CN107579233B - Preparation method of metal-doped silicon oxide molecular sieve/sulfur-carbon composite - Google Patents
Preparation method of metal-doped silicon oxide molecular sieve/sulfur-carbon composite Download PDFInfo
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Abstract
A preparation method of a metal doped silicon oxide molecular sieve/sulfur-carbon composite relates to a preparation method of a nano composite material. The invention aims to solve the problems that the existing sulfur anode material prepared by taking a porous carbon material and a porous oxide material as basic carrier materials cannot effectively limit the dissolution of polysulfide, so that the capacity of a battery is rapidly reduced, and the preparation of the porous metal oxide is difficult and the energy consumption is large. The preparation method comprises the following steps: firstly, preparing a metal-doped silicon oxide molecular sieve; secondly, preparing a sulfur-embedded metal doped silicon oxide molecular sieve; and thirdly, dipping the carbon material to obtain the metal-doped silicon oxide molecular sieve/sulfur-carbon composite. The metal-doped silicon oxide molecular sieve/sulfur-carbon composite is used as a positive electrode material for preparing a positive electrode of a lithium-sulfur battery.
Description
Technical Field
The invention relates to a preparation method of a nano composite material, in particular to a preparation method of a nano composite material suitable for a lithium-sulfur battery cathode material.
Background
The rechargeable Li-S battery has high theoretical specific energy density which is 3-5 times of that of the intercalation reaction lithium ion battery, is likely to be the development direction of the next generation energy storage system, and has wide prospect particularly for large-scale application. However, factors that limit its wide application still exist, such as high internal resistance, self-discharge phenomenon, rapid degradation of cycle capacity, etc., resulting in a large difference between the high theoretical energy density and the actual energy density. To improve these problems, a novel S electrode having an excellent structure may be designed.
After more than 20 years of research and development, the lithium ion battery reaches the limit of energy density, and generally, the capacity of an intercalation material does not exceed 300mA · h · g-1. The maximum travel of the pure lithium battery electric automobile can only reach 300km, so that the development of the electric automobile is limited, and a large-scale, high-energy-density and economic energy storage system is urgently developed. In 1962, Herbet and Ulam used elemental S as an anode electrode material for the first time, since S has many excellent properties, such as small chemical equivalent, low price and no toxicity. Many studies have been made on alkali metal-S batteries, such as Na-S batteries that can be operated at temperatures of 300 to 350 ℃ and room temperature. The overall reaction equation for an LI-S cell is: s8+16Li++16e-→8Li2S, average voltage of 2.15V corresponding to Li+The voltage of the conventional intercalation anode material is 1/2-2/3, and the theoretical capacity is 1672 mA.h.g-1The highest among the solid-state anode materials, and therefore Li-S batteries are likely to achieve the greatest energy density at the lowest cost relative to conventional lithium-ion batteries. Theoretically, the energy density and the volume density of the material can reach 2500 W.h.kg-1And 2800 W.h.L-1。
Li-S cells were first formed in 1960 by using S plus electrical conductor plus binder for the anode and an organic electrolyte to separate the two poles. This model also provides a platform for subsequent studies. In the electrolyte, the S electrode undergoes mainly 3 processes, at high potential, S occurs0→S0.5-To form soluble polysulfide ions S4 2-. This process is very rapid due to the nature of the reacting molecule, followed by S0.5-→S1-This process forms insoluble Li2S2And (3) a solid. The third stage is Li2S2To Li2The transformation of S is also the most difficult step to perform, since it requires the transport of a solid phase and is therefore relatively slow. The discharge process can be completed only by one-step oxidation, and the final product is S8 2-. It is noted that during charging, the S active material expands because of Li2The S density is lower, and the volume is reduced during the discharge process, which needs to be noticed during the actual design process.
And because the metal lithium is adopted as the cathode, Li is generated in the charging process+The dendritic lithium metal is easy to be electroplated and deposited on the surface of the negative electrode to form dendritic lithium metal, and when the dendritic lithium metal grows to a certain degree, the dendritic lithium metal finally penetrates through the diaphragm to be in contact with the positive electrode to cause internal short circuit of the battery, which is an important reason for poor cycle performance of the lithium-sulfur battery. The active substance of the Li-S battery anode, namely elemental sulfur, is an insulator of electrons and ions, and can be in close contact with a conductive agent to complete reversible electrochemical reaction, but the addition of the conductive agent can increase the negative weight and reduce the energy density of the battery. The dispersion state of the active substance sulfur in the conductive agent framework also determines the mass transfer rate and the electron conduction rate of the electrochemical reaction, and if the active substance is not uniformly dispersed, the utilization rate of the active substance can be reduced, so that the discharge capacity and the cycle performance of the battery are influenced. In addition, the Li-S battery has two discharge platforms in the charge and discharge process due to the sulfur anode, and the high-voltage platform product high polymeric lithium polysulfide is easy to dissolve in the electrolyte and the dissolved higher polymeric sulfide ions (S)8 2-S6 2-S4 2-) Can be diffused to the negative electrode to directly react with the metallic lithium to generate sulfide ions with lower valence, and then diffused back to the sulfur positive electrode to generate sulfide ions with higher valence again, which is the unique shuttle effect in the Li-S battery. It is the presence of the shuttle effect that makes the cell resistant to overcharging. However, at the same time, due to this effect, the diffusion of polysulfide ions into the lithium negative electrode will generate insoluble products, which will not diffuse back into the positive electrode but deposit on the surface of the negative electrode, causing on the one hand a deterioration in the performance of the lithium negative electrode and on the other hand an irreversible loss of battery capacity, i.e. a reduction in cycling performance.
At present, various methods are adopted to improve the electrochemical performance of the sulfur anode, for example, sulfur and a material with high conductivity are compounded to improve electronic conduction, porous material adsorption or polymer coating is adopted to limit the loss of polysulfide ions to an electrolyte main body, and a flexible material with a stable cavity and a porous material are adopted as sulfur carriers to buffer the volume strain of the sulfur anode in the circulation process. The most widely used method for improving the lithium-sulfur battery is to compound sulfur and a conductive porous material, so that the conductivity of the electrode can be improved, and the dissolution of lithium polysulfide can be limited to a certain extent. The porous material comprises a porous carbon material, a metal oxide material and the like, but although the conductivity of the porous carbon material is improved to a certain extent, due to the nonpolar nature, when the porous carbon material is applied to a positive electrode material of a lithium-sulfur battery, the porous carbon material cannot effectively adsorb polar intermediate product lithium polysulfide; however, metal oxides, especially porous metal oxides, are difficult to prepare and consume much energy, and low conductivity increases the impedance of the whole electrode, so that there are few reports.
