CN110416512B - Based on Bi4Ti3O12Preparation method of @ C/S composite material, composite material and application - Google Patents

Based on Bi4Ti3O12Preparation method of @ C/S composite material, composite material and application Download PDF

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CN110416512B
CN110416512B CN201910665307.6A CN201910665307A CN110416512B CN 110416512 B CN110416512 B CN 110416512B CN 201910665307 A CN201910665307 A CN 201910665307A CN 110416512 B CN110416512 B CN 110416512B
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composite material
lithium
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carbon
sulfur
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CN110416512A (en
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舒洪波
周颖
梁倩倩
孙婷婷
韩明雨
闵豪
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Xiangtan 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
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/362—Composites
    • H01M4/364—Composites as mixtures
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/362—Composites
    • H01M4/366—Composites as layered products
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
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    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/38—Selection of substances as active materials, active masses, active liquids of elements or alloys
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/48—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/58—Selection of substances as active materials, active masses, active liquids of inorganic compounds other than oxides or hydroxides, e.g. sulfides, selenides, tellurides, halogenides or LiCoFy; of polyanionic structures, e.g. phosphates, silicates or borates
    • H01M4/583—Carbonaceous material, e.g. graphite-intercalation compounds or CFx
    • H—ELECTRICITY
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    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M2004/026—Electrodes composed of, or comprising, active material characterised by the polarity
    • H01M2004/028—Positive electrodes
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
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    • Y02E60/10—Energy storage using batteries

Abstract

The present application relates to a Bi4Ti3O12The preparation method of the @ C/S composite material comprises the steps of firstly preparing flower-shaped bismuth titanate spherical particle composite consisting of carbon-coated flaky primary particles and then obtaining Bi4Ti3O12@ C/S composite material, the composite having a high porosity and a specific surface. The ferroelectric phase bismuth titanate can generate a spontaneous polarization effect, has strong interaction with lithium polysulfide which is heteropolar molecules, can effectively inhibit the shuttle effect of the lithium polysulfide, can generate a micro electric field by the self polarization of the bismuth titanate, and can promote the rapid conversion of the polysulfide and accelerate the oxidation-reduction reaction of the lithium-sulfur battery in the charging and discharging process due to the higher specific surface area of the bismuth titanate. In addition, carbon is coated on the bismuth titanate hollow spheres to form a series of conductive networks, so that the problem of poor conductivity of bismuth titanate is solved. When the lithium-sulfur battery positive electrode is applied to a lithium-sulfur battery positive electrode, the specific capacity, the cyclicity and the stability of the lithium-sulfur battery positive electrode can be effectively improved.

Description

Based on Bi4Ti3O12Preparation method of @ C/S composite material, composite material and application
Technical Field
The application belongs to the technical field of battery materials, and particularly relates to a Bi-based battery4Ti3O12A preparation method of the @ C/S composite material, the composite material and application.
Background
In recent years, with the rapid development of power batteries and large-scale energy storage systems, higher requirements are put on energy density, which motivatesThere has been extensive research interest in high specific energy and economical battery systems. The lithium-sulfur battery has more and more researches on the theoretical specific capacity (1675mAh/g) and the theoretical specific energy (2600Wh/kg), and far exceeds the traditional lithium ion battery. In addition, the sulfur is used as an electrode material of the lithium battery, and has the advantages of low cost and rich natural resources. Although the lithium-sulfur battery has great advantages, its practical use is seriously hindered. First, sulfur and its final discharge product (Li)2S/Li2S2) The insulating properties of (a) are not favorable for electron transport in the cathode, resulting in enhanced polarization and slow reaction kinetics, resulting in low utilization of the active material. In the cycle, S8And Li2The large volume expansion/contraction (70%) between S reactions also directly leads to severe pulverization and permanent capacity fade of the cathode. In addition, the intermediate polysulfides have high solubility in the electrolyte and shuttle back and forth, causing rapid capacity fade and low coulombic efficiency.
