negative electrode product with high reversible capacity, excellent cycle performance and commercializability, and suitable for industrial popularization and application, has become one of the problems to be solved by many first-line researchers and scientific research enterprises.
Disclosure of Invention
In view of the above, the technical problem to be solved by the invention is to provide a silicon composite material, a preparation method thereof and a lithium ion battery, in particular to a modified polyimide coated silicon/lithium silicate anode material of the lithium ion battery. 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 practical degree, 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 grain diameter of the nano silicon particles is more than or equal to 10nm;
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) Ball milling is carried out on the silicon oxide, the lithium hydroxide and the mixed solution in a protective atmosphere to obtain a silicon/lithium silicate composite material;
2) Mixing the silicon/lithium silicate composite material obtained by the steps, a polymer monomer and a solvent containing lithium salt, performing polymerization reaction, and performing spray drying and heating curing to obtain the silicon composite material.
Preferably, the particle size of the silica is 3-10 μm;
the atomic ratio of Si to O in the silicon oxide is n, n is more than or equal to 0.8 and less than 1.6;
the molar ratio of the silicon oxide to the lithium hydroxide is (6-9): 1, a step of;
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' -dimethylbiphenyl, 4' -diamino diphenyl sulfone, 2-bis [4- (2, 4-diamino phenoxy) phenyl ] propane and 1, 4-diamino cyclohexane;
the molar ratio of the dianhydride monomer to the diamine monomer is (1-1.05): 1, a step of;
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 one or more of LiBOB, liPF 6 and LiFSI;
The molar ratio of the lithium salt to the dianhydride monomer is (1-15): 100;
The solvent comprises one or more of acetone, dimethyl sulfoxide and N, N-dimethylformamide;
The step 2) specifically comprises the following steps:
the conductive carbon material, the lithium salt, the dianhydride monomer and the solvent are mixed firstly, then diamine monomer is added for polymerization reaction, then the silicon/lithium silicate composite material obtained by the steps is added, and finally the silicon composite material is obtained after spray drying and heating curing.
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 negative electrode comprises a silicon composite negative electrode material;
The silicon composite anode material comprises the silicon composite material prepared by any one of the technical schemes or the preparation method of 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 method has the advantages that the battery performance is improved through the pre-lithiation process after the modification of the existing silicon-carbon negative electrode material mainly through carbon coating, the cost is high, and the carbon coating layer and the active substance are easy to be mismatched in the circulation process, so that the electrochemical performance is influenced; the polymer coating silicon-carbon anode material adopted in the current stage has the problems that polar hetero atoms in the polymer consume lithium ions in electrolyte, influence the first cycle efficiency of the battery and the like. The invention is based on the research that hetero atoms contained in the polymer coating layer consume lithium ions in the electrolyte, thereby leading to the improvement of the first irreversible capacity.
Based on the above, the invention creatively designs a silicon composite material with a specific structure, which 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 (< 10 nm) are uniformly dispersed in a lithium silicate phase, and the modified polyimide coating layer is prepared by polymerizing dianhydride monomers and diamine monomers in a solvent containing lithium ions. The lithium silicate phase in the invention can improve lithium ion conductivity and buffer the volume expansion of silicon in the charge and discharge process. The polyimide coating layer has excellent mechanical properties, ensures that the material has higher initial effect after being modified by lithium ions, and has high reversible capacity and excellent cycle performance.
The invention also provides a preparation method of the modified polyimide coated silicon/lithium silicate anode material, which is characterized by simple mechanical ball milling to prepare the silicon/lithium silicate composite material, abandoning high-temperature calcination in the traditional preparation method, greatly reducing energy consumption, saving cost, being green and environment-friendly, having the characteristics of simple preparation process, low environmental requirement, industrialized production, high practicability and the like, and having wide application prospect in the aspect of lithium ion battery anode.