Disclosure of Invention
The invention aims to solve the problems that the dissolution of polysulfide cannot be effectively limited, the capacity of a battery is rapidly reduced, the preparation of porous metal oxide is difficult and the energy consumption is large when the conventional sulfur anode material prepared by taking a porous carbon material and a porous oxide material as a basic carrier material, and provides a preparation method of a metal-doped silicon oxide molecular sieve/sulfur-carbon composite.
A metal-doped silicon oxide molecular sieve/sulfur-carbon composite is prepared from a water dispersion of a sulfur-embedded metal-doped silicon oxide molecular sieve and a water dispersion of a carbon material, wherein the mass ratio of the sulfur-embedded metal-doped silicon oxide molecular sieve to the carbon material in the water dispersion of the carbon material is (4-10): 1; the sulfur-embedded metal doped silicon oxide molecular sieve is prepared from a metal doped silicon oxide molecular sieve and elemental sulfur, and the mass fraction of the elemental sulfur in the sulfur-embedded metal doped silicon oxide molecular sieve is 10-80%.
A method for preparing a metal-doped silicon oxide molecular sieve/sulfur-carbon composite comprises the following steps:
firstly, preparing a metal-doped silicon oxide molecular sieve:
a. dissolving a surfactant in deionized water to obtain a surfactant aqueous solution with the concentration of 0.3-10 g/L, and then adjusting the pH of the surfactant aqueous solution with the concentration of 0.3-10 g/L to 1-6 by utilizing an acidic medium to obtain an acidic surfactant aqueous solution;
b. adjusting the temperature of an acid surfactant aqueous solution to 20-60 ℃, adding a silicon source at the temperature of 20-60 ℃, stirring for reaction for 1-12 h, and standing for 12-48 h to obtain a product after standing; the molar ratio of the surfactant in the acidic surfactant aqueous solution to the silicon element in the silicon source is (0.05-1): 1;
c. transferring the product after standing into an autoclave, and performing heat preservation and aging for 1-72 h at the temperature of 35-200 ℃ to obtain an aged reactant;
d. filtering the aged reactant, washing and drying the solid obtained by filtering in sequence to obtain a dried solid, and roasting the dried solid to obtain mesoporous silicon oxide;
e. adding the metal source solution and the mesoporous silica into an isopropanol solvent, stirring and uniformly mixing, preserving the temperature at 25-200 ℃ for 12-72 h, filtering to obtain a precipitate, and washing and drying the precipitate in sequence to obtain a metal-doped silica molecular sieve; the mass ratio of the mesoporous silicon oxide to the metal elements in the metal source solution is (5-80): 1; the volume ratio of the mass of the mesoporous silicon oxide to the isopropanol solvent is (0.1-1) g:40 mL;
secondly, preparing a sulfur-embedded metal doped silicon oxide molecular sieve:
filling elemental sulfur into a metal-doped silicon oxide molecular sieve by adopting a melt impregnation method to obtain a sulfur-embedded metal-doped silicon oxide molecular sieve, wherein the mass fraction of the elemental sulfur in the sulfur-embedded metal-doped silicon oxide molecular sieve is 10-80%;
thirdly, impregnating the carbon material:
dispersing a sulfur-embedded metal doped silicon oxide molecular sieve in deionized water, magnetically stirring for 0.5-12 h to obtain aqueous dispersion of the sulfur-embedded metal doped silicon oxide molecular sieve, then adding the aqueous dispersion of the sulfur-embedded metal doped silicon oxide molecular sieve into the aqueous dispersion of a carbon material, continuously stirring for 12-48 h, precipitating, carrying out centrifugal separation to obtain a solid reactant, and sequentially washing and drying the solid reactant to obtain a metal doped silicon oxide molecular sieve/sulfur-carbon composite; the mass ratio of the sulfur-embedded metal doped silicon oxide molecular sieve in the aqueous dispersion of the sulfur-embedded metal doped silicon oxide molecular sieve to the carbon material in the aqueous dispersion of the carbon material is (4-10): 1.
The application of the metal-doped silicon oxide molecular sieve/sulfur-carbon composite is characterized in that the metal-doped silicon oxide molecular sieve/sulfur-carbon composite is used as a positive electrode material for preparing a positive electrode of a lithium-sulfur battery.
The invention has the advantages that:
firstly, a metal-doped silicon oxide molecular sieve is adopted as an S carrier. The cost is low. The process is simple, the energy consumption is low, and the large-scale production can be realized.
Secondly, the surface of the metal-doped silicon oxide molecular sieve/sulfur-carbon composite prepared by the invention is provided with hydroxyl groups, and the composite has good wettability with liquid S, so that the S can be conveniently impregnated; when the lithium-sulfur secondary battery is used for a lithium-sulfur secondary battery, the lithium polysulfide serving as a discharge intermediate can be effectively and lowly adsorbed through a Si-S bond and a metal-O polar bond formed after doping metal elements in the charging and discharging processes, and the shuttle effect is reduced, so that the lithium-sulfur secondary battery has higher sulfur utilization rate and conductivity, and the battery has high specific capacity and good cycling stability; and the introduction of Ti also improves the conductivity of the material to a certain extent.
And thirdly, the carbon material on the surface of the metal-doped silicon oxide molecular sieve/sulfur-carbon composite prepared by the invention can provide good conductivity, such as graphene oxide, weakly reduced graphene oxide and the like, which is beneficial to adsorbing dissolved lithium polysulfide back, thereby achieving the purpose of dual confinement.
Fourthly, the metal-doped silicon oxide molecular sieve/sulfur-carbon composite prepared by the invention has high specific capacity and cycling stability when being used as the anode material of the lithium-sulfur battery. The material is used for preparing the lithium battery anode to form a battery, the battery discharges at 0.1C, and the maximum discharge capacity reaches 1638 mA.h.g-1After 200 cycles, the capacity can still be maintained at 800 mA.h.g-1～850mA·h·g-1。
Fifthly, the aperture of the metal-doped silicon oxide molecular sieve prepared in the first step of the invention is 2nm to 9nmPore volume of 0.8cm3/g～4cm3Per g, specific surface area 500m2/g～1600m2/g。
Drawings
FIG. 1 is Fe-SiO prepared in example 12SEM image of/S/GO composite material;
FIG. 2 is the Ti-SiO solid prepared in example 22SEM image of/S/BC composite material;
FIG. 3 is Ni-SiO prepared in example 32SEM image of/S/CNT composite material;
FIG. 4 is the Co-SiO prepared in example 42SEM image of/S/rGO composite material;
FIG. 5 is an XRD graph in which A represents the Fe-doped SiO prepared in example 12XRD profile of composite material, wherein B represents titanium doped SiO prepared in example 22XRD profile of composite material, wherein C represents the Ni-doped SiO prepared in example 32XRD profile of composite material, D in the figure represents cobalt doped SiO prepared in example 42XRD curve of composite material;
FIG. 6 is a graph of pore size distribution, in which 1 represents the Fe-doped SiO prepared in example 12Pore size distribution curve of composite material, wherein 2 represents titanium doped SiO prepared in example 22Pore size distribution graph of composite material, wherein 3 represents the nickel-doped SiO prepared in example 32Pore size distribution of composite material, wherein 4 represents the cobalt-doped SiO prepared in example 42A composite material pore size distribution curve graph;
fig. 7 is a graph of cycle charge and discharge of GO button cell;
fig. 8 is a BC button cell cycle charge-discharge curve diagram, in which a represents a charge curve and B represents a discharge curve;
fig. 9 is a graph of cycle charge and discharge curves of the CNT button cell under different multiplying factors, wherein a represents a charge curve, and B represents a discharge curve.
