CN109698333B - Lithium-sulfur battery positive electrode material and preparation method and application thereof - Google Patents

Lithium-sulfur battery positive electrode material and preparation method and application thereof Download PDF

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CN109698333B
CN109698333B CN201811545102.6A CN201811545102A CN109698333B CN 109698333 B CN109698333 B CN 109698333B CN 201811545102 A CN201811545102 A CN 201811545102A CN 109698333 B CN109698333 B CN 109698333B
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lithium
porous carbon
positive electrode
electrode material
titanium dioxide
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CN109698333A (en
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张策
刘盛堂
厉耀华
杨晓晶
岳文博
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China Academy of Space Technology CAST
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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
    • H01M4/366—Composites as layered products
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B82—NANOTECHNOLOGY
    • B82Y—SPECIFIC USES OR APPLICATIONS OF NANOSTRUCTURES; MEASUREMENT OR ANALYSIS OF NANOSTRUCTURES; MANUFACTURE OR TREATMENT OF NANOSTRUCTURES
    • B82Y30/00—Nanotechnology for materials or surface science, e.g. nanocomposites
    • 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
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/38—Selection of substances as active materials, active masses, active liquids of elements or alloys
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/62—Selection of inactive substances as ingredients for active masses, e.g. binders, fillers
    • H01M4/624—Electric conductive fillers
    • H01M4/625—Carbon or graphite
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/62—Selection of inactive substances as ingredients for active masses, e.g. binders, fillers
    • H01M4/628—Inhibitors, e.g. gassing inhibitors, corrosion inhibitors
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    • 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 relates to a lithium-sulfur battery anode material, a preparation method and application thereof, in particular to preparation of a nano material and an electrochemical material, and belongs to the technical field of preparation of lithium ion batteries. The solvent thermal method adopted by the invention has the advantages that the required raw materials are all industrial-grade products, the preparation process and the process are simple, and the industrial production is favorably realized. The lithium-sulfur battery anode material prepared by the method has the advantages of high sulfur content, good stability, good battery performance, simple process and low cost.

Description

Lithium-sulfur battery positive electrode material and preparation method and application thereof
Technical Field
The invention relates to a lithium-sulfur battery anode material, a preparation method and application thereof, in particular to preparation of a nano material and an electrochemical material, and belongs to the technical field of preparation of lithium ion batteries.
Background
The lithium-sulfur battery as the next generation lithium ion battery expected to realize industrialization has the advantages of high specific energy, low price, good environment and the like; the theoretical energy density of the lithium ion battery reaches up to 2600Wh/kg, which is 2-5 times of the energy density of the traditional lithium ion battery (for example, the energy density of the lithium ion battery taking lithium cobaltate/graphite as the positive electrode and the negative electrode is lower than 200Wh/kg), and the lithium ion battery can meet the energy storage requirements of various electronic equipment and electric automobiles taking the lithium ion battery as the power supply. Therefore, lithium-sulfur batteries have attracted much attention from researchers, and industrial research has also begun. However, there are still some problems that limit the development and industrialization process of lithium-sulfur batteries. The method comprises the following steps: first, the active material has poor electron/ion conductivity, including elemental sulfur (S)8) Lithium sulfide (Li)2S) and lithium peroxosulfide (Li)2S2) Etc., resulting in low utilization of active materials; second, the intermediate product of the reaction is lithium polysulfide (Li)2SxX is more than or equal to 2 and less than or equal to 8) can be dissolved into the electrolyte, so that the shuttle effect is generated, the active substance loss is serious, and the coulomb efficiency is low; thirdly, the elementary sulfur can generate violent volume change in the charging and discharging process to destroy electricityPole structures, affecting battery life.
Disclosure of Invention
The technical problem to be solved by the invention is as follows: the preparation method comprises the steps of growing a layer of amorphous titanium dioxide film on the surface of porous carbon, and loading the amorphous titanium dioxide film with sulfur simple substance to obtain the anode material of the lithium-sulfur battery.
The technical solution of the invention is as follows:
a lithium-sulfur battery anode material comprises sulfur, porous carbon (marked as PC) and a coating layer;
the coating layer is nano-scale titanium dioxide;
the coating layer is coated on the surface of the porous carbon, and the sulfur is filled in the holes with the coating layer of the porous carbon.
