CN114204214B - Functionalized modified diaphragm and preparation method and application thereof - Google Patents
Functionalized modified diaphragm and preparation method and application thereof Download PDFInfo
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- CN114204214B CN114204214B CN202111508062.XA CN202111508062A CN114204214B CN 114204214 B CN114204214 B CN 114204214B CN 202111508062 A CN202111508062 A CN 202111508062A CN 114204214 B CN114204214 B CN 114204214B
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- vanadium carbide
- ketjen black
- diaphragm
- nanobelt
- lithium
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- 238000002360 preparation method Methods 0.000 title claims abstract description 13
- INZDTEICWPZYJM-UHFFFAOYSA-N 1-(chloromethyl)-4-[4-(chloromethyl)phenyl]benzene Chemical compound C1=CC(CCl)=CC=C1C1=CC=C(CCl)C=C1 INZDTEICWPZYJM-UHFFFAOYSA-N 0.000 claims abstract description 107
- 239000002127 nanobelt Substances 0.000 claims abstract description 94
- 239000004743 Polypropylene Substances 0.000 claims abstract description 79
- 229920001155 polypropylene Polymers 0.000 claims abstract description 77
- 239000003273 ketjen black Substances 0.000 claims abstract description 72
- -1 polypropylene Polymers 0.000 claims abstract description 58
- 239000002121 nanofiber Substances 0.000 claims abstract description 51
- JDZCKJOXGCMJGS-UHFFFAOYSA-N [Li].[S] Chemical compound [Li].[S] JDZCKJOXGCMJGS-UHFFFAOYSA-N 0.000 claims abstract description 43
- 239000002131 composite material Substances 0.000 claims abstract description 18
- 238000000034 method Methods 0.000 claims abstract description 15
- BNOODXBBXFZASF-UHFFFAOYSA-N [Na].[S] Chemical compound [Na].[S] BNOODXBBXFZASF-UHFFFAOYSA-N 0.000 claims abstract description 5
- 230000002194 synthesizing effect Effects 0.000 claims abstract description 5
- LFZAXBDWELNSEE-UHFFFAOYSA-N [S].[K] Chemical compound [S].[K] LFZAXBDWELNSEE-UHFFFAOYSA-N 0.000 claims abstract description 4
- VEXZGXHMUGYJMC-UHFFFAOYSA-N Hydrochloric acid Chemical compound Cl VEXZGXHMUGYJMC-UHFFFAOYSA-N 0.000 claims description 54
- 239000000243 solution Substances 0.000 claims description 39
- 239000012528 membrane Substances 0.000 claims description 37
- 239000000203 mixture Substances 0.000 claims description 22
- KWGKDLIKAYFUFQ-UHFFFAOYSA-M lithium chloride Chemical compound [Li+].[Cl-] KWGKDLIKAYFUFQ-UHFFFAOYSA-M 0.000 claims description 20
- 238000001035 drying Methods 0.000 claims description 15
- 239000011259 mixed solution Substances 0.000 claims description 15
- 239000000126 substance Substances 0.000 claims description 14
- 238000002156 mixing Methods 0.000 claims description 12
- 239000002244 precipitate Substances 0.000 claims description 12
- 238000001291 vacuum drying Methods 0.000 claims description 11
- 239000007864 aqueous solution Substances 0.000 claims description 10
- 239000000725 suspension Substances 0.000 claims description 9
- SECXISVLQFMRJM-UHFFFAOYSA-N N-Methylpyrrolidone Chemical compound CN1CCCC1=O SECXISVLQFMRJM-UHFFFAOYSA-N 0.000 claims description 8
- 239000002033 PVDF binder Substances 0.000 claims description 8
- 239000007795 chemical reaction product Substances 0.000 claims description 8
- 238000004140 cleaning Methods 0.000 claims description 8
- 239000012459 cleaning agent Substances 0.000 claims description 8
- 229920001343 polytetrafluoroethylene Polymers 0.000 claims description 8
- 239000004810 polytetrafluoroethylene Substances 0.000 claims description 8
- 229920002981 polyvinylidene fluoride Polymers 0.000 claims description 8
- 229910001220 stainless steel Inorganic materials 0.000 claims description 8
- 239000010935 stainless steel Substances 0.000 claims description 8
- 239000006228 supernatant Substances 0.000 claims description 8
- 238000009210 therapy by ultrasound Methods 0.000 claims description 8
- 239000008367 deionised water Substances 0.000 claims description 6
- 229910021641 deionized water Inorganic materials 0.000 claims description 6
- 238000003756 stirring Methods 0.000 claims description 6
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Chemical compound O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims description 6
- 238000005086 pumping Methods 0.000 claims description 5
- 238000004519 manufacturing process Methods 0.000 claims description 4
- 239000007787 solid Substances 0.000 claims description 4
- 238000011068 loading method Methods 0.000 claims description 3
- 238000003828 vacuum filtration Methods 0.000 claims 1
- 229920001021 polysulfide Polymers 0.000 abstract description 24
- 239000005077 polysulfide Substances 0.000 abstract description 24
- 150000008117 polysulfides Polymers 0.000 abstract description 24
- 229910052744 lithium Inorganic materials 0.000 abstract description 20
- WHXSMMKQMYFTQS-UHFFFAOYSA-N Lithium Chemical compound [Li] WHXSMMKQMYFTQS-UHFFFAOYSA-N 0.000 abstract description 19
- 230000000694 effects Effects 0.000 abstract description 17
- 230000000670 limiting effect Effects 0.000 abstract description 5
- 238000011161 development Methods 0.000 abstract description 3
- 229910018091 Li 2 S Inorganic materials 0.000 description 22
- 150000001875 compounds Chemical class 0.000 description 18
- 239000003792 electrolyte Substances 0.000 description 17
- SPEUIVXLLWOEMJ-UHFFFAOYSA-N 1,1-dimethoxyethane Chemical compound COC(C)OC SPEUIVXLLWOEMJ-UHFFFAOYSA-N 0.000 description 12
- XTHFKEDIFFGKHM-UHFFFAOYSA-N Dimethoxyethane Chemical compound COCCOC XTHFKEDIFFGKHM-UHFFFAOYSA-N 0.000 description 12
- 229910052717 sulfur Inorganic materials 0.000 description 12
- NINIDFKCEFEMDL-UHFFFAOYSA-N Sulfur Chemical compound [S] NINIDFKCEFEMDL-UHFFFAOYSA-N 0.000 description 11
- 238000006243 chemical reaction Methods 0.000 description 10
- 239000011593 sulfur Substances 0.000 description 10
- 238000002484 cyclic voltammetry Methods 0.000 description 9
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 description 8
- 229910052799 carbon Inorganic materials 0.000 description 8
- 239000013256 coordination polymer Substances 0.000 description 6
- 238000001000 micrograph Methods 0.000 description 6
- VDFVNEFVBPFDSB-UHFFFAOYSA-N 1,3-dioxane Chemical compound C1COCOC1 VDFVNEFVBPFDSB-UHFFFAOYSA-N 0.000 description 5
- HBBGRARXTFLTSG-UHFFFAOYSA-N Lithium ion Chemical compound [Li+] HBBGRARXTFLTSG-UHFFFAOYSA-N 0.000 description 5
- 230000008901 benefit Effects 0.000 description 5
- 230000005540 biological transmission Effects 0.000 description 5
- 229910001416 lithium ion Inorganic materials 0.000 description 5
- 239000000463 material Substances 0.000 description 5
- 238000001556 precipitation Methods 0.000 description 5
- 230000008569 process Effects 0.000 description 5
- 238000001179 sorption measurement Methods 0.000 description 5
- 238000012360 testing method Methods 0.000 description 5
- XKRFYHLGVUSROY-UHFFFAOYSA-N Argon Chemical compound [Ar] XKRFYHLGVUSROY-UHFFFAOYSA-N 0.000 description 4
- 101100317222 Borrelia hermsii vsp3 gene Proteins 0.000 description 4
- 229910013553 LiNO Inorganic materials 0.000 description 4
- 230000004913 activation Effects 0.000 description 4
- VREFGVBLTWBCJP-UHFFFAOYSA-N alprazolam Chemical compound C12=CC(Cl)=CC=C2N2C(C)=NN=C2CN=C1C1=CC=CC=C1 VREFGVBLTWBCJP-UHFFFAOYSA-N 0.000 description 4
- 230000003197 catalytic effect Effects 0.000 description 4
- 239000011248 coating agent Substances 0.000 description 4
- 238000000576 coating method Methods 0.000 description 4
- 238000002474 experimental method Methods 0.000 description 4
- 230000002349 favourable effect Effects 0.000 description 4
- GLNWILHOFOBOFD-UHFFFAOYSA-N lithium sulfide Chemical compound [Li+].[Li+].[S-2] GLNWILHOFOBOFD-UHFFFAOYSA-N 0.000 description 4
- 238000012986 modification Methods 0.000 description 4
- 230000004048 modification Effects 0.000 description 4
- 239000002074 nanoribbon Substances 0.000 description 4
- LFQSCWFLJHTTHZ-UHFFFAOYSA-N Ethanol Chemical compound CCO LFQSCWFLJHTTHZ-UHFFFAOYSA-N 0.000 description 3
- 238000001914 filtration Methods 0.000 description 3
- 150000002500 ions Chemical class 0.000 description 3
- 230000007246 mechanism Effects 0.000 description 3
- 230000006911 nucleation Effects 0.000 description 3
- 238000010899 nucleation Methods 0.000 description 3
