CN113571837B - Functional diaphragm of lithium-sulfur battery and preparation method thereof - Google Patents

Functional diaphragm of lithium-sulfur battery and preparation method thereof Download PDF

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CN113571837B
CN113571837B CN202110758147.7A CN202110758147A CN113571837B CN 113571837 B CN113571837 B CN 113571837B CN 202110758147 A CN202110758147 A CN 202110758147A CN 113571837 B CN113571837 B CN 113571837B
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pbc
sns
membrane
diaphragm
lithium
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CN113571837A (en
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黄锋林
姚莹梅
史佳倚
武双林
马琦尧
魏取福
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Jiangnan University
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • 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
    • C—CHEMISTRY; METALLURGY
    • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
    • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
    • C23C14/00—Coating by vacuum evaporation, by sputtering or by ion implantation of the coating forming material
    • C23C14/06—Coating by vacuum evaporation, by sputtering or by ion implantation of the coating forming material characterised by the coating material
    • C23C14/0623—Sulfides, selenides or tellurides
    • C—CHEMISTRY; METALLURGY
    • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
    • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
    • C23C14/00—Coating by vacuum evaporation, by sputtering or by ion implantation of the coating forming material
    • C23C14/22—Coating by vacuum evaporation, by sputtering or by ion implantation of the coating forming material characterised by the process of coating
    • C23C14/34—Sputtering
    • C23C14/35—Sputtering by application of a magnetic field, e.g. magnetron sputtering
    • 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
    • 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
    • H01M50/431—Inorganic material
    • H01M50/434—Ceramics
    • 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
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/10—Energy storage using batteries

Abstract

The invention discloses a functional diaphragm of a lithium-sulfur battery and a preparation method thereof, belonging to the field of material chemistry. The method takes BC as a diaphragm substrate, firstly prepares the PBC diaphragm by foaming hole making modification, and then obtains few-layer Ti on the surface of the PBC diaphragm by suction filtration3C2TxAqueous dispersion, finally SnS by magnetron sputtering2Is uniformly deposited on Ti3C2TxPBC membrane surface, i.e. obtaining Ti3C2Tx/SnS2-PBC composite membrane. The invention utilizes the high thermal mechanical property of the PBC film and the like to avoid the safety problem of the diaphragm caused by mechanical failure and thermal runaway; synergistic Ti3C2Txof-OH, -F, -O and SnS2The sulfur vacancy defect can be used for chemically adsorbing and rapidly capturing polysulfide, so that the shuttle effect of polysulfide is hindered, the loss of a large amount of sulfur simple substances is reduced, and finally the high-performance lithium-sulfur battery with stable circulation and long service life can be obtained.

Description

Functional diaphragm of lithium-sulfur battery and preparation method thereof
Technical Field
The invention relates to a functional diaphragm of a lithium-sulfur battery and a preparation method thereof, belonging to the field of material chemistry.
Background
Among the mature battery systems, LIB has been widely used in mobile communication, electronic devices, electric vehicles, etc. as the most promising energy-intensive commercial system. However, due to the increasing market demand and the increasing popularity of rechargeable energy vehicles, higher requirements are put on the problems of high capacity and energy density, service life and safety of a battery system, and a new generation of high-capacity batteries needs to be developed.
Lithium sulfur batteries stand out from existing battery systems because of the great advantage of high capacity characteristics in numerous secondary batteries. Sulfur (S)8) As an active material of a lithium-sulfur battery, high theoretical specific capacity (1675mAh/g) and energy density (2600Wh/kg) are provided by a multi-electron redox reaction, which is 4 times higher than the energy density of a lithium ion battery. In addition, the characteristics of high sulfur material storage, low cost, no toxicity, etc. make lithium-sulfur batteries attractive and become the best choice for developing high energy density batteries. However, the commercialization of lithium-sulfur batteries is seriously hindered by series of difficulties such as polysulfide shuttling due to the defects of commercial polyolefin-based separators.