A method for preparing a positive electrode material of a lithium-sulfur battery, which comprises the following steps:
(1) acidifying the porous carbon to obtain acidified porous carbon, and marking the acidified porous carbon as APC;
(2) dispersing the acidified porous carbon obtained in the step (1) in a nonpolar solvent, adding a titanium source, sealing, ultrasonically stirring for 4h-30d (days), centrifugally washing after the ultrasonic stirring is finished, using the nonpolar solvent during the centrifugal washing, wherein the purpose of the centrifugal washing is to remove unreacted titanate, dispersing the obtained solid in the nonpolar solvent again after the centrifugal washing is finished, carrying out solvothermal reaction for 2h-2d at the temperature of 90-240 ℃, centrifugally washing after the solvothermal reaction is finished, using the nonpolar solvent during the centrifugal washing, drying the obtained solid after the centrifugal washing is finished, wherein the drying temperature is 60-100 ℃, obtaining amorphous titanium dioxide film coated porous carbon marked as TiO2@APC；
(3) Mixing the amorphous titanium dioxide film-coated porous carbon obtained in the step (2) with elemental sulfur, uniformly mixing, and then sealing in an inert gas environment, wherein the inert gas is nitrogen, helium or argon; heating at 110-500 deg.C for 30min-12h to obtain amorphous dioxideThe porous carbon coated with the titanium film is loaded with elemental sulfur and is marked as TiO2@APC@S。
In the step (1), the porous carbon is selected from super P, Ketjen black, CMK-3 or CMK-8, and the specific surface area of the porous carbon is 200m2/g-2000m2(ii)/g, pore size is 1nm-100 nm; the reagent used in the acidification treatment is one or a mixture of more than two of nitric acid, sulfuric acid and phosphoric acid, and the acidification treatment process comprises the following steps: mixing porous carbon and a reagent, stirring at the mixing temperature of 20-140 ℃ for 10min-24h, washing with deionized water after stirring, and drying at the drying temperature of 60-100 ℃, wherein the proportional relation between the porous carbon and the reagent is 1g: 5-100 ml;
in the step (2), the nonpolar solvent is cyclohexane, hexane or petroleum ether; the titanium source is tetrabutyl titanate, tetraethyl titanate or isopropyl titanate; the ratio of the porous carbon to the titanium source is 1g (5-40 ml); the volume of the nonpolar solvent is required to be enough for stirring the porous carbon, and is not limited;
in the step (3), the mass ratio of the amorphous titanium dioxide film-coated porous carbon to the elemental sulfur is 1 (0.1-9).
The application of a positive electrode material of a lithium-sulfur battery, which comprises the following steps:
(1) ultrasonically dispersing the prepared amorphous titanium dioxide film-coated porous carbon loaded elemental sulfur and conductive carbon black in methyl pyrrolidone (NMP) for 10min-2h to obtain a turbid liquid;
(2) the turbid liquid obtained in the step (1) is dripped on a wafer and dried to obtain a positive electrode, and the drying temperature is 40-80 ℃;
(3) a lithium secondary battery was obtained using metallic lithium as a negative electrode, celgrad 2400 as a separator, and an organic liquid as an electrolyte.
In the step (1), the mass ratio of the amorphous titanium dioxide film-coated porous carbon loaded elemental sulfur to the conductive carbon black is 1: (0.1-0.5);
in the step (2), the wafer is made of carbon fiber paper, carbon felt, carbon nanotube paper or carbon aerogel paper;
in the step (3), LiTFSI with 1.0M of organic liquid is dissolved in organic solution with the volume ratio of DME to DOL of 1:1, and then lithium nitrate is added, wherein the mass of the lithium nitrate is 2% of that of the LiTFSI;
the obtained lithium secondary battery is made into a CR-2032 button battery and is stood for 2 hours for charge and discharge tests, and the test voltage range is 1.7V-2.8V.
