CN117438587B - Silicon-based anode material, preparation method and application thereof, and lithium ion battery - Google Patents
Silicon-based anode material, preparation method and application thereof, and lithium ion battery Download PDFInfo
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- CN117438587B CN117438587B CN202311743233.6A CN202311743233A CN117438587B CN 117438587 B CN117438587 B CN 117438587B CN 202311743233 A CN202311743233 A CN 202311743233A CN 117438587 B CN117438587 B CN 117438587B
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- 229910052710 silicon Inorganic materials 0.000 title claims abstract description 141
- XUIMIQQOPSSXEZ-UHFFFAOYSA-N Silicon Chemical compound [Si] XUIMIQQOPSSXEZ-UHFFFAOYSA-N 0.000 title claims abstract description 115
- 239000010703 silicon Substances 0.000 title claims abstract description 115
- 239000010405 anode material Substances 0.000 title claims abstract description 84
- HBBGRARXTFLTSG-UHFFFAOYSA-N Lithium ion Chemical compound [Li+] HBBGRARXTFLTSG-UHFFFAOYSA-N 0.000 title claims abstract description 66
- 229910001416 lithium ion Inorganic materials 0.000 title claims abstract description 66
- 238000002360 preparation method Methods 0.000 title claims abstract description 22
- 239000002041 carbon nanotube Substances 0.000 claims abstract description 96
- WMFOQBRAJBCJND-UHFFFAOYSA-M Lithium hydroxide Chemical compound [Li+].[OH-] WMFOQBRAJBCJND-UHFFFAOYSA-M 0.000 claims abstract description 91
- 239000007788 liquid Substances 0.000 claims abstract description 53
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 claims abstract description 47
- 238000002156 mixing Methods 0.000 claims abstract description 38
- 239000005543 nano-size silicon particle Substances 0.000 claims abstract description 36
- 238000005245 sintering Methods 0.000 claims abstract description 36
- 238000000498 ball milling Methods 0.000 claims abstract description 35
- 229920002239 polyacrylonitrile Polymers 0.000 claims abstract description 32
- 229910013641 LiNbO 3 Inorganic materials 0.000 claims abstract description 31
- 150000002821 niobium Chemical class 0.000 claims abstract description 28
- 238000000034 method Methods 0.000 claims abstract description 25
- 229910021393 carbon nanotube Inorganic materials 0.000 claims abstract description 24
- 229910052799 carbon Inorganic materials 0.000 claims description 21
- 229910003481 amorphous carbon Inorganic materials 0.000 claims description 16
- 239000000463 material Substances 0.000 claims description 16
- 239000007773 negative electrode material Substances 0.000 claims description 15
- 239000011248 coating agent Substances 0.000 claims description 14
- 238000000576 coating method Methods 0.000 claims description 14
- 238000011065 in-situ storage Methods 0.000 claims description 10
- 238000010438 heat treatment Methods 0.000 claims description 9
- 239000012298 atmosphere Substances 0.000 claims description 6
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- 238000004321 preservation Methods 0.000 claims description 2
- 238000004519 manufacturing process Methods 0.000 claims 1
- 239000007772 electrode material Substances 0.000 abstract description 2
- 230000002349 favourable effect Effects 0.000 abstract 1
- LFQSCWFLJHTTHZ-UHFFFAOYSA-N Ethanol Chemical compound CCO LFQSCWFLJHTTHZ-UHFFFAOYSA-N 0.000 description 50
- 210000004027 cell Anatomy 0.000 description 43
- 239000006185 dispersion Substances 0.000 description 30
- 230000008569 process Effects 0.000 description 21
- 230000001351 cycling effect Effects 0.000 description 19
- 238000003756 stirring Methods 0.000 description 19
- 238000001878 scanning electron micrograph Methods 0.000 description 17
- 239000012300 argon atmosphere Substances 0.000 description 15
- 239000010955 niobium Substances 0.000 description 15
- 239000002131 composite material Substances 0.000 description 13
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Chemical compound O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 13
- -1 niobium tetraoxide sulfate Chemical compound 0.000 description 12
- 238000012360 testing method Methods 0.000 description 12
- 239000000203 mixture Substances 0.000 description 11
- 238000001035 drying Methods 0.000 description 10
- 239000003792 electrolyte Substances 0.000 description 10
- 239000008367 deionised water Substances 0.000 description 9
- 229910021641 deionized water Inorganic materials 0.000 description 9
- 229910052744 lithium Inorganic materials 0.000 description 9
- 238000003917 TEM image Methods 0.000 description 8
- 238000009792 diffusion process Methods 0.000 description 8
- 239000010410 layer Substances 0.000 description 8
- GQYHUHYESMUTHG-UHFFFAOYSA-N lithium niobate Chemical compound [Li+].[O-][Nb](=O)=O GQYHUHYESMUTHG-UHFFFAOYSA-N 0.000 description 8
- 238000010586 diagram Methods 0.000 description 7
- 239000010416 ion conductor Substances 0.000 description 7
- 238000004806 packaging method and process Methods 0.000 description 7
- YHBDIEWMOMLKOO-UHFFFAOYSA-I pentachloroniobium Chemical compound Cl[Nb](Cl)(Cl)(Cl)Cl YHBDIEWMOMLKOO-UHFFFAOYSA-I 0.000 description 7
- 229920001343 polytetrafluoroethylene Polymers 0.000 description 7
- 239000004810 polytetrafluoroethylene Substances 0.000 description 7
- 238000009210 therapy by ultrasound Methods 0.000 description 7
- WHXSMMKQMYFTQS-UHFFFAOYSA-N Lithium Chemical compound [Li] WHXSMMKQMYFTQS-UHFFFAOYSA-N 0.000 description 6
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 description 6
- 230000014759 maintenance of location Effects 0.000 description 6
- 239000001301 oxygen Substances 0.000 description 6
- 229910052760 oxygen Inorganic materials 0.000 description 6
- 230000002829 reductive effect Effects 0.000 description 6
- 239000011856 silicon-based particle Substances 0.000 description 6
- 239000011247 coating layer Substances 0.000 description 5
- 229910013872 LiPF Inorganic materials 0.000 description 4
- 101150058243 Lipf gene Proteins 0.000 description 4
- 239000004743 Polypropylene Substances 0.000 description 4
- 229910003002 lithium salt Inorganic materials 0.000 description 4
- 159000000002 lithium salts Chemical class 0.000 description 4
- 239000002245 particle Substances 0.000 description 4
- 229920001155 polypropylene Polymers 0.000 description 4
- 239000002904 solvent Substances 0.000 description 4
- 229910008373 Li-Si-O Inorganic materials 0.000 description 3
- 229910006757 Li—Si—O Inorganic materials 0.000 description 3
- 238000001237 Raman spectrum Methods 0.000 description 3
- 238000002441 X-ray diffraction Methods 0.000 description 3
- 239000011149 active material Substances 0.000 description 3
- 239000000654 additive Substances 0.000 description 3
- 230000000996 additive effect Effects 0.000 description 3
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- 239000004020 conductor Substances 0.000 description 3
- 150000002500 ions Chemical class 0.000 description 3
- 238000011056 performance test Methods 0.000 description 3
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- 238000011069 regeneration method Methods 0.000 description 3
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- 238000007086 side reaction Methods 0.000 description 3
- RYGMFSIKBFXOCR-UHFFFAOYSA-N Copper Chemical compound [Cu] RYGMFSIKBFXOCR-UHFFFAOYSA-N 0.000 description 2
- 230000009286 beneficial effect Effects 0.000 description 2
- 239000011889 copper foil Substances 0.000 description 2
- 238000005516 engineering process Methods 0.000 description 2
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- 229910021389 graphene Inorganic materials 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
- 229910021421 monocrystalline silicon Inorganic materials 0.000 description 2
- 239000002105 nanoparticle Substances 0.000 description 2
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- 238000001228 spectrum Methods 0.000 description 2
- 238000003860 storage Methods 0.000 description 2
- 238000012546 transfer Methods 0.000 description 2
- NLHHRLWOUZZQLW-UHFFFAOYSA-N Acrylonitrile Chemical compound C=CC#N NLHHRLWOUZZQLW-UHFFFAOYSA-N 0.000 description 1
