CN116960312B - Modified silicon-based anode material and preparation method thereof - Google Patents
Modified silicon-based anode material and preparation method thereof Download PDFInfo
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- CN116960312B CN116960312B CN202311196812.3A CN202311196812A CN116960312B CN 116960312 B CN116960312 B CN 116960312B CN 202311196812 A CN202311196812 A CN 202311196812A CN 116960312 B CN116960312 B CN 116960312B
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- 239000010405 anode material Substances 0.000 title claims abstract description 88
- 238000002360 preparation method Methods 0.000 title claims abstract description 12
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N Silicium dioxide Chemical compound O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 claims abstract description 67
- 229910052710 silicon Inorganic materials 0.000 claims abstract description 59
- 239000010703 silicon Substances 0.000 claims abstract description 59
- WHXSMMKQMYFTQS-UHFFFAOYSA-N Lithium Chemical compound [Li] WHXSMMKQMYFTQS-UHFFFAOYSA-N 0.000 claims abstract description 31
- 229910052744 lithium Inorganic materials 0.000 claims abstract description 31
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical group [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 claims abstract description 25
- 229910052799 carbon Inorganic materials 0.000 claims abstract description 22
- 239000000377 silicon dioxide Substances 0.000 claims abstract description 20
- 239000011247 coating layer Substances 0.000 claims abstract description 15
- 239000010410 layer Substances 0.000 claims abstract description 15
- BPQQTUXANYXVAA-UHFFFAOYSA-N Orthosilicate Chemical compound [O-][Si]([O-])([O-])[O-] BPQQTUXANYXVAA-UHFFFAOYSA-N 0.000 claims abstract description 14
- 235000012239 silicon dioxide Nutrition 0.000 claims abstract description 12
- -1 silicon oxide compound Chemical class 0.000 claims abstract description 10
- 239000012792 core layer Substances 0.000 claims abstract description 8
- XUIMIQQOPSSXEZ-UHFFFAOYSA-N Silicon Chemical compound [Si] XUIMIQQOPSSXEZ-UHFFFAOYSA-N 0.000 claims description 72
- 150000003376 silicon Chemical class 0.000 claims description 59
- 229910052751 metal Inorganic materials 0.000 claims description 38
- 239000002184 metal Substances 0.000 claims description 32
- 238000007738 vacuum evaporation Methods 0.000 claims description 31
- OBNDGIHQAIXEAO-UHFFFAOYSA-N [O].[Si] Chemical compound [O].[Si] OBNDGIHQAIXEAO-UHFFFAOYSA-N 0.000 claims description 21
- 239000007789 gas Substances 0.000 claims description 16
- 238000010438 heat treatment Methods 0.000 claims description 13
- 239000000126 substance Substances 0.000 claims description 13
- 239000011148 porous material Substances 0.000 claims description 12
- 238000002156 mixing Methods 0.000 claims description 11
- 239000011777 magnesium Substances 0.000 claims description 10
- 239000011863 silicon-based powder Substances 0.000 claims description 10
- 239000004215 Carbon black (E152) Substances 0.000 claims description 9
- FYYHWMGAXLPEAU-UHFFFAOYSA-N Magnesium Chemical compound [Mg] FYYHWMGAXLPEAU-UHFFFAOYSA-N 0.000 claims description 9
- 238000001816 cooling Methods 0.000 claims description 9
- 229930195733 hydrocarbon Natural products 0.000 claims description 9
- 150000002430 hydrocarbons Chemical class 0.000 claims description 9
- 229910052749 magnesium Inorganic materials 0.000 claims description 9
- DGAQECJNVWCQMB-PUAWFVPOSA-M Ilexoside XXIX Chemical compound C[C@@H]1CC[C@@]2(CC[C@@]3(C(=CC[C@H]4[C@]3(CC[C@@H]5[C@@]4(CC[C@@H](C5(C)C)OS(=O)(=O)[O-])C)C)[C@@H]2[C@]1(C)O)C)C(=O)O[C@H]6[C@@H]([C@H]([C@@H]([C@H](O6)CO)O)O)O.[Na+] DGAQECJNVWCQMB-PUAWFVPOSA-M 0.000 claims description 8
- 239000011248 coating agent Substances 0.000 claims description 8
- 238000000576 coating method Methods 0.000 claims description 8
- 229910021419 crystalline silicon Inorganic materials 0.000 claims description 8
- 150000002736 metal compounds Chemical class 0.000 claims description 8
- 239000011734 sodium Substances 0.000 claims description 8
- 229910052708 sodium Inorganic materials 0.000 claims description 8
- 229910002026 crystalline silica Inorganic materials 0.000 claims description 7
- ATUOYWHBWRKTHZ-UHFFFAOYSA-N Propane Chemical compound CCC ATUOYWHBWRKTHZ-UHFFFAOYSA-N 0.000 claims description 6
- 239000012298 atmosphere Substances 0.000 claims description 6
- 238000010902 jet-milling Methods 0.000 claims description 6
- 229910044991 metal oxide Inorganic materials 0.000 claims description 6
- 150000004706 metal oxides Chemical class 0.000 claims description 6
- 150000004972 metal peroxides Chemical class 0.000 claims description 6
- VNWKTOKETHGBQD-UHFFFAOYSA-N methane Chemical compound C VNWKTOKETHGBQD-UHFFFAOYSA-N 0.000 claims description 6
- 238000012216 screening Methods 0.000 claims description 6
- 239000011265 semifinished product Substances 0.000 claims description 6
- HSFWRNGVRCDJHI-UHFFFAOYSA-N alpha-acetylene Natural products C#C HSFWRNGVRCDJHI-UHFFFAOYSA-N 0.000 claims description 5
- 125000002534 ethynyl group Chemical group [H]C#C* 0.000 claims description 5
- OYPRJOBELJOOCE-UHFFFAOYSA-N Calcium Chemical compound [Ca] OYPRJOBELJOOCE-UHFFFAOYSA-N 0.000 claims description 4
- ZLMJMSJWJFRBEC-UHFFFAOYSA-N Potassium Chemical compound [K] ZLMJMSJWJFRBEC-UHFFFAOYSA-N 0.000 claims description 4
- 229910052791 calcium Inorganic materials 0.000 claims description 4
- 239000011575 calcium Substances 0.000 claims description 4
- 229910052700 potassium Inorganic materials 0.000 claims description 4
- 239000011591 potassium Substances 0.000 claims description 4
- 229910052712 strontium Inorganic materials 0.000 claims description 4
- CIOAGBVUUVVLOB-UHFFFAOYSA-N strontium atom Chemical compound [Sr] CIOAGBVUUVVLOB-UHFFFAOYSA-N 0.000 claims description 4
- OTMSDBZUPAUEDD-UHFFFAOYSA-N Ethane Chemical compound CC OTMSDBZUPAUEDD-UHFFFAOYSA-N 0.000 claims description 3
- 229910021417 amorphous silicon Inorganic materials 0.000 claims description 3
- 150000001875 compounds Chemical class 0.000 claims description 3
- 238000007747 plating Methods 0.000 claims description 3
- 239000001294 propane Substances 0.000 claims description 3
- 230000001681 protective effect Effects 0.000 claims description 3
- 238000009830 intercalation Methods 0.000 abstract description 21
- 230000002687 intercalation Effects 0.000 abstract description 21