Advantageous effects
(1) Compared with other technologies, the preparation method of the amorphous titanium dioxide film modified porous carbon sulfur-loaded lithium-sulfur battery cathode material has the following advantages that through the solvothermal process: 1) the carbon material is coated with a layer of oxide, so that the surface polarity of the carbon material is enhanced, the carbon material has strong adsorption effect on lithium polysulfide, the shuttle of the lithium polysulfide is greatly relieved, and the effective specific surface area with adsorption effect on the lithium polysulfide reaches 669.2m2The contact area between the electrode and the electrolyte is increased, and the electrochemical activity of the material is improved; 2) the preparation of the filmed titanium dioxide has no obvious influence on the conductivity of the porous carbon, and ensures the specific surface area of the original mesoporous carbon, while the amorphous coated porous carbon has a three-dimensional through mesh structure, so that the electron transmission and the ion migration are ensured; 3) by preparing titanium dioxide with oxygen defects, the electropositivity of the titanium dioxide is improved, and the action of lithium polysulfide is enhanced. The improvement effectively improves the lithium storage specific capacity, the cycle performance and the rate capability of the lithium-sulfur battery anode material. In addition, the solvent thermal method adopted by the invention has the advantages that the required raw materials are all industrial-grade products, the preparation process and the technology are simple, and the industrial production is favorably realized. The lithium-sulfur battery anode material prepared by the method has the advantages of high sulfur content, good stability, good battery performance, simple process and low cost.
(2) The invention discloses a preparation method of a composite positive electrode material of a lithium-sulfur battery, belonging to the field of nano material preparation and electrochemical materials. The invention modifies the porous carbon material, grows a layer of inorganic compound film on the surface, loads sulfur elementary substance and uses the inorganic compound film as the anode material of the lithium sulfur battery, and has excellent battery performance, wherein the reason for growing the titanium oxide film is as follows: 1. titanium oxide can adsorb polysulfides, greatly mitigating the shuttling effect of polysulfides. 2. Titanium oxide exists as a thin film, and hardly affects the conductivity of the porous carbon. 3. The method can ensure the advantage of large specific surface area of the porous carbon to be exerted, can expose the surface of the titanium oxide to the maximum extent, and can adsorb lithium polysulfide by using the surface of the titanium oxide to inhibit the shuttle effect generated in the charging and discharging of the lithium-sulfur battery.
Drawings
FIG. 1 is a schematic representation of porous carbon APC, TiO2@APC,TiO2X-ray powder diffraction pattern of @ APC @ S; from FIG. 1, it can be seen that the porous carbon APC, TiO2@APC，TiO2The powder diffraction data of the three substances of @ APC @ S have two large bulges for porous carbon APC subjected to acidification treatment, and for diffraction between graphite layers and in-plane diffraction, when porous carbon TiO coated with one layer of amorphous titanium dioxide2The diffraction peak of @ APC has no obvious difference from the diffraction peak of the porous carbon subjected to acidification treatment, and no new diffraction peak is found, which indicates that the titanium dioxide film exists in an amorphous state, and on the other hand, indicates that the mass of the titanium dioxide film accounts for a small proportion of the total mass. And TiO22The @ APC @ S has the diffraction of elemental sulfur on the basis of the original diffraction peak, which corresponds to the JCPDF of the standard card of 08-0247, and indicates that TiO is obtained2@ APC @ S.
FIG. 2 (a) is a scanning transmission electron micrograph of APC;
in FIG. 2, (b) is TiO2Scanning transmission electron microscopy images of @ APC;
FIG. 2 (c) shows APC and TiO2The nitrogen desorption curve of @ APC;
FIG. 2 (d) shows APC and TiO2The pore size distribution plot of @ APC; from fig. 2 (a), the specific morphology of the porous carbon, which is ketjen black, can be seen clearly, the pore structure of ketjen black is observed clearly, fig. 2 (b) is the porous carbon coated with a layer of amorphous titanium dioxide, the pore structure is not obvious from fig. 2 (a), the surface coated with a layer of film, i.e. titanium dioxide, can be seen clearly, fig. 2 (c) shows that the specific surface area of ketjen black can reach 1243.2m2(iv)/g, when a titanium dioxide film is coated, itThe surface area is reduced to 669.2m2And/g, as can be easily seen from (d) in fig. 2, the pore diameter is slightly reduced after the titanium dioxide film in an amorphous state is wrapped, the pore diameter distribution is large between 3 nm and 5nm, and when a sulfur elementary substance is loaded, the sulfur elementary substance is easily infiltrated into the pores.