- 229910012851 LiCoO 2 Inorganic materials 0.000 description 1
- 229920002125 Sokalan® Polymers 0.000 description 1
- 238000000026 X-ray photoelectron spectrum Methods 0.000 description 1
- 239000002253 acid Substances 0.000 description 1
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- 239000011230 binding agent Substances 0.000 description 1
- 230000003139 buffering effect Effects 0.000 description 1
- OJIJEKBXJYRIBZ-UHFFFAOYSA-N cadmium nickel Chemical compound [Ni].[Cd] OJIJEKBXJYRIBZ-UHFFFAOYSA-N 0.000 description 1
- 230000003197 catalytic effect Effects 0.000 description 1
- 239000010406 cathode material Substances 0.000 description 1
- 239000006258 conductive agent Substances 0.000 description 1
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- 210000001787 dendrite Anatomy 0.000 description 1
- 238000011161 development Methods 0.000 description 1
- 230000018109 developmental process Effects 0.000 description 1
- 230000000694 effects Effects 0.000 description 1
- 239000011532 electronic conductor Substances 0.000 description 1
- 238000004146 energy storage Methods 0.000 description 1
- 230000007613 environmental effect Effects 0.000 description 1
- 239000001257 hydrogen Substances 0.000 description 1
- 229910052739 hydrogen Inorganic materials 0.000 description 1
- 230000000670 limiting effect Effects 0.000 description 1
- 238000006138 lithiation reaction Methods 0.000 description 1
- 238000013507 mapping Methods 0.000 description 1
- 238000013508 migration Methods 0.000 description 1
- 230000005012 migration Effects 0.000 description 1
- 230000004660 morphological change Effects 0.000 description 1
- 229910052758 niobium Inorganic materials 0.000 description 1
- GUCVJGMIXFAOAE-UHFFFAOYSA-N niobium atom Chemical compound [Nb] GUCVJGMIXFAOAE-UHFFFAOYSA-N 0.000 description 1
- 239000003208 petroleum Substances 0.000 description 1
- 229920003023 plastic Polymers 0.000 description 1
- 239000004033 plastic Substances 0.000 description 1
- 239000004584 polyacrylic acid Substances 0.000 description 1
- 239000002994 raw material Substances 0.000 description 1
- 238000006479 redox reaction Methods 0.000 description 1
- 238000000926 separation method Methods 0.000 description 1
- 239000002210 silicon-based material Substances 0.000 description 1
- 239000002002 slurry Substances 0.000 description 1
- 230000002195 synergetic effect Effects 0.000 description 1
- 238000001291 vacuum drying Methods 0.000 description 1
- 239000011800 void material Substances 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
- H01M4/62—Selection of inactive substances as ingredients for active masses, e.g. binders, fillers
- H01M4/628—Inhibitors, e.g. gassing inhibitors, corrosion inhibitors
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M10/00—Secondary cells; Manufacture thereof
- H01M10/05—Accumulators with non-aqueous electrolyte
- H01M10/052—Li-accumulators
- H01M10/0525—Rocking-chair batteries, i.e. batteries with lithium insertion or intercalation in both electrodes; Lithium-ion batteries
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M4/00—Electrodes
- H01M4/02—Electrodes composed of, or comprising, active material
- H01M4/04—Processes of manufacture in general
- H01M4/0471—Processes of manufacture in general involving thermal treatment, e.g. firing, sintering, backing particulate active material, thermal decomposition, pyrolysis
-
- 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
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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
-
- 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
- H01M4/624—Electric conductive fillers
- H01M4/625—Carbon or graphite
-
- 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
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- General Chemical & Material Sciences (AREA)
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- Manufacturing & Machinery (AREA)
- Materials Engineering (AREA)
- Battery Electrode And Active Subsutance (AREA)
Abstract
The invention relates to the technical field of electrode materials, in particular to a silicon-based anode material, a preparation method and application thereof, and a lithium ion battery. The invention provides a preparation method of a silicon-based anode material, which comprises the following steps: mixing nano silicon, niobium salt and lithium hydroxide, and performing first sintering to obtain Si@LiNbO 3 The method comprises the steps of carrying out a first treatment on the surface of the The Si@LiNbO is subjected to 3 And mixing the carbon nano tube and liquid polyacrylonitrile, performing ball milling, and performing second sintering to obtain the silicon-based anode material. The silicon-based anode material prepared by the preparation method has higher electronic conductivity, and is favorable for rapid expansion and long-cycle stability of lithium ions.
Description
Technical Field
The invention relates to the technical field of electrode materials, in particular to a silicon-based anode material, a preparation method and application thereof, and a lithium ion battery.
Background
The lithium ion battery is used as a green secondary device, and successfully replaces the traditional battery (such as a lead-acid battery, a nickel-hydrogen battery or a nickel-cadmium battery) with high pollution in the market due to the characteristics of high energy density, good cycle stability, green and environment-friendly performance, wide working temperature range and the like. Sony since 1990, the first group was LiCoO 2 Commercial lithium ion electric with anode and petroleum tar as cathodeThe cell has been introduced to the market for about 30 years, and the market size of lithium ion batteries has been greatly developed from scratch. Nowadays, lithium ion batteries are widely used in consumer electronics (e.g. cell phones, bluetooth headsets, tablet computers, notebook computers and unmanned aerial vehicles), in the field of electric traffic (e.g. racing cars, small logistics vehicles or electric vehicles) and in energy storage systems (small household and large power stations). The lithium ion battery with high energy density can provide power for the vigorous development of electric automobiles and portable electronic equipment, and plays an increasingly important role. The silicon cathode has wide natural existence, environmental friendliness and high specific capacity (3579 mA.g) -1 ) Low operating potential (0.4 v vs. li) + Li) and the like are considered as one of the most potential negative electrode materials for next-generation lithium ion batteries. However, its commercial use in lithium ion batteries is mainly hindered by particle comminution caused by the large volume expansion (about 300%) during cycling, which leads to disruption of the conductive network; meanwhile, the silicon active nano particles are easy to agglomerate in the charge and discharge process due to extremely high surface energy, so that the free energy of the surface is reduced, and the capacity fading is accelerated. In addition, the large surface area of the silicon nanoparticles increases the direct contact of the active material with the electrolyte, consumes a large amount of lithium ions, causes side reactions and irreversible capacity increase, and reduces coulombic efficiency. Therefore, it is urgent to develop a silicon-based negative electrode material with high stability.
Disclosure of Invention
The invention aims to provide a silicon-based anode material, a preparation method and application thereof, and a lithium ion battery.
In order to achieve the above object, the present invention provides the following technical solutions:
the invention provides a preparation method of a silicon-based anode material, which comprises the following steps:
mixing nano silicon, niobium salt and lithium hydroxide, and performing first sintering to obtain Si@LiNbO 3
The Si@LiNbO is subjected to 3 Carbon nanotubesAnd mixing the silicon-based anode material with liquid polyacrylonitrile, performing ball milling, and performing second sintering to obtain the silicon-based anode material.