The olefin diaphragm which is most widely commercialized at present has low production cost, good aperture controllability and stable electrochemical performance, so that the lithium ion battery is developed steadily for decades. But the poor affinity of the surface inertness of such membranes for the electrolyte is detrimental to the rapid transport of charge; the poor thermo-mechanical property and thermal stability cause various safety problems of battery explosion and fire; the large pore size poses a serious polysulfide shuttling problem that makes it the biggest challenge to limit the progress of commercialization of lithium sulfur batteries. In recent years, in order to solve many problems faced by lithium-sulfur batteries, scientists have made great efforts to modify the function of a separator, and are intended to solve the shuttling problem of lithium polysulfide, accelerate redox kinetics, promote efficient utilization of sulfur substances, and develop a secondary battery system with high capacity and long service life.
In order to solve the problems faced by lithium-sulfur batteries, a great deal of research on high-quality separators is being conductedAnd (6) adding. Using ceramic particles (Al)2O3、TiO2、SiO2And the like) to improve the heat resistance of the diaphragm, increase the mechanical strength of the diaphragm and ensure the safety and the usability of the battery. However, the use of the binder causes serious problems of an increase in the thickness of the separator, a decrease in the energy density of the battery, severe dusting of the coating, and the like, which affect the electrochemical performance of the lithium-sulfur battery. In addition, metal oxides (Al) are utilized2O3、Co3O4、MnO2) The modified polar surface can effectively capture lithium polysulfide, inhibit the deterioration of shuttle effect and reduce the loss of active materials. However, metal oxides are less than desirable in catalytically enhancing redox kinetics because of their low active sites and low conductivity. Therefore, although metal oxides have a certain polysulfide-inhibiting effect, the conversion and utilization degree of active materials for lithium-sulfur batteries is insufficient, and the object of obtaining high-performance batteries with long-term stable cycles cannot be achieved.
Disclosure of Invention
Aiming at the defects of the prior art, the invention provides titanium carbide/tin disulfide-porous bacterial cellulose (Ti)3C2Tx/SnS2PBC) functional composite diaphragm and preparation method thereof, wherein PBC is used as diaphragm substrate, and Ti is deposited on the surface of the diaphragm3C2Tx/SnS2The modified layer utilizes the high thermal mechanical property, puncture resistance and thermal stability of the PBC film, and avoids the safety problem of the diaphragm caused by mechanical failure and thermal runaway; synergistic Ti3C2Txof-OH, -F, -O and SnS2The sulfur vacancy defect can be used for chemisorption and quickly capturing polysulfide, so that the shuttle effect of polysulfide is hindered, and the loss of a large amount of sulfur simple substances is reduced; simultaneous SnS2The catalytic activity of the catalyst also accelerates the redox kinetics, so that a high-performance lithium-sulfur battery with stable cycle and long service life can be obtained.
It is a first object of the present invention to provide a Ti3C2Tx/SnS2Preparation method of PBC functional composite diaphragmA method comprising the steps of:
the first step is as follows: preparing a foamed Porous Bacterial Cellulose (PBC) diaphragm:
dissolving Azodicarbonamide (AC) and sodium hydroxide (NaOH) in water, then adding tween-80, uniformly stirring to obtain a foaming solution (AC-NaOH solution), soaking a Bacterial Cellulose (BC) film in the AC-NaOH solution, heating, washing, freeze-drying, and pressing by a press roller to obtain a PBC diaphragm;
the second step is that: preparation of less-layer Ti3C2TxAqueous dispersion:
dissolving lithium fluoride (LiF) in hydrochloric acid (HCl), stirring uniformly, and adding MXenes (Ti)3AlC2) Stirring the materials at a certain temperature to obtain Ti3AlC2Etching Al layer in the material, centrifuging and washing the mixture, adding dimethyl sulfoxide solution (DMSO) into the precipitate, stirring for 12-24 hr for intercalation, centrifuging the mixture again, washing with water to remove residual DMSO, and removing Ti3C2TxPouring the precipitate into water, performing low-temperature ultrasonic treatment under the protection of inert atmosphere, and performing solid-liquid separation to obtain few-layer Ti3C2TxAn aqueous dispersion;
the third step: preparation of Ti3C2Tx-PBC membrane:
mixing Ti3C2TxUltrasonically treating the aqueous dispersion at low temperature for a period of time, carrying out suction filtration on the surface of the PBC diaphragm obtained in the first step by utilizing vacuum filtration, drying the aqueous dispersion in vacuum, and pressing the aqueous dispersion into Ti3C2Tx-a PBC membrane;
the fourth step: preparation of Ti3C2Tx/SnS2-PBC composite membrane:
ti obtained in the third step3C2TxPBC film and SnS2The target material is fixed in a vacuum cabin body of the magnetron sputtering equipment, and the SnS is made to be sputtered under certain working air pressure and radio frequency for 10 to 60 minutes2Is uniformly deposited on Ti3C2TxPBC membrane surface, i.e. obtaining Ti3C2Tx/SnS2-PBC composite membrane.