In FIG. 3, (a) is TiO2Scanning transmission electron micrographs of @ APC composite;
FIG. 3 (b) is TiO2The carbon element profile of the @ APC composite;
in FIG. 3, (c) is TiO2The titanium element profile of the @ APC composite;
in FIG. 3, (d) is TiO2The oxygen profile of the @ APC composite; the composite TiO can be seen in FIG. 3 (a)2The pore structure of @ APC, as can be seen from FIG. 3 (b), FIG. 3 (c) and FIG. 3 (d), amorphous TiO2The film is uniformly distributed on the surface of the whole porous carbon and is uniformly distributed;
FIG. 4(a) is TiO2Scanning transmission electron micrographs of @ APC @ S composite;
FIG. 4(b) is TiO2An energy spectrum plot of @ APC @ S composite; from FIGS. 4(a) and 4(b), peaks of carbon, oxygen, titanium, and sulfur elements are clearly seen, indicating that both titanium dioxide and sulfur are present on the porous carbon material;
FIG. 5(a) is TiO2A cyclic voltammogram of @ APC @ S composite;
FIG. 5(b) shows TiO2The charging and discharging curve diagram of the @ APC @ S composite material shows that TiO2@ APC @ S shows the electrochemical process of a sulfur electrode from the perspective of FIG. 5(a), the oxidation process corresponds to the conversion from lithium sulfide to elemental sulfur, the reduction process corresponds to the conversion from elemental sulfur to lithium polysulfide and then to lithium sulfide, from the charging and discharging curve of FIG. 5(b), the discharging curve has two discharging platforms corresponding to the reduction process of a cyclic voltammogram, and the charging curve corresponds to the oxidation process of the cyclic voltammogram;
FIG. 6 is TiO2Comparison of the cycle Performance of the @ APC @ S electrode material, TiO can be seen in FIG. 62@ APC @ S composite material has specific capacity higher than that of APC @ S composite material under the same condition (the same charge and discharge rate) and is stable in circulationGood performance, and can be seen clearly that TiO is formed after the electrode material is charged and discharged at high rate of 2C2The @ APC @ S composite material can recover the charge-discharge performance with high specific capacity under the multiplying power of 0.1C, and the capacity can still maintain 1200 mAh.g after 200 cycles-1The battery still works, and the cycle performance of the APC @ S composite material is far inferior to that of the TiO2The @ APC @ S composite is stable and the battery life is also short.
Detailed Description
The invention is further illustrated by the following figures and examples.
Example 1
1g of ketjen black was acidified with 30ml of 6M nitric acid at 80 ℃ for 2 hours, and then filtered, washed with deionized water, and dried at 80 ℃. And then 0.2g of dried acidified Ketjen black is dispersed in 40ml of cyclohexane, 10ml of tetrabutyl titanate is added, sealed ultrasonic stirring is carried out for 12 days, then unreacted tetraethyl titanate is centrifugally washed, and then the mixture is dispersed in cyclohexane again and subjected to solvothermal reaction at 140 ℃ for 10 hours to obtain amorphous titanium dioxide film coated porous carbon. And finally, mixing the porous carbon coated with 0.1g of amorphous titanium dioxide film with 0.35g of elemental sulfur, sealing in an inert gas (nitrogen, helium and argon) environment, and heating at 160 ℃ for 6 hours to obtain amorphous titanium dioxide film-coated porous carbon loaded elemental sulfur which is used as a positive electrode material of a lithium-sulfur battery.
The application of a positive electrode material of a lithium-sulfur battery, which comprises the following steps:
(1) ultrasonically dispersing the prepared amorphous titanium dioxide film-coated porous carbon loaded elemental sulfur and conductive carbon black in methyl pyrrolidone (NMP) for 10min-2h to obtain a turbid liquid;
(2) the turbid liquid obtained in the step (1) is dripped on a wafer and dried to obtain a positive electrode, and the drying temperature is 40-80 ℃;
(3) a lithium secondary battery was obtained using metallic lithium as a negative electrode, celgrad 2400 as a separator, and an organic liquid as an electrolyte.
In the step (1), the mass ratio of the amorphous titanium dioxide film-coated porous carbon loaded elemental sulfur to the conductive carbon black is 1: (0.1-0.5);
in the step (2), the wafer is made of carbon fiber paper, carbon felt, carbon nanotube paper or carbon aerogel paper;
in the step (3), LiTFSI with 1.0M of organic liquid is dissolved in organic solution with the volume ratio of DME to DOL of 1:1, and then lithium nitrate is added, wherein the mass of the lithium nitrate is 2% of that of the LiTFSI;
the obtained lithium secondary battery is made into a CR-2032 button battery and is stood for 2 hours for charge and discharge tests, and the test voltage range is 1.7V-2.8V.