Preferably, the mass ratio of the nano silicon to the niobium salt to the lithium hydroxide is 2: (0.055 to 0.22): (0.009-0.36).
Preferably, the first sintering is performed in a protective atmosphere;
the temperature of the first sintering is 250-450 , and the heat preservation time is 0.5-3 h.
Preferably, the Si@LiNbO 3 The mass ratio of the carbon nano tube to the liquid polyacrylonitrile is 2: (0.04-0.1): (0.1 to 0.2).
Preferably, the ball-milling ball-material ratio is (10-30): 1, the rotating speed is 100-300 r/min, and the time is 1-6 h.
Preferably, the second sintering is performed in a protective atmosphere;
the temperature of the second sintering is 800-1000 , the time is 1-6 h, and the heating rate is 2-10 /min.
The invention also provides the silicon-based anode material prepared by the preparation method.
The invention also provides application of the silicon-based anode material in a lithium ion battery.
The invention also provides a lithium ion battery, wherein the negative electrode of the lithium ion battery comprises a silicon-based negative electrode material;
the silicon-based anode material is the silicon-based anode material according to the technical scheme.
The invention provides a preparation method of a silicon-based anode material, which comprises the following steps: mixing nano silicon, niobium salt and lithium hydroxide, and performing first sintering to obtain Si@LiNbO 3 The method comprises the steps of carrying out a first treatment on the surface of the The Si@LiNbO is subjected to 3 And mixing the carbon nano tube and liquid polyacrylonitrile, performing ball milling, and performing second sintering to obtain the silicon-based anode material. The preparation method develops an in-situ coating strategy, can effectively solve the problem of low lithium ion diffusion rate of the silicon negative electrode by coating an ion conductor, and can reduce the generation of side reaction due to direct contact between the silicon surface and electrolyte;the electronic conductor is used for improving the conductivity of the silicon negative electrode, and the problems of repeated regeneration of SEI, poor conductivity and volume expansion are well solved. Meanwhile, the Li-Nb-O ion conductor is applied to the silicon anode material for the first time, so that the rate capability of the composite material is obviously improved. The liquid acrylonitrile is used as a carbon source, and the graphene coating layer with a certain void space is formed in situ after high-temperature sintering, so that space can be provided for the expansion of nano silicon, and a good conductive network can be formed; the silicon-based anode material prepared by the preparation method has excellent initial coulombic efficiency (87%), and shows higher initial discharge capacity 2848 mA.h.g 1 Outstanding rate capability (2A g) 1 In the case of 1259 mA h g 1 ) And excellent long-cycle performance (1A g) 1 The reversible capacity after 400 times of circulation is 1000 mA.h.g 1 ). Experimental results show that the ion/electron double-conductor coating formed in situ can effectively improve electron conductivity, promote rapid diffusion of lithium ions, and help to solve the problems of regeneration of silicon-based negative electrode SEI, poor conductivity and the like.
Drawings
FIG. 1 is a schematic diagram of a preparation flow of a silicon-based anode material according to the present invention;
FIG. 2 shows that the lithium ion button half cell prepared from the silicon-based anode material of examples 1-3 has a current density of 0.5A g 1 A cycle performance curve under the condition of (2);
fig. 3 is a first charge-discharge voltage curve of a lithium ion button cell half cell prepared from the silicon-based anode material in examples 1-3;
fig. 4 is a ratio performance curve and an ac impedance chart of a lithium ion button half cell prepared from the silicon-based anode material described in examples 1-3;
FIG. 5 shows the current density of a lithium ion button cell half cell prepared from the silicon-based anode materials of examples 2, 4, and 5 at 0. A.g 1 A cycle chart and a magnification cycle chart under the condition of (a) is a cycle chart, (b) is a magnification cycle chart;
fig. 6 is an electrochemical impedance diagram of a lithium ion button cell half cell prepared from the silicon-based anode materials described in examples 2, 4, and 5;
FIG. 7 shows that the lithium ion button half cell prepared from the silicon-based anode material of example 2 was at 0.5 A.g -1 Lower cycle performance and coulombic efficiency plot;
fig. 8 is an SEM image and a TEM image of the silicon-based anode material according to example 2, wherein (a) and (b) are SEM images at different magnifications, and (c) is a TEM image;
fig. 9 is an elemental mapping diagram of a silicon-based anode material according to example 2;
FIG. 10 shows a silicon-based anode material and Si@LiNbO prepared in example 2 3 X-ray photoelectron spectrum of (2);
FIG. 11 is Si, si@LiNbO 3 And a TEM image of Si@Li-Nb-O/C/CNTs silicon-based anode material prepared in example 2;
FIG. 12 is an XRD pattern and a Raman spectrum of Si@Li-Nb-O/C/CNTs silicon-based anode material prepared in example 2 and Si;
FIG. 13 is Si, si@LiNbO 3 The cycling performance curves of the button half-cell prepared from Si/C/CNTs, si@Li-Nb-O/C/CNTs prepared in example 2 and the silicon-based negative electrode material;
FIG. 14 is a graph showing the initial library charge and discharge curves and cycle performance and coulombic efficiency at a current density of 0.3A.g-1 for a lithium ion button half cell prepared from Si@Li-Nb-O/C/CNTs silicon-based negative electrode material prepared in example 2;
FIG. 15 is a graph showing the rate capability of a button half cell prepared from Si, si/C/CNTs, si@Li-Nb-O/C/CNTs silicon-based anode material prepared in example 2, at a current density of 0.1A.g-1 to 2A.g-1;
FIG. 16 shows that the lithium ion button half cell prepared from the silicon-based anode material prepared in example 2 was 1A g -1 A cycle performance curve at current density of (2);
FIG. 17 is a cycle performance test result of the assembled button cell of the Si@Li-Nb-O/C/CNTs electrode and NCM523 described in example 2, wherein the assembled button cell of the Si@Li-Nb-O/C/CNTs electrode was subjected to electrochemical prelithiation and circulated for 2 cycles at a current density of 0.1 A.g-1, and then disassembled to prepare the button cell with NCM 523;
FIG. 18 is an SEM image of the cross section of a Si and Si@Li-Nb-O/C/CNTs electrode sheet described in example 2 before and after cycling;
FIG. 19 is an SEM image of the surfaces of Si and Si@Li-Nb-O/C/CNTs electrode sheets described in example 2 before and after cycling;
FIG. 20 is a TEM image of Si and Si@Li-Nb-O/C/CNTs electrode particles after cycling as described in example 2.
Detailed Description
As shown in fig. 1, the invention provides a preparation method of a silicon-based anode material, which comprises the following steps:
mixing nano silicon, niobium salt and lithium hydroxide, and performing first sintering to obtain Si@LiNbO 3
The Si@LiNbO is subjected to 3 And mixing the carbon nano tube and liquid polyacrylonitrile, performing ball milling, and performing second sintering to obtain the silicon-based anode material.
In the present invention, all the preparation materials are commercially available products well known to those skilled in the art unless specified otherwise.
The invention mixes nano silicon, niobium salt and lithium hydroxide, and carries out first sintering to obtain Si@LiNbO 3
In the present invention, the mixing is preferably:
mixing nano silicon and ethanol, and performing ultrasonic treatment to obtain nano silicon dispersion liquid;
mixing niobium salt and ethanol to obtain niobium salt dispersion;
mixing lithium hydroxide with deionized water to obtain a lithium hydroxide solution;
mixing the niobium salt dispersion liquid and the nano silicon dispersion liquid, stirring, adding the lithium hydroxide solution, and drying.