In view of the above problems, researchers have conducted a great deal of work to improve the performance of lithium sulfur batteries. Among them, an inorganic metal-based material is considered as a positive electrode material of a lithium-sulfur battery having a great application prospect, and more polar materials are currently applied to lithium batteries, such as metal sulfides, nitrides, phosphides, carbides, organic metal skeleton polymers, nickel-rich materials, layered double metal hydroxy compounds, and perovskite materials. Because of the strong chemical bonding capability with the intermediate polysulfide, the long-cycle stability of the lithium battery can be greatly improved. In addition, these polar substances are often complexed with carbonaceous materials. More void space can be provided and polysulfide can be effectively confined by physical and chemical fixation, and good electrical conductivity can be ensured to promote redox reaction kinetics, thereby greatly improving electrochemical performance of the sulfur positive electrode. Inorganic metal-based base materials have been widely used in the fields of adsorption, separation, hydrogen storage, catalyst carriers, supercapacitors, water purification, sewage treatment, etc. due to their wide distribution, wide variety and simple preparation process.
Disclosure of Invention
The technical problem to be solved by the invention is as follows: in order to solve the defects in the prior art, the Bi with strong cyclicity and stability is provided4Ti3O12A @ C/S composite material and a preparation method thereof.
The technical scheme adopted by the invention for solving the technical problems is as follows:
bi1Ti3O12The preparation method of the @ C/S composite material comprises the following steps:
s1: dispersing carbon in water to form a carbon dispersion;
s2: adding a mineralizer, bismuth nitrate and tetrabutyl titanate into the carbon dispersion liquid obtained in the step S1, then performing ultrasonic dispersion, and heating for 18-24h in a drying box at the temperature of 160-220 ℃;
s3: filtering the substance obtained after the S2 reaction to separate a product, washing the product with deionized water, and drying to obtain Bi4Ti3O12@ C composite material;
s4: bi obtained in step S34Ti3O12Grinding and mixing the @ C composite material and sulfur powder according to the mass ratio of 1: 0.1-1 to obtain mixed powder;
s5: heating the mixed powder obtained in the step S4 for 10-12h at the temperature of 150 ℃ and 160 ℃ under inert gas; then, the temperature is raised to 240-280 ℃ and kept for 60-90min, and the excessive sulfur on the surface is removed, thereby obtaining Bi4Ti3O12@ C/S composite material.
Preferably, Bi of the present invention4Ti3O12The preparation method of the @ C/S composite material comprises the step S1, wherein carbon is one or more than two of carbon nano tubes, graphene oxide, graphite and expanded graphite.
Preferably, Bi of the present invention4Ti3O12The preparation method of the @ C/S composite material comprises the step S1 of dispersing carbon in water, then mechanically stirring for 30-60min, then ultrasonically dispersing for 1-2h, and dispersing for 1-3h in a cell crusher.
Preferably, Bi of the present invention4Ti3O12Method for producing @ C/S composite material, step S1, concentration of carbon in carbon dispersion liquidThe degree is 3-5 mg/ml.
Preferably, Bi of the present invention4Ti3O12The preparation method of the @ C/S composite material comprises the step S2, wherein the mineralizing agent is potassium hydroxide and/or sodium hydroxide.
Preferably, Bi of the present invention4Ti3O12The preparation method of the @ C/S composite material has the mol ratio of the bismuth nitrate to the tetrabutyl titanate in the step S2 of 4: 3-6.
Preferably, Bi of the present invention4Ti3O12The preparation method of the @ C/S composite material comprises the step of preparing a mineralizer with the concentration of 2-6mol per liter of deionized water.
Preferably, Bi of the present invention4Ti3O12The preparation method of the @ C/S composite material comprises the step of preparing tetrabutyl titanate with the amount of 1-3mol per liter of deionized water.
Bi4Ti3O12@ C/S composite material of Bi as described above4Ti3O12The @ C/S composite material is prepared by a preparation method.
Bi as defined above4Ti3O12The application of the @ C/S composite material in the positive electrode material of the lithium-sulfur battery.
