CN118198363A - Lithium fluoride phase doped silicon material and preparation method and application thereof - Google Patents
Lithium fluoride phase doped silicon material and preparation method and application thereof Download PDFInfo
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- CN118198363A CN118198363A CN202410265662.5A CN202410265662A CN118198363A CN 118198363 A CN118198363 A CN 118198363A CN 202410265662 A CN202410265662 A CN 202410265662A CN 118198363 A CN118198363 A CN 118198363A
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- PQXKHYXIUOZZFA-UHFFFAOYSA-M lithium fluoride Chemical compound [Li+].[F-] PQXKHYXIUOZZFA-UHFFFAOYSA-M 0.000 title claims abstract description 117
- 239000002210 silicon-based material Substances 0.000 title claims abstract description 69
- 238000002360 preparation method Methods 0.000 title claims abstract description 14
- YCKRFDGAMUMZLT-UHFFFAOYSA-N Fluorine atom Chemical compound [F] YCKRFDGAMUMZLT-UHFFFAOYSA-N 0.000 claims abstract description 19
- 229910052731 fluorine Inorganic materials 0.000 claims abstract description 19
- 239000011737 fluorine Substances 0.000 claims abstract description 19
- 229910003002 lithium salt Inorganic materials 0.000 claims abstract description 19
- 159000000002 lithium salts Chemical class 0.000 claims abstract description 19
- 238000003756 stirring Methods 0.000 claims abstract description 19
- 238000000034 method Methods 0.000 claims abstract description 18
- 238000010438 heat treatment Methods 0.000 claims abstract description 15
- HBBGRARXTFLTSG-UHFFFAOYSA-N Lithium ion Chemical compound [Li+] HBBGRARXTFLTSG-UHFFFAOYSA-N 0.000 claims abstract description 12
- 229910001416 lithium ion Inorganic materials 0.000 claims abstract description 12
- 150000003376 silicon Chemical class 0.000 claims abstract description 12
- 238000001035 drying Methods 0.000 claims abstract description 8
- 238000000227 grinding Methods 0.000 claims abstract description 8
- 239000012266 salt solution Substances 0.000 claims abstract description 8
- 238000005245 sintering Methods 0.000 claims abstract description 8
- 239000002904 solvent Substances 0.000 claims abstract description 8
- 239000012298 atmosphere Substances 0.000 claims abstract description 6
- 239000011259 mixed solution Substances 0.000 claims abstract description 6
- 239000011833 salt mixture Substances 0.000 claims abstract description 6
- 230000001681 protective effect Effects 0.000 claims abstract description 5
- XUIMIQQOPSSXEZ-UHFFFAOYSA-N Silicon Chemical compound [Si] XUIMIQQOPSSXEZ-UHFFFAOYSA-N 0.000 claims description 34
- 229910052710 silicon Inorganic materials 0.000 claims description 27
- 239000010703 silicon Substances 0.000 claims description 27
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N Silicium dioxide Chemical compound O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 claims description 26
- 229910052814 silicon oxide Inorganic materials 0.000 claims description 22
- IEJIGPNLZYLLBP-UHFFFAOYSA-N dimethyl carbonate Chemical compound COC(=O)OC IEJIGPNLZYLLBP-UHFFFAOYSA-N 0.000 claims description 19
- -1 lithium hexafluorophosphate Chemical compound 0.000 claims description 11
- 229910052744 lithium Inorganic materials 0.000 claims description 10
- 239000002153 silicon-carbon composite material Substances 0.000 claims description 9
- XEKOWRVHYACXOJ-UHFFFAOYSA-N Ethyl acetate Chemical compound CCOC(C)=O XEKOWRVHYACXOJ-UHFFFAOYSA-N 0.000 claims description 6
- LFQSCWFLJHTTHZ-UHFFFAOYSA-N Ethanol Chemical compound CCO LFQSCWFLJHTTHZ-UHFFFAOYSA-N 0.000 claims description 4
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims description 3
- SBLRHMKNNHXPHG-UHFFFAOYSA-N 4-fluoro-1,3-dioxolan-2-one Chemical compound FC1COC(=O)O1 SBLRHMKNNHXPHG-UHFFFAOYSA-N 0.000 claims description 2
- KMTRUDSVKNLOMY-UHFFFAOYSA-N Ethylene carbonate Chemical compound O=C1OCCO1 KMTRUDSVKNLOMY-UHFFFAOYSA-N 0.000 claims description 2
- JBTWLSYIZRCDFO-UHFFFAOYSA-N ethyl methyl carbonate Chemical compound CCOC(=O)OC JBTWLSYIZRCDFO-UHFFFAOYSA-N 0.000 claims description 2
- 229910001496 lithium tetrafluoroborate Inorganic materials 0.000 claims description 2
- MCVFFRWZNYZUIJ-UHFFFAOYSA-M lithium;trifluoromethanesulfonate Chemical compound [Li+].[O-]S(=O)(=O)C(F)(F)F MCVFFRWZNYZUIJ-UHFFFAOYSA-M 0.000 claims description 2
- RUOJZAUFBMNUDX-UHFFFAOYSA-N propylene carbonate Chemical compound CC1COC(=O)O1 RUOJZAUFBMNUDX-UHFFFAOYSA-N 0.000 claims description 2