Further, in the first step, the concentration of the Azodicarbonamide (AC) in the AC-NaOH solution is 15-25g/L, the concentration of the sodium hydroxide (NaOH) is 10-32g/L, and the concentration of the Tween-80 is 0.25-0.5% (v/v).
Further, in the first step, the BC membrane is 0.5-5mm thick, the heating temperature of foaming and hole making is 50-70 ℃, and the treatment time is 20-60 min.
Further, in the second step, the concentration of the hydrochloric acid solution (HCl) is 5-10M, the mass-to-volume ratio of lithium fluoride (LiF) to the hydrochloric acid solution is 50-100g/L, and the Ti is3AlC2The mass ratio of the lithium fluoride (LiF) to the lithium fluoride (LiF) is 1: 1-3.
Furthermore, in the second step, the etching temperature is 30-40 ℃, and the etching time is 36-48 hours.
Further, the addition amount of the dimethyl sulfoxide is 8-12 mL.
Further, in the second step, the temperature of the low-temperature ultrasonic is 0-2 ℃, and the treatment time is 1-4 h; the solid-liquid separation is preferably centrifugation, and the centrifugation speed is 2000-3500 rpm.
Further, in the third step, the temperature of the low-temperature ultrasound is 0-2 ℃, and the treatment time is preferably 10-30 minutes.
Further, in the third step, the drying temperature is 50-70 ℃.
Further, in the fourth step, the vacuum degree of the vacuum chamber of the magnetron sputtering device is 6 × 10-4-7×10-4Pa, and the working air pressure is 2-4 Pa.
Further, in the fourth step, the radio frequency power is 30-50W, and the sputtered SnS2The thickness of the deposition layer is 30-200 nm.
The second purpose of the invention is to provide Ti prepared by the preparation method3C2Tx/SnS2-PBC composite membrane.
A third object of the present invention is to provideContaining the above Ti3C2Tx/SnS2-PBC composite separator lithium sulfur batteries.
It is a fourth object of the present invention to provide the above Ti3C2Tx/SnS2Application of the PBC composite membrane in the field of lithium batteries.
Compared with the prior art, the invention has the following beneficial effects:
(1) ti in the invention3C2Tx/SnS2In the preparation of the PBC functional composite diaphragm, the ultra-high thermodynamic strength, the high puncture resistance and the high temperature resistance contractibility of the PBC diaphragm substrate are utilized, the mechanical failure of the battery caused by contraction and rupture of the diaphragm due to overcharge heat and external force extrusion, the fire and explosion safety accidents such as thermal runaway and the like are avoided, and the potential safety hazard of the battery is solved by innovatively utilizing the excellent physical characteristics of the bacterial cellulose membrane.
(2) Vacuum filtration method used in the present invention, using polar Ti3C2TxStrong hydrogen bond bonding force is formed between the medium-OH, -F and hydroxyl in the PBC film, and SnS deposited by utilizing the magnetron sputtering technology2Layer (inorganic particles and Ti)3C2TxThe bonding force between PBC films) and solves the common problem that the conventional modified layer is easy to remove powder while avoiding using a binder and not increasing the thickness of the modified layer. Ti3C2TxThe high polarity not only effectively captures polysulfide, but also improves the ionic conductivity by the conductivity of the polysulfide, accelerates the transmission of lithium ions, and simultaneously utilizes SnS2The catalytic activity of the catalyst accelerates the redox kinetic process, efficiently converts and utilizes active substances, improves the cycle stability and rate capability of the lithium-sulfur battery, and prolongs the service life of the lithium-sulfur battery.