The invention has the beneficial effects that:
the invention provides a Bi4Ti3O12The preparation method of the @ C/S composite material comprises the steps of firstly preparing flower-shaped bismuth titanate spherical particle composite consisting of carbon-coated flaky primary particles and then obtaining Bi4Ti3O12@ C/S composite material, the composite having a high porosity and a specific surface. The ferroelectric phase bismuth titanate can generate a spontaneous polarization effect, has strong interaction with lithium polysulfide which is heteropolar molecules, can effectively inhibit the shuttle effect of the lithium polysulfide, can generate a micro electric field by the self polarization of the bismuth titanate, and can promote the rapid conversion of the polysulfide and accelerate the oxidation-reduction reaction of the lithium-sulfur battery in the charging and discharging process due to the higher specific surface area of the bismuth titanate. In addition, carbon is coated on the bismuth titanate hollow spheres to form a series of conductive networks, so that the problem of poor conductivity of bismuth titanate is solved. It is prepared byWhen the lithium-sulfur battery positive electrode is applied to a lithium-sulfur battery positive electrode, the specific capacity, the cyclicity and the stability of the lithium-sulfur battery positive electrode can be effectively improved.
Drawings
The technical solution of the present application is further explained below with reference to the drawings and the embodiments.
FIG. 1 shows Bi in example 14Ti3O12Scanning electron micrographs of @ CNT composites;
FIG. 2 shows Bi in example 14Ti3O12Transmission electron microscopy of @ CNT composites;
FIG. 3 shows Bi in example 14Ti3O12@ CNT for nitrogen desorption curve;
FIG. 4 shows Bi in example 14Ti3O12@ CNT pore size distribution plot;
FIG. 5 shows Bi in example 14Ti3O12The X-ray diffraction pattern of @ CNT/S composite;
FIG. 6 shows Bi in example 14Ti3O12Thermal thermogram of @ CNT/S composite.
FIG. 7 shows Bi in example 14Ti3O12The graph of the cyclic voltammetry of the @ CNT/S composite material as the positive electrode of the lithium-sulfur battery;
FIG. 8 shows Bi at 0.5C4Ti3O12A comparative graph of the cycling performance of the @ CNT/S composite material and the CNT/S as the positive electrode of the lithium-sulfur battery;
Detailed Description
It should be noted that the embodiments and features of the embodiments in the present application may be combined with each other without conflict.
Example 1
This example provides a Bi-based solution4Ti3O12The preparation method of the @ C/S composite material comprises the following steps:
weighing 120mg of CNT, dispersing in 40ml of deionized water, stirring vigorously for 30min, then dispersing ultrasonically in an ultrasonic machine for 1h, and finally dispersing in a cell crusher for 1h to obtain CNT dispersion. Under the stirring at normal temperature, taking the amount of 5mol per liter of deionized water asWeighing 200mmol of sodium hydroxide as a mineralizer, adding the sodium hydroxide into a Carbon Nano Tube (CNT) dispersion liquid, adding 40m mol of tetrabutyl titanate (1 mol per liter of deionized water) after dissolving, adding bismuth nitrate according to the molar ratio of the bismuth nitrate to the tetrabutyl titanate of 4: 3, further performing ultrasonic dispersion, pouring the dispersed mixture into a polytetrafluoroethylene inner container of a stainless steel autoclave, heating the mixture in a blast drying oven at 180 ℃ for 20 hours, naturally cooling the reaction to room temperature, performing suction filtration to separate a product, washing the product with deionized water for several times, and drying the product at 50 ℃ for 20 hours to obtain Bi4Ti3O12@ CNT composites. Adding Bi4Ti3O12Mixing the @ CNT composite material and sulfur powder, grinding the mixture into a black mixture by using an agate mortar, wherein the mass ratio of the material to the sulfur powder is 20: 80, putting the black powder into a small sealed cabin, further fixing the small sealed cabin by using a square boat, putting the small sealed cabin into a tubular furnace, introducing argon, heating at 155 ℃ for 12 hours, and heating at the rate of 1 ℃/min to melt sulfur, and feeding the molten sulfur into Bi4Ti3O12@ CNT composite material, heating to 240 deg.C, maintaining for 90min, removing excessive sulfur on surface, and obtaining Bi4Ti3O12@ CNT/S composite.