- VRSRNLHMYUACMN-UHFFFAOYSA-H trilithium;hexafluoroaluminum(3-) Chemical compound [Li+].[Li+].[Li+].[F-].[F-].[F-].[F-].[F-].[F-].[Al+3] VRSRNLHMYUACMN-UHFFFAOYSA-H 0.000 claims description 2
- 238000001291 vacuum drying Methods 0.000 claims description 2
- 238000004519 manufacturing process Methods 0.000 claims 3
- 239000011856 silicon-based particle Substances 0.000 abstract description 9
- 230000005540 biological transmission Effects 0.000 abstract description 4
- 230000004888 barrier function Effects 0.000 abstract description 3
- 238000009792 diffusion process Methods 0.000 abstract description 3
- 230000000052 comparative effect Effects 0.000 description 27
- VDVLPSWVDYJFRW-UHFFFAOYSA-N lithium;bis(fluorosulfonyl)azanide Chemical compound [Li+].FS(=O)(=O)[N-]S(F)(=O)=O VDVLPSWVDYJFRW-UHFFFAOYSA-N 0.000 description 22
- 239000000843 powder Substances 0.000 description 20
- 239000000243 solution Substances 0.000 description 20
- 239000000463 material Substances 0.000 description 16
- QSZMZKBZAYQGRS-UHFFFAOYSA-N lithium;bis(trifluoromethylsulfonyl)azanide Chemical compound [Li+].FC(F)(F)S(=O)(=O)[N-]S(=O)(=O)C(F)(F)F QSZMZKBZAYQGRS-UHFFFAOYSA-N 0.000 description 10
- 239000000725 suspension Substances 0.000 description 10
- 230000001351 cycling effect Effects 0.000 description 9
- 239000007773 negative electrode material Substances 0.000 description 8
- 230000008569 process Effects 0.000 description 8
- 230000002441 reversible effect Effects 0.000 description 7
- 239000011863 silicon-based powder Substances 0.000 description 7
- WHXSMMKQMYFTQS-UHFFFAOYSA-N Lithium Chemical compound [Li] WHXSMMKQMYFTQS-UHFFFAOYSA-N 0.000 description 6
- 230000002238 attenuated effect Effects 0.000 description 6
- 238000012360 testing method Methods 0.000 description 6
- 238000005303 weighing Methods 0.000 description 5
- 230000007774 longterm Effects 0.000 description 4
- IAZDPXIOMUYVGZ-UHFFFAOYSA-N Dimethylsulphoxide Chemical compound CS(C)=O IAZDPXIOMUYVGZ-UHFFFAOYSA-N 0.000 description 3
- 230000009286 beneficial effect Effects 0.000 description 3
- 238000005336 cracking Methods 0.000 description 3
- 238000001453 impedance spectrum Methods 0.000 description 3
- 229910010272 inorganic material Inorganic materials 0.000 description 3
- 239000011147 inorganic material Substances 0.000 description 3
- 230000004048 modification Effects 0.000 description 3
- 238000012986 modification Methods 0.000 description 3
- XKRFYHLGVUSROY-UHFFFAOYSA-N Argon Chemical compound [Ar] XKRFYHLGVUSROY-UHFFFAOYSA-N 0.000 description 2
- 229910018080 Li 15Si4 Inorganic materials 0.000 description 2
- HMDDXIMCDZRSNE-UHFFFAOYSA-N [C].[Si] Chemical compound [C].[Si] HMDDXIMCDZRSNE-UHFFFAOYSA-N 0.000 description 2
- JHRWWRDRBPCWTF-OLQVQODUSA-N captafol Chemical compound C1C=CC[C@H]2C(=O)N(SC(Cl)(Cl)C(Cl)Cl)C(=O)[C@H]21 JHRWWRDRBPCWTF-OLQVQODUSA-N 0.000 description 2
- 239000003575 carbonaceous material Substances 0.000 description 2
- 230000000694 effects Effects 0.000 description 2
- 238000009830 intercalation Methods 0.000 description 2
- 230000002687 intercalation Effects 0.000 description 2
- 230000002427 irreversible effect Effects 0.000 description 2
- 230000000670 limiting effect Effects 0.000 description 2
- 238000006138 lithiation reaction Methods 0.000 description 2
- 230000014759 maintenance of location Effects 0.000 description 2
- 238000010298 pulverizing process Methods 0.000 description 2
- 239000000377 silicon dioxide Substances 0.000 description 2
- 125000002023 trifluoromethyl group Chemical group FC(F)(F)* 0.000 description 2
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 description 1
- 229910019142 PO4 Inorganic materials 0.000 description 1
- DPXJVFZANSGRMM-UHFFFAOYSA-N acetic acid;2,3,4,5,6-pentahydroxyhexanal;sodium Chemical compound [Na].CC(O)=O.OCC(O)C(O)C(O)C(O)C=O DPXJVFZANSGRMM-UHFFFAOYSA-N 0.000 description 1
- 238000005054 agglomeration Methods 0.000 description 1
- 230000002776 aggregation Effects 0.000 description 1
- 229910052786 argon Inorganic materials 0.000 description 1
- 239000012300 argon atmosphere Substances 0.000 description 1
- 239000001768 carboxy methyl cellulose Substances 0.000 description 1
- 238000012512 characterization method Methods 0.000 description 1
- 239000003153 chemical reaction reagent Substances 0.000 description 1
- 238000007796 conventional method Methods 0.000 description 1
- 125000004122 cyclic group Chemical group 0.000 description 1
- 230000007547 defect Effects 0.000 description 1
- 238000009831 deintercalation Methods 0.000 description 1
- 238000011161 development Methods 0.000 description 1