- 230000010287 polarization Effects 0.000 description 3
- 238000012546 transfer Methods 0.000 description 3
- XPDWGBQVDMORPB-UHFFFAOYSA-N Fluoroform Chemical compound FC(F)F XPDWGBQVDMORPB-UHFFFAOYSA-N 0.000 description 2
- 238000002441 X-ray diffraction Methods 0.000 description 2
- PTXMVOUNAHFTFC-UHFFFAOYSA-N alumane;vanadium Chemical compound [AlH3].[V] PTXMVOUNAHFTFC-UHFFFAOYSA-N 0.000 description 2
- 238000004873 anchoring Methods 0.000 description 2
- 229910052786 argon Inorganic materials 0.000 description 2
- 230000009286 beneficial effect Effects 0.000 description 2
- 230000000903 blocking effect Effects 0.000 description 2
- 230000008021 deposition Effects 0.000 description 2
- 238000009792 diffusion process Methods 0.000 description 2
- 238000003411 electrode reaction Methods 0.000 description 2
- 239000008151 electrolyte solution Substances 0.000 description 2
- 238000001453 impedance spectrum Methods 0.000 description 2
- 238000001764 infiltration Methods 0.000 description 2
- 230000008595 infiltration Effects 0.000 description 2
- 230000033116 oxidation-reduction process Effects 0.000 description 2
- 239000011148 porous material Substances 0.000 description 2
- 230000004044 response Effects 0.000 description 2
- 239000002002 slurry Substances 0.000 description 2
- 238000001228 spectrum Methods 0.000 description 2
- RTYCZCFQHXCMGC-UHFFFAOYSA-N 1-methoxy-2-[2-[2-(2-methoxyethoxy)ethoxy]ethoxy]ethane Chemical compound COCCOCCOCCOCCOC.COCCOCCOCCOCCOC RTYCZCFQHXCMGC-UHFFFAOYSA-N 0.000 description 1
- 239000002841 Lewis acid Substances 0.000 description 1
- 239000011149 active material Substances 0.000 description 1
- 239000013543 active substance Substances 0.000 description 1
- 229910052782 aluminium Inorganic materials 0.000 description 1
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 description 1
- 239000003054 catalyst Substances 0.000 description 1
- 238000001816 cooling Methods 0.000 description 1
- 239000013078 crystal Substances 0.000 description 1
- 238000005520 cutting process Methods 0.000 description 1
- 238000009831 deintercalation Methods 0.000 description 1
- 238000013461 design Methods 0.000 description 1
- 230000009881 electrostatic interaction Effects 0.000 description 1
- 238000004146 energy storage Methods 0.000 description 1
- 230000007613 environmental effect Effects 0.000 description 1
- 238000011049 filling Methods 0.000 description 1
- 239000011888 foil Substances 0.000 description 1
- 125000000524 functional group Chemical group 0.000 description 1
- 239000007789 gas Substances 0.000 description 1
- 238000010438 heat treatment Methods 0.000 description 1
- 230000006872 improvement Effects 0.000 description 1
- 239000013067 intermediate product Substances 0.000 description 1
- 150000007517 lewis acids Chemical class 0.000 description 1
- 229910000625 lithium cobalt oxide Inorganic materials 0.000 description 1
- BFZPBUKRYWOWDV-UHFFFAOYSA-N lithium;oxido(oxo)cobalt Chemical compound [Li+].[O-][Co]=O BFZPBUKRYWOWDV-UHFFFAOYSA-N 0.000 description 1
- 230000014759 maintenance of location Effects 0.000 description 1
- 238000005259 measurement Methods 0.000 description 1
- 238000002844 melting Methods 0.000 description 1
- 230000008018 melting Effects 0.000 description 1
- VNWKTOKETHGBQD-UHFFFAOYSA-N methane Chemical compound C VNWKTOKETHGBQD-UHFFFAOYSA-N 0.000 description 1
- 239000011268 mixed slurry Substances 0.000 description 1
- 239000005486 organic electrolyte Substances 0.000 description 1
- 229910052760 oxygen Inorganic materials 0.000 description 1
- 239000001301 oxygen Substances 0.000 description 1
- 238000011056 performance test Methods 0.000 description 1
- 239000007774 positive electrode material Substances 0.000 description 1
- 239000000047 product Substances 0.000 description 1
- 230000001681 protective effect Effects 0.000 description 1
- 238000006479 redox reaction Methods 0.000 description 1
- 238000011160 research Methods 0.000 description 1
- 239000002904 solvent Substances 0.000 description 1
- 238000006467 substitution reaction Methods 0.000 description 1
- 238000000967 suction filtration Methods 0.000 description 1
- 150000003568 thioethers Chemical class 0.000 description 1
- 235000012431 wafers Nutrition 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
- H01M50/00—Constructional details or processes of manufacture of the non-active parts of electrochemical cells other than fuel cells, e.g. hybrid cells
- H01M50/40—Separators; Membranes; Diaphragms; Spacing elements inside cells
- H01M50/403—Manufacturing processes of separators, membranes or diaphragms
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M10/00—Secondary cells; Manufacture thereof
- H01M10/05—Accumulators with non-aqueous electrolyte
- H01M10/052—Li-accumulators
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M50/00—Constructional details or processes of manufacture of the non-active parts of electrochemical cells other than fuel cells, e.g. hybrid cells
- H01M50/40—Separators; Membranes; Diaphragms; Spacing elements inside cells
- H01M50/409—Separators, membranes or diaphragms characterised by the material
- H01M50/411—Organic material
- H01M50/414—Synthetic resins, e.g. thermoplastics or thermosetting resins
- H01M50/417—Polyolefins
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M50/00—Constructional details or processes of manufacture of the non-active parts of electrochemical cells other than fuel cells, e.g. hybrid cells
- H01M50/40—Separators; Membranes; Diaphragms; Spacing elements inside cells
- H01M50/409—Separators, membranes or diaphragms characterised by the material
- H01M50/44—Fibrous material
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M50/00—Constructional details or processes of manufacture of the non-active parts of electrochemical cells other than fuel cells, e.g. hybrid cells
- H01M50/40—Separators; Membranes; Diaphragms; Spacing elements inside cells
- H01M50/409—Separators, membranes or diaphragms characterised by the material
- H01M50/449—Separators, membranes or diaphragms characterised by the material having a layered structure
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M50/00—Constructional details or processes of manufacture of the non-active parts of electrochemical cells other than fuel cells, e.g. hybrid cells
- H01M50/40—Separators; Membranes; Diaphragms; Spacing elements inside cells
- H01M50/489—Separators, membranes, diaphragms or spacing elements inside the cells, characterised by their physical properties, e.g. swelling degree, hydrophilicity or shut down properties
- H01M50/491—Porosity
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
- Y02E60/10—Energy storage using batteries
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- Chemical & Material Sciences (AREA)
- Chemical Kinetics & Catalysis (AREA)
- Electrochemistry (AREA)
- General Chemical & Material Sciences (AREA)
- Engineering & Computer Science (AREA)
- Manufacturing & Machinery (AREA)
- Battery Electrode And Active Subsutance (AREA)
Abstract
A functional modified diaphragm and a preparation method and application thereof relate to a diaphragm and a preparation method and application thereof. The invention aims to solve the problem of limiting the development and practical application of lithium sulfur batteries due to the shuttle effect of lithium polysulfide in the lithium sulfur batteries. The functional modified diaphragm is a polypropylene diaphragm compositely modified by vanadium carbide nanobelts and Keqin black nanofibers; the vanadium carbide nanobelt and the Ketjen black nanofiber are of a three-dimensional network structure, and the mass ratio of the vanadium carbide nanobelt to the Ketjen black nanofiber is (2-10) 1; wherein the width of the vanadium carbide nano-belt is 10-50nm, the length is 100nm-20 mu m, the number of layers is 1-30, and the (002) interplanar spacing is 0.2-0.9 nm. The method comprises the following steps: 1. synthesizing vanadium carbide nanobelts; 2. vanadium carbide nano-belt and ketjen black nano-fiber composite modified polypropylene diaphragm. The functional modified diaphragm is used as a diaphragm of a lithium sulfur battery, a potassium sulfur battery or a sodium sulfur battery.