The invention mixes nano silicon and ethanol, and carries out ultrasonic treatment to obtain nano silicon dispersion liquid. In the invention, the dosage ratio of the nano silicon to the ethanol is preferably 2g: (10-40) mL, more preferably 2g: (20-30) mL, most preferably 2g:25mL; the ultrasonic process is not particularly limited, and may be performed by a process well known to those skilled in the art.
The invention mixes the niobium salt and ethanol to obtain the niobium salt dispersion liquid. In the invention, the dosage ratio of the niobium salt to the ethanol is preferably (0.055-0.22) g:5mL, more preferably (0.1 to 0.16) g:5mL, most preferably 0.11g:5mL. The mixing process is not particularly limited, and may be performed by a process well known to those skilled in the art. In the present invention, the niobium salt preferably includes niobium chloride or niobium tetraoxide sulfate, more preferably includes niobium chloride.
The invention mixes lithium hydroxide with deionized water to obtain lithium hydroxide solution. In the invention, the dosage ratio of the lithium hydroxide to the deionized water is preferably (0.009-0.36) g:5mL, more preferably (0.01 to 0.2) g:5mL, most preferably (0.018 to 0.1) g:5mL. The mixing process is not particularly limited, and may be performed by a process well known to those skilled in the art.
After the nano silicon dispersion liquid, the niobium salt dispersion liquid and the lithium hydroxide solution are obtained, the invention mixes the niobium salt dispersion liquid and the nano silicon dispersion liquid, stirs, adds the lithium hydroxide solution and dries. The mixing process is not particularly limited, and may be performed by a process well known to those skilled in the art. In the invention, the stirring time is preferably 5-20 min, more preferably 8-15 min, and most preferably 10min; the stirring speed is not particularly limited, and may be carried out at a speed well known to those skilled in the art. In the present invention, the drying means is preferably stirring, and the stirring process is not particularly limited, and may be performed by a process known to those skilled in the art.
In the invention, the mass ratio of the nano silicon to the niobium salt to the lithium hydroxide is preferably 2: (0.055 to 0.22): (0.009-0.36), more preferably 2: (0.1 to 0.16): (0.01 to 0.2), most preferably 2:0.11: (0.018-0.1).
In the present invention, the first sintering is preferably performed in a protective atmosphere, preferably an argon atmosphere; the temperature of the first sintering is preferably 250-450 , more preferably 300-400 , and most preferably 350 ; the holding time is preferably 0.5 to 3 hours, more preferably 0.8 to 2 hours, and most preferably 1 hour.
Obtaining Si@LiNbO 3 The invention then provides the Si@LiNbO 3 And mixing the carbon nano tube and liquid polyacrylonitrile, performing ball milling, and performing second sintering to obtain the silicon-based anode material.
In the present invention, the Si@LiNbO 3 The mass ratio of the carbon nano tube to the liquid polyacrylonitrile is preferably 2: (0.04-0.1): (0.1 to 0.2), more preferably 2: (0.05-0.08): (0.12 to 0.18), most preferably 2: (0.06-0.07): (0.14 to 0.16).
In the present invention, the ball milling is preferably wet ball milling, the ball milling medium of the wet ball milling is preferably ethanol, and the ethanol and Si@LiNbO 3 The dosage ratio of (1) is preferably (10-30) mL:2g, more preferably (15-25) mL:2g, most preferably 20mL:2g. In the invention, the ball-milling ball material ratio is preferably (10-30): 1, more preferably (15-25): 1, and most preferably 20:1; the rotation speed is preferably 100-300 r/min, more preferably 200-300 r/min, and most preferably 250r/min; the time is preferably 1 to 6 hours, more preferably 2 to 4 hours, and most preferably 3 hours. In the present invention, the ball milling is preferably performed in a ZQM-P2 type planetary ball mill.
The present invention also preferably includes drying after the ball milling, and the drying process is not particularly limited and may be performed by a process well known to those skilled in the art.
In the present invention, the second sintering is preferably performed in a protective atmosphere, preferably an argon atmosphere; the temperature of the second sintering is preferably 800-1000 , more preferably 850-950 , and most preferably 900 ; the time is preferably 1 to 6 hours, more preferably 2 to 5 hours, and most preferably 3 to 4 hours; the heating rate is preferably 2 to 10 /min, more preferably 3 to 8 /min, and most preferably 5 /min.
The invention also provides the silicon-based anode material prepared by the preparation method.
In the invention, the silicon-based anode material comprises Si, li-Nb-O and carbon which are coated on the surface of the Si in sequence from inside to outside; the carbon comprises liquid polyacrylonitrile-derived amorphous carbon (C) and CNTs, and the structural relationship between the C and the CNTs is that the liquid polyacrylonitrile-derived amorphous carbon grows on the CNTs in situ on the surface to form a coating structure.
In the invention, the mass ratio of Si, li-Nb-O, liquid polyacrylonitrile-derived amorphous carbon and CNT is preferably 100 (1-5): 2.5-7.5): 3-5, more preferably 100 (2-4): 7.5 (3.5-4.5), and most preferably 100:3:7.5:4.
The invention also provides application of the silicon-based anode material in a lithium ion battery.
The invention also provides a lithium ion battery, wherein the negative electrode of the lithium ion battery comprises a silicon-based negative electrode material;
the silicon-based anode material is the silicon-based anode material according to the technical scheme.
In the invention, the lithium ion battery preferably comprises a negative electrode shell, a spring plate, a gasket, a negative electrode, a diaphragm, a positive electrode, a gasket and a positive electrode shell which are sequentially arranged. The negative electrode preferably comprises a silicon-based negative electrode material; the positive electrode is preferably a ternary NCM523 positive electrode; the ternary NCM523 positive electrode is preferably purchased from Synergic materials technologies Inc.
The preparation process of the lithium ion battery is not particularly limited, and the lithium ion battery is packaged by a battery packaging machine under the pressure of 50MPa after being assembled in a glove box with the water oxygen value lower than 0.1ppm by adopting the process well known to the person skilled in the art, and then is kept stand for 24 hours at room temperature.
The silicon-based anode material, the preparation method and application thereof, and the lithium ion battery provided by the invention are described in detail below with reference to examples, but they are not to be construed as limiting the scope of the invention.
The liquid polyacrylonitrile in the examples was purchased from the eigen equation graphene technologies company, inc., and the other raw materials were all purchased from Allatin.