- 239000002270 dispersing agent Substances 0.000 description 1
- 238000001493 electron microscopy Methods 0.000 description 1
- 230000007613 environmental effect Effects 0.000 description 1
- 238000002474 experimental method Methods 0.000 description 1
- 150000002222 fluorine compounds Chemical class 0.000 description 1
- 239000007789 gas Substances 0.000 description 1
- 229910002804 graphite Inorganic materials 0.000 description 1
- 239000010439 graphite Substances 0.000 description 1
- 239000007770 graphite material Substances 0.000 description 1
- 239000001257 hydrogen Substances 0.000 description 1
- 229910052739 hydrogen Inorganic materials 0.000 description 1
- 230000006872 improvement Effects 0.000 description 1
- 229910017053 inorganic salt Inorganic materials 0.000 description 1
- 150000002500 ions Chemical class 0.000 description 1
- 238000011031 large-scale manufacturing process Methods 0.000 description 1
- 229910052751 metal Inorganic materials 0.000 description 1
- 239000002184 metal Substances 0.000 description 1
- 229910001512 metal fluoride Inorganic materials 0.000 description 1
- 229910044991 metal oxide Inorganic materials 0.000 description 1
- 150000004706 metal oxides Chemical class 0.000 description 1
- 150000002739 metals Chemical class 0.000 description 1
- VNWKTOKETHGBQD-UHFFFAOYSA-N methane Chemical compound C VNWKTOKETHGBQD-UHFFFAOYSA-N 0.000 description 1
- 239000012299 nitrogen atmosphere Substances 0.000 description 1
- 239000002245 particle Substances 0.000 description 1
- 238000011056 performance test Methods 0.000 description 1
- 230000005501 phase interface Effects 0.000 description 1
- 235000021317 phosphate Nutrition 0.000 description 1
- 150000003013 phosphoric acid derivatives Chemical class 0.000 description 1
- 238000009656 pre-carbonization Methods 0.000 description 1
- 230000002829 reductive effect Effects 0.000 description 1
- 238000002407 reforming Methods 0.000 description 1
- 238000005096 rolling process Methods 0.000 description 1
- 235000019812 sodium carboxymethyl cellulose Nutrition 0.000 description 1
- 229920001027 sodium carboxymethylcellulose Polymers 0.000 description 1
- 239000007784 solid electrolyte Substances 0.000 description 1
- 230000006641 stabilisation Effects 0.000 description 1
- 238000011105 stabilization Methods 0.000 description 1
- 229920003048 styrene butadiene rubber Polymers 0.000 description 1
- 239000002344 surface layer Substances 0.000 description 1
- 229910052723 transition metal Inorganic materials 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
- H01M4/62—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
- H01M4/36—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
Landscapes
- Chemical & Material Sciences (AREA)
- Chemical Kinetics & Catalysis (AREA)
- Electrochemistry (AREA)
- General Chemical & Material Sciences (AREA)
- Engineering & Computer Science (AREA)
- Materials Engineering (AREA)
- Manufacturing & Machinery (AREA)
- Battery Electrode And Active Subsutance (AREA)
Abstract
The invention relates to a lithium fluoride phase doped silicon material, and a preparation method and application thereof, and belongs to the technical field of silicon materials. The preparation method of the invention comprises the following steps: s1, adding a silicon-based material into a fluorine-containing lithium salt solution, and uniformly stirring to obtain a silicon/lithium salt mixed solution; the fluorine-containing lithium salt solution comprises fluorine-containing lithium salt and a solvent; s2, stirring and heating the silicon/lithium salt mixed solution until the solvent is completely volatilized, and then drying in vacuum to obtain a silicon/lithium salt mixture; and S3, grinding and sintering the silicon/lithium salt mixture in a protective atmosphere to obtain the lithium fluoride phase doped silicon material. The method of the invention utilizes the characteristics of lower lithium ion diffusion barrier and higher structural stability of lithium fluoride to realize doping lithium fluoride in the silicon material so as to relieve the volume expansion of silicon particles, improve the transmission performance of lithium ions in the silicon material and improve the charge-discharge dynamics of the silicon material.
Description
Technical Field
The invention belongs to the technical field of silicon materials, and particularly relates to a lithium fluoride phase doped silicon material, and a preparation method and application thereof.