- 238000000034 method Methods 0.000 abstract description 17
- 230000008569 process Effects 0.000 abstract description 13
- 229910052814 silicon oxide Inorganic materials 0.000 abstract description 13
- 239000007773 negative electrode material Substances 0.000 abstract description 9
- 230000008859 change Effects 0.000 abstract description 6
- 239000010439 graphite Substances 0.000 abstract description 3
- 229910002804 graphite Inorganic materials 0.000 abstract description 3
- 230000002035 prolonged effect Effects 0.000 abstract description 3
- 239000000463 material Substances 0.000 description 62
- 230000000052 comparative effect Effects 0.000 description 14
- 239000000843 powder Substances 0.000 description 14
- 238000012360 testing method Methods 0.000 description 13
- 230000001351 cycling effect Effects 0.000 description 11
- 238000001704 evaporation Methods 0.000 description 10
- 239000012071 phase Substances 0.000 description 10
- 230000008021 deposition Effects 0.000 description 9
- 238000011068 loading method Methods 0.000 description 8
- 238000009831 deintercalation Methods 0.000 description 7
- CPLXHLVBOLITMK-UHFFFAOYSA-N magnesium oxide Inorganic materials [Mg]=O CPLXHLVBOLITMK-UHFFFAOYSA-N 0.000 description 7
- HBBGRARXTFLTSG-UHFFFAOYSA-N Lithium ion Chemical compound [Li+] HBBGRARXTFLTSG-UHFFFAOYSA-N 0.000 description 6
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 description 6
- 239000013078 crystal Substances 0.000 description 6
- 229910052760 oxygen Inorganic materials 0.000 description 6
- 239000001301 oxygen Substances 0.000 description 6
- 239000002245 particle Substances 0.000 description 6
- 239000000243 solution Substances 0.000 description 6
- 239000000395 magnesium oxide Substances 0.000 description 5
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 description 4
- 230000007547 defect Effects 0.000 description 4
- 230000000694 effects Effects 0.000 description 4
- 229910001416 lithium ion Inorganic materials 0.000 description 4
- HEMHJVSKTPXQMS-UHFFFAOYSA-M Sodium hydroxide Chemical compound [OH-].[Na+] HEMHJVSKTPXQMS-UHFFFAOYSA-M 0.000 description 3
- 230000008020 evaporation Effects 0.000 description 3
- AXZKOIWUVFPNLO-UHFFFAOYSA-N magnesium;oxygen(2-) Chemical compound [O-2].[Mg+2] AXZKOIWUVFPNLO-UHFFFAOYSA-N 0.000 description 3
- 238000004321 preservation Methods 0.000 description 3
- 239000000047 product Substances 0.000 description 3
- 238000006722 reduction reaction Methods 0.000 description 3
- RYGMFSIKBFXOCR-UHFFFAOYSA-N Copper Chemical compound [Cu] RYGMFSIKBFXOCR-UHFFFAOYSA-N 0.000 description 2
- 208000032953 Device battery issue Diseases 0.000 description 2
- 239000010426 asphalt Substances 0.000 description 2
- 230000009286 beneficial effect Effects 0.000 description 2
- 230000003139 buffering effect Effects 0.000 description 2
- 239000010406 cathode material Substances 0.000 description 2
- 238000010924 continuous production Methods 0.000 description 2
- 239000011889 copper foil Substances 0.000 description 2
- 230000003111 delayed effect Effects 0.000 description 2
- 239000003792 electrolyte Substances 0.000 description 2
- 238000010348 incorporation Methods 0.000 description 2
- 238000009776 industrial production Methods 0.000 description 2
- FUJCRWPEOMXPAD-UHFFFAOYSA-N lithium oxide Chemical compound [Li+].[Li+].[O-2] FUJCRWPEOMXPAD-UHFFFAOYSA-N 0.000 description 2
- 229910001947 lithium oxide Inorganic materials 0.000 description 2
- 230000014759 maintenance of location Effects 0.000 description 2
- 229910021421 monocrystalline silicon Inorganic materials 0.000 description 2
- 229910052757 nitrogen Inorganic materials 0.000 description 2
- XXQBEVHPUKOQEO-UHFFFAOYSA-N potassium superoxide Chemical compound [K+].[K+].[O-][O-] XXQBEVHPUKOQEO-UHFFFAOYSA-N 0.000 description 2
- 239000002994 raw material Substances 0.000 description 2
- 230000009467 reduction Effects 0.000 description 2
- 238000004626 scanning electron microscopy Methods 0.000 description 2
- 238000005245 sintering Methods 0.000 description 2
- IATRAKWUXMZMIY-UHFFFAOYSA-N strontium oxide Chemical compound [O-2].[Sr+2] IATRAKWUXMZMIY-UHFFFAOYSA-N 0.000 description 2
- 238000006467 substitution reaction Methods 0.000 description 2
- 238000009423 ventilation Methods 0.000 description 2
- 239000011800 void material Substances 0.000 description 2
- SBLRHMKNNHXPHG-UHFFFAOYSA-N 4-fluoro-1,3-dioxolan-2-one Chemical compound FC1COC(=O)O1 SBLRHMKNNHXPHG-UHFFFAOYSA-N 0.000 description 1
- 239000006245 Carbon black Super-P Substances 0.000 description 1
- OIFBSDVPJOWBCH-UHFFFAOYSA-N Diethyl carbonate Chemical compound CCOC(=O)OCC OIFBSDVPJOWBCH-UHFFFAOYSA-N 0.000 description 1
- KMTRUDSVKNLOMY-UHFFFAOYSA-N Ethylene carbonate Chemical compound O=C1OCCO1 KMTRUDSVKNLOMY-UHFFFAOYSA-N 0.000 description 1
- 229910013870 LiPF 6 Inorganic materials 0.000 description 1
- 239000004743 Polypropylene Substances 0.000 description 1
- 229920002125 Sokalan® Polymers 0.000 description 1
- 230000004913 activation Effects 0.000 description 1
- 239000011149 active material Substances 0.000 description 1
- 238000004220 aggregation Methods 0.000 description 1
- 230000002776 aggregation Effects 0.000 description 1
- 239000003513 alkali Substances 0.000 description 1
- 239000012300 argon atmosphere Substances 0.000 description 1
- 239000002585 base Substances 0.000 description 1
- 239000011230 binding agent Substances 0.000 description 1
- 230000005540 biological transmission Effects 0.000 description 1
- 238000001354 calcination Methods 0.000 description 1
- BRPQOXSCLDDYGP-UHFFFAOYSA-N calcium oxide Chemical compound [O-2].[Ca+2] BRPQOXSCLDDYGP-UHFFFAOYSA-N 0.000 description 1
- 239000000292 calcium oxide Substances 0.000 description 1
- ODINCKMPIJJUCX-UHFFFAOYSA-N calcium oxide Inorganic materials [Ca]=O ODINCKMPIJJUCX-UHFFFAOYSA-N 0.000 description 1
- 239000003153 chemical reaction reagent Substances 0.000 description 1
- 239000006258 conductive agent Substances 0.000 description 1
- 230000008602 contraction Effects 0.000 description 1
- 230000001276 controlling effect Effects 0.000 description 1
- 230000002596 correlated effect Effects 0.000 description 1
- 230000000875 corresponding effect Effects 0.000 description 1
- 238000005336 cracking Methods 0.000 description 1
- 238000005520 cutting process Methods 0.000 description 1
- 125000004122 cyclic group Chemical group 0.000 description 1
- 238000013461 design Methods 0.000 description 1