The porous carbon APC, TiO obtained2@APC,TiO2The X-ray powder diffraction pattern of @ APC @ S is shown in FIG. 1, and from FIG. 1, porous carbon APC, TiO2@APC，TiO2The powder diffraction data of the three substances of @ APC @ S have two large bulges for porous carbon APC subjected to acidification treatment, and for diffraction between graphite layers and in-plane diffraction, when porous carbon TiO coated with one layer of amorphous titanium dioxide2The diffraction peak of @ APC has no obvious difference from the diffraction peak of the porous carbon subjected to acidification treatment, and no new diffraction peak is found, which indicates that the titanium dioxide film exists in an amorphous state, and on the other hand, indicates that the mass of the titanium dioxide film accounts for a small proportion of the total mass. And TiO22The @ APC @ S has the diffraction of elemental sulfur on the basis of the original diffraction peak, which corresponds to the JCPDF of the standard card of 08-0247, and indicates that TiO is obtained2@ APC @ S.
Scanning Transmission Electron micrograph of APC, TiO, as shown in (a) of FIG. 22Scanning Transmission Electron micrograph of @ APC As shown in FIG. 2 (b), APC and TiO2The Nitrogen adsorption/desorption profile of @ APC is shown in FIG. 2 (c), APC and TiO2The pore size distribution of @ APC is shown in FIG. 2 (d), and from FIG. 2 (a), the specific morphology of the porous carbon, which is Ketjen black and whose pore structure can be clearly observed, can be seen, and in FIG. 2 (b), which is the porous carbon coated with a layer of amorphous titanium dioxide, the pore structure of which is less apparent than that of FIG. 2 (a), and the surface coated with a layer of amorphous titanium dioxide can be clearly seenThe film, i.e., titanium dioxide, (c) in FIG. 2 shows that the specific surface area of Ketjen black can reach 1243.2m2(g) when coated with a titanium dioxide film, the surface area is reduced to 669.2m2And/g, as can be easily seen from (d) in fig. 2, the pore diameter is slightly reduced after the titanium dioxide film in an amorphous state is wrapped, the pore diameter distribution is large between 3 nm and 5nm, and when a sulfur elementary substance is loaded, the sulfur elementary substance is easily infiltrated into the pores.
TiO2Scanning Transmission Electron microscopy of the @ APC composite As shown in FIG. 3 (a), TiO2The carbon element distribution of the @ APC composite material is shown in FIG. 3 (b), TiO2The titanium element distribution of the @ APC composite material is shown in FIG. 3 (c), and TiO2The distribution of oxygen element in the @ APC composite material is shown in FIG. 3 (d), and from FIG. 3 (a), TiO composite material is observed2The pore structure of @ APC, as can be seen from FIG. 3 (b), FIG. 3 (c) and FIG. 3 (d), amorphous TiO2The film is uniformly distributed on the surface of the whole porous carbon and is uniformly distributed; TiO22Scanning Transmission Electron microscopy of @ APC @ S composite As shown in FIG. 4(a), TiO2The energy spectrum diagram of the @ APC @ S composite material is shown in FIG. 4(b), and peaks of carbon, oxygen, titanium and sulfur elements can be clearly seen from FIG. 4(a) and FIG. 4(b), which indicates that titanium dioxide and sulfur are both on the porous carbon material; TiO22The cyclic voltammogram of the @ APC @ S composite material is shown in FIG. 5(a), and TiO2The charge-discharge curve graph of the @ APC @ S composite material is shown in FIG. 5(b), from FIG. 5(a), TiO2@ APC @ S shows the electrochemical process of a sulfur electrode, the oxidation process corresponds to the conversion of lithium sulfide to elemental sulfur, the reduction process corresponds to the conversion of elemental sulfur to lithium polysulfide and then to lithium sulfide, from the charge-discharge curve of FIG. 5(b), the discharge curve has two discharge platforms corresponding to the reduction process of a cyclic voltammogram, and the charge curve corresponds to the oxidation process of the cyclic voltammogram; TiO22The comparison graph of the cycle performance of the @ APC @ S electrode material is shown in FIG. 6, and TiO can be seen from FIG. 62The specific capacity of the @ APC @ S composite material under the same condition (the same charge-discharge rate) is higher than that of the APC @ S composite material, the cycling stability is good, and TiO can be obviously seen after the electrode material is charged and discharged at a high multiplying power of 2C2The @ APC @ S composite material can recover the charge-discharge performance with high specific capacity under the multiplying power of 0.1C, and the capacity can still maintain 1200 mAh.g after 200 cycles-1The battery still works, and the cycle performance of the APC @ S composite material is far inferior to that of the TiO2The @ APC @ S composite is stable and the battery life is also short.