Background
Along with the development of the lithium ion battery to high energy density and high power density, the limitation of the commonly used graphite material is more and more obvious, the silicon negative electrode material has very high theoretical specific capacity which is 10 times of the theoretical specific capacity of the graphite, and has the characteristics of moderate charge and discharge platform, rich resources, environmental friendliness and the like, thereby being a novel negative electrode material with the most promising next-generation high specific energy lithium ion battery and having wide market prospect. Nevertheless, the industrial application of silicon negative electrode materials faces many problems and challenges, firstly, the ultra-large volume effect (the volume expansion in the lithium intercalation process exceeds 300%), and thus the pulverization of silicon particles is caused, and the effective contact among silicon particles is lost, and the cracking and the falling off of electrodes are caused after long-term circulation; meanwhile, a solid electrolyte phase interface film (SEI) on a silicon surface is not stable, resulting in continuous irreversible lithium ion consumption, and thus, not only is the first coulombic efficiency of a silicon material low, but also long-term cycle performance is unsatisfactory.
Because of the huge volume effect, the original SEI on the surface of the silicon-based negative electrode is extremely unstable and continuously regenerates in the cyclic process, so that artificial SEI is constructed at the interface of the silicon-based material, and the realization of SEI stabilization is one of effective strategies for improving the battery performance. The SEI film based on inorganic salt growing on the surface of the Si negative electrode has the advantages of good ion transmission performance, high mechanical strength and the like, and becomes one main stream direction of silicon material modification, so far, a plurality of inorganic materials such as carbon materials, metals, phosphates, metal oxides, fluorides and two-dimensional transition metal carbides (Mxene) are main materials of artificial SEI on the surface of the silicon material. However, the strategy of constructing inorganic SEI on the surface has a plurality of problems and defects, namely, the continuity and uniformity of the inorganic material on the silicon surface are poor, and the inorganic material has high brittleness and is easy to fall off. Thirdly, in the long-term circulation process, the surface layer can be aged, phase-changed and the like.
Disclosure of Invention
In order to solve the technical problems, the invention provides a lithium fluoride phase doped silicon material, and a preparation method and application thereof. According to the method disclosed by the invention, the characteristics of low lithium ion diffusion barrier and high structural stability of lithium fluoride are utilized for realizing the doping of lithium fluoride in the silicon material so as to relieve the volume expansion of silicon particles, improve the transmission performance of lithium ions in the silicon material and improve the charge-discharge kinetics of the silicon material, and more importantly, the generation of crystalline Li 15Si4 phase in the lithiation process of the silicon material is limited by doping lithium fluoride (LiF) phase, so that the silicon material with excellent multiplying power performance and cycle stability is obtained, and the method has important industrial application value.
The first object of the present invention is to provide a method for preparing a lithium fluoride phase-doped silicon material, comprising the steps of:
s1, adding a silicon-based material into a fluorine-containing lithium salt solution, and uniformly stirring to obtain a silicon/lithium salt mixed solution; the fluorine-containing lithium salt solution comprises fluorine-containing lithium salt and a solvent;
S2, stirring and heating the silicon/lithium salt mixed solution in the step S1 until the solvent is completely volatilized, and then drying in vacuum to obtain a silicon/lithium salt mixture;
And S3, grinding and sintering the silicon/lithium salt mixture in the step S2 under a protective atmosphere to obtain the lithium fluoride phase doped silicon material.
In one embodiment of the present invention, in S1, the fluorine-containing lithium salt is selected from one or more of lithium hexafluorophosphate, lithium bis-fluorosulfonyl imide, lithium bis-trifluoromethylsulfonyl imide, lithium hexafluoroaluminate, lithium hexafluorosilicate, lithium tetrafluoroborate, and lithium trifluoromethylsulfonate.
In one embodiment of the present invention, in S1, the solvent is selected from one or more of water, ethanol, ethylene carbonate, ethylmethyl carbonate, dimethyl carbonate, fluoroethylene carbonate, propylene carbonate, and ethyl acetate.
In one embodiment of the invention, in S1, the concentration of the fluorine-containing lithium salt solution is 0.01g/mL-0.1g/mL; the mass ratio of the fluorine-containing lithium salt to the silicon-based material is 0.1-1:10.
In one embodiment of the present invention, in S1, the silicon-based material is selected from one or more of nano-pure silicon, micro-pure silicon, silicon oxide, pre-carbonized silicon oxide, pre-lithiated silicon oxide, pre-magnesian oxide, and silicon-carbon composite material.
In one embodiment of the invention, in S1, the stirring time is 1h to 4h.
In one embodiment of the present invention, in S2, the temperature of the stirring and heating is 50 ℃ to 100 ℃.
In one embodiment of the present invention, in S2, the vacuum drying is performed at a temperature of 80 ℃ to 200 ℃ for a time of 4 hours to 8 hours.
In one embodiment of the invention, in S3, the sintering is performed at a temperature of 150 ℃ to 800 ℃ for a time of 1h to 5h, under which conditions the fluorine-containing lithium salt decomposes to produce lithium fluoride which penetrates into the bulk phase of the silicon particles.