Experimental results show that the lithium silicate in the modified polyimide coated silicon/lithium silicate anode material prepared by the invention can obviously improve the ionic conductivity of the material, and can buffer the volume effect (volume expansion) of silicon in the charge and discharge process, thereby being beneficial to improving the ionic conductivity of lithium; the polyimide coating layer has excellent mechanical properties, and ensures that the material has higher initial effect, reversible capacity and better cycle performance after being modified by lithium ions.
Detailed Description
For a further understanding of the present invention, preferred embodiments of the invention are described below in conjunction with the examples, but it should be understood that these descriptions are merely intended to illustrate further features and advantages of the invention and are not limiting of the invention claims.
All the raw materials of the present invention are not particularly limited in their sources, and may be purchased on the market 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 purity, and the present invention preferably employs analytically pure or 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 includes a lithium ion modified polyimide.
In the present invention, the nano silicon particles are preferably dispersed in the lithium silicate material in the silicon/lithium silicate composite 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 mass content of the silicon/lithium silicate composite material in the silicon composite material is preferably 93% to 99%, more preferably 94% to 98%, and still more preferably 95% to 97%.
In the present invention, the D50 particle diameter of the silicon composite material is preferably 1 to 10. Mu.m, more preferably 3 to 8. Mu.m, still more preferably 5 to 6. Mu.m.
In the present invention, the silicon composite material is preferably a lithium ion battery anode 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, 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 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, more preferably 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 is a complete and refined whole technical scheme, better ensures the specific structure and morphology of the composite material, better inhibits the volume expansion of silicon, further improves the initial effect, reversible capacity and cycle performance of the battery, and the modified polyimide coated silicon/lithium silicate anode material can be specifically:
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 10 nm) are uniformly dispersed in a lithium silicate phase, and the modified polyimide coating layer is prepared by polymerizing dianhydride monomers and diamine monomers in a solvent containing lithium ions.
Specifically, the weight content of the silicon/lithium silicate composite material in the anode material is 93% -99%, and the weight content of the modified polyimide coating layer in the anode material is 0.5% -7%.
Specifically, the modified polyimide coated silicon/lithium silicate anode material has a particle size D50 of 1 to 10 μm, preferably 3 to 7 μm.
The invention provides a preparation method of a silicon composite material, which comprises the following steps:
1) Ball milling is carried out on the silicon oxide, the lithium hydroxide and the mixed solution in a protective atmosphere to obtain a silicon/lithium silicate composite material;
2) Mixing the silicon/lithium silicate composite material obtained by the steps, a polymer monomer and a solvent containing lithium salt, performing polymerization reaction, and performing spray drying and heating curing to obtain the silicon composite material.
The method comprises the steps of ball milling silicon oxide, lithium hydroxide and mixed solution in protective atmosphere to obtain the silicon/lithium silicate composite material.
In the present invention, the particle diameter of the silica is preferably 3 to 10. Mu.m, more preferably 5 to 9. Mu.m, and still more preferably 6 to 8. Mu.m.
In the present invention, the atomic ratio of Si to O in the silicon 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 oxide to the lithium hydroxide is preferably (6 to 9): 1, more preferably (6.5 to 8.5): 1, more preferably (7 to 8): 1.
In the present invention, the mixed solution preferably includes a mixed solution of water and alcohol.
In the present invention, the time of the ball milling is preferably 6 to 10 hours, more preferably 6.5 to 9.5 hours, still more preferably 7 to 9 hours, still more preferably 7.5 to 8.5 hours.
The silicon/lithium silicate composite material obtained by the steps is mixed with a polymer monomer and a solvent containing lithium salt, then is subjected to polymerization reaction, and is subjected to spray drying and heating curing to obtain the silicon composite material.
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, more preferably pyromellitic dianhydride, benzophenone 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 '-diamino diphenyl sulfone, 2-bis [4- (2, 4-diamino phenoxy) phenyl ] propane and 1, 4-diamino cyclohexane, more preferred are 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, 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, more preferably LiBOB, liPF6 or LiFSI.