- 230000006866 deterioration Effects 0.000 description 1
- 230000001627 detrimental effect Effects 0.000 description 1
- 238000007323 disproportionation reaction Methods 0.000 description 1
- 238000001035 drying Methods 0.000 description 1
- 230000001747 exhibiting effect Effects 0.000 description 1
- 238000011049 filling Methods 0.000 description 1
- 230000016507 interphase Effects 0.000 description 1
- 230000002427 irreversible effect Effects 0.000 description 1
- 239000007791 liquid phase Substances 0.000 description 1
- HPGPEWYJWRWDTP-UHFFFAOYSA-N lithium peroxide Chemical compound [Li+].[Li+].[O-][O-] HPGPEWYJWRWDTP-UHFFFAOYSA-N 0.000 description 1
- HCWCAKKEBCNQJP-UHFFFAOYSA-N magnesium orthosilicate Chemical compound [Mg+2].[Mg+2].[O-][Si]([O-])([O-])[O-] HCWCAKKEBCNQJP-UHFFFAOYSA-N 0.000 description 1
- 239000000391 magnesium silicate Substances 0.000 description 1
- 229910052919 magnesium silicate Inorganic materials 0.000 description 1
- 235000019792 magnesium silicate Nutrition 0.000 description 1
- 238000004519 manufacturing process Methods 0.000 description 1
- 239000011259 mixed solution Substances 0.000 description 1
- 239000000203 mixture Substances 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 239000002159 nanocrystal Substances 0.000 description 1
- 239000012299 nitrogen atmosphere Substances 0.000 description 1
- 229920001155 polypropylene Polymers 0.000 description 1
- CHWRSCGUEQEHOH-UHFFFAOYSA-N potassium oxide Chemical compound [O-2].[K+].[K+] CHWRSCGUEQEHOH-UHFFFAOYSA-N 0.000 description 1
- 229910001950 potassium oxide Inorganic materials 0.000 description 1
- LIVNPJMFVYWSIS-UHFFFAOYSA-N silicon monoxide Chemical compound [Si-]#[O+] LIVNPJMFVYWSIS-UHFFFAOYSA-N 0.000 description 1
- 239000002210 silicon-based material Substances 0.000 description 1
- KKCBUQHMOMHUOY-UHFFFAOYSA-N sodium oxide Chemical compound [O-2].[Na+].[Na+] KKCBUQHMOMHUOY-UHFFFAOYSA-N 0.000 description 1
- 229910001948 sodium oxide Inorganic materials 0.000 description 1
- PFUVRDFDKPNGAV-UHFFFAOYSA-N sodium peroxide Chemical compound [Na+].[Na+].[O-][O-] PFUVRDFDKPNGAV-UHFFFAOYSA-N 0.000 description 1
- 239000007784 solid electrolyte Substances 0.000 description 1
- 239000002904 solvent Substances 0.000 description 1
- 238000003756 stirring Methods 0.000 description 1
- 239000000758 substrate Substances 0.000 description 1
Classifications
-
- 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
-
- 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
- H01M4/36—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
- H01M4/36—Selection of substances as active materials, active masses, active liquids
- H01M4/48—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides
- H01M4/485—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of mixed oxides or hydroxides for inserting or intercalating light metals, e.g. LiTi2O4 or LiTi2OxFy
-
- 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
- H01M4/58—Selection of substances as active materials, active masses, active liquids of inorganic compounds other than oxides or hydroxides, e.g. sulfides, selenides, tellurides, halogenides or LiCoFy; of polyanionic structures, e.g. phosphates, silicates or borates
- H01M4/5825—Oxygenated metallic salts or polyanionic structures, e.g. borates, phosphates, silicates, olivines
-
- 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
-
- 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
- H01M2004/026—Electrodes composed of, or comprising, active material characterised by the polarity
- H01M2004/027—Negative electrodes
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
- Y02E60/10—Energy storage using batteries
Abstract
The invention provides a modified silicon-based negative electrode material and a preparation method thereof, and particularly relates to the technical field of lithium battery negative electrode materials. The modified silicon-based anode material comprises a core layer and a shell layer, wherein the core layer comprises silicon, silicon dioxide, a non-integer ratio silicon oxide compound and silicate, and the shell layer is a carbon coating layer; the porosity of the modified silicon-based anode material is 0.5% -20%, an expansion space is reserved for the lithium intercalation process, the intrinsic volume expansion rate of the modified silicon-based anode material is 60% -120%, and after the modified silicon-based anode material is compounded with anode materials such as graphite to form a pole piece, the expansion rate of the pole piece is 10% -30%, so that the influence of volume change on the pole piece is greatly reduced, and the service life of a battery is prolonged.
Description
Technical Field
The invention relates to the technical field of lithium battery anode materials, in particular to a modified silicon-based anode material and a preparation method thereof.
Background
In recent years, the demand for battery energy density in various fields has been rapidly increased, and lithium ion batteries having higher energy density have been strongly demanded.
The silicon-based anode material is considered to be a potential anode material of the next generation of high-energy-density lithium ion battery because of higher theoretical specific capacity. Silicon oxide (SiO) is a main negative electrode material in silicon-based negative electrodes, has excellent comprehensive properties, and is currently in commercial production in small batches.
The silicon oxide is initially of a completely amorphous structure, and nano Si clusters and amorphous SiO in the silicon oxide are generated along with the progress of electrochemical circulation 2 The microstructure of the silicon oxide is changed continuously, and the cycle performance of the silicon oxide is affected. In the cycling process, the continuous intercalation and deintercalation of lithium can lead to the aggregation of Si atoms, and the continuous growth of Si clusters, on one hand, the growth of Si clusters can lead to the deterioration of the kinetics of the intercalation/deintercalation of lithium of materials, and on the other hand, the growth of Si clusters can also increase the stress variation of the clusters in the expansion and contraction processes, so that the clusters are easier to crack in the cycling process, the capacity loss and the cycling stability reduction are caused, and finally the battery failure is caused.