In one embodiment of the present invention, in S3, the protective atmosphere is selected from a nitrogen atmosphere, an argon atmosphere, or an argon-hydrogen mixed atmosphere.
A second object of the present invention is to provide a lithium fluoride phase doped silicon material prepared by the method.
The third object of the invention is to provide an application of the lithium fluoride phase doped silicon material in the field of lithium ion batteries.
Compared with the prior art, the technical scheme of the invention has the following advantages:
(1) According to the preparation method disclosed by the invention, the fluorine-containing lithium salt and the silicon powder are uniformly mixed, the characteristic that the fluorine-containing lithium salt generates lithium fluoride at high temperature is utilized, high-temperature sintering is carried out in a protective atmosphere, the generated lithium fluoride gradually diffuses into the bulk phase of the silicon material, and the bulk phase doping of the lithium fluoride in the silicon material is realized. Thus obtaining the lithium fluoride phase doped silicon material with excellent multiplying power and cycle stability.
(2) The lithium fluoride bulk phase doped silicon material has the advantages of low lithium ion diffusion barrier, high Young modulus and good stability, and the lithium fluoride bulk phase doping is beneficial to relieving the volume expansion of silicon particles in the lithium intercalation and deintercalation process, so that the continuous cracking and reforming phenomena of the SEI film on the silicon surface are inhibited; in addition, the doping of the lithium fluoride phase is also beneficial to improving the transmission performance of lithium ions in the silicon material and improving the charge-discharge dynamics of the silicon material; more importantly, the generation of crystalline Li 15Si4 phase in the lithiation process of the silicon material can be limited by doping the lithium fluoride phase, so that the silicon material with excellent rate capability and cycle stability is obtained.
(3) The preparation method disclosed by the invention is simple in process and low in cost, is beneficial to future large-scale production, and has important application prospect and value.
Drawings
In order that the invention may be more readily understood, a more particular description of the invention will be rendered by reference to specific embodiments thereof which are illustrated in the appended drawings, in which:
FIG. 1 is an electron microscopic view of the material of example 1 and comparative example 1 of the present invention;
FIG. 2 is a graph showing the first charge and discharge curves of button cells prepared from the materials of examples 1-2 and comparative example 1 of the present invention;
FIG. 3 is a 0.5C cycle chart of button cells prepared from the materials of example 1 and comparative example 1 of the present invention;
FIG. 4 is a ratio cycle chart of button cells prepared from the materials of example 1 and comparative example 1 of the present invention;
FIG. 5 is an AC impedance spectrum after 250 cycles of button cells prepared from the materials of example 1 and comparative example 1 of the present invention;
FIG. 6 is a 0.5C cycle chart of button cells prepared from the materials of example 4 and comparative example 2 of the present invention;
FIG. 7 is an AC impedance spectrum after 120 cycles of button cells prepared from the materials of example 4 and comparative example 2 of the present invention;
FIG. 8 is a 0.5C cycle chart of button cells made from the materials of example 5 and comparative example 3 of the present invention;
Fig. 9 is an ac impedance spectrum after 300 cycles of the button cell prepared from the materials of example 5 and comparative example 3 of the present invention.
Detailed Description
The present invention will be further described with reference to the accompanying drawings and specific examples, which are not intended to be limiting, so that those skilled in the art will better understand the invention and practice it.
The present invention will be further described in conjunction with the specific embodiments described below so that those skilled in the art may better understand the present invention and practice it, and it is evident that the described embodiments are only some, but not all, of the embodiments of the present invention. It should be understood that the detailed description is intended to illustrate the invention, but is not intended to limit the invention to the particular embodiments disclosed.
In the present invention, unless otherwise defined, technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs.
In the present invention, the term "and/or" as used herein includes any and all combinations of one or more of the associated listed items, unless otherwise indicated.
In the present invention, unless otherwise indicated, all the experimental methods used in the examples of the present invention are conventional methods, and materials, reagents and the like used, unless otherwise indicated, are commercially available.
In the present application, unless otherwise indicated, the terms "comprises" and/or "comprising" when used in the present specification specify the presence of stated features, integers, steps, operations, elements, or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, or groups thereof.
In the present invention, the percentages referred to in examples of the present invention and comparative examples are mass percentages unless otherwise indicated.
In the present invention, the nano-pure silicon powder used in examples and comparative examples was purchased from Shenzhen Bei Terui New energy materials Co., ltd, model number BSO-1, unless otherwise specified.
In the present invention, the pre-carbonized silica powder used in examples and comparative examples was purchased from korean continent electronics corporation under the model DMSO unless otherwise specified.
In the present invention, the silicon carbon composite powder used in examples and comparative examples was purchased from Shenzhen Bei Terui New energy materials Co., ltd, model BTRSC unless otherwise specified.