In the present invention, the molar ratio of the lithium salt to the dianhydride monomer is preferably (1 to 15): 100, more preferably (4 to 12): 100, more preferably (7 to 9): 100.
In the present invention, the solvent preferably includes one or more of acetone, dimethyl sulfoxide and N, N-dimethylformamide, more preferably acetone, dimethyl sulfoxide or N, N-dimethylformamide.
In the present invention, the step 2) is specifically preferably:
the conductive carbon material, the lithium salt, the dianhydride monomer and the solvent are mixed firstly, then diamine monomer is added for polymerization reaction, then the silicon/lithium silicate composite material obtained by the steps is added, and finally the silicon composite material is obtained after spray drying and heating curing.
In the present invention, the polymerization reaction temperature is preferably 40 to 70 ℃, more preferably 45 to 65 ℃, and still more preferably 50 to 60 ℃.
In the present invention, the polymerization time is preferably 1 to 4 hours, more preferably 1.5 to 3.5 hours, and still more preferably 2 to 3 hours.
In the present invention, the spray-drying temperature is preferably 150 to 200 ℃, more preferably 160 to 190 ℃, and still more preferably 170 to 180 ℃.
In the present invention, the temperature of the heat curing is preferably 300 to 450 ℃, more preferably 330 to 420 ℃, and still more preferably 360 to 390 ℃.
In the present invention, the time for the heat curing is preferably 2 to 6 hours, more preferably 2.5 to 5.5 hours, still more preferably 3 to 5 hours, still more preferably 3.5 to 4.5 hours.
The invention relates to a complete and refined integral preparation process, which better ensures the specific structure and morphology of a composite material, better inhibits the volume expansion of silicon, further improves the initial effect, reversible capacity and cycle performance of a battery, and the preparation method of the modified polyimide coated silicon/lithium silicate anode material comprises 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 mixed solution of silicon oxide, lithium hydroxide and water/ethanol (2:3), and performing ball milling under nitrogen atmosphere to obtain a silicon/lithium silicate composite material;
S2, preparing a modified polyimide coating layer: and (3) uniformly dispersing the silicon/lithium metasilicate composite material, the conductive carbon material and the polymer monomer in the S1 in a solvent containing lithium salt, performing polymerization reaction, and performing spray drying and heat curing to obtain the modified polyimide coated silicon/lithium metasilicate anode material.
Specifically, in the step S1, the particle size of the silicon oxide 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 oxide is n, and n is more than or equal to 0.8 and less than 1.6.
Specifically, in S1, the molar ratio of the silicon oxide 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 one of LiBOB, liPF 6 and LiFSI, and 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 required 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' -dimethylbiphenyl, 4' -diamino diphenyl sulfone, 2-bis [4- (2, 4-diamino phenoxy) phenyl ] propane and 1, 4-diamino cyclohexane.
Specifically, in S2, the spray drying temperature is 150-200 ℃, the heating curing condition is 300-450 ℃, and the heating time is 2-6 h.
The invention provides a lithium ion battery, which comprises a positive electrode and a negative electrode;
in the present invention, the anode preferably comprises a silicon composite anode material
In the present invention, the silicon composite anode material preferably includes the silicon composite material according to any one of the above technical solutions or the silicon composite material prepared by the preparation method according to any one of the above technical solutions.
The invention provides a modified polyimide coated silicon/lithium silicate anode material, a preparation method thereof and a lithium ion battery. The modified polyimide coated silicon/lithium silicate anode material with a 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 (< 10 nm) are uniformly dispersed in a lithium silicate phase, and the modified polyimide coating layer is prepared by polymerizing dianhydride monomers and diamine monomers in a solvent containing lithium ions. The lithium silicate phase in the invention can improve lithium ion conductivity and buffer the volume expansion of silicon in the charge and discharge process. The polyimide coating layer has excellent mechanical properties, ensures that the material has higher initial effect after being modified by lithium ions, and has high reversible capacity and excellent cycle performance.