Description
Technical Field
The invention relates to a diaphragm, a preparation method and application thereof.
Background
A lithium sulfur battery is one type of lithium battery. Typical lithium sulfur batteries generally employ elemental sulfur as the positive electrode and lithium metal flakes as the negative electrode. The elementary sulfur has abundant reserves in the earth and low price,Environmental protection and the like. The lithium sulfur battery using sulfur as the positive electrode material has higher theoretical specific capacity and battery theoretical specific energy which respectively reach 1675mAh/g and 2600Wh/kg, which is far higher than the capacity of the lithium cobalt oxide battery widely used in commerce<150 mAh/g). And sulfur is an element which is friendly to the environment, has no pollution to the environment basically, and is a very promising lithium battery. The reaction mechanism of lithium-sulfur batteries is different from the ion deintercalation mechanism of lithium-ion batteries, but is an electrochemical mechanism. During discharge, the negative electrode reaction is that lithium loses electrons to become lithium ions, and the positive electrode reaction is that sulfur reacts with lithium ions and electrons to generate sulfides. Intermediate product lithium polysulfide Li of reaction 2 S n (n=3 to 8) can dissolve into the organic electrolyte and can migrate between the anode and the cathode, thereby causing a shuttle effect, and being a main reason for limiting the development and practical application of the lithium-sulfur battery. In view of this problem, the present invention has been made to improve on the separator.
Currently, lithium sulfur batteries generally employ commercial microporous polypropylene (PP) films as separators, which have the advantage of good mechanical properties and chemical stability. But has the disadvantages that: low wettability, poor electrolyte retention, low ionic conductivity, no anchor polysulfide effect, etc.
Disclosure of Invention
The invention aims to solve the shuttle effect of lithium polysulfide in a lithium sulfur battery, namely the problem of limiting the development and practical application of the lithium sulfur battery, and provides a functional modified diaphragm, a preparation method and application thereof.
A functional modified diaphragm is a polypropylene diaphragm compositely modified by vanadium carbide nanobelts and ketjen black nanofibers; the vanadium carbide nanobelt and the Ketjen black nanofiber are of a three-dimensional network structure, and the mass ratio of the vanadium carbide nanobelt to the Ketjen black nanofiber is (2-10) 1; wherein the width of the vanadium carbide nano-belt is 10-50nm, the length is 100nm-20 mu m, the number of layers is 1-30, and the (002) interplanar spacing is 0.2-0.9 nm.
The preparation method of the functional modified diaphragm comprises the following steps:
1. synthesizing vanadium carbide nanobelts:
(1) adding LiF into HCl aqueous solution, and adding V 2 AlC, stirring uniformly to obtain a mixed solution;
(2) transferring the mixed solution into a polytetrafluoroethylene lining stainless steel autoclave, and preserving the polytetrafluoroethylene lining stainless steel autoclave at the temperature of 85-90 ℃ for 100-130 h to obtain black precipitate;
(3) firstly, centrifugally cleaning a black solid substance for 5-6 times by taking hydrochloric acid solution as a cleaning agent, and discarding the hydrochloric acid solution to obtain a precipitate substance after the hydrochloric acid solution is cleaned; centrifuging and cleaning the precipitate after being cleaned by the hydrochloric acid solution for 5-6 times by taking the LiCl solution as a cleaning agent, collecting supernatant, and centrifuging the supernatant for 40-45 min at the centrifugal speed of 9000 rpm to obtain a reaction product; drying the reaction product in a vacuum drying oven to obtain a vanadium carbide nano belt;
2. vanadium carbide nanobelt and ketjen black nanofiber composite modified polypropylene diaphragm:
(1) mixing ketjen black and vanadium carbide nanobelts to obtain a ketjen black/vanadium carbide nanobelt mixture;
(2) mixing the ketjen black/vanadium carbide nanobelt mixture with polyvinylidene fluoride to obtain a solute; adding the solute into N-methyl pyrrolidone, and carrying out ultrasonic treatment to obtain a suspension;
(3) and vacuum pumping is adopted to pump the suspension onto the polypropylene diaphragm through vacuum pumping filtration, and then the polypropylene diaphragm is put into a vacuum drying oven for drying, so that the functionalized modified diaphragm is obtained.
A functional modified diaphragm is used as a diaphragm of a lithium sulfur battery or a sodium sulfur battery.