Example 1
2g of nano-silicon and 25mL of ethanol are mixed, and thenPerforming ultrasonic treatment to obtain nano silicon dispersion liquid; mixing 0.055g of niobium chloride with 5mL of ethanol to obtain a niobium salt dispersion; 0.09g of LiOH H 2 Mixing O with 5mL of deionized water to obtain a lithium hydroxide solution; mixing the niobium salt dispersion liquid and the nano silicon dispersion liquid, stirring for 10min, adding the lithium hydroxide solution, stirring until the mixture is dried, and sintering for 1h at 350 in an argon atmosphere to obtain Si@LiNbO 3
2g of the Si@LiNbO 3 Adding 80mg of carbon nano tube, 150mg of liquid polyacrylonitrile and 20mL of ethanol into a polytetrafluoroethylene ball milling tank, placing into a ZQM-P2 planetary ball mill, ball milling for 3 hours, wherein the ball material ratio of the ball milling is 20:1, the rotating speed is 250r/min, drying, and sintering for 3 hours in an argon atmosphere at the temperature rising rate of 5 /min to 900 to obtain a silicon-based anode material (LiNbO therein) 3 The addition amount of CNTs is 1 percent and the addition amount of CNTs is 4 percent; the silicon-based anode material comprises Si, li-Nb-O and carbon, wherein the Li-Nb-O and the carbon are sequentially coated on the surface of the Si from inside to outside, and the carbon comprises CNTs and liquid polyacrylonitrile amorphous carbon coated on the surface of the CNTs in an in-situ growth manner; the mass ratio of the Si, the Li-Nb-O, the liquid polyacrylonitrile-derived amorphous carbon to the CNT is 100:1:2.5:4.
example 2
Mixing 2g of nano silicon with 25mL of ethanol, and performing ultrasonic treatment to obtain nano silicon dispersion; mixing 0.11g of niobium chloride with 5mL of ethanol to obtain a niobium salt dispersion; 0.018g of LiOH H 2 Mixing O with 5mL of deionized water to obtain a lithium hydroxide solution; mixing the niobium salt dispersion liquid and the nano silicon dispersion liquid, stirring for 10min, adding the lithium hydroxide solution, stirring until the mixture is dried, and sintering for 1h at 350 in an argon atmosphere to obtain Si@LiNbO 3
2g of the Si@LiNbO 3 Adding 80mg of carbon nano tube, 150mg of liquid polyacrylonitrile and 20mL of ethanol into a polytetrafluoroethylene ball milling tank, placing into a ZQM-P2 planetary ball mill, ball milling for 3 hours, wherein the ball material ratio of the ball milling is 20:1, the rotating speed is 250r/min, drying, and sintering for 3 hours in an argon atmosphere at the temperature rising rate of 5 /min to 900 to obtain a silicon-based anode material (LiNbO therein) 3 The addition amount of CNTs is 3 percent and the addition amount of CNTs is 4 percent; the silicon isThe base anode material comprises Si, li-Nb-O and carbon, wherein the Li-Nb-O and the carbon are sequentially coated on the surface of the Si from inside to outside, and the carbon comprises CNTs and liquid polyacrylonitrile amorphous carbon coated on the surface of the CNTs in an in-situ growth manner; the mass ratio of the Si, the Li-Nb-O, the liquid polyacrylonitrile-derived amorphous carbon to the CNT is 100:3:2.5: 4).
Example 3
Mixing 2g of nano silicon with 25mL of ethanol, and performing ultrasonic treatment to obtain nano silicon dispersion; mixing 0.22g of niobium chloride with 5mL of ethanol to obtain a niobium salt dispersion; 0.36g of LiOH H 2 Mixing O with 5mL of deionized water to obtain a lithium hydroxide solution; mixing the niobium salt dispersion liquid and the nano silicon dispersion liquid, stirring for 10min, adding the lithium hydroxide solution, stirring until the mixture is dried, and sintering for 1h at 350 in an argon atmosphere to obtain Si@LiNbO 3
2g of the Si@LiNbO 3 Adding 80mg of carbon nano tube, 150mg of liquid polyacrylonitrile and 20mL of ethanol into a polytetrafluoroethylene ball milling tank, placing into a ZQM-P2 planetary ball mill, ball milling for 3 hours, wherein the ball material ratio of the ball milling is 20:1, the rotating speed is 250r/min, drying, and sintering for 3 hours in an argon atmosphere at the temperature rising rate of 5 /min to 900 to obtain a silicon-based anode material (LiNbO therein) 3 The addition amount of CNTs is 5% and the addition amount of CNTs is 4%; the silicon-based anode material comprises Si, li-Nb-O and carbon, wherein the Li-Nb-O and the carbon are sequentially coated on the surface of the Si from inside to outside, and the carbon comprises CNTs and liquid polyacrylonitrile amorphous carbon coated on the surface of the CNTs in an in-situ growth manner; the mass ratio of the Si, the Li-Nb-O, the liquid polyacrylonitrile-derived amorphous carbon to the CNT is 100:5:2.5:4.
test example 1
The silicon-based anode materials described in examples 1 to 3 were assembled into lithium ion button half batteries in the order of anode casing, spring sheet, gasket, counter electrode (lithium metal electrode), separator (of Celgard 2500 type), anode (the anode material is the silicon-based anode material described in examples 1 to 3), gasket and cathode casing, respectively. The specific process is as follows: the electrode of a half battery is made of a pole piece made by a laboratory, a lithium piece with the diameter of 15.4 and mm is a counter electrode, a diaphragm is a porous polypropylene diaphragm, and electrolyte at two sides of the diaphragm is40. Mu L. The solvent in the electrolyte is EC/DEC (v/v=1:1), and the lithium salt is LiPF with the concentration of 1 mol/L 6 The additive was 5wt% FEC. And packaging by using a battery packaging machine under the pressure of 50MPa to obtain the prepared CR2032 button half battery. The whole assembly process is carried out in a glove box with the water oxygen value lower than 0.1ppm, and the packaged half battery is subjected to a test at normal temperature by using a LAND battery tester after standing for 24 hours at room temperature; the lithium ion button half cell has the current density of 0. A.g 1 The test result is shown in fig. 2, and as can be seen from fig. 2, the lithium ion button half cell prepared by the silicon-based anode material in example 2 has the highest capacity and the best cycle performance after 200 cycles of charge and discharge cycles;
fig. 3 is a graph of the first charge-discharge voltage of the lithium ion button half cell prepared by the silicon-based anode material of examples 1-3, and as can be seen from fig. 3, the first coulomb efficiency of the lithium ion button half cell prepared by the silicon-based anode material of example 1 is 78.7%, the first coulomb efficiency of the lithium ion button half cell prepared by the silicon-based anode material of example 2 is 84.4%, and the first coulomb efficiency of the lithium ion button half cell prepared by the silicon-based anode material of example 3 is 78.7%; compared with the first coulomb efficiency of 75.6 percent of the lithium ion full battery prepared by the silicon cathode material, the LiNbO is illustrated 3 The addition of (2) can improve the first coulombic efficiency of the composite material and promote the formation of stable SEI;
fig. 4 is a ratio performance curve and an ac impedance diagram of a lithium ion button half cell prepared from the silicon-based anode material described in examples 1-3, wherein (a) is a ratio performance curve and (b) is an ac impedance diagram; as is clear from FIG. 4, the sample obtained in example 2 has excellent rate performance of 2A g 1 Is circulated for 10 circles under the high current density, and the average capacity is 922 mA h g 1 And when the current density becomes 0.1A g 1 The time capacity still remains 1980 mA.h.g 1 Indicating good reversibility of the composite. The impedance after fitting of the samples obtained in example 1, example 2, and example 3, as shown in FIG. 4 (b), was 197. OMEGA., 164.5. OMEGA., and, respectively, were measured by EIS test on three samples146.6, along with LiNbO 3 The charge transfer resistance of the composite material is gradually reduced, indicating LiNbO 3 High ionic conductivity can reduce Li + Impedance to migration at the surface. To sum up, the half cell performance test result is combined to obtain 3% LiNbO 3 The addition amount is the optimal addition amount;
example 4
Mixing 2g of nano silicon with 25mL of ethanol, and performing ultrasonic treatment to obtain nano silicon dispersion; mixing 0.11g of niobium chloride with 5mL of ethanol to obtain a niobium salt dispersion; 0.018g of LiOH H 2 Mixing O with 5mL of deionized water to obtain a lithium hydroxide solution; mixing the niobium salt dispersion liquid and the nano silicon dispersion liquid, stirring for 10min, adding the lithium hydroxide solution, stirring until the mixture is dried, and sintering for 1h at 350 in an argon atmosphere to obtain Si@LiNbO 3
2g of the Si@LiNbO 3 Adding 60mg of carbon nano tube, 150mg of liquid polyacrylonitrile and 20mL of ethanol into a polytetrafluoroethylene ball milling tank, placing into a ZQM-P2 planetary ball mill, ball milling for 3 hours, wherein the ball material ratio of ball milling is 20:1, the rotating speed is 250r/min, drying, heating to 900 at a heating rate of 5 /min in argon atmosphere, and sintering for 3 hours to obtain a silicon-based anode material (Si@Li-Nb-O/C/CNTs-3%, wherein the adding amount of CNTs is 3%), the silicon-based anode material comprises Si and Li-Nb-O and carbon which are sequentially coated on the surface of the Si from inside to outside, the carbon comprises CNTs and liquid polyacrylonitrile amorphous carbon which is coated on the surface of the CNTs in situ, and the mass ratio of the Si, the Li-Nb-O, the liquid polyacrylonitrile-derived amorphous carbon to the CNTs is 100:3:2.5:3.