Weigh 0.14gBi4Ti3O12The method comprises the following steps of @ CNT/S composite material, adding 0.02g of acetylene black and 0.02g of polyvinylidene fluoride, uniformly mixing, adding N-methylpyrrolidone to prepare slurry, uniformly coating the slurry on a current collector aluminum foil, drying at 60 ℃, flattening on a compression machine to prepare a positive electrode film with the thickness of about 150 mu m, punching a wafer with the diameter of 1cm on the positive electrode film, placing the wafer in a vacuum drying box at 60 ℃ for heat treatment for more than 12 hours, naturally cooling along with the vacuum drying box, and weighing to serve as a spare electrode. The electrolyte adopts 1 mol/L1, 3-Dioxolane (DOL) of lithium bistrifluoromethanesulfonylimide (LiTFSI): ethylene glycol dimethyl ether (DME) (1: 1, v/v) mixed solution, 1 wt% of lithium nitrate as an additive, a polypropylene microporous film as a diaphragm and a metal lithium sheet as a negative electrode. Packaging the battery in a glove box in argon atmosphere, standing at 45 deg.C for 10 hr, with a cut-off voltage of 1.8-2.8V, a specific discharge capacity of 1289mAh/g at 0.1C, and circulating for 50 timesThe capacity of the battery can be kept at 978 mAh/g.
Example 2
This example provides a Bi-based solution4Ti3O12The preparation method of the @ C/S composite material comprises the following steps:
weighing 140mg of CNT, dispersing in 40ml of deionized water, stirring vigorously for 40min, then dispersing ultrasonically in an ultrasonic machine for 1.5h, and finally dispersing in a cell crusher for 1h to obtain CNT dispersion. Under normal temperature stirring, weighing 80mmol of sodium hydroxide (2 mol per liter of deionized water) as a standard, adding the sodium hydroxide as a mineralizer into a Carbon Nano Tube (CNT) dispersion liquid, adding 60mmol of tetrabutyl titanate (1.5 mol per liter of deionized water) after dissolution, adding bismuth nitrate according to the molar ratio of the bismuth nitrate to the tetrabutyl titanate of 4: 5, further performing ultrasonic dispersion, pouring the dispersed mixture into a polytetrafluoroethylene inner container of a stainless steel autoclave, heating for 24h at 160 ℃ in a forced air drying oven, performing suction filtration to separate a product after the reaction is naturally cooled to room temperature, washing for a plurality of times by deionized water, and drying for 15h at 60 ℃ to obtain Bi4Ti3O12@ CNT composites. Adding Bi4Ti3O12Mixing the @ CNT composite material and sulfur powder, grinding the mixture into a black mixture by using an agate mortar, wherein the mass ratio of the material to the sulfur powder is 20: 80, putting the black powder into a small sealed cabin, further fixing the small sealed cabin by using a square boat, putting the small sealed cabin into a tubular furnace, introducing argon, heating the small sealed cabin at 160 ℃ for 10 hours at the heating rate of 3 ℃/min to melt sulfur, and feeding the molten sulfur into Bi4Ti3O12@ CNT composite material, heating to 250 deg.C for 90min, removing excessive sulfur on surface, and obtaining Bi4Ti3O12@ CNT/S composite. The conditions for slurry mixing and battery fabrication were as described above in example 1.
Example 3
This example provides a Bi-based solution4Ti3O12The preparation method of the @ C/S composite material comprises the following steps:
weighing 160mg of Graphene Oxide (GO) and dispersing in 40ml of deionized water, violently stirring for 50min, and then ultrasonically dispersing in an ultrasonic machine for 1.5And h, finally dispersing in a cell crusher for 1.5h to obtain the GO dispersion liquid. Under normal temperature stirring, weighing 120mmol of sodium hydroxide (3 mol per liter of deionized water) as a standard, adding the sodium hydroxide as a mineralizer into a Carbon Nano Tube (CNT) dispersion liquid, adding 80mmol of tetrabutyl titanate (2 mol per liter of deionized water) after dissolution, adding bismuth nitrate according to the molar ratio of the bismuth nitrate to the tetrabutyl titanate of 1: 1, further performing ultrasonic dispersion, pouring the dispersed mixture into a polytetrafluoroethylene inner container of a stainless steel autoclave, heating the mixture in a forced air drying oven for 22h at 170 ℃, performing suction filtration to separate a product after the reaction is naturally cooled to room temperature, washing the product for a plurality of times by using deionized water, and drying the product for 10h at 80 ℃ to obtain Bi4Ti3O12@ GO composite. Adding Bi4Ti3O12Mixing the @ GO composite material and the sulfur powder, grinding the mixture into a black mixture by using an agate mortar, wherein the mass ratio of the material to the sulfur powder is 20: 80, putting the black powder into a small sealed cabin, further fixing the small sealed cabin by using a square boat, putting the small sealed cabin into a tubular furnace, introducing argon, heating at 155 ℃ for 12 hours, and heating at the rate of 5 ℃/min to melt sulfur and enter Bi4Ti3O12@ GO composite material, then raising the temperature to 260 ℃ and keeping the temperature for 70min, removing the excessive sulfur on the surface, and finally obtaining Bi4Ti3O12@ GO/S composites. The conditions for slurry mixing and battery fabrication were as described above in example 1.