The invention has the advantages that:
1. the functional modified diaphragm prepared by the invention is a polypropylene diaphragm modified by a vanadium carbide nanobelt and ketjen black nanofiber compound; the vanadium carbide nanobelt and the Keqin black nanofiber are of a three-dimensional network structure, so that physical blocking effect can be generated on lithium polysulfide dissolved in electrolyte, and shuttle benefit is effectively slowed down; in addition, the Ketjen black nanofiber is used as a conductive framework to form a network structure which is communicated with each other, so that the infiltration of electrolyte and the rapid conduction of ions/electrons are facilitated; meanwhile, the multi-size pores in the structure improve the wettability of the diaphragm, so that better electrochemical performance can be obtained;
2. the functional modified diaphragm prepared by the invention is a polypropylene diaphragm modified by a vanadium carbide nanobelt and ketjen black nanofiber compound; vanadium carbide is a typical two-dimensional layered material, has strong chemical adsorption effect on lithium polysulfide due to the special lattice structure, energy band structure and the like, can provide faster charge transfer, and catalytically accelerates the lithium polysulfide to Li 2 S conversion dynamic oxidation-reduction reaction effectively inhibits polysulfide shuttle, promotes polysulfide phase conversion, recovers shuttle polysulfide, and increases cycle times of the battery;
3. the functional modified diaphragm prepared by the invention is a polypropylene diaphragm modified by a vanadium carbide nanobelt and ketjen black nanofiber compound; the vanadium carbide is in a nano strip shape, the width is 10-50nm, the length is 100nm-20 mu m, and compared with the conventional flaky shape of the MXene material, the vanadium carbide has higher specific surface area and more edge active sites; in addition, the number of the vanadium carbide nanobelts is 1-30, the (002) interplanar spacing is 0.2-0.9 nm, which is favorable for charge transfer and creates conditions for better anchoring lithium polysulfide dissolved in electrolyte;
4. the functional modified diaphragm prepared by the invention is a polypropylene diaphragm modified by a vanadium carbide nanobelt and ketjen black nanofiber compound; the invention can optimize the performance by adjusting the layer number and the layer spacing of the vanadium carbide nanobelt, is favorable for reasonable design and accurate control of materials, and provides theoretical basis and technical support for research and practical application of lithium sulfur batteries;
5. the functional modified diaphragm prepared by the invention is a polypropylene diaphragm modified by a vanadium carbide nanobelt and ketjen black nanofiber compound; the surface of the vanadium carbide nano belt contains functional groups such as-O, -Cl, -F, -OH and the like, the binding energy of polysulfide and the surface of a diaphragm can be obviously improved through Lewis acid reaction, so that the surface of the diaphragm is polarized, dipoles are generated, dipole-dipole electrostatic interaction is formed with polar polysulfide, sufficient surface binding force and limiting effect are provided for the polar polysulfide finally, the loss of active substances and the attenuation of capacity are improved, and the performance of a battery is improved;
6. the functional modified diaphragm prepared by the invention is a polypropylene diaphragm modified by a vanadium carbide nanobelt and ketjen black nanofiber compound; coating a vanadium carbide nano-belt and ketjen black nanofiber compound on carbon paper, and using Li to prepare the nano-belt-ketjen black nanofiber composite 2 S 6 As electrolyte for manufacturing a symmetrical battery, the volt-ampere characteristic curve has obvious oxidation-reduction peak and higher response current, which shows that the vanadium carbide nanobelt and the Keqin black nanofiber composite polysulfide have obvious chemical adsorption effect and can effectively inhibit the shuttle effect;
7. the functional modified diaphragm prepared by the invention is a polypropylene diaphragm modified by a vanadium carbide nanobelt and ketjen black nanofiber compound; coating a vanadium carbide nano-belt and ketjen black nanofiber compound on carbon paper, and using Li to prepare the nano-belt-ketjen black nanofiber composite 2 S 6 Symmetrical batteries were fabricated as electrolytes with an exchange current density of j=1.608 mA cm –2 Almost ten times the exchange current density of pure carbon paper (j=0.177 mA cm –2 ) Illustrating the effect of vanadium carbide nanobelts and ketjen black nanofiber composites on Li 2 S n -to-Li 2 The S process has good catalytic action, can accelerate reaction kinetics and inhibit a shuttle effect;
8. the functional modified diaphragm prepared by the invention is a polypropylene diaphragm modified by a vanadium carbide nanobelt and ketjen black nanofiber compound; the modification process of the diaphragm is ingenious, the operation is simple and easy, the performance is excellent, and the diaphragm is favorable for commercial production;
9. the functional modified diaphragm prepared by the invention is a polypropylene diaphragm modified by a vanadium carbide nanobelt and ketjen black nanofiber compound; applying it to lithium sulfur battery, S 8 To Li 2 S 4 Has a Tafil slope of 93mVdec –1 Activation energy 28.63kJmol lower than commercial polypropylene separator –1 ，Li 2 S 4 To Li 2 The Tafil slope of S is 86mVdec –1 Activation energy 24.82kJmol lower than commercial polypropylene separator –1 And interface transmissionThe resistance is also obviously smaller than that of a commercial polypropylene diaphragm, which is beneficial to obtaining good battery performance;
10. the functional modified diaphragm prepared by the invention is a polypropylene diaphragm modified by a vanadium carbide nanobelt and ketjen black nanofiber compound; the catalyst is applied to a lithium sulfur battery and is formed by S 8 To Li 2 S 4 And is made of Li 2 S 4 To Li 2 The diffusion coefficients of lithium ions in the S process are 5.18 multiplied by 10 respectively –8 And 3.27X10 –7 cm 2 s –1 Is nearly ten times (8.25X10) –9 And 1.03X10 –8 cm 2 s –1 )；
11. The functional modified diaphragm prepared by the invention is a polypropylene diaphragm modified by a vanadium carbide nanobelt and ketjen black nanofiber compound; in Li 2 In the S precipitation experiment, the precipitation time of the vanadium carbide nanobelt and the Keqin black nanofiber compound is accelerated to 1901S from 6000S, and Li is added 2 The precipitation capacity of S is 194.0mAh g –1 To 345.5mAhg –1 Illustrating that vanadium carbide nanobelts and ketjen black nanofiber composites are effective for polysulfide to Li 2 The conversion of S has good catalytic effect;
12. the functional modified diaphragm prepared by the invention is a polypropylene diaphragm modified by a vanadium carbide nanobelt and ketjen black nanofiber compound; when applied to lithium-sulfur batteries, the shuttle benefit is well inhibited, and the modified specific capacity (1236.1 mAh g at 0.2C) is improved compared with a commercial polypropylene diaphragm -1 The method comprises the steps of carrying out a first treatment on the surface of the Commercial polypropylene separator is 876.2mAhg -1 ) Polarization overpotential (Δe=156.3 mV at 0.2C; commercial polypropylene separator was Δe= 269.7 mV), rate performance (851.5 mAhg at 2C -1 The method comprises the steps of carrying out a first treatment on the surface of the Commercial polypropylene separator was 141.4mAhg -1 ) And cycle stability (0.16% per turn decay rate after 150 cycles of 0.2C; initial discharge capacity of 1C was 1069mAhg -1 The attenuation per 1000 cycles of the cycle was 0.049% and the coulombic efficiency was 98%. The attenuation rate of each circle after 200 circles of the commercial polypropylene diaphragm is 0.27%;1C initial discharge capacity of 643.2mAh g -1 The attenuation of each circle of 600 circles is 0.113%, and the coulomb efficiency is 93％；
The polypropylene diaphragm modified by the vanadium carbide nanobelt and the Keqin black nanofiber compound can be widely applied to the energy storage fields of lithium sulfur batteries, potassium sulfur batteries, sodium sulfur batteries and the like.