Example 5
Mixing 2g of nano silicon with 25mL of ethanol, and performing ultrasonic treatment to obtain nano silicon dispersion; mixing 0.11g of niobium chloride with 5mL of ethanol to obtain a niobium salt dispersion; 0.018g of LiOH H 2 Mixing O with 5mL of deionized water to obtain a lithium hydroxide solution; mixing the niobium salt dispersion liquid and the nano silicon dispersion liquid, stirring for 10min, adding the lithium hydroxide solution, stirring until the mixture is dried, and sintering for 1h at 350 in an argon atmosphere to obtain Si@LiNbO 3
2g of the Si@LiNbO 3 Adding 100mg of carbon nano tube, 150mg of liquid polyacrylonitrile and 20mL of ethanol into a polytetrafluoroethylene ball milling tank, placing into a ZQM-P2 planetary ball mill, ball milling for 3 hours, wherein the ball material ratio of ball milling is 20:1, the rotating speed is 250r/min, drying, heating to 900 at a heating rate of 5 /min in argon atmosphere, and sintering for 3 hours to obtain a silicon-based anode material (Si@Li-Nb-O/C/CNTs-3%, wherein the adding amount of CNTs is 5%), the silicon-based anode material comprises Si and Li-Nb-O and carbon which are sequentially coated on the surface of the Si from inside to outside, the carbon comprises CNTs and liquid polyacrylonitrile amorphous carbon which is coated on the surface of the CNTs in situ, and the mass ratio of the Si, the Li-Nb-O, the liquid polyacrylonitrile-derived amorphous carbon to the CNTs is 100:3:2.5:5.
Test example 2
The silicon-based anode materials described in examples 2, 4, and 5 were assembled into a lithium ion button half cell in the order of anode casing, shrapnel, gasket, counter electrode (lithium metal electrode), separator (of Celgard 2500 type), anode (the anode material is the silicon-based anode material described in examples 1 to 3), gasket, and cathode casing, respectively. The button half-cell comprises the following specific processes: the electrode of a half battery is made of a pole piece made by a laboratory, a lithium piece with the diameter of 15.4 and mm is a counter electrode, the diaphragm is a porous polypropylene diaphragm, and electrolyte at two sides of the diaphragm is 40 mu L. The solvent in the electrolyte is EC/DEC (v/v=1:1), and the lithium salt is LiPF with the concentration of 1 mol/L 6 The additive was 5wt% FEC. And packaging by using a battery packaging machine under the pressure of 50MPa to obtain the prepared CR2032 button half battery. The whole assembly process is carried out in a glove box with the water oxygen value lower than 0.1ppm, and the packaged half battery is subjected to a test at normal temperature by using a LAND battery tester after standing for 24 hours at room temperature;
the button type full battery comprises the following specific processes: a pole piece prepared by a laboratory is used as a cathode of a half battery, ternary NCM523 with the diameter of 15.4 and mm is used as an anode, a diaphragm is a porous polypropylene diaphragm, and electrolyte at two sides of the diaphragm is 40 mu L. The solvent in the electrolyte is EC/DEC (v/v=1:1), and the lithium salt is LiPF with the concentration of 1 mol/L 6 The additive was 5wt% FEC. Packaging by using a battery packaging machine under 50MPa to obtain a prepared CR2032 buckleHalf-cells. The whole assembly process is carried out in a glove box with the water oxygen value lower than 0.1ppm, and the packaged half battery is subjected to a test at normal temperature by using a LAND battery tester after standing for 24 hours at room temperature;
FIG. 5 shows the current density of a lithium ion button cell half cell prepared from the silicon-based anode materials of examples 2, 4, and 5 at 0. A.g 1 In the following description, (a) is a cycle chart, and (b) is a cycle chart, as can be seen from (a) in fig. 5, the capacity retention rate of the lithium ion full battery prepared from the silicon-based negative electrode material in example 4 after 200 cycles is 23.4%, the capacity retention rate of the lithium ion full battery prepared from the silicon-based negative electrode material in example 5 after 200 cycles is 56.0%, and the capacity retention rate of the lithium ion full battery prepared from the silicon-based negative electrode material in example 2 after 200 cycles is 66.4%; meanwhile, the capacity of the electrode prepared by 3% of CNTs (example 4) is continuously reduced, the amount of the surface carbon nanotubes is too small to form a uniform conductive network, and the separation system becomes dead silicon after the silicon electrode is expanded, so that the capacity is gradually reduced; the electrode prepared with 5% addition (example 5) had good cycle retention but lower capacity; the carbon nanotube addition amount of 4% (example 2) shows the best effect; as is clear from FIG. 5 (b), the amount of carbon nanotubes added was 0.1 A.g 1 0.2Ag 1 0.5Ag 1 1.0Ag 1 2.0Ag 1 Specific discharge capacities of (C) are 2785 mA.h.g 1 2080mAhg 1 1725mAhg 1 2785mAhg 1 1264mAhg 1 1107mAhg 1 . Notably, the composite material was found to be 1.0A.g 1 2.0Ag 1 The discharge specific capacity of the composite material is relatively close to the discharge specific capacity, so that the composite material is excellent in rate capability;
FIG. 6 is an electrochemical impedance diagram of a lithium ion button cell half cell prepared from the silicon-based negative electrode materials described in examples 2, 4, and 5, as can be seen from FIG. 6, the diagonal line of the frequency region represents the Warburg impedance (R w ) The larger the slope, the larger the lithium ion diffusion coefficient is related to the lithium ion diffusion coefficient of the material. For a pair ofThe impedance values of the sample assembled batteries prepared in the example 4, the example 5 and the example 2 obtained by fitting the alternating current impedance are 185.5, 164.5 and 195.5 respectively, which indicates that the addition amount of the carbon nano tube is optimal by 4%;
FIG. 7 shows that the button half cell prepared from the silicon-based anode material of example 2 was at 0.5 A.g -1 As can be seen from FIG. 7, the lithium ion full cell prepared from the silicon-based negative electrode material of example 2 has a cycle performance and coulombic efficiency curve of 0.5 A.g -1 The capacity is hardly attenuated after 200 cycles under the current density of (2), because the carbon nano tube is uniformly coated on the surface of the material to construct a three-dimensional conductive network, and the Li-Nb-O layer promotes the lithium ion conduction rate and provides Li for the system when lithium is intercalated for the first time + The consumption of lithium ions is reduced, and the first coulomb efficiency is improved;
fig. 8 is an SEM image and a TEM image of the silicon-based anode material according to example 2, wherein (a) and (b) are SEM images at different magnifications, and (c) is a TEM image; as can be seen from fig. 8, in the silicon-based negative electrode material described in example 2, the carbon nanotubes are well dispersed and uniformly wound on the silicon surface to form a three-dimensional conductive network;
FIG. 9 is a schematic diagram of the silicon-based negative electrode material according to example 2, and it can be seen from FIG. 9 that the surface of the silicon particles is uniformly coated with a carbon layer and a Li-Nb-O layer, so that the formed three-dimensional conductive network can enhance the electron conductivity of the composite material, and the Li-Nb-O layer is helpful for the rapid diffusion of lithium ions to reduce the charge transfer resistance of the material;