The invention also provides a preparation method of the modified polyimide coated silicon/lithium silicate anode material, which is characterized by simple mechanical ball milling to prepare the silicon/lithium silicate composite material, abandoning high-temperature calcination in the traditional preparation method, greatly reducing energy consumption, saving cost, being green and environment-friendly, having the characteristics of simple preparation process, low environmental requirement, industrialized production, high practicability and the like, and having wide application prospect in the aspect of lithium ion battery anode.
Experimental results show that the lithium silicate in the modified polyimide coated silicon/lithium silicate anode material prepared by the invention can obviously improve the ionic conductivity of the material, and can buffer the volume effect (volume expansion) of silicon in the charge and discharge process, thereby being beneficial to improving the ionic conductivity of lithium; the polyimide coating layer has excellent mechanical properties, and ensures that the material has higher initial effect, reversible capacity and better cycle performance after being modified by lithium ions.
For further explanation of the present invention, the following describes a silicon composite material, a preparation method thereof and a lithium ion battery in detail with reference to the examples, but it should be understood that these examples are implemented on the premise of the technical scheme of the present invention, and detailed implementation and specific operation processes are given only for further explanation of the features and advantages of the present invention, and not limitation of 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) Performing mechanical ball milling on 15.0g of silicon oxide, 5.4g of lithium hydroxide and 15g of water/ethanol mixed solution (2:3) for 8 hours under nitrogen atmosphere, and performing vacuum drying 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 LiPF 6 for dissolution, adding 1mmol of 1,2,4, 5-pyromellitic dianhydride, and stirring for 2 hours at normal temperature;
(3) Heating and preserving heat at 50 ℃ in the solution, and dripping 4,4' -diaminodiphenyl ether into 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 polyimide monomer dianhydride and monomer diamine to the silicon/lithium silicate composite material is 0.02:1, and stirring for 1h;
(5) And (3) sieving a solid material obtained by spray drying the dispersion liquid, and treating the solid material at 400 ℃ for 2 hours in a nitrogen atmosphere. Finally, the polyimide coated silicon/lithium silicate anode material doped with lithium ions is obtained.
Example 2
(1) Performing mechanical ball milling on 15.0g of silicon oxide, 5.4g of lithium hydroxide and 15g of water/ethanol mixed solution (2:3) for 8 hours under nitrogen atmosphere, and performing vacuum drying 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 for dissolution, adding 1mmol of 1,2,4, 5-pyromellitic dianhydride, and stirring for 2 hours at normal temperature;
(3) Heating and preserving heat at 50 ℃ in the solution, and dripping 4,4' -diaminodiphenyl ether into 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 polyimide monomer dianhydride and monomer diamine to the silicon/lithium silicate composite material is 0.02:1, and stirring for 1h;
(5) And (3) sieving a solid material obtained by spray drying the dispersion liquid, and treating the solid material at 400 ℃ for 2 hours in a nitrogen atmosphere. Finally, the polyimide coated silicon/lithium silicate anode material doped with lithium ions is obtained.
Example 3
(1) Performing mechanical ball milling on 15.0g of silicon oxide, 5.4g of lithium hydroxide and 15g of water/ethanol mixed solution (2:3) for 8 hours under nitrogen atmosphere, and performing vacuum drying 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 for dissolution, adding 1mmol of 1,2,4, 5-pyromellitic dianhydride, and stirring for 2 hours at normal temperature;
(3) Heating and preserving heat at 50 ℃ in the solution, and dripping 4,4' -diaminodiphenyl ether into 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 polyimide monomer dianhydride and monomer diamine to the silicon/lithium silicate composite material is 0.02:1, and stirring for 1h;
(5) And (3) sieving a solid material obtained by spray drying the dispersion liquid, and treating the solid material at 400 ℃ for 2 hours in a nitrogen atmosphere. Finally, the polyimide coated silicon/lithium silicate anode material doped with lithium ions is obtained.