Example 4
This example provides a Bi-based solution4Ti3O12The preparation method of the @ C/S composite material comprises the following steps:
weighing 180mg of graphite, dispersing in 40ml of deionized water, stirring vigorously for 60min, then carrying out ultrasonic dispersion in an ultrasonic machine for 2h, and finally dispersing in a cell crusher for 2h to obtain a graphite dispersion liquid. Under normal temperature stirring, 160mmol of sodium hydroxide (4 mol per liter of deionized water) is weighed as a standard and is added into Carbon Nano Tube (CNT) dispersion liquid as a mineralizer, 100mmol of tetrabutyl titanate (2.5 mol per liter of deionized water) is added after dissolution, bismuth nitrate is added according to the molar ratio of 4: 3 of the bismuth nitrate to the tetrabutyl titanate, then further ultrasonic dispersion is carried out, and the components are separatedPouring the dispersed mixture into a polytetrafluoroethylene inner container of a stainless steel autoclave, heating for 20h at 200 ℃ in a forced air drying oven, naturally cooling to room temperature after reaction, performing suction filtration to separate a product, washing for several times by deionized water, and drying for 12h at 80 ℃ to obtain Bi4Ti3O12@ graphite composite material. Adding Bi4Ti3O12Mixing the @ graphite composite material and sulfur powder, grinding the mixture into a black mixture by using an agate mortar, wherein the mass ratio of the material to the sulfur powder is 30: 70, putting the black powder into a small sealed cabin, further fixing the small sealed cabin by using a square boat, putting the small sealed cabin into a tubular furnace, introducing nitrogen, heating the small sealed cabin at 160 ℃ for 10 hours at the heating rate of 7 ℃/min to melt sulfur, and introducing the sulfur into Bi4Ti3O12@ graphite composite material, heating to 270 deg.C, maintaining for 60min, removing excessive sulfur on surface, and obtaining Bi4Ti3O12@ graphite/S composite. The conditions for slurry mixing and battery fabrication were as described above in example 1.
Example 5
This example provides a Bi-based solution4Ti3O12The preparation method of the @ C/S composite material comprises the following steps:
weighing 200mg of expanded graphite, dispersing in 40ml of deionized water, stirring vigorously for 60min, then carrying out ultrasonic dispersion in an ultrasonic machine for 2h, and finally dispersing in a cell crusher for 3h to obtain an expanded graphite dispersion liquid. Under normal temperature stirring, weighing 240mmol of sodium hydroxide (6 mol per liter of deionized water) as a standard, adding the sodium hydroxide as a mineralizer into a Carbon Nano Tube (CNT) dispersion liquid, adding 120mmol of tetrabutyl titanate (3 mol per liter of deionized water) after dissolution, adding bismuth nitrate according to the molar ratio of the bismuth nitrate to the tetrabutyl titanate of 2: 3, further performing ultrasonic dispersion, pouring the dispersed mixture into a polytetrafluoroethylene inner container of a stainless steel autoclave, heating for 18h at 220 ℃ in a forced air drying oven, after the reaction is naturally cooled to room temperature, performing suction filtration to separate a product, washing for several times by using deionized water, and drying for 10h at 100 ℃ to obtain Bi4Ti3O12@ expanded graphite composite material. Adding Bi4Ti3O12@ expanded graphite composite material and sulfur powderGrinding the mixture into a black mixture by using an agate mortar, wherein the mass ratio of the material to the sulfur powder is 30: 70, putting the black powder into a small sealed cabin, fixing the small sealed cabin by using a ark, putting the small sealed cabin into a tubular furnace, introducing nitrogen, heating the small sealed cabin at the temperature of 155 ℃ for 12 hours at the heating rate of 9 ℃/min to melt sulfur, and feeding the sulfur into Bi4Ti3O12@ expansion graphite composite material, then raising the temperature to 280 deg.C and maintaining for 60min, removing excess sulfur on the surface and finally obtaining Bi4Ti3O12@ expanded graphite/S composite. The conditions for slurry mixing and battery fabrication were as described above in example 1.