Detailed Description
The first embodiment is as follows: the embodiment is a metal-doped silicon oxide molecular sieve/sulfur-carbon composite, which is characterized by being prepared from aqueous dispersion of a sulfur-embedded metal-doped silicon oxide molecular sieve and aqueous dispersion of a carbon material, wherein the mass ratio of the sulfur-embedded metal-doped silicon oxide molecular sieve to the carbon material in the aqueous dispersion of the sulfur-embedded metal-doped silicon oxide molecular sieve is (4-10): 1; the sulfur-embedded metal doped silicon oxide molecular sieve is prepared from a metal doped silicon oxide molecular sieve and elemental sulfur, and the mass fraction of the elemental sulfur in the sulfur-embedded metal doped silicon oxide molecular sieve is 10-80%.
The concentration of the sulfur-inserted metal-doped silica molecular sieve in the aqueous dispersion of the sulfur-inserted metal-doped silica molecular sieve of the embodiment is 0.5mg/mL to 5 mg/mL.
The concentration of the carbon material in the aqueous dispersion of the carbon material according to the present embodiment is 0.2 mg/mL-2 mg/mL.
The second embodiment is as follows: the present embodiment differs from the first embodiment in that: the aperture of the metal-doped silicon oxide molecular sieve is 2 nm-9 nm, and the pore volume is 0.8cm3/g～4cm3Per g, specific surface area 500m2/g～1600m2(ii) in terms of/g. The rest is the same as the first embodiment.
The third concrete implementation mode: the present embodiment differs from the first or second embodiment in that: the particles of the metal-doped silica molecular sieve exhibit a spherical shape, a hexagonal prism shape, or a rod shape. The others are the same as in the first or second embodiment.
The fourth concrete implementation mode: the difference between this embodiment and one of the first to third embodiments is as follows: the metal element in the metal-doped silicon oxide molecular sieve is Ti element, Fe element, Co element or Ni element. The others are the same as the first to third embodiments.
The fifth concrete implementation mode: the difference between this embodiment and one of the first to fourth embodiments is: the carbon material in the aqueous dispersion of the carbon material is carbon black, graphene oxide, weakly reduced graphene oxide or carbon micro/nano tubes. The rest is the same as the first to fourth embodiments.
The weakly reduced graphene oxide is obtained by performing heat treatment on graphene oxide at 200-1000 ℃ under vacuum, and the heat treatment time is 0.5-10 hours.
The sixth specific implementation mode: the embodiment is a preparation method of a metal-doped silicon oxide molecular sieve/sulfur-carbon composite, which is completed by the following steps:
firstly, preparing a metal-doped silicon oxide molecular sieve:
a. dissolving a surfactant in deionized water to obtain a surfactant aqueous solution with the concentration of 0.3-10 g/L, and then adjusting the pH of the surfactant aqueous solution with the concentration of 0.3-10 g/L to 1-6 by utilizing an acidic medium to obtain an acidic surfactant aqueous solution;
b. adjusting the temperature of an acid surfactant aqueous solution to 20-60 ℃, adding a silicon source at the temperature of 20-60 ℃, stirring for reaction for 1-12 h, and standing for 12-48 h to obtain a product after standing; the molar ratio of the surfactant in the acidic surfactant aqueous solution to the silicon element in the silicon source is (0.05-1): 1;
c. transferring the product after standing into an autoclave, and performing heat preservation and aging for 1-72 h at the temperature of 35-200 ℃ to obtain an aged reactant;
d. filtering the aged reactant, washing and drying the solid obtained by filtering in sequence to obtain a dried solid, and roasting the dried solid to obtain mesoporous silicon oxide;
e. adding the metal source solution and the mesoporous silica into an isopropanol solvent, stirring and uniformly mixing, preserving the temperature at 25-200 ℃ for 12-72 h, filtering to obtain a precipitate, and washing and drying the precipitate in sequence to obtain a metal-doped silica molecular sieve; the mass ratio of the mesoporous silicon oxide to the metal elements in the metal source solution is (5-80): 1; the volume ratio of the mass of the mesoporous silicon oxide to the isopropanol solvent is (0.1-1) g:40 mL;
secondly, preparing a sulfur-embedded metal doped silicon oxide molecular sieve:
filling elemental sulfur into a metal-doped silicon oxide molecular sieve by adopting a melt impregnation method to obtain a sulfur-embedded metal-doped silicon oxide molecular sieve, wherein the mass fraction of the elemental sulfur in the sulfur-embedded metal-doped silicon oxide molecular sieve is 10-80%;
thirdly, impregnating the carbon material:
dispersing a sulfur-embedded metal doped silicon oxide molecular sieve in deionized water, magnetically stirring for 0.5-12 h to obtain aqueous dispersion of the sulfur-embedded metal doped silicon oxide molecular sieve, then adding the aqueous dispersion of the sulfur-embedded metal doped silicon oxide molecular sieve into the aqueous dispersion of a carbon material, continuously stirring for 12-48 h, precipitating, carrying out centrifugal separation to obtain a solid reactant, and sequentially washing and drying the solid reactant to obtain a metal doped silicon oxide molecular sieve/sulfur-carbon composite; the mass ratio of the sulfur-embedded metal doped silicon oxide molecular sieve in the aqueous dispersion of the sulfur-embedded metal doped silicon oxide molecular sieve to the carbon material in the aqueous dispersion of the carbon material is (4-10): 1.
The melt impregnation method in step two of the present embodiment specifically includes the following steps: mixing elemental sulfur and a metal-doped silicon oxide molecular sieve, preserving heat for 6-20 h at the temperature of 158-160 ℃ under the protection of nitrogen or argon atmosphere, then heating to 250-300 ℃, and preserving heat for 0.5-3 h at the temperature of 250-300 ℃ to obtain the sulfur-embedded metal-doped silicon oxide molecular sieve, wherein the mass fraction of the elemental sulfur in the sulfur-embedded metal-doped silicon oxide molecular sieve is 10-80%.
The acidic medium in step a of this embodiment is a hydrochloric acid solution with a concentration of 1mol/L to 2mol/L or a sulfuric acid solution with a concentration of 1mol/L to 2 mol/L.