Example 1
The lithium fluoride phase doped silicon material and the preparation method thereof in the embodiment specifically comprise the following steps:
S1: 0.3g of lithium bis (fluorosulfonyl) imide is added into 10mL of dimethyl carbonate (DMC), and stirred for 1h to obtain a solution of lithium bis (fluorosulfonyl) imide/dimethyl carbonate;
s2: weighing 10g of nano pure silicon powder, adding the nano pure silicon powder into a lithium bis (fluorosulfonyl) imide/dimethyl carbonate solution, and stirring for 2 hours to obtain a homogeneous silicon/lithium bis (fluorosulfonyl) imide suspension solution;
s3: heating the homogeneous silicon/lithium bis (fluorosulfonyl) imide suspension solution to 80 ℃, stirring until the dimethyl carbonate is completely volatilized, and then drying for 4 hours at 80 ℃ in vacuum to obtain silicon/lithium bis (fluorosulfonyl) imide mixed dry powder;
s4: and (3) fully grinding the silicon/lithium bis (fluorosulfonyl) imide mixed dry powder, heating to 250 ℃ under a vacuum condition, and preserving heat for 4 hours to completely decompose the lithium bis (fluorosulfonyl) imide to generate lithium fluoride, so as to obtain the 3% lithium fluoride phase doped pure silicon negative electrode material.
Example 2 is essentially the same as example 1, except that the sintering temperature is changed from 250℃to 500 DEG C
The lithium fluoride phase doped silicon material and the preparation method thereof in the embodiment specifically comprise the following steps:
S1: 0.3g of lithium bis (fluorosulfonyl) imide is added into 10mL of dimethyl carbonate (DMC), and stirred for 1h to obtain a solution of lithium bis (fluorosulfonyl) imide/dimethyl carbonate;
s2: weighing 10g of nano pure silicon powder, adding the nano pure silicon powder into a lithium bis (fluorosulfonyl) imide/dimethyl carbonate solution, and stirring for 2 hours to obtain a homogeneous silicon/lithium bis (fluorosulfonyl) imide suspension solution;
s3: heating the homogeneous silicon/lithium bis (fluorosulfonyl) imide suspension solution to 80 ℃, stirring until the dimethyl carbonate is completely volatilized, and then drying for 4 hours at 80 ℃ in vacuum to obtain silicon/lithium bis (fluorosulfonyl) imide mixed dry powder;
s4: and (3) fully grinding the silicon/lithium bis (fluorosulfonyl) imide mixed dry powder, heating to 500 ℃ under a vacuum condition, and preserving heat for 4 hours to completely decompose the lithium bis (fluorosulfonyl) imide to generate lithium fluoride, so as to obtain the 3% lithium fluoride phase doped pure silicon negative electrode material.
Comparative example 1
Nano pure silicon powder.
Example 3 essentially the same as example 1 except that the fluorine-containing lithium salt and the silicon-based material
The lithium fluoride phase doped silicon material and the preparation method thereof in the embodiment specifically comprise the following steps:
S1: 0.3g of lithium bis (trifluoromethylsulfonyl) imide is added into 10mL of dimethyl carbonate (DMC), and stirred for 1h to obtain a solution of lithium bis (trifluoromethylsulfonyl) imide/dimethyl carbonate;
S2: weighing 10g of pre-carbonized silicon oxide powder, adding the pre-carbonized silicon oxide powder into the solution, and stirring for 2 hours to obtain a homogeneous pre-carbonized silicon oxide/bis (trifluoromethyl) sulfonimide lithium suspension solution;
S3: heating the homogenized suspension solution to 80 ℃, stirring until the dimethyl carbonate is completely volatilized, and then drying for 4 hours at 80 ℃ in vacuum to obtain pre-carbonized silicon oxide/lithium bis (trifluoromethylsulfonyl) imide mixed dry powder;
s4: and (3) fully grinding the pre-carbonized silicon oxide/lithium bis (trifluoromethylsulfonyl) imide mixed dry powder, heating to 250 ℃ under a vacuum condition, and preserving heat for 4 hours to completely decompose the lithium bis (trifluoromethylsulfonyl) imide to generate lithium fluoride, so as to obtain the 3% lithium fluoride phase doped pre-carbonized silicon oxide negative electrode material.
Example 4 is substantially the same as example 3, except that the sintering temperature is changed from 250℃to 500 ℃
The lithium fluoride phase doped silicon material and the preparation method thereof in the embodiment specifically comprise the following steps:
S1: 0.3g of lithium bis (trifluoromethylsulfonyl) imide is added into 10mL of dimethyl carbonate (DMC), and stirred for 1h to obtain a solution of lithium bis (trifluoromethylsulfonyl) imide/dimethyl carbonate;
S2: weighing 10g of pre-carbonized silicon oxide powder, adding the pre-carbonized silicon oxide powder into the solution, and stirring for 2 hours to obtain a homogeneous pre-carbonized silicon oxide/bis (trifluoromethyl) sulfonimide lithium suspension solution;
S3: heating the homogenized suspension solution to 80 ℃, stirring until the dimethyl carbonate is completely volatilized, and then drying for 4 hours at 80 ℃ in vacuum to obtain pre-carbonized silicon oxide/lithium bis (trifluoromethylsulfonyl) imide mixed dry powder;
S4: and (3) fully grinding the pre-carbonized silicon oxide/lithium bis (trifluoromethylsulfonyl) imide mixed dry powder, heating to 500 ℃ under a vacuum condition, and preserving heat for 4 hours to completely decompose the lithium bis (trifluoromethylsulfonyl) imide to generate lithium fluoride, so as to obtain the 3% lithium fluoride phase doped pre-carbonized silicon oxide negative electrode material.