Example 2
4g of carbon black super P was acidified with 40ml of a mixed acid of 4M nitric acid and 20ml of 2M sulfuric acid at 60 ℃ for 2 hours, then filtered, washed with deionized water and dried at 70 ℃. And then 0.3g of dried acidified carbon black super P is dispersed in 40ml of cyclohexane, 6ml of tetraethyl titanate is added, sealed ultrasonic stirring is carried out for 12 days, then the unreacted tetraethyl titanate is centrifugally washed, and then the unreacted tetraethyl titanate is dispersed in the cyclohexane again and thermally reacted in a solvent at 180 ℃ for 8 hours, and the amorphous titanium dioxide film-coated porous carbon is obtained after drying at 65 ℃. And finally, mixing the porous carbon coated with 0.3g of amorphous titanium dioxide film with 0.7g of elemental sulfur, sealing in an inert gas argon environment, and heating at the temperature of 155 ℃ for 10 hours to obtain amorphous titanium dioxide film-coated porous carbon loaded elemental sulfur which is used as a positive electrode material of a lithium-sulfur battery.
Example 3
1g of porous carbon CMK-3 was acidified with 30ml of 6M nitric acid at 80 ℃ for 4 hours, then filtered, washed with deionized water and dried at 90 ℃. And then 0.3g of dried acidified porous carbon CMK-3 is dispersed in 80ml of petroleum ether, then added into 8ml of isopropyl titanate, sealed and ultrasonically stirred for 12 days, then centrifugally washed to remove unreacted isopropyl titanate, then dispersed in the petroleum ether again for 1 day of 150 ℃ solvent thermal reaction, and finally dried at 70 ℃ to obtain amorphous titanium dioxide film coated porous carbon. And finally, mixing the porous carbon coated with 0.2g of amorphous titanium dioxide film with 0.6g of elemental sulfur, sealing in an inert gas nitrogen environment, and heating at the temperature of 200 ℃ for 12 hours to obtain amorphous titanium dioxide film-coated porous carbon loaded elemental sulfur which is used as a positive electrode material of a lithium-sulfur battery.
Example 4
3g of porous carbon CMK-8 was acidified with 40ml of 6M phosphoric acid at 100 ℃ for 2 hours, then filtered, washed with deionized water and dried at 100 ℃. And then 0.2g of dried acidified porous carbon CMK-8 is dispersed in 80ml of hexane, 6ml of tetrabutyl titanate is added, sealed and ultrasonically stirred for 7 days, then unreacted tetrabutyl titanate is centrifugally washed away, and then the dried acidified porous carbon CMK-8 is dispersed in hexane and subjected to solvothermal reaction at 170 ℃ for 2 days, and finally the dried porous carbon coated with the amorphous titanium dioxide film is obtained after drying at 70 ℃. And finally, mixing the porous carbon coated with 0.3g of amorphous titanium dioxide film with 1g of elemental sulfur, sealing in an inert gas helium environment, and heating at 180 ℃ for 3 hours to obtain amorphous titanium dioxide film-coated porous carbon loaded elemental sulfur which is used as a positive electrode material of a lithium-sulfur battery.
Example 5
1g of Ketjen black was acidified with 60ml of 4M nitric acid at 75 ℃ for 2 hours, washed with deionized water, centrifuged, and dried at 60 ℃. And then 0.3g of dried acidified ketjen black is dispersed in 50ml of cyclohexane, then 30ml of tetraethyl titanate is added, sealed ultrasonic stirring is carried out for 2 days, unreacted tetraethyl titanate is filtered out, then the unreacted tetraethyl titanate is dispersed in cyclohexane and subjected to solvothermal reaction for 16 hours at the temperature of 190 ℃, and amorphous titanium dioxide film-coated porous carbon is obtained after drying at the temperature of 60 ℃. And finally, mixing the porous carbon coated with 0.15g of amorphous titanium dioxide film with 0.6g of elemental sulfur, sealing in an inert gas argon environment, and heating at the temperature of 155 ℃ for 10 hours to obtain amorphous titanium dioxide film-coated porous carbon loaded elemental sulfur which is used as a positive electrode material of a lithium-sulfur battery.