(3) According to the invention, the bacterial cellulose membrane is subjected to hole widening treatment by adopting a foaming technology, the foaming three-dimensional porous bacterial cellulose PBC with larger pores is prepared, the problems that the BC membrane is highly interwoven, the meshes are compact, a certain barrier effect is provided for ion transmission, the compact structure increases the difficulty of subsequent suction filtration work, and functional groups on the BC membrane cannot be influenced are solved. Thereby effectively utilizing the properties of the PBC diaphragm substrate such as ultrahigh thermodynamic strength, high puncture resistance, high temperature shrinkage resistance and the like.
Drawings
FIG. 1 shows Ti prepared in example 13C2Tx/SnS 2500 cycles of PBC composite separator for lithium sulfur button cells.
FIG. 2 shows Ti prepared in example 13C2Tx/SnS2Rate performance plot of button lithium-sulfur cells with PBC composite separator.
Detailed Description
The present invention is further described below with reference to examples, but the embodiments of the present invention are not limited thereto.
Example 1:
the first step is as follows: preparing a PBC membrane:
3g of Azodicarbonamide (AC) and 4g of sodium hydroxide (NaOH) are dissolved in 200mL of deionized water, then 0.5mL of tween-80 is added, and the mixture is stirred uniformly to obtain a foaming solution (AC-NaOH solution). And soaking the BC membrane in an AC-NaOH solution, heating at 65 ℃ for 30min to obtain a porous BC membrane (PBC membrane), and washing with deionized water for multiple times to obtain a clean PBC membrane. Freeze-dried for 24 hours and pressed into PBC separator by compression roller.
The second step is that: preparation of less-layer Ti3C2TxAqueous dispersion:
1g of lithium fluoride (LiF) was dissolved in 20mL of 9M hydrochloric acid (HCl), and 1g of Ti was slowly added thereto after stirring uniformly3AlC2Stirring the materials at 35 ℃ for 48h for Ti3AlC2And etching the Al layer in the material. The mixture was then centrifuged and rinsed several times with deionized water. The precipitate was added with 10mL of dimethyl sulfoxide solution (DMSO) and stirred for 24 hours to conduct intercalation treatment. The mixture was then centrifuged again and the remaining DMSO was removed by washing with deionized water. Subjecting the obtained Ti to3C2TxPouring the precipitate into deionized water, carrying out low-temperature ultrasonic treatment for 2h under the protection of Ar, and centrifuging at the rotating speed of 3500rpm to obtain few-layer Ti3C2TxAn aqueous dispersion.
The third step: preparation of Ti3C2Tx-PBC membrane:
mixing Ti3C2TxCarrying out ultrasonic treatment on the aqueous dispersion for 15 minutes at low temperature, and carrying out suction filtration on the surface of a PBC (physical vapor deposition) membrane by utilizing vacuum filtration to prepare Ti3C2TxPBC composite membranes, after drying for 12 hours at 60 ℃ under vacuum, and pressing them into membranes.
The fourth step: preparation of Ti3C2Tx/SnS2-PBC composite membrane:
mixing Ti3C2TxPBC film and SnS2The target material is fixed at 6.6 x 10 of the magnetron sputtering equipment-4Pa vacuum chamber. Carrying out magnetron sputtering for 30 minutes under the working pressure of 3Pa and the radio frequency state of 50W to enable SnS2Is uniformly deposited on Ti3C2TxPBC diaphragm surface to obtain Ti3C2Tx/SnS2-PBC composite membrane, wherein SnS2The thickness of the deposited layer was 100 nm.
Example 2
The first step is as follows: preparing a PBC membrane:
3g of Azodicarbonamide (AC) and 2g of sodium hydroxide (NaOH) are dissolved in 200mL of deionized water, then 0.5mL of tween-80 is added, and the mixture is stirred uniformly to obtain a foaming solution (AC-NaOH solution). And soaking the BC membrane in an AC-NaOH solution, heating at 65 ℃ for 60min to obtain a porous BC membrane (PBC membrane), and washing with deionized water for multiple times to obtain a clean PBC membrane. Freeze-dried for 24 hours and pressed into PBC separator by a compression roller.