FIG. 10 shows a silicon-based anode material and Si@LiNbO prepared in example 2 3 As can be seen from FIG. 10, si@LiNbO 3 The peaks at 98.8 eV, 99.4 eV of the 2p spectrum are monocrystalline silicon. Si@LiNbO 3 The Nb 3d spectrum of (C) is spiked at 207.5 eV and 210.0 eV, corresponding to Nb 5+ Proved that LiNbO exists on the surface of the silicon particles after 350 sintering 3 . It was also found that silicon on the surface would undergo oxidation-reduction reaction with niobium under the catalytic action of carbon. The nano silicon surface is relatively active, and silicon particles on the surface are contacted with oxygen to form a Li-Si-O layer after oxygen is introduced, so Si in Si@Li-Nb-O/C/CNTs 4+ The content is increased, and the Nb element is also fromNb alone 5+ Becomes Nb 5+ Nb 4+ Nb 3+ The three valence states coexist. Li-Nb-O has a plurality of redox potentials (Nb 5+ /Nb 4+ Nb 4+ /Nb 3+ ) And the expansion coefficient is lower, which is beneficial to the rapid diffusion of lithium ions. In addition, the Li-Si-O formed on the silicon surface is a fast ion conductor and also helps to conduct Li +
FIG. 11 is Si, si@LiNbO 3 And TEM image of Si@Li-Nb-O/C/CNTs silicon-based anode material prepared in example 2, as can be seen from FIG. 11, liNbO 3 (113) crystal plane of (d). And then the silicon particles are sintered at the high temperature of 900 to form a uniform Li-Nb-O coating layer with the thickness of about 2 nm. The silicon active nano particles are easy to agglomerate in the charge and discharge process due to extremely high surface energy, so that the free energy of the surface is reduced, and the capacity fading is accelerated. In addition, the large surface area of the silicon nanoparticles increases the direct contact of the active material with the electrolyte, consumes a large amount of lithium ions, causes side reactions and irreversible capacity increase, and reduces coulombic efficiency. And forming a Li-Nb-O ion conductor layer on the surface after the lithium-niobium oxide coating. Li-Nb-O has a plurality of redox potentials (Nb 5+ /Nb 4+ Nb 4+ /Nb 3+ ) And the expansion coefficient is lower, which is beneficial to the rapid diffusion of lithium ions. In addition, trace Li-Si-O formation on the silicon surface [107] Is a fast ion conductor and also helps conduct Li +
FIG. 12 shows XRD patterns and Raman spectra of Si, CNTs and Si@Li-Nb-O/C/CNTs silicon-based anode materials prepared in example 2, and FIG. 12 shows XRD and Raman spectra of Si, CNTs, si@Li-Nb-O/C/CNTs. Si@Li-Nb-O/C/CNTs are well matched with XRD diffraction peaks of monocrystalline silicon and completely coincide with PDF#77-2111.
FIG. 13 is a graph of Si, si/C/CNTs (2 g of Si, 80mg of carbon nanotubes, 150mg of liquid polyacrylonitrile and 20mL of ethanol are added into a polytetrafluoroethylene ball milling tank, the mixture is placed into a ZQM-P2 planetary ball mill, ball milling is performed for 3 hours, the ball-to-material ratio of the ball milling is 20:1, the rotation speed is 250r/min, the mixture is dried, and the mixture is heated to 900 at a heating rate of 5 /min in an argon atmosphere and sintered for 3 hours, thereby obtaining a silicon-based anode material (LiNbO therein) 3 Is added to (a)0% by weight, 4% by weight of CNTs)), si@LiNbO 3 And lithium ion button half cell prepared by the silicon-based anode material prepared in example 2 (the assembly process of button cell is to use a laboratory self-made anode sheet (anode preparation: active material, binder (polyacrylic acid) and conductive agent (Super P) are weighed and ground according to the proportion of 80:10:10), mixed uniformly, then placed into a stirring and defoaming box, added with proper amount of deionized water, sealed and placed into an A-310 stirring and defoaming machine for 2000 r min -1 Stirring for 20 minutes, uniformly coating the slurry on the surface of the copper foil, and drying for more than 10 h in a vacuum drying oven at 70 ; cutting the dried copper foil into a wafer with the diameter of 14 mm to obtain an electrode plate required for testing, sealing the wafer by a plastic self-sealing bag, placing the wafer in a glove box for storage) as an electrode of a half cell, taking a lithium plate with the diameter of 15.4 mm as a counter electrode, taking a porous polypropylene diaphragm as the diaphragm, taking electrolyte (the solvent is EC/DEC (v/v=1:1) at two sides of the diaphragm, and taking lithium salt as LiPF of 1 mol/L 6 ) All 40 l, button cell was assembled in a glove box with argon atmosphere and left to stand 24h to stand-by) in the cycle performance curve (test conditions: long cycle and multiplying power test are carried out within the voltage range of 0.01-2V, and the first two circles use 0.1 A.g -1 Activation was performed at 0.5 A.g -1 As can be seen from fig. 13, the doubly coated composite material showed almost no capacity fade after 200 cycles with optimal cycle performance, the initial coulombic efficiency of the si@li-Nb-O/C/CNTs electrode was as high as 87% under the action of the ion conductor and the three-dimensional conductive network, and the coulombic efficiency after 8 cycles was as high as 99%, and remained above 99.3%. The lithium niobate is proved to be a good ion conductor, and the first coulombic efficiency of the silicon electrode can be improved. The first discharge capacity of Si@Li-Nb-O/C/CNTs is mA.h.g -1 The discharge capacity of the pure silicon electrode reaches 3382 mA h g -1 But the capacity fade after 50 cycles was 0 because the silicon negative electrode expands up to 360% in volume during lithium storage. The ion and electron double-conductor coating layer and the three-dimensional conductive network provide buffering for the volume expansion of silicon, so that the volume expansion is effectively inhibited, and the circulation stability of the material is improved;
FIG. 14 shows the initial coulombic efficiency of a lithium ion button cell half-cell prepared from Si@Li-Nb-O/C/CNTs silicon-based anode material prepared in example 2 and a total internal temperature of 0.3 A.g -1 As can be seen from fig. 14, the silicon-based material has a low lithiation potential, which can effectively inhibit the formation of lithium dendrites, and the lithium niobium oxide coating layer provides lithium ions in the first charge and discharge, thereby effectively improving the first coulombic efficiency. The lithium metal half cell prepared by the Si@Li-Nb-O/C/CNTs composite material is 0. A.g -1 The capacity at current density is kept at 1600 mA h g -1 The above;
FIG. 15 is a graph showing Si, si/C/CNTs (2 g of Si, 80mg of carbon nanotubes, 150mg of liquid polyacrylonitrile and 20mL of ethanol are added into a polytetrafluoroethylene ball milling tank, the mixture is placed into a ZQM-P2 planetary ball mill, ball milling is performed for 3 hours, the ball-to-material ratio of the ball milling is 20:1, the rotation speed is 250r/min, the mixture is dried, and the mixture is heated to 900 at a heating rate of 5 /min in an argon atmosphere and sintered for 3 hours, thereby obtaining a silicon-based anode material (LiNbO therein) 3 0% of CNTs and 4%) of Si@LiNbO) 3 And Si@Li-Nb-O/C/CNTs silicon-based anode material prepared in example 2, the button half cell prepared from the Si@Li-Nb-O/C/CNTs silicon-based anode material is 0.1 A.g -1 To 2 A.g -1 As can be seen from FIG. 15, the coated Si@Li-Nb-O/C/CNTs composite material shows the best multiplying power performances of 0.1, 0.2, 0.5, 1 and 2 A.g -1 The average reversible discharge capacities of the Si@Li-Nb-O/C/CNTs electrodes during cycling are 2303, 1773, 1377, 1263 and mA.h.g respectively -1 . The lithium niobium oxide has higher multiplying power performance, and the average capacity of the composite material after coating is almost consistent under high current density, and has good reversibility;