In the third step of this embodiment, the concentration of the sulfur-inserted metal-doped silica molecular sieve in the aqueous dispersion of the sulfur-inserted metal-doped silica molecular sieve is 0.5mg/mL to 5 mg/mL.
In the third step of the present embodiment, the concentration of the carbon material in the aqueous dispersion of a carbon material is 0.2 mg/mL-2 mg/mL.
The pore diameter of the metal-doped silicon oxide molecular sieve prepared in the first step of the embodiment is 2nm to 9nm, and the pore volume is 0.8cm3/g～4cm3Per g, specific surface area 500m2/g～1600m2/g。
The most widely studied today are porous carbon materials and porous oxide materials as the base support material to improve electrical conductivity and limit sulfur leaching. 1. The use of a flexible material for coating improves the conductivity, but does not effectively limit the elution of polysulfide. 2. Most carbon materials are 3-free, porous oxides that are difficult to synthesize and generally require pyrolysis, or complex steps, to achieve. The embodiment solves the problems of polar adsorption, electric conduction and volume expansion, and the preparation method is simple.
The seventh embodiment: the present embodiment differs from the sixth embodiment in that: the silicon source in the step one b is methyl orthosilicate, ethyl orthosilicate or butyl orthosilicate. The rest is the same as the sixth embodiment.
The specific implementation mode is eight: the difference between this embodiment and one of the sixth and seventh embodiments is: in the first step a, the pH value of a surfactant aqueous solution with the concentration of 0.3-10 g/L is adjusted to 2-6 by using an acidic medium. The rest is the same as the sixth or seventh embodiment.
The specific implementation method nine: the present embodiment differs from the sixth to eighth embodiments in that: in the first step a, the pH value of a surfactant aqueous solution with the concentration of 0.3-10 g/L is adjusted to 3-5 by using an acidic medium. The others are the same as the sixth to eighth embodiments.
The detailed implementation mode is ten: the difference between this embodiment and one of the sixth to ninth embodiments is: in the step one e, the concentration of the metal source in the metal source solution is 0.1 mg/mL-3 mg/mL, and the metal source is a titanium compound, an iron compound, a cobalt compound or a nickel compound. The rest is the same as the sixth to ninth embodiments.
The concrete implementation mode eleven: the sixth to tenth embodiments are different from the first to fourth embodiments in that: in step one a the surfactant is a triblock copolymer P123 or a triblock copolymer F127. The others are the same as the sixth to tenth embodiments.
The specific implementation mode twelve: the present embodiment differs from one of the sixth to eleventh embodiments in that: in the step one b, the molar ratio of the surfactant in the acidic surfactant aqueous solution to the silicon element in the silicon source is (0.05-0.7): 1. The others are the same as the embodiments six to eleven.
The specific implementation mode is thirteen: the sixth to twelfth points of this embodiment are different from the first to twelfth points of the embodiment: in the step one b, the molar ratio of the surfactant in the acidic surfactant aqueous solution to the silicon element in the silicon source is (0.2-0.5): 1. The rest is the same as the embodiments six to twelve.
The specific implementation mode is fourteen: the present embodiment differs from one of the sixth to thirteenth embodiments in that: in the first step a, the surfactant is dissolved in deionized water to obtain a surfactant aqueous solution with the concentration of 0.5 g/L-5 g/L. The others are the same as those in the sixth to thirteenth embodiments.
The concrete implementation mode is fifteen: the sixth to fourteenth embodiments are different from the first to fourteenth embodiments in that: in the first step a, the surfactant is dissolved in deionized water to obtain a surfactant aqueous solution with the concentration of 1 g/L-4 g/L. The others are the same as the embodiments six to fourteen.
The specific implementation mode is sixteen: the difference between this embodiment and one of the sixth to fifteenth embodiments is: in the step one b, the temperature of the aqueous solution of the acidic surfactant is adjusted to 30-50 ℃, and a silicon source is added at the temperature of 30-50 ℃. The others are the same as the embodiments six to fifteen.
Seventeenth embodiment: the sixth to sixteenth differences from the present embodiment are: in the step one b, the temperature of the aqueous solution of the acidic surfactant is adjusted to 35-40 ℃, and a silicon source is added at the temperature of 35-40 ℃. The others are the same as the embodiments six to sixteen.
The specific implementation mode is eighteen: the present embodiment differs from one of the sixth to seventeenth embodiments in that: and in the step one b, stirring and reacting for 3-10 h, and standing for 12-48 h. The others are the same as in the sixth to seventeenth embodiments.
The detailed embodiment is nineteen: the present embodiment differs from the sixth to eighteen embodiments in that: and in the step one b, stirring and reacting for 4-6 h, and standing for 12-48 h. The rest is the same as the sixth to eighteen embodiments.
The specific implementation mode twenty: the present embodiment differs from one of the sixth to nineteenth embodiments in that: in the step one c, the temperature is kept at 35-200 ℃ for aging for 12-48 h. The others are the same as the embodiments six to nineteen.
The specific implementation mode is twenty one: the sixth to twenty embodiments of the present invention are different from the first to sixth embodiments in that: in the step one d, the roasting temperature of roasting the dried solid is 150-600 ℃. The others are the same as the embodiments six to twenty.
Specific embodiment twenty-two: the difference between this embodiment and the sixth to twenty-first embodiment is as follows: in the step one d, the roasting temperature for roasting the dried solid is 200-500 ℃. The rest is the same as the embodiments six to twenty-one.
Specific embodiment twenty-three: the difference between this embodiment and one of the sixth to twenty-second embodiments is: in the step one d, the roasting temperature of roasting the dried solid is 400-500 ℃. The rest is the same as the embodiments six to twenty-two.
Twenty-four specific embodiments: the difference between this embodiment and one of the sixth to twenty-third embodiments is: and d, roasting the dried solid for 1-10 h. The others are the same as those in the sixth to twenty-third embodiments.
The specific implementation mode is twenty five: the difference between this embodiment and one of the sixth to twenty-fourth embodiments is: and d, roasting the dried solid for 3-8 h. The rest is the same as the embodiments six to twenty-four.
The specific implementation mode is twenty-six: the difference between this embodiment and the sixth to the twenty-fifth embodiment is as follows: and d, roasting the dried solid for 4-6 h. The others are the same as the embodiments six to twenty-five.
The specific implementation mode is twenty-seven: the difference between this embodiment and the sixth to twenty-sixth embodiment is: and in the third step, the carbon material in the aqueous dispersion of the carbon material is carbon black, graphene oxide, weakly reduced graphene oxide or carbon micro/nano tubes. The others are the same as the embodiments six to twenty-six.
The weakly reduced graphene oxide is obtained by performing heat treatment on graphene oxide at 200 ℃ under vacuum, and the heat treatment time is 0.5-10 hours.