The second step is that: preparation of less-layer Ti3C2TxAqueous dispersion:
1g of lithium fluoride (LiF) was dissolved in 20mL of 7M hydrochloric acid (HCl), and 0.5g of Ti was slowly added thereto after stirring uniformly3AlC2Stirring the materials at 35 ℃ for 48h for Ti3AlC2And etching the Al layer in the material. The mixture was then centrifuged and rinsed several times with deionized water. The precipitate was added with 10mL of dimethyl sulfoxide solution (DMSO) and stirred for 12 hours to conduct intercalation treatment. The mixture was then centrifuged again and deionizedAnd washing with water to remove residual DMSO. Subjecting the obtained Ti to3C2TxPouring the precipitate into deionized water, performing low-temperature ultrasonic treatment for 1h under the protection of Ar, and centrifuging at the rotating speed of 2000rpm to obtain a few layers of Ti3C2TxAn aqueous dispersion.
The third step: preparation of Ti3C2Tx-PBC membrane:
mixing Ti3C2TxThe aqueous dispersion is subjected to ultrasonic treatment for 10 minutes at low temperature, and is subjected to suction filtration on the surface of a PBC membrane by utilizing vacuum filtration to prepare Ti3C2Tx-PBC composite separator, after drying for 12 hours at 70 ℃ under vacuum, and pressing it into a separator.
The fourth step: preparation of Ti3C2Tx/SnS2-PBC composite membrane:
mixing Ti3C2TxPBC film and SnS2The target material is fixed at 6 x 10 of the magnetron sputtering equipment-4Pa vacuum chamber. Carrying out magnetron sputtering for 60 minutes under the working pressure of 2Pa and the radio frequency state of 40W to enable SnS2Is uniformly deposited on Ti3C2TxPBC membrane surface to obtain Ti3C2Tx/SnS2-PBC composite membrane, wherein SnS2The thickness of the deposited layer was 180 nm.
Example 3
The first step is as follows: preparing a PBC membrane:
3g of Azodicarbonamide (AC) and 2g of sodium hydroxide (NaOH) are dissolved in 200mL of deionized water, then 0.5mL of tween-80 is added, and the mixture is stirred uniformly to obtain a foaming solution (AC-NaOH solution). And soaking the BC membrane in an AC-NaOH solution, heating at 55 ℃ for 45min to obtain a porous BC membrane (PBC membrane), and washing with deionized water for multiple times to obtain a clean PBC membrane. Freeze-dried for 24 hours and pressed into PBC separator by compression roller.
The second step is that: preparation of less-layer Ti3C2TxAqueous dispersion:
1g of lithium fluoride (LiF) was dissolved in 10mL of a 5M hydrochloric acid (HCl) solution, and 0.33g of Ti was slowly added thereto after stirring uniformly3AlC2Stirring the materials at 40 ℃ for 36h for Ti3AlC2And etching the Al layer in the material. The mixture was then centrifuged and rinsed multiple times with deionized water. The precipitate was added with 10mL of dimethyl sulfoxide solution (DMSO) and stirred for 24 hours to conduct intercalation treatment. The mixture was then centrifuged again and the remaining DMSO was removed by washing with deionized water. Subjecting the obtained Ti to3C2TxPouring the precipitate into deionized water, performing low-temperature ultrasonic treatment for 4h under the protection of Ar, and centrifuging at 3000rpm to obtain few-layer Ti3C2TxAn aqueous dispersion.
The third step: preparation of Ti3C2Tx-PBC membrane:
mixing Ti3C2TxThe aqueous dispersion is subjected to ultrasonic treatment for 30 minutes at low temperature, and is subjected to suction filtration on the surface of a PBC membrane by utilizing vacuum filtration to prepare Ti3C2Tx-PBC composite separator, after drying at 50 ℃ under vacuum for 12 hours, and pressing it into a separator.
The fourth step: preparation of Ti3C2Tx/SnS2-PBC composite membrane:
mixing Ti3C2TxPBC film and SnS2The target material is fixed at 7 x 10 of the magnetron sputtering equipment-4Pa vacuum chamber. Carrying out magnetron sputtering for 10 minutes under the working pressure of 4Pa and the radio frequency state of 50W to enable SnS2Is uniformly deposited on Ti3C2TxPBC membrane surface to obtain Ti3C2Tx/SnS2-PBC composite membrane, wherein SnS2The thickness of the deposited layer was 30 nm.
Comparative example 1
The lithium sulfur battery separator was a commercial polypropylene separator.