From the practical standpoint, the intrinsic volume expansion rate of the silicon-based anode material should be less than 80%, and preferably can be less than 30%. The silicon oxide material with the most commercialized potential at present has the specific capacity of 1600-1700 mAh g -1 The intrinsic volume expansion rate is about 160%, which is far from practical requirements, so that structural design is necessary to reduce the volume expansion rate of the material.
In view of this, the present invention has been made.
Disclosure of Invention
The invention aims to provide a modified silicon-based negative electrode material, which aims to solve the technical problems of poor kinetics of lithium intercalation/deintercalation caused by volume change, capacity loss caused by cracking and reduction of battery failure caused by cycle stability in the silicon-based negative electrode material in the prior art.
The second purpose of the invention is to provide a preparation method of the modified silicon-based anode material.
In order to achieve the above object of the present invention, the following technical solutions are specifically adopted:
the first aspect of the invention provides a modified silicon-based anode material, which comprises a core layer and a shell layer, wherein the core layer comprises silicon, silicon dioxide, a non-integer ratio silicon oxide compound and silicate, and the shell layer is a carbon coating layer;
wherein the silica, the non-integer ratio of silica compound, and the silicate are a continuous phase; the average grain diameter of the silicon is 1nm-20nm, the silicon is a discontinuous phase and is dispersed in the continuous phase;
the porosity of the modified silicon-based anode material is 0.5% -20%.
Alternatively, the diameter of the holes is 2nm-50nm;
the pores include open pores and closed pores; the theoretical density of the discharge hole structure of the modified silicon-based anode material is 2.3g/cm 3 -2.83g/cm 3 True density of closed cells is 2.2g/cm 3 -2.6g/cm 3 。
Optionally, the silicon comprises crystalline silicon and amorphous silicon, and the mass ratio of the crystalline silicon in the silicon is 5% -95%.
The silica includes crystalline silica and amorphous silica, and the mass ratio of the crystalline silica in the silica is 5% to 95%.
Alternatively, the silicon to oxygen atomic ratio is 1:0.95-1.05.
The silicon-oxygen atomic ratio of the non-integer ratio silicon-oxygen compound is 0.5-2:1.
Optionally, the silicate is a non-integer ratio compound, and the metal elements in the silicate comprise monovalent metal elements and/or divalent metal elements;
the mass ratio of the metal element in the modified silicon-based anode material is 0.2% -20%;
the monovalent metal element includes at least one of lithium, sodium, and potassium;
the divalent metal element comprises at least one of magnesium, calcium and strontium;
the molar ratio of the monovalent metal element to the silicon is 1-4:1;
the molar ratio of the divalent metal element to silicon is 1-2:1.
Optionally, the thickness of the carbon coating layer is 2nm-20nm.
The carbon in the carbon coating layer accounts for 0.5-5% of the mass of the modified silicon-based anode material.
The second aspect of the invention provides a preparation method of the modified silicon-based anode material, which comprises the following steps:
A. uniformly mixing silicon powder, silicon dioxide powder and metal simple substance or metal compound, and then carrying out vacuum evaporation to obtain a semi-finished product of the modified silicon-based anode material;
B. and (3) carrying out jet milling on the semi-finished product, introducing hydrocarbon gas in a protective gas atmosphere to coat to obtain a shell layer, and cooling and screening to obtain the modified silicon-based anode material.
Further, the metal simple substance comprises monovalent metal simple substance and/or divalent metal simple substance;
the metal compound includes at least one of monovalent metal oxide, monovalent metal peroxide, divalent metal oxide, and divalent metal peroxide.
Further, the vacuum degree of the vacuum evaporation is 0Pa-50Pa, and the time of the vacuum evaporation is 8h-12h.
The temperature of the heating end of the vacuum evaporation plating is 1200-1500 ℃; the temperature of the vacuum evaporation collecting end is 700-900 ℃.
Further, in the step B, the temperature of the coating is 800-1200 ℃ and the time is 1-5 h.
Further, the hydrocarbon gas includes at least one of methane, ethane, propane, ethylene, propylene, and acetylene.
The flow rate of the hydrocarbon gas is 1L/min-5L/min, and the introducing time is 30min-60min.
Compared with the prior art, the invention has at least the following beneficial effects:
according to the modified silicon-based anode material provided by the invention, silicon is a discontinuous phase and is dispersed in the continuous phase, so that the compactness of the material is improved. The average grain diameter of silicon is 1nm-20nm, the silicon has low crystallinity, and the silicon exists in the anode material in the form of monocrystalline silicon, so that the conductivity and the stability of the anode material are improved. Meanwhile, the grain size of the silicon is in the nanometer level, so that the grain size of the prepared anode material is lower, and the damage of the volume expansion of the silicon to the anode material grains and the electrode is reduced. The modified silicon-oxygen anode material is used in a battery, so that Si clusters are effectively reduced, and the kinetics of lithium intercalation/deintercalation of the battery is improved; meanwhile, the capacity loss is delayed, and the cycling stability of the battery is improved. In addition, the porosity of the modified silicon-based anode material is 0.5% -20%, an expansion space is reserved for the lithium intercalation process, the intrinsic volume expansion rate is 60% -120%, and after the modified silicon-based anode material is compounded with anode materials such as graphite to form a pole piece, the expansion rate of the pole piece is 10% -30%, so that the influence of volume change on the pole piece is greatly reduced, and the service life of a battery is prolonged.
The preparation method of the modified silicon-based anode material provided by the invention has the advantages of continuous process and high degree of mechanization, realizes precise control of the preparation method, has better uniformity and stability of products, and is suitable for large-scale industrial production.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings that are needed in the description of the embodiments or the prior art will be briefly described, and it is obvious that the drawings in the description below are some embodiments of the present invention, and other drawings can be obtained according to the drawings without inventive effort for a person skilled in the art.
Fig. 1 is an SEM photograph of the modified silicon-based anode material provided in example 1 before lithium intercalation;
FIG. 2 is an SEM photograph of the modified silicon-based anode material provided in comparative example 1 before lithium intercalation;
fig. 3 is an SEM photograph of the modified silicon-based anode material provided in example 1 after lithium intercalation;
FIG. 4 is an SEM photograph of the modified silicon-based anode material provided in comparative example 1 after lithium intercalation;
FIG. 5 is an SEM photograph of the modified silicon oxygen anode material provided in example 2;
fig. 6 is an SEM photograph of the silicon oxygen anode material provided in example 5.