Drawings
FIG. 1 is an X-ray diffraction spectrum, in which V 2 CT X Vanadium carbide nanobelt prepared in step one of the example, V 2 AlC is vanadium aluminum carbide;
FIG. 2 is a low power transmission electron microscope image of the vanadium carbide nanobelt prepared in step one of the examples;
FIG. 3 is a high power transmission electron microscope image of the vanadium carbide nanobelt prepared in the first step of the example;
FIG. 4 is Li 2 S 6 Solution and ketjen black/vanadium carbide nanoribbon mixture/Li 2 S 6 Digital images after 3 hours of standing the solutions respectively;
FIG. 5 is a CV curve of a symmetric battery, in which 1 is a CP symmetric battery and 2 is KB/V 2 CT X -CP symmetric cells;
FIG. 6 shows the exchange current density of a symmetrical cell, in which 1 is a CP symmetrical cell and 2 is KB/V 2 CT X -CP symmetric cells;
FIG. 7 is Li 2 Constant voltage discharge curve of S nucleation experiment, in the figure, 1 is CP battery, 2 is KB/V 2 CT X -a CP battery;
FIG. 8 is a low power scanning electron microscope image of the functionalized modified membrane prepared in step two (3) of the example;
FIG. 9 is a CV curve of a lithium sulfur battery with a PP membrane and a functionalized modified membrane prepared in example I, respectively, wherein the PP membrane is shown in FIG. 2, and the functionalized modified membrane prepared in example I is shown in FIG. 1;
fig. 10 is an impedance spectrum of a lithium sulfur battery with a PP membrane, a functionalized modified membrane prepared in example one, and fig. 1 with a PP membrane and fig. 2 with a functionalized modified membrane prepared in example one;
fig. 11 is a charge-discharge curve of a lithium-sulfur battery with a separator prepared according to the first embodiment, wherein 1 is the 1 st turn, 2 is the 10 th turn, 3 is the 20 th turn, 4 is the 50 th turn, 5 is the 100 th turn, and 6 is the 150 th turn;
fig. 12 is a charge-discharge curve of a lithium sulfur battery with a PP separator, in which 1 is 1 st turn, 2 is 10 th turn, 3 is 20 th turn, 4 is 50 th turn, 5 is 100 th turn, and 6 is 150 th turn;
fig. 13 is a graph showing the first cycle characteristics of a lithium-sulfur battery in which the separator is PP, and the functionalized modified separator prepared in example one, respectively, and fig. 1 shows the separator PP, and fig. 2 shows the functionalized modified separator prepared in example one;
fig. 14 shows the first cycle characteristics of a lithium-sulfur battery with PP as the separator and the functionalized modified separator prepared in example one, wherein PP as the separator in fig. 1 and PP as the separator in fig. 2 as the separator;
FIG. 15 is a digital image of the lithium negative electrode side of a lithium sulfur battery with PP, the functionalized modified separator prepared in example one after 150 cycles at 0.2C, wherein the separator in (a) is PP and the separator in (b) is the functionalized modified separator prepared in example one;
fig. 16 shows the rate characteristics of the lithium sulfur battery with PP as the separator and 2 as the separator of the functionalized modified separator prepared in example one.
Detailed Description
The following examples further illustrate the invention but are not to be construed as limiting the invention. Modifications and substitutions to methods, procedures, or conditions of the present invention without departing from the spirit of the invention are intended to be within the scope of the present invention.
The first embodiment is as follows: the functional modified diaphragm is a polypropylene diaphragm compositely modified by vanadium carbide nanobelts and ketjen black nanofibers; the vanadium carbide nanobelt and the Ketjen black nanofiber are of a three-dimensional network structure, and the mass ratio of the vanadium carbide nanobelt to the Ketjen black nanofiber is (2-10) 1; wherein the width of the vanadium carbide nano-belt is 10-50nm, the length is 100nm-20 mu m, the number of layers is 1-30, and the (002) interplanar spacing is 0.2-0.9 nm.
The second embodiment is as follows: the present embodiment differs from the specific embodiment in that: the load capacity of the vanadium carbide nano-belt and the Keqin black nano-fiber on the polypropylene diaphragm is 0.1-5 mg/cm 2 . The other steps are the same as in the first embodiment.
And a third specific embodiment: this embodiment differs from the first or second embodiment in that: the preparation method of the functional modified diaphragm comprises the following steps:
1. synthesizing vanadium carbide nanobelts:
(1) adding LiF into HCl aqueous solution, and adding V 2 AlC, stirring uniformly to obtain a mixed solution;
(2) transferring the mixed solution into a polytetrafluoroethylene lining stainless steel autoclave, and preserving the polytetrafluoroethylene lining stainless steel autoclave at the temperature of 85-90 ℃ for 100-130 h to obtain black precipitate;
(3) firstly, centrifugally cleaning a black solid substance for 5-6 times by taking hydrochloric acid solution as a cleaning agent, and discarding the hydrochloric acid solution to obtain a precipitate substance after the hydrochloric acid solution is cleaned; centrifuging and cleaning the precipitate after being cleaned by the hydrochloric acid solution for 5-6 times by taking the LiCl solution as a cleaning agent, collecting supernatant, and centrifuging the supernatant for 40-45 min at the centrifugal speed of 9000 rpm to obtain a reaction product; drying the reaction product in a vacuum drying oven to obtain a vanadium carbide nano belt;
2. vanadium carbide nanobelt and ketjen black nanofiber composite modified polypropylene diaphragm:
(1) mixing ketjen black and vanadium carbide nanobelts to obtain a ketjen black/vanadium carbide nanobelt mixture;
(2) mixing the ketjen black/vanadium carbide nanobelt mixture with polyvinylidene fluoride to obtain a solute; adding the solute into N-methyl pyrrolidone, and carrying out ultrasonic treatment to obtain a suspension;
(3) and vacuum pumping is adopted to pump the suspension onto the polypropylene diaphragm through vacuum pumping filtration, and then the polypropylene diaphragm is put into a vacuum drying oven for drying, so that the functionalized modified diaphragm is obtained. The other steps are the same as those of the first or second embodiment.
The specific embodiment IV is as follows: one difference between this embodiment and the first to third embodiments is that: the volume ratio of the mass of LiF to the HCl aqueous solution in the step one (1) is (2 g-4 g) 20mL; the mass fraction of the HCl aqueous solution in the step one (1) is 5% -38%. The other steps are the same as those of the first to third embodiments.
Fifth embodiment: one to four differences between the present embodiment and the specific embodiment are: v described in step one (1) 2 The volume ratio of AlC mass to HCl aqueous solution is (0.6 g-1 g): 20mL. Other steps are the same as those of the first to fourth embodiments.
Specific embodiment six: the present embodiment differs from the first to fifth embodiments in that: the hydrochloric acid solution in the step one (3) is formed by mixing 20mL of hydrochloric acid with the mass fraction of 37% and 180mL of deionized water. Other steps are the same as those of the first to fifth embodiments.
Seventh embodiment: one difference between the present embodiment and the first to sixth embodiments is that: the LiCl solution in the step one (3) is prepared by dissolving 7.63-8 g of LiCl into 180mL of deionized water; the temperature of the vacuum drying oven in the step one (3) is 60 ℃, and the drying time is 10-12 h. Other steps are the same as those of embodiments one to six.
Eighth embodiment: one difference between the present embodiment and the first to seventh embodiments is that: the mass ratio of the ketjen black to the vanadium carbide nano-belt in the second step (1) is 2:8; and (2) the mass ratio of the ketjen black/vanadium carbide nanobelt mixture to polyvinylidene fluoride in the step (2) is 9:1. The other steps are the same as those of embodiments one to seven.
Detailed description nine: one of the differences between this embodiment and the first to eighth embodiments is: the volume ratio of the mass of the solute to the N-methyl pyrrolidone in the second step (2) is (0.5 g-1.2 g) 10mL; the power of the ultrasonic treatment in the step two (2) is 100W-500W, and the time of the ultrasonic treatment is 2 h-3 h; the temperature of the vacuum drying oven in the second step (3) is 60 ℃, and the drying time is 10-12 h. Other steps are the same as those of embodiments one to eight.
Detailed description ten: the present embodiment is a functional modified separator used as a separator for lithium-sulfur batteries, potassium-sulfur batteries, or sodium-sulfur batteries.