Comparative example 2
The PBC diaphragm of the porous bacterial cellulose is directly used as the diaphragm of the lithium-sulfur battery.
3g of Azodicarbonamide (AC) and 4g of sodium hydroxide (NaOH) are dissolved in 200mL of deionized water, then 0.5mL of tween-80 is added, and the mixture is stirred uniformly to obtain a foaming solution (AC-NaOH solution). And soaking the BC membrane in an AC-NaOH solution, heating at 65 ℃ for 30min to obtain a porous BC membrane (PBC membrane), and washing with deionized water for multiple times to obtain a clean PBC membrane. Freeze-dried for 24 hours and pressed into PBC separator by compression roller.
Comparative example 3
The lithium-sulfur battery diaphragm is titanium carbide modified porous bacterial cellulose Ti3C2Tx-a PBC membrane.
The first step is as follows: PBC separator was prepared as in example 1;
the second step: preparation of few-layer Ti3C2TxAqueous dispersion as in example 1;
the third step: preparation of Ti3C2Tx-PBC membrane:
mixing Ti3C2TxCarrying out ultrasonic treatment on the aqueous dispersion at low temperature for 15 minutes, and carrying out suction filtration on the surface of the PBC membrane by utilizing vacuum filtration to prepare Ti3C2TxPBC composite diaphragm, drying at 60 deg.C under vacuum for 12 hr, and pressing into diaphragm to obtain Ti3C2Tx-a PBC membrane.
Comparative example 4
The lithium-sulfur battery diaphragm is tin disulfide modified porous bacterial cellulose SnS2-a PBC membrane.
The first step is as follows: PBC separator was prepared as in example 1;
the second step is that: preparation of SnS2-PBC membrane:
combining PBC film with SnS2The target material is fixed at 6.6 x 10 of the magnetron sputtering equipment-4Pa vacuum chamber. Carrying out magnetron sputtering for 30 minutes under the working pressure of 3Pa and the radio frequency state of 50W to enable SnS2Uniformly depositing on the surface of the PBC membrane to obtain SnS2-PBC composite membrane, wherein SnS2The thickness of the deposited layer was 100 nm.
Comparative example 5
The lithium-sulfur battery diaphragm is commercial polypropylene Ti modified by titanium carbide and tin disulfide3C2Tx/SnS2-a PP separator.
The first step is as follows: preparation of less-layer Ti3C2TxAqueous dispersion as in example 1;
the third step: preparation of Ti3C2Tx-a PP separator:
mixing Ti3C2TxPerforming ultrasonic treatment on the aqueous dispersion at low temperature for 15 minutes, and performing suction filtration on the surface of a PP film by using vacuum filtration to prepare Ti3C2Tx-PP composite separator, after drying at 60 ℃ under vacuum for 12 hours, and pressing it into a separator.
The fourth step: preparation of Ti3C2Tx/SnS2-PP composite separator:
mixing Ti3C2Tx-PP films and SnS2The target material is fixed at 6.6 x 10 of the magnetron sputtering equipment-4Pa vacuum chamber. Carrying out magnetron sputtering for 30 minutes under the working pressure of 3Pa and the radio frequency state of 50W to enable SnS2Is uniformly deposited on Ti3C2TxPP separator surface to obtain Ti3C2Tx/SnS2-PP composite separator, wherein SnS2The thickness of the deposited layer was 100 nm.
Comparative example 6
The lithium-sulfur battery diaphragm is titanium carbide and tin disulfide modified bacterial cellulose Ti3C2Tx/SnS2-BC membrane:
the first step is as follows: preparation of few-layer Ti3C2TxAqueous dispersion as in example 1;
the second step is that: preparation of Ti3C2Tx-BC membrane:
mixing Ti3C2TxCarrying out ultrasonic treatment on the aqueous dispersion at low temperature for 15 minutes, and carrying out vacuum filtration on the aqueous dispersion to prepare Ti on the surface of the BC membrane3C2Tx-BC composite membranes, after drying under vacuum at 60 ℃ for 12 hours, and pressing them into membranes.