Detailed Description
For the purpose of making the objects, technical solutions and advantages of the present invention more apparent, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention, and it is apparent that the described embodiments are only some embodiments of the present invention, not all embodiments of the present invention.
The terms "comprises," "comprising," "including," or any other variation thereof, are intended to cover a specific feature, number, step, operation, element, component, or combination of the foregoing, which may be used in various embodiments of the present invention, and are not intended to first exclude the presence of or increase the likelihood of one or more other features, numbers, steps, operations, elements, components, or combinations of the foregoing.
Furthermore, the terms "first," "second," "third," and the like are used merely to distinguish between descriptions and should not be construed as indicating or implying relative importance.
The first aspect of the invention provides a modified silicon-based anode material, which comprises a core layer and a shell layer, wherein the core layer comprises silicon, silicon dioxide, a non-integer ratio silicon oxide compound and silicate, and the shell layer is a carbon coating layer;
wherein the silica, the non-integer ratio of silica compound, and the silicate are a continuous phase; the average grain diameter of the silicon is 1nm-20nm, the silicon is a discontinuous phase and is dispersed in the continuous phase;
the porosity of the modified silicon-based anode material is 0.5% -20%.
According to the modified silicon-based anode material provided by the invention, silicon is a discontinuous phase and is dispersed in the continuous phase, so that the compactness of the material is improved. The average grain diameter of silicon is 1nm-20nm, the silicon has low crystallinity, and the silicon exists in the anode material in the form of monocrystalline silicon, so that the conductivity and the stability of the anode material are improved. Meanwhile, the grain size of the silicon is in the nanometer level, so that the grain size of the prepared anode material is lower, and the damage of the volume expansion of the silicon to the anode material grains and the electrode is reduced. The modified silicon-oxygen anode material is used in a battery, so that Si clusters are effectively reduced, and the kinetics of lithium intercalation/deintercalation of the battery is improved; meanwhile, the capacity loss is delayed, and the cycling stability of the battery is improved. In addition, the porosity of the modified silicon-based anode material is 0.5% -20%, an expansion space is reserved for the lithium intercalation process, the intrinsic volume expansion rate is 60% -120%, and after the modified silicon-based anode material is compounded with anode materials such as graphite to form a pole piece, the expansion rate of the pole piece is 10% -30%, so that the influence of volume change on the pole piece is greatly reduced, and the service life of a battery is prolonged.
In the silicon with the average grain diameter of 1nm-20nm, crystalline silicon exists in the modified silicon-based anode material mainly because the grain size of the silicon is related to the doping amount and the temperature of each step, the silicon grain is generated by disproportionation reaction of silicon oxide and reduction reaction of a modifying element, and the determined doping amount and the temperature of each step are determined, so that the grain size of the material is determined. The grain size of the finally produced material is within the range of the doping amount conditions and various heat treatment temperature conditions set in the foregoing.
In some embodiments of the invention, the average particle size of the silicon in the modified silicon-based anode material is typically, but not limited to, 1nm, 5nm, 10nm, 15nm, or 20nm.
Alternatively, the diameter of the pores is 2nm-50nm.
In the sintering process of the modified silicon-based anode material, holes exist in the material, so that a volume expansion space is provided for the silicon-based anode material in lithium intercalation, and the volume change of the silicon-based material is reduced. Typically, but not by way of limitation, the diameter of the pores is typically, but not limited to, 2nm, 10nm, 20nm, 30nm, 40nm or 50nm.
The pores include open pores and closed pores; the theoretical density of the discharge hole structure of the modified silicon-based anode material is 2.3g/cm 3 -2.83g/cm 3 True density of closed cells is 2.2g/cm 3 -2.6g/cm 3 。
Typically, but not by way of limitation, modified siliconThe theoretical density of the base anode material is 2.3g/cm 3 、2.4g/cm 3 、2.5g/cm 3 、2.6g/cm 3 、2.7g/cm 3 、2.8g/cm 3 Or 2.83g/cm 3 The method comprises the steps of carrying out a first treatment on the surface of the True density of 2.2g/cm containing closed cells 3 、2.3g/cm 3 、2.4g/cm 3 、2.5g/cm 3 Or 2.6g/cm 3 。
Optionally, the silicon comprises crystalline silicon and amorphous silicon, and the mass ratio of the crystalline silicon in the silicon is 5% -95%. In some embodiments of the invention, the mass ratio of crystalline silicon is typically, but not limited to, 5%, 15%, 25%, 35%, 45%, 55%, 65%, 75%, 85% or 95%.
The silica includes crystalline silica and amorphous silica, and the mass ratio of the crystalline silica in the silica is 5% to 95%. In some embodiments of the invention, the crystalline silica is typically, but not limited to, 5%, 15%, 25%, 35%, 45%, 55%, 65%, 75%, 85% or 95% by mass.
Alternatively, the silicon to oxygen atomic ratio is 1:0.95-1.05. When the silicon-oxygen atomic ratio is larger than 1:0.95, a connected inert buffer layer is difficult to form, the expansion rate is large, and the material circulation stability is poor; when the silicon-oxygen atomic ratio is less than 1:1.05, the specific capacity of the material is lower, the first effect is reduced, the dynamic performance is poor, and the practical requirement is not met. In some embodiments of the invention, the silicon to oxygen atomic ratio is typically, but not limited to, 1:0.95, 1:0.98, 1:1, 1:1.03, or 1:1.05. Considering volume change rate, cycle stability, specific capacity, first coulombic efficiency and lithium intercalation/deintercalation kinetic performance, the silicon-oxygen atomic ratio is in the range, and the material has optimal comprehensive performance. The silicon-oxygen atomic ratio of the non-integer ratio silicon-oxygen compound is 0.5-2:1. In the modified silicon-based anode material, the silicon atomic ratio in the non-whole ratio silicon oxide is typically but not limited to 0.5:1, 1:1, 1.5:1 or 2:1.
Optionally, the silicate is a non-integer ratio compound, and the metal elements in the silicate comprise monovalent metal elements and/or divalent metal elements; the silicate is added, so that the mechanical property of the modified silicon-oxygen anode material is improved, and the cycling stability and the first coulombic efficiency of the material are improved.
The mass ratio of the metal element in the modified silicon-based anode material is 0.2% -20%;
the monovalent metal element includes at least one of lithium, sodium, and potassium;
the divalent metal element comprises at least one of magnesium, calcium and strontium;
the molar ratio of the monovalent metal element to the silicon is 1-4:1;
the molar ratio of the divalent metal element to silicon is 1-2:1.