The specific implementation mode is twenty-eight: the application of the metal-doped silicon oxide molecular sieve/sulfur-carbon composite is characterized in that the metal-doped silicon oxide molecular sieve/sulfur-carbon composite is used as a positive electrode material for a positive electrode of a lithium-sulfur battery.
The lithium salt in the lithium-sulfur battery is lithium hexafluorophosphate, lithium perchlorate, lithium hexafluoroarsenate, lithium trifluoromethanesulfonate or lithium bis-trifluoromethanesulfonate imide.
Adding vinylidene fluoride into N-methyl pyrrolidone to prepare a vinylidene fluoride-N-methyl pyrrolidone mixture with 10 mass percent of vinylidene fluoride, then uniformly mixing metal-doped silicon oxide molecular sieve/sulfur-carbon composite, acetylene black and the vinylidene fluoride-N-methyl pyrrolidone mixture to obtain anode slurry, wherein the mass ratio of the metal-doped silicon oxide molecular sieve/sulfur-carbon composite to the acetylene black is 8:1, the mass ratio of the metal-doped silicon oxide molecular sieve/sulfur-carbon composite to the vinylidene fluoride in the vinylidene fluoride-N-methyl pyrrolidone mixture is 8:1, blade-coating the anode slurry on an aluminum foil with the thickness of 50-150 mu m, drying to obtain a battery anode, assembling a button battery by taking a lithium sheet as a cathode and a microporous membrane as a diaphragm, and testing the performance of the battery, the discharge capacity reaches up to 1638 mA.h.g at 0.1C-1After 200 cycles, the capacity can still be maintained at 800 mA.h.g-1～850mA·h·g-1。
The following tests were carried out to confirm the effects of the present invention
Example 1: a method for preparing a metal-doped silicon oxide molecular sieve/sulfur-carbon composite comprises the following steps:
firstly, preparing a metal-doped silicon oxide molecular sieve:
a. dissolving 2g of triblock copolymer P123 in deionized water to obtain a surfactant aqueous solution with the concentration of 0.3g/L, and then adjusting the pH of the surfactant aqueous solution with the concentration of 0.3g/L to 1 by utilizing a hydrochloric acid solution with the concentration of 1mol/L to obtain an acid surfactant aqueous solution;
b. adjusting the temperature of an aqueous solution of an acidic surfactant to 38 ℃, adding 4.2g of ethyl orthosilicate at the temperature of 38 ℃, stirring to react for 2 hours, and standing for 12 hours;
c. transferring the product after standing into an autoclave, and performing heat preservation and aging for 12 hours at the temperature of 100 ℃ to obtain an aged reactant;
d. filtering the aged reactant, repeatedly cleaning the solid obtained by filtering with alcohol and deionized water until the washed deionized water is neutral, drying to obtain a dried solid, and roasting the dried solid for 1h at the temperature of 150 ℃ in the air atmosphere to obtain mesoporous silicon oxide;
e. adding a ferrous sulfate solution with the concentration of 0.1mg/mL and mesoporous silica into 40mL of isopropanol solvent, uniformly stirring, preserving heat at 200 ℃ for 24 hours, filtering to obtain a precipitate, and sequentially washing and drying the precipitate to obtain a metal-doped silica molecular sieve; the mass ratio of the mesoporous silicon oxide to the Fe element in the ferrous sulfate solution is 5: 1; the volume ratio of the mass of the mesoporous silicon oxide to the isopropanol solvent is 0.1g:40 mL;
secondly, preparing a sulfur-embedded metal doped silicon oxide molecular sieve:
the method is characterized in that elemental sulfur is filled in a metal-doped silicon oxide molecular sieve by adopting a melt impregnation method, and the specific process is as follows:
mixing elemental sulfur and a metal-doped silicon oxide molecular sieve, preserving heat for 6 hours at 158 ℃ under the protection of nitrogen atmosphere, then heating to 250 ℃, and preserving heat for 3 hours at 250 ℃ to obtain a sulfur-embedded metal-doped silicon oxide molecular sieve, wherein the mass fraction of the elemental sulfur in the sulfur-embedded metal-doped silicon oxide molecular sieve is 10%;
thirdly, impregnating the carbon material:
dispersing the sulfur-embedded metal-doped silicon oxide molecular sieve in deionized water, magnetically stirring for 0.5h to obtain aqueous dispersion of the sulfur-embedded metal-doped silicon oxide molecular sieve with the concentration of 1mg/mL, adding the aqueous dispersion of the sulfur-embedded metal-doped silicon oxide molecular sieve with the concentration of 1mg/mL into aqueous dispersion of graphene oxide with the concentration of 1mg/mL, continuously stirring for 24h, precipitating, and centrifuging to obtain the graphene oxide nano-particlesWashing and drying the solid reactant in sequence to obtain the metal doped silicon oxide molecular sieve/sulfur-carbon composite (namely Fe-SiO)2(ii)/S/GO composite); the mass ratio of the sulfur-embedded metal doped silicon oxide molecular sieve in the aqueous dispersion of the sulfur-embedded metal doped silicon oxide molecular sieve to the graphene oxide in the aqueous dispersion of the graphene oxide is 4: 1.
Fe-SiO prepared in this example2the/S/GO composite material is shown in figure 1, and figure 1 shows Fe-SiO prepared in example 12The SEM image of the/S/GO composite material shows that spherical molecular sieve particles are tightly wrapped by graphene oxide, the particles are uniformly distributed, an effective electron ion transmission path is provided, in addition, the shuttle effect is reduced to a certain extent due to the wrapping of the graphene oxide, the electrochemical activity is improved, and the cycle life is prolonged.