FIG. 16 shows that the lithium ion button half cell prepared from the silicon-based anode material prepared in example 2 was 1A g -1 As is clear from FIG. 16, the cycle performance curve at the current density of (2) was kept 1000.3 mA.h.g after 400 cycles -1 The capacity retention was 80%. The lithium niobium oxide and carbon nano tube double coating structure has strong structural stability;
the results of the cycle performance test of the assembled half cell of the Si@Li-Nb-O/C/CNTs electrode and NCM523, in which the assembled half cell of the Si@Li-Nb-O/C/CNTs electrode was subjected to electrochemical prelithiation and cycled for 2 cycles at a current density of 0.1 A.g-1, and then disassembled and cycled with NCM523 to prepare a full cell are shown in FIG. 17, and as can be seen from FIG. 17, NCM523// Si@Li-Nb-O/C/CNTs were cycled at a current density of 0.1C, the initial coulombic efficiency was 85%, and the capacity retention after 35 cycles was 66%;
FIG. 18 is a SEM image of the cross section of a Si and Si@Li-Nb-O/C/CNTs electrode sheet before and after cycling, as described in example 2, wherein (a) is a cross section SEM image of a Si electrode sheet before cycling, (C) is a cross section SEM image of a Si electrode sheet after cycling, (b) is a cross section SEM image of a Si@Li-Nb-O/C/CNTs electrode sheet before cycling, as described in example 2, and (d) is a cross section SEM image of a Si@Li-Nb-O/C/CNTs electrode sheet after cycling, as described in example 2; FIG. 19 is a SEM image of the cross section of a Si and Si@Li-Nb-O/C/CNTs electrode sheet before and after cycling, as described in example 2, wherein (a) is a surface SEM image of the Si electrode sheet before cycling, (b) is a surface SEM image of the Si electrode sheet after cycling, (C) is a cross section SEM image of the Si@Li-Nb-O/C/CNTs electrode sheet before cycling, as described in example 2, and (d) is a cross section SEM image of the Si@Li-Nb-O/C/CNTs electrode sheet after cycling, as described in example 2; FIG. 20 is a TEM image of Si and Si@Li-Nb-O/C/CNTs electrodes described in example 2 after cycling; as can be seen from FIG. 18, the Si@Li-Nb-O/C/CNTs electrode has only 4% volume expansion after 100 cycles, while the Si electrode has a high volume expansion rate as high as 139%, which proves that the double-coated structure has good structural stability. The excellent electrochemical performance is attributed to the ion/electron double coating and the three-dimensional conductive network, and the coating structure can promote the rapid diffusion of lithium ions and enhance the electronic conductivity; the Si@Li-Nb-O/C/CNTs electrode can still keep a complete particle state after 100 times of circulation, and a thicker SEI layer is generated on the surface of the Si electrode, so that the lithium niobium oxide and carbon nano tube double-layer coating can effectively inhibit repeated regeneration of SEI and improve electrochemical stability, and the electrode has excellent circulation performance. To further verify the structural stability of the composite, the post-cycling pole piece was tested using TEM, and the results showed that no complete silicon particles were observed for the Si electrode after 100 cycles, as the huge volume expansion after repeated cycling resulted in more fresh surface exposure and in a decay in cycling ability. As can be seen from fig. 19, fig. 19 (b) shows that after 100 cycles, various broken cracks are formed on the surface of the Si electrode (fig. 19 (a) is a surface SEM image of the Si electrode before the cycle test), however, the si@li-Nb-O/C/CNTs electrode has no significant morphological changes before (C) and after (d) in fig. 19) the cycle test, and the results further demonstrate that the lithium-niobium oxide coating layer and the three-dimensional conductive network constructed by the carbon nanotubes have good structural stability; as can be seen from fig. 20, the presence of the two-conductor coating and the network of CNTs effectively suppressed the volume expansion of silicon, and the complete particles were still observed even after 100 cycles, indicating the lithium niobium oxide coating and the three-dimensional conductive network, providing a buffer for the expansion of Si particles to give the electrode excellent long-cycle stability.
The foregoing is merely a preferred embodiment of the present invention, and it should be noted that it will be apparent to those skilled in the art that modifications and variations can be made without departing from the original scope of the invention, and these modifications and variations should also be regarded as being within the scope of the invention.
Claims (7)
1. The preparation method of the silicon-based anode material is characterized by comprising the following steps:
mixing nano silicon, niobium salt and lithium hydroxide, and performing first sintering to obtain Si@LiNbO 3 The method comprises the steps of carrying out a first treatment on the surface of the The mass ratio of the nano silicon to the niobium salt to the lithium hydroxide is 2: (0.055 to 0.22): (0.009-0.36);
the Si@LiNbO is subjected to 3 Mixing the carbon nano tube and liquid polyacrylonitrile, performing ball milling, and performing second sintering to obtain the silicon-based anode material; the Si@LiNbO 3 The mass ratio of the carbon nano tube to the liquid polyacrylonitrile is 2: (0.04-0.1): (0.1 to 0.2);
the silicon-based anode material comprises Si, li-Nb-O and carbon which are coated on the surface of the Si from inside to outside in sequence; the carbon comprises liquid polyacrylonitrile derived amorphous carbon and CNTs, and the structural relationship between the amorphous carbon and the CNTs is that the liquid polyacrylonitrile derived amorphous carbon grows on the CNTs in situ to form a coating structure.
2. The method of manufacturing according to claim 1, wherein the first sintering is performed in a protective atmosphere;
the temperature of the first sintering is 250-450 , and the heat preservation time is 0.5-3 h.
3. The preparation method of claim 1, wherein the ball-milled ball-material ratio is (10-30): 1, the rotating speed is 100-300 r/min, and the time is 1-6 h.
4. The method of claim 1, wherein the second sintering is performed in a protective atmosphere;
the temperature of the second sintering is 800-1000 , the time is 1-6 h, and the heating rate is 2-10 /min.
5. The silicon-based anode material prepared by the preparation method of any one of claims 1-4.
6. The use of the silicon-based anode material of claim 5 in a lithium ion battery.
7. A lithium ion battery is characterized in that a negative electrode of the lithium ion battery comprises a silicon-based negative electrode material;
the silicon-based anode material is the silicon-based anode material according to claim 5.
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