The third step: preparation of Ti3C2Tx/SnS2-BC composite membrane:
mixing Ti3C2Tx-BC film and SnS2The target material is fixed on the magnetic control6.6X 10 of sputtering apparatus-4Pa vacuum chamber. Carrying out magnetron sputtering for 30 minutes under the working pressure of 3Pa and the radio frequency state of 50W to enable SnS2Is uniformly deposited on Ti3C2Tx-BC membrane surface to obtain Ti3C2Tx/SnS2-BC composite membrane, wherein SnS2The thickness of the deposited layer was 100 nm.
The test method comprises the following steps:
the titanium carbide and tin disulfide modified porous bacterial cellulose membranes prepared in examples 1, 2 and 3 are used as lithium sulfur battery diaphragms, and the titanium carbide and tin disulfide modified porous bacterial cellulose membranes prepared in comparative examples 1, 2, 3, 4 and 5 and 6 are used as lithium sulfur battery diaphragms according to a button lithium sulfur battery assembly method.
The ionic conductivity and the interfacial impedance were tested using an electrochemical workstation, in which the parameters were set as follows
And (3) ion conductivity test: the parameters are set as follows: high frequency 106Hz, low frequency 1Hz, amplitude 0.01V;
and (3) interface impedance testing: the parameters are set as follows: high frequency 106Hz, low frequency 1Hz, amplitude 0.02V.
And (3) carrying out cycle performance and rate performance tests by using a battery test system, wherein the parameters are set as follows:
and (3) testing the cycle performance:
the discharge voltage was 1.5V, the charge voltage was 3V, and the charge/discharge current was set to 1675 current density (0.2) mass of active material (0.00036g) 0.1206mA, and 500 cycles were performed.
And (3) rate performance test:
discharge at 0.2C: the discharge voltage was 1.5V, the charge voltage was 3V, and the charge/discharge current was 1675 × 0.2 × mass of active material 0.1206mA, 5 cycles. After the completion of the charge and discharge, 0.5C charge and discharge were carried out.
Discharging at 0.5C: the discharge voltage was 1.5V, the charge voltage was 3V, and the charge/discharge current was set to 1675 × 0.5 × mass of active material 0.3015mA, 5 cycles. After the completion of the charge and discharge, 1C charge and discharge were carried out.
Discharging at 1C: the discharge voltage was 1.5V, the charge voltage was 3V, and the charge/discharge current was set to 1675 × 1 × the mass of the active material was 0.603mA, and 5 cycles were performed. After the end, 2C charging and discharging are carried out.
Discharging at 2C: the discharge voltage was 1.5V, the charge voltage was 3V, the charge-discharge current was 1675 × 2 × the mass of the active material was 1.206mA, and the number of cycles was 5. After the completion of the charge and discharge, 5C charge and discharge were carried out.
Discharging at 5C: the discharge voltage was 1.5V, the charge voltage was 3V, the charge-discharge current was 1675 × 5 × the mass of the active material was 3.015mA, and the number of cycles was 5. After the completion of the charge and discharge, 0.2C charge and discharge were carried out.
From FIG. 1, it can be seen that Ti prepared in example 13C2Tx/SnS2Initial discharge capacity of the PBC composite separator at 0.2C of 1390.9mAhg-1After 500 times of charging and discharging, 862.1mAhg of battery capacity remains-1The battery capacity decays slowly, with only 0.07% of capacity decay per week. From FIG. 2, it can be seen that Ti prepared in example 13C2Tx/SnS2PBC composite diaphragm decreases the battery capacity with the increase of discharge rate, and when it is discharged again at 0.2C, Ti3C2Tx/SnS2The capacity of the PBC composite membrane can be returned almost to the original level. Shows that under the condition of large current density, the Ti prepared by the invention3C2Tx/SnS2The PBC composite diaphragm still has rapid lithium ion migration capacity and rapid reaction power, thereby accelerating polysulfide conversion and improving the utilization rate of active substances.
Table 1 shows performance test data of the separators prepared in examples 1 to 3 and comparative examples 1 to 6. As can be seen from Table 1: compared with comparative examples 1-6, the battery separators prepared in examples 1, 2 and 3 have higher ionic conductivity, can accelerate the further reaction of polysulfide and lithium, and improve the utilization rate of active substances; the interface impedance is obviously reduced, which shows that the interface compatibility of the diaphragm is improved; the discharge capacity is improved, the effect of further reducing polysulfide into low-order sulfide is obvious, in addition, the capacity is slowly attenuated after 500 times of charge and discharge, the adsorption blocking effect of the modified diaphragm on polysulfide is better, and the long-term circulation stability of the battery is obviously improved.