Optionally, the thickness of the carbon coating layer is 2nm-20nm. The carbon coating layer improves the stability of silicon and a non-integer ratio silicon oxygen compound in the cathode material, and improves the conductivity of the cathode material. When the thickness of the carbon coating layer is less than 1nm, the surface of the material cannot be well protected, and in addition, the conductivity of the surface of the material is insufficient, so that the electrochemical performance of the battery is not exerted; when the thickness of the carbon coating layer is higher than 20nm, the carbon content of the material is obviously increased, the specific capacity of the material is reduced as an inactive substance, and in addition, the thicker carbon layer can obstruct lithium ion transmission, so that the electrochemical performance of the battery is not exerted. Typical, but non-limiting, carbon coating thicknesses are 1nm, 3nm, 5nm, 7nm, 9nm, 11nm, 13nm, 15nm, 17nm, 19nm, or 20nm.
The carbon in the carbon coating layer accounts for 0.5-5% of the mass of the modified silicon-based anode material.
The second aspect of the invention provides a preparation method of the modified silicon-based anode material, which comprises the following steps:
A. uniformly mixing silicon powder, silicon dioxide powder and metal simple substance or metal compound, and then carrying out vacuum evaporation to obtain a semi-finished product of the modified silicon-based anode material;
B. and (3) carrying out jet milling on the semi-finished product, introducing hydrocarbon gas in a protective gas atmosphere to coat to obtain a shell layer, and cooling and screening to obtain the modified silicon-based anode material.
The preparation method of the modified silicon-based anode material provided by the invention has the advantages of continuous process and high degree of mechanization, realizes precise control of the preparation method, has better uniformity and stability of products, and is suitable for large-scale industrial production.
Further, the metal simple substance comprises a monovalent metal simple substance and/or a divalent metal simple substance. In particular embodiments, the elemental metal is typically, but not limited to, lithium, sodium, potassium, magnesium, calcium, or strontium.
The metal compound includes at least one of monovalent metal oxide, monovalent metal peroxide, divalent metal oxide, and divalent metal peroxide.
In some embodiments of the present invention, the metal compound is typically, but not limited to, lithium oxide, sodium oxide, potassium oxide, magnesium oxide, calcium oxide, strontium oxide, lithium peroxide, sodium peroxide, or potassium peroxide.
Vacuum evaporation is a process method in which silicon, silicon dioxide and metal or metal compound are evaporated and gasified by a certain heating evaporation mode under vacuum condition, and particles fly to the surface of a substrate to be condensed and formed. By adjusting the process of the vacuum evaporation process, such as the deposition temperature, the deposited material can be in a completely amorphous structure, and silicon nanocrystals can be contained in the deposited material.
Further, the vacuum degree of the vacuum evaporation is 0Pa-50Pa, and the time of the vacuum evaporation is 8h-12h.
The temperature of the heating end of the vacuum evaporation plating is 1200-1500 ℃; the temperature of the vacuum evaporation collecting end is 700-900 ℃. The temperature of the vacuum evaporation collecting end is controlled, so that the vacuum evaporation collecting end has certain crystallinity during evaporation, the microscopic deposition morphology is improved, defects generated in the evaporation process are reduced, and the material has smaller grain size and a denser structure after being coated by carbon, so that the circulation stability and the first coulomb efficiency of the material are improved, and the material has more excellent electrochemical performance.
In some embodiments of the present invention, the temperature of the vacuum evaporation heating end is typically, but not limited to, 1200 ℃, 1300 ℃, 1400 ℃, or 1500 ℃; the temperature of the collection end of the vacuum evaporation is typically, but not limited to 700 ℃, 800 ℃, or 900 ℃.
Further, in the step B, the temperature of the coating is 800-1200 ℃ and the time is 1-5 h.
Further, the hydrocarbon gas includes at least one of methane, ethane, propane, ethylene, propylene, and acetylene.
The flow rate of the hydrocarbon gas is 1L/min-5L/min, and the introducing time is 30min-60min.
The invention is further illustrated by the following specific examples and comparative examples, however, it should be understood that these examples are for the purpose of illustration only in greater detail and should not be construed as limiting the invention in any way. The raw materials used in the examples and comparative examples of the present invention were conducted under conventional conditions or conditions recommended by the manufacturer, without specifying the specific conditions. The reagents or apparatus used were conventional products commercially available without the manufacturer's attention.
Example 1
The embodiment provides a modified silicon-based anode material, which comprises the following steps:
1. adding 10Kg of silicon powder, 13.5Kg of silicon dioxide powder and 5.3Kg of magnesia powder into a high-speed mixer, uniformly mixing, loading the materials into a vacuum evaporation furnace, heating to 1350 ℃, collecting to 800 ℃, and vacuum evaporating for 10h under 5 Pa.
2. Cooling the material subjected to vacuum evaporation, carrying out jet milling treatment to obtain powder with an average particle size of 5 mu m, and carrying out liquid phase mixing on the obtained powder through emulsified asphalt, wherein the mass of the powder and the proportion of the asphalt are 100: and 5, sintering the mixed materials in a rotary furnace with nitrogen atmosphere, wherein the calcining temperature is 800 ℃, the heat preservation time is 3 and h, and cooling and screening to obtain the modified silicon-based anode material.
Example 2
The embodiment provides a modified silicon-based anode material, which comprises the following steps:
1. adding 10Kg of silicon powder, 13.5Kg of silicon dioxide powder and 5.3Kg of magnesia powder into a high-speed mixer, uniformly mixing, loading the materials into a vacuum evaporation furnace, heating to 1350 ℃, collecting to 800 ℃, and vacuum evaporating for 10h under 5 Pa.
2. And cooling the material subjected to vacuum evaporation, performing jet milling treatment to obtain powder with an average particle diameter of 5 mu m, adding the powder into a nitrogen protection atmosphere rotary furnace to prepare a carbon coating layer, wherein the coating temperature is 900 ℃, and the heat preservation time is 3 hours. In the process, after the temperature reaches 900 ℃, acetylene gas is introduced into the furnace, the gas flow is 2L/min, the ventilation time is 40min, and the modified silicon-oxygen anode material is obtained after cooling and screening.
Example 3
The embodiment provides a modified silicon-based anode material, which comprises the following steps:
1. adding 10Kg of silicon powder, 13.5Kg of silicon dioxide powder and 5.3Kg of sodium hydroxide powder into a high-speed mixer, uniformly mixing, loading the materials into a vacuum evaporation furnace, heating to 1350 ℃, collecting to 900 ℃, and vacuum evaporating for 8 hours under 5 Pa.
2. As in example 2.
Example 4
The embodiment provides a modified silicon-based anode material, which comprises the following steps:
1. adding 10Kg of silicon powder, 13.5Kg of silicon dioxide powder and 3.96Kg of lithium oxide powder into a high-speed mixer, uniformly mixing, loading the materials into a vacuum evaporation furnace, heating the materials to 1500 ℃, collecting the materials to 700 ℃, and vacuum evaporating the materials for 10 hours under the condition of 5 Pa.
2. As in example 2.
Example 5
The difference between the modified silicon-based anode material provided in this embodiment and embodiment 2 is that in step 1, the temperature of the collecting end is 600 ℃, and the other raw materials and steps are the same as those in embodiment 2, and are not described here again.