FIG. 1 shows Bi for lithium-sulfur battery prepared in example 1 of the present invention4Ti3O12Scanning electron microscope picture of @ CNT material, it can be seen from FIG. 1 that Bi is prepared4Ti3O12@ CNT material is formed by coating Bi with CNT4Ti3O12This effectively improves the conductivity of the composite material, and moreover, Bi can be seen4Ti3O12The flower-shaped spherical particles with the particles stacked by flaky primary particles have higher specific surface area and are beneficial to the conversion of polysulfide in the charge-discharge process.
FIG. 2 shows Bi for lithium-sulfur battery prepared in example 1 of the present invention4Ti3O12Transmission electron microscope picture of @ CNT material, it can be seen from FIG. 2 that Bi is prepared4Ti3O12The @ CNT material is flower-shaped hollow particles formed by stacking sheets, has higher specific surface area and space, is favorable for sulfur loading and polysulfide conversion due to the structure, and is coated on the surface to form a conductive network, so that the conductive capacity of the material is improved.
FIG. 3 shows Bi for lithium-sulfur battery prepared in example 1 of the present invention4Ti3O12The nitrogen adsorption and desorption curve of the @ CNT material can be seen from FIG. 3, and the prepared Bi4Ti3O12The adsorption-desorption curve of the @ CNT material belongs to a V-type adsorption isothermal curve, belongs to a macroporous type, and has a specific surface area as high as 131m2/g。
FIG. 4 shows Bi for lithium-sulfur battery prepared in example 1 of the present invention4Ti3O12@ CNT Material pore size distribution Curve, it can be seen from FIG. 4 that Bi is produced4Ti3O12The pore diameter of the @ CNT material is mainly distributed between 50 nm and 100nm, which shows that the pore structure of the material is mainly macroporous, and meanwhile, partial mesopores exist, and the pore volume of the material is as high as 0.90cm3/g。
FIG. 5 shows Bi for lithium-sulfur battery prepared in example 1 of the present invention4Ti3O12X-ray diffraction Pattern of @ CNT/S composite, as can be seen from FIG. 5, Bi produced4Ti3O12The @ CNT/S composite material shows a characteristic peak of sulfur, which indicates that the sulfur is uniformly distributed in the carbon material, and further indicates that the preparation process is good.
FIG. 6 shows Bi for lithium-sulfur battery prepared in example 1 of the present invention4Ti3O12Thermogravimetric of @ CNT/S composite, as can be seen from FIG. 6, Bi produced4Ti3O12The sulphur content of the @ CNT/S composite is 72.5%.
FIG. 7 shows Bi for lithium-sulfur battery prepared in example 1 of the present invention4Ti3O12@ CNT/S composite as positive electrode Cyclic Voltammetry (CV) curve, and FIG. 8 is Bi for lithium-sulfur battery prepared in example 1 of the present invention4Ti3O12Comparison of 0.5C cycle Performance for @ CNT/S composite and CNT/S as Positive electrode, it can be seen from FIG. 7 that Bi is produced4Ti3O12The @ CNT/S composite material has good cycle stability and reversibility, and the prepared Bi can be seen from FIG. 84Ti3O12@ CNT/S composite material has initial discharge capacity of 998mAh/g under the condition that current density is 0.5C, capacity of 827mAh/g is still remained after 300 times of circulation, capacity retention rate is 82.8%, while initial discharge capacity of CNT/S with the same sulfur capacity is only 772mAh/g, capacity of 395mAh/g is remained after 300 times of circulation, and capacity retention rate is 51.1%.