TABLE 1 Performance test data of separators prepared in examples 1 to 3 and comparative examples 1 to 6
Figure BDA0003148608030000081
Figure BDA0003148608030000091
Although the present invention has been described with reference to the preferred embodiments, it should be understood that various changes and modifications can be made therein by those skilled in the art without departing from the spirit and scope of the invention as defined in the appended claims.

Claims (8)

1. Ti3C2Tx/SnS2-a method for preparing a PBC functional composite separator, characterized in that said method comprises the steps of:
the first step is as follows: preparing a foaming porous bacterial cellulose diaphragm:
dissolving azodicarbonamide and sodium hydroxide in water, then adding tween-80, stirring uniformly to obtain a foaming solution, soaking the bacterial cellulose membrane in the foaming solution, heating, washing, freeze-drying, pressing by a press roll to obtain a foaming porous bacterial cellulose membrane, namely a PBC membrane; heating at 50-70 deg.C for 20-60 min;
the second step is that: preparation of less-layer Ti3C2TxAqueous dispersion:
dissolving lithium fluoride in hydrochloric acid solution, stirring uniformly, and adding Ti3AlC2Stirring the materials at a certain temperature to obtain Ti3AlC2Etching Al layer in the material, centrifuging and washing the mixture, adding dimethyl sulfoxide into the precipitate, stirring for 12-24 hr for intercalation, centrifuging the mixture again, washing with water to remove residual dimethyl sulfoxide, and removing Ti3C2TxPouring the precipitate into water, performing low-temperature ultrasonic treatment under the protection of inert atmosphere, and performing solid-liquid separation to obtain Ti with few layers3C2TxAn aqueous dispersion; the low-temperature ultrasonic treatment is carried out at the temperature of 0-2 ℃ for 1-4 h;
the third step: preparation of Ti3C2Tx-PBC membrane:
mixing Ti3C2TxUltrasonically treating the aqueous dispersion at low temperature for a period of time, carrying out suction filtration on the surface of the PBC diaphragm obtained in the first step by utilizing vacuum filtration, drying the aqueous dispersion in vacuum, and pressing the aqueous dispersion into Ti3C2Tx-a PBC membrane; the low-temperature ultrasonic treatment is carried out at the temperature of 0-2 ℃ for 10-30 minutes;
the fourth step: preparation of Ti3C2Tx/SnS2-PBC composite membrane:
ti obtained in the third step3C2TxPBC membrane and SnS2The target material is fixed in a vacuum cabin body of the magnetron sputtering equipment, and the SnS is made to be sputtered under certain working air pressure and radio frequency for 10 to 60 minutes2Is uniformly deposited on Ti3C2TxPBC membrane surface to obtain Ti3C2Tx/SnS2-a PBC composite membrane; the vacuum degree of the vacuum chamber body of the magnetron sputtering equipment is 6 multiplied by 10-4-7×10-4Pa, radio frequency power of 30-50W, SnS of sputtering2The thickness of the deposition layer is 30-200 nm.
2. The method according to claim 1, wherein in the first step, the concentration of azodicarbonamide in the foaming solution is 15-25g/L, the concentration of sodium hydroxide is 10-32g/L, and the concentration of Tween-80 is 0.25-0.5%.
3. The method according to claim 1, wherein in the second step, the etching temperature is 30-40 ℃ and the etching time is 36-48 hours.
4. The method according to claim 1, wherein in the fourth step, the working pressure of the vacuum chamber of the magnetron sputtering apparatus is 2 to 4 Pa.
5. The method according to claim 1, wherein in the fourth step, the sputtered SnS2The thickness of the deposition layer is 50-150 nm.
6. Ti produced by the production method according to any one of claims 1 to 53C2Tx/SnS2-PBC composite membrane.
7. Comprising the Ti of claim 63C2Tx/SnS2-PBC composite separator lithium sulfur batteries.
8. Ti according to claim 63C2Tx/SnS2Application of PBC composite separator in the field of lithium-sulfur batteries.
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