Embodiment one: the preparation method of the functional modified diaphragm comprises the following steps:
1. synthesizing vanadium carbide nanobelts:
(1) 3g LiF was added to 20mL of 18.5% by mass HCl aqueous solution followed by 0.8. 0.8g V 2 AlC, stirring uniformly to obtain a mixed solution;
(2) transferring the mixed solution into a 50mL polytetrafluoroethylene lining stainless steel autoclave, and preserving the polytetrafluoroethylene lining stainless steel autoclave at the temperature of 85 ℃ for 120 hours to obtain a black precipitate;
(3) firstly, centrifugally cleaning a black solid substance for 6 times by taking a hydrochloric acid solution as a cleaning agent, and discarding the hydrochloric acid solution to obtain a precipitate substance after the hydrochloric acid solution is cleaned; centrifuging and cleaning the precipitate after being cleaned by the hydrochloric acid solution for 6 times by taking the LiCl solution as a cleaning agent, collecting supernatant, and centrifuging the supernatant at a centrifugal speed of 9000 rpm for 45min to obtain a reaction product; drying the reaction product in a vacuum drying oven at 60 ℃ for 12 hours to obtain a vanadium carbide nano belt;
the hydrochloric acid solution in the step one (3) is formed by mixing 20mL of hydrochloric acid with mass fraction of 37% and 180mL of deionized water;
the LiCl solution in the step one (3) is prepared by dissolving 7.63-8 g of LiCl into 180mL of deionized water;
2. vanadium carbide nanobelt and ketjen black nanofiber composite modified polypropylene diaphragm:
(1) mixing ketjen black and vanadium carbide nanobelts to obtain a ketjen black/vanadium carbide nanobelt mixture;
the mass ratio of the ketjen black to the vanadium carbide nano-belt in the second step (1) is 2:8;
(2) mixing the ketjen black/vanadium carbide nanobelt mixture with polyvinylidene fluoride to obtain a solute; adding the solute into N-methyl pyrrolidone, and performing ultrasonic treatment for 2 hours under the power of 180W to obtain a suspension;
the mass ratio of the ketjen black/vanadium carbide nanobelt mixture to polyvinylidene fluoride in the step two (2) is 9:1;
the volume ratio of the mass of the solute to the N-methylpyrrolidone in the second step (2) is 0.8g to 10mL;
(3) vacuum-extracting, vacuum-filtering to obtain suspension, and drying in vacuum oven at 60deg.C for 12 hr to obtain vanadium carbide nanobelt and Keqin black nanofiber composite functionalized modified polypropylene membrane (KB/V) 2 CT X -PP) with a mass loading of 0.5-5 mgcm -2 The method comprises the steps of carrying out a first treatment on the surface of the In addition, the suspension is subjected to suction filtration and drying to obtain a vanadium carbide nano-belt and ketjen black nanofiber compound (KB/V) 2 CT X )；
The polypropylene separator in step two (3) is a commercial polypropylene separator (Celgard 2400).
FIG. 1 is an X-ray diffraction spectrum, in which V 2 CT X Vanadium carbide nanobelt prepared in step one of the example, V 2 AlC is vanadium aluminum carbide;
in fig. 1, diffraction peaks all belong to vanadium carbide, and thus, it is known that the product synthesized in this example is a vanadium carbide crystal material.
FIG. 2 is a low power transmission electron microscope image of the vanadium carbide nanobelt prepared in step one of the examples;
FIG. 3 is a high power transmission electron microscope image of the vanadium carbide nanobelt prepared in the first step of the example;
as can be seen from fig. 2 and 3, vanadium carbide has a nanoribbon morphology, a width of 10-20nm and a length of greater than 100nm, and provides a higher specific surface area and more edge active sites than the conventional platelet morphology of MXene materials. In addition, the number of the vanadium carbide nanobelts is 5-8, the (002) interplanar spacing is 0.76nm, which is favorable for charge transfer and creates conditions for better anchoring the lithium polysulfide dissolved in the electrolyte.
Adsorption test can be seen:
(1) Lithium sulfide (Li) was added in a mass ratio of 1:5 2 S) addition of sulfur in admixture with 1, 2-Dimethoxyethane (DME) and 1, 3-DiMixing the above mixed solution with oxygen alkane (DOL) and stirring at 60deg.C for 24 hr to obtain Li 2 S 6 A solution;
the volume ratio of the 1, 2-Dimethoxyethane (DME) to the 1, 3-Dioxane (DOL) in the mixed solution of the 1, 2-Dimethoxyethane (DME) and the 1, 3-Dioxane (DOL) is 1:1;
the volume ratio of the amount of the lithium sulfide substance to the mixed solution of 1, 2-Dimethoxyethane (DME) and 1, 3-Dioxane (DOL) is 0.01mol:1L.
(2) 20mg of Ketjen black/vanadium carbide nanoribbon mixture was added to 3mL Li 2 S 6 Standing for 3h in the solution to obtain the ketjen black/vanadium carbide nanobelt mixture/Li 2 S 6 A solution;
the mass ratio of ketjen black to vanadium carbide nanobelts in the ketjen black/vanadium carbide nanobelt mixture in the step (2) is 2:8.
FIG. 4 is Li 2 S 6 Solution and ketjen black/vanadium carbide nanoribbon mixture/Li 2 S 6 Digital images after 3 hours of standing the solutions respectively;
as can be seen from FIG. 4, li is added to the Ketjen black/vanadium carbide nanobelt mixture 2 S 6 The color of the solution is changed from brown yellow to transparent, which indicates that the Ketjen black/vanadium carbide nanobelt mixture is specific to Li 2 S 6 Has strong chemical adsorption effect.
Assembling a symmetrical battery:
in assembled Keqin black/vanadium carbide symmetrical cell (KB/V) 2 CT X -CP) dispersing ketjen black and vanadium carbide nanobelts in absolute ethyl alcohol in a mass ratio of 2:8, wherein the volume ratio of the ketjen black to the absolute ethyl alcohol is 1g:50mL, so as to obtain slurry; coating the slurry on Carbon Paper (CP) with diameter of 15 mm with a liquid-transferring gun, thoroughly drying, and respectively serving as a working electrode and a counter electrode, wherein the mass load of active material is 1.0mgcm -2 The electrolyte was added at a concentration of 0.5mol L at 30. Mu.L DOL/DME (30. Mu.L DOL to DME volumes 1:1) -1 Li of (2) 2 S 6 In the solution, a ketjen black/vanadium carbide symmetrical cell (KB/V) is obtained 2 CT X -CP)；
In assembling the CP symmetric cell, carbon Paper (CP) with a diameter of 15 mm was used as the working electrode and the counter electrode, respectively, and 30. Mu.L DOL/DME (30. Mu.L, DOL and DME were 1:1 in volume) was added to a concentration of 0.5mol L -1 Li of (2) 2 S 6 Obtaining a CP symmetrical battery in the solution;
as a control, the assembled Ketjen black/vanadium carbide symmetric cell and the assembled CP symmetric cell were subjected to Cyclic Voltammetry (CV) testing on a VMP3 electrochemical workstation (BioLogic, france) with a CV sweep rate in the range of 10mV -1 The voltage window is between-0.8V and 0.8V.
FIG. 5 is a CV curve of a symmetric battery, in which 1 is a CP symmetric battery and 2 is KB/V 2 CT X -CP symmetric cells;
as can be seen from fig. 5, the CV curve has a distinct oxidation-reduction peak and a higher response current, which indicates that the vanadium carbide nanobelt has a distinct chemical adsorption effect with the ketjen black nanofiber composite polysulfide, and can effectively inhibit the shuttle effect.
FIG. 6 shows the exchange current density of a symmetrical cell, in which 1 is a CP symmetrical cell and 2 is KB/V 2 CT X -CP symmetric cells;
as can be seen from fig. 6, the exchange current density is j=1.608 mA cm –2 Almost ten times the exchange current density of pure carbon paper (j=0.177 mA cm –2 ) Illustrating the effect of vanadium carbide nanobelts and ketjen black nanofiber composites on Li 2 S n -to-Li 2 The S process has good catalytic action, can accelerate reaction kinetics and inhibit a shuttle effect.