Example 4
(1) Performing mechanical ball milling on 15.0g of silicon oxide, 5.4g of lithium hydroxide and 15g of water/ethanol mixed solution (2:3) for 8 hours under nitrogen atmosphere, and performing vacuum drying 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 for dissolution, adding 1mmol of 1,2,4, 5-pyromellitic dianhydride, and stirring for 2 hours at normal temperature;
(3) Heating and preserving heat at 50 ℃ in the solution, and dripping 4,4' -diaminodiphenyl ether into 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 polyimide monomer dianhydride and monomer diamine to the silicon/lithium silicate composite material is 0.04:1, and stirring for 1h;
(5) And (3) sieving a solid material obtained by spray drying the dispersion liquid, and treating the solid material at 400 ℃ for 2 hours in a nitrogen atmosphere. Finally, the polyimide coated silicon/lithium silicate anode material doped with lithium ions is obtained.
Example 5
(1) Performing mechanical ball milling on 15.0g of silicon oxide, 5.4g of lithium hydroxide and 15g of water/ethanol mixed solution (2:3) for 8 hours under nitrogen atmosphere, and performing vacuum drying 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 for dissolution, adding 1mmol of 1,2,4, 5-pyromellitic dianhydride, and stirring for 2 hours at normal temperature;
(3) Heating and preserving heat at 50 ℃ in the solution, and dripping 4,4' -diaminodiphenyl ether into 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 polyimide monomer dianhydride and monomer diamine to the silicon/lithium silicate composite material is 0.04:1, and stirring for 1h;
(5) And (3) sieving a solid material obtained by spray drying the dispersion liquid, and treating the solid material at 400 ℃ for 2 hours in a nitrogen atmosphere. Finally, the polyimide coated silicon/lithium silicate anode material doped with lithium ions is obtained.
Comparative example 1
Ball milling raw material silicon is selected as a cathode material.
Comparative example 2
Performing mechanical ball milling on 15.0g of silicon oxide, 5.4g of lithium hydroxide and 15g of water/ethanol mixed solution (2:3) for 8 hours under nitrogen atmosphere, and performing vacuum drying to obtain a silicon/lithium silicate composite material;
comparative example 3
(1) Performing mechanical ball milling on 15.0g of silicon oxide, 5.4g of lithium hydroxide and 15g of water/ethanol mixed solution (2:3) for 8 hours under nitrogen atmosphere, and performing vacuum drying 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 for 2 hours at normal temperature;
(3) Heating and preserving heat at 50 ℃ in the solution, and dripping 4,4' -diaminodiphenyl ether into 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 polyimide monomer dianhydride and monomer diamine to the silicon/lithium silicate composite material is 0.02:1, and stirring for 1h;
(5) And (3) sieving a solid material obtained by spray drying the dispersion liquid, and treating the solid material at 400 ℃ for 2 hours in a nitrogen atmosphere. Finally, the polyimide coated silicon/lithium silicate anode material doped with lithium ions is obtained.
Example 6
The silicon anode materials prepared in examples 1 to 5 and comparative examples 1 to 3 were subjected to electrical property detection, and the main steps include:
The active substances are as follows: conductive agent: binder=8:1:1 mass ratio (solids content 40-45%); coating the slurry on a copper foil, and preparing a pole piece through vacuum drying, rolling and cutting; lithium sheets are used as a counter electrode, a polyethylene-polypropylene composite diaphragm is used as a diaphragm, and 1.0mol/L LiPF 6 (EC/DMC/EMC=1:1:1) containing 5% of FEC is used as electrolyte to assemble the button cell. The charge and discharge current is 0.1C, and the voltage interval is 0.002-2.0V.
Referring to table 1, table 1 is electrical property detection data of the silicon anode materials prepared in the examples and comparative examples of the present invention.