Example 2: a method for preparing a metal-doped silicon oxide molecular sieve/sulfur-carbon composite comprises the following steps:
firstly, preparing a metal-doped silicon oxide molecular sieve:
a. dissolving 2g of triblock copolymer P123 in deionized water to obtain a surfactant aqueous solution with the concentration of 10g/L, and then adjusting the pH value of the surfactant aqueous solution with the concentration of 10g/L to 6 by using a hydrochloric acid solution with the concentration of 2mol/L to obtain an acid surfactant aqueous solution;
b. adjusting the temperature of an aqueous solution of an acidic surfactant to 45 ℃, adding 3g of ethyl orthosilicate at the temperature of 45 ℃, stirring to react for 2 hours, and standing for 12 hours;
c. transferring the product after standing into an autoclave, and carrying out heat preservation and aging for 12h at the temperature of 35 ℃ to obtain an aged reactant;
d. filtering the aged reactant, repeatedly cleaning the solid obtained by filtering with alcohol and deionized water until the washed deionized water is neutral, drying to obtain a dried solid, and roasting the dried solid for 6 hours at the temperature of 400 ℃ in an air atmosphere to obtain mesoporous silicon oxide;
e. adding 3mg/mL isopropyl titanate solution and mesoporous silica into 40mL isopropanol solvent, stirring and uniformly mixing, preserving heat at 180 ℃ for 15h, filtering to obtain precipitate, and sequentially washing and drying the precipitate to obtain a metal-doped silica molecular sieve; the mass ratio of the mesoporous silicon oxide to the Ti element in the isopropyl titanate solution is 80: 1; the volume ratio of the mass of the mesoporous silicon oxide to the isopropanol solvent is 1g:40 mL;
secondly, preparing a sulfur-embedded metal doped silicon oxide molecular sieve:
the method is characterized in that elemental sulfur is filled in a metal-doped silicon oxide molecular sieve by adopting a melt impregnation method, and the specific process is as follows:
mixing elemental sulfur and a metal-doped silicon oxide molecular sieve, preserving heat for 20 hours at 160 ℃ under the protection of nitrogen atmosphere, then heating to 300 ℃, and preserving heat for 0.5 hour at 300 ℃ to obtain a sulfur-embedded metal-doped silicon oxide molecular sieve, wherein the mass fraction of the elemental sulfur in the sulfur-embedded metal-doped silicon oxide molecular sieve is 30%;
thirdly, impregnating the carbon material:
dispersing a sulfur-embedded metal doped silicon oxide molecular sieve in deionized water, magnetically stirring for 12h to obtain aqueous dispersion of the sulfur-embedded metal doped silicon oxide molecular sieve with the concentration of 5mg/mL, adding the aqueous dispersion of the sulfur-embedded metal doped silicon oxide molecular sieve with the concentration of 5mg/mL into aqueous dispersion of carbon black with the concentration of 1mg/mL, continuously stirring for 12h, precipitating, centrifugally separating to obtain a solid reactant, washing and drying the solid reactant in sequence to obtain a metal doped silicon oxide molecular sieve/sulfur-carbon composite (namely Ti-SiO2a/S/BC composite); the mass ratio of the sulfur-embedded metal doped silicon oxide molecular sieve in the aqueous dispersion of the sulfur-embedded metal doped silicon oxide molecular sieve to the carbon black in the aqueous dispersion of the carbon black is 10: 1.
Ti-SiO prepared in this example2the/S/BC composite material is shown in FIG. 2, and FIG. 2 shows Ti-SiO prepared in example 22The SEM image of the/S/BC composite material shows that carbon black particles are attached to the surfaces of hexagonal prism-shaped molecular sieve particles, the particles are uniformly distributed, an effective electron ion transmission path is provided, and the electrochemical activity is improved.
Example 3: a method for preparing a metal-doped silicon oxide molecular sieve/sulfur-carbon composite comprises the following steps:
firstly, preparing a metal-doped silicon oxide molecular sieve:
a. dissolving 2g of triblock copolymer P123 in deionized water to obtain a surfactant aqueous solution with the concentration of 0.5g/L, and then adjusting the pH of the surfactant aqueous solution with the concentration of 0.5g/L to 3 by utilizing a hydrochloric acid solution with the concentration of 1mol/L to obtain an acid surfactant aqueous solution;
b. adjusting the temperature of an aqueous solution of an acidic surfactant to 50 ℃, adding 5g of ethyl orthosilicate at the temperature of 50 ℃, stirring to react for 2 hours, and standing for 24 hours;
c. transferring the product after standing into an autoclave, and performing heat preservation and aging for 24 hours at the temperature of 180 ℃ to obtain an aged reactant;
d. filtering the aged reactant, repeatedly cleaning the solid obtained by filtering with alcohol and deionized water until the washed deionized water is neutral, drying to obtain a dried solid, and roasting the dried solid for 8 hours at the temperature of 200 ℃ in the air atmosphere to obtain mesoporous silicon oxide;
e. adding a nickel sulfamate solution with the concentration of 2mg/mL and mesoporous silica into 40mL of isopropanol solvent, uniformly stirring, preserving the temperature at 120 ℃ for 24 hours, filtering to obtain a precipitate, and sequentially washing and drying the precipitate to obtain a metal-doped silica molecular sieve; the mass ratio of the mesoporous silicon oxide to the Ni element in the nickel sulfamate solution is 20: 1; the volume ratio of the mass of the mesoporous silicon oxide to the isopropanol solvent is 0.2g:40 mL;
secondly, preparing a sulfur-embedded metal doped silicon oxide molecular sieve:
the method is characterized in that elemental sulfur is filled in a metal-doped silicon oxide molecular sieve by adopting a melt impregnation method, and the specific process is as follows:
mixing elemental sulfur and a metal-doped silicon oxide molecular sieve, preserving heat for 10 hours at the temperature of 150 ℃ under the protection of nitrogen atmosphere, then heating to 250 ℃, and preserving heat for 2 hours at the temperature of 250 ℃ to obtain a sulfur-embedded metal-doped silicon oxide molecular sieve, wherein the mass fraction of the elemental sulfur in the sulfur-embedded metal-doped silicon oxide molecular sieve is 60%;
thirdly, impregnating the carbon material:
dispersing the sulfur-embedded metal-doped silicon oxide molecular sieve in deionized water, magnetically stirring for 10h to obtain aqueous dispersion of the sulfur-embedded metal-doped silicon oxide molecular sieve with the concentration of 2mg/mL, then adding the aqueous dispersion of the sulfur-embedded metal-doped silicon oxide molecular sieve with the concentration of 0.5mg/mL into the aqueous dispersion of the carbon nano tube with the concentration of 1mg/mL, continuously stirring for 24h, precipitating, centrifugally separating to obtain a solid reactant, washing and drying the solid reactant in sequence to obtain a metal-doped silicon oxide molecular sieve/sulfur-carbon composite (namely Ni-SiO solid carbon composite)2a/S/CN composite); the mass ratio of the sulfur-embedded metal doped silicon oxide molecular sieve in the aqueous dispersion of the sulfur-embedded metal doped silicon oxide molecular sieve to the carbon nano tubes in the aqueous dispersion of the carbon nano tubes is 6: 1.
Ni-SiO prepared in this example2the/S/CNT composite is shown in FIG. 3, and FIG. 3 shows Ni-SiO prepared in example 32SEM image of the/S/CNT composite material shows that rod-shaped molecular sieve particles and carbon nanotubes are uniformly dispersed, an effective electron ion transmission path is provided, and electrochemical activity is improved.