Comparative example 2
Pre-carbonization of the silicon oxide powder.
Example 5 is substantially the same as example 1, except that the silicon-based material
The lithium fluoride phase doped silicon material and the preparation method thereof in the embodiment specifically comprise the following steps:
S1: 0.3g of lithium bis (fluorosulfonyl) imide is added into 10mL of dimethyl carbonate (DMC), and stirred for 1h to obtain a solution of lithium bis (fluorosulfonyl) imide/dimethyl carbonate;
S2: weighing 10g of silicon-carbon composite material powder, adding the powder into the solution, and stirring for 2 hours to obtain a homogeneous silicon-carbon composite material/lithium bis (fluorosulfonyl) imide suspension solution;
S3: heating the homogenized suspension solution to 80 ℃, stirring until the dimethyl carbonate is completely volatilized, and then drying for 4 hours at 80 ℃ in vacuum to obtain silicon-carbon composite material/lithium bis (fluorosulfonyl) imide mixed dry powder;
s4: and (3) fully grinding the silicon-carbon composite material/lithium bis (fluorosulfonyl) imide mixed dry powder, heating to 250 ℃ under a vacuum condition, and preserving heat for 4 hours to completely decompose the lithium bis (fluorosulfonyl) imide to generate lithium fluoride, so as to obtain the 3% lithium fluoride phase doped silicon-carbon composite material.
Comparative example 3
Silicon carbon composite powder.
Test example 1
The materials of example 1 and comparative example 1 were subjected to electron microscopy characterization, and the results are shown in fig. 1. As can be seen from fig. 1, the silicon particles of example 1 are more uniform than the original silicon particles of the left figure, the agglomeration phenomenon of the silicon particles of comparative example 1 is more serious, and the particles are larger.
Test example 2
Silicon materials of examples 1 to 5 and comparative examples 1 to 3 were respectively taken, and 0.7g of the silicon materials, 0.15g of the conductive carbon black, 0.1g of the sodium carboxymethyl cellulose and 0.05g of the styrene-butadiene rubber were slurried in a water dispersing agent, and then coated and dried to prepare a silicon negative electrode sheet, and after rolling and slicing, the silicon negative electrode sheet was vacuum-dried at 120 ℃, and then assembled into a C2032 button cell in a glove box filled with argon gas, and electrochemical performance test was performed:
(1) First discharge capacity/first charge capacity: discharge and charge capacities obtained by first cycling under a current condition of 0.05C;
(2) First coulombic efficiency: in a silicon negative electrode half-cell system, the first coulombic efficiency is the first discharge capacity divided by the first charge capacity;
(3) Capacity retention rate: dividing the discharge capacity of the nth turn by the discharge capacity of the first turn under the charge-discharge condition of 0.5C current;
(4) Multiplying power cycle test: maintaining the discharge condition of the current of 0.2C unchanged, and sequentially carrying out charging tests at 0.2C, 0.5C, 1C, 2C, 5C and 10C to obtain the charging capacity which is the rate capability;
(4) Ac impedance test after 120, 250, 300 cycles: the battery after a certain number of cycles was discharged to 60% dod (depth of discharge), and ac impedance test was performed in 60% dod state, frequency range: 10 -2Hz-105 Hz, perturbation voltage is 5mV;
The results are shown in Table 1 and FIGS. 2-9:
TABLE 1
As can be seen from the first-round data of examples 1-2, comparative example 1 and the first-round charge-discharge curve of fig. 2 in table 1, the pure silicon material after bulk doping with lithium fluoride exhibits higher coulombic efficiency than the original pure silicon material without any treatment, which indicates that the SEI generated by the pure silicon material after bulk doping with lithium fluoride is more stable during the first charge-discharge process and the first-round irreversible lithium consumption is significantly suppressed.
In addition to the improvement of the first charge-discharge performance, it can be seen from fig. 3 to 4 that the pure silicon electrode after bulk doping with lithium fluoride exhibits more excellent cycle stability and high-rate charge-discharge performance than the original pure silicon material without any treatment; capacity retention for 100 cycles under the same conditions was 78.1% and 16.8%, respectively; reversible capacities under the condition of 10C high magnification are 2136.7mAh/g and 350.1mAh/g respectively. As can be seen from fig. 5, the pure silicon electrode doped with the lithium fluoride phase has a smaller resistance after cycling, which is an important factor for maintaining long-term cycling stability.
For the pre-carbonized silicon oxide material, the bulk phase doping of lithium fluoride can also obviously improve the cycling stability of the material, and as can be seen from fig. 6-7, the bulk phase doping of lithium fluoride not only improves the first circle coulomb efficiency of the material, but also obviously reduces the impedance of the pre-carbonized silicon oxide material in the cycling and obviously improves the cycling stability. As can be seen from fig. 8-9, after doping the silicon-carbon material with lithium fluoride phase, the cycling stability is obviously improved, and the impedance after cycling is greatly reduced.