Li on the surface of vanadium carbide 2 Nucleation deposition of S:
li with mass ratio of 1:7 2 The mixture of S and S was added to tetraethylene glycol dimethyl ether (tetraglyme) containing 1.0M LiTFSI and stirred at 60℃for 24 hours to give 0.25MLi 2 S 8 A catholyte;
in this experiment, 0.8mg of the vanadium carbide nanobelt prepared in example 1 was compounded with ketjen black nanofiber (KB/V) 2 CT X ) Dispersing into 8 mu L of absolute ethyl alcohol to obtain a solution; to be obtainedCoating the solution on Carbon Paper (CP) with diameter of 10mm, and drying at 60deg.C for 2 hr to obtain KB/V 2 CT X A working electrode. KB/V 2 CT X Is 1.0mg cm -2 . At KB/V 2 CT X 20 mu L of Li is added on the working electrode 2 S 8 An electrolyte solution was added to the counter electrode in an amount of 20. Mu.L containing 2wt% LiNO 3 Li of (2) 2 S 8 And (3) an electrolyte. The cell was discharged at a constant current of 0.112mA using a VMP3 electrochemical workstation (BioLogic, france) until the voltage reached 2.06V consuming the higher order polysulfide, then discharged at a constant current to 2.05V, causing Li to 2 S nucleates, as shown in FIG. 7.
Li 2 S 8 The electrolyte is prepared according to the following steps:
lithium sulfide (Li 2 S) mixing with sulfur, adding into a mixed solution of 1, 2-Dimethoxyethane (DME) and 1, 3-Dioxane (DOL), and stirring at 60deg.C for 24 hr to obtain Li 2 S 8 A solution; lithium sulfide (Li) 2 S) to a volume ratio of 1, 2-Dimethoxyethane (DME) and 1, 3-Dioxane (DOL) mixed solution of 11.5 mg/1 mL;
as a control, 20. Mu.L of Li was added to a Carbon Paper (CP) working electrode 2 S 8 An electrolyte solution was added to the counter electrode in an amount of 20. Mu.L containing 2wt% LiNO 3 Li of (2) 2 S 8 And (3) an electrolyte. The cell was discharged at a constant current of 0.112mA using a VMP3 electrochemical workstation (BioLogic, france) until the voltage reached 2.06V, and then discharged at a constant current to 2.05V, as shown in fig. 7.
FIG. 7 is Li 2 Constant voltage discharge curve of S nucleation experiment, in the figure, 1 is CP battery, 2 is KB/V 2 CT X -a CP battery;
as can be seen from FIG. 7, the vanadium carbide nanobelt and Keqin black nanofiber composite (KB/V 2 CT X ) Accelerating the precipitation time from 6000s to 1901s, and adding Li 2 The precipitation capacity of S is 194.0mAh g –1 Is promoted to 345.5mAh g –1 Illustrating that vanadium carbide nanobelts and ketjen black nanofiber composites are effective for polysulfide to Li 2 The conversion of S has a good catalytic effect.
FIG. 8 is a low power scanning electron microscope image of the functionalized modified membrane prepared in step two (3) of the example;
as can be seen from FIG. 8, the thickness of the functionalized modified membrane was 15.5. Mu.m. The vanadium carbide nanobelt and the Keqin black nanofiber are of a three-dimensional network structure, so that physical blocking effect can be generated on lithium polysulfide dissolved in electrolyte, and shuttle benefit is effectively slowed down. And the Ketjen black nanofiber is used as a conductive framework to form a network structure which is communicated with each other, so that the infiltration of electrolyte and the rapid conduction of ions/electrons are facilitated. Meanwhile, the multi-size pores in the structure improve the wettability of the diaphragm, and better electrochemical performance can be obtained.
Assembling and electrochemical testing of a lithium-sulfur battery:
a) Preparation of C/S Positive electrode
Filling the uniformly mixed C/S (mass ratio is 1:3) with protective gas, and then placing the mixture into a reaction kettle, and heating the mixture for 12h at 155 ℃ by adopting a melting method. After cooling to room temperature, the obtained C/S mixture, conductive carbon black and PVDF are ground uniformly in a mass ratio of 8:1:1, and are treated by ultrasonic for 30min by using NMP as a solvent, then the mixed slurry is coated on an aluminum foil to be used as an anode by using an automatic coating machine, and the prepared electrode is dried in a vacuum oven at 60 ℃ for 12h. Finally cutting the electrode plate into wafers with the diameter of 13mm, wherein the sulfur loading amount is 1.3mg/cm 2 。
b) Assembling a lithium-sulfur battery:
electrochemical performance was tested with a model 2025 cell and assembled in an argon filled glove box. The C/S compound is used as a positive electrode, the lithium sheet is used as a negative electrode, and the diaphragm is the functional modified diaphragm KB/V prepared in the first embodiment 2 CT X -PP; the electrolyte used was 1.0M lithium bis (trifluoromethane) sulfonyl imide salt (LiTFSI) containing 2wt% LiNO 3 DOL/DME (volume ratio of 1:1) in the mixed solution. The ratio of the electrolyte to the sulfur was 15 mu Lmg -1 。
c) As a control, the electrochemical performance was tested with a cell model 2025, assembled in an argon filled glove box. The C/S composite is used as positive electrode, the lithium sheet is used as negative electrode, and the diaphragm is PP (commercial polypropylene diaphragm Celgard 2400) and the electrolyte is 1.0M bis (trifluoromethane) sulfonylLithium imide salt (LiTFSI) containing 2wt% LiNO 3 DOL/DME (volume ratio of 1:1) in the mixed solution. The ratio of the electrolyte to the sulfur was 15 mu Lmg -1 。
d) Electrochemical testing
The charge and discharge performance test of lithium sulfur battery was carried out on LAND battery test system (Wuhan CT2001A, china) with a voltage range of 1.7-2.8V at room temperature. Specific capacities of 0.1C,0.2C,0.5C,1C, and 2C (1c=1675 mA/g) were measured under constant-current charge and discharge, respectively. Cyclic Voltammograms (CV) were tested on a VMP3 electrochemical workstation (BioLogic, france) at a scan rate of 0.1mV/s and a voltage in the range of 1.7-2.8V. The Electrochemical Impedance (EIS) measurement frequency ranges from 0.01Hz to 100kHz, see fig. 9 and 10.
FIG. 9 is a CV curve of a lithium sulfur battery with a PP membrane and a functionalized modified membrane prepared in example I, respectively, wherein the PP membrane is shown in FIG. 2, and the functionalized modified membrane prepared in example I is shown in FIG. 1;
fig. 10 is an impedance spectrum of a lithium sulfur battery with a PP membrane, a functionalized modified membrane prepared in example one, and fig. 1 with a PP membrane and fig. 2 with a functionalized modified membrane prepared in example one;
as can be seen from fig. 9 and 10, S 8 To Li 2 S 4 Has a Tafil slope of 93mV dec –1 Activation energy 28.63kJ mol lower than commercial polypropylene membrane –1 ，Li 2 S 4 To Li 2 The Tafil slope of S is 86mV dec –1 Activation energy 24.82kJ mol lower than commercial polypropylene separator –1 . Example one prepared functionalized modified separator was prepared from S 8 To Li 2 S 4 And is made of Li 2 S 4 To Li 2 The diffusion coefficients of lithium ions in the S process are 5.18 multiplied by 10 respectively –8 And 3.27X10 –7 cm 2 s –1 Is nearly ten times (8.25X10) –9 And 1.03X10 –8 cm 2 s –1 ) And the interface transmission resistance is obviously smaller than that of a commercial polypropylene diaphragm, which is beneficial to obtaining good battery performance.