Example 6
The embodiment provides a modified silicon-based anode material, which comprises the following steps:
1. adding 10.9Kg of silicon powder, 13.5Kg of silicon dioxide powder and 5.3Kg of magnesium oxide powder into a high-speed mixer, uniformly mixing, loading the materials into a vacuum evaporation furnace, heating to 1350 ℃, collecting to 800 ℃, and vacuum evaporating for 10h.
2. As in example 2.
Example 7
The embodiment provides a modified silicon-based anode material, which comprises the following steps:
1. adding 9.2Kg of silicon powder, 13.5Kg of silicon dioxide powder and 5.3Kg of magnesium oxide powder into a high-speed mixer, uniformly mixing, loading the materials into a vacuum evaporation furnace, heating to 1350 ℃, collecting to 800 ℃, and vacuum evaporating for 10h.
2. As in example 2.
Comparative example 1
This comparative example provides a silicon-based anode material comprising the steps of:
1. adding 10Kg of silicon powder and 21.4Kg of silicon dioxide powder into a high-speed mixer, mixing uniformly, loading the materials into a vacuum evaporation furnace, heating to 1350 ℃, collecting to 800 ℃, and vacuum evaporating for 10h under the condition of 5 Pa.
2. And cooling the material subjected to vacuum evaporation, performing jet milling treatment to obtain powder with an average particle diameter of 5 mu m, adding the powder into a nitrogen protection atmosphere rotary furnace to prepare a carbon coating layer, wherein the coating temperature is 900 ℃, and the heat preservation time is 3 hours. And in the process, after the temperature reaches 900 ℃, introducing acetylene gas into the furnace, wherein the gas flow is 2L/min, the ventilation time is 40min, and cooling and screening to obtain the modified silicon-based anode material.
Test example 1
XRD was performed on the materials obtained in examples 1 to 7 and comparative example 1 by smoothly filling the powder material into XRD sample test grooves, placing the test grooves into XRD sample card grooves, setting the test angle to 10-80 DEG, and the scan speed to 7 DEG/min, and using the apparatus of D/max 2500 of Rigaku corporation, japan. The XRD diffraction peaks and Si crystal sizes obtained are shown in table 1 below.
TABLE 1
As can be seen from table 1, the comparison of example 2 and example 5, by controlling the deposition temperature, yields materials with and without silicon crystals at the time of deposition, and both materials with silicon crystals initially have smaller grain sizes after the same coating treatment, and examples 3 and 4, it can be seen that the thermal effects of sodium and lithium are more compared to magnesium, and thus the sodium and lithium doped materials have larger grain sizes. As can be seen from examples 2, 6 and 7, the silicon-oxygen ratio is positively correlated with the grain size, and the grain size is large when the silicon-oxygen ratio is large and small when the silicon-oxygen ratio is small. Comparative example 1 was not doped so the grain size was minimal.
Test example 2
The materials obtained in examples 1 to 7 and comparative example 1 were tested for true density using a true densitometer, theoretical density data of silica and magnesium silicate were searched for and the theoretical density of the material was calculated from the magnesium content of the material, and the porosity was calculated from the difference between the theoretical density and the true density, and the obtained data are shown in table 2 below.
TABLE 2
As can be seen from table 2, since the cells produced are closed cells and are not open to the atmosphere, the true density test included a closed cell volume that was lower than the theoretical density of a material that was completely void free. The porosity is only related to the Mg doping amount, so that the porosities of examples 1, 2 and 5 are not different, but sodium and lithium elements have no pore-forming effect, so that the porosities of examples 3, 4 and comparative example 1 are lower, the true density is close to the theoretical density, and in examples 6 and 7, the overall porosity is reduced and the true density is slightly improved due to the introduction of additional silicon and oxygen.
Test example 3
The anode materials provided in examples 1-7 and comparative example 1 were assembled into a battery, as follows:
1. preparing a pole piece: the negative electrode material, the conductive agent (Super-P) and the polyacrylic acid (PAA) binder are mixed according to the mass ratio of 80:10:10, uniformly stirring and coating the mixture on a copper foil current collector, airing at room temperature, placing the copper foil current collector into a vacuum oven, and further drying at 60 ℃ for 12 hours to obtain the pole piece.
2. And (3) battery assembly: cutting the obtained pole piece into round pole piece with diameter of 10 mm, and active material loading of 1.3 mg/cm 2 The method comprises the steps of carrying out a first treatment on the surface of the Metallic lithium sheet as counter electrode, 1 mol/L LiPF 6 (the solvent was a mixed solution of ethylene carbonate and diethyl carbonate in a volume ratio of 1:1, 5% by volume of fluoroethylene carbonate was added as an electrolyte, a polypropylene microporous separator was assembled into 2032-type coin cells in a glove box under an argon atmosphere, and 50 μl of the electrolyte was added to each cell.
And (3) carrying out electrical property test on the obtained 2032 type button battery: the charge and discharge cut-off voltages were 1.5V and 0.005V, respectively, and then activation was performed at 0.05C magnification and charge and discharge cycling was performed at 0.5C magnification, and the electrochemical performance results for the different materials of table 3 were obtained.
TABLE 3 electrochemical performance results for different materials
As can be seen from table 3, example 1 and example 2 have the same magnesium incorporation, and the silicon crystal size and porosity are almost the same, thus exhibiting similar capacity, first effect and capacity retention; the sodium element incorporated in example 3 does not bond well with silica, and brings serious residual alkali problem, resulting in poor electrical properties; the lithium element in example 4 has the lowest relative atomic mass corresponding to the unit charge, so that the first coulomb efficiency of the material can be effectively improved without reducing too much capacity, but the buffer network formed by the lithium element has no hole structure for buffering volume expansion, so that the cycling stability is poor; example 5 has the same incorporation amount and the same void fraction as examples 1 and 2, has similar capacity and first coulombic efficiency as examples 1 and 2, but relatively poor capacity retention or cycling stability due to the larger silicon crystal size; examples 6 and 7 compared with example 2, example 6, which has a higher capacity with higher silicon oxide, has a slightly lower initial coulombic efficiency due to the increase in volume expansion ratio, and the buffer layer content containing oxygen is also reduced, resulting in lower cycling stability than example 2, example 7, which has a lower silicon oxide content, resulting in a lower active silicon duty cycle, a lower specific capacity, and a higher oxygen content, resulting in more initial irreversible lithium consumption, lower initial coulombic efficiency, and excessive buffer layer, which slows down the kinetics of material intercalation/deintercalation, and thus the cycling stability is not as good as example 2. In summary, moderate silica ratio and deposition temperature are controlled, and holes for buffering volume expansion are constructed in the structure of the material by a magnesium element doping method, so that the volume expansion rate of the material can be effectively reduced by adjusting the size of silicon crystals, and the repeated generation of particles, pole piece stripping and SEI (solid electrolyte interphase) is inhibited, so that the material has better cycle stability.