As can be seen from fig. 3, 6 and 8, the reversible capacity of the button cell of example 1 after 250 cycles is 1474.5mAh/g, and the reversible capacity of the button cell of comparative example 1 after 250 cycles is 0.2mAh/g; the reversible capacity of the button cell of example 4 after 120 cycles was 644.3mAh/g, and the reversible capacity of the button cell of comparative example 2 after 120 cycles was 228.8mAh/g; the reversible capacity of the button cell of example 5 after 300 cycles was 1462.5mAh/g, and the reversible capacity of the button cell of comparative example 3 after 300 cycles was 675.1mAh/g; indicating that after a certain number of cycles, the capacity of the examples performs much higher than the comparative examples.
As can be seen from Table 1, FIG. 3, FIG. 6 and FIG. 8, the untreated pure silicon electrode of comparative example 1 was severely attenuated and the capacity was attenuated to 0 at around 150 cycles since 70 cycles were started, as compared with examples 1-2. The untreated silica electrode of comparative example 2 was more severely attenuated compared to examples 3-4, and the capacity was attenuated to 32% at around 120 cycles. The untreated silicon carbon electrode of comparative example 3 was severely attenuated compared to example 5, and the capacity was attenuated to 44% at around 300 turns. It can be seen that the lithium fluoride phase-doped silicon material of the examples has excellent cycling stability.
In conclusion, lithium fluoride bulk doping is realized in the silicon material, so that on one hand, the volume expansion of the silicon material is relieved, and pulverization of the silicon material and cracking of the pole piece are avoided; on the other hand, the lithium conducting property of the silicon material can be improved, and the dynamic performance of the silicon material is improved, so that the electrical performance of the silicon negative electrode serving as the negative electrode material of the lithium ion battery is obviously improved.
It is apparent that the above examples are given by way of illustration only and are not limiting of the embodiments. Other variations and modifications of the present invention will be apparent to those of ordinary skill in the art in light of the foregoing description. It is not necessary here nor is it exhaustive of all embodiments. And obvious variations or modifications thereof are contemplated as falling within the scope of the present invention.
Claims (10)
1. The preparation method of the lithium fluoride phase doped silicon material is characterized by comprising the following steps of:
s1, adding a silicon-based material into a fluorine-containing lithium salt solution, and uniformly stirring to obtain a silicon/lithium salt mixed solution; the fluorine-containing lithium salt solution comprises fluorine-containing lithium salt and a solvent;
S2, stirring and heating the silicon/lithium salt mixed solution in the step S1 until the solvent is completely volatilized, and then drying in vacuum to obtain a silicon/lithium salt mixture;
And S3, grinding and sintering the silicon/lithium salt mixture in the step S2 under a protective atmosphere to obtain the lithium fluoride phase doped silicon material.
2. The method for producing a lithium fluoride phase-doped silicon material according to claim 1, wherein in S1, the fluorine-containing lithium salt is selected from one or more of lithium hexafluorophosphate, lithium bis-fluorosulfonyl imide, lithium bis-trifluoromethylsulfonyl imide, lithium hexafluoroaluminate, lithium hexafluorosilicate, lithium tetrafluoroborate, and lithium trifluoromethylsulfonate.
3. The method of preparing a lithium fluoride phase-doped silicon material according to claim 1, wherein in S1, the solvent is one or more selected from the group consisting of water, ethanol, ethylene carbonate, ethylmethyl carbonate, dimethyl carbonate, fluoroethylene carbonate, propylene carbonate, and ethyl acetate.
4. The method for producing a lithium fluoride phase-doped silicon material according to claim 1, wherein in S1, the concentration of the fluorine-containing lithium salt solution is 0.01g/mL to 0.1g/mL; the mass ratio of the fluorine-containing lithium salt to the silicon-based material is 0.1-1:10.
5. The method of preparing a lithium fluoride phase-doped silicon material according to claim 1, wherein in S1, the silicon-based material is selected from one or more of nano-pure silicon, micro-pure silicon, silicon oxide, pre-carbonized silicon oxide, pre-lithiated silicon oxide, pre-magnesiated silicon oxide, and silicon-carbon composite.
6. The method for producing a lithium fluoride phase-doped silicon material according to claim 1, wherein in S2, the temperature of stirring and heating is 50 ℃ to 100 ℃.
7. The method for preparing a lithium fluoride phase-doped silicon material according to claim 1, wherein in S2, the vacuum drying is performed at a temperature of 80 ℃ to 200 ℃ for a time of 4h to 8h.
8. The method for preparing a lithium fluoride phase-doped silicon material according to claim 1, wherein in S3, the sintering temperature is 150 ℃ to 800 ℃ for 1h to 5h.
9. A lithium fluoride phase doped silicon material prepared by the method of any one of claims 1 to 8.
10. Use of a lithium fluoride phase-doped silicon material of claim 9 in the field of lithium ion batteries.
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