Fig. 11 is a charge-discharge curve of a lithium-sulfur battery with a separator prepared according to the first embodiment, wherein 1 is the 1 st turn, 2 is the 10 th turn, 3 is the 20 th turn, 4 is the 50 th turn, 5 is the 100 th turn, and 6 is the 150 th turn;
fig. 12 is a charge-discharge curve of a lithium sulfur battery with a PP separator, in which 1 is 1 st turn, 2 is 10 th turn, 3 is 20 th turn, 4 is 50 th turn, 5 is 100 th turn, and 6 is 150 th turn;
as can be seen from FIGS. 11 and 12, the initial capacity of the lithium-sulfur battery in which the separator was the functionalized modified separator prepared in example one was 1236.1mAhg at 0.2C -1 Polarization overpotential Δe=156.3 mV; commercial polypropylene separator with initial capacity of 876.2mAhg -1 Polarization overpotential Δe= 269.7 illustrates that the functionalized modified separator prepared in example one can anchor lithium polysulfide well, weaken the shuttle effect, and improve the battery performance.
Fig. 13 is a graph showing the first cycle characteristics of a lithium-sulfur battery in which the separator is PP, and the functionalized modified separator prepared in example one, respectively, and fig. 1 shows the separator PP, and fig. 2 shows the functionalized modified separator prepared in example one;
fig. 14 shows the first cycle characteristics of a lithium-sulfur battery with PP as the separator and the functionalized modified separator prepared in example one, wherein PP as the separator in fig. 1 and PP as the separator in fig. 2 as the separator;
as can be seen from fig. 13 and 14, the attenuation rate of each cycle is 0.16% after the lithium sulfur battery with the separator being the functionalized modified separator prepared in example one circulates for 150 cycles; 1C initial discharge capacity of 1069mAh g -1 The attenuation per 1000 cycles of the cycle was 0.049% and the coulombic efficiency was 98%. The attenuation rate of each circle after 200 circles of the commercial polypropylene diaphragm is 0.27%;1C initial discharge capacity of 643.2mAh g -1 The attenuation per cycle of 600 cycles was 0.113% and the coulombic efficiency was 93%. Therefore, the functionalized modified diaphragm prepared in the first embodiment can well improve the cycle performance of the lithium-sulfur battery.
FIG. 15 is a digital image of the lithium negative electrode side of a lithium sulfur battery with PP, the functionalized modified separator prepared in example one after 150 cycles at 0.2C, wherein the separator in (a) is PP and the separator in (b) is the functionalized modified separator prepared in example one;
as can be seen from fig. 15, the two diaphragms differ in color. The surface of the PP diaphragm has obvious brown yellow sulfur deposition after circulation, which indicates that the PP diaphragm can not well prevent the shuttle effect of lithium polysulfide. In contrast, the surface of the composite membrane prepared in the first embodiment is clean after circulation, which indicates that the composite membrane prepared in the first embodiment can well anchor lithium polysulfide and prevent the shuttle effect.
Fig. 16 shows the rate characteristics of the lithium sulfur battery with PP as the separator and 2 as the separator of the functionalized modified separator prepared in example one.
As can be seen from FIG. 16, at 2C, the capacities of the lithium-sulfur batteries in which the separator was PP and the functionalized modified separator prepared in example one were 141.4mAhg, respectively -1 And 851.5mAhg -1 It is demonstrated that lithium sulfur batteries using the functionalized modified separator prepared in example one have better rate capability.
The above description is only of the preferred embodiments of the present invention and is not intended to limit the present invention, but various modifications and variations can be made to the present invention by those skilled in the art. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.
Claims (10)
1. The preparation method of the functional modified diaphragm is characterized by comprising the following steps of:
1. synthesizing vanadium carbide nanobelts:
(1) adding LiF into HCl aqueous solution, and adding V 2 AlC, stirring uniformly to obtain a mixed solution;
(2) transferring the mixed solution into a polytetrafluoroethylene lining stainless steel autoclave, and then preserving the polytetrafluoroethylene lining stainless steel autoclave for 100-130 h at the temperature of 85-90 ℃ to obtain black precipitate;
(3) firstly, centrifugally cleaning a black solid substance for 5-6 times by taking a hydrochloric acid solution as a cleaning agent, and discarding the hydrochloric acid solution to obtain a precipitate substance cleaned by the hydrochloric acid solution; centrifuging and cleaning the precipitate after being cleaned by the hydrochloric acid solution for 5-6 times by taking the LiCl solution as a cleaning agent, collecting supernatant, and centrifuging the supernatant at the centrifugal speed of 9000 rpm for 40-45 min to obtain a reaction product; drying the reaction product in a vacuum drying oven to obtain a vanadium carbide nano belt;
2. vanadium carbide nanobelt and ketjen black nanofiber composite modified polypropylene diaphragm:
(1) mixing ketjen black and vanadium carbide nanobelts to obtain a ketjen black/vanadium carbide nanobelt mixture;
(2) mixing the ketjen black/vanadium carbide nanobelt mixture with polyvinylidene fluoride to obtain a solute; adding the solute into N-methyl pyrrolidone, and carrying out ultrasonic treatment to obtain a suspension;
(3) pumping the suspension onto a polypropylene diaphragm through vacuum filtration, and then putting the polypropylene diaphragm into a vacuum drying oven for drying to obtain the functionalized modified diaphragm.
2. The preparation method of the functionalized modified membrane according to claim 1, wherein the volume ratio of the mass of LiF to the volume of HCl aqueous solution in the step one (1) is (2 g-4 g) 20mL; the mass fraction of the HCl aqueous solution in the step one (1) is 5% -38%.
3. The method for producing a functionalized modified membrane according to claim 1, wherein V in the step one (1) 2 The volume ratio of AlC mass to HCl aqueous solution is (0.6 g-1 g): 20mL.
4. The method for preparing a functionalized modified membrane according to claim 1, wherein the hydrochloric acid solution in the step one (3) is formed by mixing 20mL of hydrochloric acid with a mass fraction of 37% and 180mL of deionized water.
5. The method for preparing the functionalized modified membrane according to claim 1, wherein the LiCl solution in the step one (3) is prepared by dissolving 7.63-8 g LiCl in 180mL deionized water; the temperature of the vacuum drying oven in the first step (3) is 60 ℃, and the drying time is 10-12 hours.
6. The method for producing a functionalized modified membrane according to claim 1, wherein the step two (1) is
The mass ratio of the ketjen black to the vanadium carbide nano-belt is 2:8; and (2) the mass ratio of the ketjen black/vanadium carbide nanobelt mixture to polyvinylidene fluoride in the step (2) is 9:1.
7. The method for preparing a functionalized modified membrane according to claim 1, wherein the volume ratio of the solute to the N-methylpyrrolidone in the second step (2) is (0.5 g-1.2 g): 10mL; the power of the ultrasonic treatment in the second step (2) is 100-500W, and the time of the ultrasonic treatment is 2-3 h; and step two, the temperature of the vacuum drying oven in the step (3) is 60 ℃, and the drying time is 10-12 hours.
8. The functionalized modified membrane prepared by the preparation method of claim 1, wherein the functionalized modified membrane is a polypropylene membrane compositely modified by vanadium carbide nanobelts and ketjen black nanofibers; the vanadium carbide nanobelt and the Ketjen black nanofiber are of a three-dimensional network structure, and the mass ratio of the vanadium carbide nanobelt to the Ketjen black nanofiber is (2-10) 1; wherein the width of the vanadium carbide nano-belt is 10-50nm, the length is 100-20 mu m, the number of layers is 1-30, and the (002) interplanar spacing is 0.2-0.9 nm.
9. The functionalized modified membrane according to claim 8, wherein the loading amount of the vanadium carbide nanobelt and the ketjen black nanofibers on the polypropylene membrane is 0.1-5 mg/cm 2 。
10. Use of a functionalized modified membrane according to claim 8, characterized in that the functionalized modified membrane is used as a membrane for lithium-sulfur batteries, potassium-sulfur batteries or sodium-sulfur batteries.
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