Claims (9)

1. A preparation method of a lithium-sulfur battery positive electrode material is characterized by comprising the following steps:
(1) acidifying the porous carbon to obtain acidified porous carbon;
(2) dispersing the acidified porous carbon obtained in the step (1) in a nonpolar solvent, adding a titanium source, sealing, ultrasonically stirring, centrifugally washing after the ultrasonic stirring is finished, dispersing the obtained solid in the nonpolar solvent again after the centrifugal washing is finished, carrying out a solvothermal reaction at the temperature of 90-240 ℃ for 2h-2d, centrifugally washing after the solvothermal reaction is finished, drying the obtained solid after the centrifugal washing is finished at the drying temperature of 60-100 ℃ to obtain amorphous titanium dioxide film coated porous carbon;
(3) and (3) mixing the porous carbon coated by the amorphous titanium dioxide film obtained in the step (2) with elemental sulfur, sealing in an inert gas environment after uniform mixing, and heating at the heating temperature of 110-500 ℃ for 30min-12h after sealing to obtain the amorphous titanium dioxide film coated porous carbon loaded elemental sulfur.
2. The method for preparing a positive electrode material for a lithium-sulfur battery according to claim 1, wherein: in the step (1), the porous carbon is super P, Ketjen black, CMK-3 or CMK-8, and the specific surface area of the porous carbon is 200m2/g-2000m2The pore diameter is 1nm-100 nm.
3. The method for preparing a positive electrode material for a lithium-sulfur battery according to claim 1, wherein: in the step (1), the reagent used in the acidification treatment is one or a mixture of more than two of nitric acid, sulfuric acid and phosphoric acid, and the acidification treatment process is as follows: mixing porous carbon and a reagent, stirring at the mixing temperature of 20-140 ℃ for 10min-24h, washing with deionized water after stirring, and drying at the drying temperature of 60-100 ℃, wherein the proportional relation between the porous carbon and the reagent is 1g: 5-100 ml.
4. The method for preparing a positive electrode material for a lithium-sulfur battery according to claim 1, wherein: in the step (2), the nonpolar solvent is cyclohexane, hexane or petroleum ether.
5. The method for preparing a positive electrode material for a lithium-sulfur battery according to claim 1, wherein: in the step (2), the titanium source is tetrabutyl titanate, tetraethyl titanate or isopropyl titanate.
6. The method for preparing a positive electrode material for a lithium-sulfur battery according to claim 1, wherein: in the step (2), the ratio of the porous carbon to the titanium source is 1g (5-40 ml).
7. The method for preparing a positive electrode material for a lithium-sulfur battery according to claim 1, wherein: in the step (3), the mass ratio of the amorphous titanium dioxide film-coated porous carbon to the elemental sulfur is 1 (0.1-9).
8. Use of a positive electrode material for a lithium-sulphur battery, prepared according to claim 1, characterized in that the steps of the method comprise:
(1) ultrasonically dispersing the prepared amorphous titanium dioxide film-coated porous carbon loaded elemental sulfur and conductive carbon black in methyl pyrrolidone for 10min-2h to obtain a turbid liquid;
(2) the turbid liquid obtained in the step (1) is dripped on a wafer and dried to obtain a positive electrode, and the drying temperature is 40-80 ℃;
(3) a lithium secondary battery was obtained using metallic lithium as a negative electrode, celgrad 2400 as a separator, and an organic liquid as an electrolyte.
9. The use of the positive electrode material for a lithium-sulfur battery according to claim 8, wherein: in the step (1), the mass ratio of the amorphous titanium dioxide film-coated porous carbon loaded elemental sulfur to the conductive carbon black is 1: (0.1-0.5);
in the step (2), the wafer is made of carbon fiber paper, carbon felt, carbon nanotube paper or carbon aerogel paper;
in the step (3), LiTFSI with 1.0M of organic liquid is dissolved in organic solution with the volume ratio of DME to DOL being 1:1, and lithium nitrate is added, wherein the mass of the lithium nitrate is 2% of that of the LiTFSI.
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