Example 4: a method for preparing a metal-doped silicon oxide molecular sieve/sulfur-carbon composite comprises the following steps:
firstly, preparing a metal-doped silicon oxide molecular sieve:
a. dissolving 2g of triblock copolymer P123 in deionized water to obtain a surfactant aqueous solution with the concentration of 3g/L, and then adjusting the pH value of the surfactant aqueous solution with the concentration of 3g/L to 4 by using a hydrochloric acid solution with the concentration of 2mol/L to obtain an acid surfactant aqueous solution;
b. adjusting the temperature of an aqueous solution of an acidic surfactant to 38 ℃, adding 10g of ethyl orthosilicate at the temperature of 38 ℃, stirring to react for 2 hours, and standing for 48 hours;
c. transferring the product after standing into a high-pressure kettle, and performing heat preservation and aging for 48 hours at the temperature of 200 ℃ to obtain an aged reactant;
d. filtering the aged reactant, repeatedly cleaning the solid obtained by filtering with alcohol and deionized water until the washed deionized water is neutral, drying to obtain a dried solid, and roasting the dried solid for 5 hours at the temperature of 150 ℃ in the air atmosphere to obtain mesoporous silicon oxide;
e. adding a cobalt acetate solution with the concentration of 1mg/mL and mesoporous silica into 40mL of isopropanol solvent, uniformly stirring, preserving the temperature at 25 ℃ for 12h, filtering to obtain a precipitate, and sequentially washing and drying the precipitate to obtain a metal-doped silica molecular sieve; the mass ratio of the mesoporous silicon oxide to the Co element in the cobalt acetate solution is 60: 1; the volume ratio of the mass of the mesoporous silicon oxide to the isopropanol solvent is 0.8g:40 mL;
secondly, preparing a sulfur-embedded metal doped silicon oxide molecular sieve:
the method is characterized in that elemental sulfur is filled in a metal-doped silicon oxide molecular sieve by adopting a melt impregnation method, and the specific process is as follows:
mixing elemental sulfur and a metal-doped silicon oxide molecular sieve, preserving heat for 12 hours at 159 ℃ under the protection of nitrogen atmosphere, then heating to 280 ℃, and preserving heat for 1 hour at 280 ℃ to obtain a sulfur-embedded metal-doped silicon oxide molecular sieve, wherein the mass fraction of the elemental sulfur in the sulfur-embedded metal-doped silicon oxide molecular sieve is 80%;
thirdly, impregnating the carbon material:
dispersing a sulfur-embedded metal-doped silicon oxide molecular sieve in deionized water, magnetically stirring for 8 hours to obtain aqueous dispersion of the sulfur-embedded metal-doped silicon oxide molecular sieve with the concentration of 2mg/mL, then adding the aqueous dispersion of the sulfur-embedded metal-doped silicon oxide molecular sieve with the concentration of 1mg/mL into the aqueous dispersion of the weakly reduced graphene oxide with the concentration of 1mg/mL, continuously stirring for 20 hours, precipitating, centrifugally separating to obtain a solid reactant, washing and drying the solid reactant in sequence to obtain a metal-doped silicon oxide molecular sieve/sulfur-carbon composite (namely Co-SiO)2(ii)/S/rGO composite); the mass ratio of the sulfur-embedded metal-doped silicon oxide molecular sieve in the aqueous dispersion of the sulfur-embedded metal-doped silicon oxide molecular sieve to the weakly reduced graphene oxide in the aqueous dispersion of the weakly reduced graphene oxide is 5: 1.
The weakly reduced graphene oxide described in step three of this example is obtained by heat-treating graphene oxide at 500 ℃ under vacuum for 10 hours.
Co-SiO prepared in this example2the/S/rGO composite material is shown in FIG. 4, and FIG. 4 shows the Co-SiO prepared in example 42SEM images of the/S/rGO composite material provide effective electron ion transmission paths, and in addition, the shuttle effect is reduced to a certain extent due to the coating of the reduced graphene oxide, so that the electrochemical activity is improved, and the cycle life is prolonged.
The metal-doped silica molecular sieves obtained in examples 1 to 4 were examined by small-angle X-ray powder diffraction, and the results are shown in FIG. 5, in which FIG. 5 is an XRD graph, and A represents the iron-doped SiO molecular sieve prepared in example 12XRD profile of composite material, wherein B represents titanium doped SiO prepared in example 22XRD profile of composite material, wherein C represents the Ni-doped SiO prepared in example 32XRD profile of composite material, D in the figure represents cobalt doped SiO prepared in example 42The XRD curve of the composite material, as shown in fig. 5, shows that in the XRD spectrum of the small angle range, 4 samples all show peaks satisfying the bragg equation, which represents that the prepared metal-doped molecular sieve has a pore structure with regular mine drainage.
The metal-doped silica molecular sieves prepared in the first step of examples 1 to 4 were tested by nitrogen isothermal adsorption and desorption test, and the test results are shown in fig. 6, where fig. 6 is a pore size distribution graph, and fig. 1 shows the fe-doped SiO molecular sieves prepared in example 12Pore size distribution curve of composite material, wherein 2 represents titanium doped SiO prepared in example 22Pore size distribution graph of composite material, wherein 3 represents the nickel-doped SiO prepared in example 32Pore size distribution of composite material, wherein 4 represents the cobalt-doped SiO prepared in example 42As can be seen from the pore size distribution curve chart of the composite material, 4 samples still keep the pore size distribution of 2-9 nm after doping, which is beneficial to permeating sulfur into pore channels.
Example 5: assembling the GO button cell:
adding vinylidene fluoride into N-methyl pyrrolidone to prepare a vinylidene fluoride-N-methyl pyrrolidone mixture with 10 mass percent of vinylidene fluoride, then uniformly mixing the metal-doped silicon oxide molecular sieve/sulfur-carbon composite prepared in example 1, acetylene black and the vinylidene fluoride-N-methyl pyrrolidone mixture to obtain positive electrode slurry, wherein the mass ratio of the metal-doped silicon oxide molecular sieve/sulfur-carbon composite to the acetylene black is 8:1, the mass ratio of the metal-doped silicon oxide molecular sieve/sulfur-carbon composite to the vinylidene fluoride in the vinylidene fluoride-N-methyl pyrrolidone mixture is 8:1, coating the positive electrode slurry on an aluminum foil, drying the aluminum foil with the thickness of 50 mu m to obtain a battery positive electrode, and assembling a button GO battery by taking a lithium sheet as a negative electrode and a microporous membrane as a diaphragm,
the GO button cell is subjected to cyclic charge and discharge detection, the multiplying power current is 0.1C, the detection result is shown in figure 7, figure 7 is a cyclic charge and discharge curve graph of the GO button cell, it can be seen from figure 7 that the charge curve and the discharge curve are overlapped, and the initial discharge capacity of the cell is 1600mA h g-1Left and right, close to the theoretical capacity. After 500 cycles of cyclic charge and discharge, 800mAh g is still maintained-1The capacity of (a) indicates that the battery has high cycling stability.