TABLE 1
As shown in the test results in Table 1, the modified polyimide coated silicon/lithium silicate anode material improves the ionic conductivity of the anode 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. Through the mutual synergistic effect, the first efficiency and the cycle performance of the material are improved.
The modified polyimide coated silicon/lithium silicate anode material, the preparation method thereof and the lithium ion battery provided by the invention are described in detail, and specific examples are used for describing the principles and the implementation modes of the invention, and the description of the examples is only used for helping understand the method and the core idea of the invention, including the best mode, and also enables any person skilled in the art to practice the invention, including making and using any device or system and implementing any combined method. It should be noted that it will be apparent to those skilled in the art that various modifications and adaptations of the invention can be made without departing from the principles of the invention and these modifications and adaptations are intended to be within the scope of the invention as defined in the following claims. The scope of the patent protection 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 language 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;
In the silicon/lithium silicate composite material, nano silicon particles are dispersed in a lithium silicate material;
the grain diameter of the nano silicon particles is more than or equal to 10nm;
The lithium ion doped polyimide comprises lithium ion modified polyimide;
the silicon composite material further comprises a conductive carbon material;
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 preparation method of the silicon composite material is characterized by comprising the following steps:
1) Ball milling is carried out on the silicon oxide, the lithium hydroxide and the mixed solution in a protective atmosphere to obtain a silicon/lithium silicate composite material;
2) The conductive carbon material, the lithium salt, the dianhydride monomer and the solvent are mixed firstly, then diamine monomer is added for polymerization reaction, then the silicon/lithium silicate composite material obtained by the steps is added, and finally the silicon composite material is obtained after spray drying and heating curing.
2. The silicon composite material according to claim 1, wherein the mass content of the silicon/lithium silicate composite material in the silicon composite material is 93% -99%;
the D50 particle size of the silicon composite material is 1-10 mu m.
3. The silicon composite of claim 1, wherein the silicon composite is a lithium ion battery anode material.
4. The silicon composite of claim 1, wherein the conductive carbon material comprises one or more of conductive carbon black, acetylene black, carbon nanotubes, graphene, and carbon fibers.
5. The silicon composite material according to claim 1, wherein the particle size of the silica is 3 to 10 μm;
the atomic ratio of Si to O in the silicon oxide is n, n is more than or equal to 0.8 and less than 1.6;
The molar ratio of the silicon oxide to the lithium hydroxide is (6-9): 1.
6. The silicon composite of claim 1, wherein the mixed solution comprises a mixed solution of water and alcohol;
the ball milling time is 6-10 hours.
7. The silicon composite of claim 1, wherein the dianhydride monomer comprises one or more of pyromellitic dianhydride, benzophenone dianhydride, biphenyl dianhydride, and diphenyl ether dianhydride;
The diamine monomer comprises one or more of p-phenylenediamine, 4' -diamino-3, 3' -dimethylbiphenyl, 4' -diamino diphenyl sulfone, 2-bis [4- (2, 4-diamino phenoxy) phenyl ] propane and 1, 4-diamino cyclohexane;
The molar ratio of the dianhydride monomer to the diamine monomer is (1-1.05): 1.
8. The silicon composite of claim 1, wherein the lithium salt comprises one or more of LiBOB, liPF 6, and LiFSI;
The molar ratio of the lithium salt to the dianhydride monomer is (1-15): 100;
the solvent comprises one or more of acetone, dimethyl sulfoxide and N, N-dimethylformamide.
9. The silicon composite material according to claim 1, wherein the polymerization reaction temperature is 40-70 ℃;
the polymerization reaction time is 1-4 hours;
the temperature of the spray drying is 150-200 ℃;
the temperature of the heating and curing is 300-450 ℃;
and the heating and curing time is 2-6 hours.
10. A lithium ion battery is characterized by comprising a positive electrode and a negative electrode;
the negative electrode comprises a silicon composite negative electrode material;
The silicon composite anode material comprises the silicon composite material according to any one of claims 1 to 9.
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