Test example 4
The negative electrode materials obtained in example 1 and comparative example 1 were subjected to scanning electron microscopy, which was Japanese electron JEOL JSM-6701F, and SEM photographs obtained were shown in FIGS. 1 and 2.
SEM photographs obtained by scanning electron microscopy of the negative electrode material after lithium intercalation in test example 2 are shown in fig. 3 and 4.
As measured from fig. 1, 2, 3 and 4, the thickness of example 1 before lithium intercalation is 24.6um, the thickness after lithium intercalation is 30.8um, the volume expansion rate is 25.2%, the thickness of comparative example 1 before lithium intercalation is 24.0um, the thickness after lithium intercalation is 40.2um, the volume expansion rate is 67.5%, and the volume expansion rate is greatly reduced when the material is intercalated by magnesium doped in the pores generated in the material.
Test example 5
The negative electrode materials obtained in example 2 and example 5 were used as a Scanning Electron Microscope (SEM) which was japan electron JEOL JSM-6701F, and the obtained SEM photographs were shown in fig. 5 and 6.
As can be seen from fig. 5 and fig. 6, fig. 5 shows the result of the deposition of example 2 at a higher temperature, the high temperature deposition makes the microstructure of the material as a whole denser, and has fewer defects, which is more beneficial to improve the structural stability and the first coulombic efficiency of the material, and fig. 6 shows the result of the deposition of example 5 at a lower temperature, the microstructure of the low temperature deposited material as a whole has more defects, channels and interfaces, which are detrimental to the structural stability of the material, and the reversibility of lithium ions at these positions is reduced, which results in the first efficiency of the material being reduced. The deposition temperature is controlled, so that the material is deposited more uniformly and compactly, the generation of defects is reduced, and the cyclic stability and the first coulomb efficiency of the material are improved.
Test example 6
The materials on the negative electrode sheet used in test example 2 were measured for thickness before and after lithium intercalation, respectively, and the instrument used for measuring thickness was a scanning electron microscope, and the obtained data are shown in table 4.
TABLE 4 Table 4
As can be seen from table 4, the rule of expansion rate is basically consistent with the rule of porosity and electrochemical performance of the material, and the volume expansion rate of examples 3, 4 and comparative example 1 is large because of lower porosity; examples 1, 2, 5, 6, 7 are similar in porosity and similar in pole piece expansion rate; example 6 the volume expansion rate was slightly higher because additional silicon was introduced.
Finally, it should be noted that: the above examples are only specific embodiments of the present invention, and are not intended to limit the scope of the present invention, but it should be understood by those skilled in the art that the present invention is not limited thereto, and that the present invention is described in detail with reference to the foregoing examples: any person skilled in the art may modify or easily conceive of the technical solution described in the foregoing embodiments, or perform equivalent substitution of some of the technical features, while remaining within the technical scope of the present disclosure; such modifications, changes or substitutions do not depart from the spirit and scope of the technical solutions of the embodiments of the present invention, and are intended to be included in the scope of the present invention. Therefore, the protection scope of the present invention shall be subject to the protection scope of the claims.
Claims (7)
1. The modified silicon-based anode material is characterized by comprising a core layer and a shell layer, wherein the core layer comprises silicon, silicon dioxide, a non-integer ratio silicon oxygen compound and silicate, and the shell layer is a carbon coating layer;
wherein the silica, the non-integer ratio of silica compound, and the silicate are a continuous phase; the average grain diameter of the silicon is 1nm-20nm, the silicon is a discontinuous phase and is dispersed in the continuous phase;
the porosity of the modified silicon-based anode material is 0.5% -20%; the diameter of the hole is 2nm-50nm;
the pores include open pores and closed pores; the theoretical density of the discharge hole structure of the modified silicon-based anode material is 2.3g/cm 3 -2.83g/cm 3 True density of closed cells is 2.2g/cm 3 -2.6g/cm 3 ；
The preparation method of the modified silicon-based anode material comprises the following steps:
A. uniformly mixing silicon powder, silicon dioxide powder and metal simple substance or metal compound, and then carrying out vacuum evaporation, wherein the vacuum degree of the vacuum evaporation is 0Pa-50Pa, and the time of the vacuum evaporation is 8h-12h; the temperature of the heating end of the vacuum evaporation plating is 1200-1500 ℃; the temperature of the vacuum evaporation collecting end is 700-900 ℃; obtaining a semi-finished product of the modified silicon-based anode material;
B. and (3) after carrying out jet milling on the semi-finished product, introducing hydrocarbon gas in a protective gas atmosphere, coating for 1-5 hours at 800-1200 ℃ to obtain a shell layer, and cooling and screening to obtain the modified silicon-based anode material.
2. The modified silicon-based anode material according to claim 1, wherein the silicon comprises crystalline silicon and amorphous silicon, and the mass ratio of the crystalline silicon in the silicon is 5% to 95%;
the silica includes crystalline silica and amorphous silica, and the mass ratio of the crystalline silica in the silica is 5% to 95%.
3. The modified silicon-based anode material according to claim 1, wherein the silicon-oxygen atomic ratio is 1:0.95-1.05;
the silicon-oxygen atomic ratio of the non-integer ratio silicon-oxygen compound is 0.5-2:1.
4. The modified silicon-based anode material according to claim 1, wherein the silicate is a non-integer ratio compound, and the metal element in the silicate comprises a monovalent metal element and/or a divalent metal element;
the mass ratio of the metal element in the modified silicon-based anode material is 0.2% -20%;
the monovalent metal element includes at least one of lithium, sodium, and potassium;
the divalent metal element comprises at least one of magnesium, calcium and strontium;
the molar ratio of the monovalent metal element to the silicon is 1-4:1;
the molar ratio of the divalent metal element to silicon is 1-2:1.
5. The modified silicon-based anode material according to claim 1, wherein the thickness of the carbon coating layer is 2nm to 20nm;
the carbon in the carbon coating layer accounts for 0.5-5% of the mass of the modified silicon-based anode material.
6. The modified silicon-based anode material according to claim 1, wherein the metal simple substance comprises a monovalent metal simple substance and/or a divalent metal simple substance;
the metal compound includes at least one of monovalent metal oxide, monovalent metal peroxide, divalent metal oxide, and divalent metal peroxide.
7. The modified silicon-based anode material according to claim 1, wherein the hydrocarbon gas comprises at least one of methane, ethane, propane, ethylene, propylene, and acetylene;
the flow rate of the hydrocarbon gas is 1L/min-5L/min, and the introducing time is 30min-60min.
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| CN111072038B (en) * | 2019-12-27 | 2021-01-01 | 江西壹金新能源科技有限公司 | Modified silicon monoxide material for lithium ion battery cathode and preparation method thereof |
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