Example 6: assembling the BC button cell:
adding vinylidene fluoride into N-methyl pyrrolidone to prepare a vinylidene fluoride-N-methyl pyrrolidone mixture with 10 mass percent of vinylidene fluoride, then uniformly mixing the metal-doped silicon oxide molecular sieve/sulfur-carbon composite prepared in the embodiment 2, acetylene black and the vinylidene fluoride-N-methyl pyrrolidone mixture to obtain positive electrode slurry, wherein the mass ratio of the metal-doped silicon oxide molecular sieve/sulfur-carbon composite to the acetylene black is 8:1, the mass ratio of the metal-doped silicon oxide molecular sieve/sulfur-carbon composite to the vinylidene fluoride in the vinylidene fluoride-N-methyl pyrrolidone mixture is 8:1, scraping the positive electrode slurry onto an aluminum foil, drying the aluminum foil with the thickness of 100 mu m to obtain a battery positive electrode, and assembling a button BC battery by taking a lithium sheet as a negative electrode and a microporous membrane as a diaphragm,
the BC button cell is subjected to cyclic charge-discharge detection, the multiplying power current is 0.1C, the detection result is shown in figure 8, figure 8 is a cyclic charge-discharge curve chart of the BC button cell, A in the chart represents a charge curve, B in the chart represents a discharge curve, and the open circuit is connectedAs can be seen from FIG. 8, the charge curve and the discharge curve almost coincide, and the initial discharge capacity of the battery is 1500mA h g-1Left and right, close to the theoretical capacity. After 200 cycles of charge and discharge, the voltage still maintains 500mA h g-1The reason for the shorter cycle life of the GO cell than that prepared in example 5 is that the flexible coating of GO not only limits the lithium polysulfide dissolution to some extent, but also the GO surface functional groups provide a part of the adsorption of lithium polysulfide. But the ratio of the charge-discharge capacity of the material is always close to 100 percent, which shows that the material has high reaction dynamic activity and strong activity.
Example 7: assembling the CNT button cell:
adding vinylidene fluoride into N-methyl pyrrolidone to prepare a vinylidene fluoride-N-methyl pyrrolidone mixture with 10 mass percent of vinylidene fluoride, then uniformly mixing the metal-doped silicon oxide molecular sieve/sulfur-carbon composite prepared in the embodiment 3, acetylene black and the vinylidene fluoride-N-methyl pyrrolidone mixture to obtain positive electrode slurry, wherein the mass ratio of the metal-doped silicon oxide molecular sieve/sulfur-carbon composite to the acetylene black is 8:1, the mass ratio of the metal-doped silicon oxide molecular sieve/sulfur-carbon composite to the vinylidene fluoride in the vinylidene fluoride-N-methyl pyrrolidone mixture is 8:1, blade-coating the positive electrode slurry on an aluminum foil, drying the aluminum foil with the thickness of 150 mu m to obtain a battery positive electrode, and assembling a button BC battery by taking a lithium sheet as a negative electrode and a microporous membrane as a diaphragm,
the charging and discharging detection of the CNT button cell under different multiplying factors is carried out, the detection result is shown in fig. 9, fig. 9 is a cyclic charging and discharging curve chart of the CNT button cell under different multiplying factors, in the graph, A represents a charging curve, in the graph, B represents a discharging curve, in the process that the current is increased from 0.1C to 2C, the capacity of the material is gradually reduced, and when the current is reduced back to 0.1C, the capacity of the material is immediately restored to the initial level, which indicates that the material has high reaction power.
Claims (3)
1. A method for preparing a metal-doped silicon oxide molecular sieve/sulfur-carbon composite is characterized by comprising the following steps:
firstly, preparing a metal-doped silicon oxide molecular sieve:
a. dissolving a surfactant in deionized water to obtain a surfactant aqueous solution with the concentration of 0.3-10 g/L, and then adjusting the pH of the surfactant aqueous solution with the concentration of 0.3-10 g/L to 1-6 by utilizing an acidic medium to obtain an acidic surfactant aqueous solution; the surfactant is a triblock copolymer P123 or a triblock copolymer F127;
b. adjusting the temperature of an acid surfactant aqueous solution to 20-60 ℃, adding a silicon source at the temperature of 20-60 ℃, stirring for reaction for 1-12 h, and standing for 12-48 h to obtain a product after standing; the molar ratio of the surfactant in the acidic surfactant aqueous solution to the silicon element in the silicon source is (0.05-1): 1;
c. transferring the product after standing into an autoclave, and performing heat preservation and aging for 1-72 h at the temperature of 35-200 ℃ to obtain an aged reactant;
d. filtering the aged reactant, washing and drying the solid obtained by filtering in sequence to obtain a dried solid, and roasting the dried solid to obtain mesoporous silicon oxide;
e. adding the metal source solution and the mesoporous silica into an isopropanol solvent, stirring and uniformly mixing, preserving the temperature at 25-200 ℃ for 12-72 h, filtering to obtain a precipitate, and washing and drying the precipitate in sequence to obtain a metal-doped silica molecular sieve; the mass ratio of the mesoporous silicon oxide to the metal elements in the metal source solution is (5-80): 1; the volume ratio of the mass of the mesoporous silicon oxide to the isopropanol solvent is (0.1-1) g:40 mL; the concentration of a metal source in the metal source solution is 0.1 mg/mL-3 mg/mL, and the metal source is a titanium compound, an iron compound, a cobalt compound or a nickel compound; the aperture of the metal-doped silicon oxide molecular sieve is 2 nm-9 nm, and the pore volume is 0.8cm3/g～4cm3Per g, specific surface area 500m2/g～1600m2(ii)/g; the particles of the metal-doped silicon oxide molecular sieve are spherical, hexagonal prism-shaped or rod-shaped;
secondly, preparing a sulfur-embedded metal doped silicon oxide molecular sieve:
filling elemental sulfur into a metal-doped silicon oxide molecular sieve by adopting a melt impregnation method to obtain a sulfur-embedded metal-doped silicon oxide molecular sieve, wherein the mass fraction of the elemental sulfur in the sulfur-embedded metal-doped silicon oxide molecular sieve is 10-80%;
thirdly, impregnating the carbon material:
dispersing a sulfur-embedded metal doped silicon oxide molecular sieve in deionized water, magnetically stirring for 0.5-12 h to obtain aqueous dispersion of the sulfur-embedded metal doped silicon oxide molecular sieve, then adding the aqueous dispersion of the sulfur-embedded metal doped silicon oxide molecular sieve into the aqueous dispersion of a carbon material, continuously stirring for 12-48 h, precipitating, carrying out centrifugal separation to obtain a solid reactant, and sequentially washing and drying the solid reactant to obtain a metal doped silicon oxide molecular sieve/sulfur-carbon composite; the mass ratio of the sulfur-embedded metal doped silicon oxide molecular sieve to the carbon material in the aqueous dispersion of the carbon material is (4-10): 1; and in the third step, the carbon material in the aqueous dispersion of the carbon material is graphene oxide or weakly reduced graphene oxide.
2. The method of claim 1, wherein the silicon source in step (b) is methyl orthosilicate, ethyl orthosilicate, or butyl orthosilicate.
3. The method of claim 1, wherein the calcination temperature of the dried solid in the first step is 150-600 ℃; the roasting time is 1-10 h.
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