In conclusion, the ferroelectric phase Bi is synthesized by a simple one-step hydrothermal method4Ti3O12The @ C composite material is used as a main material of a positive electrode of the lithium-sulfur battery. Carbon with excellent conductivity for electron transport and lithium ion diffusionProvides a strong conductive network, and is beneficial to improving the kinetics of electrochemical reaction and the utilization rate of sulfur. Bi4Ti3O12The @ C composite has a good specific surface area and a pore structure that is favorable for encapsulating sulfur. More importantly, the physical constraint of the hollow porous bismuth titanate spheres on sulfur and the chemical adsorption of the 'spontaneous polarization' effect caused by the ferroelectricity of bismuth titanate on polar polysulfide are mutually cooperated, so that the shuttle effect can be effectively inhibited, the irreversible loss of active substances is greatly reduced, the cycle performance of the lithium-sulfur battery is very stable, and the rate capability of the battery can be effectively improved. Using Bi with a sulfur content of 72.5%4Ti3O12The @ CNT/S composite material is used as the lithium-sulfur battery of the anode, the initial discharge specific capacity is up to 998mAh/g under the multiplying power of 0.5C, and the capacity is still 827mAh/g after 300 cycles.
In light of the foregoing description of the preferred embodiments according to the present application, it is to be understood that various changes and modifications may be made without departing from the spirit and scope of the invention. The technical scope of the present application is not limited to the contents of the specification, and must be determined according to the scope of the claims.

Claims (9)

1. Bi4Ti3O12The preparation method of the @ C/S composite material is characterized by comprising the following steps of:
s1: dispersing carbon in water to form a carbon dispersion;
s2: adding a mineralizer, bismuth nitrate and tetrabutyl titanate into the carbon dispersion liquid obtained in the step S1, then performing ultrasonic dispersion, and heating for 18-24h in a drying box at the temperature of 160-220 ℃;
s3: filtering the substance obtained after the S2 reaction to separate a product, washing the product with deionized water, and drying to obtain Bi4Ti3O12@ C composite material;
s4: bi obtained in step S34Ti3O12Grinding and mixing the @ C composite material and sulfur powder according to the mass ratio of 1: 0.1-1 to obtain mixed powder;
s5: heating the mixed powder obtained in the step S4 for 10-12h at the temperature of 150 ℃ and 160 ℃ under inert gas; then, the temperature is raised to 240-280 ℃ and kept for 60-90min, and the redundant sulfur on the surface is removed, thereby obtaining the Bi4Ti3O12@ C/S composite material;
in step S2, the mineralizer is potassium hydroxide and/or sodium hydroxide.
2. The Bi according to claim 14Ti3O12The preparation method of the @ C/S composite material is characterized in that carbon in the step S1 is one or more than two of carbon nano tubes, graphene oxide, graphite and expanded graphite.
3. The Bi according to claim 24Ti3O12The preparation method of the @ C/S composite material is characterized in that in the step S1, after carbon is dispersed in water, mechanical stirring is firstly used for 30-60min, then ultrasonic dispersion is carried out for 1-2h, and dispersion is carried out for 1-3h in a cell crusher.
4. The Bi according to claim 34Ti3O12The preparation method of the @ C/S composite material is characterized in that the concentration of carbon in the carbon dispersion liquid in the step S1 is 3-5 mg/ml.
5. The Bi according to claim 14Ti3O12The preparation method of the @ C/S composite material is characterized in that the molar ratio of bismuth nitrate to tetrabutyl titanate in the step S2 is 4: 3-6.
6. The Bi according to claim 14Ti3O12The preparation method of the @ C/S composite material is characterized in that the concentration of a mineralizer is 2-6mol per liter of deionized water.
7. The Bi according to claim 14Ti3O12The preparation method of the @ C/S composite material is characterized in that the amount of tetrabutyl titanate is 1-3mol per liter of deionized water.
8. Bi4Ti3O12@ C/S composite material, characterized by being made of Bi according to any one of claims 1 to 74Ti3O12The @ C/S composite material is prepared by a preparation method.
9. Bi according to claim 84Ti3O12The application of the @ C/S composite material in the positive electrode material of the lithium-sulfur battery.
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CN105845916A (en) * 2016-06-01 2016-08-10 中国计量大学 Composite material based on ferroelectric oxide and sulfur and application thereof in lithium sulfur batteries
CN106532016A (en) * 2016-12-28 2017-03-22 西北工业大学 Lithium-sulfur battery composite positive electrode material and preparation method thereof

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